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Sample records for added electron donor

  1. Electron Donor-Acceptor Quenching and Photoinduced Electron Transfer for Coumarin Dyes.

    DTIC Science & Technology

    1983-10-31

    Mechanism of cousarin photodegradation . Ithe behavior of eoiuma dyes is water ad In aqueous detergent media,. and the effsects of medism aud, additives on...D-i36 345 ELECTRON DONOR-ACCEPTOR UENCHING AND PHOTOINDUCED i/i Ai ELECTRON TRANSFER FOR COUMARIN DYES (U) BOSTON UNIY MR DEPT OF CHEMISTRY G JONES...TYPE OF REPORT & PEIOD COVERED Electron Donor-acceptor Quenching and Photo- Technical, 1/1/82-10/31/82 induced Electron Transfer for Coumarin Dyes S

  2. Accelerating Quinoline Biodegradation and Oxidation with Endogenous Electron Donors.

    PubMed

    Bai, Qi; Yang, Lihui; Li, Rongjie; Chen, Bin; Zhang, Lili; Zhang, Yongming; Rittmann, Bruce E

    2015-10-06

    Quinoline, a recalcitrant heterocyclic compound, is biodegraded by a series of reactions that begin with mono-oxygenations, which require an intracellular electron donor. Photolysis of quinoline can generate readily biodegradable products, such as oxalate, whose bio-oxidation can generate endogenous electron donors that ought to accelerate quinoline biodegradation and, ultimately, mineralization. To test this hypothesis, we compared three protocols for the biodegradation of quinoline: direct biodegradation (B), biodegradation after photolysis of 1 h (P1h+B) or 2 h (P2h+B), and biodegradation by adding oxalate commensurate to the amount generated from photolysis of 1 h (O1+B) or 2 h (O2+B). The experimental results show that P1h+B and P2h+B accelerated quinoline biodegradation by 19% and 50%, respectively, compared to B. Protocols O1+B and O2+B also gave 19% and 50% increases, respectively. During quinoline biodegradation, its first intermediate, 2-hydroxyquinoline, accumulated gradually in parallel to quinoline loss but declined once quinoline was depleted. Mono-oxygenation of 2-hydroxyquinoline competed with mono-oxygenation of quinoline, but the inhibition was relieved when extra electrons donors were added from oxalate, whether formed by UV photolysis or added exogenously. Rapid oxalate oxidation stimulated both mono-oxygenations, which accelerated the overall quinoline oxidation that provided the bulk of the electron donor.

  3. The development of organic super electron donors.

    PubMed

    Zhou, Shengze; Farwaha, Hardeep; Murphy, John A

    2012-01-01

    In the past decade, a host of exceptionally strong organic electron donors has been designed and prepared; their redox potentials are more negative than any previous neutral organic donors and extend beyond E(1/2) = -1 V vs. the saturated calomel electrode (SCE). Their ability to reduce a wide range of organic functional groups has been demonstrated and this article provides an overview of the main advances in the area and the guiding principles for the design of these reagents.

  4. Electron Donor Acceptor Interactions. Final Progress Report

    SciTech Connect

    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.

  5. Accelerating biodegradation of a monoazo dye Acid Orange 7 by using its endogenous electron donors.

    PubMed

    Sun, Weihua; Zhang, Chengji; Chen, Jun; Zhang, Bingbing; Zhang, Hongzhuan; Zhang, Yongming; Chen, Lujun

    2017-02-15

    Biodegradation of a monoazo dye - Acid Orange 7 (AO7) was investigated by using an internal circulation baffled biofilm reactor. For accelerating AO7 biodegradation, endogenous electron donors produced from AO7 by UV photolysis were added into the reactor. The result shows that AO7 removal rate can be accelerated by using its endogenous electron donors, such as sulfanilic and aniline. When initial AO7 concentration was 13.6mg/L, electron donors generated by 8h UV photolysis were added into the same system. The biodegradation rate 0.4mg(0.05)h(-1) was enhanced 60% than that without adding electron donor. Furthermore, sulfanilic and aniline were found to be the main endogenous electron carriers, which could accelerate the steps of the azo dye biodegradation.

  6. Solvent as electron donor: Donor/acceptor electronic coupling is a dynamical variable

    SciTech Connect

    Castner, E.W. Jr.; Kennedy, D.; Cave, R.J.

    2000-04-06

    The authors combine analysis of measurements by femtosecond optical spectroscopy, computer simulations, and the generalized Mulliken-Hush (GMH) theory in the study of electron-transfer reactions and electron donor-acceptor interactions. The study focus is on ultrafast photoinduced electron-transfer reactions from aromatic amine solvent donors to excited-state acceptors. The experimental results from femtosecond dynamical measurements fall into three categories: six coumarin acceptors reductively quenched by N,N-dimethylaniline (DMA), eight electron-donating amine solvents reductively quenching coumarin 152 (7-(dimethylamino)-4-(trifluoromethyl)-coumarin), and reductive quenching dynamics of two coumarins by DMA as a function of dilution in the nonreactive solvents toluene and chlorobenzene. Applying a combination of molecular dynamics trajectories, semiempirical quantum mechanical calculations (of the relevant adiabatic electronic states), and GMH theory to the C152/DMA photoreaction, the authors calculate the electron donor/acceptor interaction parameter H{sub DA} at various time frames, H{sub DA} is strongly modulated by both inner-sphere and outer-sphere nuclear dynamics, leading us to conclude that H{sub DA} must be considered as a dynamical variable.

  7. Tailored donor-acceptor polymers with an A-D1-A-D2 structure: controlling intermolecular interactions to enable enhanced polymer photovoltaic devices.

    PubMed

    Qin, Tianshi; Zajaczkowski, Wojciech; Pisula, Wojciech; Baumgarten, Martin; Chen, Ming; Gao, Mei; Wilson, Gerry; Easton, Christopher D; Müllen, Klaus; Watkins, Scott E

    2014-04-23

    Extensive efforts have been made to develop novel conjugated polymers that give improved performance in organic photovoltaic devices. The use of polymers based on alternating electron-donating and electron-accepting units not only allows the frontier molecular orbitals to be tuned to maximize the open-circuit voltage of the devices but also controls the optical band gap to increase the number of photons absorbed and thus modifies the other critical device parameter-the short circuit current. In fact, varying the nonchromophoric components of a polymer is often secondary to the efforts to adjust the intermolecular aggregates and improve the charge-carrier mobility. Here, we introduce an approach to polymer synthesis that facilitates simultaneous control over both the structural and electronic properties of the polymers. Through the use of a tailored multicomponent acceptor-donor-acceptor (A-D-A) intermediate, polymers with the unique structure A-D1-A-D2 can be prepared. This approach enables variations in the donor fragment substituents such that control over both the polymer regiochemistry and solubility is possible. This control results in improved intermolecular π-stacking interactions and therefore enhanced charge-carrier mobility. Solar cells using the A-D1-A-D2 structural polymer show short-circuit current densities that are twice that of the simple, random analogue while still maintaining an identical open-circuit voltage. The key finding of this work is that polymers with an A-D1-A-D2 structure offer significant performance benefits over both regioregular and random A-D polymers. The chemical synthesis approach that enables the preparation of A-D1-A-D2 polymers therefore represents a promising new route to materials for high-efficiency organic photovoltaic devices.

  8. Donor-based single electron pumps with tunable donor binding energy.

    PubMed

    Lansbergen, G P; Ono, Y; Fujiwara, A

    2012-02-08

    We report on single electron pumping via a tunable number of individual donors. We use a device that essentially consists of a silicon nanowire with local arsenic implantation between a set of fine gates. A temperature-dependent characterization of the pumped current allows us to extract the ionization energy of a single arsenic donor. We observe the ionization energy to be tunable by the gate electric field over a large range of energies.

  9. Stark Tuning of Donor Electron Spins of Silicon

    SciTech Connect

    Bradbury, Forrest R.; Tyryshkin, Alexei M.; Sabouret, Guillaume; Bokor, Jeff; Schenkel, Thomas; Lyon, Stephen A.

    2006-03-23

    We report Stark shift measurements for {sup 121}Sb donor electron spins in silicon using pulsed electron spin resonance. Interdigitated metal gates on top of a Sb-implanted {sup 28}Si epi-layer are used to apply electric fields. Two Stark effects are resolved: a decrease of the hyperfine coupling between electron and nuclear spins of the donor and a decrease in electron Zeeman g-factor. The hyperfine term prevails at X-band magnetic fields of 0.35T, while the g-factor term is expected to dominate at higher magnetic fields. A significant linear Stark effect is also resolved presumably arising from strain.

  10. Stark tuning of donor electron spins in silicon

    SciTech Connect

    Bradbury, F.R.; Tyryshkin, A.M.; Sabouret, G.; Bokor, J.; Schenkel, T.; Lyon, S.A.

    2006-03-12

    We report Stark shift measurements for 121Sb donor electronspins in silicon using pulsed electron spin resonance. Interdigitatedmetal gates on top of a Sb-implanted 28Si epi-layer are used to applyelectric fields. Two Stark effects are resolved: a decrease of thehyperfine coupling between electron and nuclear spins of the donor and adecrease in electron Zeeman g-factor. The hyperfine term prevails atX-band magnetic fields of 0.35T, while the g-factor term is expected todominate at higher magnetic fields. A significant linear Stark effect isalso resolved presumably arising from strain.

  11. Electron Donor Potential of Eastern North Dakota Shale Formations

    NASA Astrophysics Data System (ADS)

    Salinas Klapperich, R. J.; Korom, S. F.

    2007-12-01

    We have a network of 16 in situ mesocosms (ISMs) used to study aquifer denitrification at 9 sites in North Dakota and Minnesota. The site in the Elk Valley aquifer in northeastern North Dakota has the highest denitrification rates and the greatest concentration of electron donors (organic carbon ~0.4%, pyrite as S ~0.4%, and ferrous iron ~0.3%) in the sediments. In contrast, denitrification rates at our other ISM sites are lower (or even below detection), as are the electron donor concentrations in the sediments. Knowing that the sediments at all of our ISM sites were placed as outwash during the last Wisconsinan glaciation (~12ka), we wonder what caused the variation in electron donor supplies in our aquifers. It has been suggested that variations is the electron donor concentrations in the various Late Cretaceous shale strata exposed during glaciation may help explain the variation in electron donor concentrations in overlying aquifers formed nearby. The purpose of this study is to evaluate the amount of electron donors available in these bedrock units. Bedrock samples (n = 39) from 20 sites in eastern North Dakota were obtained by drilling during the summer of 2006 in conjunction with the North Dakota State Water Commission. Samples were frozen before analysis for bulk mineralogical content by X-ray diffraction, organic carbon, pyrite as inorganic S, and ferrous iron contents. It was hypothesized that the Pierre Shale would have the highest donor concentration, but it appears that other formations, such as the Carlile and Greenhorn contain higher concentrations of electron donors. Organic carbon concentrations in the Pierre (< 0.01% to 1.0%) are relatively low while concentrations in the Carlile (3.5% - 6.5%) and Greenhorn (~8.5%) are significantly higher. Pyrite as inorganic S concentrations in the Pierre (< 0.01% to 0.2%), Carlile (0.3% - 0.5%), and Greenhorn (~0.5%) are similarly distributed. In the future, it may be possible to create a qualitative index

  12. On the effect of nuclear bridge modes on donor-acceptor electronic coupling in donor-bridge-acceptor molecules

    NASA Astrophysics Data System (ADS)

    Davis, Daly; Toroker, Maytal Caspary; Speiser, Shammai; Peskin, Uri

    2009-03-01

    We report a theoretical study of intra-molecular electronic coupling in a symmetric DBA (donor-bridge-acceptor) complex, in which a donor electronic site is coupled to an acceptor site by way of intervening orbitals of a molecular bridge unit. In the off-resonant (deep tunneling) regime of electronic transport, the lowest unoccupied molecular orbitals (MO's) of the DBA system are split into distinguishable donor/acceptor and bridge orbitals. The effect of geometrical changes at the bridge on the donor/acceptor electronic energy manifold is studied for local stretching and bending modes. It is demonstrated that the energy splitting in the manifold of donor/acceptor unoccupied MOs changes in response to such changes, as assumed in simple McConnell-type models. Limitations of the simple models are revealed where the electronic charging of the bridge orbitals correlates with increasing donor/acceptor orbital energy splitting only for stretching but not for bending bridge modes.

  13. Electron donor preference of a reductive dechlorinating consortium

    USGS Publications Warehouse

    Lorah, M.M.; Majcher, E.; Jones, E.; Driedger, G.; Dworatzek, S.; Graves, D.

    2005-01-01

    A wetland sediment-derived microbial consortium was developed by the USGS and propagated in vitro to large quantities by SiREM Laboratory for use in bioaugmentation applications. The consortium had the capacity to completely dechlorinate 1,1,2,2-tetrachloroethene, tetrachloroethylene, trichloroethylene, 1,1,2-trichloroethane, cis- and trans-1,2-dichoroethylene, 1.1-dichloroethylene, 1,2-dichloroethane, vinyl chloride, carbon tetrachloride and chloroform. A suite of electron donors with characteristics useful for bioaugmentation applications was tested. The electron donors included lactate (the donor used during WBC-2 development), ethanol, chitin (Chitorem???), hydrogen releasing compound (HRC???), emulsified vegetable oil (Newman Zone???), and hydrogen gas. Ethanol, lactate, and chitin were particularly effective with respect to stimulating, supporting, and sustaining reductive dechlorination of the broad suite of chemicals that WBC-2 biodegraded. Chitorem??? was the most effective "slow release" electron donor tested. This is an abstract of a paper presented at the Proceedings of the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).

  14. Coordinating Electron Transport Chains to an Electron Donor.

    PubMed

    Villegas, Carmen; Wolf, Maximilian; Joly, Damien; Delgado, Juan Luis; Guldi, Dirk M; Martín, Nazario

    2015-10-16

    Two electron transport chains (2 and 3) featuring two fullerenes with different electron acceptor strengths have been synthesized, characterized, and coordinated to a light harvesting/electron donating zinc porphyrin. Electrochemical assays corroborate the redox gradients along the designed electron transport chains, and complementary absorption and fluorescence titrations prove the assembly of ZnP-2 and ZnP-3 hybrids.

  15. Thiocyanate, a plausible physiological electron donor of gastric peroxidase.

    PubMed Central

    Das, D; De, P K; Banerjee, R K

    1995-01-01

    Gastric peroxidase (GPO) was purified to apparent homogeneity to characterize its major physiological electron donor. The enzyme (RZ = 0.7), with a subunit molecular mass of 50 kDa, is a glycoprotein, with a relative abundance of aspartic and glutamic acid over arginine and lysine. It has a Soret maximum at 412 nm, which is shifted to 426 nm by H2O2 due to formation of compound II. Although the physiological electron donors I-, Br- and SCN-, but not Cl-, are oxidized by GPO optimally at acid pH, only I- and SCN- are oxidized appreciably at physiological pH. Considering that the I- concentration in stomach is less than 1 microM, whereas the SCN- concentration is about 250 microM, SCN- may act as a major electron donor for GPO. Moreover, SCN- oxidation remains unaltered in the presence of physiological concentrations of other halides. The second-order rate constant for the reaction of GPO with H2O2 (k1) and compound I with SCN- (k2) at pH 7 was found to be 8 x 10(7) M-1.s-1 and 2 x 10(5) M-1.s-1 respectively. GPO has significant pseudocatalase activity also in the presence of I- or Br-, but it is blocked by SCN-. The SCN- oxidation product OSCN- may be reduced back to SCN- by cellular GSH, and GSSG may be reduced back to GSH by glutathione reductase and NADPH. In a system reconstituted with pure glutathione reductase, NADPH, GSH, SCN- and H2O2. GPO-catalysed SCN- oxidation could be coupled to NADPH oxidation. This system where GPO utilizes SCN- as the major physiological electron donor may operate efficiently to scavenge intracellular H2O2. Images Figure 1 PMID:7826354

  16. Organic electron donors as powerful single-electron reducing agents in organic synthesis.

    PubMed

    Broggi, Julie; Terme, Thierry; Vanelle, Patrice

    2014-01-07

    One-electron reduction is commonly used in organic chemistry for the formation of radicals by the stepwise transfer of one or two electrons from a donor to an organic substrate. Besides metallic reagents, single-electron reducers based on neutral organic molecules have emerged as an attractive novel source of reducing electrons. The past 20 years have seen the blossoming of a particular class of organic reducing agents, the electron-rich olefins, and their application in organic synthesis. This Review gives an overview of the different types of organic donors and their specific characteristics in organic transformations.

  17. 2012 ELECTRON DONOR-ACCEPTOR INTERACTIONS GORDON RESEARCH CONFERENCE, AUGUST 5-10, 2012

    SciTech Connect

    McCusker, James

    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.

  18. Discovery and Development of Organic Super-Electron-Donors

    PubMed Central

    2014-01-01

    Based on simple ideas of electron-rich alkenes, exemplified by tetrakis(dimethylamino)ethene, TDAE, and on additional driving force associated with aromatization, families of very powerful neutral organic super-electron-donors (SEDs) have been developed. In the ground state, they carry out metal-free reductions of a range of functional groups. Iodoarenes are reduced either to aryl radicals or, with stronger donors, to aryl anions. Reduction to aryl radicals allows the initiation of very efficient transition-metal-free coupling of haloarenes to arenes. The donors also reduce alkyl halides, arenesulfonamides, triflates, and triflamdes, Weinreb amides, and acyloin derivatives. Under photoactivation at 365 nm, they are even more powerful and reductively cleave aryl chlorides. They reduce unactivated benzenes to the corresponding radical anions and display original selectivities in preferentially reducing benzenes over malonates or cyanoacetates. Additionally, they reductively cleave ArC–X, ArX–C (X = N or O) and ArC–C bonds, provided that the two resulting fragments are somewhat stabilized. PMID:24605904

  19. Electron capture processes in ZnS: The role of Al related and other donors

    NASA Astrophysics Data System (ADS)

    Przybylińska, H.; Godlewski, M.

    1986-12-01

    A transient electron spin resonance experiment shows that the Al-related donor in ZnS plays an insignificant role in electron-capture processes, which are dominated by a 35-meV native donor of unknown nature. The methods of determining effective capture cross sections of these donors are discussed.

  20. Evaluation of sustainable electron donors for nitrate removal in different water media.

    PubMed

    Fowdar, Harsha S; Hatt, Belinda E; Breen, Peter; Cook, Perran L M; Deletic, Ana

    2015-11-15

    An external electron donor is usually included in wastewater and groundwater treatment systems to enhance nitrate removal through denitrification. The choice of electron donor is critical for both satisfactory denitrification rates and sustainable long-term performance. Electron donors that are waste products are preferred to pure organic chemicals. Different electron donors have been used to treat different water types and little is known as to whether there are any electron donors that are suitable for multiple applications. Seven different carbon rich waste products, including liquid and solid electron donors, were studied in comparison to pure acetate. Batch-scale tests were used to measure their ability to reduce nitrate concentrations in a pure nutrient solution, light greywater, secondary-treated wastewater and tertiary-treated wastewater. The tested electron donors removed oxidised nitrogen (NOx) at varying rates, ranging from 48 mg N/L/d (acetate) to 0.3 mg N/L/d (hardwood). The concentrations of transient nitrite accumulation also varied across the electron donors. The different water types had an influence on NOx removal rates, the extent of which was dependent on the type of electron donor. Overall, the highest rates were recorded in light greywater, followed by the pure nutrient solution and the two partially treated wastewaters. Cotton wool and rice hulls were found to be promising electron donors with good NOx removal rates, lower leachable nutrients and had the least variation in performance across water types.

  1. [KEEPING THE ELECTRON-DONOR PROPERTIES OF DRINKING WATER].

    PubMed

    Gibert, K K; Stekhin, A A; Iakovleva, G V; Sul'ina, Iu S

    2015-01-01

    In a study there was performed the experimental evaluation of long-term structural--physical changes of the phase of associated water in drinking water treated in hypomagnetic conditions according to the the technology providing the retention of of ortho/para isomers of water in the presence of a catalyst--triplet oxygen. According to the results of measurements ofparameters of nano-associates formed in the water there was found a series ofconsistencies, allowing to determine the mechanisms of the impact of hypomagnetic treatment on the catalytic properties ofwater and long-term stability of its activated state, that provides the long-term maintenance of high biological activity of drinking water. In particular, under hypomagnetic conditions of the treatment there is formed denser packing of amorphous ice--VI in the composition of associates peroxide, serving as a kind of "reservoir" of atmospheric gases. In such a "reservoir" there realized higher pressure, compared with normal geophysical conditions, that stimulates the gas-phase reactions with the formation of dimers and trimers of oxygen existing in the 2-electron--active configurations with binding energies of 0.3 eVand ~0.2 eV providing phase modulation, resulting in condensation of environment additional electrons on paramagnetic oxygen, which provides the long-term maintenance of the electron--donor ability of water and electrically non-equilibrium state.

  2. Comparison between acetate and hydrogen as electron donors and implications for the reductive dehalogenation of PCE and TCE

    NASA Astrophysics Data System (ADS)

    Lee, Il-Su; Bae, Jae-Ho; McCarty, Perry L.

    2007-10-01

    Bioremediation by reductive dehalogenation of groundwater contaminated with tetrachloroethene (PCE) or trichloroethene (TCE) is generally carried out through the addition of a fermentable electron donor such as lactate, benzoate, carbohydrates or vegetable oil. These fermentable donors are converted by fermenting organisms into acetate and hydrogen, either of which might be used by dehalogenating microorganisms. Comparisons were made between H 2 and acetate on the rate and extent of reductive dehalogenation of PCE. PCE dehalogenation with H 2 alone was complete to ethene, but with acetate alone it generally proceeded only about half as fast and only to cis-1,2-dichloroethene (cDCE). Additionally, acetate was not used as an electron donor in the presence of H 2. These findings suggest the fermentable electron donor requirement for PCE dehalogenation to ethene can be reduced up to 50% by separating PCE dehalogenation into two stages, the first of which uses acetate for the conversion of PCE to cDCE, and the second uses H 2 for the conversion of cDCE to ethene. This can be implemented with a recycle system in which the fermentable substrate is added down-gradient, where the hydrogen being produced by fermentation effects cDCE conversion into ethene. The acetate produced is recycled up-gradient to achieve PCE conversion into cDCE. With the lower electron donor usage required, potential problems of aquifer clogging, excess methane production, and high groundwater chemical oxygen demand (COD) can be greatly reduced.

  3. Ubisemiquinone is the electron donor for superoxide formation by complex III of heart mitochondria.

    PubMed

    Turrens, J F; Alexandre, A; Lehninger, A L

    1985-03-01

    Much evidence indicates that superoxide is generated from O2 in a cyanide-sensitive reaction involving a reduced component of complex III of the mitochondrial respiratory chain, particularly when antimycin A is present. Although it is generally believed that ubisemiquinone is the electron donor to O2, little experimental evidence supporting this view has been reported. Experiments with succinate as electron donor in the presence of antimycin A in intact rat heart mitochondria, which contain much superoxide dismutase but little catalase, showed that myxothiazol, which inhibits reduction of the Rieske iron-sulfur center, prevented formation of hydrogen peroxide, determined spectrophotometrically as the H2O2-peroxidase complex. Similarly, depletion of the mitochondria of their cytochrome c also inhibited formation of H2O2, which was restored by addition of cytochrome c. These observations indicate that factors preventing the formation of ubisemiquinone also prevent H2O2 formation. They also exclude ubiquinol, which remains reduced under these conditions, as the reductant of O2. Since cytochrome b also remains fully reduced when myxothiazol is added to succinate- and antimycin A-supplemented mitochondria, reduced cytochrome b may also be excluded as the reductant of O2. These observations, which are consistent with the Q-cycle reactions, by exclusion of other possibilities leave ubisemiquinone as the only reduced electron carrier in complex III capable of reducing O2 to O2-.

  4. Thermodynamic targeting of microbial perchlorate reduction by selective electron donors.

    PubMed

    Van Trump, James Ian; Coates, John D

    2009-04-01

    Here we describe 2,6-anthrahydroquinone disulfonate (AH(2)DS) as a model thermodynamically 'targeting' electron donor capable of selectively stimulating respiratory processes relevant to the bioremediation of perchlorate. Pure cultures of Dechloromonas aromatica, Dechloromonas agitata and Azospira suillum, as well as uncharacterized microbial consortia, were capable of stoichiometrically reducing perchlorate to chloride upon oxidation of AH(2)DS to the corresponding quinone 2,6-anthraquinone disulfonate (AQDS). No degradation of the anthraquinone structure was observed, and no organism tested grew by this metabolism. Thermodynamic calculations suggest that AH(2)DS oxidation should support nitrate and perchlorate reduction, whereas sulfate reduction and methanogenesis are predicted to be unfavorable. Mixed community microcosms oxidizing AH(2)DS reduced nitrate and perchlorate, whereas sulfate reduction never occurred. In contrast, microcosms amended with acetate respired nitrate, perchlorate and sulfate, as would be predicted by thermodynamic calculation. Our results suggest that the thermodynamic properties of hydroquinones allow for targeted stimulation of only a subset of potential respiratory processes. This observation could help improve enhanced in situ bioremediation of perchlorate by negating many of the detrimental aspects of biofouling.

  5. A novel D2-A-D1-A-D2-type donor-acceptor conjugated small molecule based on a benzo[1,2-b:4,5-b‧]dithiophene core for solution processed organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Yu, Junting; Zhu, Weiguo; Tan, Hua; Peng, Qing

    2017-01-01

    A novel D2-A-D1-A-D2-type donor-acceptor conjugated small molecule (DTPA-Q-BDT-Q-DTPA) with a benzo[1,2-b:4,5-b‧]dithiophene (BDT) core and two D2-A arms has been synthesized and employed as electron donor for organic solar cells. Solution-processed organic photovoltaic (OPV) devices were fabricated with a configuration of ITO/PEDOT:PSS/DTPA-Q-BDT-Q-DTPA:[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM)/LiF/Al. A power conversion efficiency (PCE) of 1.22% with an open-circuit voltage (VOC) of 0.64 V, a short-circuit current (JSC) of 6.10 mA cm-2, and a fill factor (FF) of 31.0% was achieved. The PCE is 2.9 times higher than that in the other devices using D2-A-type small molecule TPA-Q-TPA as donor.

  6. Electronic properties of the residual donor in unintentionally doped β-Ga2O3

    NASA Astrophysics Data System (ADS)

    Son, N. T.; Goto, K.; Nomura, K.; Thieu, Q. T.; Togashi, R.; Murakami, H.; Kumagai, Y.; Kuramata, A.; Higashiwaki, M.; Koukitu, A.; Yamakoshi, S.; Monemar, B.; Janzén, E.

    2016-12-01

    Electron paramagnetic resonance was used to study the donor that is responsible for the n-type conductivity in unintentionally doped (UID) β-Ga2O3 substrates. We show that in as-grown materials, the donor requires high temperature annealing to be activated. In partly activated materials with the donor concentration in the 1016 cm-3 range or lower, the donor is found to behave as a negative-U center (often called a DX center) with the negative charge state DX- lying ˜16-20 meV below the neutral charge state d0 (or Ed), which is estimated to be ˜28-29 meV below the conduction band minimum. This corresponds to a donor activation energy of Ea˜44-49 meV. In fully activated materials with the donor spin density close to ˜1 × 1018 cm-3, donor electrons become delocalized, leading to the formation of impurity bands, which reduces the donor activation energy to Ea˜15-17 meV. The results clarify the electronic structure of the dominant donor in UID β-Ga2O3 and explain the large variation in the previously reported donor activation energy.

  7. An Evaluation of Formic Acid as an Electron Donor for Palladium (PD) Catalyzed Destruction of Nitroaromatic Compounds

    DTIC Science & Technology

    2006-05-31

    AN EVALUATION OF FORMIC ACID AS AN ELECTRON DONOR FOR PALLADIUM (PD) CATALYZED DESTRUCTION OF NITROAROMATIC COMPOUNDS Mark R. Stevens, Capt...AN EVALUATION OF FORMIC ACID AS AN ELECTRON DONOR FOR PALLADIUM (PD) CATALYZED DESTRUCTION OF NITROAROMATIC COMPOUNDS THESIS...UNLIMITED. AFIT/GEM/ENV/04M-19 AN EVALUATION OF FORMIC ACID AS AN ELECTRON DONOR FOR PALLADIUM (PD) CATALYZED DESTRUCTION OF

  8. Monitoring electron donor metabolism under variable electron acceptor conditions using 13C-labeled lactate

    NASA Astrophysics Data System (ADS)

    Bill, M.; Conrad, M. E.; Yang, L.; Beller, H. R.; Brodie, E. L.

    2010-12-01

    Three sets of flow-through columns constructed with aquifer sediment from Hanford (WA) were used to study reduction of Cr(VI) to poorly soluble Cr(III) under denitrifying, sulfate-reducing/fermentative, and iron-reducing conditions with lactate as the electron donor. In order to understand the relationship between electron donors and biomarkers, and to determine the differences in carbon isotope fractionation resulting from different microbial metabolic processes, we monitored the variation in carbon isotopes in dissolved inorganic carbon (DIC), in total organic carbon (TOC), and in lactate, acetate and propionate. The greatest enrichment in 13C in columns was observed under denitrifying conditions. The δ13C of DIC increased by ~1750 to ~2000‰ fifteen days after supplementation of natural abundance lactate with a 13C-labeled lactate tracer (for an influent δ13C of ~2250‰ for the lactate) indicating almost complete oxidation of the electron donor. The denitrifying columns were among the most active columns and had the highest cell counts and the denitrification rate was highly correlated with Cr(VI) reduction rate. δ13C values of DIC ranged from ~540 to ~1170‰ for iron-reducing conditions. The lower enrichment in iron columns was related to the lower biological activity observed with lower yields of RNA and cell numbers in the column effluents. The carbon isotope shift in the sulfate-reducing ~198 to ~1960‰ for sulfate-reducing conditions reflecting the lower levels of the lactate in these columns. Additionally, in two of the sulfate columns, almost complete fermentation of the lactate occurred, producing acetate and propionate with the labeled carbon signature, but relatively smaller amounts of inorganic carbon. For all electron-accepting conditions, TOC yielded similar δ13C values as lactate stock solutions. Differences in C use efficiency, metabolic rate or metabolic pathway contributed to the differing TOC δ13C to DIC δ13C ratios between treatments

  9. Stimulation of KatG catalase activity by peroxidatic electron donors.

    PubMed

    Ndontsa, Elizabeth N; Moore, Robert L; Goodwin, Douglas C

    2012-09-15

    Catalase-peroxidases (KatGs) use a peroxidase scaffold to support robust catalase activity, an ability no other member of its superfamily possesses. Because catalase turnover requires H(2)O(2) oxidation, whereas peroxidase turnover requires oxidation of an exogenous electron donor, it has been anticipated that the latter should inhibit catalase activity. To the contrary, we report peroxidatic electron donors stimulated catalase activity up to 14-fold, particularly under conditions favorable to peroxidase activity (i.e., acidic pH and low H(2)O(2) concentrations). We observed a "low-" and "high-K(M)" component for catalase activity at pH 5.0. Electron donors increased the apparent k(cat) for the "low-K(M)" component. During stimulated catalase activity, less than 0.008 equivalents of oxidized donor accumulated for every H(2)O(2) consumed. Several classical peroxidatic electron donors were effective stimulators of catalase activity, but pyrogallol and ascorbate showed little effect. Stopped-flow evaluation showed that a Fe(III)-O(2)(·-)-like intermediate dominated during donor-stimulated catalatic turnover, and this intermediate converted directly to the ferric state upon depletion of H(2)O(2). In this respect, the Fe(III)-O(2)(·-) -like species was more prominent and persistent than in the absence of the donor. These results point toward a much more central role for peroxidase substrates in the unusual catalase mechanism of KatG.

  10. Effects of electron donors on the microbial reductive dechlorination of hexachlorocyclohexane and on the environment.

    PubMed

    Cui, Zhaojie; Meng, Fanli; Hong, Jinglan; Li, Xiangzhi; Ren, Xiaohua

    2012-06-01

    The reductive biotransformation of α-, β-, γ-, and δ-hexachlorocyclohexane isomers was investigated using five alternative electron donors (i.e., glucose plus methanol, glucose only, methanol only, acetate, and ethanol) in a batch assay of an HCH-dechlorinating anaerobic culture. In addition, a life cycle assessment was conducted using the IMPACT2002+ method to evaluate the environmental effects of HCH bioremediation with the aforementioned electron donors. Results showed that the electron donors methanol plus glucose, ethanol, glucose, and methanol can significantly enhance the biotransformation of each HCH isomer. However, the amended electron donors and the byproduct of the anoxic/anaerobic systems may negatively affect the environment (e.g., respiratory inorganic, land occupation, global warming, and non-renewable energy categories). These effects are attributed to the electron donor production processes. To avoid secondary pollutants, a linear relationship between the upper bound electron donor applications and HCH concentration was observed from an environmental perspective. Results indicated that the methanol scenario was the most suitable option for the current research.

  11. Geometry for the Primary Electron Donor and the Bacteriopheophytin Acceptor in Rhodopseudomonas viridis Photosynthetic Reaction Centers

    PubMed Central

    Tiede, D. M.; Choquet, Y.; Breton, J.

    1985-01-01

    The tetrapyrrole electron donors and acceptors (bacteriochlorophyll, BCh; bacteriopheophytin, BPh) within the bacterial photosynthetic reaction center (RC) are arranged with a specific geometry that permits rapid (picosecond time scale) electron tunneling to occur between them. Here we have measured the angle between the molecular planes of the bacteriochlorophyll dimer (primary donor), B2, and the acceptor bacteriopheophytin, H, by analyzing the dichroism of the absorption change associated with H reduction, formed by photoselection with RCs of Rhodopseudomonas viridis. This angle between molecular planes is found to be 60° ± 2. This means that the ultrafast electron tunneling must occur between donors and acceptors that are fixed by the protein to have a noncoplanar alignment. Nearly perpendicular alignments have been determined for other electron tunneling complexes involving RCs. These geometries can be contrasted with models proposed for heme-heme electron transfer complexes, which have emphasized that mutually parallel orientations should permit the most kinetically facile transfers. PMID:19431588

  12. Thermodynamic consequence of the new attribution of bands in the electronic absorption spectrum of electron donor-iodine-solvent systems

    NASA Astrophysics Data System (ADS)

    Abramov, Sergey P.

    1999-06-01

    The subject review pays attention to the peculiarities in behaviour of bands in the electronic absorption spectra of electron donor-iodine-solvent systems, the appearance of which is associated with the intermolecular interaction of molecular iodine with electron donor organic molecules. The new concept of the bands’ attribution to the isomeric equilibrium molecular charge-transfer complexes (CTCs) of CTC-I and CTC-II types is considered. The features of possible phase transitions in the solid state are discussed on the basis of the thermodynamic properties and electronic structures of the CTC-I and CTC-II in electron donor-iodine-solvent systems. The stabilisation of the CTC-II structure with the temperature lowering coincided in many cases with the electrons’ localisation in the solid state structures having charge-transfer bonds.

  13. Metabolic response of Geobacter sulfurreducens towards electron donor/acceptor variation

    PubMed Central

    2010-01-01

    Background Geobacter sulfurreducens is capable of coupling the complete oxidation of organic compounds to iron reduction. The metabolic response of G. sulfurreducens towards variations in electron donors (acetate, hydrogen) and acceptors (Fe(III), fumarate) was investigated via 13C-based metabolic flux analysis. We examined the 13C-labeling patterns of proteinogenic amino acids obtained from G. sulfurreducens cultured with 13C-acetate. Results Using 13C-based metabolic flux analysis, we observed that donor and acceptor variations gave rise to differences in gluconeogenetic initiation, tricarboxylic acid cycle activity, and amino acid biosynthesis pathways. Culturing G. sulfurreducens cells with Fe(III) as the electron acceptor and acetate as the electron donor resulted in pyruvate as the primary carbon source for gluconeogenesis. When fumarate was provided as the electron acceptor and acetate as the electron donor, the flux analysis suggested that fumarate served as both an electron acceptor and, in conjunction with acetate, a carbon source. Growth on fumarate and acetate resulted in the initiation of gluconeogenesis by phosphoenolpyruvate carboxykinase and a slightly elevated flux through the oxidative tricarboxylic acid cycle as compared to growth with Fe(III) as the electron acceptor. In addition, the direction of net flux between acetyl-CoA and pyruvate was reversed during growth on fumarate relative to Fe(III), while growth in the presence of Fe(III) and acetate which provided hydrogen as an electron donor, resulted in decreased flux through the tricarboxylic acid cycle. Conclusions We gained detailed insight into the metabolism of G. sulfurreducens cells under various electron donor/acceptor conditions using 13C-based metabolic flux analysis. Our results can be used for the development of G. sulfurreducens as a chassis for a variety of applications including bioremediation and renewable biofuel production. PMID:21092215

  14. Electrically Detected Magnetic Resonance of Neutral Donors Interacting with a Two-Dimensional Electron Gas

    SciTech Connect

    Lo, C. C.; Lang, V.; George, R. E.; Morton, J. J. L.; Tyryshkin, A. M.; Lyon, A.; Bokor, J.; Schenkel, T.

    2011-04-20

    We have measured the electrically detected magnetic resonance of donor-doped silicon field-effect transistors in resonant X- (9.7 GHz) and W-band (94 GHz) microwave cavities. The two-dimensional electron gas (2DEG) resonance signal increases by two orders of magnitude from X- to W-band, while the donor resonance signals are enhanced by over one order of magnitude. Bolometric effects and spin-dependent scattering are inconsistent with the observations. We propose that polarization transfer from the donor to the 2DEG is the main mechanism giving rise to the spin resonance signals.

  15. On the cascade capture of electrons at donors in GaAs quantum wells

    SciTech Connect

    Aleshkin, V. Ya.

    2015-09-15

    The impact parameter for the cascade capture of electrons at a charged donor in a GaAs quantum well is calculated. A simple approximate analytical expression for the impact parameter is suggested. The temperature dependence of the impact parameter for the case of electron scattering by the piezoelectric potential of acoustic phonons is determined.

  16. ESR Experiments on a Single Donor Electron in Isotopically Enriched Silicon

    NASA Astrophysics Data System (ADS)

    Tracy, Lisa; Luhman, Dwight; Carr, Stephen; Borchardt, John; Bishop, Nathaniel; Ten Eyck, Gregory; Pluym, Tammy; Wendt, Joel; Witzel, Wayne; Blume-Kohout, Robin; Nielsen, Erik; Lilly, Michael; Carroll, Malcolm

    In this talk we will discuss electron spin resonance experiments in single donor silicon qubit devices fabricated at Sandia National Labs. A self-aligned device structure consisting of a polysilicon gate SET located adjacent to the donor is used for donor electron spin readout. Using a cryogenic HEMT amplifier next to the silicon device, we demonstrate spin readout at 100 kHz bandwidth and Rabi oscillations with 0.96 visibility. Electron spin resonance measurements on these devices show a linewidth of 30 kHz and coherence times T2* = 10 us and T2 = 0.3 ms. We also discuss estimates of the fidelity of our donor electron spin qubit measurements using gate set tomography. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000. ESR Experiments on a Single Donor Electron in Isotopically Enriched Silicon.

  17. Electron donor-acceptor quenching and photoinduced electron transfer for coumarin dyes. Technical report, 1 January-31 October 1982

    SciTech Connect

    Jones, G. II; Griffin, S.F.; Choi, C.; Bergmark, W.R.

    1983-10-31

    The fluorescence of 7-aminocoumarins is quenched by a variety of organic electron donors or acceptors in acetonitrile. In general, donors with half-wave oxidation potentials less positive than 1.0 V vs SCE and acceptors with reduction potentials less negative than -1.5 V vs SCE are candidates for diffusion limited quenching of coumarin singlet states. Profiles of quenching rates are consistent with calculated free energies for electron transfer between excited coumarins and donors or acceptors. In flash photolysis experiments electron transfer for several dyes and quenchers (e.g., methyl viologen) is demonstrated. Relatively low yields of net electron transfer are consistently obtained due to inefficient ionic photodissociation via singlet quenching or a low yield of more photoactive coumarin triplets. Electrochemical properties of the coumarins have been investigated by cyclic voltammetry with the indications of reversible oxidation and irreversible reduction as important processes.

  18. Carbon Monoxide as an Electron Donor for the Biological Reduction of Sulphate

    PubMed Central

    Parshina, Sofiya N.; Sipma, Jan; Henstra, Anne Meint; Stams, Alfons J. M.

    2010-01-01

    Several strains of Gram-negative and Gram-positive sulphate-reducing bacteria (SRB) are able to use carbon monoxide (CO) as a carbon source and electron donor for biological sulphate reduction. These strains exhibit variable resistance to CO toxicity. The most resistant SRB can grow and use CO as an electron donor at concentrations up to 100%, whereas others are already severely inhibited at CO concentrations as low as 1-2%. Here, the utilization, inhibition characteristics, and enzymology of CO metabolism as well as the current state of genomics of CO-oxidizing SRB are reviewed. Carboxydotrophic sulphate-reducing bacteria can be applied for biological sulphate reduction with synthesis gas (a mixture of hydrogen and carbon monoxide) as an electron donor. PMID:20628586

  19. Stereochemical Properties of Multidentate Nitrogen Donor Ligands and Their Copper Complexes by Electronic CD and DFT.

    PubMed

    Poopari, Mohammad Reza; Dezhahang, Zahra; Xu, Yunjie

    2016-07-01

    UV-Vis and electronic circular dichroism (ECD) spectroscopy, complemented with Density Functional Theory (DFT) calculations, were used to elucidate the structural diversities of three multidentate nitrogen donor ligands and two associated copper complexes in solution directly. The three chiral salen ligands all consist of trans-cyclohexane-1,2-diamine as a chiral scaffold and also of pyridine rings as chromophores, differing only in the linking groups between the two functional groups mentioned above. Very different ECD intensities and somewhat different ECD patterns were observed for these ligands and satisfactorily interpreted theoretically. For the geometry optimization and spectral simulation of the open-shell metal complexes, the LANL2DZ basis set with effective core potential for the Cu and Cl atoms and pure cc-pVTZ for the rest of the atoms was utilized. The performance of the same calculations with the polarization functions (f,g) from the cc-pVTZ basis added to the LANL2DZ basis was compared. While the three ligands exhibit different conformational flexibility, the associated copper complexes show great rigidity imposed by the metal-ligand coordination, taking on a single structure in each case. In addition, dispersion interactions were shown to change the conformational stability ordering of the ligands noticeably and to exert considerable influence on the simulated UV-Vis and ECD spectra. Chirality 28:545-555, 2016. © 2016 Wiley Periodicals, Inc.

  20. Photocurrent generation through electron-exciton interaction at the organic semiconductor donor/acceptor interface.

    PubMed

    Chen, Lijia; Zhang, Qiaoming; Lei, Yanlian; Zhu, Furong; Wu, Bo; Zhang, Ting; Niu, Guoxi; Xiong, Zuhong; Song, Qunliang

    2013-10-21

    In this work, we report our effort to understand the photocurrent generation that is contributed via electron-exciton interaction at the donor/acceptor interface in organic solar cells (OSCs). Donor/acceptor bi-layer heterojunction OSCs, of the indium tin oxide/copper phthalocyanine (CuPc)/fullerene (C60)/molybdenum oxide/Al type, were employed to study the mechanism of photocurrent generation due to the electron-exciton interaction, where CuPc and C60 are the donor and the acceptor, respectively. It is shown that the electron-exciton interaction and the exciton dissociation processes co-exist at the CuPc/C60 interface in OSCs. Compared to conventional donor/acceptor bi-layer OSCs, the cells with the above configuration enable holes to be extracted at the C60 side while electrons can be collected at the CuPc side, resulting in a photocurrent in the reverse direction. The photocurrent thus observed is contributed to primarily by the charge carriers that are generated by the electron-exciton interaction at the CuPc/C60 interface, while charges derived from the exciton dissociation process also exist at the same interface. The mechanism of photocurrent generation due to electron-exciton interaction in the OSCs is further investigated, and it is manifested by the transient photovoltage characteristics and the external quantum efficiency measurements.

  1. Enhanced microscopic nonlinear optical properties of novel Y-type chromophores with dual electron donor groups

    NASA Astrophysics Data System (ADS)

    Tang, Xiang; Pan, Lin; Jia, Kun; Tang, Xianzhong

    2016-03-01

    In this Letter, novel Y-type chromophores with dual electron donor groups, containing either styryl or azobenzene based π-conjugated bridge structures, were synthesized and their chemical structures, molecular configuration, microscopic optical properties as well as thermal properties were systematically characterized. The experimental results indicated that eight times increasing of second-order molecular hyperpolarizability as well as 50-100 nm blue shift of maximum absorption band for azobenzene based chromophore were observed by introducing Y-type dual electron donor groups, which was derived from the highly efficient 'total charge transfer' in this kind of chromophore as confirmed by the density functional theory calculation.

  2. Diarylindenotetracenes via a selective cross-coupling/C-H functionalization: electron donors for organic photovoltaic cells.

    PubMed

    Gu, Xingxian; Luhman, Wade A; Yagodkin, Elisey; Holmes, Russell J; Douglas, Christopher J

    2012-03-16

    A direct synthesis of new donor materials for organic photovoltaic cells is reported. Diaryindenotetracenes were synthesized utilizing a Kumada-Tamao-Corriu cross-coupling of peri-substituted tetrachlorotetracene with spontaneous indene annulation via C-H activation. Vacuum deposited planar heterojunction organic photovoltaic cells incorporating these molecules as electron donors exhibit power conversion efficiencies exceeding 1.5% with open-circuit voltages ranging from 0.7 to 1.1 V when coupled with C(60) as an electron acceptor.

  3. Autotrophic antimonate bio-reduction using hydrogen as the electron donor.

    PubMed

    Lai, Chun-Yu; Wen, Li-Lian; Zhang, Yin; Luo, Shan-Shan; Wang, Qing-Ying; Luo, Yi-Hao; Chen, Ran; Yang, Xiaoe; Rittmann, Bruce E; Zhao, He-Ping

    2016-01-01

    Antimony (Sb), a toxic metalloid, is soluble as antimonate (Sb(V)). While bio-reduction of Sb(V) is an effective Sb-removal approach, its bio-reduction has been coupled to oxidation of only organic electron donors. In this study, we demonstrate, for the first time, the feasibility of autotrophic microbial Sb(V) reduction using hydrogen gas (H2) as the electron donor without extra organic carbon source. SEM and EDS analysis confirmed the production of the mineral precipitate Sb2O3. When H2 was utilized as the electron donor, the consortium was able to fully reduce 650 μM of Sb(V) to Sb(III) in 10 days, a rate comparable to the culture using lactate as the electron donor. The H2-fed culture directed a much larger fraction of it donor electrons to Sb(V) reduction than did the lactate-fed culture. While 98% of the electrons from H2 were used to reduce Sb(V) by the H2-fed culture, only 12% of the electrons from lactate was used to reduce Sb(V) by the lactate-fed culture. The rest of the electrons from lactate went to acetate and propionate through fermentation, to methane through methanogenesis, and to biomass synthesis. High-throughput sequencing confirmed that the microbial community for the lactate-fed culture was much more diverse than that for the H2-fed culture, which was dominated by a short rod-shaped phylotype of Rhizobium (α-Protobacteria) that may have been active in Sb(V) reduction.

  4. Spectral probes of the holographic Fermi ground state: Dialing between the electron star and AdS Dirac hair

    SciTech Connect

    Cubrovic, Mihailo; Liu Yan; Schalm, Koenraad; Sun Yawen; Zaanen, Jan

    2011-10-15

    We argue that the electron star and the anti-de Sitter (AdS) Dirac hair solution are two limits of the free charged Fermi gas in AdS. Spectral functions of holographic duals to probe fermions in the background of electron stars have a free parameter that quantifies the number of constituent fermions that make up the charge and energy density characterizing the electron star solution. The strict electron star limit takes this number to be infinite. The Dirac hair solution is the limit where this number is unity. This is evident in the behavior of the distribution of holographically dual Fermi surfaces. As we decrease the number of constituents in a fixed electron star background the number of Fermi surfaces also decreases. An improved holographic Fermi ground state should be a configuration that shares the qualitative properties of both limits.

  5. Spin Measurements of an Electron Bound to a Single Phosphorous Donor in Silicon

    NASA Astrophysics Data System (ADS)

    Luhman, D. R.; Nguyen, K.; Tracy, L. A.; Carr, S. M.; Borchardt, J.; Bishop, N. C.; Ten Eyck, G. A.; Pluym, T.; Wendt, J.; Carroll, M. S.; Lilly, M. P.

    2014-03-01

    The spin of an electron bound to a single donor implanted in silicon is potentially useful for quantum information processing. We report on our efforts to measure and manipulate the spin of an electron bound to a single P donor in silicon. A low number of P donors are implanted using a self-aligned process into a silicon substrate in close proximity to a single-electron-transistor (SET) defined by lithographically patterned polysilicon gates. The SET is used to sense the occupancy of the electron on the donor and for spin read-out. An adjacent transmission line allows the application of microwave pulses to rotate the spin of the electron. We will present data from various experiments designed to exploit these capabilities. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. The work was supported by Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

  6. Computational design of co-polymer electron donors for bulk heterojunction photovoltaic solar cells

    NASA Astrophysics Data System (ADS)

    Shin, Yongwoo; Liu, Jiakai; Lin, Xi

    2014-03-01

    In this work, our recently developed adapted Su-Schrieffer-Heeger Hamiltonian is used to systematically explore the optoelectronic properties of thousands of pi-conjugated structures. New physical insights on the structure-property relationship are extracted and transformed into practical guiding rules in the donor materials design. For the power-efficient copolymer structures, we find that the energy variation of frontier orbitals can be controlled either independently or collectively, depending on their specific donor or acceptor structures. In particular, we find that having five-membered conjugated carbon rings in the acceptor units is essential to break the electron-hole charge conjugation symmetry, so that the LUMO levels of the copolymer can be reduced dramatically while holding the HOMO energy levels in the donor units constant. On the other hand, by incorporating heteroatoms into the donors units, we can vary the HOMO levels of the copolymers independently. Effects of introducing various side groups (-R, -O, -CO, -COO, and thiophene) on the primitive donor and acceptor structures are investigated and their results are discussed in details. Finally, unexpected localized states are found, for the first time, in our calculations for a few special co-polymer structures. These localized states, with electrons localized on one end of the copolymer chain and holes on the other end, contain large dipole moments and therefore may be treated as a new design dimension when these copolymers are placed in polar and non-polar solvent environments.

  7. Influence of electron donor on the minimum sulfate concentration required for sulfate reduction in a petroleum hydrocarbon-contaminated aquifer

    USGS Publications Warehouse

    Vroblesky, D.A.; Bradley, P.M.; Chapelle, F.H.

    1996-01-01

    Fluctuations in the availability of electron donor (petroleum hydrocarbons) affected the competition between sulfate-reducing bacteria (SRB) and methanogenic bacteria (MB) for control of electron flow in a petroleum hydrocarbon-contaminated aquifer. The data suggest that abundant electron donor availability allowed MB to sequester a portion of the electron flow even when sulfate was present in sufficient concentrations to support sulfate reduction. For example, in an area of abundant electron-donor availability, SRB appeared to be unable to sequester the electron flow from MB in the presence of 1.4 mg/L sulfate. The data also suggest that when electron-donor availability was limited, SRB outcompeted MB for available substrate at a lower concentration of sulfate than when electron donor was plentiful. For example, in an area of limited electron-donor availability, SRB appeared to maintain dominance of electron flow at sulfate concentrations less than 1 mg/L. The presence of abundant electron donor and a limited amount of sulfate reduced competition for available substrate, allowing both SRB and MB to metabolize available substrates concurrently.

  8. Donor acceptor electronic couplings in π-stacks: How many states must be accounted for?

    NASA Astrophysics Data System (ADS)

    Voityuk, Alexander A.

    2006-04-01

    Two-state model is commonly used to estimate the donor-acceptor electronic coupling Vda for electron transfer. However, in some important cases, e.g. for DNA π-stacks, this scheme fails to provide accurate values of Vda because of multistate effects. The Generalized Mulliken-Hush method enables a multistate treatment of Vda. In this Letter, we analyze the dependence of calculated electronic couplings on the number of the adiabatic states included in the model. We suggest a simple scheme to determine this number. The superexchange correction of the two-state approximation is shown to provide good estimates of the electronic coupling.

  9. On controlling the electronic states of shallow donors using a finite-size metal gate

    SciTech Connect

    Levchuk, E. A. Makarenko, L. F.

    2016-01-15

    The effect of an external electric field on the states of a shallow donor near a semiconductor surface is numerically simulated. A disk-shaped metal gate is considered as an electric-field source. The wavefunctions and energies of bound states are determined by the finite-element method. The critical characteristics of electron relocation between the donor and gate are determined for various gate diameters and boundary conditions, taking into account dielectric mismatch. The empirical dependences of these characteristics on the geometrical parameters and semiconductor properties are obtained. A simple trial function is proposed, which can be used to calculate the critical parameters using the Ritz variational method.

  10. Nuclear-driven electron spin rotations in a coupled silicon quantum dot and single donor system

    NASA Astrophysics Data System (ADS)

    Harvey-Collard, Patrick; Jacobson, Noah Tobias; Rudolph, Martin; Ten Eyck, Gregory A.; Wendt, Joel R.; Pluym, Tammy; Lilly, Michael P.; Pioro-Ladrière, Michel; Carroll, Malcolm S.

    Single donors in silicon are very good qubits. However, a central challenge is to couple them to one another. To achieve this, many proposals rely on using a nearby quantum dot (QD) to mediate an interaction. In this work, we demonstrate the coherent coupling of electron spins between a single 31P donor and an enriched 28Si metal-oxide-semiconductor few-electron QD. We show that the electron-nuclear spin interaction can drive coherent rotations between singlet and triplet electron spin states. Moreover, we are able to tune electrically the exchange interaction between the QD and donor electrons. The combination of single-nucleus-driven rotations and voltage-tunable exchange provides all elements for future all-electrical control of a spin qubit, and requires only a single dot and no additional magnetic field gradients. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  11. Quantification of Desulfovibrio vulgaris dissimilatory sulfite reductase gene expression during electron donor- and electron acceptor-limited growth.

    PubMed

    Villanueva, Laura; Haveman, Shelley A; Summers, Zara M; Lovley, Derek R

    2008-09-01

    Previous studies have suggested that levels of transcripts for dsrA, a gene encoding a subunit of the dissimilatory sulfite reductase, are not directly related to the rates of sulfate reduction in sediments under all conditions. This phenomenon was further investigated with chemostat-grown Desulfovibrio vulgaris. Under sulfate-limiting conditions, dsrA transcript levels increased as the bulk rates of sulfate reduction in the chemostat increased, but transcript levels were similar at all sulfate reduction rates under electron donor-limiting conditions. When both electron donor- and electron acceptor-limiting conditions were considered, there was a direct correspondence between dsrA transcript levels and the rates of sulfate reduction per cell. These results suggest that dsrA transcript levels may provide important information on the metabolic state of sulfate reducers.

  12. Exfoliation and supramolecular functionalization of graphene with an electron donor perylenediimide derivative.

    PubMed

    Martín-Gomis, Luis; Karousis, Nikos; Fernández-Lázaro, Fernando; Petsalakis, Ioannis D; Ohkubo, Kei; Fukuzumi, Shunichi; Tagmatarchis, Nikos; Sastre-Santos, Ángela

    2017-02-06

    The liquid exfoliation of graphite to few layered graphene sheets together with the non-covalent supramolecular functionalization of exfoliated graphene by the synthesized N,N'-di(2-ethylhexyl)-1-(N''''-methylpiperazin-N'''-yl)perylene-3,4,9,10-tetracarboxydiimide (Pip-PDI) is reported. The aromatic Pip-PDI has the ability to non-covalently interact with the exfoliated graphene sheets, stabilizing them and preventing their reassembly. On the other hand, the presence of the piperazine moiety on the bay position of the PDI core makes it an ideal electron donor, nicely coupled with the electron accepting exfoliated graphene, hence, forming a novel donor-acceptor nanoensemble, which was characterized by complementary spectroscopic and microscopy techniques. Theoretical calculations predicted the absence of a meaningful charge-separated state within the Pip-PDI/graphene ensemble, which was also proven by time-resolved fluorescence and transient absorption measurements.

  13. Gradient ascent pulse engineering approach to CNOT gates in donor electron spin quantum computing

    SciTech Connect

    Tsai, D.-B.; Goan, H.-S.

    2008-11-07

    In this paper, we demonstrate how gradient ascent pulse engineering (GRAPE) optimal control methods can be implemented on donor electron spin qubits in semiconductors with an architecture complementary to the original Kane's proposal. We focus on the high fidelity controlled-NOT (CNOT) gate and we explicitly find the digitized control sequences for a controlled-NOT gate by optimizing its fidelity using the effective, reduced donor electron spin Hamiltonian with external controls over the hyperfine A and exchange J interactions. We then simulate the CNOT-gate sequence with the full spin Hamiltonian and find that it has an error of 10{sup -6} that is below the error threshold of 10{sup -4} required for fault-tolerant quantum computation. Also the CNOT gate operation time of 100 ns is 3 times faster than 297 ns of the proposed global control scheme.

  14. Atomistic simulations of adiabatic coherent electron transport in triple donor systems

    NASA Astrophysics Data System (ADS)

    Rahman, Rajib; Park, Seung H.; Cole, Jared H.; Greentree, Andrew D.; Muller, Richard P.; Klimeck, Gerhard; Hollenberg, Lloyd C. L.

    2009-07-01

    A solid-state analog of stimulated Raman adiabatic passage can be implemented in a triple-well solid-state system to coherently transport an electron across the wells with exponentially suppressed occupation in the central well at any point of time. Termed coherent-tunneling adiabatic passage (CTAP), this method provides a robust way to transfer quantum information encoded in the electronic spin across a chain of quantum dots or donors. Using large-scale atomistic tight-binding simulations involving over 3.5×106 atoms, we verify the existence of a CTAP pathway in a realistic solid-state system: gated triple donors in silicon. Realistic gate profiles from commercial tools were combined with tight-binding methods to simulate gate control of the donor to donor tunnel barriers in the presence of crosstalk. As CTAP is an adiabatic protocol, it can be analyzed by solving the time-independent problem at various stages of the pulse justifying the use of time-independent tight-binding methods to this problem. This work also involves the first atomistic treatment to translate the three-state-based quantum-optics type of modeling into a solid-state description beyond the ideal localization assumption. Our results show that a three-donor CTAP transfer, with interdonor spacing of 15 nm can occur on time scales greater than 23 ps, well within experimentally accessible regimes. The method not only provides a tool to guide future CTAP experiments but also illuminates the possibility of system engineering to enhance control and transfer times.

  15. Algae as an electron donor promoting sulfate reduction for the bioremediation of acid rock drainage.

    PubMed

    Ayala-Parra, Pedro; Sierra-Alvarez, Reyes; Field, Jim A

    2016-11-05

    This study assessed bioremediation of acid rock drainage in simulated permeable reactive barriers (PRB) using algae, Chlorella sorokiniana, as the sole electron donor for sulfate-reducing bacteria. Lipid extracted algae (LEA), the residues of biodiesel production, were compared with whole cell algae (WCA) as an electron donor to promote sulfate-reducing activity. Inoculated columns containing anaerobic granular sludge were fed a synthetic medium containing H2SO4 and Cu(2+). Sulfate, sulfide, Cu(2+) and pH were monitored throughout the experiment of 123d. Cu recovered in the column packing at the end of the experiment was evaluated using sequential extraction. Both WCA and LEA promoted 80% of sulfate removal (12.7mg SO4(2-) d(-1)) enabling near complete Cu removal (>99.5%) and alkalinity generation raising the effluent pH to 6.5. No noteworthy sulfate reduction, alkalinity formation and Cu(2+) removal were observed in the endogenous control. In algae amended-columns, Cu(2+) was precipitated with biogenic H2S produced by sulfate reduction. Formation of CuS was evidenced by sequential extraction and X-ray diffraction. LEA and WCA provided similar levels of electron donor based on the COD balance. The results demonstrate an innovative passive remediation system using residual algae biomass from the biodiesel industry.

  16. Implanted bismuth donors in 28-Si: Process development and electron spin resonance measurements

    NASA Astrophysics Data System (ADS)

    Weis, C. D.; Lo, C. C.; Lang, V.; George, R. E.; Tyryshkin, A. M.; Bokor, J.; Lyon, S. A.; Morton, J. J. L.; Schenkel, T.

    2012-02-01

    Spins of donor atoms in silicon are excellent qubit candidates. Isotope engineered substrates provide a nuclear spin free host environment, resulting in long spin coherence times [1,2]. The capability of swapping quantum information between electron and nuclear spins can enable quantum communication and gate operation via the electron spin and quantum memory via the nuclear spin [2]. Spin properties of donor qubit candidates in silicon have been studied mostly for phosphorous and antimony [1-3]. Bismuth donors in silicon exhibit a zero field splitting of 7.4 GHz and have attracted attention as potential nuclear spin memory and spin qubit candidates [4,5] that could be coupled to superconducting resonators [4,6]. We report on progress in the formation of bismuth doped 28-Si epi layers by ion implantation, electrical dopant activation and their study via pulsed electron spin resonance measurements showing narrow linewidths and good coherence times. [4pt] [1] A. M. Tyryshkin, et al. arXiv: 1105.3772 [2] J. J. L. Morton, et al. Nature (2008) [3] T. Schenkel, et al APL 2006; F. R. Bradbury, et al. PRL (2006) [4] R. E. George, et al. PRL (2010) [5] G. W. Morley, et al. Nat Mat (2010) [6] M. Hatridge, et al. PRB (2011), R. Vijay, et al. APL (2010) This work was supported by NSA (100000080295) and DOE (DE-AC02-05CH11231).

  17. Photoinduced electron transfer interaction of anthraquinones with aniline quenchers: Influence of methyl substitution in aniline donors

    NASA Astrophysics Data System (ADS)

    Sivakumar, V.; Ponnamma, Deepalekshmi; Hussein, Yasser H. A.

    2017-02-01

    Photoinduced electron transfer between triplet state of 9,10-anthraquinone (AQ) and its two derivatives: 2-chloro-9,10-anthraquinone (CAQ) and sodium anthraquinone-2-sulfonate (AQS) and ground state aniline (AN) and its dimethyl substitutions: 2,3-dimethylaniline (2,3-DMA), 2,6-dimethylaniline (2,6-DMA), 3,5-dimethylaniline (3,5-DMA) and N,N-dimethylaniline (N,N-DMA) is studied using nanosecond laser flash photolysis at room temperature. Detection of radical bands of quinone anions and aniline cations along with their formation and/or decay kinetics are used to confirm the electron transfer (ET) process. In MeCN medium, AN quenches the triplet state of CAQ (CAQT) but not the triplets AQT or AQST. However in aqueous medium, AN quenches AQST and forms radical ion pair. All the DMAs can react through ET with all the triplet quinones at different degrees of efficiency in MeCN medium. Noticeably, the ring substituted DMAs are less efficient in electron donation to AQT or AQST while the N,N-DMA shows high efficiency in donating electron to all triplet quinones in MeCN medium. Charge distribution of donor molecules, in MeCN medium is calculated using density functional theory (DFT), and shows an enhancement of electron density of the ring of N,N-DMA, making it an ideal electron donor for ET studies compared to other DMAs. This systematic selection and usage of anilines with electrochemically tunable quinones can be viewed as a working model of donor-acceptor system that can be utilized in photoinduced ET applications.

  18. Tuning the photodriven electron transport within the columnar perylenediimide stacks by changing the π-extent of the electron donors.

    PubMed

    Supur, Mustafa; Fukuzumi, Shunichi

    2013-02-21

    Photodriven electron-transport properties of the self-assemblies of N,N'-di(2-(trimethylammoniumiodide)ethylene)perylenediimide stacks (TAIPDI)(n) with three electron donors, disodium 4,4'-bis(2-sulfonatostyryl)biphenyl (BSSBP, stilbene-420), sodium 9,10-dimethoxyanthracene-2-sulfonate (DANS) and disodium 6-amino-1,3-naphthalenedisulfonate (ANADS) have been studied in water. These electron donors vary in their π-extent to adjust the electronic coupling and the distance with the PDI stacks. Possessing the largest π-extent, BSSBP has strong π-π interactions as well as ionic interactions with (TAIPDI)(n). Instead of π-stacking with TAIPDI planes, DANS and ANADS, with a relatively small π-extent, are embedded in the side chains of TAIPDIs via ionic interactions, resulting in a distance increment from the aromatic TAIPDI cores. After excitation, the BSSBP-(TAIPDI)(n) system exhibits fast charge separation (0.70 ps) and relatively slow charge recombination (485 ps) due to intermolecular electron delocalization along the TAIPDI stacks. On the other hand, charge separation in DANS-(TAIPDI)(n) and ANADS-(TAIPDI)(n) occurs within 1.5 and 1.6 ns, respectively, calculated from the quenching of singlet excited states. The lifetimes of charge-separated states are determined to be 44 and 96 μs, at least 10(5) times slower than that of BSSBP-(TAIPDI)(n) due to remarkably improved electron transport throughout the (TAIPDI)(n).

  19. Short-lived electron transfer in donor-bridge-acceptor systems

    NASA Astrophysics Data System (ADS)

    Psiachos, D.

    2016-10-01

    We investigate time-dependent electron transfer (ET) in benchmark donor-bridge-acceptor systems. For the small bridge sizes studied, we obtain results far different from the perturbation theory which underlies scattering-based approaches, notably a lack of destructive interference in the ET for certain arrangements of bridge molecules. We also calculate wavepacket transmission in the non-steady-state regime, finding a featureless spectrum, while for the current we find two types of transmission: sequential and direct, where in the latter, the current transmission increases as a function of the energy of the transferred electron, a regime inaccessible by conventional scattering theory.

  20. Ab initio calculations of the electronic structure of silicon nanocrystals doped with shallow donors (Li, P)

    SciTech Connect

    Kurova, N. V. Burdov, V. A.

    2013-12-15

    The results of ab initio calculations of the electronic structure of Si nanocrystals doped with shallow donors (Li, P) are reported. It is shown that phosphorus introduces much more significant distortions into the electronic structure of the nanocrystal than lithium, which is due to the stronger central cell potential of the phosphorus ion. It is found that the Li-induced splitting of the ground state in the conduction band of the nanocrystal into the singlet, doublet, and triplet retains its inverse structure typical for bulk silicon.

  1. Photoinduced electron transfer in rigidly linked dimethoxynapthalene-N-methylpyridinium donor-acceptor molecules

    NASA Astrophysics Data System (ADS)

    Clayton, Andrew H. A.; Ghiggino, Kenneth P.; Wilson, Gerard J.; Keyte, Peter J.; Paddon-Row, Michael N.

    1992-07-01

    Photoinduced electron transfer (ET) is studied in a series of novel molecules containing a dimethoxynaphthalene (DMN) donor and either a pyridine (P) or N-methylpyridinium (P-Me +) acceptor covalently linked via a rigid nonbornalogous bridge ( n sigma bonds in length). ET rates of the order of 10 10 s -1 were measured for the DMN- n-P-Me + series ( n = 4, 6), while no appreciable ET was observed for the DMN- n-P compounds. Electronic and nuclear factors are discussed and the results rationalized in terms of Marcus—Hush and non-adiabatic ET theories.

  2. Impact of Electron Donor selection on In-situ Biosequestration of Uranium

    NASA Astrophysics Data System (ADS)

    Tabatabaei, S.; Zhong, H.; Abel, E. J.; Field, J.; Brusseau, M. L. L.

    2015-12-01

    In-situ biosequestration, wherein electron-donating substrates are injected to promote microbial-associated sequestration of contaminants, is one promising enhanced-attenuation technique for remediation of groundwater containing arsenic, uranium, selenium, and similar constituents. A pilot-scale test of in-situ biosequestration for uranium in groundwater is in process at a former uranium mining site in Monument Valley, Arizona. Complementary bench experiments were conducted to examine the impact of different electron donors on the effectiveness of biosequestration. Aqueous and sediment samples were collected before and after the injection for monitoring changes in sediment properties, mineral geochemical composition, microbial community composition, and microbial activity.

  3. High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

    PubMed Central

    Geraghty, Paul B; Lee, Calvin; Subbiah, Jegadesan; Wong, Wallace W H; Banal, James L; Jameel, Mohammed A; Smith, Trevor A

    2016-01-01

    The synthesis of key 4-alkyl-substituted 5-(trimethylsilyl)thiophene-2-boronic acid pinacol esters 3 allowed a simplified alkylthiophene catenation process to access bis-, ter-, quater-, and quinquethiophene π-bridges for the synthesis of acceptor–π-bridge-donor– π-bridge-acceptor (A–π-D–π-A) electron donor molecules. Based on the known benzodithiophene-terthiophene-rhodanine (BTR) material, the BXR series of materials, BMR (X = M, monothiophene), BBR (X = B, bithiophene), known BTR (X = T, terthiophene), BQR (X = Q, quaterthiophene), and BPR (X = P(penta), quinquethiophene) were synthesised to examine the influence of chromophore extension on the device performance and stability for OPV applications. The BT x R (x = 4, butyl, and x = 8, octyl) series of materials were synthesised by varying the oligothiophene π-bridge alkyl substituent to examine structure–property relationships in OPV device performance. The devices assembled using electron donors with an extended chromophore (BQR and BPR) are shown to be more thermally stable than the BTR containing devices, with un-optimized efficiencies up to 9.0% PCE. BQR has been incorporated as a secondary donor in ternary blend devices with PTB7-Th resulting in high-performance OPV devices with up to 10.7% PCE. PMID:28144297

  4. Solution-processable donor-acceptor polymers with modular electronic properties and very narrow bandgaps.

    PubMed

    Foster, Michael E; Zhang, Benjamin A; Murtagh, Dustin; Liu, Yi; Sfeir, Matthew Y; Wong, Bryan M; Azoulay, Jason D

    2014-09-01

    Bridgehead imine-substituted cyclopentadithiophene structural units, in combination with highly electronegative acceptors that exhibit progressively delocalized π-systems, afford donor-acceptor (DA) conjugated polymers with broad absorption profiles that span technologically relevant wavelength (λ) ranges from 0.7 < λ < 3.2 μm. A joint theoretical and experimental study demonstrates that the presence of the cross-conjugated substituent at the donor bridgehead position results in the capability to fine-tune structural and electronic properties so as to achieve very narrow optical bandgaps (Eg (opt) < 0.5 eV). This strategy affords modular DA copolymers with broad- and long-wavelength light absorption in the infrared and materials with some of the narrowest bandgaps reported to date.

  5. Non-fullerene organic solar cells based on diketopyrrolopyrrole polymers as electron donors and ITIC as an electron acceptor.

    PubMed

    Jiang, Xudong; Xu, Yunhua; Wang, Xiaohui; Wu, Yang; Feng, Guitao; Li, Cheng; Ma, Wei; Li, Weiwei

    2017-03-15

    In this work, we provide systematic studies on the non-fullerene solar cells based on diketopyrrolopyrrole (DPP) polymers as electron donors and a well-known electron acceptor ITIC. ITIC has been widely reported in non-fullerene solar cells with high power conversion efficiencies (PCEs) above 10%, when it is combined with a wide band gap conjugated polymer, while its application in small band gap DPP polymers has never been reported. Herein, we select four DPP polymers containing different thienyl linkers, resulting in distinct absorption spectra, energy levels and crystalline properties. Non-fullerene solar cells based on DPP polymers as donors and ITIC as an acceptor show PCEs of 1.9-4.1% and energy loss of 0.55-0.82 eV. The PCEs are much lower than those of cells based on fullerene derivatives due to the poor miscibility between the DPP polymers and ITIC, as confirmed by the morphology and charge transport investigation. The results indicate that it is important to tune the miscibility between the donor and acceptor in order to realize optimized micro-phase separation, which can further enhance the performance of DPP polymer based non-fullerene solar cells.

  6. Effect of donor orientation on ultrafast intermolecular electron transfer in coumarin-amine systems

    SciTech Connect

    Singh, P. K.; Nath, S.; Bhasikuttan, A. C.; Kumbhakar, M.; Mohanty, J.; Sarkar, S. K.; Mukherjee, T.; Pal, H.

    2008-09-21

    Effect of donor amine orientation on nondiffusive ultrafast intermolecular electron transfer (ET) reactions in coumarin-amine systems has been investigated using femtosecond fluorescence upconversion measurements. Intermolecular ET from different aromatic and aliphatic amines used as donor solvents to the excited coumarin-151 (C151) acceptor occurs with ultrafast rates such that the shortest fluorescence lifetime component ({tau}{sub 1}) is the measure of the fastest ET rate ({tau}{sub 1}={tau}{sub ET}{sup fast}=(k{sub ET}{sup fast}){sup -1}), assigned to the C151-amine contact pairs in which amine donors are properly oriented with respect to C151 to maximize the acceptor-donor electronic coupling (V{sub el}). It is interestingly observed that as the amine solvents are diluted by suitable diluents (either keeping solvent dielectric constant similar or with increasing dielectric constant), the {tau}{sub 1} remains almost in the similar range as long as the amine dilution does not cross a certain critical limit, which in terms of the amine mole fraction (x{sub A}) is found to be {approx}0.4 for aromatic amines and {approx}0.8 for aliphatic amines. Beyond these dilutions in the two respective cases of the amine systems, the {tau}{sub 1} values are seen to increase very sharply. The large difference in the critical x{sub A} values involving aromatic and aliphatic amine donors has been rationalized in terms of the largely different orientational restrictions for the ET reactions as imposed by the aliphatic (n-type) and aromatic ({pi}-type) nature of the amine donors [A. K. Satpati et al., J. Mol. Struct. 878, 84 (2008)]. Since the highest occupied molecular orbital (HOMO) of the n-type aliphatic amines is mostly centralized at the amino nitrogen, only some specific orientations of these amines with respect to the close-contact acceptor dye [also of {pi}-character; A. K. Satpati et al., J. Mol. Struct. 878, 84 (2008) and E. W. Castner et al., J. Phys. Chem. A 104, 2869

  7. Electron-donor dopant, method of improving conductivity of polymers by doping therewith, and a polymer so treated

    DOEpatents

    Liepins, Raimond; Aldissi, Mahmoud

    1988-01-01

    Polymers with conjugated backbones, both polyacetylene and polyaromatic heterocyclic types, are doped with electron-donor agents to increase their electrical conductivity. The electron-donor agents are either electride dopants made in the presence of lithium or dopants derived from alkalides made in the presence of lithium. The dopants also contain a metal such as cesium and a trapping agent such as a crown ether.

  8. Electron-donor dopant, method of improving conductivity of polymers by doping therewith, and a polymer so treated

    DOEpatents

    Liepins, R.; Aldissi, M.

    1984-07-27

    Polymers with conjugated backbones, both polyacetylene and polyaromatic heterocyclic types, are doped with electron-donor agents to increase their electrical conductivity. The electron-donor agents are either electride dopants made in the presence of lithium or dopants derived from alkalides made in the presence of lithium. The dopants also contain a metal such as cesium and a trapping agent such as a crown ether.

