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Sample records for reaction centers probed

  1. Nuclear Reaction Data Centers

    International Nuclear Information System (INIS)

    McLane, V.; Nordborg, C.; Lemmel, H.D.; Manokhin, V.N.

    1988-01-01

    The cooperating Nuclear Reaction Data Centers are involved in the compilation and exchange of nuclear reaction data for incident neutrons, charged particles and photons. Individual centers may also have services in other areas, e.g., evaluated data, nuclear structure and decay data, reactor physics, nuclear safety; some of this information may also be exchanged between interested centers. 20 refs., 1 tab

  2. Utilizing the dynamic stark shift as a probe for dielectric relaxation in photosynthetic reaction centers during charge separation.

    Science.gov (United States)

    Guo, Zhi; Lin, Su; Woodbury, Neal W

    2013-09-26

    In photosynthetic reaction centers, the electric field generated by light-induced charge separation produces electrochromic shifts in the transitions of reaction center pigments. The extent of this Stark shift indirectly reflects the effective field strength at a particular cofactor in the complex. The dynamics of the effective field strength near the two monomeric bacteriochlorophylls (BA and BB) in purple photosynthetic bacterial reaction centers has been explored near physiological temperature by monitoring the time-dependent Stark shift during charge separation (dynamic Stark shift). This dynamic Stark shift was determined through analysis of femtosecond time-resolved absorbance change spectra recorded in wild type reaction centers and in four mutants at position M210. In both wild type and the mutants, the kinetics of the dynamic Stark shift differ from those of electron transfer, though not in the same way. In wild type, the initial electron transfer and the increase in the effective field strength near the active-side monomer bacteriochlorophyll (BA) occur in synchrony, but the two signals diverge on the time scale of electron transfer to the quinone. In contrast, when tyrosine is replaced by aspartic acid at M210, the kinetics of the BA Stark shift and the initial electron transfer differ, but transfer to the quinone coincides with the decay of the Stark shift. This is interpreted in terms of differences in the dynamics of the local dielectric environment between the mutants and the wild type. In wild type, comparison of the Stark shifts associated with BA and BB on the two quasi-symmetric halves of the reaction center structure confirm that the effective dielectric constants near these cofactors are quite different when the reaction center is in the state P(+)QA(-), as previously determined by Steffen et al. at 1.5 K (Steffen, M. A.; et al. Science 1994, 264, 810-816). However, it is not possible to determine from static, low-temperature measurments if the

  3. Hydrogen bonds in the vicinity of the special pair of the bacterial reaction center probed by hydrostatic high-pressure absorption spectroscopy.

    Science.gov (United States)

    Kangur, Liina; Jones, Michael R; Freiberg, Arvi

    2017-12-01

    Using the native bacteriochlorophyll a pigment cofactors as local probes, we investigated the response to external hydrostatic high pressure of reaction center membrane protein complexes from the photosynthetic bacterium Rhodobacter sphaeroides. Wild-type and engineered complexes were used with a varied number (0, 1 or 2) of hydrogen bonds that bind the reaction center primary donor bacteriochlorophyll cofactors to the surrounding protein scaffold. A pressure-induced breakage of hydrogen bonds was established for both detergent-purified and membrane-embedded reaction centers, but at rather different pressures: between 0.2 and 0.3GPa and at about 0.55GPa, respectively. The free energy change associated with the rupture of the single hydrogen bond present in wild-type reaction centers was estimated to be equal to 13-14kJ/mol. In the mutant with two symmetrical hydrogen bonds (FM197H) a single cooperative rupture of the two bonds was observed corresponding to an about twice stronger bond, rather than a sequential rupture of two individual bonds. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Nuclear reactions as structure probes

    International Nuclear Information System (INIS)

    Fernandez, Bernard; Cugnon, Joseph; Roussel-Chomaz, Patricia; Sparenberg, Jean-Marc; Oliveira Santos, Francois de; Bauge, Eric; Poves, Alfredo; Keeley, Nicholas; Simenel, Cedric; Avez, Benoit; Lacroix, Denis; Baye, Daniel; Cortina-Gil, Dolores; Pons, Alexandre

    2007-09-01

    This publication gathers courses which aim at giving a view on new experiments which are performed by using radioactive beams, notably low intensity beams, in different accelerators, and allow the structure of very exotic nuclei to be characterized. Experimental as well as theoretical aspects are thus addressed. The contributions propose: a brief history of nuclear reactions and of instruments used to study them from the discovery of nucleus to the DWBA (Distorted Wave Born Approximation); an overview of nuclear reactions; experimental techniques; the theory of collisions at low energy; resonant elastic scattering, inelastic scattering and astrophysical reactions; to probe nuclear structure with nucleons; shell model and spectroscopic factors; analysis of transfer reactions and determination of spectroscopic factors; microscopic approaches of nuclear dynamics; theoretical aspects of dissociation reactions; experimental aspects of knockout reactions; research in oenology with the chemical characterisation of defective ageing of dry white wines

  5. Probing the Energy Transfer Dynamics of Photosynthetic Reaction Center Complexes Through Hole-Burning and Single-Complex Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Kerry Joseph [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    Photosynthesis is the process by which light energy is used to drive reactions that generate sugars to supply energy for cellular processes. It is one of the most important fundamental biological reactions and occurs in both prokaryotic (e.g. bacteria) and eukaryotic (e.g. plants and algae) organisms. Photosynthesis is also remarkably intricate, requiring the coordination of many different steps and reactions in order to successfully transform absorbed solar energy into a biochemical usable form of energy. However, the net reaction for all photosynthetic organisms can be reduced to the following, deceptively general, equation developed by Van Niel[1] H2 - D + Aimplieshv A - H2 + D where H2-D is the electron donor, e.g. H2O, H2S. A is the electron acceptor, e.g. CO2, and A-H2 is the synthesized sugar. Amazingly, this simple net equation is responsible for creating the oxidizing atmosphere of Earth and the recycling of CO2, both of which are necessary for the sustainment of the global ecosystem.

  6. Probing reaction dynamics with GDR decay

    International Nuclear Information System (INIS)

    Beene, J.R.

    1994-01-01

    The giant dipole resonance (GDR) has been a prolific source of information on the physics of the nucleus. Mostly it has taught us about nuclear structure, but recently experiments have utilized the GDR as a probe of nuclear reaction dynamics. In this report two examples of such investigations are discussed involving very different reactions and probing time scales that differ by a factor of ∼10 3

  7. Surface sampling concentration and reaction probe

    Science.gov (United States)

    Van Berkel, Gary J; Elnaggar, Mariam S

    2013-07-16

    A method of analyzing a chemical composition of a specimen is described. The method can include providing a probe comprising an outer capillary tube and an inner capillary tube disposed co-axially within the outer capillary tube, where the inner and outer capillary tubes define a solvent capillary and a sampling capillary in fluid communication with one another at a distal end of the probe; contacting a target site on a surface of a specimen with a solvent in fluid communication with the probe; maintaining a plug volume proximate a solvent-specimen interface, wherein the plug volume is in fluid communication with the probe; draining plug sampling fluid from the plug volume through the sampling capillary; and analyzing a chemical composition of the plug sampling fluid with an analytical instrument. A system for performing the method is also described.

  8. Photopion reactions, a probe for nuclear critical opalescence

    International Nuclear Information System (INIS)

    Delorme, J.

    1980-07-01

    It is shown that photopion reactions are a good probe of the nuclear pion field for momenta characteristic of pion condensation. They are thus a direct detector of critical opalescence. Best conditions for experimental detection are discussed

  9. Probing chirality with a femtosecond reaction microscope

    Directory of Open Access Journals (Sweden)

    Janssen M. H. M.

    2013-03-01

    Full Text Available Detection of molecular chirality with high sensitivity and selectivity is important for many analytical and practical applications. Photoionization has emerged as a very sensitive probe of chirality in molecules. We show here that a table top setup with a femtosecond laser and a single imaging detector for both photoelectrons and photoions enables detection of chirality up to 3 orders of magnitude better than the existing conventional absorption based techniques.

  10. Surface chemical reactions probed with scanning force microscopy

    NARCIS (Netherlands)

    Werts, M.P L; van der Vegte, E.W.; Hadziioannou, G

    1997-01-01

    In this letter we report the study of surface chemical reactions with scanning force microscopy (SFM) with chemical specificity. Using chemically modified SFM probes, we can determine the local surface reaction conversion during a chemical surface modification. The adhesion forces between a

  11. Model photo reaction centers via genetic engineering

    Energy Technology Data Exchange (ETDEWEB)

    Zhiyu Wang; DiMagno, T.J.; Popov, M.; Norris, J.R. [Argonne National Lab., IL (United States)]|[Chicago Univ., IL (United States). Dept. of Chemistry; Chikin Chan; Fleming, G. [Chicago Univ., IL (United States). Dept. of Chemistry; Jau Tang; Hanson, D.; Schiffer, M. [Argonne National Lab., IL (United States)

    1992-12-31

    A series of reaction centers of Rhodococcus capsulatus isolated from a set of mutated organisms modified by site-directed mutagenesis at residues M208 and L181 are described. Changes in the amino acid at these sites affect both the energetics of the systems as well as the chemical kinetics for the initial ET event. Two empirical relations among the different mutants for the reduction potential and the ET rate are presented.

  12. Model photo reaction centers via genetic engineering

    Energy Technology Data Exchange (ETDEWEB)

    Zhiyu Wang; DiMagno, T.J.; Popov, M.; Norris, J.R. (Argonne National Lab., IL (United States) Chicago Univ., IL (United States). Dept. of Chemistry); Chikin Chan; Fleming, G. (Chicago Univ., IL (United States). Dept. of Chemistry); Jau Tang; Hanson, D.; Schiffer, M. (Argonne National Lab., IL (United States))

    1992-01-01

    A series of reaction centers of Rhodococcus capsulatus isolated from a set of mutated organisms modified by site-directed mutagenesis at residues M208 and L181 are described. Changes in the amino acid at these sites affect both the energetics of the systems as well as the chemical kinetics for the initial ET event. Two empirical relations among the different mutants for the reduction potential and the ET rate are presented.

  13. Chemical reactions induced and probed by positive muons

    International Nuclear Information System (INIS)

    Ito, Yasuo

    1990-01-01

    The application of μ + science, collectively called μSR, but encompassing a variety of methods including muon spin rotation, muon spin relaxation, muon spin repolarization, muon spin resonance and level-crossing resonance, to chemistry is introduced emphasizing the special aspects of processes which are 'induced and probed' by the μ + itself. After giving a general introduction to the nature and methods of muon science and a short history of muon chemistry, selected topics are given. One concerns the usefulness of muonium as hydrogen-like probes of chemical reactions taking polymerization of vinyl monomers and reaction with thiosulphate as examples. Probing solitons in polyacetylene induced and probed by μ + is also an important example which shows the unique nature of muonium. Another important topic is 'lost polarization'. Although this term is particular to muonium. Another important topic is 'lost polarization'. Although this term is particular to muon chemistry, the chemistry underlining the phenomenon of lost polarization has an importance to both radiation and hot atom chemistries. (orig.)

  14. Reactions probing effects of quark clusters in nuclei

    International Nuclear Information System (INIS)

    Lassila, K.E.; Sukhatme, U.P.

    1988-01-01

    We study signatures of quark clusters in reactions which probe quarks in nuclei. We examine the EMC effect and use physical arguments to establish features of valence and ocean parton distributions in multiquark clusters. We predict from these distributions ratios of structure functions and cross sections measured with neutrino, antineutrinos and proton beams. It appears that a unique determination of the source of the EMC effect will be possible. 6 refs., 4 figs

  15. Correlations between reaction product yields as a tool for probing heavy-ion reaction scenarios

    International Nuclear Information System (INIS)

    Gawlikowicz, W.; Agnihotri, D. K.; Baldwin, S. A.; Schroeder, W. U.; Toke, J.; Charity, R. J.; Sarantites, D. G.; Sobotka, L. G.; Souza, R. T. de; Barczyk, T.; Grotowski, K.; Micek, S.; Planeta, R.; Sosin, Z.

    2010-01-01

    Experimental multidimensional joint distributions of neutrons and charged reaction products were analyzed for 136 Xe + 209 Bi reactions at E/A=28, 40, and 62 MeV and were found to exhibit several different types of prominent correlation patterns. Some of these correlations have a simple explanation in terms of the system excitation energy and pose little challenge to most statistical decay theories. However, several other types of correlation patterns are difficult to reconcile with some, but not other, possible reaction scenarios. In this respect, correlations between the average atomic numbers of intermediate-mass fragments, on the one hand, and light particle multiplicities, on the other, are notable. This kind of multiparticle correlation provides a useful tool for probing reaction scenarios, which is different from the traditional approach of interpreting inclusive yields of individual reaction products.

  16. Enriched reaction center preparation from green photosynthetic bacteria. [Chlorobium limicola

    Energy Technology Data Exchange (ETDEWEB)

    Olson, J M; Giddings, Jr, T H; Shaw, E K

    1976-01-01

    Bacteriochlorophyll a reaction-center complex I from Chlorobium limicola f. thiosulfatophilum 6230 (Tassajara) was incubated in 2 M guanidine . HCl and then chromatographed on cross-linked dextran or agarose gel. Two principal components were separated: a larger component with photochemical activity (bacteriochlorophyll a reaction-center complex II) and a smaller component without activity (bacteriochlorophyll a protein). Complex II contains carotenoid, bacteriochlorophyll a, reaction center(s), and cytochromes b and c, but lacks the well characterized bacteriochlorophyll a protein contained in Complex I. Complex II carries out a light-induced reduction of cytochrome b along with an oxidation of cytochrome c.

  17. Probing the influence of the center atom coordination structure in iron phthalocyanine multi-walled carbon nanotube-based oxygen reduction reaction catalysts by X-ray absorption fine structure spectroscopy

    Science.gov (United States)

    Peng, Yingxiang; Li, Zhipan; Xia, Dingguo; Zheng, Lirong; Liao, Yi; Li, Kai; Zuo, Xia

    2015-09-01

    Three different pentacoordinate iron phthalocyanine (FePc) electrocatalysts with an axial ligand (pyridyl group, Py) anchored to multi-walled carbon nanotubes (MWCNTs) are prepared by a microwave method as high performance composite electrocatalysts (FePc-Py/MWCNTs) for the oxygen reduction reaction (ORR). For comparison, tetracoordinate FePc electrocatalysts without an axial ligand anchored to MWCNTs (FePc/MWCNTs) are assembled in the same way. Ultraviolet-visible spectrophotometry (UV-Vis), Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HRTEM) are used to characterize the obtained electrocatalysts. The electrocatalytic activity of the samples is measured by linear sweep voltammetry (LSV), and the onset potential of all of the FePc-Py/MWCNTs electrocatalysts is found to be more positive than that of their FePc/MWCNTs counterparts. X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy are employed to elucidate the relationship between molecular structure and electrocatalytic activity. XPS indicates that higher concentrations of Fe3+ and pyridine-type nitrogen play critical roles in determining the electrocatalytic ORR activity of the samples. XAFS spectroscopy reveals that the FePc-Py/MWCNTs electrocatalysts have a coordination geometry around Fe that is closer to the square pyramidal structure, a higher concentration of Fe3+, and a smaller phthalocyanine ring radius compared with those of FePc/MWCNTs.

  18. Probing the pairing interaction through two-neutron transfer reactions

    Directory of Open Access Journals (Sweden)

    Margueron J.

    2012-12-01

    Full Text Available The treatment of the pairing interaction in mean-field-based models is addressed. In particular, the possibility to use pair transfers as A tool to better constrain this interaction is discussed. First, pairing inter-actions with various density dependencies (surface/volume mixing are used in the microscopic Hartree-Fock-Bogoliubov + quasiparticle random-phase approximation model to generate the form factors to be used in reaction calculations. Cross sections for (p,t two-neutron transfer reactions are calculated in the one-step zero-range distorted-wave Born approximation for some Tin isotopes and for incident proton energies from 15 to 35 MeV. Three different surface/volume mixings of A zero-range density-dependent pairing interaction are employed in the microscopic calculations and the sensitivity of the cross sections to the different mixings is analyzed. Differences among the three different theoretical predictions are found espacially for the nucleus 136Sn and they are more important at the incident proton energy of 15 MeV. We thus indicate (p,t two-neutron transfer reactions with very neutron-rich Sn isotopes and at proton energies around 15 MeV as good experimental cases where the surface/volume mixing of the pairing interaction may be probed. In the second part of the manuscript, ground-state to ground-state transitions are investigated. Approximations made to estimate two-nucleon transfer probabilities in ground-state to ground-state transitions and the physical interpretation of these probabilities are discussed. Probabilities are often calculated by approximating both ground states of the initial nucleus A and of the final nucleus A±2 by the same quasiparticle vacuum. We analyze two improvements of this approach. First, the effect of using two different ground states with average numbers of particles A and A±2 is quantified. Second, by using projection techniques, the role of particle number restoration is analyzed. Our analysis

  19. Mathematical Model of Synthesis Catalyst with Local Reaction Centers

    Directory of Open Access Journals (Sweden)

    I. V. Derevich

    2017-01-01

    Full Text Available The article considers a catalyst granule with a porous ceramic passive substrate and point active centers on which an exothermic synthesis reaction occurs. A rate of the chemical reaction depends on the temperature according to the Arrhenius law. Heat is removed from the pellet surface in products of synthesis due to heat transfer. In our work we first proposed a model for calculating the steady-state temperature of a catalyst pellet with local reaction centers. Calculation of active centers temperature is based on the idea of self-consistent field (mean-field theory. At first, it is considered that powers of the reaction heat release at the centers are known. On the basis of the found analytical solution, which describes temperature distribution inside the granule, the average temperature of the reaction centers is calculated, which then is inserted in the formula for heat release. The resulting system of transcendental algebraic equations is transformed into a system of ordinary differential equations of relaxation type and solved numerically to achieve a steady-state value. As a practical application, the article considers a Fischer-Tropsch synthesis catalyst granule with active cobalt metallic micro-particles. Cobalt micro-particles are the centers of the exothermic reaction of hydrocarbons macromolecular synthesis. Synthesis occurs as a result of absorption of the components of the synthesis gas on metallic cobalt. The temperature distribution inside the granule for a single local center and reaction centers located on the same granule diameter is found. It was found that there is a critical temperature of reactor exceeding of which leads to significant local overheating of the centers - thermal explosion. The temperature distribution with the local reaction centers is qualitatively different from the granule temperature, calculated in the homogeneous approximation. It is shown that, in contrast to the homogeneous approximation, the

  20. The three-dimensional structures of bacterial reaction centers.

    Science.gov (United States)

    Olson, T L; Williams, J C; Allen, J P

    2014-05-01

    This review presents a broad overview of the research that enabled the structure determination of the bacterial reaction centers from Blastochloris viridis and Rhodobacter sphaeroides, with a focus on the contributions from Duysens, Clayton, and Feher. Early experiments performed in the laboratory of Duysens and others demonstrated the utility of spectroscopic techniques and the presence of photosynthetic complexes in both oxygenic and anoxygenic photosynthesis. The laboratories of Clayton and Feher led efforts to isolate and characterize the bacterial reaction centers. The availability of well-characterized preparations of pure and stable reaction centers allowed the crystallization and subsequent determination of the structures using X-ray diffraction. The three-dimensional structures of reaction centers revealed an overall arrangement of two symmetrical branches of cofactors surrounded by transmembrane helices from the L and M subunits, which also are related by the same twofold symmetry axis. The structure has served as a framework to address several issues concerning bacterial photosynthesis, including the directionality of electron transfer, the properties of the reaction center-cytochrome c 2 complex, and the coupling of proton and electron transfer. Together, these research efforts laid the foundation for ongoing efforts to address an outstanding question in oxygenic photosynthesis, namely the molecular mechanism of water oxidation.

  1. Probing cluster structures through sub-barrier transfer reactions

    Directory of Open Access Journals (Sweden)

    Rafferty D. C.

    2016-01-01

    Full Text Available Multinucleon transfer probabilities and excitation energy distributions have been measured in 16,18O, 19F + 208Pb at energies between 90% - 100% of the Coulomb barrier. A strong 2p2n enhancement is observed for all reactions, though most spectacularly in the 18O induced reaction. Results are interpreted in terms of the Semiclassical model, which seems to suggest α-cluster transfer in all studied systems. The relation to cluster-states in the projectile is discussed, with the experimental results consistent with previous structure studies. Dissipation of energy in the collisions of 18O is compared between different reaction modes, with cluster transfer associated with dissipation over a large number of internal states. Cluster transfer is shown to be a long range dissipation mechanism, which will inform the development of future models to treat these dynamic processes in reactions.

  2. Probing the RAFT process using a model reaction between alkoxyamine and dithioester

    NARCIS (Netherlands)

    Zhou, Y.

    2012-01-01

    A small-molecular model reaction was designed to probe the reversible addition–fragmentation chain transfer (RAFT) process. In this reaction, alkoxyamine releases radicals that react in situ with dithioester through the RAFT process, generating new radicals through the fragmentation of the

  3. Bio-Photoelectrochemical Solar Cells Incorporating Reaction Center and Reaction Center Plus Light Harvesting Complexes

    Science.gov (United States)

    Yaghoubi, Houman

    Harvesting solar energy can potentially be a promising solution to the energy crisis now and in the future. However, material and processing costs continue to be the most important limitations for the commercial devices. A key solution to these problems might lie within the development of bio-hybrid solar cells that seeks to mimic photosynthesis to harvest solar energy and to take advantage of the low material costs, negative carbon footprint, and material abundance. The bio-photoelectrochemical cell technologies exploit biomimetic means of energy conversion by utilizing plant-derived photosystems which can be inexpensive and ultimately the most sustainable alternative. Plants and photosynthetic bacteria harvest light, through special proteins called reaction centers (RCs), with high efficiency and convert it into electrochemical energy. In theory, photosynthetic RCs can be used in a device to harvest solar energy and generate 1.1 V open circuit voltage and ~1 mA cm-2 short circuit photocurrent. Considering the nearly perfect quantum yield of photo-induced charge separation, efficiency of a protein-based solar cell might exceed 20%. In practice, the efficiency of fabricated devices has been limited mainly due to the challenges in the electron transfer between the protein complex and the device electrodes as well as limited light absorption. The overarching goal of this work is to increase the power conversion efficiency in protein-based solar cells by addressing those issues (i.e. electron transfer and light absorption). This work presents several approaches to increase the charge transfer rate between the photosynthetic RC and underlying electrode as well as increasing the light absorption to eventually enhance the external quantum efficiency (EQE) of bio-hybrid solar cells. The first approach is to decrease the electron transfer distance between one of the redox active sites in the RC and the underlying electrode by direct attachment of the of protein complex

  4. Probing properties of neutron stars with terrestrial nuclear reactions

    International Nuclear Information System (INIS)

    Li Baoan; Chen Liewen; Ko, C.M.; Steiner, Andrew W.; Yong Gaochan

    2006-01-01

    Heavy-ion reactions induced by neutron-rich nuclei provide the unique opportunity in terrestrial laboratories to constrain the nuclear symmetry energy Esym in a broad density range. A conservative constraint, 32(ρ/ρ0)0.7 < Esym(ρ) < 32(ρ/ρ0)1.1, around the nuclear matter saturation density ρ0 has recently been obtained from analyzing the isospin diffusion data within a transport model for intermediate energy heavy-ion reactions. This subsequently puts a stringent constraint on properties of neutron stars, especially their radii and cooling mechanisms

  5. Isotope yield ratios as a probe of the reaction dynamics

    International Nuclear Information System (INIS)

    Trautmann, W.; Hildenbrand, K.D.; Lynen, U.; Mueller, W.F.J.; Rabe, H.J.; Sann, H.; Stelzer, H.; Trockel, R.; Wada, R.; Brummund, N.; Glasow, R.; Kampert, K.H.; Santo, R.; Eckert, E.M.; Pochodzalla, J.; Bock, I.; Pelte, D.

    1987-04-01

    Isotopically resolved yields of particles and complex fragments from 12 C and 18 O induced reactions on 53 Ni, 54 Ni, Ag, and 197 Au in the intermediate range of bombarding energies 30 MeV ≤ E/A ≤ 84 MeV were measured. The systematic variation of the deduced isotope yield ratios with projectile and target is used to determine the degree of N/Z equilibration achieved and to establish time scales for the reaction process. A quantum statistical model is employed in order to derive entropies of the emitting systems from the measured isotope yield ratios. (orig.)

  6. Quantum measurement corrections to CIDNP in photosynthetic reaction centers

    International Nuclear Information System (INIS)

    Kominis, Iannis K

    2013-01-01

    Chemically induced dynamic nuclear polarization is a signature of spin order appearing in many photosynthetic reaction centers. Such polarization, significantly enhanced above thermal equilibrium, is known to result from the nuclear spin sorting inherent in the radical pair mechanism underlying long-lived charge-separated states in photosynthetic reaction centers. We will show here that the recently understood fundamental quantum dynamics of radical-ion-pair reactions open up a new and completely unexpected pathway toward obtaining chemically induced dynamic nuclear polarization signals. The fundamental decoherence mechanism inherent in the recombination process of radical pairs is shown to produce nuclear spin polarizations of the order of 10 4 times (or more) higher than the thermal equilibrium value at the Earth's magnetic field relevant to natural photosynthesis. This opens up the possibility of a fundamentally new exploration of the biological significance of high nuclear polarizations in photosynthesis. (paper)

  7. Probing the nuclear structure with heavy-ion reactions

    International Nuclear Information System (INIS)

    Broglia, R.A.

    1982-01-01

    Nuclei display distortions in both ordinary space and in gauge space. It is suggested that it is possible to learn about the spatial distribution of the Nilsson orbitals and about the change of the pairing gap with the rotational frequency through the analysis of one- and two-nucleon transfer reactions induced in heavy-ion collisions

  8. (p,n) and (n,p) reactions as probes of isovector giant monopole resonances

    International Nuclear Information System (INIS)

    Auerbach, N.; Bowman, J.D.; Franey, M.A.; Love, W.G.

    1983-01-01

    Nucleon charge exchange reactions are explored as prospective probes of isovector giant monopole resonances. Using charge exchange transition densities based on random-phase approximation sum rules, distorted wave impulse approximation calculations are made for the (p,n) and (n,p) reactions exciting the isovector giant monopole resonances in several nuclei at bombarding energies of 120 and 800 MeV. Based on our calculations, the charge exchange reactions at 800 MeV appear more promising

  9. Engineering Metallic Nanoparticles for Enhancing and Probing Catalytic Reactions.

    Science.gov (United States)

    Collins, Gillian; Holmes, Justin D

    2016-07-01

    Recent developments in tailoring the structural and chemical properties of colloidal metal nanoparticles (NPs) have led to significant enhancements in catalyst performance. Controllable colloidal synthesis has also allowed tailor-made NPs to serve as mechanistic probes for catalytic processes. The innovative use of colloidal NPs to gain fundamental insights into catalytic function will be highlighted across a variety of catalytic and electrocatalytic applications. The engineering of future heterogenous catalysts is also moving beyond size, shape and composition considerations. Advancements in understanding structure-property relationships have enabled incorporation of complex features such as tuning surface strain to influence the behavior of catalytic NPs. Exploiting plasmonic properties and altering colloidal surface chemistry through functionalization are also emerging as important areas for rational design of catalytic NPs. This news article will highlight the key developments and challenges to the future design of catalytic NPs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Probing nuclei with high-energy hadronic reactions

    International Nuclear Information System (INIS)

    Moss, J.M.

    1995-01-01

    I review the subject of hadron-nucleus collisions at energies where peturbative theory is applicable. Reactions studied experimentally at the Fermilab Tevatron and CERN's Super Proton Synchrotron include the Drell-Yan Process, direct photon production, quarkonium production, and open charm production. I conclude with an observation about a new era of proton-nucleus and nucleus-nucleus experiments which will be carried out at the hadron colliders, RHIC and LHC

  11. Low Energy Electrons as Probing Tool for Astrochemical Reaction Mechanisms

    Science.gov (United States)

    Hendrik Bredehöft, Jan; Swiderek, Petra; Hamann, Thorben

    The complexity of molecules found in space varies widely. On one end of the scale of molecular complexity is the hydrogen molecule H2 . Its formation from H atoms is if not understood than at least thoroughly investigated[1]. On the other side of said spectrum the precursors to biopolymers can be found, such as amino acids[2,3], sugars[4], lipids, cofactors[5], etc, and the kerogen-like organic polymer material in carbonaceous meteorites called "black stuff" [6]. These have also received broad attention in the last decades. Sitting in the middle between these two extremes are simple molecules that are observed by radio astronomy throughout the Universe. These are molecules like methane (CH4 ), methanol (CH3 OH), formaldehyde (CH2 O), hydrogen cyanide (HCN), and many many others. So far more than 40 such species have been identified.[7] They are often used in laboratory experiments to create larger complex molecules on the surface of simulated interstellar dust grains.[2,8] The mechanisms of formation of these observed starting materials for prebiotic chemistry is however not always clear. Also the exact mechanisms of formation of larger molecules in photochemical experiments are largely unclear. This is mostly due to the very complex chemistry going on which involves many different radicals and ions. The creation of radicals and ions can be studied in detail in laboratory simulations. They can be created in a setup mimicking interstellar grain chemistry using slow electrons. There is no free electron radiation in space. What can be found though is a lot of radiation of different sorts. There is electromagnetic radiation (UV light, X-Rays, rays, etc.) and there is particulate radiation as well in the form of high energy ions. This radiation can provide energy that drives chemical reactions in the ice mantles of interstellar dust grains. And while the multitude of different kinds of radiation might be a little confusing, they all have one thing in common: Upon

  12. The (n,p) reaction as a probe of nuclear structure

    International Nuclear Information System (INIS)

    Jackson, K.P.; Celler, A.

    1988-08-01

    An account is given of some results of studies of the (n,p) reaction on nuclear targets at TRIUMF. The (n,p) reaction, inducing spin flip transitions in isospin space, appears to exhibit a unique sensitivity to certain aspects of nuclear structure. The TRIUMF facility is the first to exploit the (n,p) reaction as a detailed probe of nuclear structure at energies above 65 MeV. In the (n,p) reaction Fermi transitions are absent, but there is a dramatic impact on Gamow-Teller and other collective transactions. Some nuclear transition matrix elements can be estimated on the basis of (n,p) measurements. Experiments have been carried out at TRIUMF on Li 6 , Fe 5 4, and Zr 9 0 targets. The calibration of the (n,p) reaction as a probe of the Gamow-Teller strength B + GT has been achieved for three targets. (L.L.) (45 refs., 10 figs.)

  13. Electron transfer reactions to probe the electrode/solution interface

    Energy Technology Data Exchange (ETDEWEB)

    Capitanio, F.; Guerrini, E.; Colombo, A.; Trasatti, S. [Milan Univ., Milan (Italy). Dept. of Physical Chemistry and Electrochemistry

    2008-07-01

    The reactions that occur at the interface between an electrode and an electrolyte were examined with particular reference to the interaction of different electrode surfaces with redox couples. A semi-integration or convolution technique was used to study the kinetics of electron transfer on different electrode materials with different hydrophilic behaviour, such as Boron-Doped-Diamond (BDD), Au and Pt. Standard reversible redox couples were also investigated, including (Fe3+/2+, Fe(CN)63-/4-, Ru(NH3)63+/2+, Co(NH3)63+/2+, Ir4+/3+, V4+/5+ and V3+/2+). The proposed method proved to be simple, straightforward and reliable since the obtained kinetic information was in good agreement with data in the literature. It was concluded that the kinetics of the electrode transfer reactions depend on the chemical nature of the redox couple and electrode material. The method should be further extended to irreversible couples and other electrode materials such as mixed oxide electrodes. 3 refs., 2 figs.

  14. Conformational regulation of charge recombination reactions in a photosynthetic bacterial reaction center

    DEFF Research Database (Denmark)

    Katona, Gergely; Snijder, Arjan; Gourdon, Pontus Emanuel

    2005-01-01

    In bright light the photosynthetic reaction center (RC) of Rhodobacter sphaeroides stabilizes the P(+)(870).Q(-)(A) charge-separated state and thereby minimizes the potentially harmful effects of light saturation. Using X-ray diffraction we report a conformational change that occurs within the cy...... the cytoplasmic domain of this RC in response to prolonged illumination with bright light. Our observations suggest a novel structural mechanism for the regulation of electron transfer reactions in photosynthesis....

  15. The Type 1 Homodimeric Reaction Center in Heliobacterium modesticaldum

    Energy Technology Data Exchange (ETDEWEB)

    Golbeck, John [Pennsylvania State Univ., University Park, PA (United States)

    2018-01-15

    In this funding period, we (i) found that strong illumination of Heliobacterium modesticaldum cells results in saturation of the electron acceptor pool, leading to reduction of the acceptor side and the creation of a back-reacting state that gives rise to delayed fluorescence; (ii) noted that when the FX cluster is reduced in purified reaction centers, no electron transfer occurs beyond A0, even though a quinone is present; (iii) observed by photochemically induced dynamic nuclear polarization (photo-CIDNP) studies of whole cells of Heliobacterium mobilis that primary charge separation is retained even after conversion of the majority of BChl g to Chl aF. ; and (iv) purified a homogeneous preparation of reaction center cores, which led to promising crystallization trials to obtain a three-dimensional structure.

  16. Imaging the reactions of molecular dications: a new probe of dicationic reaction dynamics and energetics

    International Nuclear Information System (INIS)

    Wan-Ping Hu, S.; Harper, S.M.; Price, S.D.

    2002-01-01

    Experiments which generated angularly resolved data to prove the dynamics of dication chemical reactions were performed using a position sensitive coincidence (PSCO) apparatus, to detect in coincidence both of the charged products from such reaction. It consists of a ion source, a hemispherical energy analyser, and a time-of-flight mass spectrometer. Initial experiments to test the apparatus performance were runned on the atomic electron transfer reaction: Ne 2+ + Ar → Ne + + Ar + . Angular distributions, translational and internal energies of the product ions were extracted, as well as the scattering diagram among other data. (nevyjel)

  17. A multi-pathway model for photosynthetic reaction center

    International Nuclear Information System (INIS)

    Qin, M.; Shen, H. Z.; Yi, X. X.

    2016-01-01

    Charge separation occurs in a pair of tightly coupled chlorophylls at the heart of photosynthetic reaction centers of both plants and bacteria. Recently it has been shown that quantum coherence can, in principle, enhance the efficiency of a solar cell, working like a quantum heat engine. Here, we propose a biological quantum heat engine (BQHE) motivated by Photosystem II reaction center (PSII RC) to describe the charge separation. Our model mainly considers two charge-separation pathways which is more than that typically considered in the published literature. We explore how these cross-couplings increase the current and power of the charge separation and discuss the effects of multiple pathways in terms of current and power. The robustness of the BQHE against the charge recombination in natural PSII RC and dephasing induced by environments is also explored, and extension from two pathways to multiple pathways is made. These results suggest that noise-induced quantum coherence helps to suppress the influence of acceptor-to-donor charge recombination, and besides, nature-mimicking architectures with engineered multiple pathways for charge separations might be better for artificial solar energy devices considering the influence of environments.

  18. Combining ligation reaction and capillary gel electrophoresis to obtain reliable long DNA probes.

    Science.gov (United States)

    García-Cañas, Virginia; Mondello, Monica; Cifuentes, Alejandro

    2011-05-01

    New DNA amplification methods are continuously developed for sensitive detection and quantification of specific DNA target sequences for, e.g. clinical, environmental or food applications. These new applications often require the use of long DNA oligonucleotides as probes for target sequences hybridization. Depending on the molecular technique, the length of DNA probes ranges from 40 to 450 nucleotides, solid-phase chemical synthesis being the strategy generally used for their production. However, the fidelity of chemical synthesis of DNA decreases for larger DNA probes. Defects in the oligonucleotide sequence result in the loss of hybridization efficiency, affecting the sensitivity and selectivity of the amplification method. In this work, an enzymatic procedure has been developed as an alternative to solid-phase chemical synthesis for the production of long oligonucleotides. The enzymatic procedure for probe production was based on ligation of short DNA sequences. Long DNA probes were obtained from smaller oligonucleotides together with a short sequence that acts as bridge stabilizing the molecular complex for DNA ligation. The ligation reactions were monitored by capillary gel electrophoresis with laser-induced fluorescence detection (CGE-LIF) using a bare fused-silica capillary. The capillary gel electrophoresis-LIF method demonstrated to be very useful and informative for the characterization of the ligation reaction, providing important information about the nature of some impurities, as well as for the fine optimization of the ligation conditions (i.e. ligation cycles, oligonucleotide and enzyme concentration). As a result, the yield and quality of the ligation product were highly improved. The in-lab prepared DNA probes were used in a novel multiplex ligation-dependent genome amplification (MLGA) method for the detection of genetically modified maize in samples. The great possibilities of the whole approach were demonstrated by the specific and sensitive

  19. Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution

    Science.gov (United States)

    Kolb, V.; Orgel, L. E.; Miller, S. L. (Principal Investigator)

    1994-01-01

    We have prepared a [32P]-labled oligonucleotide probe carrying a free primary amine at its 3'-terminus. This probe is used to initiate polymerization of aziridine (ethyleneimine) in aqueous solution. The nature of the oligomeric products and the kinetics of their formation are then monitored by gel electrophoresis. Our results are generally consistent with those obtained using conventional techniques. We have also investigated the effect of polyanionic templates on the rate of oligomerization of aziridine. We find that water-soluble polyanions generally accelerate the polymerization. The sodium salt of polymethacrylic acid is the most effective of the templates that we studied. The methods introduced in this paper should be applicable to a variety of polymerization reactions in aqueous solution. They should greatly simplify the screening of potentially prebiotic polymerization reactions.

  20. Probing deformed orbitals with vector A( vector e, e' N)B reactions

    International Nuclear Information System (INIS)

    Garrido, E.; Caballero, J.A.; Moya de Guerra, E.; Sarriguren, P.; Udias, J.M.

    1995-01-01

    We present results for response functions and asymmetries in the nuclear reactions 37 vector Ar( vector e, e' n) 36 Ar and 37 vector K( vector e,e' p) 36 Ar at quasifree kinematics. We compare PWIA results obtained using deformed HF wave functions with PWIA and DWIA results obtained assuming a spherical mean field. We show that the complex structure of the deformed orbitals can be probed by coincidence measurements with polarized beam and targets. ((orig.))

  1. A sensitive DNA biosensor based on a facile sulfamide coupling reaction for capture probe immobilization

    International Nuclear Information System (INIS)

    Wang, Qingxiang; Ding, Yingtao; Gao, Feng; Jiang, Shulian; Zhang, Bin; Ni, Jiancong; Gao, Fei

    2013-01-01

    Graphical abstract: A novel DNA biosensor was fabricated through a facile sulfamide coupling reaction between probe DNA and the sulfonic dye of 1-amino-2-naphthol-4-sulfonic acid that electrodeposited on a glassy carbon electrode. -- Highlights: •A versatile sulfonic dye of ANS was electrodeposited on a GCE. •A DNA biosensor was fabricated based on a facile sulfamide coupling reaction. •High probe DNA density of 3.18 × 10 13 strands cm −2 was determined. •A wide linear range and a low detection limit were obtained. -- Abstract: A novel DNA biosensor was fabricated through a facile sulfamide coupling reaction. First, the versatile sulfonic dye molecule of 1-amino-2-naphthol-4-sulfonate (AN-SO 3 − ) was electrodeposited on the surface of a glassy carbon electrode (GCE) to form a steady and ordered AN-SO 3 − layer. Then the amino-terminated capture probe was covalently grafted to the surface of SO 3 − -AN deposited GCE through the sulfamide coupling reaction between the amino groups in the probe DNA and the sulfonic groups in the AN-SO 3 − . The step-by-step modification process was characterized by electrochemistry and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Using Ru(NH 3 ) 6 3+ as probe, the probe density and the hybridization efficiency of the biosensor were determined to be 3.18 × 10 13 strands cm −2 and 86.5%, respectively. The hybridization performance of the biosensor was examined by differential pulse voltammetry using Co(phen) 3 3+/2+ (phen = 1,10-phenanthroline) as the indicator. The selectivity experiments showed that the biosensor presented distinguishable response after hybridization with the three-base mismatched, non-complementary and complementary sequences. Under the optimal conditions, the oxidation peak currents of Co(phen) 3 3+/2+ increased linearly with the logarithm values of the concentration of the complementary sequences in the range from 1.0 × 10 −13 M to 1.0 × 10 −8 M with

  2. Regulation of Germinal Center Reactions by B and T Cells

    Directory of Open Access Journals (Sweden)

    Yeonseok Chung

    2013-10-01

    Full Text Available Break of B cell tolerance to self-antigens results in the development of autoantibodies and, thus, leads to autoimmunity. How B cell tolerance is maintained during active germinal center (GC reactions is yet to be fully understood. Recent advances revealed several subsets of T cells and B cells that can positively or negatively regulate GC B cell responses in vivo. IL-21-producing CXCR5+ CD4+ T cells comprise a distinct lineage of helper T cells—termed follicular helper T cells (TFH—that can provide help for the development of GC reactions where somatic hypermutation and affinity maturation take place. Although the function of TFH cells is beneficial in generating high affinity antibodies against infectious agents, aberrant activation of TFH cell or B cell to self-antigens results in autoimmunity. At least three subsets of immune cells have been proposed as regulatory cells that can limit such antibody-mediated autoimmunity, including follicular regulatory T cells (TFR, Qa-1 restricted CD8+ regulatory T cells (CD8+TREG, and regulatory B cells (BREG. In this review, we will discuss our current understanding of GC B cell regulation with specific emphasis on the newly identified immune cell subsets involved in this process.

  3. Isolated photosystem I reaction centers on a functionalized gated high electron mobility transistor.

    Science.gov (United States)

    Eliza, Sazia A; Lee, Ida; Tulip, Fahmida S; Mostafa, Salwa; Greenbaum, Elias; Ericson, M Nance; Islam, Syed K

    2011-09-01

    In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers (RC) called Photosystem I (PS I) and Photosystem II (PS II). The captured photon triggers rapid charge separation and the photon energy is converted into an electrostatic potential across the nanometer-scale (~6 nm) reaction centers. The exogenous photovoltages from a single PS I RC have been previously measured using the technique of Kelvin force probe microscopy (KFM). However, biomolecular photovoltaic applications require two-terminal devices. This paper presents for the first time, a micro-device for detection and characterization of isolated PS I RCs. The device is based on an AlGaN/GaN high electron mobility transistor (HEMT) structure. AlGaN/GaN HEMTs show high current throughputs and greater sensitivity to surface charges compared to other field-effect devices. PS I complexes immobilized on the floating gate of AlGaN/GaN HEMTs resulted in significant changes in the device characteristics under illumination. An analytical model has been developed to estimate the RCs of a major orientation on the functionalized gate surface of the HEMTs. © 2011 IEEE

  4. Isolated Photosystem I Reaction Centers on a Functionalized Gated High Electron Mobility Transistor

    Energy Technology Data Exchange (ETDEWEB)

    Eliza, Sazia A. [University of Tennessee, Knoxville (UTK); Lee, Ida [ORNL; Tulip, Fahmida S [ORNL; Islam, Syed K [University of Tennessee, Knoxville (UTK); Mostafa, Salwa [University of Tennessee, Knoxville (UTK); Greenbaum, Elias [ORNL; Ericson, Milton Nance [ORNL

    2011-01-01

    In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers (RC) called Photosystem I (PS I) and Photosystem II (PS II). The captured photon triggers rapid charge separation and the photon energy is converted into an electrostatic potential across the nanometer-scale nm reaction centers. The exogenous photovoltages from a single PS I RC have been previously measured using the technique of Kelvin force probe microscopy (KFM). However, biomolecular photovoltaic applications require two-terminal devices. This paper presents for the first time, a micro-device for detection and characterization of isolated PS I RCs. The device is based on an AlGaN/GaN high electron mobility transistor (HEMT) structure. AlGaN/GaN HEMTs show high current throughputs and greater sensitivity to surface charges compared to other field-effect devices. PS I complexes immobilized on the floating gate of AlGaN/GaN HEMTs resulted in significant changes in the device characteristics under illumination. An analytical model has been developed to estimate the RCs of a major orientation on the functionalized gate surface of the HEMTs.

  5. Photonuclear reaction as a probe for α -clustering nuclei in the quasi-deuteron region

    Science.gov (United States)

    Huang, B. S.; Ma, Y. G.; He, W. B.

    2017-03-01

    Photon-nuclear reaction in a transport model frame, namely an extended quantum molecular dynamics model, has been realized at the photon energy of 70-140 MeV in the quasi-deuteron regime. For an important application, we pay a special focus on photonuclear reactions of 12C(γ ,n p )10B where 12C is considered as different configurations including α clustering. Obvious differences for some observables have been observed among different configurations, which can be attributed to spatial-momentum correlation of a neutron-proton pair inside nucleus, and therefore it gives us a sensitive probe to distinguish the different configurations including α clustering with the help of the photonuclear reaction mechanism.

  6. In situ composition measurements of Bunsen reaction solution by radiation probes

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, Shinji; Nagaya, Yasunobu [Japan Atomic Energy Agency (Japan)

    2010-07-01

    Measuring equipments are integral to chemical process controls. A stable hydrogen production by the Iodine-Sulfur thermochemical water-splitting process is relatively difficult because of lack of existing in situ composition measurement techniques for multiple components and corrosive solution. Composition regulations of Bunsen reaction solution is particularly important, since a closed cycle system provided with this process causes that the many streams with different composition return to this section. Accordingly Bunsen solution becomes changeable composition. Radiation probes have a potential for applications to determine this multiple component solution while the non-contact approach avoids the corrosive issues. Moreover the probes have features of the promptness, contact-less and sequential use. Laboratory scale experiments to evaluate these possibilities of the measurement were conducted with use of simulated Bunsen solution, HIx solution and H{sub 2}SO{sub 4} solution, containing HI, I2, H{sub 2}SO{sub 4} and H{sub 2}O and sealed radiation sources. Radiations were counted, which were interacted with the solutions in various compositions around room temperature contained in vessels. For HIx solution, the obtained counting rates were correlated with hydrogen volume concentrations; moreover, the application of the Monte Carlo method suggests possibilities that the detector responses for HIx solution by the radiation probes are predictable. For H{sub 2}SO{sub 4} solution, iodine atoms had significant influences on the relationship between output values of two gamma-ray density meters, cesium source as higher energy and barium source as lower energy. This results suggest that the neutron ray probe, the gamma-ray probes of both lower energy and higher energy have possibilities to determine the composition of Bunsen solution of HIx and H{sub 2}SO{sub 4} solutions. (orig.)

  7. Collective flow as a probe of heavy-ion reaction dynamics

    International Nuclear Information System (INIS)

    Awes, T.C.

    1997-01-01

    Collective flow of nuclear matter probes the dynamics of heavy-ion reactions and can provide information about the nuclear-matter equation of state. In particular, the incident energy dependences of collective flow may be a sensitive means to deduce the existence of a Quark Gluon Plasma phase in the equation of state. Collective flow measurements from 30 A MeV to 200 A GeV incident energies are briefly reviewed. Preliminary results on collective flow from the WA98 experiment at the CERN SPS are presented

  8. Probing the Surface of Platinum during the Hydrogen Evolution Reaction in Alkaline Electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Stoerzinger, Kelsey A. [Physical; Favaro, Marco [Advanced; Joint; Chemical; Ross, Philip N. [Materials; Yano, Junko [Joint; Molecular; Liu, Zhi [State; Division; Hussain, Zahid [Advanced; Crumlin, Ethan J. [Advanced; Joint Center

    2017-11-02

    Understanding the surface chemistry of electrocatalysts in operando can bring insight into the reaction mechanism, and ultimately the design of more efficient materials for sustainable energy storage and conversion. Recent progress in synchrotron based X-ray spectroscopies for in operando characterization allows us to probe the solid/liquid interface directly while applying an external potential, applied here to the model system of Pt in alkaline electrolyte for the hydrogen evolution reaction (HER). We employ ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to identify the oxidation and reduction of Pt-oxides and hydroxides on the surface as a function of applied potential, and further assess the potential for hydrogen adsorption and absorption (hydride formation) during and after the HER. This new window into the surface chemistry of Pt in alkaline brings insight into the nature of the rate limiting step, the extent of H ad/absorption and it’s persistence at more anodic potentials.

  9. Single-particle states in ^112Cd probed with the ^111Cd(d,p) reaction

    Science.gov (United States)

    Garrett, P. E.; Jamieson, D.; Demand, G. A.; Finlay, P.; Green, K. L.; Leach, K. G.; Phillips, A. A.; Sumithrarachchi, C. S.; Svensson, C. E.; Triambak, S.; Wong, J.; Ball, G. C.; Hertenberger, R.; Wirth, H.-F.; Kr"Ucken, R.; Faestermann, T.

    2009-10-01

    As part of a program of detailed spectroscopy of the Cd isotopes, the single-particle neutron states in ^112Cd have been probed with the ^111Cd(d,p) reaction. Beams of polarized 22 MeV deuterons, obtained from the LMU/TUM Tandem Accelerator, bombarded a target of ^111Cd. The protons from the reaction, corresponding to excitation energies up to 3 MeV in ^112Cd, were momentum analyzed with the Q3D spectrograph. Cross sections and analyzing powers were fit to results of DWBA calculations, and spectroscopic factors were determined. The results from the experiment, and implications for the structure of ^112Cd, will be presented.

  10. Probing the 8He ground state via the 8He(p,t)6He reaction

    International Nuclear Information System (INIS)

    Keeley, N.; Skaza, F.; Lapoux, V.; Alamanos, N.; Auger, F.; Beaumel, D.; Becheva, E.; Blumenfeld, Y.; Delaunay, F.; Drouart, A.; Gillibert, A.; Giot, L.; Kemper, K.W.; Nalpas, L.; Pakou, A.; Pollacco, E.C.; Raabe, R.; Roussel-Chomaz, P.; Rusek, K.; Scarpaci, J.-A.; Sida, J.-L.; Stepantsov, S.; Wolski, R.

    2007-01-01

    The weakly-bound 8 He nucleus exhibits a neutron halo or thick neutron skin and is generally considered to have an α+4n structure in its ground state, with the four valence neutrons each occupying 1p 3/2 states outside the α core. The 8 He(p,t) 6 He reaction is a sensitive probe of the ground state structure of 8 He, and we present a consistent analysis of new and existing data for this reaction at incident energies of 15.7 and 61.3A MeV, respectively. Our results are incompatible with the usual assumption of a pure (1p 3/2 ) 4 structure and suggest that other configurations such as (1p 3/2 ) 2 (1p 1/2 ) 2 may be present with significant probability in the ground state wave function of 8 He

  11. Light particle emission as a probe of reaction mechanism and nuclear excitation

    International Nuclear Information System (INIS)

    Guerreau, D.

    1989-01-01

    The central part of these lectures will be dealing with the problem of energy dissipation. A good understanding of the mechanisms for the dissipation requires to study both peripheral and central collisions or, in other words, to look at the impact paramenter dependence. This should also provide valuable information on the time scale. In order to probe the reaction mechanism and nuclear excitation, one of the most powerful tool is unquestionably the observation of light particle emission, including neutrons and charged particles. Several examples will be discussed related to peripheral collisions (the fate of transfer reactions, the excitation energy generation, the production of projectile-like fragments) as well as inner collisions for which extensive studies have demonstrated the strength of intermediate energy heavy ions for the production of very hot nuclei and detailed study of their decay properties

  12. Moessbauer spectroscopy on the reaction center of Rhodopseudomonas viridis

    International Nuclear Information System (INIS)

    Frolov, E.; Goldanskii, V.I.; Birk, A.; Parak, F.; Fritzsch, G.; Sinning, I.; Michel, H.

    1992-01-01

    Proteins called 'reaction centers' (RC) can be isolated from many photosynthetic bacteria. They have one non-heme iron in a quinone acceptor region. The RC of Rhodopseudomonas viridis contains an additional tightly bound tetra-heme cytochrome c subunit. The electronic configuration of both cytochrome and the non-heme iron has been studied in the crystallized protein by Moessbauer spectroscopy at different redox potentials, pH-values, and with an addition of o-phenanthroline. At high potentials (E h =+500 mV) all heme irons are in the low spin Fe 3+ -state, and at low potential (E h = 1 50 mV) they are low spin Fe 2+ with the same Moessbauer parameters for all hemes independent of pH. Redox titrations change the relative area of the reduced and oxidized states in agreement with other methods. The non-heme iron shows a high spin Fe 2+ configuration independent of E h and pH with parameters comparable to those of Rhodopseudomonas sphaeroides. Surprisingly, there is strong evidence for another non-heme iron species in part of the molecules with a Fe 2+ low spin configuration. Incubation with o-phenanthroline decreases the relative Fe 2+ hs-area and increases the contribution of Fe 2+ ls-area. Above 210 K the mean square displacement, 2 >, of the RC-crystals increases more than linearly with temperature. This may be correlated with the increase of the electron transfer rate and indicates that intramolecular mobility influences the functional activity of a protein. (orig.)

  13. The generation of radiolabeled DNA and RNA probes with polymerase chain reaction

    International Nuclear Information System (INIS)

    Schowalter, D.B.; Sommer, S.S.

    1989-01-01

    By including a radioactive triphosphate during polymerase chain reaction (PCR), probes of very high specific activity can be generated. The advantages of PCR labeling include (1) uniform labeling with a specific activity of 5 X 10(9) cpm/micrograms or higher (sensitivity of detection: 0.028 pg of target DNA per 24 h); (2) ease of regulation of both the specific activity and the amount of labeled probe produced; (3) efficient labeling of fragments less than 500 bp; (4) efficient incorporation over a wide range of input DNA template; (5) labeling with subnanogram amounts of input DNA; and (6) direct labeling of genomic DNA. The minimal amount of input DNA allows a virtually unlimited number of PCR labeling reactions to be performed on DNA generated by one amplification under the previously described nonlabeling conditions. This obviates the need for CsCl gradients or other large scale methods of DNA preparation. The above advantages except for the very high specific activity can also be achieved by transcript labeling after an amplification where one or both of PCR primers contain a phage promoter sequence

  14. Styrene oligomerization as a molecular probe reaction for zeolite acidity: a UV-Vis spectroscopy and DFT study

    NARCIS (Netherlands)

    Buurmans, I.L.C.; Pidko, E.A.; Groot, de J.M.; Stavitski, E.; Santen, van R.A.; Weckhuysen, B.M.

    2010-01-01

    A series of H-ZSM-5 crystallites with different framework Si/Al ratios was studied by analyzing the kinetics and reaction mechanism of the oligomerization of 4-fluorostyrene as molecular probe reaction for Brønsted acidity. The formation of carbocationic species was followed by UV-Vis spectroscopy.

  15. Volatile emission in dry seeds as a way to probe chemical reactions during initial asymptomatic deterioration.

    Science.gov (United States)

    Mira, Sara; Hill, Lisa M; González-Benito, M Elena; Ibáñez, Miguel Angel; Walters, Christina

    2016-03-01

    The nature and kinetics of reactions in dry seeds determines how long the seeds survive. We used gas chromatography to assay volatile organic compounds (VOCs) emitted from seeds of three unrelated species as a means to non-invasively probe chemical changes during very dry, dry, and humid storage (seeds were dried to 5.5, 33, and 75% relative humidity at room temperature). VOCs emitted from seeds stored in humid conditions reflected fermentation-type reactions, with methanol and ethanol being predominant in Lactuca sativa and Carum carvi, and acetaldehyde and acetone being predominant in Eruca vesicaria. Dried C. carvi seeds continued to emit fermentation-type products, although at slower rates than the seeds stored in humid conditions. In contrast, drying caused a switch in VOC emission in L. sativa and E. vesicaria seeds towards higher emission of pentane and hexanal, molecules considered to be byproducts from the peroxidation of polyunsaturated fatty acids. Longevity correlated best with the rate of fermentation-type reactions and appeared unrelated to the rate of lipid peroxidation. Emission of VOCs decreased when seed species were mixed together, indicating that seeds adsorbed VOCs. Adsorption of VOCs did not appear to damage seeds, as longevity was not affected in seed mixtures. Collectively, the study shows similarity among species in the types of reactions that occur in dry seeds, but high diversity in the substrates, and hence the byproducts, of the reactions. Moreover, the study suggests that the most abundant VOCs arise from degradation of storage reserves within seed cells, and that these reactions and their byproducts are not, in themselves, damaging. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  16. Using (n,xnγ) reactions to probe collective nuclear structure

    International Nuclear Information System (INIS)

    Yates, S.W.; Brown, T.B.; Warr, N.; Hannant, C.D.