  9. Dissimilatory arsenate reduction with sulfide as electron donor: experiments with mono lake water and Isolation of strain MLMS-1, a chemoautotrophic arsenate respirer.

    PubMed

    Hoeft, Shelley E; Kulp, Thomas R; Stolz, John F; Hollibaugh, James T; Oremland, Ronald S

    2004-05-01

    Anoxic bottom water from Mono Lake, California, can biologically reduce added arsenate without any addition of electron donors. Of the possible in situ inorganic electron donors present, only sulfide was sufficiently abundant to drive this reaction. We tested the ability of sulfide to serve as an electron donor for arsenate reduction in experiments with lake water. Reduction of arsenate to arsenite occurred simultaneously with the removal of sulfide. No loss of sulfide occurred in controls without arsenate or in sterilized samples containing both arsenate and sulfide. The rate of arsenate reduction in lake water was dependent on the amount of available arsenate. We enriched for a bacterium that could achieve growth with sulfide and arsenate in a defined, mineral medium and purified it by serial dilution. The isolate, strain MLMS-1, is a gram-negative, motile curved rod that grows by oxidizing sulfide to sulfate while reducing arsenate to arsenite. Chemoautotrophy was confirmed by the incorporation of H(14)CO(3)(-) into dark-incubated cells, but preliminary gene probing tests with primers for ribulose-1,5-biphosphate carboxylase/oxygenase did not yield PCR-amplified products. Alignment of 16S rRNA sequences indicated that strain MLMS-1 was in the delta-Proteobacteria, located near sulfate reducers like Desulfobulbus sp. (88 to 90% similarity) but more closely related (97%) to unidentified sequences amplified previously from Mono Lake. However, strain MLMS-1 does not grow with sulfate as its electron acceptor.

  10. Dissimilatory arsenate reduction with sulfide as electron donor: Experiments with Mono Lake water and isolation of strain MLMS-1, a chemoautotrophic arsenate respirer

    USGS Publications Warehouse

    Hoeft, S.E.; Kulp, T.R.; Stolz, J.F.; Hollibaugh, J.T.; Oremland, R.S.

    2004-01-01

    Anoxic bottom water from Mono Lake, California, can biologically reduce added arsenate without any addition of electron donors. Of the possible in situ inorganic electron donors present, only sulfide was sufficiently abundant to drive this reaction. We tested the ability of sulfide to serve as an electron donor for arsenate reduction in experiments with lake water. Reduction of arsenate to arsenite occurred simultaneously with the removal of sulfide. No loss of sulfide occurred in controls without arsenate or in sterilized samples containing both arsenate and sulfide. The rate of arsenate reduction in lake water was dependent on the amount of available arsenate. We enriched for a bacterium that could achieve growth with sulfide and arsenate in a defined, mineral medium and purified it by serial dilution. The isolate, strain MLMS-1, is a gram-negative, motile curved rod that grows by oxidizing sulfide to sulfate while reducing arsenate to arsenite. Chemoautotrophy was confirmed by the incorporation of H14CO3- into dark-incubated cells, but preliminary gene probing tests with primers for ribulose-1,5-biphosphate carboxylase/oxygenase did not yield PCR-amplified products. Alignment of 16S rRNA sequences indicated that strain MLMS-1 was in the ??-Proteobacteria, located near sulfate reducers like Desulfobulbus sp. (88 to 90% similarity) but more closely related (97%) to unidentified sequences amplified previously from Mono Lake. However, strain MLMS-1 does not grow with sulfate as its electron acceptor.

  11. Dissimilatory arsenate reduction with sulfide as the electron donor--Experiments with Mono Lake water and isolation of strain MLMS-1, a chemoautotrophic arsenate-respirer

    USGS Publications Warehouse

    Hoeft, Shelley E.; Kulp, Thomas R.; Stolz, John F.; Hollibaugh, James T.; Oremland, Ronald S.

    2004-01-01

    Anoxic bottom water from Mono Lake, California, can biologically reduce added arsenate without any addition of electron donors. Of the possible in situ inorganic electron donors present, only sulfide was sufficiently abundant to drive this reaction. We tested the ability of sulfide to serve as an electron donor for arsenate reduction in experiments with lake water. Reduction of arsenate to arsenite occurred simultaneously with the removal of sulfide. No loss of sulfide occurred in controls without arsenate or in sterilized samples containing both arsenate and sulfide. The rate of arsenate reduction in lake water was dependent on the amount of available arsenate. We enriched for a bacterium that could achieve growth with sulfide and arsenate in a defined, mineral medium and purified it by serial dilution. The isolate, strain MLMS-1, is a gram-negative, motile curved rod that grows by oxidizing sulfide to sulfate while reducing arsenate to arsenite. Chemoautotrophy was confirmed by the incorporation of H14CO3− into dark-incubated cells, but preliminary gene probing tests with primers for ribulose-1,5-biphosphate carboxylase/oxygenase did not yield PCR-amplified products. Alignment of 16S rRNA sequences indicated that strain MLMS-1 was in the δ-Proteobacteria, located near sulfate reducers like Desulfobulbus sp. (88 to 90% similarity) but more closely related (97%) to unidentified sequences amplified previously from Mono Lake. However, strain MLMS-1 does not grow with sulfate as its electron acceptor.

  12. Triazole bridges as versatile linkers in electron donor-acceptor conjugates

    PubMed Central

    de Miguel, Gustavo; Wielopolski, Mateusz; Schuster, David I.; Fazio, Michael A; Lee, Olivia P.; Haley, Christopher K.; Ortiz, Angy L.; Echegoyen, Luis; Clark, Timothy; Guldi, Dirk M.

    2011-01-01

    Aromatic triazoles have been frequently used as π-conjugated linkers in intramolecular electron transfer processes. To gain a deeper understanding of the electron mediating function of triazoles, we have synthesized a family of new triazole-based electron donor-acceptor conjugates. We have connected porphyrins and fullerenes through a central triazole moiety – (ZnP-Tri-C60) – each with a single change in their connection through the linker. An extensive photophysical and computational investigation reveals that the electron transfer dynamics – charge separation and charge recombination – in the different ZnP-Tri-C60 conjugates reflect a significant influence of the connectivity at the triazole linker. Except for m4m-ZnP-Tri-C60 17, the conjugates exhibit through-bond electron transfer with varying rate constants. Since the through-bond distance is nearly equal in the ZnP-Tri-C60 conjugates, the variation in charge separation and charge recombination dynamics is mainly associated with the electronic properties of the conjugates, including orbital energies, electron affinity, and the energies of the excited states. The changes of the electronic couplings are, in turn, a consequence of the different connectivity patterns at the triazole moieties. PMID:21702513

  13. Triazole bridges as versatile linkers in electron donor-acceptor conjugates.

    PubMed

    de Miguel, Gustavo; Wielopolski, Mateusz; Schuster, David I; Fazio, Michael A; Lee, Olivia P; Haley, Christopher K; Ortiz, Angy L; Echegoyen, Luis; Clark, Timothy; Guldi, Dirk M

    2011-08-24

    Aromatic triazoles have been frequently used as π-conjugated linkers in intramolecular electron transfer processes. To gain a deeper understanding of the electron-mediating function of triazoles, we have synthesized a family of new triazole-based electron donor-acceptor conjugates. We have connected zinc(II)porphyrins and fullerenes through a central triazole moiety--(ZnP-Tri-C(60))--each with a single change in their connection through the linker. An extensive photophysical and computational investigation reveals that the electron transfer dynamics--charge separation and charge recombination--in the different ZnP-Tri-C(60) conjugates reflect a significant influence of the connectivity at the triazole linker. Except for the m4m-ZnP-Tri-C(60)17, the conjugates exhibit through-bond photoinduced electron transfer with varying rate constants. Since the through-bond distance is nearly the same for all the synthesized ZnP-Tri-C(60) conjugates, the variation in charge separation and charge recombination dynamics is mainly associated with the electronic properties of the conjugates, including orbital energies, electron affinity, and the energies of the excited states. The changes of the electronic couplings are, in turn, a consequence of the different connectivity patterns at the triazole moieties.

  14. Process integration and electron spin coherence of donor atom implants in silicon

    NASA Astrophysics Data System (ADS)

    Schenkel, T.; Persaud, A.; Tyryshkin, A. M.; Lyon, S. A.; Bokor, J.; Lo, C. C.; Desousa, R.; Chakarov, I.

    2007-03-01

    We implanted low doses (2 to 4 x 10^11cm-2) of P, Sb, and Bi ions into isotopically enriched silicon (28-Si) and characterized diffusion, electrical activation and electron spin coherence after rapid thermal annealing. Phosphorus and bismuth both exhibit enhanced segregation to an imperfect Si/SiO2 interface, while dopant movement is suppressed for antimony ions. Pulsed electron spin resonance shows that spin echo decay is sensitive to the dopant depths, and the interface quality. At 5.2 K, a spin de-coherence time, T2, of 0.3 ms is found for Sb profiles peaking 50 nm below a Si/SiO2 interface, increasing to 0.75 ms when the surface is passivated with hydrogen. These measurements provide benchmark data for the development of devices in which quantum information is encoded in donor electron spins [1]. [1] T. Schenkel, et al., Appl. Phys. Lett. 88, 112101 (2006).

  15. Giant Reduction of InN Surface Electron Accumulation: Compensation of Surface Donors by Mg Dopants

    NASA Astrophysics Data System (ADS)

    Linhart, W. M.; Chai, J.; Morris, R. J. H.; Dowsett, M. G.; McConville, C. F.; Durbin, S. M.; Veal, T. D.

    2012-12-01

    Extreme electron accumulation with sheet density greater than 1013cm-2 is almost universally present at the surface of indium nitride (InN). Here, x-ray photoemission spectroscopy and secondary ion mass spectrometry are used to show that the surface Fermi level decreases as the Mg concentration increases, with the sheet electron density falling to below 108cm-2. Surface space-charge calculations indicate that the lowering of the surface Fermi level increases the density of unoccupied donor-type surface states and that these are largely compensated by Mg acceptors in the near-surface hole depletion region rather than by accumulated electrons. This is a significant step towards the realization of InN-based optoelectronic devices.

  16. The coordination chemistry of organo-hydride donors: new prospects for efficient multi-electron reduction.

    PubMed

    McSkimming, Alex; Colbran, Stephen B

    2013-06-21

    In biological reduction processes the dihydronicotinamides NAD(P)H often transfer hydride to an unsaturated substrate bound within an enzyme active site. In many cases, metal ions in the active site bind, polarize and thereby activate the substrate to direct attack by hydride from NAD(P)H cofactor. This review looks more widely at the metal coordination chemistry of organic donors of hydride ion--organo-hydrides--such as dihydronicotinamides, other dihydropyridines including Hantzsch's ester and dihydroacridine derivatives, those derived from five-membered heterocycles including the benzimidazolines and benzoxazolines, and all-aliphatic hydride donors such as hexadiene and hexadienyl anion derivatives. The hydride donor properties--hydricities--of organo-hydrides and how these are affected by metal ions are discussed. The coordination chemistry of organo-hydrides is critically surveyed and the use of metal-organo-hydride systems in electrochemically-, photochemically- and chemically-driven reductions of unsaturated organic and inorganic (e.g. carbon dioxide) substrates is highlighted. The sustainable electrocatalytic, photochemical or chemical regeneration of organo-hydrides such as NAD(P)H, including for driving enzyme-catalysed reactions, is summarised and opportunities for development are indicated. Finally, new prospects are identified for metal-organo-hydride systems as catalysts for organic transformations involving 'hydride-borrowing' and for sustainable multi-electron reductions of unsaturated organic and inorganic substrates directly driven by electricity or light or by renewable reductants such as formate/formic acid.

  17. Identifying electron transfer coordinates in donor-bridge-acceptor systems using mode projection analysis

    PubMed Central

    Yang, Xunmo; Keane, Theo; Delor, Milan; Meijer, Anthony J. H. M.; Weinstein, Julia; Bittner, Eric R.

    2017-01-01

    We report upon an analysis of the vibrational modes that couple and drive the state-to-state electronic transfer branching ratios in a model donor-bridge-acceptor system consisting of a phenothiazine-based donor linked to a naphthalene-monoimide acceptor via a platinum-acetylide bridging unit. Our analysis is based upon an iterative Lanczos search algorithm that finds superpositions of vibronic modes that optimize the electron/nuclear coupling using input from excited-state quantum chemical methods. Our results indicate that the electron transfer reaction coordinates between a triplet charge-transfer state and lower lying charge-separated and localized excitonic states are dominated by asymmetric and symmetric modes of the acetylene groups on either side of the central atom in this system. In particular, we find that while a nearly symmetric mode couples both the charge-separation and charge-recombination transitions more or less equally, the coupling along an asymmetric mode is far greater suggesting that IR excitation of the acetylene modes preferentially enhances charge-recombination transition relative to charge-separation. PMID:28233775

  18. Cultivation of high-rate sulfate reducing sludge by pH-based electron donor dosage.

    PubMed

    Paulo, Paula L; Kleerebezem, Robbert; Lettinga, Gatze; Lens, Piet N L

    2005-07-21

    A novel self-regulating bioreactor concept for sulfate reduction is proposed aiming for high biomass concentrations and treatment capacities. The system consists of a cell suspension of sulfate reducing bacteria in a continuous stirred tank reactor (30 degrees C) fed with a mixture of both electron donor and electron acceptor (formic acid and sulfuric acid, respectively), nutrients and phosphate buffer via a pH controller. The pH rise due to sulfate reduction is balanced with dosage of the sulfate reducing substrates as acids. The reactor concept was shown to be capable of full sulfate reduction without competition for the electron donor by methanogens and acetogens. Activity assays revealed that hardly any methanogenic activity on formate was left in the suspension by the end of the continuous run (130 days). In addition, the sulfidogenic activity with formate and H2/CO2 had increased, respectively, 3.9 and 11.6 times at the end of the experimental run. The evolution of the particle size distribution of the cell suspension over time indicated that newly grown cells have the tendency to attach together in flocs or to the existing agglomerates.

  19. Influence of different electron donors and acceptors on dehalorespiration of tetrachloroethene by Desulfitobacterium frappieri TCE1

    SciTech Connect

    Gerritse, J.; Drzyzga, O.; Kloetstra, G.; Keijmel, M.; Wiersum, L.P.; Hutson, R.; Collins, M.D.; Gottschal, J.C.

    1999-12-01

    Strain TCE1, a strictly anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene (PCE) and trichloroethane (TCE), was isolated by selective enrichment from a PCE-dechlorinating chemostat mixed culture. Strain TCE1 is a gram-positive, motile, curved rod-shaped organism that is 2 to 4 by 0.6 to 0.8 {micro}m and has approximately six lateral flagella. The pH and temperature optima for growth are 7.2 and 35 C, respectively. On the basis of a comparative 16S rRNA sequence analysis, this bacterium was identified as a new strain of Desulfitobacterium frappieri, because it exhibited 99.7% relatedness to the D. frappieri type strain, strain PCP-1. Growth with H{sub 2}, format, L-lactate, butyrate, crotonate, or ethanol as the electron donor depends on the availability of an external electron acceptor. Pyruvate and serine can also be used fermentatively. Electron donors (except format and H{sub 2}) are oxidized to acetate and CO{sub 2}. when L-lactate is the growth substrate, strain TCE1 can use the following electron acceptors: PCE and TCE (to produce cis-1,2-dichloroethene), sulfite and thiosulfate (to produce sulfide), nitrate (to produce nitrite), and fumarate (to produce succinate). Strain TCE1 is not able to reductively dechlorinate 3-chloro-4-hydroxyphenylacetate. The growth yields of the newly isolated bacterium when PCE is the electron acceptor are similar to those obtained for other dehalorespiring anaerobes (e.g., Desulfitobacterium sp. strain PCE1 and Desulfitobacterium hafniense) and the maximum specific reductive dechlorination rates are 4 to 16 times higher. Dechlorination of PCE and TCE is an inducible process. In PCE-limited chemostat cultures of strain TCE1, dechlorination is strongly inhibited by sulfite but not by other alternative electron acceptors, such as fumate or nitrate.

  20. Single-electron quantization at room temperature in a-few-donor quantum dot in silicon nano-transistors

    NASA Astrophysics Data System (ADS)

    Samanta, Arup; Muruganathan, Manoharan; Hori, Masahiro; Ono, Yukinori; Mizuta, Hiroshi; Tabe, Michiharu; Moraru, Daniel

    2017-02-01

    Quantum dots formed by donor-atoms in Si nanodevices can provide a breakthrough for functionality at the atomic level with one-by-one control of electrons. However, single-electron effects in donor-atom devices have only been observed at low temperatures mainly due to the low tunnel barriers. If a few donor-atoms are closely coupled as a molecule to form a quantum dot, the ground-state energy level is significantly deepened, leading to higher tunnel barriers. Here, we demonstrate that such an a-few-donor quantum dot, formed by selective conventional doping of phosphorus (P) donors in a Si nano-channel, sustains Coulomb blockade behavior even at room temperature. In this work, such a quantum dot is formed by 3 P-donors located near the center of the selectively-doped area, which is consistent with a statistical analysis. This finding demonstrates practical conditions for atomic- and molecular-level electronics based on donor-atoms in silicon nanodevices.

  1. Enhanced photoproduction of hydrogen peroxide by humic substances in the presence of phenol electron donors.

    PubMed

    Zhang, Yi; Simon, Kelli A; Andrew, Andrea A; Del Vecchio, Rossana; Blough, Neil V

    2014-11-04

    Addition of a series of phenol electron donors to solutions of humic substances (HS) enhanced substantially the initial rates of hydrogen peroxide (H2O2) photoproduction (RH2O2), with enhancement factors (EF) ranging from a low of ∼3 for 2,4,6-trimethylphenol (TMP) to a high of ∼15 for 3,4-dimethoxyphenol (DMOP). The substantial inhibition of the enhanced RH2O2 following borohydride reduction of the HS, as well as the dependence of RH2O2 on phenol and dioxygen concentrations are consistent with a mechanism in which the phenols react with the triplet excited states of (aromatic) ketones within the HS to form initially a phenoxy and ketyl radical. The ketyl radical then reacts rapidly with dioxygen to regenerate the ketone and form superoxide (O2-), which subsequently dismutates to H2O2. However, as was previously noted for the photosensitized loss of TMP, the incomplete inhibition of the enhanced RH2O2 following borohydride reduction suggests that there may remain another pool of oxidizing triplets. The results demonstrate that H2O2 can be generated through an additional pathway in the presence of sufficiently high concentrations of appropriate electron donors through reaction with the excited triplet states of aromatic ketones and possibly of other species such as quinones. However, in some cases, the much lower ratio of H2O2 produced to phenol consumed suggests that secondary reactions could alter this ratio significantly.

  2. Size and temperature dependence of the electron-phonon scattering by donors in nanowire transistors

    NASA Astrophysics Data System (ADS)

    Bescond, M.; Carrillo-Nuñez, H.; Berrada, S.; Cavassilas, N.; Lannoo, M.

    2016-08-01

    Due to the constant size reduction, single-donor-based nanowire transistors receive an increasing interest from the semi-conductor industry. In this work we theoretically investigate the coupled influence of electron-phonon scattering, temperature and size (cross-section and channel length) on the properties of such systems. The aim is to determine under what conditions the localized character of the donor has a remarkable impact on the current characteristics. We use a quantum non-equilibrium Green's function approach in which the acoustic electron-phonon scattering is treated through local self-energies. We first show how this widely used approach, valid at high temperatures, can be extended to lower temperatures. Our simulations predict a hysteresis in the current when reducing the temperature down to 150 K. We also find that acoustic phonons degrade the current characteristics while their optical counterparts might have a beneficial impact with an increase of the ON-current. Finally we discuss the influence of nanowire length and cross-section and emphasize the complexity of precisely controlling the dopant level at room temperature.

  3. Evaluation of sustained release polylactate electron donors for removal of hexavalent chromium from contaminated groundwater

    SciTech Connect

    Brodie, E.L.; Joyner, D. C.; Faybishenko, B.; Conrad, M. E.; Rios-Velazquez, C.; Mork, B.; Willet, A.; Koenigsberg, S.; Herman, D.; Firestone, M. K.; Hazen, T. C.; Malave, Josue; Martinez, Ramon

    2011-02-15

    To evaluate the efficacy of bioimmobilization of Cr(VI) in groundwater at the Department of Energy Hanford site, we conducted a series of microcosm experiments using a range of commercial electron donors with varying degrees of lactate polymerization (polylactate). These experiments were conducted using Hanford Formation sediments (coarse sand and gravel) immersed in Hanford groundwater, which were amended with Cr(VI) and several types of lactate-based electron donors (Hydrogen Release Compound, HRC; primer-HRC, pHRC; extended release HRC) and the polylactate-cysteine form (Metal Remediation Compound, MRC). The results showed that polylactate compounds stimulated an increase in bacterial biomass and activity to a greater extent than sodium lactate when applied at equivalent carbon concentrations. At the same time, concentrations of headspace hydrogen and methane increased and correlated with changes in the microbial community structure. Enrichment of Pseudomonas spp. occurred with all lactate additions, and enrichment of sulfate-reducing Desulfosporosinus spp. occurred with almost complete sulfate reduction. The results of these experiments demonstrate that amendment with the pHRC and MRC forms result in effective removal of Cr(VI) from solution most likely by both direct (enzymatic) and indirect (microbially generated reductant) mechanisms.

  4. Field Evidence for Co-Metabolism of Trichloroethene Stimulated by Addition of Electron Donor to Groundwater

    SciTech Connect

    Conrad, Mark E.; Brodie, Eoin L.; Radtke, Corey W.; Bill, Markus; Delwiche, Mark E.; Lee, M. Hope; Swift, Dana L.; Colwell, Frederick S.

    2010-05-17

    For more than 10 years, electron donor has been injected into the Snake River aquifer beneath the Test Area North site of the Idaho National Laboratory for the purpose of stimulating microbial reductive dechlorination of trichloroethene (TCE) in groundwater. This has resulted in significant TCE removal from the source area of the contaminant plume and elevated dissolved CH4 in the groundwater extending 250 m from the injection well. The delta13C of the CH4 increases from 56o/oo in the source area to -13 o/oo with distance from the injection well, whereas the delta13C of dissolved inorganic carbon decreases from 8 o/oo to -13 o/oo, indicating a shift from methanogenesis to methane oxidation. This change in microbial activity along the plume axis is confirmed by PhyloChip microarray analyses of 16S rRNA genes obtained from groundwater microbial communities, which indicate decreasing abundances of reductive dechlorinating microorganisms (e.g., Dehalococcoides ethenogenes) and increasing CH4-oxidizing microorganisms capable of aerobic co-metabolism of TCE (e.g., Methylosinus trichosporium). Incubation experiments with 13C-labeled TCE introduced into microcosms containing basalt and groundwater from the aquifer confirm that TCE co-metabolism is possible. The results of these studies indicate that electron donor amendment designed to stimulate reductive dechlorination of TCE may also stimulate co-metabolism of TCE.

  5. Carbon Monoxide Promotes Respiratory Hemoproteins Iron Reduction Using Peroxides as Electron Donors

    PubMed Central

    Sher, Elena A.; Shaklai, Mati; Shaklai, Nurith

    2012-01-01

    The physiological role of the respiratory hemoproteins (RH), hemoglobin and myoglobin, is to deliver O2 via its binding to their ferrous (FeII) heme-iron. Under variety of pathological conditions RH proteins leak to blood plasma and oxidized to ferric (FeIII, met) forms becoming the source of oxidative vascular damage. However, recent studies have indicated that both metRH and peroxides induce Heme Oxygenase (HO) enzyme producing carbon monoxide (CO). The gas has an extremely high affinity for the ferrous heme-iron and is known to reduce ferric hemoproteins in the presence of suitable electron donors. We hypothesized that under in vivo plasma conditions, peroxides at low concentration can assist the reduction of metRH in presence of CO. The effect of CO on interaction of metRH with hydrophilic or hydrophobic peroxides was analyzed by following Soret and visible light absorption changes in reaction mixtures. It was found that under anaerobic conditions and low concentrations of RH and peroxides mimicking plasma conditions, peroxides served as electron donors and RH were reduced to their ferrous carboxy forms. The reaction rates were dependent on CO as well as peroxide concentrations. These results demonstrate that oxidative activity of acellular ferric RH and peroxides may be amended by CO turning on the reducing potential of peroxides and facilitating the formation of redox-inactive carboxyRH. Our data suggest the possible role of HO/CO in protection of vascular system from oxidative damage. PMID:22427940

  6. Carbon monoxide promotes respiratory hemoproteins iron reduction using peroxides as electron donors.

    PubMed

    Sher, Elena A; Shaklai, Mati; Shaklai, Nurith

    2012-01-01

    The physiological role of the respiratory hemoproteins (RH), hemoglobin and myoglobin, is to deliver O(2) via its binding to their ferrous (Fe(II)) heme-iron. Under variety of pathological conditions RH proteins leak to blood plasma and oxidized to ferric (Fe(III), met) forms becoming the source of oxidative vascular damage. However, recent studies have indicated that both metRH and peroxides induce Heme Oxygenase (HO) enzyme producing carbon monoxide (CO). The gas has an extremely high affinity for the ferrous heme-iron and is known to reduce ferric hemoproteins in the presence of suitable electron donors. We hypothesized that under in vivo plasma conditions, peroxides at low concentration can assist the reduction of metRH in presence of CO. The effect of CO on interaction of metRH with hydrophilic or hydrophobic peroxides was analyzed by following Soret and visible light absorption changes in reaction mixtures. It was found that under anaerobic conditions and low concentrations of RH and peroxides mimicking plasma conditions, peroxides served as electron donors and RH were reduced to their ferrous carboxy forms. The reaction rates were dependent on CO as well as peroxide concentrations. These results demonstrate that oxidative activity of acellular ferric RH and peroxides may be amended by CO turning on the reducing potential of peroxides and facilitating the formation of redox-inactive carboxyRH. Our data suggest the possible role of HO/CO in protection of vascular system from oxidative damage.

  7. Characterization of U(VI) reduction in contaminated sediments with slow-degrading electron donor source

    NASA Astrophysics Data System (ADS)

    Wu, W.; Watson, D. B.; Zhang, G.; Mehlhorn, T.; Lowe, K.; Earles, J.; Phillips, J.; Kelly, S. D.; Boyanov, M.; Kemner, K. M.; Schadt, C.; Criddle, C. S.; Jardine, P. M.; Brooks, S. C.

    2011-12-01

    In order to select sustainable, high efficiency and cost effective electron donor source, oleate and emulsified vegetable oil (EVO) were tested uranium (VI) reduction in comparison with ethanol in microcosms using uranium contaminated sediments and groundwater from the US DOE Oak Ridge Integrated Field Research Challenge (ORIFRC) site. The effect of initial sulfate concentration on U(VI) reduction was also tested. Both oleate and EVO were effective electron donor sources for U(VI) reduction. Accumulation of acetate as a major product and the removal of aqueous U(VI) were observed and were associated with sulfate reduction. Both oleate and EVO supported U(VI) reduction but at slower rates with a comparable but slightly lower extent of reduction than ethanol. X-ray absorption near-edge spectroscopy (XANES) analysis confirmed reduction of U(VI) to U(IV). The extent of U(VI) reduction in solid phase was negatively influenced by aqueous calcium concentration. The majority of electrons of the three substrates were consumed by sulfate reduction, Fe(III) reduction, and methanogenesis. Initial U(VI) concentration in the aqueous phase increased with increased sulfate concentration (1 versus 5 mM), likely due to U(VI) desorption from the solid phase. At the higher initial sulfate concentration more U(VI) was reduced and fewer electrons were used in methanogenesis. Analysis of bacterial and archeal populations using 16S rRNA gene libraries showed a significant increase in Deltaproteobacteria after biostimulation. The microbial community structures developed with oleate and EVO were significantly distinct from those developed with ethanol. Bacteria similar to Desulforegula spp. was predominant for oleate and EVO degradation but were not observed in ethanol-amended microcosms. Known U(VI)-reducing bacteria in the microcosms amended with the three electron donor sources included iron(III) reducing Geobacter spp. but in lower abundances than sulfate-reducing Desulfovibrio spp. The

  8. Spectral Fine Tuning of Cyanine Dyes: Electron Donor-Acceptor Substituted Analogues of Thiazole Orange†

    PubMed Central

    Rastede, Elizabeth E.; Tanha, Matteus; Yaron, David; Watkins, Simon C.; Waggoner, Alan S.; Armitage, Bruce A.

    2015-01-01

    The introduction of electron donor and acceptor groups at strategic locations on a fluorogenic cyanine dye allows fine-tuning of the absorption and emission spectra while preserving the ability of the dye to bind to biomolecular hosts such as double-stranded DNA and a single-chain antibody fragment originally selected for binding to the parent unsubstituted dye, thiazole orange (TO). The observed spectral shifts are consistent with calculated HOMO-LUMO energy gaps and reflect electron density localization on the quinoline half of TO in the LUMO. A dye bearing donating methoxy and withdrawing trifluoromethyl groups on the benzothiazole and quinoline rings, respectively, shifts the absorption spectrum to sufficiently longer wavelengths to allow excitation at green wavelengths as opposed to the parent dye, which is optimally excited in the blue. PMID:26171668

  9. Isolation of acetogenic bacteria that induce biocorrosion by utilizing metallic iron as the sole electron donor.

    PubMed

    Kato, Souichiro; Yumoto, Isao; Kamagata, Yoichi

    2015-01-01

    Corrosion of iron occurring under anoxic conditions, which is termed microbiologically influenced corrosion (MIC) or biocorrosion, is mostly caused by microbial activities. Microbial activity that enhances corrosion via uptake of electrons from metallic iron [Fe(0)] has been regarded as one of the major causative factors. In addition to sulfate-reducing bacteria and methanogenic archaea in marine environments, acetogenic bacteria in freshwater environments have recently been suggested to cause MIC under anoxic conditions. However, no microorganisms that perform acetogenesis-dependent MIC have been isolated or had their MIC-inducing mechanisms characterized. Here, we enriched and isolated acetogenic bacteria that induce iron corrosion by utilizing Fe(0) as the sole electron donor under freshwater, sulfate-free, and anoxic conditions. The enriched communities produced significantly larger amounts of Fe(II) than the abiotic controls and produced acetate coupled with Fe(0) oxidation prior to CH4 production. Microbial community analysis revealed that Sporomusa sp. and Desulfovibrio sp. dominated in the enrichments. Strain GT1, which is closely related to the acetogen Sporomusa sphaeroides, was eventually isolated from the enrichment. Strain GT1 grew acetogenetically with Fe(0) as the sole electron donor and enhanced iron corrosion, which is the first demonstration of MIC mediated by a pure culture of an acetogen. Other well-known acetogenic bacteria, including Sporomusa ovata and Acetobacterium spp., did not grow well on Fe(0). These results indicate that very few species of acetogens have specific mechanisms to efficiently utilize cathodic electrons derived from Fe(0) oxidation and induce iron corrosion.

  10. A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells.

    PubMed

    Sorohhov, Gleb; Yi, Chenyi; Grätzel, Michael; Decurtins, Silvio; Liu, Shi-Xia

    2015-01-01

    Two new photosensitizers featured with a cyanoacrylic acid electron acceptor (A) and a hybrid electron donor (D) of cyclopentadithiophene and dithiafulvenyl, either directly linked or separated by a phenyl ring, were synthesized and characterized. Both of them undergo two reversible oxidations and strongly absorb in the visible spectral region due to a photo-induced intramolecular charge-transfer (ICT) transition. To a great extent, the electronic interaction between the D and A units is affected by the presence of a phenyl spacer. Without a phenyl ring, the D unit appears more difficult to oxidize due to a strong electron-withdrawing effect of the A moiety. In sharp contrast, the insertion of the phenyl ring between the D and A units leads to a broken π-conjugation and therefore, the oxidation potentials remain almost unchanged compared to those of an analogue without the A group, suggesting that the electronic coupling between D and A units is relatively weak. As a consequence, the lowest-energy absorption band shows a slight hypsochromic shift upon the addition of the phenyl spacer, indicative of an increased HOMO-LUMO gap. In turn, the direct linkage of D and A units leads to an effective π-conjugation, thus substantially lowering the HOMO-LUMO gap. Moreover, the application in dye-sensitized solar cells was investigated, showing that the power conversion efficiency increases by the insertion of the phenyl unit.

  11. A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells

    PubMed Central

    Sorohhov, Gleb; Yi, Chenyi; Grätzel, Michael; Decurtins, Silvio

    2015-01-01

    Summary Two new photosensitizers featured with a cyanoacrylic acid electron acceptor (A) and a hybrid electron donor (D) of cyclopentadithiophene and dithiafulvenyl, either directly linked or separated by a phenyl ring, were synthesized and characterized. Both of them undergo two reversible oxidations and strongly absorb in the visible spectral region due to a photo-induced intramolecular charge-transfer (ICT) transition. To a great extent, the electronic interaction between the D and A units is affected by the presence of a phenyl spacer. Without a phenyl ring, the D unit appears more difficult to oxidize due to a strong electron-withdrawing effect of the A moiety. In sharp contrast, the insertion of the phenyl ring between the D and A units leads to a broken π-conjugation and therefore, the oxidation potentials remain almost unchanged compared to those of an analogue without the A group, suggesting that the electronic coupling between D and A units is relatively weak. As a consequence, the lowest-energy absorption band shows a slight hypsochromic shift upon the addition of the phenyl spacer, indicative of an increased HOMO–LUMO gap. In turn, the direct linkage of D and A units leads to an effective π-conjugation, thus substantially lowering the HOMO–LUMO gap. Moreover, the application in dye-sensitized solar cells was investigated, showing that the power conversion efficiency increases by the insertion of the phenyl unit. PMID:26199660

  12. Shewanella spp. Use Acetate as an Electron Donor for Denitrification but Not Ferric Iron or Fumarate Reduction

    PubMed Central

    Yoon, Sukhwan; Sanford, Robert A.

    2013-01-01

    Lactate but not acetate oxidation was reported to support electron acceptor reduction by Shewanella spp. under anoxic conditions. We demonstrate that the denitrifiers Shewanella loihica strain PV-4 and Shewanella denitrificans OS217 utilize acetate as an electron donor for denitrification but not for fumarate or ferric iron reduction. PMID:23396327

  13. [Effect of permeabilization on sulfate reduction activity of Desulfovibrio vulgaris Hildenborough cells in the presence of different electron donors].

    PubMed

    Xu, Hui-Wei; Zhang, Xu; Li, Li-Ming; Zheng, Guang-Jie; Li, Guang-He

    2013-01-01

    The Desulfovibrio vulgaris Hildenborough (DvH) cells permeabilized with ethanol were used as biocatalysts to enhance hydrogenotrophic sulfate conversion. The effect of permeabilization extent of DvH cells on sulfate reduction was studied in the presence of different electron donors. When hydrogen was used as an electron donor, the highest level of sulfate reduction activity attained in cells treated with 10% ethanol (V/V), followed by 15% -ethanol treated cells. Furthermore, sulfate reduction activity markedly decreased when the ethanol concentration exceeded 15%. However, when lactate was used as the electron donor, the optimum ethanol concentration of the permeabilizing reagent was 20%, followed by 15% and 10%. Even when ethanol concentration reached 25%, DvH cells remained their partial activity with lactate. In a word, sulfate reduction activity of DvH cells responded differently in the presence of different donors. This was because the oxidation process of H2 and lactate occurred at different positions in DvH cells, and consequently intracellular electron transport pathway differed. To ensure the integrity of the electron transport chain between the donor and the accepter was a key factor for determining the permeabilization extent and for the application of cell permeabilization technology.

  14. Tuning the Electronic Coupling and Electron Transfer in Mo2 Donor-Acceptor Systems by Variation of the Bridge Conformation.

    PubMed

    Kang, Mei Ting; Meng, Miao; Tan, Ying Ning; Cheng, Tao; Liu, Chun Y

    2016-02-24

    Assembling two quadruply bonded dimolybdenum units [Mo2 (DAniF)3 ](+) (DAniF=N,N'-di(p-anisyl)formamidinate) with 1,4-naphthalenedicarboxylate and its thiolated derivatives produced three complexes [{Mo2 (DAniF)3 }2 (μ-1,4-O2 CC10 H6 CO2 )], [{Mo2 (DAniF)3 }2 (μ-1,4-OSCC10 H6 COS)], and [{Mo2 (DAniF)3 }2 (μ-1,4-S2 CC10 H6 CS2 )]. In the X-ray structures, the naphthalene bridge deviates from the plane defined by the two Mo-Mo bond vectors with the torsion angle increasing as the chelating atoms of the bridging ligand vary from O to S. The mixed-valent species exhibit intervalence transition absorption bands with high energy and very low intensity. In comparison with the data for the phenylene analogues, the optically determined electronic coupling matrix elements (Hab =258-345 cm(-1) ) are lowered by a factor of two or more, and the electron-transfer rate constants (ket ≈10(11)  s(-1) ) are reduced by about one order of magnitude. These results show that, when the electron-transporting ability of the bridge and electron-donating (electron-accepting) ability of the donor (acceptor) are both variable, the former plays a dominant role in controlling the intramolecular electron transfer. DFT calculations revealed that increasing the torsion angle enlarges the HOMO-LUMO energy gap by elevating the (bridging) ligand-based LUMO energy. Therefore, our experimental results and theoretical analyses verify the superexchange mechanism for electronic coupling and electron transfer.

  15. Application of acetate, lactate, and fumarate as electron donors in microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Vasyliv, Oresta M.; Bilyy, Oleksandr I.; Ferensovych, Yaroslav P.; Hnatush, Svitlana O.

    2013-09-01

    Microbial fuel cells (MFCs) are devices that use bacteria as the catalysts to oxidize organic and inorganic matter and generate current. Up to now, several classes of extracellular electron transfer mechanisms have been elucidated for various microorganisms. Shewanellaceae and Geobacteraceae families include the most of model exoelectrogenic microorganisms. Desulfuromonas acetoxidans bacterium inhabits aquatic sedimental sulfur-containing environments and is philogenetically close to representatives of Geobacteraceae family. Two chamber microbial fuel cell (0.3 l volume) was constructed with application of D. acetoxidans IMV B-7384 as anode biocatalyst. Acetic, lactic and fumaric acids were separately applied as organic electron donors for bacterial growth in constructed MFC. Bacterial cultivation in MFC was held during twenty days. Lactate oxidation caused electric power production with the highest value up to 0.071 mW on 64 hour of D. acetoxidans IMV B-7384 growth. Addition of acetic and fumaric acids into bacterial growth medium caused maximal power production up to 0.075 and 0.074 mW respectively on the 40 hour of their growth. Increasing of incubation time up to twentieth day caused decrease of generated electric power till 0.018 mW, 0.042 mW and 0.047 mW under usage of lactic, acetic and fumaric acids respectively by investigated bacteria. Power generation by D. acetoxidans IMV B-7384 was more stabile and durable under application of acetic and fumaric acids as electron donors in constructed MFC, than under addition of lactic acid in the same concentration into the growth medium.

  16. Chemostat Studies of TCE-Dehalogenating Anaerobic Consortia under Excess and Limited Electron Donor Addition

    NASA Astrophysics Data System (ADS)

    Semprini, L.; Azizian, M.; Green, J.; Mayer-Blackwell, K.; Spormann, A. M.

    2015-12-01

    Two cultures - the Victoria Strain (VS) and the Evanite Strain (EV), enriched with the organohalide respiring bacteria Dehalococcoides mccartyi - were grown in chemostats for more than 4 years at a mean cell residence time of 50 days. The slow doubling rate represents growth likely experienced in the subsurface. The chemostats were fed formate as an electron donor and trichloroethene (TCE) as the terminal electron acceptor. Under excess formate conditions, stable operation was observed with respect to TCE transformation, steady-state hydrogen (H2) concentrations (40 nM), and the structure of the dehalogenating community. Both cultures completely transformed TCE to ethene, with minor amounts of vinyl chloride (VC) observed, along with acetate formation. When formate was limited, TCE was transformed incompletely to ethene (40-60%) and VC (60- 40%), and H2 concentrations ranged from 1 to 3 nM. The acetate concentration dropped below detection. Batch kinetic studies of TCE transformation with chemostat harvested cells found transformation rates of c-DCE and VC were greatly reduced when the cells were grown with limited formate. Upon increasing formate addition to the chemostats, from limited to excess, essentially complete transformation of TCE to ethene was achieved. The increase in formate was associated with an increase in H2 concentration and the production of acetate. Results of batch kinetic tests showed increases in transformation rates for TCE and c-DCE by factors of 3.5 and 2.5, respectively, while VC rates increased by factors of 33 to 500, over a six month period. Molecular analysis of chemostat samples is being performed to quantify the changes in copy numbers of reductase genes and to determine whether shifts in the strains of Dehalococcoides mccartyi where responsible for the observed rate increases. The results demonstrate the importance of electron donor supply for successful in-situ remediation.

  17. Autotrophic perchlorate reduction kinetics of a microbial consortium using elemental sulfur as an electron donor.

    PubMed

    Gao, Mengchun; Wang, Sen; Jin, Chunji; She, Zonglian; Zhao, Congcong; Zhao, Yangguo; Zhang, Jian; Ren, Yun

    2015-07-01

    The perchlorate reduction kinetic parameters of a microbial consortium using elemental sulfur (S(0)) as an electron donor were investigated in batch experiments. Standard Monod substrate utilization and biomass accumulation models were employed to fit the experimental data for microbial perchlorate reduction. The maximum observed yield coefficient for the microbial consortium was 0.19 mg dry weight (DW) mg(-1) ClO4 (-), suggesting that the microbial consortium had a slow growth rate using S(0) as the electron donor. The maximum specific substrate utilization rate (q max) and half saturation constant (K s) for microbial perchlorate reduction were 0.14 mg ClO4 (-) mg(-1) DW day(-1) and 5.71 mg L(-1), respectively, which indicated that the microbial consortium could effectively utilize perchlorate as an electron acceptor. The variation of q max with pH was described well by using a Gaussian peak equation, and the maximal value of q max was obtained at pH 6.7. The presence of nitrate in perchlorate-contaminated water delayed the onset of sulfur autotrophic perchlorate reduction. The modified Gompertz equation could adequately describe the formation of Cl(-) and SO4(2-) during the process of sulfur autotrophic perchlorate reduction. The SO4(2-) production exceeded the theoretical SO4(2-) production due to S(0) disproportionation. The kinetic parameters for microbial perchlorate reduction are essential to design biological treatment systems, as well as to predict and evaluate their performance.

  18. 2010 Electron Donor-Acceptor Interactions Gordon Research Conference, August 8 - 13, 2010.

    SciTech Connect

    Gerald Meyer

    2010-08-18

    The Gordon Research Conference on Electron Donor Acceptor Interactions (GRC EDAI) presents and advances the current frontiers in experimental and theoretical studies of Electron Transfer Processes and Energy Conversion. The fundamental concepts underpinning the field of electron transfer and charge transport phenomena are understood, but fascinating experimental discoveries and novel applications based on charge transfer processes are expanding the discipline. Simultaneously, global challenges for development of viable and economical alternative energy resources, on which many researchers in the field focus their efforts, are now the subject of daily news headlines. Enduring themes of this conference relate to photosynthesis, both natural and artificial, and solar energy conversion. More recent developments include molecular electronics, optical switches, and nanoscale charge transport structures of both natural (biological) and man-made origin. The GRC EDAI is one of the major international meetings advancing this field, and is one of the few scientific meetings where fundamental research in solar energy conversion has a leading voice. The program includes sessions on coupled electron transfers, molecular solar energy conversion, biological and biomimetic systems, spin effects, ultrafast reactions and technical frontiers as well as electron transport in single molecules and devices. In addition to disseminating the latest advances in the field of electron transfer processes, the conference is an excellent forum for scientists from different disciplines to meet and initiate new directions; for scientists from different countries to make contacts; for young scientists to network and establish personal contacts with other young scientists and with established scientists who, otherwise, might not have the time to meet young people. The EDAI GRC also features an interactive atmosphere with lively poster sessions, a few of which are selected for oral presentations.

  19. In situ bioremediation of nitrate and perchlorate in vadose zone soil for groundwater protection using gaseous electron donor injection technology.

    PubMed

    Evans, Patrick J; Trute, Mary M

    2006-12-01

    When present in the vadose zone, potentially toxic nitrate and perchlorate anions can be persistent sources of groundwater contamination. Gaseous electron donor injection technology (GEDIT), an anaerobic variation of petroleum hydrocarbon bioventing, involves injecting electron donor gases, such as hydrogen or ethyl acetate, into the vadose zone, to stimulate biodegradation of nitrate and perchlorate. Laboratory microcosm studies demonstrated that hydrogen and ethanol promoted nitrate and perchlorate reduction in vadose zone soil and that moisture content was an important factor. Column studies demonstrated that transport of particular electron donors varied significantly; ethyl acetate and butyraldehyde were transported more rapidly than butyl acetate and ethanol. Nitrate removal in the column studies, up to 100%, was best promoted by ethyl acetate. Up to 39% perchlorate removal was achieved with ethanol and was limited by insufficient incubation time. The results demonstrate that GEDIT is a promising remediation technology warranting further validation.

  20. Effects of donor-acceptor electronic interactions on the rates of gas-phase metallocene electron-exchange reactions

    SciTech Connect

    Phelps, D.K.; Gord, J.R.; Freiser, B.S.; Weaver, M.J. )

    1991-05-30

    Rate constants for electron self-exchange, k{sub ex}, of five cobaltocenium-cobaltocene and ferrocenium-ferrocene couples in the gas phase have been measured by means of Fourier transform ion cyclotron resonance mass spectrometry in order to explore the possible effects of donor-acceptor electronic coupling on gas-phase redox reactivity. The systems studied, Cp{sub 2}Co{sup +/0}, Cp{sub 2}Fe{sup +/0} (Cp = cyclopentadienyl), the decamethyl derivative Cp{prime}{sub 2}Fe{sup +/0}, carboxymethyl(cobaltocenium-cobaltocene) (Cp{sub 2}{sup e}Co{sup +/0}), and hydroxymethyl(ferrocenium-ferrocene) (HMFc{sup +/0}), were selected in view of the substantial variations in electronic coupling inferred on the basis of their solvent-dependent reactivities and theoretical grounds. The sequence of k{sub ex} values determined in the gas phase, Cp{sub 2}{sup e}Co{sup +/0} {approx} Cp{sub 2}Co{sup +/0} > Cp{prime}{sub 2}Fe{sup +/0} > HMFc{sup +/0} > Cp{sub 2}Fe{sup +/0}, is roughly similar to that observed in solution, although the magnitude (up to 5-fold) of the k{sub ex} variations is smaller in the former case. The likely origins of these differences in gas-phase reactivity are discussed in light of the known variations in the electronic coupling matrix element H{sub 12}, inner-shell reorganization energy {Delta}E*, and gas-phase ion-molecule interaction energy {Delta}E{sub w} extracted from solution-phase rates, structural data, and theoretical calculations. It is concluded that the observed variations in gas-phase k{sub ex} values, especially for Cp{sub 2}Fe{sup +/0} versus Cp{sub 2}Co{sup +/0}, arise predominantly from the presence of weaker donor-acceptor orbital overlap for the ferrocene couples, yielding inefficient electron tunneling for a substantial fraction of the gas-phase ion-molecule encounters. The anticipated differences as well as similarities of such nonadiabatic effects for gas-phase and solution electron-transfer processes are briefly outlined.

  1. Diversity and ubiquity of bacteria capable of utilizing humic substances as electron donors for anaerobic respiration.

    PubMed

    Coates, John D; Cole, Kimberly A; Chakraborty, Romy; O'Connor, Susan M; Achenbach, Laurie A

    2002-05-01

    Previous studies have demonstrated that reduced humic substances (HS) can be reoxidized by anaerobic bacteria such as Geobacter, Geothrix, and Wolinella species with a suitable electron acceptor; however, little is known of the importance of this metabolism in the environment. Recently we investigated this metabolism in a diversity of environments including marine and aquatic sediments, forest soils, and drainage ditch soils. Most-probable-number enumeration studies were performed using 2,6-anthrahydroquinone disulfonate (AHDS), an analog for reduced HS, as the electron donor with nitrate as the electron acceptor. Anaerobic organisms capable of utilizing reduced HS as an electron donor were found in all environments tested and ranged from a low of 2.31 x 10(1) in aquifer sediments to a high of 9.33 x 10(6) in lake sediments. As part of this study we isolated six novel organisms capable of anaerobic AHDS oxidation. All of the isolates coupled the oxidation of AHDS to the reduction of nitrate with acetate (0.1 mM) as the carbon source. In the absence of cells, no AHDS oxidation was apparent, and in the absence of AHDS, no cell density increase was observed. Generally, nitrate was reduced to N(2). Analysis of the AHDS and its oxidized form, 2,6-anthraquinone disulfonate (AQDS), in the medium during growth revealed that the anthraquinone was not being biodegraded as a carbon source and was simply being oxidized as an energy source. Determination of the AHDS oxidized and nitrate reduced accounted for 109% of the theoretical electron transfer. In addition to AHDS, all of these isolates could also couple the oxidation of reduced humic substances to the reduction of nitrate. No HS oxidation occurred in the absence of cells and in the absence of a suitable electron acceptor, demonstrating that these organisms were capable of utilizing natural HS as an energy source and that AHDS serves as a suitable analog for studying this metabolism. Alternative electron donors included

  2. An unconventional halogen bond with carbene as an electron donor: An ab initio study

    NASA Astrophysics Data System (ADS)

    Li, Qingzhong; Wang, Yilei; Liu, Zhenbo; Li, Wenzuo; Cheng, Jianbo; Gong, Baoan; Sun, Jiazhong

    2009-02-01

    An unconventional halogen bond has been proved to exist in H2C-BrH complex. The halogen bond energy of H2C-BrH complex is calculated at four levels of theory [MP2, MP4, CCSD, and CCSD(T)]. The result shows that the carbene is a better electron donor. The substitution effect is prominent in this interaction. For example, the interaction energy in H2C-BrCN complex is increased by more than 300% relative to H2C-BrH complex. The analyses of NBO, AIM, and energy components were used to unveil the nature of the interaction. The results show that this novel halogen bond has similar characteristics to hydrogen bonds.

  3. Stibinidene and Bismuthinidene as Two-Electron Donors for Transition Metals (Co and Mn).

    PubMed

    Vránová, Iva; Alonso, Mercedes; Jambor, Roman; Růžička, Aleš; Erben, Milan; Dostál, Libor

    2016-05-23

    The reaction of stibinidene and bismuthinidene ArM [where Ar=C6 H3 -2,6-(CH=NtBu)2 ; M=Sb (1), Bi (2)] with transition metal (TM) carbonyls Co2 (CO)8 and Mn2 (CO)10 produced unprecedented ionic complexes [(ArM)2 Co(CO)3 ](+) [Co(CO)4 ](-) and [(ArM)2 Mn(CO)4 ](+) [Mn(CO)5 ](-) [where M=Sb (3, 5), Bi (4, 6)]. The pnictinidenes 1 and 2 behaved as two-electron donors in this set of compounds. Besides the M→TM bonds, the topological analysis also revealed a number of secondary interactions contributing to the stabilization of cationic parts of titled complexes.

  4. Photoinduced biphasic hydrogen evolution: decamethylosmocene as a light-driven electron donor.

    PubMed

    Ge, Peiyu; Olaya, Astrid J; Scanlon, Micheál D; Hatay Patir, Imren; Vrubel, Heron; Girault, Hubert H

    2013-07-22

    Excitation of the weak electron donor decamethylosmocene on illumination with white light produces an excited-state species capable of reducing organically solubilized protons under biphasic conditions. Insight into the mechanism and kinetics of light-driven biphasic hydrogen evolution are obtained by analysis with gas chromatography, cyclic voltammetry, and UV/Vis and (1)H NMR spectroscopy. Formation of decamethylosmocenium hydride, which occurs prior to hydrogen evolution, is a rapid step relative to hydrogen release and takes place independently of light activation. Remarkably, hydride formation occurs with greater efficiency (ca. 90% conversion) under biphasic conditions than when the reaction is carried out in an acidified single organic phase (ca. 20% conversion). Cyclic voltammetry studies reveal that decamethylosmocene has a higher proton affinity than either decamethylferrocene or osmocene.

  5. Chloroboron (III) subnaphthalocyanine as an electron donor in bulk heterojunction photovoltaic cells.

    PubMed

    Chen, Guo; Sasabe, Hisahiro; Sano, Takeshi; Wang, Xiao-Feng; Hong, Ziruo; Kido, Junji; Yang, Yang

    2013-12-06

    In this work, chloroboron (III) subnaphthalocyanine (SubNc) was used as an electron donor, combined with a [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) or fullerene C70 acceptor in bulk heterojunction photovoltaic cells. In spite of the limited solubility of SubNc in organic solvents, the solution processed device exhibited an efficiency of 4.0% under 1 sun, AM1.5G solar irradiation at room temperature, and 5.0% at 80 ° C due to the temperature-dependence of the carrier mobilities. SubNc:C70 bulk heterojunctions were also fabricated via thermal co-evaporation, demonstrating an efficiency of 4.4%. This result shows that SubNc is a promising material for photovoltaic applications via various processing techniques, such as vacuum deposition and wet coating.

  6. Type IV pili of Acidithiobacillus ferrooxidans can transfer electrons from extracellular electron donors.

    PubMed

    Li, Yongquan; Li, Hongyu

    2014-03-01

    Studies on Acidithiobacillus ferrooxidans accepting electrons from Fe(II) have previously focused on cytochrome c. However, we have discovered that, besides cytochrome c, type IV pili (Tfp) can transfer electrons. Here, we report conduction by Tfp of A. ferrooxidans analyzed with a conducting-probe atomic force microscope (AFM). The results indicate that the Tfp of A. ferrooxidans are highly conductive. The genome sequence of A. ferrooxidans ATCC 23270 contains two genes, pilV and pilW, which code for pilin domain proteins with the conserved amino acids characteristic of Tfp. Multiple alignment analysis of the PilV and PilW (pilin) proteins indicated that pilV is the adhesin gene while pilW codes for the major protein element of Tfp. The likely function of Tfp is to complete the circuit between the cell surface and Fe(II) oxides. These results indicate that Tfp of A. ferrooxidans might serve as biological nanowires transferring electrons from the surface of Fe(II) oxides to the cell surface.

  7. Electronic structure and spatial distribution of the spin density of shallow nitrogen donors in the SiC lattice

    NASA Astrophysics Data System (ADS)

    Muzafarova, M. V.; Il'in, I. V.; Anisimov, A. N.; Mokhov, E. N.; Soltamov, V. A.; Baranov, P. G.

    2016-12-01

    The discovery of unique magnetooptical properties of paramagnetic centers in silicon carbide, which make it possible to control spins of small arrays of centers of atomic sizes to single centers at room temperatures, using the techniques of optical detection of the magnetic resonance, posed a number of problems, among which one of the main ones is the creation of conditions under which spin relaxation effects are minimized. As studies of properties of spin nitrogen-vacancy centers in diamond showed, the main contribution to spin relaxation is made by the interaction with nitrogen donors, being a major impurity in diamond. A similar problem exists for silicon carbide, since nitrogen donors are also basic background impurities. The objective of this work is to study the spatial distribution of the spin density of nitrogen donors in two basic silicon carbide polytypes, i.e., 4 H-SiC and 6 H-SiC, to use this information for minimizing the interaction of nitrogen donors with paramagnetic centers in silicon carbide. The results of the study are analyzed by magnetic resonance methods; the spin density distribution on the nearest coordination spheres of nitrogen donors occupying carbon sites in silicon carbide is determined. It is concluded that paramagnetic centers in the 4 H-SiC polytype, including silicon vacancies, can be more stable to the interactions with unpaired donor electrons, since electrons are not localized on the coordination sphere closest to the paramagnetic center in this case.

  8. The influence of the nature of an electron donor solvent on the solvation state of tert-butyl-substituted dibenzenediisoindol macroring according to the NMR data

    NASA Astrophysics Data System (ADS)

    Aleksandriiskii, V. V.; Islyaikin, M. K.; Burmistrov, V. A.

    2007-11-01

    The influence of the nature of electron donors on the conformational and solvation state of a symmetrical tert-butyl-substituted macroheterocyclic compound was studied in binary mixtures containing electron donor solvating solvents and tetrachloromethane by 1H NMR spectroscopy and semiempirical quantum-chemical methods. The structure of H-complexes was determined. The macroring was found to selectively bind electron donors containing carbonyl and thiocarbonyl groups.

  9. Donor ionization in size controlled silicon nanocrystals: The transition from defect passivation to free electron generation

    NASA Astrophysics Data System (ADS)

    Crowe, I. F.; Papachristodoulou, N.; Halsall, M. P.; Hylton, N. P.; Hulko, O.; Knights, A. P.; Yang, P.; Gwilliam, R. M.; Shah, M.; Kenyon, A. J.

    2013-01-01

    We studied the photoluminescence spectra of silicon and phosphorus co-implanted silica thin films on (100) silicon substrates as a function of isothermal annealing time. The rapid phase segregation, formation, and growth dynamics of intrinsic silicon nanocrystals are observed, in the first 600 s of rapid thermal processing, using dark field mode X-TEM. For short annealing times, when the nanocrystal size distribution exhibits a relatively small mean diameter, formation in the presence of phosphorus yields an increase in the luminescence intensity and a blue shift in the emission peak compared with intrinsic nanocrystals. As the mean size increases with annealing time, this enhancement rapidly diminishes and the peak energy shifts further to the red than the intrinsic nanocrystals. These results indicate the existence of competing pathways for the donor electron, which depends strongly on the nanocrystal size. In samples containing a large density of relatively small nanocrystals, the tendency of phosphorus to accumulate at the nanocrystal-oxide interface means that ionization results in a passivation of dangling bond (Pb-centre) type defects, through a charge compensation mechanism. As the size distribution evolves with isothermal annealing, the density of large nanocrystals increases at the expense of smaller nanocrystals, through an Ostwald ripening mechanism, and the majority of phosphorus atoms occupy substitutional lattice sites within the nanocrystals. As a consequence of the smaller band-gap, ionization of phosphorus donors at these sites increases the free carrier concentration and opens up an efficient, non-radiative de-excitation route for photo-generated electrons via Auger recombination. This effect is exacerbated by an enhanced diffusion in phosphorus doped glasses, which accelerates silicon nanocrystal growth.

  10. Temporal transcriptomic analyses of Desulfovibrio vulgarisHildenborough during electron donor depletion

    SciTech Connect

    Clark, M.E.; He, Q.; He, Z.; Alm, E.; Huang, K.; Hazen, T.C.; Arkin, A.P.; Wall, J.D.; Zhou, J.; Fields, M.W.

    2006-05-20

    Desulfovibrio vulgaris was cultivated in a defined mediumand biomass was sampled over time for approximately 70 h to characterizethe shifts in gene expression as cells transitioned from exponential tostationary phase during electron donor depletion. In addition to temporaltranscriptomics; total protein, carbohydrate, lactate, acetate, andsulfate levels were measured. The microarray data were analyzed forstatistically significant expression changes, hierarchical clusteranalysis, and promoter element prediction, and were validated viaquantitative PCR. As the cells transitioned from exponential tostationary-phase a majority of the down-expressed genes were involved intranslation and transcription, and this trend continued in the remainingtime points. Intracellular trafficking and secretion, ion transport, andcoenzyme metabolism showed a general increase in relative expression asthe cells entered stationary phase. As expected, DNA replicationmachinery was down expressed, and genes involved in DNA repair increasedin expression during stationary-phase. Genes involved in amino acidacquisition, carbohydrate metabolism, energy production, and cellenvelope biogenesis did not exhibit uniform transcriptional responses.Interestingly, most phage-related genes were up-expressed at the onset ofstationary-phase. This result suggested that nutrient depletion mayimpact community dynamics and DNA transfer mechanisms of sulfate-reducingbacteria via phage cycle. The putative feoAB system (in addition to otherpresumptive iron metabolism genes) was significantly up-expressed, andsuggested the possible importance of Fe2+ acquisition undermetal-reducing conditions. A large subset of carbohydrate-related geneshad altered gene expression, and the total cellular carbohydrate levelsdeclined during the growth phase transition. Interestingly, the D.vulgaris genome does not contain a putative rpoS gene, a common attributeof the d-Proteobacteria genomes sequenced to date, and other putative

  11. Boron as an Electron-Pair Donor for B⋅⋅⋅Cl Halogen Bonds.

    PubMed

    Alkorta, Ibon; Elguero, José; Del Bene, Janet E

    2016-10-05

    MP2/aug'-cc-pVTZ calculations were performed to investigate boron as an electron-pair donor in halogen-bonded complexes (CO)2 (HB):ClX and (N2 )2 (HB):ClX, for X=F, Cl, OH, NC, CN, CCH, CH3 , and H. Equilibrium halogen-bonded complexes with boron as the electron-pair donor are found on all of the potential surfaces, except for (CO)2 (HB):ClCH3 and (N2 )2 (HB):ClF. The majority of these complexes are stabilized by traditional halogen bonds, except for (CO)2 (HB):ClF, (CO)2 (HB):ClCl, (N2 )2 (HB):ClCl, and (N2 )2 (HB):ClOH, which are stabilized by chlorine-shared halogen bonds. These complexes have increased binding energies and shorter B-Cl distances. Charge transfer stabilizes all complexes and occurs from the B lone pair to the σ* Cl-A orbital of ClX, in which A is the atom of X directly bonded to Cl. A second reduced charge-transfer interaction occurs in (CO)2 (HB):ClX complexes from the Cl lone pair to the π* C≡O orbitals. Equation-of-motion coupled cluster singles and doubles (EOM-CCSD) spin-spin coupling constants, (1x) J(B-Cl), across the halogen bonds are also indicative of the changing nature of this bond. (1x) J(B-Cl) values for both series of complexes are positive at long distances, increase as the distance decreases, and then decrease as the halogen bonds change from traditional to chlorine-shared bonds, and begin to approach the values for the covalent bonds in the corresponding ions [(CO)2 (HB)-Cl](+) and [(N2 )2 (HB)-Cl](+) . Changes in (11) B chemical shieldings upon complexation correlate with changes in the charges on B.

  12. Phenothiazine-Anthraquinone Donor-Acceptor Molecules: Synthesis, Electronic Properties and DFT-TDDFT Computational Study

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-Wei; Mao, Wei-Li; Hu, Yun-Xia; Tian, Zi-Qi; Wang, Zhi-Lin; Meng, Qing-Jin

    2009-08-01

    Two donor-acceptor molecules with different π-electron conjugative units, 1-((10-methyl-10H-phenothiazin-3-yl)ethynyl)anthracene-9,10-dione (AqMp) and 1,1'-(10-methyl-10H-phenothiazine-3,7-diyl)bis(ethyne-2,1-diyl)dianthracene-9,10-dione (Aq2Mp), have been synthesized and investigated for their photochemical and electrochemical properties. Density functional theory (DFT) calculations provide insights into their molecular geometry, electronic structures, and properties. These studies satisfactorily explain the electrochemistry of the two compounds and indicate that larger conjugative effect leads to smaller HOMO-LUMO gap (Eg) in Aq2Mp. Both compounds show ICT and π → π* transitions in the UV-visible range in solution, and Aq2Mp has a bathochromic shift and shows higher oscillator strength of the absorption, which has been verified by time-dependent DFT (TDDFT) calculations. The differences between AqMp and Aq2Mp indicate that the structural and conjugative effects have great influence on the electronic properties of the molecules.

  13. Denitrification potential in stream sediments impacted by acid mine drainage: Effects of pH, various electron donors, and iron

    USGS Publications Warehouse

    Baeseman, J.L.; Smith, R.L.; Silverstein, J.

    2006-01-01

    Acid mine drainage (AMD) contaminates thousands of kilometers of stream in the western United States. At the same time, nitrogen loading to many mountain watersheds is increasing because of atmospheric deposition of nitrate and increased human use. Relatively little is known about nitrogen cycling in acidic, heavy-metal-laden streams; however, it has been reported that one key process, denitrification, is inhibited under low pH conditions. The objective of this research was to investigate the capacity for denitrification in acidified streams. Denitrification potential was assessed in sediments from several Colorado AMD-impacted streams, ranging from pH 2.60 to 4.54, using microcosm incubations with fresh sediment. Added nitrate was immediately reduced to nitrogen gas without a lag period, indicating that denitrification enzymes were expressed and functional in these systems. First-order denitrification potential rate constants varied from 0.046 to 2.964 day-1. The pH of the microcosm water increased between 0.23 and 1.49 pH units during denitrification. Additional microcosm studies were conducted to examine the effects of initial pH, various electron donors, and iron (added as ferrous and ferric iron). Decreasing initial pH decreased denitrification; however, increasing pH had little effect on denitrification rates. The addition of ferric and ferrous iron decreased observed denitrification potential rate constants. The addition of glucose and natural organic matter stimulated denitrification potential. The addition of hydrogen had little effect, however, and denitrification activity in the microcosms decreased after acetate addition. These results suggest that denitrification can occur in AMD streams, and if stimulated within the environment, denitrification might reduce acidity. ?? Springer Science+Business Media, Inc. 2006.

  14. Mobility relaxation and electron trapping in a donor/acceptor copolymer

    NASA Astrophysics Data System (ADS)

    Schubert, Marcel; Preis, Eduard; Blakesley, James C.; Pingel, Patrick; Scherf, Ullrich; Neher, Dieter

    2013-01-01

    To address the nature of charge transport and the origin of severe (intrinsic) trapping in electron-transporting polymers, transient and steady-state charge transport measurements have been conducted on the prototype donor/acceptor copolymer poly[2,7-(9,9-dialkyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PFTBTT). A charge-generation layer technique is used to selectively address transport of the desired charge carrier type, to perform time-of-flight measurements on samples with <200 nm thickness, and to combine the time-of-flight and the photocharge extraction by linearly increasing voltage (photo-CELIV) techniques to investigate charge carrier dynamics over a wide time range. Significant trapping of free electrons is observed in the bulk of dioctyl-substituted PFTBTT (alt-PF8TBTT), introducing a strong relaxation of the charge carrier mobility with time. We used Monte-Carlo simulation to simulate the measured transient data and found that all measurements can be modeled with a single parameter set, with the charge transport behavior determined by multiple trapping and detrapping of electrons in an exponential trap distribution. The influence of the concomitant mobility relaxation on the transient photocurrent characteristics in photo-CELIV experiments is discussed and shown to explain subtle features that were seen in former publications but were not yet assigned to electron trapping. Comparable studies on PFTBTT copolymers with chemical modifications of the side chains and backbone suggest that the observed electron trapping is not caused by a distinct chemical species but rather is related to interchain interactions.

  15. The Nature of the Donor Motif in Acceptor-Bridge-Donor Dyes as an Influence in the Electron Photo-Injection Mechanism in DSSCs.

    PubMed

    Zarate, Ximena; Schott-Verdugo, Stephan; Rodriguez-Serrano, Angela; Schott, Eduardo

    2016-03-10

    The combination and balance of acceptor(A)-bridge-donor(D) architecture of molecules confer suitable attributes and/or properties to act as efficient light-harvesting and sensitizers in dye sensitized solar cells (DSSCs). An important process in a DSSC performance is the electron photoinjection (PI) mechanism which can take place either via type I (indirect), that consists in injecting from the excited state of the dye to the semiconductor, or type II (direct), where the PI is from the ground state of the dye to the semiconductor upon photoexcitation. Here, we present a computational study about the role of the donor motif in the PI mechanisms displayed from a family of 11 A-bridge-D structured dyes to a (TiO2)15 anatase cluster. To this end, different donor motifs (D1-D11) were evaluated while the A and bridge motifs remained the same. All the computations were carried out within the DFT framework, using the B3LYP, PW91, PBE, M06L and CAM-B3LYP functionals. The 6-31G(d) basis set was employed for nonmetallic atoms and the LANL2DZ pseudopotential for Ti atoms. The solvation effects were incorporated using the polarized continuum model (PCM) for acetonitrile. As benchmark systems, alizarin and naphthalenediol dyes were analyzed, as they are known to undergo Type I and Type II PI pathways in DSSCs, respectively. Donors in the studied family of dyes could influence to drive Type I or II PI since it was found that D2 could show some Type II PI route, showing a new absorption band, although with CAM-B3LYP this shows a very low oscillator strength, while the remaining dyes behave according to Type I photoinjectors. Finally, the photovoltaic parameters that govern the light absorption process were evaluated, as the use of these criteria could be applied to predict the efficiency of the studied dyes in DSSCs devices.

  16. Charge separation distance for flexible donor-bridge-acceptor systems after electron-transfer quenching.

    PubMed

    Zhou, Jinwei; Lukin, Leonid V; Braun, Charles L

    2008-08-21

    Photoinduced transient dipole experiments are used to measure the effective charge separation distance, which is equivalent to the photoinduced change in dipole moment divided by the electron charge of flexible electron-donor/acceptor systems, D-(CH2)n-A, where D is 4- N,N-dimethylaniline, A is 9-anthryl, and n = 3, 4. We find that the dipole moments increase strongly with solvent polarity. For the compound with n = 4 (DBA4), analysis of dipole signals indicates that the effective charge separation distances in toluene, 1,4-dioxane, ethyl acetate, tetrahydrofuran, dichloromethane, 1,2-dichloroethane, 2-methylpentanone-3, 3-pentanone, and benzonitrile are 2.2, 2.5, 4.5, 4.7, 5.5, 5.5, 4.8, and 6.3 A, respectively. These values can be understood as the root-mean-square charge separation distance in the solutions of different solvents. We assume that the folded contact configuration has a separation distance of 3.5 A, the extended, solvent-separated configuration has a separation distance of 8.0 A, and that they are the only two stable species after electron-transfer quenching. The formation efficiencies of contact radical ion pairs (CRIPs) and solvent-separated radical ion pairs (SSRIPs) are estimated in different solvents. The results indicate that a significant fraction of the ion pairs exist as solvent-separated ion pairs when the dielectric constant of the solvent is larger than 10. These results indicate that electron-transfer quenching can indeed happen at large separations in polar solvents. They also reveal that there is a barrier for ion pairs formed at large separations, hindering collapse to a contact separation of around 3.5 A.

  17. Reductive dechlorination of trichloroethene DNAPL source zones: source zone architecture versus electron donor availability

    NASA Astrophysics Data System (ADS)

    Krol, M.; Kokkinaki, A.; Sleep, B.

    2014-12-01

    The persistence of dense-non-aqueous-phase liquids (DNAPLs) in the subsurface has led practitioners and regulatory agencies to turn towards low-maintenance, low-cost remediation methods. Biological degradation has been suggested as a possible solution, based on the well-proven ability of certain microbial species to break down dissolved chlorinated ethenes under favorable conditions. However, the biodegradation of pure phase chlorinated ethenes is subject to additional constraints: the continuous release of electron acceptor at a rate governed by mass transfer kinetics, and the temporal and spatial heterogeneity of DNAPL source zones which leads to spatially and temporally variable availability of the reactants for reductive dechlorination. In this work, we investigate the relationship between various DNAPL source zone characteristics and reaction kinetics using COMPSIM, a multiphase groundwater model that considers non-equilibrium mass transfer and Monod-type kinetics for reductive dechlorination. Numerical simulations are performed for simple, homogeneous trichloroethene DNAPL source zones to demonstrate the effect of single source zone characteristics, as well as for larger, more realistic heterogeneous source zones. It is shown that source zone size, and mass transfer kinetics may have a decisive effect on the predicted bio-enhancement. Finally, we evaluate the performance of DNAPL bioremediation for realistic, thermodynamically constrained, concentrations of electron donor. Our results indicate that the latter may be the most important limitation for the success of DNAPL bioremediation, leading to reduced bio-enhancement and, in many cases, comparable performance with water flooding.

  18. Longitudinal spin relaxation of donor-bound electrons in direct band-gap semiconductors

    NASA Astrophysics Data System (ADS)

    Linpeng, Xiayu; Karin, Todd; Durnev, M. V.; Barbour, Russell; Glazov, M. M.; Sherman, E. Ya.; Watkins, S. P.; Seto, Satoru; Fu, Kai-Mei C.

    2016-09-01

    We measure the donor-bound electron longitudinal spin-relaxation time (T1) as a function of magnetic field (B ) in three high-purity direct band-gap semiconductors: GaAs, InP, and CdTe, observing a maximum T1 of 1.4, 0.4, and 1.2 ms, respectively. In GaAs and InP at low magnetic field, up to ˜2 T, the spin-relaxation mechanism is strongly density and temperature dependent and is attributed to the random precession of the electron spin in hyperfine fields caused by the lattice nuclear spins. In all three semiconductors at high magnetic field, we observe a power-law dependence T1∝B-ν with 3 ≲ν ≲4 . Our theory predicts that the direct spin-phonon interaction is important in all three materials in this regime in contrast to quantum dot structures. In addition, the "admixture" mechanism caused by Dresselhaus spin-orbit coupling combined with single-phonon processes has a comparable contribution in GaAs. We find excellent agreement between high-field theory and experiment for GaAs and CdTe with no free parameters, however a significant discrepancy exists for InP.

  19. Electron donors supporting growth and electroactivity of Geobacter sulfurreducens anode biofilms.

    PubMed

    Speers, Allison M; Reguera, Gemma

    2012-01-01

    Geobacter bacteria efficiently oxidize acetate into electricity in bioelectrochemical systems, yet the range of fermentation products that support the growth of anode biofilms and electricity production has not been thoroughly investigated. Here, we show that Geobacter sulfurreducens oxidized formate and lactate with electrodes and Fe(III) as terminal electron acceptors, though with reduced efficiency compared to acetate. The structure of the formate and lactate biofilms increased in roughness, and the substratum coverage decreased, to alleviate the metabolic constraints derived from the assimilation of carbon from the substrates. Low levels of acetate promoted formate carbon assimilation and biofilm growth and increased the system's performance to levels comparable to those with acetate only. Lactate carbon assimilation also limited biofilm growth and led to the partial oxidization of lactate to acetate. However, lactate was fully oxidized in the presence of fumarate, which redirected carbon fluxes into the tricarboxylic acid (TCA) cycle, and by acetate-grown biofilms. These results expand the known ranges of electron donors for Geobacter-driven fuel cells and identify microbial constraints that can be targeted to develop better-performing strains and increase the performance of bioelectrochemical systems.

  20. Alcohol production through volatile fatty acids reduction with hydrogen as electron donor by mixed cultures.

    PubMed

    Steinbusch, Kirsten J J; Hamelers, Hubertus V M; Buisman, Cees J N

    2008-09-01

    In this research we demonstrated a new method to produce alcohols. It was experimentally feasible to produce ethanol, propanol and butanol from solely volatile fatty acids (VFAs) with hydrogen as electron donor. In batch tests, VFAs such as acetic, propionic and butyric acids were reduced by mixed microbial cultures with a headspace of 1.5 bar of hydrogen. Observed alcohol concentrations were 3.69+/-0.25 mM of ethanol, 8.08+/-0.85 mM of propanol and 3.66+/-0.05 mM of n-butanol. The conversion efficiency based on the electron balance was 55.1+/-5.6% with acetate as substrate, 50.3+/-4.7% with propionate and 46.7+/-2.2% with n-butyrate. Methane was the most predominant by-product in each batch experiment, 33.6+/-9.6% of VFA and hydrogen was converted to methane with acetate as substrate; which was 27.1+/-7.1% with propionate and 36.6+/-2.2% with n-butyrate. This VFAs reducing renewable fuel production process does not require carbohydrates like fermentable sugars, but uses biomass with high water content or low sugar content that is unsuitable as feedstock for current fermentation processes. This so-called low-grade biomass is abundantly present in many agricultural areas and is economically very attractive feedstock for the production of biofuels.