    2000-01-01

    Complete text of publication follows. The (n,n'γ) reaction has been utilized at the University of Kentucky accelerator laboratory for many years to study the structure of stable nuclei (1,2). Through the use of γ-ray excitation function and angular distribution measurements, detailed level schemes of stable nuclei can be established. In recent years, the Doppler-shift attenuation method (DSAM) has been applied following the inelastic neutron scattering reaction to determine the lifetimes of nuclear states (3), and collimated neutron 'beams' have been employed in γ-γ coincidence measurements with an array of HPGe detectors in a close geometry (4,5). Recently, γ-ray detection facilities (6,7) for reactions induced by spallation neutrons, with energies of several hundred MeV, have become available at the Los Alamos Neutron Science Center (LANSCE), and initial measurements indicate that a large variety of reactions are possible. Evidence has been obtained for reactions with as many as 27 particles emitted (7). While the mechanisms of such reactions may be of interest, the primary spectroscopic advantage of utilizing higher-energy neutrons appears to be that neutron-rich nuclei which are not normally available for study with fusion-evaporation reactions can be accessed. As a complement to these measurements with very energetic neutrons, (n2nγ) and (n,3nγ) reaction studies have been explored with neutrons from the 2 H(d,n) and 3 H(d,n) reactions and the facilities at the University of Kentucky. Neutron energies as high as 22 MeV have been employed. Initial evaluations have focussed on data from the 186 W(n,2nγ) 185 W and 186 W(n,3nγ) 184 W reactions and indicate that a great deal of information can be obtained. The advantages of these measurements, as well as comparisons with data from reactions with spallation neutrons, will be presented. This work was supported under grant PHY-9803784 from the U.S. National Science Foundation. (author)

  17. A self-centering active probing technique for kinematic parameter identification and verification of articulated arm coordinate measuring machines

    International Nuclear Information System (INIS)

    Santolaria, J; Brau, A; Velázquez, J; Aguilar, J J

    2010-01-01

    A crucial task in the procedure of identifying the parameters of a kinematic model of an articulated arm coordinate measuring machine (AACMM) or robot arm is the process of capturing data. In this paper a capturing data method is analyzed using a self-centering active probe, which drastically reduces the capture time and the required number of positions of the gauge as compared to the usual standard and manufacturer methods. The mathematical models of the self-centering active probe and AACMM are explained, as well as the mathematical model that links the AACMM global reference system to the probe reference system. We present a self-calibration method that will allow us to determine a homogeneous transformation matrix that relates the probe's reference system to the AACMM last reference system from the probing of a single sphere. In addition, a comparison between a self-centering passive probe and self-centering active probe is carried out to show the advantages of the latter in the procedures of kinematic parameter identification and verification of the AACMM

  18. Polymerase chain reaction as a tool for developing stress protein probes

    Energy Technology Data Exchange (ETDEWEB)

    Cochrane, B.J.; Mattley, Y.D. (Univ. of South Florida, Tampa, FL (United States). Dept. of Biology); Snell, T.W. (Georgia Inst. of Tech., Atlanta, GA (United States). Div. of Biology)

    1994-08-01

    Because of the high degree of evolutionary conservation of stress proteins, potential exists for the development of nucleic acid probes from particular species that could be used to monitor stress-related changes in mRNA abundance. The polymerase chain reaction (PCR) is a powerful tool that can be applied to the generation of these probes, provided that primer sequences can be identified that specifically amplify sequences of interest from a wide variety of organisms. The authors identified such sequences from multiple alignments of published chaperonin and stress-70 sequences, and tested their ability to amplify appropriately sized fragments from genomic DNA from a variety of vertebrates and invertebrates. Although no primer pair could be used successfully with all species, the authors were able to derive specific products from most species by testing different pairs. One primer pair for chaperonin proved particularly useful. Products were obtained from all tested species, and with a single exception (human), these primers appeared to amplify a single copy sequence. The authors determined the nucleotide sequence of the product obtained from the rotifer Brachionus plicatilis and determined by phylogenetic analysis of the inferred protein product that the product obtained is most likely derived from a rotifer DNA template. Finally, the authors show that this product can be used to detect changes in abundance of homologous mRNA in heat-stressed rotifers.

  19. Nuclear Reaction Data File for Astrophysics (NRDF/A) in Hokkaido University Nuclear Reaction Data Center

    International Nuclear Information System (INIS)

    Kato, Kiyoshi; Kimura, Masaaki; Furutachi, Naoya; Makinaga, Ayano; Togashi, Tomoaki; Otuka, Naohiko

    2010-01-01

    The activities of the Japan Nuclear Reaction Data Centre is explained. The main task of the centre is data compilation of Japanese nuclear reaction data in collaboration of the International Network of Nuclear Reaction Data Centres. As one of recent activities, preparation of a new database (NRDF/A) and evaluation of astronuclear reaction data are reported. Collaboration in the nuclear data activities among Asian countries is proposed.

  20. Assembly of photosynthetic reaction center with ABA tri-block polymersomes: highlights on the protein localization.

    KAUST Repository

    Tangorra, Roberto Rocco

    2015-07-07

    The reconstitution of the integral membrane protein photosynthetic reaction center (RC) in polymersomes, i. e. artificial closed vesicles, was achieved by the micelle-to-vesicle transition technique, a very mild protocol based on size exclusion chromatography often used to drive the incorporation of proteins contemporarily to liposomes formation. An optimized protocol was used to successfully reconstitute the protein in a fully active state in polymersomes formed by the tri-block copolymers PMOXA22-PDMS61-PMOXA22. The RC is very sensitive to its solubilizing environment and was used to probe the positioning of the protein in the vesicles. According to charge-recombination experiments and to the enzymatic activity assay, the RC is found to accommodate in the PMOXA22 region of the polymersome, facing the water bulk solution, rather than in the PDMS61 transmembrane-like region. Furthermore, polymersomes were found to preserve protein integrity efficiently as the biomimetic lipid bilayers but show a much longer temporal stability than lipid based vesicles.

  1. Assembly of photosynthetic reaction center with ABA tri-block polymersomes: highlights on the protein localization.

    KAUST Repository

    Tangorra, Roberto Rocco; Operamolla, Alessandra; Milano, Francesco; Hassan Omar, Omar; Henrard, John; Comparelli, Roberto; Italiano, Francesca; Agostiano, Angela; De Leo, Vincenzo; Marotta, Roberto; Falqui, Andrea; Farinola, Gianluca; Trotta, Massimo

    2015-01-01

    The reconstitution of the integral membrane protein photosynthetic reaction center (RC) in polymersomes, i. e. artificial closed vesicles, was achieved by the micelle-to-vesicle transition technique, a very mild protocol based on size exclusion chromatography often used to drive the incorporation of proteins contemporarily to liposomes formation. An optimized protocol was used to successfully reconstitute the protein in a fully active state in polymersomes formed by the tri-block copolymers PMOXA22-PDMS61-PMOXA22. The RC is very sensitive to its solubilizing environment and was used to probe the positioning of the protein in the vesicles. According to charge-recombination experiments and to the enzymatic activity assay, the RC is found to accommodate in the PMOXA22 region of the polymersome, facing the water bulk solution, rather than in the PDMS61 transmembrane-like region. Furthermore, polymersomes were found to preserve protein integrity efficiently as the biomimetic lipid bilayers but show a much longer temporal stability than lipid based vesicles.

  2. ¹⁹F magnetic resonance probes for live-cell detection of peroxynitrite using an oxidative decarbonylation reaction.

    Science.gov (United States)

    Bruemmer, Kevin J; Merrikhihaghi, Sara; Lollar, Christina T; Morris, Siti Nur Sarah; Bauer, Johannes H; Lippert, Alexander R

    2014-10-21

    We report a newly discovered oxidative decarbonylation reaction of isatins that is selectively mediated by peroxynitrite (ONOO(-)) to provide anthranilic acid derivatives. We have harnessed this rapid and selective transformation to develop two reaction-based probes, 5-fluoroisatin and 6-fluoroisatin, for the low-background readout of ONOO(-) using (19)F magnetic resonance spectroscopy. 5-fluoroisatin was used to non-invasively detect ONOO(-) formation in living lung epithelial cells stimulated with interferon-γ (IFN-γ).

  3. Chalcogenide metal centers for oxygen reduction reaction: Activity and tolerance

    International Nuclear Information System (INIS)

    Feng Yongjun; Gago, Aldo; Timperman, Laure; Alonso-Vante, Nicolas

    2011-01-01

    This mini-review summarizes materials design methods, oxygen reduction kinetics, tolerance to small organic molecules and fuel cell performance of chalcogenide metal catalysts, particularly, ruthenium (Ru x Se y ) and non-precious transition metals (M x X y : M = Co, Fe and Ni; X = Se and S). These non-platinum catalysts are potential alternatives to Pt-based catalysts because of their comparable catalytic activity (Ru x Se y ), low cost, high abundance and, in particular, a high tolerance to small organic molecules. Developing trends of synthesis methods, mechanism of oxygen reduction reaction and applications in direct alcohol fuel cells as well as the substrate effect are highlighted.

  4. Reaction pathways of photoexcited retinal in proteorhodopsin studied by pump-dump-probe spectroscopy.

    Science.gov (United States)

    Rupenyan, Alisa; van Stokkum, Ivo H M; Arents, Jos C; van Grondelle, Rienk; Hellingwerf, Klaas J; Groot, Marie Louise

    2009-12-17

    Proteorhodopsin (pR) is a membrane-embedded proton pump from the microbial rhodopsin family. Light absorption by its retinal chromophore initiates a photocycle, driven by trans/cis isomerization on the femtosecond to picosecond time scales. Here, we report a study on the photoisomerization dynamics of the retinal chromophore of pR, using dispersed ultrafast pump-dump-probe spectroscopy. The application of a pump pulse initiates the photocycle, and with an appropriately tuned dump pulse applied at a time delay after the dump, the molecules in the initial stages of the photochemical process can be de-excited and driven back to the ground state. In this way, we were able to resolve an intermediate on the electronic ground state that represents chromophores that are unsuccessful in isomerization. In particular, the fractions of molecules that undergo slow isomerization (20 ps) have a high probability to enter this state rather than the isomerized K-state. On the ground state reaction surface, return to the stable ground state conformation via a structural or vibrational relaxation occurs in 2-3 ps. Inclusion of this intermediate in the kinetic scheme led to more consistent spectra of the retinal-excited state, and to a more accurate estimation of the quantum yield of isomerization (Phi = 0.4 at pH 6).

  5. Initial dynamics of the Norrish Type I reaction in acetone: probing wave packet motion.

    Science.gov (United States)

    Brogaard, Rasmus Y; Sølling, Theis I; Møller, Klaus B

    2011-02-10

    The Norrish Type I reaction in the S(1) (nπ*) state of acetone is a prototype case of ketone photochemistry. On the basis of results from time-resolved mass spectrometry (TRMS) and photoelectron spectroscopy (TRPES) experiments, it was recently suggested that after excitation the wave packet travels toward the S(1) minimum in less than 30 fs and stays there for more than 100 picoseconds [Chem. Phys. Lett.2008, 461, 193]. In this work we present simulated TRMS and TRPES signals based on ab initio multiple spawning simulations of the dynamics during the first 200 fs after excitation, getting quite good agreement with the experimental signals. We can explain the ultrafast decay of the experimental signals in the following manner: the wave packet simply travels, mainly along the deplanarization coordinate, out of the detection window of the ionizing probe. This window is so narrow that subsequent revival of the signal due to the coherent deplanarization vibration is not observed, meaning that from the point of view of the experiment the wave packets travels directly to the S(1) minimum. This result stresses the importance of pursuing a closer link to the experimental signal when using molecular dynamics simulations in interpreting experimental results.

  6. 11. IAEA consultants' meeting of the nuclear reaction data centers. Obninsk, 7-11 October 1991

    International Nuclear Information System (INIS)

    Lemmel, H.D.

    1992-03-01

    This report summarizes the 1991 co-ordination meeting in Obninsk, Russia, of the national and regional nuclear reaction data centers, convened by the IAEA at regular intervals. The main topics are: the international exchange of nuclear reaction data by means of the ''EXFOR'' system, and the further development of this system; the ''CINDA'' system as an international index and bibliography to neutron reaction data; the sharing of the workload for speedy and reliable nuclear data compilation; the exchanged and documentation of evaluated data libraries in ENDF format, with the goal of rendering data center services to data users in IAEA Member States by means of computer retrievals, online services and printed materials

  7. Photosynthetic antennas and reaction centers: Current understanding and prospects for improvement

    Energy Technology Data Exchange (ETDEWEB)

    Blankenship, R.E. [Arizona State Univ., Tempe, AZ (United States)

    1996-09-01

    A brief introduction to the principles, structures and kinetic processes that take place in natural photosynthetic reaction center complexes is presented. Energy is first collected by an antenna system, and is transferred to a reaction center complex where primary electron transfer takes place. Secondary reactions lead to oxidation of water and reduction of CO{sub 2} in some classes of organisms. Antenna systems are highly regulated to maximize energy collection efficiency while avoiding photodamage. Some areas that are presently not well understood are listed.

  8. All-oxide Raman-active traps for light and matter: probing redox homeostasis model reactions in aqueous environment.

    Science.gov (United States)

    Alessandri, Ivano; Depero, L E

    2014-04-09

    Core-shell colloidal crystals can act as very efficient traps for light and analytes. Here it is shown that Raman-active probes can be achieved using SiO2-TiO2 core-shell beads. These systems are successfully tested in monitoring of glutathione redox cycle at physiological concentration in aqueous environment, without need of any interfering enhancers. These materials represent a promising alternative to conventional, metal-based SERS probes for investigating chemical and biochemical reactions under real working conditions. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Co-ordination of the nuclear reaction data centers. Report on an IAEA advisory group meeting

    International Nuclear Information System (INIS)

    Schwerer, O.; Lemmel, H.D.

    1996-11-01

    This report summarizes the 1996 co-ordination meeting in Brookhaven, U.S.A., of the national and regional nuclear reaction data center, convened by the IAEA at regular intervals. The main topics are: the international exchange of nuclear reaction data by means of the ''EXFOR'' system, and the further development of this system; the ''CINDA'' system as an international index and bibliography to neutron reaction data; the sharing of the workload for speedy and reliable nuclear data compilation and data center services; the exchange and documentation of evaluated data libraries in ''ENDF'' format; the rapid advances of online electronic information technologies, with the goal of rendering data center services to data users in IAEA Member States by means of computer retrievals, online services and printed materials. The scope of data covers microscopic cross-sections and related parameters of nuclear reactions induced by neutrons, charged-particles and photons. (author). Refs, figs, tabs

  10. Co-ordination of the nuclear reactions data centers. Report on an IAEA advisory group meeting

    International Nuclear Information System (INIS)

    Pronyaev, V.G.; Schwerer, O.

    1998-07-01

    This report summarizes the 1998 co-ordination meeting at the IAEA Headquarters in Vienna of the regional, national and specialized nuclear reaction data centers, concerned by the IAEA at two-year intervals. The main topics are: the international exchange of nuclear reaction data by means of the ''EXFOR'' system, and the further development of this system; the ''CINDA'' system as an international index and bibliography to neutron reaction data; the sharing of the workload for speedy and reliable nuclear data compilation and data center services; the exchange and documentation of evaluated data libraries in ''ENDF'' format; the rapid advances of online electronic information technologies, with goal of rendering data center services to data users in IAEA Member States by means of computer retrievals, online services and printed materials. The scope of data covers microscopic cross-sections and related parameters of nuclear reactions induced by neutrons, charged-particles and photons. (author)

  11. Co-ordination of the nuclear reaction data centers. Report on an IAEA advisory group meeting

    Energy Technology Data Exchange (ETDEWEB)

    Schwerer, O; Lemmel, H D [eds.

    1996-11-01

    This report summarizes the 1996 co-ordination meeting in Brookhaven, U.S.A., of the national and regional nuclear reaction data center, convened by the IAEA at regular intervals. The main topics are: the international exchange of nuclear reaction data by means of the ``EXFOR`` system, and the further development of this system; the ``CINDA`` system as an international index and bibliography to neutron reaction data; the sharing of the workload for speedy and reliable nuclear data compilation and data center services; the exchange and documentation of evaluated data libraries in ``ENDF`` format; the rapid advances of online electronic information technologies, with the goal of rendering data center services to data users in IAEA Member States by means of computer retrievals, online services and printed materials. The scope of data covers microscopic cross-sections and related parameters of nuclear reactions induced by neutrons, charged-particles and photons. (author). Refs, figs, tabs.

  12. Co-ordination of the nuclear reactions data centers. Report on an IAEA advisory group meeting

    Energy Technology Data Exchange (ETDEWEB)

    Pronyaev, V G; Schwerer, O [eds.

    1998-07-01

    This report summarizes the 1998 co-ordination meeting at the IAEA Headquarters in Vienna of the regional, national and specialized nuclear reaction data centers, concerned by the IAEA at two-year intervals. The main topics are: the international exchange of nuclear reaction data by means of the ``EXFOR`` system, and the further development of this system; the ``CINDA`` system as an international index and bibliography to neutron reaction data; the sharing of the workload for speedy and reliable nuclear data compilation and data center services; the exchange and documentation of evaluated data libraries in ``ENDF`` format; the rapid advances of online electronic information technologies, with goal of rendering data center services to data users in IAEA Member States by means of computer retrievals, online services and printed materials. The scope of data covers microscopic cross-sections and related parameters of nuclear reactions induced by neutrons, charged-particles and photons. (author) Refs, figs, tabs

  13. The breakdown of vinyl ethers as a two-center synchronous reaction

    Science.gov (United States)

    Pokidova, T. S.; Shestakov, A. F.

    2009-11-01

    The experimental data on the molecular decomposition of vinyl ethers of various structures to alkanes and the corresponding aldehydes or ketones in the gas phase were analyzed using the method of intersecting parabolas. The enthalpies and kinetic parameters of decomposition were calculated for 17 reactions. The breakdown of ethers is a two-center concerted reaction characterized by a very high classical potential barrier to the thermally neutral reaction (180-190 kJ/mol). The kinetic parameters (activation energies and rate constants) of back reactions of the formation of vinyl ethers in the addition of aldehydes or ketones to alkanes were calculated using the method of intersecting parabolas. The factors that influenced the activation energy of the decomposition and formation of ethers were discussed. Quantum-chemical calculations of several vinyl ether decomposition reactions were performed. Ether formation reactions were compared with the formation of unsaturated alcohols as competitive reactions, which can occur in the interaction of carbonyl compounds with alkenes.

  14. Molecular electronics of a single photosystem I reaction center: Studies with scanning tunneling microscopy and spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, I.; Lee, J.W.; Warmack, R.J.; Allison, D.P.; Greenbaum, E. [Oak Ridge National Lab., TN (United States)

    1995-03-14

    Thylakoids and photosystem I (PSI) reaction centers were imaged by scanning tunneling microscopy. The thylakoids were isolated from spinach chloroplasts, and PSI reaction centers were extracted from thylakoid membranes. Because thylakoids are relatively thick nonconductors, they were sputter-coated with Pd/Au before imaging. PSI photosynthetic centers and chemically platinized PSI were investigated without sputter-coating. They were mounted on flat gold substrates that had been treated with mercaptoacetic acid to help bind the proteins. With tunneling spectroscopy, the PSI centers displayed a semiconductor-like response with a band gap of 1.8 eV. Lightly platinized (platinized for 1 hr) centers displayed diode-like conduction that resulted in dramatic contrast changes between images taken with opposite bias voltages. The electronic properties of this system were stable under long-term storage. 42 refs., 7 figs.

  15. An integrated high temperature environmental cell for atom probe tomography studies of gas-surface reactions: Instrumentation and results

    International Nuclear Information System (INIS)

    Dumpala, S.; Broderick, S.R.; Bagot, P.A.J.; Rajan, K.

    2014-01-01

    An integrated environmental cell has been designed and developed for the latest generation of Atom Probe Tomography LEAP™ instruments, allowing controlled exposure of samples to gases at high temperatures. Following treatment, samples can be transferred through the LEAP vacuum system for subsequent APT analysis, which provides detailed information on changes to chemical microstructures following the reactions with near-atomic resolution. A full description of the cell is presented, along with some sample results on the oxidation of aluminum and two platinum-group alloys, demonstrating the capability of combining exposure/characterization functionality in a single instrument. - Highlights: • Designed and built atom probe environmental cell for in situ reactions. • Investigated Al oxidation, and demonstrated improvement with new cell. • in situ APT analysis of Pt-alloys showed surface segregation of Rh and Ir

  16. Photochemical primary process of photo-Fries rearrangement reaction of 1-naphthyl acetate as studied by MFE probe.

    Science.gov (United States)

    Gohdo, Masao; Takamasu, Tadashi; Wakasa, Masanobu

    2011-01-14

    Photo-Fries rearrangement reactions of 1-naphthyl acetate (NA) in n-hexane and in cyclohexane were studied by the magnetic field effect probe (MFE probe) under magnetic fields (B) of 0 to 7 T. Transient absorptions of the 1-naphthoxyl radical, T-T absorption of NA, and a short-lifetime intermediate (τ = 24 ns) were observed by a nanosecond laser flash photolysis technique. In n-hexane, the yield of escaped 1-naphthoxyl radicals dropped dramatically upon application of a 3 mT field, but then the yield increased with increasing B for 3 mT < B≤ 7 T. These observed MFEs can be explained by the hyperfine coupling and the Δg mechanisms through the singlet radical pair. The fact that MFEs were observed for the present photo-Fries rearrangement reaction indicates the presence of a singlet radical pair intermediate with a lifetime as long as several tens of nanoseconds.

  17. Non-Covalent Fluorescent Labeling of Hairpin DNA Probe Coupled with Hybridization Chain Reaction for Sensitive DNA Detection.

    Science.gov (United States)

    Song, Luna; Zhang, Yonghua; Li, Junling; Gao, Qiang; Qi, Honglan; Zhang, Chengxiao

    2016-04-01

    An enzyme-free signal amplification-based assay for DNA detection was developed using fluorescent hairpin DNA probes coupled with hybridization chain reaction (HCR). The hairpin DNAs were designed to contain abasic sites in the stem moiety. Non-covalent labeling of the hairpin DNAs was achieved when a fluorescent ligand was bound to the abasic sites through hydrogen bonding with the orphan cytosine present on the complementary strand, accompanied by quench of ligand fluorescence. As a result, the resultant probes, the complex formed between the hairpin DNA and ligand, showed almost no fluorescence. Upon hybridization with target DNA, the probe underwent a dehybridization of the stem moiety containing an abasic site. The release of ligand from the abasic site to the solution resulted in an effective fluorescent enhancement, which can be used as a signal. Compared with a sensing system without HCR, a 20-fold increase in the sensitivity was achieved using the sensing system with HCR. The fluorescent intensity of the sensing system increased with the increase in target DNA concentration from 0.5 nM to 100 nM. A single mismatched target ss-DNA could be effectively discriminated from complementary target DNA. Genotyping of a G/C single-nucleotide polymorphism of polymerase chain reaction (PCR) products was successfully demonstrated with the sensing system. Therefore, integrating HCR strategy with non-covalent labeling of fluorescent hairpin DNA probes provides a sensitive and cost-effective DNA assay. © The Author(s) 2016.

  18. Resident Reactions to Person-Centered Communication by Long-Term Care Staff.

    Science.gov (United States)

    Savundranayagam, Marie Y; Sibalija, Jovana; Scotchmer, Emma

    2016-09-01

    Long-term care staff caregivers who are person centered incorporate the life history, preferences, and feelings of residents with dementia during care interactions. Communication is essential for person-centered care. However, little is known about residents' verbal reactions when staff use person-centered communication. Accordingly, this study investigated the impact of person-centered communication and missed opportunities for such communication by staff on resident reactions. Conversations (N = 46) between staff-resident dyads were audio-recorded during routine care tasks over 12 weeks. Staff utterances were coded for person-centered communication and missed opportunities. Resident utterances were coded for positive reactions, such as cooperation, and negative reactions, such as distress. Linear regression analyses revealed that the more staff used person-centered communication, the more likely that residents reacted positively. Additionally, the more missed opportunities in a conversation, the more likely that the residents reacted negatively. Conversation illustrations elaborate on the quantitative findings and implications for staff training are discussed. © The Author(s) 2016.

  19. Investigations of reactions between pure refractory metals and light gases with the field ion microscope and atom probe

    International Nuclear Information System (INIS)

    Krautz, E.; Haiml, G.

    1989-01-01

    The initial stages of selected reactions of the refractory metals tungsten, niobium and tantalum with hydrogen, oxygen, nitrogen and methane have been studied with the field ion microscope in atomic resolution whereby the composition of single net planes converages and surface zones could absolutely be analyzed with the atom probe by using field desorption under defined conditions at low temperatures. 14 refs., 9 figs. (Author)

  20. Ultraselective electrochemiluminescence biosensor based on locked nucleic acid modified toehold-mediated strand displacement reaction and junction-probe.

    Science.gov (United States)

    Zhang, Xi; Zhang, Jing; Wu, Dongzhi; Liu, Zhijing; Cai, Shuxian; Chen, Mei; Zhao, Yanping; Li, Chunyan; Yang, Huanghao; Chen, Jinghua

    2014-12-07

    Locked nucleic acid (LNA) is applied in toehold-mediated strand displacement reaction (TMSDR) to develop a junction-probe electrochemiluminescence (ECL) biosensor for single-nucleotide polymorphism (SNP) detection in the BRCA1 gene related to breast cancer. More than 65-fold signal difference can be observed with perfectly matched target sequence to single-base mismatched sequence under the same conditions, indicating good selectivity of the ECL biosensor.

  1. Vasovagal reactions in whole blood donors at three REDS-II blood centers in Brazil.

    OpenAIRE

    Gonçalez, TT; Sabino, EC; Schlumpf, KS; Wright, DJ; Leao, S; Sampaio, D; Takecian, PL; Proietti, AB; Murphy, E; Busch, M; Custer, B; NHLBI Retrovirus Epidemiology Donor Study-II REDS-II, International Component,

    2012-01-01

    In Brazil little is known about adverse reactions during donation and the donor characteristics that may be associated with such events. Donors are offered snacks and fluids before donating and are required to consume a light meal after donation. For these reasons the frequency of reactions may be different than those observed in other countries.A cross-sectional study was conducted of eligible whole blood donors at three large blood centers located in Brazil between July 2007 and December 20...

  2. Vasovagal reactions in whole blood donors at 3 REDS-II blood centers in Brazil

    Science.gov (United States)

    Goncalez, T. T.; Sabino, E. C.; Schlumpf, K.S.; Wright, D.J.; Leao, S.; Sampaio, D.; Takecian, P. L.; Carneiro-Proietti, AB; Murphy, E.; Busch, M.; Custer, B.

    2013-01-01

    Background In Brazil little is known about adverse reactions during donation and the donor characteristics that may be associated with such events. Donors are offered snacks and fluids prior to donating and are required to consume a light meal after donation. For these reasons the frequency of reactions may be different than those observed in other countries. Methods A cross-sectional study was conducted of eligible whole blood donors at three large blood centers located in Brazil between July 2007 and December 2009. Vasovagal reactions (VVRs) along with donor demographic and biometric data were collected. Reactions were defined as any presyncopal or syncopal event during the donation process. Multivariable logistic regression was performed to identify predictors of VVRs. Results Of 724,861 donor presentations, 16,129 (2.2%) VVRs were recorded. Rates varied substantially between the three centers: 53, 290 and 381 per 10,000 donations in Recife, São Paulo and Belo Horizonte, respectively. Although the reaction rates varied, the donor characteristics associated with VVRs were similar [younger age (18–29), replacement donors, first time donors, low estimated blood volume (EBV)]. In multivariable analysis controlling for differences between the donor populations in each city younger age, first-time donor status and lower EBV were the factors most associated with reactions. Conclusion Factors associated with VVRs in other locations are also evident in Brazil. The difference in VVR rates between the three centers might be due to different procedures for identifying and reporting the reactions. Potential interventions to reduce the risk of reactions in Brazil should be considered. PMID:22073941

  3. Biological diversity of photosynthetic reaction centers and the solid-state photo-CIDNP effect

    NARCIS (Netherlands)

    Roy, Esha

    2007-01-01

    Photosynthetic reaction centers (RCs) from plants, heliobacteria and green sulphur bacteria has been investigated with photochemically induced dynamic nuclear polarization (photo-CIDNP) MAS NMR. In photosystem (PS) I of spinach, all signals appear negative which is proposed by a predominance of the

  4. The effects of light-induced reduction of the photosystem II reaction center

    Czech Academy of Sciences Publication Activity Database

    Kutý, Michal

    2009-01-01

    Roč. 8, č. 15 (2009), s. 923-933 ISSN 1610-2940 R&D Projects: GA MŠk(CZ) LC06010 Institutional research plan: CEZ:AV0Z60870520 Keywords : Photosystem II * Reaction center * Pheophytin Subject RIV: CE - Biochemistry Impact factor: 2.336, year: 2009

  5. Functional LH1 antenna complexes influence electron transfer in bacterial photosynthetic reaction centers

    NARCIS (Netherlands)

    Visschers, R.W.; Vulto, S.I.E.; Jones, M.R.; van Grondelle, R.; Kraayenhof, R.

    1999-01-01

    The effect of the light harvesting 1 (LH1) antenna complex on the driving force for light-driven electron transfer in the Rhodobacter sphaeroides reaction center has been examined. Equilibrium redox titrations show that the presence of the LH1 antenna complex influences the free energy change for

  6. Functional LH1 antenna complexes influence electron transfer in bacterial photosynthetic reaction centers.

    NARCIS (Netherlands)

    Visschers, R.W.; Vulto, S.I.E.; Jones, M.R.; van Grondelle, R.; Kraayenhof, R.

    1999-01-01

    The effect of the light harvesting 1 (LH1) antenna complex on the driving force for light-driven electron transfer in the Rhodobacter sphaeroides reaction center has been examined. Equilibrium redox titrations show that the presence of the LH1 antenna complex influences the free energy change for

  7. Reactions of carbon radicals generated by 1,5-transposition of reactive centers

    Directory of Open Access Journals (Sweden)

    ZIVORAD CEKOVIC

    2005-03-01

    Full Text Available Radical intermediates can undergo specific reactions, such as intramolecular rearrangements, i.e., the transpositions of radical centers, which are not known in classical ionic organic reactions. 1,5-Transposition of a radical center to a non-activated carbon atom are of great synthetic importance. It can be successfully applied for the introduction of different functional groups (oxygen, nitrogen, sulfur, halogens onto a carbon atom remote from the present functional group. In addition to functionalization of a remote non-activated carbon atom, the formation of new C-C bonds on the d-carbon atom have also been achieved. 1,5-Transposition of the radical centers takes place from alkoxyl, aminyl and carbon radicals to a remote carbon atom. Relocation of the radical centers preferentially involves 1,5-transfer of a hydrogen atom, although migrations of some other groups are known. The reactions of the carbon radical generated by 1,5-relocation of the radical center are presented and their synthetic applications are reviewed.

  8. Molar extinction coefficients and other properties of an improved reaction center preparation from Rhodopseudomonas viridis

    Energy Technology Data Exchange (ETDEWEB)

    Clayton, R.K.; Clayton, B.J.

    1978-01-01

    Reaction centers have been purified from chromatophores of Rhodopseudomonas viridis by treatment with lauryl dimethyl amine oxide followed by hydroxyapatite chromatography and precipitation with ammonium sulfate. The absorption spectrum at low temperature shows bands at 531 and 543 nm, assigned to two molecules of bacteriopheophytin b. The 600 nm band of bacteriochlorophyll b is resolved at low temperature into components at 601 and 606.5 nm. At room temperature the light-induced difference spectrum shows a negative band centered at 615 nm, where the absorption spectrum shows only a week shoulder adjacent to the 600 nm band. The fluorescence spectrum shows a band at 1000 nm and no fluorescence corresponding to the 830 nm absorption band. Two molecules of cytochrome 558 and three of cytochrome 552 accompany each reaction center. The differential extinction coefficient (reduced minus oxidized) of cytochrome 558 nm was estimated as 20 +- 2 mM/sup -1/.cm/sup -1/ through a coupled reaction with equine cytochrome c. The extinction coefficient of reaction centers at 960 nm was determined to be 123 +- 25 mM/sup -1/.cm/sup -1/ by measuring the light-induced bleaching of P-960 and the coupled oxidation of cytochrome 558. The corresponding extinction coefficient at 830 nm is 300 +- 65 mM/sup -1/.cm/sup -1/. The absorbance ratio ..cap alpha../sub 280nm/..cap alpha../sub 830nm/ in our preparations was 2.1, and there was 190 kg protein per mol of reaction centers. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed three major components of apparent molecular weights 31,000, 37,000, and 41,000.

  9. Carbon-13 Labeling Used to Probe Cure and Degradation Reactions of High- Temperature Polymers

    Science.gov (United States)

    Meador, Mary Ann B.; Johnston, J. Christopher

    1998-01-01

    High-temperature, crosslinked polyimides are typically insoluble, intractible materials. Consequently, in these systems it has been difficult to follow high-temperature curing or long-term degradation reactions on a molecular level. Selective labeling of the polymers with carbon-13, coupled with solid nuclear magnetic resonance spectrometry (NMR), enables these reactions to be followed. We successfully employed this technique to provide insight into both curing and degradation reactions of PMR-15, a polymer matrix resin used extensively in aircraft engine applications.

  10. Electrochemical probing into the active sites of graphitic-layer encapsulated iron oxygen reduction reaction electrocatalysts

    DEFF Research Database (Denmark)

    Zhong, Lijie; Jensen, Jens Oluf; Cleemann, Lars Nilausen

    2018-01-01

    is still unclear compared with the well-recognized surface coordinated FeNx/C structure. Using the strong complexing effect of the iron component with anions, cyanide (CN−) in alkaline and thiocyanate (SCN−) in acidic media, the metal containing active sites are electrochemically probed. Three...

  11. Probing the structure of unstable nuclei through the recoiled proton tagged knockout reaction

    International Nuclear Information System (INIS)

    Ye, Y.; Cao, Z.; Jiang, D.

    2010-01-01

    Recoiled proton tagged knockout reaction experiments were carried-out for 8 He at 82,5 MeV/u in RIKEN and for 6 He at 65 MeV/u in Lanzhou. The very preliminary results for the distinguish of the reaction mechanism are presented and compared to the kinematics calculation. (authors)

  12. Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chen Li [Department of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Goettingen (Germany); Ueta, Hirokazu; Beck, Rainer D. [Laboratoire de Chimie Physique Moleculaire, Ecole Polytechnique Federale de Lausanne (Switzerland); Bisson, Regis [Aix-Marseille Universite, PIIM, CNRS, UMR 7345, 13397 Marseille (France)

    2013-05-15

    We report the design and characterization of a new molecular-beam/surface-science apparatus for quantum state-resolved studies of gas/surface reaction dynamics combining optical state-specific reactant preparation in a molecular beam by rapid adiabatic passage with detection of surface-bound reaction products by reflection absorption infrared spectroscopy (RAIRS). RAIRS is a non-invasive infrared spectroscopic detection technique that enables online monitoring of the buildup of reaction products on the target surface during reactant deposition by a molecular beam. The product uptake rate obtained by calibrated RAIRS detection yields the coverage dependent state-resolved reaction probability S({theta}). Furthermore, the infrared absorption spectra of the adsorbed products obtained by the RAIRS technique provide structural information, which help to identify nascent reaction products, investigate reaction pathways, and determine branching ratios for different pathways of a chemisorption reaction. Measurements of the dissociative chemisorption of methane on Pt(111) with this new apparatus are presented to illustrate the utility of RAIRS detection for highly detailed studies of chemical reactions at the gas/surface interface.

  13. Using muonium to probe the kinetics of the reaction between the H atom and OH"- in superheated water

    International Nuclear Information System (INIS)

    Ghandi, K.; Alcorn, C.; Brodovitch, J.-C.; Driedger, E.; Mozafari, M.; Percival, P.W.

    2011-01-01

    Operation of a supercritical-water-cooled nuclear reactor requires knowledge of water chemistry over a wide range of conditions. The considerable knowledge gap for conditions above the operating temperature of current-generation CANDU reactors is the target of this study. Since the H atom is difficult to probe at the desired temperatures and pressures, muonium is used as an alternative. In the current CANDU reactors, coolant pH is controlled using LiOH. We are studying how the rate constants for the reaction of muonium with LiOH and NaOH change with temperature and pressure. (author)

  14. Using muonium to probe the kinetics of the reaction between the H atom and OH{sup -} in superheated water

    Energy Technology Data Exchange (ETDEWEB)

    Ghandi, K.; Alcorn, C. [Mount Allison Univ., Sackville, NB (Canada); Brodovitch, J.-C. [Simon Fraser Univ., Burnaby, BC (Canada); Driedger, E. [Mount Allison Univ., Sackville, NB (Canada); Mozafari, M. [Simon Fraser Univ., Burnaby, BC (Canada); Percival, P.W. [Simon Fraser Univ., Burnaby, BC (Canada); TRIUMF, Vancouver, BC (Canada)

    2011-07-01

    Operation of a supercritical-water-cooled nuclear reactor requires knowledge of water chemistry over a wide range of conditions. The considerable knowledge gap for conditions above the operating temperature of current-generation CANDU reactors is the target of this study. Since the H atom is difficult to probe at the desired temperatures and pressures, muonium is used as an alternative. In the current CANDU reactors, coolant pH is controlled using LiOH. We are studying how the rate constants for the reaction of muonium with LiOH and NaOH change with temperature and pressure. (author)

  15. A Fluorescent Molecular Probe for the Detection of Hydrogen Based on Oxidative Addition Reactions with Crabtree-Type Hydrogenation Catalysts.

    Science.gov (United States)

    Kos, Pavlo; Plenio, Herbert

    2015-11-02

    A Crabtree-type Ir(I) complex tagged with a fluorescent dye (bodipy) was synthesized. The oxidative addition of H2 converts the weakly fluorescent Ir(I) complex (Φ=0.038) into a highly fluorescent Ir(III) species (Φ=0.51). This fluorogenic reaction can be utilized for the detection of H2 and to probe the oxidative addition step in the catalytic hydrogenation of olefins. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Multi-nucleon transfer: a probe to investigate the reaction mechanism around the barrier

    International Nuclear Information System (INIS)

    Mandal, Samit K.

    2014-01-01

    The investigation of multi-nucleon transfer mechanism offers valuable information on the pairing interactions that enhance the transfer of nucleon pairs across heavy ions involved in the reaction. These reactions are also a useful tool to study exotic nuclei far from the stability line, which can be explored with the new generation radioactive beam facility. In this talk, multi-nucleon transfer reaction mechanisms between heavy ions and their effect on the reaction dynamics around the coulomb barrier energies have been discussed. Experimental results will be presented with a semi classical description of multi nucleon transfer reaction calculation. One and two nucleon transfer cross sections reproduced using a quantum mechanical coupled channel calculations will also be discussed. A feasibility of investigation of multi-nucleon transfer mechanism to explore the pairing correlation at moderate spin states with radioactive beams will be discussed. (author)

  17. High-pressure modulation of the structure of the bacterial photochemical reaction center at physiological and cryogenic temperatures

    Science.gov (United States)

    Timpmann, Kõu; Kangur, Liina; Lõhmus, Ants; Freiberg, Arvi

    2017-07-01

    The optical absorption and fluorescence response to external high pressure of the reaction center membrane chromoprotein complex from the wild-type non-sulfur photosynthetic bacterium Rhodobacter sphaeroides was investigated using the native pigment cofactors as local molecular probes of the reaction center structure at physiological (ambient) and cryogenic (79 K) temperatures. In detergent-purified complexes at ambient temperature, abrupt blue shift and accompanied broadening of the special pair band was observed at about 265 MPa. These reversible in pressure features were assigned to a pressure-induced rupture of a lone hydrogen bond that binds the photo-chemically active L-branch primary electron donor bacteriochlorophyll cofactor to the surrounding protein scaffold. In native membrane-protected complexes the hydrogen bond rupture appeared significantly restricted and occurred close to about 500 MPa. The free energy change associated with the rupture of the special pair hydrogen bond in isolate complexes was estimated to be equal to about 12 kJ mol-1. In frozen samples at cryogenic temperatures the hydrogen bond remained apparently intact up to the maximum utilized pressure of 600 MPa. In this case, however, heterogeneous spectral response of the cofactors from the L-and M-branches was observed due to anisotropic build-up of the protein structure. While in solid phase, the special pair fluorescence as a function of pressure exactly followed the respective absorption spectrum at a constant Stokes shift, at ambient temperature, the two paths began to deviate strongly from one other at the hydrogen bond rupture pressure. This effect was tentatively interpreted by different emission properties of hydrogen-bound and hydrogen-unbound special pair exciton states.

  18. Kinetics of the reaction between H· and superheated water probed with muonium

    Energy Technology Data Exchange (ETDEWEB)

    Alcorn, C. [Mount Allison Univ., Sackville, NB (Canada); Brodovitch, J.-C. [Simon Fraser Univ., Burnaby, BC (Canada); Ghandi, K.; Kennedy, A. [Mount Allison Univ., Sackville, NB (Canada); Percival, P.W. [Simon Fraser Univ., Burnaby, BC (Canada); TRIUMF, Vancouver, BC (Canada); Smith, M. [Mount Allison Univ., Sackville, NB (Canada)

    2011-07-01

    Safe operation of a supercritical water cooled reactor requires knowledge of the reaction kinetics of transient species formed by the radiolysis of water in the temperature range 300-650{sup o}C. By using a light isotope of the H·atom, it is possible to study its chemistry in water over this range of temperatures. Arguably, the most important reaction to study is that of the H·atom with the bulk solvent. This reaction could provide an in situ source of H{sub 2} gas, which is added to CANDU reactors to suppress oxidative corrosion. The work described here concerns studies of the reaction of muonium with H{sub 2}O and D{sub 2}O at temperatures up to 450{sup o}C.

  19. Kinetics of the reaction between H· and superheated water probed with muonium

    International Nuclear Information System (INIS)

    Alcorn, C.; Brodovitch, J.-C.; Ghandi, K.; Kennedy, A.; Percival, P.W.; Smith, M.

    2011-01-01

    Safe operation of a supercritical water cooled reactor requires knowledge of the reaction kinetics of transient species formed by the radiolysis of water in the temperature range 300-650"oC. By using a light isotope of the H·atom, it is possible to study its chemistry in water over this range of temperatures. Arguably, the most important reaction to study is that of the H·atom with the bulk solvent. This reaction could provide an in situ source of H_2 gas, which is added to CANDU reactors to suppress oxidative corrosion. The work described here concerns studies of the reaction of muonium with H_2O and D_2O at temperatures up to 450"oC.

  20. Probing the short range behavior of nuclei with high PT photo- and electro-nuclear reactions

    International Nuclear Information System (INIS)

    Laget, J.M.

    1990-01-01

    The short range behavior of the nucleus and the use of the nucleus as a filter are studied. Special emphasis is given to photon and hadron induced reactions. The components of the nuclear wave function are described. The evidences of hard scattering processes in reactions induced by real photons as well as by hadrons on free nucleus are reviewed. The spin observables are also investigated. The perspectives opened by these studies in the nuclear environment are considered

  1. Kinetics of intercalation of fluorescent probes in magnesium-aluminium layered double hydroxide within a multiscale reaction-diffusion framework

    Science.gov (United States)

    Saliba, Daniel; Al-Ghoul, Mazen

    2016-11-01

    We report the synthesis of magnesium-aluminium layered double hydroxide (LDH) using a reaction-diffusion framework (RDF) that exploits the multiscale coupling of molecular diffusion with chemical reactions, nucleation and growth of crystals. In an RDF, the hydroxide anions are allowed to diffuse into an organic gel matrix containing the salt mixture needed for the precipitation of the LDH. The chemical structure and composition of the synthesized magnesium-aluminium LDHs are determined using powder X-ray diffraction (PXRD), thermo-gravimetric analysis, differential scanning calorimetry, solid-state nuclear magnetic resonance (SSNMR), Fourier transform infrared and energy dispersive X-ray spectroscopy. This novel technique also allows the investigation of the mechanism of intercalation of some fluorescent probes, such as the neutral three-dimensional rhodamine B (RhB) and the negatively charged two-dimensional 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), using in situ steady-state fluorescence spectroscopy. The incorporation of these organic dyes inside the interlayer region of the LDH is confirmed via fluorescence microscopy, solid-state lifetime, SSNMR and PXRD. The activation energies of intercalation of the corresponding molecules (RhB and HPTS) are computed and exhibit dependence on the geometry of the involved probe (two or three dimensions), the charge of the fluorescent molecule (anionic, cationic or neutral) and the cationic ratio of the corresponding LDH. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.

  2. Geometric phase and quantum interference in photosynthetic reaction center: Regulation of electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yuming, E-mail: ymsun@ytu.edu.cn; Su, Yuehua; Dai, Zhenhong; Wang, WeiTian

    2016-10-20

    Photosynthesis is driven by electron transfer in reaction centers in which the functional unit is composed of several simple molecules C{sub 2}-symmetrically arranged into two branches. In view of quantum mechanism, both branches are possible pathways traversed by the transferred electron. Due to different evolution of spin state along two pathways in transmembrane electric potential (TEP), quantum state of the transferred electron at the bridged site acquires a geometric phase difference dependent on TEP, the most efficient electron transport takes place in a specific range of TEP beyond which electron transfer is dramatically suppressed. What’s more, reaction center acts like elaborately designed quantum device preparing polarized spin dependent on TEP for the transferred electron to regulate the reduction potential at bridged site. In brief, electron transfer generates the TEP, reversely, TEP modulates the efficiency of electron transfer. This may be an important approach to maintaining an appreciable pH environment in photosynthesis.

  3. Neutron-proton bremsstrahlung from intermediate energy heavy-ion reactions as a probe of the nuclear symmetry energy?

    International Nuclear Information System (INIS)

    Yong, G.-C.; Li Baoan; Chen Liewen

    2008-01-01

    Hard photons from neutron-proton bremsstrahlung in intermediate energy heavy-ion reactions are examined as a potential probe of the nuclear symmetry energy within a transport model. Effects of the symmetry energy on the yields and spectra of hard photons are found to be generally smaller than those due to the currently existing uncertainties of both the in-medium nucleon-nucleon cross sections and the photon production probability in the elementary process pn→pnγ. Very interestingly, nevertheless, the ratio of hard photon spectra R 1/2 (γ) from two reactions using isotopes of the same element is not only approximately independent of these uncertainties but also quite sensitive to the symmetry energy. For the head-on reactions of 132 Sn + 124 Sn and 112 Sn + 112 Sn at E beam /A=50 MeV, for example, the R 1/2 (γ) displays a rise up to 15% when the symmetry energy is reduced by about 20% at ρ=1.3ρ 0 which is the maximum density reached in these reactions

  4. Nuclear Reaction and Structure Databases of the National Nuclear Data Center

    International Nuclear Information System (INIS)

    Pritychenko, B.; Arcilla, R.; Herman, M. W.; Oblozinsky, P.; Rochman, D.; Sonzogni, A. A.; Tuli, J. K.; Winchell, D. F.

    2006-01-01

    The National Nuclear Data Center (NNDC) collects, evaluates, and disseminates nuclear physics data for basic research and applied nuclear technologies. In 2004, the NNDC migrated all databases into modern relational database software, installed new generation of Linux servers and developed new Java-based Web service. This nuclear database development means much faster, more flexible and more convenient service to all users in the United States. These nuclear reaction and structure database developments as well as related Web services are briefly described

  5. Functional type 2 photosynthetic reaction centers found in the rare bacterial phylum Gemmatimonadetes

    OpenAIRE

    Zeng, Yonghui; Feng, Fuying; Medová, Hana; Dean, Jason; Koblížek, Michal

    2014-01-01

    Photosynthesis is one of the most fundamental biological processes on Earth. To date, species capable of performing (bacterio)chlorophyll-based phototrophy have been reported in six bacterial phyla. Here we report a phototrophic bacterium belonging to the rare and understudied phylum Gemmatimonadetes. This strain, isolated from a freshwater lake in the Gobi Desert, contains fully functional photosynthetic reaction centers. Its photosynthesis genes appear to originate from an ancient horizonta...

  6. Electrostatic dominoes: long distance propagation of mutational effects in photosynthetic reaction centers of Rhodobacter capsulatus.

    Science.gov (United States)

    Sebban, P; Maróti, P; Schiffer, M; Hanson, D K

    1995-07-04

    Two point mutants from the purple bacterium Rhodobacter capsulatus, both modified in the M protein of the photosynthetic reaction center, have been studied by flash-induced absorbance spectroscopy. These strains carry either the M231Arg --> Leu or M43ASN --> Asp mutations, which are located 9 and 15 A, respectively, from the terminal electron acceptor QB. In the wild-type Rb. sphaeroides structure, M231Arg is involved in a conserved salt bridge with H125Glu and H232Glu and M43Asn is located among several polar residues that form or surround the QB binding site. These substitutions were originally uncovered in phenotypic revertants isolated from the photosynthetically incompetent L212Glu-L213Asp --> Ala-Ala site-specific double mutant. As second-site suppressor mutations, they have been shown to restore the proton transfer function that is interrupted in the L212Ala-L213Ala double mutant. The electrostatic effects that are induced in reaction centers by the M231Arg --> Leu and M43Asn --> Asp substitutions are roughly the same in either the double-mutant or wild-type backgrounds. In a reaction center that is otherwise wild type in sequence, they decrease the free energy gap between the QA- and QB- states by 24 +/- 5 and 45 +/- 5 meV, respectively. The pH dependences of K2, the QA-QB QAQB- equilibrium constant, are altered in reaction centers that carry either of these substitutions, revealing differences in the pKas of titratable groups compared to the wild type.(ABSTRACT TRUNCATED AT 250 WORDS)

  7. A single residue controls electron transfer gating in photosynthetic reaction centers

    Czech Academy of Sciences Publication Activity Database

    Shlyk, O.; Samish, I.; Matěnová, M.; Dulebo, A.; Poláková, H.; Kaftan, David; Scherz, A.

    2017-01-01

    Roč. 7, MAR 16 (2017), s. 1-13, č. článku 44580. ISSN 2045-2322 R&D Projects: GA ČR GA15-00703S; GA MŠk(CZ) LO1416 Institutional support: RVO:61388971 Keywords : BACTERIAL REACTION CENTERS * INDUCED STRUCTURAL-CHANGES * ATOMIC-FORCE MICROSCOPE Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 4.259, year: 2016

  8. Model of deep centers formation and reactions in electron irradiated InP

    International Nuclear Information System (INIS)

    Sibille, A.; Suski, J.; Gilleron, M.

    1986-01-01

    We present a model of the production of deep centers and their reactions following electron irradiations in InP. We propose that the dominant hole traps in p-InP and electron traps in p + n InP junctions are complexes between shallow acceptors and a common intrinsic entity, the phosphorus interstitial or vacancy. The reactions observed below and above room temperature are then due to a local mobility of this entity, which can be obtained as well by thermal as by electronic stimulation of the reactions. This model implies the long-range migration (at least down to 16 K) of this entity, and explains the strongly different behavior of n-InP compared to p-InP samples

  9. Incidence of transfusion reactions: a multi-center study utilizing systematic active surveillance and expert adjudication

    Science.gov (United States)

    Hendrickson, Jeanne E.; Roubinian, Nareg H.; Chowdhury, Dhuly; Brambilla, Don; Murphy, Edward L.; Wu, Yanyun; Ness, Paul M.; Gehrie, Eric A.; Snyder, Edward L.; Hauser, R. George; Gottschall, Jerome L.; Kleinman, Steve; Kakaiya, Ram; Strauss, Ronald G.

    2017-01-01

    Background Prevalence estimates of serious hazards of transfusion vary widely. We hypothesized that the current reporting infrastructure in the United States fails to capture many transfusion reactions, and undertook a multi-center study utilizing active surveillance, data review, and adjudication to test this hypothesis. Study Design and Methods A retrospective record review was completed for a random sample of 17% of all inpatient transfusion episodes over 6 months at 4 academic tertiary care hospitals, with an episode defined as all blood products released to a patient in 6 hours. Data were recorded by trained clinical research nurses, and serious reactions were adjudicated by a panel of transfusion medicine experts. Results Of 4857 transfusion episodes investigated, 1.1% were associated with a serious reaction. Transfusion associated circulatory overload (TACO) was the most frequent serious reaction noted, being identified in 1% of transfusion episodes. Despite clinical notes describing a potential transfusion association in 59% of these cases, only 5.1% were reported to the transfusion service. Suspected transfusion related acute lung injury (TRALI/possible TRALI), anaphylactic, and hypotensive reactions were noted in 0.08%, 0.02%, and 0.02% of transfusion episodes. Minor reactions, including febrile non-hemolytic and allergic, were noted in 0.62% and 0.29% of transfusion episodes, with 30–50% reported to the transfusion service. Conclusion Underreporting of cardiopulmonary transfusion reactions is striking among academic, tertiary care hospitals. Complete and accurate reporting is essential to identify, define, establish pathogenesis, and mitigate/treat transfusion reactions. A better understanding of the failure to report may improve the accuracy of passive reporting systems. PMID:27460200

  10. Probing the Rate-Determining Step of the Claisen-Schmidt Condensation by Competition Reactions

    Science.gov (United States)

    Mak, Kendrew K. W.; Chan, Wing-Fat; Lung, Ka-Ying; Lam, Wai-Yee; Ng, Weng-Cheong; Lee, Siu-Fung

    2007-01-01

    Competition experiments are a useful tool for preliminary study of the linear free energy relationship of organic reactions. This article describes a physical organic experiment for upper-level undergraduates to identify the rate-determining step of the Claisen-Schmidt condensation of benzaldehyde and acetophenone by studying the linear free…

  11. Kinetics of the reaction between H· and superheated water probed with muonium

    International Nuclear Information System (INIS)

    Alcorn, Chris D.; Brodovitch, Jean-Claude; Percival, Paul W.; Smith, Marisa; Ghandi, Khashayar

    2014-01-01

    Highlights: • Rate constants for reactions of H with water resolve a controversy. • H reacts with superheated water via two channels. • The findings have important implications for the safety of some nuclear power reactors. - Abstract: Safe operation of supercritical water-cooled reactors requires knowledge of the kinetics of transient species formed by the radiolysis of water in the range 300–650 °C. Using muonium, it is possible to study aqueous H · atom chemistry over this temperature range. An important reaction to study is that of the H · atom with water itself, because it is a potential source of molecular H 2 . The concentration of H 2 is important to plant coolant chemistry, as H 2 is currently added to suppress oxidative corrosion in CANDU reactors. The reaction of muonium with H 2 O and D 2 O was studied experimentally up to 450 °C, and also via quantum chemical computations to investigate possible isotope effects. Our results suggest that although the H · atom abstraction from H 2 O is important at temperatures above 300 °C, the electron-producing channel (H · + H 2 O ⇌ H 3 O + + e aq - ) is significant at temperatures up to 300 °C, and becomes the dominant reaction channel at lower temperatures

  12. Probing short-range correlations in asymmetric nuclei with quasi-free pair knockout reactions

    Science.gov (United States)

    Stevens, Sam; Ryckebusch, Jan; Cosyn, Wim; Waets, Andreas

    2018-02-01

    Short-range correlations (SRC) in asymmetric nuclei with an unusual neutron-to-proton ratio can be studied with quasi-free two-nucleon knockout processes following the collision between accelerated ions and a proton target. We derive an approximate factorized cross section for those SRC-driven p (A ,p‧N1N2) reactions. Our reaction model hinges on the factorization properties of SRC-driven A (e ,e‧N1N2) reactions for which strong indications are found in theory-experiment comparisons. In order to put our model to the test we compare its predictions with results of 12C (p ,p‧ pn) measurements conducted at Brookhaven National Laboratory (BNL) and find a fair agreement. The model can also reproduce characteristic features of SRC-driven two-nucleon knockout reactions, like back-to-back emission of the correlated nucleons. We study the asymmetry dependence of nuclear SRC by providing predictions for the ratio of proton-proton to proton-neutron knockout cross sections for the carbon isotopes 9-15C thereby covering neutron excess values (N - Z) / Z between -0.5 and +0.5.

  13. Kinetics of the reaction between H{sup ·} and superheated water probed with muonium

    Energy Technology Data Exchange (ETDEWEB)

    Alcorn, Chris D. [Department of Chemistry and Biochemistry, Mount Allison University, Sackville, New Brunswick E4L 1G8 (Canada); Brodovitch, Jean-Claude [Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Percival, Paul W. [Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3 (Canada); Smith, Marisa [Department of Chemistry and Biochemistry, Mount Allison University, Sackville, New Brunswick E4L 1G8 (Canada); Ghandi, Khashayar, E-mail: kghandi@mta.ca [Department of Chemistry and Biochemistry, Mount Allison University, Sackville, New Brunswick E4L 1G8 (Canada)

    2014-05-19

    Highlights: • Rate constants for reactions of H with water resolve a controversy. • H reacts with superheated water via two channels. • The findings have important implications for the safety of some nuclear power reactors. - Abstract: Safe operation of supercritical water-cooled reactors requires knowledge of the kinetics of transient species formed by the radiolysis of water in the range 300–650 °C. Using muonium, it is possible to study aqueous H{sup ·} atom chemistry over this temperature range. An important reaction to study is that of the H{sup ·} atom with water itself, because it is a potential source of molecular H{sub 2}. The concentration of H{sub 2} is important to plant coolant chemistry, as H{sub 2} is currently added to suppress oxidative corrosion in CANDU reactors. The reaction of muonium with H{sub 2}O and D{sub 2}O was studied experimentally up to 450 °C, and also via quantum chemical computations to investigate possible isotope effects. Our results suggest that although the H{sup ·} atom abstraction from H{sub 2}O is important at temperatures above 300 °C, the electron-producing channel (H{sup ·} + H{sub 2}O ⇌ H{sub 3}O{sup +} + e{sub aq}{sup -}) is significant at temperatures up to 300 °C, and becomes the dominant reaction channel at lower temperatures.

  14. Reaction (γ,2e) and (e,3e) as probe of electron correlation in atoms

    International Nuclear Information System (INIS)

    Amusia, M.Y.

    1995-01-01

    Cross sections of the (γ,2e) and (e,3e) reactions contain information about the two vacancy-energy spectrum and electron-pair correlations in initial and final states of the target atom. Physical pictures of these processes are presented for two- and many-electron atoms. The simplest mechanisms are discussed, demonstrating some features which await experimental confirmation. Attention is given to high photon energy and the relativistic energy region of these reactions. The energy distribution of outgoing relativistic electrons is qualitatively different from the nonrelativistic case. The origin and types of corrections to the simplest mechanisms, and possible means of their detection, are discussed. In addition, the role of different resonances: shape, giant, autoionizational, and Feshbach-type are considered. Results of calculations are compared with experimental data, mainly on double photoionization cross sections. Different possible objects as targets for the reactions are considered, including negative ions, excited atoms, molecules, and clusters. The modification of these reactions due to photon emission is discussed. The future of the domain is outlined

  15. Reactions (γ,2e) and (e,3e) as probes of electronic correlations in atoms

    International Nuclear Information System (INIS)

    Amusia, M.Ya.

    1993-01-01

    Cross sections of the (γ,2e) and (e,3e) reactions carry information on two vacancy energy spectrum and on electron pair correlations in initial and final states of the target atom. Physical pictures of these processes are presented for two- and many-electron atoms. Simplest mechanisms of them are discussed, demonstrating some features which are waiting for experimental confirmation. Attention is given to high photon energy and even to relativistic energy region of these reactions. The energy distribution of outgoing relativistic electrons is qualitatively different from what it is for the nonrelativistic case. Origin and types of corrections to the simplest mechanisms and possible means of their detection are discussed. Role of different resonances: shape, giant, autoionizational, and Feschbach-type are considered. Results of calculations are compared with experimental data, mainly on double photoionization cross sections. Different possible objects as targets for the reactions are mentioned, including negative ions, excited atoms, molecules and clusters. Modification of the type of these reactions due to rather probable emission of the photon is discussed. Future of the domain is outlined. (orig.)

  16. Initial Dynamics of The Norrish Type I Reaction in Acetone: Probing Wave Packet Motion

    DEFF Research Database (Denmark)

    Brogaard, Rasmus Y.; Sølling, Theis I.; Møller, Klaus Braagaard

    2011-01-01

    The Norrish Type I reaction in the S1 (nπ*) state of acetone is a prototype case of ketone photochemistry. On the basis of results from time-resolved mass spectrometry (TRMS) and photoelectron spectroscopy (TRPES) experiments, it was recently suggested that after excitation the wave packet travels...

  17. Probing α-particle wave functions using (rvec d,α) reactions

    International Nuclear Information System (INIS)

    Crosson, E.R.; Lemieux, S.K.; Ludwig, E.J.; Thompson, W.J.; Bisenberger, M.; Hertenberger, R.; Hofer, D.; Kader, H.; Schiemenz, P.; Graw, G.; Eiro, A.M.; Santos, F.D.

    1993-01-01

    Wave functions of the α particle corresponding to different S- and D-state deuteron-deuteron overlaps, left-angle dd|α right-angle, were investigated using exact finite-range distorted-wave Born-approximation (DWBA) analyses of (rvec d,α) reactions. Cross sections, vector, and tensor-analyzing powers were measured for (rvec d,α) reactions populating the lowest J π =7 + state in 56 Co at bombarding energies E d of 16 and 22 MeV, the lowest 7 + state in 48 Sc at E d =16 MeV, and the lowest 7 + state in 46 Sc at E d =22 MeV. We find that DWBA analyses of tensor-analyzing powers produce satisfactory agreement with the data and that A xx is especially sensitive to the D-state component of α-particle wave functions generated by different realistic nucleon-nucleon interactions

  18. Spin distribution studies: a sensitive probe for in-complete fusion reaction dynamics

    International Nuclear Information System (INIS)

    Singh, Pushpendra P.; Singh, B.P.; Unnati; Sharma, Bhavna; Sharma, Manoj Kumar; Singh, D.; Afzal Ansari, M.; Prasad, R.; Rakesh Kumar; Golda, K.S.; Muralithar, S.; Singh, R.P.; Bhowmik, R.K.; Bhardwaj, H.D.

    2006-01-01

    With the view to get the conclusive information on critical angular momentum involvement for various degrees of incomplete fusion, an in-beam particle-gamma coincidence experiment has been performed in 16 O + 169 Tm system at ≅ 5.6 MeV/nucleon. Spin distributions for different reaction products have been measured by studying the relative population of different levels in a rotational band

  19. Probing the nuclear symmetry energy at high densities with nuclear reactions

    Science.gov (United States)

    Leifels, Y.

    2017-11-01

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

  20. Probing the electronic structure of redox species and direct determination of intrinsic reorganization energies of electron transfer reactions

    International Nuclear Information System (INIS)

    Wang, Xue-Bin; Wang, Lai-Sheng

    2000-01-01

    An experimental technique capable of directly determining the intrinsic reorganization energies of bimolecular electron transfer reactions is described. Appropriate solution phase redox species are prepared in the gas phase using electrospray ionization and probed using photodetachment spectroscopy. Five metal complex anions involved in the Fe 2+ -Fe 3+ redox couple are investigated and the intramolecular reorganization energies are measured directly from spectral features due to removing the most loosely bound 3d electron from the Fe(II)-complexes. The photodetachment spectra also yield electronic structure information about the Fe 2+ -Fe 3+ redox couple and provide a common electronic structure origin for the reducing capability of the Fe(II)-complexes, the most common redox reagents. (c) 2000 American Institute of Physics

  1. TaqMan probe real-time polymerase chain reaction assay for the quantification of canine DNA in chicken nugget.

    Science.gov (United States)

    Rahman, Md Mahfujur; Hamid, Sharifah Bee Abd; Basirun, Wan Jefrey; Bhassu, Subha; Rashid, Nur Raifana Abdul; Mustafa, Shuhaimi; Mohd Desa, Mohd Nasir; Ali, Md Eaqub

    2016-01-01

    This paper describes a short-amplicon-based TaqMan probe quantitative real-time PCR (qPCR) assay for the quantitative detection of canine meat in chicken nuggets, which are very popular across the world, including Malaysia. The assay targeted a 100-bp fragment of canine cytb gene using a canine-specific primer and TaqMan probe. Specificity against 10 different animals and plants species demonstrated threshold cycles (Ct) of 16.13 ± 0.12 to 16.25 ± 0.23 for canine DNA and negative results for the others in a 40-cycle reaction. The assay was tested for the quantification of up to 0.01% canine meat in deliberately spiked chicken nuggets with 99.7% PCR efficiency and 0.995 correlation coefficient. The analysis of the actual and qPCR predicted values showed a high recovery rate (from 87% ± 28% to 112% ± 19%) with a linear regression close to unity (R(2) = 0.999). Finally, samples of three halal-branded commercial chicken nuggets collected from different Malaysian outlets were screened for canine meat, but no contamination was demonstrated.

  2. Japan Nuclear Reaction Data Center (JCPRG), Faculty of Science, Hokkaido University, Steering Committee progress report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-11-15

    The Japan Nuclear Reaction Data Center (JCPRG) was approved as an organisation of Faculty of Science, Hokkaido University and established on April 1, 2007. In addition to nuclear data activities carried out by JCPRG (Japan-Charged Particle Nuclear Reaction Data Group), the centre is concerned with the evaluation of nuclear reaction data in nucleosynthesis in the universe. In order efficiently to compile reaction data obtained by using radioactive ion beam, the centre signed a research contract with RIKEN Nishina Center. We are scanning 16 journals for Japanese charged-particle and photo-nuclear nuclear reaction data compilation. From April 2006 to March 2007, CPND and PhND in 45 references (453 records, 1.83 MB) have been newly compiled for NRDF. Usually new data are released at the JCPRG web site several months prior to EXFOR. Since the 2006 NRDC meeting, we have made 104 new entries and have revised or deleted 142 old entries. Intensive numerical data compilations have been done. These data were shown in tabular form in dissertations which are (partially) published in Journals. About 30 new entries were compiled from these data. We have prepared CINDA batches for CPND published in Japan every half year. Each batch covers 6 issues of each of 4 Japanese journals JPJ, PTP, NST and JNRS. Bibliographies for neutron induced reaction data have been compiled by JAEA Nuclear Data Center as before. A new web-based NRDF search and plot system on MySQL was released in July, 2007. New compilation, which has been finalized for NRDF, but not for EXFOR, can be obtained from this site. DARPE (another NRDF search and plot system written in Perl) is also available at http://www.jcprg.org/darpe/. EXFOR/ENDF (http://www.jcprg.org/exfor/) search and plot system is available. We have also developed following utilities: PENDL (http://www.jcprg.org/endf/) and RENORM (http://www.jcprg.org/renorm). We are developing a new search system of CINDA. This is an extension of EXFOR/ENDF search

  3. Spectroscopic investigation of sulfonate phthalocyanine to probe enzyme reactions for heavy metals detection

    International Nuclear Information System (INIS)

    Chaure, Shweta; Paul, Deepen; Vadagma, Pankaj; Ray, Asim K.

    2010-01-01

    Optical absorption and Raman spectra of the sulfonated copper phthalocyanine (CuTsPc) layer were exploited for detection of cadmium (Cd) contaminants in water. Acetylcholine esterase was immobilized by freely suspending them in calcium alginate microbeads and this gel was then spincoated on the drop cast sulfonated copper phthalocyanine film on a glass substrate to form a bilayer. The inhibition of catalytic reaction between acetylcholine chloride and enzyme due to Cd contaminants was monitored by recording changes in spectra of drop cast CuTsPc as an indicator. The detection limit of cadmium content in water was found to be 1 ppm.

  4. Spectroscopic investigation of sulfonate phthalocyanine to probe enzyme reactions for heavy metals detection

    Energy Technology Data Exchange (ETDEWEB)

    Chaure, Shweta; Paul, Deepen; Vadagma, Pankaj [School of Engineering and Material Science, Queen Mary, University of London, London E1 4NS (United Kingdom); Ray, Asim K., E-mail: a.k.ray@qmul.ac.uk [School of Engineering and Material Science, Queen Mary, University of London, London E1 4NS (United Kingdom)

    2010-01-15

    Optical absorption and Raman spectra of the sulfonated copper phthalocyanine (CuTsPc) layer were exploited for detection of cadmium (Cd) contaminants in water. Acetylcholine esterase was immobilized by freely suspending them in calcium alginate microbeads and this gel was then spincoated on the drop cast sulfonated copper phthalocyanine film on a glass substrate to form a bilayer. The inhibition of catalytic reaction between acetylcholine chloride and enzyme due to Cd contaminants was monitored by recording changes in spectra of drop cast CuTsPc as an indicator. The detection limit of cadmium content in water was found to be 1 ppm.

  5. Probing the interactions of charmed mesons with nuclei in anti p-induced reactions

    International Nuclear Information System (INIS)

    Golubeva, Ye.S.; Cassing, W.; Kondratyuk, L.A.

    2002-01-01

    We study the perspectives of resonant and nonresonant charmed-meson production in anti p+A reactions within the Multiple Scattering Monte Carlo (MSMC) approach. We calculate the production of the resonances Ψ(3770), Ψ(4040) and Ψ(4160) on various nuclei, their propagation and decay to D, anti D, D * , anti DD * , D s , anti D s in the medium and vacuum, respectively. The modifications of the open charm vector mesons in the nuclear medium are found to be rather moderate or even small such that dilepton spectroscopy will require an invariant mass resolution of a few MeV. Furthermore, the elastic and inelastic interactions of the open charm mesons in the medium are taken into account, which can be related to (u, d)-, s- or c-quark exchange with nucleons. It is found that by studying the D/ anti D ratio for low momenta in the laboratory (≤2-2.2 GeV/c) as a function of the target mass A stringent constraints on the c-quark exchange cross-section can be obtained. On the other hand, the ratios D - s /D + s as well as D/D - s and D/D + s at low momenta as a function of A will permit to fix independently the strength of the s-quark exchange reaction in D - s N scattering. (orig.)

  6. Glutathiolactaldehyde as a probe of the overall stereochemical course of glyoxalase-I catalyzed reactions

    International Nuclear Information System (INIS)

    Brush, E.J.; Kozarich, J.W.

    1986-01-01

    The overall stereochemical course of the reactions catalyzed by glyoxalase-I (GX-I) has remained elusive as the substrates are equilibrium mixtures of rapidly interconverting diastereomeric thiohemiacetals. However, with the discovery of inverse substrate processing by Kozarich and coworkers, it is possible to design GX-I substrate analogs that are intrinsically more stable than the thiohemiacetals. Hence, Chari and Kozarich reported that glutathiohydroxyacetone (GHA, GSCH 2 COCH 2 OH) undergoes GX-I catalyzed exchange of the pro-S hydroxymethyl proton with solvent deuterium. Their data suggest that GX-I processes a single diastereomeric thiohemiacetal, and are consistent with a cis-enediol intermediate. To test this hypothesis and to follow the overall stereochemistry on a single substrate, they have prepared glutathiolactaldehyde (GLA, GSCH 2 CHOHCHO) as a potential inverse substrate. Human erythrocyte GX-I catalyzes the isomerization of GLA to GHA as evidenced by UV and NMR spectra of the product. Solvent deuterium is incorporated into the hydroxymethyl position, and NMR data suggest that incorporation is stereospecific. Furthermore, 50% of the expected amount of GHA is produced indicating that only one diastereomer of GLA is processed by GX-I. Identification of the absolute stereochemistry of the substrate diastereomer will lead to a clarification of the overall stereochemical and mechanistic course of GX-I catalyzed reactions

  7. Spectroscopic properties of reaction center pigments in photosystem II core complexes: revision of the multimer model.

    Science.gov (United States)

    Raszewski, Grzegorz; Diner, Bruce A; Schlodder, Eberhard; Renger, Thomas

    2008-07-01

    Absorbance difference spectra associated with the light-induced formation of functional states in photosystem II core complexes from Thermosynechococcus elongatus and Synechocystis sp. PCC 6803 (e.g., P(+)Pheo(-),P(+)Q(A)(-),(3)P) are described quantitatively in the framework of exciton theory. In addition, effects are analyzed of site-directed mutations of D1-His(198), the axial ligand of the special-pair chlorophyll P(D1), and D1-Thr(179), an amino-acid residue nearest to the accessory chlorophyll Chl(D1), on the spectral properties of the reaction center pigments. Using pigment transition energies (site energies) determined previously from independent experiments on D1-D2-cytb559 complexes, good agreement between calculated and experimental spectra is obtained. The only difference in site energies of the reaction center pigments in D1-D2-cytb559 and photosystem II core complexes concerns Chl(D1). Compared to isolated reaction centers, the site energy of Chl(D1) is red-shifted by 4 nm and less inhomogeneously distributed in core complexes. The site energies cause primary electron transfer at cryogenic temperatures to be initiated by an excited state that is strongly localized on Chl(D1) rather than from a delocalized state as assumed in the previously described multimer model. This result is consistent with earlier experimental data on special-pair mutants and with our previous calculations on D1-D2-cytb559 complexes. The calculations show that at 5 K the lowest excited state of the reaction center is lower by approximately 10 nm than the low-energy exciton state of the two special-pair chlorophylls P(D1) and P(D2) which form an excitonic dimer. The experimental temperature dependence of the wild-type difference spectra can only be understood in this model if temperature-dependent site energies are assumed for Chl(D1) and P(D1), reducing the above energy gap from 10 to 6 nm upon increasing the temperature from 5 to 300 K. At physiological temperature, there are

  8. Proton conduction within the reaction centers of Rhodobacter capsulatus: the electrostatic role of the protein.

    OpenAIRE

    Maróti, P; Hanson, D K; Baciou, L; Schiffer, M; Sebban, P

    1994-01-01

    Light-induced charge separation in the photosynthetic reaction center results in delivery of two electrons and two protons to the terminal quinone acceptor QB. In this paper, we have used flash-induced absorbance spectroscopy to study three strains that share identical amino acid sequences in the QB binding site, all of which lack the protonatable amino acids Glu-L212 and Asp-L213. These strains are the photosynthetically incompetent site-specific mutant Glu-L212/Asp-L213-->Ala-L212/Ala-L213 ...

  9. Microfluidic technology platforms for synthesizing, labeling and measuring the kinetics of transport and biochemical reactions for developing molecular imaging probes

    Energy Technology Data Exchange (ETDEWEB)

    Phelps, Michael E. [Univ. of California, Los Angeles, CA (United States)

    2009-09-01

    Radiotracer techniques are used in environmental sciences, geology, biology and medicine. Radiotracers with Positron Emission Tomography (PET) provided biological examinations of ~3 million patients 2008. Despite the success of positron labeled tracers in many sciences, there is limited access in an affordable and convenient manner to develop and use new tracers. Integrated microfluidic chips are a new technology well matched to the concentrations of tracers. Our goal is to develop microfluidic chips and new synthesis approaches to enable wide dissemination of diverse types of tracers at low cost, and to produce new generations of radiochemists for which there are many unfilled jobs. The program objectives are to: 1. Develop an integrated microfluidic platform technology for synthesizing and 18F-labeling diverse arrays of different classes of molecules. 2. Incorporate microfluidic chips into small PC controlled devices (“Synthesizer”) with a platform interfaced to PC for electronic and fluid input/out control. 3. Establish a de-centralized model with Synthesizers for discovering and producing molecular imaging probes, only requiring delivery of inexpensive [18F]fluoride ion from commercial PET radiopharmacies vs the centralized approach of cyclotron facilities synthesizing and shipping a few different types of 18F-probes. 4. Develop a position sensitive avalanche photo diode (PSAPD) camera for beta particles embedded in a microfluidic chip for imaging and measuring transport and biochemical reaction rates to valid new 18F-labeled probes in an array of cell cultures. These objectives are met within a research and educational program integrating radio-chemistry, synthetic chemistry, biochemistry, engineering and biology in the Crump Institute for Molecular Imaging. The Radiochemistry Training Program exposes PhD and post doctoral students to molecular imaging in vitro in cells and microorganisms in microfluidic chips and in vivo with PET, from new technologies

  10. Luminescent materials: probing the excited state of emission centers by spectroscopic methods

    International Nuclear Information System (INIS)

    Mihóková, E; Nikl, M

    2015-01-01

    We review recent methods employed to study the excited state of rare-earth centers in various luminescent and scintillating materials. The focus is on processes that help determine localization of the excited state within the material band gap, namely photoionization and thermally stimulated ionization. Then the tunneling process between the luminescence center and the trapping state is addressed. We describe the experimental implementation of methods recently developed to study these processes. We report theoretical models helping the data interpretation. We also present application to currently investigated materials. (topical review)

  11. Probing the reaction mechanism of IspH protein by x-ray structure analysis

    KAUST Repository

    Gräwert, Tobias

    2009-12-28

    Isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) represent the two central intermediates in the biosynthesis of isoprenoids. The recently discovereddeoxyxylulose 5-phosphate pathway generates a mixture of IPP and DMAPP in its final step by reductive dehydroxylation of 1-hydroxy-2-methyl- 2-butenyl 4-diphosphate. This conversion is catalyzed by IspH protein comprising a central iron-sulfur cluster as electron transfer cofactor in the active site. The five crystal structures of IspH in complex with substrate, converted substrate, products and PPi reported in this article provide unique insights into the mechanism of this enzyme. While IspH protein crystallizes with substrate bound to a [4Fe-4S] cluster, crystals of IspH in complex with IPP, DMAPP or inorganic pyrophosphate feature [3Fe-4S] clusters. The IspH:substrate complex reveals a hairpin conformation of the ligand with the C(1) hydroxyl group coordinated to the unique site in a [4Fe-4S] cluster of aconitase type. The resulting alkoxide complex is coupled to a hydrogen-bonding network, which serves as proton reservoir via a Thr167 proton relay. Prolonged x-ray irradiation leads to cleavage of the C(1)-O bond (initiated by reducing photo electrons). The data suggest a reaction mechanism involving a combination of Lewis-acid activation and proton coupled electron transfer. The resulting allyl radical intermediate can acquire a second electron via the iron-sulfur cluster. The reaction may be terminated by the transfer of a proton from the β-phosphate of the substrate to C(1) (affording DMAPP) or C(3) (affording IPP).

  12. Probing the reaction mechanism of IspH protein by x-ray structure analysis

    KAUST Repository

    Grä wert, Tobias; Span, Ingrid; Eisenreich, Wolfgang; Rohdich, Felix; Eppinger, Jö rg; Bacher, Adelbert; Groll, Michael

    2009-01-01

    Isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) represent the two central intermediates in the biosynthesis of isoprenoids. The recently discovereddeoxyxylulose 5-phosphate pathway generates a mixture of IPP and DMAPP in its final step by reductive dehydroxylation of 1-hydroxy-2-methyl- 2-butenyl 4-diphosphate. This conversion is catalyzed by IspH protein comprising a central iron-sulfur cluster as electron transfer cofactor in the active site. The five crystal structures of IspH in complex with substrate, converted substrate, products and PPi reported in this article provide unique insights into the mechanism of this enzyme. While IspH protein crystallizes with substrate bound to a [4Fe-4S] cluster, crystals of IspH in complex with IPP, DMAPP or inorganic pyrophosphate feature [3Fe-4S] clusters. The IspH:substrate complex reveals a hairpin conformation of the ligand with the C(1) hydroxyl group coordinated to the unique site in a [4Fe-4S] cluster of aconitase type. The resulting alkoxide complex is coupled to a hydrogen-bonding network, which serves as proton reservoir via a Thr167 proton relay. Prolonged x-ray irradiation leads to cleavage of the C(1)-O bond (initiated by reducing photo electrons). The data suggest a reaction mechanism involving a combination of Lewis-acid activation and proton coupled electron transfer. The resulting allyl radical intermediate can acquire a second electron via the iron-sulfur cluster. The reaction may be terminated by the transfer of a proton from the β-phosphate of the substrate to C(1) (affording DMAPP) or C(3) (affording IPP).

  13. Exchange anisotropy as a probe of antiferromagnetism in expanded face-centered-tetragonal Mn(001) layers

    NARCIS (Netherlands)

    Kohlhepp, J.T.; Wieldraaijer, H.; Jonge, de W.J.M.

    2006-01-01

    Manganese (Mn) grows coherent and with an expanded metastable face-centered-tetragonal (e-fct) structure on ultrathin fct Co(001)/Cu(001) template layers. From the temp. dependence of the obsd. unidirectional Mn/Co interface exchange anisotropy, an antiferromagnetic state with a blocking temp.

  14. An efficient synthesis of α-amino-δ-valerolactones by the ugi five-center three-component reaction

    International Nuclear Information System (INIS)

    Kim, Young Bae; Lee, Duck Hyung; Park, Soo Jung; Keum, Gyo Chang; Jang, Min Seok; Kang, Soon Bang; Kim, You Seung

    2002-01-01

    A novel approach to α-amino-δ-valerolactones derivatives 8 by the intramolecular Ugi five-center three-component reaction (U-5C-3CR) using the multifunctional starting material, L-pentahomoserine 5 is described

  15. Power spectra as a diagnostic tool in probing statistical/nonstatistical behavior in unimolecular reactions

    Science.gov (United States)

    Chang, Xiaoyen Y.; Sewell, Thomas D.; Raff, Lionel M.; Thompson, Donald L.

    1992-11-01

    The possibility of utilizing different types of power spectra obtained from classical trajectories as a diagnostic tool to identify the presence of nonstatistical dynamics is explored by using the unimolecular bond-fission reactions of 1,2-difluoroethane and the 2-chloroethyl radical as test cases. In previous studies, the reaction rates for these systems were calculated by using a variational transition-state theory and classical trajectory methods. A comparison of the results showed that 1,2-difluoroethane is a nonstatistical system, while the 2-chloroethyl radical behaves statistically. Power spectra for these two systems have been generated under various conditions. The characteristics of these spectra are as follows: (1) The spectra for the 2-chloroethyl radical are always broader and more coupled to other modes than is the case for 1,2-difluoroethane. This is true even at very low levels of excitation. (2) When an internal energy near or above the dissociation threshold is initially partitioned into a local C-H stretching mode, the power spectra for 1,2-difluoroethane broaden somewhat, but discrete and somewhat isolated bands are still clearly evident. In contrast, the analogous power spectra for the 2-chloroethyl radical exhibit a near complete absence of isolated bands. The general appearance of the spectrum suggests a very high level of mode-to-mode coupling, large intramolecular vibrational energy redistribution (IVR) rates, and global statistical behavior. (3) The appearance of the power spectrum for the 2-chloroethyl radical is unaltered regardless of whether the initial C-H excitation is in the CH2 or the CH2Cl group. This result also suggests statistical behavior. These results are interpreted to mean that power spectra may be used as a diagnostic tool to assess the statistical character of a system. The presence of a diffuse spectrum exhibiting a nearly complete loss of isolated structures indicates that the dissociation dynamics of the molecule will

  16. Engineered Photosystem II reaction centers optimize photochemistry versus photoprotection at different solar intensities.

    Science.gov (United States)

    Vinyard, David J; Gimpel, Javier; Ananyev, Gennady M; Mayfield, Stephen P; Dismukes, G Charles

    2014-03-12

    The D1 protein of Photosystem II (PSII) provides most of the ligating amino acid residues for the Mn4CaO5 water-oxidizing complex (WOC) and half of the reaction center cofactors, and it is present as two isoforms in the cyanobacterium Synechococcus elongatus PCC 7942. These isoforms, D1:1 and D1:2, confer functional advantages for photosynthetic growth at low and high light intensities, respectively. D1:1, D1:2, and seven point mutations in the D1:2 background that are native to D1:1 were expressed in the green alga Chlamydomonas reinhardtii. We used these nine strains to show that those strains that confer a higher yield of PSII charge separation under light-limiting conditions (where charge recombination is significant) have less efficient photochemical turnover, measured in terms of both a lower WOC turnover probability and a longer WOC cycle period. Conversely, these same strains under light saturation (where charge recombination does not compete) confer a correspondingly faster O2 evolution rate and greater protection against photoinhibition. Taken together, the data clearly establish that PSII primary charge separation is a trade-off between photochemical productivity (water oxidation and plastoquinone reduction) and charge recombination (photoprotection). These trade-offs add up to a significant growth advantage for the two natural isoforms. These insights provide fundamental design principles for engineering of PSII reaction centers with optimal photochemical efficiencies for growth at low versus high light intensities.

  17. The ({sup 18}O, {sup 16}O) reaction as a probe for nuclear spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cappuzzello, F.; Bondì, M.; Nicolosi, D.; Tropea, S. [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, I-95125 Catania, Italy and Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania (Italy); Agodi, A.; Carbone, D.; Cavallaro, M.; Cunsolo, A. [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, I-95125 Catania (Italy); Borello-Lewin, T.; Rodrigues, M. R. D. [Instituto de Física - Universidade de São Paulo, Rua do Matão Travessa R Nr.187, 05508-090 Cidade Universitária, São Paulo (Brazil); De Napoli, M. [INFN - Sezione di Catania, Via S. Sofia 64, I-95125 Catania (Italy); Linares, R. [Instituto de Física, Universidade Federal Fluminense, Avenida Litoranea s/n, Gragoata, 24210-340, Niteroi, RJ (Brazil); Foti, A. [Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania, Italy and INFN - Sezione di Catania, Via S. Sofia 64, I-95125 Catania (Italy)

    2014-11-11

    The response of nuclei to the ({sup 18}O, {sup 16}O) two-neutron transfer reaction at 84 MeV incident energy has been systematically studied at the Catania INFN-LNS laboratory. The experiments were performed using several solid targets from light ({sup 9}Be, {sup 11}B, {sup 12,13}C, {sup 16}O, {sup 28}Si) to heavy ones ({sup 58,64}Ni, {sup 120}Sn, {sup 208}Pb). The {sup 16}O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer. Exploiting the large momentum acceptance (−10%, +14%) and solid angle (50 msr) of the spectrometer, energy spectra were obtained with a relevant yield up to about 20 MeV excitation energy. The application of the powerful trajectory reconstruction technique did allow to get energy spectra with energy resolution of about 150 keV and angular distributions with angular resolution better than 0.3°. A common feature observed with light nuclei is the appearance of unknown resonant structures at high excitation energy. The strong population of these latter together with the measured width can reveal the excitation of a collective mode connected with the transfer of a pair.

  18. Passivation Layer and Cathodic Redox Reactions in Sodium-Ion Batteries Probed by HAXPES.

    Science.gov (United States)

    Doubaji, Siham; Philippe, Bertrand; Saadoune, Ismael; Gorgoi, Mihaela; Gustafsson, Torbjorn; Solhy, Abderrahim; Valvo, Mario; Rensmo, Håkan; Edström, Kristina

    2016-01-08

    The cathode material P2-Nax Co2/3 Mn2/9 Ni1/9 O2, which could be used in Na-ion batteries, was investigated through synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). Nondestructive analysis was made through the electrode/electrolyte interface of the first electrochemical cycle to ensure access to information not only on the active material, but also on the passivation layer formed at the electrode surface and referred to as the solid permeable interface (SPI). This investigation clearly shows the role of the SPI and the complexity of the redox reactions. Cobalt, nickel, and manganese are all electrochemically active upon cycling between 4.5 and 2.0 V; all are in the 4+ state at the end of charging. Reduction to Co(3+), Ni(3+), and Mn(3+) occurs upon discharging and, at low potential, there is partial reversible reduction to Co(2+) and Ni(2+). A thin layer of Na2 CO3 and NaF covers the pristine electrode and reversible dissolution/reformation of these compounds is observed during the first cycle. The salt degradation products in the SPI show a dependence on potential. Phosphates mainly form at the end of the charging cycle (4.5 V), whereas fluorophosphates are produced at the end of discharging (2.0 V). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Probing adsorption phenomena on a single crystal Pt-alloy surface under oxygen reduction reaction conditions

    DEFF Research Database (Denmark)

    Bondarenko, Alexander S.; Stephens, Ifan E.L.; Bech, Lone

    2012-01-01

    The adsorption dynamics of *OH and *O species at Pt(111) and Cu/Pt(111) near-surface alloy (NSA) surfaces in oxygen-free and O2-saturated 0.1M HClO4 was investigated. Subsurface Cu modifies the electronic structure at the Pt(111) surface resulting in weaker bonding to adsorbates like *OH, *H or *O....... This provides a basis for the high oxygen reduction activity of the NSA, as predicted by density functional theory calculations. The shift in *OH adsorption of around 0.16V towards more positive potentials can be clearly monitored in absence of O2 and under the oxygen reduction reaction (ORR) conditions...... for the Cu/Pt(111) NSA. In both cases, for Pt(111) and NSA, the *OH(*O) adsorption dynamics is very similar in the absence of oxygen and under ORR conditions. Therefore, theoretical assumptions about the coverage of adsorbates in the absence of oxygen can be reasonably extrapolated to the situation when...

  20. Pigment organization and their interactions in reaction centers of photosystem II: optical spectroscopy at 6 K of reaction centers with modified pheophytin composition.

    Science.gov (United States)

    Germano, M; Shkuropatov, A Y; Permentier, H; de Wijn, R; Hoff, A J; Shuvalov, V A; van Gorkom, H J

    2001-09-25

    Photosystem II reaction centers (RC) with selectively exchanged pheophytin (Pheo) molecules as described in [Germano, M., Shkuropatov, A. Ya., Permentier, H., Khatypov, R. A., Shuvalov, V. A., Hoff, A. J., and van Gorkom, H. J. (2000) Photosynth. Res. 64, 189-198] were studied by low-temperature absorption, linear and circular dichroism, and triplet-minus-singlet absorption-difference spectroscopy. The ratio of extinction coefficients epsilon(Pheo)/epsilon(Chl) for Q(Y) absorption in the RC is approximately 0.40 at 6 K and approximately 0.45 at room temperature. The presence of 2 beta-carotenes, one parallel and one perpendicular to the membrane plane, is confirmed. Absorption at 670 nm is due to the perpendicular Q(Y) transitions of the two peripheral chlorophylls (Chl) and not to either Pheo. The "core" pigments, two Pheo and four Chl absorb in the 676-685 nm range. Delocalized excited states as predicted by the "multimer model" are seen in the active branch. The inactive Pheo and the nearby Chl, however, mainly contribute localized transitions at 676 and 680 nm, respectively, although large CD changes indicate that exciton interactions are present on both branches. Replacement of the active Pheo prevents triplet formation, causes an LD increase at 676 and 681 nm, a blue-shift of 680 nm absorbance, and a bleach of the 685 nm exciton band. The triplet state is mainly localized on the Chl corresponding to B(A) in purple bacteria. Both Pheo Q(Y) transitions are oriented out of the membrane plane. Their Q(X) transitions are parallel to that plane, so that the Pheos in PSII are structurally similar to their homologues in purple bacteria.

  1. Probing adsorption phenomena on a single crystal Pt-alloy surface under oxygen reduction reaction conditions

    International Nuclear Information System (INIS)

    Bondarenko, Alexander S.; Stephens, Ifan E.L.; Bech, Lone; Chorkendorff, Ib

    2012-01-01

    Highlights: ► Impedance spectroscopy of Cu/Pt(1 1 1) near-surface alloy and Pt(1 1 1). ► Presence of oxygen changes little the adsorption dynamics. ► Adsorption dynamics similar on alloy and Pt(1 1 1). ► Electrosorption phenomena on alloy shifted in potential, relative to Pt(1 1 1). - Abstract: The adsorption dynamics of *OH and *O species at Pt(1 1 1) and Cu/Pt(1 1 1) near-surface alloy (NSA) surfaces in oxygen-free and O 2 -saturated 0.1 M HClO 4 was investigated. Subsurface Cu modifies the electronic structure at the Pt(1 1 1) surface resulting in weaker bonding to adsorbates like *OH, *H or *O. This provides a basis for the high oxygen reduction activity of the NSA, as predicted by density functional theory calculations. The shift in *OH adsorption of around 0.16 V towards more positive potentials can be clearly monitored in absence of O 2 and under the oxygen reduction reaction (ORR) conditions for the Cu/Pt(1 1 1) NSA. In both cases, for Pt(1 1 1) and NSA, the *OH(*O) adsorption dynamics is very similar in the absence of oxygen and under ORR conditions. Therefore, theoretical assumptions about the coverage of adsorbates in the absence of oxygen can be reasonably extrapolated to the situation when oxygen reduction takes place at the surface. A ∼5-fold improvement in the ORR activity over the Pt(1 1 1) at 0.9 V (RHE) was measured for the Cu/Pt(1 1 1) near-surface alloy.

  2. Evaluation of a polymerase chain reaction reverse hybridization line probe assay for the detection and identification of medically important fungi in bronchoalveolar lavage fluids.

    NARCIS (Netherlands)

    Meletiadis, J.; Melchers, W.J.G.; Meis, J.F.G.M.; Hurk, P.J.J.C. van den; Jannes, G.; Verweij, P.E.

    2003-01-01

    An assay system in which polymerase chain reaction (PCR) amplification of the ITS-1 region of ribosomal DNA (rDNA) is combined with a reverse-hybridization line probe assay (LiPA) was used for the identification of six Candida species and four Aspergillus species in pure cultures of clinical

  3. How exciton-vibrational coherences control charge separation in the photosystem II reaction center.

    Science.gov (United States)

    Novoderezhkin, Vladimir I; Romero, Elisabet; van Grondelle, Rienk

    2015-12-14

    In photosynthesis absorbed sun light produces collective excitations (excitons) that form a coherent superposition of electronic and vibrational states of the individual pigments. Two-dimensional (2D) electronic spectroscopy allows a visualization of how these coherences are involved in the primary processes of energy and charge transfer. Based on quantitative modeling we identify the exciton-vibrational coherences observed in 2D photon echo of the photosystem II reaction center (PSII-RC). We find that the vibrations resonant with the exciton splittings can modify the delocalization of the exciton states and produce additional states, thus promoting directed energy transfer and allowing a switch between the two charge separation pathways. We conclude that the coincidence of the frequencies of the most intense vibrations with the splittings within the manifold of exciton and charge-transfer states in the PSII-RC is not occurring by chance, but reflects a fundamental principle of how energy conversion in photosynthesis was optimized.

  4. Chemical proprieties of the iron-quinone complex in mutated reaction centers of Rb. sphaeroides

    International Nuclear Information System (INIS)

    Hałas, Agnieszka; Derrien, Valerie; Sebban, Pierre; Matlak, Krzysztof; Korecki, Józef; Kruk, Jerzy; Burda, Kvĕtoslava

    2012-01-01

    We investigated type II bacterial photosynthetic reaction centers, which contain a quinone - iron complex (Q A -Fe-Q B ) on their acceptor side. Under physiological conditions it was observed mainly in a reduced high spin state but its low spin ferrous states were also observed. Therefore, it was suggested that it might regulate the dynamical properties of the iron–quinone complex and the protonation and deprotonation events in its neighbourhood. In order to get insight into the molecular mechanism of the NHFe low spin state formation, we preformed Mössbauer studies of a wild type of Rb. sphaeroides and its two mutated forms. Our Mössbauer measurements show that the hydrophobicity of the Q A binding site can be crucial for stabilization of the high spin ferrous state of NHFe.

  5. Alumina plate containing photosystem I reaction center complex oriented inside plate-penetrating silica nanopores.

    Science.gov (United States)

    Kamidaki, Chihiro; Kondo, Toru; Noji, Tomoyasu; Itoh, Tetsuji; Yamaguchi, Akira; Itoh, Shigeru

    2013-08-22

    The photosynthetic photosystem I reaction center complex (PSI-RC), which has a molecular diameter of 21 nm with 100 pigments, was incorporated into silica nanopores with a 100-nm diameter that penetrates an alumina plate of 60-μm thickness to make up an inorganic-biological hybrid photocell. PSI-RCs, purified from a thermophilic cyanobacterium, were stable inside the nanopores and rapidly photoreduced a mediator dye methyl viologen. The reduced dye was more stable inside nanopores suggesting the decrease of dissolved oxygen. The analysis by a cryogenic electron spin paramagnetic resonance indicated the oriented arrangement of RCs inside the 100-nm nanopores, with their surface parallel to the silica wall and perpendicular to the plane of the alumina plate. PSI RC complex in the semicrystalline orientation inside silica nanopores can be a new type of light energy conversion unit to supply strong reducing power selectively to other molecules inside or outside nanopores.

  6. Kinetics of several oxygenated carbon-centered free radical reactions with NO2.

    Science.gov (United States)

    Rissanen, Matti P; Arppe, Suula L; Timonen, Raimo S

    2013-05-16

    Five oxygenated carbon-centered free radical reactions with nitrogen dioxide (NO2) have been studied in direct time-resolved measurements. Experiments were conducted in a temperature-controlled flow tube reactor coupled to a 193 nm exciplex laser photolysis and a resonance gas lamp photoionization mass spectrometer. Reactions were investigated under pseudofirst-order conditions, with the NO2 concentrations of the experiments in great excess over the initial radical concentrations ([R]0 CH3CO radical reactions with NO2 and, hence, includes the three smallest hydroxyalkyl radical species (CH2OH, CH2CH2OH, and CH3CHOH). The obtained rate coefficients are high with the temperature-dependent rate coefficients given by a formula k(T) = k300K × (T/300 K)(-n) as (in units of cm(3) molecule(-1) s(-1)): k(CH2OH + NO2) = (8.95 ± 2.70) × 10(-11) × (T/300 K)(-0.54±0.27) (T = 298-363 K), k(CH2CH2OH + NO2) = (5.99 ± 1.80) × 10(-11) × (T/300 K)(-1.49±0.45)(T = 241-363 K), k(CH3CHOH + NO2) = (7.48 ± 2.24) × 10(-11) × (T/300 K)(-1.36±0.41) (T = 266-363 K), k(CH3OCH2 + NO2) = (7.85 ± 2.36) × 10(-11) × (T/300 K)(-0.93±0.28) (T = 243-363 K), and k(CH3CO + NO2) = (2.87 ± 0.57) × 10(-11) × (T/300 K)(-2.45±0.49) (T = 241-363 K), where the uncertainties refer to the estimated overall uncertainties of the values obtained. The determined rate coefficients show negative temperature dependence with no apparent bath gas pressure dependence under the current experimental conditions (241-363 K and about 1-3 Torr helium). This behavior is typical for a radical-radical addition mechanism with no potential energy barrier above the energy of the separated reactants in the entrance channel of the reaction. Unfortunately the absence of detected product signals prevented gaining deeper insight into the reaction mechanism.

  7. Interplay between excitation kinetics and reaction-center dynamics in purple bacteria

    International Nuclear Information System (INIS)

    Caycedo-Soler, Felipe; RodrIguez, Ferney J; Quiroga, Luis; Johnson, Neil F

    2010-01-01

    Photosynthesis is arguably the fundamental process of life, since it enables energy from the Sun to enter the food chain on the Earth. It is a remarkable non-equilibrium process in which photons are converted to many-body excitations, which traverse a complex biomolecular membrane, where they are captured and fuel chemical reactions within a reaction center (RC) in order to produce nutrients. The precise nature of these dynamical processes-which lie at the interface between quantum and classical behavior and involve both noise and coordination-is still being explored. Here, we focus on a striking recent empirical finding concerning an illumination-driven transition in the biomolecular membrane architecture of the purple bacteria Rsp. photometricum. Using stochastic realizations to describe a hopping rate model for excitation transfer, we show numerically and analytically that this surprising shift in preferred architectures can be traced to the interplay between the excitation kinetics and the RC dynamics. The net effect is that the bacteria profit from efficient metabolism at low illumination intensities while using dissipation to avoid an oversupply of energy at high illumination intensities.

  8. Center of gravity estimation using a reaction board instrumented with fiber Bragg gratings

    Science.gov (United States)

    Oliveira, Rui; Roriz, Paulo; Marques, Manuel B.; Frazão, Orlando

    2018-03-01

    The purpose of the present work is to construct a reaction board based on fiber Bragg gratings (FBGs) that could be used for estimation of the 2D coordinates of the projection of center of gravity (CG) of an object. The apparatus is consisted of a rigid equilateral triangular board mounted on three supports at the vertices, two of which have cantilevers instrumented with FBGs. When an object of known weight is placed on the board, the bending strain of the cantilevers is measured by a proportional wavelength shift of the FBGs. Applying the equilibrium conditions of a rigid body and proper calibration procedures, the wavelength shift is used to estimate the vertical reaction forces and moments of force at the supports and the coordinates of the object's CG projection on the board. This method can be used on a regular basis to estimate the CG of the human body or objects with complex geometry and density distribution. An example is provided for the estimation of the CG projection coordinates of two orthopaedic femur bone models, one intact, and the other with a hip stem implant encased. The clinical implications of changing the normal CG location by means of a prosthesis have been discussed.

  9. Protein sequences and redox titrations indicate that the electron acceptors in reaction centers from heliobacteria are similar to Photosystem I

    Science.gov (United States)

    Trost, J. T.; Brune, D. C.; Blankenship, R. E.

    1992-01-01

    Photosynthetic reaction centers isolated from Heliobacillus mobilis exhibit a single major protein on SDS-PAGE of 47 000 Mr. Attempts to sequence the reaction center polypeptide indicated that the N-terminus is blocked. After enzymatic and chemical cleavage, four peptide fragments were sequenced from the Heliobacillus mobilis apoprotein. Only one of these sequences showed significant specific similarity to any of the protein and deduced protein sequences in the GenBank data base. This fragment is identical with 56% of the residues, including both cysteines, found in highly conserved region that is proposed to bind iron-sulfur center Fx in the Photosystem I reaction center peptide that is the psaB gene product. The similarity to the psaA gene product in this region is 48%. Redox titrations of laser-flash-induced photobleaching with millisecond decay kinetics on isolated reaction centers from Heliobacterium gestii indicate a midpoint potential of -414 mV with n = 2 titration behavior. In membranes, the behavior is intermediate between n = 1 and n = 2, and the apparent midpoint potential is -444 mV. This is compared to the behavior in Photosystem I, where the intermediate electron acceptor A1, thought to be a phylloquinone molecule, has been proposed to undergo a double reduction at low redox potentials in the presence of viologen redox mediators. These results strongly suggest that the acceptor side electron transfer system in reaction centers from heliobacteria is indeed analogous to that found in Photosystem I. The sequence similarities indicate that the divergence of the heliobacteria from the Photosystem I line occurred before the gene duplication and subsequent divergence that lead to the heterodimeric protein core of the Photosystem I reaction center.

  10. Identification of human rotavirus serotype by hybridization to polymerase chain reaction-generated probes derived from a hyperdivergent region of the gene encoding outer capsid protein VP7

    International Nuclear Information System (INIS)

    Flores, J.; Sears, J.; Schael, I.P.; White, L.; Garcia, D.; Lanata, C.; Kapikian, A.Z.

    1990-01-01

    We have synthesized 32 P-labeled hybridization probes from a hyperdivergent region (nucleotides 51 to 392) of the rotavirus gene encoding the VP7 glycoprotein by using the polymerase chain reaction method. Both RNA (after an initial reverse transcription step) and cloned cDNA from human rotavirus serotypes 1 through 4 could be used as templates to amplify this region. High-stringency hybridization of each of the four probes to rotavirus RNAs dotted on nylon membranes allowed the specific detection of corresponding sequences and thus permitted identification of the serotype of the strains dotted. The procedure was useful when applied to rotaviruses isolated from field studies

  11. Identification of human rotavirus serotype by hybridization to polymerase chain reaction-generated probes derived from a hyperdivergent region of the gene encoding outer capsid protein VP7

    Energy Technology Data Exchange (ETDEWEB)

    Flores, J.; Sears, J.; Schael, I.P.; White, L.; Garcia, D.; Lanata, C.; Kapikian, A.Z. (National Institutes of Health, Bethesda, MD (USA))

    1990-08-01

    We have synthesized {sup 32}P-labeled hybridization probes from a hyperdivergent region (nucleotides 51 to 392) of the rotavirus gene encoding the VP7 glycoprotein by using the polymerase chain reaction method. Both RNA (after an initial reverse transcription step) and cloned cDNA from human rotavirus serotypes 1 through 4 could be used as templates to amplify this region. High-stringency hybridization of each of the four probes to rotavirus RNAs dotted on nylon membranes allowed the specific detection of corresponding sequences and thus permitted identification of the serotype of the strains dotted. The procedure was useful when applied to rotaviruses isolated from field studies.

  12. Study of the Mn-binding sites in photosystem II using antibodies raised against lumenal regions of the D1 and D2 reaction center proteins

    Energy Technology Data Exchange (ETDEWEB)

    Dalmasso, Enrique Agustin [Univ. of California, Berkeley, CA (United States)

    1992-04-01

    The experiments discussed in this thesis focus on identifying the protein segments or specific amino acids which provide ligands to the Mn cluster of photosystem II (PS II). This Mn cluster plays a central role in the oxygen-evolving complex (OEC) of PS II. The Mn cluster is thought to be bound by lumenal regions of the PS II reaction center proteins known as D1 and D2. First, several peptides were synthesized which correspond to specific lumenal segments of the D1 and D2 proteins. Next, polyclonal antibodies were successfully elicited using three of these peptides. The peptides recognized by these antibodies correspond to protein segments of the spinach reaction center proteins: Ile-321 to Ala-344 of D1 (D1-a), Asp-319 to Arg-334 of D1 (D1-b), and Val-300 to Asn-319 of D2 (D2-a). These antibodies were then used in assays which were developed to structurally or functionally probe the potential Mn-binding regions of the D1 and D2 proteins.

  13. Probing the Outflowing Multiphase Gas ∼1 kpc below the Galactic Center

    Energy Technology Data Exchange (ETDEWEB)

    Savage, Blair D.; Kim, Tae-Sun; Wakker, Bart P. [Department of astronomy, University of Wisconsin, Madison, 475 North Charter Street, Madison, WI 53706 (United States); Fox, Andrew J. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218 (United States); Massa, Derck [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); Bordoloi, Rongmon [MIT-Kavli Center for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Jenkins, Edward B. [Princeton University Observatory, Princeton, NJ 08544 (United States); Lehner, Nicolas [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Bland-Hawthorn, Joss [Institute of Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Lockman, Felix J. [Green Bank Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Hernandez, Svea [Department of Astrophysics, Radboud University, Nijmegen, PO Box 9010, 6500 GL Nijmegen (Netherlands)

    2017-10-01

    Comparison of interstellar medium (ISM) absorption in the UV spectrum of LS 4825, a B1 Ib−II star d  = 21 ± 5 kpc from the Sun toward l  = 1.°67 and b  = −6.°63, with ISM absorption toward an aligned foreground star at d  < 7.0 ± 1.7 kpc, allows us to isolate and study gas associated with the Milky Way nuclear wind. Spectra from the Space Telescope Imaging Spectrograph show low-ionization absorption out to d  < 7 kpc (e.g., O i, C ii, Mg ii, Si ii, Fe ii, S ii) only between 0 and 40 km s{sup −1}, while absorption at d  > 7 kpc, ∼1 kpc below the Galactic plane, is complex and spans −290 to +94 km s{sup −1}. The intermediate and high ions Si iii, C iv, Si iv, and N v show extremely strong absorption with multiple components from −283 to 107 km s{sup −1}, implying that the ISM ∼1 kpc below the Galactic center has a substantial reservoir of plasma and more gas containing C iv and N v than in the Carina OB1 association at z  = 0 kpc. Abundances and physical conditions are presented for many absorption components. The high ion absorption traces cooling transition temperature plasma probably driven by the outflowing hot gas, while the extraordinarily large thermal pressure, p / k  ∼ 10{sup 5} cm{sup −3} K{sup −1}, in an absorption component at −114 km s{sup −1} probably arises from the ram pressure of the outflowing hot gas. The observations are consistent with a flow whose ionization structure in the high ions can be understood through a combination of nonequilibrium radiative cooling and turbulent mixing.

  14. Bacterial Reaction Centers Purified with Styrene Maleic Acid Copolymer Retain Native Membrane Functional Properties and Display Enhanced Stability**

    Science.gov (United States)

    Swainsbury, David J K; Scheidelaar, Stefan; van Grondelle, Rienk; Killian, J Antoinette; Jones, Michael R

    2014-01-01

    Integral membrane proteins often present daunting challenges for biophysical characterization, a fundamental issue being how to select a surfactant that will optimally preserve the individual structure and functional properties of a given membrane protein. Bacterial reaction centers offer a rare opportunity to compare the properties of an integral membrane protein in different artificial lipid/surfactant environments with those in the native bilayer. Here, we demonstrate that reaction centers purified using a styrene maleic acid copolymer remain associated with a complement of native lipids and do not display the modified functional properties that typically result from detergent solubilization. Direct comparisons show that reaction centers are more stable in this copolymer/lipid environment than in a detergent micelle or even in the native membrane, suggesting a promising new route to exploitation of such photovoltaic integral membrane proteins in device applications. PMID:25212490

  15. [High activity antiretroviral therapy change associated to adverse drug reactions in a specialized center in Venezuela].

    Science.gov (United States)

    Subiela, José D; Dapena, Elida

    2016-03-01

    Adverse drug reactions (ADRs) represent the first cause of change of the first-line highly active antiretroviral therapy (HAART) regimen, therefore, they constitute the main limiting factor in the long-term follow up of HIV patients in treatment. A retrospective study was carried out in a specialized center in Lara State, Venezuela, including 99 patients over 18 years of age who had change of first-line HAART regimen due to ADRs, between 2010 and 2013. The aims of this research were to describe the sociodemographic and clinical variables, frequency of ADRs related to change of HAART, duration of the first-line HAART regimen, to determine the drugs associated with ARVs and to identify the risk factors. The ADRs constituted 47.5% of all causes of change of first-line HAART regimen, the median duration was 1.08±0.28 years. The most frequent ADRs were anemia (34.3%), hypersensitivity reactions (20.2%) and gastrointestinal intolerance (13.1%). The most frequent ARV regimen type was the protease inhibitors-based regimen (59.6%), but zidovudine was the ARV most linked to ADRs (41.4%). The regression analysis showed increased risk of ADRs in singles and students in the univariate analysis and heterosexuals and homosexuals in multivariate analysis; and decreased risk in active workers. The present work shows the high prevalence of ADRs in the studied population and represents the first case-based study that describes the pharmacoepidemiology of a cohort of HIV-positive patients treated in Venezuela.

  16. Proton conduction within the reaction centers of Rhodobacter capsulatus: the electrostatic role of the protein.

    Science.gov (United States)

    Maróti, P; Hanson, D K; Baciou, L; Schiffer, M; Sebban, P

    1994-06-07

    Light-induced charge separation in the photosynthetic reaction center results in delivery of two electrons and two protons to the terminal quinone acceptor QB. In this paper, we have used flash-induced absorbance spectroscopy to study three strains that share identical amino acid sequences in the QB binding site, all of which lack the protonatable amino acids Glu-L212 and Asp-L213. These strains are the photosynthetically incompetent site-specific mutant Glu-L212/Asp-L213-->Ala-L212/Ala-L213 and two different photocompetent derivatives that carry both alanine substitutions and an intergenic suppressor mutation located far from QB (class 3 strain, Ala-Ala + Arg-M231-->Leu; class 4 strain, Ala-Ala + Asn-M43-->Asp). At pH 8 in the double mutant, we observe a concomitant decrease of nearly 4 orders of magnitude in the rate constants of second electron and proton transfer to QB compared to the wild type. Surprisingly, these rates are increased to about the same extent in both types of suppressor strains but remain > 2 orders of magnitude smaller than those of the wild type. In the double mutant, at pH 8, the loss of Asp-L213 and Glu-L212 leads to a substantial stabilization (> or = 60 meV) of the semiquinone energy level. Both types of compensatory mutations partially restore, to nearly the same level, the original free energy difference for electron transfer from primary quinone QA to QB. The pH dependence of the electron and proton transfer processes in the double-mutant and the suppressor strains suggests that when reaction centers of the double mutant are shifted to lower pH (1.5-2 units), they function like those of the suppressor strains at physiological pH. Our data suggest that the main effect of the compensatory mutations is to partially restore the negative electrostatic environment of QB and to increase an apparent "functional" pK of the system for efficient proton transfer to the active site. This emphasizes the role of the protein in tuning the

  17. [On the influence of local molecular environment on the redox potential of electron transfer cofactors in bacterial photosynthetic reaction centers].

    Science.gov (United States)

    Krasil'nikov, P M; Noks, P P; Rubin, A B

    2011-01-01

    The addition of cryosolvents (glycerol, dimethylsulfoxide) to a water solution containing bacterial photosynthetic reaction centers changes the redox potential of the bacteriochlorophyll dimer, but does not affect the redox potential of the quinone primary acceptor. It has been shown that the change in redox potential can be produced by changes of the electrostatic interactions between cofactors and the local molecular environment modified by additives entered into the solution. The degree of influence of a solvent on the redox potential of various cofactors is determined by degree of availability of these cofactors for molecules of solvent, which depends on the arrangement of cofactors in the structure of reaction centers.