  1. Hydrogen, acetate, and lactate as electron donors for microbial manganese reduction in a manganese-rich coastal marine sediment.

    PubMed

    Vandieken, Verona; Finke, Niko; Thamdrup, Bo

    2014-03-01

    The role of hydrogen, acetate, and lactate as electron donors for microbial manganese reduction was investigated in manganese-rich marine sediment from Gullmar Fjord (Sweden). Here, manganese reduction accounted for 50% of the anaerobic carbon oxidation at 0-15 cm sediment depth. In anoxic incubations from 0 to 5 cm depth, where manganese reduction dominated completely as terminal electron-accepting process, the combined contribution of acetate and lactate as electron donors for manganese reducers corresponded to < ¼ of the electron flow. The concentrations, ¹⁴C-radiotracer turnover rates, and contributions to carbon oxidation of acetate and lactate associated with manganese reduction were similar to those found in deeper horizons dominated by concomitant iron and sulfate reduction and sulfate reduction alone, respectively. By contrast, hydrogen concentrations increased considerably with sediment depth, indicating thermodynamic control of the competition between the electron-accepting processes, and hydrogen may have contributed substantially to the > 75% of the electron flow that did not involve acetate and lactate. Alternatively, the oxidation of more complex organic substrates could be involved. Our study provides the first direct evidence of substrate utilization by a natural manganese-reducing community and indicates similar mechanisms of thermodynamic control and competition for electron donors as known from sediments dominated by iron reduction, sulfate reduction, or methanogenesis.

  2. Self-assembly properties of semiconducting donor-acceptor-donor bithienyl derivatives of tetrazine and thiadiazole-effect of the electron accepting central ring.

    PubMed

    Zapala, Joanna; Knor, Marek; Jaroch, Tomasz; Maranda-Niedbala, Agnieszka; Kurach, Ewa; Kotwica, Kamil; Nowakowski, Robert; Djurado, David; Pecaut, Jacques; Zagorska, Malgorzata; Pron, Adam

    2013-11-26

    Scanning tunneling microscopy was used to study the effect of the electron-accepting unit and the alkyl substituent's position on the type and extent of 2D supramolecular organization of penta-ring donor-acceptor-donor (DAD) semiconductors, consisting of either tetrazine or thiadiazole central acceptor ring symmetrically attached to two bithienyl groups. Microscopic observations of monomolecular layers on HOPG of four alkyl derivatives of the studied adsorbates indicate significant differences in their 2D organizations. Ordered monolayers of thiadiazole derivatives are relatively loose and, independent of the position of alkyl substituents, characterized by large intermolecular separation of acceptor units in the adjacent molecules located in the face-to-face configuration. The 2D supramolecular architecture in both derivatives of thiadiazole is very sensitive to the alkyl substituent's position. Significantly different behavior is observed for derivatives of tetrazine (which is a stronger electron acceptor). Stronger intermolecular DA interactions in these adsorbates generate an intermolecular shift in the monolayer, which is a dominant factor determining the 2D structural organization. As a consequence of this molecular arrangement, tetrazine groups (A segments) face thiophene rings (D segments) of the neighboring molecules. Monolayers of tetrazine derivatives are therefore much more densely packed and characterized by similar π-stacking of molecules independently of the position of alkyl substituents. Moreover, a comparative study of 3D supramolecular organization, deduced from the X-ray diffraction patterns, is also presented clearly confirming the polymorphism of the studied adsorbates.

  3. Electron donor-dependent radionuclide reduction and nanoparticle formation by Anaeromyxobacter dehalogenans strain 2CP-C.

    SciTech Connect

    Marshall, Matthew J.; Dohnalkova, Alice; Kennedy, David W.; Plymale, Andrew E.; Thomas, Sara H.; Loffler, F. E.; Sanford, Robert; Zachara, John M.; Fredrickson, Jim K.; Beliaev, Alex S.

    2009-01-15

    Anaeromyxobacter dehalogenans strain 2CP-C can rapidly reduce U(VI) or Tc(VII) to U(IV)O2(s) or Tc(IV)O2(S) using either acetate or H2 as an electron donor source. Kinetic studies reveal that the H2-driven reduction of either U(VI) or Tc(VII) is faster than the acetate-driven reduction. The sub-cellular localization of reduced UO2 is extracellular while TcO2 nanoparticles are both periplasmic and extracellular. While electron donor-specific differences in UO2 nanoparticle aggregate size were observed, the association of UO2 nanoparticles with an exopolymeric substance (EPS) was observed and found to be independent of electron donor source. Electron donor-specific localization differences were not observed in cells incubated with Tc(VII). These finding have direct implications on immobilization strategies for highly soluble radionuclide contaminants in subsurface waters and the development of microbially assisted biostimulation efforts.

  4. Probing the donor side of photosystem II in spinach chloroplasts and algae using electron paramagnetic resonance

    SciTech Connect

    Boska, M.D.

    1985-11-01

    this work concerns electron transfer reactions in photosystem II (PS II). Investigations carried out in this work examine the redox reaction rates in PS II using EPR. In Tris-washed PS II preparations from spinach, it is observed that the oxidation kinetics of S II/sub f/, the EPR signal formed by Z/sup +/ after deactivation of oxygen evolution, mirror the reduction kinetics of P680/sup +/ seen by EPR in samples poised at a variety of pH's. These data agree with previous data on the optically measured reduction kinetics of P680/sup +/. The oxidation kinetics of S II/sub vf/, the EPR transient seen from Z/sup +/ in samples active in O/sub 2/ evolving samples, were instrument limited (t/sub 1/2/ less than 4 ..mu..s) and thus could not be directly measured. These results taken together support a model where Z donates electrons directly to P680/sup +/. The examination of the oxidation and reduction kinetics of S II in monovalent and divalent salt-washed PS II preparations from spinach correlated most of the change of Z oxidation and re-reduction kinetics seen upon Tris-treatment with the loss of a 33 kDa polypeptide associated with the donor side of PS II. These data coupled with observations of stead-state light-induced amplitude changes in S II give evidence for the existance of an electron carrier between the water-splitting enzyme and Z. Observation of S II amplitude and kinetics in highly resolved PS II protein complexes from Synechoccus sp., consisting of either a 5 polypeptide PS II core complex (E-1) or a 4 polypeptide PS II core complex (CP2b), localize Z and P680 within the 4 polypeptide complex. 187 refs., 17 figs., 7 tabs.

  5. Temporal transcriptomic analysis as Desulfovibrio vulgaris Hildenborough transitions into stationary phase during electron donor depletion.

    PubMed

    Clark, M E; He, Q; He, Z; Huang, K H; Alm, E J; Wan, X-F; Hazen, T C; Arkin, A P; Wall, J D; Zhou, J-Z; Fields, M W

    2006-08-01

    Desulfovibrio vulgaris was cultivated in a defined medium, and biomass was sampled for approximately 70 h to characterize the shifts in gene expression as cells transitioned from the exponential to the stationary phase during electron donor depletion. In addition to temporal transcriptomics, total protein, carbohydrate, lactate, acetate, and sulfate levels were measured. The microarray data were examined for statistically significant expression changes, hierarchical cluster analysis, and promoter element prediction and were validated by quantitative PCR. As the cells transitioned from the exponential phase to the stationary phase, a majority of the down-expressed genes were involved in translation and transcription, and this trend continued at the remaining times. There were general increases in relative expression for intracellular trafficking and secretion, ion transport, and coenzyme metabolism as the cells entered the stationary phase. As expected, the DNA replication machinery was down-expressed, and the expression of genes involved in DNA repair increased during the stationary phase. Genes involved in amino acid acquisition, carbohydrate metabolism, energy production, and cell envelope biogenesis did not exhibit uniform transcriptional responses. Interestingly, most phage-related genes were up-expressed at the onset of the stationary phase. This result suggested that nutrient depletion may affect community dynamics and DNA transfer mechanisms of sulfate-reducing bacteria via the phage cycle. The putative feoAB system (in addition to other presumptive iron metabolism genes) was significantly up-expressed, and this suggested the possible importance of Fe2+ acquisition under metal-reducing conditions. The expression of a large subset of carbohydrate-related genes was altered, and the total cellular carbohydrate levels declined during the growth phase transition. Interestingly, the D. vulgaris genome does not contain a putative rpoS gene, a common attribute of

  6. Liquid-liquid mass transfer of partitioning electron donors in chlorinated solvent source zones.

    PubMed

    Cápiro, Natalie L; Granbery, Emmie K; Lebrón, Carmen A; Major, David W; McMaster, Michaye L; Pound, Michael J; Löffler, Frank E; Pennell, Kurt D

    2011-02-15

    A combination of batch and column experiments evaluated the mass transfer of two candidate partitioning electron donors (PEDs), n-hexanol (nHex) and n-butyl acetate (nBA), for enhanced bioremediation of trichloroethene (TCE)-dense nonaqueous phase liquid (DNAPL). Completely mixed batch reactor experiments yielded equilibrium TCE-DNAPL and water partition coefficients (KNW) for nHex and nBA of 21.7 ± 0.27 and 330.43 ± 6.7, respectively, over a range of initial PED concentrations up to the aqueous solubility limit of ca. 5000 mg/L. First-order liquid-liquid mass transfer rates determined in batch reactors with nBA or nHex concentrations near the aqueous solubility were 0.22 min(-1) and 0.11 min(-1), respectively. Liquid-liquid mass transfer under dynamic flow conditions was assessed in one-dimensional (1-D) abiotic columns packed with Federal Fine Ottawa sand containing a uniform distribution of residual TCE-DNAPL. Following pulse injection of PED solutions at pore-water velocities (vp) ranging from 1.2 to 6.0 m/day, effluent concentration measurements demonstrated that both nHex and nBA partitioned strongly into residual TCE-DNAPL with maximum effluent levels not exceeding 35% and 7%, respectively, of the applied concentrations of 4000 to 5000 mg/L. PEDs persisted at effluent concentrations above 5 mg/L for up to 16 and 80 pore volumes for nHex and nBA, respectively. Mathematical simulations yielded KNW values ranging from 44.7 to 48.2 and 247 to 291 and liquid-liquid mass transfer rates of 0.01 to 0.03 min(-1) and 0.001 to 0.006 min(-1) for nHex and nBA, respectively. The observed TCE-DNAPL and water mass transfer behavior suggests that a single PED injection can persist in a treated source zone for prolonged time periods, thereby reducing the need for, or frequency of, repeated electron donor injections to support bacteria that derive reducing equivalents for TCE reductive dechlorination from PED fermentation.

  7. Fragment charge difference method for estimating donor-acceptor electronic coupling: Application to DNA π-stacks

    NASA Astrophysics Data System (ADS)

    Voityuk, Alexander A.; Rösch, Notker

    2002-09-01

    The purpose of this communication is two-fold. We introduce the fragment charge difference (FCD) method to estimate the electron transfer matrix element HDA between a donor D and an acceptor A, and we apply this method to several aspects of hole transfer electronic couplings in π-stacks of DNA, including systems with several donor-acceptor sites. Within the two-state model, our scheme can be simplified to recover a convenient estimate of the electron transfer matrix element HDA=(1-Δq2)1/2(E2-E1)/2 based on the vertical excitation energy E2-E1 and the charge difference Δq between donor and acceptor. For systems with strong charge separation, Δq≳0.95, one should resort to the FCD method. As favorable feature, we demonstrate the stability of the FCD approach for systems which require an approach beyond the two-state model. On the basis of ab initio calculations of various DNA related systems, we compared three approaches for estimating the electronic coupling: the minimum splitting method, the generalized Mulliken-Hush (GMH) scheme, and the FCD approach. We studied the sensitivity of FCD and GMH couplings to the donor-acceptor energy gap and found both schemes to be quite robust; they are applicable also in cases where donor and acceptor states are off resonance. In the application to π-stacks of DNA, we demonstrated for the Watson-Crick pair dimer [(GC),(GC)] how structural changes considerably affect the coupling strength of electron hole transfer. For models of three Watson-Crick pairs, we showed that the two-state model significantly overestimates the hole transfer coupling whereas simultaneous treatment of several states leads to satisfactory results.

  8. Remarkable Dependence of the Final Charge Separation Efficiency on the Donor-Acceptor Interaction in Photoinduced Electron Transfer.

    PubMed

    Higashino, Tomohiro; Yamada, Tomoki; Yamamoto, Masanori; Furube, Akihiro; Tkachenko, Nikolai V; Miura, Taku; Kobori, Yasuhiro; Jono, Ryota; Yamashita, Koichi; Imahori, Hiroshi

    2016-01-11

    The unprecedented dependence of final charge separation efficiency as a function of donor-acceptor interaction in covalently-linked molecules with a rectilinear rigid oligo-p-xylene bridge has been observed. Optimization of the donor-acceptor electronic coupling remarkably inhibits the undesirable rapid decay of the singlet charge-separated state to the ground state, yielding the final long-lived, triplet charge-separated state with circa 100% efficiency. This finding is extremely useful for the rational design of artificial photosynthesis and organic photovoltaic cells toward efficient solar energy conversion.

  9. Fresh look at electron-transfer mechanisms via the donor/acceptor bindings in the critical encounter complex.

    PubMed

    Rosokha, Sergiy V; Kochi, Jay K

    2008-05-01

    Seminal insights provided by the iconic R. S. Mulliken and his "charge-transfer" theory, H. Taube and his "outer/inner-sphere" mechanisms, R. A. Marcus and his "two-state non-adiabatic" theory, and N. S. Hush and his "intervalence" theory are each separately woven into the rich panoramic tapestry constituting chemical research into electron-transfer dynamics, and its mechanistic dominance for the past half century and more. In this Account, we illustrate how the simultaneous melding of all four key concepts allows sharp focus on the charge-transfer character of the critical encounter complex to evoke the latent facet of traditional electron-transfer mechanisms. To this end, we exploit the intervalence (electronic) transition that invariably accompanies the diffusive encounter of electron-rich organic donors (D) with electron-poor acceptors (A) as the experimental harbinger of the collision complex, which is then actually isolated and X-ray crystallographically established as loosely bound pi-stacked pairs of various aromatic and olefinic donor/acceptor dyads with uniform interplanar separations of r(DA) = 3.1 +/- 0.2 A. These X-ray structures, together with the spectral measurements of their intervalence transitions, lead to the pair of important electron-transfer parameters, H(DA) (electronic coupling element) versus lambdaT (reorganization energy), the ratio of which generally defines the odd-electron mobility within such an encounter complex in terms of the resonance stabilization of the donor/acceptor assembly [D, A] as opposed to the reorganization-energy penalty required for its interconversion to the electron-transfer state [D(+*), A(-*)]. We recognize the resonance-stabilization energy relative to the intrinsic activation barrier as the mechanistic binding factor, Q = 2H(DA)/lambdaT, to represent the quantitative measure of the highly variable continuum of inner-sphere/outer-sphere interactions that are possible within various types of precursor complexes

  10. An Effort to Increase Organ Donor Registration Through Intergroup Competition and Electronic Word of Mouth.

    PubMed

    Smith, Sandi W; Hitt, Rose; Park, Hee Sun; Walther, Joseph; Liang, Yuhua Jake; Hsieh, Gary

    2016-01-01

    The effort to increase Web organ donation registrations in Michigan by enhancing 2 types of university campaigns with social media strategies informed by social identity theory is the focus of this research. The two campaigns focused on either ingroup or rivalry outgroup social identification, and each was enhanced with individually focused social media in the first year of the campaign and with electronic word of mouth in Year 2 of the campaign. Results indicated that individually focused social media such as Facebook ads worked well in rivalry campaigns (in which registrations increased two times over baseline) but not in ingroup identification campaigns (in which registrations decreased significantly over baseline when ads were introduced in the first year of each type of campaign). Electronic word-of-mouth strategies worked well in both ingroup identification campaigns (in which registrations increased two times over baseline) and rivalry campaigns (in which registrations rose almost eight times over baseline, when strategies were introduced in the second year of each type of campaign).

  11. Modelling Methane Production and Sulfate Reduction in Anaerobic Granular Sludge Reactor with Ethanol as Electron Donor

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Dai, Xiaohu; Wang, Qilin; Pan, Yuting; Ni, Bing-Jie

    2016-10-01

    In this work, a mathematical model based on growth kinetics of microorganisms and substrates transportation through biofilms was developed to describe methane production and sulfate reduction with ethanol being a key electron donor. The model was calibrated and validated using experimental data from two case studies conducted in granule-based Upflow Anaerobic Sludge Blanket reactors. The results suggest that the developed model could satisfactorily describe methane and sulfide productions as well as ethanol and sulfate removals in both systems. The modeling results reveal a stratified distribution of methanogenic archaea, sulfate-reducing bacteria and fermentative bacteria in the anaerobic granular sludge and the relative abundances of these microorganisms vary with substrate concentrations. It also indicates sulfate-reducing bacteria can successfully outcompete fermentative bacteria for ethanol utilization when COD/SO42‑ ratio reaches 0.5. Model simulation suggests that an optimal granule diameter for the maximum methane production efficiency can be achieved while the sulfate reduction efficiency is not significantly affected by variation in granule size. It also indicates that the methane production and sulfate reduction can be affected by ethanol and sulfate loading rates, and the microbial community development stage in the reactor, which provided comprehensive insights into the system for its practical operation.

  12. Modelling Methane Production and Sulfate Reduction in Anaerobic Granular Sludge Reactor with Ethanol as Electron Donor

    PubMed Central

    Sun, Jing; Dai, Xiaohu; Wang, Qilin; Pan, Yuting; Ni, Bing-Jie

    2016-01-01

    In this work, a mathematical model based on growth kinetics of microorganisms and substrates transportation through biofilms was developed to describe methane production and sulfate reduction with ethanol being a key electron donor. The model was calibrated and validated using experimental data from two case studies conducted in granule-based Upflow Anaerobic Sludge Blanket reactors. The results suggest that the developed model could satisfactorily describe methane and sulfide productions as well as ethanol and sulfate removals in both systems. The modeling results reveal a stratified distribution of methanogenic archaea, sulfate-reducing bacteria and fermentative bacteria in the anaerobic granular sludge and the relative abundances of these microorganisms vary with substrate concentrations. It also indicates sulfate-reducing bacteria can successfully outcompete fermentative bacteria for ethanol utilization when COD/SO42− ratio reaches 0.5. Model simulation suggests that an optimal granule diameter for the maximum methane production efficiency can be achieved while the sulfate reduction efficiency is not significantly affected by variation in granule size. It also indicates that the methane production and sulfate reduction can be affected by ethanol and sulfate loading rates, and the microbial community development stage in the reactor, which provided comprehensive insights into the system for its practical operation. PMID:27731395

  13. Optical Hyperpolarization and Detection of Electron and Nuclear Spins of Phosphorus Donors in Highly Enriched Silicon-28

    NASA Astrophysics Data System (ADS)

    Yang, Albion

    The linewidths of optical transitions associated with shallow impurities have been shown in recent studies to be much narrower in isotopically enriched 28Si as compared to natural Si. This is true of the no-phonon P donor bound exciton transition in 28Si, and using photoluminescence excitation spectroscopy, fine structure previously not seen in natural Si is revealed. Under a small external magnetic field, the P bound exciton transition shows a complicated structure consisting of six sets of doublets, with the doublet splitting being due to the splitting of the donor ground state by the hyperfine interaction between the spin of the donor electron and that of the 31P nucleus. The electron spin populations and the 31P nuclear spin populations can be determined by measuring the relative intensities of the hyperfine components in the photoluminescence excitation spectrum. Additionally, the predominant Auger recombination channel of these bound excitons is used to observe the same resolved hyperfine components in the photocurrent spectrum. By selectively ionizing donors in a specific hyperfine state via optical pumping of a specific hyperfine component, large polarizations of the electron and nuclear spins of 31P donors can be achieved at low field. Electron and nuclear polarizations of 90% and 76%, respectively, are obtained in less than a second, providing an initialization mechanism for qubits based on these spins, and enabling further ESR and NMR studies on dilute 31P in 28Si. A measurement of the homogeneous linewidth of the transitions associated with the 31P bound exciton, determined by spectral hole burning, is also presented. The observed 10 neV linewidth is only four times the limit set by the bound exciton lifetime.

  14. Electron-transfer and acid-base properties of a two-electron oxidized form of quaterpyrrole that acts as both an electron donor and an acceptor.

    PubMed

    Zhang, Min; E, Wenbo; Ohkubo, Kei; Sanchez-Garcia, David; Yoon, Dae-Wi; Sessler, Jonathan L; Fukuzumi, Shunichi; Kadish, Karl M

    2008-02-21

    Electron-transfer interconversion between the four-electron oxidized form of a quaterpyrrole (abbreviated as P4 for four pyrroles) and the two-electron oxidized form (P4H2) as well as between P4H2 and its fully reduced form (P4H4) bearing analogous substituents in the alpha- and beta-pyrrolic positions was studied by means of cyclic voltammetry and UV-visible spectroelectrochemistry combined with ESR and laser flash photolysis measurements. The two-electron oxidized form, P4H2, acts as both an electron donor and an electron acceptor. The radical cation (P4H2*+) and radical anion (P4H2*-) are both produced by photoinduced electron transfer from dimeric 1-benzyl-1,4-dihydronicotinamide to P4H2, whereas the cation radical form of the compound is also produced by electron-transfer oxidation of P4H2 with [Ru(bpy)3]3+. The ESR spectra of P4H2*+ and P4H2*- were recorded at low temperature and exhibit spin delocalization over all four pyrrole units. Thus, the two-electron oxidized form of the quaterpyrrole (P4H2) displays redox and electronic features analogous to those seen in the case of porphyrins and may be considered as a simple, open-chain model of this well-studied tetrapyrrolic macrocycle. The dynamics of deprotonation from P4H2*+ and disproportionation of P4H2 were examined by laser flash photolysis measurements of photoinduced electron-transfer oxidation and reduction of P4H2, respectively.

  15. Specific solute solvent interactions and dual fluorescence of electron donor substituted bis-pyrazoquinoline in binary mixed solvents

    NASA Astrophysics Data System (ADS)

    Rotkiewicz, Krystyna; Rettig, Wolfgang; Köhler, Gottfried; Rechthaler, Karl; Danel, Andrzej; Grabka, Danuta

    2004-12-01

    Some extended electron donor and acceptor substituted π-electron systems, composed of a dimethyl- or diethylanilino (DMA or DEA, respectively) group as electron donor and bis-pyrazoloquinoline (DPPQ) or bis-pyrazolopyridine (DMPP) derivatives as acceptors, were studied with the aim to elucidate the contributions of various solute interactions with solvent molecules upon intramolecular charge separation. Steady state and time resolved fluorescence studies were performed for DMA-DPPQ, DMA-DMPP and DEA-DMPP in alcohols and their binary mixtures with heptane. The decay kinetics of the fluorescence of DMA-DPPQ was also studied in neat 1-propanol in dependence of the temperature between 170 and 293 K. Several different fluorescent species, which were ascribed to different complexes with alcohol molecules, contribute to the fluorescence of the various compounds in these binary mixtures and account for the complex fluorescence decay. A simplified consecutive model is proposed to explain the decay behaviour of the excited species.

  16. Charge transport in organic donor-acceptor mixed-stack crystals: the role of nonlocal electron-phonon couplings.

    PubMed

    Zhu, Lingyun; Geng, Hua; Yi, Yuanping; Wei, Zhixiang

    2017-02-08

    The charge-transport properties in C8BTBT-FnTCNQ and DMQtT-F4TCNQ mixed-stack crystals have been investigated by means of density functional theory, molecular dynamics and kinetic Monte Carlo simulations. The super-exchange nature of charge transport in these crystals is elucidated by the Larsson partition-based electronic coupling method that was developed recently by us. Compared with hole transport, in addition to the donor HOMO-acceptor LUMO interaction, the interaction between the donor HOMO-1 and the acceptor LUMO will also make an important contribution to electron transport. Moreover, this additional interaction plays an opposite role and results in electron-dominant and hole-dominant transport in the C8BTBT-FnTCNQ and DMQtT-F4TCNQ crystals, respectively. Most importantly, our calculations point out that the nonlocal electron-phonon couplings are very weak and much smaller than the electronic couplings in all the studied crystals. This implies that the nonlocal couplings have little influence on charge transport. In contrast to the experimental measurements, the external reorganization energies are thus expected to play an essential role in determining charge carrier mobilities. These findings pave the way for rational design of high performance organic donor-acceptor mixed-stack semiconductors.

  17. Synthesis and photophysical properties of new catenated electron donor-acceptor materials with magnesium and free base porphyrins as donors and C60 as the acceptor

    NASA Astrophysics Data System (ADS)

    Kirner, Sabrina V.; Guldi, Dirk M.; Megiatto, Jackson D., Jr.; Schuster, David I.

    2014-12-01

    A new series of nanoscale electron donor-acceptor systems with [2]catenane architectures has been synthesized, incorporating magnesium porphyrin (MgP) or free base porphyrin (H2P) as electron donor and C60 as electron acceptor, surrounding a central tetrahedral Cu(i)-1,10-phenanthroline (phen) complex. Model catenated compounds incorporating only one or none of these photoactive moieties were also prepared. The synthesis involved the use of Sauvage's metal template protocol in combination with the 1,3-dipolar cycloaddition of azides and alkynes (``click chemistry''), as in other recent reports from our laboratories. Ground state electron interactions between the individual constituents was probed using electrochemistry and UV-vis absorption spectroscopy, while events occurring following photoexcitation in tetrahydrofuran (under both aerobic and anaerobic conditions) at various wavelengths were followed by means of time-resolved transient absorption and emission spectroscopies on the femtosecond and nanosecond time scales, respectively, complemented by measurements of quantum yields for generation of singlet oxygen. From similar studies with model catenates containing one or neither of the chromophores, the events following photoexcitation could be elucidated. The results were compared with those previously reported for analogous catenates based on zinc porphyrin (ZnP). It was determined that a series of energy transfer (EnT) and electron transfer (ET) processes take place in the present catenates, ultimately generating long-distance charge separated (CS) states involving oxidized porphyrin and reduced C60 moieties, with lifetimes ranging from 400 to 1060 nanoseconds. Shorter lived short-distance CS states possessing oxidized copper complexes and reduced C60, with lifetimes ranging from 15 to 60 ns, were formed en route to the long-distance CS states. The dynamics of the ET processes were analyzed in terms of their thermodynamic driving forces. It was clear that

  18. Influence of electron donors and copper concentration on geochemical and mineralogical processes under conditions of biological sulphate reduction

    NASA Astrophysics Data System (ADS)

    Wolicka, Dorota; Borkowski, Andrzej

    2014-03-01

    Sulphidogenous microorganism communities were isolated from soil polluted by crude oil. The study was focused on determining the influence of 1) copper (II) concentration on the activity of selected microorganism communities and 2) the applied electron donor on the course and evolution of mineral-forming processes under conditions favouring growth of sulphate-reducing bacteria (SRB). The influence of copper concentration on the activity of selected microorganism communities and the type of mineral phases formed was determined during experiments in which copper (II) chloride at concentrations of 0.1, 0.2, 0.5 and 0.7 g/L was added to SRB cultures. The experiments were performed in two variants: with ethanol (4 g/L) or lactate (4 g/L) as the sole carbon source. In order to determine the taxonomic composition of the selected microorganism communities, the 16S rRNA method was used. Results of this analysis confirmed the presence of Desulfovibrio, Desulfohalobium, Desulfotalea, Thermotoga, Solibacter, Gramella, Anaeromyxobacter and Myxococcus sp. in the stationary cultures. The post-culture sediments contained covelline (CuS) and digenite (Cu9S5 ). Based on the results, it can be stated that the type of carbon source applied during incubation plays a crucial role in determining the mineral composition of the post-culture sediments. Thus, regardless of the amount of copper ion introduced to a culture with lactate as the sole carbon source, no copper sulphide was observed in the post-culture sediments. Cultures with ethanol as the sole carbon source, on the other hand, yielded covelline or digenite in all post-culture sediments.

  19. Designing calcium release channel inhibitors with enhanced electron donor properties: stabilizing the closed state of ryanodine receptor type 1.

    PubMed

    Ye, Yanping; Yaeger, Daniel; Owen, Laura J; Escobedo, Jorge O; Wang, Jialu; Singer, Jeffrey D; Strongin, Robert M; Abramson, Jonathan J

    2012-01-01

    New drugs with enhanced electron donor properties that target the ryanodine receptor from skeletal muscle sarcoplasmic reticulum (RyR1) are shown to be potent inhibitors of single-channel activity. In this article, we synthesize derivatives of the channel activator 4-chloro-3-methyl phenol (4-CmC) and the 1,4-benzothiazepine channel inhibitor 4-[-3{1-(4-benzyl) piperidinyl}propionyl]-7-methoxy-2,3,4,5-tetrahydro-1,4-benzothiazepine (K201, JTV519) with enhanced electron donor properties. Instead of activating channel activity (~100 μM), the 4-methoxy analog of 4-CmC [4-methoxy-3-methyl phenol (4-MmC)] inhibits channel activity at submicromolar concentrations (IC(50) = 0.34 ± 0.08 μM). Increasing the electron donor characteristics of K201 by synthesizing its dioxole congener results in an approximately 16 times more potent RyR1 inhibitor (IC(50) = 0.24 ± 0.05 μM) compared with K201 (IC(50) = 3.98 ± 0.79 μM). Inhibition is not caused by an increased closed time of the channel but seems to be caused by an open state block of RyR1. These alterations to chemical structure do not influence the ability of these drugs to affect Ca(2+)-dependent ATPase activity of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase type 1. Moreover, the FKBP12 protein, which stabilizes RyR1 in a closed configuration, is shown to be a strong electron donor. It seems as if FKBP12, K201, its dioxole derivative, and 4-MmC inhibit RyR1 channel activity by virtue of their electron donor characteristics. These results embody strong evidence that designing new drugs to target RyR1 with enhanced electron donor characteristics results in more potent channel inhibitors. This is a novel approach to the design of new, more potent drugs with the aim of functionally modifying RyR1 single-channel activity.

  20. Triphenylamine-based organic dyes with julolidine as the secondary electron donor for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Wu, Guohua; Kong, Fantai; Li, Jingzhe; Fang, Xiaqin; Li, Yi; Dai, Songyuan; Chen, Qianqian; Zhang, Xianxi

    2013-12-01

    Two novel donor-donor-π-conjugated-acceptor (D-D-π-A) metal-free organic dyes (JTPA1 and JTPA2) with a julolidine moiety as the secondary electron donor for dye-sensitized solar cells (DSSCs) are synthesized. Their absorption spectra, electrochemical and photovoltaic properties are extensively investigated and compared with TPA2 dye. Transient absorption measurements show that both sensitizers are quickly regenerated and the dye cations are efficiently intercepted by the redox mediator. Both dyes show good performance as DSSC photosensitizers. In particular, a DSSC using JTPA2 with rhodanine-3-acetic acid shows better photovoltaic performance with a short-circuit photocurrent density (Jsc) of 9.30 mA cm-2, an open-circuit photovoltage (Voc) of 509 mV and a fill factor (FF) of 0.68, corresponding to an overall conversion efficiency (η) of 3.2% under AM 1.5 irradiation (100 mW cm-2). Under similar test conditions, ruthenium-based N719 dye gives an efficiency of 6.7%. Compared to TPA2, the dye regeneration rate, the short-circuit photocurrent density and the conversion efficiency of JTPA2 are doubled by introducing a julolidine unit. Our findings show that the julolidine unit may be an excellent electron donor system for organic dyes harvesting solar irradiation.

  1. Estimation of electronic coupling in π-stacked donor-bridge-acceptor systems: Correction of the two-state model

    NASA Astrophysics Data System (ADS)

    Voityuk, Alexander A.

    2006-02-01

    Comparison of donor-acceptor electronic couplings calculated within two-state and three-state models suggests that the two-state treatment can provide unreliable estimates of Vda because of neglecting the multistate effects. We show that in most cases accurate values of the electronic coupling in a π stack, where donor and acceptor are separated by a bridging unit, can be obtained as Ṽda=(E2-E1)μ12/Rda+(2E3-E1-E2)2μ13μ23/Rda2, where E1, E2, and E3 are adiabatic energies of the ground, charge-transfer, and bridge states, respectively, μij is the transition dipole moments between the states i and j, and Rda is the distance between the planes of donor and acceptor. In this expression based on the generalized Mulliken-Hush approach, the first term corresponds to the coupling derived within a two-state model, whereas the second term is the superexchange correction accounting for the bridge effect. The formula is extended to bridges consisting of several subunits. The influence of the donor-acceptor energy mismatch on the excess charge distribution, adiabatic dipole and transition moments, and electronic couplings is examined. A diagnostic is developed to determine whether the two-state approach can be applied. Based on numerical results, we showed that the superexchange correction considerably improves estimates of the donor-acceptor coupling derived within a two-state approach. In most cases when the two-state scheme fails, the formula gives reliable results which are in good agreement (within 5%) with the data of the three-state generalized Mulliken-Hush model.

  2. Microscopic simulations of electronic excitations in donor-acceptor heterojunctions of small-molecule based solar cells

    NASA Astrophysics Data System (ADS)

    Baumeier, Bjoern

    2015-03-01

    Fundamental processes involving electronic excitations govern the functionality of molecular materials in which the dynamics of excitons and charges is determined by an interplay of molecular electronic structure and morphological order. To understand, e.g., charge separation and recombination at donor-acceptor heterojunctions in organic solar cells, knowledge about the microscopic details influencing these dynamics in the bulk and across the interface is required. For a set of prototypical heterojunctions of small-molecule donor materials with C60, we employ a hybrid QM/MM approach linking density-functional and many-body Green's functions theory and analyze the charged and neutral electronic excitations therein. We pay special attention the spatially-resolved electron/hole transport levels, as well as the relative energies of Frenkel and charge-transfer excitations at the interface. Finally, we link the molecular architecture of the donor material, its orientation on the fullerene substrate as well as mesoscale order to the solar cell performance.

  3. Characterization of sheep lacrimal-gland peroxidase and its major physiological electron donor.

    PubMed Central

    Mazumdar, A; Chatterjee, R; Adak, S; Ghosh, A; Mondal, C; Banerjee, R K

    1996-01-01

    A soluble sheep lacrimal-gland peroxidase was purified to apparent homogeneity. It had a native molecular mass of 75 kDa with a subunit molecular mass of 82 kDa and an isoelectric point of 6.5. Western blotting showed that it shares some of the enzyme antigenic determinants in common with other soluble peroxidases. The enzyme exhibits a Soret peak at 410 nm which is shifted to 431 nm by 5 equiv. of H2O2 due to the formation of compound II. The latter is, however, unstable and gradually returns to the native state. The enzyme forms complexes with CN- and N3- and is reduced by dithionite showing a characteristic reduced peroxidase spectrum. Although the enzyme oxidizes I-, SCN- and Br- optimally at pH 5.5., 5.25 and 5.0 respectively, at physiological pH, it oxidizes I- and SCN- only. Since extracellular SCN- concentration is much higher than I-, SCN- may act as the major electron donor to the enzyme. The second-order rate constants for the reaction of the enzyme with H2O2 (k+1) and of compound I with SCN- (k+2) were 4 X 10(7) M-1 X s-1 and 8.1 X 10(5) M-1 X s-1 respectively. A plot of log Vmax against pH yields a sigmoidal curve consistent with a single ionizable group on the enzyme with a pK(a) value of 5.75, controlling thiocyanate oxidation. In a coupled system with the peroxidase, H2O2, SCN-, GSH, NADPH and glutathione reductase, peroxidase-catalysed SCN- oxidation by H2O2 could be coupled to NADPH consumption. The system is proposed to operate in vivo for the efficient elimination of endogenous H2O2. PMID:8670050

  4. Enhanced Alcaligenes faecalis Denitrification Rate with Electrodes as the Electron Donor.

    PubMed

    Wang, Xin; Yu, Ping; Zeng, Cuiping; Ding, Hongrui; Li, Yan; Wang, Changqiu; Lu, Anhuai

    2015-08-15

    The utilization by Alcaligenes faecalis of electrodes as the electron donor for denitrification was investigated in this study. The denitrification rate of A. faecalis with a poised potential was greatly enhanced compared with that of the controls without poised potentials. For nitrate reduction, although A. faecalis could not reduce nitrate, at three poised potentials of +0.06, -0.06, and -0.15 V (versus normal hydrogen electrode [NHE]), the nitrate was partially reduced with -0.15- and -0.06-V potentials at rates of 17.3 and 28.5 mg/liter/day, respectively. The percentages of reduction for -0.15 and -0.06 V were 52.4 and 30.4%, respectively. Meanwhile, for nitrite reduction, the poised potentials greatly enhanced the nitrite reduction. The nitrite reduction rates for three poised potentials (-0.06, -0.15, and -0.30 V) were 1.98, 4.37, and 3.91 mg/liter/h, respectively. When the potentials were cut off, the nitrite reduction rate was maintained for 1.5 h (from 2.3 to 2.25 mg/liter/h) and then greatly decreased, and the reduction rate (0.38 mg/liter/h) was about 1/6 compared with the rate (2.3 mg/liter/h) when potential was on. Then the potentials resumed, but the reduction rate did not resume and was only 2 times higher than the rate when the potential was off.

  5. Spin dynamics of photogenerated triradicals in fixed distance electron donor-chromophore-acceptor-TEMPO molecules.

    PubMed

    Mi, Qixi; Chernick, Erin T; McCamant, David W; Weiss, Emily A; Ratner, Mark A; Wasielewski, Michael R

    2006-06-15

    The stable free radical 2,2,6,6-tetramethylpiperidinoxyl (TEMPO, T*) was covalently attached to the electron acceptor in a donor-chromophore-acceptor (D-C-A) system, MeOAn-6ANI-Phn-A-T*, having well-defined distances between each component, where MeOAn = p-methoxyaniline, 6ANI = 4-(N-piperidinyl)naphthalene-l,8-dicarboximide, Ph = 2,5-dimethylphenyl (n = 0,1), and A = naphthalene-1,8:4,5-bis(dicarboximide) (NI) or pyromellitimide (PI). Using both time-resolved optical and EPR spectroscopy, we show that T* influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+*-6ANI-Phn-A-*-T*), resulting in modulation of the charge recombination rate within the triradical compared with the corresponding biradical lacking T*. The observed spin-spin exchange interaction between the photogenerated radicals MeOAn+* and A-* is not altered by the presence of T*, which interacts most strongly with A-* and accelerates radical pair intersystem crossing. Charge recombination within the triradicals results in the formation of 2,4(MeOAn-6ANI-Phn-3*NI-T*) or 2,4(MeOAn-3*6ANI-Phn-PI-T*) in which T* is strongly spin polarized in emission. Normally, the spin dynamics of correlated radical pairs do not produce a net spin polarization; however, the rate at which the net spin polarization appears on T* closely follows the photogenerated radical ion pair decay rate. This effect is attributed to antiferromagnetic coupling between T* and the local triplet state 3NI, which is populated following charge recombination. These results are explained using a switch in the spin basis set between the triradical and the three-spin charge recombination product having both T* and 3*NI or 3*6ANI present.

  6. 9-fluorenemethanol: an internal electron donor to fine tune olefin polymerization activity.

    PubMed

    Gnanakumar, Edwin S; Rao Chokkapu, Eswara; Kunjir, Shrikant; Ajithkumar, T G; Rajamohanan, P R; Chakraborty, Debashis; Gopinath, Chinnakonda S

    2014-06-28

    A new MgCl2 based molecular adduct has been synthesized with 9-fluorenemethanol (9FM) as a novel internal electron donor (IED), along with ethanol (EtOH) (MgCl2·n9FM·xEtOH). The above molecular adduct has been subjected to a variety of structural, spectroscopic and morphological characterization techniques. The results of the solid state (13)C CPMAS NMR technique suggests the coordination of 9FM to MgCl2. Observation of a low angle diffraction peak at 2θ = 5.7° (d = 15.5 Å) underscores the coordination of 9FM along the z-axis, and ethanol in the molecular adduct. Active Ziegler-Natta catalysts were prepared by two different synthesis methods; the conventional method to obtain a high surface area active catalyst, and other one with 9FM as an integral part of the active catalyst in order to study the influence of 9FM as an IED over the active sites. The active catalysts were also characterized thoroughly with different analytical tools. The XRD results show (003) facets of δ-MgCl2 (α-MgCl2) for the conventional (non-conventional) titanated catalyst. Results of the ethylene polymerization activity study reveals that the conventionally prepared highly porous active catalyst shows 1.7-2.5 times higher activity than the non-conventional prepared catalyst; however, the latter shows a low molecular weight distribution and confirms the role of the Lewis base as an IED.

  7. Enhanced Alcaligenes faecalis Denitrification Rate with Electrodes as the Electron Donor

    PubMed Central

    Wang, Xin; Yu, Ping; Zeng, Cuiping; Ding, Hongrui; Wang, Changqiu

    2015-01-01

    The utilization by Alcaligenes faecalis of electrodes as the electron donor for denitrification was investigated in this study. The denitrification rate of A. faecalis with a poised potential was greatly enhanced compared with that of the controls without poised potentials. For nitrate reduction, although A. faecalis could not reduce nitrate, at three poised potentials of +0.06, −0.06, and −0.15 V (versus normal hydrogen electrode [NHE]), the nitrate was partially reduced with −0.15- and −0.06-V potentials at rates of 17.3 and 28.5 mg/liter/day, respectively. The percentages of reduction for −0.15 and −0.06 V were 52.4 and 30.4%, respectively. Meanwhile, for nitrite reduction, the poised potentials greatly enhanced the nitrite reduction. The nitrite reduction rates for three poised potentials (−0.06, −0.15, and −0.30 V) were 1.98, 4.37, and 3.91 mg/liter/h, respectively. When the potentials were cut off, the nitrite reduction rate was maintained for 1.5 h (from 2.3 to 2.25 mg/liter/h) and then greatly decreased, and the reduction rate (0.38 mg/liter/h) was about 1/6 compared with the rate (2.3 mg/liter/h) when potential was on. Then the potentials resumed, but the reduction rate did not resume and was only 2 times higher than the rate when the potential was off. PMID:26048940

  8. Organic substrates as electron donors in permeable reactive barriers for removal of heavy metals from acid mine drainage.

    PubMed

    Kijjanapanich, P; Pakdeerattanamint, K; Lens, P N L; Annachhatre, A P

    2012-12-01

    This research was conducted to select suitable natural organic substrates as potential carbon sources for use as electron donors for biological sulphate reduction in a permeable reactive barrier (PRB). A number of organic substrates were assessed through batch and continuous column experiments under anaerobic conditions with acid mine drainage (AMD) obtained from an abandoned lignite coal mine. To keep the heavy metal concentration at a constant level, the AMD was supplemented with heavy metals whenever necessary. Under anaerobic conditions, sulphate-reducing bacteria (SRB) converted sulphate into sulphide using the organic substrates as electron donors. The sulphide that was generated precipitated heavy metals as metal sulphides. Organic substrates, which yielded the highest sulphate reduction in batch tests, were selected for continuous column experiments which lasted over 200 days. A mixture of pig-farm wastewater treatment sludge, rice husk and coconut husk chips yielded the best heavy metal (Fe, Cu, Zn and Mn) removal efficiencies of over 90%.

  9. Electron transport behaviors through donor-induced quantum dot array in heavily n-doped junctionless nanowire transistors

    SciTech Connect

    Ma, Liuhong; Han, Weihua Wang, Hao; Hong, Wenting; Lyu, Qifeng; Yang, Xiang; Yang, Fuhua

    2015-01-21

    We investigated single electron tunneling through a phosphorus donor-induced quantum dot array in heavily n-doped junctionless nanowire transistor. Seven subpeaks splitting in current oscillations are clearly observed due to the coupling of quantum dot array under the bias voltage below 1.0 mV at the temperature of 6 K. The conduction system can be well described by a two-band Hubbard model. The activation energy of phosphorus donors is tuned by the gate voltage to be 7.0 meV for the lower Hubbard band and 4.4 meV for the upper Hubbard band due to the localization effects below threshold voltage. The evolution of electron behaviors in the quantum dots is identified by adjusting the gate voltage from quantum-dot regime to one-dimensional regime.

  10. Simultaneous nitrification and denitrification using stored substrate (PHB) as the electron donor in an SBR.

    PubMed

    Third, Katie A; Burnett, Natalie; Cord-Ruwisch, Ralf

    2003-09-20

    The potential for PHB (poly-beta-hydroxybutyrate) to serve as the electron donor for effective simultaneous nitrification and denitrification (SND) was investigated in a 2-L sequencing batch reactor (SBR) using a mixed culture and acetate as the organic substrate. During the feast period (i.e., acetate present), heterotrophic respiration activity was high and nitrification was prevented due to the inability of nitrifying bacteria to compete with heterotrophs for oxygen. Once acetate was depleted the oxidation rate of PHB was up to 6 times slower than that of soluble acetate and nitrification could proceed due to the decreased competition for oxygen. The slow nature of PHB degradation meant that it was an effective substrate for SND, as it was oxidised at a similar rate to ammonium and was therefore available for SND throughout the entire aerobic period. The percentage of nitrogen removed via SND increased at lower DO concentrations during the famine period, with up to 78% SND achieved at a DO concentration of 0.5 mg L(-1). However, the increased percentage of SND at a low DO concentration was compromised by a 2-times slower rate of nitrogen removal. A moderate DO concentration of 1 mg L(-1) was optimal for both SND efficiency (61%) and rate (4.4 mmol N x Cmol x(-1) x h(-1)). Electron flux analysis showed that the period of highest SND activity occurred during the first hour of the aerobic famine period, when the specific oxygen uptake rate (SOUR) was highest. It is postulated that a high SOUR due to NH(4) (+) and PHB oxidation decreases oxygen penetration into the floc, creating larger zones for anoxic denitrification. The accumulation of nitrate towards the end of the SND period showed that SND was finally limited by the rate of denitrification. As PHB degradation was found to follow first-order kinetics (df(PHB)/dt = -0.19 x f(PHB)), higher PHB concentrations would be expected to drive SND faster by increasing the availability rate of reducing power and reducing

  11. Comparison of contact angle measurement and microbial adhesion to solvents for assaying electron donor-electron acceptor (acid-base) properties of bacterial surface.

    PubMed

    Hamadi, Fatima; Latrache, Hassan

    2008-08-01

    The electron donor-electron acceptor (acid-base properties) of cell surfaces of a series of bacteria were determined by two methods, namely, Microbial Adhesion to Solvents (MATS) and Contact Angle Measurements (CAM) combined with equation of Van Oss. The efficiency of these two methods was then compared. Pseudomonas aeruginosa ATCC 27853, Bacillus subtilis ILP 142B, Staphylococcus aureus ATCC 25923 and four Escherichia coli strains including HB101, AL52, O128B12 and ATCC 25922, acid-base properties were examined under the two different conditions mentioned above. The results showed that the correlation between acid-base properties determined by MATS and CAM was very weak. We have also found that when the microbial cell surface was electron donor by CAM method, similar result was found by MATS, but the reverse was not always true. In contrast, a good correlation between the two methods was obtained when the four E. coli strains were examined.

  12. Bar-Coded Pyrosequencing Reveals the Responses of PBDE-Degrading Microbial Communities to Electron Donor Amendments

    PubMed Central

    Xu, Meiying; Chen, Xingjuan; Qiu, Mengde; Zeng, Xiaowei; Xu, Jian; Deng, Daiyong; Sun, Guoping; Li, Xiang; Guo, Jun

    2012-01-01

    Polybrominated diphenyl ethers (PBDEs) can be reductively degraded by microorganisms under anaerobic conditions. However, little is known about the effect of electron donors on microbial communities involved in PBDEs degradation. Here we employed 454 Titanium pyrosequencing to examine the phylogenetic diversity, composition, structure and dynamics of microbial communities from microcosms under the conditions of different electron donor amendments. The community structures in each of the five alternate electron donor enrichments were significantly shifted in comparison with those of the control microcosm. Commonly existing OTUs between the treatment and control consortia increased from 5 to 17 and more than 50% of OTUs increased around 13.7 to 186 times at least in one of the microcosms after 90-days enrichment. Although the microbial communities at different taxonomic levels were significantly changed by different environmental variable groups in redundancy analysis, significant correlations were observed between the microbial communities and PBDE congener profiles. The lesser-brominated PBDE congeners, tri-BDE congener (BDE-32) and hexa-BDE, were identified as the key factors shaping the microbial community structures at OTU level. Some rare populations, including the known dechlorinating bacterium, Dehalobacter, showed significant positive-correlation with the amounts of PBDE congeners in the consortia. The same results were also observed on some unclassified bacteria. These results suggest that PBDEs-degrading microbial communities can be successfully enriched, and their structures and compositions can be manipulated through adjusting the environmental parameters. PMID:22295086

  13. A combined FTIR and infrared emission spectroscopy investigation of layered double hydroxide as an effective electron donor

    NASA Astrophysics Data System (ADS)

    Zhang, Jia; Wei, Feng; Liang, Ying; Zhou, Jizhi; Xi, Yunfei; Qian, Guangren; Frost, Ray

    2016-02-01

    A novel method has been presented to characterize electron transfer in layered double hydroxides (LDHs) utilizing an investigation combing FTIR and infrared emission spectroscopy. At room temperature, electron could transfer to interlayer Fe3 + through monodentate ligand cyanide, and resulted in a reduction of 40% Fe3 + to Fe2 +. When the environmental temperature increased from 25 to 300 °C, reduction of Fe3 + and Ni2 + increased to 94% and 42%. Furthermore, electron also transferred to interlayer cation through multidentate ligand EDTA. As a result, LDHs has been proven to be an effective electron donor, and FTIR was a feasible tool in characterizing this property by monitoring the valence state of cations. It was also concluded that octahedral units with OH- groups in LDH layer functioned as electron donor centers. Driving force for electron transfer is attributed to the charge density difference between cation layer and probe anion. These results could help to explain the mechanism of various applications of LDHs in catalysis and photocatalysis.

  14. A biphenyl containing two electron-donating and two electron-accepting moieties: a rigid and small donor-acceptor-donor ladder system.

    PubMed

    Greulich, Tobias W; Suzuki, Naoya; Daniliuc, Constantin G; Fukazawa, Aiko; Yamaguchi, Eriko; Studer, Armido; Yamaguchi, Shigehiro

    2016-02-07

    Ladder π-conjugated materials and also push-pull systems belong to important classes of compounds for the development of organic electronic devices. In this communication, a novel π-conjugated material that unifies the properties of both of these classes is presented. The material comprises a rigid biphenyl framework, which bears two bridging electron-accepting phosphine oxide moieties as well as two electron-donating amino groups. The structure and photophysical properties of this compound are discussed and compared with those of a related system lacking the second P-moiety.

  15. Flexible bacterial strains that oxidize arsenite in anoxic or aerobic conditions and utilize hydrogen or acetate as alternative electron donors.

    PubMed

    Rodríguez-Freire, Lucía; Sun, Wenjie; Sierra-Alvarez, Reyes; Field, Jim A

    2012-02-01

    Arsenic is a carcinogenic compound widely distributed in the groundwater around the world. The fate of arsenic in groundwater depends on the activity of microorganisms either by oxidizing arsenite (As(III)), or by reducing arsenate (As(V)). Because of the higher toxicity and mobility of As(III) compared to As(V), microbial-catalyzed oxidation of As(III) to As(V) can lower the environmental impact of arsenic. Although aerobic As(III)-oxidizing bacteria are well known, anoxic oxidation of As(III) with nitrate as electron acceptor has also been shown to occur. In this study, three As(III)-oxidizing bacterial strains, Azoarcus sp. strain EC1-pb1, Azoarcus sp. strain EC3-pb1 and Diaphorobacter sp. strain MC-pb1, have been characterized. Each strain was tested for its ability to oxidize As(III) with four different electron acceptors, nitrate, nitrite, chlorate and oxygen. Complete As(III) oxidation was achieved with both nitrate and oxygen, demonstrating the novel ability of these bacterial strains to oxidize As(III) in either anoxic or aerobic conditions. Nitrate was only reduced to nitrite. Different electron donors were used to study their suitability in supporting nitrate reduction. Hydrogen and acetate were readily utilized by all the cultures. The flexibility of these As(III)-oxidizing bacteria to use oxygen and nitrate to oxidize As(III) as well as organic and inorganic substrates as alternative electron donors explains their presence in non-arsenic-contaminated environments. The findings suggest that at least some As(III)-oxidizing bacteria are flexible with respect to electron-acceptors and electron-donors and that they are potentially widespread in low arsenic concentration environments.

  16. Developing an Accelerator Driven System (ADS) based on electron accelerators and heavy water

    NASA Astrophysics Data System (ADS)

    Feizi, H.; Ranjbar, A. H.

    2016-02-01

    An ADS based on electron accelerators has been developed specifically for energy generation and medical applications. Monte Carlo simulations have been performed using FLUKA code to design a hybrid electron target and the core components. The composition, geometry of conversion targets and the coolant system have been optimized for electron beam energies of 20 to 100 MeV . Furthermore, the photon and photoneutron energy spectra, distribution and energy deposition for various incoming electron beam powers have been studied. Light-heavy water of various mixtures have been used as heat removal for the targets, as γ-n converters and as neutron moderators. We have shown that an electron LINAC, as a neutron production driver for ADSs, is capable of producing a neutron output of > 3.5 × 1014 (n/s/mA). Accordingly, the feasibility of an electron-based ADS employing the designed features is promising for energy generation and high intense neutron production which have various applications such as medical therapies.

  17. Comparative study of donor-induced quantum dots in Si nano-channels by single-electron transport characterization and Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Tyszka, K.; Moraru, D.; Samanta, A.; Mizuno, T.; Jabłoński, R.; Tabe, M.

    2015-06-01

    We comparatively study donor-induced quantum dots in Si nanoscale-channel transistors for a wide range of doping concentration by analysis of single-electron tunneling transport and surface potential measured by Kelvin probe force microscopy (KPFM). By correlating KPFM observations of donor-induced potential landscapes with simulations based on Thomas-Fermi approximation, it is demonstrated that single-electron tunneling transport at lowest gate voltages (for smallest coverage of screening electrons) is governed most frequently by only one dominant quantum dot, regardless of doping concentration. Doping concentration, however, primarily affects the internal structure of the quantum dot. At low concentrations, individual donors form most of the quantum dots, i.e., "donor-atom" quantum dots. In contrast, at high concentrations above metal-insulator transition, closely placed donors instead of individual donors form more complex quantum dots, i.e., "donor-cluster" quantum dots. The potential depth of these "donor-cluster" quantum dots is significantly reduced by increasing gate voltage (increasing coverage of screening electrons), leading to the occurrence of multiple competing quantum dots.

  18. Comparative study of donor-induced quantum dots in Si nano-channels by single-electron transport characterization and Kelvin probe force microscopy

    SciTech Connect

    Tyszka, K.; Moraru, D.; Samanta, A.; Mizuno, T.; Tabe, M.; Jabłoński, R.

    2015-06-28

    We comparatively study donor-induced quantum dots in Si nanoscale-channel transistors for a wide range of doping concentration by analysis of single-electron tunneling transport and surface potential measured by Kelvin probe force microscopy (KPFM). By correlating KPFM observations of donor-induced potential landscapes with simulations based on Thomas-Fermi approximation, it is demonstrated that single-electron tunneling transport at lowest gate voltages (for smallest coverage of screening electrons) is governed most frequently by only one dominant quantum dot, regardless of doping concentration. Doping concentration, however, primarily affects the internal structure of the quantum dot. At low concentrations, individual donors form most of the quantum dots, i.e., “donor-atom” quantum dots. In contrast, at high concentrations above metal-insulator transition, closely placed donors instead of individual donors form more complex quantum dots, i.e., “donor-cluster” quantum dots. The potential depth of these “donor-cluster” quantum dots is significantly reduced by increasing gate voltage (increasing coverage of screening electrons), leading to the occurrence of multiple competing quantum dots.

  19. Donor-impurity-related optical response and electron Raman scattering in GaAs cone-like quantum dots

    NASA Astrophysics Data System (ADS)

    Gil-Corrales, A.; Morales, A. L.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.

    2017-02-01

    The donor-impurity-related optical absorption, relative refractive index changes, and Raman scattering in GaAs cone-like quantum dots are theoretically investigated. Calculations are performed within the effective mass and parabolic band approximations, using the variational procedure to include the electron-impurity correlation effects. The study involves 1 s -like, 2px-like, and 2pz-like states. The conical structure is chosen in such a way that the cone height is large enough in comparison with the base radius thus allowing the use a quasi-analytic solution of the uncorrelated Schrödinger-like electron states.

  20. ELECTRON DONOR ACCEPTOR DESCRIPTORS OF THE SINGLE AND DOUBLE BONDED SUBSTITUENT AND HETEROATOM INCORPORATION EFFECTS. A REVIEW.

    PubMed

    Mazurek, Andrzej

    2016-01-01

    The properties of the series of Electron Donor-Acceptor (EDA) descriptors of classical substituent effect (sEDA(I), pEDA(I)), double bonded substituent effect (sEDA(=), pEDA(=)), heteroatom incorporation effect in monocyclic systems (sEDA(II), pEDA(II)), and in ring-junction position (sEDA(III), pEDA(III)), are reviewed. The descriptors show the amount of electrons donated to or withdrawn from the σ-(sEDA) or π(pEDA) valence orbitals by the substituent or incorporant. The new descriptors are expected to enrich the potency of QSAR analyses in drug design and materials chemistry.

  1. Humin as an electron donor for enhancement of multiple microbial reduction reactions with different redox potentials in a consortium.

    PubMed

    Zhang, Dongdong; Zhang, Chunfang; Xiao, Zhixing; Suzuki, Daisuke; Katayama, Arata

    2015-02-01

    A solid-phase humin, acting as an electron donor, was able to enhance multiple reductive biotransformations, including dechlorination of pentachlorophenol (PCP), dissimilatory reduction of amorphous Fe (III) oxide (FeOOH), and reduction of nitrate, in a consortium. Humin that was chemically reduced by NaBH4 served as an electron donor for these microbial reducing reactions, with electron donating capacities of 0.013 mmol e(-)/g for PCP dechlorination, 0.15 mmol e(-)/g for iron reduction, and 0.30 mmol e(-)/g for nitrate reduction. Two pairs of oxidation and reduction peaks within the humin were detected by cyclic voltammetry analysis. 16S rRNA gene sequencing-based microbial community analysis of the consortium incubated with different terminal electron acceptors, suggested that Dehalobacter sp., Bacteroides sp., and Sulfurospirillum sp. were involved in the PCP dechlorination, dissimilatory iron reduction, and nitrate reduction, respectively. These findings suggested that humin functioned as a versatile redox mediator, donating electrons for multiple respiration reactions with different redox potentials.

  2. Loading pentapod deca(organo)[60]fullerenes with electron donors: from photophysics to photoelectrochemical bilayers.

    PubMed

    Matsuo, Yutaka; Ichiki, Takahiko; Radhakrishnan, Shankara Gayathri; Guldi, Dirk M; Nakamura, Eiichi

    2010-05-12

    A pentapod deca(aryl)[60]fullerene, C(60)(C(6)H(4)CO(2)H)(5)(C(6)H(4)Fc)(5)Me(2) (4; Fc = ferrocenyl), bearing five carboxylic acid and five ferrocenyl groups was synthesized through top and bottom functionalization of [60]fullerene by means of copper-mediated penta-addition reactions. For electrochemical measurements (i.e., E(ox) = 0.08 V, five-electron oxidation of the ferrocenyl groups; E(red) = -1.89 and -2.28 V for the fullerene part vs Fc/Fc(+)), we used an ester-protected compound, C(60)(C(6)H(4)CO(2)Et)(5)(C(6)H(4)Fc)(5)Me(2) (2), and 4 was probed by performing femtosecond flash photolysis experiments in a variety of organic solvents. Importantly, the formation of a radical ion pair state was corroborated with lifetimes of up to 333 ps in toluene. In complementary studies, penta(carboxylic acid)-penta(ferrocenyl) compound 4 was deposited on indium-tin oxide (ITO) electrodes with a surface coverage (i.e., 0.14 nmol/cm(2)) that corresponded to a unique bilayer structure. Decisive for the bilayer motif is the presence of five ferrocenyl groups, which are assembled with a merry-go-round-shaped arrangement on the [60]fullerene. The novel 4/ITO photoelectrode gave rise to a cathodic photocurrent with a 12% quantum yield in the presence of methyl viologen, whereas an anodic photocurrent was generated in the presence of ascorbic acid for a C(60)(C(6)H(4)CO(2)H)(5)(C(6)H(5))(5)Me(2) (5)/ITO photoelectrode. Photophysical investigations revealed that the difference in photocurrent, that is, cathodic versus anodic photocurrents, is related to the nature of the excited state feature in 4 (i.e., charge separated state) and 5 (i.e., triplet excited state). The unique molecular architecture of 4, in combination with its remarkable donor-acceptor properties, validates the use of the pentapod deca(aryl)[60]fullerene in photoelectrochemically active molecular devices.

  3. BPM ANALOG FRONT-END ELECTRONICS BASED ON THE AD8307 LOG AMPLIFIER

    SciTech Connect

    R. SHURTER; ET AL

    2000-06-01

    Beam position monitor (BPM) signal-processing electronics utilizing the Analog Devices AD8307 logarithmic amplifier has been developed for the Low Energy Demonstration Accelerator (LEDA), part of the Accelerator Production of Tritium (APT) project at Los Alamos. The low-pass filtered 350 MHz fundamental signal from each of the four microstrip electrodes in a BPM is ''detected'' by an AD8307 log amp, amplified and scaled to accommodate the 0 to +5V input of an analog-to-digital (A/D) converter. The resultant four digitized signals represent a linear power relationship to the electrode signals, which are in turn related to beam current and position. As the AD8307 has a potential dynamic range of approximately 92 dB, much attention must be given to noise reduction, sources of which can be digital signals on the same board, power supplies, inter-channel coupling, stray RF and others. This paper will describe the operational experience of this particular analog front-end electronic circuit design.

  4. The separation distance distribution in electron-donor-acceptor systems and the wavelength dependence of free ion yields

    NASA Astrophysics Data System (ADS)

    Zhou, Jinwei; Findley, Bret R.; Braun, Charles L.; Sutin, Norman

    2001-06-01

    We recently reported that free radical ion quantum yields for electron-donor-acceptor (EDA) systems of alkylbenzenes-tetracyanoethylene (TCNE) exhibit a remarkable wavelength dependence in dichloromethane, a medium polarity solvent. We proposed that weak absorption by long-distance, unassociated or "random" D⋯A pairs is mainly responsible for the free radical ion yield. Here a model for the wavelength dependence of the free ion yield is developed for four systems in which differing degrees of EDA complex formation are present: 1,3,5-tri-tert-butylbenzene-TCNE in which only random pairs exist due to the bulky groups on the electron donor, and toluene—TCNE, 1,3,5-triethylbenzene-TCNE and 1,3,5-trimethylbenzene-TCNE. Mulliken-Hush theory is used to determine the excitation distance distribution of unassociated, random pairs at different wavelengths. For each absorption distribution, free radical ion yields at different wavelengths are then calculated using Onsager's result for the ion separation probability. Encouraging agreement between the calculated yields and our experimental results is obtained. As far as we are aware, this is the first time that photoexcitation of unassociated donor/acceptor pairs has been invoked as the source of separated radical ion pairs.

  5. Excess-electron injection and transfer in terthiophene-modified DNA: terthiophene as a photosensitizing electron donor for thymine, cytosine, and adenine.

    PubMed

    Park, Man Jae; Fujitsuka, Mamoru; Kawai, Kiyohiko; Majima, Tetsuro

    2012-02-13

    Excess-electron transfer (EET) in DNA has attracted wide attention owing to its close relation to DNA repair and nanowires. To clarify the dynamics of EET in DNA, a photosensitizing electron donor that can donate an excess electron to a variety of DNA sequences has to be developed. Herein, a terthiophene (3T) derivative was used as the photosensitizing electron donor. From the dyad systems in which 3T was connected to a single nucleobase, it was revealed that (1) 3T* donates an excess electron efficiently to thymine, cytosine, and adenine, despite adenine being a well-known hole conductor. The free-energy dependence of the electron-transfer rate was explained on the basis of the Marcus theory. From the DNA hairpins, it became clear that (1) 3T* can donate an excess electron not only to the adjacent nucleobase but also to the neighbor one nucleobase further along and so on. From the charge-injection rate, the possibilities of smaller β value and/or charge delocalization were discussed. In addition, EET through consecutive cytosine nucleobases was suggested.

  6. A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Hao, Yan; Yang, Wenxing; Zhang, Lei; Jiang, Roger; Mijangos, Edgar; Saygili, Yasemin; Hammarström, Leif; Hagfeldt, Anders; Boschloo, Gerrit

    2016-12-01

    Photoelectrochemical approach to solar energy conversion demands a kinetic optimization of various light-induced electron transfer processes. Of great importance are the redox mediator systems accomplishing the electron transfer processes at the semiconductor/electrolyte interface, therefore affecting profoundly the performance of various photoelectrochemical cells. Here, we develop a strategy--by addition of a small organic electron donor, tris(4-methoxyphenyl)amine, into state-of-art cobalt tris(bipyridine) redox electrolyte--to significantly improve the efficiency of dye-sensitized solar cells. The developed solar cells exhibit efficiency of 11.7 and 10.5%, at 0.46 and one-sun illumination, respectively, corresponding to a 26% efficiency improvement compared with the standard electrolyte. Preliminary stability tests showed the solar cell retained 90% of its initial efficiency after 250 h continuous one-sun light soaking. Detailed mechanistic studies reveal the crucial role of the electron transfer cascade processes within the new redox system.

  7. 2004 Electron Donor Acceptor Interactions Gordon Conference - August 8-13, 2004

    SciTech Connect

    GUILFORD JONES BOSTON UNIVERSITY PHOTONICS CENTER 8 ST. MARY'S ST BOSTON, MA 02215

    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.

  8. Syntheses of D-A-A Type Small Molecular Donor Materials Having Various Electron Accepting Moiety for Organic Photovoltaic Application.

    PubMed

    Kim, Nahyeon; Park, Sangman; Lee, Myong-Hoon; Lee, Jaemin; Lee, Changjin; Yoon, Sung Cheol

    2016-03-01

    Small molecular donor, DTDCTB achieved a high power conversion efficiency (PCE) value of 6.6 ± 0.2% in vacuum-deposited planar mixed heterojunction (PMHJ) structure. However, the same material just recorded PCE of 0.34% in solution processed small molecule based bulk heterjunction (BHJ) organic photovoltaic cells. For the improvement of organic photovoltaic cells (OPVs), In this study, we designed and synthesized several D-A-A (donor-acceptor-acceptor) type molecular electron donating materials. Ditolylaminothienyl moiety as an electron donating group connected to 1,2,5-benzothiadiazole as a conjugated electron accepting unit, simultaneously with an electron accepting terminal group such as cyano alkyl acetate and N-alkyl rhodanine. The thermal, photophysical, and electrochemical properties of prepared small molecules were investigated by DSC, UV/Vis spectroscopy and Cyclic Voltametry, respectively. As a result, 0.89% of PCE can be obtained from OPV using a mixture of DTATBTER and PCBM as an active layer with a Voc of 0.87 V, a Jsc of 3.20 mA/cm2, and a fill factor of 31.9%.

  9. Efficient spirobifluorene-core electron-donor material for application in solution-processed organic solar cells

    NASA Astrophysics Data System (ADS)

    Nazim, M.; Ameen, Sadia; Akhtar, M. Shaheer; Shin, Hyung Shik

    2016-10-01

    Efficient spirobifluorene-based organic small molecule (RTh-Sp-CF3) was synthesized in a simple manner via Suzuki coupling reaction containing an alkyl bithiophene as donor and 3,5-bis (trifluoromethyl) benzene as acceptor unit. The spirobifluorene-based small molecule was utilized as an electron-donor materials with well-known electron-acceptor material, phenyl-C61-butyric acid methyl ester (PC61BM) in the solution-processed small molecule organic solar cells (SMOSCs). The incorporation of 3,5-bis (trifluoromethyl) benzene unit as electron-acceptor has significantly tuned the energy levels of small molecule and obtained the HOMO and LUMO energy levels of -5.35 eV and -3.92 eV, respectively. SMOSCs fabricated with RTh-Sp-CF3 accomplished an overall power conversion efficiency (PCE) of ∼2.12% with short circuit current (JSC) of ∼8.42 mA/cm2 and the open-circuit voltage (VOC) of ∼0.66 V. The reasonable JSC and VOC of devices might be attributed to the presence of strong electron-withdrawing fluorine units in RTh-Sp-CF3, which resulted from the improved absorption and electrochemical properties.

  10. Inside the alkalinity engine: the role of electron donors in the organomineralization potential of sulfate-reducing bacteria.

    PubMed

    Gallagher, K L; Kading, T J; Braissant, O; Dupraz, C; Visscher, P T

    2012-11-01

    Mineral precipitation in microbial mats may have been the key to their preservation as fossil stromatolites, potentially documenting evidence of the earliest life on Earth. Two factors that contribute to carbonate mineral precipitation are the saturation index (SI) and the presence of nucleation sites. Both of these can be influenced by micro-organisms, which can either alter SI through their metabolisms, or produce and consume organic substances such as extracellular polymeric substances (EPS) that can affect nucleation. It is the balance of individual metabolisms within the mat community that determines the pH and the dissolved inorganic carbon concentration, thereby potentially increasing the alkalinity and consequently the SI. Sulfate-reducing bacteria (SRB) are an important component of this 'alkalinity engine.' The activity of SRB often peaks in layers where CaCO(3) precipitates, and mineral precipitation has been demonstrated in SRB cultures; however, the effect of their metabolism on the alkalinity engine and actual contribution to mineral precipitation is the subject of controversy. Here, we show through culture experiments, theoretical calculations, and geochemical modeling studies that the pH, alkalinity, and organomineralization potential will vary depending on the type of electron donor. Specifically, hydrogen and formate can increase the pH, but electron donors like lactate and ethanol, and to a lesser extent glycolate, decrease the pH. The implication of this for the lithification of mats is that the combination of processes supplying electron donors and the utilization of these compounds by SRB may be critical to promoting mineral precipitation.

  11. Spectrophotometric study of the charge transfer complexation of some porphyrin derivatives as electron donors with tetracyanoethylene.

    PubMed

    El-Zaria, Mohamed E

    2008-01-01

    Charge transfer complexes (CTC) of 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetra(4-tolyl)porphyrin (TTP), 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMP), Zn-5,10,15,20-tetraphenylporphyrin (Zn-TPP), and Zn-5,10,15,20-tetra(4-tolyl)porphyrin (Zn-TTP) with tetracyanoethylene (TCNE) have been studied at various temperatures in CH(2)Cl(2) and CCl(4). The data are discussed in terms of equilibrium constant (K(CT)), molar extinction coefficient (epsilon(CT)), thermodynamic standard reaction quantities (DeltaG degrees , DeltaH degrees and DeltaS degrees ), oscillator strength (f), and transition dipole moment (mu). The spectrum obtained for TPP/TCNE, TTP/TCNE, and TMP/TCNE systems shows two main absorption bands at 475 and 690nm, which are not due to the absorption of any of the reactants. These bands are characteristic of an intermolecular charge transfer involving the overlap of the lowest unoccupied molecular orbital (LUMO) of the acceptor with the highest occupied molecular orbital (HOMO) of the donor. The results reveal that the interaction between the donors and acceptor is due to pi-pi(*) transitions by the formation of radical ion pairs. The stoichiometry of the complexes was found to be 1:1 ratio by the Job and straight line methods between donors and acceptor with the maximum absorption bands at wavelengths of 475 and 690nm. The observed data show salvation effects on the spectral and thermodynamics properties of CTC. The ionization potential of the donors and the dissociation energy of the CTC were also determined and are found to be constant.

  12. Spectrophotometric study of the charge transfer complexation of some porphyrin derivatives as electron donors with tetracyanoethylene

    NASA Astrophysics Data System (ADS)

    El-Zaria, Mohamed E.

    2008-01-01

    Charge transfer complexes (CTC) of 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetra(4-tolyl)porphyrin (TTP), 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMP), Zn-5,10,15,20-tetraphenylporphyrin (Zn-TPP), and Zn-5,10,15,20-tetra(4-tolyl)porphyrin (Zn-TTP) with tetracyanoethylene (TCNE) have been studied at various temperatures in CH 2Cl 2 and CCl 4. The data are discussed in terms of equilibrium constant ( KCT), molar extinction coefficient ( ɛCT), thermodynamic standard reaction quantities (Δ G°, Δ H° and Δ S°), oscillator strength ( f), and transition dipole moment ( μ). The spectrum obtained for TPP/TCNE, TTP/TCNE, and TMP/TCNE systems shows two main absorption bands at 475 and 690 nm, which are not due to the absorption of any of the reactants. These bands are characteristic of an intermolecular charge transfer involving the overlap of the lowest unoccupied molecular orbital (LUMO) of the acceptor with the highest occupied molecular orbital (HOMO) of the donor. The results reveal that the interaction between the donors and acceptor is due to π-π * transitions by the formation of radical ion pairs. The stoichiometry of the complexes was found to be 1:1 ratio by the Job and straight line methods between donors and acceptor with the maximum absorption bands at wavelengths of 475 and 690 nm. The observed data show salvation effects on the spectral and thermodynamics properties of CTC. The ionization potential of the donors and the dissociation energy of the CTC were also determined and are found to be constant.

  13. Green's function calculation of through-bond electronic coupling in donor bridge acceptor model systems

    NASA Astrophysics Data System (ADS)

    de Santana, O. L.; da Gama, A. A. S.

    1999-12-01

    The Green's function formalism is applied for the calculation of the effective through-bond donor-acceptor coupling in model molecular systems. The calculation is performed at a Hartree-Fock (self-consistent) level, by using semiempirical AM1 and CNDO/S, and ab initio STO-3G methods. The results are compared with that obtained from the splitting of the appropriate levels, by using the Koopmans' theorem, within each one of the selected quantum chemical methods.

  14. Influence of donor-acceptor distance variation on photoinduced electron and proton transfer in rhenium(I)-phenol dyads.