  18. Kinetics of Several Oxygen-Containing Carbon-Centered Free Radical Reactions with Nitric Oxide.

    Science.gov (United States)

    Rissanen, Matti P; Ihlenborg, Marvin; Pekkanen, Timo T; Timonen, Raimo S

    2015-07-16

    Kinetics of four carbon-centered, oxygen-containing free radical reactions with nitric oxide (NO) were investigated as a function of temperature at a few Torr pressure of helium, employing flow tube reactors coupled to a laser-photolysis/resonance-gas-discharge-lamp photoionization mass spectrometer (LP-RPIMS). Rate coefficients were directly determined from radical (R) decay signals under pseudo-first-order conditions ([R]0 ≪ [NO]). The obtained rate coefficients showed negative temperature dependences, typical for a radical-radical association process, and can be represented by the following parametrizations (all in units of cm(3) molecule(-1) s(-1)): k(CH2OH + NO) = (4.76 × 10(-21)) × (T/300 K)(15.92) × exp[50700/(RT)] (T = 266-363 K, p = 0.79-3.44 Torr); k(CH3CHOH + NO) = (1.27 × 10(-16)) × (T/300 K)(6.81) × exp[28700/(RT)] (T = 241-363 K, p = 0.52-3.43 Torr); k(CH3OCH2 + NO) = (3.58 ± 0.12) × 10(-12) × (T/300 K)(-3.17±0.14) (T = 221-363 K, p = 0.50-0.80 Torr); k(T)3 = 9.62 × 10(-11) × (T/300 K)(-5.99) × exp[-7100/(RT)] (T = 221-473 K, p = 1.41-2.95 Torr), with the uncertainties given as standard errors of the fits and the overall uncertainties estimated as ±20%. The rate of CH3OCH2 + NO reaction was measured in two density ranges due to its observed considerable pressure dependence, which was not found in the studied hydroxyalkyl reactions. In addition, the CH3CO + NO rate coefficient was determined at two temperatures resulting in k298K(CH3CO + NO) = (5.6 ± 2.8) × 10(-13) cm(3) molecule(-1) s(-1). No products were found during these experiments, reasons for which are briefly discussed.

  19. Early bacteriopheophytin reduction in charge separation in reaction centers of Rhodobacter sphaeroides.

    Science.gov (United States)

    Zhu, Jingyi; van Stokkum, Ivo H M; Paparelli, Laura; Jones, Michael R; Groot, Marie Louise

    2013-06-04

    A question at the forefront of biophysical sciences is, to what extent do quantum effects and protein conformational changes play a role in processes such as biological sensing and energy conversion? At the heart of photosynthetic energy transduction lie processes involving ultrafast energy and electron transfers among a small number of tetrapyrrole pigments embedded in the interior of a protein. In the purple bacterial reaction center (RC), a highly efficient ultrafast charge separation takes place between a pair of bacteriochlorophylls: an accessory bacteriochlorophyll (B) and bacteriopheophytin (H). In this work, we applied ultrafast spectroscopy in the visible and near-infrared spectral region to Rhodobacter sphaeroides RCs to accurately track the timing of the electron on BA and HA via the appearance of the BA and HA anion bands. We observed an unexpectedly early rise of the HA⁻ band that challenges the accepted simple picture of stepwise electron transfer with 3 ps and 1 ps time constants. The implications for the mechanism of initial charge separation in bacterial RCs are discussed in terms of a possible adiabatic electron transfer step between BA and HA, and the effect of protein conformation on the electron transfer rate. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  20. Fragment molecular orbital study on electron tunneling mechanisms in bacterial photosynthetic reaction center.

    Science.gov (United States)

    Kitoh-Nishioka, Hirotaka; Ando, Koji

    2012-11-01

    The tunneling mechanisms of electron transfers (ETs) in photosynthetic reaction center of Blastochloris viridis are studied by the ab initio fragment molecular orbital (FMO) method combined with the generalized Mulliken-Hush (GMH) and the bridge Green function (GF) calculations of the electronic coupling T(DA) and the tunneling current method for the ET pathway analysis at the fragment-based resolution. For the ET from batctriopheophytin (H(L)) to menaquinone (MQ), a major tunneling current through Trp M250 and a minor back flow via Ala M215, Ala M216, and His M217 are quantified. For the ET from MQ to ubiquinone, the major tunneling pathway via the nonheme Fe(2+) and His L190 is identified as well as minor pathway via His M217 and small back flows involving His L230, Glu M232, and His M264. At the given molecular structure from X-ray experiment, the spin state of the Fe(2+) ion, its replacement by Zn(2+), or its removal are found to affect the T(DA) value by factors within 2.2. The calculated T(DA) values, together with experimentally estimated values of the driving force and the reorganization energy, give the ET rates in reasonable agreement with experiments.

  1. Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides.

    Science.gov (United States)

    Vermaas, Josh V; Taguchi, Alexander T; Dikanov, Sergei A; Wraight, Colin A; Tajkhorshid, Emad

    2015-03-31

    Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis across a vast number of organisms. Prior experimental results have shown that the photosynthetic reaction center (RC) from Rhodobacter sphaeroides is only fully functional with a limited set of methoxy-bearing quinones, suggesting that specific interactions with this substituent are required to drive electron transport and the formation of quinol. The nature of these interactions has yet to be determined. Through parameterization of a CHARMM-compatible quinone force field and subsequent molecular dynamics simulations of the quinone-bound RC, we have investigated and characterized the interactions of the protein with the quinones in the Q(A) and Q(B) sites using both equilibrium simulation and thermodynamic integration. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the Q(B) site and the amide nitrogen of GlyL225 that we implicate in locking the orientation of the 2-methoxy group, thereby tuning the redox potential difference between the quinones occupying the Q(A) and Q(B) sites. Disruption of this interaction leads to weaker binding in a ubiquinone analogue that lacks a 2-methoxy group, a finding supported by reverse electron transfer electron paramagnetic resonance experiments of the Q(A)⁻Q(B)⁻ biradical and competitive binding assays.

  2. Purification and spectroscopic characterization of photosystem II reaction center complexes isolated with or without Triton X-100.

    NARCIS (Netherlands)

    Eijckelhoff, C.; van Roon, H.; Groot, M.L.; van Grondelle, R.; Dekker, J.P.

    1996-01-01

    The pigment composition of the isolated photosystem II reaction center complex in its most stable and pure form currently is a matter of considerable debate. In this contribution, we present a new method based on a combination of gel filtration chromatography and diode array detection to analyze the

  3. Report on the consultants` meeting on technical aspects of the co-operation of nuclear reaction data centers

    Energy Technology Data Exchange (ETDEWEB)

    Lemmel, H D; Schwerer, O; Wienke, H [eds.

    1995-10-01

    The IAEA Nuclear Data Section convenes in annual intervals coordination meetings of the Network of the Nuclear Reaction Data Center. The present meeting dealt with technical matters of the nuclear data compilation and exchange by means of the jointly operated computerized systems CINDA, EXFOR, ENDF and others. Refs, figs and tabs.

  4. A new pathway for transmembrane electron transfer in photosynthetic reaction centers of Rhodobacter sphaeroides not involving the excited special pair.

    NARCIS (Netherlands)

    van Brederode, M.E.; Jones, M.R.; van Mourik, F.; van Stokkum, I.H.M.; van Grondelle, R.

    1997-01-01

    It is generally accepted that electron transfer in bacterial photosynthesis is driven by the first singlet excited state of a special pair of bacteriochlorophylls (P*). We have examined the first steps of electron transfer in a mutant of the Rhodobacter sphaeroides reaction center in which charge

  5. A new pathway for transmembrane electron transfer in photosyntetic reaction centers of Rhodobacter sphaeroides not involving the excited special pair.

    NARCIS (Netherlands)

    van Brederode, M.E.; Jones, M.R.; van Mourik, F.; van Stokkum, I.H.M.; van Grondelle, R.

    1997-01-01

    It is generally accepted that electron transfer in bacterial photosynthesis is driven by the first singlet excited state of a special pair of bacteriochlorophylls (P*). We have examined the first steps of electron transfer in a mutant of the Rhodobacter sphaeroides reaction center in which charge

  6. Report on the consultants' meeting on technical aspects of the co-operation of nuclear reaction data centers

    International Nuclear Information System (INIS)

    Lemmel, H.D.; Schwerer, O.; Wienke, H.

    1995-10-01

    The IAEA Nuclear Data Section convenes in annual intervals coordination meetings of the Network of the Nuclear Reaction Data Center. The present meeting dealt with technical matters of the nuclear data compilation and exchange by means of the jointly operated computerized systems CINDA, EXFOR, ENDF and others. Refs, figs and tabs

  7. Alkyl Bromides as Mechanistic Probes of Reductive Dehalogenation: Reactions of Vicinal Dibromide Stereoisomers with Zero-Valent Metals

    National Research Council Canada - National Science Library

    Totten, Lisa

    2000-01-01

    The mechanism through which zero-valent metals (most notably iron and zinc) reduce alkyl polyhalides in aqueous solution at room temperature was investigated using several stereoisomers of vicinal dibromides as probe compounds...

  8. A potential fluorescent probe: Maillard reaction product from glutathione and ascorbic acid for rapid and label-free dual detection of Hg(2+) and biothiols.

    Science.gov (United States)

    Dong, Jiang Xue; Song, Xiao Fang; Shi, Yan; Gao, Zhong Feng; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

    2016-07-15

    Maillard reactions and their fluorescent products have drawn much attention in the fields of food and life science, however, the application of fluorescent products separated from the reaction as an indicator for detection of certain substances in sensor field has not been mentioned. In this article, we report on an easy-to-synthesize and water-soluble fluorescent probe separated from the typical Maillard reaction products of glutathione and ascorbic acid, with excellent stability and high quantum yield (18.2%). The further application of the probe has been explored for dual detection of Hg(2+) and biothiols including cysteine, homocysteine, and glutathione, which is based on Hg(2+)-induced fluorescence quenching of the Maillard reaction fluorescent products (MRFPs) and the fluorescence recovery as the introduction of biothiols. This sensing system exhibits a good selectivity and sensitivity, and the linear ranges for Hg(2+), cysteine, homocysteine, and glutathione are 0.05-12, 0.5-10, 0.3-20, and 0.3-20μM, respectively. The detection limits for Hg(2+), cysteine, homocysteine, and glutathione are 22, 47, 96, and 30nM at a signal-to-noise ratio of 3, respectively. Furthermore, the practical applications of this sensor for Hg(2+) and biothiols determination in water samples and human plasma sample have been demonstrated with satisfactory results. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Comparison of Ground Reaction Forces, Center of Pressure and Body Center of Mass Changes in the Voluntary, Semi-Voluntary and Involuntary Gait Termination in Healthy Young Men

    Directory of Open Access Journals (Sweden)

    behrooz teymourian

    2016-03-01

    Full Text Available Objective: The aim of this study was comparing the ground reaction forces, center of pressure and body center of mass changes in voluntary, semi-voluntary and involuntary gait termination in healthy young men. Methods: In this study, 12 young men performed termination of gait in three different patterns. The variable of peak antero-posterior and vertical forces in two directions at both limbs, the time to reach peak and average forces in every limb in both directions, the center of pressure displacement of medio-lateral and antero-posterior direction for each limb and the net center of pressure and the displacement of the center of mass motion in all three motion plates were recorded using motion analysis system and force plate.The repeated measurements test was used to compare three patterns of gait termination at significance level of p&le0.5. Results: The results showed a significant difference in variables of peak antero-posterior force, the time to reach peak antero-posterior force and mean antero-posterior forces of the leading limb, the peak antero-posterior force of the trialing limbs, the depth force of leading limbs, medio-lateral cop of leading limbs displacement and vertical displacement of the center of mass, among different patterns of gait termination. Conclusion: While walking, the probability of a fall or collision damage, when a sudden or unexpected stop is required, increases. Therefore, more coordination between neuromuscular systems is required.

  10. Quinone reduction via secondary B-branch electron transfer in mutant bacterial reaction centers.

    Science.gov (United States)

    Laible, Philip D; Kirmaier, Christine; Udawatte, Chandani S M; Hofman, Samuel J; Holten, Dewey; Hanson, Deborah K

    2003-02-18

    Symmetry-related branches of electron-transfer cofactors-initiating with a primary electron donor (P) and terminating in quinone acceptors (Q)-are common features of photosynthetic reaction centers (RC). Experimental observations show activity of only one of them-the A branch-in wild-type bacterial RCs. In a mutant RC, we now demonstrate that electron transfer can occur along the entire, normally inactive B-branch pathway to reduce the terminal acceptor Q(B) on the time scale of nanoseconds. The transmembrane charge-separated state P(+)Q(B)(-) is created in this manner in a Rhodobacter capsulatus RC containing the F(L181)Y-Y(M208)F-L(M212)H-W(M250)V mutations (YFHV). The W(M250)V mutation quantitatively blocks binding of Q(A), thereby eliminating Q(B) reduction via the normal A-branch pathway. Full occupancy of the Q(B) site by the native UQ(10) is ensured (without the necessity of reconstitution by exogenous quinone) by purification of RCs with the mild detergent, Deriphat 160-C. The lifetime of P(+)Q(B)(-) in the YFHV mutant RC is >6 s (at pH 8.0, 298 K). This charge-separated state is not formed upon addition of competitive inhibitors of Q(B) binding (terbutryn or stigmatellin). Furthermore, this lifetime is much longer than the value of approximately 1-1.5 s found when P(+)Q(B)(-) is produced in the wild-type RC by A-side activity alone. Collectively, these results demonstrate that P(+)Q(B)(-) is formed solely by activity of the B-branch carriers in the YFHV RC. In comparison, P(+)Q(B)(-) can form by either the A or B branches in the YFH RC, as indicated by the biexponential lifetimes of approximately 1 and approximately 6-10 s. These findings suggest that P(+)Q(B)(-) states formed via the two branches are distinct and that P(+)Q(B)(-) formed by the B side does not decay via the normal (indirect) pathway that utilizes the A-side cofactors when present. These differences may report on structural and energetic factors that further distinguish the functional

  11. Report compiled by Research Center for Carbonaceous Resources, Institute for Chemical Reaction Science, Tohoku University; Tohoku Daigaku Hanno Kagaku Kenkyusho tanso shigen hanno kenkyu center hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1994-04-01

    The Research Center for Carbonaceous Resources was established in April 1991 for the purpose of developing a comprehensive process for converting carbonaceous resources into clean fuels or into materials equipped with advanced functions. In this report, the track records etc. of the center are introduced. Under study in the conversion process research department is the organization of a comprehensive coal conversion process which will be a combination of solvent extraction, catalytic decomposition, and catalytic gasification, whose goal is to convert coal in a clean way at high efficiency. Under study in the conversion catalyst research department are the development of a coal denitrogenation method, development of a low-temperature gasification method by use of inexpensive catalysts, synthesis of C{sub 2} hydrocarbons in a methane/carbon dioxide reaction, etc. Other endeavors under way involve the designing and development of new organic materials such as new carbon materials and a study of the foundation on which such efforts stand, that is, the study of the control of reactions between solids. Furthermore, in the study of interfacial reaction control, the contact gasification of coal, brown coal ion exchange capacity and surface conditions, carbonization of cation exchanged brown coal, etc., are being developed. (NEDO)

  12. Photochemistry and reactions of OH- defects and F centers in alkali halides

    International Nuclear Information System (INIS)

    Morato, S.P.; Luety, F.

    1978-01-01

    Aditively colored KCl:OH - crystals showed under a combined UV and VIS irradiation, a nearly complete and irreversible destruction of all F centers and visible absorption in the crystal. Only upon heating the crystal above 650 0 C the F center coloration becomes partially restored. The photodissociation of the OH - (under UV light) together with the photoionization of the F center (under VIS light) produces a not effects where all the F centers are converted into U centers. These photoreactions produces high contrast visible images that are completely stable under light at RT. Besides the optical information storage aspect of this effect these photoreaction s can also be used for controlled production of Usub(A) centers if the crystal also contains a foreign metallic impurity such a Na + ion [pt

  13. Quantitative in situ monitoring of an elevated temperature reaction using a water-cooled mid-infrared fiber-optic probe.

    Science.gov (United States)

    Maclaurin, P; Crabb, N C; Wells, I; Worsfold, P J; Coombs, D

    1996-04-01

    A novel water-cooled mid-infrared fiber-optic probe is described which is heatable to 230 °C. The probe has chalcogenide fibers and a ZnSe internal reflection element and is compact and fully flexible, allowing access to a wide range of standard laboratory reaction vessels and fume cupboard arrangements. Performance is demonstrated via the in situ analysis of an acid-catalyzed esterification reaction in toluene at 110 °C, and the results are compared with those from a conventional extractive sampling loop flow cell arrangement. Particular emphasis is given to the quantitative interpretation of the spectroscopic data, using gas chromatographic reference data. Calibration data are presented for univariate and partial least squares models, with an emphasis on procedures for improving the quality of interpreparation calibration and prediction through the use of focused reference analysis regimes. Subset univariate procedures are presented that yield relative errors of spectroscopy combined with bias correction partial least squares procedures for the efficient in situ quantitative analysis of laboratory scale reactions.

  14. Hybridization chain reaction-based colorimetric aptasensor of adenosine 5'-triphosphate on unmodified gold nanoparticles and two label-free hairpin probes.

    Science.gov (United States)

    Gao, Zhuangqiang; Qiu, Zhenli; Lu, Minghua; Shu, Jian; Tang, Dianping

    2017-03-15

    This work designs a new label-free aptasensor for the colorimetric determination of small molecules (adenosine 5'-triphosphate, ATP) by using visible gold nanoparticles as the signal-generation tags, based on target-triggered hybridization chain reaction (HCR) between two hairpin DNA probes. The assay is carried out referring to the change in the color/absorbance by salt-induced aggregation of gold nanoparticles after the interaction with hairpins, gold nanoparticles and ATP. To construct such an assay system, two hairpin DNA probes with a short single-stranded DNA at the sticky end are utilized for interaction with gold nanoparticles. In the absence of target ATP, the hairpin DNA probes can prevent gold nanoparticles from the salt-induced aggregation through the interaction of the single-stranded DNA at the sticky end with gold nanoparticles. Upon target ATP introduction, the aptamer-based hairpin probe is opened to expose a new sticky end for the strand-displacement reaction with another complementary hairpin, thus resulting in the decreasing single-stranded DNA because of the consumption of hairpins. In this case, gold nanoparticles are uncovered owing to the formation of double-stranded DNA, which causes their aggregation upon addition of the salt, thereby leading to the change in the red-to-blue color. Under the optimal conditions, the HCR-based colorimetric assay presents good visible color or absorbance responses for the determination of target ATP at a concentration as low as 1.0nM. Importantly, the methodology can be further extended to quantitatively or qualitatively monitor other small molecules or biotoxins by changing the sequence of the corresponding aptamer. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. On the nature of organic and inorganic centers that bifurcate electrons, coupling exergonic and endergonic oxidation-reduction reactions.

    Science.gov (United States)

    Peters, John W; Beratan, David N; Schut, Gerrit J; Adams, Michael W W

    2018-04-19

    Bifurcating electrons to couple endergonic and exergonic electron-transfer reactions has been shown to have a key role in energy conserving redox enzymes. Bifurcating enzymes require a redox center that is capable of directing electron transport along two spatially separate pathways. Research into the nature of electron bifurcating sites indicates that one of the keys is the formation of a low potential oxidation state to satisfy the energetics required of the endergonic half reaction, indicating that any redox center (organic or inorganic) that can exist in multiple oxidation states with sufficiently separated redox potentials should be capable of electron bifurcation. In this Feature Article, we explore a paradigm for bifurcating electrons down independent high and low potential pathways, and describe redox cofactors that have been demonstrated or implicated in driving this unique biochemistry.

  16. Reaction

    African Journals Online (AJOL)

    abp

    19 oct. 2017 ... Reaction to Mohamed Said Nakhli et al. concerning the article: "When the axillary block remains the only alternative in a 5 year old child". .... Bertini L1, Savoia G, De Nicola A, Ivani G, Gravino E, Albani A et al ... 2010;7(2):101-.

  17. Glial reaction in visual centers upon whole-body combined irradiation with microwaves and x-radiation

    International Nuclear Information System (INIS)

    Logvinov, S.V.

    1989-01-01

    A single whole-body preirradiation with thermogenous microwaves modifies the dynamics of the glial reactions of visual centers of ginea pigs induced by median lethal X-radiation doses. A combination of the two factors products the synergistic effect, estimated by the degree of alteration of astrocytes and oligodendroglyocytes at early times after exposure, leads to early activation of microglia, and reduces radiation-induced alterations in glia at later times (25-60 days)

  18. Development of species-specific DNA probes for Campylobacter jejuni, Campylobacter coli, and Campylobacter lari by polymerase chain reaction fingerprinting

    NARCIS (Netherlands)

    Giesendorf, B A; van Belkum, A; Koeken, A; Stegeman, H; Henkens, M H; van der Plas, J; Goossens, H; Niesters, H G; Quint, W G

    The application of polymerase chain reaction (PCR) fingerprinting assays enables discrimination between species and strains of microorganisms. PCR primers aiming at arbitrary sequences in combination with primers directed against the repetitive extragenic palindrome (REP) or enterobacterial

  19. Reaction-based small-molecule fluorescent probes for dynamic detection of ROS and transient redox changes in living cells and small animals.

    Science.gov (United States)

    Lü, Rui

    2017-09-01

    Dynamic detection of transient redox changes in living cells and animals has broad implications for human health and disease diagnosis, because intracellular redox homeostasis regulated by reactive oxygen species (ROS) plays important role in cell functions, normal physiological functions and some serious human diseases (e.g., cancer, Alzheimer's disease, diabetes, etc.) usually have close relationship with the intracellular redox status. Small-molecule ROS-responsive fluorescent probes can act as powerful tools for dynamic detection of ROS and redox changes in living cells and animals through fluorescence imaging techniques; and great advances have been achieved recently in the design and synthesis of small-molecule ROS-responsive fluorescent probes. This article highlights up-to-date achievements in designing and using the reaction-based small-molecule fluorescent probes (with high sensitivity and selectivity to ROS and redox cycles) in the dynamic detection of ROS and transient redox changes in living cells and animals through fluorescence imaging. Copyright © 2017. Published by Elsevier Ltd.

  20. The binding of quinone to the photosynthetic reaction centers: kinetics and thermodynamics of reactions occurring at the QB-site in zwitterionic and anionic liposomes.

    Science.gov (United States)

    Mavelli, Fabio; Trotta, Massimo; Ciriaco, Fulvio; Agostiano, Angela; Giotta, Livia; Italiano, Francesca; Milano, Francesco

    2014-07-01

    Liposomes represent a versatile biomimetic environment for studying the interaction between integral membrane proteins and hydrophobic ligands. In this paper, the quinone binding to the QB-site of the photosynthetic reaction centers (RC) from Rhodobacter sphaeroides has been investigated in liposomes prepared with either the zwitterionic phosphatidylcholine (PC) or the negatively charged phosphatidylglycerol (PG) to highlight the role of the different phospholipid polar heads. Quinone binding (K Q) and interquinone electron transfer (L AB) equilibrium constants in the two type of liposomes were obtained by charge recombination reaction of QB-depleted RC in the presence of increasing amounts of ubiquinone-10 over the temperature interval 6-35 °C. The kinetic of the charge recombination reactions has been fitted by numerically solving the ordinary differential equations set associated with a detailed kinetic scheme involving electron transfer reactions coupled with quinone release and uptake. The entire set of traces at each temperature was accurately fitted using the sole quinone release constants (both in a neutral and a charge separated state) as adjustable parameters. The temperature dependence of the quinone exchange rate at the QB-site was, hence, obtained. It was found that the quinone exchange regime was always fast for PC while it switched from slow to fast in PG as the temperature rose above 20 °C. A new method was introduced in this paper for the evaluation of constant K Q using the area underneath the charge recombination traces as the indicator of the amount of quinone bound to the QB-site.

  1. Probing surface sites of TiO2: reactions with [HRe(CO)5] and [CH3Re(CO)5].

    Science.gov (United States)

    Lobo-Lapidus, Rodrigo J; Gates, Bruce C

    2010-10-04

    Two carbonyl complexes of rhenium, [HRe(CO)(5)] and [CH(3)Re(CO)(5)], were used to probe surface sites of TiO(2) (anatase). These complexes were adsorbed from the gas phase onto anatase powder that had been treated in flowing O(2) or under vacuum to vary the density of surface OH sites. Infrared (IR) spectra demonstrate the variation in the number of sites, including Ti(+3)-OH and Ti(+4)-OH. IR and extended X-ray absorption fine structure (EXAFS) spectra show that chemisorption of the rhenium complexes led to their decarbonylation, with formation of surface-bound rhenium tricarbonyls, when [HRe(CO)(5)] was adsorbed, or rhenium tetracarbonyls, when [CH(3)Re(CO)(5)] was adsorbed. These reactions were accompanied by the formation of water and surface carbonates and removal of terminal hydroxyl groups associated with Ti(+3) and Ti(+4) ions on the anatase. Data characterizing the samples after adsorption of [HRe(CO)(5)] or [CH(3)Re(CO)(5)] determined a ranking of the reactivity of the surface OH sites, with the Ti(+3)-OH groups being the more reactive towards the rhenium complexes but the less likely to be dehydroxylated. The two rhenium pentacarbonyl probes provided complementary information, suggesting that the carbonate species originate from carbonyl ligands initially bonded to the rhenium and from hydroxyl groups of the titania surface, with the reaction leading to the formation of water and bridging hydroxyl groups on the titania. The results illustrate the value of using a family of organometallic complexes as probes of oxide surface sites.

  2. Reverse line blot probe design and polymerase chain reaction optimization for bloodmeal analysis of ticks from the eastern United States.

    Science.gov (United States)

    Scott, M C; Harmon, J R; Tsao, J I; Jones, C J; Hickling, G J

    2012-05-01

    Determining the host preference of vector ticks is vital to elucidating the eco-epidemiology of the diseases they spread. Detachment of ticks from captured hosts can provide evidence of feeding on those host species, but only for those species that are feasible to capture. Recently developed, highly sensitive molecular assays show great promise in allowing host selection to be determined from minute traces of host DNA that persist in recently molted ticks. Using methods developed in Europe as a starting-point, we designed 12S rDNA mitochondrial gene probes suitable for use in a reverse line blot (RLB) assay of ticks feeding on common host species in the eastern United States. This is the first study to use the 12S mitochondrial gene in a RLB bloodmeal assay in North America. The assay combines conventional PCR with a biotin-labeled primer and reverse line blots that can be stripped and rehybridized up to 20 times, making the method less expensive and more straightforward to interpret than previous methods of tick bloodmeal identification. Probes were designed that target the species, genus, genus group, family, order, or class of eight reptile, 13 birds, and 32 mammal hosts. After optimization, the RLB assay correctly identified the current hostspecies for 99% of ticks [Amblyomma americanum (L.) and eight other ixodid tick species] collected directly from known hosts. The method identified previous-host DNA for approximately half of all questing ticks assayed. Multiple bloodmeal determinations were obtained in some instances from feeding and questing ticks; this pattern is consistent with previous RLB studies but requires further investigation. Development of this probe library, suitable for eastern U.S. ecosystems, opens new avenues for eco-epidemiological investigations of this region's tick-host systems.

  3. Aromatic C-Nitroso Compounds and Their Dimers: A Model for Probing the Reaction Mechanisms in Crystalline Molecular Solids

    Directory of Open Access Journals (Sweden)

    Ivana Biljan

    2017-12-01

    Full Text Available This review is focused on the dimerization and dissociation of aromatic C-nitroso compounds and their dimers, the reactions that could be used as a convenient model for studying the thermal organic solid-state reaction mechanisms. This molecular model is simple because it includes formation or breaking of only one covalent bond between two nitrogen atoms. The crystalline molecular solids of nitroso dimers (azodioxides dissociate by photolysis under the cryogenic conditions, and re-dimerize by slow warming. The thermal re-dimerization reaction is examined under the different topotactic conditions in crystals: disordering, surface defects, and phase transformations. Depending on the conditions, and on the molecular structure, aromatic C-nitroso compounds can associate to form one-dimensional polymeric structures and are able to self-assemble on gold surfaces.

  4. Re-examining the 26Mg(α ,α')26Mg reaction: Probing astrophysically important states in 26Mg

    Science.gov (United States)

    Adsley, P.; Brümmer, J. W.; Li, K. C. W.; Marín-Lámbarri, D. J.; Kheswa, N. Y.; Donaldson, L. M.; Neveling, R.; Papka, P.; Pellegri, L.; Pesudo, V.; Pool, L. C.; Smit, F. D.; van Zyl, J. J.

    2017-11-01

    Background: The 22Ne(α ,n )25Mg reaction is one of the neutron sources for the s process in massive stars. The properties of levels in 26Mg above the α -particle threshold control the strengths of the 22Ne(α ,n )25Mg and 22Ne(α ,γ )26Mg reactions. The strengths of these reactions as functions of temperature are one of the major uncertainties in the s process. Purpose: Information on the existence, spin, and parity of levels in 26Mg can assist in constraining the strengths of the 22Ne(α ,γ )26Mg and 22Ne(α ,n )25Mg reactions, and therefore in constraining s -process abundances. Methods: Inelastically scattered α particles from a 26Mg target were momentum-analyzed in the K600 magnetic spectrometer at iThemba LABS, South Africa. The differential cross sections of states were deduced from the focal-plane trajectory of the scattered α particles. Based on the differential cross sections, spin and parity assignments to states are made. Results: A newly assigned 0+ state was observed in addition to a number of other states, some of which can be associated with states observed in other experiments. Some of the deduced Jπ values of the states observed in the present study show discrepancies with those assigned in a similar experiment performed at RCNP Osaka. The reassignments and additions of the various states can strongly affect the reaction rate at low temperatures. Conclusion: The number, location, and assignment of levels in 26Mg that may contribute to the 22Ne+α reactions are not clear. Future experimental investigations of 26Mg must have an extremely good energy resolution to separate the contributions from different levels. Coincidence experiments of 26Mg provide a possible route for future investigations.

  5. The $\\Xi^- +d\\to n+\\Lambda+\\Lambda$ reaction as a probe of the $\\Lambda\\Lambda$ interaction

    OpenAIRE

    Afnan, I. R.

    1997-01-01

    Within the framework of the Faddeev equations we demonstrate that a $\\Lambda\\Lambda-\\Xi N$ interaction that gives a $\\Lambda\\Lambda$ scattering length comparable to the $nn$ scattering length, and the binding energy of $^{\\ 6}_{\\Lambda\\Lambda}$He as an $\\alpha\\Lambda\\Lambda-\\alpha\\Xi N$ system, produces a final state interaction peak in the neutron spectrum for the reaction $\\Xi^- d \\to n\\Lambda\\Lambda$. This suggests that this reaction could be used to constrain the $\\Lambda\\Lambda$ scatteri...

  6. Probing functional groups at the gas-aerosol interface using heterogeneous titration reactions: a tool for predicting aerosol health effects?

    Science.gov (United States)

    Setyan, Ari; Sauvain, Jean-Jacques; Guillemin, Michel; Riediker, Michael; Demirdjian, Benjamin; Rossi, Michel J

    2010-12-17

    The complex chemical and physical nature of combustion and secondary organic aerosols (SOAs) in general precludes the complete characterization of both bulk and interfacial components. The bulk composition reveals the history of the growth process and therefore the source region, whereas the interface controls--to a large extent--the interaction with gases, biological membranes, and solid supports. We summarize the development of a soft interrogation technique, using heterogeneous chemistry, for the interfacial functional groups of selected probe gases [N(CH(3))(3), NH(2)OH, CF(3)COOH, HCl, O(3), NO(2)] of different reactivity. The technique reveals the identity and density of surface functional groups. Examples include acidic and basic sites, olefinic and polycyclic aromatic hydrocarbon (PAH) sites, and partially and completely oxidized surface sites. We report on the surface composition and oxidation states of laboratory-generated aerosols and of aerosols sampled in several bus depots. In the latter case, the biomarker 8-hydroxy-2'-deoxyguanosine, signaling oxidative stress caused by aerosol exposure, was isolated. The increase in biomarker levels over a working day is correlated with the surface density N(i)(O3) of olefinic and/or PAH sites obtained from O(3) uptakes as well as with the initial uptake coefficient, γ(0), of five probe gases used in the field. This correlation with γ(0) suggests the idea of competing pathways occurring at the interface of the aerosol particles between the generation of reactive oxygen species (ROS) responsible for oxidative stress and cellular antioxidants.

  7. Enzyme-free electrochemical detection of microRNA-21 using immobilized hairpin probes and a target-triggered hybridization chain reaction amplification strategy

    International Nuclear Information System (INIS)

    Liu, Hongying; Bei, Xiaoqiong; Xia, Qiuting; Fu, Yan; Zhang, Shi; Liu, Maochuan; Fan, Kai; Zhang, Mingzhen; Yang, Yong

    2016-01-01

    We describe a sensitive enzyme-free bioassay for the determination of microRNA-21. It is based on a combination of target-triggered hybridization chain reaction, tagging with CdTe quantum dots (QDs), and anodic stripping voltammetry. Firstly, a thiolated capture hairpin probe SH-HP1 was immobilized on the surface of a gold electrode. HP1 unfolds in the presence of microRNA-21. If hairpin probe 2 (HP2) is present, a HP1-HP2 complex will be formed which possesses an exposed stem of HP2, and microRNA is released in parallel. The released microRNA-21 triggers a hybridization chain reaction and this leads to form an exposed DNA segment of HP2 and cycle use microRNA-21. With the aid of assistant DNA A1 and A2, the exposed DNA segment of HP2 progressed to a long double strand. The strand is rich in CdTe QDs with the help of QDs-A1. Then, the attached QDs were dissolved with HNO 3 to give dissolved Cd(II) ions. Finally, the corresponding electrochemical current response of Cd(II) is monitored by anodic stripping voltammetry and used to quantify the concentration of microRNA-21. More microRNA-21 participated in this reaction increases the number of CdTe QDs, which results in increased electrochemical current. Thus, an ultrasensitive detection of microRNA-21 is accomplished by anodic stripping voltammetry. This gene assay displays a detection limit as low as 33 aM. It can discriminate between complementary DNA sequence and single-base mismatched DNA, indicating its high specificity. (author)

  8. Modification of quinone electrochemistry by the proteins in the biological electron transfer chains: examples from photosynthetic reaction centers

    Science.gov (United States)

    Gunner, M. R.; Madeo, Jennifer; Zhu, Zhenyu

    2009-01-01

    Quinones such as ubiquinone are the lipid soluble electron and proton carriers in the membranes of mitochondria, chloroplasts and oxygenic bacteria. Quinones undergo controlled redox reactions bound to specific sites in integral membrane proteins such as the cytochrome bc1 oxidoreductase. The quinone reactions in bacterial photosynthesis are amongst the best characterized, presenting a model to understand how proteins modulate cofactor chemistry. The free energy of ubiquinone redox reactions in aqueous solution and in the QA and QB sites of the bacterial photosynthetic reaction centers (RCs) are compared. In the primary QA site ubiquinone is reduced only to the anionic semiquinone (Q•−) while in the secondary QB site the product is the doubly reduced, doubly protonated quinol (QH2). The ways in which the protein modifies the relative energy of each reduced and protonated intermediate are described. For example, the protein stabilizes Q•− while destabilizing Q= relative to aqueous solution through electrostatic interactions. In addition, kinetic and thermodynamic mechanisms for stabilizing the intermediate semiquinones are compared. Evidence for the protein sequestering anionic compounds by slowing both on and off rates as well as by binding the anion more tightly is reviewed. PMID:18979192

  9. Probing the role of Skyrme interactions on the fission dynamics of the {sup 6}Li + {sup 238}U reaction

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Ishita; Kumar, Raj; Sharma, Manoj K. [Thapar University, School of Physics and Materials Science, Patiala (India)

    2017-06-15

    The performance of selected five Skyrme forces (out of a set of 240), tested by Dutra et al., is analyzed in view of fusion-fission dynamics. These forces are assumed to perform better for neutron-rich systems, so the choice of the reaction is accordingly made by opting for a neutron-rich target in {sup 6}Li + {sup 238}U reaction. This reaction is diagnosed further in reference to fusion hindrance within the dynamical approach of the cluster-decay model (DCM). In order to reduce the computational time, three Skyrme forces are figured out with the criteria that these forces cover the barrier characteristics of the remaining two forces as well. The fission cross-sections are successfully addressed at low energies for the {sup 6}Li + {sup 238}U reaction. However, at relatively higher energies, the excitation functions show theoretical suppression with respect to experimental data, which may be associated with the possible existence of incomplete fusion (ICF). For ICF, we have considered that the {sup 6}Li broke into {sup 4}He + {sup 2}H, as mentioned in the experimental work. The calculations of ICF are carried out for the {sup 4}He + {sup 238}U reaction with the selected Skyrme forces at E{sub c.m.} = 26.20 and 27.51 MeV. These forces address the data nicely for the compound nucleus (CN) as well as ICF processes. Here, the NRAPR force seems to require lesser barrier modification as compared to the other forces, therefore it can be used as an alternate choice for calculating the interaction potential. Additionally, the prediction of cross-sections at lower energies has been done with DCM using the NRAPR force. The l-dependent % barrier modification of the Skyrme forces undertaken is also worked out in reference to fusion hindrance at below barrier energies. (orig.)

  10. Tight-binding model of the photosystem II reaction center: application to two-dimensional electronic spectroscopy

    International Nuclear Information System (INIS)

    Gelzinis, Andrius; Valkunas, Leonas; Abramavicius, Darius; Fuller, Franklin D; Ogilvie, Jennifer P; Mukamel, Shaul

    2013-01-01

    We propose an optimized tight-binding electron–hole model of the photosystem II (PSII) reaction center (RC). Our model incorporates two charge separation pathways and spatial correlations of both static disorder and fast fluctuations of energy levels. It captures the main experimental features observed in time-resolved two-dimensional (2D) optical spectra at 77 K: peak pattern, lineshapes and time traces. Analysis of 2D spectra kinetics reveals that specific regions of the 2D spectra of the PSII RC are sensitive to the charge transfer states. We find that the energy disorder of two peripheral chlorophylls is four times larger than the other RC pigments. (paper)

  11. Tight-binding model of the photosystem II reaction center: application to two-dimensional electronic spectroscopy

    Science.gov (United States)

    Gelzinis, Andrius; Valkunas, Leonas; Fuller, Franklin D.; Ogilvie, Jennifer P.; Mukamel, Shaul; Abramavicius, Darius

    2013-07-01

    We propose an optimized tight-binding electron-hole model of the photosystem II (PSII) reaction center (RC). Our model incorporates two charge separation pathways and spatial correlations of both static disorder and fast fluctuations of energy levels. It captures the main experimental features observed in time-resolved two-dimensional (2D) optical spectra at 77 K: peak pattern, lineshapes and time traces. Analysis of 2D spectra kinetics reveals that specific regions of the 2D spectra of the PSII RC are sensitive to the charge transfer states. We find that the energy disorder of two peripheral chlorophylls is four times larger than the other RC pigments.

  12. Probing the parton densities of virtual photons with the reaction γ*γ → jets at LEP

    International Nuclear Information System (INIS)

    Poetter, B.

    1999-01-01

    We present a next-to-leading order calculation of jet production in γ * γ collisions from e + e - scattering in a region where the virtuality Q 2 of the probing virtual photon is small compared to the transverse jet energy. The calculation is based on the phase-space slicing method. The initial state singularity of the virtual photon is factorized into the structure function of the virtual photon, using the MS-bar factorization scheme for virtual photons. Numerical results are presented for LEP2 conditions. The perturbative stability of the pure direct virtual photon approach is compared to that of including resolved virtual photons in different regions of Q 2 . We make predictions for cross sections which suggest that different parametrizations of virtual photon parton densities should be distinguishable by measurements of jet cross sections at LEP

  13. Optimised padlock probe ligation and microarray detection of multiple (non-authorised GMOs in a single reaction

    Directory of Open Access Journals (Sweden)

    Schoen Cor D

    2008-12-01

    Full Text Available Abstract Background To maintain EU GMO regulations, producers of new GM crop varieties need to supply an event-specific method for the new variety. As a result methods are nowadays available for EU-authorised genetically modified organisms (GMOs, but only to a limited extent for EU-non-authorised GMOs (NAGs. In the last decade the diversity of genetically modified (GM ingredients in food and feed has increased significantly. As a result of this increase GMO laboratories currently need to apply many different methods to establish to potential presence of NAGs in raw materials and complex derived products. Results In this paper we present an innovative method for detecting (approved GMOs as well as the potential presence of NAGs in complex DNA samples containing different crop species. An optimised protocol has been developed for padlock probe ligation in combination with microarray detection (PPLMD that can easily be scaled up. Linear padlock probes targeted against GMO-events, -elements and -species have been developed that can hybridise to their genomic target DNA and are visualised using microarray hybridisation. In a tenplex PPLMD experiment, different genomic targets in Roundup-Ready soya, MON1445 cotton and Bt176 maize were detected down to at least 1%. In single experiments, the targets were detected down to 0.1%, i.e. comparable to standard qPCR. Conclusion Compared to currently available methods this is a significant step forward towards multiplex detection in complex raw materials and derived products. It is shown that the PPLMD approach is suitable for large-scale detection of GMOs in real-life samples and provides the possibility to detect and/or identify NAGs that would otherwise remain undetected.

  14. Optimised padlock probe ligation and microarray detection of multiple (non-authorised) GMOs in a single reaction.

    Science.gov (United States)

    Prins, Theo W; van Dijk, Jeroen P; Beenen, Henriek G; Van Hoef, Am Angeline; Voorhuijzen, Marleen M; Schoen, Cor D; Aarts, Henk J M; Kok, Esther J

    2008-12-04

    To maintain EU GMO regulations, producers of new GM crop varieties need to supply an event-specific method for the new variety. As a result methods are nowadays available for EU-authorised genetically modified organisms (GMOs), but only to a limited extent for EU-non-authorised GMOs (NAGs). In the last decade the diversity of genetically modified (GM) ingredients in food and feed has increased significantly. As a result of this increase GMO laboratories currently need to apply many different methods to establish to potential presence of NAGs in raw materials and complex derived products. In this paper we present an innovative method for detecting (approved) GMOs as well as the potential presence of NAGs in complex DNA samples containing different crop species. An optimised protocol has been developed for padlock probe ligation in combination with microarray detection (PPLMD) that can easily be scaled up. Linear padlock probes targeted against GMO-events, -elements and -species have been developed that can hybridise to their genomic target DNA and are visualised using microarray hybridisation.In a tenplex PPLMD experiment, different genomic targets in Roundup-Ready soya, MON1445 cotton and Bt176 maize were detected down to at least 1%. In single experiments, the targets were detected down to 0.1%, i.e. comparable to standard qPCR. Compared to currently available methods this is a significant step forward towards multiplex detection in complex raw materials and derived products. It is shown that the PPLMD approach is suitable for large-scale detection of GMOs in real-life samples and provides the possibility to detect and/or identify NAGs that would otherwise remain undetected.

  15. $\\beta$- decay of $^{58}$Zn. A critical test for the charge-exchange reaction as a probe for the $\\beta$- decay strength distribution

    CERN Multimedia

    2002-01-01

    % IS353 \\\\ \\\\ Due to its importance in fundamental physics and astrophysics, a great effort both theoretically and experimentally is devoted to study Gamow Teller (GT)-strength. The GT-strength and its distribution play a key role in late stellar evolution. During the pre-supernova core-collapse of massive stars, the electron capture and nuclear $\\beta$ -decay determine the electron-to-baryon ratio, which influences the infall dynamics and the mass of the final core. The cross-section of the charge-exchange reaction at forward angles with energies above 100~MeV is expected to be proportional to the squares of Fermi and GT matrix elements. This proportionality should provide a Q-value free method to probe the weak interaction strength and renormalization effects in nuclei. Thus charge-exchange reactions are often used to determine the experimental GT-strength. However, the connection between the GT-strength and the cross-section of the charge-exchange reaction is partially model-dependent and the question aris...

  16. Probing the Statistical Decay and α-clustering effects in 12C + 12C and 14N + 10B reactions

    Directory of Open Access Journals (Sweden)

    Morelli L.

    2014-03-01

    Full Text Available An experimental campaign has been undertaken at Laboratori Nazionali di Legnaro (LNL INFN, Italy, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation reactions. On the experimental side, a first reaction: 12C+12C at 95 MeV beam energy has been measured, using the GARFIELD + Ring Counter (RCo apparatuses. Fusion-evaporation events have been exclusively selected out of the entire data set. The comparison to a dedicated Hauser-Feshbach calculation allows us to give constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg. Out-of-equilibrium aα emission has been evidenced and attributed both to an entrance channel effect (favoured by the cluster nature of reaction partners, and, in more dissipative events, to the persistence of cluster correlations well above the 24Mg threshold for 6 α’s decay. In order to study the same 24Mg compound nucleus at similar excitation energy with respect to this first reaction a new measurement, 14N + 10B at 5.7 A.MeV, was performed at LNL laboratories with the same experimental setup. The comparison between the two systems would allow us to further constrain the level density of light nuclei in the mass-excitation energy range of interest. In this perspective, deviations from a statistical behaviour can be used as a tool to get information on nuclear clustering, both in the ground-state for projectile and target and in the hot source formed in the collision.

  17. Probing the rate-determining region of the potential energy surface for a prototypical ion-molecule reaction.

    Science.gov (United States)

    Xie, Changjian; Liu, Xinguo; Sweeny, Brendan C; Miller, Thomas M; Ard, Shaun G; Shuman, Nicholas S; Viggiano, Albert A; Guo, Hua

    2018-03-13

    We report a joint experimental-theoretical study of the F -  + HCl → HF + Cl - reaction kinetics. The experimental measurement of the rate coefficient at several temperatures was made using the selected ion flow tube method. Theoretical rate coefficients are calculated using the quasi-classical trajectory method on a newly developed global potential energy surface, obtained by fitting a large number of high-level ab initio points with augmentation of long-range electrostatic terms. In addition to good agreement between experiment and theory, analyses suggest that the ion-molecule reaction rate is significantly affected by shorter-range interactions, in addition to the traditionally recognized ion-dipole and ion-induced dipole terms. Furthermore, the statistical nature of the reaction is assessed by comparing the measured and calculated HF product vibrational state distributions to that predicted by the phase space theory.This article is part of the theme issue 'Modern theoretical chemistry'. © 2018 The Author(s).

  18. DNA probes

    International Nuclear Information System (INIS)

    Castelino, J.

    1992-01-01

    The creation of DNA probes for detection of specific nucleotide segments differs from ligand detection in that it is a chemical rather than an immunological reaction. Complementary DNA or RNA is used in place of the antibody and is labelled with 32 P. So far, DNA probes have been successfully employed in the diagnosis of inherited disorders, infectious diseases, and for identification of human oncogenes. The latest approach to the diagnosis of communicable and parasitic infections is based on the use of deoxyribonucleic acid (DNA) probes. The genetic information of all cells is encoded by DNA and DNA probe approach to identification of pathogens is unique because the focus of the method is the nucleic acid content of the organism rather than the products that the nucleic acid encodes. Since every properly classified species has some unique nucleotide sequences that distinguish it from every other species, each organism's genetic composition is in essence a finger print that can be used for its identification. In addition to this specificity, DNA probes offer other advantages in that pathogens may be identified directly in clinical specimens

  19. DNA probes

    Energy Technology Data Exchange (ETDEWEB)

    Castelino, J

    1993-12-31

    The creation of DNA probes for detection of specific nucleotide segments differs from ligand detection in that it is a chemical rather than an immunological reaction. Complementary DNA or RNA is used in place of the antibody and is labelled with {sup 32}P. So far, DNA probes have been successfully employed in the diagnosis of inherited disorders, infectious diseases, and for identification of human oncogenes. The latest approach to the diagnosis of communicable and parasitic infections is based on the use of deoxyribonucleic acid (DNA) probes. The genetic information of all cells is encoded by DNA and DNA probe approach to identification of pathogens is unique because the focus of the method is the nucleic acid content of the organism rather than the products that the nucleic acid encodes. Since every properly classified species has some unique nucleotide sequences that distinguish it from every other species, each organism`s genetic composition is in essence a finger print that can be used for its identification. In addition to this specificity, DNA probes offer other advantages in that pathogens may be identified directly in clinical specimens 10 figs, 2 tabs

  20. Reduction reactions of water soluble cyano-cobalt(III)-porphyrins: Metal versus ligand centered processes

    International Nuclear Information System (INIS)

    Mosseri, S.; Neta, P.; Harriman, A.; Hambright, P.

    1990-01-01

    Reduction reactions of dicyano-cobalt(III)-porphyrins [potential in vivo cyanide scavenger drugs] were studied by radiolytic and electrochemical methods using the water soluble tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP). For [(CN)2CoIIITPPS]-, reduction occurs stepwise to the CoII, CoI, and finally to the phlorin anion. This behavior is similar to that of the cobalt porphyrins in the absence of cyanide, except that the cyanide ligand shifts the reduction potentials to much more negative values. On the other hand, under radiolytic conditions, [(CN)2CoIIITMPyP]- is reduced on the porphyrin macrocycle by one electron to give the CoIII pi-radical anion, which disproportionates into the initial complex and the two-electron ring reduced CoIII phlorin. The radical anion is also formed by intramolecular electron transfer subsequent to the reaction of CoIITMPyP and cyanide. The results are compared with the chemistry of Vitamin B-12

  1. Anisotropy and vortex behaviour in BiSrCaCuO thin films and multilayers probed by columnar pinning centers

    International Nuclear Information System (INIS)

    Raffy, H.; Murrills, C.D.; Pomar, A.; Stiufiuc, G.; Stiufiuc, R.; Li, Z.Z.

    2006-01-01

    In this paper we review typical mixed state transport results obtained on a variety of Bi 2 Sr 2 Ca n-1 Cu n O y thin films and artificial multilayers, which allowed us to cover the range from low to high anisotropy. The vortex behaviour, 2D or 3D, probed by the pinning properties of columnar defects, is shown to be highly dependant on the anisotropy, and therefore on the microstructure of the system. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  2. Density functional theoretical study on the C-F and C-O oxidative addition reaction at an AI center

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Seong [Dept. of Science Education, Kyungnam University, Masan (Korea, Republic of); Cho, Hyun; Hwang, Sungu [Dept. of Nanomechatronics Engineering, Pusan National University, Miryang (Korea, Republic of)

    2017-02-15

    In this study, B3LYP/LACVP** level calculations were chosen because the level of theory was applied successfully to calculations of the thermodynamic and kinetic features of the oxidative addition reactions of alkyl and aryl halides to pincer-type complexes. This study examined the effects of the substituents on the phenyl rings of the Al(I) center. Isopropyl side chains in the phenyl rings attached to N atoms of the pincer ligand were replaced with a methyl (Me) (2) or tertiary butyl ( t Bu) group. The oxidative addition of C[BOND]F and C[BOND]O bonds to an Al (I) center was investigated computationally by DFT calculations. The geometries, thermodynamic, and kinetic features were in good agreement with the experimental data, as in previous studies on the transition metal complexes. The computational results showed that the DFT calculations could provide qualitative insight into the reactivity and thermodynamics of the oxidative addition reactions of C[BOND]F bonds.

  3. Designing a time-effective TaqMan probe-based real-time polymerase chain reaction protocol for the identification of Yersinia enterocolitica in raw pork meat

    Directory of Open Access Journals (Sweden)

    Milena Alicja Stachelska

    2017-01-01

    Full Text Available The aim of this study was to design a time-effective method comprising a short pre-enrichment step in a non-selective broth in combination with the TaqMan probe applied in the real-time polymerase chain reaction to detect Yersinia enterocolitica strains in raw pork meat. The method enabled to detect 1 colony forming unit per 25 mg of Yersinia enterocolitica in pork meat. The specificity and reliability of the method was not diminished by the company of microflora naturally present in meat. The method was found successful to detect pathogenic Yersinia enterocolitica strains in pork meat. It is advised to be used for assessing the microbial risk and for controlling the microbial quality of meat and meat products.

  4. Gamma rays as probe of fission and quasi-fission dynamics in the reaction 32S + 197Au near the Coulomb barrier

    Science.gov (United States)

    Pulcini, A.; Vardaci, E.; Kozulin, E.; Ashaduzzaman, M.; Borcea, C.; Bracco, A.; Brambilla, S.; Calinescu, S.; Camera, F.; Ciemala, M.; de Canditiis, B.; Dorvaux, O.; Harca, I. M.; Itkis, I.; Kirakosyan, V. V.; Knyazheva, G.; Kozulina, N.; Kolesov, I. V.; La Rana, G.; Maj, A.; Matea, I.; Novikov, K.; Petrone, C.; Quero, D.; Rath, P.; Saveleva, E.; Schmitt, C.; Sposito, G.; Stezowski, O.; Trzaska, W. H.; Wilson, J.

    2018-05-01

    Compound nucleus fission and quasi-fission are both binary decay channels whose common properties make the experimental separation between them difficult. A way to achieve this separation could be to probe the angular momentum of the binary fragments. This can be done detecting gamma rays in coincidence with the two fragments. As a case study, the reaction 32S + 197Au near the Coulomb barrier has been performed at the Tandem ALTO facility at IPN ORSAY. ORGAM and PARIS, two different gamma detectors arrays, are coupled with the CORSET detector, a two-arm time-of-flight spectrometer. TOF-TOF data were analyzed to reconstruct the mass-energy distribution of the primary fragments coupled with gamma multiplicity and spectroscopic analysis. Preliminary results of will be shown.

  5. An in situ spatially resolved analytical technique to simultaneously probe gas phase reactions and temperature within the packed bed of a plug flow reactor.

    Science.gov (United States)

    Touitou, Jamal; Burch, Robbie; Hardacre, Christopher; McManus, Colin; Morgan, Kevin; Sá, Jacinto; Goguet, Alexandre

    2013-05-21

    This paper reports the detailed description and validation of a fully automated, computer controlled analytical method to spatially probe the gas composition and thermal characteristics in packed bed systems. As an exemplar, we have examined a heterogeneously catalysed gas phase reaction within the bed of a powdered oxide supported metal catalyst. The design of the gas sampling and the temperature recording systems are disclosed. A stationary capillary with holes drilled in its wall and a moveable reactor coupled with a mass spectrometer are used to enable sampling and analysis. This method has been designed to limit the invasiveness of the probe on the reactor by using the smallest combination of thermocouple and capillary which can be employed practically. An 80 μm (O.D.) thermocouple has been inserted in a 250 μm (O.D.) capillary. The thermocouple is aligned with the sampling holes to enable both the gas composition and temperature profiles to be simultaneously measured at equivalent spatially resolved positions. This analysis technique has been validated by studying CO oxidation over a 1% Pt/Al2O3 catalyst and the spatial resolution profiles of chemical species concentrations and temperature as a function of the axial position within the catalyst bed are reported.

  6. Development of an event-specific hydrolysis probe quantitative real-time polymerase chain reaction assay for Embrapa 5.1 genetically modified common bean (Phaseolus vulgaris).

    Science.gov (United States)

    Treml, Diana; Venturelli, Gustavo L; Brod, Fábio C A; Faria, Josias C; Arisi, Ana C M

    2014-12-10

    A genetically modified (GM) common bean event, namely Embrapa 5.1, resistant to the bean golden mosaic virus (BGMV), was approved for commercialization in Brazil. Brazilian regulation for genetically modified organism (GMO) labeling requires that any food containing more than 1% GMO be labeled. The event-specific polymerase chain reaction (PCR) method has been the primary trend for GMO identification and quantitation because of its high specificity based on the flanking sequence. This work reports the development of an event-specific assay, named FGM, for Embrapa 5.1 detection and quantitation by use of SYBR Green or hydrolysis probe. The FGM assay specificity was tested for Embrapa 2.3 event (a noncommercial GM common bean also resistant to BGMV), 46 non-GM common bean varieties, and other crop species including maize, GM maize, soybean, and GM soybean. The FGM assay showed high specificity to detect the Embrapa 5.1 event. Standard curves for the FGM assay presented a mean efficiency of 95% and a limit of detection (LOD) of 100 genome copies in the presence of background DNA. The primers and probe developed are suitable for the detection and quantitation of Embrapa 5.1.

  7. Genotyping of Trypanosoma cruzi Sublineage in Human Samples from a North-East Argentina Area by Hybridization with DNA Probes and Specific Polymerase Chain Reaction (PCR)

    Science.gov (United States)

    Diez, Cristina; Lorenz, Virginia; Ortiz, Silvia; Gonzalez, Verónica; Racca, Andrea; Bontempi, Iván; Manattini, Silvia; Solari, Aldo; Marcipar, Iván

    2010-01-01

    We have evaluated blood samples of chronic and congenital Trypanosoma cruzi-infected patients from the city of Reconquista located in the northeast of Argentina where no information was previously obtained about the genotype of infecting parasites. Fourteen samples of congenital and 19 chronical patients were analyzed by hybridization with DNA probes of minicircle hypervariable regions (mHVR). In congenital patients, 50% had single infections with TcIId, 7% single infections with TcIIe, 29% mixed infections with TcIId/e, and 7% had mixed infections with TcIId/b and 7% TcIId/b, respectively. In Chronical patients, 52% had single infections with TcIId, 11% single infections with TcIIe, 26% had mixed infections with TcIId/e, and 11% had non-identified genotypes. With these samples, we evaluated the minicircle lineage-specific polymerase chain reaction assay (MLS-PCR), which involves a nested PCR to HVR minicircle sequences and we found a correlation with hybridization probes of 96.4% for TcIId and 54.8% for TcIIe. PMID:20064998

  8. Light-particle emission as a probe of the rotational degrees of freedom in deep-inelastic reactions

    International Nuclear Information System (INIS)

    Sobotka, L.G.