    PubMed

    Kuss-Petermann, Martin; Wolf, Hilke; Stalke, Dietmar; Wenger, Oliver S

    2012-08-01

    A homologous series of four molecules in which a phenol unit is linked covalently to a rhenium(I) tricarbonyl diimine photooxidant via a variable number of p-xylene spacers (n = 0-3) was synthesized and investigated. The species with a single p-xylene spacer was structurally characterized to get some benchmark distances. Photoexcitation of the metal complex in the shortest dyad (n = 0) triggers release of the phenolic proton to the acetonitrile/water solvent mixture; a H/D kinetic isotope effect (KIE) of 2.0 ± 0.4 is associated with this process. Thus, the shortest dyad basically acts like a photoacid. The next two longer dyads (n = 1, 2) exhibit intramolecular photoinduced phenol-to-rhenium electron transfer in the rate-determining excited-state deactivation step, and there is no significant KIE in this case. For the dyad with n = 1, transient absorption spectroscopy provided evidence for release of the phenolic proton to the solvent upon oxidation of the phenol by intramolecular photoinduced electron transfer. Subsequent thermal charge recombination is associated with a H/D KIE of 3.6 ± 0.4 and therefore is likely to involve proton motion in the rate-determining reaction step. Thus, some of the longer dyads (n = 1, 2) exhibit photoinduced proton-coupled electron transfer (PCET), albeit in a stepwise (electron transfer followed by proton transfer) rather than concerted manner. Our study demonstrates that electronically strongly coupled donor-acceptor systems may exhibit significantly different photoinduced PCET chemistry than electronically weakly coupled donor-bridge-acceptor molecules.

  15. Self-association and electron transfer in donor-acceptor dyads connected by meta-substituted oligomers.

    PubMed

    Molina-Ontoria, Agustín; Fernández, Gustavo; Wielopolski, Mateusz; Atienza, Carmen; Sánchez, Luis; Gouloumis, Andreas; Clark, Timothy; Martín, Nazario; Guldi, Dirk M

    2009-09-02

    The synthesis of a new series of electron donor-acceptor conjugates (5, 10, 13, and 16) in which the electron acceptor--C(60)--and the electron donor--pi-extended tetrathiafulvalene (exTTF)--are bridged by means of m-phenyleneethynylene spacers of variable length is reported. The unexpected self-association of these hybrids was first detected to occur in the gas phase by means of MALDI-TOF spectrometry and subsequently corroborated in solution by utilizing concentration-dependent and variable-temperature (1)H NMR experiments. Furthermore, the ability of these new conjugates to form wirelike structures upon deposition onto a mica surface has been demonstrated by AFM spectroscopy. In light of their photoactivity and redoxactivity, 5, 10, 13, and 16 were probed in concentration-dependent photophysical experiments. Importantly, absorption and fluorescence revealed subtle dissimilarities for the association constants, that is, a dependence on the length of the m-phenylene spacers. The binding strength is in 5 greatly reduced when compared with those in 10, 13, and 16. Not only that, the spacer length also plays a decisive role in governing excited-state interactions in the corresponding electron donor-acceptor conjugates (5, 10, 13, and 16). To this end, 5, in which the photo- and electroactive constituents are bridged by just one aromatic ring, displays--exclusively and independent of the concentration (10(-6) to 10(-4) M)--efficient intramolecular electron transfer events on the basis of a "through-bond" mechanism. On the contrary, the lack of conjugation throughout the bridges in 10 (two m-phenyleneethynylene rings), 13 (three m-phenyleneethynylene rings), and 16 (four m-phenyleneethynylene rings) favors at low concentration (10(-6) M) "through space" intramolecular electron transfer events. These are, however, quite ineffective and, in turn, lead to excited-state deactivations that are at high concentrations (10(-4) M) dominated by intracomplex electron transfer

  16. Three Redox States of a Diradical Acceptor-Donor-Acceptor Triad: Gating the Magnetic Coupling and the Electron Delocalization.

    PubMed

    Souto, Manuel; Lloveras, Vega; Vela, Sergi; Fumanal, Maria; Ratera, Imma; Veciana, Jaume

    2016-06-16

    The diradical acceptor-donor-acceptor triad 1(••), based on two polychlorotriphenylmethyl (PTM) radicals connected through a tetrathiafulvalene(TTF)-vinylene bridge, has been synthesized. The generation of the mixed-valence radical anion, 1(•-), and triradical cation species, 1(•••+), obtained upon electrochemical reduction and oxidation, respectively, was monitored by optical and ESR spectroscopy. Interestingly, the modification of electron delocalization and magnetic coupling was observed when the charged species were generated and the changes have been rationalized by theoretical calculations.

  17. Structure-property optimizations in donor polymers via electronics, substituents, and side chains toward high efficiency solar cells.

    PubMed

    Uy, Rycel L; Price, Samuel C; You, Wei

    2012-07-26

    Many advances in organic photovoltaic efficiency are not yet fully understood and new insight into structure-property relationships is required to push this technology into broad commercial use. The aim of this article is not to comprehensively review recent work, but to provide commentary on recent successes and forecast where researchers should look to enhance the efficiency of photovoltaics. By lowering the LUMO level, utilizing electron-withdrawing substituents advantageously, and employing appropriate side chains on donor polymers, researchers can elucidate further aspects of polymer-PCBM interactions while ultimately developing materials that will push past 10% efficiency.

  18. Photoinduced intramolecular charge transfer in push-pull polyenes: effects of solvation, electron-donor group, and polyenic chain length.

    PubMed

    Akemann, Walther; Laage, Damien; Plaza, Pascal; Martin, Monique M; Blanchard-Desce, Mireille

    2008-01-17

    Subpicosecond absorption spectroscopy is used to characterize the primary photoinduced processes in a class of push-pull polyenes bearing a julolidine end group as the electron donor and a diethylthiobarbituric acid end group as the electron acceptor. The excited-state decay time and relaxation pathway have been studied for four polyenes of increasing chain length (n = 2-5 double bonds) in aprotic solvents of different solvation time, polarity, and viscosity. Intramolecular charge transfer (ICT) leading to a transient state of cyanine-like structure (fully conjugated with no bond length alternation) is observed in all polar solvents at a solvent dependent rate, but the reaction is not observed in cyclohexane, a nonpolar solvent. In polar solvents, the reaction time increases with the average solvation time but remains slightly larger, except in the viscous solvent triacetin. These facts are interpreted as an indication that both solvent reorganization and internal restructuring are involved in the ICT-state formation. The observed photodynamics resemble those we previously found for another class of polyenes bearing a dibutylaniline group as the donor, including a similar charge-transfer rate in spite of the larger electron donor character of the julolidine group. This observation brings further support to the proposal that an intramolecular coordinate is involved in the charge-transfer reaction, possibly a torsional motion of the donor end group. On the other hand, relaxation of the ICT state leads to cis-trans isomerization or crossing to the triplet state, depending on the length of the polyenic chain. In dioxane, tetrahydrofuran, and triacetin, the ICT state of the shorter chains (n = 2, 3) relaxes to the isomer with a viscosity-dependent rate, while that of the longer ones (n = 4, 5) leads to the triplet state with a viscosity-independent rate, as expected. In acetonitrile, the ICT-state lifetime is generally much shorter. A change from photoisomerization to

  19. Computational characterization of competing energy and electron transfer states in bimetallic donor-acceptor systems for photocatalytic conversion

    NASA Astrophysics Data System (ADS)

    Fredin, Lisa A.; Persson, Petter

    2016-09-01

    The rapidly growing interest in photocatalytic systems for direct solar fuel production such as hydrogen generation from water splitting is grounded in the unique opportunity to achieve charge separation in molecular systems provided by electron transfer processes. In general, both photoinduced and catalytic processes involve complicated dynamics that depend on both structural and electronic effects. Here the excited state landscape of metal centered light harvester-catalyst pairs is explored using density functional theory calculations. In weakly bound systems, the interplay between structural and electronic factors involved can be constructed from the various mononuclear relaxed excited states. For this study, supramolecular states of electron transfer and excitation energy transfer character have been constructed from constituent full optimizations of multiple charge/spin states for a set of three Ru-based light harvesters and nine transition metal catalysts (based on Ru, Rh, Re, Pd, and Co) in terms of energy, structure, and electronic properties. The complete set of combined charge-spin states for each donor-acceptor system provides information about the competition of excited state energy transfer states with the catalytically active electron transfer states, enabling the identification of the most promising candidates for photocatalytic applications from this perspective.

  20. Impact of temperature and non-Gaussian statistics on electron transfer in donor-bridge-acceptor molecules

    DOE PAGES

    Waskasi, Morteza M.; Newton, Marshall D.; Matyushov, Dmitry V.

    2017-03-06

    A combination of experimental data and theoretical analysis provides evidence of a bell-shaped kinetics of electron transfer in the Arrhenius coordinates ln k vs 1/T . This kinetic law is a temperature analog of the familiar Marcus bell-shaped dependence based on ln k vs the reaction free energy. These results were obtained for reactions of intramolecular charge shift between the donor and acceptor separated by a rigid spacer studied experimentally by Miller and co-workers. The non-Arrhenius kinetic law is a direct consequence of the solvent reorganization energy and reaction driving force changing approximately as hyperbolic functions with temperature. The reorganizationmore » energy decreases and the driving force increases when temperature is increased. The point of equality between them marks the maximum of the activationless reaction rate. Reaching the consistency between the kinetic and thermodynamic experimental data requires the non-Gaussian statistics of the donor-acceptor energy gap described by the Q-model of electron transfer. Furthermore, the theoretical formalism combines the vibrational envelope of quantum vibronic transitions with the Q-model describing the classical component of the Franck-Condon factor and a microscopic solvation model of the solvent reorganization energy and the reaction free energy.« less

  1. Transition Metal Donor-Peptide-Acceptor Complexes: From Intramolecular Electron Transfer Reactions to the Study of Reactive Intermediates

    SciTech Connect

    Isied, Stephan S.

    2003-03-11

    The trans-polyproline (PII) oligomers (Figure 1) are unusually rigid peptide structures which have been extensively studied by our group for peptide mediated intramolecular electron transfer (ET) at long distances. We have previously studied ET across a series of metal ion donor (D) acceptor (A) oligoproline peptides with different distances, driving forces and reorganizational energies. The majority of these experiments involve generating the ET intermediate using pulse radiolysis methods, although more recently photochemical methods are also used. Results of these studies showed that ET across peptides can vary by more than twelve orders of magnitude. Using ruthenium bipyridine donors, ET reaction rate constants across several proline residues (n = 4 - 9) occurred in the millisecond (ms) to {micro}s timescale, thus limiting the proline peptide conformational motions to only minor changes (far smaller than the large changes that occur on the ms to sec timescale, such as trans to cis proline isomerization). The present report describes our large data base of experimental results for D-peptide-A complexes in terms of a model where the involvement of both superexchange and hopping (hole and electron) mechanisms account for the long range ET rate constants observed. Our data shows that the change from superexchange to hopping mechanisms occurs at different distances depending on the type of D and A and their interactions with the peptides. Our model is also consistent with generalized models for superexchange and hopping which have been put forward by a number of theoretical groups to account for long range ET phenomena.

  2. Impact of Temperature and Non-Gaussian Statistics on Electron Transfer in Donor-Bridge-Acceptor Molecules.

    PubMed

    Waskasi, Morteza M; Newton, Marshall D; Matyushov, Dmitry V

    2017-03-06

    A combination of experimental data and theoretical analysis provides evidence of a bell-shaped kinetics of electron transfer in the Arrhenius coordinates ln k vs 1/T. This kinetic law is a temperature analog of the familiar Marcus bell-shaped dependence based on ln k vs the reaction free energy. These results were obtained for reactions of intramolecular charge shift between the donor and acceptor separated by a rigid spacer studied experimentally by Miller and co-workers. The non-Arrhenius kinetic law is a direct consequence of the solvent reorganization energy and reaction driving force changing approximately as hyperbolic functions with temperature. The reorganization energy decreases and the driving force increases when temperature is increased. The point of equality between them marks the maximum of the activationless reaction rate. Reaching the consistency between the kinetic and thermodynamic experimental data requires the non-Gaussian statistics of the donor-acceptor energy gap described by the Q-model of electron transfer. The theoretical formalism combines the vibrational envelope of quantum vibronic transitions with the Q-model describing the classical component of the Franck-Condon factor and a microscopic solvation model of the solvent reorganization energy and the reaction free energy.

  3. Donor-linked di(perylene bisimide)s: arrays exhibiting fast electron transfer for photosynthesis mimics.

    PubMed

    Wu, Yishi; Zhen, Yonggang; Wang, Zhaohui; Fu, Hongbing

    2013-02-28

    The first example of donor-linked di(perylene bisimide)s is reported. UV-vis absorption spectra of these newly synthesized dyads showed intense absorption across the entire visible region, demonstrating their excellent light-harvesting activities. The severe fluorescence quenching event probed by steady-state fluorescence spectroscopy and the free-energy calculations suggested the possibility of electron transfer (ET) in these arrays upon photoexcitation. Further femtosecond transient absorption spectra clarified that the fluorescence quenching was due to fast intramolecular ET. The rate of the charge separation (CS) was found to be as high as 10(12) s(-1) in CH(2)Cl(2). It was suggested that the large ET driving forces, strong donor-acceptor electronic coupling, and relatively small reorganization energy of diPBI accounted for the rapid ET process in a synergic manner. The fate of the generated radical ion pair depended on the solvent used. Rapid charge recombination to ground state occurred for the dyads in polar CH(2)Cl(2) and for diPBI-TPA in nonpolar toluene. However, sufficient (3)diPBI* population was attained via efficient spin-orbit coupled intersystem crossing from the charge-separated state for diPBI-PdTPP in toluene. These photophysical properties are interpreted as the cooperation between thermodynamic feasibility and kinetic manipulation.

  4. 2008 Electron Donor Acceptor Interactions Gordon Research Conference-August 3-8, 2009

    SciTech Connect

    Malcolm Forbes and Nancy Ryan Gray

    2009-09-19

    The conference presents and advances the current frontiers in experimental and theoretical studies of Electron Transfer and Transport in Molecular and Nano-scale Systems. The program includes sessions on coupled electron transfers, molecular solar energy conversion, biological and biomimetic systems, spin effects, ultrafast reactions and technical frontiers as well as electron transport in single molecules and devices.

  5. Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

    PubMed Central

    Nonnenmacher, Michael; Buck, Dominik M

    2016-01-01

    Summary Rh(CO)2Cl(NHC) complexes of dipyrido-annelated N-heterocyclic carbenes were prepared. From the C–H coupling constant of the respective imidazolium salts and the N–C–N angle of the N-heterocyclic carbene (NHC), a weaker σ-donor character than that of typical unsaturated NHCs is expected. However, the IR stretching frequencies of their Rh(CO)2Cl complexes suggest an electron-donor character even stronger than that of saturated NHCs. We ascribe this to the extremely weak π-acceptor character of the dipyrido-annelated NHCs caused by the conjugated 14 πe− system that thus allows for an enhanced Rh–CO backbonding. This extremely low π-acceptor ability is also corroborated by the 77Se NMR chemical shift of −55.8 ppm for the respective selenourea, the lowest value ever measured for imidazole derived selenoureas. DFT-calculations of the free carbene confirm the low σ-donor character by the fact that the σ-orbital of the carbene is the HOMO−1 that lies 0.58 eV below the HOMO which is located at the π-system. Natural population analysis reveals the lowest occupation of the pπ-orbital for the saturated carbene carbon atom and the highest for the pyrido-annelated carbene. Going from the free carbene to the Rh(CO)2Cl(NHC) complexes, the increase in occupancy of the complete π-system of the carbene ligand upon coordination is lowest for the pyrido-annelated carbene and highest for the saturated carbene. PMID:27829895

  6. Impact of Organic Carbon Electron Donors on Microbial Community Development under Iron- and Sulfate-Reducing Conditions.

    PubMed

    Kwon, Man Jae; O'Loughlin, Edward J; Boyanov, Maxim I; Brulc, Jennifer M; Johnston, Eric R; Kemner, Kenneth M; Antonopoulos, Dionysios A

    2016-01-01

    Although iron- and sulfate-reducing bacteria in subsurface environments have crucial roles in biogeochemical cycling of C, Fe, and S, how specific electron donors impact the compositional structure and activity of native iron- and/or sulfate-reducing communities is largely unknown. To understand this better, we created bicarbonate-buffered batch systems in duplicate with three different electron donors (acetate, lactate, or glucose) paired with ferrihydrite and sulfate as the electron acceptors and inoculated them with subsurface sediment as the microbial inoculum. Sulfate and ferrihydrite reduction occurred simultaneously and were faster with lactate than with acetate. 16S rRNA-based sequence analysis of the communities over time revealed that Desulfotomaculum was the major driver for sulfate reduction coupled with propionate oxidation in lactate-amended incubations. The reduction of sulfate resulted in sulfide production and subsequent abiotic reduction of ferrihydrite. In contrast, glucose promoted faster reduction of ferrihydrite, but without reduction of sulfate. Interestingly, the glucose-amended incubations led to two different biogeochemical trajectories among replicate bottles that resulted in distinct coloration (white and brown). The two outcomes in geochemical evolution might be due to the stochastic evolution of the microbial communities or subtle differences in the initial composition of the fermenting microbial community and its development via the use of different glucose fermentation pathways available within the community. Synchrotron-based x-ray analysis indicated that siderite and amorphous Fe(II) were formed in the replicate bottles with glucose, while ferrous sulfide and vivianite were formed with lactate or acetate. These data sets reveal that use of different C utilization pathways projects significant changes in microbial community composition over time that uniquely impact both the geochemistry and mineralogy of subsurface environments.

  7. Impact of Organic Carbon Electron Donors on Microbial Community Development under Iron- and Sulfate-Reducing Conditions

    PubMed Central

    Kwon, Man Jae; O’Loughlin, Edward J.; Boyanov, Maxim I.; Brulc, Jennifer M.; Johnston, Eric R.; Kemner, Kenneth M.; Antonopoulos, Dionysios A.

    2016-01-01

    Although iron- and sulfate-reducing bacteria in subsurface environments have crucial roles in biogeochemical cycling of C, Fe, and S, how specific electron donors impact the compositional structure and activity of native iron- and/or sulfate-reducing communities is largely unknown. To understand this better, we created bicarbonate-buffered batch systems in duplicate with three different electron donors (acetate, lactate, or glucose) paired with ferrihydrite and sulfate as the electron acceptors and inoculated them with subsurface sediment as the microbial inoculum. Sulfate and ferrihydrite reduction occurred simultaneously and were faster with lactate than with acetate. 16S rRNA-based sequence analysis of the communities over time revealed that Desulfotomaculum was the major driver for sulfate reduction coupled with propionate oxidation in lactate-amended incubations. The reduction of sulfate resulted in sulfide production and subsequent abiotic reduction of ferrihydrite. In contrast, glucose promoted faster reduction of ferrihydrite, but without reduction of sulfate. Interestingly, the glucose-amended incubations led to two different biogeochemical trajectories among replicate bottles that resulted in distinct coloration (white and brown). The two outcomes in geochemical evolution might be due to the stochastic evolution of the microbial communities or subtle differences in the initial composition of the fermenting microbial community and its development via the use of different glucose fermentation pathways available within the community. Synchrotron-based x-ray analysis indicated that siderite and amorphous Fe(II) were formed in the replicate bottles with glucose, while ferrous sulfide and vivianite were formed with lactate or acetate. These data sets reveal that use of different C utilization pathways projects significant changes in microbial community composition over time that uniquely impact both the geochemistry and mineralogy of subsurface environments

  8. Complete bromate and nitrate reduction using hydrogen as the sole electron donor in a rotating biofilm-electrode reactor.

    PubMed

    Zhong, Yu; Li, Xin; Yang, Qi; Wang, Dongbo; Yao, Fubing; Li, Xiaoming; Zhao, Jianwei; Xu, Qiuxiang; Zhang, Chang; Zeng, Guangming

    2016-04-15

    Simultaneous reduction of bromate and nitrate was investigated using a rotating biofilm-electrode reactor (RBER) with graphite carbon (GC) rods as anode and activated carbon fiber (ACF) bonded with steel ring as cathode. In RBER, the community of denitrifying bacteria immobilized on the cathode surface could completely utilize hydrogen (H2) as the electron donor, which was internally produced by the electrolysis of water. The short-term test confirmed that the RBER system could reduce 150-800μg/L bromate to below 10μg/L under autotrophic conditions. The reduced bromate was considered to be roughly equivalent to the amount of bromide in effluent, indicating that bromate was completely reduced to bromide without accumulation of by-products. The long-term test (over 120 days) showed that the removal fluxes of bromate and nitrate could be improved by increasing the electric current and decreasing the hydraulic retention time (HRT). But nitrite in effluent was significantly accumulated when the electric current was beyond 10mA and the HRT was less than 6h. The maximum bromate reduction rate estimated by the Monod equation was 109.12μg/Lh when the electric current was 10mA and HRT was 12h. It was proposed that the electron transfer process in RBER produced H2 on the surface of the ACF cathode, and the microbial cultures attached closely on the cathode which could completely utilize H2 as electron donors for reduction of bromate and nitrate.

  9. A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells.

    PubMed

    Hao, Yan; Yang, Wenxing; Zhang, Lei; Jiang, Roger; Mijangos, Edgar; Saygili, Yasemin; Hammarström, Leif; Hagfeldt, Anders; Boschloo, Gerrit

    2016-12-21

    Photoelectrochemical approach to solar energy conversion demands a kinetic optimization of various light-induced electron transfer processes. Of great importance are the redox mediator systems accomplishing the electron transfer processes at the semiconductor/electrolyte interface, therefore affecting profoundly the performance of various photoelectrochemical cells. Here, we develop a strategy-by addition of a small organic electron donor, tris(4-methoxyphenyl)amine, into state-of-art cobalt tris(bipyridine) redox electrolyte-to significantly improve the efficiency of dye-sensitized solar cells. The developed solar cells exhibit efficiency of 11.7 and 10.5%, at 0.46 and one-sun illumination, respectively, corresponding to a 26% efficiency improvement compared with the standard electrolyte. Preliminary stability tests showed the solar cell retained 90% of its initial efficiency after 250 h continuous one-sun light soaking. Detailed mechanistic studies reveal the crucial role of the electron transfer cascade processes within the new redox system.

  10. U(VI) bioreduction with emulsified vegetable oil as the electron donor-Model application to a field test

    SciTech Connect

    Tang, Guoping; Watson, David B; Wu, Wei-min; Schadt, Christopher Warren; Parker, Jack C; Brooks, Scott C

    2013-01-01

    A one-time 2-hour emulsified vegetable oil (EVO) injection in a fast flowing aquifer decreased U discharge to a stream for over a year. Using a comprehensive biogeochemical model developed in the companion article based on microcosm tests, we approximately matched the observed acetate, nitrate, Fe, U, and sulfate concentrations, and described the major evolution trends of multiple microbial functional groups in the field test. While the lab-determined parameters were generally applicable in the field-scale simulation, the EVO hydrolysis rate constant was estimated to be an order of magnitude greater in the field than in the microcosms. The model predicted substantial biomass (sulfate reducers) and U(IV) accumulation near the injection wells and along the side boundaries of the treatment zone where electron donors (long-chain fatty acids) from the injection wells met electron acceptors (sulfate) from the surrounding environment. While EVO retention and hydrolysis characteristics were expected to control treatment longevity, modeling results indicated that electron acceptors such as sulfate may not only compete for electrons but also play a conducive role in degrading complex substrates and enhancing U(VI) reduction and immobilization. As a result, the spacing of the injection wells could be optimized for effective sustainable bioremediation.

  11. A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells

    PubMed Central

    Hao, Yan; Yang, Wenxing; Zhang, Lei; Jiang, Roger; Mijangos, Edgar; Saygili, Yasemin; Hammarström, Leif; Hagfeldt, Anders; Boschloo, Gerrit

    2016-01-01

    Photoelectrochemical approach to solar energy conversion demands a kinetic optimization of various light-induced electron transfer processes. Of great importance are the redox mediator systems accomplishing the electron transfer processes at the semiconductor/electrolyte interface, therefore affecting profoundly the performance of various photoelectrochemical cells. Here, we develop a strategy—by addition of a small organic electron donor, tris(4-methoxyphenyl)amine, into state-of-art cobalt tris(bipyridine) redox electrolyte—to significantly improve the efficiency of dye-sensitized solar cells. The developed solar cells exhibit efficiency of 11.7 and 10.5%, at 0.46 and one-sun illumination, respectively, corresponding to a 26% efficiency improvement compared with the standard electrolyte. Preliminary stability tests showed the solar cell retained 90% of its initial efficiency after 250 h continuous one-sun light soaking. Detailed mechanistic studies reveal the crucial role of the electron transfer cascade processes within the new redox system. PMID:28000672

  12. Delocalization of unpaired electrons in acceptor-bridge-donor molecular structures as monitored by CW-EPR spectroscopy

    NASA Astrophysics Data System (ADS)

    Krzyminiewski, R.; Bielewicz, A.; Kudynska, J.; Buckmaster, H. A.; Brycki, B.

    1996-02-01

    This paper reports the application of EPR spectroscopy to study the spin density distribution of unpaired electrons in acceptor-hydrogen bridge-donor molecular complexes created by irradiation of the organic molecule piperidine with different substitutional acid groups. 9 GHz CW-EPR measurements were made at 290 K onpolycrystalline samples which were γ-irradiated with a 170 kGy dose. Measurements were also made on UV-irradiated frozen methanol solutions at 77 K. It was conclded that the ionizing radiation generates the ion radical by the removal of one hydrogen atom from the piperidine ring and that significant delocalization of the unpaired electron occurs on this ring. It was found that increasing the electronegativity of the hydrogen bridge causes a significant increase in the nitrogen hyperfine interaction and the observation of an additional hyperfine splitting which implies that a significant change in the spin density distribution of the unpaired electron has occurred. Measurements were also made on irradiated stilbene to study a π-bridge molecular structure. It was found that the ionizing radiation generates the radical by the addition of one hydrogen atom to a phenyl ring and that significant delocalization of the unpaired electron occurs on the π-bridge connecting the two phenyl rings and on one of these rings.

  13. Effect of high electron donor supply on dissimilatory nitrate reduction pathways in a bioreactor for nitrate removal.

    PubMed

    Behrendt, Anna; Tarre, Sheldon; Beliavski, Michael; Green, Michal; Klatt, Judith; de Beer, Dirk; Stief, Peter

    2014-11-01

    The possible shift of a bioreactor for NO3(-) removal from predominantly denitrification (DEN) to dissimilatory nitrate reduction to ammonium (DNRA) by elevated electron donor supply was investigated. By increasing the C/NO3(-) ratio in one of two initially identical reactors, the production of high sulfide concentrations was induced. The response of the dissimilatory NO3(-) reduction processes to the increased availability of organic carbon and sulfide was monitored in a batch incubation system. The expected shift from a DEN- towards a DNRA-dominated bioreactor was not observed, also not under conditions where DNRA would be thermodynamically favorable. Remarkably, the microbial community exposed to a high C/NO3(-) ratio and sulfide concentration did not use the most energy-gaining process.

  14. Intramolecular electron transfer within a covalent, fixed-distance donor-acceptor molecule in an ionic liquid.

    PubMed

    Lockard, Jenny V; Wasielewski, Michael R

    2007-10-11

    Intramolecular photoinduced charge separation and recombination within the donor-acceptor molecule 4-(N-pyrrolidino)naphthalene-1,8-imide-pyromellitimide, 5ANI-PI, are studied using ultrafast transient absorption spectroscopy in the room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide [EMIM][Tf2N]. The rate constants of both photoinduced charge separation and charge recombination for 5ANI-PI in [EMIM][Tf2N] are comparable to those observed in pyridine, which has a static dielectric constant similar to that of [EMIM][Tf2N] but a viscosity that is nearly 2 orders of magnitude lower than that of [EMIM][Tf2N]. The electron-transfer dynamics of 5ANI-PI in [EMIM][Tf2N] are compared to those in pyridine as a function of temperature and are discussed in the context of recently reported ionic liquid solvation studies.

  15. Long-wavelength acoustic-mode-enhanced electron emission from Se and Te donors in silicon

    NASA Astrophysics Data System (ADS)

    Korotchenkov, O. A.; Grimmeiss, H. G.

    1995-11-01

    An enhancement of the thermal emission rates from Se and Te double donors in silicon was observed by applying external vibrational excitation in the MHz frequency range. The excitation was performed either by resonant sample vibrations at frequencies of the lowest eigenmodes or by Lamb waves in a plate. Emission rates were measured by using both deep-level transient spectroscopy and single-shot capacitance techniques. Possible explanations for the observed enhancement of the emission rates are either thermal disturbances due to thermoelastic losses of mechanical energy or nonlinear effects in conjunction with oscillating stresses in solids. Our data are inconsistent with possible thermal disturbances. A tentative model is therefore proposed, suggesting that changes in the equilibrium position of impurity atoms exhibiting low-frequency oscillations yield enhanced emission rates. These changes depend upon the local surrounding of the impurity atoms and ``hardness'' of the interatomic interaction rather than the strength. Vibrational perturbations as discussed in this paper may be an effective tool to obtain new information on defects in solids.

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

    NASA Astrophysics Data System (ADS)

    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

  17. Current oscillations in semi-insulating GaAs associated with field-enhanced capture of electrons by the major deep donor EL2

    NASA Technical Reports Server (NTRS)

    Kaminska, M.; Parsey, J. M.; Lagowski, J.; Gatos, H. C.

    1982-01-01

    Current oscillations thermally activated by the release of electrons from deep levels in undoped semiinsulating GaAs were observed for the first time. They were attributed to electric field-enhanced capture of electrons by the dominant deep donor EL2 (antisite AsGa defect). This enhanced capture is due to the configurational energy barrier of EL2, which is readily penetrated by hot electrons.

  18. Production of no carrier added 80mBr for investigation of Auger electron toxicity.

    PubMed

    Mease, R C; DeJesus, O T; Gatley, S J; Harper, P V; Desombre, E R; Friedman, A M

    1991-01-01

    80mBr (half-life = 4.43 h) is an Auger electron emitting nuclide with convenient properties for investigating Auger electron cytotoxicity and with potential for labeling in vivo radiotherapeutic agents. We have investigated three cyclotron target systems capable of generating 80mBr of sufficiently high specific radioactivity (no carrier added) for biomedical experiments. A 83Kr gas target irradiated with 21.5 MeV deuterons made 80mBr at a production yield of 1.6 +/- 0.2 mCi/muAh at saturation. A five-fold increase in 80mBr yield was obtained from 15 MeV proton irradiation of thin elemental Se enriched in 80Se targets although technical improvements are expected to further raise this production yield. This route is therefore superior for current medical cyclotrons. Irradiation of a reusable 80Se copper selenide target also yielded multi-millicurie amounts of 80mBr, and recovery of radiobromine by dry distillation is faster and more convenient than in the elemental Se target, but an optimum copper selenide target for 80mBr production has not yet been built.

  19. Synthesis, electronic structure and catalytic activity of ruthenium-iodo-carbonyl complexes with thioether containing NNS donor ligand

    NASA Astrophysics Data System (ADS)

    Jana, Subrata; Jana, Mahendra Sekhar; Biswas, Sujan; Sinha, Chittaranjan; Mondal, Tapan Kumar

    2014-05-01

    The ruthenium carbonyl complexes 1 and 2 with redox noninnocent NNS donor ligand, 1-methyl-2-{(o-thiomethyl)phenylazo}imidazole (L) have been synthesized and characterized by various analytical and spectroscopic (IR, UV-Vis and 1H NMR) techniques. The complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 1.11 V for 1 and 0.76 V for 2 along with two successive one electron ligand reductions. Catalytic activity of the compounds has been investigated to the oxidation of PhCH2OH to PhCHO, 2-butanol (C4H9OH) to 2-butanone, 1-phenylethanol (PhC2H4OH) to acetophenone, cyclopentanol (C5H9OH) to cyclopentanone, cyclohexanol to cyclohexanone, cycloheptanol to cycloheptanone and cycloctanol to cycloctanone using N-methylmorpholine-N-oxide (NMO) as oxidant. The catalytic efficiency of 2 is greater than complex 1 and well correlate with the metal oxidation potential. DFT, NBO and TDDFT calculations in DFT/B3LYP/6-31G(d)/lanL2TZ(f) method are employed to interpret the structural and electronic features of the complexes.

  20. Possibility of the existence of donor-acceptor interactions in bis(azole)amines: an electronic structure analysis.

    PubMed

    Bhatia, Sonam; Bharatam, Prasad V

    2014-06-06

    Donor-stabilized divalent N(I) systems have recently gained attention in the field of organic chemistry. Existence of low-valent nitrogen(I) species with moderate nucleophilicities in several pharmacophoric functionalities is prompting extensive exploration in this field. Quantum chemical analysis on the imidazole, oxazole, and thiazole derivatives of thiazole-2-amine indicated that these species preferably exist in the iminic state. Electronic structure analysis of these systems suggested the existence of hidden divalent N(I) character in a neutral state (L → N-R) and the explicit divalent N(I) character (L → N ← L)(+) in the protonated state. The strength of L → N interaction in these systems was analyzed, and the variations in the nucleophilicity trend at the coordinating nitrogen center were rationalized by estimating the electronic (TEP (Tolman electronic parameter) and MESP minimum (V(min))) as well as steric parameters (r-repulsiveness and ΔH elimination of CO group, in L → Ni(CO)3) of the coordinating ligands L. The importance of energetically preferred ionic and tautomeric representations of thiazol-2-amine derivatives in iminic and aminic forms was also demonstrated by carrying out comparative docking analysis with the enzyme lymphocyte-specific kinase (Lck).

  1. "Push-pull" 1,8-naphthalic anhydride with multiple triphenylamine groups as electron donor

    NASA Astrophysics Data System (ADS)

    Wang, Limin; Shi, Yan; Zhao, Yingyuan; Liu, Heyuan; Li, Xiyou; Bai, Ming

    2014-01-01

    In this paper, the "push-pull" molecules consisting of different number of triphenylamino groups and 1,8-naphthalic anhydride ring were designed and synthesized. The UV-vis absorption and emission spectra of these compounds were recorded. Along with the increase on the number of the electron donating triphenylamino groups, both the absorption and emission bands show significant red shift. More importantly, the fluorescence quantum yields drop sharply along with the increase on the number of triphenylamino groups. The molecular structure, the frontier molecular orbital energies and the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest un-occupied molecular orbital (LUMO) were calculated with DFT method. The calculated results indicate that the connection of more electron donating triphenylamino groups in molecule caused a change for the first excited state from an intramolecular charge transfer (ICT) state to an intramolecular electron transfer state (ET). This change on the first excited state has led to the fluorescence quenching.

  2. Halogen bonding. The role of the polarizability of the electron-pair donor.

    PubMed

    Duarte, Darío J R; Sosa, Gladis L; Peruchena, Nélida M; Alkorta, Ibon

    2016-03-14

    The nature of F-BrX-R interactions (with X = F, Cl, Br, I and R = -H, -F) has been investigated through theoretical calculation of molecular potential electrostatic (MEP), molecular polarizability, atoms in molecules (AIM) analysis and energetic decomposition analysis (EDA). A detailed analysis of the MEPs reveals that considering only the static electrostatic interactions is not sufficient to explain the nature of these interactions. The molecular polarizabilities of X-R molecules suggest that the deformation capacity of the electronic cloud of the lone pairs of the X atom plays an important role in the stability of these complexes. The topological analysis of the L(r) = -¼∇(2)ρ(r) function and the detailed analysis of the atomic quadrupole moments reveal that the BrX interactions are electrostatic in nature. The electron acceptor Br atom causes a polarization of the electronic cloud (electronic induction) on the valence shell of the X atom. Finally, the electrostatic forces and charge transfer play an important role not only in the stabilization of the complex, but also in the determination of the molecular geometry of equilibrium. The dispersive and polarization forces do not influence the equilibrium molecular geometry.

  3. Graphene and Donor-Acceptor Molecules/Nanoparticle Composites for Advanced Electronics Technologies

    DTIC Science & Technology

    2013-06-26

    induced by carbon and boron fullerenes (C60, C70, C80 and B80). Spin-polarized first-principles calculations were performed on zigzag boron− nitride ...structures and electronic properties of two-dimensional single-layer graphene in the presence of non-covalent interactions induced by carbon and boron...fullerenes (C60, C70, C80 and B80) and spin-polarized first-principles calculations performed on zigzag boron− nitride nanoribbons (z-BNNRs) with lines

  4. 5' modification of duplex DNA with a ruthenium electron donor-acceptor pair using solid-phase DNA synthesis

    NASA Technical Reports Server (NTRS)

    Frank, Natia L.; Meade, Thomas J.

    2003-01-01

    Incorporation of metalated nucleosides into DNA through covalent modification is crucial to measurement of thermal electron-transfer rates and the dependence of these rates with structure, distance, and position. Here, we report the first synthesis of an electron donor-acceptor pair of 5' metallonucleosides and their subsequent incorporation into oligonucleotides using solid-phase DNA synthesis techniques. Large-scale syntheses of metal-containing oligonucleotides are achieved using 5' modified phosporamidites containing [Ru(acac)(2)(IMPy)](2+) (acac is acetylacetonato; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (3) and [Ru(bpy)(2)(IMPy)](2+) (bpy is 2,2'-bipyridine; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (4). Duplexes formed with the metal-containing oligonucleotides exhibit thermal stability comparable to the corresponding unmetalated duplexes (T(m) of modified duplex = 49 degrees C vs T(m) of unmodified duplex = 47 degrees C). Electrochemical (3, E(1/2) = -0.04 V vs NHE; 4, E(1/2) = 1.12 V vs NHE), absorption (3, lambda(max) = 568, 369 nm; 4, lambda(max) = 480 nm), and emission (4, lambda(max) = 720 nm, tau = 55 ns, Phi = 1.2 x 10(-)(4)) data for the ruthenium-modified nucleosides and oligonucleotides indicate that incorporation into an oligonucleotide does not perturb the electronic properties of the ruthenium complex or the DNA significantly. In addition, the absence of any change in the emission properties upon metalated duplex formation suggests that the [Ru(bpy)(2)(IMPy)](2+)[Ru(acac)(2)(IMPy)](2+) pair will provide a valuable probe for DNA-mediated electron-transfer studies.

  5. Sulfur-based mixotrophic denitrification corresponding to different electron donors and microbial profiling in anoxic fluidized-bed membrane bioreactors.

    PubMed

    Zhang, Lili; Zhang, Chao; Hu, Chengzhi; Liu, Huijuan; Bai, Yaohui; Qu, Jiuhui

    2015-11-15

    Sulfur-based mixotrophic denitrifying anoxic fluidized bed membrane bioreactors (AnFB-MBR) were developed for the treatment of nitrate-contaminated groundwater with minimized sulfate production. The nitrate removal rates obtained in the methanol- and ethanol-fed mixotrophic denitrifying AnFB-MBRs reached 1.44-3.84 g NO3 -N/L reactor d at a hydraulic retention time of 0.5 h, which were significantly superior to those reported in packed bed reactors. Compared to methanol, ethanol was found to be a more effective external carbon source for sulfur-based mixotrophic denitrification due to lower sulfate and total organic carbon concentrations in the effluent. Using pyrosequencing, the phylotypes of primary microbial groups in the reactor, including sulfur-oxidizing autotrophic denitrifiers, methanol- or ethanol-supported heterotrophic denitrifiers, were investigated in response to changes in electron donors. Principal component and heatmap analyses indicated that selection of electron donating substrates largely determined the microbial community structure. The abundance of Thiobacillus decreased from 45.1% in the sulfur-oxidizing autotrophic denitrifying reactor to 12.0% and 14.2% in sulfur-based methanol- and ethanol-fed mixotrophic denitrifying bioreactors, respectively. Heterotrophic Methyloversatilis and Thauera bacteria became more dominant in the mixotrophic denitrifying bioreactors, which were possibly responsible for the observed methanol- and ethanol-associated denitrification.

  6. Comparative analysis of cyanobacterial and plant peroxiredoxins and their electron donors: peroxidase activity and susceptibility to overoxidation.

    PubMed

    Lindahl, Marika; Cejudo, Francisco Javier

    2013-01-01

    Peroxiredoxins (Prxs) are peroxidases that use thiol-based catalytic mechanisms implying redox-active cysteines. The different Prx families have homologs in all photosynthetic organisms, including plants, algae, and cyanobacteria. However, recent studies show that the physiological reduction systems that provide Prxs with reducing equivalents to sustain their activities differ considerably between cyanobacterial strains. Thus, for example, the filamentous cyanobacterium Anabaena sp. PCC 7120 is similar to the chloroplast in that it possesses an abundant 2-Cys Prx, which receives electrons from the NADPH-dependent thioredoxin reductase C (NTRC). In contrast, the unicellular cyanobacterium Synechocystis sp. PCC 6803, which lacks NTRC, has little 2-Cys Prx but high amounts of PrxII and 1-Cys Prx. The characterization of cyanobacterial Prxs and their electron donors relies on straightforward enzymatic assays and tools to study the physiological relevance of these systems. Here, we present methods to measure peroxidase activities in vitro and peroxide decomposition in vivo. Several approaches to detect overoxidation of the active site cysteine in cyanobacterial 2-Cys Prxs are also described.

  7. Magnetic field enhanced electroluminescence in organic light emitting diodes based on electron donor-acceptor exciplex blends

    NASA Astrophysics Data System (ADS)

    Baniya, Sangita; Basel, Tek; Sun, Dali; McLaughlin, Ryan; Vardeny, Zeev Valy

    2016-03-01

    A useful process for light harvesting from injected electron-hole pairs in organic light emitting diodes (OLED) is the transfer from triplet excitons (T) to singlet excitons (S) via reverse intersystem crossing (RISC). This process adds a delayed electro-luminescence (EL) emission component that is known as thermally activated delayed fluorescence (TADF). We have studied electron donor (D)/acceptor(A) blends that form an exciplex manifold in which the energy difference, ΔEST between the lowest singlet (S1) and triplet (T1) levels is relatively small (<100 meV), and thus allows RISC at ambient temperature. We found that the EL emission in OLED based on the exciplex blend is enhanced up to 40% by applying a relatively weak magnetic field of 50 mT at ambient. Moreover the MEL response is activated with activation energy similar that of the EL emission. This suggests that the large magneto-EL originates from an additional spin-mixing channel between singlet and triplet states of the generated exciplexes, which is due to TADF. We will report on the MEL dependencies on the temperature, bias voltage, and D-A materials for optimum OLED performance. Supported by SAMSUNG Global Research Outreach (GRO) program, and also by the NSF-Material Science & Engineering Center (MRSEC) program at the University of Utah (DMR-1121252).

  8. Pseudoazurin from Sinorhizobium meliloti as an electron donor to copper-containing nitrite reductase: influence of the redox partner on the reduction potentials of the enzyme copper centers.

    PubMed

    Ferroni, Félix M; Marangon, Jacopo; Neuman, Nicolás I; Cristaldi, Julio C; Brambilla, Silvina M; Guerrero, Sergio A; Rivas, María G; Rizzi, Alberto C; Brondino, Carlos D

    2014-08-01

    Pseudoazurin (Paz) is the physiological electron donor to copper-containing nitrite reductase (Nir), which catalyzes the reduction of NO2 (-) to NO. The Nir reaction mechanism involves the reduction of the type 1 (T1) copper electron transfer center by the external physiological electron donor, intramolecular electron transfer from the T1 copper center to the T2 copper center, and nitrite reduction at the type 2 (T2) copper catalytic center. We report the cloning, expression, and characterization of Paz from Sinorhizobium meliloti 2011 (SmPaz), the ability of SmPaz to act as an electron donor partner of S. meliloti 2011 Nir (SmNir), and the redox properties of the metal centers involved in the electron transfer chain. Gel filtration chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis together with UV-vis and EPR spectroscopies revealed that as-purified SmPaz is a mononuclear copper-containing protein that has a T1 copper site in a highly distorted tetrahedral geometry. The SmPaz/SmNir interaction investigated electrochemically showed that SmPaz serves as an efficient electron donor to SmNir. The formal reduction potentials of the T1 copper center in SmPaz and the T1 and T2 copper centers in SmNir, evaluated by cyclic voltammetry and by UV-vis- and EPR-mediated potentiometric titrations, are against an efficient Paz T1 center to Nir T1 center to Nir T2 center electron transfer. EPR experiments proved that as a result of the SmPaz/SmNir interaction in the presence of nitrite, the order of the reduction potentials of SmNir reversed, in line with T1 center to T2 center electron transfer being thermodynamically more favorable.

  9. Development of imide- and imidazole-containing electron acceptors for use in donor-acceptor conjugated compounds and polymers

    NASA Astrophysics Data System (ADS)

    Li, Duo

    Conjugated organic compounds and polymers have attracted significant attention due to their potential application in electronic devices as semiconducting materials, such as organic solar cells (OSCs). In order to tune band gaps, donor-acceptor (D-A) structure is widely used, which has been proved to be one of the most effective strategies. This thesis consists of three parts: 1) design, syntheses and characterization of new weak acceptors based on imides and the systematic study of the structure-property relationship; (2) introduction of weak and strong acceptors in one polymer to achieve a broad coverage of light absorption and improve the power conversion efficiency (PCE); (3) modification of benzothiadiazole (BT) acceptor in order to increase the electron withdrawing ability. Imide-based electron acceptors, 4-(5-bromothiophen-2-y1)-2-(2-ethylhexyl)-9- phenyl- 1H-benzo[f]isoindole-1,3(2H)-dione (BIDO-1) and 4,9-bis(5-bromothiophen-2-yl)-2-(2-ethylhexyl)-benzo[f]isoindole-1,3-dione (BIDO-2), were designed and synthesized. In this design, naphthalene is selected as its main core to maintain a planar structure, and thienyl groups are able to facilitate the bromination reaction and lower the band gap. BIDO-1 and BIDO-2 were successfully coupled with different donors by both Suzuki cross-coupling and Stille cross-coupling reactions. Based on the energy levels and band gaps of the BIDO-containing compounds and polymers, BIDO-1 and BIDO-2 are proved to be weak electron acceptors. Pyromellitic diimide (PMDI) was also studied and found to be a stronger electron acceptor than BIDO . In order to obtain broad absorption coverage, both weak acceptor ( BIDO-2) and strong acceptor diketopyrrolopyrrole (DPP) were introduced in the same polymer. The resulting polymers show two absorption bands at 400 and 600 nm and two emission peaks at 500 and 680 nm. The band gaps of the polymers are around 1.6 eV, which is ideal for OSC application. The PCE of 1.17% was achieved. Finally

  10. Added-value from a multi-criteria selection of donor catchments in the prediction of continuous streamflow series at ungauged pollution control-sites

    NASA Astrophysics Data System (ADS)

    Drogue, Gilles; Ben Khediri, Wiem; Conan, Céline

    2016-05-01

    We explore the potential of a multi-criteria selection of donor catchments in the prediction of continuous streamflow series by the spatial proximity method. Three criteria have been used: (1) spatial proximity; (2) physical similarity; (3) stream gauging network topology. An extensive assessment of our spatial proximity method variant is made on a 149 catchment-data set located in the Rhine-Meuse catchment. The competitiveness of the method is evaluated against spatial interpolation of catchment model parameters with ordinary kriging. We found that the spatial proximity approach is more efficient than ordinary kriging. When distance to upstream/downstream stream gauge stations is considered as a second order criterion in the selection of donor catchments, an unprecedented level of efficiency is reached for nested catchments. Nevertheless, the spatial proximity method does not take advantage from physical similarity between donor catchments and receiver catchments because catchments that are the most hydrologically similar to each catchment poorly match with the catchments that are the most physically similar to each catchment.

  11. Ammonia synthesis using a stable electride as an electron donor and reversible hydrogen store

    NASA Astrophysics Data System (ADS)

    Kitano, Masaaki; Inoue, Yasunori; Yamazaki, Youhei; Hayashi, Fumitaka; Kanbara, Shinji; Matsuishi, Satoru; Yokoyama, Toshiharu; Kim, Sung-Wng; Hara, Michikazu; Hosono, Hideo

    2012-11-01

    Industrially, the artificial fixation of atmospheric nitrogen to ammonia is carried out using the Haber-Bosch process, but this process requires high temperatures and pressures, and consumes more than 1% of the world's power production. Therefore the search is on for a more environmentally benign process that occurs under milder conditions. Here, we report that a Ru-loaded electride [Ca24Al28O64]4+(e-)4 (Ru/C12A7:e-), which has high electron-donating power and chemical stability, works as an efficient catalyst for ammonia synthesis. Highly efficient ammonia synthesis is achieved with a catalytic activity that is an order of magnitude greater than those of other previously reported Ru-loaded catalysts and with almost half the reaction activation energy. Kinetic analysis with infrared spectroscopy reveals that C12A7:e- markedly enhances N2 dissociation on Ru by the back donation of electrons and that the poisoning of ruthenium surfaces by hydrogen adatoms can be suppressed effectively because of the ability of C12A7:e- to store hydrogen reversibly.

  12. Electron donor concentrations in sediments and sediment properties at the agricultural chemicals team research site near New Providence, Iowa, 2006-07

    USGS Publications Warehouse

    Maharjan, Bijesh; Korom, Scott F.; Smith, Erik A.

    2013-01-01

    The concentrations of electron donors in aquifer sediments are important to the understanding of the fate and transport of redox-sensitive constituents in groundwater, such as nitrate. For a study by the U.S. Geological Survey National Water-Quality Assessment Program, 50 sediment samples were collected from below the water table from 11 boreholes at the U.S. Geological Survey Agricultural Chemicals Team research site near New Providence, Iowa, during 2006-07. All samples were analyzed for gravel, sand (coarse, medium, and fine), silt, clay, Munsell soil color, inorganic carbon content, and for the following electron donors: organic carbon, ferrous iron, and inorganic sulfide. A subset of 14 sediment samples also was analyzed for organic sulfur, but all of these samples had concentrations less than the method detection limit; therefore, the presence of this potential electron donor was not considered further. X-ray diffraction analyses provided important semi-quantitative information of well-crystallized dominant minerals within the sediments that might be contributing electron donors.

  13. Acidification due to microbial dechlorination near a trichloroethene DNAPL is overcome with pH buffer or formate as electron donor: experimental demonstration in diffusion-cells.

    PubMed

    Philips, Jo; Maes, Nele; Springael, Dirk; Smolders, Erik

    2013-04-01

    Acidification due to microbial dechlorination of trichloroethene (TCE) can limit the bio-enhanced dissolution of TCE dense non-aqueous phase liquid (DNAPL). This study related the dissolution enhancement of a TCE DNAPL to the pH buffer capacity of the medium and the type of electron donor used. In batch systems, dechlorination was optimal at pH7.1-7.5, but was completely inhibited below pH6.2. In addition, dechlorination in batch systems led to a smaller pH decrease at an increasing pH buffer capacity or with the use of formate instead of lactate as electron donor. Subsequently, bio-enhanced TCE DNAPL dissolution was quantified in diffusion-cells with a 5.5 cm central sand layer, separating a TCE DNAPL layer from an aqueous top layer. Three different pH buffer capacities (2.9 mM-17.9 mM MOPS) and lactate or formate as electron donor were applied. In the lactate fed diffusion-cells, the DNAPL dissolution enhancement factor increased from 1.5 to 2.2 with an increase of the pH buffer capacity. In contrast, in the formate fed diffusion-cells, the DNAPL dissolution enhancement factor (2.4±0.3) was unaffected by the pH buffer capacity. Measurement of the pore water pH confirmed that the pH decreased less with an increased pH buffer capacity or with formate instead of lactate as electron donor. These results suggest that the significant impact of acidification on bio-enhanced DNAPL dissolution can be overcome by the amendment of a pH buffer or by applying a non acidifying electron donor like formate.

  14. [Potential Carbon Fixation Capability of Non-photosynthetic Microbial Community at Different Depth of the South China Sea and Its Response to Different Electron Donors].

    PubMed

    Fang, Feng; Wang, Lei; Xi, Xue-fei; Hu, Jia-jun; Fu, Xiao-hua; Lu, Bing; Xu, Dian-sheng

    2015-05-01

    The seawater samples collected from many different areas with different depth in the South China Sea were cultivated using different electron donors respectively. And the variation in the potential carbon fixation capability ( PCFC ) of non-photosynthetic microbial community (NPMC) in seawater with different depth was determined after a cycle of cultivation through the statistic analysis. In addition, the cause for the variation was clarified through analyzing key gene abundance regarding CO2 fixation and characteristics of seawater with different depth. The result showed that the PCFCs of NPMC in seawater with different depth were generally low and had no significant difference when using NaNO2 as the electron donor. The PCFC of NPMC in surface seawater was higher than that in deep seawater when using H2 as the electron donor, on the contrary, the PCFC of NPMC in deep seawater was higher than that in surface seawater when using Na2S2O3 as the electron donor. The abundance of the main CO2 fixation gene cbbL in surface seawater was higher than that in deep seawater while the cbbM gene abundance in deep seawater was higher than that in surface seawater. Most hydrogen-oxidizing bacteria had the cbbL gene, and most sulfur bacteria had the cbbM gene. The tendency of seawater cbbL/cbbM gene abundance with the change of depth revealed that there were different kinds of bacteria accounting for the majority in NPMC fixing CO2 at different depth of ocean, which led to different response of PCFC of NPMC at different depth of the sea to different electron donors. The distributions of dissolved oxygen and inorganic carbon concentration with the change of the depth of the sea might be an important reason leading to the difference of NPMC structure and even the difference of PCFC at different depth of the sea.

  15. Complexation and Electronic Communication between Corannulene-Based Buckybowls and a Curved Truxene-TTF Donor.

    PubMed

    Gallego, María; Calbo, Joaquín; Krick Calderon, Rafael M; Pla, Paula; Hsieh, Ya-Chu; Pérez, Emilio M; Wu, Yao-Ting; Ortí, Enrique; Guldi, Dirk M; Martín, Nazario

    2017-03-13

    The association behavior of an electron-donating, bowl-shaped, truxene-based tetrathiafulvalene (truxTTF) with two corannulene-based fullerene fragments, C32 H12 and C38 H14 , is investigated in several solvents. Formation of 1:1 complexes is followed by absorption titrations and complemented by density functional theory (DFT) calculations. The binding constants are in the range log Ka =2.9-3.5. DFT calculations reveal that the most stable arrangement is the conformation in which the 1,3-dithiole ring of truxTTF is placed inside the concave cavity of the corannulene derivative. This arrangement is confirmed experimentally by NMR measurements, and implies that a combination of π-π and CH-π interactions is the driving force for association. Time-dependent DFT calculations reproduce the experimental UV/Vis titrations and provide a detailed understanding of the spectral changes observed. Femtosecond transient absorption studies reveal the processes occurring after photoexcitation of either C32 H12 or C38 H14 and their supramolecular associates with truxTTF. In the case of truxTTF⋅C38 H14 , photoexcitation yields the charge-separated state truxTTF(.+) ⋅C38 H14(.-) with a lifetime of approximately 160 ps.

  16. Potential benefits of triethylamine as n-electron donor in the estimation of forskolin by electronic absorption and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Raju, Gajula; Ram Reddy, A.

    2016-02-01

    Diterpenoid forskolin was isolated from Coleus forskolii. The electronic absorption and emission studies of forskolin were investigated in various solvents with an aim to improve its detection limits. The two chromophores present in the diterpenoid are not conjugated leading to the poor absorption and emission of UV light. The absorption and fluorescence spectra were solvent specific. In the presence of a monodentate ligand, triethylamine the detection of forskolin is improved by 3.63 times in ethanol with the fluorescence method and 3.36 times in DMSO by the absorption spectral method. The longer wavelength absorption maximum is blue shifted while the lower energy fluorescence maximum is red shifted in the presence of triethylamine. From the wavelength of fluorescence maxima of the exciplex formed between excited forskolin and triethylamine it is concluded that the order of reactivity of hydroxyl groups in the excited state forskolin is in the reverse order to that of the order of the reactivity of hydroxyl groups in its ground state.

  17. Potential benefits of triethylamine as n-electron donor in the estimation of forskolin by electronic absorption and emission spectroscopy.

    PubMed

    Raju, Gajula; Reddy, A Ram

    2016-02-05

    Diterpenoid forskolin was isolated from Coleus forskolii. The electronic absorption and emission studies of forskolin were investigated in various solvents with an aim to improve its detection limits. The two chromophores present in the diterpenoid are not conjugated leading to the poor absorption and emission of UV light. The absorption and fluorescence spectra were solvent specific. In the presence of a monodentate ligand, triethylamine the detection of forskolin is improved by 3.63 times in ethanol with the fluorescence method and 3.36 times in DMSO by the absorption spectral method. The longer wavelength absorption maximum is blue shifted while the lower energy fluorescence maximum is red shifted in the presence of triethylamine. From the wavelength of fluorescence maxima of the exciplex formed between excited forskolin and triethylamine it is concluded that the order of reactivity of hydroxyl groups in the excited state forskolin is in the reverse order to that of the order of the reactivity of hydroxyl groups in its ground state.

  18. Recycling of mixed plastic waste from electrical and electronic equipment. Added value by compatibilization.

    PubMed

    Vazquez, Yamila V; Barbosa, Silvia E

    2016-07-01

    Plastic waste from electrical and electronic equipment (WEEE) grows up exponentially fast in the last two decades. Either consumption increase of technological products, like cellphones or computers, or the short lifetime of this products contributes to this rise generating an accumulation of specific plastic materials such ABS (Acrylonitrile-Butadiene-Styrene), HIPS (High impact Polystyrene), PC (Polycarbonate), among others. All of they can be recycled by themselves. However, to separate them by type is neither easy nor economically viable, then an alternative is recycling them together as a blend. Taking into account that could be a deterioration in final properties, to enhance phase adhesion and add value to a new plastic WEEE blend a compatibilization is needed. In this work, a systematical study of different compatibilizers for blends of HIPS and ABS from WEEE was performed. A screening analysis was carried out by adding two different compatibilizer concentration (2wt% and 20wt%) on a HIPS/ABS physical blend 80/20 proportion from plastic e-waste. Three copolymers were selected as possible compatibilizers by their possible affinity with initial plastic WEEE. A complete characterization of each WEEE was performed and compatibilization efficiency was evaluated by comparing either mechanical or morphological blends aspects. Considering blends analyzed in this work, the best performance was achieved by using 2% of styrene-acrylonitrile rubber, obtaining a compatibilized blend with double ultimate strength and modulus respect to the physical blend, and also improve mechanical properties of initial WEEE plastics. The proposed way is a promise route to improve benefit of e-scrap with sustainable, low costs and easy handling process. Consequently, social recycling interest will be encouraged by both ecological and economical points of view.

  19. An Inexpensive Co-Intercalated Layered Double Hydroxide Composite with Electron Donor-Acceptor Character for Photoelectrochemical Water Splitting.

    PubMed

    Zheng, Shufang; Lu, Jun; Yan, Dongpeng; Qin, Yumei; Li, Hailong; Evans, David G; Duan, Xue

    2015-07-15

    In this paper, the inexpensive 4,4-diaminostilbene-2,2-disulfonate (DAS) and 4,4-dinitro-stilbene-2,2- disulfonate (DNS) anions with arbitrary molar ratios were successfully co-intercalated into Zn2Al-layered double hydroxides (LDHs). The DAS(50%)-DNS/LDHs composite exhibited the broad UV-visible light absorption and fluorescence quenching, which was a direct indication of photo-induced electron transfer (PET) process between the intercalated DAS (donor) and DNS (acceptor) anions. This was confirmed by the matched HOMO/LUMO energy levels alignment of the intercalated DAS and DNS anions, which was also compatible for water splitting. The DAS(50%)-DNS/LDHs composite was fabricated as the photoanode and Pt as the cathode. Under the UV-visible light illumination, the enhanced photo-generated current (4.67 mA/cm(2) at 0.8 V vs. SCE) was generated in the external circuit, and the photoelectrochemical water split was realized. Furthermore, this photoelectrochemical water splitting performance had excellent crystalline, electrochemical and optical stability. Therefore, this novel inorganic/organic hybrid photoanode exhibited potential application prospect in photoelectrochemical water splitting.

  20. An ESEEM study of the oxidized electron donor of plant photosystem II: Evidence that D ? is a neutral tyrosine radical

    NASA Astrophysics Data System (ADS)

    Evelo, R. G.; Hoff, A. J.; Dikanov, S. A.; Tyryshkin, A. M.

    1989-09-01

    Electron spin-echo envelope modulation (ESEEM) has been performed on the tyrosyl radical D ? in photosystem II of plants and algae. This radical was investigated in PS II-enriched subchloroplast particles, and in perdeuterated and 15N-substituted Chlorella vulgaris algae. From the ESEEM analysis in the time and frequency domain, two proton hyperfine interactions were determined. One of these protons has hyperfine parameters aiso=27.2 MHz, T11=-3.1 MHz and T22/ T11=0.5. The second proton, which is easily exchangeable by deuterium, has parameters aiso=±1.6 MHz, T11=∓8.4 MHz and T22/ T11=1. The hyperfine parameters of the first proton are characteristic of a β-methylene proton, whereas those of the second indicate that it is a proton hydrogen bonded to the tyrosyl oxygen. We conclude that the oxidized tyrosyl donor is a neutral hydrogen-bonded radical.

  1. An Inexpensive Co-Intercalated Layered Double Hydroxide Composite with Electron Donor-Acceptor Character for Photoelectrochemical Water Splitting

    PubMed Central

    Zheng, Shufang; Lu, Jun; Yan, Dongpeng; Qin, Yumei; Li, Hailong; Evans, David G.; Duan, Xue

    2015-01-01

    In this paper, the inexpensive 4,4-diaminostilbene-2,2-disulfonate (DAS) and 4,4-dinitro-stilbene-2,2- disulfonate (DNS) anions with arbitrary molar ratios were successfully co-intercalated into Zn2Al-layered double hydroxides (LDHs). The DAS(50%)-DNS/LDHs composite exhibited the broad UV-visible light absorption and fluorescence quenching, which was a direct indication of photo-induced electron transfer (PET) process between the intercalated DAS (donor) and DNS (acceptor) anions. This was confirmed by the matched HOMO/LUMO energy levels alignment of the intercalated DAS and DNS anions, which was also compatible for water splitting. The DAS(50%)-DNS/LDHs composite was fabricated as the photoanode and Pt as the cathode. Under the UV-visible light illumination, the enhanced photo-generated current (4.67 mA/cm2 at 0.8 V vs. SCE) was generated in the external circuit, and the photoelectrochemical water split was realized. Furthermore, this photoelectrochemical water splitting performance had excellent crystalline, electrochemical and optical stability. Therefore, this novel inorganic/organic hybrid photoanode exhibited potential application prospect in photoelectrochemical water splitting. PMID:26174201

  2. Use of organic substrates as electron donors for biological sulfate reduction in gypsiferous mine soils from Nakhon Si Thammarat (Thailand).

    PubMed

    Kijjanapanich, Pimluck; Annachhatre, Ajit P; Esposito, Giovanni; Lens, Piet N L

    2014-04-01

    Soils in some mining areas contain a high gypsum content, which can give adverse effects to the environment and may cause many cultivation problems, such as a low water retention capacity and low fertility. The quality of such mine soils can be improved by reducing the soil's gypsum content. This study aims to develop an appropriate in situ bioremediation technology for abbreviating the gypsum content of mine soils by using sulfate reducing bacteria (SRB). The technology was applied to a mine soil from a gypsum mine in the southern part of Thailand which contains a high sulfate content (150 g kg(-1)). Cheap organic substrates with low or no cost, such as rice husk, pig farm wastewater treatment sludge and coconut husk chips were mixed (60:20:20 by volume) and supplied to the soil as electron donors for the SRB. The highest sulfate removal efficiency of 59% was achieved in the soil mixed with 40% organic mixture, corresponding to a reduction of the soil gypsum content from 25% to 7.5%. For economic gains, this treated soil can be further used for agriculture and the produced sulfide can be recovered as the fertilizer elemental sulfur.

  3. Electron and donor-impurity-related Raman scattering and Raman gain in triangular quantum dots under an applied electric field

    NASA Astrophysics Data System (ADS)

    Tiutiunnyk, Anton; Akimov, Volodymyr; Tulupenko, Viktor; Mora-Ramos, Miguel E.; Kasapoglu, Esin; Morales, Alvaro L.; Duque, Carlos Alberto

    2016-04-01

    The differential cross-section of electron Raman scattering and the Raman gain are calculated and analysed in the case of prismatic quantum dots with equilateral triangle base shape. The study takes into account their dependencies on the size of the triangle, the influence of externally applied electric field as well as the presence of an ionized donor center located at the triangle's orthocenter. The calculations are made within the effective mass and parabolic band approximations, with a diagonalization scheme being applied to obtain the eigenfunctions and eigenvalues of the x- y Hamiltonian. The incident and secondary (scattered) radiation have been considered linearly-polarized along the y-direction, coinciding with the direction of the applied electric field. For the case with an impurity center, Raman scattering with the intermediate state energy below the initial state one has been found to show maximum differential cross-section more than by an order of magnitude bigger than that resulting from the scheme with lower intermediate state energy. The Raman gain has maximum magnitude around 35 nm dot size and electric field of 40 kV/cm for the case without impurity and at maximum considered values of the input parameters for the case with impurity. Values of Raman gain of the order of up to 104cm-1 are predicted in both cases.

  4. The electronic structure and second-order nonlinear optical properties of donor-acceptor acetylenes - A detailed investigation of structure-property relationships

    NASA Technical Reports Server (NTRS)

    Stiegman, A. E.; Graham, Eva; Khundkar, Lutfur R.; Perry, Joseph W.; Cheng, L.-T.; Perry, Kelly J.

    1991-01-01

    A series of donor-acceptor acetylene compounds was synthesized in which systematic changes in both the conjugation length and the donor-acceptor strength were made. The effect of these structural changes on the spectroscopic and electronic properties of the molecules and, ultimately, on the measured second-order molecular hyperpolarizabilities (beta) was investigated. It was found that increases in the donor-acceptor strength resulted in increases in the magnitude of beta. For this class of molecules, the increase is dominated by the energy of the intramolecular charge-transfer transition, while factors such as the ground to excited-state dipole moment change and the transition-moment integral are much less important. Increasing the conjugation length from one to two acetylene linkers did not result in an increase in the value of beta; however, beta increased sharply in going from two acetylenes to three. This increase is attributed to the superposition of several nearly isoenergetic excited states.

  5. Correlation of hydrogen-atom abstraction reaction efficiencies for aryl radicals with their vertical electron affinities and the vertical ionization energies of the hydrogen-atom donors.

    PubMed

    Jing, Linhong; Nash, John J; Kenttämaa, Hilkka I

    2008-12-31

    The factors that control the reactivities of aryl radicals toward hydrogen-atom donors were studied by using a dual-cell Fourier-transform ion cyclotron resonance mass spectrometer. Hydrogen-atom abstraction reaction efficiencies for two substrates, cyclohexane and isopropyl alcohol, were measured for 23 structurally different, positively charged aryl radicals, which included dehydrobenzenes, dehydronaphthalenes, dehydropyridines, and dehydro(iso)quinolines. A logarithmic correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) vertical electron affinities (EA) of the aryl radicals. Transition state energies calculated for the reaction of three of the aryl radicals with isopropyl alcohol were found to correlate linearly with their (calculated) EAs. No correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) enthalpy changes for the reactions. Measurement of the reaction efficiencies for the reactions of 15 different hydrogen-atom donors with two selected aryl radicals revealed a logarithmic correlation between the hydrogen-atom abstraction reaction efficiencies and the vertical ionization energies (IE) of the hydrogen-atom donors, but not the lowest homolytic X-H (X = heavy atom) bond dissociation energies of the hydrogen-atom donors. Examination of the hydrogen-atom abstraction reactions of 29 different aryl radicals and 18 different hydrogen-atom donors showed that the reaction efficiency increases (logarithmically) as the difference between the IE of the hydrogen-atom donor and the EA of the aryl radical decreases. This dependence is likely to result from the increasing polarization, and concomitant stabilization, of the transition state. Thus, the hydrogen-atom abstraction reaction efficiency for an aryl radical can be "tuned" by structural changes that influence either the vertical EA of the aryl radical or the vertical IE of the hydrogen atom donor.

  6. Correlation of Hydrogen-Atom Abstraction Reaction Efficiencies for Aryl Radicals with their Vertical Electron Affinities and the Vertical Ionization Energies of the Hydrogen Atom Donors

    PubMed Central

    Jing, Linhong; Nash, John J.

    2009-01-01

    The factors that control the reactivities of aryl radicals toward hydrogen-atom donors were studied by using a dual-cell Fourier-transform ion cyclotron resonance mass spectrometer (FT – ICR). Hydrogen-atom abstraction reaction efficiencies for two substrates, cyclohexane and isopropanol, were measured for twenty-three structurally different, positively-charged aryl radicals, which included dehydrobenzenes, dehydronaphthalenes, dehydropyridines, and dehydro(iso)quinolines. A logarithmic correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) vertical electron affinities (EA) of the aryl radicals. Transition state energies calculated for three of the aryl radicals with isopropanol were found to correlate linearly with their (calculated) EAs. No correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) enthalpy changes for the reactions. Measurement of the reaction efficiencies for the reactions of several different hydrogen-atom donors with a few selected aryl radicals revealed a logarithmic correlation between the hydrogen-atom abstraction reaction efficiencies and the vertical ionization energies (IE) of the hydrogen-atom donors, but not the lowest homolytic X – H (X = heavy atom) bond dissociation energies of the hydrogen-atom donors. Examination of the hydrogen-atom abstraction reactions of twenty-nine different aryl radicals and eighteen different hydrogen-atom donors showed that the reaction efficiency increases (logarithmically) as the difference between the IE of the hydrogen-atom donor and the EA of the aryl radical decreases. This dependence is likely to result from the increasing polarization, and concomitant stabilization, of the transition state as the energy difference between the neutral and ionic reactants decreases. Thus, the hydrogen-atom abstraction reaction efficiency for an aryl radical can be “tuned” by structural changes that influence either

  7. Tuning the Rectification Ratio by Changing the Electronic Nature (Open-Shell and Closed-Shell) in Donor-Acceptor Self-Assembled Monolayers.

    PubMed

    Souto, Manuel; Yuan, Li; Morales, Dayana C; Jiang, Li; Ratera, Imma; Nijhuis, Christian A; Veciana, Jaume

    2017-03-16

    This Communication describes the mechanism of charge transport across self-assembled monolayers (SAMs) of two donor-acceptor systems consisting of a polychlorotriphenylmethyl (PTM) electron-acceptor moiety linked to an electron-donor ferrocene (Fc) unit supported by ultraflat template-stripped Au and contacted by a eutectic alloy of gallium and indium top contacts. The electronic and supramolecular structures of these SAMs were well characterized. The PTM unit can be switched between the nonradical and radical forms, which influences the rectification behavior of the junction. Junctions with nonradical units rectify currents via the highest occupied molecular orbital (HOMO) with a rectification ratio R = 99, but junctions with radical units have a new accessible state, a single-unoccupied molecular orbital (SUMO), which turns rectification off and drops R to 6.

  8. Electron Transfer within Self-Assembling Cyclic Tetramers Using Chlorophyll-Based Donor-Acceptor Building Blocks

    SciTech Connect

    Gunderson, Victoria L; Smeigh, Amanda L; Kim, Chul Hoon; Co, Dick T; Wasielewski, Michael R

    2012-05-09

    The synthesis and photoinduced charge transfer properties of a series of Chl-based donor-acceptor triad building blocks that self-assemble into cyclic tetramers are reported. Chlorophyll a was converted into zinc methyl 3-ethylpyrochlorophyllide a (Chl) and then further modified at its 20-position to covalently attach a pyromellitimide (PI) acceptor bearing a pyridine ligand and one or two naphthalene-1,8:4,5-bis(dicarboximide) (NDI) secondary electron acceptors to give Chl-PI-NDI and Chl-PI-NDI2. The pyridine ligand within each ambident triad enables intermolecular Chl metal-ligand coordination in dry toluene, which results in the formation of cyclic tetramers in solution, as determined using small- and wide-angle X-ray scattering at a synchrotron source. Femtosecond and nanosecond transient absorption spectroscopy of the monomers in toluene-1% pyridine and the cyclic tetramers in toluene shows that the selective photoexcitation of Chl results in intramolecular electron transfer from 1*Chl to PI to form Chl+.-PI-.-NDI and Chl+.-PI-.-NDI2. This initial charge separation is followed by a rapid charge shift from PI-. to NDI and subsequent charge recombination of Chl+.-PI-NDI-. and Chl+.-PI-(NDI)NDI-. on a 5-30 ns time scale. Charge recombination in the Chl-PI-NDI2 cyclic tetramer (τCR = 30 ± 1 ns in toluene) is slower by a factor of 3 relative to the monomeric building blocks (τCR = 10 ± 1 ns in toluene-1% pyridine). This indicates that the self-assembly of these building blocks into the cyclic tetramers alters their structures in a way that lengthens their charge separation lifetimes, which is an advantageous strategy for artificial photosynthetic systems.

  9. Impact of Different In Vitro Electron Donor/Acceptor Conditions on Potential Chemolithoautotrophic Communities from Marine Pelagic Redoxclines

    PubMed Central

    Labrenz, Matthias; Jost, Günter; Pohl, Christa; Beckmann, Sabrina; Martens-Habbena, Willm; Jürgens, Klaus

    2005-01-01

    Anaerobic or microaerophilic chemolithoautotrophic bacteria have been considered to be responsible for CO2 dark fixation in different pelagic redoxclines worldwide, but their involvement in redox processes is still not fully resolved. We investigated the impact of 17 different electron donor/acceptor combinations in water of pelagic redoxclines from the central Baltic Sea on the stimulation of bacterial CO2 dark fixation as well as on the development of chemolithoautotrophic populations. In situ, the highest CO2 dark fixation rates, ranging from 0.7 to 1.4 μmol liter−1 day−1, were measured directly below the redoxcline. In enrichment experiments, chemolithoautotrophic CO2 dark fixation was maximally stimulated by the addition of thiosulfate, reaching values of up to 9.7 μmol liter−1 CO2 day−1. Chemolithoautotrophic nitrate reduction proved to be an important process, with rates of up to 33.5 μmol liter−1 NO3− day−1. Reduction of Fe(III) or Mn(IV) was not detected; nevertheless, the presence of these potential electron acceptors influenced the development of stimulated microbial assemblages. Potential chemolithoautotrophic bacteria in the enrichment experiments were displayed on 16S ribosomal complementary DNA single-strand-conformation polymorphism fingerprints and identified by sequencing of excised bands. Sequences were closely related to chemolithoautotrophic Thiomicrospira psychrophila and Maorithyas hadalis gill symbiont (both Gammaproteobacteria) and to an uncultured nitrate-reducing Helicobacteraceae bacterium (Epsilonproteobacteria). Our data indicate that this Helicobacteraceae bacterium could be of general importance or even a key organism for autotrophic nitrate reduction in pelagic redoxclines. PMID:16269695

  10. Characterization of a Rhodobacter capsulatus reaction center mutant that enhances the distinction between spectral forms of the initial electron donor.

    PubMed

    Eastman, J E; Taguchi, A K; Lin, S; Jackson, J A; Woodbury, N W

    2000-12-05

    A large scale mutation of the Rhodobacter capsulatus reaction center M-subunit gene, sym2-1, has been constructed in which amino acid residues M205-M210 have been changed to the corresponding L subunit amino acids. Two interconvertable spectral forms of the initial electron donor are observed in isolated reaction centers from this mutant. Which conformation dominates depends on ionic strength, the nature of the detergent used, and the temperature. Reaction centers from this mutant have a ground-state absorbance spectrum that is very similar to wild-type when measured immediately after purification in the presence of high salt. However, upon subsequent dialysis against a low ionic strength buffer or the addition of positively charged detergents, the near-infrared spectral band of P (the initial electron donor) in sym2-1 reaction centers is shifted by over 30 nm to the blue, from 852 to 820 nm. Systematically varying either the ionic strength or the amount of charged detergent reveals an isobestic point in the absorbance spectrum at 845 nm. The wild-type spectrum also shifts with ionic strength or detergent with an isobestic point at 860 nm. The large spectral separation between the two dominant conformational forms of the sym2-1 reaction center makes detailed measurements of each state possible. Both of the spectral forms of P bleach in the presence of light. Electrochemical measurements of the P/P+ midpoint potential of sym2-1 reaction centers show an increase of about 30 mV upon conversion from the long-wavelength form to the short-wavelength form of the mutant. The rate constant of initial electron transfer in both forms of the mutant reaction centers is essentially the same, suggesting that the spectral characteristics of P are not critical for charge separation. The short-wavelength form of P in this mutant also converts to the long-wavelength form as a function of temperature between room temperature and 130 K, again giving rise to an isobestic point, in this

  11. Universally improving effect of mixed electron donors on the CO₂ fixing efficiency of non-photosynthetic microbial communities from marine environments.

    PubMed

    Hu, Jiajun; Wang, Lei; Zhang, Shiping; Wang, Yuanqing; Jin, Fangming; Fu, Xiaohua; Li, Huirong

    2014-08-01

    The universality of improved CO₂ fixing upon the addition of mixed electron donors (MEDs) composed of Na₂S, NO₂(-), and S₂O₃(2-) to non-photosynthetic microbial communities (NPMCs) obtained from 12 locations in four oceans of the world was validated. The CO₂ fixing efficiencies of NPMCs were universally enhanced by MED compared with those obtained using H₂ alone as electron donor, with average increase of about 276%. An increase in microbial inoculation concentration could increase the net amount of CO₂ fixing to 853.34 mg/L in the presence of MED. NO₂(-) and S₂O₃(2-) may play the roles of both electron acceptor and electron donor under aerobic conditions, which may improve the energy utilization efficiency of NPMC and enhance the CO₂ fixation efficiency. The sequence determination of 16S ribosomal deoxyribonucleic acid (rDNA) from 150 bacteria of NPMC showed that more than 50% of the bacteria were symbiotic and there were many heterotrophic bacteria such as Vibrio natriegens. These results indicate that NPMC acts as a symbiotic CO₂ fixing system. The interaction between autotrophic and heterotrophic bacteria may be a crucial factor supporting ladder utilization and recycling of energy/carbon source.

  12. Controlling electron transfer dynamics in donor-bridge-acceptor molecules by increasing unpaired spin density on the bridge.

    PubMed

    Chernick, Erin T; Mi, Qixi; Vega, Amy M; Lockard, Jenny V; Ratner, Mark A; Wasielewski, Michael R

    2007-06-21

    A t-butylphenylnitroxide (BPNO*) stable radical is attached to an electron donor-bridge-acceptor (D-B-A) system having well-defined distances between the components: MeOAn-6ANI-Ph(BPNO*)-NI, where MeOAn=p-methoxyaniline, 6ANI=4-(N-piperidinyl)naphthalene-1,8-dicarboximide, Ph=phenyl, and NI=naphthalene-1,8:4,5-bis(dicarboximide). MeOAn-6ANI, BPNO*, and NI are attached to the 1, 3, and 5 positions of the Ph bridge, respectively. Time-resolved optical and EPR spectroscopy show that BPNO* influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+*-6ANI-Ph(BPNO*)-NI-*), resulting in slower charge recombination within the triradical, as compared to the corresponding biradical lacking BPNO*. The observed spin-spin exchange interaction between the photogenerated radicals MeOAn+* and NI-* is not altered by the presence of BPNO*. However, the increased spin density on the bridge greatly increases radical pair (RP) intersystem crossing from the photogenerated singlet RP to the triplet RP. Rapid formation of the triplet RP makes it possible to observe a biexponential decay of the total RP population with components of tau=740 ps (0.75) and 104 ns (0.25). Kinetic modeling shows that the faster decay rate is due to rapid establishment of an equilibrium between the triplet RP and the neutral triplet state resulting from charge recombination, whereas the slower rate monitors recombination of the singlet RP to ground state.

  13. A comparison of the substrate and electron-donor specificities of the methane mono-oxygenases from three strains of methane-oxidizing bacteria.

    PubMed Central

    Stirling, D I; Colby, J; Dalton, H

    1979-01-01

    1. Methane mono-oxygenase from Methylosinus trichosporium has the same broad substrate specificity as the analogous enzyme from Methylococcus capsulatus (Bath); the enzyme from Methylomonas methanica is more specific. 2. Contrary to previous reports, NAD(P)H and not ascorbate is the required electron donor for the enzyme from Methylosinus trichosporium. 3. It is concluded that these three bacteria contain similar methane mono-oxygenases. PMID:106847

  14. Arsenite as an Electron Donor for Anoxygenic Photosynthesis: Description of Three Strains of Ectothiorhodospira from Mono Lake, California and Big Soda Lake, Nevada

    PubMed Central

    Hoeft McCann, Shelley; Boren, Alison; Hernandez-Maldonado, Jaime; Stoneburner, Brendon; Saltikov, Chad W.; Stolz, John F.; Oremland, Ronald S.

    2016-01-01

    Three novel strains of photosynthetic bacteria from the family Ectothiorhodospiraceae were isolated from soda lakes of the Great Basin Desert, USA by employing arsenite (As(III)) as the sole electron donor in the enrichment/isolation process. Strain PHS-1 was previously isolated from a hot spring in Mono Lake, while strain MLW-1 was obtained from Mono Lake sediment, and strain BSL-9 was isolated from Big Soda Lake. Strains PHS-1, MLW-1, and BSL-9 were all capable of As(III)-dependent growth via anoxygenic photosynthesis and contained homologs of arxA, but displayed different phenotypes. Comparisons were made with three related species: Ectothiorhodospira shaposhnikovii DSM 2111, Ectothiorhodospira shaposhnikovii DSM 243T, and Halorhodospira halophila DSM 244. All three type cultures oxidized arsenite to arsenate but did not grow with As(III) as the sole electron donor. DNA–DNA hybridization indicated that strain PHS-1 belongs to the same species as Ect. shaposhnikovii DSM 2111 (81.1% sequence similarity), distinct from Ect. shaposhnikovii DSM 243T (58.1% sequence similarity). These results suggest that the capacity for light-driven As(III) oxidation is a common phenomenon among purple photosynthetic bacteria in soda lakes. However, the use of As(III) as a sole electron donor to sustain growth via anoxygenic photosynthesis is confined to novel isolates that were screened for by this selective cultivation criterion. PMID:28035953

  15. Arsenite as an Electron Donor for Anoxygenic Photosynthesis: Description of Three Strains of Ectothiorhodospira from Mono Lake, California and Big Soda Lake, Nevada.

    PubMed

    Hoeft McCann, Shelley; Boren, Alison; Hernandez-Maldonado, Jaime; Stoneburner, Brendon; Saltikov, Chad W; Stolz, John F; Oremland, Ronald S

    2016-12-26

    Three novel strains of photosynthetic bacteria from the family Ectothiorhodospiraceae were isolated from soda lakes of the Great Basin Desert, USA by employing arsenite (As(III)) as the sole electron donor in the enrichment/isolation process. Strain PHS-1 was previously isolated from a hot spring in Mono Lake, while strain MLW-1 was obtained from Mono Lake sediment, and strain BSL-9 was isolated from Big Soda Lake. Strains PHS-1, MLW-1, and BSL-9 were all capable of As(III)-dependent growth via anoxygenic photosynthesis and contained homologs of arxA, but displayed different phenotypes. Comparisons were made with three related species: Ectothiorhodospira shaposhnikovii DSM 2111, Ectothiorhodospira shaposhnikovii DSM 243(T), and Halorhodospira halophila DSM 244. All three type cultures oxidized arsenite to arsenate but did not grow with As(III) as the sole electron donor. DNA-DNA hybridization indicated that strain PHS-1 belongs to the same species as Ect. shaposhnikovii DSM 2111 (81.1% sequence similarity), distinct from Ect. shaposhnikovii DSM 243(T) (58.1% sequence similarity). These results suggest that the capacity for light-driven As(III) oxidation is a common phenomenon among purple photosynthetic bacteria in soda lakes. However, the use of As(III) as a sole electron donor to sustain growth via anoxygenic photosynthesis is confined to novel isolates that were screened for by this selective cultivation criterion.

  16. Arsenite as an electron donor for anoxygenic photosynthesis: Description of three strains of Ectothiorhodospria from Mono Lake, California, and Big Soda Lake, Nevada

    USGS Publications Warehouse

    McCann, Shelley; Boren, Alison; Hernandez-Maldonado, Jaime; Stoneburner, Brendon; Saltikov, Chad W; Stolz, John F.; Oremland, Ronald S.

    2017-01-01

    Three novel strains of photosynthetic bacteria from the family Ectothiorhodospiraceae were isolated from soda lakes of the Great Basin Desert, USA by employing arsenite (As(III)) as the sole electron donor in the enrichment/isolation process. Strain PHS-1 was previously isolated from a hot spring in Mono Lake, while strain MLW-1 was obtained from Mono Lake sediment, and strain BSL-9 was isolated from Big Soda Lake. Strains PHS-1, MLW-1, and BSL-9 were all capable of As(III)-dependent growth via anoxygenic photosynthesis and contained homologs of arxA, but displayed different phenotypes. Comparisons were made with three related species: Ectothiorhodospira shaposhnikovii DSM 2111, Ectothiorhodospira shaposhnikovii DSM 243T, and Halorhodospira halophila DSM 244. All three type cultures oxidized arsenite to arsenate but did not grow with As(III) as the sole electron donor. DNA–DNA hybridization indicated that strain PHS-1 belongs to the same species as Ect. shaposhnikovii DSM 2111 (81.1% sequence similarity), distinct from Ect. shaposhnikovii DSM 243T (58.1% sequence similarity). These results suggest that the capacity for light-driven As(III) oxidation is a common phenomenon among purple photosynthetic bacteria in soda lakes. However, the use of As(III) as a sole electron donor to sustain growth via anoxygenic photosynthesis is confined to novel isolates that were screened for by this selective cultivation criterion.

  17. Phosphorus as a simultaneous electron-pair acceptor in intermolecular P···N pnicogen bonds and electron-pair donor to Lewis acids.

    PubMed

    Del Bene, Janet E; Alkorta, Ibon; Sánchez-Sanz, Goar; Elguero, José

    2013-04-11

    Ab initio MP2/aug'-cc-pVTZ calculations have been performed to investigate the structures and energies of binary complexes LA:PH2F and LA:PH3 and of ternary complexes LA:H2FP:NFH2 and LA:H3P:NH3 in which the pnicogen-bonded P atom also acts as an electron-pair donor to a Lewis acid (LA), for LA = BH3, NCH, ClH, FH, FCl, and HLi. Hydrogen bonds, halogen bonds, and dative covalent bonds are found at P in some cases, depending on the nature of the Lewis acid. HLi forms a lithium bond with P only in the binary complex HLi:PH3. The binding energies of ternary complexes exhibit a classical synergistic effect, although the computed cooperativity may be overestimated due to neglect of the interaction of the Lewis acid with NH2F or NH3 in some cases. The hydrogen-bonding Lewis acids appear to have little effect on the strength of the P···N bond, while the remaining Lewis acids strengthen the pnicogen bond. (31)P absolute chemical shieldings increase in LA:H2FP:NFH2 complexes relative to the corresponding LA:PH2F complexes as the positive charge on P decreases, while chemical shieldings decrease in LA:H3P:NH3 relative to the corresponding LA:PH3 complexes as the positive charge increases. Absolute values of (1p)J(P-N) spin-spin coupling constants in complexes LA:H2FP:NFH2 decrease as the P-N distance decreases. It appears that this behavior is associated with the presence of a second intermolecular interaction, whether electron-donation by P or hydrogen bond formation at P-F.

  18. No-carrier-added (NCA) aryl ([sup 18]F) fluorides via the nucleophilic aromatic substitution of electron rich aromatic rings

    DOEpatents

    Yushin Ding; Fowler, J.S.; Wolf, A.P.

    1993-10-19

    A method for synthesizing no-carrier-added (NCA) aryl [.sup.18 F] fluoride substituted aromatic aldehyde compositions bearing an electron donating group is described. The method of the present invention includes the step of reacting aromatic nitro aldehydes having a suitably protected hydroxyl substitutent on an electron rich ring. The reaction is The U.S. Government has rights in this invention pursuant to Contract Number DE-AC02-76CH00016, between the U.S. Department of Energy and Associated Universities Inc.

  19. No-carrier-added (NCA) aryl (18E) fluorides via the nucleophilic aromatic substitution of electron rich aromatic rings

    DOEpatents

    Ding, Yu-Shin; Fowler, Joanna S.; Wolf, Alfred P.

    1993-01-01

    A method for synthesizing no-carrier-added (NCA) aryl [.sup.18 F] fluoride substituted aromatic aldehyde compositions bearing an electron donating group is described. The method of the present invention includes the step of reacting aromatic nitro aldehydes having a suitably protected hydroxyl substitutent on an electron rich ring. The reaction is The U.S. Government has rights in this invention pursuant to Contract Number DE-AC02-76CH00016, between the U.S. Department of Energy and Associated Universities Inc.

  20. Scanning electron microscopic analysis of endothelial cell coverage and quality in large vessels from multi-organ donors: effects of preservation on endothelial cell integrity.

    PubMed

    van Leeuwen, E B; Molema, G; van Luyn, M J; de Jong, K P; Dijk, F; Slooff, M J; Ruiters, M H; van der Meer, J

    2000-06-01

    Endothelial cell integrity (coverage and quality) of large donor vessels is important because these vessels are used for vascular reconstructions in solid-organ transplantation. Disruption of the endothelial cell monolayer will initiate blood coagulation and may lead to thrombosis of large vessels, often resulting in the loss of the transplanted organ. Iliac arteries and veins, removed from 10 heart-beating multi-organ donors at the end of the donor procedure, were analyzed using scanning electron microscopy at three different time points of preservation. Endothelial cell coverage and quality were determined immediately after removal from the donor, after 10 h (time of transplantation) and 7 d storage in 'University of Wisconsin' cold preservation solution (UW). Endothelial cell coverage decreased during the preservation of arteries, but was maintained in veins. Storage of the veins for 7 d in plastic bags showed a decreased endothelial cell coverage compared to storage in glass vials. Early removal of the blood vessels and proper storage, free floating and in clean UW, may improve maintenance of the endothelial cell integrity. These findings may be important in order to reduce the risk of thrombosis and, consequently, organ failure after transplantation. Furthermore, vessels with maintained endothelial cell integrity after 7 d may be used for in vitro research.

  1. Effective treatment of alkaline Cr(VI) contaminated leachate using a novel Pd-bionanocatalyst: Impact of electron donor and aqueous geochemistry

    PubMed Central

    Watts, Mathew P.; Coker, Victoria S.; Parry, Stephen A.; Thomas, Russell A.P.; Kalin, Robert; Lloyd, Jonathan R.

    2015-01-01

    Palladium catalysts offer the potential for the effective treatment of a variety of priority reducible pollutants in natural waters. In this study, microbially synthesized magnetite nanoparticles were functionalized with Pd(0), creating a highly reactive, magnetically recoverable, nano-scale catalyst (Pd-BnM). This was then investigated for the treatment of model Cr(VI) contaminated solutions at a range of pH values, and also alkaline Cr(VI) contaminated leachates from chromite ore processing residue (COPR); a contaminant issue of global concern. The sample of COPR used in this study was obtained from a site in Glasgow, UK, where extensive Cr(VI) contamination has been reported. In initial experiments Pd-BnM was supplied with H2 gas or formate as electron donors, and Cr(VI) removal from model synthetic solutions was quantified at various pH values (2–12). Effective removal was noted at neutral to environmentally relevant alkaline (pH 12) pH values, while the use of formate as an electron donor resulted in loss of performance under acidic conditions (pH 2). Reaction kinetics were then assessed with increasing Pd-BnM loading in both model pH 12 Cr(VI) solutions and the COPR leachate. When formate was used as the electron donor for Pd-BnM, to treat COPR leachate, there was significant inhibition of Cr(VI) removal. In contrast, a promotion of reaction rate, was observed when H2 was employed. Upon sustained reaction with model Cr(VI) solutions, in the presence of excess electron donor (formate or H2), appreciable quantities of Cr(VI) were removed before eventual inactivation of the catalyst. Faster onset of inactivation was reported in the COPR leachates, removing 4% and 64% of Cr(VI) observed from model Cr(VI) solutions, when formate and H2 were used as electron donors, respectively. XAS, TEM-EDX and XPS analysis of the catalysts that had been inactivated in the model solution, showed that the surface had an extensive covering of reduced Cr(III), most likely as a Cr

  2. Effective treatment of alkaline Cr(VI) contaminated leachate using a novel Pd-bionanocatalyst: Impact of electron donor and aqueous geochemistry.

    PubMed

    Watts, Mathew P; Coker, Victoria S; Parry, Stephen A; Thomas, Russell A P; Kalin, Robert; Lloyd, Jonathan R

    2015-07-01

    Palladium catalysts offer the potential for the effective treatment of a variety of priority reducible pollutants in natural waters. In this study, microbially synthesized magnetite nanoparticles were functionalized with Pd(0), creating a highly reactive, magnetically recoverable, nano-scale catalyst (Pd-BnM). This was then investigated for the treatment of model Cr(VI) contaminated solutions at a range of pH values, and also alkaline Cr(VI) contaminated leachates from chromite ore processing residue (COPR); a contaminant issue of global concern. The sample of COPR used in this study was obtained from a site in Glasgow, UK, where extensive Cr(VI) contamination has been reported. In initial experiments Pd-BnM was supplied with H2 gas or formate as electron donors, and Cr(VI) removal from model synthetic solutions was quantified at various pH values (2-12). Effective removal was noted at neutral to environmentally relevant alkaline (pH 12) pH values, while the use of formate as an electron donor resulted in loss of performance under acidic conditions (pH 2). Reaction kinetics were then assessed with increasing Pd-BnM loading in both model pH 12 Cr(VI) solutions and the COPR leachate. When formate was used as the electron donor for Pd-BnM, to treat COPR leachate, there was significant inhibition of Cr(VI) removal. In contrast, a promotion of reaction rate, was observed when H2 was employed. Upon sustained reaction with model Cr(VI) solutions, in the presence of excess electron donor (formate or H2), appreciable quantities of Cr(VI) were removed before eventual inactivation of the catalyst. Faster onset of inactivation was reported in the COPR leachates, removing 4% and 64% of Cr(VI) observed from model Cr(VI) solutions, when formate and H2 were used as electron donors, respectively. XAS, TEM-EDX and XPS analysis of the catalysts that had been inactivated in the model solution, showed that the surface had an extensive covering of reduced Cr(III), most likely as a Cr

  3. Motivations for Giving of Alumni Donors, Lapsed Donors and Non-Donors: Implications for Christian Higher Education

    ERIC Educational Resources Information Center

    Rugano, Emilio Kariuki

    2011-01-01

    This descriptive and causal comparative study sought to identify motivations for alumni donor acquisition and retention in Christian institutions of higher learning. To meet this objective, motivations for alumni donors, lapsed donors, and non-donors were analyzed and compared. Data was collected through an electronic survey of a stratified sample…

  4. Donor-Acceptor Interaction Determines the Mechanism of Photoinduced Electron Injection from Graphene Quantum Dots into TiO2: π-Stacking Supersedes Covalent Bonding.

    PubMed

    Long, Run; Casanova, David; Fang, Wei-Hai; Prezhdo, Oleg V

    2017-02-22

    Interfacial electron transfer (ET) constitutes the key step in conversion of solar energy into electricity and fuels. Required for fast and efficient charge separation, strong donor-acceptor interaction is typically achieved through covalent chemical bonding and leads to fast, adiabatic ET. Focusing on interfaces of pyrene, coronene, and a graphene quantum dot (GQD) with TiO2, we demonstrate the opposite situation: covalent bonding leads to weak coupling and nonadiabatic (NA) ET, while through-space π-electron interaction produces adiabatic ET. Using real-time time-dependent density functional theory combined with NA molecular dynamics, we simulate photoinduced ET into TiO2 from flat and vertically placed molecules and GQD containing commonly used carboxylic acid linkers. Both arrangements can be achieved experimentally with GQDs and other two-dimensional materials, such as MoS2. The weak through-bond donor-acceptor coupling is attributed to the π-electron withdrawing properties of the carboxylic acid group. The calculated ET time scales are in excellent agreement with pump-probe optical experiments. The simulations show that the ET proceeds faster than energy relaxation. The electron couples to a broad spectrum of vibrational modes, ranging from 100 cm(-1) large-scale motions to 1600 cm(-1) C-C stretches. Compared to graphene/TiO2 heterojunctions, the molecule/TiO2 and GQD/TiO2 systems exhibit energy gaps, allowing for longer-lived excited states and hot electron injection, facilitating charge separation and higher voltage. The reported state-of-the-art simulations generate a detailed time-domain, atomistic description of the interfacial charge and energy transfer and relaxation processes, and demonstrate that the fundamental principles leading to efficient charge separation in nanoscale materials depend strongly and often unexpectedly on the type of donor-acceptor interaction. Understanding these principles is critical to the development of highly efficient

  5. Engaging Copper(III) Corrole as an Electron Acceptor: Photoinduced Charge Separation in Zinc Porphyrin-Copper Corrole Donor-Acceptor Conjugates.

    PubMed

    Ngo, Thien H; Zieba, David; Webre, Whitney A; Lim, Gary N; Karr, Paul A; Kord, Scheghajegh; Jin, Shangbin; Ariga, Katsuhiko; Galli, Marzia; Goldup, Steve; Hill, Jonathan P; D'Souza, Francis

    2016-01-22

    An electron-deficient copper(III) corrole was utilized for the construction of donor-acceptor conjugates with zinc(II) porphyrin (ZnP) as a singlet excited state electron donor, and the occurrence of photoinduced charge separation was demonstrated by using transient pump-probe spectroscopic techniques. In these conjugates, the number of copper corrole units was varied from 1 to 2 or 4 units while maintaining a single ZnP entity to observe the effect of corrole multiplicity in facilitating the charge-separation process. The conjugates and control compounds were electrochemically and spectroelectrochemically characterized. Computational studies revealed ground state geometries of the compounds and the electron-deficient nature of the copper(III) corrole. An energy level diagram was established to predict the photochemical events by using optical, emission, electrochemical, and computational data. The occurrence of charge separation from singlet excited zinc porphyrin and charge recombination to yield directly the ground state species were evident from the diagram. Femtosecond transient absorption spectroscopy studies provided spectral evidence of charge separation in the form of the zinc porphyrin radical cation and copper(II) corrole species as products. Rates of charge separation in the conjugates were found to be of the order of 10(10)  s(-1) and increased with increasing multiplicity of copper(III) corrole entities. The present study demonstrates the importance of copper(III) corrole as an electron acceptor in building model photosynthetic systems.

  6. Electron spin polarization transfer to the charge-separated state from locally excited triplet configuration: theory and its application to characterization of geometry and electronic coupling in the electron donor-acceptor system.

    PubMed

    Kobori, Yasuhiro; Fuki, Masaaki; Murai, Hisao

    2010-11-18

    We present a theoretical model of analysis of the time-resolved electron paramagnetic resonance (TREPR) spectrum of the charge-separated (CS) state generated by the photoinduced electron transfer (ET) reaction via the locally excited triplet state in an electron donor-acceptor (D-A) system with a fixed molecular orientation. We show, by the stochastic-Liouville equation, that chemically induced dynamic electron polarization (CIDEP) of the triplet mechanism is explained by lack of transfer of quantum coherence terms in the primary triplet spin state, resulting in net emissive or absorptive electron spin polarization (ESP) which is dependent on anisotropy of the singlet-triplet intersystem crossing in the precursor excited state. This disappearance of the coherence is clearly shown to occur when the photoinduced ET rate is smaller than the angular frequency of the Zeeman splitting: the transferred coherence terms are averaged to be zero due to effective quantum oscillations during the time that the chemical reaction proceeds. The above theory has been applied to elucidate the molecular geometries and spin-spin exchange interactions (2J) of the CS states for both folded and extended conformers by computer simulations of TREPR spectra of the zinc porphyrin-fullerene dyad (ZnP-C(60)) bridged by diphenyldisilane. On the extended conformation, the electronic coupling is estimated from the 2J value. It has been revealed that the coupling term is smaller than the reported electronic interactions of the porphyrin-C(60) systems bridged by diphenylamide spacers. The difference in the electronic couplings has been explained by the difference in the LUMO levels of the bridge moieties that mediate the superexchange coupling for the long-range ET reaction.

  7. Ad lib smoking in post-traumatic stress disorder: an electronic diary study.

    PubMed

    Beckham, Jean C; Wiley, Matthew T; Miller, Susannah C; Dennis, Michelle F; Wilson, Sarah M; McClernon, F Joseph; Calhoun, Patrick S

    2008-07-01

    Using ambulatory methods for 1 week of monitoring, this study investigated the association between smoking and situational cues in 22 smokers with post-traumatic stress disorder (PTSD) and 23 smokers without PTSD. Generalized estimating equations contrasted 1,759 smoking and 1,088 nonsmoking situations by group status controlling for multiple covariates. PTSD smokers reported higher stress and PTSD symptoms across daily activities. For all smokers, higher nicotine dependence, craving, food and caffeine consumption, and being outside were related to smoking. PTSD smokers were more likely to smoke when experiencing PTSD symptoms, anxiety, and stress. Following smoking, smokers with PTSD reported a significant reduction in negative affect. These results are consistent with previous ambulatory findings regarding mood in smokers, and underscore that in smokers with PTSD, PTSD symptom variables as well as stress and anxiety are significantly associated with ad lib smoking.

  8. (η(4)-Butadiene)Sn(0) Complexes: A New Approach for Zero-Valent p-Block Elements Utilizing a Butadiene as a 4π-Electron Donor.

    PubMed

    Kuwabara, Takuya; Nakada, Marisa; Hamada, Jumpei; Guo, Jing Dong; Nagase, Shigeru; Saito, Masaichi

    2016-09-07

    Research on zero-valent p-block elements is a recent hot topic in synthetic and theoretical chemistry because of their novel electronic states having two lone pairs in both the s- and p-orbitals. It is considered that σ-donating ligands bearing large substituents are essential to stabilize these species. Herein, we propose a new approach using butadiene as a 4π-electron donor to stabilize zero-valent group 14 elements. During our study to explore the coordination chemistry of stannacyclopentadienyl ligands, unexpected products, in which the tin atom is coordinated by a butadiene in a η(4)-fashion, were obtained. Because butadiene is a neutral 4π-electron donating ligand, the formal oxidation number of the tin atoms of the products should be zero, which is supported by X-ray diffraction analysis and theoretical calculations. A mechanism for the formation of the products is also described.

  9. Reduction of electron accumulation at InN(0001) surfaces via saturation of surface states by potassium and oxygen as donor- or acceptor-type adsorbates

    SciTech Connect

    Eisenhardt, A.; Reiß, S.; Krischok, S. Himmerlich, M.

    2014-01-28

    The influence of selected donor- and acceptor-type adsorbates on the electronic properties of InN(0001) surfaces is investigated implementing in-situ photoelectron spectroscopy. The changes in work function, surface band alignment, and chemical bond configurations are characterized during deposition of potassium and exposure to oxygen. Although an expected opponent charge transfer characteristic is observed with potassium donating its free electron to InN, while dissociated oxygen species extract partial charge from the substrate, a reduction of the surface electron accumulation occurs in both cases. This observation can be explained by adsorbate-induced saturation of free dangling bonds at the InN resulting in the disappearance of surface states, which initially pin the Fermi level and induce downward band bending.

  10. Low-frequency spectra of the hexamethylbenzene/tetracyanoethylene electron donor-acceptor complexes in solution studied by terahertz time-domain spectroscopy.

    PubMed

    Yamamoto, Kohji; Kabir, Md Humayun; Hayashi, Michitoshi; Tominaga, Keisuke

    2005-05-07

    We have measured the frequency dependent extinction coefficients and refractive indices of electron donor-acceptor (EDA) complexes consisting of hexamethylbenzene (HMB; electron donor) and tetracyanoethylene (TCNE; electron acceptor) in the low-frequency region by terahertz time-domain spectroscopy (THz-TDS). A mixture of the 1:1 (DA) and 2:1 (D2A) EDA complexes exist in carbon tetrachloride solution, and we successfully obtained the spectral components of the 1:1 and 2:1 EDA complexes separately by analyzing the concentration dependence of the THz spectra. The 1:1 and 2:1 complexes show quite different THz spectra of the extinction coefficient, reflecting unique features of dynamics, fluctuations and intermolecular interactions of these complexes. Polarization-selective THz-TDS on the crystalline DA complex shows two peaks at 53 and 70 cm(-1) in the spectral component perpendicular to the crystal axis. On the other hand, the crystalline D2A complex exhibits peaks at 42 and 50 cm(-1) in the perpendicular spectral component. We compare the obtained spectra of the crystalline complex and the results of molecular orbital calculations at the HF/6-31G(d) level of theory to discuss the intermolecular vibrational modes of the complexes.

  11. The role of local environment on the electronic properties of a novel blue-emitting donor-acceptor compound

    NASA Astrophysics Data System (ADS)

    Legaspi, Christian M.; Stubbs, Regan E.; Yaron, David J.; Peteanu, Linda A.; Kemboi, Abraham; Picker, Jesse; Fossum, Eric

    2016-09-01

    With the rising popularity of organic light-emitting diodes (OLEDs) in display applications, demand for more efficient blue emitters has increased. We have recently synthesized a novel blue-emitting, donor-acceptor system employing carbazole as the donor and a benzothiazole derivative as the acceptor, BTZ-CBZ. We find that the solution-phase emission of BTZ-CBZ is highly dependent on solvent polarity, both in lineshape and emission maximum, showing a Stokes shift of 50 nm in methylcyclohexane and 150 nm in acetonitrile. This is expected behavior for donor-acceptor compounds due to the presence of a charge-transfer excited state. However, the solid state properties are more important for OLED devices. Using time-dependent density functional theory calculations employing the linear-response (LR) and state-specific (SS) polarizable continuum model (PCM), we explore the effects of solvent reorganization on the emission properties of BTZ-CBZ. SS-PCM reproduces the solvatochromism behavior of BTZ-CBZ in solution, but LR-PCM shows effectively no shift with solvent polarity. We surmise that this is because solvent reorganization is necessary for the solvatochromic effect to occur. The effect of rigid matrices on the emission of BTZ-CBZ has direct implications on its viability as a blue emitter in solid-state OLEDs and which molecular environments will be ideal for devices.

  12. Spectral investigations of multiple charge transfer complex of p-nitrophenol as an electron acceptor with donor p-dimethylaminobenzaldehyde

    NASA Astrophysics Data System (ADS)

    Naeem, A.; Khan, I. M.; Ahmad, A.

    2011-10-01

    The convincing evidence have been given that both the interactions π-π and π-π* (between p-nitrophenol ( p-NTP) and p-dimethylaminobenzaldehyde ( p-DAB)) are simultaneously involved. This has been established by using IR spectrometry. Association constant K evaluated by the method of Foster under the condition [A]0 = [D]0 with apply in this equation, [A]0/ A = 1/ Kɛλ[D]0 + 2/ɛλ, where [A]0 is the initial concentration of acceptor equal to [D]0, A is the absorbance of the complex at λ, K is the association constant, and ɛλ is the molar absorptivity of the complex at λ. In the IR spectral studies of several related organic compounds, one comes to the conclusion that p-NTP shows a broad band centred at 1600 cm-1 and to nitro asymmetric stretching vibrations. In the complex while the 1500 cm-1 band remains without shift, the broad band localized at 1600 cm-1 shift to 1610 cm-1. A shift of 10 cm-1 shows weak interactions. Studies on molecular complexes of organ metallic donors and acceptors are of very recent origin. Though alkyl donors have been extensively studied, very few studies have appeared on aryl donors.

  13. Influence of π-conjugation structural changes on intramolecular charge transfer and photoinduced electron transfer in donor-π-acceptor dyads.

    PubMed

    Kim, So-Yoen; Cho, Yang-Jin; Lee, Ah-Rang; Son, Ho-Jin; Han, Won-Sik; Cho, Dae Won; Kang, Sang Ook

    2016-12-21

    The influence of π-conjugation structural changes on photoinduced electron transfer (PET) and intramolecular charge transfer (ICT) processes in π-conjugated donor (D)-acceptor (A) dyads (D-π-A) was investigated. Three types of D-π-A dyads were prepared through the modification of the structure of their π-conjugated linker, including D-π-A (1) and D-πtw-A (2) having a twisted π-conjugation, and D-π-Si-π-A (3) with a π-conjugation severed by a Si-atom. In these dyads, carbazole (Cz) and oxadiazole (Oz) moieties act as an electron donor and acceptor, respectively. The emission maxima of dyads 1 and 3 red-shifted with the increase in polarity, which could be attributed to the ICT process. The fluorescence lifetimes of dyads 1 and 3 were 2.64 and 4.29 ns in CH2Cl2, respectively. In contrast, dyad 2 showed dual emission at 350 and 470 nm in CH2Cl2. The emission of dyad 2 at 380 nm corresponded to the monomer fluorescence in the locally excited state. Moreover, the emission at 470 nm increased simultaneously with the diminishing of the fluorescence at 380 nm. This emission band can be assigned as the intramolecular exciplex emission, and showed a strong solvatochromic shift. The low emission quantum yield (<3%) of dyad 2 is due to the PET process. In dyad 2, the cationic and anionic radical species generated by the PET process were confirmed by femtosecond transient absorption (fs-TA) spectroscopy. Upon photoexcitation at 290 or 340 nm, the A or D moieties can be selectively excited. Upon excitation at 290 nm, the acceptor moiety can be excited to the (1)A* state, thus the photoinduced hole transfer (PHT) takes place from (1)A* to D through the HOMO levels within a few picoseconds. On the other hand, when the donor moiety is excited at 340 nm, the PET process occurs from (1)D* to A. Based on the fs-TA studies, it was found that the dynamics and mechanisms for the electron (or charge) transfer were strongly affected by the variation of the π-conjugation of the

  14. Boron Doped diamond films as electron donors in photovoltaics: An X-ray absorption and hard X-ray photoemission study

    SciTech Connect

    Kapilashrami, M.; Zegkinoglou, I.; Conti, G.; Nemšák, S.; Conlon, C. S.; Fadley, C. S.; Törndahl, T.; Fjällström, V.; Lischner, J.; Louie, Steven G.; Hamers, R. J.; Zhang, L.; Guo, J.-H.; Himpsel, F. J.

    2014-10-14

    Highly boron-doped diamond films are investigated for their potential as transparent electron donors in solar cells. Specifically, the valence band offset between a diamond film (as electron donor) and Cu(In,Ga)Se₂ (CIGS) as light absorber is determined by a combination of soft X-ray absorption spectroscopy and hard X-ray photoelectron spectroscopy, which is more depth-penetrating than standard soft X-ray photoelectron spectroscopy. In addition, a theoretical analysis of the valence band is performed, based on GW quasiparticle band calculations. The valence band offset is found to be small: VBO=VBM{sub CIGS} – VBM{sub diamond}=0.3 eV±0.1 eV at the CIGS/Diamond interface and 0.0 eV±0.1 eV from CIGS to bulk diamond. These results provide a promising starting point for optimizing the band offset by choosing absorber materials with a slightly lower valence band maximum.

  15. On chirality transfer in electron donor-acceptor complexes. A prediction for the sulfinimine···BF3 system.

    PubMed

    Rode, Joanna E; Dobrowolski, Jan Cz

    2012-01-01

    Stabilization energies of the electron donor-acceptor sulfinimine···BF(3) complexes calculated at either the B3LYP/aug-cc-pVTZ or the MP2/aug-cc-pVTZ level do not allow to judge, whether the N- or O-atom in sulfinimine is stronger electron-donor to BF(3) . The problem seems to be solvable because chirality transfer phenomenon between chiral sulfinimine and achiral BF(3) is expected to be vibrational circular dichroism (VCD) active. Moreover, the bands associated with the achiral BF(3) molecule are predicted to be the most intense in the entire spectrum. However, the VCD band robustness analyses show that most of the chirality transfer modes of BF(3) are unreliable. Conversely, variation of VCD intensity with change of intermolecular distance, angle, and selected dihedrals between the complex partners shows that to establish the robustness of chirality transfer mode. It is also necessary to determine the influence of the potential energy surface (PES) shape on the VCD intensity. At the moment, there is still no universal criterion for the chirality transfer mode robustness and the conclusions formulated based on one system cannot be directly transferred even to a quite similar one. However, it is certain that more attention should be focused on relation of PES shape and the VCD mode robustness problem.

  16. 15N electron nuclear double resonance of the primary donor cation radical P+.865 in reaction centers of Rhodopseudomonas sphaeroides: additional evidence for the dimer model.

    PubMed Central

    Lubitz, W; Isaacson, R A; Abresch, E C; Feher, G

    1984-01-01

    Four 15N hyperfine coupling constants, including signs, have been measured by electron nuclear double resonance (ENDOR) and electron nuclear nuclear triple resonance (TRIPLE) for the bacteriochlorophyll a radical cation, BChla+., in vitro and for the light-induced primary donor radical cation, P+.865, in reaction centers of Rhodopseudomonas sphaeroides R-26. A comparison of the data shows that the hyperfine coupling constants have the same sign in both radicals and are, on the average, smaller by a factor of 2 in P+.865. These results provide additional evidence that P+.865 is a bacteriochlorophyll dimer and are in contradiction with the monomer structure of P+.865 recently proposed by O'Malley and Babcock. The reduction factors of the individual 15N couplings, together with the evidence from proton ENDOR data and molecular orbital calculations, indicate a dimer structure in which only two rings (either I and I or III and III) of the bacteriochlorophyll macrocycles overlap. PMID:6096857

  17. Acetate, lactate, propionate, and isobutyrate as electron donors for iron and sulfate reduction in Arctic marine sediments, Svalbard.

    PubMed

    Finke, Niko; Vandieken, Verona; Jørgensen, Bo Barker

    2007-01-01

    The contribution of volatile fatty acids (VFA) as e(-)-donors for anaerobic terminal oxidation of organic carbon through iron and sulfate reduction was studied in Arctic fjord sediment. Dissolved inorganic carbon, Fe(2+), VFA concentrations, and sulfate reduction were monitored in slurries from the oxidized (0-2 cm) and the reduced (5-9 cm) zone. In the 0-2 cm layer, 2/3 of the mineralization could be attributed to sulfate reduction and 1/3 to iron reduction. In the 5-9 cm layer, sulfate reduction was the sole mineralization process. Acetate and lactate turnover rates were measured by radiotracer. Inhibition of sulfate reduction with selenate resulted in the accumulation of acetate, propionate, and isobutyrate. The acetate turnover rates determined by radiotracer and accumulation after inhibition were similar. VFA turnover accounted for 21% and 52% of the mineralization through sulfate reduction in the 0-2 and 5-9 cm layer, respectively. Acetate and lactate turnover in the inhibited 0-2 cm slurry was attributed to iron reduction and accounted for 10% and 2% of the iron reduction. Therefore, 88% and 79% of the iron and sulfate reduction in the 0-2 cm layer, respectively, must be fueled by alternative e(-)-donors. The accumulation of VFA in the selenate-inhibited 0-2 cm slurry did not enhance iron reduction, indicating that iron reducers were not limited by VFA availability.

  18. Rational design of aggregation-induced emission luminogen with weak electron donor-acceptor interaction to achieve highly efficient undoped bilayer OLEDs.

    PubMed

    Chen, Long; Jiang, Yibin; Nie, Han; Hu, Rongrong; Kwok, Hoi Sing; Huang, Fei; Qin, Anjun; Zhao, Zujin; Tang, Ben Zhong

    2014-10-08

    In this work, two tailored luminogens (TPE-NB and TPE-PNPB) consisting of tetraphenylethene (TPE), diphenylamino, and dimesitylboryl as a π-conjugated linkage, electron donor, and electron acceptor, respectively, are synthesized and characterized. Their thermal stabilities, photophysical properties, solvachromism, fluorescence decays, electronic structures, electrochemical behaviors, and electroluminescence (EL) properties are investigated systematically, and the impacts of electron donor-acceptor (D-A) interaction on optoelectronic properties are discussed. Due to the presence of a TPE unit, both luminogens show aggregation-induced emission, but strong D-A interaction causes a decrease in emission efficiency and red-shifts in photoluminescence and EL emissions. The luminogen, TPE-PNPB, with a weak D-A interaction fluoresces strongly in solid film with a high fluorescence quantum yield of 94%. The trilayer OLED [ITO/NPB (60 nm)/TPE-PNPB (20 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm)] utilizing TPE-PNPB as a light emitter shows a peak luminance of 49 993 cd m(-2) and high EL efficiencies up to 15.7 cd A(-1), 12.9 lm W(-1), and 5.12%. The bilayer OLED [ITO/TPE-PNPB (80 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm)] adopting TPE-PNPB as a light emitter and hole transporter simultaneously affords even better EL efficiencies of 16.2 cd A(-1), 14.4 lm W(-1), and 5.35% in ambient air, revealing that TPE-PNPB is an eximious p-type light emitter.

  19. Catalytic Friedel-Crafts C-H Borylation of Electron-Rich Arenes: Dramatic Rate Acceleration by Added Alkenes.

    PubMed

    Yin, Qin; Klare, Hendrik F T; Oestreich, Martin

    2017-03-20

    In the electrophilic C-H borylation of electron-rich aromatic compounds with catecholborane, the catalytic generation of the boron electrophile is initiated by heterolysis of the B-H bond by various Lewis and Brønsted acids, with a boronium ion formed exclusively. After ligand dissociation, the corresponding borenium ion undergoes regioselective electrophilic aromatic substitution on aniline derivatives as well as nitrogen-containing heterocycles. The catalysis is optimized using B(C6 F5 )3 as the initiator and proceeds without the addition of an external base or dihydrogen acceptor. Temperatures above 80 °C are generally required to secure efficient turnover in these Friedel-Crafts-type reactions. Mechanistic experiments reveal that regeneration of the boronium/borenium ion with dihydrogen release is rate-determining. This finding finally led to the discovery that, with added alkenes, catalytic C-H borylations can, for the first time, be carried out at room temperature.

  20. A Continuous Flow Column Study of the Anaerobic Transformation of a CAH Mixture of Tetrachloroethene and Carbon Tetrachloride Using Formate as an Electron Donor

    NASA Astrophysics Data System (ADS)

    Semprini, L.; Azizian, M. F.; Kim, Y.

    2011-12-01

    Many groundwater sites are contaminated with mixtures of chlorinated aliphatic hydrocarbons (CAHs) that represent a challenge when biological remediation processes are being considered. This is especially challenging when high concentrations of CAHs are present.Trichloromethane (CF), for example, has been observed to inhibit and potentially exert toxicity on reductive dehalogenation of tetrachloroethene (PCE) and trichloroethene (TCE). Results will be presented from a continuous flow column study where the simultaneous transformation of PCE and carbon tetrachloride (CT) was achieved. The column was packed with a quartz sand and bioaugmented with the Evanite Culture (EV) that is capable of transforming PCE to ethene. The column was fed a synthetic groundwater that was amended with PCE to achieve an influent concentration near its solubility limit (0.10 mM) and formate (1.5 mM) that reacts to produce hydrogen as the ultimate electron donor. The column was operated for over 1600 days prior to the addition of CT. During this period PCE was transformed mainly to vinyl chloride (VC) and ethene (ETH) and minor amounts of cis-dichloroethene (cis-DCE) and TCE. The transformation extent achieved based on the column effluent concentrations ranged from about 50% ETH, 30% VC, and 20 cis-DCE up to 80% ETH and 20% VC. When the column was fed sulfate, it was completely transformed via sulfate reduction. Ferrous iron production from ferric iron reduction was observed early in the study. Acetate was also formed as a result of homoacetogenesis from hydrogen utilization. CT addition (0.015 mM) was started at 1600 days while PCE addition was continued. During the first 25 days of CT addition, CT concentrations gradually increased to 50% of the injection concentration and chloromethane (CM) and CF were observed as transformation products. CT concentrations then decreased with over 98% transformation achieved.CM was removed to below the detection limit and CF concentration decreases to

  1. Electronic and Spatial Structures of Water-Soluble Dinitrosyl Iron Complexes with Thiol-Containing Ligands Underlying Their Ability to Act as Nitric Oxide and Nitrosonium Ion Donors

    PubMed Central

    Vanin, Anatoly F.; Burbaev, Dosymzhan Sh.

    2011-01-01

    The ability of mononuclear dinitrosyl iron commplexes (M-DNICs) with thiolate ligands to act as NO donors and to trigger S-nitrosation of thiols can be explain only in the paradigm of the model of the [Fe+(NO+)2] core ({Fe(NO)2}7 according to the Enemark-Feltham classification). Similarly, the {(RS−)2Fe+(NO+)2}+ structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d7 electron configuration of the iron atom and predominant localization of the unpaired electron on MO(dz2) and the square planar structure of M-DNIC. On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands. Under these conditions, the positive charge on the nitrosyl ligands diminishes appreciably, the interaction of the ligands with hydroxyl ions or with thiols slows down and the hydrolysis of nitrosyl ligands and the S-nitrosating effect of the latter are not manifested. Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC. PMID:22505886

  2. Electronic and optical properties of novel carbazole-based donor-acceptor compounds for applications in blue-emitting organic light-emitting diodes

    DOE PAGES

    Legaspi, Christian M.; Stubbs, Regan E.; Yaron, David J.; ...

    2015-08-20

    We report that organic light-emitting diodes (OLEDs) have received a significant attention over the past decade due to their energy-saving potential. We have recently synthesized two novel carbazole-based donor-acceptor compounds and analyzed their optical properties to determine their suitability for use as blue emitters in OLEDs. These compounds show remarkable photo-stability and high quantum yields in the blue region of the spectrum. In addition, they have highly solvatochromic emission. In non-polar solvents, bright, blue-shifted (λmax ≈ 398 nm), and highly structured emission is seen. With increasing solvent dielectric constant, the emission becomes weaker, red-shifted (λmax ≈ 507 nm), and broad.more » We aim to determine the underlying cause of these changes. Electronic structure calculations indicate the presence of multiple excited states with comparable oscillator strength. These states are of interest because there are several with charge-transfer (CT) character, and others centered on the donor moiety. We theorize that CT states play a role in the observed changes in emission lineshape and may promote charge mobility for electrofluorescence in OLEDs. In the future, we plan to use Stark spectroscopy to analyze the polarity of excited states and transient absorption spectroscopy to observe the dynamics in the excited state.« less

  3. Electronic and optical properties of novel carbazole-based donor-acceptor compounds for applications in blue-emitting organic light-emitting diodes

    SciTech Connect

    Legaspi, Christian M.; Stubbs, Regan E.; Yaron, David J.; Peteanu, Linda A.; Sfeir, Matthew Y.; Kemboi, Abraham; Picker, Jesse; Fossum, Eric

    2015-08-20

    We report that organic light-emitting diodes (OLEDs) have received a significant attention over the past decade due to their energy-saving potential. We have recently synthesized two novel carbazole-based donor-acceptor compounds and analyzed their optical properties to determine their suitability for use as blue emitters in OLEDs. These compounds show remarkable photo-stability and high quantum yields in the blue region of the spectrum. In addition, they have highly solvatochromic emission. In non-polar solvents, bright, blue-shifted (λmax ≈ 398 nm), and highly structured emission is seen. With increasing solvent dielectric constant, the emission becomes weaker, red-shifted (λmax ≈ 507 nm), and broad. We aim to determine the underlying cause of these changes. Electronic structure calculations indicate the presence of multiple excited states with comparable oscillator strength. These states are of interest because there are several with charge-transfer (CT) character, and others centered on the donor moiety. We theorize that CT states play a role in the observed changes in emission lineshape and may promote charge mobility for electrofluorescence in OLEDs. In the future, we plan to use Stark spectroscopy to analyze the polarity of excited states and transient absorption spectroscopy to observe the dynamics in the excited state.

  4. Copolymer semiconductors comprising thiazolothiazole or benzobisthiazole, or benzobisoxazole electron acceptor subunits, and electron donor subunits, and their uses in transistors and solar cells

    DOEpatents

    Jenekhe, Samson A; Subramaniyan, Selvam; Ahmed, Eilaf; Xin, Hao; Kim, Felix Sunjoo

    2014-10-28

    The inventions disclosed, described, and/or claimed herein relate to copolymers comprising copolymers comprising electron accepting A subunits that comprise thiazolothiazole, benzobisthiazole, or benzobisoxazoles rings, and electron donating subunits that comprise certain heterocyclic groups. The copolymers are useful for manufacturing organic electronic devices, including transistors and solar cells. The invention also relates to certain synthetic precursors of the copolymers. Methods for making the copolymers and the derivative electronic devices are also described.

  5. Long-range coupling of electron-hole pairs in spatially separated organic donor-acceptor layers

    PubMed Central

    Nakanotani, Hajime; Furukawa, Taro; Morimoto, Kei; Adachi, Chihaya

    2016-01-01

    Understanding exciton behavior in organic semiconductor molecules is crucial for the development of organic semiconductor-based excitonic devices such as organic light-emitting diodes and organic solar cells, and the tightly bound electron-hole pair forming an exciton is normally assumed to be localized on an organic semiconducting molecule. We report the observation of long-range coupling of electron-hole pairs in spatially separated electron-donating and electron-accepting molecules across a 10-nanometers-thick spacer layer. We found that the exciton energy can be tuned over 100 megaelectron volts and the fraction of delayed fluorescence can be increased by adjusting the spacer-layer thickness. Furthermore, increasing the spacer-layer thickness produced an organic light-emitting diode with an electroluminescence efficiency nearly eight times higher than that of a device without a spacer layer. Our results demonstrate the first example of a long-range coupled charge-transfer state between electron-donating and electron-accepting molecules in a working device. PMID:26933691

  6. (Dibenzoylmethanato)boron difluoride derivatives containing triphenylamine moieties: a new type of electron-donor/π-acceptor system for dye-sensitized solar cells.

    PubMed

    Mizuno, Yosuke; Yisilamu, Yilihamu; Yamaguchi, Tomoya; Tomura, Masaaki; Funaki, Takashi; Sugihara, Hideki; Ono, Katsuhiko

    2014-10-06

    (Dibenzoylmethanato)boron difluoride derivatives containing triphenylamine moieties were synthesized as a new type of electron-donor/π-acceptor system. These new compounds exhibited long-wavelength absorptions in the UV/Vis spectra, and reversible oxidation and reduction waves in cyclic voltammetry experiments. Their amphoteric redox properties are based on their resonance hybrid forms, in which a positive charge is delocalized on the triphenylamine moieties and a negative charge is localized on the boron atoms. Molecular orbital (MO) calculations indicate that their HOMO and LUMO energies vary with the number of phenylene rings connected to the difluoroboron-chelating ring. This is useful for optimizing the HOMO and LUMO levels to an iodine redox (I(-)/I3(-)) potential and a titanium dioxide conduction band, respectively. Dye-sensitized solar cells fabricated by using these compounds as dye sensitizers exhibited solar-to-electric power conversion efficiencies of 2.7-4.4 % under AM 1.5 solar light.

  7. Effects of acceptor-donor complexes on electronic structure properties in co-doped TiO2: A first-principles study

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Cai, L. L.; Yuan, X. B.; Hu, G. C.; Ren, J. F.

    2016-07-01

    We theoretically investigate the doping effects induced by impurity complexes on the electronic structures of anatase TiO2 based on the density functional theory. Mono-doping and co-doping effects are discussed separately. The results show that the impurity doping can make the band-edges shift. The induced defect levels in the band gaps by impurity doping reduce the band gap predominantly. The compensated acceptor-donor pairs in the co-doped TiO2 will improve the photoelectrochemical activity. From the calculations, it is also found that (S+Zr)-co-doped TiO2 has the ideal band gap and band edge, at the same time, the binding energy is higher than other systems, so (S+Zr)-co-doping in TiO2 is more promise in photoelectrochemical experiments.

  8. Production and Identification of N-Glucosylrubropunctamine and N-Glucosylmonascorubramine from Monascus ruber and Occurrence of Electron Donor-Acceptor Complexes in These Red Pigments

    PubMed Central

    Hajjaj, H.; Klaebe, A.; Loret, M. O.; Tzedakis, T.; Goma, G.; Blanc, P. J.

    1997-01-01

    The filamentous fungus Monascus ruber produces water-soluble red pigments in a submerged culture when grown in a chemically defined medium containing glucose as a carbon source and monosodium glutamate as a nitrogen source. Two new molecules with polyketide structures, N-glucosylrubropunctamine and N-glucosylmonascorubramine, constituting under some conditions 10% of the total extracellular coloring matter when glucose as a carbon source was in excess (20 g/liter), were isolated and structurally characterized by high-pressure liquid chromatography, Dionex methods, (sup1)H and (sup13)C nuclear magnetic resonance spectroscopy, and mass spectrometry. The occurrence of the electron donor-acceptor complex effect was demonstrated by UV spectroscopy, polarography, and thin-layer voltammetry. The use of n-butanol as an extraction solvent stabilized the pigments against the effects of daylight for several months, promoting the stability of this type of complex. PMID:16535644

  9. Electron-Rich CpIr(biphenyl-2,2′-diyl) Complexes with π–Accepting Carbon Donor Ligands

    PubMed Central

    Graeupner, Jonathan; Brewster, Timothy P.; Blakemore, James D.; Schley, Nathan D.; Thomsen, Julianne M.; Brudvig, Gary W.; Hazari, Nilay; Crabtree, Robert H.

    2013-01-01

    Cp*IrIII and CpIrIII complexes have attracted interest as catalysts for oxidative transformations, and highly oxidizing iridium species are postulated as key intermediates in both catalytic water and C–H bond oxidation. Strongly electron-donating ligand sets have been shown to stabilize IrIV complexes. We describe the synthesis and reactivity of complexes containing the CpIr(biphenyl-2,2′-diyl) moiety stabilized by a series of strong donor carbon-based ligands. The oxidation chemistry of these complexes has been characterized electrochemically, and a singly oxidized IrIV species has been observed by X-band EPR for the complex CpIr(biph)(p-CNCH2SO2C6H4CH3). PMID:24474841

  10. Triplet properties and interactions of the primary electron donor and antenna chromophores in membranes of Heliobacterium chlorum, studied with ADMR spectroscopy.

    PubMed

    Vrieze, J; van de Meent, E J; Hoff, A J

    1998-10-20

    The triplet states of antenna and reaction center bacteriochlorophyll (BChl) g in membranes of Heliobacterium chlorum were studied by optically detected magnetic resonance in zero magnetic field, using absorbance detection. A variety of triplet states was detected, which were all localized on single BChl g chromophores as concluded from a comparison with the triplet state of monomeric BChl g in organic solvents. With the aid of the microwave-induced absorbance difference spectra, we assign a triplet state with zero-field splitting parameters |D| = 727.5 and |E| = 254. 5 MHz to that of the primary donor. The low |E| value indicates that the BChls of the primary donor are monoligated. The intensities of the zero-field transitions were strongly dependent on the redox state of the secondary electron acceptors. A triplet state with |D| = 690-705 MHz and |E| =230 MHz, present under all redox conditions, is associated with antenna BChl g absorbing at 814 nm. Its triplet yield was independent of the redox conditions; we conclude therefore that the antenna chromophores absorbing at 814 nm are not connected with the reaction center at cryogenic temperatures (1.2 K). In addition, relatively strong signals were detected belonging to triplet states with |D| and |E| of 663-680 and 220-227 MHz, respectively, whose amplitudes were dependent on the redox conditions. Triplet states with these zero-field splitting parameters are located on antenna chromophores absorbing between 798-814 nm; their zero-field transitions and absorbance difference spectra indicate a considerable heterogeneity. The concentration of triplet states of antenna chromophores absorbing around 800 nm decreased markedly upon prolonged excitation at 1.2 K. This phenomenon is attributed to quenching of excitations on antenna pigments by stable charge separation in the closely connected reaction center, possibly involving a low-quantum yield menaquinone electron acceptor.

  11. Biogeochemical Modeling of In Situ U(VI) Reduction and Immobilization with Emulsified Vegetable Oil as the Electron Donor at a Field Site in Oak Ridge, Tennessee

    NASA Astrophysics Data System (ADS)

    Tang, G.; Parker, J.; Wu, W.; Schadt, C. W.; Watson, D. B.; Brooks, S. C.; Orifrc Team

    2011-12-01

    A comprehensive biogeochemical model was developed to quantitatively describe the coupled hydrologic, geochemical and microbiological processes that occurred following injection of emulsified vegetable oil (EVO) as the electron donor to immobilize U(VI) at the Oak Ridge Integrated Field Research Challenge site (ORIFRC) in Tennessee. The model couples the degradation of EVO, production and oxidation of long-chain fatty acids (LCFA), glycerol, hydrogen and acetate, reduction of nitrate, manganese, ferrous iron, sulfate and uranium, and methanoganesis with growth of multiple microbial groups. The model describes the evolution of geochemistry and microbial populations not only in the aqueous phase as typically observed, but also in the mineral phase and therefore enables us to evaluate the applicability of rates from the literature for field scale assessment, estimate the retention and degradation rates of EVO and LCFA, and assess the influence of the coupled processes on fate and transport of U(VI). Our results suggested that syntrophic bacteria or metal reducers might catalyze LCFA oxidation in the downstream locations when sulfate was consumed, and competition between methanogens and others for electron donors and slow growth of methanogen might contribute to the sustained reducing condition. Among the large amount of hydrologic, geochemical and microbiological parameter values, the initial biomass, and the interactions (e.g., inhibition) of the microbial functional groups, and the rate and extent of Mn and Fe oxide reduction appear as the major sources of uncertainty. Our model provides a platform to conduct numerical experiments to study these interactions, and could be useful for further iterative experimental and modeling investigations into the bioreductive immobiliztion of radionuclide and metal contaminants in the subsurface.

  12. Theoretical characterization of photoinduced electron transfer in rigidly linked donor-acceptor molecules: the fragment charge difference and the generalized Mulliken-Hush schemes

    NASA Astrophysics Data System (ADS)

    Lee, Sheng-Jui; Chen, Hung-Cheng; You, Zhi-Qiang; Liu, Kuan-Lin; Chow, Tahsin J.; Chen, I.-Chia; Hsu, Chao-Ping

    2010-10-01

    We calculate the electron transfer (ET) rates for a series of heptacyclo[6.6.0.02,6.03,13.014,11.05,9.010,14]-tetradecane (HCTD) linked donor-acceptor molecules. The electronic coupling factor was calculated by the fragment charge difference (FCD) [19] and the generalized Mulliken-Hush (GMH) schemes [20]. We found that the FCD is less prone to problems commonly seen in the GMH scheme, especially when the coupling values are small. For a 3-state case where the charge transfer (CT) state is coupled with two different locally excited (LE) states, we tested with the 3-state approach for the GMH scheme [30], and found that it works well with the FCD scheme. A simplified direct diagonalization based on Rust's 3-state scheme was also proposed and tested. This simplified scheme does not require a manual assignment of the states, and it yields coupling values that are largely similar to those from the full Rust's approach. The overall electron transfer (ET) coupling rates were also calculated.

  13. Effects of donor-acceptor groups on the structural and electronic properties of 4-(methoxymethyl)-6-methyl-5-nitro-2-oxo-1,2-dihydropyridine-3-carbonitrile

    NASA Astrophysics Data System (ADS)

    Gümüş, Hacer Pir; Tamer, Ömer; Avcı, Davut; Atalay, Yusuf

    2014-11-01

    Quantum chemical calculations on the geometric parameters, harmonic vibrational wavenumbers and 1H and 13C nuclear magnetic resonance (NMR) chemical shifts values of 4-(methoxymethyl)-6-methyl-5-nitro-2-oxo-1,2-dihydropyridine-3-carbonitrile [C9H9N3O4] molecule in ground state were performed using the ab initio HF and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p) basis set. The results of optimized molecular structure were presented and compared with X-ray diffraction results. The theoretical vibrational frequencies and 1H and 13C NMR chemical shifts values were compared with experimental values of the investigated molecule. The observed and calculated values were found to be in good agreement. Since the title compound contains different electron-donor and -acceptor groups as well as lone pair electrons, and multiple bonds, the effects of these groups on the structural and electronic properties are found out. In addition, conformational, natural bond orbital (NBO), nonlinear optical (NLO) analysis, frontier molecular orbital energies, molecular surfaces, Mulliken charges and atomic polar tensor based charges were investigated using HF and DFT methods.

  14. Evidence on Anaerobic Methane Oxidation (AOM) in a boreal cultivated peatland with natural and added electron acceptors

    NASA Astrophysics Data System (ADS)

    Dorodnikov, Maxim; Silvennoinen, Hanna; Martikainen, Pertti; Dörsch, Peter

    2015-04-01

    Anaerobic oxidation of methane (AOM) is a process of methane (CH4) consumption under anoxic conditions driven by microorganisms, which oxidize CH4 with various alternate electron acceptors (AEA): sulfate, nitrate, nitrite, metals-(Fe, Mn, Cu), organic compounds. AOM is common in marine ecosystems, where microbial sulfate reduction (SR) consumes most of the CH4 produced in sediments. Despite the global significance of AOM, the exact mechanisms and relevance of the process in terrestrial ecosystems are almost unknown. In the current study the occurrence of AOM was tested for two organic soil horizons (30 and 40 cm depth) and one mineral sub-soil (sand, 50 cm depth) of a cultivated boreal peatland (Linnansuo, Eastern Finland, energy crop Phalaris arundinacea - reed canarygrass) under controlled conditions with the addition of 13C-labeled CH4 and two common AEAs - SO4-2 and Fe+3. Concentrations of CH4, CO2 and O2 were continuously measured during 10 days of incubation and CO2 was sampled periodically under anaerobic conditions for stable 13C analysis. Oxygen dynamics revealed negligible O2 contamination during incubation and its trace amounts (0.05-0.8% from the atmospheric) were accounted in the net CH4 uptake. Application of 13C-enriched CH4 (4.9 atom%) allowed to track the label in CO2 as the end-product of AOM. The highest 13CO2 enrichment (up to 60‰) was observed in mineral sub-soil, however AOM was quantitatively more pronounced in the upper 30 cm horizon (2.1 vs. 0.2 μg CO2 g soil DW-1 in the 50 cm sub-soil). The highest AOM rate of 8.9 ng CO2 g soil DW-1 h-1 was estimated for the control treatment where no AEAs were added indicating sufficient amount of naturally available AEAs, likely organic compounds. This rate was 50 times more intensive (on the C basis) than the CH4 production potential of the same soil. In contrast, external AEAs decreased AOM rates but added Fe+3 stimulated decomposition of native SOM (as seen from the most depleted 13CO2 signatures

  15. Boosting the photocatalytic performance of (001) BiOI: enhancing donor density and separation efficiency of photogenerated electrons and holes.

    PubMed

    Fan, Wenjie; Li, Haibo; Zhao, Fengyi; Xiao, Xujing; Huang, Yongchao; Ji, Hongbing; Tong, Yexiang

    2016-04-18

    Herein, we demonstrate a simple strategy to boost the photocatalytic performance of BiOI by introducing oxygen defects into the BiOI. The oxygen-deficient BiOI exhibits superior photocatalytic performance for the degradation of formaldehyde gas. The enhancement of photocatalytic activity is due to the enhanced separation and migration efficiency of photogenerated electrons and holes.

  16. [Kidney grafts from elderly donors].

    PubMed

    Hiesse, Christian; Pessione, Fabienne; Cohen, Sophie

    2003-06-07

    FROM AN EPIDEMIOLOGICAL POINT OF VIEW: The epidemiology of renal transplantation had greatly changed over the past 10 years. The increasing number of patients with renal failure and candidates for transplantation increases the demand for grafts, whereas the sampling rate of organs remains stable. The mean age of the donors is rising, hence underlining the question of the use of organs of so-called "borderline" quality. THE WEAK POINTS OF ELDERLY GRAFTS: Aging of the kidneys affects the structure of the parenchyma and renal function, which decreases, notably in hypertensive persons. The elderly graft exhibits a critical mass of nephrons that is insufficient to fulfil the functional requirements of a poorly equipped recipient. The recipient is more sensitive to the added agressions: prolonged ischemia and immunological and medicinal agressions. THE RESULTS OF RENAL GRAFT FROM ELDERLY DONORS: They are quantitatively and qualitatively inferior to those of renal transplants from "ideal" donors. The donor's age is a significant factor influencing negatively influences the survival of the transplanted kidney, but dependent on past vascular history. Good results regarding the maintenance of dialysis are obtained by selecting the donors and by avoiding added risk factors. THE ASSESSMENT OF A GRAFT FROM AN ELDERLY DONOR: This, basically, relies on clinical criteria: donor's history, cause of death and accurate measurement of the renal function. A biopsy of the graft, at the time of sampling, provides useful information. TRANSPLANTATION STRATEGY OF A GRAFT FROM AN ELDERLY DONOR: Donor-recipient matching by age is a common approach. Grafting of both kidneys in the same recipient is a method presently under assessment. The episode of ischemia must be reduced and the immunosuppressive therapy adapted.

  17. Donor Tag Game

    MedlinePlus

    ... Games > Donor Tag Game Printable Version Donor Tag Game This feature requires version 6 or later of ... LGBTQ+ Donors Blood Donor Community Real Stories SleevesUp Games Facebook Avatars and Badges Banners eCards Enter your ...

  18. Fluorescent and colorimetric probes for mercury(II): tunable structures of electron donor and π-conjugated bridge.

    PubMed

    Cheng, Xiaohong; Li, Shuang; Jia, Huizhen; Zhong, Aoshu; Zhong, Cheng; Feng, Jun; Qin, Jingui; Li, Zhen

    2012-02-06

    A new series of intramolecular-charge-transfer (ICT) molecules (compounds 1, 2, and 3) were synthesized by attaching various electron-donating thiophenes groups to a triphenylamine backbone with an aldehyde group as the electron acceptor. Based on the protection reaction between ethanethiol and aldehyde, the corresponding dithioacetals (compounds S1, S2, and S3) were prepared to serve as novel colorimetric and fluorescent chemosensors for Hg(2+) ions. Also, compound S1 was further utilized to construct the chemical-reaction-based conjugated polymer probe (PS1) towards Hg(2+) ions. In the presence of as little as 10 nM Hg(2+), compound PS1 displayed an apparent change in the fluorescent intensity. The sensing processes were revealed to be mediated by ICT, as confirmed by time-dependent DFT calculations. Furthermore, compound S1 was successfully applied to microscopic imaging for the detection of Hg(2+) in HeLa cells with ratiometric fluorescent methods.

  19. Photoinduced electron donor/acceptor processes in colloidal II-VI semiconductor quantum dots and nitroxide free radicals

    NASA Astrophysics Data System (ADS)

    Dutta, Poulami

    Electron transfer (ET) processes are one of the most researched topics for applications ranging from energy conversion to catalysis. An exciting variation is utilizing colloidal semiconductor nanostructures to explore such processes. Semiconductor quantum dots (QDs) are emerging as a novel class of light harvesting, emitting and charge-separation materials for applications such as solar energy conversion. Detailed knowledge of the quantitative dissociation of the photogenerated excitons and the interfacial charge- (electron/hole) transfer is essential for optimization of the overall efficiency of many such applications. Organic free radicals are the attractive counterparts for studying ET to/from QDs because these undergo single-electron transfer steps in reversible fashion. Nitroxides are an exciting class of stable organic free radicals, which have recently been demonstrated to be efficient as redox mediators in dye-sensitized solar cells, making them even more interesting for the aforementioned studies. This dissertation investigates the interaction between nitroxide free radicals TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), 4-amino-TEMPO (4-amino- 2,2,6,6-tetramethylpiperidine-1-oxyl) and II-VI semiconductor (CdSe and CdTe) QDs. The nature of interaction in these hybrids has been examined through ground-state UV-Vis absorbance, steady state and time-resolved photoluminescence (PL) spectroscopy, transient absorbance, upconversion photoluminescence spectroscopy and electron paramagnetic resonance (EPR). The detailed analysis of the PL quenching indicates that the intrinsic charge transfer is ultrafast however, the overall quenching is still limited by the lower binding capacities and slower diffusion related kinetics. Careful analysis of the time resolved PL decay kinetics reveal that the decay rate constants are distributed and that the trap states are involved in the overall quenching process. The ultrafast hole transfer from CdSe QDs to 4-Amino TEMPO observed

  20. Superexchange contributions to distance dependence of electron transfer/transport: exchange and electronic coupling in oligo(para-phenylene)- and oligo(2,5-thiophene)-bridged donor-bridge-acceptor biradical complexes.

    PubMed

    Kirk, Martin L; Shultz, David A; Stasiw, Daniel E; Lewis, Geoffrey F; Wang, Guangbin; Brannen, Candice L; Sommer, Roger D; Boyle, Paul D

    2013-11-13

    The preparation and characterization of three new donor-bridge-acceptor biradical complexes are described. Using variable-temperature magnetic susceptibility, EPR hyperfine coupling constants, and the results of X-ray crystal structures, we evaluate both exchange and electronic couplings as a function of bridge length for two quintessential molecular bridges: oligo(para-phenylene), β = 0.39 Å(-1) and oligo(2,5-thiophene), β = 0.22 Å(-1). This report represents the first direct comparison of exchange/electronic couplings and distance attenuation parameters (β) for these bridges. The work provides a direct measurement of superexchange contributions to β, with no contribution from incoherent hopping. The different β values determined for oligo(para-phenylene) and oligo(2,5-thiophene) are due primarily to the D-B energy gap, Δ, rather than bridge-bridge electronic couplings, H(BB). This is supported by the fact that the H(BB) values extracted from the experimental data for oligo(para-phenylene) (H(BB) = 11,400 cm(-1)) and oligo(2,5-thiophene) (12,300 cm(-1)) differ by <10%. The results presented here offer unique insight into the intrinsic molecular factors that govern H(DA) and β, which are important for understanding the electronic origin of electron transfer and electron transport mediated by molecular bridges.

  1. Dissection of the triple tryptophan electron transfer chain in Escherichia coli DNA photolyase: Trp382 is the primary donor in photoactivation.

    PubMed

    Byrdin, Martin; Eker, André P M; Vos, Marten H; Brettel, Klaus

    2003-07-22

    In Escherichia coli photolyase, excitation of the FAD cofactor in its semireduced radical state (FADH*) induces an electron transfer over approximately 15 A from tryptophan W306 to the flavin. It has been suggested that two additional tryptophans are involved in an electron transfer chain FADH* <-- W382 <-- W359 <-- W306. To test this hypothesis, we have mutated W382 into redox inert phenylalanine. Ultrafast transient absorption studies showed that, in WT photolyase, excited FADH* decayed with a time constant tau approximately 26 ps to fully reduced flavin and a tryptophan cation radical. In W382F mutant photolyase, the excited flavin was much longer lived (tau approximately 80 ps), and no significant amount of product was detected. We conclude that, in WT photolyase, excited FADH* is quenched by electron transfer from W382. On a millisecond scale, a product state with extremely low yield ( approximately 0.5% of WT) was detected in W382F mutant photolyase. Its spectral and kinetic features were similar to the fully reduced flavin/neutral tryptophan radical state in WT photolyase. We suggest that, in W382F mutant photolyase, excited FADH* is reduced by W359 at a rate that competes only poorly with the intrinsic decay of excited FADH* (tau approximately 80 ps), explaining the low product yield. Subsequently, the W359 cation radical is reduced by W306. The rate constants of electron transfer from W382 to excited FADH* in WT and from W359 to excited FADH* in W382F mutant photolyase were estimated and related to the donor-acceptor distances.

  2. Observation of proton-coupled electron transfer by transient absorption spectroscopy in a hydrogen-bonded, porphyrin donor-acceptor assembly.

    PubMed

    Damrauer, Niels H; Hodgkiss, Justin M; Rosenthal, Joel; Nocera, Daniel G

    2004-05-20

    Proton-coupled electron transfer (PCET) kinetics of a Zn(II) porphyrin donor noncovalently bound to a naphthalene-diimide acceptor through an amidinium-carboxylate interface have been investigated by time-resolved spectroscopy. The S1 singlet excited-state of a Zn(II) 2-amidinium-5,10,15,20-tetramesitylporphyrin chloride (ZnP-beta-AmH+) donor is sufficiently energetic (2.04 eV) to reduce a carboxylate-diimide acceptor (DeltaG degrees = -460 mV, THF). Static quenching of the porphyrin fluorescence is observed and time-resolved measurements reveal more than a 3-fold reduction in the S1 lifetime of the porphyrin upon amidinium-carboxylate formation (THF, 298 K). Picosecond transient absorption spectra of the free ZnP-beta-AmH+ in THF reveal the existence of an excited-state isosbestic point between the S1 and T1 states at lambdaprobe = 650 nm, providing an effective 'zero-kinetics' background on which to observe the formation of PCET photoproducts. Distinct rise and decay kinetics are attributed to the build-up and subsequent loss of intermediates resulting from a forward and reverse PCET reaction, respectively (kPCET(fwd) = 9 x 108 s-1 and kPCET(rev) = 14 x 108 s-1). The forward rate constant is nearly 2 orders of magnitude slower than that measured for covalently linked Zn(II) porphyrin-acceptor dyads of comparable driving force and D-A distance, establishing the importance of a proximal proton network in controlling charge transport.

  3. Electron Spin Density on the N-Donor Atoms of Cu(II)-(Bis)oxamidato Complexes As Probed by a Pulse ELDOR Detected NMR.

    PubMed

    Aliabadi, Azar; Zaripov, Ruslan; Salikhov, Kev; Voronkova, Violeta; Vavilova, Evgeniya; Abdulmalic, Mohammad A; Rüffer, Tobias; Büchner, Bernd; Kataev, Vladislav

    2015-10-29

    We have applied the pulse ELDOR detected NMR (EDNMR) technique to determine the tensors of the transferred Cu (S = 1/2) - (14)N (I = 1) hyperfine (HF) interaction in single crystals of diamagnetically diluted mononuclear o-phenylenebis(N(R)-oxamide) complexes of [(n)Bu4N]2[Cu(opboR2)] (R = Et 1, (n)Pr 2) (1%) in a host lattice of [(n)Bu4N]2[Ni(opboR2)] (R = Et 3, (n)Pr 4) (99%) (1@3 and 2@4)). To facilitate the analysis of our EDNMR data and to analyze possible manifestations of the nuclear quadrupole interaction in the EDNMR spectra, we have treated a model electron-nuclear system of the coupled S = 1/2 and I = 1 spins using the spin density matrix formalism. It appears that this interaction yields a peculiar asymmetry of the EDMR spectra that manifests not only in the shift of the positions of the EDNMR lines that correspond to the forbidden EPR transitions, as expected, but also in the intensities of the EDNMR lines. The symmetric shape of the experimental spectra suggests the conclusion that, in the studied complexes, the quadrupole interaction is negligible. This has simplified the analysis of the spectra. The HF tensors of all four N donor atoms could be accurately determined. On the basis of the HF tensors, an estimate of the spin density transferred from the central paramagnetic Cu(II) ion to the N donor atoms reveals its unequal distribution. We discuss possible implications of our estimates for the magnetic exchange paths and interaction strengths in respective trinuclear complexes [Cu3(opboR2) (pmdta)2](NO3)2 (R = Et 6, (n)Pr 7).