    1982-05-01

    The emission of alpha particles in coincidence with the most deeply inelastic heavy-ion reactions has been studied for 181 Ta + 165 Ho at 1354 MeV laboratory energy and /sup nat/Ag + 84 Kr at 664 MeV. Alpha particle energy spectra and angular distributions, in coincidence with a projectile-like fragment, were acquired both in the reaction plane and out of the reaction plane at a fixed in-plane angle. The in-plane data for both systems are employed to show that the bulk of the alpha particles in coincidence with the deep-inelastic exit channel can be explained by evaporation from the fully accelerated fragments. Average velocity diagrams, α-particle energy spectra as a function of angle in several rest frames, and α-particle angular distributions are presented. The out-of-plane alpha particle angular distributions and the gamma-ray multiplicities are used to study the transfer and partitioning of angular momentum between the two fragments. For the /sup nat/Ag + 84 Kr system, individual fragment spins are extracted form the alpha particle angular distributions as a function of mass asymmetry while the sum of the fragment spins is derived from the gamma-ray multiplicities. These data, together with the fragment kinetic energies, are consistent with rigid rotation of an intermediate complex consisting of two substantially deformed spheroids in near proximity. These data also indicate that some angular momentum fractionation exists at the largest asymmetries examined. Out-of-plane alpha particle distributions, gamma-ray multiplicities, fragment spins as well as the formalism for the spin evaluation at various levels of sophistication are presented

  9. Light-particle emission as a probe of the rotational degrees of freedom in deep-inelastic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sobotka, L.G.

    1982-05-01

    The emission of alpha particles in coincidence with the most deeply inelastic heavy-ion reactions has been studied for /sup 181/Ta/sup +/ /sup 165/Ho at 1354 MeV laboratory energy and /sup nat/Ag + /sup 84/Kr at 664 MeV. Alpha particle energy spectra and angular distributions, in coincidence with a projectile-like fragment, were acquired both in the reaction plane and out of the reaction plane at a fixed in-plane angle. The in-plane data for both systems are employed to show that the bulk of the alpha particles in coincidence with the deep-inelastic exit channel can be explained by evaporation from the fully accelerated fragments. Average velocity diagrams, ..cap alpha..-particle energy spectra as a function of angle in several rest frames, and ..cap alpha..-particle angular distributions are presented. The out-of-plane alpha particle angular distributions and the gamma-ray multiplicities are used to study the transfer and partitioning of angular momentum between the two fragments. For the /sup nat/Ag + /sup 84/Kr system, individual fragment spins are extracted form the alpha particle angular distributions as a function of mass asymmetry while the sum of the fragment spins is derived from the gamma-ray multiplicities. These data, together with the fragment kinetic energies, are consistent with rigid rotation of an intermediate complex consisting of two substantially deformed spheroids in near proximity. These data also indicate that some angular momentum fractionation exists at the largest asymmetries examined. Out-of-plane alpha particle distributions, gamma-ray multiplicities, fragment spins as well as the formalism for the spin evaluation at various levels of sophistication are presented.

  10. Nuclear clusters as a probe for expansion flow in heavy ion reactions at (10 endash 15)A GeV

    International Nuclear Information System (INIS)

    Mattiello, R.; Mattiello, R.; Sorge, H.; Stoecker, H.; Greiner, W.

    1997-01-01

    A phase space coalescence description based on the Wigner-function method for cluster formation in relativistic nucleus-nucleus collisions is presented. The momentum distributions of nuclear clusters d, t, and He are predicted for central Au(11.6A GeV)Au and Si(14.6A GeV)Si reactions in the framework of the relativistic quantum molecular dynamics transport approach. Transverse expansion leads to a strong shoulder-arm shape and different inverse slope parameters in the transverse spectra of nuclear clusters deviating markedly from thermal distributions. A clear open-quotes bounce-off close-quote close-quote event shape is seen: The averaged transverse flow velocities in the reaction plane are for clusters larger than for protons. The cluster yields, particularly at low p t at midrapidities, and the in-plane (anti)flow of clusters and pions change if suitably strong baryon potential interactions are included. This allows one to study the transient pressure at high density via the event shape analysis of nucleons, nucleon clusters, and other hadrons. copyright 1997 The American Physical Society

  11. Stereoselective synthesis of organosulfur compounds incorporating N-aromatic heterocyclic motifs and quaternary carbon centers via a sulfa-Michael triggered tandem reaction.

    Science.gov (United States)

    Qin, Tianyou; Cheng, Lu; Zhang, Sean Xiao-An; Liao, Weiwei

    2015-06-14

    A novel sulfa-Michael addition (SMA)-triggered tandem reaction was developed by combining a SMA reaction with a simultaneous rearomatization process utilizing a less reactive carbonyl group as an intramolecular electrophile partner, which provided a unique synthetic route to access various organosulfur compounds incorporating an N-aromatic heterocyclic motif and quaternary carbon centers.

  12. Molecular modeling and computational simulation of the photosystem-II reaction center to address isoproturon resistance in Phalaris minor.

    Science.gov (United States)

    Singh, Durg Vijay; Agarwal, Shikha; Kesharwani, Rajesh Kumar; Misra, Krishna

    2012-08-01

    Isoproturon is the only herbicide that can control Phalaris minor, a competitive weed of wheat that developed resistance in 1992. Resistance against isoproturon was reported to be due to a mutation in the psbA gene that encodes the isoproturon-binding D1 protein. Previously in our laboratory, a triazole derivative of isoproturon (TDI) was synthesized and found to be active against both susceptible and resistant biotypes at 0.5 kg/ha but has shown poor specificity. In the present study, both susceptible D1((S)), resistant D1((R)) and D2 proteins of the PS-II reaction center of P. minor have been modeled and simulated, selecting the crystal structure of PS-II from Thermosynechococcus elongatus (2AXT.pdb) as template. Loop regions were refined, and the complete reaction center D1/D2 was simulated with GROMACS in lipid (1-palmitoyl-2-oleoylglycero-3-phosphoglycerol, POPG) environment along with ligands and cofactor. Both S and R models were energy minimized using steepest decent equilibrated with isotropic pressure coupling and temperature coupling using a Berendsen protocol, and subjected to 1,000 ps of MD simulation. As a result of MD simulation, the best model obtained in lipid environment had five chlorophylls, two plastoquinones, two phenophytins and a bicarbonate ion along with cofactor Fe and oxygen evolving center (OEC). The triazole derivative of isoproturon was used as lead molecule for docking. The best worked out conformation of TDI was chosen for receptor-based de novo ligand design. In silico designed molecules were screened and, as a result, only those molecules that show higher docking and binding energies in comparison to isoproturon and its triazole derivative were proposed for synthesis in order to get more potent, non-resistant and more selective TDI analogs.

  13. Perturbative QCD as a probe of hadron structure: Volume 2. Proceedings of RIKEN BNL Research Center workshop

    International Nuclear Information System (INIS)

    1997-01-01

    The workshop brought together about thirty invited participants from around the world, and an almost equal number of Brookhaven users and staff, to discuss recent developments and future prospects for hadronic strong interaction studies at high energy, particularly relating to the RHIC project at Brookhaven. RIKEN and Brookhaven have long traditions in and commitments to the study of the strong interactions, and the advent of the RHIC collider will open new opportunities both for relativistic heavy ion and polarized proton-proton studies. Activities at the RIKEN BNL Research Center are intended to focus on physics opportunities stimulated by this new facility. Thus, one of the purposes of the center is to provide a forum where workers in the field can gather to share and develop their ideas in a stimulating environment. The purpose of the workshop was both to delineate theoretical problems and stimulate collaborations to address them. The workshop focused primarily, but not exclusively, on spin and small-x physics

  14. A DIAMANT Wedding For AFRODITE: Probing Structure and Characterizing Reaction Properties Via Charged-Particle-γ Correlations

    International Nuclear Information System (INIS)

    Mullins, S. M.; Murray, S. H. T.; Bark, R. A.; Gueorguieva, E.; Lawrie, J. J.; Lieder, E. O.; Lieder, R. M.; Papka, P.; Nyako, B. M.; Timar, J.; Berek, G.; Gal, J.; Kalinka, G.; Molnar, J.; Krasznahorkay, A.; Zolnai, L.; Juhasz, K.; Lipoglavsek, M.; Ntshangase, S. S.; Scheurer, J. N.

    2008-01-01

    The DIAMANT-AFRODITE combination has been used to investigate incomplete fusions reactions via the 13 C+ 170 Er entrance channel. The intensity of 176 Hf (populated via the α 3n exit channel) is ∼8% of 178 W (populated via 5n evaporation) which is ∼8 times stronger than that expected from complete fusion. Moreover, 2αxn exit channels leading to Yb nuclei are observed with intensities that are ∼30-to-40% of 176 Hf, for which no yield is expected from complete fusion. A comparison of the intensities from the two-α- and one-α-gated data is consistent with fragmentation of the 13 C beam into (α-α-α-n) which suggests that the population of Yb nuclei results from fusion (or ''massive transfer'') of one the break-up α-particles. A campaign of measurements is scheduled for late 2007 with further investigations planned for 2008, including the continuation of the study of superdeformation in 32 S

  15. Strong Metal Support Interaction of Pt and Ru Nanoparticles Deposited on HOPG Probed by the H-D Exchange Reaction

    DEFF Research Database (Denmark)

    Fiordaliso, Elisabetta M.; Dahl, Søren; Chorkendorff, Ib

    2012-01-01

    The interaction between metals and support is investigated in the case of 50 Å Pt and 50 Å Ru films deposited on a HOPG substrate. The films are prepared by electron beam physical vapor deposition and annealed in UHV to temperatures up to 700 °C. The equilibrium hydrogen exchange rate between...... adsorbed and gas phase at 1 bar is measured before and after annealing. The rate is measured in the temperature range of 40–200 °C at 1 bar, by utilization of the H-D exchange reaction. Experiments are performed on fresh cleaved and sputtered HOPG, which give similar results. We find that annealing...... the films from 150 up to 700 °C increases the amount of carbon present in the films up to 95%, as derived by surface analysis, indicating the formation of a carbon layer on top of the metal films. The exchange rate decreases dramatically with increasing carbon content on the films for both metals, pointing...

  16. Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

    International Nuclear Information System (INIS)

    Reppert, Mike; Kell, Adam; Pruitt, Thomas; Jankowiak, Ryszard

    2015-01-01

    The vibrational spectral density is an important physical parameter needed to describe both linear and non-linear spectra of multi-chromophore systems such as photosynthetic complexes. Low-temperature techniques such as hole burning (HB) and fluorescence line narrowing are commonly used to extract the spectral density for a given electronic transition from experimental data. We report here that the lineshape function formula reported by Hayes et al. [J. Phys. Chem. 98, 7337 (1994)] in the mean-phonon approximation and frequently applied to analyzing HB data contains inconsistencies in notation, leading to essentially incorrect expressions in cases of moderate and strong electron-phonon (el-ph) coupling strengths. A corrected lineshape function L(ω) is given that retains the computational and intuitive advantages of the expression of Hayes et al. [J. Phys. Chem. 98, 7337 (1994)]. Although the corrected lineshape function could be used in modeling studies of various optical spectra, we suggest that it is better to calculate the lineshape function numerically, without introducing the mean-phonon approximation. New theoretical fits of the P870 and P960 absorption bands and frequency-dependent resonant HB spectra of Rb. sphaeroides and Rps. viridis reaction centers are provided as examples to demonstrate the importance of correct lineshape expressions. Comparison with the previously determined el-ph coupling parameters [Johnson et al., J. Phys. Chem. 94, 5849 (1990); Lyle et al., ibid. 97, 6924 (1993); Reddy et al., ibid. 97, 6934 (1993)] is also provided. The new fits lead to modified el-ph coupling strengths and different frequencies of the special pair marker mode, ω sp , for Rb. sphaeroides that could be used in the future for more advanced calculations of absorption and HB spectra obtained for various bacterial reaction centers

  17. Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

    Energy Technology Data Exchange (ETDEWEB)

    Reppert, Mike; Kell, Adam; Pruitt, Thomas [Department of Chemistry, Kansas State University, Manhattan, Kansas 66506 (United States); Jankowiak, Ryszard, E-mail: ryszard@ksu.edu [Department of Chemistry, Kansas State University, Manhattan, Kansas 66506 (United States); Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

    2015-03-07

    The vibrational spectral density is an important physical parameter needed to describe both linear and non-linear spectra of multi-chromophore systems such as photosynthetic complexes. Low-temperature techniques such as hole burning (HB) and fluorescence line narrowing are commonly used to extract the spectral density for a given electronic transition from experimental data. We report here that the lineshape function formula reported by Hayes et al. [J. Phys. Chem. 98, 7337 (1994)] in the mean-phonon approximation and frequently applied to analyzing HB data contains inconsistencies in notation, leading to essentially incorrect expressions in cases of moderate and strong electron-phonon (el-ph) coupling strengths. A corrected lineshape function L(ω) is given that retains the computational and intuitive advantages of the expression of Hayes et al. [J. Phys. Chem. 98, 7337 (1994)]. Although the corrected lineshape function could be used in modeling studies of various optical spectra, we suggest that it is better to calculate the lineshape function numerically, without introducing the mean-phonon approximation. New theoretical fits of the P870 and P960 absorption bands and frequency-dependent resonant HB spectra of Rb. sphaeroides and Rps. viridis reaction centers are provided as examples to demonstrate the importance of correct lineshape expressions. Comparison with the previously determined el-ph coupling parameters [Johnson et al., J. Phys. Chem. 94, 5849 (1990); Lyle et al., ibid. 97, 6924 (1993); Reddy et al., ibid. 97, 6934 (1993)] is also provided. The new fits lead to modified el-ph coupling strengths and different frequencies of the special pair marker mode, ω{sub sp}, for Rb. sphaeroides that could be used in the future for more advanced calculations of absorption and HB spectra obtained for various bacterial reaction centers.

  18. 2H(p, pp) n reaction as a probe of the short-range nuclear force

    International Nuclear Information System (INIS)

    Haftel, M.I.; Petersen, E.L.; Wallace, J.M.

    1976-01-01

    We examine the feasibility of using the 2 H(p, pp) n reaction as a means of extracting information about the short-range behavior of the nuclear force not obtainable from N-N scattering experiments. To do this we use several separable potentials and examine the predicted cross section in various regions of phase space and for beam energies between 14 and 65 MeV. The questions that we address are likely to be insensitive to Coulomb effects. Both the form factor and the energy dependence of the potentials have been modified from the usual Yamaguchi form. The form of the energy dependence is chosen to obtain phase-shift equivalence for two different form factors while guaranteeing a unitary two-body scattering amplitude. The sensitivity of breakup results to the on-shell and off-shell aspects of the nuclear force is examined and discussed. Significant on-shell sensitivity occurs for breakup amplitudes in all states and for cross sections over all regions of phase space. Off-shell sensitivity appears only in the S = 1/2, L = 0 breakup amplitudes, with all S = 3/2 and all L > 0 amplitudes exhibiting negligible off-shell dependence. This result leads to only a very small (< or = 5%) off-shell sensitivity for quasifree scattering. However, cross sections far from quasifree scattering, and in particular cross sections in the final-state interaction region of phase space, exhibit as much as a 50% variation for phase-shift-equivalent potentials. This sensitivity is small at low beam energy and increases with increasing energy. The energy dependence at negative energies of one potential is also altered to adjust the triton binding energy. This enables us to compare phase-shift-equivalent potentials differing off shell but predicting the same triton binding energy. The energy dependence of this potential is somewhat unconventional. Fixing of the triton binding energy reduces the off-shell sensitivity appreciably only for E approximately-less-than 20 MeV

  19. Lowest Q2 Measurement of the γ*p→ Δ Reaction: Probing the Pionic Contribution

    Energy Technology Data Exchange (ETDEWEB)

    Stave, Sean C. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2006-06-01

    The first excited state of the proton, the Delat, can be reached through a magnetic dipole spin flip of one of the quarks (M1) or through electric and Coulomb quadrupole terms (E2 and C2) which indicate a deviation from spherical symmetry. The quark models using the color hyperfine interaction underestimate the size of the quadrupole terms by more than an order of magnitude. Models using the pion cloud do a much better job of describing the data. This is expected due to the spontaneous breaking of chiral symmetry which leads to a cloud of virtual p wave pions which introduce the non-spherical amplitudes. The data presented in this work fill gaps in the low Q², long distance region where the pion cloud is expected to dominate and to produce significant Q2 variation. The p(e¯, ép)π° reaction was measured in the Δ region at Q² = 0.060 (GeV/c)², the lowest Q² to date for pion electroproduction, utilizing out-of-plane magnetic spectrometers at the Mainz Microtron in Germany. This work reports results for the dominant transition magnetic dipole amplitude and the quadrupole to dipole ratios obtained from fitting the new data with models using a three parameter, resonant multipole fit: M³/²1+ = (40.33 +- 0.63stat+syst +-model)(10-³/mπ+), E2/M1=Re(E³/²1+M³/²1+) = (-2.28+- 0.29stat+syst +- 0.20model)%, and C2/M1 =Re(S³/²1+/M³/²1+) poles disagree with predictions of the quark models but are in reasonable agreement with a chiral extrapolation of lattice QCD, chiral effective field theory and dynamical model results confirming the dominance and general Q² variation of the long range pionic contribution. While there is qualitative agreement with the models, there is no quantitative agreement thus indicating the need for further improvement of the models.

  20. Kinetic Isotope Effect Determination Probes the Spin of the Transition State, Its Stereochemistry, and Its Ligand Sphere in Hydrogen Abstraction Reactions of Oxoiron(IV) Complexes.

    Science.gov (United States)

    Mandal, Debasish; Mallick, Dibyendu; Shaik, Sason

    2018-01-16

    This Account outlines interplay of theory and experiment in the quest to identify the reactive-spin-state in chemical reactions that possess a few spin-dependent routes. Metalloenzymes and synthetic models have forged in recent decades an area of increasing appeal, in which oxometal species bring about functionalization of hydrocarbons under mild conditions and via intriguing mechanisms that provide a glimpse of Nature's designs to harness these reactions. Prominent among these are oxoiron(IV) complexes, which are potent H-abstractors. One of the key properties of oxoirons is the presence of close-lying spin-states, which can mediate H-abstractions. As such, these complexes form a fascinating chapter of spin-state chemistry, in which chemical reactivity involves spin-state interchange, so-called two-state reactivity (TSR) and multistate reactivity (MSR). TSR and MSR pose mechanistic challenges. How can one determine the structure of the reactive transition state (TS) and its spin state for these mechanisms? Calculations can do it for us, but the challenge is to find experimental probes. There are, however, no clear kinetic signatures for the reactive-spin-state in such reactions. This is the paucity that our group has been trying to fill for sometime. Hence, it is timely to demonstrate how theory joins experiment in realizing this quest. This Account uses a set of the H-abstraction reactions of 24 synthetic oxoiron(IV) complexes and 11 hydrocarbons, together undergoing H-abstraction reactions with TSR/MSR options, which provide experimentally determined kinetic isotope effect (KIE exp ) data. For this set, we demonstrate that comparing KIE exp results with calculated tunneling-augmented KIE (KIE TC ) data leads to a clear identification of the reactive spin-state during H-abstraction reactions. In addition, generating KIE exp data for a reaction of interest, and comparing these to KIE TC values, provides the mechanistic chemist with a powerful capability to

  1. Evaluation of multiplex ligation-dependent probe amplification analysis versus multiplex polymerase chain reaction assays in the detection of dystrophin gene rearrangements in an Iranian population subset

    Directory of Open Access Journals (Sweden)

    Nayereh Nouri

    2014-01-01

    Full Text Available Background: The Duchenne muscular dystrophy (DMD gene is located in the short arm of the X chromosome (Xp21. It spans 2.4 Mb of the human genomic DNA and is composed of 79 exons. Mutations in the Dystrophin gene result in DMD and Becker muscular dystrophy. In this study, the efficiency of multiplex ligation-dependent probe amplification (MLPA over multiplex polymerase chain reaction (PCR assays in an Iranian population was investigated. Materials and Methods: Multiplex PCR assays and MLPA analysis were carried out in 74 patients affected with DMD. Results: Multiplex PCR detected deletions in 51% of the patients with DMD. MLPA analysis could determine all the deletions detected by the multiplex PCR. Additionally, MLPA was able to identify one more deletion and duplication in patients without detectable mutations by multiplex PCR. Moreover, MLPA precisely determined the exact size of the deletions. Conclusion: Although MLPA analysis is more sensitive for detection of deletions and duplications in the dystrophin gene, multiplex PCR might be used for the initial analysis of the boys affected with DMD in the Iranian population as it was able to detect 95% of the rearrangements in patients with DMD.

  2. Quantitative Tetraplex Real-Time Polymerase Chain Reaction Assay with TaqMan Probes Discriminates Cattle, Buffalo, and Porcine Materials in Food Chain.

    Science.gov (United States)

    Hossain, M A Motalib; Ali, Md Eaqub; Sultana, Sharmin; Asing; Bonny, Sharmin Quazi; Kader, Md Abdul; Rahman, M Aminur

    2017-05-17

    Cattle, buffalo, and porcine materials are widely adulterated, and their quantification might safeguard health, religious, economic, and social sanctity. Recently, conventional polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (RFLP) assays have been documented but they are just suitable for identification, cannot quantify adulterations. We described here a quantitative tetraplex real-time PCR assay with TaqMan Probes to quantify contributions from cattle, buffalo, and porcine materials simultaneously. Amplicon-sizes were very short (106-, 90-, and 146-bp for cattle, buffalo, and porcine) because longer targets could be broken down, bringing serious ambiguity in molecular diagnostics. False negative detection was eliminated through an endogenous control (141-bp site of eukaryotic 18S rRNA). Analysis of 27 frankfurters and 27 meatballs reflected 84-115% target recovery at 0.1-10% adulterations. Finally, a test of 36 commercial products revealed 71% beef frankfurters, 100% meatballs, and 85% burgers contained buffalo adulteration, but no porcine was found in beef products.

  3. The evolutionary pathway from anoxygenic to oxygenic photosynthesis examined by comparison of the properties of photosystem II and bacterial reaction centers.

    Science.gov (United States)

    Allen, J P; Williams, J C

    2011-01-01

    In photosynthetic organisms, such as purple bacteria, cyanobacteria, and plants, light is captured and converted into energy to create energy-rich compounds. The primary process of energy conversion involves the transfer of electrons from an excited donor molecule to a series of electron acceptors in pigment-protein complexes. Two of these complexes, the bacterial reaction center and photosystem II, are evolutionarily related and structurally similar. However, only photosystem II is capable of performing the unique reaction of water oxidation. An understanding of the evolutionary process that lead to the development of oxygenic photosynthesis can be found by comparison of these two complexes. In this review, we summarize how insight is being gained by examination of the differences in critical functional properties of these complexes and by experimental efforts to alter pigment-protein interactions of the bacterial reaction center in order to enable it to perform reactions, such as amino acid and metal oxidation, observable in photosystem II.

  4. Differentiating inflamed and normal lungs by the apparent reaction rate constants of lactate dehydrogenase probed by hyperpolarized (13)C labeled pyruvate.

    Science.gov (United States)

    Xu, He N; Kadlececk, Stephen; Shaghaghi, Hoora; Zhao, Huaqing; Profka, Harilla; Pourfathi, Mehrdad; Rizi, Rahim; Li, Lin Z

    2016-02-01

    Clinically translatable hyperpolarized (HP) (13)C-NMR can probe in vivo enzymatic reactions, e.g., lactate dehydrogenase (LDH)-catalyzed reaction by injecting HP (13)C-pyruvate into the subject, which is converted to (13)C labeled lactate by the enzyme. Parameters such as (13)C-lactate signals and lactate-to-pyruvate signal ratio are commonly used for analyzing the HP (13)C-NMR data. However, the biochemical/biological meaning of these parameters remains either unclear or dependent on experimental settings. It is preferable to quantify the reaction rate constants with a clearer physical meaning. Here we report the extraction of the kinetic parameters of the LDH reaction from HP (13)C-NMR data and investigate if they can be potential predictors of lung inflammation. Male Sprague-Dawley rats (12 controls, 14 treated) were used. One dose of bleomycin (2.5 U/kg) was administered intratracheally to the treatment group. The lungs were removed, perfused, and observed by the HP-NMR technique, where a HyperSense dynamic nuclear polarization system was used to generate the HP (13)C-pyruvate for injecting into the lungs. A 20 mm (1)H/(13)C dual-tuned coil in a 9.4-T Varian vertical bore NMR spectrometer was employed to acquire the (13)C spectral data every 1 s over a time period of 300 s using a non-selective, 15-degree radiofrequency pulse. The apparent rate constants of the LDH reaction and their ratio were quantified by applying ratiometric fitting analysis to the time series data of (13)C labeled pyruvate and lactate. The apparent forward rate constant kp =(3.67±3.31)×10(-4) s(-1), reverse rate constant kl =(4.95±2.90)×10(-2) s(-1), rate constant ratio kp /kl =(7.53±5.75)×10(-3) for the control lungs; kp =(11.71±4.35)×10(-4) s(-1), kl =(9.89±3.89)×10(-2) s(-1), and kp /kl =(12.39±4.18)×10(-3) for the inflamed lungs at the 7(th) day post treatment. Wilcoxon rank-sum test showed that the medians of these kinetic parameters of the 7-day cohort were significantly

  5. Electron transfer. 93. Further reactions of transition-metal-center oxidants with vitamin B12s (Cob(I)alamin)

    International Nuclear Information System (INIS)

    Pillai, G.C.; Ghosh, S.K.; Gould, E.S.

    1988-01-01

    Vitamin B 12s (cob(I)alamin) reduces europium(III), titanium(IV) (TiO(C 2 O 4 ) 2 2- ), and uranium(VI) in aqueous solution. These oxidants undergo one-electron changes, leading in each case to the cobalt product cob(II)alamin (B 12r ). The reduction of Eu 3+ , which is inhibited by TES buffer, but not by glycine, is outer sphere. Its limiting specific rate (1 x 10 2 M -1 s -1 ), incorporated in the Marcus treatment, yields a B 12s ,B 12r self-exchange rate of 10 4.8±0.5 M -1 s -1 . Reductions of TiO(C 2 O 4 ) 2 2- are accelerated by H + and by acetic acid. Kinetic patterns suggest three competing reaction paths involving varying degrees of protonation of the Ti(IV) center or its association with acetic acid. The very rapid reduction of U(VI) (k = 4 x 10 6 M -1 s -1 ) yields U(V) in several buffering media, even when B 12s is taken in excess. The much slower conversion of U(V) to U(IV), although thermodynamically favored, appears to be retarded by the extensive reorganization of the coordination sphere of oxo-bound U(V) that must accompany its acceptance of an additional electron. The observed specific rate for the B 12s -U(VI) reaction is in reasonable agreement, in the framework of the Marcus formalism, with reported values of the formal potential and the self-exchange rate for U(V,VI). 37 references, 4 tables

  6. B-side charge separation in bacterial photosynthetic reaction centers: nanosecond time scale electron transfer from HB- to QB.

    Science.gov (United States)

    Kirmaier, Christine; Laible, Philip D; Hanson, Deborah K; Holten, Dewey

    2003-02-25

    We report time-resolved optical measurements of the primary electron transfer reactions in Rhodobacter capsulatus reaction centers (RCs) having four mutations: Phe(L181) --> Tyr, Tyr(M208) --> Phe, Leu(M212) --> His, and Trp(M250) --> Val (denoted YFHV). Following direct excitation of the bacteriochlorophyll dimer (P) to its lowest excited singlet state P, electron transfer to the B-side bacteriopheophytin (H(B)) gives P(+)H(B)(-) in approximately 30% yield. When the secondary quinone (Q(B)) site is fully occupied, P(+)H(B)(-) decays with a time constant estimated to be in the range of 1.5-3 ns. In the presence of excess terbutryn, a competitive inhibitor of Q(B) binding, the observed lifetime of P(+)H(B)(-) is noticeably longer and is estimated to be in the range of 4-8 ns. On the basis of these values, the rate constant for P(+)H(B)(-) --> P(+)Q(B)(-) electron transfer is calculated to be between approximately (2 ns)(-)(1) and approximately (12 ns)(-)(1), making it at least an order of magnitude smaller than the rate constant of approximately (200 ps)(-)(1) for electron transfer between the corresponding A-side cofactors (P(+)H(A)(-) --> P(+)Q(A)(-)). Structural and energetic factors associated with electron transfer to Q(B) compared to Q(A) are discussed. Comparison of the P(+)H(B)(-) lifetimes in the presence and absence of terbutryn indicates that the ultimate (i.e., quantum) yield of P(+)Q(B)(-) formation relative to P is 10-25% in the YFHV RC.

  7. Spectral properties of chlorines and electron transfer with their participation in the photosynthetic reaction center of photosystem II

    Science.gov (United States)

    Shchupak, E. E.; Ivashin, N. V.

    2014-02-01

    Structural factors that provide localization of excited states and determine the properties of primary donor and acceptor of electron in the reaction center of photosystem II (PSII RC) are studied. The results of calculations using stationary and time-dependent density functional theory indicate an important role of protein environments of chlorophylls PA, PB, BA, and BB and pheophytins HA and HB in the area with a radius of no greater than ≤10 Å in the formation of excitonic states of PSII RC. When the neighboring elements are taken into account, the wavelength of long-wavelength Q y transition of chlorophyll molecules is varied by about 10 nm. The effect is less developed for pheophytin molecules (Δλ ≅ 2 nm). The following elements strongly affect energy of the transition: HisA198 and HisD197 amino-acid residues that serve as ligands of magnesium atoms affect PA and PB, respectively; MetA183 affects PA; MetA172 and MetD198 affect BA; water molecules that are located above the planes of the BA and BB macrocycles form H bonds with carbonyl groups; and phytol chains of PA and PB affect BA, BB, HA, and HB. The analysis of excitonic states, mutual positions of molecular orbitals of electron donors and acceptors, and matrix elements of electron transfer reaction shows that (i) charge separation between BA and HA and PB and BA is possible in the active A branch of cofactors of PSII RC and (ii) electron transfer is blocked at the BB - HB fragment in inactive B branch of PSII RC.

  8. Electronically stimulated deep-center reactions in electron-irradiated InP: Comparison between experiment and recombination-enhancement theories

    International Nuclear Information System (INIS)

    Sibille, A.

    1987-01-01

    We present a detailed study of the recombination enhancement of several defect reactions involving the main deep centers in low-temperature electron-irradiated InP. A fairly good agreement is obtained with the Weeks-Tully-Kimerling theory for the activation energies of the enhanced process. On the other hand, a thorough investigation of a thermally and electronically stimulated defect transformation shows evidence that one major approximation (local vibrational equilibrium) fails, and that the recently proposed [H. Sumi, Phys. Rev. B 29, 4616 (1984)] mechanism of coherent recombination on deep centers is responsible for altered reaction rates at high injection levels

  9. Menaquinone-7 in the reaction center complex of the green sulfur bacterium Chlorobium vibrioforme functions as the electron acceptor A1

    DEFF Research Database (Denmark)

    Kjaer, B; Frigaard, N-U; Yang, F

    1998-01-01

    Photosynthetically active reaction center complexes were prepared from the green sulfur bacterium Chlorobium vibrioforme NCIMB 8327, and the content of quinones was determined by extraction and high-performance liquid chromatography. The analysis showed a stoichiometry of 1.7 molecules of menaqui......Photosynthetically active reaction center complexes were prepared from the green sulfur bacterium Chlorobium vibrioforme NCIMB 8327, and the content of quinones was determined by extraction and high-performance liquid chromatography. The analysis showed a stoichiometry of 1.7 molecules...

  10. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff Mathiasen, Anne-Gitte

    2013-01-01

    Mobile probing is a method, developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time and space......). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings point...... to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face). The development...

  11. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff, Anne-Gitte

    2012-01-01

    Mobile probing is a method, which has been developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time...... and space). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings...... point to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face...

  12. Equilibration kinetics in isolated and membrane-bound photosynthetic reaction centers upon illumination: a method to determine the photoexcitation rate.

    Science.gov (United States)

    Manzo, Anthony J; Goushcha, Alexander O; Barabash, Yuri M; Kharkyanen, Valery N; Scott, Gary W

    2009-07-01

    Kinetics of electron transfer, following variation of actinic light intensity, for photosynthetic reaction centers (RCs) of purple bacteria (isolated and membrane-bound) were analyzed by measuring absorbance changes in the primary photoelectron donor absorption band at 865 nm. The bleaching of the primary photoelectron donor absorption band in RCs, following a sudden increase of illumination from the dark to an actinic light intensity of I(exp), obeys a simple exponential law with the rate constant alphaI(exp) + k(rec), in which alpha is a parameter relating the light intensity, measured in mW/cm(2), to a corresponding theoretical rate in units of reciprocal seconds, and k(rec) is the effective rate constant of the charge recombination in the photosynthetic RCs. In this work, a method for determining the alpha parameter value is developed and experimentally verified for isolated and membrane-bound RCs, allowing for rigorous modeling of RC macromolecule dynamics under varied photoexcitation conditions. Such modeling is necessary for RCs due to alterations of the forward photoexcitation rates and relaxation rates caused by illumination history and intramolecular structural dynamics effects. It is demonstrated that the classical Bouguer-Lambert-Beer formalism can be applied for the samples with relatively low scattering, which is not necessarily the case with strongly scattering media or high light intensity excitation.

  13. Reaction Control System Thruster Cracking Consultation: NASA Engineering and Safety Center (NESC) Materials Super Problem Resolution Team (SPRT) Findings

    Science.gov (United States)

    MacKay, Rebecca A.; Smith, Stephen W.; Shah, Sandeep R.; Piascik, Robert S.

    2005-01-01

    The shuttle orbiter s reaction control system (RCS) primary thruster serial number 120 was found to contain cracks in the counter bores and relief radius after a chamber repair and rejuvenation was performed in April 2004. Relief radius cracking had been observed in the 1970s and 1980s in seven thrusters prior to flight; however, counter bore cracking had never been seen previously in RCS thrusters. Members of the Materials Super Problem Resolution Team (SPRT) of the NASA Engineering and Safety Center (NESC) conducted a detailed review of the relevant literature and of the documentation from the previous RCS thruster failure analyses. It was concluded that the previous failure analyses lacked sufficient documentation to support the conclusions that stress corrosion cracking or hot-salt cracking was the root cause of the thruster cracking and lacked reliable inspection controls to prevent cracked thrusters from entering the fleet. The NESC team identified and performed new materials characterization and mechanical tests. It was determined that the thruster intergranular cracking was due to hydrogen embrittlement and that the cracking was produced during manufacturing as a result of processing the thrusters with fluoride-containing acids. Testing and characterization demonstrated that appreciable environmental crack propagation does not occur after manufacturing.

  14. Energetic change of the primary quinone in photosynthetic reaction center. Mutation, delayed fluorescence and model calculations (Theses of the Ph.D. dissertation)

    International Nuclear Information System (INIS)

    Rinyu, L.

    2007-01-01

    Complete text of publication follows. Photosynthesis is one of the basic metabolic processes of living organisms. Photosynthesizing species (bacteria, algae and higher class plants) convert the energy of light into other forms of free energy (redox potential, electro- chemical potential of ions and protons and phosphate-potential) which are directly suit- able either to cover the energy need of the vital processes of the cell or to storage. In reaction center (RC) protein of photo- synthetic bacteria, electron transfer is initiated upon light excitation from the excited bacteriochlorophyll dimer (P) to the secondary quinone (Q B ) via bacteriopheophytine (Bph) and the primary quinone (Q A ). In Rhodobacter sphaeroides purple bacteria, both quinones are ubiquinone-10, but due to the different protein environment, their electrochemical properties is highly different. Whereas Q A makes one-electron chemistry, Q B can be doubly reduced to form hydroquinone, Q B H 2 by uptake of two protons. Q B H 2 subsequently leaves the RC and is replaced by an oxidized quinone from to membrane pool. The semiquinones are important intermediates in the quinone reduction cycle of the RC. The redox midpoint potentials of the Q/Q - redox pairs (E m ) are also different: the Q A /Q A - has 60 mV more negative potential than the Q B /Q B - couple (pH 8) to make the (interquinone) electron transfer favorable. For fine tuning of the midpoint redox potentials of the quinones, the protein assures appropriate steric and electrostatic environment. The most important aim of this study was the design and production of reaction center mutants in the binding pocket of the primary quinone to investigate the effect of the amino acids of the protein and lipids of the membrane on the thermodynamics of the primary quinone. The first priority was the determination of the absolute free energy gap between the P* and the P + Q A - states in wild type and mutant reaction centers by comparison of the

  15. Pathways and timescales of primary charge separation in the photosystem II reaction center as revealed by a simultaneous fit of time-resolved fluorescence and transient absorption

    NARCIS (Netherlands)

    Novoderezhkin, V.I.; Andrizhiyevskaya, E.G.; Dekker, J.P.; van Grondelle, R.

    2005-01-01

    We model the dynamics of energy transfer and primary charge separation in isolated photosystem II (PSII) reaction centers. Different exciton models with specific site energies of the six core pigments and two peripheral chlorophylls (Chls) in combination with different charge transfer schemes have

  16. Notable light-free catalytic activity for pollutant destruction over flower-like BiOI microspheres by a dual-reaction-center Fenton-like process.

    Science.gov (United States)

    Wang, Liang; Yan, Dengbiao; Lyu, Lai; Hu, Chun; Jiang, Ning; Zhang, Lili

    2018-10-01

    BiOI is widely used as photocatalysts for pollutant removal, water splitting, CO 2 reduction and organic transformation due to its excellent photoelectric properties. Here, we report for the first time that a light-free catalyst consisting of the flower-like BiOI microspheres (f-BiOI MSs) exposing (1 0 1) and (1 1 0) crystal planes prepared by a hydrothermal method in ethylene glycol environment can rapidly eliminate the refractory BPA within only ∼3 min through a Fenton-like process. The reaction activity is ∼190 times higher than that of the conventional Fenton catalyst Fe 2 O 3 . A series of characterizations and experiments reveal the formation of the dual reaction centers on f-BiOI MSs. The electron-rich O centers efficiently reduce H 2 O 2 to OH, while the electron-poor oxygen vacancies capture electrons from the adsorbed pollutants and divert them to the electron-rich area during the Fenton-like reactions. By these processes, pollutants are degraded and mineralized quickly in a wide pH range. Our findings address the problems of the classical Fenton reaction and are useful for the development of efficient Fenton-like catalysts through constructing dual reaction centers. Copyright © 2018 Elsevier Inc. All rights reserved.

  17. Ultrasensitive Single Fluorescence-Labeled Probe-Mediated Single Universal Primer-Multiplex-Droplet Digital Polymerase Chain Reaction for High-Throughput Genetically Modified Organism Screening.

    Science.gov (United States)

    Niu, Chenqi; Xu, Yuancong; Zhang, Chao; Zhu, Pengyu; Huang, Kunlun; Luo, Yunbo; Xu, Wentao

    2018-05-01

    As genetically modified (GM) technology develops and genetically modified organisms (GMOs) become more available, GMOs face increasing regulations and pressure to adhere to strict labeling guidelines. A singleplex detection method cannot perform the high-throughput analysis necessary for optimal GMO detection. Combining the advantages of multiplex detection and droplet digital polymerase chain reaction (ddPCR), a single universal primer-multiplex-ddPCR (SUP-M-ddPCR) strategy was proposed for accurate broad-spectrum screening and quantification. The SUP increases efficiency of the primers in PCR and plays an important role in establishing a high-throughput, multiplex detection method. Emerging ddPCR technology has been used for accurate quantification of nucleic acid molecules without a standard curve. Using maize as a reference point, four heterologous sequences ( 35S, NOS, NPTII, and PAT) were selected to evaluate the feasibility and applicability of this strategy. Surprisingly, these four genes cover more than 93% of the transgenic maize lines and serve as preliminary screening sequences. All screening probes were labeled with FAM fluorescence, which allows the signals from the samples with GMO content and those without to be easily differentiated. This fiveplex screening method is a new development in GMO screening. Utilizing an optimal amplification assay, the specificity, limit of detection (LOD), and limit of quantitation (LOQ) were validated. The LOD and LOQ of this GMO screening method were 0.1% and 0.01%, respectively, with a relative standard deviation (RSD) < 25%. This method could serve as an important tool for the detection of GM maize from different processed, commercially available products. Further, this screening method could be applied to other fields that require reliable and sensitive detection of DNA targets.

  18. Reactive scattering from oriented molecules: The three-center reaction K+ICl --> KI+Cl, KCl+I

    Science.gov (United States)

    Loesch, H. J.; Möller, J.

    1992-12-01

    In a crossed molecular beam experiment, we have measured the angular and time-of-flight (TOF) distributions of the products KCl and KI formed in the reaction K+ICl→KI+Cl, KCl+I at an elevated collision energy of Etr=1.64 eV. Employing the brute force method, we have prepared an oriented ICl beam and studied in addition also the orientation dependence of these distributions. The results are (i) KCl is the dominant product, but also KI is substantially formed with a branching ratio of 4:1; (ii) the double differential reaction cross section in the center-of-mass frame (contour maps) indicates that all products are preferentially forward scattered and constrained to the forward hemisphere; (iii) the KCl flux consists of two distinct components which differ markedly in kinetic energy and dependence on the ICl orientation; there are also indications of the existence of two components of KI; (iv) 65%, 84%, and 64% of the available energy is vested into the internal degrees of freedom for the fast, slow component of KCl and KI, respectively; (v) the existence of two components can be rationalized on the basis of the harpooning mechanism where the jumping electron accesses the ground state or one of the low excited states of the ICl- ion and triggers the subsequent explosion of the ion with more or less kinetic energy of the fragments depending on the initially populated state; (vi) the energies released during dissociation of ICl- in the 2Σ ground state and the first 2Π state are ≤0.19 and ≤1.2 eV, respectively; (vii) the fast KCl component features a negative steric effect suggesting favorable product formation for attacks of K to the I end of ICl, the steric effect of the slow KI component is positive, i.e., attacks to the Cl end form products favorably; the other components exhibit no significant steric effect; (viii) the steric effects can be quantitatively rationalized using the same model as mentioned above; (ix) the magnitude of the steric effect suggests a

  19. Purple-bacterial photosynthetic reaction centers and quantum-dot hybrid-assemblies in lecithin liposomes and thin films.

    Science.gov (United States)

    Lukashev, Eugeny P; Knox, Petr P; Gorokhov, Vladimir V; Grishanova, Nadezda P; Seifullina, Nuranija Kh; Krikunova, Maria; Lokstein, Heiko; Paschenko, Vladimir Z

    2016-11-01

    Quantum dots (QDs) absorb ultraviolet and long-wavelength visible light energy much more efficiently than natural bacterial light-harvesting proteins and can transfer the excitation energy to photosynthetic reaction centers (RCs). Inclusion of RCs combined with QDs as antennae into liposomes opens new opportunities for using such hybrid systems as a basis for artificial energy-transforming devices that potentially can operate with greater efficiency and stability than devices based only on biological components or inorganic components alone. RCs from Rhodobacter sphaeroides and QDs (CdSe/ZnS with hydrophilic covering) were embedded in lecithin liposomes by extrusion of a solution of multilayer lipid vesicles through a polycarbonate membrane or by dialysis of lipids and proteins dispersed with excess detergent. The efficiency of RC and QD interaction within the liposomes was estimated using fluorescence excitation spectra of the photoactive bacteriochlorophyll of the RCs and by measuring the fluorescence decay kinetics of the QDs. The functional activity of the RCs in hybrid complexes was fully maintained, and their stability was even increased. The efficiency of energy transfer between QDs and RCs and conditions of long-term stability of function of such hybrid complexes in film preparations were investigated as well. It was found that dry films containing RCs and QDs, maintained at atmospheric humidity, are capable of maintaining their functional activity for at least some months as judged by measurements of their spectral characteristics, efficiency of energy transfer from QDs to RCs and RC electron transport activity. Addition of trehalose to the films increases the stability further, especially for films maintained at low humidity. These stable hybrid film structures are promising for further studies towards developing new phototransformation devices for biotechnological applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Photosynthesis Is Widely Distributed among Proteobacteria as Demonstrated by the Phylogeny of PufLM Reaction Center Proteins

    Directory of Open Access Journals (Sweden)

    Johannes F. Imhoff

    2018-01-01

    Full Text Available Two different photosystems for performing bacteriochlorophyll-mediated photosynthetic energy conversion are employed in different bacterial phyla. Those bacteria employing a photosystem II type of photosynthetic apparatus include the phototrophic purple bacteria (Proteobacteria, Gemmatimonas and Chloroflexus with their photosynthetic relatives. The proteins of the photosynthetic reaction center PufL and PufM are essential components and are common to all bacteria with a type-II photosynthetic apparatus, including the anaerobic as well as the aerobic phototrophic Proteobacteria. Therefore, PufL and PufM proteins and their genes are perfect tools to evaluate the phylogeny of the photosynthetic apparatus and to study the diversity of the bacteria employing this photosystem in nature. Almost complete pufLM gene sequences and the derived protein sequences from 152 type strains and 45 additional strains of phototrophic Proteobacteria employing photosystem II were compared. The results give interesting and comprehensive insights into the phylogeny of the photosynthetic apparatus and clearly define Chromatiales, Rhodobacterales, Sphingomonadales as major groups distinct from other Alphaproteobacteria, from Betaproteobacteria and from Caulobacterales (Brevundimonas subvibrioides. A special relationship exists between the PufLM sequences of those bacteria employing bacteriochlorophyll b instead of bacteriochlorophyll a. A clear phylogenetic association of aerobic phototrophic purple bacteria to anaerobic purple bacteria according to their PufLM sequences is demonstrated indicating multiple evolutionary lines from anaerobic to aerobic phototrophic purple bacteria. The impact of pufLM gene sequences for studies on the environmental diversity of phototrophic bacteria is discussed and the possibility of their identification on the species level in environmental samples is pointed out.

  1. Identification of protein W, the elusive sixth subunit of the Rhodopseudomonas palustris reaction center-light harvesting 1 core complex.

    Science.gov (United States)

    Jackson, Philip J; Hitchcock, Andrew; Swainsbury, David J K; Qian, Pu; Martin, Elizabeth C; Farmer, David A; Dickman, Mark J; Canniffe, Daniel P; Hunter, C Neil

    2018-02-01

    The X-ray crystal structure of the Rhodopseudomonas (Rps.) palustris reaction center-light harvesting 1 (RC-LH1) core complex revealed the presence of a sixth protein component, variably referred to in the literature as helix W, subunit W or protein W. The position of this protein prevents closure of the LH1 ring, possibly to allow diffusion of ubiquinone/ubiquinol between the RC and the cytochrome bc 1 complex in analogous fashion to the well-studied PufX protein from Rhodobacter sphaeroides. The identity and function of helix W have remained unknown for over 13years; here we use a combination of biochemistry, mass spectrometry, molecular genetics and electron microscopy to identify this protein as RPA4402 in Rps. palustris CGA009. Protein W shares key conserved sequence features with PufX homologs, and although a deletion mutant was able to grow under photosynthetic conditions with no discernible phenotype, we show that a tagged version of protein W pulls down the RC-LH1 complex. Protein W is not encoded in the photosynthesis gene cluster and our data indicate that only approximately 10% of wild-type Rps. palustris core complexes contain this non-essential subunit; functional and evolutionary consequences of this observation are discussed. The ability to purify uniform RC-LH1 and RC-LH1-protein W preparations will also be beneficial for future structural studies of these bacterial core complexes. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  2. A sensitive detection method for MPLW515L or MPLW515K mutation in chronic myeloproliferative disorders with locked nucleic acid-modified probes and real-time polymerase chain reaction.

    OpenAIRE

    Alessandro, Pancrazzi; Paola, Guglielmelli; Vanessa, Ponziani; Gaetano, Bergamaschi; Alberto, Bosi; Giovanni, Barosi; Alessandro M, Vannucchi

    2008-01-01

    Acquired mutations in the juxtamembrane region of MPL (W515K or W515L), the receptor for thrombopoietin, have been described in patients with primary myelofibrosis or essential thrombocythemia, which are chronic myeloproliferative disorders. We have developed a real-time polymerase chain reaction assay for the detection and quantification of MPL mutations that is based on locked nucleic acid fluorescent probes. Mutational analysis was performed using DNA from granulocytes. Reference curves we...

  3. A novel single fluorophore-labeled double-stranded oligonucleotide probe for fluorescence-enhanced nucleic acid detection based on the inherent quenching ability of deoxyguanosine bases and competitive strand-displacement reaction.

    Science.gov (United States)

    Zhang, Yingwei; Tian, Jingqi; Li, Hailong; Wang, Lei; Sun, Xuping

    2012-01-01

    We develop a novel single fluorophore-labeled double-stranded oligonucleotide (OND) probe for rapid, nanostructure-free, fluorescence-enhanced nucleic acid detection for the first time. We further demonstrate such probe is able to well discriminate single-base mutation in nucleic acid. The design takes advantage of an inherent quenching ability of guanine bases. The short strand of the probe is designed with an end-labeled fluorophore that is placed adjacent to two guanines as the quencher located on the long opposite strand, resulting in great quenching of dye fluorescence. In the presence of a target complementary to the long strand of the probe, a competitive strand-displacement reaction occurs and the long strand forms a more stable duplex with the target, resulting in the two strands of the probe being separated from each other. As a consequence of this displacement, the fluorophore and the quencher are no longer in close proximity and dye fluorescence increases, signaling the presence of target.

  4. [Prevalence of reactions secundary to mosquito bites Aedes aegypti at en el Regional Center of Allergy and Clinical Immunology, University Hospital, de Monterrey, Nuevo Leon].

    Science.gov (United States)

    González Diaz, Sandra Nora; Cruz, Alfredo Arias; Sedó Mejía, Giovanni A; Rojas Lozano, Antonio A; Valenzuela, Enrique Avitia; Vidaurri Ojeda, Alma C

    2010-01-01

    although systemic reactions resulting from hymenoptera stings have been studied extensively, the prevalence of allergic reactions to mosquitoes is unknown. to investigate the prevalence of allergic reactions to Aedes aegypti bites in patients seeking treatment at the Allergy and Clinical Immunology Regional Center of Jose E Gonzalez University Hospital in Monterrey, Mexico. we carried out a cross-sectional, descriptive study that included patients receiving skin tests for aeroallergens; skin sensitivity to mosquito bites was also tested. A questionnaire was used to obtain information about previous allergic reactions to mosquito bites. a total of 482 patients between 2 and 60 years of age were included; 53% were female, 407 (84.4%) had a history of local reactions to mosquito bites. Twelve patients (2.4%) stated a history of large local reaction; three (0.6%) of them with a positive skin prick test, one (0.2%) of those had systemic reaction history to mosquito. Eighty five (17.6%) patients had a positive mosquito skin test and 307 (63.6%) had a positive skin test for at least one aeroallergen. Seventy-eight (91.7%) of the 85 patients with a positive mosquito skin test had a history of local skin reactions to mosquito bite (odds ratio: 2.303 [confidence interval (CI) 1.037-5.10]. There was no statistically significance association between allergic diseases and mosquito allergy. adverse reactions and allergic reactions to mosquito bites occur frequently. However mosquito allergy is low. Further studies are required to determine the prevalence of mosquito allergy in the general population.

  5. Reactions on catalytic probe surface during oxygen plasma treatment of polyether sulphone: Reakcije na površini katalitične sonde med plazemsko obdelavo polieter sulfona:

    OpenAIRE

    Mozetič, Miran

    1998-01-01

    Experiments on the behavior of a nickel catalytic probe during activation of the surface of polyether sulphone in oxygen plasma are described. The temperature of the probe mounted 30 cm apart from inductively coupled RF oxygen plasma was measured for the case of empty dischaarge vessel and the case a sample with the dimensions of 8 cm x 1.2 cm x 0.4 cm was mounted in the middle of the discharge coil. It was found that both the maximum temperature and the first time derivative of the probe was...

  6. Site Energies of Active and Inactive Pheophytins in the Reaction Center of Photosystem II from Chlamydomonas Reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Acharya, K.; Neupane, B.; Zazubovich, V.; Sayre, R. T.; Picorel, R.; Seibert, M.; Jankowiak, R.

    2012-03-29

    It is widely accepted that the primary electron acceptor in various Photosystem II (PSII) reaction center (RC) preparations is pheophytin {alpha} (Pheo {alpha}) within the D1 protein (Pheo{sub D1}), while Pheo{sub D2} (within the D2 protein) is photochemically inactive. The Pheo site energies, however, have remained elusive, due to inherent spectral congestion. While most researchers over the past two decades placed the Q{sub y}-states of Pheo{sub D1} and Pheo{sub D2} bands near 678-684 and 668-672 nm, respectively, recent modeling [Raszewski et al. Biophys. J. 2005, 88, 986-998; Cox et al. J. Phys. Chem. B 2009, 113, 12364-12374] of the electronic structure of the PSII RC reversed the assignment of the active and inactive Pheos, suggesting that the mean site energy of Pheo{sub D1} is near 672 nm, whereas Pheo{sub D2} ({approx}677.5 nm) and Chl{sub D1} ({approx}680 nm) have the lowest energies (i.e., the Pheo{sub D2}-dominated exciton is the lowest excited state). In contrast, chemical pigment exchange experiments on isolated RCs suggested that both pheophytins have their Q{sub y} absorption maxima at 676-680 nm [Germano et al. Biochemistry 2001, 40, 11472-11482; Germano et al. Biophys. J. 2004, 86, 1664-1672]. To provide more insight into the site energies of both Pheo{sub D1} and Pheo{sub D2} (including the corresponding Q{sub x} transitions, which are often claimed to be degenerate at 543 nm) and to attest that the above two assignments are most likely incorrect, we studied a large number of isolated RC preparations from spinach and wild-type Chlamydomonas reinhardtii (at different levels of intactness) as well as the Chlamydomonas reinhardtii mutant (D2-L209H), in which the active branch Pheo{sub D1} is genetically replaced with chlorophyll {alpha} (Chl {alpha}). We show that the Q{sub x}-/Q{sub y}-region site energies of Pheo{sub D1} and Pheo{sub D2} are {approx}545/680 nm and {approx}541.5/670 nm, respectively, in good agreement with our previous assignment

  7. Comparison of calculated and experimental isotope edited FTIR difference spectra for purple bacterial photosynthetic reaction centers with different quinones incorporated into the QA binding site.

    Directory of Open Access Journals (Sweden)

    Nan eZhao

    2013-08-01

    Full Text Available Previously we have shown that ONIOM type (QM/MM calculations can be used to simulate isotope edited FTIR difference spectra for neutral ubiquinone in the QA binding site in Rhodobacter sphaeroides photosynthetic reaction centers. Here we considerably extend upon this previous work by calculating isotope edited FTIR difference spectra for reaction centers with a variety of unlabeled and 18O labeled foreign quinones incorporated into the QA binding site. Isotope edited spectra were calculated for reaction centers with 2,3-dimethoxy-5,6-dimethyl-1,4-benzoquinone (MQ0, 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ, and 2,3-dimethyl-l,4-naphthoquinone (DMNQ incorporated, and compared to corresponding experimental spectra. The calculated and experimental spectra agree well, further demonstrating the utility and applicability of our ONIOM approach for calculating the vibrational properties of pigments in protein binding sites.The normal modes that contribute to the bands in the calculated spectra, their composition, frequency and intensity, and how these quantities are modified upon 18O labeling, are presented. This computed information leads to a new and more detailed understanding/interpretation of the experimental FTIR difference spectra. Hydrogen bonding to the carbonyl groups of the incorporated quinones is shown to be relatively weak. It is also shown that there is some asymmetry in hydrogen bonding, accounting for 10-13 cm-1 separation in the frequencies of the carbonyl vibrational modes of the incorporated quinones. The extent of asymmetry H-bonding could only be established by considering the spectra for various types of quinones incorporated into the QA binding site. The quinones listed above are tail-less. Spectra were also calculated for reaction centers with corresponding tail containing quinones incorporated, and it is found that replacement of the quinone methyl group by a phytyl or prenyl chain does not alter ONIOM calculated s

  8. Evolution of direct mechanisms with incident energy from the Coulomb-barrier to relativistic energies. - Two-center effects in nucleon transfer between nuclei. - Signatures of nucleon promotion in heavy ion reactions at barrier energies

    International Nuclear Information System (INIS)

    Oertzen, W. von; Voit, H.; Imanishi, B.

    1988-10-01

    This report contains a review article considering the evolution of direct mechanisms with incident energy in heavy ion reactions and two theoretical articles concerning two-center effects in transfer reactions between heavy ions and the nucleon promotion in heavy ion reactions. See hints under the relevant topics. (HSI)

  9. Nuclear Data Center (NDC) of Korea Atomic Energy Research Institute (KAERI). Progress Report to the IAEA Technical Meeting of Nuclear Reaction Data Centers (NRDC)

    International Nuclear Information System (INIS)

    Lee, Young-Ouk

    2012-01-01

    Nuclear Data Center (NDC, former Nuclear Data Evaluation Lab.) of Korea Atomic Energy Research Institute (KAERI) has a director, 10 permanent staffs (2 in evaluation, 1 in measurement, 2 in atomic and molecular data, 2 in processing and validation, 3 in applications), one PhD student and one secretary. KAERI/NDC recently expanded its scope of work into the atomic and molecular data where two permanent staffs are involved. Mission of KAERI/NDC is disseminating outcomes of international network as well as promoting domestic nuclear data activities and related applications.

  10. Characterization of hypersensitivity reactions reported among Andrographis paniculata users in Thailand using Health Product Vigilance Center (HPVC) database.

    Science.gov (United States)

    Suwankesawong, Wimon; Saokaew, Surasak; Permsuwan, Unchalee; Chaiyakunapruk, Nathorn

    2014-12-24

    Andrographis paniculata (andrographis) is one of the herbal products that are widely used for various indications. Hypersensitivity reactions have been reported among subjects receiving Andrographis paniculata in Thailand. Understanding of characteristics of patients, adverse events, and clinical outcomes is essential for ensuring population safety.This study aimed to describe the characteristics of hypersensitivity reactions reported in patients receiving andrographis containing products in Thailand using national pharmacovigilance database. Thai Vigibase data from February 2001 to December 2012 involving andrographis products were used. This database includes the reports submitted through the spontaneous reporting system and intensive monitoring programmes. The database contained patient characteristic, adverse events associated with andrographis products, and details on seriousness, causality, and clinical outcomes. Case reports were included for final analysis if they met the inclusion criteria; 1) reports with andrographis being the only suspected cause, 2) reports with terms consistent with the constellation of hypersensitivity reactions, and 3) reports with terms considered critical terms according to WHO criteria. Descriptive statistics were used. A total of 248 case reports of andrographis-associated adverse events were identified. Only 106 case reports specified andrographis herbal product as the only suspected drug and reported at least one term consistent with constellation of hypersensitivity reactions. Most case reports (89%) came from spontaneous reporting system with no previously documented history of drug allergy (88%). Of these, 18 case reports were classified as serious with 16 cases requiring hospitalization. For final assessment, the case reports with terms consistent with constellation of hypersensitivity reactions and critical terms were included. Thirteen case reports met such criteria including anaphylactic shock (n = 5), anaphylactic

  11. Adverse reactions of Methylphenidate in children with attention deficit-hyperactivity disorder: Report from a referral center

    Science.gov (United States)

    Khajehpiri, Zahra; Mahmoudi-Gharaei, Javad; Faghihi, Toktam; Karimzadeh, Iman; Khalili, Hossein; Mohammadi, Mostafa

    2014-01-01

    Objective: The aim of the current study was to determine various aspects of methylphenidate adverse reactions in children with attention deficit-hyperactivity disorder (ADHD) in Iran. Methods: During the 6 months period, all children under methylphenidate treatment alone or along with other agents attending a university-affiliated psychology clinic were screened regarding all subjective and objective adverse drug reactions (ADRs) of methylphenidate. Causality and seriousness of detected ADRs were assessed by relevant World Health Organization definitions. The Schumock and Thornton questionnaire was used to determine preventability of ADRs. Findings: Seventy-one patients including 25 girls and 46 boys with ADHD under methylphenidate treatment were enrolled within the study period. All (100%) ADHD children under methylphenidate treatment developed at least one ADR. Anorexia (74.3%), irritability (57.1%), and insomnia (47.2%) were the most frequent methylphenidate-related adverse reactions. Except for one, all other detected ADRs were determined to be mild. In addition, no ADR was considered to be preventable and serious. Conclusion: Our data suggested that although methylphenidate related adverse reactions were common in children with ADHD, but they were mainly mild and nonserious. PMID:25535621

  12. Quasielastic reactions

    International Nuclear Information System (INIS)

    Henning, W.

    1979-01-01

    Quasielastic reaction studies, because of their capability to microscopically probe nuclear structure, are still of considerable interest in heavy-ion reactions. The recent progress in understanding various aspects of the reaction mechanism make this aim appear closer. The relation between microscopic and macroscopic behavior, as suggested, for example, by the single proton transfer data to individual final states or averaged excitation energy intervals, needs to be explored. It seems particularly useful to extend measurements to higher incident energies, to explore and understand nuclear structure aspects up to the limit of the energy range where they are important

  13. Magnitude and direction of the change in dipole moment associated with excitation of the primary electron donor in Rhodopseudomonas sphaeroides reaction centers

    Energy Technology Data Exchange (ETDEWEB)

    Lockhart, D.J.; Boxer, S.G.

    1987-02-10

    The magnitude and direction of the change in dipole moment, ..delta mu.., associated with the Q/sub y/ transition of the dimeric primary electron donor (special pair or P870) in Rhodopseudomonas sphaeroides reaction centers have been measured by Stark spectroscopy at 20 /sup 0/C. The magnitude of ..delta mu.. is found to be f/sup -1/ (10.3 +/- 0.7) D, where f is a correction factor for the local dielectric properties of the protein matrix. With the spherical cavity approximation and an effective local dielectric constant of 2, f = 1.2, and absolute value of ..delta mu.. is 8.6 +/- 0.6 D. Absolute value of ..delta mu.. for the Q/sub y/ transition of the special pair is approximately a factor of 3.4 and 2 greater than for the monomeric bacteriochlorophylls and bacteriopheophytins, respectively, in the reaction center. The angle between ..delta mu.. and the transition dipole moment for excitation of the first singlet electron state of the special pair was found to be 24 +/- 2/sup 0/. The measured values are combined to suggest a physical model in which the lowest excited singlet state of the special pair has substantial charge-transfer character and where charge is separated between the two monomers comprising the dimeric special pair. This leads to the hypothesis that the first charge-separated state in bacterial photosynthesis is formed directly upon photoexcitation. These data provide stringent values for comparison with theoretical calculations of the electronic structure of the chromophores in the reaction center.

  14. Conformational differences between the methoxy groups of QA and QB site ubisemiquinones in bacterial reaction centers: a key role for methoxy group orientation in modulating ubiquinone redox potential.

    Science.gov (United States)

    Taguchi, Alexander T; O'Malley, Patrick J; Wraight, Colin A; Dikanov, Sergei A

    2013-07-09

    Ubiquinone is an almost universal, membrane-associated redox mediator. Its ability to accept either one or two electrons allows it to function in critical roles in biological electron transport. The redox properties of ubiquinone in vivo are determined by its environment in the binding sites of proteins and by the dihedral angle of each methoxy group relative to the ring plane. This is an attribute unique to ubiquinone among natural quinones and could account for its widespread function with many different redox complexes. In this work, we use the photosynthetic reaction center as a model system for understanding the role of methoxy conformations in determining the redox potential of the ubiquinone/semiquinone couple. Despite the abundance of X-ray crystal structures for the reaction center, quinone site resolution has thus far been too low to provide a reliable measure of the methoxy dihedral angles of the primary and secondary quinones, QA and QB. We performed 2D ESEEM (HYSCORE) on isolated reaction centers with ubiquinones (13)C-labeled at the headgroup methyl and methoxy substituents, and have measured the (13)C isotropic and anisotropic components of the hyperfine tensors. Hyperfine couplings were compared to those derived by DFT calculations as a function of methoxy torsional angle allowing estimation of the methoxy dihedral angles for the semiquinones in the QA and QB sites. Based on this analysis, the orientation of the 2-methoxy groups are distinct in the two sites, with QB more out of plane by 20-25°. This corresponds to an ≈50 meV larger electron affinity for the QB quinone, indicating a substantial contribution to the experimental difference in redox potentials (60-75 mV) of the two quinones. The methods developed here can be readily extended to ubiquinone-binding sites in other protein complexes.

  15. A Perspective on the Maillard Reaction and the Analysis of Protein Glycation by Mass Spectrometry: Probing the Pathogenesis of Chronic Disease

    OpenAIRE

    Zhang, Qibin; Ames, Jennifer M.; Smith, Richard D.; Baynes, John W.; Metz, Thomas O.

    2009-01-01

    The Maillard reaction, starting from the glycation of protein and progressing to the formation of advanced glycation end-products (AGEs), is implicated in the development of complications of diabetes mellitus, as well as in the pathogenesis of cardiovascular, renal, and neurodegenerative diseases. In this perspective review, we provide an overview on the relevance of the Maillard reaction in the pathogenesis of chronic disease and discuss traditional approaches and recent developments in the ...

  16. Report on the consultants` meeting on co-ordination of the nuclear reaction data centers (technical aspects)

    Energy Technology Data Exchange (ETDEWEB)

    Schwerer, O; Wienke, H [eds.

    1997-10-01

    The report summarizes the co-ordination meeting of the network of Nuclear Reaction Data Centres organized by the IAEA in 1997. The meeting was attended by technical staff from ten member centres of the network (representing USA, Russia, China, Japan, Hungary, OECD-NEA and IAEA) to discuss technical matters of the nuclear data compilation and exchange by means of the jointly operated computerized systems CINDA, EXFOR, ENDF and others. Observers from Belgium and Ukraine also attended the meeting. The document includes status reports of all centres and selected working papers. Refs, figs, tabs.

  17. Report on the consultants' meeting on co-ordination of the nuclear reaction data centers (technical aspects)

    International Nuclear Information System (INIS)

    Schwerer, O.; Wienke, H.

    1997-10-01

    The report summarizes the co-ordination meeting of the network of Nuclear Reaction Data Centres organized by the IAEA in 1997. The meeting was attended by technical staff from ten member centres of the network (representing USA, Russia, China, Japan, Hungary, OECD-NEA and IAEA) to discuss technical matters of the nuclear data compilation and exchange by means of the jointly operated computerized systems CINDA, EXFOR, ENDF and others. Observers from Belgium and Ukraine also attended the meeting. The document includes status reports of all centres and selected working papers

  18. Probing Metal Carbonation Reactions of CO2 in a Model System Containing Forsterite and H2O Using Si-29, C-13 Magic Angle Sample Spinning NMR Spectroscopy

    Science.gov (United States)

    Hu, J.; Kwak, J.; Hoyt, D. W.; Sears, J. A.; Rosso, K. M.; Felmy, A. R.

    2009-12-01

    Ex situ solid state NMR have been used for the first time to study fundamental mineral carbonation processes and reaction extent relevant to geologic carbon sequestration using a model silicate mineral forsterite (Mg2SiO4)+scCO2 with and without H2O. Run conditions were 80C and 96 bar. Si-29 NMR clearly shows that in the absence of CO2, the role of H2O is to hydrolyze surface Mg-O-Si bonds to produce Mg2+, and mono- and oligomeric hydroxylated silica species. The surface hydrolysis products contain only Q0 (Si(OH)4) and Q1 (Si(OH)3OSi) species. An equilibrium between Q0, Q1 and Mg2+ with a saturated concentration equivalent to less than 3.2% of the Mg2SiO4 conversion is obtained at a reaction time of up to 7 days. Using scCO2 without H2O, no reaction is observed within 7 days. Using both scCO2 and H2O, the surface reaction products for silica are mainly Q3 (SiOH(OSi)3) species accompanied by a lesser amount of Q2 (Si(OH)2(OSi)2) and Q4 (Si(OSi)4). However, no Q0 and Q1 were detected, indicating the carbonic acid formation/deprotonation and magnesite (MgCO3) precipitation reactions are faster than the forsterite hydrolysis process. Thus it can be concluded that the Mg2SiO4 hydrolysis process is the rate limiting step of the overall mineral carbonation process. Si-29 NMR combined with XRD, TEM, SAED and EDX further reveal that the reaction is a surface reaction with the Mg2SiO4 crystallite in the core and with condensed Q2-Q4 species forming amorphous surface layers. C-13 MAS NMR identified a possible reaction intermediates as (MgCO3)4*Mg(OH)2*5H2O. However, at long reaction times only crystallite magnesite MgCO3 products are observed. This research is part of a broader effort at PNNL to develop experimental tools and fundamental insights into chemical transformations affecting subsurface CO2 reactive transport. Si-29 (left) and C-13 (right) MAS NMR spectra of Mg2SiO4 under various reaction conditions. Si-29 NMR reveals that in scCO2 without H2O, no reaction is

  19. Size dependent reactivity of metal nanoparticles and alloys supported on HOPG, probed by the H-D exchange and the NH3 decomposition reactions

    DEFF Research Database (Denmark)

    Fiordaliso, Elisabetta Maria

    this investigation have been summarized in a scientific article which has been submitted to the Journal of Physical Chemistry. The second reaction investigated in this thesis is the NH3 decomposition reaction, relevant for hydrogen storage and production in a COx free environment, which has been performed on Ru, Ir......, Rh and Pt thin films, on Ru nanoparticles and on Ir/Ru alloys. Preliminary results indicated that Ru is the most active among the selected metals, but no definitive conclusions can be drawn on the effect of the particle diameter on the decomposition rate. In the case of the Ru/Ir alloys, it is found...

  20. A Perspective on the Maillard Reaction and the Analysis of Protein Glycation by Mass Spectrometry: Probing the Pathogenesis of Chronic Disease

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qibin; Ames, Jennifer M.; Smith, Richard D.; Baynes, John; Metz, Thomas O.

    2008-12-18

    The Maillard reaction, starting from the glycation of protein and progressing to the formation of advanced glycation end-products (AGEs), is implicated in the development of complications of diabetes mellitus, as well as in the pathogenesis of cardiovascular, renal, and neurodegenerative diseases. In this perspective review, we provide on overview on the relevance of the Maillard reaction in the pathogenesis of chronic disease and discuss traditional approaches and recent developments in the analysis of glycated proteins by mass spectrometry. We propose that proteomics approaches, particularly bottom-up proteomics, will play a significant role in analyses of clinical samples leading to the identification of new markers of disease development and progression.

  1. A perspective on the Maillard reaction and the analysis of protein glycation by mass spectrometry: probing the pathogenesis of chronic disease.

    Science.gov (United States)

    Zhang, Qibin; Ames, Jennifer M; Smith, Richard D; Baynes, John W; Metz, Thomas O

    2009-02-01

    The Maillard reaction, starting from the glycation of protein and progressing to the formation of advanced glycation end-products (AGEs), is implicated in the development of complications of diabetes mellitus, as well as in the pathogenesis of cardiovascular, renal, and neurodegenerative diseases. In this perspective review, we provide an overview on the relevance of the Maillard reaction in the pathogenesis of chronic disease and discuss traditional approaches and recent developments in the analysis of glycated proteins by mass spectrometry. We propose that proteomics approaches, particularly bottom-up proteomics, will play a significant role in analyses of clinical samples leading to the identification of new markers of disease development and progression.

  2. Oxidation reaction of ferrocytochrome C by ferricyanide as a probe to effects of alcohols on structure and reactivity of the protein. Technical progress report

    Energy Technology Data Exchange (ETDEWEB)

    Ilan, Y.; Shafferman, A.

    1977-05-01

    Results are reported on the effect of ethanol on the oxidation of ferrocytochrome c by ferricyanide and its cumulative effect with pH and temperature, on structure and spectra of cytochrome c. It is concluded that low concentrations of alcohols which do not change dramatically the structure and physical properties of cytochrome c, but produce changes in the structure of water, cause small changes in the structure of the protein. This is manifested by the shift in the pKa, and also in the retardation of the redox reactions. This indicates that water molecules participate in the reaction complex of cytochrome c with its redox substrates. (DLC)

  3. The importance of a hot-sequential mechanism in triplet-state formation by charge recombination in reaction centers of bacterial photosynthesis

    International Nuclear Information System (INIS)

    Saito, K.; Mukai, K.; Sumi, H.

    2006-01-01

    In photosynthesis, pigment-excitation energies in the antenna system produced by light harvesting are transferred among antenna pigments toward the core antenna, where they are captured by the reaction center and initially fixed in the form of a charge separation. Primary charge separation between an oxidized special pair (P + ) and a reduced bacteriopheohytin (H - ) is occasionally intervened by recombination, and a spin-triplet state ( 3 P*) is formed on P in the bacterial reaction center. The 3 P* state is harmful to bio-organisms, inducing the formation of the highly damaging singlet oxygen species. Therefore, understanding the 3 P*-formation mechanism is important. The 3 P* formation is mediated by a state |m> of intermediate charge separation between P and the accessory chlorophyll, which is located between P and H. It will be shown theoretically in the present work that at room temperature, not only the mechanism of superexchange by quantum-mechanical virtual mediation at |m>, but also a hot-sequential mechanism contributes to the mediation. In the latter, although |m> is produced as a real state, the final state 3 P* is quickly formed during thermalization of phonons in the protein matrix in |m>. In the former, the final state is formed more quickly before dephasing-thermalization of phonons in |m>. 3 P* is unistep formed from the charge-separated state in the both mechanisms

  4. A Combined Probe-Molecule, Mössbauer, Nuclear Resonance Vibrational Spectroscopy, and Density Functional Theory Approach for Evaluation of Potential Iron Active Sites in an Oxygen Reduction Reaction Catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kneebone, Jared L. [Univ. of Rochester, Rochester, NY (United States); Daifuku, Stephanie L. [Univ. of Rochester, Rochester, NY (United States); Kehl, Jeffrey A. [Univ. of Rochester, Rochester, NY (United States); Wu, Gang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chung, Hoon T. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hu, Michael Y. [Argonne National Lab. (ANL), Argonne, IL (United States); Alp, E. Ercan [Argonne National Lab. (ANL), Argonne, IL (United States); More, Karren L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zelenay, Piotr [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Holby, Edward F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Neidig, Michael L. [Univ. of Rochester, Rochester, NY (United States)

    2017-07-06

    While non-precious metal M-N-C (M = Fe or Co) catalysts have been developed that are effective for the oxygen reduction reaction in polymer electrolyte fuel cells, no consensus has yet been reached regarding the nature of the M sites in these heterogeneous catalysts that are responsible for reaction with dioxygen (O2). While multiple studies have developed correlations between Fe distributions in as-prepared catalysts and ORR activity, the direct identification of sites reactive towards O2 or O2-analog molecules remains a significant challenge. In the present study, we demonstrate a new approach to identifying and characterizing potential Fe active sites in complex ORR catalysts that combines an effective probe molecule (NO(g)) Mössbauer spectroscopy and nuclear resonance vibrational spectroscopy (NRVS) with density functional theory (DFT) calculations. Mössbauer spectroscopic studies demonstrate that NO(g) treatment of electrochemically reduced PANI-57Fe-C leads to selective reaction with only a sub-set of the Fe species present. Nuclear resonance vibrational spectroscopic studies identified new Fe-ligand vibrations associated with the site reactive towards NO(g). DFT calculations of vibrational properties of a small selection of previously proposed active site structures suggest that graphene zig-zag edge hosted Fe-N structures may be responsible for the observed vibrational behavior with NO(g) probe molecules. Moreover, such sites are likely also reactive to O2, possibly serving as the ORR active sites in the synthesized materials.

  5. Probing the semi-magicity of $^{68}$Ni via the $^{3}$H($^{66}$Ni,$^{68}$Ni)p two-neutron transfer reaction in inverse kinematics

    CERN Multimedia

    Reiter, P; Blazhev, A A; Kruecken, R; Franchoo, S; Mertzimekis, T; Darby, I G; Van de walle, J; Raabe, R; Elseviers, J; Gernhaeuser, R A; Sorlin, O H; Georgiev, G P; Bree, N C F; Habs, D; Chapman, R; Gaudefroy, L; Diriken, J V J; Jenkins, D G; Kroell, T; Axiotis, M; Huyse, M L; Patronis, N

    We propose to perform the two-neutron transfer reaction $^{3}$H($^{66}$Ni, $^{68}$Ni)$p$ using the ISOLDE radioactive ion beam at 2.7 $A$ MeV and the MINIBALL + T-REX setup to characterize the 0$^{+}$ and 2$^{+}$ states in $^{68}$Ni.

  6. Monitoring of an esterification reaction by on-line direct liquid sampling mass spectrometry and in-line mid infrared spectrometry with an attenuated total reflectance probe

    International Nuclear Information System (INIS)

    Owen, Andrew W.; McAulay, Edith A.J.; Nordon, Alison; Littlejohn, David; Lynch, Thomas P.; Lancaster, J. Steven; Wright, Robert G.

    2014-01-01

    Highlights: • High efficiency thermal vaporiser designed and used for on-line reaction monitoring. • Concentration profiles of all reactants and products obtained from mass spectra. • By-product formed from the presence of an impurity detected by MS but not MIR. • Mass spectrometry can detect trace and bulk components unlike molecular spectrometry. - Abstract: A specially designed thermal vaporiser was used with a process mass spectrometer designed for gas analysis to monitor the esterification of butan-1-ol and acetic anhydride. The reaction was conducted at two scales: in a 150 mL flask and a 1 L jacketed batch reactor, with liquid delivery flow rates to the vaporiser of 0.1 and 1.0 mL min −1 , respectively. Mass spectrometry measurements were made at selected ion masses, and classical least squares multivariate linear regression was used to produce concentration profiles for the reactants, products and catalyst. The extent of reaction was obtained from the butyl acetate profile and found to be 83% and 76% at 40 °C and 20 °C, respectively, at the 1 L scale. Reactions in the 1 L reactor were also monitored by in-line mid-infrared (MIR) spectrometry; off-line gas chromatography (GC) was used as a reference technique when building partial least squares (PLS) multivariate calibration models for prediction of butyl acetate concentrations from the MIR spectra. In validation experiments, good agreement was achieved between the concentration of butyl acetate obtained from in-line MIR spectra and off-line GC. In the initial few minutes of the reaction the profiles for butyl acetate derived from on-line direct liquid sampling mass spectrometry (DLSMS) differed from those of in-line MIR spectrometry owing to the 2 min transfer time between the reactor and mass spectrometer. As the reaction proceeded, however, the difference between the concentration profiles became less noticeable. DLSMS had advantages over in-line MIR spectrometry as it was easier to generate

  7. Probe Storage

    NARCIS (Netherlands)

    Gemelli, Marcellino; Abelmann, Leon; Engelen, Johannes Bernardus Charles; Khatib, M.G.; Koelmans, W.W.; Zaboronski, Olog; Campardo, Giovanni; Tiziani, Federico; Laculo, Massimo

    2011-01-01

    This chapter gives an overview of probe-based data storage research over the last three decades, encompassing all aspects of a probe recording system. Following the division found in all mechanically addressed storage systems, the different subsystems (media, read/write heads, positioning, data

  8. Cultural probes

    DEFF Research Database (Denmark)

    Madsen, Jacob Østergaard

    The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation.......The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation....

  9. High spatial resolution Kelvin probe force microscopy with coaxial probes

    International Nuclear Information System (INIS)

    Brown, Keith A; Westervelt, Robert M; Satzinger, Kevin J

    2012-01-01

    Kelvin probe force microscopy (KPFM) is a widely used technique to measure the local contact potential difference (CPD) between an AFM probe and the sample surface via the electrostatic force. The spatial resolution of KPFM is intrinsically limited by the long range of the electrostatic interaction, which includes contributions from the macroscopic cantilever and the conical tip. Here, we present coaxial AFM probes in which the cantilever and cone are shielded by a conducting shell, confining the tip–sample electrostatic interaction to a small region near the end of the tip. We have developed a technique to measure the true CPD despite the presence of the shell electrode. We find that the behavior of these probes agrees with an electrostatic model of the force, and we observe a factor of five improvement in spatial resolution relative to unshielded probes. Our discussion centers on KPFM, but the field confinement offered by these probes may improve any variant of electrostatic force microscopy. (paper)

  10. 1-acetylvinyl acrylates: new captodative olefins bearing an internal probe for the evaluation of the relative reactivity of captodative against electron-deficient double bonds in Diels-Alder and Friedel-Crafts reactions

    International Nuclear Information System (INIS)

    Herrera, Rafael; Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Mich.; Jimenez-Vazquez, Hugo A.; Delgado, Francisco; Tamariz, Joaquin; Soederberg, Bjoern C.G.

    2005-01-01

    The captodative olefins 1-acetylvinyl esters of methacrylic and trans-crotonic acids, 3a and 3b, have been prepared. The presence of a second double bond in the molecule, acting as an internal probe, allowed us to compare their relative reactivity in Diels-Alder and Friedel-Crafts reactions. The reactivity was evaluated with cyclopentadiene (6) as diene in Diels-Alder cycloadditions, and with furan (9) and thiophene (10) as heteroaromatic Friedel-Crafts substrates. In both processes, the captodative enone double bond proved to be more reactive than that in the acrylic moiety. FMO theory accounted for this chemo selectivity as a consequence of the major π contribution of the enone to the LUMO of these molecules. The slight exo stereoselectivity observed in the cycloaddition to 6 parallels the higher stability of the corresponding transition state, according to the results of B3LYP/6-311G(d,p) calculations. (author)

  11. Search for ternary fragmentation in the reaction 856 MeV 98Mo + 51V: Kinematic probing of intermediate-mass-fragment emissions

    International Nuclear Information System (INIS)

    Vardaci, Emanuele; Kaplan, Morton; Parker, Winifred E.; Moses, David J.; Boger, J.T.; Gilfoyle, G.T.; McMahan, M.A.; Montoya, M.

    2000-05-01

    A new technique has been applied to coincidence measurements between fission fragments (FF) and intermediate mass fragments (IMF) emitted from the composite system 149 65 Tb at an excitation energy of 224 MeV. The method permits simultaneous observation of IMF emissions along and normal to the FF separation axes. For the integrated total of 0.10 +-0.02 IMF emitted per fission, we find no significant correlation with FF direction, suggesting that IMFs associated with fission reactions are predominantly emitted from the system prior to fission

  12. Separate photosensitizers mediate degradation of the 32-kDa photosystem II reaction center protein in the visible and UV spectral regions

    International Nuclear Information System (INIS)

    Greenberg, B.M.; Gaba, V.; Canaani, O.; Malkin, S.; Mattoo, A.K.; Edelman, M.

    1989-01-01

    A component of the photosystem II reaction center, the 32-kDa protein, is rapidly turned over in the light. The mechanism of its light-dependent metabolism is largely unknown. We quantified the rate of 32-kDa protein degradation over a broad spectral range (UV, visible, and far red). The quantum yield for degradation was highest in the UVB (280-320 nm) region. Spectral evidence demonstrates two distinctly different photosensitizers for 32-kDa protein degradation. The data implicate the bulk photosynthetic pigments (primarily chlorophyll) in the visible and far red regions, and plastoquinone (in one or more of its redox states) in the UV region. A significant portion of 32-kDa protein degradation in sunlight is attributed to UVB irradiance

  13. Correlation of paramagnetic states and molecular structure in bacterial photosynthetic reaction centers: The symmetry of the primary electron donor in Rhodopseudomonas viridis and Rhodobacter sphaeroides R-26

    International Nuclear Information System (INIS)

    Norris, J.R.; Budil, D.E.; Gast, P.; Chang, C.H.; El-Kabbani, O.; Schiffer, M.

    1989-01-01

    The orientation of the principal axes of the primary electron donor triplet state measured in single crystals of photosynthetic reaction centers is compared to the x-ray structures of the bacteria Rhodobacter (Rb.) sphaeroides R-26 and Rhodopseudomonas (Rps.) viridis. The primary donor of Rps. viridis is significantly different from that of Rb. sphaeroides. The measured directions of the axes indicate that triplet excitation is almost completely localized on the L-subunit half of the dimer in Rps. viridis but is more symmetrically distributed on the dimeric donor in Rb. sphaeroides R-26. The large reduction of the zero field splitting parameters relative to monomeric bacteriochlorophyll triplet in vitro suggests significant participation of asymmetrical charge transfer electronic configurations in the special pair triplet state of both organisms

  14. Aborted germinal center reactions and B cell memory by follicular T cells specific for a B cell receptor V region peptide.

    Science.gov (United States)

    Heiser, Ryan A; Snyder, Christopher M; St Clair, James; Wysocki, Lawrence J

    2011-07-01

    A fundamental problem in immunoregulation is how CD4(+) T cells react to immunogenic peptides derived from the V region of the BCR that are created by somatic mechanisms, presented in MHC II, and amplified to abundance by B cell clonal expansion during immunity. BCR neo Ags open a potentially dangerous avenue of T cell help in violation of the principle of linked Ag recognition. To analyze this issue, we developed a murine adoptive transfer model using paired donor B cells and CD4 T cells specific for a BCR-derived peptide. BCR peptide-specific T cells aborted ongoing germinal center reactions and impeded the secondary immune response. Instead, they induced the B cells to differentiate into short-lived extrafollicular plasmablasts that secreted modest quantities of Ig. These results uncover an immunoregulatory process that restricts the memory pathway to B cells that communicate with CD4 T cells via exogenous foreign Ag.

  15. Photochemical reactions in biological systems: probing the effect of the environment by means of hybrid quantum chemistry/molecular mechanics simulations.

    Science.gov (United States)

    Boggio-Pasqua, Martial; Burmeister, Carl F; Robb, Michael A; Groenhof, Gerrit

    2012-06-14

    Organisms have evolved a wide variety of mechanisms to utilize and respond to light. In many cases, the biological response is mediated by structural changes that follow photon absorption in a protein complex. The initial step in such cases is normally the photoisomerization of a highly conjugated prosthetic group. To understand better the factors controlling the isomerization, we perform atomistic molecular dynamics simulations. In this perspective article we briefly review the key theoretical concepts of photochemical reactions and present a practical simulation scheme for simulating photochemical reactions in biomolecular systems. In our scheme, a multi-configurational quantum mechanical description is used to model the electronic rearrangement for those parts of the system that are involved in the photon absorption. For the remainder, typically consisting of the apo-protein and the solvent, a simple force field model is used. The interactions in the systems are thus computed within a hybrid quantum/classical framework. Forces are calculated on-the-fly, and a diabatic surface hopping procedure is used to model the excited-state decay. To demonstrate how this method is used we review our studies on photoactivation of the photoactive yellow protein, a bacterial photoreceptor. We will show what information can be obtained from the simulations, and, by comparing to recent experimental findings, what the limitations of our simulations are.

  16. Mobile probes

    DEFF Research Database (Denmark)

    Ørngreen, Rikke; Jørgensen, Anna Neustrup; Noesgaard, Signe Schack

    2016-01-01

    A project investigating the effectiveness of a collection of online resources for teachers' professional development used mobile probes as a data collection method. Teachers received questions and tasks on their mobile in a dialogic manner while in their everyday context as opposed...... to in an interview. This method provided valuable insight into the contextual use, i.e. how did the online resource transfer to the work practice. However, the research team also found that mobile probes may provide the scaffolding necessary for individual and peer learning at a very local (intra-school) community...... level. This paper is an initial investigation of how the mobile probes process proved to engage teachers in their efforts to improve teaching. It also highlights some of the barriers emerging when applying mobile probes as a scaffold for learning....

  17. Optical probe

    International Nuclear Information System (INIS)

    Denis, J.; Decaudin, J.M.

    1984-01-01

    The probe includes optical means of refractive index n, refracting an incident light beam from a medium with a refractive index n1>n and reflecting an incident light beam from a medium with a refractive index n2 [fr

  18. Counting probe

    International Nuclear Information System (INIS)

    Matsumoto, Haruya; Kaya, Nobuyuki; Yuasa, Kazuhiro; Hayashi, Tomoaki

    1976-01-01

    Electron counting method has been devised and experimented for the purpose of measuring electron temperature and density, the most fundamental quantities to represent plasma conditions. Electron counting is a method to count the electrons in plasma directly by equipping a probe with the secondary electron multiplier. It has three advantages of adjustable sensitivity, high sensitivity of the secondary electron multiplier, and directional property. Sensitivity adjustment is performed by changing the size of collecting hole (pin hole) on the incident front of the multiplier. The probe is usable as a direct reading thermometer of electron temperature because it requires to collect very small amount of electrons, thus it doesn't disturb the surrounding plasma, and the narrow sweep width of the probe voltage is enough. Therefore it can measure anisotropy more sensitively than a Langmuir probe, and it can be used for very low density plasma. Though many problems remain on anisotropy, computer simulation has been carried out. Also it is planned to provide a Helmholtz coil in the vacuum chamber to eliminate the effect of earth magnetic field. In practical experiments, the measurement with a Langmuir probe and an emission probe mounted to the movable structure, the comparison with the results obtained in reverse magnetic field by using a Helmholtz coil, and the measurement of ionic sound wave are scheduled. (Wakatsuki, Y.)

  19. Orientations of Iron-Sulfur Clusters FA and FB in the Homodimeric Type-I Photosynthetic Reaction Center of Heliobacterium modesticaldum.

    Science.gov (United States)

    Kondo, Toru; Matsuoka, Masahiro; Azai, Chihiro; Itoh, Shigeru; Oh-Oka, Hirozo

    2016-05-12

    Orientations of the FA and FB iron-sulfur (FeS) clusters in a structure-unknown type-I homodimeric heriobacterial reaction center (hRC) were studied in oriented membranes of the thermophilic anaerobic photosynthetic bacterium Heliobacterium modesticaldum by electron paramagnetic resonance (EPR), and compared with those in heterodimeric photosystem I (PS I). The Rieske-type FeS center in the cytochrome b/c complex showed a well-oriented EPR signal. Illumination at 14 K induced an FB(-) signal with g-axes of gz = 2.066, gy = 1.937, and gx = 1.890, tilted at angles of 60°, 60°, and 45°, respectively, with respect to the membrane normal. Chemical reduction with dithionite produced an additional signal of FA(-), which magnetically interacted with FB(-), with gz = 2.046, gy = 1.942, and gx = 1.911 at 30°, 60°, and 90°, respectively. The angles and redox properties of FA(-) and FB(-) in hRC resemble those of FB(-) and FA(-), respectively, in PS I. Therefore, FA and FB in hRC, named after their g-value similarities, seem to be located like FB and FA, not like FA and FB, respectively, in PS I. The reducing side of hRC could resemble those in PS I, if the names of FA and FB are interchanged with each other.

  20. Immobilised histidine tagged β2-adrenoceptor oriented by a diazonium salt reaction and its application in exploring drug-protein interaction using ephedrine and pseudoephedrine as probes.

    Science.gov (United States)

    Li, Qian; Bian, Liujiao; Zhao, Xinfeng; Gao, Xiaokang; Zheng, Jianbin; Li, Zijian; Zhang, Youyi; Jiang, Ru; Zheng, Xiaohui

    2014-01-01

    A new oriented method using a diazonium salt reaction was developed for linking β2-adrenoceptor (β2-AR) on the surface of macroporous silica gel. Stationary phase containing the immobilised receptor was used to investigate the interaction between β2-AR and ephedrine plus pseudoephedrine by zonal elution. The isotherms of the two drugs best fit the Langmuir model. Only one type of binding site was found for ephedrine and pseudoephedrine targeting β2-AR. At 37 °C, the association constants during the binding were (5.94±0.05)×103/M for ephedrine and (3.80±0.02) ×103/M for pseudoephedrine, with the binding sites of (8.92±0.06) ×10-4 M. Thermodynamic studies showed that the binding of the two compounds to β2-AR was a spontaneous reaction with exothermal processes. The ΔGθ, ΔHθ and ΔSθ for the interaction between ephedrine and β2-AR were -(22.33±0.04) kJ/mol, -(6.51±0.69) kJ/mol and 50.94±0.31 J/mol·K, respectively. For the binding of pseudoephedrine to the receptor, these values were -(21.17±0.02) kJ/mol, -(7.48±0.56) kJ/mol and 44.13±0.01 J/mol·K. Electrostatic interaction proved to be the driving force during the binding of the two drugs to β2-AR. The proposed immobilised method will have great potential for attaching protein to solid substrates and realizing the interactions between proteins and drugs.

  1. Immobilised histidine tagged β2-adrenoceptor oriented by a diazonium salt reaction and its application in exploring drug-protein interaction using ephedrine and pseudoephedrine as probes.

    Directory of Open Access Journals (Sweden)

    Qian Li

    Full Text Available A new oriented method using a diazonium salt reaction was developed for linking β2-adrenoceptor (β2-AR on the surface of macroporous silica gel. Stationary phase containing the immobilised receptor was used to investigate the interaction between β2-AR and ephedrine plus pseudoephedrine by zonal elution. The isotherms of the two drugs best fit the Langmuir model. Only one type of binding site was found for ephedrine and pseudoephedrine targeting β2-AR. At 37 °C, the association constants during the binding were (5.94±0.05×103/M for ephedrine and (3.80±0.02 ×103/M for pseudoephedrine, with the binding sites of (8.92±0.06 ×10-4 M. Thermodynamic studies showed that the binding of the two compounds to β2-AR was a spontaneous reaction with exothermal processes. The ΔGθ, ΔHθ and ΔSθ for the interaction between ephedrine and β2-AR were -(22.33±0.04 kJ/mol, -(6.51±0.69 kJ/mol and 50.94±0.31 J/mol·K, respectively. For the binding of pseudoephedrine to the receptor, these values were -(21.17±0.02 kJ/mol, -(7.48±0.56 kJ/mol and 44.13±0.01 J/mol·K. Electrostatic interaction proved to be the driving force during the binding of the two drugs to β2-AR. The proposed immobilised method will have great potential for attaching protein to solid substrates and realizing the interactions between proteins and drugs.

  2. Unifying principles in homodimeric type I photosynthetic reaction centers: properties of PscB and the FA, FB and FX iron-sulfur clusters in green sulfur bacteria.

    Science.gov (United States)

    Jagannathan, Bharat; Golbeck, John H

    2008-12-01

    The photosynthetic reaction center from the green sulfur bacterium Chlorobium tepidum (CbRC) was solubilized from membranes using Triton X-100 and isolated by sucrose density ultra-centrifugation. The CbRC complexes were subsequently treated with 0.5 M NaCl and ultrafiltered over a 100 kDa cutoff membrane. The resulting CbRC cores did not exhibit the low-temperature EPR resonances from FA- and FB- and were unable to reduce NADP+. SDS-PAGE and mass spectrometric analysis showed that the PscB subunit, which harbors the FA and FB clusters, had become dissociated, and was now present in the filtrate. Attempts to rebind PscB onto CbRC cores were unsuccessful. Mössbauer spectroscopy showed that recombinant PscB contains a heterogeneous mixture of [4Fe-4S]2+,1+ and other types of Fe/S clusters tentatively identified as [2Fe-2S]2+,1+ clusters and rubredoxin-like Fe3+,2+ centers, and that the [4Fe-4S]2+,1+ clusters which were present were degraded at high ionic strength. Quantitative analysis confirmed that the amount of iron and sulfide in the recombinant protein was sub-stoichiometric. A heme-staining assay indicated that cytochrome c551 remained firmly attached to the CbRC cores. Low-temperature EPR spectroscopy of photoaccumulated CbRC complexes and CbRC cores showed resonances between g=5.4 and 4.4 assigned to a S=3/2 ground spin state [4Fe-4S]1+ cluster and at g=1.77 assigned to a S=1/2 ground spin state [4Fe-4S]1+ cluster, both from FX-. These results unify the properties of the acceptor side of the Type I homodimeric reaction centers found in green sulfur bacteria and heliobacteria: in both, the FA and FB iron-sulfur clusters are present on a salt-dissociable subunit, and FX is present as an interpolypeptide [4Fe-4S]2+,1+ cluster with a significant population in a S=3/2 ground spin state.

  3. Detection of subgenomic mRNA of feline coronavirus by real-time polymerase chain reaction based on primer-probe energy transfer (P-sg-QPCR).

    Science.gov (United States)

    Hornyák, Akos; Bálint, Adám; Farsang, Attila; Balka, Gyula; Hakhverdyan, Mikhayil; Rasmussen, Thomas Bruun; Blomberg, Jonas; Belák, Sándor

    2012-05-01

    Feline infectious peritonitis is one of the most severe devastating diseases of the Felidae. Upon the appearance of clinical signs, a cure for the infected animal is impossible. Therefore rapid and proper diagnosis for both the presence of the causative agent, feline coronavirus (FCoV) and the manifestation of feline infectious peritonitis is of paramount importance. In the present work, a novel real-time RT-PCR method is described which is able to detect FCoV and to determine simultaneously the quantity of the viral RNA. The new assay combines the M gene subgenomic messenger RNA (sg-mRNA) detection and the quantitation of the genome copies of FCoV. In order to detect the broadest spectrum of potential FCoV variants and to achieve the most accurate results in the detection ability the new assay is applying the primer-probe energy transfer (PriProET) principle. This technology was chosen since PriProET is very robust to tolerate the nucleotide substitutions in the target area. Therefore, this technology provides a very broad-range system, which is able to detect simultaneously many variants of the virus(es) even if the target genomic regions show large scale of variations. The detection specificity of the new assay was proven by positive amplification from a set of nine different FCoV strains and negative from the tested non-coronaviral targets. Examination of faecal samples of healthy young cats, organ samples of perished animals, which suffered from feline infectious peritonitis, and cat leukocytes from uncertain clinical cases were also subjected to the assay. The sensitivity of the P-sg-QPCR method was high, since as few as 10 genome copies of FCoV were detected. The quantitative sg-mRNA detection method revealed more than 10-50,000 times increase of the M gene sg-mRNA in organ materials of feline infectious peritonitis cases, compared to those of the enteric FCoV variants present in the faeces of normal, healthy cats. These results indicate the applicability of

  4. Electrospray ionization mass spectrometric investigations of [alpha]-dicarbonyl compounds--Probing intermediates formed in the course of the nonenzymatic browning reaction of l-ascorbic acid

    Science.gov (United States)

    Schulz, Anke; Trage, Claudia; Schwarz, Helmut; Kroh, Lothar W.

    2007-05-01

    A new method is presented which allows the simultaneous detection of various [alpha]-dicarbonyl compounds generated in the course of the nonenzymatic browning reaction initiated by thermal treatment of l-ascorbic acid, namely: glyoxal, methylglyoxal, diacetyl, 3-deoxy-l-pentosone, and l-threosoneE 3-Deoxy-l-threosone was successfully identified as a new C4-[alpha]-dicarbonyl structure for the first time in the degradation of Vitamin C by application of this non-chromatographic mass spectrometric approach. Moreover, a more detailed elucidation of the mechanistic scenario with respect to the oxidative and nonoxidative pathways is presented by using dehydro-l-ascorbic acid and 2,3-diketo-l-gulonic acid instead of l-ascorbic acid as a starting material. Furthermore, the postulated pathways are corroborated with the aid of 13C-isotopic labeling studies. The investigations were extended to baby food, and the successful detection of [alpha]-dicarbonyl compounds characteristic for Vitamin C degradation proved the matrix tolerance of the introduced method.

  5. Probing the semi-magicity of $^{68}$Ni via the $^{66}$Ni(t,p)$^{68}$Ni two-neutron transfer reaction in inverse kinematics

    CERN Document Server

    AUTHOR|(CDS)2079390; Van Duppen, Piet

    The region around the nucleus $^{68}$Ni, with a shell closure for its protons at Z=28 and a harmonic oscillator shell gap for its neutrons at N=40, has drawn considerable interest over the past decades. $^{68}$Ni has properties that are typical for a doubly-magic nucleus, such as a high excitation energy and low B($E2:2^{+} \\rightarrow 0^{+}$) transition probability for the first excited 2$^{+}$ level and a 0$^{+}$ level as the first excited state. However, it has been suggested that the magic properties of $^{68}$Ni arise due to the fact that the N=40 separates the negative parity $pf$-shell from the positive parity 1$g_{9/2}$ orbital, and indeed, recent mass measurements have not revealed a clear N = 40 energy gap. Despite all additional information that was acquired over the last decade the specific role of the N=40 is not yet understood and a new experimental approach to study $^{68}$Ni was proposed. Namely, a two-neutron transfer reaction on $^{66}$Ni to characterize and disentangle the structure of the ...

  6. A sensitive detection method for MPLW515L or MPLW515K mutation in chronic myeloproliferative disorders with locked nucleic acid-modified probes and real-time polymerase chain reaction.

    Science.gov (United States)

    Pancrazzi, Alessandro; Guglielmelli, Paola; Ponziani, Vanessa; Bergamaschi, Gaetano; Bosi, Alberto; Barosi, Giovanni; Vannucchi, Alessandro M

    2008-09-01

    Acquired mutations in the juxtamembrane region of MPL (W515K or W515L), the receptor for thrombopoietin, have been described in patients with primary myelofibrosis or essential thrombocythemia, which are chronic myeloproliferative disorders. We have developed a real-time polymerase chain reaction assay for the detection and quantification of MPL mutations that is based on locked nucleic acid fluorescent probes. Mutational analysis was performed using DNA from granulocytes. Reference curves were obtained using cloned fragments of MPL containing either the wild-type or mutated sequence; the predicted sensitivity level was at least 0.1% mutant allele in a wild-type background. None of the 60 control subjects presented with a MPLW515L/K mutation. Of 217 patients with myelofibrosis, 19 (8.7%) harbored the MPLW515 mutation, 10 (52.6%) with the W515L allele. In one case, both the W515L and W515K alleles were detected by real-time polymerase chain reaction. By comparing results obtained with conventional sequencing, no erroneous genotype attribution using real-time polymerase chain reaction was found, whereas one patient considered wild type according to sequence analysis actually harbored a low W515L allele burden. This is a simple, sensitive, and cost-effective procedure for large-scale screening of the MPLW515L/K mutation in patients suspected to have a myeloproliferative disorder. It can also provide a quantitative estimate of mutant allele burden that might be useful for both patient prognosis and monitoring response to therapy.

  7. Conductivity Probe

    Science.gov (United States)

    2008-01-01

    The Thermal and Electrical Conductivity Probe (TECP) for NASA's Phoenix Mars Lander took measurements in Martian soil and in the air. The needles on the end of the instrument were inserted into the Martian soil, allowing TECP to measure the propagation of both thermal and electrical energy. TECP also measured the humidity in the surrounding air. The needles on the probe are 15 millimeters (0.6 inch) long. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  8. Molecular Imaging Probe Development using Microfluidics

    Science.gov (United States)

    Liu, Kan; Wang, Ming-Wei; Lin, Wei-Yu; Phung, Duy Linh; Girgis, Mark D.; Wu, Anna M.; Tomlinson, James S.; Shen, Clifton K.-F.

    2012-01-01

    In this manuscript, we review the latest advancement of microfluidics in molecular imaging probe development. Due to increasing needs for medical imaging, high demand for many types of molecular imaging probes will have to be met by exploiting novel chemistry/radiochemistry and engineering technologies to improve the production and development of suitable probes. The microfluidic-based probe synthesis is currently attracting a great deal of interest because of their potential to deliver many advantages over conventional systems. Numerous chemical reactions have been successfully performed in micro-reactors and the results convincingly demonstrate with great benefits to aid synthetic procedures, such as purer products, higher yields, shorter reaction times compared to the corresponding batch/macroscale reactions, and more benign reaction conditions. Several ‘proof-of-principle’ examples of molecular imaging probe syntheses using microfluidics, along with basics of device architecture and operation, and their potential limitations are discussed here. PMID:22977436

  9. Aromatic residues located close to the active center are essential for the catalytic reaction of flap endonuclease-1 from hyperthermophilic archaeon Pyrococcus horikoshii.

    Science.gov (United States)

    Matsui, Eriko; Abe, Junko; Yokoyama, Hideshi; Matsui, Ikuo

    2004-04-16

    Flap endonuclease-1 (FEN-1) possessing 5'-flap endonuclease and 5'-->3' exonuclease activity plays important roles in DNA replication and repair. In this study, the kinetic parameters of mutants at highly conserved aromatic residues, Tyr33, Phe35, Phe79, and Phe278-Phe279, in the vicinity of the catalytic centers of FEN-1 were examined. The substitution of these aromatic residues with alanine led to a large reduction in kcat values, although these mutants retained Km values similar to that of the wild-type enzyme. Notably, the kcat of Y33A and F79A decreased 333-fold and 71-fold, respectively, compared with that of the wild-type enzyme. The aromatic residues Tyr33 and Phe79, and the aromatic cluster Phe278-Phe279 mainly contributed to the recognition of the substrates without the 3' projection of the upstream strand (the nick, 5'-recess-end, single-flap, and pseudo-Y substrates) for the both exo- and endo-activities, but played minor roles in recognizing the substrates with the 3' projection (the double flap substrate and the nick substrate with the 3' projection). The replacement of Tyr33, Phe79, and Phe278-Phe279, with non-charged aromatic residues, but not with aliphatic hydrophobic residues, recovered the kcat values almost fully for the substrates without the 3' projection of the upstream strand, suggesting that the aromatic groups of Tyr33, Phe79, and Phe278-Phe279 might be involved in the catalytic reaction, probably via multiple stacking interactions with nucleotide bases. The stacking interactions of Tyr33 and Phe79 might play important roles in fixing the template strand and the downstream strand, respectively, in close proximity to the active center to achieve the productive transient state leading to the hydrolysis.

  10. Role of Rhodobacter sphaeroides photosynthetic reaction center residue M214 in the composition, absorbance properties, and conformations of H(A) and B(A) cofactors.

    Science.gov (United States)

    Saer, Rafael G; Hardjasa, Amelia; Rosell, Federico I; Mauk, A Grant; Murphy, Michael E P; Beatty, J Thomas

    2013-04-02

    In the native reaction center (RC) of Rhodobacter sphaeroides, the side chain of (M)L214 projects orthogonally toward the plane and into the center of the A branch bacteriopheophytin (BPhe) macrocycle. The possibility that this side chain is responsible for the dechelation of the central Mg(2+) of bacteriochlorophyll (BChl) was investigated by replacement of (M)214 with residues possessing small, nonpolar side chains that can neither coordinate nor block access to the central metal ion. The (M)L214 side chain was also replaced with Cys, Gln, and Asn to evaluate further the requirements for assembly of the RC with BChl in the HA pocket. Photoheterotrophic growth studies showed no difference in growth rates of the (M)214 nonpolar mutants at a low light intensity, but the growth of the amide-containing mutants was impaired. The absorbance spectra of purified RCs indicated that although absorbance changes are associated with the nonpolar mutations, the nonpolar mutant RC pigment compositions are the same as in the wild-type protein. Crystal structures of the (M)L214G, (M)L214A, and (M)L214N mutants were determined (determined to 2.2-2.85 Å resolution), confirming the presence of BPhe in the HA pocket and revealing alternative conformations of the phytyl tail of the accessory BChl in the BA site of these nonpolar mutants. Our results demonstrate that (i) BChl is converted to BPhe in a manner independent of the aliphatic side chain length of nonpolar residues replacing (M)214, (ii) BChl replaces BPhe if residue (M)214 has an amide-bearing side chain, (iii) (M)214 side chains containing sulfur are not sufficient to bind BChl in the HA pocket, and (iv) the (M)214 side chain influences the conformation of the phytyl tail of the BA BChl.

  11. Pattern of Adverse Drug Reactions in Children Attending the Department of Pediatrics in a Tertiary Care Center: A Prospective Observational Study

    Directory of Open Access Journals (Sweden)

    Kishour Kumar Digra

    2015-01-01

    Full Text Available AIM To study the pattern of various adverse drug reactions (ADRs occurring in children attending the Department of Pediatrics, SMGS Hospital, Jammu over 1 year. Subjects and Methods This was a prospective study, with study population of patients attending Department of Pediatrics over a period of 1 year. A structured format was used to enroll the participants. A pilot study was conducted to test the suitability of the format and feasibility of the study. The study was carried out to review various pattern of ADRs by using the Naranjo probability scale, and severity was assessed by using the Hartwig severity scale. ADRs were classified according to the classification used by the Adverse Drug Reaction Monitoring Center, Central Drugs Standard Control Organization, New Delhi, India. Results In the present study, 104 patients were found to have developed acute drug reactions. Among these, 83.6% were type B, 14.42% type A, and 1.92% were type U. Furthermore, 25.96% ADRs were due to anticonvulsants, followed by antibiotics (22.11%, antipyretics (11.53%, vaccination (8.65%, steroids (6.73%, decongestants (5.67%, snake antivenom and antiemetics (3.84%, and fluids, insulin, and antacids (1.92%. The patients’ dermatological system was involved in 67.30%, followed by the central nervous system (CNS in 11.53% patients. Renal system was involved in 6.73% patients. Cardiac, musculoskeletal, metabolic, and other systems were involved in 4.80%, 3.84%, 2.88%, and 0.96%, respectively. According to the Hartwig severity scale of ADRs, 64.4% patients had moderate ADRs, 29.8% patients had severe ADRs, and 5.76% had mild ADRs. In the present study, 64.4% patients expressed moderate severity, whereas 29.8% expressed high severity and 5.76% expressed mild ADRs. Conclusion ADRs were seen in 71% of the patients between 1 and 5 years of age, 26% in the age group of 5–10 years, and 3% were more than 10 years old. Anticonvulsants (25.96% and antibiotics (22.11% were

  12. Probe specificity

    International Nuclear Information System (INIS)

    Laget, J.M.

    1986-11-01

    Specificity and complementarity of hadron and electron probes must be systematically developed to answer three questions currently asked in intermediate energy nuclear physics: what is nucleus structure at short distances, what is nature of short range correlations, what is three body force nature [fr

  13. Charge stabilization by reaction center protein immobilized to carbon nanotubes functionalized by amine groups and poly(3-thiophene acetic acid) conducting polymer

    Energy Technology Data Exchange (ETDEWEB)

    Szabo, T.; Magyar, M.; Nagy, L. [Department of Medical Physics and Informatics, University of Szeged, H-6720 Szeged (Hungary); Nemeth, Z.; Hernadi, K. [Department of Applied and Environmental Chemistry, University of Szeged, H-6720 Szeged (Hungary); Endrodi, B.; Bencsik, G.; Visy, Cs. [Department of Physical Chemistry and Materials Science, University of Szeged, H-6720 Szeged (Hungary); Horvath, E.; Magrez, A.; Forro, L. [Institute of Physics of Complex Matter, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

    2012-12-15

    A large number of studies have indicated recently that photosynthetic reaction center proteins (RC) bind successfully to nanostructures and their functional activity is largely retained. The major goal of current research is to find the most efficient systems and conditions for the photoelectric energy conversion and for the stability of this bio-nanocomposite. In our studies, we immobilized the RC protein on multiwalled carbon nanotubes (MWNT) through specific chemical binding to amine functional groups and through conducting polymer (poly(3-thiophene acetic acid), PTAA). Both structural (TEM, AFM) and functional (absorption change and conductivity) measurements has shown that RCs could be bound effectively to functionalized CNTs. The kinetics of the light induced absorption change indicated that RCs were still active in the composite and there was an interaction between the protein cofactors and the CNTs. The light generated photocurrent was measured in an electrochemical cell with transparent CNT electrode designed specially for this experiment. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Electrostatics of the photosynthetic bacterial reaction center. Protonation of Glu L 212 and Asp L 213 - A new method of calculation.

    Science.gov (United States)

    Ptushenko, Vasily V; Cherepanov, Dmitry A; Krishtalik, Lev I

    2015-12-01

    Continuum electrostatic calculation of the transfer energies of anions from water into aprotic solvents gives the figures erroneous by order of magnitude. This is due to the hydrogen bond disruption that suggests the necessity to reconsider the traditional approach of the purely electrostatic calculation of the transfer energy from water into protein. In this paper, the method combining the experimental estimates of the transfer energies from water into aprotic solvent and the electrostatic calculation of the transfer energies from aprotic solvent into protein is proposed. Hydrogen bonds between aprotic solvent and solute are taken into account by introducing an imaginary aprotic medium incapable to form hydrogen bonds with the solute. Besides, a new treatment of the heterogeneous intraprotein dielectric permittivity based on the microscopic protein structure and electrometric measurements is elaborated. The method accounts semi-quantitatively for the electrostatic effect of diverse charged amino acid substitutions in the donor and acceptor parts of the photosynthetic bacterial reaction center from Rhodobacter sphaeroides. Analysis of the volatile secondary acceptor site QB revealed that in the conformation with a minimal distance between quinone QB and Glu L 212 the proton uptake upon the reduction of QB is prompted by Glu L 212 in alkaline and by Asp L 213 in slightly acidic regions. This agrees with the pH dependences of protonation degrees and the proton uptake. The method of pK calculation was applied successfully also for dissociation of Asp 26 in bacterial thioredoxin. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Cantilevered probe detector with piezoelectric element

    Science.gov (United States)

    Adams, Jesse D; Sulchek, Todd A; Feigin, Stuart C

    2013-04-30

    A disclosed chemical detection system for detecting a target material, such as an explosive material, can include a cantilevered probe, a probe heater coupled to the cantilevered probe, and a piezoelectric element disposed on the cantilevered probe. The piezoelectric element can be configured as a detector and/or an actuator. Detection can include, for example, detecting a movement of the cantilevered probe or a property of the cantilevered probe. The movement or a change in the property of the cantilevered probe can occur, for example, by adsorption of the target material, desorption of the target material, reaction of the target material and/or phase change of the target material. Examples of detectable movements and properties include temperature shifts, impedance shifts, and resonant frequency shifts of the cantilevered probe. The overall chemical detection system can be incorporated, for example, into a handheld explosive material detection system.