  4. The C-type Arabidopsis thioredoxin reductase ANTR-C acts as an electron donor to 2-Cys peroxiredoxins in chloroplasts

    SciTech Connect

    Moon, Jeong Chan; Jang, Ho Hee; Chae, Ho Byoung; Lee, Jung Ro; Lee, Sun Yong; Jung, Young Jun; Shin, Mi Rim; Lim, Hye Song |; Chung, Woo Sik |; Yun, Dae-Jin |; Lee, Kyun Oh; Lee, Sang Yeol . E-mail: sylee@gsnu.ac.kr

    2006-09-22

    2-Cys peroxiredoxins (Prxs) play important roles in the antioxidative defense systems of plant chloroplasts. In order to determine the interaction partner for these proteins in Arabidopsis, we used a yeast two-hybrid screening procedure with a C175S-mutant of Arabidopsis 2-Cys Prx-A as bait. A cDNA encoding an NADPH-dependent thioredoxin reductase (NTR) isotype C was identified and designated ANTR-C. We demonstrated that this protein effected efficient transfer of electrons from NADPH to the 2-Cys Prxs of chloroplasts. Interaction between 2-Cys Prx-A and ANTR-C was confirmed by a pull-down experiment. ANTR-C contained N-terminal TR and C-terminal Trx domains. It exhibited both TR and Trx activities and co-localized with 2-Cys Prx-A in chloroplasts. These results suggest that ANTR-C functions as an electron donor for plastidial 2-Cys Prxs and represents the NADPH-dependent TR/Trx system in chloroplasts.

  5. Species dependence of the redox potential of the primary electron donor p700 in photosystem I of oxygenic photosynthetic organisms revealed by spectroelectrochemistry.

    PubMed

    Nakamura, Akimasa; Suzawa, Tomoyuki; Kato, Yuki; Watanabe, Tadashi

    2011-05-01

    The redox potential of the primary electron donor P700, E(m)(P700/P700(+)), of Photosystem I (PSI) has been determined for 10 oxygenic photosynthesis organisms, ranging from cyanobacteria, red algae, green algae to higher plants, by spectroelectrochemistry with an optically transparent thin-layer electrode (OTTLE) cell to elucidate the scattering by as much as 150 mV in reported values of E(m)(P700/P700(+)). The E(m)(P700/P700(+)) values determined within error ranges of ± 1-4 mV exhibited a significant species dependence, with a span >70 mV, from +398 to +470 mV vs. the standard hydrogen electrode (SHE). The E(m)(P700/P700(+)) value appears to change systematically in going from cyanobacteria and primitive eukaryotic red algae, then to green algae and higher plants. From an evolutionary point of view, this result suggests that the species believed to appear later in evolution of photosynthetic organisms exhibit higher values of E(m)(P700/P700(+)). Further, the species dependence of E(m)(P700/P700(+)) seems to originate in the species-dependent redox potentials of soluble metalloproteins, Cyt c(6) and plastocyanin, which re-reduce the oxidized P700 in the electron transfer chain.

  6. An electronic spectroscopic study of micellisation of surfactants and solvation of homomicelles formed by cationic or anionic surfactants using a solvatochromic electron donor acceptor dye.

    PubMed

    Kedia, Niraja; Sarkar, Amrita; Purkayastha, Pradipta; Bagchi, Sanjib

    2014-10-15

    Solvatochromic absorption and fluorescence bands of a donor-acceptor dye have been utilised for following the micellisation and for probing the polarity of the aqueous homomicellar phase provided separately by cationic (cetyltrimethylammonimum bromide, CTAB and dodecyltrimethylammonimum bromide, DTAB) and anionic (sodium dodecyl sulphate, SDS) surfactant. Results indicate that for a low concentration of surfactant (below cmc) the dye forms a dimer in aqueous solution. In a micellar media, however, the dye exists as monomers. A strong dye-micelle interaction, as indicated by the shift of the solvatochromic intramolecular charge transfer band of the dye, has also been indicated. The absorption and fluorescence parameters of the dye have been utilised for studying the onset of aggregation of the surfactants. An iterative procedure has been developed for the estimation of cmc and the distribution coefficient (KD) of the dye between the aqueous and the micellar phase. All the parameters provide convergent values of cmc. A high value of KD indicates that the dye exists predominantly in the micellar phase. The solvatochromic parameters characterising the dipolarity-polarisability (π(*)) and H-bond donation ability (α) of modes of solvation interaction in different micellar media have been estimated. The dye is found to distribute itself between two regions in a catanionic vesicle formed by surfactants SDS and DTAB, one being relatively polar than other. The distribution coefficients have been found out using the fluorescence data.

  7. Donor states in inverse opals

    SciTech Connect

    Mahan, G. D.

    2014-09-21

    We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikely to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.

  8. Donor states in inverse opals

    NASA Astrophysics Data System (ADS)

    Mahan, G. D.

    2014-09-01

    We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikely to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.

  9. Deep proton tunneling in the electronically adiabatic and non-adiabatic limits: comparison of the quantum and classical treatment of donor-acceptor motion in a protein environment.

    PubMed

    Benabbas, Abdelkrim; Salna, Bridget; Sage, J Timothy; Champion, Paul M

    2015-03-21

    Analytical models describing the temperature dependence of the deep tunneling rate, useful for proton, hydrogen, or hydride transfer in proteins, are developed and compared. Electronically adiabatic and non-adiabatic expressions are presented where the donor-acceptor (D-A) motion is treated either as a quantized vibration or as a classical "gating" distribution. We stress the importance of fitting experimental data on an absolute scale in the electronically adiabatic limit, which normally applies to these reactions, and find that vibrationally enhanced deep tunneling takes place on sub-ns timescales at room temperature for typical H-bonding distances. As noted previously, a small room temperature kinetic isotope effect (KIE) does not eliminate deep tunneling as a major transport channel. The quantum approach focuses on the vibrational sub-space composed of the D-A and hydrogen atom motions, where hydrogen bonding and protein restoring forces quantize the D-A vibration. A Duschinsky rotation is mandated between the normal modes of the reactant and product states and the rotation angle depends on the tunneling particle mass. This tunnel-mass dependent rotation contributes substantially to the KIE and its temperature dependence. The effect of the Duschinsky rotation is solved exactly to find the rate in the electronically non-adiabatic limit and compared to the Born-Oppenheimer (B-O) approximation approach. The B-O approximation is employed to find the rate in the electronically adiabatic limit, where we explore both harmonic and quartic double-well potentials for the hydrogen atom bound states. Both the electronically adiabatic and non-adiabatic rates are found to diverge at high temperature unless the proton coupling includes the often neglected quadratic term in the D-A displacement from equilibrium. A new expression is presented for the electronically adiabatic tunnel rate in the classical limit for D-A motion that should be useful to experimentalists working near

  10. Deep proton tunneling in the electronically adiabatic and non-adiabatic limits: Comparison of the quantum and classical treatment of donor-acceptor motion in a protein environment

    SciTech Connect

    Benabbas, Abdelkrim; Salna, Bridget; Sage, J. Timothy; Champion, Paul M.

    2015-03-21

    Analytical models describing the temperature dependence of the deep tunneling rate, useful for proton, hydrogen, or hydride transfer in proteins, are developed and compared. Electronically adiabatic and non-adiabatic expressions are presented where the donor-acceptor (D-A) motion is treated either as a quantized vibration or as a classical “gating” distribution. We stress the importance of fitting experimental data on an absolute scale in the electronically adiabatic limit, which normally applies to these reactions, and find that vibrationally enhanced deep tunneling takes place on sub-ns timescales at room temperature for typical H-bonding distances. As noted previously, a small room temperature kinetic isotope effect (KIE) does not eliminate deep tunneling as a major transport channel. The quantum approach focuses on the vibrational sub-space composed of the D-A and hydrogen atom motions, where hydrogen bonding and protein restoring forces quantize the D-A vibration. A Duschinsky rotation is mandated between the normal modes of the reactant and product states and the rotation angle depends on the tunneling particle mass. This tunnel-mass dependent rotation contributes substantially to the KIE and its temperature dependence. The effect of the Duschinsky rotation is solved exactly to find the rate in the electronically non-adiabatic limit and compared to the Born-Oppenheimer (B-O) approximation approach. The B-O approximation is employed to find the rate in the electronically adiabatic limit, where we explore both harmonic and quartic double-well potentials for the hydrogen atom bound states. Both the electronically adiabatic and non-adiabatic rates are found to diverge at high temperature unless the proton coupling includes the often neglected quadratic term in the D-A displacement from equilibrium. A new expression is presented for the electronically adiabatic tunnel rate in the classical limit for D-A motion that should be useful to experimentalists working

  11. Impacts of nitrate and electron donor on perchlorate reduction and microbial community composition in a biologically activated carbon reactor.

    PubMed

    Zhu, Yanping; Wu, Min; Gao, Naiyun; Chu, Wenhai; Wang, Shuaifeng

    2016-12-01

    The sensitivity of perchlorate reduction and microbial composition to varied nitrate and acetate loadings was studied in a biologically activated carbon reactor with perchlorate loading and empty bed contact time fixed at 5 mg/L and 226 min, respectively. In stage 1, the sole electron acceptor ClO4(-) realized complete removal with ≥21.95 mg C/L of acetate supply. As nitrate loading gradually increased to 5 mg/L (stage 2), perchlorate reduction was slightly promoted and both ClO4(-) and NO3(-) were completely removed at an acetate loading of 29.7 mg C/L. When nitrate loading continued increasing to 10-60 mg/L (stage 3), perchlorate reduction converted to be inhibited, along with nondetectable NO3(-) and approximately exhausted DOC in effluent. When acetate loading increased to 43.9 mg C/L in stage 4, both ClO4(-) and NO3(-) were again removed, though lags still existed in perchlorate reduction. β-Proteobacteria accounted for about 60%, 55%, 58%, 61% and 12% in samples from the base and top of the filter in stage 1 and those from the base, middle and top in stage 4, respectively. These findings implied that ratio of NO3(-) to ClO4(-) loadings and acetate loading were two key factors impacting ClO4(-) reduction and microbial structure along the filter.

  12. Photodynamic therapy with decacationic [60]fullerene monoadducts: effect of a light absorbing electron-donor antenna and micellar formulation

    PubMed Central

    Yin, Rui; Wang, Min; Huang, Ying-Ying; Huang, Huang-Chiao; Avci, Pinar; Chiang, Long Y; Hamblin, Michael R

    2014-01-01

    We report the synthesis and anticancer photodynamic properties of two new decacationic fullerene (LC14) and red light-harvesting antenna-fullerene conjugated monoadduct (LC15) derivatives. The antenna of LC15 was attached covalently to C60> with distance of only <3.0 Ǻ to facilitate ultrafast intramolecular photoinduced-electron-transfer (for type-I photochemistry) and photon absorption at longer wavelengths. Because LC15 was hydrophobic we compared formulation in CremophorEL micelles with direct dilution from dimethylacetamide. LC14 produced more 1O2 than LC15, while LC15 produced much more HO· than LC14 as measured by specific fluorescent probes. When delivered by DMA, LC14 killed more HeLa cells than LC15 when excited by UVA light, while LC15 killed more cells when excited by white light consistent with the antenna effect. However LC15 was more effective than LC14 when delivered by micelles regardless of the excitation light. Micellar delivery produced earlier apoptosis and damage to the endoplasmic reticulum as well as to lysosomes and mitochondria. PMID:24333585

  13. Electronic structure of donor-spacer-acceptor molecules of potential interest for molecular electronics. IV. Geometry and device properties of P3CNQ and Q3CNQ

    NASA Astrophysics Data System (ADS)

    Broo, Anders; Zerner, Michael C.

    1995-07-01

    Z-β-(1-hexadecyl-4-quinolinium)-α-cyano-4-styryldicyanomethanide (C 16H 33-Q3CNQ) and the pyridinium analogue Z-β-(1-hexadecyl-4-pyridinium)-α-cyano-4-styryldicyanomethanide (C 16H 33-P3NCQ) are two very promising candidates for molecular device design. We obtain the geometry of the ground and excited state of these systems using the PM3 quantum mechanical model. The absorption spectra in vacuum and in solution are calculated using the INDO/Cl model, and compared to experimental spectra. The solvatochromic shift of the absorption spectra was calculated using a self-consistent reaction field approach. The observed bleaching of Langmuir-Blodgett films and solutions of C 16H 33-Q3CNQ and C 16H 33-P3CNQ is explained as resulting from a twisted configuration formed without barrier upon absorption into a twisted intramolecular charge transfer state. The observed rectification is explained from a ground state potential energy surface with two minima, one of which is characterized by a very large dipole moment. The relative energy of these minima is easily shifted by an electric field. The overall electron transport rate is found to be very small due to the small electronic coupling between the mono-layers of the L-B film. Thus, the electron transport through the sample is likely through defects of the L-B film. A way to increase the electronic coupling between the mono-layers is also discussed.

  14. Photocatalytic reduction of CO2 and protons using water as an electron donor over potassium tantalate nanoflakes

    NASA Astrophysics Data System (ADS)

    Li, Kimfung; Handoko, Albertus D.; Khraisheh, Majeda; Tang, Junwang

    2014-07-01

    amounts of CH4 is produced from CO2 photoreduction. Upon addition of a silver cocatalyst on KTO, the reduction selectivity has been controlled to favour CO2 photoreduction, and the CO2 to CO yield has been doubled compared to bare KTaO3. Electronic supplementary information (ESI) available: Borosilicate glass transmittance spectrum and whole XRD pattern fitting (LeBail) results. See DOI: 10.1039/c4nr01490a

  15. Oxygen-independent alkane formation by non-heme iron-dependent cyanobacterial aldehyde decarbonylase: investigation of kinetics and requirement for an external electron donor.

    PubMed

    Eser, Bekir E; Das, Debasis; Han, Jaehong; Jones, Patrik R; Marsh, E Neil G

    2011-12-13

    Cyanobacterial aldehyde decarbonylase (cAD) is, structurally, a member of the di-iron carboxylate family of oxygenases. We previously reported that cAD from Prochlorococcus marinus catalyzes the unusual hydrolysis of aldehydes to produce alkanes and formate in a reaction that requires an external reducing system but does not require oxygen [Das et al. (2011) Angew. Chem. 50, 7148-7152]. Here we demonstrate that cADs from divergent cyanobacterial classes, including the enzyme from N. puntiformes that was reported to be oxygen dependent, catalyze aldehyde decarbonylation at a much faster rate under anaerobic conditions and that the oxygen in formate derives from water. The very low activity (<1 turnover/h) of cAD appears to result from inhibition by the ferredoxin reducing system used in the assay and the low solubility of the substrate. Replacing ferredoxin with the electron mediator phenazine methosulfate allowed the enzyme to function with various chemical reductants, with NADH giving the highest activity. NADH is not consumed during turnover, in accord with the proposed catalytic role for the reducing system in the reaction. With octadecanal, a burst phase of product formation, k(prod) = 3.4 ± 0.5 min(-1), is observed, indicating that chemistry is not rate-determining under the conditions of the assay. With the more soluble substrate, heptanal, k(cat) = 0.17 ± 0.01 min(-1) and no burst phase is observed, suggesting that a chemical step is limiting in the reaction of this substrate.

  16. Spectroscopic studies of molecular interactions involving 2,6-diethylaniline and N-ethylaniline donors and iodine as an electron acceptor in different solvents

    NASA Astrophysics Data System (ADS)

    El-Gogary, Tarek M.; Diab, Mostafa A.; El-Tantawy, Shreen F.

    2007-01-01

    The charge-transfer complexes of 2,6-diethylaniline (DEA) and N-ethylaniline (NEA) with iodine, as a typical σ-acceptor were studied spectrophotometrically in chloroform, dichloromethane and carbontetrachloride solutions. Spectral data, formation constants and effect of solvent have been determined. Spectral characteristics and formation constants are discussed in the terms of donor molecular structure and solvent polarity. The stoichiometry of the complexes was established to be 1:1. For this purpose, optical data were subjected to the form of the Rose-Drago equation for 1:1 equilibria. The formation constant ( KAD) and molar absorptivities ( ɛλ) of complexes were determined by least square method. Electronic absorption spectra of the anilines were measured in different solvents. Spectral data were reported and band maxima were assigned to the appropriate molecular orbital transitions. Quantum chemical calculations were performed with the aid of the Gaussian 98 set of programs. The structure were fully optimized at MP2 level using 6-31 + G** basis set. The computations show that DEA is not planner with the amino group having a somewhat sp 3 hybridization-like character.

  17. Synergistic, reconstruction and bonding effects during the adsorption of internal electron donors and TiCl4 on MgCl2 surface: A periodic-DFT investigation

    NASA Astrophysics Data System (ADS)

    Shetty, Sharankumar

    2016-11-01

    In the present study, periodic-DFT approach has been employed to investigate the synergistic, reconstruction and bonding effects during the adsorption of different classes of internal electron donors (IDs) and TiCl4 on the MgCl2 (104) and (110) surfaces. The results indicate that the monoesters possess more than one binding mode and hence have different adsorption behavior compared to ketone in agreement with the experimental data. Chelate coordination of diesters on (104) surface reconstruct the Mg site, while on the (110) surface chelate coordination contributes to stable coordination. The results of monoesters and di-esters also suggest that the bulkiness of the groups can affect the adsorption energies. Adsorption of diether indicate higher stabilization on (110) surface compared to (104) surface. The results suggest that the adsorption energies of IDs increased in the presence of co-adsorbed TiCl4 compared to the absence of TiCl4. This is attributed to the strong bonding of ID with the surface as evident from the difference charge density analysis and attractive lateral interaction between the co-adsorbed IDs and TiCl4.

  18. The role of amino acid electron-donor/acceptor atoms in host-cell binding peptides is associated with their 3D structure and HLA-binding capacity in sterile malarial immunity induction

    SciTech Connect

    Patarroyo, Manuel E.; Almonacid, Hannia; Moreno-Vranich, Armando

    2012-01-20

    Highlights: Black-Right-Pointing-Pointer Fundamental residues located in some HABPs are associated with their 3D structure. Black-Right-Pointing-Pointer Electron-donor atoms present in {beta}-turn, random, distorted {alpha}-helix structures. Black-Right-Pointing-Pointer Electron-donor atoms bound to HLA-DR53. Black-Right-Pointing-Pointer Electron-acceptor atoms present in regular {alpha}-helix structure bound to HLA-DR52. -- Abstract: Plasmodium falciparum malaria continues being one of the parasitic diseases causing the highest worldwide mortality due to the parasite's multiple evasion mechanisms, such as immunological silence. Membrane and organelle proteins are used during invasion for interactions mediated by high binding ability peptides (HABPs); these have amino acids which establish hydrogen bonds between them in some of their critical binding residues. Immunisation assays in the Aotus model using HABPs whose critical residues had been modified have revealed a conformational change thereby enabling a protection-inducing response. This has improved fitting within HLA-DR{beta}1{sup Asterisk-Operator} molecules where amino acid electron-donor atoms present in {beta}-turn, random or distorted {alpha}-helix structures preferentially bound to HLA-DR53 molecules, whilst HABPs having amino acid electron-acceptor atoms present in regular {alpha}-helix structure bound to HLA-DR52. This data has great implications for vaccine development.

  19. The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units.

    PubMed

    Farcas, Aurica; Resmerita, Ana-Maria; Aubert, Pierre-Henri; Farcas, Flavian; Stoica, Iuliana; Airinei, Anton

    2014-01-01

    We report on the synthesis as well as the optical, electrochemical and morphological properties of two polyrotaxanes (4a and 4b), which consist of electron-accepting 9,9-dicyanomethylenefluorene 1 as an inclusion complex in persilylated β- or γ-cyclodextrin (TMS-β-CD, TMS-γ-CD) (1a, 1b) and methyltriphenylamine as an electron-donating molecule. They are statistically distributed into the conjugated chains of 9,9-dioctylfluorene 3 and compared with those of the corresponding non-rotaxane 4 counterpart. Rotaxane formation results in improvements of the solubility, the thermal stability, and the photophysical properties. Polyrotaxanes 4a and 4b exhibited slightly red-shifted absorption bands with respect to the non-rotaxane 4 counterpart. The fluorescence lifetimes of polyrotaxanes follow a mono-exponential decay with a value of τ = 1.14 ns compared with the non-rotaxane, where a bi-exponential decay composed of a main component with a relative short time of τ1 = 0.88 (57.08%) and a minor component with a longer lifetime of τ2 = 1.56 ns (42.92%) were determined. The optical and electrochemical band gaps (ΔE g) as well as the ionization potential and electronic affinity characterized by smaller values compared to the values of any of the constituents. AFM reveals that the film surface of 4a and 4b displays a granular morphology with a lower dispersity supported by a smaller roughness exponent compared with the non-rotaxane counterpart.

  20. Protein influence on charge-asymmetry of the primary donor in photosynthetic bacterial reaction centers containing a heterodimer: effects on photophysical properties and electron transfer.

    PubMed

    Harris, Michelle A; Luehr, Craig A; Faries, Kaitlyn M; Wander, Marc; Kressel, Lucas; Holten, Dewey; Hanson, Deborah K; Laible, Philip D; Kirmaier, Christine

    2013-04-18

    The substantial electronic distinctions between bacteriochlorophyll (BChl) and its Mg-free analogue bacteriopheophytin (BPh) are exploited in two sets of Rhodobacter capsulatus reaction center (RC) mutants that contain a heterodimeric BChl-BPh primary electron donor (D). The BPh component of the M-heterodimer (Mhd) or L-heterodimer (Lhd) obtains from substituting a Leu for His M200 or for His L173, respectively. Lhd-β and Mhd-β RCs serve as the initial templates in the two mutant sets, where β denotes that the L-side BPh acceptor (HL) has been replaced by a BChl (due to substituting His for Leu M212). Three variants each of Lhd-β and Mhd-β mutants were constructed: (1) a swap (denoted YF) of the native Phe (L181) and Tyr (M208) residues, which flank D and the nearby M- and L-side monomeric BChl cofactors, respectively, giving Tyr (L181) and Phe (M208); (2) addition of a hydrogen bond (denoted L131LH) to the ring V keto group of the L-macrocycle of D, via replacing the native Leu at L131 with His; (3) the combination of 1 and 2. A low yield of electron transfer (ET) to the M-side BPh (HM) is observed in all four Lhd-containing RCs. Comparison with the yield of ET to β on the L-side shows that electron density on the L-macrocycle of D* favors ET to the M-side cofactors and vice versa. Increasing or decreasing the electronic asymmetry of D* via the YF, L131LH mutations or the combination results in consistent trends in the characteristics of the long-wavelength ground state absorption band of D, the rate constant of internal conversion of D* to the ground state, and the rate constants for ET to both the L- and M-side cofactors. A surprising correlation is that an increase in the charge asymmetry in D* not only increases the D* internal-conversion rate constant, but also the rate constants for ET to both the L- and M-side cofactors, spanning time scales of tens of picoseconds to several nanoseconds. The YF swap has a previously unrecognized effect on the

  1. Nitrogen related shallow thermal donors in silicon

    NASA Astrophysics Data System (ADS)

    Fujita, N.; Jones, R.; Öberg, S.; Briddon, P. R.

    2007-07-01

    In this letter, the authors investigate the electrical properties of nitrogen related shallow thermal donor (STD) candidates and their concentrations under different doping conditions by means of density functional theory. Experimentally, the existence of STDs containing one nitrogen atom and both even and odd numbers of oxygen atoms has been proposed. However, so far first principles studies have not presented a candidate for the latter. Here, they show that the NO defect possesses a shallow donor level. Adding one or two more oxygen atoms results in the donor level to become shallower. The fraction of shallow nitrogen related donors to N dimers increases in material with low concentration of nitrogen.

  2. [Influence of the interaction between iron oxide and electron donor substances on 1,1,1-trichloro- 2, 2-bis (p-chlorophenyl) ethane ( DDT) reductive dechlorination in hydragric acrisols].

    PubMed

    Liu, Cui-Ying; Xu, Xiang-Hua; Wang, Zhuang; Yao, Tong-Yan

    2014-11-01

    The interaction between iron oxide and electron donor substance have significant influences on electron transfer and the growth of iron-reducing bacteria, which may affect the reductive dechlorination of polychlorinated organic compounds in soil. Anaerobic soil incubation experiment was conducted to study the effect and its mechanism of iron oxide (goethite), electron donor substances (butyrate and ethanol), and their interaction on DDT reductive dechlorination in Hydragric Acrisols. Results showed that after 6 weeks of anaerobic incubation, the extractable residues of DDT were between 1.29% and 2.01% of initial DDT amounts in soils, which was attributed to the dechlorinated degradation of DDT and formation of bound residues of DDT and its dechlorinated products. The main product of DDT anaerobic dechlorination was 1,1-dichloro-2,2-bis (p-chloro-phenyl) ethane (DDD). During the prophase of incubation, the application of butyrate or ethanol led to the decreased pH and increased Eh for reaction system, thus inhibited DDT dechlorination. The applications of only goethite or goethite and electron donor substances resulted in the increased soil pH, decreased soil Eh and increased Fe( II ) contents, thus accelerated DDT dechlorination. There was no significant interaction between butyrate and iron oxide on DDT dechlorination, whereas there was antagonistic action between ethanol and iron oxide on DDT dechlorination. The results will be of great significance for developing efficient and in-situ remediation technology of DDT contaminated soil.

  3. Phonon induced spin relaxation times of single donors and donor clusters in silicon

    NASA Astrophysics Data System (ADS)

    Hsueh, Yuling; Buch, Holger; Hollenberg, Lloyd; Simmons, Michelle; Klimeck, Gerhard; Rahman, Rajib

    2014-03-01

    The phonon induced relaxation times (T1) of electron spins bound to single phosphorous (P) donors and P donor clusters in silicon is computed using the atomistic tight-binding method. The electron-phonon Hamiltonian is directly computed from the strain dependent tight-binding Hamiltonian, and the relaxation time is computed from Fermi's Golden Rule using the donor states and the electron-phonon Hamiltonian. The self-consistent Hartree method is used to compute the multi-electron wavefunctions in donor clusters. The method takes into account the full band structure of silicon including the spin-orbit interaction, and captures both valley repopulation and single valley g-factor shifts in a unified framework. The single donor relaxation rate varies proportionally to B5, and is of the order of seconds at B =2T, both in good agreement with experimental single donor data (A. Morello et. al., Nature 467, 687 (2010)). T1 calculations in donor clusters show variations for different electron numbers and donor numbers and locations. The computed T1 in a 4P:5e donor cluster match well with a scanning tunneling microscope patterned P donor cluster (H. Buch et. al., Nature Communications 4, 2017 (2013)).

  4. In Situ Generation of Electron Donor to Assist Signal Amplification on Porphyrin-Sensitized Titanium Dioxide Nanostructures for Ultrasensitive Photoelectrochemical Immunoassay.

    PubMed

    Shu, Jian; Qiu, Zhenli; Zhuang, Junyang; Xu, Mingdi; Tang, Dianping

    2015-10-28

    An ultrasensitive photoelectrochemical (PEC) immunoassay protocol for quantitative detection of low-abundant proteins at a low potential was designed by utilizing porphyrin-sensitized titanium dioxide (TiO2) nanostructures. Experimental results demonstrated that the water-soluble 5,10,15,20-tetra(4-sulfophenyl)-21H,23H-porphyrin (TSPP) could be bound onto titanium dioxide via the sulfonic group. TSPP-sensitized TiO2 nanostructures exhibited better photoelectrochemical responses and stability in comparison with TiO2 nanoparticles alone under continuous illumination. Using carcinoembryonic antigen (CEA) as a model analyte, a typical PEC immunosensor by using TSPP-TiO2 as the affinity support of anti-CEA capture antibody (Ab1) to facilitate the improvement of photocurrent response was developed. Bioconjugates of secondary antibody and glucose oxidase with gold nanoparticles (Ab2/GOx-AuNPs) was introduced by an antigen-antibody immunoreaction. AuNP acted as a powerful scaffold to bind with bioactive molecules, while GOx catalyzed glucose to in situ generate hydrogen peroxide (H2O2). The generated H2O2 as a sacrificial electron donor could be oxidized by the photogenerated holes to assist the signal amplification at a low potential under light excitation, thus eliminating interference from other species coexisting in the samples. Under optimal conditions, the PEC immunosensor showed a good linear relationship ranging from 0.02 to 40 ng mL(-1) with a low detection limit of 6 pg mL(-1) CEA. The precision, reproducibility, and specificity were acceptable. In addition, the method accuracy was also evaluated for quantitatively monitoring human serum samples, giving results matching with the referenced CEA ELISA kit.

  5. Co-existence of physiologically similar sulfate-reducing bacteria in a full-scale sulfidogenic bioreactor fed with a single organic electron donor

    PubMed Central

    Dar, Shabir A.; Stams, Alfons J. M.; Kuenen, J. Gijs

    2007-01-01

    A combination of culture-dependent and independent methods was used to study the co-existence of different sulfate-reducing bacteria (SRB) in an upflow anaerobic sludge bed reactor treating sulfate-rich wastewater. The wastewater was fed with ethanol as an external electron donor. Twenty six strains of SRB were randomly picked and isolated from the highest serial dilution that showed growth (i.e. 108). Repetitive enterobacterial palindromic polymerase chain reaction and whole cell protein profiling revealed a low genetic diversity, with only two genotypes among the 26 strains obtained in the pure culture. The low genetic diversity suggests the absence of micro-niches within the reactor, which might be due to a low spatial and temporal micro-heterogeneity. The total 16S rDNA sequencing of two representative strains L3 and L7 indicated a close relatedness to the genus Desulfovibrio. The two strains differed in as many as five physiological traits, which might allow them to occupy distinct niches and thus co-exist within the same habitat. Whole cell hybridisation with fluorescently labeled oligonucleotide probes was performed to characterise the SRB community in the reactor. The isolated strains Desulfovibrio L3 and Desulfovibrio L7 were the most dominant SRB, representing 30–35% and 25–35%, respectively, of the total SRB community. Desulfobulbus-like bacteria contributed for 20–25%, and the Desulfobacca acetoxidans-specific probe targeted approximately 15–20% of the total SRB. The whole cell hybridisation results thus revealed a consortium of four different species of SRB that can be enriched and maintained on a single energy source in a full-scale sulfidogenic reactor. PMID:17440719

  6. Hexameric oligomerization of mitochondrial peroxiredoxin PrxIIF and formation of an ultrahigh affinity complex with its electron donor thioredoxin Trx-o

    PubMed Central

    Barranco-Medina, Sergio; Krell, Tino; Bernier-Villamor, Laura; Sevilla, Francisca; Lázaro, Juan-José; Dietz, Karl-Josef

    2008-01-01

    Mitochondria from plants, yeast, and animals each contain at least one peroxiredoxin (Prx) that is involved in peroxide detoxification and redox signalling. The supramolecular dynamics of atypical type II Prx targeted to the mitochondrion was addressed in pea. Microcalorimetric (ITC) titrations identified an extremely high-affinity binding between the mitochondrial PsPrxIIF and Trx-o with a KD of 126±14 pM. Binding was driven by a favourable enthalpy change (ΔH= –60.6 kcal mol−1) which was counterbalanced by unfavourable entropy changes (TΔS= –47.1 kcal mol−1). This is consistent with the occurrence of large conformational changes during binding which was abolished upon site-directed mutaganesis of the catalytic C59S and C84S. The redox-dependent interaction was confirmed by gel filtration of mitochondrial extracts and co-immunoprecipitation from extracts. The heterocomplex of PsPrxIIF and Trx-o reduced peroxide substrates more efficiently than free PsPrxIIF suggesting that Trx-o serves as an efficient and specific electron donor to PsPrxIIF in vivo. Other Trx-s tested by ITC analysis failed to interact with PsPrxIIF indicating a specific recognition of PsPrxIIF by Trx-o. PsPrxIIF exists primarily as a dimer or a hexamer depending on the redox state. In addition to the well-characterized oligomerization of classical 2-Cys Prx the results also show that atypical Prx undergo large structural reorganization with implications for protein–protein interaction and function. PMID:18632730

  7. Near-interfacial thermal donor generation during processing of (100)Si/low-κ Si-oxycarbide insulator structures revealed by electron spin resonance

    NASA Astrophysics Data System (ADS)

    Stesmans, A.; Iacovo, S.; Nguyen, S.; Afanas'ev, V. V.; Baklanov, M. R.; Urbanowicz, A. M.

    2014-09-01

    A low-temperature multifrequency electron spin resonance (ESR) study has been carried out on Cz-(110)Si/insulator structures with organosilicate films of low dielectric constant κ grown at 300 °C using the plasma-enhanced chemical vapor deposition method (PECVD). After subjection to a short-term UV-irradiation-assisted thermal curing treatment at 430 °C to remove the organic component from the low-κ film and obtain optimal porosity, the NL8 ESR spectrum of C2v symmetry is observed, characterized by g1 (//[100] = 1.999 83(8), g2(//[011] = 1.992 74(8), g3 = (//[1\\bar{1}0]) = 2.001 15(8). Based on previous insight, this reveals the generation in the c-Si substrate of singly ionized thermal double donor (TDD) defects with a core containing oxygen atoms. Remarkably, the generation is found to be highly nonuniform, and the defect density depth profile shows an exponential-like decay (decay length ˜3.8 μm) from the oxide/Si interface inward the Si substrate, thus exposing the defect formation as an interface-administered effect. Upon analysis, the strain induced by interfacial stress in the c-Si beneath the interface is suggested as the major driving component in the enhancement of TDD formation during thermal treatment, suggesting that substantial stress is involved with PECVD organosilicate low-κ glasses. The result represents a different and affirmative illustration of the influence of strain on TDD formation. Based on the principal g values, the observed TDD is closest to the NL81 type, the one formed first in bulk c-Si through oxygen agglomeration during short-term thermal treatment.

  8. Influence of the Terminal Electron Donor in D-D-π-A Organic Dye-Sensitized Solar Cells: Dithieno[3,2-b:2',3'-d]pyrrole versus Bis(amine).

    PubMed

    Dai, Panpan; Yang, Lin; Liang, Mao; Dong, Huanhuan; Wang, Peng; Zhang, Chunyao; Sun, Zhe; Xue, Song

    2015-10-14

    With respect to the electron-withdrawing acceptors of D-A-π-A organic dyes, reports on the second electron-donating donors for D-D-π-A organic dyes are very limited. Both of the dyes have attracted significant attention in the field of dye-sensitized solar cells (DSCs). In this work, four new D-D-π-A organic dyes with dithieno[3,2-b:2',3'-d]pyrrole (DTP) or bis(amine) donor have been designed and synthesized for a investigation of the influence of the terminal electron donor in D-D-π-A organic dye-sensitized solar cells. It is found that DTP is a promising building block as the terminal electron donor when introduced in the dithiophenepyrrole direction, but not just a good bridge, which exhibits several characteristics: (i) efficiently increasing the maximum molar absorption coefficient and extending the absorption bands; (ii) showing stronger charge transfer interaction as compared with the pyrrole direction; (iii) beneficial to photocurrent generation of DSCs employing cobalt electrolytes. DSCs based on M45 with the Co-phen electrolyte exhibit good light-to-electric energy conversion efficiencies as high as 9.02%, with a short circuit current density (JSC) of 15.3 mA cm(-2), open circuit voltage (VOC) of 867 mV and fill factor (FF) of 0.68 under AM 1.5 illumination (100 mW cm(-2)). The results demonstrate that N,S-heterocycles such as DTP unit could be promising candidates for application in highly efficient DSCs employing cobalt electrolyte.

  9. The influence of impurity profiles on mobility of two-dimensional electron gas in AlGaAs/InGaAs/GaAs heterostructures modulation-doped by donors and acceptors

    NASA Astrophysics Data System (ADS)

    Protasov, D. Yu.; Zhuravlev, K. S.

    2017-03-01

    The low-temperature mobility of two-dimensional electron gas (2DEG) limited scattering by ionized impurities, alloy disorder, acoustic and optical phonons, and interface roughness was calculated for novel pseudomorphic modulation-doped by donors and acceptors InGaAs/AlGaAs quantum well structures promising for high power microwave transistors. Due to the high 2DEG density in the quantum well intersubband transitions were taken into account. Scattering by the ionized donors from δ-layer located in AlGaAs barriers dominates, whereas scattering by the ionized acceptors occupying the most part of AlGaAs barriers is negligibly weak. The width of donor doping profile is a key parameter to control 2DEG mobility, thus, increasing of the profile width from 0.25 nm to 4 nm due to segregation and diffusion of donor atoms halves the mobility. We have proposed a few approaches for the weakening of Coulomb scattering and the increase in 2DEG mobility in the novel heterostructures. The predicted mobility enhancement due to δ-layer splitting into two δ-sublayers was verified experimentally.

  10. No-carrier-added (NCA) aryl [{sup 18}F]fluorides via the nucleophilic aromatic substitution of electron rich aromatic rings

    SciTech Connect

    Ding, Yu-Shin; Fowler, J.S.; Wolf, A.P.

    1991-12-31

    A method for synthesizing no-carrier-added (NCA) aryl [{sup 18}F] fluoride substituted aromatic aldehyde compositions bearing an electron donating group is described. The method includes the step of reacting aromatic nitro aldehydes having a suitably protected hydroxyl substituent on an electron rich ring. The reaction is carried out by nucleophilic aromatic substitution with a no-carrier-added (NCA) [{sup 18}F]fluoride ion. The method can be used to synthesize various no-carrier-added aryl [{sup 18}F]fluoride compositions, including 6-[{sup 18}F]fluoro-L-DOPA, 2-[{sup 18}F]fluorotyrosine, 6-[{sup 18}F]fluoronorepinephrine, and 6-[{sup 18}F]fluorodopamine. In those instances when a racemic mixture of enantiomers is produced by the present invention, such as in the synthesis of 6-[{sup 18}F]fluoronorepinephrine, a preferred method also includes resolution of the racemic mixture on a chiral HPLC column. This procedure results in a high yield of enantiomerically pure [{sup 18}F] labeled isomers, for example [-]-6-[{sup 18}F]fluoronorepinephrine and [+]-6-[{sup 18}F]fluoronorepinephrine.

  11. Rational Design of High-Performance Wide-Bandgap (≈2 eV) Polymer Semiconductors as Electron Donors in Organic Photovoltaics Exhibiting High Open Circuit Voltages (≈1 V).

    PubMed

    Chochos, Christos L; Katsouras, Athanasios; Gasparini, Nicola; Koulogiannis, Chrysanthos; Ameri, Tayebeh; Brabec, Christoph J; Avgeropoulos, Apostolos

    2017-01-01

    Systematic optimization of the chemical structure of wide-bandgap (≈2.0 eV) "donor-acceptor" copolymers consisting of indacenodithiophene or indacenodithieno[3,2-b]thiophene as the electron-rich unit and thieno[3,4-c]pyrrole-4,6-dione as the electron-deficient moiety in terms of alkyl side chain engineering and distance of the electron-rich and electron-deficient monomers within the repeat unit of the polymer chain results in high-performance electron donor materials for organic photovoltaics. Specifically, preliminary results demonstrate extremely high open circuit voltages (V oc s) of ≈1.0 V, reasonable short circuit current density (J sc ) of around 11 mA cm(-2) , and moderate fill factors resulting in efficiencies close to 6%. All the devices are fabricated in an inverted architecture with the photoactive layer processed by doctor blade equipment, showing the compatibility with roll-to-roll large-scale manufacturing processes. From the correlation of the chemical structure-optoelectronic properties-photovoltaic performance, a rational guide toward further optimization of the chemical structure in this family of copolymers, has been achieved.

  12. Modeling Groundwater-Quality Data from In-Situ Mesocosms Using PHREEQC to Provide Insights into the Electron Donors Involved in Denitrification in the Karlsruhe Aquifer, ND

    NASA Astrophysics Data System (ADS)

    Korom, S. F.; Tesfay, T.

    2009-12-01

    Groundwater nitrate concentrations in the Karlsruhe aquifer in north-central North Dakota increased in the mid-1990s. In response, state regulators developed a remediation plan that included research into the natural denitrifying capabilities of the aquifer, including the analysis of aquifer sediment samples and the installation of a pair of in-situ mesocosms (ISMs) below the water table to study denitrification reactions. Sediment analysis showed concentrations of the potential electron donors ferrous iron, inorganic sulfide, and organic carbon (OC). X-ray diffraction showed the dominant minerals are quartz, plagioclase feldspar, alkali feldspar, calcite, and dolomite, with lesser amounts of ferrous-iron silicates (chlorite, hornblende, biotite) and pyrite. In the ISMs tracer tests were initiated by pumping groundwater from them, amending it with sodium nitrate and sodium bromide (Br was used as a tracer for nitrate), and pumping the amended water back into the ISMs. The large size of the ISMs (> 180 L of aquifer sediments) allowed large samples (> 1 L) to be taken from the ISMs about every two months for over two years. Samples were analyzed for major ions and saturation indices [SI = log (ion activity product/equilibrium constant)] computed. Any loss of nitrate beyond that attributable to dilution, based on the Br tracer, was considered denitrified. Major sulfate minerals were undersaturated in the ISMs; therefore, any increase in sulfate was attributed to the oxidation of pyrite. PHREEQC was used to determine if the remaining nitate lost to denitrification could be explained best by a reaction with ferrous-iron silicate (as grunerite), organic carbon (as CH2O), or a 50/50 stoichiometric mix of both. After each simulation, the modeled groundwater was “equilibrated” with quartz, albite, anorthite, calcite, dolomite, chlorite, and magnesite, such that the modeled groundwater and the actual groundwater had the same SI values for these minerals. Simulated

  13. Solicited kidney donors: Are they coerced?

    PubMed

    Serur, David; Bretzlaff, Gretchen; Christos, Paul; Desrosiers, Farrah; Charlton, Marian

    2015-12-01

    Most non-directed donors (NDDs) decide to donate on their own and contact the transplant centre directly. Some NDDs decide to donate in response to community solicitation such as newspaper ads or donor drives. We wished to explore whether subtle coercion might be occurring in such NDDs who are part of a larger community. One successful organization in a community in Brooklyn, NY, provides about 50 NDDs per year for recipients within that community. The donors answer ads in local papers and attend donor drives. Herein, we evaluated the physical and emotional outcomes of community-solicited NDDs in comparison to traditional NDDs who come from varied communities and are not responding to a specific call for donation. An assessment of coercion was used as well.

  14. Solicited kidney donors: Are they coerced?

    PubMed Central

    SERUR, DAVID; BRETZLAFF, GRETCHEN; CHRISTOS, PAUL; DESROSIERS, FARRAH; CHARLTON, MARIAN

    2016-01-01

    Most non-directed donors (NDDs) decide to donate on their own and contact the transplant centre directly. Some NDDs decide to donate in response to community solicitation such as newspaper ads or donor drives. We wished to explore whether subtle coercion might be occurring in such NDDs who are part of a larger community. One successful organization in a community in Brooklyn, NY, provides about 50 NDDs per year for recipients within that community. The donors answer ads in local papers and attend donor drives. Herein, we evaluated the physical and emotional outcomes of community-solicited NDDs in comparison to traditional NDDs who come from varied communities and are not responding to a specific call for donation. An assessment of coercion was used as well. PMID:26511772

  15. Value-added Synthesis of Graphene: Recycling Industrial Carbon Waste into Electrodes for High-Performance Electronic Devices.

    PubMed

    Seo, Hong-Kyu; Kim, Tae-Sik; Park, Chibeom; Xu, Wentao; Baek, Kangkyun; Bae, Sang-Hoon; Ahn, Jong-Hyun; Kim, Kimoon; Choi, Hee Cheul; Lee, Tae-Woo

    2015-11-16

    We have developed a simple, scalable, transfer-free, ecologically sustainable, value-added method to convert inexpensive coal tar pitch to patterned graphene films directly on device substrates. The method, which does not require an additional transfer process, enables direct growth of graphene films on device substrates in large area. To demonstrate the practical applications of the graphene films, we used the patterned graphene grown on a dielectric substrate directly as electrodes of bottom-contact pentacene field-effect transistors (max. field effect mobility ~0.36 cm(2)·V(-1)·s(-1)), without using any physical transfer process. This use of a chemical waste product as a solid carbon source instead of commonly used explosive hydrocarbon gas sources for graphene synthesis has the dual benefits of converting the waste to a valuable product, and reducing pollution.

  16. Value-added Synthesis of Graphene: Recycling Industrial Carbon Waste into Electrodes for High-Performance Electronic Devices

    PubMed Central

    Seo, Hong-Kyu; Kim, Tae-Sik; Park, Chibeom; Xu, Wentao; Baek, Kangkyun; Bae, Sang-Hoon; Ahn, Jong-Hyun; Kim, Kimoon; Choi, Hee Cheul; Lee, Tae-Woo

    2015-01-01

    We have developed a simple, scalable, transfer-free, ecologically sustainable, value-added method to convert inexpensive coal tar pitch to patterned graphene films directly on device substrates. The method, which does not require an additional transfer process, enables direct growth of graphene films on device substrates in large area. To demonstrate the practical applications of the graphene films, we used the patterned graphene grown on a dielectric substrate directly as electrodes of bottom-contact pentacene field-effect transistors (max. field effect mobility ~0.36 cm2·V−1·s−1), without using any physical transfer process. This use of a chemical waste product as a solid carbon source instead of commonly used explosive hydrocarbon gas sources for graphene synthesis has the dual benefits of converting the waste to a valuable product, and reducing pollution. PMID:26567845

  17. Efficiency enhancement of planar perovskite solar cells by adding zwitterion/LiF double interlayers for electron collection.

    PubMed

    Sun, Kuan; Chang, Jingjing; Isikgor, Furkan Halis; Li, Pengcheng; Ouyang, Jianyong

    2015-01-21

    Double interlayers consisting of a zwitterionic small molecule layer and a LiF layer were introduced between the electron transport layer and the cathode of perovskite solar cells. The double interlayers improve the photovoltaic efficiency to 13.2%, which is higher than that of control devices without the double interlayer (9.2%) or with LiF (11.0%) or rhodamine 101 zwitterion (12.1%) alone.

  18. Adding the Third Dimension to Virus Life Cycles: Three-Dimensional Reconstruction of Icosahedral Viruses from Cryo-Electron Micrographs

    PubMed Central

    Baker, T. S.; Olson, N. H.; Fuller, S. D.

    1999-01-01

    Viruses are cellular parasites. The linkage between viral and host functions makes the study of a viral life cycle an important key to cellular functions. A deeper understanding of many aspects of viral life cycles has emerged from coordinated molecular and structural studies carried out with a wide range of viral pathogens. Structural studies of viruses by means of cryo-electron microscopy and three-dimensional image reconstruction methods have grown explosively in the last decade. Here we review the use of cryo-electron microscopy for the determination of the structures of a number of icosahedral viruses. These studies span more than 20 virus families. Representative examples illustrate the use of moderate- to low-resolution (7- to 35-Å) structural analyses to illuminate functional aspects of viral life cycles including host recognition, viral attachment, entry, genome release, viral transcription, translation, proassembly, maturation, release, and transmission, as well as mechanisms of host defense. The success of cryo-electron microscopy in combination with three-dimensional image reconstruction for icosahedral viruses provides a firm foundation for future explorations of more-complex viral pathogens, including the vast number that are nonspherical or nonsymmetrical. PMID:10585969

  19. Volunteer donor apheresis.

    PubMed

    Waxman, Dan A

    2002-02-01

    Volunteer donor apheresis has evolved from early plasmapheresis procedures that collected single components into technically advanced multicomponent procedures that can produce combinations of red blood cells, platelets, and plasma units. Blood collection and utilization is increasing annually in the United States. The number of apheresis procedures is also increasing such that single donor platelet transfusions now exceed platelet concentrates from random donors. Donor qualifications for apheresis vary from those of whole blood. Depending on the procedure, the donor weight, donation interval, and platelet count must be taken into consideration. Adverse effects of apheresis are well known and fortunately occur in only a very small percentage of donors. The recruitment of volunteer donors is one of the most challenging aspects of a successful apheresis program. As multicomponent apheresis becomes more commonplace, it is important for collection centers to analyze the best methods to recruit and collect donors.

  20. Hairy AdS solitons

    NASA Astrophysics Data System (ADS)

    Anabalón, Andrés; Astefanesei, Dumitru; Choque, David

    2016-11-01

    We construct exact hairy AdS soliton solutions in Einstein-dilaton gravity theory. We examine their thermodynamic properties and discuss the role of these solutions for the existence of first order phase transitions for hairy black holes. The negative energy density associated to hairy AdS solitons can be interpreted as the Casimir energy that is generated in the dual filed theory when the fermions are antiperiodic on the compact coordinate.

  1. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Spectrum and Binding Energy of an Off-Center Hydrogenic Donor in a Spherical Quantum Dot

    NASA Astrophysics Data System (ADS)

    Yuan, Jian-Hui; Huang, Jin-Sheng; Yin, Miao; Zeng, Qi-Jun; Zhang, Jun-Pei

    2010-08-01

    Off-center impurity effects in a spherical quantum dot are theoretically studied by degenerate perturbation method in strong confinement. The energy levels and binding energies are computed for the typical GaAs material as function of the donor position. The numerical results show the quantum size effect. We note that the energy levels and binding energies are not only related to the position of donor and the strength of confinement, but also related to the fold of degenerate states. We can see obviously that gaps will appear among the degenerate states and the splitting of energy levels and binding energies will appear as the position of the impurity is shifted away off the center.

  2. Added Sugars

    MedlinePlus

    ... need sugar to function properly. Added sugars contribute zero nutrients but many added calories that can lead to extra pounds or even obesity, thereby reducing heart health. If you think of your daily calorie needs as a budget, you want to “spend” ...

  3. Value Added?

    ERIC Educational Resources Information Center

    UCLA IDEA, 2012

    2012-01-01

    Value added measures (VAM) uses changes in student test scores to determine how much "value" an individual teacher has "added" to student growth during the school year. Some policymakers, school districts, and educational advocates have applauded VAM as a straightforward measure of teacher effectiveness: the better a teacher,…

  4. Charge-transfer (CT) orbitals for the one-electron description of CT excitations in a wide range of donor-acceptor separations

    NASA Astrophysics Data System (ADS)

    Gritsenko, O. V.

    2017-01-01

    A transformation of the virtual Kohn-Sham orbitals is proposed to a set of charge-transfer orbitals (CTOs) adapted to description of CT excitations. The CTO scheme offers a simple estimate of the CT excitation energy with an orbital energy difference. This estimate reproduces well the reference values of the configuration interaction (CI) method in a wide range of donor-acceptor separations in the paradigmatic He -Be complex. CTO-based orbital energy and shape indices are proposed to assess the suitability of the CT description with virtual orbitals of a given basis set. Both indices yield correct trends for the Kohn-Sham and Hartree-Fock orbitals.

  5. Donor-dependent extent of uranium reduction for bioremediation of contaminated sediment microcosms.

    PubMed

    Madden, Andrew S; Palumbo, Anthony V; Ravel, Bruce; Vishnivetskaya, Tatiana A; Phelps, Tommy J; Schadt, Christopher W; Brandt, Craig C

    2009-01-01

    Bioremediation of uranium was investigated in microcosm experiments containing contaminated sediments from Oak Ridge, Tennessee to explore the importance of electron donor selection for uranium reduction rate and extent. In these experiments, all of the electron donors, including ethanol, glucose, methanol, and methanol with added humic acids, stimulated the reduction and immobilization of aqueous uranium by the indigenous microbial community. Uranium loss from solution began after the completion of nitrate reduction but essentially concurrent with sulfate reduction. When electron donor concentrations were normalized for their equivalent electron donor potential yield, the rates of uranium reduction were nearly equivalent for all treatments (0.55-0.95 micromol L(-1) d(-1)). Uranium reduction with methanol proceeded after a 15-d longer lag time relative to that of ethanol or glucose. Significant differences were not found with the inclusion of humic acids. The extent of U reduction in sediment slurries measured by XANES at various time periods after the start of the experiment increased in the order of ethanol (5-7% reduced at 77 and 153 d), glucose (49% reduced at 53 d), and methanol (93% reduced at 90 d). The microbial diversity of ethanol- and methanol-amended microcosms in their late stage of U reduction was analyzed with 16S rRNA gene amplification. Members of the Geobacteraceae were found in all microcosms as well as other potential uranium-reducing organisms, such as Clostridium and Desulfosporosinus. The effectiveness of methanol relative to ethanol at reducing aqueous and sediment-hosted uranium suggests that bioremediation strategies that encourage fermentative poising of the subsurface to a lower redox potential may be more effective for long-term uranium immobilization as compared with selecting an electron donor that is efficiently metabolized by known uranium-reducing microorganisms.

  6. Donor-dependent Extent of Uranium Reduction for Bioremediation of Contaminated Sediment Microcosms

    SciTech Connect

    Madden, Andrew S.; Palumbo, Anthony V.; Ravel, Bruce; Vishnivetskaya, Tatiana A.; Phelps, Tommy J.; Schadt, Christopher W.; Brandt, Craig C.

    2009-03-16

    Bioremediation of uranium was investigated in microcosm experiments containing contaminated sediments from Oak Ridge, Tennessee to explore the importance of electron donor selection for uranium reduction rate and extent. In these experiments, all of the electron donors, including ethanol, glucose, methanol, and methanol with added humic acids, stimulated the reduction and immobilization of aqueous uranium by the indigenous microbial community. Uranium loss from solution began after the completion of nitrate reduction but essentially concurrent with sulfate reduction. When electron donor concentrations were normalized for their equivalent electron donor potential yield, the rates of uranium reduction were nearly equivalent for all treatments (0.55-0.95 {micro}mol L{sup -1} d{sup -1}). Uranium reduction with methanol proceeded after a 15-d longer lag time relative to that of ethanol or glucose. Significant differences were not found with the inclusion of humic acids. The extent of U reduction in sediment slurries measured by XANES at various time periods after the start of the experiment increased in the order of ethanol (5-7% reduced at 77 and 153 d), glucose (49% reduced at 53 d), and methanol (93% reduced at 90 d). The microbial diversity of ethanol- and methanol-amended microcosms in their late stage of U reduction was analyzed with 16S rRNA gene amplification. Members of the Geobacteraceae were found in all microcosms as well as other potential uranium-reducing organisms, such as Clostridium and Desulfosporosinus. The effectiveness of methanol relative to ethanol at reducing aqueous and sediment-hosted uranium suggests that bioremediation strategies that encourage fermentative poising of the subsurface to a lower redox potential may be more effective for long-term uranium immobilization as compared with selecting an electron donor that is efficiently metabolized by known uranium-reducing microorganisms.

  7. Donor-dependent Extent of Uranium Reduction for Bioremediation of Contaminated Sediment Microcosms

    SciTech Connect

    Palumbo, Anthony Vito; Ravel, Bruce; Phelps, Tommy Joe; Schadt, Christopher Warren; Brandt, Craig C

    2009-01-01

    Bioremediation of uranium was investigated in microcosm experiments containing contaminated sediments from Oak Ridge, Tennessee to explore the importance of electron donor selection for uranium reduction rate and extent. In these experiments, all of the electron donors, including ethanol, glucose, methanol, and methanol with added humic acids, stimulated the reduction and immobilization of aqueous uranium by the indigenous microbial community. Uranium loss from solution began after the completion of nitrate reduction but essentially concurrent with sulfate reduction. When electron donor concentrations were normalized for their equivalent electron donor potential yield, the rates of uranium reduction were nearly equivalent for all treatments (0.55-0.95 {micro}mol L{sup -1} d{sup -1}). Uranium reduction with methanol proceeded after a 15-d longer lag time relative to that of ethanol or glucose. Significant differences were not found with the inclusion of humic acids. The extent of U reduction in sediment slurries measured by XANES at various time periods after the start of the experiment increased in the order of ethanol (5-7% reduced at 77 and 153 d), glucose (49% reduced at 53 d), and methanol (93% reduced at 90 d). The microbial diversity of ethanol- and methanol-amended microcosms in their late stage of U reduction was analyzed with 16S rRNA gene amplification. Members of the Geobacteraceae were found in all microcosms as well as other potential uranium-reducing organisms, such as Clostridium and Desulfosporosinus. The effectiveness of methanol relative to ethanol at reducing aqueous and sediment-hosted uranium suggests that bioremediation strategies that encourage fermentative poising of the subsurface to a lower redox potential may be more effective for long-term uranium immobilization as compared with selecting an electron donor that is efficiently metabolized by known uranium-reducing microorganisms.

  8. O-Glycosyl Donors

    NASA Astrophysics Data System (ADS)

    López, J. Cristóbal

    O-Glycosyl donors, despite being one of the last successful donors to appear, have developed themselves into a burgeoning class of glycosyl donors. They can be classified in two main types: O-alkyl and O-aryl (or hetaryl) glycosyl donors. They share, however, many characteristics, they can be (1) synthesized from aldoses, either by modified Fisher glycosidation (O-alkyl) or by nucleophilic aromatic substitution (O-aryl or O-hetaryl), (2) stable to diverse chemical manipulations, (3) directly used for saccharide coupling, and (4) chemoselectively activated. Among these, n-pentenyl glycosides stand apart. They were the first O-alkyl glycosyl donors to be described and have paved the way to many conceptual developments in oligosaccharide synthesis. The development of the chemoselectivity-based "armed-disarmed" approach for saccharide coupling, including its stereoelectronic or torsional variants, now extended to other kinds of glycosyl donors, was first recognized in n-pentenyl glycosides. The chemical manipulation of the anomeric substituent in the glycosyl donor to induce reactivity differences between related species (sidetracking) was also introduced in n-pentenyl glycosides. An evolution of this concept, the "latent-active" strategy for glycosyl couplings, first described in thioglycosyl donors (vide infra), has been elegantly applied to O-glycosyl donors. Thus, allyl and vinyl glycosides, 2-(benzyloxycarbonyl)benzyl (BCB) glycosides and 2'-carboxybenzyl (CB) glycosides are useful "latent-active" glycosyl pairs. Finally, unprotected 3-methoxy-2-pyridyl (MOP) glycosides have been used in glycosylation processes with moderate success.

  9. ADS pilot program Plan

    NASA Technical Reports Server (NTRS)

    Clauson, J.; Heuser, J.

    1981-01-01

    The Applications Data Service (ADS) is a system based on an electronic data communications network which will permit scientists to share the data stored in data bases at universities and at government and private installations. It is designed to allow users to readily locate and access high quality, timely data from multiple sources. The ADS Pilot program objectives and the current plans for accomplishing those objectives are described.

  10. Donor Telomere Length SAA

    Cancer.gov

    A new NCI study has found that, among patients with severe aplastic anemia who received a hematopoietic cell transplant from an unrelated donor, those whose donor white blood cells had longer telomeres had higher survival rates five-years after transplant

  11. Rich Donors, Poor Countries

    ERIC Educational Resources Information Center

    Thomas, M. A.

    2012-01-01

    The shifting ideological winds of foreign aid donors have driven their policy towards governments in poor countries. Donors supported state-led development policies in poor countries from the 1940s to the 1970s; market and private-sector driven reforms during the 1980s and 1990s; and returned their attention to the state with an emphasis on…

  12. D-A-D-π-D-A-D type diketopyrrolopyrrole based small molecule electron donors for bulk heterojunction organic solar cells.

    PubMed

    Patil, Yuvraj; Misra, Rajneesh; Sharma, Abhishek; Sharma, Ganesh D

    2016-06-22

    Two organic small molecules based on diketopyrrolopyrrole (DPP) units having a D-A-D-π-D-A-D structure denoted as and were synthesized. Their optical and electrochemical properties relevant to organic solar cells were investigated. The wider optical absorption coverage from 450-800 nm, the highest occupied molecular orbital (HOMO) (-5.23 eV and -5.34 eV for and , respectively) and the lowest unoccupied molecular orbital (LUMO) (-3.47 and -3.45 eV for and , respectively) make these small molecules suitable as donors for bulk heterojunction organic solar cells. The bulk heterojunction (BHJ) organic solar cells based on an active layer consists of a blend of these small molecules as donors and PC71BM as an acceptor with an optimized weight ratio of 1 : 2 cast from chloroform (CF) showed overall power conversion efficiencies (PCEs) of 1.98% (with Jsc = 5.38 mA cm(-2), Voc = 0.84 V and FF = 0.42) and 1.85% (with Jsc = 4.56 mA cm(-2), Voc = 0.96 V and FF = 0.42) for and respectively. The relatively high Voc value based on the based device has been attributed to the deeper HOMO of compared to . The optimized  : PC71BM (1 : 2) and  : PC71BM (1 : 2) active layers were subjected to two step annealing (TSA), i.e. thermal annealing and subsequent solvent vapor annealing and the corresponding BHJ organic solar cells showed a PCE of 5.28% (Jsc = 11.53 mA cm(-2), Voc = 0.79 V and FF = 0.58) and 5.52% (Jsc = 10.84 mA cm(-2), Voc = 0.91 V and FF = 0.56), respectively. The enhancement in PCE is mainly due to the improvement in Jsc and FF, related to light absorption in an active layer, a better nanoscale morphology, and an increase in the crystalline nature of the active layer and balanced charge transport, induced by the TSA treatment.

  13. Adding Value.

    ERIC Educational Resources Information Center

    Orsini, Larry L.; Hudack, Lawrence R.; Zekan, Donald L.

    1999-01-01

    The value-added statement (VAS), relatively unknown in the United States, is used in financial reports by many European companies. Saint Bonaventure University (New York) has adapted a VAS to make it appropriate for not-for-profit universities by identifying stakeholder groups (students, faculty, administrators/support personnel, creditors, the…

  14. Effect of Bridge Alteration on Ground- and Excited-State Properties of Ruthenium(II) Complexes with Electron-Donor-Substituted Dipyrido[3,2-a:2',3'-c]phenazine Ligands.

    PubMed

    Shillito, Georgina E; Larsen, Christopher B; McLay, James R W; Lucas, Nigel T; Gordon, Keith C

    2016-11-07

    A series of Ru(II) 2,2'-bipyridine (bpy) complexes with an electron-accepting dipyrido[3,2-a:2',3'-c]phenazine (dppz) ligand coupled to an electron-donating triarylamine (TAA) group have been investigated. Systematic alteration of a bridging unit between the dppz and TAA allowed exploration into how communication between the donor and acceptor is perturbed by distance, as well as by steric and electronic effects. The effect of the bridging group on the electronic properties of the systems was characterized using a variety of spectroscopic methods, including Fourier transform-Raman (FT-Raman) spectroscopy, resonance Raman spectroscopy, and transient resonance Raman (TR(2)) spectroscopy. These methods were used in conjunction with ground- and excited-state absorption spectroscopy, electrochemical studies, and DFT calculations. The ground-state electronic absorption spectra show distinct variation with the bridging group, with the wavelength observed for the lowest energy electronic transition ranging from 449 nm to 522 nm, accompanied by large changes in the molar absorptivity. The lowest-energy Franck-Condon state was determined to be intra-ligand charge transfer (ILCT) in nature for most compounds. The presence of higher-energy metal-to-ligand charge transfer (MLCT) Ru(II) → bpy and Ru(II) → dppz transitions was also confirmed via resonance Raman spectroscopy. The TR(2) spectra showed characteristic dppz(• -) and TAA(• +) vibrations, indicating that the THEXI state formed was also ILCT in nature. Excited-state lifetime measurements reveal that the rate of decay is in accordance with the energy gap law and is not otherwise affected by the nature of the bridging unit.

  15. Application-oriented computational studies on a series of D-π-A structured porphyrin sensitizers with different electron-donor groups.

    PubMed

    Fan, Chencheng; Zhang, Bao; Li, Yuanchao; Liang, Yuxia; Xue, Xiaodong; Feng, Yaqing

    2015-11-11

    A series of D-π-A zinc porphyrin sensitizers bearing a substituted iminodibenzyl group at the porphyrin meso position, which is expected to have different electron-donating abilities, were designed. Theoretical studies were performed to examine the photovoltaic properties of these molecules in dye-sensitized solar cells (DSSCs). In particular, the important concepts, the Fukui function and the extended condensed Fukui function, are employed to describe the electron-donating abilities accurately at the quantitative level. Tangui Le Bahers model was adopted to analyze charge transfer (CT) during electron transition. A correlation between the electron donating abilities of the derived iminodibenzyl group and CT was built to evaluate the cell performance based on sensitizers . The theoretical studies showed that porphyrins bearing an extremely strong electron-donating group (EDG) would fail in the generation of photocurrent in the closed circuit when applied in DSSCs due to the higher level of the HOMO energy than the redox potential of the redox couple (I(-)/I3(-)). The one with a weaker EDG () is expected to show better photovoltaic performance than porphyrin with an unsubstituted iminodibenzyl group. This study demonstrates a reliable method involving the employment of the Fukui function, the extended condensed Fukui function and the Tangui Le Bahers model for the evaluation of newly designed D-π-A type porphyrin sensitizers for use in DSSCs, and as guidance for future molecular design.

  16. [Motivations of oocytes donors].

    PubMed

    Cauvin, P

    2009-01-01

    Oocyte donation is a complex situation that requires the applicant couple to deal with the presence of the donor in the history of the child conception. Accepting the eggs is not the same thing than accepting the donor. Her place in the child's life depends on how his parents will accept her phantasmal reality beyond her real person. Paying attention to the story told by the donors on their motivations may help parents internalize this conception to three. We show from two clinical observations, that the generosity of donors is connected to personal issues that do not relate to unborn child or its parents. If there are two mothers in oocyte donation, they are not really in competition because there are also two children: the child conceived through donation is that of the project of the couple, the child to which the donor thinks, is and will remain in phantasmal domain, i.e. linked to the personal history of the donor. We also show that the psychological interview fully responds to the donor expectations when it seeks to highlight her motives.

  17. 2,3-Dipentyldithieno[3,2-f:2',3'-h]quinoxaline-Based Organic Dyes for Efficient Dye-Sensitized Solar Cells: Effect of π-Bridges and Electron Donors on Solar Cell Performance.

    PubMed

    Huang, Zu-Sheng; Zang, Xu-Feng; Hua, Tao; Wang, Lingyun; Meier, Herbert; Cao, Derong

    2015-09-16

    Five novel metal-free organic dyes DQ1-5 containing a dipentyldithieno[3,2-f:2',3'-h]quinoxaline (DPQ) unit were synthesized and applied in dye-sensitized solar cells (DSSCs), where DPQ was employed as a π-spacer for the first time. Their photophysical, electrochemical, and theoretical calculations and photovoltaic properties were systematically investigated. All the five dyes show broad photoresponse. Especially the absorption edges of DQ3-5 extend to 800 nm on the TiO2 films. The inserted electron-rich unit 3,4-ethylenedioxythiophene or electron-withdrawing group benzothiadiazole (BTD) in DPQ-based dyes can greatly influence the optoelectronic properties of the dyes. In addition, the different electron donors also significantly affect the performance of the DSSCs. Under standard global AM 1.5 solar light conditions, the DQ5 sensitized solar cell obtained a power conversion efficiency of 7.12%. The result indicates that the rigid DPQ-based organic dye is a promising candidate for efficient DSSCs.

  18. Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C(t)Bu2)4 (M = V, Nb, Ta).

    PubMed

    Damon, Peter L; Liss, Cameron J; Lewis, Richard A; Morochnik, Simona; Szpunar, David E; Telser, Joshua; Hayton, Trevor W

    2015-10-19

    Addition of 4 equiv of Li(N═C(t)Bu2) to VCl3 in THF, followed by addition of 0.5 equiv of I2, generates the homoleptic V(IV) ketimide complex, V(N═C(t)Bu2)4 (1), in 42% yield. Similarly, reaction of 4 equiv of Li(N═C(t)Bu2) with NbCl4(THF)2 in THF affords the homoleptic Nb(IV) ketimide complex, Nb(N═C(t)Bu2)4 (2), in 55% yield. Seeking to extend the series to the tantalum congener, a new Ta(IV) starting material, TaCl4(TMEDA) (3), was prepared via reduction of TaCl5 with Et3SiH, followed by addition of TMEDA. Reaction of 3 with 4 equiv of Li(N═C(t)Bu2) in THF results in the isolation of a Ta(V) ketimide complex, Ta(Cl)(N═C(t)Bu2)4 (5), which can be isolated in 32% yield. Reaction of 5 with Tl(OTf) yields Ta(OTf)(N═C(t)Bu2)4 (6) in 44% yield. Subsequent reduction of 6 with Cp*2Co in toluene generates the homoleptic Ta(IV) congener Ta(N═C(t)Bu2)4 (7), although the yields are poor. All three homoleptic group 5 ketimide complexes exhibit squashed tetrahedral geometries in the solid state, as determined by X-ray crystallography. This geometry leads to a d(x(2)-y(2))(1) ((2)B1 in D(2d)) ground state, as supported by DFT calculations. EPR spectroscopic analysis of 1 and 2, performed at X- and Q-band frequencies (∼9 and 35 GHz, respectively), further supports the (2)B1 ground-state assignment, whereas comparison of 1, 2, and 7 with related group 5 tetra(aryl), tetra(amido), and tetra(alkoxo) complexes shows a higher M-L covalency in the ketimide-metal interaction. In addition, a ligand field analysis of 1 and 2 demonstrates that the ketimide ligand is both a strong π-donor and strong π-acceptor, an unusual combination found in very few organometallic ligands.

  19. Quantifying the electron donor and acceptor ability of the ketimide ligands in M(N=CtBu2)4 (M = V, Nb, Ta)

    PubMed Central

    Damon, Peter L.; Liss, Cameron J.; Lewis, Richard A.; Morochnik, Simona; Szpunar, David E.; Telser, Joshua; Hayton, Trevor W.

    2015-01-01

    Addition of 4 equiv of Li(N=CtBu2) to VCl3 in THF, followed by addition of 0.5 equiv I2, generates the homoleptic V(IV) ketimide complex, V(N=CtBu2)4 (1), in 42% yield. Similarly, reaction of 4 equiv of Li(N=CtBu2) with NbCl4(THF)2 in THF affords the homoleptic Nb(IV) ketimide complex, Nb(N=CtBu2)4 (2), in 55% yield. Seeking to extend the series to the tantalum congener, a new Ta(IV) starting material, TaCl4(TMEDA) (3), was prepared via reduction of TaCl5 with Et3SiH, followed by addition of TMEDA. Reaction of 3 with 4 equiv of Li(N=CtBu2) in THF results in a isolation of a Ta(V) ketimide complex, Ta(Cl)(N=CtBu2)4 (5), which can be isolated in 32% yield. Reaction of 5 with Tl(OTf) yields Ta(OTf)(N=CtBu2)4 (6) in 44% yield. Subsequent reduction of 6 with Cp*2Co in toluene generates the homoleptic Ta(IV) congener Ta(N=CtBu2)4 (7), although the yields are poor. All three homoleptic Group 5 ketimide complexes exhibit squashed tetrahedral geometries in the solid state, as determined by X-ray crystallography. This geometry leads to a dx2−y21 (2B1 in D2d) ground state, as supported by DFT calculations. EPR spectroscopic analysis of 1 and 2, performed at X- and Q-band frequencies (~9 and 35 GHz, respectively), further supports the 2B1 ground state assignment, while comparison of 1, 2, and 7 with related Group 5 tetra(aryl), tetra(amido) and tetra(alkoxo) complexes shows a higher M-L covalency in the ketimide-metal interaction. In addition, a ligand field analysis of 1 and 2 demonstrates that the ketimide ligand is both a strong π-donor and strong π-acceptor, an unusual combination found in very few organometallic ligands. PMID:26419513

  20. Laparoscopic donor nephrectomy.

    PubMed

    Deger, S; Giessing, M; Roigas, J; Wille, A H; Lein, M; Schönberger, B; Loening, S A

    2005-01-01

    Laparoscopic live donor nephrectomy (LDN) has removed disincentives of potential donors and may bear the potential to increase kidney donation. Multiple modifications have been made to abbreviate the learning curve while at the same time guarantee the highest possible level of medical quality for donor and recipient. We reviewed the literature for the evolution of the different LDN techniques and their impact on donor, graft and operating surgeon, including the subtleties of different surgical accesses, vessel handling and organ extraction. We performed a literature search (PubMed, DIMDI, medline) to evaluate the development of the LDN techniques from 1995 to 2003. Today more than 200 centres worldwide perform LDN. Hand-assistance has led to a spread of LDN. Studies comparing open and hand-assisted LDN show a reduction of operating and warm ischaemia times for the hand-assisted LDN. Different surgical access sites (trans- or retroperitoneal), different vessel dissection approaches, donor organ delivery techniques, delivery sites and variations of hand-assistance techniques reflect the evolution of LDN. Proper techniques and their combination for the consecutive surgical steps minimize both warm ischaemia time and operating time while offering the donor a safe minimally invasive laparoscopic procedure. LDN has breathed new life into the moribund field of living kidney donation. Within a few years LDN could become the standard approach in living kidney donation. Surgeons working in this field must be trained thoroughly and well acquainted with the subtleties of the different LDN techniques and their respective advantages and disadvantages.

  1. The Determination of Molecular Quantities from Measurements on Macroscopic Systems.V. Existence and Properties of 1:1 and 2:1-Electron-Donor-Acceptor Complexes of Hexamethylbenzene with Tetracyanoethylene

    NASA Astrophysics Data System (ADS)

    Liptay, Wolfgang; Rehm, Torsten; Wehning, Detlev; Schanne, Lothar; Baumann, Wolfram; Lang, Werner

    1982-12-01

    The formation of electron-donor-acceptor complexes of hexamethylbenzene (HMB) with tetracyanoethylene (TCNE) was investigated by measurements of the optical absorptions, the densities, the permittivities and the electro-optical absorptions of solutions in CCl4. The careful evaluation of data based on some previously reported models, has shown that the assumption of the formation of the 1: 1 and the 2 : 1 complex agrees with all experimental data, but that the assumption of the formation of only the 1: 1 complex is contradictory to experimental facts even if the activity effects on the equilibrium constant and of the solvent dependences of observed molar quantities are taken into account. The evaluation leads to the molar optical absorption coefficients and the molar volumes of both complexes and to their electric dipole moments in the electronic ground state and the considered excited state. According to these results the complexes are of the sandwich type HMB-TCNE and HMB-TCNE-HMB. In spite of the fact that the 2: 1 complex owns a center of symmetry, at least approximately, there is a rather large electric dipole moment in its excited state. Furthermore, values for the equilibrium constants and for the standard reaction enthalpies of both complex formation reactions are estimated from experimental data.

  2. Photoionization in micelles: Addition of charged electron acceptors

    NASA Astrophysics Data System (ADS)

    Stenland, Chris; Kevan, Larry

    The relative photoyield of the electron donor N, N, N', N'-tetramethylbenzidine (TMB), solubilized in sodium and lithium dodecyl sulfate micelles with added charged electron acceptors was investigated. It was attempted to control the acceptor distance from a charged micellar interface by differently charged acceptors, cationic dimethyl viologen and anionic ferricyanide. However, back electron transfer from both cationic and anionic acceptors was found to be efficient. Thus simple electrostatic arguments for control of the photoyield do not seem applicable. Salt effects associated with the added ionic acceptors which partially neutralize the ionic micellar interface are suggested to be an important factor.

  3. Absence of beta-amyloid in cortical cataracts of donors with and without Alzheimer's disease.

    PubMed

    Michael, Ralph; Rosandić, Jurja; Montenegro, Gustavo A; Lobato, Elvira; Tresserra, Francisco; Barraquer, Rafael I; Vrensen, Gijs F J M

    2013-01-01

    Eye lenses from human donors with and without Alzheimer's disease (AD) were studied to evaluate the presence of amyloid in cortical cataract. We obtained 39 lenses from 21 postmortem donors with AD and 15 lenses from age-matched controls provided by the Banco de Ojos para Tratamientos de la Ceguera (Barcelona, Spain). For 17 donors, AD was clinically diagnosed by general physicians and for 4 donors the AD diagnosis was neuropathologically confirmed. Of the 21 donors with AD, 6 had pronounced bilateral cortical lens opacities and 15 only minor or no cortical opacities. As controls, 7 donors with pronounced cortical opacities and 8 donors with almost transparent lenses were selected. All lenses were photographed in a dark field stereomicroscope. Histological sections were analyzed using a standard and a more sensitive Congo red protocol, thioflavin staining and beta-amyloid immunohistochemistry. Brain tissue from two donors, one with cerebral amyloid angiopathy and another with advanced AD-related changes and one cornea with lattice dystrophy were used as positive controls for the staining techniques. Thioflavin, standard and modified Congo red staining were positive in the control brain tissues and in the dystrophic cornea. Beta-amyloid immunohistochemistry was positive in the brain tissues but not in the cornea sample. Lenses from control and AD donors were, without exception, negative after Congo red, thioflavin, and beta-amyloid immunohistochemical staining. The results of the positive control tissues correspond well with known observations in AD, amyloid angiopathy and corneas with lattice dystrophy. The absence of staining in AD and control lenses with the techniques employed lead us to conclude that there is no beta-amyloid in lenses from donors with AD or in control cortical cataracts. The inconsistency with previous studies of Goldstein et al. (2003) and Moncaster et al. (2010), both of which demonstrated positive Congo red, thioflavin, and beta

  4. Evidence for cytochrome b5 as an electron donor in ricinoleic acid biosynthesis in microsomal preparations from developing castor bean (Ricinus communis L.).

    PubMed Central

    Smith, M A; Jonsson, L; Stymne, S; Stobart, K

    1992-01-01

    The major b-type cytochrome in microsomal membrane preparations from developing endosperm of castor bean (Ricinus communis) was cytochrome b5. Cytochrome P-450 was also present. The microsomal membranes had delta 12-hydroxylase activity and catalysed the NAD(P)H-dependent hydroxylation of oleate to yield ricinoleic acid. CO had no effect on the hydroxylase activity. Rabbit polyclonal antibodies were raised against the hydrophilic cytochrome b5 fragment purified from cauliflower (Brassica oleracea) floret microsomes. The anti-(cytochrome b5) IgG inhibited delta 12-hydroxylase, delta 12-desaturase and cytochrome c reductase activity in the microsomes. The results indicate that electrons from NAD(P)H were transferred to the site of hydroxylation via cytochrome b5 and that cytochrome P-450 was not involved. Images Fig. 1. PMID:1417766

  5. NADH:Cytochrome b5 Reductase and Cytochrome b5 Can Act as Sole Electron Donors to Human Cytochrome P450 1A1-Mediated Oxidation and DNA Adduct Formation by Benzo[a]pyrene

    PubMed Central

    2016-01-01

    Benzo[a]pyrene (BaP) is a human carcinogen that covalently binds to DNA after activation by cytochrome P450 (P450). Here, we investigated whether NADH:cytochrome b5 reductase (CBR) in the presence of cytochrome b5 can act as sole electron donor to human P450 1A1 during BaP oxidation and replace the canonical NADPH:cytochrome P450 reductase (POR) system. We also studied the efficiencies of the coenzymes of these reductases, NADPH as a coenzyme of POR, and NADH as a coenzyme of CBR, to mediate BaP oxidation. Two systems containing human P450 1A1 were utilized: human recombinant P450 1A1 expressed with POR, CBR, epoxide hydrolase, and cytochrome b5 in Supersomes and human recombinant P450 1A1 reconstituted with POR and/or with CBR and cytochrome b5 in liposomes. BaP-9,10-dihydrodiol, BaP-7,8-dihydrodiol, BaP-1,6-dione, BaP-3,6-dione, BaP-9-ol, BaP-3-ol, a metabolite of unknown structure, and two BaP-DNA adducts were generated by the P450 1A1-Supersomes system, both in the presence of NADPH and in the presence of NADH. The major BaP-DNA adduct detected by 32P-postlabeling was characterized as 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-BaP (assigned adduct 1), while the minor adduct is probably a guanine adduct derived from 9-hydroxy-BaP-4,5-epoxide (assigned adduct 2). BaP-3-ol as the major metabolite, BaP-9-ol, BaP-1,6-dione, BaP-3,6-dione, an unknown metabolite, and adduct 2 were observed in the system using P450 1A1 reconstituted with POR plus NADPH. When P450 1A1 was reconstituted with CBR and cytochrome b5 plus NADH, BaP-3-ol was the predominant metabolite too, and an adduct 2 was also generated. Our results demonstrate that the NADH/cytochrome b5/CBR system can act as the sole electron donor both for the first and second reduction of P450 1A1 during the oxidation of BaP in vitro. They suggest that NADH-dependent CBR can replace NADPH-dependent POR in the P450 1A1-catalyzed metabolism of BaP. PMID:27404282

  6. Empirical Establishment of Oligonucleotide Probe Design Criteria; Use of Microarrays with Different Probe Sizes for Monitoring Gene Expression; Temporal Transcriptomic Analysis as Desulfovibrio vulgaris Hildenborough Transitions into Stationary Phase during Electron Donor Depletion

    SciTech Connect

    He, Q.; He, Z.; Huang, K. H.; Alm, E. J.; Wan, X. F.; Hazen, T. C.; Arkin, A. P.; Wall, J. D.; Zhou, J. Z.; Fields, M. W.

    2005-07-15

    stationary phase during electron donor depletion. In addition to temporal transcriptomics, total protein, carbohydrate, lactate, acetate, and sulfate levels were measured. The microarray data were examined for statistically significant expression changes, hierarchical cluster analysis, and promoter element prediction and were validated by quantitative PCR. ..... Our results indicated that in addition to expected changes (e.g., energy conversion, protein turnover, translation, transcription, and DNA replication and repair), genes related to phage, stress response, carbohydrate flux, the outer envelope, and iron homeostasis played important roles as D. vulgaris cells experienced electron donor depletion.

  7. Improved photochromic properties on viologen-based inorganic-organic hybrids by using π-conjugated substituents as electron donors and stabilizers.

    PubMed

    Lin, Rong-Guang; Xu, Gang; Wang, Ming-Sheng; Lu, Gang; Li, Pei-Xin; Guo, Guo-Cong

    2013-02-04

    A series of inorganic-organic hybrid compounds L(2)(Bi(2)Cl(10)) (L = HMV(2+) = N-proton-N'-methyl-4,4'-bipyridinium for 1, L = HBzV(2+) = N-proton-N'-benzyl-4,4'-bipyridinium for 2, and L = HPeV(2+) = N-proton-N'-phenethyl-4,4'-bipyridinium for 3) have been successfully synthesized by an in situ solvothermal reaction. Compounds 1-3, with the same metal halide as anions but different asymmetric viologen molecules as cations, are ideal model compounds for investigating the detailed effect of different photochromically active molecules on the photochromic properties of the hybrids. Compound 1 shows no photochromic behavior, but compounds 2 and 3 possess photochromism and show a faster photoresponse rate than other reported viologen metal halide hybrids. Studies on the relationship between the structure and photochromic behavior clearly reveal that π-conjugated substituents could be used to improve the photoresponsibility and enrich the developed color efficiently and that the π···π interaction among organic components may not only be a powerful factor to stabilize the viologen monocation radical but also act as the second path of electron transfer from the π-conjugated substituent to the viologen cation for the photochromic process, which significantly influences the photochromic properties.

  8. Panchromatic donor-acceptor-donor conjugated oligomers for dye-sensitized solar cell applications.

    PubMed

    Stalder, Romain; Xie, Dongping; Islam, Ashraful; Han, Liyuan; Reynolds, John R; Schanze, Kirk S

    2014-06-11

    We report on a sexithienyl and two donor-acceptor-donor oligothiophenes, employing benzothiadiazole and isoindigo as electron-acceptors, each functionalized with a phosphonic acid group for anchoring onto TiO2 substrates as light-harvesting molecules for dye sensitized solar cells (DSSCs). These dyes absorb light to wavelengths as long as 700 nm, as their optical HOMO/LUMO energy gaps are reduced from 2.40 to 1.77 eV with increasing acceptor strength. The oligomers were adsorbed onto mesoporous TiO2 films on fluorine doped tin oxide (FTO)/glass substrates and incorporated into DSSCs, which show AM1.5 power conversion efficiencies (PCEs) ranging between 2.6% and 6.4%. This work demonstrates that the donor-acceptor-donor (D-A-D) molecular structures coupled to phosphonic acid anchoring groups, which have not been used in DSSCs, can lead to high PCEs.

  9. Living Donor Liver Transplantation

    MedlinePlus

    ... instructions before and after surgery. • Have a compatible blood type. • Have an emotional tie with the recipient. • Not ... test is to find out if the donor's blood type matches the recipient’s blood type. Next, the transplant ...

  10. Dialing for Donors

    ERIC Educational Resources Information Center

    Schaffhauser, Dian

    2012-01-01

    When times get tough, grown children often turn to their parents for help--for some extra cash, even somewhere to stay. For colleges and universities, that role is filled by alumni donors. In 2011, with education budgets slashed across the country, giving accounted for 6.5 percent of college expenditures, according to the Council for Aid to…

  11. ADS in a Nutshell

    NASA Astrophysics Data System (ADS)

    Demleitner, M.; Eichhorn, G.; Grant, C. S.; Accomazzi, A.; Murray, S. S.; Kurtz, M. J.

    1999-05-01

    The bibliographic databases maintained by the NASA Astrophysics Data System are updated approximately biweekly with records gathered from over 125 sources all over the world. Data are either sent to us electronically, retrieved by our staff via semi-automated procedures, or entered in our databases through supervised OCR procedures. PERL scripts are run on the data to convert them from their incoming format to our standard format so that they can be added to the master database at SAO. Once new data has been added, separate index files are created for authors, objects, title words, and text word, allowing these fields to be searched for individually or in combination with each other. During the indexing procedure, discipline-specific knowledge is taken into account through the use of rule-based procedures performing string normalization, context-sensitive word translation, and synonym and stop word replacement. Once the master text and index files have been updated at SAO, an automated procedure mirrors the changes in the database to the ADS mirror site via a secure network connection. The use of a public domain software tool called rsync allows incremental updating of the database files, with significant savings in the amount of data being transferred. In the past year, the ADS Abstract Service databases have grown by approximately 30%, including 50% growth in Physics, 25% growth in Astronomy and 10% growth in the Instrumentation datasets. The ADS Abstract Service now contains over 1.4 million abstracts (475K in Astronomy, 430K in Physics, 510K in Instrumentation, and 3K in Preprints), 175,000 journal abstracts, and 115,000 full text articles. In addition, we provide links to over 40,000 electronic HTML articles at other sites, 20,000 PDF articles, and 10,000 postscript articles, as well as many links to other external data sources.

  12. Separation of donor and recipient bacteria by column chromatography.

    PubMed

    Zsigray, R M; Fulk, G E; Lawton, W D

    1970-08-01

    When donor and recipient strains of Escherichia coli were added to columns containing Cellex-P (a cation-exchange cellulose), more than 80% of the female cells passed through the column but only 11% or less of the male cells were eluted. However, when donor strains were blended before their addition to the column, the majority of these cells were eluted. These results indicated that the filamentous appendages termed F pili (which are removed by blending) were the structures responsible for the adherence of donor cells to the cellulose.

  13. Microwave assisted synthesis of bithiophene based donor-acceptor-donor oligomers and their optoelectronic performances

    NASA Astrophysics Data System (ADS)

    Bathula, Chinna; Buruga, Kezia; Lee, Sang Kyu; Khazi, Imtiyaz Ahmed M.; Kang, Youngjong

    2017-07-01

    In this article we present the synthesis of two novel bithiophene based symmetrical π conjugated oligomers with donor-acceptor-donor (D-A-D) structures by microwave assisted PdCl2(dppf) catalyzed Suzuki coupling reaction. These molecules contain electron rich bithiophene as a donor, dithienothiadiazole[3,4-c]pyridine and phthalic anhydride units as acceptors. The shorter reaction time, excellent yields and easy product isolation are the advantages of this method. The photophysical prerequisites for electronic application such as strong and broad optical absorption, thermal stability, and compatible energy levels were determined for synthesized oligomers. Optical band gap for the oligomers is found to be 1.72-1.90 eV. The results demonstrated the novel oligomers to be promising candidates in organic optoelectronic applications.

  14. Being a Living Donor: Risks

    MedlinePlus

    ... Living Donation / Being a Living Donor / Risks Facts History Organs Frequently Asked Questions Discussing Living Donation Types Related Non-Related Non-Directed Paired Donation Blood Type Incompatible Positive Crossmatch Being a Living Donor ...

  15. Selection against genetic defects in semen donors.

    PubMed

    Smith, P E

    1984-08-01

    Artificial insemination donor selection requires predicting which men are likely to beget the healthiest offspring. Methods are developed for calculating the "offspring excess recurrence risk", delta R, for an anomaly in the offspring of an afflicted father. Mainly from published family survey and population data delta R is computed for 38 disorders. From a small survey a value for the with-treatment "affliction burden", Bt, is assigned to each anomaly. For each disorder the "offspring excess burden expectation" is delta RBt. Defects such as cataract, hereditary Parkinson disease, psoriasis, seropositive rheumatoid arthritis, and schizophrenia have such a high delta RBt that they are individually sufficient cause for rejecting a donor candidate. A candidate may be rejected because of a combination of lesser defects with sigma delta RBt exceeding an acceptable limit. A limit should also be placed on Bt, because the affliction burden for Tay-Sachs disease or cystic fibrosis is intolerable, however infrequent. Most of the important hereditary defects are late onset, and for the older donor the opportunity to select more directly against late-onset disorders offsets the added risk of newly-arising gene mutations. The most careful donor selection cannot completely eliminate the risk of a child inheriting some disorder, but selection can reduce the average total burden by as much as 17%.

  16. National Marrow Donor Program

    DTIC Science & Technology

    2009-08-14

    Recipient Pair HLA typing project to characterize class I and class II alleles of donor/recipient paired samples from NMDP’s Repository was initiated...24 • Initiated investigation of the first class II non-ARS mismatch (DRB1*140101/1454) where both alleles have been seen in the same genotype... MHC Major Histocompatibility Complex B-LCLs B-Lymphocytic Cell Lines MICA MHC Class I-Like Molecule, Chain A BARDA Biomedical Advanced Research and

  17. Orientifolded locally AdS3 geometries

    NASA Astrophysics Data System (ADS)

    Loran, F.; Sheikh-Jabbari, M. M.

    2011-01-01

    Continuing the analysis of [Loran F and Sheikh-Jabbari M M 2010 Phys. Lett. B 693 184-7], we classify all locally AdS3 stationary axi-symmetric unorientable solutions to AdS3 Einstein gravity and show that they are obtained by applying certain orientifold projection on AdS3, BTZ or AdS3 self-dual orbifold, respectively, O-AdS3, O-BTZ and O-SDO geometries. Depending on the orientifold fixed surface, the O-surface, which is either a space-like 2D plane or a cylinder, or a light-like 2D plane or a cylinder, one can distinguish four distinct cases. For the space-like orientifold plane or cylinder cases, these geometries solve AdS3 Einstein equations and are hence locally AdS3 everywhere except at the O-surface, where there is a delta-function source. For the light-like cases, the geometry is a solution to Einstein equations even at the O-surface. We discuss the causal structure for static, extremal and general rotating O-BTZ and O-SDO cases as well as the geodesic motion on these geometries. We also discuss orientifolding Poincaré patch AdS3 and AdS2 geometries as a way to geodesic completion of these spaces and comment on the 2D CFT dual to the O-geometries.

  18. Complications of donor apheresis.

    PubMed

    Winters, Jeffrey L

    2006-07-01

    A decreasing blood donor pool in the presence of increasing blood transfusion demands has resulted in the need to maximally utilize each blood donor. This has led to a trend in the increasing use of automated blood collections. While apheresis donation shares many reactions and injuries with whole blood donation, because of the differences, unique complications also exist. Overall, evidence in the literature suggests that the frequency of reactions to apheresis donation is less than that seen in whole blood donation, though the risk of reactions requiring hospitalization is substantially greater. The most common apheresis-specific reaction is hypocalcemia due to citrate anticoagulation, which, while usually mild, has the potential for severely injuring the donor. Other reactions to apheresis donation are uncommon (e.g., hypotension) or rare (e.g., air embolism). More worrisome, and in need of additional study, are the long-term effects of apheresis donation. Recent evidence suggests that repeated apheresis platelet donations may adversely effect thrombopoiesis as well as bone mineralization. Granulocyte donation has also been implicated in unexpected long-term consequences.

  19. Cross-conjugated chromophores: synthesis of iso-polydiacetylenes with Donor/Acceptor substitution

    PubMed

    Ciulei; Tykwinski

    2000-11-16

    The iterative construction of cross-conjugated donor (D), acceptor (A), and donor-acceptor (D-A) substituted iso-polydiacetylene (iso-PDA) oligomers has been achieved utilizing palladium-catalyzed cross-coupling techniques. Structure-property relationships for these compounds have been analyzed for cross-conjugated pi-electronic communication as a result of contributions from donor, acceptor, or donor-acceptor functionalization.

  20. Warped AdS3 black holes

    NASA Astrophysics Data System (ADS)

    Anninos, Dionysios; Li, Wei; Padi, Megha; Song, Wei; Strominger, Andrew

    2009-03-01

    Three dimensional topologically massive gravity (TMG) with a negative cosmological constant -l-2 and positive Newton constant G admits an AdS3 vacuum solution for any value of the graviton mass μ. These are all known to be perturbatively unstable except at the recently explored chiral point μl = 1. However we show herein that for every value of μl ≠ 3 there are two other (potentially stable) vacuum solutions given by SL(2,Bbb R) × U(1)-invariant warped AdS3 geometries, with a timelike or spacelike U(1) isometry. Critical behavior occurs at μl = 3, where the warping transitions from a stretching to a squashing, and there are a pair of warped solutions with a null U(1) isometry. For μl > 3, there are known warped black hole solutions which are asymptotic to warped AdS3. We show that these black holes are discrete quotients of warped AdS3 just as BTZ black holes are discrete quotients of ordinary AdS3. Moreover new solutions of this type, relevant to any theory with warped AdS3 solutions, are exhibited. Finally we note that the black hole thermodynamics is consistent with the hypothesis that, for μl > 3, the warped AdS3 ground state of TMG is holographically dual to a 2D boundary CFT with central charges c_R-formula and c_L-formula.

  1. Warped AdS3 black holes

    NASA Astrophysics Data System (ADS)

    Song, Wei; Anninos, Dionysios; Li, Wei; Padi, Megha; Strominger, Andrew

    2009-03-01

    Three dimensional topologically massive gravity (TMG) with a negative cosmological constant -ell-2 and positive Newton constant G admits an AdS3 vacuum solution for any value of the graviton mass μ. These are all known to be perturbatively unstable except at the recently explored chiral point μell = 1. However we show herein that for every value of μell ≠ 3 there are two other (potentially stable) vacuum solutions given by SL(2,Bbb R) × U(1)-invariant warped AdS3 geometries, with a timelike or spacelike U(1) isometry. Critical behavior occurs at μell = 3, where the warping transitions from a stretching to a squashing, and there are a pair of warped solutions with a null U(1) isometry. For μell > 3, there are known warped black hole solutions which are asymptotic to warped AdS3. We show that these black holes are discrete quotients of warped AdS3 just as BTZ black holes are discrete quotients of ordinary AdS3. Moreover new solutions of this type, relevant to any theory with warped AdS3 solutions, are exhibited. Finally we note that the black hole thermodynamics is consistent with the hypothesis that, for μell > 3, the warped AdS3 ground state of TMG is holographically dual to a 2D boundary CFT with central charges c_R-formula and c_L-formula.

  2. Production of Native Donors in ZnO by Annealing at High Temperature in Zn Vapor

    SciTech Connect

    Halliburton, L. E.; Giles, N. C.; Garces, N. Y.; Luo, Ming; Xu, Chunchuan; Bai, Lihai; Boatner, Lynn A

    2005-01-01

    Zinc oxide crystals grown by the seeded chemical vapor transport method have been annealed in zinc vapor at 1100 {sup o}C for 30 min. These thermochemical reduction treatments produce a deep red coloration in the crystals and increase their n-type electrical conductivity. Electron paramagnetic resonance (EPR), optical absorption, and Hall measurements were used to monitor changes in the crystals. After an anneal, an intense optical absorption band is present that extends from the band edge out to approximately 550 nm, and the EPR signal near g = 1.96 (due to shallow donors and/or conduction-band electrons), the free-carrier absorption, and the Hall electron concentration are all larger. Hydrogen was not present during these anneals, thus leaving oxygen vacancies and zinc interstitials as candidates for the added donors. Neutral oxygen vacancies are produced at high temperature by the additive-coloration mechanism, and are responsible for the broad near-edge absorption band. The observed increase in the number of free carriers is a result of either (1) the formation of zinc interstitials or (2) having the ground state of the neutral oxygen vacancy near the conduction band.

  3. The Advantages of Using Electronic Processes for Commenting on and Exchanging the Written Work of Students with Learning Disabilities and/or AD/HD

    ERIC Educational Resources Information Center

    Carmichael, Stephen; Alden, Peg

    2006-01-01

    Researchers have explored the impact of computer-assisted feedback and electronic mail on students' writing, but most of the work to date seems to have focused on second language writers, peer response, or response as part of an online composition course. Although research has documented the importance of certain generic features of word…

  4. Optical Control of Donor Spin Qubits in Silicon

    PubMed Central

    Gullans, M. J.; Taylor, J. M.

    2016-01-01

    We show how to achieve optical, spin-selective transitions from the ground state to excited orbital states of group-V donors (P, As, Sb, Bi) in silicon. We consider two approaches based on either resonant, far-infrared (IR) transitions of the neutral donor or resonant, near-IR excitonic transitions. For far-IR light, we calculate the dipole matrix elements between the valley-orbit and spin-orbit split states for all the goup-V donors using effective mass theory. We then calculate the maximum rate and amount of electron-nuclear spin-polarization achievable through optical pumping with circularly polarized light. We find this approach is most promising for Bi donors due to their large spin-orbit and valley-orbit interactions. Using near-IR light, spin-selective excitation is possible for all the donors by driving a two-photon Λ-transition from the ground state to higher orbitals with even parity. We show that externally applied electric fields or strain allow similar, spin-selective Λ-transition to odd-parity excited states. We anticipate these results will be useful for future spectroscopic investigations of donors, quantum control and state preparation of donor spin qubits, and for developing a coherent interface between donor spin qubits and single photons. PMID:28127227

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

    PubMed

    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.

  6. [Psychosomatic selection of living liver donors].

    PubMed

    Erim, Y; Senf, W

    2001-01-01

    In the Essen University Clinic for Psychotherapy and Psychosomatics, between January and December 2000, 54 potential liver donors and 12 kidney donors were examined. All the kidney donors were found to be suitable; 7 potential liver donors were rejected on psychosomatic grounds. Reasons for the rejection were addiction (1 donor), suspected financial dependency of the donor on the recipient (1 donor) and, in the case of one donor not related to the recipient, the apparent lack of a special emotional attachment. During the actual evaluation interview, 4 potential donors reversed their original decision. Such a psychosomatic evaluation is a great help for donors in clarifying their motives and their decision.

  7. Segmented strings in AdS 3

    NASA Astrophysics Data System (ADS)

    Callebaut, Nele; Gubser, Steven S.; Samberg, Andreas; Toldo, Chiara

    2015-11-01

    We study segmented strings in flat space and in AdS 3. In flat space, these well known classical motions describe strings which at any instant of time are piecewise linear. In AdS 3, the worldsheet is composed of faces each of which is a region bounded by null geodesics in an AdS 2 subspace of AdS 3. The time evolution can be described by specifying the null geodesic motion of kinks in the string at which two segments are joined. The outcome of collisions of kinks on the worldsheet can be worked out essentially using considerations of causality. We study several examples of closed segmented strings in AdS 3 and find an unexpected quasi-periodic behavior. We also work out a WKB analysis of quantum states of yo-yo strings in AdS 5 and find a logarithmic term reminiscent of the logarithmic twist of string states on the leading Regge trajectory.

  8. Scalable quantum computer architecture with coupled donor-quantum dot qubits

    DOEpatents

    Schenkel, Thomas; Lo, Cheuk Chi; Weis, Christoph; Lyon, Stephen; Tyryshkin, Alexei; Bokor, Jeffrey

    2014-08-26

    A quantum bit computing architecture includes a plurality of single spin memory donor atoms embedded in a semiconductor layer, a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, wherein a first voltage applied across at least one pair of the aligned quantum dot and donor atom controls a donor-quantum dot coupling. A method of performing quantum computing in a scalable architecture quantum computing apparatus includes arranging a pattern of single spin memory donor atoms in a semiconductor layer, forming a plurality of quantum dots arranged with the semiconductor layer and aligned with the donor atoms, applying a first voltage across at least one aligned pair of a quantum dot and donor atom to control a donor-quantum dot coupling, and applying a second voltage between one or more quantum dots to control a Heisenberg exchange J coupling between quantum dots and to cause transport of a single spin polarized electron between quantum dots.

  9. Facile and Promising Method for Michael Addition of Indole and Pyrrole to Electron-Deficient trans-β-Nitroolefins Catalyzed by a Hydrogen Bond Donor Catalyst Feist's Acid and Preliminary Study of Antimicrobial Activity

    PubMed Central

    Al Majid, Abdullah M. A.; Islam, Mohammad Shahidul; Barakat, Assem; Al-Agamy, Mohamed H. M.; Naushad, Mu.

    2014-01-01

    The importance of cooperative hydrogen-bonding effects has been demonstrated using novel 3-methylenecyclopropane-1,2-dicarboxylic acid (Feist's acid (FA)) as hydrogen bond donor catalysts for the addition of indole and pyrrole to trans-β-nitrostyrene derivatives. Because of the hydrogen bond donor (HBD) ability, Feist's acid (FA) has been introduced as a new class of hydrogen bond donor catalysts for the activation of nitroolefin towards nucleophilic substitution reaction. It has effectively catalyzed the Michael addition of indoles and pyrrole to β-nitroolefins under optimum reaction condition to furnish the corresponding Michael adducts in good to excellent yields (up to 98%). The method is general, atom-economical, convenient, and eco-friendly and could provide excellent yields and regioselectivities. Some newly synthesized compounds were for examined in vitro antimicrobial activity and their preliminary results are reported. PMID:24574906

  10. Facile and promising method for michael addition of indole and pyrrole to electron-deficient trans-β-nitroolefins catalyzed by a hydrogen bond donor catalyst Feist's acid and preliminary study of antimicrobial activity.

    PubMed

    Al Majid, Abdullah M A; Islam, Mohammad Shahidul; Barakat, Assem; Al-Agamy, Mohamed H M; Naushad, Mu

    2014-01-01

    The importance of cooperative hydrogen-bonding effects has been demonstrated using novel 3-methylenecyclopropane-1,2-dicarboxylic acid (Feist's acid (FA)) as hydrogen bond donor catalysts for the addition of indole and pyrrole to trans-β-nitrostyrene derivatives. Because of the hydrogen bond donor (HBD) ability, Feist's acid (FA) has been introduced as a new class of hydrogen bond donor catalysts for the activation of nitroolefin towards nucleophilic substitution reaction. It has effectively catalyzed the Michael addition of indoles and pyrrole to β-nitroolefins under optimum reaction condition to furnish the corresponding Michael adducts in good to excellent yields (up to 98%). The method is general, atom-economical, convenient, and eco-friendly and could provide excellent yields and regioselectivities. Some newly synthesized compounds were for examined in vitro antimicrobial activity and their preliminary results are reported.

  11. [Clinical evaluation of living donor].

    PubMed

    Scolari, Maria Piera; Comai, G; La Manna, G; Liviano D'Arcangelo, G; Monti, M; Feliciangeli, G; Stefoni, S

    2009-01-01

    When possible, living donor transplantation represents the best therapeutic strategy for patients suffering from chronic renal failure. Studying the donor allows a complete and thorough clinical, laboratory and instrumental assessment that guarantees good organ function whilst protecting the health of the donor. The main parameters considered within this framework are age, renal function, nephrological complications, comorbidities (diabetes, hypertension, obesity, etc.), malignancies, and infection. Moreover, particular attention is paid to the sociopsychological aspects of the donation, particularly related to the donor, the recipient, and the entire family situation.

  12. Donor cell leukemia.

    PubMed

    Ruiz-Arguelles, Alejandro

    2012-04-01

    Minimal residual disease refers to the tumour cells that are still present in a given patient after completion of a therapeutic scheme. The demonstration and quantification of residual neoplastic cells has a crucial impact in clinical decision making, for it might prompt continuation of treatment, while the absence of such cells might serve as evidence to withdraw therapy. Therefore, both sensitivity and specificity of the methods used to unravel residual neoplastic cells must be highly reliable and robust. Flow cytometry has been widely used for this purpose, and its clinical performance depends mainly on the criteria of interpretation, rather than in the technique by itself; molecular biology techniques have proved to be highly sensitive and specific but unfortunately they cannot be used in all patients or in all types of leukemia. Finally, the development of donor cell leukemia in transplanted patients, might mimic residual disease and add more confusion to an already controversial issue. These topics are discussed in this paper.

  13. Mapping Polymer Donors toward High-Efficiency Fullerene Free Organic Solar Cells.

    PubMed

    Lin, Yuze; Zhao, Fuwen; Wu, Yang; Chen, Kai; Xia, Yuxin; Li, Guangwu; Prasad, Shyamal K K; Zhu, Jingshuai; Huo, Lijun; Bin, Haijun; Zhang, Zhi-Guo; Guo, Xia; Zhang, Maojie; Sun, Yanming; Gao, Feng; Wei, Zhixiang; Ma, Wei; Wang, Chunru; Hodgkiss, Justin; Bo, Zhishan; Inganäs, Olle; Li, Yongfang; Zhan, Xiaowei

    2017-01-01

    Five polymer donors with distinct chemical structures and different electronic properties are surveyed in a planar and narrow-bandgap fused-ring electron acceptor (IDIC)-based organic solar cells, which exhibit power conversion efficiencies of up to 11%.

  14. Urinary biomarkers after donor nephrectomy.

    PubMed

    Hoogendijk-van den Akker, Judith M; Warlé, Michiel C; van Zuilen, Arjan D; Kloke, Heinrich J; Wever, Kim E; d'Ancona, Frank C H; Ӧzdemir, Denise M D; Wetzels, Jack F M; Hoitsma, Andries J

    2015-05-01

    As the beginning of living-donor kidney transplantation, physicians have expressed concern about the possibility that unilateral nephrectomy can be harmful to a healthy individual. To investigate whether the elevated intra-abdominal pressure (IAP) during laparoscopic donor nephrectomy causes early damage to the remaining kidney, we evaluated urine biomarkers after laparoscopic donor nephrectomy. We measured albumin and alpha-1-microglobulin (α-1-MGB) in urine samples collected during and after open and laparoscopic donor nephrectomy and laparoscopic cholecystectomy and colectomy. Additionally, kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) were measured in urine samples collected during and after laparoscopic donor nephrectomy and colectomy. The same biomarkers were studied in patients randomly assigned to standard or low IAP during laparoscopic donor nephrectomy. We observed a peak in urinary albumin excretion during all procedures. Urine α-1-MGB rose in the postoperative period with a peak on the third postoperative day after donor nephrectomy. Urine α-1-MGB did not increase after laparoscopic cholecystectomy and colectomy. After laparoscopic nephrectomy, we observed slight increases in urine KIM-1 during surgery and in urine NGAL at day 2-3 after the procedure. After laparoscopic colectomy, both KIM-1 and NGAL were increased in the postoperative period. There were no differences between the high- and low-pressure procedure. Elevated urinary α-1-MGB suggests kidney damage after donor nephrectomy, occurring irrespective of IAP during the laparoscopic procedure.

  15. Reevaluating the dead donor rule.

    PubMed

    Collins, Mike

    2010-04-01

    The dead donor rule justifies current practice in organ procurement for transplantation and states that organ donors must be dead prior to donation. The majority of organ donors are diagnosed as having suffered brain death and hence are declared dead by neurological criteria. However, a significant amount of unrest in both the philosophical and the medical literature has surfaced since this practice began forty years ago. I argue that, first, declaring death by neurological criteria is both unreliable and unjustified but further, the ethical principles which themselves justify the dead donor rule are better served by abandoning that rule and instead allowing individuals who have suffered severe and irreversible brain damage to become organ donors, even though they are not yet dead and even though the removal of their organs would be the proximal cause of death.

  16. Dynamics of homology searching during gene conversion in Saccharomyces cerevisiae revealed by donor competition.

    PubMed

    Coïc, Eric; Martin, Joshua; Ryu, Taehyun; Tay, Sue Yen; Kondev, Jané; Haber, James E

    2011-12-01

    One of the least understood aspects of homologous recombination is the process by which the ends of a double-strand break (DSB) search the entire genome for homologous templates that can be used to repair the break. We took advantage of the natural competition between the alternative donors HML and HMR employed during HO endonuclease-induced switching of the budding yeast MAT locus. The strong mating-type-dependent bias in the choice of the donors is enforced by the recombination enhancer (RE), which lies 17 kb proximal to HML. We investigated factors that improve the use of the disfavored donor. We show that the normal heterochromatic state of the donors does not impair donor usage, as donor choice is not affected by removing this epigenetic silencing. In contrast, increasing the length of homology shared by the disfavored donor increases its use. This result shows that donor choice is not irrevocable and implies that there are several encounters between the DSB ends and even the favored donor before recombination is accomplished. The increase by adding more homology is not linear; these results can be explained by a thermodynamic model that determines the energy cost of using one donor over the other. An important inference from this analysis is that when HML is favored as the donor, RE causes a reduction in its effective genomic distance from MAT from 200 kb to ∼20 kb, which we hypothesize occurs after the DSB is created, by epigenetic chromatin modifications around MAT.

  17. Transport Measurements on Si Nanostructures with Counted Sb Donors

    NASA Astrophysics Data System (ADS)

    Singh, Meenakshi; Bielejec, Edward; Garratt, Elias; Ten Eyck, Gregory; Bishop, Nathaniel; Wendt, Joel; Luhman, Dwight; Carroll, Malcolm; Lilly, Michael

    2014-03-01

    Donor based spin qubits are a promising platform for quantum computing. Single qubits using timed implant of donors have been demonstrated.1 Extending this to multiple qubits requires precise control over the placement and number of donors. Such control can be achieved by using a combination of low-energy heavy-ion implants (to reduce depth straggle), electron-beam lithography (to define position), focused ion beam (to localize implants to one lithographic site) and counting the number of implants with a single ion detector.2 We report transport measurements on MOS quantum dots implanted with 5, 10 and 20 Sb donors using the approach described above. A donor charge transition is identified by a charge offset in the transport characteristics. Correlation between the number of donors and the charge offsets is studied. These results are necessary first steps towards fabricating donor nanostructures for two qubit interactions. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. The work was supported by Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000. 1J. J. Pla et al., Nature 496, 334 (2013) 2J. A. Seamons et al., APL 93, 043124 (2008).

  18. Hepatitis B surface antigen in blood donors: further observations.

    PubMed

    Szmuness, W; Hirsch, R L; Prince, A M; Levine, R W; Harley, E J; Ikram, H

    1975-02-01

    A survey of 128,000 volunteer blood donors from the Greater New York metropolitan area revealed that first-time male donors were positive for hepatitis B surface antigen (HBsAg) 2.5 times more frequently than were first-time female donors; Negroes and Mongols were positive four to 20 times more frequently than Caucasians. The ratio of ad to ay seemed to be higher in non-Caucasian antigen carriers than in Caucasian carriers. Among both Caucasians and non-Caucasians the rate of positivity declined after the age of 50. An excess prevalence of HBsAg was observed in donors with the lowest level of education and in those with the highest level. HBsAg was detectable nine times less frequently among repeat donors than among first-time donors (0.2 vs.1.90 per 1,000). Detection of HBsAg was unrelated to ABO-Rh blood groups. Several mechanisms for these wide variations of antigen detection are possible.

  19. Living kidney donors and ESRD.

    PubMed

    Ross, Lainie Friedman

    2015-07-01

    There are more than 325 living kidney donors who have developed end-stage renal disease and have been listed on the Organ Procurement and Transplantation Network (OPTN)/United Network for Organ Sharing (UNOS) deceased donor kidney wait list. The OPTN/UNOS database records where these kidney donors are listed and, if they donated after April 1994, where that donation occurred. These 2 locations are often not the same. In this commentary, I examine whether a national living donor registry should be created and whether transplantation centers should be notified when one of their living kidney donors develops end-stage renal disease. I consider and refute 5 potential objections to center notification. I explain that transplantation centers should look back at these cases and input data into a registry to attempt to identify patterns that could improve donor evaluation protocols. Creating a registry and mining the information it contains is, in my view, our moral and professional responsibility to future patients and the transplantation endeavor. As individuals and as a community, we need to acknowledge the many unknown risks of living kidney donation and take responsibility for identifying these risks. We then must share information about these risks, educate prospective donors about them, and attempt to minimize them.

  20. AdS duals of matrix strings

    NASA Astrophysics Data System (ADS)

    Morales, Jose F.; Samtleben, Henning

    2003-06-01

    We review recent work on the holographic duals of type II and heterotic matrix string theories described by warped AdS3 supergravities. In particular, we compute the spectra of Kaluza-Klein primaries for type I, II supergravities on warped AdS3 × S7 and match them with the primary operators in the dual two-dimensional gauge theories. The presence of non-trivial warp factors and dilaton profiles requires a modification of the familiar dictionary between masses and 'scaling' dimensions of fields and operators. We present these modifications for the general case of domain wall/QFT correspondences between supergravities on warped AdSd+1 × Sq geometries and super Yang-Mills theories with 16 supercharges.

  1. Electron Acceptor-Electron Donor Interactions. XV and XVI.

    DTIC Science & Technology

    mixtures exhibit simple eutectic phase diagrams and the thermochromic effect is interpreted as a randomized structure in the liquid , whereas the solid is a...two-phase aggregate of isolated acceptor and onor crystals . The charge-transfer spectra of solutions of tungsten and molybdenum hexafluorides and iodine heptafluoride in n-hexane and cyclohexane were obtained.

  2. Mechnical tuning of ionized donors in silicon

    NASA Astrophysics Data System (ADS)

    Franke, David P.; Hrubesch, Florian M.; Kuenzl, Markus; Itoh, Kohei M.; Hoehne, Felix; Dreher, Lukas; Brandt, Martin S.

    2015-03-01

    Ionized donors in silicon have been shown to have extraordinarily long coherence times, exceeding tens of minutes even at room temperature, which, combined with the very advanced state of silicon technology, makes them attractive candidates for the realization of solid state qubits. The corresponding near perfect isolation from their environment, however, renders the individual addressing and coupling of such qubits a major challenge on the way towards a spin quantum computer based on ionized donors. We show that the application of strain to the silicon host crystal leads to shifts of the nuclear spin resonance frequencies of 75As+ due to the nuclear quadrupole interaction with crystal fields. This shift can be larger than the resonance linewidth already for modest strains, as we demonstrate by electrically detected electron nuclear double resonance (ED ENDOR) measurements on arsenic donors in strained silicon. We discuss how quadrupole interactions could allow for the individual addressing of ionized nuclear spins by mechanical tuning of their resonance frequency and, possibly, permit the elastic coupling of nuclear spin qubits to a mechanical resonator.

  3. How to Motivate Whole Blood Donors to Become Plasma Donors

    PubMed Central

    2014-01-01

    This study tested the efficacy of interventions to recruit new plasma donors among whole blood donors. A sample of 924 donors was randomized to one of three conditions: control; information only by nurse; and information plus self-positive image message by nurse (SPI). Participants in the control condition only received a leaflet describing the plasma donation procedure. In the two experimental conditions the leaflet was explained face-to-face by a nurse. The dependent variables were the proportion of new plasma donors and the number of donations at six months. Overall, 141 (15.3%) new plasma donors were recruited at six months. There were higher proportions of new plasma donors in the two experimental conditions compared to the control condition (P < .001); the two experimental conditions did not differ. Also, compared to the control condition, those in the experimental conditions (all Ps < .001) gave plasma more often (information only by nurse:  d = .26; SPI: d = .32); the SPI intervention significantly outperformed (P < .05) the information only by nurse condition. The results suggest that references to feelings of SPI such as feeling good and being proud and that giving plasma is a rewarding personal experience favor a higher frequency of plasma donation. PMID:25530909

  4. How to motivate whole blood donors to become plasma donors.

    PubMed

    Godin, Gaston; Germain, Marc

    2014-01-01

    This study tested the efficacy of interventions to recruit new plasma donors among whole blood donors. A sample of 924 donors was randomized to one of three conditions: control; information only by nurse; and information plus self-positive image message by nurse (SPI). Participants in the control condition only received a leaflet describing the plasma donation procedure. In the two experimental conditions the leaflet was explained face-to-face by a nurse. The dependent variables were the proportion of new plasma donors and the number of donations at six months. Overall, 141 (15.3%) new plasma donors were recruited at six months. There were higher proportions of new plasma donors in the two experimental conditions compared to the control condition (P < .001); the two experimental conditions did not differ. Also, compared to the control condition, those in the experimental conditions (all Ps < .001) gave plasma more often (information only by nurse:  d = .26; SPI: d = .32); the SPI intervention significantly outperformed (P < .05) the information only by nurse condition. The results suggest that references to feelings of SPI such as feeling good and being proud and that giving plasma is a rewarding personal experience favor a higher frequency of plasma donation.

  5. Haemostatic effects of adrenaline-lidocaine subcutaneous infiltration at donor sites.

    PubMed

    Gacto, P; Miralles, F; Pereyra, J J; Perez, A; Martínez, E

    2009-05-01

    This study sought methods in burn surgery to reduce postoperative pain and blood loss at donor sites. A prospective, randomised, controlled, blinded trial included 56 people undergoing burn surgery, divided into two groups. Both groups received subcutaneous infiltration at donor sites, with either 1:500,000 adrenaline solution containing added lidocaine or with 0.45% normal saline (controls). Outcome measurements included amount of intraoperative bleeding, need for electrocautery, days the hydrocolloid dressing remained on donor sites, percentage of re-epithelialised skin at donor sites 1 week after surgery and viability of skin grafts. Results indicated that subcutaneous adrenaline-lidocaine infiltration at donor sites reduced intraoperative bleeding, decreased postoperative pain, shortened the duration of surgery and general anaesthesia and accelerated re-epithelialisation at the donor site. The overall graft take in both groups was similar.

  6. Donors in Ge as qubits —Establishing physical attributes

    NASA Astrophysics Data System (ADS)

    Baena, A.; Saraiva, A. L.; Menezes, Marcos G.; Koiller, Belita

    2016-10-01

    Quantum electronic devices at the single-impurity level demand the understanding of the physical attributes of dopants with an unprecedented accuracy. Germanium-based technologies have been developed recently, creating the necessity to adapt the latest theoretical tools to the unique electronic structure of this material. We investigate basic properties of donors in Ge which are not known experimentally, but are indispensable for qubit implementations. Our approach provides a description of the wave function at multiscale, associating microscopic information from density functional theory and envelope functions from state-of-the-art multivalley effective mass calculations, including a central-cell correction designed to reproduce the energetics of all group-V donor species (P, As, Sb and Bi). With this formalism, we predict the binding energies of negatively ionized donors (D- state). Furthermore, we investigate the signatures of buried donors to be expected from scanning tunneling microscopy (STM). The naive assumption that attributes of donor electrons in other semiconductors may be extrapolated to Ge is shown to fail, similarly to earlier attempts to recreate in Si qubits designed for GaAs. Our results suggest that the mature techniques available for qubit realizations may be adapted to germanium to some extent, but the peculiarities of the Ge band structure will demand new ideas for fabrication and control.

  7. Singlet-triplet donor-quantum-dot qubit in silicon

    NASA Astrophysics Data System (ADS)

    Harvey-Collard, Patrick; Ten Eyck, Gregory A.; Wendt, Joel R.; Pluym, Tammy; Lilly, Michael P.; Carroll, Malcolm S.; Pioro-Ladrière, Michel

    2015-03-01

    Electron spins bound to phosphorus (P) donors in silicon (Si) are promising qubits due to their high fidelities, but donor-donor coupling is challenging. We propose an alternative two-electron singlet-triplet quantum-dot (QD) and donor (D) hybrid qubit. A QD is formed at a MOS 28-Si interface and is tunnel-coupled to implanted P. The proposed two-axis system is defined by the exchange and contact hyperfine interactions. We demonstrate that a few electron QD can be formed and tuned to interact with a donor. We investigate the spin filling of the QD-D system through charge-sensed (CS) magnetospectroscopy and identify spin-up loading consistent with a singlet-triplet splitting of ~100 μeV near a QD-D anti-crossing. We also demonstrate an enhanced CS readout contrast and time window due to the restricted relaxation path of the D through the QD. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  8. Donor selection in heart transplantation

    PubMed Central

    Emani, Sitaramesh; Sai-Sudhakar, Chittoor B.; Higgins, Robert S. D.; Whitson, Bryan A.

    2014-01-01

    There is increased scrutiny on the quality in health care with particular emphasis on institutional heart transplant survival outcomes. An important aspect of successful transplantation is appropriate donor selection. We review the current guidelines as well as areas of controversy in the selection of appropriate hearts as donor organs to ensure optimal outcomes. This decision is paramount to the success of a transplant program as well as recipient survival and graft function post-transplant. PMID:25132976

  9. An AdS Crunch in Supergravity

    NASA Astrophysics Data System (ADS)

    Hertog, Thomas

    2004-12-01

    We review some properties of N=8 gauged supergravity in four dimensions with modified, but AdS invariant boundary conditions on the m2 = -2 scalars. There is a one-parameter class of asymptotic conditions on these fields and the metric components, for which the full AdS symmetry group is preserved. The generators of the asymptotic symmetries are finite, but acquire a contribution from the scalar fields. For a large class of such boundary conditions, we find there exist black holes with scalar hair that are specified by a single conserved charge. Since Schwarschild-AdS is a solution too for all boundary conditions, this provides an example of black hole non-uniqueness. We also show there exist solutions where smooth initial data evolve to a big crunch singularity. This opens up the possibility of using the dual conformal field theory to obtain a fully quantum description of the cosmological singularity, and we report on a preliminary study of this.

  10. Quadrupolar effects on nuclear spins of neutral arsenic donors in silicon

    NASA Astrophysics Data System (ADS)

    Franke, David P.; Pflüger, Moritz P. D.; Mortemousque, Pierre-André; Itoh, Kohei M.; Brandt, Martin S.

    2016-04-01

    We present electrically detected electron nuclear double resonance measurements of the nuclear spins of ionized and neutral arsenic donors in strained silicon. In addition to a reduction of the hyperfine coupling, we find significant quadrupole interactions of the nuclear spin of the neutral donors of the order of 10 kHz. By comparing these to the quadrupole shifts due to crystal fields measured for the ionized donors, we identify the effect of the additional electron on the electric field gradient at the nucleus. This extra component is expected to be caused by the coupling to electric field gradients created due to changes in the electron wave function under strain.

  11. Effect of laser irradiation of donor blood on erythrocyte shape.

    PubMed

    Baibekov, I M; Ibragimov, A F; Baibekov, A I

    2012-04-01

    Changes in erythrocyte shape in donor blood during storage and after irradiation with He-Ne laser and infrared laser were studied by scanning electron microscopy, thick drop express-method, and morphometry. It was found that laser irradiation delayed the appearance of erythrocytes of pathological shapes (echinocytes, stomatocytes, etc.) in the blood; He-Ne laser produced a more pronounced effect.

  12. Design and synthesis of molecular donors for solution-processed high-efficiency organic solar cells.

    PubMed

    Coughlin, Jessica E; Henson, Zachary B; Welch, Gregory C; Bazan, Guillermo C

    2014-01-21

    efficient molecular donors that achieve power conversion efficiencies greater than 7%. The molecules are based on a modular D(1)-A-D(2)-A-D(1) architecture, where A is an asymmetric electron deficient heterocycle, which allowed us to quickly access a library of compounds and develop structure-property-performance relationships. Modifications to the D1 and D2 units enable spectral coverage throughout the entire visible region and control of HOMO energy levels, while adjustments to the pendant alkyl substituents dictate molecular solubility, thermal transition temperatures, and solid-state organizational tendencies. Additionally, we discuss regiochemical considerations that highlight how individual atom placements can significantly influence molecular and subsequently device characteristics. Our results demonstrate the utility of this architecture for generating promising materials to be integrated into organic photovoltaic devices, call attention to areas for improvement, and provide guiding principles to sustain the steady increases necessary to move this technology forward.

  13. Cadaveric donor selection and management.

    PubMed

    Studer, Sean M; Orens, Jonathan B

    2004-12-01

    The current availability of lung donors is far exceeded by the number of potential transplant recipients who are waiting for an organ. This disparity results in significant morbidity and mortality for those on the waiting list. Although it is desirable to increase overall consent rates for organ donation, doing so requires an intervention to affect societal response. In contrast, increased procurement of organs from marginal donors and improved donor management may be realized through increased study and practice changes within the transplant community. Transplantation of organs from marginal or extended-criteria donors may result in some increase in complications or mortality, but this possibility must be weighed against the morbidity and risk of death risk faced by individuals on the waiting list. The effects of this trade-off are currently being studied in kidney transplantation, and perhaps in the near future lung transplantation may benefit from a similar analysis. Until that time, the limited data regarding criteria for donor acceptability must be incorporated into practice to maximize the overall benefits of lung transplantation.

  14. Dengue antibodies in blood donors

    PubMed Central

    Ribas-Silva, Rejane Cristina; Eid, Andressa Ahmad

    2012-01-01

    Background Dengue is an urban arbovirus whose etiologic agent is a virus of the genus Flavorius with four distinct antigen serotypes (DENV-1, DENV-2, DENV-3 and DENV-4) that is transmitted to humans through the bite of the mosquito Aedes aegypti. The Campo Mourão region in Brazil is endemic for dengue fever. Obtective The aim of this study was to evaluate the presence of IgG and IgM antibodies specific to the four serotypes of dengue in donors of the blood donor service in the city of Campo Mourão. Methods Epidemiological records were evaluated and 4 mL of peripheral blood from 213 blood donors were collected in tubes without anticoagulant. Serum was then obtained and immunochromatographic tests were undertaken (Imuno-Rápido Dengue IgM/IgGTM). Individuals involved in the study answered a social and epidemiological questionnaire on data which included age, gender and diagnosis of dengue. Results Only three (1.4%) of the 213 blood tests were positive for IgG anti-dengue antibodies. No donors with IgM antibody, which identifies acute infection, were identified. Conclusions The results of the current analysis show that the introduction of quantitative or molecular serological methods to determine the presence of anti-dengue antibodies or the detection of the dengue virus in blood donors in endemic regions should be established so that the quality of blood transfusions is guaranteed. PMID:23049418

  15. Alcohols as hydrogen-donor solvents for treatment of coal

    DOEpatents

    Ross, David S.; Blessing, James E.

    1981-01-01

    A method for the hydroconversion of coal by solvent treatment at elevated temperatures and pressure wherein an alcohol having an .alpha.-hydrogen atom, particularly a secondary alcohol such as isopropanol, is utilized as a hydrogen donor solvent. In a particular embodiment, a base capable of providing a catalytically effective amount of the corresponding alcoholate anion under the solvent treatment conditions is added to catalyze the alcohol-coal reaction.

  16. Interplay between interstitial and substitutional hydrogen donors in ZnO

    NASA Astrophysics Data System (ADS)

    Koch, S. Â. G.; Lavrov, E. Â. V.; Weber, J.

    2014-06-01

    A Raman study on hydrogen donors in ZnO reveals the properties of bond-centered hydrogen (HBC) and hydrogen trapped in the oxygen vacancy (HO). The donors are identified by their electronic 1s→2s(2p) transitions and their characteristic local vibrational modes. The HO donor was detected preferentially below the sample surface, where a high oxygen vacancy concentration is generated by thermal treatment of the samples. HBC and HO exhibit different thermal stabilities and their concentrations depend strongly on the sample history. Molecular hydrogen is an essential part of the interplay of the two hydrogen donors.

  17. Optical hyperpolarization of nitrogen donor spins in bulk diamond

    NASA Astrophysics Data System (ADS)

    Loretz, M.; Takahashi, H.; Segawa, T. F.; Boss, J. M.; Degen, C. L.

    2017-02-01

    We report hyperpolarization of the electronic spins associated with substitutional nitrogen defects in bulk diamond crystals. Hyperpolarization is achieved by optical pumping of nitrogen vacancy centers followed by rapid cross relaxation at the energy level matching condition in a 51 mT bias field. The maximum observed donor spin polarization is 0.9 % , corresponding to an enhancement of 25 compared to the thermal Boltzmann polarization. A further accumulation of polarization is impeded by an anomalous optical saturation effect that we attribute to charge state conversion processes. Hyperpolarized nitrogen donors may form a useful resource for increasing the efficiency of diamond-based dynamic nuclear polarization devices.

  18. The use of neoplastic donors to increase the donor pool.

    PubMed

    Fiaschetti, P; Pretagostini, R; Stabile, D; Peritore, D; Oliveti, A; Gabbrielli, F; Cenci, S; Ricci, A; Vespasiano, F; Grigioni, W F

    2012-09-01

    The aim of the study was to evaluate the experience of the Centre-Sud Transplant Organization (OCST) area using cadaveric donor with neoplastic diseases to evaluate the possibility of transmission to recipients. From January 1, 2003, to December 31, 2010, the neoplastic risk has been reported to be 5.4% (377/4654 referred donors). In 2003, the number of donors with a tumor and their mean age were respectively: 60 (10.3%) and 59.6 ± 19.9; 2004: 33 (5.2%) and 61.4 ± 15.9; 2005: 32 (6%) and 62.8 ± 15.5; 2006: 46 (7%) and 60.7 ± 19.1; 2007: 51 (7%) and 58.9 ± 16; in 2008: 58 (7%) and 59.7 ± 19.6; 2009: 47 (7%) and 57 ± 26; 2010: 49 (7%) and 64 ± 16. The organ most affected by tumor has been the central nervous system (18%). The tumor was diagnosed before in 325 (86%) cases, versus during organ retrieval in 48 (12.7%) donor operations but before, which four cases (1%) occured after transplantation. According to the histological types and grades, 28 evaluated donors (8.2%) were suitable for transplantation. The histological types were: thyroid carcinoma (n = 3); prostate carcinoma (n = 8), renal clear cell carcinoma (n = 7), oncocytoma (n = 1), meningiomas (n = 2), dermofibrosarcoma (n = 1); verrucous carcinoma of the vulva (n = 1), colon adenocarcinoma (n = 1), grade II astrocytoma (n = 1), adrenal gland tumor (n = 1), gastric GIST (n = 1), oligodendroglioma (n = 1). Forty-five organs were retrieved (22 livers, 19 kidneys, 3 hearts, and 1 pancreas) and transplanted into 44 recipients with 1 liver-kidney combined transplantation. Four recipients died due to causes not related to the tumor. No donor-transmitted tumor was detected among the recipients. Donation is absolutely not indicated in cases of tumors with high metastatic potential and high grades. Performing an accurate evaluation of the donor, taking into account the histological grade, currently can allow, organ retrieval and transplantation with an acceptable risk.

  19. Statistical exchange-coupling errors and the practicality of scalable silicon donor qubits

    NASA Astrophysics Data System (ADS)

    Song, Yang; Das Sarma, S.

    2016-12-01

    Recent experimental efforts have led to considerable interest in donor-based localized electron spins in Si as viable qubits for a scalable silicon quantum computer. With the use of isotopically purified 28Si and the realization of extremely long spin coherence time in single-donor electrons, the recent experimental focus is on two-coupled donors with the eventual goal of a scaled-up quantum circuit. Motivated by this development, we simulate the statistical distribution of the exchange coupling J between a pair of donors under realistic donor placement straggles, and quantify the errors relative to the intended J value. With J values in a broad range of donor-pair separation ( 5 <|R |<60 nm), we work out various cases systematically, for a target donor separation R0 along the [001], [110] and [111] Si crystallographic directions, with |R0|=10 ,20 or 30 nm and standard deviation σR=1 ,2 ,5 or 10 nm. Our extensive theoretical results demonstrate the great challenge for a prescribed J gate even with just a donor pair, a first step for any scalable Si-donor-based quantum computer.

  20. A Theoretical and Synthetic Investigation of New Donors for Organic Electro-Optic Chromophores: Understanding the Effects of Structure and Substituents on Donor Strength

    NASA Astrophysics Data System (ADS)

    Phillips-Sylvain, Nathaniel

    Understanding of the intricate connection between shape, structure and property has al- lowed many challenges facing the adoption of organic chromophores for electro-optic (EO) applications to be overcome. Still, there is much to be learned about designing donors that localize electron density in the ground state, but not in the electronically polarized state to allow for enhanced charge transfer, and thus, large first-order molecular hyperpolarizability (beta). To address this, density functional theory has been used to evaluate a large number of potential donors based on alkyl, aryl, saturated and unsaturated heterocycles. These were coupled to the tricyanopyrroline (TCP) acceptor by a simple vinylic bridge to identify new high beta, high number density materials. Saturated heterocylces were found to off the largest improvements over traditional dialkyl donors, with the predicted systems rivaling much longer polyene-based chromophores with a trifluoromethyl, phenyl-tricyanofuran (CF 3PhTCF). Other potential candidates where based on diaryl amines donors which are a natural progression from previous heteroaryl chromophores. These systems were typified by a greater degree of localized electron density - by as much as 20% - at the donor and were found to exhibit characteristics that might described as a double-donor. Several novel chromophores based on these new donors were synthesized to verify the theoretical results and evaluate their potential for use in EO devices.

  1. AdS3: the NHEK generation

    NASA Astrophysics Data System (ADS)

    Bena, Iosif; Heurtier, Lucien; Puhm, Andrea

    2016-05-01

    It was argued in [1] that the five-dimensional near-horizon extremal Kerr (NHEK) geometry can be embedded in String Theory as the infrared region of an infinite family of non-supersymmetric geometries that have D1, D5, momentum and KK monopole charges. We show that there exists a method to embed these geometries into asymptotically- {AdS}_3× {S}^3/{{Z}}_N solutions, and hence to obtain infinite families of flows whose infrared is NHEK. This indicates that the CFT dual to the NHEK geometry is the IR fixed point of a Renormalization Group flow from a known local UV CFT and opens the door to its explicit construction.

  2. AdS2 holographic dictionary

    NASA Astrophysics Data System (ADS)

    Cvetič, Mirjam; Papadimitriou, Ioannis

    2016-12-01

    We construct the holographic dictionary for both running and constant dilaton solutions of the two dimensional Einstein-Maxwell-Dilaton theory that is obtained by a circle reduction from Einstein-Hilbert gravity with negative cosmological constant in three dimensions. This specific model ensures that the dual theory has a well defined ultraviolet completion in terms of a two dimensional conformal field theory, but our results apply qualitatively to a wider class of two dimensional dilaton gravity theories. For each type of solutions we perform holographic renormalization, compute the exact renormalized one-point functions in the presence of arbitrary sources, and derive the asymptotic symmetries and the corresponding conserved charges. In both cases we find that the scalar operator dual to the dilaton plays a crucial role in the description of the dynamics. Its source gives rise to a matter conformal anomaly for the running dilaton solutions, while its expectation value is the only non trivial observable for constant dilaton solutions. The role of this operator has been largely overlooked in the literature. We further show that the only non trivial conserved charges for running dilaton solutions are the mass and the electric charge, while for constant dilaton solutions only the electric charge is non zero. However, by uplifting the solutions to three dimensions we show that constant dilaton solutions can support non trivial extended symmetry algebras, including the one found by Compère, Song and Strominger [1], in agreement with the results of Castro and Song [2]. Finally, we demonstrate that any solution of this specific dilaton gravity model can be uplifted to a family of asymptotically AdS2 × S 2 or conformally AdS2 × S 2 solutions of the STU model in four dimensions, including non extremal black holes. The four dimensional solutions obtained by uplifting the running dilaton solutions coincide with the so called `subtracted geometries', while those obtained

  3. Single-Donor Leukophoretic Technique

    NASA Technical Reports Server (NTRS)

    Eberhardt, R. N.

    1977-01-01

    Leukocyte separation-and-retrieval device utilizes granulocyte and monocyte property of leukoadhesion to glass surfaces as basis of their separation from whole blood. Device is used with single donor technique and has application in biological and chemical processing, veterinary research and clinical care.

  4. Surface code architecture for donors and dots in silicon with imprecise and nonuniform qubit couplings

    NASA Astrophysics Data System (ADS)

    Pica, G.; Lovett, B. W.; Bhatt, R. N.; Schenkel, T.; Lyon, S. A.

    2016-01-01

    A scaled quantum computer with donor spins in silicon would benefit from a viable semiconductor framework and a strong inherent decoupling of the qubits from the noisy environment. Coupling neighboring spins via the natural exchange interaction according to current designs requires gate control structures with extremely small length scales. We present a silicon architecture where bismuth donors with long coherence times are coupled to electrons that can shuttle between adjacent quantum dots, thus relaxing the pitch requirements and allowing space between donors for classical control devices. An adiabatic SWAP operation within each donor/dot pair solves the scalability issues intrinsic to exchange-based two-qubit gates, as it does not rely on subnanometer precision in donor placement and is robust against noise in the control fields. We use this SWAP together with well established global microwave Rabi pulses and parallel electron shuttling to construct a surface code that needs minimal, feasible local control.

  5. ABAB Phthalocyanines: Scaffolds for Building Unprecedented Donor-π-Acceptor Chromophores.

    PubMed

    Fazio, Ettore; Jaramillo-García, Javier; Medel, María; Urbani, Maxence; Grätzel, Michael; Nazeerudin, Mohammad K; de la Torre, Gema; Torres, Tomas

    2017-02-01

    Unique donor-π-acceptor phthalocyanines have been synthesized through the asymmetric functionalization of an ABAB phthalocyanine, crosswise functionalized with two iodine atoms through Pd-catalyzed cross-coupling reactions with adequate electron-donor and electron-acceptor moieties. These push-pull molecules have been optically and electrochemically characterized, and their ability to perform as chromophores for dye-sensitized solar cells has been tested.

  6. Live donor transplantation--the incompetent donor: comparative law.

    PubMed

    Wolfman, Samuel; Shaked, Tali

    2008-12-01

    Informed consent of the patient to medical treatment is an essential prerequisite for any invasive medical procedure. However in emergency cases, when the patient is unable to sign a consent form due to unconsciousness or to psychotic state, than the primary medical consideration shall take place. In such a case, in order to save life or even prevent a major medical hazard to the patient, doctors are allowed, in certain cases and in accordance with well accepted medical practice, to perform invasive procedures, major surgery or risky pharmacological treatment, without the explicit consent of the patient. All the above refers to the cases when avoidance of such non-consented treatment may harm severely the health and wellbeing of the patient and there is no doubt that such treatment is for the ultimate benefit of the patient. The question, however, shall arise when such a medical procedure is not necessarily for the benefit of the patient, but rather for the benefit of somebody else. Such is the case in the transplantation area and the question of living donor-donee relationship. This paper shall analyze the legal situation in cases of non competent donors whose consent cannot be considered legal consent given in full understanding and out of free will. It will also compare three legal systems, the Israeli, the American and the traditional Jewish law, with regard to the different approaches to this human problem, where the autonomy of the donor may be sacrificed for the purpose of saving life of another person.

  7. Charge transport and exciton dissociation in organic solar cells consisting of dipolar donors mixed with C70

    NASA Astrophysics Data System (ADS)

    Griffith, Olga L.; Liu, Xiao; Amonoo, Jojo A.; Djurovich, Peter I.; Thompson, Mark E.; Green, Peter F.; Forrest, Stephen R.

    2015-08-01

    We investigate dipolar donor materials mixed with a C70 acceptor in an organic photovoltaic (OPV) cell. Dipolar donors that have donor-acceptor-acceptor (d-a-a') structure result in high conductivity pathways due to close coupling between neighboring molecules in the mixed films. We analyze the charge transfer properties of the dipolar donor:C70 mixtures and corresponding neat donors using a combination of time-resolved electroluminescence from intermolecular polaron pair states and conductive tip atomic force microscopy, from which we infer that dimers of the d-a-a' donors tend to form a continuous network of nanocrystalline clusters within the blends. Additional insights are provided by quantum-mechanical calculations of hole transfer coupling and hopping rates between donor molecules using nearest-neighbor donor packing motifs taken from crystal structural data. The approximation using only nearest-neighbor interactions leads to good agreement between donor hole hopping rates and the conductive properties of the donor:C70 blends. This represents a significant simplification from requiring details of the nano- and mesoscale morphologies of thin films to estimate their electronic characteristics. Using these dipolar donors, we obtain a maximum power conversion efficiency of 9.6 ±0.5 % under 1 sun, AM1.5G simulated illumination for an OPV comprised of an active layer containing a dipolar donor mixed with C70.

  8. Amphiphilic NO-donor antioxidants.

    PubMed

    Chegaev, Konstantin; Lazzarato, Loretta; Rolando, Barbara; Marini, Elisabetta; Lopez, Gloria V; Bertinaria, Massimo; Di Stilo, Antonella; Fruttero, Roberta; Gasco, Alberto

    2007-02-01

    Models of amphiphilic NO-donor antioxidants 24-26 were designed and synthesized. The products were obtained by linking a lipophilic tail (C(6), C(8), C(10)) with a polar head constituted by the 2,6-dimethoxyphenol antioxidant joined to the NO-donor 3-furoxancarboxamide substructure through a bridge containing a quaternary ammonium group. Compound 23, containing the shortest C(2)-alkyl chain, was also studied as a reference. The antioxidant properties (TBARS and LDL oxidation assays) and the vasodilator properties of the compounds were studied in vitro. The ability of these products to interact with phospholipid vesicles was also investigated by NMR techniques. The results indicate that both activities are modulated by the ability of the compounds to accumulate on phospholipid layers.

  9. 21 CFR 630.6 - Donor notification.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 7 2010-04-01 2010-04-01 false Donor notification. 630.6 Section 630.6 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) BIOLOGICS GENERAL REQUIREMENTS FOR BLOOD, BLOOD COMPONENTS, AND BLOOD DERIVATIVES § 630.6 Donor notification. (a) Notification of donors. You, an...

  10. A compact planar low-energy-gap molecule with a donor-acceptor-donor nature based on a bimetal dithiolene complex.

    PubMed

    Hayashi, Mikihiro; Otsubo, Kazuya; Kato, Tatsuhisa; Sugimoto, Kunihisa; Fujiwara, Akihiko; Kitagawa, Hiroshi

    2015-11-11

    We present the first report of a compact, planar and low-energy-gap molecule based on a π-conjugated bimetal system comprising a tetrathiooxalate (tto) skeleton. The observed low HOMO-LUMO energy gap (1.19 eV) is attributed to its donor-acceptor-donor (D-A-D) nature because the skeleton acts as an electron acceptor as well as a tiny and noninnocent bridging moiety.

  11. Electrical current through individual pairs of phosphorus donor atoms and silicon dangling bonds

    NASA Astrophysics Data System (ADS)

    Ambal, K.; Rahe, P.; Payne, A.; Slinkman, J.; Williams, C. C.; Boehme, C.

    2016-01-01

    Nuclear spins of phosphorus [P] donor atoms in crystalline silicon are among the most coherent qubits found in nature. For their utilization in scalable quantum computers, distinct donor electron wavefunctions must be controlled and probed through electrical coupling by application of either highly localized electric fields or spin-selective currents. Due to the strong modulation of the P-donor wavefunction by the silicon lattice, such electrical coupling requires atomic spatial accuracy. Here, the spatially controlled application of electrical current through individual pairs of phosphorus donor electron states in crystalline silicon and silicon dangling bond states at the crystalline silicon (100) surface is demonstrated using a high-resolution scanning probe microscope operated under ultra-high vacuum and at a temperature of 4.3K. The observed pairs of electron states display qualitatively reproducible current-voltage characteristics with a monotonous increase and intermediate current plateaus.

  12. Electrical current through individual pairs of phosphorus donor atoms and silicon dangling bonds

    PubMed Central

    Ambal, K.; Rahe, P.; Payne, A.; Slinkman, J.; Williams, C. C.; Boehme, C.

    2016-01-01

    Nuclear spins of phosphorus [P] donor atoms in crystalline silicon are among the most coherent qubits found in nature. For their utilization in scalable quantum computers, distinct donor electron wavefunctions must be controlled and probed through electrical coupling by application of either highly localized electric fields or spin-selective currents. Due to the strong modulation of the P-donor wavefunction by the silicon lattice, such electrical coupling requires atomic spatial accuracy. Here, the spatially controlled application of electrical current through individual pairs of phosphorus donor electron states in crystalline silicon and silicon dangling bond states at the crystalline silicon (100) surface is demonstrated using a high‐resolution scanning probe microscope operated under ultra‐high vacuum and at a temperature of 4.3K. The observed pairs of electron states display qualitatively reproducible current-voltage characteristics with a monotonous increase and intermediate current plateaus. PMID:26758087

  13. Designing shallow donors in diamond

    NASA Astrophysics Data System (ADS)

    Moussa, Jonathan

    2015-03-01

    The production of n-type semiconducting diamond has been a long-standing experimental challenge. The first-principles simulation of shallow dopants in semiconductors has been a long-standing theoretical challenge. A desirable theoretical goal is to identify impurities that will act as shallow donors in diamond and assess their experimental viability. I will discuss this identification process for the LiN4 donor complex. It builds a scientific argument from several models and computational results in the absence of computational tools that are both trustworthy and computationally tractable for this task. I will compare the theoretical assessment of viability with recent experimental efforts to co-dope diamond with lithium and nitrogen. Finally, I discuss the computational tools needed to facilitate future work on this problem and some preliminary simulations of donors near diamond surfaces. Sandia National Laboratories is a multi-program lab managed and operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  14. Enhanced Oxidative Bioremediation of cis-Dichloroethene (cis-DCE) and Vinyl Chloride (VC) using Electron Shuttles

    DTIC Science & Technology

    2010-02-01

    the production of reduced iron sulfides, sulfate reduction may utilize available substrate (electron donor) at the expense of biotic reductive...systems illustrated the usefulness of adding gypsum to the organic substrate (equivalent to the mulch in a biowall) to increase sulfide production and...Using the sulfate mass balance, and the duration of the test, a sulfide production rate for each proposed substrate would then be determined. In

  15. AD(H)D.

    PubMed

    Harrison, Christopher; Charles, Janice; Britt, Helena

    2008-06-01

    The BEACH program (Bettering the Evaluation and Care of Health) shows that management of attention deficit (hyperactivity) disorder (AD(H)D) was rare in general practice, occurring only six times per 1,000 encounters with children aged 5-17 years, between April 2000 and December 2007. This suggests that general practitioners manage AD(H)D about 46,000 times for this age group nationally each year.

  16. Artificial corneas versus donor corneas for repeat corneal transplants

    PubMed Central

    Akpek, Esen K; Alkharashi, Majed; Hwang, Frank S; Ng, Sueko M; Lindsley, Kristina

    2014-01-01

    Background Individuals who have failed one or more full thickness penetrating keratoplasties (PKs) may be offered repeat corneal surgery using an artificial or donor cornea. An artificial or prosthetic cornea is known as a keratoprosthesis. Both donor and artificial corneal transplantations involve removal of the diseased and opaque recipient cornea (or the previously failed cornea) and replacement with another donor or prosthetic cornea. Objectives To assess the effectiveness of artificial versus donor corneas in individuals who have had one or more failed donor corneal transplantations. Search methods We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2013, Issue 10), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2013), EMBASE (January 1980 to November 2013), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to November 2013), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 27 November 2013. Selection criteria Two review authors independently assessed reports from the electronic searches to identify randomized controlled trials (RCTs) or controlled clinical trials (CCTs). We resolved discrepancies by discussion or consultation with a third review author. Data collection and analysis For discussion purposes, we assessed findings from observational cohort studies and non-comparative case series. No data synthesis was performed. Main results We did not identify any RCTs or CCTs comparing artificial corneas with donor corneas for repeat corneal transplantations. Authors

  17. Organic electronic devices with multiple solution-processed layers

    DOEpatents

    Forrest, Stephen R.; Lassiter, Brian E.; Zimmerman, Jeramy D.

    2015-08-04

    A method of fabricating a tandem organic photosensitive device involves depositing a first layer of an organic electron donor type material film by solution-processing of the organic electron donor type material dissolved in a first solvent; depositing a first layer of an organic electron acceptor type material over the first layer of the organic electron donor type material film by a dry deposition process; depositing a conductive layer over the interim stack by a dry deposition process; depositing a second layer of the organic electron donor type material over the conductive layer by solution-processing of the organic electron donor type material dissolved in a second solvent, wherein the organic electron acceptor type material and the conductive layer are insoluble in the second solvent; depositing a second layer of an organic electron acceptor type material over the second layer of the organic electron donor type material film by a dry deposition process, resulting in a stack.

  18. Heteroaromatic donors in donor-acceptor-donor based fluorophores facilitate zinc ion sensing and cell imaging.

    PubMed

    Sreejith, Sivaramapanicker; Divya, Kizhumuri P; Jayamurthy, Purushothaman; Mathew, Jomon; Anupama, V N; Philips, Divya Susan; Anees, Palappuravan; Ajayaghosh, Ayyappanpillai

    2012-11-01

    The excited state intra molecular charge transfer (ICT) property of fluorophores has been extensively used for the design of fluorescent chemosensors. Herein, we report the synthesis and properties of three donor–π-acceptor–π-donor (D–π-A–π-D) based molecular probes BP, BT and BA. Two heteroaromatic rings, pyrrole (BP), and thiophene (BT) and a non-heteroaromatic ring N-alkoxy aniline (BA) were selected as donor moieties which were linked to a bipyridine binding site through a vinylic linkage. The heteroaromatic systems BP and BT perform selective and ratiometric emission signalling for zinc ions whereas the non-heteroaromatic probe BA does not. The advantages of the D–π-A–π-D design strategy in the design of ICT based probes for the selective fluorescent ratiometric signalling of zinc ions in biological media is discussed. Further, the use of BP, BT and BA for imaging Zn(2+) ions from MCF-7 cell lines is demonstrated.