  16. Standard Gibbs free energies of reactions of ozone with free radicals in aqueous solution: quantum-chemical calculations.

    Science.gov (United States)

    Naumov, Sergej; von Sonntag, Clemens

    2011-11-01

    Free radicals are common intermediates in the chemistry of ozone in aqueous solution. Their reactions with ozone have been probed by calculating the standard Gibbs free energies of such reactions using density functional theory (Jaguar 7.6 program). O(2) reacts fast and irreversibly only with simple carbon-centered radicals. In contrast, ozone also reacts irreversibly with conjugated carbon-centered radicals such as bisallylic (hydroxycylohexadienyl) radicals, with conjugated carbon/oxygen-centered radicals such as phenoxyl radicals, and even with nitrogen- oxygen-, sulfur-, and halogen-centered radicals. In these reactions, further ozone-reactive radicals are generated. Chain reactions may destroy ozone without giving rise to products other than O(2). This may be of importance when ozonation is used in pollution control, and reactions of free radicals with ozone have to be taken into account in modeling such processes.

  17. Femtosecond visible/visible and visible/mid-IR pump-probe study of the photosystem II core antenna complex CP47

    NARCIS (Netherlands)

    Groot, M.L.; Breton, J.; van Wilderen, L.; Dekker, J.P.; van Grondelle, R.

    2004-01-01

    CP47 is one of the two core antenna proteins of Photosystem II involved in the transfer of solar energy toward the photochemically active reaction center, the D1D2cytb559 complex. We have performed vis/vis and vis/mid-IR pump-probe experiments at room temperature as a first step in linking the

  18. Modeling the bacterial photosynthetic reaction center. VII. Full simulation of the intervalence hole-transfer absorption spectrum of the special-pair radical cation

    International Nuclear Information System (INIS)

    Reimers, Jeffrey R.; Hush, Noel S.

    2003-01-01

    reaction centers from photosystems I, II, etc., facilitating a deeper understanding of the role of the special pair in initiating primary charge separation during photosynthesis

  19. Manipulating the Energetics and Rates of Electron Transfer in Rhodobacter capsulatus Reaction Centers with Asymmetric Pigment Content

    Energy Technology Data Exchange (ETDEWEB)

    Faries, Kaitlyn M. [Department; Dylla, Nicholas P. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Hanson, Deborah K. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Holten, Dewey [Department; Laible, Philip D. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Kirmaier, Christine [Department

    2017-07-17

    Seemingly redundant parallel pathways for electron transfer (ET), composed of identical sets of cofactors, are a cornerstone feature of photosynthetic reaction centers (RCs) involved in light-energy conversion. In native bacterial RCs, both A and B branches house one bacteriochlorophyll (BChl) and one bacteriopheophytin (BPh), but the A branch is used exclusively. Described herein are the results-obtained for two Rhodobacter capsulatus RCs with an unnaturally high degree of cofactor asymmetry, two BPh on the RC's B side and two BChl on the A side. These pigment changes derive, respectively, from the His(M180)Leu mutation [a BPh ((Phi(B)) replaces the B-side BChl (BB)], and the Leu(M212)His mutation [a BChl (beta(A))) replaces the A-side BPh (H-A)]. Additionally, Tyr(M208)Phe was employed to disfavor ET to the A branch; in one mutant, Val(M131)Glu creates a hydrogen bond to H-B to enhance ET to H-B. In both Phi(B) mutants, the decay kinetics of the excited primary ET donor (P*) resolve three populations with lifetimes of similar to 9 ps (50-60%), similar to 40 ps (10-20%), and similar to 200 ps (20-30%), with P+Phi(-)(B) formed predominantly from the 9 ps fraction. The 50-60% yield of P+Phi(B)- is the highest yet observed for a Phi(B)-containing RC. The results provide insight into factors needed for efficient multistep ET.

  20. The rate of second electron transfer to QB(-) in bacterial reaction center of impaired proton delivery shows hydrogen-isotope effect.

    Science.gov (United States)

    Maróti, Ágnes; Wraight, Colin A; Maróti, Péter

    2015-02-01

    The 2nd electron transfer in reaction center of photosynthetic bacterium Rhodobacter sphaeroides is a two step process in which protonation of QB(-) precedes interquinone electron transfer. The thermal activation and pH dependence of the overall rate constants of different RC variants were measured and compared in solvents of water (H2O) and heavy water (D2O). The electron transfer variants where the electron transfer is rate limiting (wild type and M17DN, L210DN and H173EQ mutants) do not show solvent isotope effect and the significant decrease of the rate constant of the second electron transfer in these mutants is due to lowering the operational pKa of QB(-)/QBH: 4.5 (native), 3.9 (L210DN), 3.7 (M17DN) and 3.1 (H173EQ) at pH7. On the other hand, the proton transfer variants where the proton transfer is rate limiting demonstrate solvent isotope effect of pH-independent moderate magnitude (2.11±0.26 (WT+Ni(2+)), 2.16±0.35 (WT+Cd(2+)) and 2.34±0.44 (L210DN/M17DN)) or pH-dependent large magnitude (5.7 at pH4 (L213DN)). Upon deuteration, the free energy and the enthalpy of activation increase in all proton transfer variants by about 1 kcal/mol and the entropy of activation becomes negligible in L210DN/M17DN mutant. The results are interpreted as manifestation of equilibrium and kinetic solvent isotope effects and the structural, energetic and kinetic possibility of alternate proton delivery pathways are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Langmuir-Blodgett and X-ray diffraction studies of isolated photosystem II reaction centers in monolayers and multilayers: physical dimensions of the complex.

    Science.gov (United States)

    Uphaus, R A; Fang, J Y; Picorel, R; Chumanov, G; Wang, J Y; Cotton, T M; Seibert, M

    1997-04-01

    The photosystem II (PSII) reaction center (RC) is a hydrophobic intrinsic protein complex that drives the water-oxidation process of photosynthesis. Unlike the bacterial RC complex, an X-ray crystal structure of the PSII RC is not available. In order to determine the physical dimensions of the isolated PSII RC complex, we applied Langmuir techniques to determine the cross-sectional area of an isolated RC in a condensed monolayer film. Low-angle X-ray diffraction results obtained by examining Langmuir-Blodgett multilayer films of alternating PSII RC/Cd stearate monolayers were used to determine the length (or height; z-direction, perpendicular to the plane of the original membrane) of the complex. The values obtained for a PSII RC monomer were 26 nm2 and 4.8 nm, respectively, and the structural integrity of the RC in the multilayer film was confirmed by several approaches. Assuming a cylindrical-type RC structure, the above dimensions lead to a predicted volume of about 125 nm3. This value is very close to the expected volume of 118 nm3, calculated from the known molecular weight and partial specific volume of the PSII RC proteins. This same type of comparison was also made with the Rhodobacter sphaeroides RC based on published data, and we conclude that the PSII RC is much shorter in length and has a more regular solid geometric structure than the bacterial RC. Furthermore, the above dimensions of the PSII RC and those of PSII core (RC plus proximal antenna) proteins protruding outside the plane of the PSII membrane into the lumenal space as imaged by scanning tunneling microscopy (Seibert, Aust. J. Pl. Physiol. 22, 161-166, 1995) fit easily into the known dimensions of the PSII core complex visualized by others as electron-density projection maps. From this we conclude that the in situ PSII core complex is a dimeric structure containing two copies of the PSII RC.

  2. Calculation of Transactinide Homolog Isotope Production Reactions Possible with the Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory

    International Nuclear Information System (INIS)

    Moody, K.J.; Shaughnessy, D.A.; Gostic, J.M.

    2011-01-01

    The LLNL heavy element group has been investigating the chemical properties of the heaviest elements over the past several years. The properties of the transactinides (elements with Z > 103) are often unknown due to their low production rates and short half-lives, which require lengthy cyclotron irradiations in order to make enough atoms for statistically significant evaluations of their chemistry. In addition, automated chemical methods are often required to perform consistent and rapid chemical separations on the order of minutes for the duration of the experiment, which can last from weeks to months. Separation methods can include extraction chromatography, liquid-liquid extraction, or gas-phase chromatography. Before a lengthy transactinide experiment can be performed at an accelerator, a large amount of preparatory work must be done both to ensure the successful application of the chosen chemical system to the transactinide chemistry problem being addressed, and to evaluate the behavior of the lighter elemental homologs in the same chemical system. Since transactinide chemistry is literally performed on one single atom, its chemical properties cannot be determined from bulk chemical matrices, but instead must be inferred from the behavior of the lighter elements that occur in its chemical group and in those of its neighboring elements. By first studying the lighter group homologs in a particular chemical system, when the same system is applied to the transactinide element under investigation, its decay properties can be directly compared to those of the homologues, thereby allowing an inference of its own chemistry. The Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory (LLNL) includes a 1 MV Tandem accelerator, capable of accelerating light ions such as protons to energies of roughly 15 MeV. By using the CAMS beamline, tracers of transactinide homolog elements can be produced both for development of chemical systems and

  3. Calculation of Transactinide Homolog Isotope Production Reactions Possible with the Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Moody, K J; Shaughnessy, D A; Gostic, J M

    2011-11-29

    The LLNL heavy element group has been investigating the chemical properties of the heaviest elements over the past several years. The properties of the transactinides (elements with Z > 103) are often unknown due to their low production rates and short half-lives, which require lengthy cyclotron irradiations in order to make enough atoms for statistically significant evaluations of their chemistry. In addition, automated chemical methods are often required to perform consistent and rapid chemical separations on the order of minutes for the duration of the experiment, which can last from weeks to months. Separation methods can include extraction chromatography, liquid-liquid extraction, or gas-phase chromatography. Before a lengthy transactinide experiment can be performed at an accelerator, a large amount of preparatory work must be done both to ensure the successful application of the chosen chemical system to the transactinide chemistry problem being addressed, and to evaluate the behavior of the lighter elemental homologs in the same chemical system. Since transactinide chemistry is literally performed on one single atom, its chemical properties cannot be determined from bulk chemical matrices, but instead must be inferred from the behavior of the lighter elements that occur in its chemical group and in those of its neighboring elements. By first studying the lighter group homologs in a particular chemical system, when the same system is applied to the transactinide element under investigation, its decay properties can be directly compared to those of the homologues, thereby allowing an inference of its own chemistry. The Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory (LLNL) includes a 1 MV Tandem accelerator, capable of accelerating light ions such as protons to energies of roughly 15 MeV. By using the CAMS beamline, tracers of transactinide homolog elements can be produced both for development of chemical systems and

  4. Structure and function of cytochrome c2 in electron transfer complexes with the photosynthetic reaction center of Rhodobacter sphaeroides: optical linear dichroism and EPR.

    Science.gov (United States)

    Drepper, F; Mathis, P

    1997-02-11

    The photosynthetic reaction center (RC) and its secondary electron donor the water-soluble cytochrome (cyt) c2 from the purple bacterium Rhodobacter sphaeroides have been used in cross-linked and non-cross-linked complexes, oriented in compressed gels or partially dried multilayers, to study the respective orientation of the primary donor P (BChl dimer) and of cyt c2. Three methods were used: (i) Polarized optical absorption spectra at 295 and 10 K were measured and the linear dichroism of the two individual transitions (Qx, Qy), which are nearly degenerate within the alpha-band of reduced cyt c2, was determined. Attribution of the polarization directions to the molecular axes within the heme plane yielded the average cyt orientation in the complexes. (ii) Time-resolved flash absorption measurements using polarized light allowed determination of the orientation of cyt c2 in complexes which differ in their kinetics of electron transfer. (iii) EPR spectroscopy of ferricyt c2 in cross-linked RC-cyt c2 complexes was used to determine the angle between the heme and the membrane plane. The results suggest the following structural properties for the docking of cyt c2 to the RC: (i) In cross-linked complexes, the two cytochromes displaying half-lives of 0.7 and 60 micros for electron transfer to P+ are similarly oriented (difference plane is parallel to the symmetry axis of the RC (0 degrees +/- 10 degrees). Moreover, the Qy transition, which is assumed to be polarized within the ring III-ring I direction of the heme plane, makes an angle of 56 degrees +/- 1 degree with the symmetry axis. (iii) The dichroism spectrum for the fast phase (0.7 micros) for the non-cross-linked cyt c2-RC complex suggests an orientation similar to that of cross-linked cyt c2, but the heme plane is tilted about 20 degrees closer to the membrane. An alternative model is that two or more bound states of cyt c2 with heme plane tilt angles between 0 degrees and 30 degrees allow the fast electron

  5. Conformational heterogeneity of the bacteriopheophytin electron acceptor HA in reaction centers from Rhodopseudomonas viridis revealed by Fourier transform infrared spectroscopy and site-directed mutagenesis.

    Science.gov (United States)

    Breton, J; Bibikova, M; Oesterhelt, D; Nabedryk, E

    1999-08-31

    The light-induced Fourier transform infrared (FTIR) difference spectra corresponding to the photoreduction of either the HA bacteriopheophytin electron acceptor (HA-/HA spectrum) or the QA primary quinone (QA-/QA spectrum) in photosynthetic reaction centers (RCs) of Rhodopseudomonas viridis are reported. These spectra have been compared for wild-type (WT) RCs and for two site-directed mutants in which the proposed interactions between the carbonyls on ring V of HA and the RC protein have been altered. In the mutant EQ(L104), the putative hydrogen bond between the protein and the 9-keto C=O of HA should be affected by changing Glu L104 to a Gln. In the mutant WF(M250), the van der Waals interactions between Trp M250 and the 10a-ester C=O of HA should be modified. The characteristic effects of both mutations on the FTIR spectra support the proposed interactions and allow the IR modes of the 9-keto and 10a-ester C=O of HA and HA- to be assigned. Comparison of the HA-/HA and QA-/QA spectra leads us to conclude that the QA-/QA IR signals in the spectral range above 1700 cm-1 are largely dominated by contributions from the electrostatic response of the 10a-ester C=O mode of HA upon QA photoreduction. A heterogeneity in the conformation of the 10a-ester C=O mode of HA in WT RCs, leading to three distinct populations of HA, appears to be related to differences in the hydrogen-bonding interactions between the carbonyls of ring V of HA and the RC protein. The possibility that this structural heterogeneity is related to the observed multiexponential kinetics of electron transfer and the implications for primary processes are discussed. The effect of 1H/2H exchange on the QA-/QA spectra of the WT and mutant RCs shows that neither Glu L104 nor any other exchangeable carboxylic residue changes appreciably its protonation state upon QA reduction.

  6. Report on the second consultants' meeting of nuclear reaction data centers Kiev, USSR, 11-16 April 1977. Including the thirteenth four-center meeting and the third meeting on charged particle nuclear data compilation

    International Nuclear Information System (INIS)

    Lemmel, H.D.

    1977-10-01

    This second ''NRDC meeting'' combined the 13th ''four centers meeting'' (consultants' meeting of the four neutron nuclear data centers) with the third ''CPND meeting'' (consultants' meeting on charged particle nuclear data compilation). In Part I of the meeting, the neutron data centers held a special session on neutron data matters, in particular on the jointly operated neutron data index CINDA, whereas all items of more general interest, in particular the data exchange system EXFOR, were treated in Part II of the meeting

  7. Probing luminescence centers in Na rich feldspar

    DEFF Research Database (Denmark)

    Prasad, Amit Kumar; Lapp, Torben; Kook, Myung Ho

    2016-01-01

    our understanding of the luminescence mechanisms and recombination sites, in a sample of Na rich plagioclase feldspar (oligoclase). Both the UV and violet–blue emissions show resonant excitations arising from a distribution of energy levels. We propose, contrary to the general understanding...

  8. Results of an investigation to determine local flow characteristics at the air data probe locations using an 0.030-scale model (45-0) of the space shuttle vehicle orbiter configuration 140A/B (modified) in the NASA Ames Research Center unitary plan wind tunnel (OA161, A, B, C), volume 1

    Science.gov (United States)

    Nichols, M. E.

    1976-01-01

    Results are presented of wind tunnel test 0A161 of a 0.030-scale model 45-0 of the configuration 140A/B (modified) space shuttle vehicle orbiter in the NASA Ames Research Center Unitary Plan Wind Tunnel facilities. The purpose of this test was to determine local total and static pressure environments for the air data probe locations and relative effectiveness of alternate flight-test probe configurations. Testing was done in the Mach number range from 0.30 to 3.5. Angle of attack was varied from -8 to 25 degrees while sideslip varied between -8 and 8 degrees.

  9. Tuning cofactor redox potentials: the 2-methoxy dihedral angle generates a redox potential difference of >160 mV between the primary (Q(A)) and secondary (Q(B)) quinones of the bacterial photosynthetic reaction center.

    Science.gov (United States)

    Taguchi, Alexander T; Mattis, Aidas J; O'Malley, Patrick J; Dikanov, Sergei A; Wraight, Colin A

    2013-10-15

    Only quinones with a 2-methoxy group can act simultaneously as the primary (QA) and secondary (QB) electron acceptors in photosynthetic reaction centers from Rhodobacter sphaeroides. (13)C hyperfine sublevel correlation measurements of the 2-methoxy in the semiquinone states, SQA and SQB, were compared with quantum mechanics calculations of the (13)C couplings as a function of the dihedral angle. X-ray structures support dihedral angle assignments corresponding to a redox potential gap (ΔEm) between QA and QB of ~180 mV. This is consistent with the failure of a ubiquinone analogue lacking the 2-methoxy to function as QB in mutant reaction centers with a ΔEm of ≈160-195 mV.

  10. Gravity Probe B Inspection

    Science.gov (United States)

    2000-01-01

    The space vehicle Gravity Probe B (GP-B) is the relativity experiment developed at Stanford University to test two extraordinary predictions of Albert Einstein's general theory of relativity. The experiment will measure, very precisely, the expected tiny changes in the direction of the spin axes of four gyroscopes contained in an Earth-orbiting satellite at a 400-mile altitude. So free are the gyroscopes from disturbance that they will provide an almost perfect space-time reference system. They will measure how space and time are very slightly warped by the presence of the Earth, and, more profoundly, how the Earth's rotation very slightly drags space-time around with it. These effects, though small for the Earth, have far-reaching implications for the nature of matter and the structure of the Universe. GP-B is among the most thoroughly researched programs ever undertaken by NASA. This is the story of a scientific quest in which physicists and engineers have collaborated closely over many years. Inspired by their quest, they have invented a whole range of technologies that are already enlivening other branches of science and engineering. In this photograph, engineer Gary Reynolds is inspecting the inside of the probe neck during probe thermal repairs. GP-B is scheduled for launch in April 2004 and managed for NASA by the Marshall Space Flight Center. Development of the GP-B is the responsibility of Stanford University along with major subcontractor Lockheed Martin Corporation. (Image credit to Russ Leese, Gravity Probe B, Stanford University)

  11. Factors associated with acute oral mucosal reaction induced by radiotherapy in head and neck squamous cell carcinoma: A retrospective single-center experience.

    Science.gov (United States)

    Tao, Zhenchao; Gao, Jin; Qian, Liting; Huang, Yifan; Zhou, Yan; Yang, Liping; He, Jian; Yang, Jing; Wang, Ru; Zhang, Yangyang

    2017-12-01

    To investigate risk factors for acute oral mucosal reaction during head and neck squamous cell carcinoma radiotherapy.A retrospective study of patients with head and neck squamous cell carcinoma who underwent radiotherapy from November 2013 to May 2016 in Anhui Provincial Cancer Hospital was conducted. Data on the occurrence and severity of acute oral mucositis were extracted from clinical records. Based on the Radiation Therapy Oncology Group (RTOG) grading of acute radiation mucosal injury, the patients were assigned into acute reaction (grades 2-4) and minimum reaction (grades 0-1) groups. Preradiotherapy characteristics and treatment factors were compared between the 2 groups. Multivariate logistic regression analysis was used to detect the independent factors associated with acute oral mucosal reactions.Eighty patients completed radiotherapy during the study period. Oral mucosal reactions were recorded as 25, 31, and 24 cases of grades 1, 2, and 3 injuries, respectively. Significant differences between acute reaction and minimum reaction groups were detected in cancer lymph node (N) staging, smoking and diabetes history, pretreatment platelet count and T-Helper/T-Suppressor lymphocyte (Th/Ts) ratio, concurrent chemotherapy, and total and single irradiation doses.Multivariate analysis showed that N stage, smoking history, single dose parapharyngeal irradiation, and pretreatment platelet count were independent risk factors for acute radiation induced oral mucosal reaction. Smoking history, higher grading of N stage, higher single dose irradiation, and lower preirradiation platelet count may increase the risk and severity of acute radiation oral mucosal reaction in radiotherapy of head and neck cancer patients. Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.

  12. [Development of a Fluorescence Probe for Live Cell Imaging].

    Science.gov (United States)

    Shibata, Aya

    2017-01-01

    Probes that detect specific biological materials are indispensable tools for deepening our understanding of various cellular phenomena. In live cell imaging, the probe must emit fluorescence only when a specific substance is detected. In this paper, we introduce a new probe we developed for live cell imaging. Glutathione S-transferase (GST) activity is higher in tumor cells than in normal cells and is involved in the development of resistance to various anticancer drugs. We previously reported the development of a general strategy for the synthesis of probes for detection of GST enzymes, including fluorogenic, bioluminogenic, and 19 F-NMR probes. Arylsulfonyl groups were used as caging groups during probe design. The fluorogenic probes were successfully used to quantitate very low levels of GST activity in cell extracts and were also successfully applied to the imaging of microsomal MGST1 activity in living cells. The bioluminogenic and 19 F-NMR probes were able to detect GST activity in Escherichia coli cells. Oligonucleotide-templated reactions are powerful tools for nucleic acid sensing. This strategy exploits the target strand as a template for two functionalized probes and provides a simple molecular mechanism for multiple turnover reactions. We developed a nucleophilic aromatic substitution reaction-triggered fluorescent probe. The probe completed its reaction within 30 s of initiation and amplified the fluorescence signal from 0.5 pM target oligonucleotide by 1500 fold under isothermal conditions. Additionally, we applied the oligonucleotide-templated reaction for molecular releasing and peptide detection.

  13. Quick-Reaction Report on the Audit of Defense Base Realignment and Closure Budget Data for Naval Training Center Great Lakes, Illinois

    National Research Council Canada - National Science Library

    Granetto, Paul

    1994-01-01

    .... The Hull Technician School will share building 520 with the Advanced Hull Technician School, which is being realigned from the Naval Training Center San Diego, California, under project P-608T...

  14. Proximal Probes Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Proximal Probes Facility consists of laboratories for microscopy, spectroscopy, and probing of nanostructured materials and their functional properties. At the...

  15. Probe Techniques. Introductory Remarks

    Energy Technology Data Exchange (ETDEWEB)

    Emeleus, K. G. [School of Physics and Applied Mathematics, Queen' s University, Belfast (United Kingdom)

    1968-04-15

    In this brief introduction to the session on probes, the history of theii development is first touched on briefly. Reference is then made to the significance of the work to be described by Medicus, for conductivity and recombination calculations, and by Lam and Su, for a wide range of medium and higher pressure plasmas. Finally, a number of other probe topics are mentioned, including multiple probes; probes in electronegative plasmas; resonance probes; probes in noisy discharges; probes as oscillation detectors; use of probes where space-charge is not negligible. (author)

  16. Petasis/Diels-Alder/Cyclization Cascade Reactions for the Generation of Scaffolds with Multiple Stereogenic Centers and Orthogonal Handles for Library Production

    DEFF Research Database (Denmark)

    Flagstad, Thomas; Azevedo, Carlos M. G.; Min, Geanna

    2018-01-01

    A new effective strategy for the synthesis of sp3‐rich small molecules for library production is presented. The key steps to generate complexity highlight Petasis 3‐component reaction followed by an intramolecular Diels‐Alder and cyclization to generate a densely enriched tricyclic or tetracyclic...

  17. Kinetic studies on the reaction of cob(II)alamin with hypochlorous acid: Evidence for one electron oxidation of the metal center and corrin ring destruction.

    Science.gov (United States)

    Dassanayake, Rohan S; Farhath, Mohamed M; Shelley, Jacob T; Basu, Soumitra; Brasch, Nicola E

    2016-10-01

    Kinetic and mechanistic studies on the reaction of a major intracellular vitamin B 12 form, cob(II)alamin (Cbl(II)), with hypochlorous acid/hypochlorite (HOCl/OCl - ) have been carried out. Cbl(II) (Co(II)) is rapidly oxidized by HOCl to predominately aquacobalamin/hydroxycobalamin (Cbl(III), Co(III)) with a second-order rate constant of 2.4×10 7 M -1 s -1 (25.0°C). The stoichiometry of the reaction is 1:1. UHPLC/HRMS analysis of the product mixture of the reaction of Cbl(II) with 0.9mol equiv. HOCl provides support for HOCl being initially reduced to Cl and subsequent H atom abstraction from the corrin macrocycle occurring, resulting in small amounts of corrinoid species with two or four H atoms fewer than the parent cobalamin. Upon the addition of excess (H)OCl further slower reactions are observed. Finally, SDS-PAGE experiments show that HOCl-induced damage to bovine serum albumin does not occur in the presence of Cbl(II), providing support for Cbl(II) being an efficient HOCl trapping agent. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Quick-Reaction Report on the Audit of Defense Base Realignment and Closure Budget Data for Naval Training Center Great Lakes, Illinois

    Science.gov (United States)

    1994-05-19

    the audit of project P-608T, Building Modifications, as they relate to project P-557S. Because...project P-608T was addressed in Report No. 94-108, Quick-Reaction Report on the Audit of Defense Base Realignment and Closure Budget Data for Naval Station Treasure Island, California, May 19,

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

    Science.gov (United States)

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

    2002-01-01

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

  20. Selected ion flow tube (SIFT) studies of the reactions of H3O+, NO+ and O-2(+center dot) with six volatile phytogenic esters

    Czech Academy of Sciences Publication Activity Database

    Sovová, K.; Dryahina, Kseniya; Španěl, Patrik

    2011-01-01

    Roč. 300, č. 1 (2011), s. 31-38 ISSN 1387-3806 R&D Projects: GA ČR GA202/09/0800; GA ČR GA203/09/0256 Institutional research plan: CEZ:AV0Z40400503 Keywords : SIFT-MS * ion-molecule reactions * plant esters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.549, year: 2011

  1. Efficient Destruction of Pollutants in Water by a Dual-Reaction-Center Fenton-like Process over Carbon Nitride Compounds-Complexed Cu(II)-CuAlO2.

    Science.gov (United States)

    Lyu, Lai; Yan, Dengbiao; Yu, Guangfei; Cao, Wenrui; Hu, Chun

    2018-04-03

    Carbon nitride compounds (CN) complexed with the in-situ-produced Cu(II) on the surface of CuAlO 2 substrate (CN-Cu(II)-CuAlO 2 ) is prepared via a surface growth process for the first time and exhibits exceptionally high activity and efficiency for the degradation of the refractory pollutants in water through a Fenton-like process in a wide pH range. The reaction rate for bisphenol A removal is ∼25 times higher than that of the CuAlO 2 . According to the characterization, Cu(II) generation on the surface of CuAlO 2 during the surface growth process results in the marked decrease of the surface oxygen vacancies and the formation of the C-O-Cu bridges between CN and Cu(II)-CuAlO 2 in the catalyst. The electron paramagnetic resonance (EPR) analysis and density functional theory (DFT) calculations demonstrate that the dual reaction centers are produced around the Cu and C sites due to the cation-π interactions through the C-O-Cu bridges in CN-Cu(II)-CuAlO 2 . During the Fenton-like reactions, the electron-rich center around Cu is responsible for the efficient reduction of H 2 O 2 to • OH, and the electron-poor center around C captures electrons from H 2 O 2 or pollutants and diverts them to the electron-rich area via the C-O-Cu bridge. Thus, the catalyst exhibits excellent catalytic performance for the refractory pollutant degradation. This study can deepen our understanding on the enhanced Fenton reactivity for water purification through functionalizing with organic solid-phase ligands on the catalyst surface.

  2. Muons as hyperfine interaction probes in chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Ghandi, Khashayar, E-mail: kghandi@triumf.ca; MacLean, Amy [Mount Allison University, Department of Chemistry & Biochemistry (Canada)

    2015-04-15

    Spin polarized positive muons injected in matter serve as magnetic probes for the investigation of physical and chemical properties of free radicals, mechanisms of free radical reactions and their formations, and radiation effects. All muon techniques rely on the evolution of spin polarization (of the muon) and in that respect are similar to conventional magnetic resonance techniques. The applications of the muon as a hyperfine probe in several fields in chemistry are described.

  3. Muons as hyperfine interaction probes in chemistry

    International Nuclear Information System (INIS)

    Ghandi, Khashayar; MacLean, Amy

    2015-01-01

    Spin polarized positive muons injected in matter serve as magnetic probes for the investigation of physical and chemical properties of free radicals, mechanisms of free radical reactions and their formations, and radiation effects. All muon techniques rely on the evolution of spin polarization (of the muon) and in that respect are similar to conventional magnetic resonance techniques. The applications of the muon as a hyperfine probe in several fields in chemistry are described

  4. Workgroup Report by the Joint Task Force Involving American Academy of Allergy, Asthma & Immunology (AAAAI); Food Allergy, Anaphylaxis, Dermatology and Drug Allergy (FADDA) (Adverse Reactions to Foods Committee and Adverse Reactions to Drugs, Biologicals, and Latex Committee); and the Centers for Disease Control and Prevention Botulism Clinical Treatment Guidelines Workgroup-Allergic Reactions to Botulinum Antitoxin: A Systematic Review.

    Science.gov (United States)

    Schussler, Edith; Sobel, Jeremy; Hsu, Joy; Yu, Patricia; Meaney-Delman, Dana; Grammer, Leslie C; Nowak-Wegrzyn, Anna

    2017-12-27

    Naturally occurring botulism is rare, but a large number of cases could result from unintentional or intentional contamination of a commercial food. Despeciated, equine-derived, heptavalent botulinum antitoxin (HBAT) is licensed in the United States. Timely treatment reduces morbidity and mortality, but concerns that botulinum antitoxin can induce anaphylaxis exist. We sought to quantify the allergy risk of botulinum antitoxin treatment and the usefulness of skin testing to assess this risk. We conducted a systematic review of (1) allergic reactions to botulinum antitoxin and (2) the predictive value of skin testing (ST) before botulinum antitoxin administration. We searched 5 scientific literature databases, reviewed articles' references, and obtained data from the HBAT manufacturer and from the Centers for Disease Control and Prevention. Anaphylaxis incidence was determined for HBAT and previously employed botulinum antitoxins. We calculated the positive predictive value (PPV) and negative predictive value (NPV) of ST for anaphylaxis related to HBAT and other botulinum antitoxins. Seven articles were included. Anaphylaxis incidence was 1.64% (5/305 patients) for HBAT and 1.16% (8/687 patients) for all other botulinum antitoxins (relative risk, 1.41 [95% confidence interval, .47-4.27]; P = .5). Observed values for both PPV and NPV for HBAT-ST (33 patients) were 100%. Observed PPVs and NPVs of ST for other botulinum antitoxins (302 patients) were 0-56% and 50%-100%, respectively. There were no reports of fatal anaphylaxis. Considering the <2 % rate of anaphylaxis, fatal outcomes, modest predictive value of ST, resource requirements for ST, and the benefits of early treatment, data do not support delaying HBAT administration to perform ST in a mass botulinum toxin exposure. Anaphylactic reactions may occur among 1%-2% of botulinum antitoxin recipients and will require epinephrine and antihistamine treatment and, possibly, intensive care. Published by Oxford

  5. Results of an air data probe investigation utilizing a 0.10 scale orbiter forebody (model 57-0) in the Ames Research Center 14-foot wind tunnel (OA220)

    Science.gov (United States)

    Esparza, V.; Thornton, D. E.

    1976-01-01

    Results are presented of a 0.10 scale orbiter forebody test with left and right mounted air data probes (ADP) as well as a flight test probe (nose boom). Left and right ADP data were obtained at Mach numbers of .3, .4, .5, .6, .7, .8, .85, .9, .95, .98, 1.05 and 1.1 through a Reynolds number range of 1.3 to 4.4 million. Nose boom data were obtained at Mach numbers of .3, .4, .5, .6, .7, .9 and .98.

  6. Hall probe magnetometer for SSC magnet cables

    International Nuclear Information System (INIS)

    Cross, R.W.; Goldfarb, R.B.

    1991-01-01

    The authors of this paper constructed a Hall probe magnetometer to measure the magnetization hysteresis loops of Superconducting Super Collider magnet cables. The instrument uses two Hall-effect field sensors to measure the applied field H and the magnetic induction B. Magnetization M is calculated from the difference of the two quantities. The Hall probes are centered coaxially in the bore of a superconducting solenoid with the B probe against the sample's broad surface. An alternative probe arrangement, in which M is measured directly, aligns the sample probe parallel to the field. The authors measured M as a function of H and field cycle rate both with and without a dc transport current. Flux creep as a function of current was measured from the dependence of ac loss on the cycling rate and from the decay of magnetization with time. Transport currents up to 20% of the critical current have minimal effect on magnetization and flux creep

  7. Mobile Game Probes

    DEFF Research Database (Denmark)

    Borup Lynggaard, Aviaja

    2006-01-01

    This paper will examine how probes can be useful for game designers in the preliminary phases of a design process. The work is based upon a case study concerning pervasive mobile phone games where Mobile Game Probes have emerged from the project. The new probes are aimed towards a specific target...... group and the goal is to specify the probes so they will cover the most relevant areas for our project. The Mobile Game Probes generated many interesting results and new issues occurred, since the probes came to be dynamic and favorable for the process in new ways....

  8. Identifying the public's concerns and the Centers for Disease Control and Prevention's reactions during a health crisis: An analysis of a Zika live Twitter chat.

    Science.gov (United States)

    Glowacki, Elizabeth M; Lazard, Allison J; Wilcox, Gary B; Mackert, Michael; Bernhardt, Jay M

    2016-12-01

    The arrival of the Zika virus in the United States caused much concern among the public because of its ease of transmission and serious consequences for pregnant women and their newborns. We conducted a text analysis to examine original tweets from the public and responses from the Centers for Disease Control and Prevention (CDC) during a live Twitter chat hosted by the CDC. Both the public and the CDC expressed concern about the spread of Zika virus, but the public showed more concern about the consequences it had for women and babies, whereas the CDC focused more on symptoms and education. Copyright © 2016 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  9. Fabrication of all diamond scanning probes for nanoscale magnetometry

    OpenAIRE

    Appel Patrick; Neu Elke; Ganzhorn Marc; Barfuss Arne; Batzer Marietta; Gratz Micha; Tschoepe Andreas; Maletinsky Patrick

    2016-01-01

    The electronic spin of the nitrogen vacancy (NV) center in diamond forms an atomically sized, highly sensitive sensor for magnetic fields. To harness the full potential of individual NV centers for sensing with high sensitivity and nanoscale spatial resolution, NV centers have to be incorporated into scanning probe structures enabling controlled scanning in close proximity to the sample surface. Here, we present an optimized procedure to fabricate single-crystal, all-diamond scanning probes s...

  10. Retrospective analysis of non-laboratory-based adverse drug reactions induced by intravenous radiocontrast agents in a Joint Commission International-accredited academic medical center hospital in China

    Directory of Open Access Journals (Sweden)

    Chen QL

    2017-04-01

    Full Text Available Qin-lan Chen,1 Xiao-ying Zhao,2 Xiao-mi Wang,1 Na Lv,2 Ling-ling Zhu,3 Hui-min Xu,4 Quan Zhou4 1Radiology Nursing Unit, Division of Nursing, 2Department of Quality Management, 3Geriatric VIP Care Ward, Division of Nursing, 4Department of Pharmacy, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, People’s Republic of China Abstract: The authors retrospectively analyzed the pattern and characteristics of non-laboratory-based adverse drug reactions (ADRs induced by intravenous radiocontrast agents in a large-scale hospital in China during 2014–2015. There were 314 ADR cases among 118,208 patients receiving enhanced CT or MRI examinations. The frequency of moderate/severe ADRs defined by Chinese Society of Radiology (ie, severe vomiting, systematic urticaria, facial swelling, dyspnea, vasovagal reaction, laryngeal edema, seizure, trembling, convulsions, unconsciousness, shock, death, and other unexpected adverse reactions was rare (0.0431%, whereas the mild ADRs were uncommon (0.2225% and accounted for 83.76% of ADRs. Frequency of ADRs induced by iodinated contrast agents was related with examination site, sex, and type of patient settings (P<0.01 and was higher compared with gadolinium contrast agents (0.3676% vs 0.0504%, P<0.01. From 2014 to 2015, frequencies of total and moderate/severe ADRs induced by iodinated contrast agents decreased significantly (0.4410% vs 0.2947%, P<0.01; 0.0960% vs 0.0282%, P<0.01, respectively. Frequency of ADRs differed among different iodinated contrast and gadolinium contrast (P<0.05 agents. Iopromide’s ADR frequency in 2014 was significantly higher compared with iopamidol, ioversol, or iohexol (P<0.01. Frequency of moderate/severe ADRs induced by iodixanol was 4.1–5.4 times that of iohexol, iopromide, or iopamidol. Rash was the predominant ADR subtype (84.39% and occurred more frequently with iodixanol compared with iohexol, iopamidol, or ioversol (P<0

  11. Reaction dynamics of the four-centered elimination CH2OH + --> CHO + +H2: Measurement of kinetic energy release distribution and classical trajectory calculation

    Science.gov (United States)

    Lee, Tae Geol; Park, Seung C.; Kim, Myung Soo

    1996-03-01

    Mass-analyzed ion kinetic energy (MIKE) spectrum of CHO+ generated in the unimolecular dissociation of CH2OH+ was measured. Kinetic energy release distribution (KERD) was evaluated by analyzing the spectrum according to the algorithm developed previously. The average kinetic energy release evaluated from the distribution was extraordinarily large, 1.63 eV, corresponding to 75% of the reverse barrier of the reaction. A global analytical potential energy surface was constructed such that the experimental energetics was represented and that various features in the ab initio potential energy surface were closely reproduced. Classical trajectory calculation was carried out with the global analytical potential energy surface to investigate the causes for the extraordinarily large kinetic energy release. Based on the detailed dynamical calculations, it was found that the strained bending forces at the transition state and strengthening of the CO bond from double to triple bond character were mainly responsible for such a significant kinetic energy release. In addition, the dissociation products H2 and CHO+ ion were found to be rotationally excited in the trajectory calculations. This was attributed to the asymmetry of the transition state and the release of asymmetric bending forces. Also, the bending vibrational modes of CHO+ and the H2 stretching mode, which are coupled with the bending coordinates, were found to be moderately excited.

  12. Reaction-Based Reactive Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center

    Energy Technology Data Exchange (ETDEWEB)

    Burgos, W.D.

    2009-09-02

    This report summarizes research conducted in conjunction with a project entitled “Reaction-Based Reactive Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center”, which was funded through the Integrative Studies Element of the former NABIR Program (now the Environmental Remediation Sciences Program) within the Office of Biological and Environmental Research. Dr. William Burgos (The Pennsylvania State University) was the overall PI/PD for the project, which included Brian Dempsey (Penn State), Gour-Tsyh (George) Yeh (Central Florida University), and Eric Roden (formerly at The University of Alabama, now at the University of Wisconsin) as separately-funded co-PIs. The project focused on development of a mechanistic understanding and quantitative models of coupled Fe(III)/U(VI) reduction in FRC Area 2 sediments. The work builds on our previous studies of microbial Fe(III) and U(VI) reduction, and was directly aligned with the Scheibe et al. ORNL FRC Field Project at Area 2.

  13. Structural studies on reaction centers from thermophilic photosynthetic bacteria and its functional utilizations. Tainetsusei kogosei saikin ni yuraisuru kogosei hanno chushin no kozo kaimei to kino kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Nozawa, T; Morishita, Y; Kobayashi, M; Kanno, S [Tohoku University, Sendai (Japan). Faculty of Engineering

    1992-10-31

    This paper describes the results of the experiment in which crystallization of protein of reactive center purified from the photosynthetic film of thermophilic purple sulfur photosynthetic bacterium Chromatium tepidum whose hyrogen donor in photosynthesis is H2S instead of H2O was attempted. Crystallization was carried out by the vapor diffusion method and particularly by using ethylene glycol as precipitator at 4[degree]C after various investigations on the conditions of crystallization. By X-ray diffraction, this crystal was found to belong to the rhombic system, and it was estimated that the lattice constants, a, b, c equal to 140[angstrom], 190[angstrom] and 80[angstrom] respectively. This bacterium is a thermophilic bacterium having the optimum growth temperature of 48-50 [degree]C and utilizes CO2 or H2CO3 as corbon source, ammonium, urea etc. as nitrogen source and thiosulfate as sulfur source. Moreover, another purpose of this investigation was to determine the thermophilic location by elucidating its configuration (although, as a result, the analysis of configuration had no sufficient resolution). It was confirmed that the enzyme system of photosynthetic film and its cytoplasm obtained by ultrasonic spallation of this cell have CO2 fixing activity utilizing light energy. 23 refs., 14 figs., 3 tabs.

  14. Concurrent validity and reliability of using ground reaction force and center of pressure parameters in the determination of leg movement initiation during single leg lift.

    Science.gov (United States)

    Aldabe, Daniela; de Castro, Marcelo Peduzzi; Milosavljevic, Stephan; Bussey, Melanie Dawn

    2016-09-01

    Postural adjustment evaluations during single leg lift requires the initiation of heel lift (T1) identification. T1 measured by means of motion analyses system is the most reliable approach. However, this method involves considerable workspace, expensive cameras, and time processing data and setting up laboratory. The use of ground reaction forces (GRF) and centre of pressure (COP) data is an alternative method as its data processing and setting up is less time consuming. Further, kinetic data is normally collected using frequency samples higher than 1000Hz whereas kinematic data are commonly captured using 50-200Hz. This study describes the concurrent-validity and reliability of GRF and COP measurements in determining T1, using a motion analysis system as reference standard. Kinematic and kinetic data during single leg lift were collected from ten participants. GRF and COP data were collected using one and two force plates. Displacement of a single heel marker was captured by means of ten Vicon(©) cameras. Kinetic and kinematic data were collected using a sample frequency of 1000Hz. Data were analysed in two stages: identification of key events in the kinetic data, and assessing concurrent validity of T1 based on the chosen key events with T1 provided by the kinematic data. The key event presenting the least systematic bias, along with a narrow 95% CI and limits of agreement against the reference standard T1, was the Baseline COPy event. Baseline COPy event was obtained using one force plate and presented excellent between-tester reliability. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Probe-diverse ptychography

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, I., E-mail: isaac.russellpeterson@rmit.edu.au [ARC Centre of Excellence for Coherent X-ray Science, the University of Melbourne, School of Physics, Victoria 3010 (Australia); Harder, R. [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Robinson, I.K. [Research Complex at Harwell, Didcot, Oxfordshire OX11 0DE (United Kingdom); London Centre for Nanotechnology, University College London, London WC1H 0AH (United Kingdom)

    2016-12-15

    We propose an extension of ptychography where the target sample is scanned separately through several probes with distinct amplitude and phase profiles and a diffraction image is recorded for each probe and each sample translation. The resulting probe-diverse dataset is used to iteratively retrieve high-resolution images of the sample and all probes simultaneously. The method is shown to yield significant improvement in the reconstructed sample image compared to the image obtained using the standard single-probe ptychographic phase-retrieval scheme.

  16. Traversing probe system

    International Nuclear Information System (INIS)

    Mashburn, D.N.; Stevens, R.H.; Woodall, H.C.

    1977-01-01

    This invention comprises a rotatable annular probe-positioner which carries at least one radially disposed sensing probe, such as a Pitot tube having a right-angled tip. The positioner can be coaxially and rotatably mounted within a compressor casing or the like and then actuated to orient the sensing probe as required to make measurements at selected stations in the annulus between the positioner and compressor casing. The positioner can be actuated to (a) selectively move the probe along its own axis, (b) adjust the yaw angle of the right-angled probe tip, and (c) revolve the probe about the axis common to the positioner and casing. A cam plate engages a cam-follower portion of the probe and normally rotates with the positioner. The positioner includes a first-motor-driven ring gear which effects slidable movement of the probe by rotating the positioner at a time when an external pneumatic cylinder is actuated to engage the cam plate and hold it stationary. When the pneumatic cylinder is not actuated, this ring gear can be driven to revolve the positioner and thus the probe to a desired circumferential location about the above-mentioned common axis. A second motor-driven ring gear included in the positioner can be driven to rotate the probe about its axis, thus adjusting the yaw angle of the probe tip. The positioner can be used in highly corrosive atmosphere, such as gaseous uranium hexafluoride. 10 claims, 6 figures

  17. Traversing probe system

    Science.gov (United States)

    Mashburn, Douglas N.; Stevens, Richard H.; Woodall, Harold C.

    1977-01-01

    This invention comprises a rotatable annular probe-positioner which carries at least one radially disposed sensing probe, such as a Pitot tube having a right-angled tip. The positioner can be coaxially and rotatably mounted within a compressor casing or the like and then actuated to orient the sensing probe as required to make measurements at selected stations in the annulus between the positioner and compressor casing. The positioner can be actuated to (a) selectively move the probe along its own axis, (b) adjust the yaw angle of the right-angled probe tip, and (c) revolve the probe about the axis common to the positioner and casing. A cam plate engages a cam-follower portion of the probe and normally rotates with the positioner. The positioner includes a first-motor-driven ring gear which effects slidable movement of the probe by rotating the positioner at a time when an external pneumatic cylinder is actuated to engage the cam plate and hold it stationary. When the pneumatic cylinder is not actuated, this ring gear can be driven to revolve the positioner and thus the probe to a desired circumferential location about the above-mentioned common axis. A second motor-driven ring gear included in the positioner can be driven to rotate the probe about its axis, thus adjusting the yaw angle of the probe tip. The positioner can be used in highly corrosive atmosphere, such as gaseous uranium hexafluoride.

  18. Retrospective analysis of multiplex polymerase chain reaction-based molecular diagnostics (SES in 70 patients with suspected central nervous system infections: A single-center study

    Directory of Open Access Journals (Sweden)

    Rama Krishnan Tiruppur Chinnappan Ramalingam

    2016-01-01

    Full Text Available Background: Central nervous system (CNS infections present a grave health care challenge due to high morbidity and mortality. Clinical findings and conventional laboratory assessments are not sufficiently distinct for specific etiologic diagnosis. Identification of pathogens is a key to appropriate therapy. Aim: In this retrospective observational study, we evaluated the efficacy and clinical utility of syndrome evaluation system (SES for diagnosing clinically suspected CNS infections. Materials and Methods: This retrospective analysis included inpatients in our tertiary level neurointensive care unit (NICU and ward from February 2010 to December 2013. Cerebrospinal fluid (CSF samples of 70 patients, clinically suspected of having CNS infections, were subjected to routine laboratory tests, culture, imaging, and SES. We analyzed the efficacy of SES in the diagnosis of CNS infections and its utility in therapeutic decision-making. Results: SES had a clinical sensitivity of 57.4% and clinical specificity of 95.6%. Streptococcus pneumoniae and Pseudomonas aeruginosa were the top two bacterial pathogens, whereas Herpes simplex virus (HSV was the most common viral pathogen. Polymicrobial infections were detected in 32.14% of SES-positive cases. SES elicited a change in the management in 30% of the patients from initial empiric therapy. At discharge, 51 patients recovered fully while 11 patients had partial recovery. Three-month follow-up showed only six patients to have neurological deficits. Conclusion: In a tertiary care center, etiological microbial diagnosis is central to appropriate therapy and outcomes. Sensitive and accurate multiplex molecular diagnostics play a critical role in not only identifying the causative pathogen but also in helping clinicians to institute appropriate therapy, reduce overuse of antimicrobials, and ensure superior clinical outcomes.

  19. Retrospective analysis of multiplex polymerase chain reaction-based molecular diagnostics (SES) in 70 patients with suspected central nervous system infections: A single-center study.

    Science.gov (United States)

    Ramalingam, Rama Krishnan Tiruppur Chinnappan; Chakraborty, Dipanjan

    2016-01-01

    Central nervous system (CNS) infections present a grave health care challenge due to high morbidity and mortality. Clinical findings and conventional laboratory assessments are not sufficiently distinct for specific etiologic diagnosis. Identification of pathogens is a key to appropriate therapy. In this retrospective observational study, we evaluated the efficacy and clinical utility of syndrome evaluation system (SES) for diagnosing clinically suspected CNS infections. This retrospective analysis included inpatients in our tertiary level neurointensive care unit (NICU) and ward from February 2010 to December 2013. Cerebrospinal fluid (CSF) samples of 70 patients, clinically suspected of having CNS infections, were subjected to routine laboratory tests, culture, imaging, and SES. We analyzed the efficacy of SES in the diagnosis of CNS infections and its utility in therapeutic decision-making. SES had a clinical sensitivity of 57.4% and clinical specificity of 95.6%. Streptococcus pneumoniae and Pseudomonas aeruginosa were the top two bacterial pathogens, whereas Herpes simplex virus (HSV) was the most common viral pathogen. Polymicrobial infections were detected in 32.14% of SES-positive cases. SES elicited a change in the management in 30% of the patients from initial empiric therapy. At discharge, 51 patients recovered fully while 11 patients had partial recovery. Three-month follow-up showed only six patients to have neurological deficits. In a tertiary care center, etiological microbial diagnosis is central to appropriate therapy and outcomes. Sensitive and accurate multiplex molecular diagnostics play a critical role in not only identifying the causative pathogen but also in helping clinicians to institute appropriate therapy, reduce overuse of antimicrobials, and ensure superior clinical outcomes.

  20. Electrical resistivity probes

    Science.gov (United States)

    Lee, Ki Ha; Becker, Alex; Faybishenko, Boris A.; Solbau, Ray D.

    2003-10-21

    A miniaturized electrical resistivity (ER) probe based on a known current-voltage (I-V) electrode structure, the Wenner array, is designed for local (point) measurement. A pair of voltage measuring electrodes are positioned between a pair of current carrying electrodes. The electrodes are typically about 1 cm long, separated by 1 cm, so the probe is only about 1 inch long. The electrodes are mounted to a rigid tube with electrical wires in the tube and a sand bag may be placed around the electrodes to protect the electrodes. The probes can be positioned in a borehole or on the surface. The electrodes make contact with the surrounding medium. In a dual mode system, individual probes of a plurality of spaced probes can be used to measure local resistance, i.e. point measurements, but the system can select different probes to make interval measurements between probes and between boreholes.

  1. Development of DNA probes for Candida albicans

    International Nuclear Information System (INIS)

    Cheung, L.L.; Hudson, J.B.

    1988-01-01

    An attempt was made to produce DNA probes that could be used as a rapid and efficient means of detecting candidiasis (invasive Candida infection) in immunocompromised patients. Whole DNA from Candida albicans was digested with restriction endonuclease, and the resulting fragments were randomly cloned into a plasmid vector. Several recombinant plasmids were evaluated for cross-hybridization to various other Candida species, other fungal DNAs, and to nonfungal DNAs. Cross reactions were observed between the probes and different yeasts, but none with unrelated DNAs. Some recombinants were genus-specific, and two of these were applied to the analysis of C. albicans growth curves. It became evident that, although both 32 P- and biotin-labelled probes could be made quite sensitive, a possible limitation in their diagnostic potential was the poor liberation of Candida DNA from cells. Thus, better methods of treatment of clinical specimens will be required before such probes will be useful in routine diagnosis

  2. Development of DNA probes for Candida albicans

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, L.L.; Hudson, J.B.

    1988-07-01

    An attempt was made to produce DNA probes that could be used as a rapid and efficient means of detecting candidiasis (invasive Candida infection) in immunocompromised patients. Whole DNA from Candida albicans was digested with restriction endonuclease, and the resulting fragments were randomly cloned into a plasmid vector. Several recombinant plasmids were evaluated for cross-hybridization to various other Candida species, other fungal DNAs, and to nonfungal DNAs. Cross reactions were observed between the probes and different yeasts, but none with unrelated DNAs. Some recombinants were genus-specific, and two of these were applied to the analysis of C. albicans growth curves. It became evident that, although both /sup 32/P- and biotin-labelled probes could be made quite sensitive, a possible limitation in their diagnostic potential was the poor liberation of Candida DNA from cells. Thus, better methods of treatment of clinical specimens will be required before such probes will be useful in routine diagnosis.

  3. Gravity Probe B Encapsulated

    Science.gov (United States)

    2004-01-01

    In this photo, the Gravity Probe B (GP-B) space vehicle is being encapsulated atop the Delta II launch vehicle. The GP-B is the relativity experiment developed at Stanford University to test two extraordinary predictions of Albert Einstein's general theory of relativity. The experiment will measure, very precisely, the expected tiny changes in the direction of the spin axes of four gyroscopes contained in an Earth-orbiting satellite at a 400-mile altitude. So free are the gyroscopes from disturbance that they will provide an almost perfect space-time reference system. They will measure how space and time are very slightly warped by the presence of the Earth, and, more profoundly, how the Earth's rotation very slightly drags space-time around with it. These effects, though small for the Earth, have far-reaching implications for the nature of matter and the structure of the Universe. GP-B is among the most thoroughly researched programs ever undertaken by NASA. This is the story of a scientific quest in which physicists and engineers have collaborated closely over many years. Inspired by their quest, they have invented a whole range of technologies that are already enlivening other branches of science and engineering. Launched April 20, 2004 , the GP-B program was managed for NASA by the Marshall Space Flight Center. Development of the GP-B is the responsibility of Stanford University along with major subcontractor Lockheed Martin Corporation. (Image credit to Russ Underwood, Lockheed Martin Corporation).

  4. Constructive nanolithography and nanochemistry : local probe oxidation and chemical modification

    NARCIS (Netherlands)

    Wouters, D.; Schubert, U.S.

    2003-01-01

    The possibility to prepare and use submicrometer-sized patterns in successive functionalization reactions with quaternary ammonium salts and (functional) chlorosilanes, as well as cationic gold nanoparticles, is presented. Submicrometer-sized structures were prepared by local probe oxidation of

  5. Hyperpolarized NMR Probes for Biological Assays

    Directory of Open Access Journals (Sweden)

    Sebastian Meier

    2014-01-01

    Full Text Available During the last decade, the development of nuclear spin polarization enhanced (hyperpolarized molecular probes has opened up new opportunities for studying the inner workings of living cells in real time. The hyperpolarized probes are produced ex situ, introduced into biological systems and detected with high sensitivity and contrast against background signals using high resolution NMR spectroscopy. A variety of natural, derivatized and designed hyperpolarized probes has emerged for diverse biological studies including assays of intracellular reaction progression, pathway kinetics, probe uptake and export, pH, redox state, reactive oxygen species, ion concentrations, drug efficacy or oncogenic signaling. These probes are readily used directly under natural conditions in biofluids and are often directly developed and optimized for cellular assays, thus leaving little doubt about their specificity and utility under biologically relevant conditions. Hyperpolarized molecular probes for biological NMR spectroscopy enable the unbiased detection of complex processes by virtue of the high spectral resolution, structural specificity and quantifiability of NMR signals. Here, we provide a survey of strategies used for the selection, design and use of hyperpolarized NMR probes in biological assays, and describe current limitations and developments.

  6. Two-center three-electron bonding in ClNH{sub 3} revealed via helium droplet infrared laser Stark spectroscopy: Entrance channel complex along the Cl + NH{sub 3} → ClNH{sub 2} + H reaction

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Christopher P.; Douberly, Gary E., E-mail: douberly@uga.edu [Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556 (United States); Xie, Changjian; Guo, Hua [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Kaufmann, Matin [Department of Physical Chemistry II, Ruhr-University Bochum, D-44801 Bochum (Germany)

    2016-04-28

    Pyrolytic dissociation of Cl{sub 2} is employed to dope helium droplets with single Cl atoms. Sequential addition of NH{sub 3} to Cl-doped droplets leads to the formation of a complex residing in the entry valley to the substitution reaction Cl + NH{sub 3} → ClNH{sub 2} + H. Infrared Stark spectroscopy in the NH stretching region reveals symmetric and antisymmetric vibrations of a C{sub 3v} symmetric top. Frequency shifts from NH{sub 3} and dipole moment measurements are consistent with a ClNH{sub 3} complex containing a relatively strong two-center three-electron (2c–3e) bond. The nature of the 2c–3e bonding in ClNH{sub 3} is explored computationally and found to be consistent with the complexation-induced blue shifts observed experimentally. Computations of interconversion pathways reveal nearly barrierless routes to the formation of this complex, consistent with the absence in experimental spectra of two other complexes, NH{sub 3}Cl and Cl–HNH{sub 2}, which are predicted in the entry valley to the hydrogen abstraction reaction Cl + NH{sub 3} → HCl + NH{sub 2}.