  19. An organic donor/acceptor lateral superlattice at the nanoscale.

    PubMed

    Otero, Roberto; Ecija, David; Fernandez, Gustavo; Gallego, José María; Sanchez, Luis; Martín, Nazario; Miranda, Rodolfo

    2007-09-01

    A precise control of the nanometer-scale morphology in systems containing mixtures of donor/acceptor molecules is a key factor to improve the efficiency of organic photovoltaic devices. Here we report on a scanning tunneling microscopy study of the first stages of growth of 2-[9-(1,3-dithiol-2-ylidene)anthracen-10(9H)-ylidene]-1,3-dithiole, as electron donor, and phenyl-C61-butyric acid methyl ester, as electron acceptor, on a Au(111) substrate under ultrahigh vacuum conditions. Due to differences in bonding strength with the substrate and different interactions with the Au(111) herringbone surface reconstruction, mixed thin films spontaneously segregate into a lateral superlattice of interdigitated nanoscale stripes with a characteristic width of about 10-20 nm, a morphology that has been predicted to optimize the efficiency of organic solar cells.

  20. [Serum ferritin in donors with regular plateletpheresis].

    PubMed

    Ma, Chun-Hui; Guo, Ru-Hua; Wu, Wei-Jian; Yan, Jun-Xiong; Yu, Jin-Lin; Zhu, Ye-Hua; He, Qi-Tong; Luo, Yi-Hong; Huang, Lu; Ye, Rui-Yun

    2011-04-01

    This study was aimed to evaluate the impact of regular donating platelets on serum ferritin (SF) of donors. A total of 93 male blood donors including 24 initial plateletpheresis donors and 69 regular plateletpheresis donors were selected randomly. Their SF level was measured by ELISA. The results showed that the SF level of initial plateletpheresis donors and regular plateletpheresis donors were 91.08 ± 23.38 µg/L and 57.16 ± 35.48 µg/L respectively, and all were in normal levels, but there was significant difference between the 2 groups (p < 0.05). The SF level decreased when the donation frequency increased, there were no significant differences between the groups with different donation frequency. Correlation with lifetime donations of platelets was not found. It is concluded that regular plateletpheresis donors may have lower SF level.

  1. Simulation shows that HLA-matched stem cell donors can remain unidentified in donor searches

    PubMed Central

    Sauter, Jürgen; Solloch, Ute V.; Giani, Anette S.; Hofmann, Jan A.; Schmidt, Alexander H.

    2016-01-01

    The heterogeneous nature of HLA information in real-life stem cell donor registries may hamper unrelated donor searches. It is even possible that fully HLA-matched donors with incomplete HLA information are not identified. In our simulation study, we estimated the probability of these unnecessarily failed donor searches. For that purpose, we carried out donor searches in several virtual donor registries. The registries differed by size, composition with respect to HLA typing levels, and genetic diversity. When up to three virtual HLA typing requests were allowed within donor searches, the share of unnecessarily failed donor searches ranged from 1.19% to 4.13%, thus indicating that non-identification of completely HLA-matched stem cell donors is a problem of practical relevance. The following donor registry characteristics were positively correlated with the share of unnecessarily failed donor searches: large registry size, high genetic diversity, and, most strongly correlated, large fraction of registered donors with incomplete HLA typing. Increasing the number of virtual HLA typing requests within donor searches up to ten had a smaller effect. It follows that the problem of donor non-identification can be substantially reduced by complete high-resolution HLA typing of potential donors. PMID:26876789

  2. Effects of Cu deficiency on photosynthetic electron transport

    SciTech Connect

    Droppa, M.; Terry, N.; Horvath, G.

    1984-04-01

    The role of copper (Cu) in photosynthetic electron transport was explored by using Cu deficiency in sugar beet as an experimental approach. Copper influenced electron transport at two sites in addition to plastocyanin. Under mild deficiency (0.84 nmol of Cu per cm/sup 2/ of leaf area), electron transport between the two photosystems (PS) is inhibited but not electron transport within PS I or PS II measured separately. The chlorophyll/plastoquinone ratio was normal in Cu-deficient plants. However, the breakpoint in the Arrhenius plot of electron transport was shifted towards a higher temperature. It is concluded that Cu is necessary to maintain the appropriate membrane fluidity to ensure the mobility of plastoquinone molecules to transfer electrons between the two photosystems. Under severe deficiency (0.22 nmol of Cu per cm/sup 2/ of leaf area) both PS II and PS I electron transports were inhibited and to the same extent. PS II electron transport activity could not be restored by adding artifical electron donors. Polypeptides with M/sub r/s of 28,000 and 13,500 were missing in Cu-deficient chloroplast membranes. In PS II particles prepared from normal chloroplasts of spinach, 2 atoms of Cu per reaction center are present. We conclude that Cu influences PS II electron transport either directly, by participation in electron transfer as a constituent of an electron carrier, or indirectly, via the polypeptide composition of the membrane in the PS II complex.

  3. Design directed self-assembly of donor-acceptor polymers.

    PubMed

    Marszalek, Tomasz; Li, Mengmeng; Pisula, Wojciech

    2016-09-21

    Donor-acceptor polymers with an alternating array of donor and acceptor moieties have gained particular attention during recent years as active components of organic electronics. By implementation of suitable subunits within the conjugated backbone, these polymers can be made either electron-deficient or -rich. Additionally, their band gap and light absorption can be precisely tuned for improved light-harvesting in solar cells. On the other hand, the polymer design can also be modified to encode the desired supramolecular self-assembly in the solid-state that is essential for an unhindered transport of charge carriers. This review focuses on three major factors playing a role in the assembly of donor-acceptor polymers on surfaces which are (1) nature, geometry and substitution position of solubilizing alkyl side chains, (2) shape of the conjugated polymer defined by the backbone curvature, and (3) molecular weight which determines the conjugation length of the polymer. These factors adjust the fine balance between attractive and repulsive forces and ensure a close polymer packing important for an efficient charge hopping between neighboring chains. On the microscopic scale, an appropriate domain formation with a low density of structural defects in the solution deposited thin film is crucial for the charge transport. The charge carrier transport through such thin films is characterized by field-effect transistors as basic electronic elements.

  4. Donor free radical explosive composition

    DOEpatents

    Walker, Franklin E. [15 Way Points Rd., Danville, CA 94526; Wasley, Richard J. [4290 Colgate Way, Livermore, CA 94550

    1980-04-01

    An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1500 and 10,000 meters per second and a minor amount of a donor additive comprising an organic compound or mixture of organic compounds capable of releasing low molecular weight free radicals or ions under mechanical or electrical shock conditions and which is not an explosive, or an inorganic compound or mixture of inorganic compounds capable of releasing low molecular weight free radicals or ions under mechanical or electrical shock conditions and selected from ammonium or alkali metal persulfates.

  5. Adding and Deleting Images

    EPA Pesticide Factsheets

    Images are added via the Drupal WebCMS Editor. Once an image is uploaded onto a page, it is available via the Library and your files. You can edit the metadata, delete the image permanently, and/or replace images on the Files tab.

  6. What Value "Value Added"?

    ERIC Educational Resources Information Center

    Richards, Andrew

    2015-01-01

    Two quantitative measures of school performance are currently used, the average points score (APS) at Key Stage 2 and value-added (VA), which measures the rate of academic improvement between Key Stage 1 and 2. These figures are used by parents and the Office for Standards in Education to make judgements and comparisons. However, simple…

  7. Laparoscopic donor nephrectomy versus open donor nephrectomy: recipient's perspective.

    PubMed

    Jamale, Tukaram E; Hase, Niwrutti K; Iqbal, Anwar M

    2012-11-01

    Effects of laparoscopic donor nephrectomy (LDN) on graft function, especially early post-transplant, have been controversial. To assess and compare early and late graft function in kidneys procured by open and laparoscopic methods, a retrospective observational study was carried out on 37 recipients-donors who underwent LDN after introduction of this technique in February 2007 at our center, a tertiary care nephrology referral center. Demographic, immunological and intraoperative variables as well as immunosuppressive protocols and number of human leukocyte antigen (HLA) mismatches were noted. Early graft function was assessed by serum creatinine on Days two, five, seven, 14 and 28 and at the time of discharge. Serum creatinine values at three months and at one year post-transplant were considered as the surrogates of late graft function. Data obtained were compared with the data from 33 randomly selected kidney transplants performed after January 2000 by the same surgical team, in whom open donor nephrectomy was used. Pearson's chi square test, Student's t test and Mann-Whitney U test were used for statistical analysis. Early graft function (serum creatinine on Day five 2.15 mg/dL vs 1.49 mg/dL, P = 0.027) was poorer in the LDN group. Late graft function as assessed by serum creatinine at three months (1.45 mg/dL vs 1.31 mg/dL, P = 0.335) and one year (1.56 mg/dL vs 1.34 mg/dL, P = 0.275) was equivalent in the two groups. Episodes of early acute graft dysfunction due to acute tubular necrosis were significantly higher in the LDN group (37.8% vs 12.1%, Z score 2.457, P = 0.014). Warm ischemia time was significantly prolonged in the LDN group (255 s vs 132.5 s, P = 0.002). LDN is associated with slower recovery of graft function and higher incidence of early acute graft dysfunction due to acute tubular necrosis. Late graft function at one year is however comparable.

  8. Hydroperoxides as Hydrogen Bond Donors

    NASA Astrophysics Data System (ADS)

    Møller, Kristian H.; Tram, Camilla M.; Hansen, Anne S.; Kjaergaard, Henrik G.

    2016-06-01

    Hydroperoxides are formed in the atmosphere following autooxidation of a wide variety of volatile organics emitted from both natural and anthropogenic sources. This raises the question of whether they can form hydrogen bonds that facilitate aerosol formation and growth. Using a combination of Fourier transform infrared spectroscopy, FT-IR, and ab initio calculations, we have compared the gas phase hydrogen bonding ability of tert-butylhydroperoxide (tBuOOH) to that of tert-butanol (tBuOH) for a series of bimolecular complexes with different acceptors. The hydrogen bond acceptor atoms studied are nitrogen, oxygen, phosphorus and sulphur. Both in terms of calculated redshifts and binding energies (BE), our results suggest that hydroperoxides are better hydrogen bond donors than the corresponding alcohols. In terms of hydrogen bond acceptor ability, we find that nitrogen is a significantly better acceptor than the other three atoms, which are of similar strength. We observe a similar trend in hydrogen bond acceptor ability with other hydrogen bond donors including methanol and dimethylamine.

  9. [Clinical selection of blood donors].

    PubMed

    Danic, B

    2003-06-01

    For 20 years, the organization set up to insure the blood transfusion safety has never stopped strengthening. It is based on clinical and epidemiological selection of the blood donation candidates, biologic selection of blood donations and different physico-chemical techniques for pathogens reduction or inactivation in blood products. In France, this organization is optimized by the assertion of the voluntary and non-remunerated character of blood donation registered in the law of January 4th, 1993. The blood donors selection is structured in three successive stages. The first stage is the pre-donation information. The second stage begins with reading and filling out an info-questionnaire which prepare for an interview with a physician. This interview is specially directed to prevention of transfusion-transmitted infections and the prevention of adverse reactions after a 400 to 600 mL collection of whole blood or components. Finally, the third stage is the delivery of a post-donation information which invites the donor to contact the "établissement français du sang" (EFS) in case of a new event arisen after the donation or in case of reviewing of its own answers during the medical interview.

  10. Ultrafast Non-Förster Intramolecular Donor-Acceptor Excitation Energy Transfer.

    PubMed

    Athanasopoulos, Stavros; Alfonso Hernandez, Laura; Beljonne, David; Fernandez-Alberti, Sebastian; Tretiak, Sergei

    2017-04-06

    Ultrafast intramolecular electronic energy transfer in a conjugated donor-acceptor system is simulated using nonadiabatic excited-state molecular dynamics. After initial site-selective photoexcitation of the donor, transition density localization is monitored throughout the S2 → S1 internal conversion process, revealing an efficient unidirectional donor → acceptor energy-transfer process. Detailed analysis of the excited-state trajectories uncovers several salient features of the energy-transfer dynamics. While a weak temperature dependence is observed during the entire electronic energy relaxation, an ultrafast initially temperature-independent process allows the molecular system to approach the S2-S1 potential energy crossing seam within the first ten femtoseconds. Efficient energy transfer occurs in the absence of spectral overlap between the donor and acceptor units and is assisted by a transient delocalization phenomenon of the excited-state wave function acquiring Frenkel-exciton character at the moment of quantum transition.

  11. Gamete donors' expectations and experiences of contact with their donor offspring

    PubMed Central

    Kirkman, Maggie; Bourne, Kate; Fisher, Jane; Johnson, Louise; Hammarberg, Karin

    2014-01-01

    STUDY QUESTION What are the expectations and experiences of anonymous gamete donors about contact with their donor offspring? SUMMARY ANSWER Rather than consistently wanting to remain distant from their donor offspring, donors' expectations and experiences of contact with donor offspring ranged from none to a close personal relationship. WHAT IS KNOWN ALREADY Donor conception is part of assisted reproduction in many countries, but little is known about its continuing influence on gamete donors' lives. STUDY DESIGN, SIZE, DURATION A qualitative research model appropriate for understanding participants' views was employed; semi-structured interviews were conducted during January–March 2013. PARTICIPANTS/MATERIALS, SETTING, METHODS Before 1998, gamete donors in Victoria, Australia, were subject to evolving legislation that allowed them to remain anonymous or (from 1988) to consent to the release of identifying information. An opportunity to increase knowledge of donors' expectations and experiences of contact with their donor offspring recently arose in Victoria when a recommendation was made to introduce mandatory identification of donors on request from their donor offspring, with retrospective effect. Pre-1998 donors were invited through an advertising campaign to be interviewed about their views, experiences and expectations; 36 sperm donors and 6 egg donors participated. MAIN RESULTS AND THE ROLE OF CHANCE This research is unusual in achieving participation by donors who would not normally identify themselves to researchers or government inquiries. Qualitative thematic analysis revealed that most donors did not characterize themselves as parents of their donor offspring. Donors' expectations and experiences of contact with donor offspring ranged from none to a close personal relationship. LIMITATIONS, REASONS FOR CAUTION It is not possible to establish whether participants were representative of all pre-1998 donors. WIDER IMPLICATIONS OF THE FINDINGS Anonymous

  12. Enhancement in Organic Photovoltaic Efficiency through the Synergistic Interplay of Molecular Donor Hydrogen Bonding and -Stacking

    SciTech Connect

    Shewmon, Nathan; Watkins, Davita; Galindo, Johan; Zerdan, Raghida; Chen, Jihua; Keum, Jong Kahk; Roitberg, Adrian; Xue, Jiangeng; Castellano, Ronald

    2015-07-20

    For organic photovoltaic (OPV) cells based on the bulk heterojunction (BHJ) structure, it remains challenging to rationally control the degree of phase separation and percolation within blends of donors and acceptors to secure optimal charge separation and transport. Reported is a bottom-up, supramolecular approach to BHJ OPVs wherein tailored hydrogen bonding (H-bonding) interactions between π-conjugated electron donor molecules encourage formation of vertically aligned donor π-stacks while simultaneously suppressing lateral aggregation; the programmed arrangement facilitates fine mixing with fullerene acceptors and efficient charge transport. The approach is illustrated using conventional linear or branched quaterthiophene donor chromophores outfitted with terminal functional groups that are either capable or incapable of self-complementary H-bonding. When applied to OPVs, the H-bond capable donors yield a twofold enhancement in power conversion efficiency relative to the comparator systems, with a maximum external quantum efficiency of 64%. H-bond promoted assembly results in redshifted absorption (in neat films and donor:C 60 blends) and enhanced charge collection efficiency despite disparate donor chromophore structure. Both features positively impact photocurrent and fill factor in OPV devices. Film structural characterization by atomic force microscopy, transmission electron microscopy, and grazing incidence wide angle X-ray scattering reveals a synergistic interplay of lateral H-bonding interactions and vertical π-stacking for directing the favorable morphology of the BHJ.

  13. Enhancement in Organic Photovoltaic Efficiency through the Synergistic Interplay of Molecular Donor Hydrogen Bonding and -Stacking

    DOE PAGES

    Shewmon, Nathan; Watkins, Davita; Galindo, Johan; ...

    2015-07-20

    For organic photovoltaic (OPV) cells based on the bulk heterojunction (BHJ) structure, it remains challenging to rationally control the degree of phase separation and percolation within blends of donors and acceptors to secure optimal charge separation and transport. Reported is a bottom-up, supramolecular approach to BHJ OPVs wherein tailored hydrogen bonding (H-bonding) interactions between π-conjugated electron donor molecules encourage formation of vertically aligned donor π-stacks while simultaneously suppressing lateral aggregation; the programmed arrangement facilitates fine mixing with fullerene acceptors and efficient charge transport. The approach is illustrated using conventional linear or branched quaterthiophene donor chromophores outfitted with terminal functional groupsmore » that are either capable or incapable of self-complementary H-bonding. When applied to OPVs, the H-bond capable donors yield a twofold enhancement in power conversion efficiency relative to the comparator systems, with a maximum external quantum efficiency of 64%. H-bond promoted assembly results in redshifted absorption (in neat films and donor:C 60 blends) and enhanced charge collection efficiency despite disparate donor chromophore structure. Both features positively impact photocurrent and fill factor in OPV devices. Film structural characterization by atomic force microscopy, transmission electron microscopy, and grazing incidence wide angle X-ray scattering reveals a synergistic interplay of lateral H-bonding interactions and vertical π-stacking for directing the favorable morphology of the BHJ.« less

  14. [Assessment and selection of kidney living donors].

    PubMed

    Gentil Govantes, Miguel Ángel; Pereira Palomo, Porfirio

    2010-01-01

    Donor protection should always be taken account during the selection and assessment of a living donor. On these terms, the evaluation of a potential donor must include these issues: 1) The donor act is altruistic, consciousness and out of coercion; 2) Life expectancy and quality of life of the recipient will improve after the living donor kidney transplantation; 3) The donor has normal renal function and the potential risk of developing nephropathy in the long term follow up is scarce (familiar nephropathies and other processes that may increase the potential risk for renal disease in the future, like severe hypertension, diabetes, etc must be ruled out). The glomerular filtrate should meet criteria for the normal function corresponding to age furthermore the absence of proteinuria and urine smear is normal; 4) The screening in the donor should contemplate those clinical situations or diseases non related to the kidney function but might elevate the surgical and/or anesthesia risk besides disease transmission to the recipient (as neoplasia or infections); 5) The surgical act is possible without technical difficulties and always performed after a negative result of the crossmatch between donor and recipient. The living donor evaluation process will follow a different schedule based on each particular case and the center facilities. Any case, the mentioned process is divided in two parts: The first one contains an initial screening (using non invasive and low cost tests) that allows discarding contraindications for donation (in both donor and recipient). In a second phase the assessment of the donor varies with donor characteristics. However, a test for renal function is mandatory besides imaging techniques (like angioTC), screening for transmissible diseases and a detailed evaluation for psychosocial aspects preferably made by professional. Moreover Spanish policy on living donation requires a report with information about the consent for donation developed by an

  15. Effect of a metallic gate on the energy levels of a shallow donor

    SciTech Connect

    Slachmuylders, A. F.; Partoens, B.; Peeters, F. M.; Magnus, W.

    2008-02-25

    We have investigated the effect of a metallic gate on the bound states of a shallow donor located near the gate. We calculate the energy spectrum as a function of the distance between the metallic gate and the donor and find an anticrossing behavior in the energy levels for certain distances. We show how a transverse electric field can tune the average position of the electron with respect to the metallic gate and the impurity.

  16. Extended Criteria Donors in Liver Transplantation.

    PubMed

    Vodkin, Irine; Kuo, Alexander

    2017-05-01

    Mortality rates on the liver transplant waiting list are increasing. The shortage of organs has resulted in higher utilization of extended criteria donors (ECDs), with centers pushing the limits of what is acceptable for transplantation. Donor quality is more appropriately represented as a continuum of risk, and careful selection and matching of ECD grafts with recipients may lead to excellent outcomes. Although there is no precise definition for what constitutes an ECD liver, this review focuses on frequently cited characteristics, including donor age, steatosis, donation after cardiac death, and donors with increased risk of disease transmission.

  17. Novel guidelines for organ donor cancer screening.

    PubMed

    Hassanain, Mazen

    2014-05-20

    Donor transmitted malignancy is a real disastrous risk when dealing with expanded criteria donors. As donor age is increasing, guidelines for cancer screening of the elderly brain dead organ donors must be evidence-based but systematic review of such is sparse. Based on a review of published literature and our 20 years' experience, we propose a new series of guidelines concerning screening for the four most common malignancies: breast colon, lung and prostate cancer. Prospective testing of the efficacy of such protocol will then follow.

  18. Expanding the coordination chemistry of donor-stabilized group-14 metalenes.

    PubMed

    Cabeza, Javier A; García-Álvarez, Pablo; Polo, Diego

    2013-02-07

    The transformation of an amidinate germylene, equipped with just one accessible lone pair of electrons on the Ge atom, into a bidentate 4-electron donor κ(2)Ge,N-ligand, has been achieved for the first time, opening new doors to the non-carbene-like coordination chemistry of heavier carbene analogues.

  19. Adding calcium improves lithium ferrite core

    NASA Technical Reports Server (NTRS)

    Lessoff, H.

    1969-01-01

    Adding calcium increases uniformity of grain growth over a wide range of sintering temperatures and reduces porosity within the grain. Ferrite cores containing calcium have square hysteresis loops and high curie temperatures, making them useful in coincident current memories of digital electronic computers.

  20. Organic photosensitizers with a heteroleptic dual donor for dye-sensitized solar cells.

    PubMed

    Kim, Joo Young; Kim, Young Sik

    2012-04-01

    Using DFT and TDDFT calculations, we investigated the substitution effect in the electronic and optical properties of dye sensitizers with a dual donor composed of triphenylamine and/or indoline moieties. Due to replacement with the dual donor moieties, the HOMO levels were split into HOMO and HOMO - 1 levels, and the bandgaps between the HOMO and LUMO levels decreased, leading to the creation of bathochromically extended absorption spectra. Nearly degenerated splitting of the HOMO levels resulted from the similarity of the electronic structure between the HOMO and the HOMO - 1 levels, delocalized over both dual-donor moieties, when replacing the dual donors. It was shown that the additional electron-donating group creates an additional absorption band and causes a cascading two-electron process aiding the charge separation process. Owing to a more panchromatic attribute, easier energy transfer and feasible retardation of the recombination between the injected electrons and the electrolyte, it is expected that dyeTI will show better performance than the other dyes (dyeT dyeTT and dyeIT) as denoted here in terms of the conversion efficiency of dye-sensitized solar cells (DSSCs). This work presents the probable benefits of dye sensitizers with dual-donor moieties and provides insight into the development of more efficient dye sensitizers for DSSCs through modification of the Frontier molecular orbitals.

  1. Differences in social representation of blood donation between donors and non-donors: an empirical study

    PubMed Central

    Guarnaccia, Cinzia; Giannone, Francesca; Falgares, Giorgio; Caligaris, Aldo Ozino; Sales-Wuillemin, Edith

    2016-01-01

    Background Both donors and non-donors have a positive image of blood donation, so donors and non-donors do not differ regarding their views on donation but do differ in converting their opinion into an active deed of donation. Several studies have identified altruism and empathy as the main factors underlying blood donation. However, a mixture of various motivational factors mould the complex behaviour of donation. This paper presents an exploratory study on differences of social representations of blood donation between blood donors and non-donors, in order to understand the reasons that bring someone to take the decision to become a blood donor. Materials and methods Participants filled in the Adapted Self-Report Altruism Scale, Toronto Empathy Questionnaire and answered a test of verbal association. Descriptive and correlation analyses were carried out on quantitative data, while a prototypic analysis was used for qualitative data. Results The study was carried out on a convenience sample of 786 individuals, 583 donors (mean age: 35.40 years, SD: 13.01 years; 39.3% female) and 203 non-donors (mean age: 35.10 years, SD: 13.30 years; 67.5% female). Social representations of donors seem to be more complex and articulated than those of non-donors. The terms that appear to be central were more specific in donors (life, needle, blood, help, altruism were the words most associated by non-donors; life, aid, altruism, solidarity, health, love, gift, generosity, voluntary, control, needed, useful, needle were the words most associated by donors). Furthermore, non-donors associated a larger number of terms referring to negative aspects of blood donation. Discussion Aspects related to training and the accuracy of any information on blood donation seem to be important in the decision to become a donor and stabilise the behaviour of donation over time, thus ensuring the highest levels of quality and safety in blood establishments. PMID:26674814

  2. Spectroscopy of donor-pi-acceptor complexes for solar cells

    NASA Astrophysics Data System (ADS)

    Himpsel, F. J.; Zegkinoglou, I.; Johnson, P. S.; Pemmaraju, C. D.; Prendergast, D.; Ragoussi, M.-E.; de la Torre, G.; Pickup, D. F.; Ortega, J. E.

    2014-03-01

    A recent improvement in the design of dye sensitized solar cells has been the combination of light absorbing, electron-donating, and electron-withdrawing groups within the same sensitizer molecule. This dye architecture has contributed to increase the energy conversion efficiency, leading to record efficiency values. Here we investigate a zinc(II)-porphyrin-based complex with triphenylamine donor groups and carboxyl linkers for the attachment to an oxide acceptor. The unoccupied orbitals of these three moieties are probed by element-selective X-ray absorption spectroscopy at the N 1s, C 1s, and Zn 2p edges, complemented by time-dependent density functional theory. The attachment of electron-donating groups to the porphyrin ring significantly delocalizes the highest occupied molecular orbital (HOMO) of the molecule. This leads to a spatial separation between the HOMO and the lowest unoccupied molecular orbital (LUMO), reducing the recombination rate of photoinduced electrons and holes.

  3. Preferential inhibition of the plasma membrane NADH oxidase (NOX) activity by diphenyleneiodonium chloride with NADPH as donor

    NASA Technical Reports Server (NTRS)

    Morre, D. James

    2002-01-01

    The cell-surface NADH oxidase (NOX) protein of plant and animal cells will utilize both NADH and NADPH as reduced electron donors for activity. The two activities are distinguished by a differential inhibition by the redox inhibitor diphenyleneiodonium chloride (DPI). Using both plasma membranes and cells, activity with NADPH as donor was markedly inhibited by DPI at submicromolar concentrations, whereas with NADH as donor, DPI was much less effective or had no effect on the activity. The possibility of the inhibition being the result of two different enzymes was eliminated by the use of a recombinant NOX protein. The findings support the concept that NOX proteins serve as terminal oxidases for plasma membrane electron transport involving cytosolic reduced pyridine nucleotides as the natural electron donors and with molecular oxygen as the electron acceptor.

  4. 21 CFR 630.6 - Donor notification.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... the reason for that decision; (ii) Where appropriate, the types of donation of blood or blood... GENERAL REQUIREMENTS FOR BLOOD, BLOOD COMPONENTS, AND BLOOD DERIVATIVES § 630.6 Donor notification. (a) Notification of donors. You, an establishment that collects blood or blood components, must make...

  5. 21 CFR 630.6 - Donor notification.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... the reason for that decision; (ii) Where appropriate, the types of donation of blood or blood... GENERAL REQUIREMENTS FOR BLOOD, BLOOD COMPONENTS, AND BLOOD DERIVATIVES § 630.6 Donor notification. (a) Notification of donors. You, an establishment that collects blood or blood components, must make...

  6. 21 CFR 630.6 - Donor notification.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... the reason for that decision; (ii) Where appropriate, the types of donation of blood or blood... GENERAL REQUIREMENTS FOR BLOOD, BLOOD COMPONENTS, AND BLOOD DERIVATIVES § 630.6 Donor notification. (a) Notification of donors. You, an establishment that collects blood or blood components, must make...

  7. Fecal microbiota transplantation and donor standardization.

    PubMed

    Owens, Casey; Broussard, Elizabeth; Surawicz, Christina

    2013-09-01

    Clostridium difficile diarrhea is a common and severe infectious disease. Antibiotics, which are standard initial treatment, are less effective for treating refractory or recurrent infection. Fecal microbiota transplantation, where healthy donor stool is transplanted into a patient, is an alternative to antibiotic therapy that requires standardization for donors and patients.

  8. Payment for donor kidneys: pros and cons.

    PubMed

    Friedman, E A; Friedman, A L

    2006-03-01

    Continuous growth of the end stage renal disease population treated by dialysis, outpaces deceased donor kidneys available, lengthens the waiting time for a deceased donor transplant. As estimated by the United States Department of Health & Human Services: '17 people die each day waiting for transplants that can't take place because of the shortage of donated organs.' Strategies to expand the donor pool--public relations campaigns and Drivers' license designation--have been mainly unsuccessful. Although illegal in most nations, and viewed as unethical by professional medical organizations, the voluntary sale of purchased donor kidneys now accounts for thousands of black market transplants. The case for legalizing kidney purchase hinges on the key premise that individuals are entitled to control of their body parts even to the point of inducing risk of life. One approach to expanding the pool of kidney donors is to legalize payment of a fair market price of about 40,000 dollars to donors. Establishing a federal agency to manage marketing and purchase of donor kidneys in collaboration with the United Network for Organ Sharing might be financially self-sustaining as reduction in costs of dialysis balances the expense of payment to donors.

  9. Negotiating boundaries: Accessing donor gametes in India

    PubMed Central

    Widge, A.; Cleland, J.

    2011-01-01

    Background: This paper documents how couples and providers access donor materials for conception in the Indian context and perceptions about using them. The objective is to facilitate understanding of critical issues and relevant concerns. Methods: A postal survey was conducted with a sample of 6000 gynaecologists and in-depth interviews were conducted with 39 gynaecologists in four cities. Results: Donor gametes are relatively more acceptable than a few years ago, especially if confidentiality can be maintained, though lack of availability of donor materials is sometimes an impediment to infertility treatment. Donor sperms are usually accessed from in-house or commercial sperm banks, pathology laboratories, IVF centres, professional donors, relatives or friends. There is scepticism about screening procedures of sperm banks. Donor eggs are usually accessed from voluntary donors, friends, relatives, egg sharing programmes, donation from other patients, advertising and commercial donors. There are several concerns regarding informed consent for using donated gametes, using relatives and friends gametes, the unregulated use of gametes and embryos, record keeping and documentation, unethical and corrupt practices and commercialisation. Conclusion: These issues need to be addressed by patients, providers and regulatory authorities by providing information, counselling, ensuring informed consent, addressing exploitation and commercialisation, ensuring monitoring, proper documentation and transparency. PMID:24753849

  10. 21 CFR 630.6 - Donor notification.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... of donation of blood or blood components that the donor should not donate in the future; (3) Where... the reason for that decision; (ii) Where appropriate, the types of donation of blood or blood... GENERAL REQUIREMENTS FOR BLOOD, BLOOD COMPONENTS, AND BLOOD DERIVATIVES § 630.6 Donor notification....

  11. 42 CFR 35.64 - Donors.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Donors. 35.64 Section 35.64 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICAL CARE AND EXAMINATIONS HOSPITAL AND STATION MANAGEMENT Contributions for the Benefit of Patients § 35.64 Donors. Authorized contributions...

  12. 42 CFR 35.64 - Donors.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Donors. 35.64 Section 35.64 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICAL CARE AND EXAMINATIONS HOSPITAL AND STATION MANAGEMENT Contributions for the Benefit of Patients § 35.64 Donors. Authorized contributions...

  13. 42 CFR 35.64 - Donors.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Donors. 35.64 Section 35.64 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICAL CARE AND EXAMINATIONS HOSPITAL AND STATION MANAGEMENT Contributions for the Benefit of Patients § 35.64 Donors. Authorized contributions...

  14. The Experience of Living Kidney Donors

    ERIC Educational Resources Information Center

    Brown, Judith Belle; Karley, Mary Lou; Boudville, Neil; Bullas, Ruth; Garg, Amit X.; Muirhead, Norman

    2008-01-01

    This article describes the experiences, feelings, and ideas of living kidney donors. Using a phenomenological, qualitative research approach, the authors interviewed 12 purposefully selected living kidney donors (eight men and four women), who were between four and 29 years since donation. Interviews were audiotaped, and transcribed verbatim, and…

  15. Organ donors: deceased or alive? Quo vadis?

    PubMed

    Rozental, R

    2006-01-01

    Irrespectively of universal shortage of donor organs there is a tendency of increasing the number of transplantations from living and deceased donors. Each of these two methods has positive and negative features. The main obstacles using living donors are health hazard, necessity to solve certain donor's social and psychological problems, possibility of organ trade and moving. The main problems connected with organ retrieval from deceased donors are possible conflicts with public opinion: difficulties in interpretation of brain death, legislation, obtaining of informed consent from donor's relatives, etc. Future progress in organ transplantation may take place through activation of organ retrieval from deceased donors. The most perspective ways are change to presumed consent in all countries, establishing of centralized system of donor detection and registration, intensification of transplant coordination, active contacts with mass-media, etc. It is necessary to increase (enhance) participation of the members of the public in organ donation process, to develop solidarity among the public members and to involve public authorities to deal with this problem. Bioethical standards should be put in accordance with common progress and some ethical traditions should be changed.

  16. Donor behavior of Sb in ZnO

    SciTech Connect

    Liu, H. Y.; Izyumskaya, N.; Avrutin, V.; Oezguer, Ue.; Morkoc, H.; Yankovich, A. B.; Kvit, A. V.; Voyles, P. M.

    2012-08-01

    Electrical behavior of Sb in ZnO:Sb layers doped in a wide concentration range was studied using temperature dependent Hall effect measurements. The layers were grown by plasma-enhanced molecular beam epitaxy, and the Sb concentration was changed by varying the Sb flux, resulting in electron concentrations in the range of 10{sup 16} to nearly 10{sup 20} cm{sup -3}. Upon annealing, the electron concentration increased slightly and more notable was that the electron mobility significantly improved, reaching a room-temperature value of 110 cm{sup 2}/V s and a low-temperature value of 145 cm{sup 2}/V s, close to the maximum of {approx}155 cm{sup 2}/V s set by ionized impurity scattering. Hall data and structural data suggest that Sb predominantly occupies Zn sublattice positions and acts as a shallow donor in the whole concentration range studied. In the layers with high Sb content ({approx}1 at. %), acceptor-type compensating defects (possibly Sb on oxygen sites and/or point-defect complexes involving Sb{sub O}) are formed. The increase of electron concentration with increasing oxygen pressure and the increase in ZnO:Sb lattice parameter at high Sb concentrations suggest that acceptors involving Sb{sub O} rather than Sb{sub Zn}-2V{sub Zn} complexes are responsible for the compensation of the donors.

  17. Non Heart-Beating Donors in England

    PubMed Central

    Chaib, Eleazar

    2008-01-01

    When transplantation started all organs were retrieved from patients immediately after cardio-respiratory arrest, i.e. from non-heart-beating donors. After the recognition that death resulted from irreversible damage to the brainstem, organ retrieval rapidly switched to patients certified dead after brainstem testing. These heart-beating-donors have become the principal source of organs for transplantation for the last 30 years. The number of heart-beating-donors are declining and this is likely to continue, therefore cadaveric organs from non-heart-beating donor offers a large potential of resources for organ transplantation. The aim of this study is to examine clinical outcomes of non-heart-beating donors in the past 10 years in the UK as an way of decreasing pressure in the huge waiting list for organs transplantation. PMID:18297216

  18. Kinetics of thermal donor generation in silicon

    NASA Technical Reports Server (NTRS)

    Mao, B.-Y.; Lagowski, J.; Gatos, H. C.

    1984-01-01

    The generation kinetics of thermal donors at 450 C in Czochralski-grown silicon was found to be altered by high-temperature preannealing (e.g., 1100 C for 30 min). Thus, when compared with as-grown Si, high-temperature preannealed material exhibits a smaller concentration of generated thermal donors and a faster thermal donor saturation. A unified mechanism of nucleation and oxygen diffusion-controlled growth (based on solid-state plate transformation theory) is proposed to account for generation kinetics of thermal donors at 450 C, in as-grown and high-temperature preannealed Czochralski silicon crystals. This mechanism is consistent with the main features of the models which have been proposed to explain the formation of oxygen thermal donors in silicon.

  19. Donor Conception and "Passing," or; Why Australian Parents of Donor-Conceived Children Want Donors Who Look Like Them.

    PubMed

    Wong, Karen-Anne

    2017-03-01

    This article explores the processes through which Australian recipients select unknown donors for use in assisted reproductive technologies and speculates on how those processes may affect the future life of the donor-conceived person. I will suggest that trust is an integral part of the exchange between donors, recipients, and gamete agencies in donor conception and heavily informs concepts of relatedness, race, ethnicity, kinship, class, and visibility. The decision to be transparent (or not) about a child's genetic parentage affects recipient parents' choices of donor, about who is allowed to "know" children's genetic backgrounds, and how important it is to be able to "pass" as an unassisted conception. In this way, recipients must trust the process, institutions, and individuals involved in their treatment, as well as place trust in the future they imagine for their child. The current market for donor gametes reproduces normative conceptions of the nuclear family, kinship, and relatedness by facilitating "matching" donors to recipients by phenotype and cultural affinities. Recipient parents who choose not to prioritize "matching," and actively disclose the process of children's conceptions, may embark on a project of queering heteronormative family structures and place great trust in both their own children and changing social attitudes to reduce stigma and generate acceptance for non-traditional families.

  20. Donor, dad, or…? Young adults with lesbian parents' experiences with known donors.

    PubMed

    Goldberg, Abbie E; Allen, Katherine R

    2013-06-01

    In this exploratory qualitative study of 11 young adults, ages 19-29 years, we examine how young people who were raised by lesbian parents make meaning out of and construct their relationships with known donors. In-depth interviews were conducted to examine how participants defined their family composition, how they perceived the role of their donors in their lives, and how they negotiated their relationships with their donors. Findings indicate that mothers typically chose known donors who were family friends, that the majority of participants always knew who their donors were, and that their contact with donors ranged from minimal to involved. Further, participants perceived their donors in one of three ways: as strictly donors and not members of their family; as extended family members but not as parents; and as fathers. The more limited role of donors in participants' construction of family relationships sheds light on how children raised in lesbian, gay, and bisexual families are contributing to the redefinition and reconstruction of complex kinship arrangements. Our findings hold implications for clinicians who work with lesbian-mother families, and suggest that young adulthood is an important developmental phase during which interest in and contact with the donor may shift, warranting a transfer of responsibility from mother to offspring in terms of managing the donor-child relationship.

  1. Effects of Alkylthio and Alkoxy Side Chains in Polymer Donor Materials for Organic Solar Cells.

    PubMed

    Cui, Chaohua; Wong, Wai-Yeung

    2016-02-01

    Side chains play a considerable role not only in improving the solubility of polymers for solution-processed device fabrication, but also in affecting the molecular packing, electron affinity and thus the device performance. In particular, electron-donating side chains show unique properties when employed to tune the electronic character of conjugated polymers in many cases. Therefore, rational electron-donating side chain engineering can improve the photovoltaic properties of the resulting polymer donors to some extent. Here, a survey of some representative examples which use electron-donating alkylthio and alkoxy side chains in conjugated organic polymers for polymer solar cell applications will be presented. It is envisioned that an analysis of the effect of such electron-donating side chains in polymer donors would contribute to a better understanding of this kind of side chain behavior in solution-processed conjugated organic polymers for polymer solar cells.

  2. Bright Solid-State Emission of Disilane-Bridged Donor-Acceptor-Donor and Acceptor-Donor-Acceptor Chromophores.

    PubMed

    Shimada, Masaki; Tsuchiya, Mizuho; Sakamoto, Ryota; Yamanoi, Yoshinori; Nishibori, Eiji; Sugimoto, Kunihisa; Nishihara, Hiroshi

    2016-02-24

    The development of disilane-bridged donor-acceptor-donor (D-Si-Si-A-Si-Si-D) and acceptor-donor-acceptor (A-Si-Si-D-Si-Si-A) compounds is described. Both types of compound showed strong emission (λem =ca. 500 and ca. 400 nm, respectively) in the solid state with high quantum yields (Φ: up to 0.85). Compound 4 exhibited aggregation-induced emission enhancement in solution. X-ray diffraction revealed that the crystal structures of 2, 4, and 12 had no intermolecular π-π interactions to suppress the nonradiative transition in the solid state.

  3. The Relationship Between Verified Organ Donor Designation and Patient Demographic and Medical Characteristics.

    PubMed

    Sehgal, N K R; Scallan, C; Sullivan, C; Cedeño, M; Pencak, J; Kirkland, J; Scott, K; Thornton, J D

    2016-04-01

    Previous studies on the correlates of organ donation consent have focused on self-reported willingness to donate and on self-reported medical suitability to donate. However, these may be subject to social desirability bias and inaccurate assessments of medical suitability. The authors sought to overcome these limitations by directly verifying donor designation on driver's licenses and by abstracting comorbid conditions from electronic health records. Using a cross-sectional study design, they reviewed the health records of 2070 randomly selected primary care patients at a large urban safety-net medical system to obtain demographic and medical characteristics. They also examined driver's licenses that were scanned into electronic health records as part of the patient registration process for donor designation. Overall, 943 (46%) patients were designated as a donor on their driver's license. On multivariate analysis, donor designation was positively associated with age 35-54 years, female sex, nonblack race, speaking English or Spanish, being employed, having private insurance, having an income >$45 000, and having fewer comorbid conditions. These demographic and medical characteristics resulted in patient subgroups with donor designation rates ranging from 21% to 75%. In conclusion, patient characteristics are strongly related to verified donor designation. Further work should tailor organ donation efforts to specific subgroups.

  4. Transport of spin qubits with donor chains under realistic experimental conditions

    SciTech Connect

    Mohiyaddin, Fahd A.; Kalra, Rachpon; Laucht, Arne; Rahman, Rajib; Klimeck, Gerhard; Morello, Andrea

    2016-07-25

    The ability to transport quantum information across some distance can facilitate the design and operation of a quantum processor. One-dimensional spin chains provide a compact platform to realize scalable spin transport for a solid-state quantum computer. Here, we model odd-sized donor chains in silicon under a range of experimental nonidealities, including variability of donor position within the chain. We show that the tolerance against donor placement inaccuracies is greatly improved by operating the spin chain in a mode where the electrons are confined at the Si-SiO2 interface. We then estimate the required time scales and exchange couplings, and the level of noise that can be tolerated to achieve high-fidelity transport. As a result, we also propose a protocol to calibrate and initialize the chain, thereby providing a complete guideline for realizing a functional donor chain and utilizing it for spin transport.

  5. Transport of spin qubits with donor chains under realistic experimental conditions

    DOE PAGES

    Mohiyaddin, Fahd A.; Kalra, Rachpon; Laucht, Arne; ...

    2016-07-25

    The ability to transport quantum information across some distance can facilitate the design and operation of a quantum processor. One-dimensional spin chains provide a compact platform to realize scalable spin transport for a solid-state quantum computer. Here, we model odd-sized donor chains in silicon under a range of experimental nonidealities, including variability of donor position within the chain. We show that the tolerance against donor placement inaccuracies is greatly improved by operating the spin chain in a mode where the electrons are confined at the Si-SiO2 interface. We then estimate the required time scales and exchange couplings, and the levelmore » of noise that can be tolerated to achieve high-fidelity transport. As a result, we also propose a protocol to calibrate and initialize the chain, thereby providing a complete guideline for realizing a functional donor chain and utilizing it for spin transport.« less

  6. Cross-talk compensation of hyperfine control in donor-qubit architectures

    NASA Astrophysics Data System (ADS)

    Kandasamy, G.; Wellard, C. J.; Hollenberg, L. C. L.

    2006-09-01

    We theoretically investigate cross-talk in hyperfine gate control of donor-qubit quantum computer architectures, in particular the Kane proposal. By solving the Poisson and Schrödinger equations numerically for the gated donor system, we calculate the change in hyperfine coupling and thus the error in spin-rotation for the donor nuclear-electron spin system, as the gate-donor distance is varied. We thus determine the effect of cross-talk—the inadvertent effect on non-target neighbouring qubits—which occurs due to closeness of the control gates (20-30 nm). The use of compensation protocols is investigated, whereby the extent of cross-talk is limited by the application of compensation bias to a series of gates. In the light of these factors, architectural implications are then considered.

  7. Synthesis and Characterization of Organic Dyes Containing Various Donors and Acceptors

    PubMed Central

    Wu, Tzi-Yi; Tsao, Ming-Hsiu; Chen, Fu-Lin; Su, Shyh-Gang; Chang, Cheng-Wen; Wang, Hong-Paul; Lin, Yuan-Chung; Ou-Yang, Wen-Chung; Sun, I-Wen

    2010-01-01

    New organic dyes comprising carbazole, iminodibenzyl, or phenothiazine moieties, respectively, as the electron donors, and cyanoacetic acid or acrylic acid moieties as the electron acceptors/anchoring groups were synthesized and characterized. The influence of heteroatoms on carbazole, iminodibenzyl and phenothiazine donors, and cyano-substitution on the acid acceptor is evidenced by spectral, electrochemical, photovoltaic experiments, and density functional theory calculations. The phenothiazine dyes show solar-energy-to-electricity conversion efficiency (η) of 3.46–5.53%, whereas carbazole and iminodibenzyl dyes show η of 2.43% and 3.49%, respectively. PMID:20162019

  8. Living donor liver transplantation in Egypt

    PubMed Central

    Marwan, Ibrahim

    2016-01-01

    In Egypt there is no doubt that chronic liver diseases are a major health concern. Hepatitis C virus (HCV) prevalence among the 15−59 years age group is estimated to be 14.7%. The high prevalence of chronic liver diseases has led to increasing numbers of Egyptian patients suffering from end stage liver disease (ESLD), necessitating liver transplantation (LT). We reviewed the evolution of LT in Egypt and the current status. A single center was chosen as an example to review the survival and mortality rates. To date, deceased donor liver transplantation (DDLT) has not been implemented in any program though Egyptian Parliament approved the law in 2010. Living donor liver transplantation (LDLT) seemed to be the only logical choice to save many patients who are in desperate need for LT. By that time, there was increase in number of centers doing LDLT (13 centers) and increase in number of LDLT cases [2,400] with improvement of the results. Donor mortality rate is 1.66 per 1,000 donors; this comprised four donors in the Egyptian series. The exact recipient survival is not accurately known however, and the one-year, three-year and five-year survival were 73.17%, 70.83% and 64.16% respectively in the International Medical Center (IMC) in a series of 145 adult to adult living donor liver transplantation (AALDLT) cases. There was no donor mortality in this series. LDLT are now routinely and successfully performed in Egypt with reasonable donor and recipient outcomes. Organ shortage remains the biggest hurdle facing the increasing need for LT. Although LDLT had reasonable outcomes, it carries considerable risks to healthy donors. For example, it lacks cadaveric back up, and is not feasible for all patients. The initial success in LDLT should drive efforts to increase the people awareness about deceased organ donation in Egypt. PMID:27115003

  9. Living donor liver transplantation in Egypt.

    PubMed

    Amer, Khaled E; Marwan, Ibrahim

    2016-04-01

    In Egypt there is no doubt that chronic liver diseases are a major health concern. Hepatitis C virus (HCV) prevalence among the 15-59 years age group is estimated to be 14.7%. The high prevalence of chronic liver diseases has led to increasing numbers of Egyptian patients suffering from end stage liver disease (ESLD), necessitating liver transplantation (LT). We reviewed the evolution of LT in Egypt and the current status. A single center was chosen as an example to review the survival and mortality rates. To date, deceased donor liver transplantation (DDLT) has not been implemented in any program though Egyptian Parliament approved the law in 2010. Living donor liver transplantation (LDLT) seemed to be the only logical choice to save many patients who are in desperate need for LT. By that time, there was increase in number of centers doing LDLT (13 centers) and increase in number of LDLT cases [2,400] with improvement of the results. Donor mortality rate is 1.66 per 1,000 donors; this comprised four donors in the Egyptian series. The exact recipient survival is not accurately known however, and the one-year, three-year and five-year survival were 73.17%, 70.83% and 64.16% respectively in the International Medical Center (IMC) in a series of 145 adult to adult living donor liver transplantation (AALDLT) cases. There was no donor mortality in this series. LDLT are now routinely and successfully performed in Egypt with reasonable donor and recipient outcomes. Organ shortage remains the biggest hurdle facing the increasing need for LT. Although LDLT had reasonable outcomes, it carries considerable risks to healthy donors. For example, it lacks cadaveric back up, and is not feasible for all patients. The initial success in LDLT should drive efforts to increase the people awareness about deceased organ donation in Egypt.

  10. Supersymmetry of AdS and flat IIB backgrounds

    NASA Astrophysics Data System (ADS)

    Beck, S.; Gutowski, J.; Papadopoulos, G.

    2015-02-01

    We present a systematic description of all warped AdS n × w M 10- n and IIB backgrounds and identify the a priori number of supersymmetries N preserved by these solutions. In particular, we find that the AdS n backgrounds preserve for n ≤ 4 and for 4 < n ≤ 6 supersymmetries and for suitably restricted. In addition under some assumptions required for the applicability of the maximum principle, we demonstrate that the Killing spinors of AdS n backgrounds can be identified with the zero modes of Dirac-like operators on M 10- n establishing a new class of Lichnerowicz type theorems. Furthermore, we adapt some of these results to backgrounds with fluxes by taking the AdS radius to infinity. We find that these backgrounds preserve for 2 < n ≤ 4 and for 4 < n ≤ 7 supersymmetries. We also demonstrate that the Killing spinors of AdS n × w M 10- n do not factorize into Killing spinors on AdS n and Killing spinors on M 10- n .

  11. [Value-Added--Adding Economic Value in the Food Industry].

    ERIC Educational Resources Information Center

    Welch, Mary A., Ed.

    1989-01-01

    This booklet focuses on the economic concept of "value added" to goods and services. A student activity worksheet illustrates how the steps involved in processing food are examples of the concept of value added. The booklet further links food processing to the idea of value added to the Gross National Product (GNP). Discussion questions,…

  12. Interventional radiology in living donor liver transplant.

    PubMed

    Cheng, Yu-Fan; Ou, Hsin-You; Yu, Chun-Yen; Tsang, Leo Leung-Chit; Huang, Tung-Liang; Chen, Tai-Yi; Hsu, Hsien-Wen; Concerjero, Allan M; Wang, Chih-Chi; Wang, Shih-Ho; Lin, Tsan-Shiun; Liu, Yueh-Wei; Yong, Chee-Chien; Lin, Yu-Hung; Lin, Chih-Che; Chiu, King-Wah; Jawan, Bruno; Eng, Hock-Liew; Chen, Chao-Long

    2014-05-28

    The shortage of deceased donor liver grafts led to the use of living donor liver transplant (LDLT). Patients who undergo LDLT have a higher risk of complications than those who undergo deceased donor liver transplantation (LT). Interventional radiology has acquired a key role in every LT program by treating the majority of vascular and non-vascular post-transplant complications, improving graft and patient survival and avoiding, in the majority of cases, surgical revision and/or re-transplant. The aim of this paper is to review indications, diagnostic modalities, technical considerations, achievements and potential complications of interventional radiology procedures after LDLT.

  13. Donor Retention in Online Crowdfunding Communities: A Case Study of DonorsChoose.org

    PubMed Central

    Althoff, Tim; Leskovec, Jure

    2016-01-01

    Online crowdfunding platforms like DonorsChoose.org and Kick-starter allow specific projects to get funded by targeted contributions from a large number of people. Critical for the success of crowdfunding communities is recruitment and continued engagement of donors. With donor attrition rates above 70%, a significant challenge for online crowdfunding platforms as well as traditional offline non-profit organizations is the problem of donor retention. We present a large-scale study of millions of donors and donations on DonorsChoose.org, a crowdfunding platform for education projects. Studying an online crowdfunding platform allows for an unprecedented detailed view of how people direct their donations. We explore various factors impacting donor retention which allows us to identify different groups of donors and quantify their propensity to return for subsequent donations. We find that donors are more likely to return if they had a positive interaction with the receiver of the donation. We also show that this includes appropriate and timely recognition of their support as well as detailed communication of their impact. Finally, we discuss how our findings could inform steps to improve donor retention in crowdfunding communities and non-profit organizations. PMID:27077139

  14. Donor Retention in Online Crowdfunding Communities: A Case Study of DonorsChoose.org.

    PubMed

    Althoff, Tim; Leskovec, Jure

    2015-05-01

    Online crowdfunding platforms like DonorsChoose.org and Kick-starter allow specific projects to get funded by targeted contributions from a large number of people. Critical for the success of crowdfunding communities is recruitment and continued engagement of donors. With donor attrition rates above 70%, a significant challenge for online crowdfunding platforms as well as traditional offline non-profit organizations is the problem of donor retention. We present a large-scale study of millions of donors and donations on DonorsChoose.org, a crowdfunding platform for education projects. Studying an online crowdfunding platform allows for an unprecedented detailed view of how people direct their donations. We explore various factors impacting donor retention which allows us to identify different groups of donors and quantify their propensity to return for subsequent donations. We find that donors are more likely to return if they had a positive interaction with the receiver of the donation. We also show that this includes appropriate and timely recognition of their support as well as detailed communication of their impact. Finally, we discuss how our findings could inform steps to improve donor retention in crowdfunding communities and non-profit organizations.

  15. The Kupffer Cell Number Affects the Outcome of Living Donor Liver Transplantation from Elderly Donors

    PubMed Central

    Hidaka, Masaaki; Eguchi, Susumu; Takatsuki, Mitsuhisa; Soyama, Akihiko; Ono, Shinichiro; Adachi, Tomohiko; Natsuda, Koji; Kugiyama, Tota; Hara, Takanobu; Okada, Satomi; Imamura, Hajime; Miuma, Satoshi; Miyaaki, Hisamitsu

    2016-01-01

    Background There have been no previous reports how Kupffer cells affect the outcome of living donor liver transplantation (LDLT) with an elderly donor. The aim of this study was to elucidate the influence of Kupffer cells on LDLT. Methods A total of 161 adult recipients underwent LDLT. The graft survival, prognostic factors for survival, and graft failure after LDLT were examined between cases with a young donor (<50, n = 112) and an elderly donor (≥50, N = 49). The Kupffer cells, represented by CD68-positive cell in the graft, were examined in the young and elderly donors. Results In a multivariable analysis, a donor older than 50 years, sepsis, and diabetes mellitus were significant predictors of graft failure after LDLT. The CD68 in younger donors was significantly more expressed than that in elderly donors. The group with a less number of CD68-positive cells in the graft had a significantly poor survival in the elderly donor group and prognostic factor for graft failure. Conclusions The worse outcome of LDLT with elderly donors might be related to the lower number of Kupffer cells in the graft, which can lead to impaired recovery of the liver function and may predispose patients to infectious diseases after LDLT. PMID:27819035

  16. The effect of donor characteristics on survival after unrelated donor transplantation for hematologic malignancy

    PubMed Central

    Kollman, Craig; Spellman, Stephen R.; Zhang, Mei-Jie; Hassebroek, Anna; Anasetti, Claudio; Antin, Joseph H.; Champlin, Richard E.; Confer, Dennis L.; DiPersio, John F.; Fernandez-Viña, Marcelo; Hartzman, Robert J.; Horowitz, Mary M.; Hurley, Carolyn K.; Karanes, Chatchada; Maiers, Martin; Mueller, Carlheinz R.; Perales, Miguel-Angel; Setterholm, Michelle; Woolfrey, Ann E.; Yu, Neng

    2016-01-01

    There are >24 million registered adult donors, and the numbers of unrelated donor transplantations are increasing. The optimal strategy for prioritizing among comparably HLA-matched potential donors has not been established. Therefore, the objective of the current analyses was to study the association between donor characteristics (age, sex, parity, cytomegalovirus serostatus, HLA match, and blood group ABO match) and survival after transplantation for hematologic malignancy. The association of donor characteristics with transplantation outcomes was examined using either logistic or Cox regression models, adjusting for patient disease and transplantation characteristics associated with outcomes in 2 independent datasets: 1988 to 2006 (N = 6349; training cohort) and 2007 to 2011 (N = 4690; validation cohort). All donor-recipient pairs had allele-level HLA typing at HLA-A, -B, -C, and -DRB1, which is the current standard for selecting donors. Adjusting for patient disease and transplantation characteristics, survival was better after transplantation of grafts from young donors (aged 18-32 years) who were HLA matched to recipients (P < .001). These findings were validated for transplantations that occurred between 2007 and 2011. For every 10-year increment in donor age, there is a 5.5% increase in the hazard ratio for overall mortality. Increasing HLA disparity was also associated with worsening survival. Donor age and donor-recipient HLA match are important when selecting adult unrelated donors. Other donor characteristics such as sex, parity, and cytomegalovirus serostatus were not associated with survival. The effect of ABO matching on survival is modest and must be studied further before definitive recommendations can be offered. PMID:26527675

  17. Picosecond dynamics of a silicon donor based terahertz detector device

    SciTech Connect

    Bowyer, Ellis T.; Li, Juerong; Litvinenko, K. L.; Murdin, B. N. E-mail: yuxm@pku.edu.cn; Villis, B. J.; Erfani, Morteza; Matmon, Guy; Aeppli, Gabriel; Ortega, Jean-Michel; Prazeres, Rui; Dong, Li; Yu, Xiaomei E-mail: yuxm@pku.edu.cn

    2014-07-14

    We report the characteristics of a simple complementary metal-oxide-semiconductor compatible terahertz detector device with low response time (nanoseconds) determined using a short-pulse, high intensity free-electron laser. The noise equivalent power was 1 × 10{sup −11} W Hz{sup −1/2}. The detector has an enhanced response over narrow bands, most notably at 9.5 THz, with a continuum response at higher frequencies. Using such a device, the dynamics of donors in silicon can be explored, a system which has great potential for quantum information processing.

  18. Fundamental Electronic Properties of Donor-Type Graphite Intercalated Compounds.

    DTIC Science & Technology

    1984-08-01

    Wiedenmann Laboratoire de Diffraction Neutronique , Department de Recherche Fondamentale, Centre d’Etudes Nucleaires, 85X, F-38 041 Grenoble, France...due to anisotropic *lec- anomalies. tron-phonon interaction. The surprising change to activated behavior below SOK suggests local- lies are... activated process but the 100 A (e along c - 2, ni - 1018/c*3 )1 6 , the results are not well represented by the con- nonlinear Thomas-Fearm calculation

  19. AdS3 Solutions of IIB Supergravity

    SciTech Connect

    Kim, Nakwoo

    2005-12-02

    We consider pure D3-brane configurations of IIB string theory which lead to supergravity solutions containing an AdS3 factor. They can provide new examples of AdS3/CFT2 examples on D3-branes whose worldvolume is partially compactified. When the internal 7 dimensional space is non-compact, they are related to fluctuations of higher dimensional AdS/CFT duality examples, thus dual to the BPS operators of D = 4 superconformal field theories. We find that supersymmetry requires the 7 dimensional space is warped Hopf-fibration of (real) 6 dimensional Kahler manifolds.

  20. Action growth for AdS black holes

    NASA Astrophysics Data System (ADS)

    Cai, Rong-Gen; Ruan, Shan-Ming; Wang, Shao-Jiang; Yang, Run-Qiu; Peng, Rong-Hui

    2016-09-01

    Recently a Complexity-Action (CA) duality conjecture has been proposed, which relates the quantum complexity of a holographic boundary state to the action of a Wheeler-DeWitt (WDW) patch in the anti-de Sitter (AdS) bulk. In this paper we further investigate the duality conjecture for stationary AdS black holes and derive some exact results for the growth rate of action within the Wheeler-DeWitt (WDW) patch at late time approximation, which is supposed to be dual to the growth rate of quantum complexity of holographic state. Based on the results from the general D-dimensional Reissner-Nordström (RN)-AdS black hole, rotating/charged Bañados-Teitelboim-Zanelli (BTZ) black hole, Kerr-AdS black hole and charged Gauss-Bonnet-AdS black hole, we present a universal formula for the action growth expressed in terms of some thermodynamical quantities associated with the outer and inner horizons of the AdS black holes. And we leave the conjecture unchanged that the stationary AdS black hole in Einstein gravity is the fastest computer in nature.

  1. A Time for Flexible Donor Agreements.

    ERIC Educational Resources Information Center

    Fischer, Gerald B.

    2003-01-01

    Discusses why volatile markets and new donor expectations make now a good time to rework payout rates and gift agreements to bolster financial and strategic performance. Suggests seven options for action. (EV)

  2. The dead donor rule: a defense.

    PubMed

    Birch, Samuel C M

    2013-08-01

    Miller, Truog, and Brock have recently argued that the "dead donor rule," the requirement that donors be determined to be dead before vital organs are procured for transplantation, cannot withstand ethical scrutiny. In their view, the dead donor rule is inconsistent with existing life-saving practices of organ transplantation, lacks a cogent ethical rationale, and is not necessary for maintenance of public trust in organ transplantation. In this paper, the second of these claims will be evaluated. (The first and third are not addressed.) The claim that the dead donor rule lacks a cogent ethical rationale will be shown to be an expression of the contemporary rejection of the moral significance of the traditional distinction between killing and allowing to die. The moral significance of this traditional distinction, and the associated norm that doctors should not kill their patients, will be defended, and this critique of it shown to be unsuccessful.

  3. Citrate anticoagulation: Are blood donors donating bone?

    PubMed

    Bialkowski, Walter; Bruhn, Roberta; Edgren, Gustaf; Papanek, Paula

    2016-10-01

    An estimated 2.4 million volunteer apheresis blood donation procedures were performed in the United States in 2010, and increases in the proportion of transfused blood products derived from apheresis blood collections have been consistently reported. Anticoagulation is required during apheresis and is achieved with citrate. Donor exposure to citrate causes an acute physiological response to maintain serum mineral homeostasis. Some data are available on the sequelae of this acute response in the days and weeks following exposure, raising questions about bone mineral density in regular apheresis donors. New research is emerging that addresses the potential long-term health outcomes of repeated citrate exposure. This article reviews the acute physiological response to citrate anticoagulation in volunteer blood donors, presents contrasting perspectives on the potential effects of citrate exposure on bone density, and identifies key knowledge gaps in our understanding of long-term health outcomes in apheresis donors. J. Clin. Apheresis 31:459-463, 2016. © 2015 Wiley Periodicals, Inc.

  4. Becoming a Blood Stem Cell Donor

    MedlinePlus Videos and Cool Tools

    ... donors at http://www.marrow.org . Category Science & Technology License Standard YouTube License Show more Show less ... views 10:58 Susan Solomon: The promise of research with stem cells - Duration: 14:59. TED 61, ...

  5. Value Added in English Schools

    ERIC Educational Resources Information Center

    Ray, Andrew; McCormack, Tanya; Evans, Helen

    2009-01-01

    Value-added indicators are now a central part of school accountability in England, and value-added information is routinely used in school improvement at both the national and the local levels. This article describes the value-added models that are being used in the academic year 2007-8 by schools, parents, school inspectors, and other…

  6. Constructing the AdS dual of a Fermi liquid: AdS black holes with Dirac hair

    NASA Astrophysics Data System (ADS)

    Čubrović, Mihailo; Zaanen, Jan; Schalm, Koenraad

    2011-10-01

    We provide evidence that the holographic dual to a strongly coupled charged Fermi liquid has a non-zero fermion density in the bulk. We show that the pole-strength of the stable quasiparticle characterizing the Fermi surface is encoded in the AdS probability density of a single normalizable fermion wavefunction in AdS. Recalling Migdal's theorem which relates the pole strength to the Fermi-Dirac characteristic discontinuity in the number density at ω F , we conclude that the AdS dual of a Fermi liquid is described by occupied on-shell fermionic modes in AdS. Encoding the occupied levels in the total spatially averaged probability density of the fermion field directly, we show that an AdS Reissner-Nordström black holein a theory with charged fermions has a critical temperature, at which the system undergoes a first-order transition to a black hole with a non-vanishing profile for the bulk fermion field. Thermodynamics and spectral analysis support that the solution with non-zero AdS fermion-profile is the preferred ground state at low temperatures.

  7. Donor-derived myeloid sarcoma in two kidney transplant recipients from a single donor.

    PubMed

    Palanisamy, Amudha; Persad, Paul; Koty, Patrick P; Douglas, Laurie L; Stratta, Robert J; Rogers, Jeffrey; Reeves-Daniel, Amber M; Orlando, Giuseppe; Farney, Alan C; Beaty, Michael W; Pettenati, Mark J; Iskandar, Samy S; Grier, David D; Kaczmorski, Scott A; Doares, William H; Gautreaux, Michael D; Freedman, Barry I; Powell, Bayard L

    2015-01-01

    We report the rare occurrence of donor-derived myeloid sarcoma in two kidney transplant patients who received organs from a single deceased donor. There was no evidence of preexisting hematologic malignancy in the donor at the time of organ recovery. Both recipients developed leukemic involvement that appeared to be limited to the transplanted organ. Fluorescence in situ hybridization (FISH) and molecular genotyping analyses confirmed that the malignant cells were of donor origin in each patient. Allograft nephrectomy and immediate withdrawal of immunosuppression were performed in both cases; systemic chemotherapy was subsequently administered to one patient. Both recipients were in remission at least one year following the diagnosis of donor-derived myeloid sarcoma. These cases suggest that restoration of the immune system after withdrawal of immunosuppressive therapy and allograft nephrectomy may be sufficient to control HLA-mismatched donor-derived myeloid sarcoma without systemic involvement.

  8. Donor-Derived Myeloid Sarcoma in Two Kidney Transplant Recipients from a Single Donor

    PubMed Central

    Palanisamy, Amudha; Persad, Paul; Koty, Patrick P.; Douglas, Laurie L.; Stratta, Robert J.; Rogers, Jeffrey; Reeves-Daniel, Amber M.; Orlando, Giuseppe; Farney, Alan C.; Beaty, Michael W.; Pettenati, Mark J.; Iskandar, Samy S.; Grier, David D.; Kaczmorski, Scott A.; Doares, William H.; Gautreaux, Michael D.; Freedman, Barry I.; Powell, Bayard L.

    2015-01-01

    We report the rare occurrence of donor-derived myeloid sarcoma in two kidney transplant patients who received organs from a single deceased donor. There was no evidence of preexisting hematologic malignancy in the donor at the time of organ recovery. Both recipients developed leukemic involvement that appeared to be limited to the transplanted organ. Fluorescence in situ hybridization (FISH) and molecular genotyping analyses confirmed that the malignant cells were of donor origin in each patient. Allograft nephrectomy and immediate withdrawal of immunosuppression were performed in both cases; systemic chemotherapy was subsequently administered to one patient. Both recipients were in remission at least one year following the diagnosis of donor-derived myeloid sarcoma. These cases suggest that restoration of the immune system after withdrawal of immunosuppressive therapy and allograft nephrectomy may be sufficient to control HLA-mismatched donor-derived myeloid sarcoma without systemic involvement. PMID:25977825

  9. Donor identification 'kills gamete donation'? A response.

    PubMed

    Allan, Sonia

    2012-12-01

    Two Australian government inquiries have recently called for the release of information to donor-conceived people about their gamete donors. A national inquiry, recommended 'as a matter of priority' that uniform legislation to be passed nationwide. A state-based inquiry argued that all donor-conceived people should have access to information and called for the enactment of retrospective legislation that would override donor anonymity. This paper responds to an opinion piece published in Human Reproduction in October 2012 by Professor Pennings in which he criticized such recommendations and questioned the motives of people that advocate for information release. I answer the arguments of Pennings, and argue that all parties affected by donor conception should be considered, and a compromise reached. The contact veto system is one such compromise. I discuss the education and support services recommended by the Victorian government and question Pennings' assertions that legislation enabling information release will lead to a decrease in gamete donation. Finally, I rebut Pennings' assertion that there is a 'hidden agenda' behind the call for information release. There is no such agenda in my work. If there is from others, then it is their discriminatory views that need to be addressed, not the move toward openness and honesty or the call for information by donor-conceived people.

  10. Living unrelated donor kidney transplantation between spouses.

    PubMed

    Haberal, M; Gulay, H; Tokyay, R; Oner, Z; Enunlu, T; Bilgin, N

    1992-01-01

    From November 3, 1975 to November 3, 1990, 874 kidney transplants were performed at out centers. Of these, 675 (77.2%) were from living donors and 199 (22.8%) were from cadaver donors. Five hundred eighty (66.4%) of the living donors were first degree related while 99 (11.3%) were unrelated or second degree related donors, 29 of which were spouses. All donor recipient pairs were ABO-compatible, with the exception of one pair. Donor recipient relations were wife to husband in 25 cases and husband to wife in 4 cases. All were first grafts and started functioning during surgery. In this series, the follow-up for the recipients was 4 to 64 months (mean 33.5 +/- 4.5 months). One-year patient survival and graft survival rates were 92.4% and 81.9%, respectively. Two-year patient survival and graft survival rates were 92.4% and 78.2%, respectively. The single ABO-incompatible case is also doing well, 21 months postoperatively. This study demonstrates that the interspouse kidney transplantation may be used when cadaver organ shortage is a problem. While providing the couple with a better quality of life, interspouse kidney transplantation also enables the couple to share the joy of giving and receiving the "gift of life" from one another.

  11. KSC CENTER DIRECTOR ACCEPTS PLAQUE FOR RECORD-SETTING BONE MARROW DONOR REGISTRATION DRIVE

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Kennedy Space Center's Bone Marrow Donor Registration Drive Chairman Dr. George A. Martin and Center Director Jay Honeycutt (left to right) accept a plaque from the Leukemia Society of America's Associate Executive Director Martin Bernstine and the American Red Cross' Southeast Regional Director Jeff Koenreich. Representatives from the American Red Cross and the Leukemia Society of America came to KSC to honor those involved in the record-setting Bone Marrow Donor Registration Drive held here earlier this year. Over 900 potential donors were added to the National Bone Marrow Registry as a result of the KSC drive. The drive established a new record for the most people registered in a single day for the American Red Cross in the three state region of which Florida is a part.

  12. AdS-Carroll branes

    NASA Astrophysics Data System (ADS)

    Clark, T. E.; ter Veldhuis, T.

    2016-11-01

    Coset methods are used to determine the action of a co-dimension one brane (domain wall) embedded in (d + 1)-dimensional AdS space in the Carroll limit in which the speed of light goes to zero. The action is invariant under the non-linearly realized symmetries of the AdS-Carroll spacetime. The Nambu-Goldstone field exhibits a static spatial distribution for the brane with a time varying momentum density related to the brane's spatial shape as well as the AdS-C geometry. The AdS-C vector field dual theory is obtained.

  13. ADS Based on Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Pan, Weimin; Dai, Jianping

    An accelerator-driven system (ADS), which combines a particle accelerator with a subcritical core, is commonly regarded as a promising device for the transmutation of nuclear waste, as well as a potential scheme for thorium-based energy production. So far the predominant choice of the accelerator for ADS is a superconducting linear accelerator (linac). This article gives a brief overview of ADS based on linacs, including the motivation, principle, challenges and research activities around the world. The status and future plan of the Chinease ADS (C-ADS) project will be highlighted and discussed in depth as an example.

  14. No-drain DIEP Flap Donor-site Closure Using Barbed Progressive Tension Sutures

    PubMed Central

    Nagarkar, Purushottam; Lakhiani, Chrisovalantis; Cheng, Angela; Lee, Michael; Teotia, Sumeet

    2016-01-01

    Background: The use of progressive tension sutures has been shown to be comparable to the use of abdominal drains in abdominoplasty. However, the use of barbed progressive tension sutures (B-PTSs) in deep inferior epigastric artery perforator (DIEP) flap donor-site closure has not been investigated. Methods: A retrospective chart review was performed on patients with DIEP flap reconstruction in a 3-year period at 2 institutions by 2 surgeons. Patients were compared by method of DIEP donor-site closure. Group 1 had barbed running progressive tension sutures without drain placement. Group 2 had interrupted progressive tension closure with abdominal drain placement (PTS-AD). Group 3 had closure with only abdominal drain placement (AD). Data collected included demographics, perioperative data, and postoperative outcomes. Results: Seventy-five patients underwent DIEP reconstruction (25 B-PTS, 25 PTS-AD, and 25 AD). Patient characteristics—age, body mass index, comorbidities, smoking status, and chemotherapy—were not significantly different between groups. Rate of seroma was 1.3% (B-PTS = 0%, PTS-AD = 4%, AD = 0%), wound dehiscence 16% (B-PTS = 8%, PTS-AD = 16%, AD = 24%), and umbilical necrosis 5.3% (B-PTS = 0%, PTS-AD = 0%, AD = 16%). No hematomas were observed in any patients. No statistically significant difference was found between complication rates across groups. Conclusions: Use of B-PTSs for abdominal closure after DIEP flap harvest can obviate the need for abdominal drains. Complication rates following this technique are not significantly different from closure using progressive tension suture and abdominal drain placement. This practice can prevent the use of abdominal drains, which can promote patient mobility, increase independence upon discharge, and contribute to patient satisfaction. PMID:27200234

  15. Sperm donors describe the experience of contact with their donor-conceived offspring

    PubMed Central

    Hertz, R.; Nelson, M.K.; Kramer, W.

    2015-01-01

    This study explores the attitudes and experiences of 57 sperm donors who responded to a survey posted online in the United States and indicated that they had had contact with their donor-conceived offspring or the parents of their donor-conceived offspring. On average, 18 years had elapsed since the respondents donated sperm. In the interim between donating and having contact with offspring, most had become curious about their offspring. Most made contact through a bank or online registry. Most respondents had communicated with at least one offspring at least once and most had exchanged photos with offspring. Approximately two-thirds had met in person once; the same proportion had communicated over email or text. Other forms of communication were less common. Almost half of the respondents now considered their donor-conceived offspring to be like a family member. At the same time, donors are respectful of the integrity of the family in which their offspring were raised. Donors with contact are open to having their partners and children know their donor-conceived offspring. Although contact is generally positive, donors report that establishing boundaries and defining the relationship can be very difficult. Some donors also urge those who are thinking of donating to consider the consequences and some suggest avoiding anonymity. There were no significant differences in attitudes and experiences between those who donated anonymously and those who had been identity-release for their offspring when they turned 18. PMID:26175887

  16. Outcomes of shipped live donor kidney transplants compared with traditional living donor kidney transplants.

    PubMed

    Treat, Eric G; Miller, Eric T; Kwan, Lorna; Connor, Sarah E; Maliski, Sally L; Hicks, Elisabeth M; Williams, Kristen C; Whitted, Lauren A; Gritsch, Hans A; McGuire, Suzanne M; Mone, Thomas D; Veale, Jeffrey L

    2014-11-01

    The disparity between kidney transplant candidates and donors necessitates innovations to increase organ availability. Transporting kidneys allows for living donors and recipients to undergo surgery with a familiar transplant team, city, friends, and family. The effect of shipping kidneys and prolonged cold ischemia time (CIT) with living donor transplantation outcomes is not clearly known. This retrospective matched (age, gender, race, and year of procedure) cohort study compared allograft outcomes for shipped live donor kidney transplants and nonshipped li