  7. A Crowdsourcing Evaluation of the NIH Chemical Probes

    Science.gov (United States)

    Oprea, Tudor I.; Bologa, Cristian G.; Boyer, Scott; Curpan, Ramona F.; Glen, Robert C.; Hopkins, Andrew L.; Lipinski, Christopher A.; Marshall, Garland R.; Martin, Yvonne C.; Ostopovici-Halip, Liliana; Rishton, Gilbert; Ursu, Oleg; Vaz, Roy J.; Waller, Chris; Waldmann, Herbert; Sklar, Larry A.

    2013-01-01

    Between 2004 and 2008, the NIH molecular libraries and imaging initiative (MLI) pilot phase funded ten high-throughput Screening Centers, resulting in the deposition of 691 assays into PubChem and the nomination of 64 chemical probes. We crowdsourced the MLI output to 11 experts, who expressed medium or high levels of confidence in 48 of these 64 probes. PMID:19536101

  8. A Crowdsourcing Evaluation of the NIH Chemical Probes

    OpenAIRE

    Oprea, Tudor I.; Bologa, Cristian G.; Boyer, Scott; Curpan, Ramona F.; Glen, Robert C.; Hopkins, Andrew L.; Lipinski, Christopher A.; Marshall, Garland R.; Martin, Yvonne C.; Ostopovici-Halip, Liliana; Rishton, Gilbert; Ursu, Oleg; Vaz, Roy J.; Waller, Chris; Waldmann, Herbert

    2009-01-01

    Between 2004 and 2008, the NIH molecular libraries and imaging initiative (MLI) pilot phase funded ten high-throughput Screening Centers, resulting in the deposition of 691 assays into PubChem and the nomination of 64 chemical probes. We crowdsourced the MLI output to 11 experts, who expressed medium or high levels of confidence in 48 of these 64 probes.

  9. Integrated microfluidic probe station.

    Science.gov (United States)

    Perrault, C M; Qasaimeh, M A; Brastaviceanu, T; Anderson, K; Kabakibo, Y; Juncker, D

    2010-11-01

    The microfluidic probe (MFP) consists of a flat, blunt tip with two apertures for the injection and reaspiration of a microjet into a solution--thus hydrodynamically confining the microjet--and is operated atop an inverted microscope that enables live imaging. By scanning across a surface, the microjet can be used for surface processing with the capability of both depositing and removing material; as it operates under immersed conditions, sensitive biological materials and living cells can be processed. During scanning, the MFP is kept immobile and centered over the objective of the inverted microscope, a few micrometers above a substrate that is displaced by moving the microscope stage and that is flushed continuously with the microjet. For consistent and reproducible surface processing, the gap between the MFP and the substrate, the MFP's alignment, the scanning speed, the injection and aspiration flow rates, and the image capture need all to be controlled and synchronized. Here, we present an automated MFP station that integrates all of these functionalities and automates the key operational parameters. A custom software program is used to control an independent motorized Z stage for adjusting the gap, a motorized microscope stage for scanning the substrate, up to 16 syringe pumps for injecting and aspirating fluids, and an inverted fluorescence microscope equipped with a charge-coupled device camera. The parallelism between the MFP and the substrate is adjusted using manual goniometer at the beginning of the experiment. The alignment of the injection and aspiration apertures along the scanning axis is performed using a newly designed MFP screw holder. We illustrate the integrated MFP station by the programmed, automated patterning of fluorescently labeled biotin on a streptavidin-coated surface.

  10. Gravity Probe B Assembled

    Science.gov (United States)

    2000-01-01

    In this photo, the Gravity Probe B (GP-B) space vehicle is being assembled at the Sunnyvale, California location of the Lockheed Martin Corporation. The GP-B is the relativity experiment developed at Stanford University to test two extraordinary predictions of Albert Einstein's general theory of relativity. The experiment will measure, very precisely, the expected tiny changes in the direction of the spin axes of four gyroscopes contained in an Earth-orbiting satellite at a 400-mile altitude. So free are the gyroscopes from disturbance that they will provide an almost perfect space-time reference system. They will measure how space and time are very slightly warped by the presence of the Earth, and, more profoundly, how the Earth's rotation very slightly drags space-time around with it. These effects, though small for the Earth, have far-reaching implications for the nature of matter and the structure of the Universe. GP-B is among the most thoroughly researched programs ever undertaken by NASA. This is the story of a scientific quest in which physicists and engineers have collaborated closely over many years. Inspired by their quest, they have invented a whole range of technologies that are already enlivening other branches of science and engineering. Launched April 20, 2004 , the GP-B program was managed for NASA by the Marshall Space Flight Center. Development of the GP-B is the responsibility of Stanford University along with major subcontractor Lockheed Martin Corporation. (Image credit to Russ Underwood, Lockheed Martin Corporation).

  11. Intramolecular charge transfer of 4-(dimethylamino)benzonitrile probed by time-resolved fluorescence and transient absorption: No evidence for two ICT states and a πσ* reaction intermediate

    International Nuclear Information System (INIS)

    Zachariasse, Klaas A.; Druzhinin, Sergey I.; Senyushkina, Tamara; Kovalenko, Sergey A.

    2009-01-01

    For the double exponential fluorescence decays of the locally excited (LE) and intramolecular charge transfer (ICT) states of 4-(dimethylamino)benzonitrile (DMABN) in acetonitrile (MeCN) the same times τ 1 and τ 2 are observed. This means that the reversible LE ICT reaction, starting from the initially excited LE state, can be adequately described by a two state mechanism. The most important factor responsible for the sometimes experimentally observed differences in the nanosecond decay time, with τ 1 (LE) 1 (ICT), is photoproduct formation. By employing a global analysis of the LE and ICT fluorescence response functions with a time resolution of 0.5 ps/channel in 1200 channels reliable kinetic and thermodynamic data can be obtained. The arguments presented in the literature in favor of a πσ* state with a bent CN group as an intermediate in the ICT reaction of DMABN are discussed. From the appearance of an excited state absorption (ESA) band in the spectral region between 700 and 800 nm in MeCN for N,N-dimethylanilines with CN, Br, F, CF 3 , and C(=O)OC 2 H 2 p-substituents, it is concluded that this ESA band cannot be attributed to a πσ * state, as only the C-C≡N group can undergo the required 120 deg. bending.

  12. Room temperature redox reaction by oxide ion migration at carbon/Gd-doped CeO2 heterointerface probed by an in situ hard x-ray photoemission and soft x-ray absorption spectroscopies

    Directory of Open Access Journals (Sweden)

    Takashi Tsuchiya, Shogo Miyoshi, Yoshiyuki Yamashita, Hideki Yoshikawa, Kazuya Terabe, Keisuke Kobayashi and Shu Yamaguchi

    2013-01-01

    Full Text Available In situ hard x-ray photoemission spectroscopy (HX-PES and soft x-ray absorption spectroscopy (SX-XAS have been employed to investigate a local redox reaction at the carbon/Gd-doped CeO2 (GDC thin film heterointerface under applied dc bias. In HX-PES, Ce3d and O1s core levels show a parallel chemical shift as large as 3.2 eV, corresponding to the redox window where ionic conductivity is predominant. The window width is equal to the energy gap between donor and acceptor levels of the GDC electrolyte. The Ce M-edge SX-XAS spectra also show a considerable increase of Ce3+ satellite peak intensity, corresponding to electrochemical reduction by oxide ion migration. In addition to the reversible redox reaction, two distinct phenomena by the electrochemical transport of oxide ions are observed as an irreversible reduction of the entire oxide film by O2 evolution from the GDC film to the gas phase, as well as a vigorous precipitation of oxygen gas at the bottom electrode to lift off the GDC film. These in situ spectroscopic observations describe well the electrochemical polarization behavior of a metal/GDC/metal capacitor-like two-electrode cell at room temperature.

  13. Probe tests microweld strength

    Science.gov (United States)

    1965-01-01

    Probe is developed to test strength of soldered, brazed or microwelded joints. It consists of a spring which may be adjusted to the desired test pressure by means of a threaded probe head, and an indicator lamp. Device may be used for electronic equipment testing.

  14. High Pressure Scanning Tunneling Microscopy Studies of Adsorbate Structure and Mobility during Catalytic Reactions. Novel Design of an Ultra High Pressure, High Temperature Scanning Tunneling Microscope System for Probing Catalytic Conversions

    International Nuclear Information System (INIS)

    Tang, David Chi-Wai

    2005-01-01

    The aim of the work presented therein is to take advantage of scanning tunneling microscope's (STM) capability for operation under a variety of environments under real time and at atomic resolution to monitor adsorbate structures and mobility under high pressures, as well as to design a new generation of STM systems that allow imaging in situ at both higher pressures (35 atm) and temperatures (350 C). The design of a high pressure, high temperature scanning tunneling microscope system, that is capable of monitoring reactions in situ at conditions from UHV and ambient temperature up to 1 atm and 250 C, is briefly presented along with vibrational and thermal analysis, as this system serves as a template to improve upon during the design of the new ultra high pressure, high temperature STM. Using this existing high pressure scanning tunneling microscope we monitored the co-adsorption of hydrogen, ethylene and carbon dioxide on platinum (111) and rhodium (111) crystal faces in the mTorr pressure range at 300 K in equilibrium with the gas phase. During the catalytic hydrogenation of ethylene to ethane in the absence of CO the metal surfaces are covered by an adsorbate layer that is very mobile on the time scale of STM imaging. We found that the addition of CO poisons the hydrogenation reaction and induces ordered structures on the single crystal surfaces. Several ordered structures were observed upon CO addition to the surfaces pre-covered with hydrogen and ethylene: a rotated (√19 x √19)R23.4 o on Pt(111), and domains of c(4 x 2)-CO+C 2 H 3 , previously unobserved (4 x 2)-CO+3C 2 H 3 , and (2 x 2)-3CO on Rh(111). A mechanism for CO poisoning of ethylene hydrogenation on the metal single crystals was proposed, in which CO blocks surface metal sites and reduces adsorbate mobility to limit adsorption and reaction rate of ethylene and hydrogen. In order to observe heterogeneous catalytic reactions that occur well above ambient pressure and temperature that more closely

  15. Direct single-molecule dynamic detection of chemical reactions.

    Science.gov (United States)

    Guan, Jianxin; Jia, Chuancheng; Li, Yanwei; Liu, Zitong; Wang, Jinying; Yang, Zhongyue; Gu, Chunhui; Su, Dingkai; Houk, Kendall N; Zhang, Deqing; Guo, Xuefeng

    2018-02-01

    Single-molecule detection can reveal time trajectories and reaction pathways of individual intermediates/transition states in chemical reactions and biological processes, which is of fundamental importance to elucidate their intrinsic mechanisms. We present a reliable, label-free single-molecule approach that allows us to directly explore the dynamic process of basic chemical reactions at the single-event level by using stable graphene-molecule single-molecule junctions. These junctions are constructed by covalently connecting a single molecule with a 9-fluorenone center to nanogapped graphene electrodes. For the first time, real-time single-molecule electrical measurements unambiguously show reproducible large-amplitude two-level fluctuations that are highly dependent on solvent environments in a nucleophilic addition reaction of hydroxylamine to a carbonyl group. Both theoretical simulations and ensemble experiments prove that this observation originates from the reversible transition between the reactant and a new intermediate state within a time scale of a few microseconds. These investigations open up a new route that is able to be immediately applied to probe fast single-molecule physics or biophysics with high time resolution, making an important contribution to broad fields beyond reaction chemistry.

  16. Reaction-Based Reactive Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center, Subproject to Co-PI Eric E. Roden. Final Report

    International Nuclear Information System (INIS)

    Roden, Eric E.

    2011-01-01

    This report summarizes research conducted in conjunction with a project entitled 'Reaction-Based Reactive Transport Modeling of Iron Reduction and Uranium Immobilization at Area 2 of the NABIR Field Research Center', which was funded through the Integrative Studies Element of the former NABIR Program (now the Environmental Remediation Sciences Program) within the Office of Biological and Environmental Research. Dr. William Burgos (The Pennsylvania State University) was the overall PI/PD for the project, which included Brian Dempsey (Penn State), Gour-Tsyh (George) Yeh (Central Florida University), and Eric Roden (formerly at The University of Alabama, now at the University of Wisconsin) as separately-funded co-PIs. The project focused on development of a mechanistic understanding and quantitative models of coupled Fe(III)/U(VI) reduction in FRC Area 2 sediments. The work builds on our previous studies of microbial Fe(III) and U(VI) reduction, and was directly aligned with the Scheibe et al. ORNL FRC Field Project at Area 2.

  17. Impact differences in ground reaction force and center of mass between the first and second landing phases of a drop vertical jump and their implications for injury risk assessment.

    Science.gov (United States)

    Bates, Nathaniel A; Ford, Kevin R; Myer, Gregory D; Hewett, Timothy E

    2013-04-26

    The drop vertical jump (DVJ) task is commonly used to assess biomechanical performance measures that are associated with ACL injury risk in athletes. Previous investigations have solely assessed the first landing phase. We examined the first and second landings of a DVJ for differences in the magnitude of vertical ground reaction force (vGRF) and position of center of mass (CoM). A cohort of 239 adolescent female basketball athletes completed a series of DVJ tasks from an initial box height of 31 cm. Dual force platforms and a three dimensional motion capture system recorded force and positional data for each trial. There was no difference in peak vGRF between landings (p=0.445), but side-to-side differences increased from the first to second landing (p=0.007). Participants demonstrated a lower minimum CoM during stance in the first landing than the second landing (p<0.001). The results have important implications for the future assessment of ACL injury risk behaviors in adolescent female athletes. Greater side-to-side asymmetry in vGRF and higher CoM during impact indicate the second landing of a DVJ may exhibit greater perturbation and better represent in-game mechanics associated with ACL injury risk. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Nuclear reactions

    International Nuclear Information System (INIS)

    Lane, A.M.

    1980-01-01

    In reviewing work at Harwell over the past 25 years on nuclear reactions it is stated that a balance has to be struck in both experiment and theory between work on cross-sections of direct practical relevance to reactors and on those relevant to an overall understanding of reaction processes. The compound nucleus and direct process reactions are described. Having listed the contributions from AERE, Harwell to developments in nuclear reaction research in the period, work on the optical model, neutron capture theory, reactions at doorway states with fine structure, and sum-rules for spectroscopic factors are considered in more detail. (UK)

  19. Inference of protein diffusion probed via fluorescence correlation spectroscopy

    Science.gov (United States)

    Tsekouras, Konstantinos

    2015-03-01

    Fluctuations are an inherent part of single molecule or few particle biophysical data sets. Traditionally, ``noise'' fluctuations have been viewed as a nuisance, to be eliminated or minimized. Here we look on how statistical inference methods - that take explicit advantage of fluctuations - have allowed us to draw an unexpected picture of single molecule diffusional dynamics. Our focus is on the diffusion of proteins probed using fluorescence correlation spectroscopy (FCS). First, we discuss how - in collaboration with the Bustamante and Marqusee labs at UC Berkeley - we determined using FCS data that individual enzymes are perturbed by self-generated catalytic heat (Riedel et al, Nature, 2014). Using the tools of inference, we found how distributions of enzyme diffusion coefficients shift in the presence of substrate revealing that enzymes performing highly exothermic reactions dissipate heat by transiently accelerating their center of mass following a catalytic reaction. Next, when molecules diffuse in the cell nucleus they often appear to diffuse anomalously. We analyze FCS data - in collaboration with Rich Day at the IU Med School - to propose a simple model for transcription factor binding-unbinding in the nucleus to show that it may give rise to apparent anomalous diffusion. Here inference methods extract entire binding affinity distributions for the diffusing transcription factors, allowing us to precisely characterize their interactions with different components of the nuclear environment. From this analysis, we draw key mechanistic insight that goes beyond what is possible by simply fitting data to ``anomalous diffusion'' models.

  20. Probing the Influence of the Conjugated Structure and Halogen Atoms of Poly-Iron-Phthalocyanine on the Oxygen Reduction Reaction by X-ray Absorption Spectroscopy and Density Functional Theory

    International Nuclear Information System (INIS)

    Peng, Yingxiang; Cui, Lufang; Yang, Shifeng; Fu, Jingjing; Zheng, Lirong; Liao, Yi; Li, Kai; Zuo, Xia; Xia, Dingguo

    2015-01-01

    Metal-phthalocyanine (MPc) macrocyclic catalysts have been perceived as promising alternatives to Pt and Pt-based catalysts for the oxygen reduction reaction (ORR). However, the effect of different MPc molecular structures on the ORR has rarely been reported in depth. Herein, iron-phthalocyanine polymers (poly-FePcs) and multi-walled carbon nanotubes (MWCNTs) composites with different structures were synthesized using microwave method. The relationship between their molecular structure and electrocatalytic activity was fully revealed by density functional theory (DFT) and X-ray fine absorption spectroscopy (XAFS). DFT calculations revealed that the introduction of halogen atoms can increase the ion potential (IP) and the dioxo-binding energy () of the poly-FePcs. Meanwhile, their conjugated structure not only facilitates electronic transmission, but also significantly increases . XAFS analysis indicated that the poly-FePc/MWCNTs composites had a square planar structure and a smaller of phthalocyanine ring (Fe-N 4 structure) skeleton structure radius when a larger conjugated structure or introduced halogen atoms was present. The experimental results suggest that the these changes in properties arising from the different structures of the MPc macrocyclic compounds led to a huge effect on their ORR electrochemical activities, and provide a guide to obtaining promising electrochemical catalysts

  1. Hard probes 2006 Asilomar

    CERN Multimedia

    2006-01-01

    "The second international conference on hard and electromagnetic probes of high-energy nuclear collisions was held June 9 to 16, 2006 at the Asilomar Conference grounds in Pacific Grove, California" (photo and 1/2 page)

  2. Neutrons as a probe

    International Nuclear Information System (INIS)

    Iizumi, Masashi

    1993-01-01

    As an introduction to the symposium a brief overview will be given about the features of neutrons as a probe. First it will be pointed out that the utilization of neutrons as a probe for investigating the structural and dynamical properties of condensed matters is a benign gift eventuated from the release of atomic energy initiated by Enrico Fermi exactly half century ago. Features of neutrons as a probe are discussed in accordance with the four basic physical properties of neutrons as an elementary particle; (1) no electric charge (the interaction with matter is nuclear), (2) the mass of neutron is 1 amu, (3) spin is 1/2 and (4) neutrons have magnetic dipole moment. Overview will be given on the uniqueness of neutrons as a probe and on the variety in the way they are used in the wide research area from the pure science to the industrial applications. (author)

  3. Adjustable Pitot Probe

    Science.gov (United States)

    Ashby, George C., Jr.; Robbins, W. Eugene; Horsley, Lewis A.

    1991-01-01

    Probe readily positionable in core of uniform flow in hypersonic wind tunnel. Formed of pair of mating cylindrical housings: transducer housing and pitot-tube housing. Pitot tube supported by adjustable wedge fairing attached to top of pitot-tube housing with semicircular foot. Probe adjusted both radially and circumferentially. In addition, pressure-sensing transducer cooled internally by water or other cooling fluid passing through annulus of cooling system.

  4. Scanning probe microscopy competency development

    Energy Technology Data Exchange (ETDEWEB)

    Hawley, M.E.; Reagor, D.W.; Jia, Quan Xi [and others

    1998-12-31

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The project collaborators developed an ultra-high vacuum scanning tunneling microscope (UHV-STM) capability, integrated it with existing scanning probe microscopes, and developed new, advanced air-based scanning force techniques (SPMs). Programmatic, basic, and industrially related laboratory research requires the existence of SPMs, as well as expertise capable of providing local nano-scale information. The UHV-STM capability, equipped with load-lock system and several surface science techniques, will allow introduction, examination, and reaction of surfaces prepared under well-controlled vacuum conditions, including the examination of morphology and local bonding associated with the initial stages of film growth under controlled growth conditions. The resulting capabilities will enable the authors to respond to a variety of problems requiring local characterization of conducting and nonconducting surfaces in liquids, air, and UHV.

  5. Nuclear critical opalescence and electromagnetic probes

    International Nuclear Information System (INIS)

    Delorme, J.

    1980-01-01

    A description of nuclear critical opalescence is presented with emphasis on the information which can be gained from electromagnetic probes. The connection with standard nuclear physics treatments is given. Experimental possibilities are reviewed. Present information from electron scattering is shown to be unconclusive. The maximum sensitivity to critical phenomena would be attained by measurements of longitudinal spin form factors. Photopion reactions are analyzed in this spirit and found to be promising

  6. Nuclear critical opalescence and electromagnetic probes

    International Nuclear Information System (INIS)

    Delorme, J.

    1981-01-01

    A description of nuclear critical opalescence is presented with emphasis on the information which can be gained from electromagnetic probes. The connection with standard nuclear physics treatments is given. Experimental possibilities are reviewed. Present information from electron scattering is shown to be unconclusive. The maximum sensitivity to critical phenomena would be attained by measurements of longitudinal spin form factors. Photopion reactions are analyzed in this spirit and found to be promising. (orig.)

  7. Plutonium helps probe protein, superconductor

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    Scientists are finding that plutonium can be a useful research tool that may help them answer important questions in fields as diverse as biochemistry and solid-state physics. This paper reports that U.S. research involving plutonium is confined to the Department of Energy's national laboratories and centers around nuclear weapons technology, waste cleanup and disposal, and health effects. But at Los Alamos National Laboratory, scientists also are using plutonium to probe the biochemical behavior of calmodulin, a key calcium-binding protein that mediates calcium-regulated processes in biological systems. At Argonne National Laboratory, another team is trying to learn how a superconductor's properties are affected by the 5f electrons of an actinide like plutonium

  8. The effects of protein crowding in bacterial photosynthetic membranes on the flow of quinone redox species between the photochemical reaction center and the ubiquinol-cytochrome c2 oxidoreductase.

    Science.gov (United States)

    Woronowicz, Kamil; Sha, Daniel; Frese, Raoul N; Sturgis, James N; Nanda, Vikas; Niederman, Robert A

    2011-08-01

    Atomic force microscopy (AFM) of the native architecture of the intracytoplasmic membrane (ICM) of a variety of species of purple photosynthetic bacteria, obtained at submolecular resolution, shows a tightly packed arrangement of light harvesting (LH) and reaction center (RC) complexes. Since there are no unattributed structures or gaps with space sufficient for the cytochrome bc(1) or ATPase complexes, they are localized in membrane domains distinct from the flat regions imaged by AFM. This has generated a renewed interest in possible long-range pathways for lateral diffusion of UQ redox species that functionally link the RC and the bc(1) complexes. Recent proposals to account for UQ flow in the membrane bilayer are reviewed, along with new experimental evidence provided from an analysis of intrinsic near-IR fluorescence emission that has served to test these hypotheses. The results suggest that different mechanism of UQ flow exist between species such as Rhodobacter sphaeroides, with a highly organized arrangement of LH and RC complexes and fast RC electron transfer turnover, and Phaeospirillum molischianum with a more random organization and slower RC turnover. It is concluded that packing density of the peripheral LH2 antenna in the Rba. sphaeroides ICM imposes constraints that significantly slow the diffusion of UQ redox species between the RC and cytochrome bc(1) complex, while in Phs. molischianum, the crowding of the ICM with LH3 has little effect upon UQ diffusion. This supports the proposal that in this type of ICM, a network of RC-LH1 core complexes observed in AFM provides a pathway for long-range quinone diffusion that is unaffected by differences in LH complex composition or organization.

  9. Selective binding of carotenoids with a shorter conjugated chain to the LH2 antenna complex and those with a longer conjugated chain to the reaction center from Rubrivivax gelatinosus.

    Science.gov (United States)

    Kakitani, Yoshinori; Fujii, Ritsuko; Hayakawa, Yoshihiro; Kurahashi, Masahiro; Koyama, Yasushi; Harada, Jiro; Shimada, Keizo

    2007-06-19

    Rubrivivax gelatinosus having both the spheroidene and spirilloxanthin biosynthetic pathways produces carotenoids (Cars) with a variety of conjugated chains, which consist of different numbers of conjugated double bonds (n), including the C=C (m) and C=O (o) bonds. When grown under anaerobic conditions, the wild type produces Cars for which n = m = 9-13, whereas under semiaerobic conditions, it additionally produces Cars for which n = m + o = 10 + 1, 13 + 1, and 13 + 2. On the other hand, a mutant, in which the latter pathway is genetically blocked, produces only Cars for which n = 9 and 10 under anaerobic conditions and n = 9, 10, and 10 + 1 under semianaerobic conditions. Those Cars that were extracted from the LH2 complex (LH2) and the reaction center (RC), isolated from the wild-type and the mutant Rvi. gelatinosus, were analyzed by HPLC, and their structures were determined by mass spectrometry and 1H NMR spectroscopy. The selective binding of Cars to those pigment-protein complexes has been characterized as follows. (1) Cars with a shorter conjugated chain are selectively bound to LH2 whereas Cars with a longer conjugated chain to the RC. (2) Shorter chain Cars with a hydroxyl group are bound to LH2 almost exclusively. This rule holds either in the absence or in the presence of the keto group. The natural selection of shorter chain Cars by LH2 and longer chain Cars by the RC is discussed, on the basis of the results now available, in relation to the light-harvesting and photoprotective functions of Cars.

  10. Comparison of Path Length and Ranges of Movement of the Center of Pressure and Reaction Time and Between Paired-Play and Solo-Play of a Virtual Reality Game.

    Science.gov (United States)

    Portnoy, Sigal; Hersch, Ayelet; Sofer, Tal; Tresser, Sarit

    2017-06-01

    To test whether paired-play will induce longer path length and ranges of movement of the center of pressure (COP), which reflects on balance performance and stability, compared to solo-play and to test the difference in the path length and ranges of movement of the COP while playing the virtual reality (VR) game with the dominant hand compared to playing it with the nondominant hand. In this cross-sectional study 20 children (age 6.1 ± 0.7 years old) played an arm movement controlled VR game alone and with a peer while each of them stood on a pressure measuring pad to track the path length and ranges of movement of the COP. The total COP path was significantly higher during the paired-play (median 295.8 cm) compared to the COP path during the solo-play (median 189.2 cm). No significant differences were found in the reaction time and the mediolateral and anterior-posterior COP ranges between solo-play and paired-play. No significant differences were found between the parameters extracted during paired-play with the dominant or nondominant hand. Our findings imply that the paired-play is advantageous compared to solo-play since it induces a greater movement for the child, during which, higher COP velocities are reached that may contribute to improving the balance control of the child. Apart from the positive social benefits of paired-play, this positive effect on the COP path length is a noteworthy added value in the clinical setting when treating children with balance disorder.

  11. Model for resonant plasma probe.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Johnson, William Arthur; Hebner, Gregory Albert; Jorgenson, Roy E.; Coats, Rebecca Sue

    2007-04-01

    This report constructs simple circuit models for a hairpin shaped resonant plasma probe. Effects of the plasma sheath region surrounding the wires making up the probe are determined. Electromagnetic simulations of the probe are compared to the circuit model results. The perturbing effects of the disc cavity in which the probe operates are also found.

  12. Outsourced Probe Data Effectiveness on Signalized Arterials

    Energy Technology Data Exchange (ETDEWEB)

    Young, Stanley E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sharifi, Elham [University of Maryland; Eshragh, Sepideh [University of Maryland; Hamedi, Masoud [University of Maryland; Juster, Reuben M. [University of Maryland; Kaushik, Kartik [University of Maryland

    2017-07-31

    This paper presents results of an I-95 Corridor Coalition sponsored project to assess the ability of outsourced vehicle probe data to provide accurate travel time on signalized roadways for the purposes of real-time operations as well as performance measures. The quality of outsourced probe data on freeways has led many departments of transportation to consider such data for arterial performance monitoring. From April 2013 through June of 2014, the University of Maryland Center for Advanced Transportation Technology gathered travel times from several arterial corridors within the mid-Atlantic region using Bluetooth traffic monitoring (BTM) equipment, and compared these travel times with the data reported to the I95 Vehicle Probe Project (VPP) from an outsourced probe data vendor. The analysis consisted of several methodologies: (1) a traditional analysis that used precision and bias speed metrics; (2) a slowdown analysis that quantified the percentage of significant traffic disruptions accurately captured in the VPP data; (3) a sampled distribution method that uses overlay methods to enhance and analyze recurring congestion patterns. (4) Last, the BTM and VPP data from each 24-hour period of data collection were reviewed by the research team to assess the extent to which VPP captured the nature of the traffic flow. Based on the analysis, probe data is recommended only on arterial roadways with signal densities (measured in signals per mile) up to one, and it should be tested and used with caution for signal densities between one and two, and is not recommended when signal density exceeds two.

  13. Convective heat flow probe

    Science.gov (United States)

    Dunn, James C.; Hardee, Harry C.; Striker, Richard P.

    1985-01-01

    A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packer-type seals are provided along the probe above and below the heater pads.

  14. International Conference on Spin Observables of Nuclear Probes

    CERN Document Server

    Goodman, Charles; Walker, George; Spin Observables of Nuclear Probes

    1988-01-01

    The proceedings of the "International Conference on Spin Observables of Nuclear Probes" are presented in this volume. This conference was held in Telluride, Colorado, March 14 -17, 1988, and was the fourth in the Telluride series of nuclear physics conferences. A continuing theme in the Telluride conference series has been the complementarity of various intermediate-energy projectiles for elucidating the nucleon-nucleon interaction and nuclear structure. Earlier conferences have contributed significantly to an understanding of spin currents in nuclei, in particular the distribution of Gamow-Teller strength using charge-exchange reactions. The previous conference on "Antinucleon and Nucleon Nucleus Interactions" compared nuclear information from tra­ tional probes to recent results from antinucleon reactions. The 1988 conference on Spin Observables of Nuclear Probes, put special emphasis on spin observables and brought together experts using spin information to probe nuclear structure. Spin observabl...

  15. Double Displacement: an Improved Bioorthogonal Reaction Strategy for Templated Nucleic Acid Detection

    OpenAIRE

    Kleinbaum, Daniel J.; Miller, Gregory P.; Kool, Eric T.

    2010-01-01

    Quenched autoligation probes have been employed previously in a target-templated nonenzymatic ligation strategy for detecting nucleic acids in cells by fluorescence. A common source of background signal in such probes is undesired reaction with water and other cellular nucleophiles. Here we describe a new class of self-ligating probes, double displacement (DD) probes, that rely on two displacement reactions to fully unquench a nearby fluorophore. Three potential double displacement architectu...

  16. Theory of NMR probe design

    International Nuclear Information System (INIS)

    Schnall, M.D.

    1988-01-01

    The NMR probe is the intrinsic part of the NMR system which allows transmission of a stimulus to a sample and the reception of a resulting signal from a sample. NMR probes are used in both imaging and spectroscopy. Optimal probe design is important to the production of adequate signal/moise. It is important for anyone using NMR techniques to understand how NMR probes work and how to optimize probe design

  17. Accelerator Center for Energy Research (ACER)

    Data.gov (United States)

    Federal Laboratory Consortium — The Accelerator Center for Energy Research (ACER) exploits radiation chemistry techniques to study chemical reactions (and other phenomena) by subjecting samples to...

  18. A comprehensive survey of nuclear reactions; Panorama des reactions nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Cugnon, J. [Liege Univ., IFPA, AGO Dept. (Belgium)

    2007-07-01

    The various mechanisms of nuclear reactions are surveyed and classified in different regimes, based on the notions of coherent mechanisms and hard versus soft processes. The emphasis is put on the concepts at the basis of the understanding of these regimes and on the elements of nuclear structure which are involved in these different regimes, as well as the on the possibility of extracting this information. Due to lack of space and for pedagogical reasons, the discussion is limited to nucleon-induced and light-ion-induced reactions. However, a few remarks are given concerning some specific probes, such as weakly bound projectiles or neutron-rich nuclei. (author)

  19. One-Probe Search

    DEFF Research Database (Denmark)

    Östlin, Anna; Pagh, Rasmus

    2002-01-01

    We consider dictionaries that perform lookups by probing a single word of memory, knowing only the size of the data structure. We describe a randomized dictionary where a lookup returns the correct answer with probability 1 - e, and otherwise returns don't know. The lookup procedure uses an expan...

  20. Probing the Solar System

    Science.gov (United States)

    Wilkinson, John

    2013-01-01

    Humans have always had the vision to one day live on other planets. This vision existed even before the first person was put into orbit. Since the early space missions of putting humans into orbit around Earth, many advances have been made in space technology. We have now sent many space probes deep into the Solar system to explore the planets and…

  1. Probing the Solar Interior

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 3; Issue 3. Probing the Solar Interior Hearing the Heartbeats of the Sun. Ashok Ambastha. General ... Author Affiliations. Ashok Ambastha1. Joint In-Charge Udaipur Solar Observatory Physical Research laboratory P.O. Box No. 198 Udaipur 313 001, India ...

  2. Flexible position probe assembly

    International Nuclear Information System (INIS)

    Schmitz, J.J.

    1977-01-01

    The combination of a plurality of tubular transducer sections and a flexible supporting member extending through the tubular transducer sections forms a flexible elongated probe of a design suitable for monitoring the level of an element, such as a nuclear magnetically permeable control rod or liquid. 3 claims, 23 figures

  3. cycloaddition reactions

    Indian Academy of Sciences (India)

    Unknown

    Molecular Modeling Group, Organic Chemical Sciences, Indian Institute of Chemical Technology,. Hyderabad ... thus obtained are helpful to model the regioselectivity ... compromise to model Diels–Alder reactions involving ...... acceptance.

  4. Role of the PufX protein in photosynthetic growth of Rhodobacter sphaeroides. 2. PufX is required for efficient ubiquinone/ubiquinol exchange between the reaction center QB site and the cytochrome bc1 complex.

    Science.gov (United States)

    Barz, W P; Verméglio, A; Francia, F; Venturoli, G; Melandri, B A; Oesterhelt, D

    1995-11-21

    The PufX membrane protein is essential for photosynthetic growth of Rhodobacter sphaeroides because it is required for multiple-turnover electron transfer under anaerobic conditions [see accompanying article; Barz, W. P., Francia, F., Venturoli, G., Melandri, B. A., Verméglio, A., & Oesterhelt, D. (1995) Biochemistry 34, 15235-15247]. In order to understand the molecular role of PufX, light-induced absorption spectroscopy was performed using a pufX- mutant, a pufX+ strain, and two suppressor mutants. We show that the reaction center (RC) requires PufX for its functionality under different redox conditions than the cytochrome bc1 complex: When the kinetics of flash-induced reduction of cytochrome b561 were monitored in chromatophores, we observed a requirement of PufX for turnover of the cytochrome bc1 complex only at high redox potential (Eh > 140 mV), suggesting a function of PufX in lateral ubiquinol transfer from the RC. In contrast, PufX is required for multiple turnover of the RC only under reducing conditions: When the Q pool was partially oxidized in vivo using oxygen or electron acceptors like dimethyl sulfoxide or trimethylamine N-oxide, the deletion of PufX had no effect on light-driven electron flow through the RC. Flash train experiments under anaerobic in vivo conditions revealed that RC photochemistry does not depend on PufX for the first two flash excitations. Following the third and subsequent flashes, however, efficient charge separation requires PufX, indicating an important role of PufX for fast Q/QH2 exchange at the QB site of the RC. We show that the Q/QH2 exchange rate is reduced approximately 500-fold by the deletion of PufX when the Q pool is nearly completely reduced, demonstrating an essential role of PufX for the access of ubiquinone to the QB site. The fast ubiquinone/ubiquinol exchange is partially restored by suppressor mutations altering the macromolecular antenna structure. These results suggest an indirect role of PufX in

  5. The unusually strong hydrogen bond between the carbonyl of Q(A) and His M219 in the Rhodobacter sphaeroides reaction center is not essential for efficient electron transfer from Q(A)(-) to Q(B).

    Science.gov (United States)

    Breton, Jacques; Lavergne, Jérôme; Wakeham, Marion C; Nabedryk, Eliane; Jones, Michael R

    2007-06-05

    In native reaction centers (RCs) from photosynthetic purple bacteria the primary quinone (QA) and the secondary quinone (QB) are interconnected via a specific His-Fe-His bridge. In Rhodobacter sphaeroides RCs the C4=O carbonyl of QA forms a very strong hydrogen bond with the protonated Npi of His M219, and the Ntau of this residue is in turn coordinated to the non-heme iron atom. The second carbonyl of QA is engaged in a much weaker hydrogen bond with the backbone N-H of Ala M260. In previous work, a Trp side chain was introduced by site-directed mutagenesis at the M260 position in the RC of Rb. sphaeroides, resulting in a complex that is completely devoid of QA and therefore nonfunctional. A photochemically competent derivative of the AM260W mutant was isolated that contains a Cys side chain at the M260 position (denoted AM260(W-->C)). In the present work, the interactions between the carbonyl groups of QA and the protein in the AM260(W-->C) suppressor mutant have been characterized by light-induced FTIR difference spectroscopy of the photoreduction of QA. The QA-/QA difference spectrum demonstrates that the strong interaction between the C4=O carbonyl of QA and His M219 is lost in the mutant, and the coupled CO and CC modes of the QA- semiquinone are also strongly perturbed. In parallel, a band assigned to the perturbation of the C5-Ntau mode of His M219 upon QA- formation in the native RC is lacking in the spectrum of the mutant. Furthermore, a positive band between 2900 and 2400 cm-1 that is related to protons fluctuating within a network of highly polarizable hydrogen bonds in the native RC is reduced in amplitude in the mutant. On the other hand, the QB-/QB FTIR difference spectrum is essentially the same as for the native RC. The kinetics of electron transfer from QA- to QB were measured by the flash-induced absorption changes at 780 nm. Compared to native RCs the absorption transients are slowed by a factor of about 2 for both the slow phase (in the

  6. EDITORIAL: Probing the nanoworld Probing the nanoworld

    Science.gov (United States)

    Miles, Mervyn

    2009-10-01

    In nanotechnology, it is the unique properties arising from nanometre-scale structures that lead not only to their technological importance but also to a better understanding of the underlying science. Over the last twenty years, material properties at the nanoscale have been dominated by the properties of carbon in the form of the C60 molecule, single- and multi-wall carbon nanotubes, nanodiamonds, and recently graphene. During this period, research published in the journal Nanotechnology has revealed the amazing mechanical properties of such materials as well as their remarkable electronic properties with the promise of new devices. Furthermore, nanoparticles, nanotubes, nanorods, and nanowires from metals and dielectrics have been characterized for their electronic, mechanical, optical, chemical and catalytic properties. Scanning probe microscopy (SPM) has become the main characterization technique and atomic force microscopy (AFM) the most frequently used SPM. Over the past twenty years, SPM techniques that were previously experimental in nature have become routine. At the same time, investigations using AFM continue to yield impressive results that demonstrate the great potential of this powerful imaging tool, particularly in close to physiological conditions. In this special issue a collaboration of researchers in Europe report the use of AFM to provide high-resolution topographical images of individual carbon nanotubes immobilized on various biological membranes, including a nuclear membrane for the first time (Lamprecht C et al 2009 Nanotechnology 20 434001). Other SPM developments such as high-speed AFM appear to be making a transition from specialist laboratories to the mainstream, and perhaps the same may be said for non-contact AFM. Looking to the future, characterisation techniques involving SPM and spectroscopy, such as tip-enhanced Raman spectroscopy, could emerge as everyday methods. In all these advanced techniques, routinely available probes will

  7. Probing Electrochemical Reactions at a Plasma-Liquid Interface

    Science.gov (United States)

    2015-03-16

    shift in the absorption spectrum. However, unlike conventional electrochemical systems with a solid cathode , the electrons enter the solution with...yields of the well-understood reduction of silver (Ag+) were measured. In electrochemistry, metals are electrodeposited on a substrate and the weight is...nanoparticles, which can disperse and in some cases dissolve. In order to measure the weight in a manner similar to electrodeposition experiments, we

  8. Lanthanide ions as absorption spectral probes in biochemical reactions

    International Nuclear Information System (INIS)

    Misra, S.N.

    1989-01-01

    The interactions of adenine, adenosine, adenosine 5'-monophosphate, 5'-diphosphate and 5'-triphosphate with Pr(III) and Nd(III) in different stoichiometries and at varying pH levels have been investigated by electronic spectral studies. The intra 4f-4f transitions yield sharp bands which were analysed individually by Gaussian curve analysis. The energy interaction (Fsup(k),Esup(k)) spin orbit interaction (ζ4f), bonding(b), nephelauxetic (β,δ) and intensity parameters (Tsub(τ.P)) have been computed on HP-1000/45 computer using regression analyses refined by least square fit. The nature of bonding, coordination environment, outer and inner sphere coordination have been interpreted in terms of the magnitude of these parameters as compared to the lanthanide free ion. In order to supplicate the solution studies the crystalline compounds of AMP, ADP and ATP with Pr(III) and Nd(III) have been isolated and characterized by IR, 1 H and 31 P NMR studies. The infrared spectral data indicated weak interaction with the imidazole nitrogen of adenine moiety and bidentate attachment of oxygen. (author). 10 refs

  9. Direct Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Austern, N. [University of Pittsburgh, Pittsburgh, PA (United States)

    1963-01-15

    In order to give a unified presentation of one point of view, these lectures are devoted only to a detailed development of the standard theories of direct reactions, starting from basic principles. Discussion is given of the present status of the theories, of the techniques used for practical calculation, and of possible future developments. The direct interaction (DI) aspects of a reaction are those which involve only a few of the many degrees of freedom of a nucleus. In fact the minimum number of degrees of freedom which must be involved in a reaction are those required to describe the initial and final channels, and DI studies typically consider these degrees of freedom and no others. Because of this simplicity DI theories may be worked out in painstaking detail. DI processes concern only part of the wave function for a problem. The other part involves complicated excitations of many degrees of freedom, and gives the compound nucleus (CN) effects. While it is extremely interesting to learn how to separate DI and CN effects in an orderly manner, if they are both present in a reaction, no suitable method has yet been found. Instead, current work stresses the kinds of reactions and the kinds of final states in which DI effects dominate and in which CN effects may almost be forgotten. The DI cross-sections which are studied are often extremely large, comparable to elastic scattering cross-sections. (author)

  10. Modular Rake of Pitot Probes

    Science.gov (United States)

    Dunlap, Timothy A.; Henry, Michael W.; Homyk, Raymond P.

    2004-01-01

    The figure presents selected views of a modular rake of 17 pitot probes for measuring both transient and steady-state pressures in a supersonic wind tunnel. In addition to pitot tubes visible in the figure, the probe modules contain (1) high-frequency dynamic-pressure transducers connected through wires to remote monitoring circuitry and (2) flow passages that lead to tubes that, in turn, lead to remote steady-state pressure transducers. Prior pitot-probe rakes were fabricated as unitary structures, into which the individual pitot probes were brazed. Repair or replacement of individual probes was difficult, costly, and time-consuming because (1) it was necessary to remove entire rakes in order to unbraze individual malfunctioning probes and (2) the heat of unbrazing a failed probe and of brazing a new probe in place could damage adjacent probes. In contrast, the modules in the present probe are designed to be relatively quickly and easily replaceable with no heating and, in many cases, without need for removal of the entire rake from the wind tunnel. To remove a malfunctioning probe, one first removes a screw-mounted V-cross-section cover that holds the probe and adjacent probes in place. Then one removes a screw-mounted cover plate to gain access to the steady-state pressure tubes and dynamicpressure wires. Next, one disconnects the tube and wires of the affected probe. Finally, one installs a new probe in the reverse of the aforementioned sequence. The wire connections can be made by soldering, but to facilitate removal and installation, they can be made via miniature plugs and sockets. The connections between the probe flow passages and the tubes leading to the remote pressure sensors can be made by use of any of a variety of readily available flexible tubes that can be easily pulled off and slid back on for removal and installation, respectively.

  11. Heavy ion beam probing

    International Nuclear Information System (INIS)

    Hickok, R.L.

    1980-07-01

    This report consists of the notes distributed to the participants at the IEEE Mini-Course on Modern Plasma Diagnostics that was held in Madison, Wisconsin in May 1980. It presents an overview of Heavy Ion Beam Probing that briefly describes the principles and discuss the types of measurements that can be made. The problems associated with implementing beam probes are noted, possible variations are described, estimated costs of present day systems, and the scaling requirements for large plasma devices are presented. The final chapter illustrates typical results that have been obtained on a variety of plasma devices. No detailed calculations are included in the report, but a list of references that will provide more detailed information is included

  12. Probing lipid membrane electrostatics

    Science.gov (United States)

    Yang, Yi

    The electrostatic properties of lipid bilayer membranes play a significant role in many biological processes. Atomic force microscopy (AFM) is highly sensitive to membrane surface potential in electrolyte solutions. With fully characterized probe tips, AFM can perform quantitative electrostatic analysis of lipid membranes. Electrostatic interactions between Silicon nitride probes and supported zwitterionic dioleoylphosphatidylcholine (DOPC) bilayer with a variable fraction of anionic dioleoylphosphatidylserine (DOPS) were measured by AFM. Classical Gouy-Chapman theory was used to model the membrane electrostatics. The nonlinear Poisson-Boltzmann equation was numerically solved with finite element method to provide the potential distribution around the AFM tips. Theoretical tip-sample electrostatic interactions were calculated with the surface integral of both Maxwell and osmotic stress tensors on tip surface. The measured forces were interpreted with theoretical forces and the resulting surface charge densities of the membrane surfaces were in quantitative agreement with the Gouy-Chapman-Stern model of membrane charge regulation. It was demonstrated that the AFM can quantitatively detect membrane surface potential at a separation of several screening lengths, and that the AFM probe only perturbs the membrane surface potential by external field created by the internai membrane dipole moment. The analysis yields a dipole moment of 1.5 Debye per lipid with a dipole potential of +275 mV for supported DOPC membranes. This new ability to quantitatively measure the membrane dipole density in a noninvasive manner will be useful in identifying the biological effects of the dipole potential. Finally, heterogeneous model membranes were studied with fluid electric force microscopy (FEFM). Electrostatic mapping was demonstrated with 50 nm resolution. The capabilities of quantitative electrostatic measurement and lateral charge density mapping make AFM a unique and powerful

  13. Induced current heating probe

    International Nuclear Information System (INIS)

    Thatcher, G.; Ferguson, B.G.; Winstanley, J.P.

    1984-01-01

    An induced current heating probe is of thimble form and has an outer conducting sheath and a water flooded flux-generating unit formed from a stack of ferrite rings coaxially disposed in the sheath. The energising coil is made of solid wire which connects at one end with a coaxial water current tube and at the other end with the sheath. The stack of ferrite rings may include non-magnetic insulating rings which help to shape the flux. (author)

  14. Reaction mechanisms

    International Nuclear Information System (INIS)

    Nguyen Trong Anh

    1988-01-01

    The 1988 progress report of the Reaction Mechanisms laboratory (Polytechnic School, France), is presented. The research topics are: the valence bond methods, the radical chemistry, the modelling of the transition states by applying geometric constraints, the long range interactions (ion - molecule) in gaseous phase, the reaction sites in gaseous phase and the mass spectroscopy applications. The points of convergence between the investigations of the mass spectroscopy and the theoretical chemistry teams, as well as the purposes guiding the research programs, are discussed. The published papers, the conferences, the congress communications and the thesis, are also reported [fr

  15. Far Western: probing membranes.

    Science.gov (United States)

    Einarson, Margret B; Pugacheva, Elena N; Orlinick, Jason R

    2007-08-01

    INTRODUCTIONThe far-Western technique described in this protocol is fundamentally similar to Western blotting. In Western blots, an antibody is used to detect a query protein on a membrane. In contrast, in a far-Western blot (also known as an overlay assay) the antibody is replaced by a recombinant GST fusion protein (produced and purified from bacteria), and the assay detects the interaction of this protein with target proteins on a membrane. The membranes are washed and blocked, incubated with probe protein, washed again, and subjected to autoradiography. The GST fusion (probe) proteins are often labeled with (32)P; alternatively, the membrane can be probed with unlabeled GST fusion protein, followed by detection using commercially available GST antibodies. The nonradioactive approach is substantially more expensive (due to the purchase of antibody and detection reagents) than using radioactively labeled proteins. In addition, care must be taken to control for nonspecific interactions with GST alone and a signal resulting from antibody cross-reactivity. In some instances, proteins on the membrane are not able to interact after transfer. This may be due to improper folding, particularly in the case of proteins expressed from a phage expression library. This protocol describes a way to overcome this by washing the membrane in denaturation buffer, which is then serially diluted to permit slow renaturation of the proteins.

  16. NASA's interstellar probe mission

    International Nuclear Information System (INIS)

    Liewer, P.C.; Ayon, J.A.; Wallace, R.A.; Mewaldt, R.A.

    2000-01-01

    NASA's Interstellar Probe will be the first spacecraft designed to explore the nearby interstellar medium and its interaction with our solar system. As envisioned by NASA's Interstellar Probe Science and Technology Definition Team, the spacecraft will be propelled by a solar sail to reach >200 AU in 15 years. Interstellar Probe will investigate how the Sun interacts with its environment and will directly measure the properties and composition of the dust, neutrals and plasma of the local interstellar material which surrounds the solar system. In the mission concept developed in the spring of 1999, a 400-m diameter solar sail accelerates the spacecraft to ∼15 AU/year, roughly 5 times the speed of Voyager 1 and 2. The sail is used to first bring the spacecraft to ∼0.25 AU to increase the radiation pressure before heading out in the interstellar upwind direction. After jettisoning the sail at ∼5 AU, the spacecraft coasts to 200-400 AU, exploring the Kuiper Belt, the boundaries of the heliosphere, and the nearby interstellar medium

  17. Einstein Inflationary Probe (EIP)

    Science.gov (United States)

    Hinshaw, Gary

    2004-01-01

    I will discuss plans to develop a concept for the Einstein Inflation Probe: a mission to detect gravity waves from inflation via the unique signature they impart to the cosmic microwave background (CMB) polarization. A sensitive CMB polarization satellite may be the only way to probe physics at the grand-unified theory (GUT) scale, exceeding by 12 orders of magnitude the energies studied at the Large Hadron Collider. A detection of gravity waves would represent a remarkable confirmation of the inflationary paradigm and set the energy scale at which inflation occurred when the universe was a fraction of a second old. Even a strong upper limit to the gravity wave amplitude would be significant, ruling out many common models of inflation, and pointing to inflation occurring at much lower energy, if at all. Measuring gravity waves via the CMB polarization will be challenging. We will undertake a comprehensive study to identify the critical scientific requirements for the mission and their derived instrumental performance requirements. At the core of the study will be an assessment of what is scientifically and experimentally optimal within the scope and purpose of the Einstein Inflation Probe.

  18. Neutrino spectroscopy can probe the dark matter content in the Sun.

    Science.gov (United States)

    Lopes, Ilídio; Silk, Joseph

    2010-10-22

    After being gravitationally captured, low-mass cold dark-matter particles (mass range from 5 to ~50 × 10(9) electron volts) are thought to drift to the center of the Sun and affect its internal structure. Solar neutrinos provide a way to probe the physical processes occurring in the Sun's core. Solar neutrino spectroscopy, in particular, is expected to measure the neutrino fluxes produced in nuclear reactions in the Sun. Here, we show how the presence of dark-matter particles inside the Sun will produce unique neutrino flux distributions in (7)Be-ν and (8)B-ν, as well as (13)N-ν, (15)O-ν, and (17)F-ν.

  19. Effects of Mach number on pitot-probe displacement in a turbulent boundary layer

    Science.gov (United States)

    Allen, J. M.

    1974-01-01

    Experimental pitot-probe-displacement data have been obtained in a turbulent boundary layer at a local free-stream Mach number of 4.63 and unit Reynolds number of 6.46 million meter. The results of this study were compared with lower Mach number results of previous studies. It was found that small probes showed displacement only, whereas the larger probes showed not only displacement but also distortion of the shape of the boundary-layer profile. The distortion pattern occurred lower in the boundary layer at the higher Mach number than at the the lower Mach number. The maximum distortion occurred when the center of the probe was about one probe diameter off the test surface. For probes in the wall contact position, the indicated Mach numbers were, for all probes tested, close to the true profile. Pitot-probe displacement was found to increase significantly with increasing Mach number.

  20. Probing Local Ionic Dynamics in Functional Oxides: From Nanometer to Atomic Scale

    Science.gov (United States)

    Kalinin, Sergei

    2014-03-01

    Vacancy-mediated electrochemical reactions in oxides underpin multiple applications ranging from electroresistive memories, to chemical sensors to energy conversion systems such as fuel cells. Understanding the functionality in these systems requires probing reversible (oxygen reduction/evolution reaction) and irreversible (cathode degradation and activation, formation of conductive filaments) electrochemical processes. In this talk, I summarize recent advances in probing and controlling these transformations locally on nanometer level using scanning probe microscopy. The localized tip concentrates the electric field in the nanometer scale volume of material, inducing local transition. Measured simultaneously electromechanical response (piezoresponse) or current (conductive AFM) provides the information on the bias-induced changes in material. Here, I illustrate how these methods can be extended to study local electrochemical transformations, including vacancy dynamics in oxides such as titanates, LaxSr1-xCoO3, BiFeO3, and YxZr1-xO2. The formation of electromechanical hysteresis loops and their bias-, temperature- and environment dependences provide insight into local electrochemical mechanisms. In materials such as lanthanum-strontium cobaltite, mapping both reversible vacancy motion and vacancy ordering and static deformation is possible, and can be corroborated by post mortem STEM/EELS studies. In ceria, a broad gamut of electrochemical behaviors is observed as a function of temperature and humidity. The possible strategies for elucidation ionic motion at the electroactive interfaces in oxides using high-resolution electron microscopy and combined ex-situ and in-situ STEM-SPM studies are discussed. In the second part of the talk, probing electrochemical phenomena on in-situ grown surfaces with atomic resolution is illustrated. I present an approach based on the multivariate statistical analysis of the coordination spheres of individual atoms to reveal

  1. Nine New Fluorescent Probes

    Science.gov (United States)

    Lin, Tsung-I.; Jovanovic, Misa V.; Dowben, Robert M.

    1989-06-01

    Absorption and fluorescence spectroscopic studies are reported here for nine new fluorescent probes recently synthesized in our laboratories: four pyrene derivatives with substituents of (i) 1,3-diacetoxy-6,8-dichlorosulfonyl, (ii) 1,3-dihydroxy-6,8-disodiumsulfonate, (iii) 1,3-disodiumsulfonate, and (iv) l-ethoxy-3,6,8-trisodiumsulfonate groups, and five [7-julolidino] coumarin derivatives with substituents of (v) 3-carboxylate-4-methyl, (vi) 3- methylcarboxylate, (vii) 3-acetate-4-methyl, (viii) 3-propionate-4-methyl, and (ix) 3-sulfonate-4-methyl groups. Pyrene compounds i and ii and coumarin compounds v and vi exhibit interesting absorbance and fluorescence properties: their absorption maxima are red shifted compared to the parent compound to the blue-green region, and the band width broadens considerably. All four blue-absorbing dyes fluoresce intensely in the green region, and the two pyrene compounds emit at such long wavelengths without formation of excimers. The fluorescence properties of these compounds are quite environment-sensitive: considerable spectral shifts and fluorescence intensity changes have been observed in the pH range from 3 to 10 and in a wide variety of polar and hydrophobic solvents with vastly different dielectric constants. The high extinction and fluorescence quantum yield of these probes make them ideal fluorescent labeling reagents for proteins, antibodies, nucleic acids, and cellular organelles. The pH and hydrophobicity-dependent fluorescence changes can be utilized as optical pH and/or hydrophobicity indicators for mapping environmental difference in various cellular components in a single cell. Since all nine probes absorb in the UV, but emit at different wavelengths in the visible, these two groups of compounds offer an advantage of utilizing a single monochromatic light source (e.g., a nitrogen laser) to achieve multi-wavelength detection for flow cytometry application. As a first step to explore potential application in

  2. Allergic reactions

    Science.gov (United States)

    ... that don't bother most people (such as venom from bee stings and certain foods, medicines, and pollens) can ... person. If the allergic reaction is from a bee sting, scrape the ... more venom. If the person has emergency allergy medicine on ...

  3. Whole genomic DNA probe for detection of Porphyromonas endodontalis.

    Science.gov (United States)

    Nissan, R; Makkar, S R; Sela, M N; Stevens, R

    2000-04-01

    The purpose of the present study was to develop a DNA probe for Porphyromonas endodontalis. Pure cultures of P. endodontalis were grown in TYP medium, in an anaerobic chamber. DNA was extracted from the P. endodontalis and labeled using the Genius System by Boehringer Mannheim. The labeled P. endodontalis DNA was used in dot-blot hybridization reactions with homologous (P. endodontalis) and unrelated bacterial samples. To determine specificity, strains of 40 other oral bacterial species (e.g. Porphyromonas gingivalis, Porphyromonas asaccharolytica, and Prevotella intermedia) were spotted and reacted with the P. endodontalis DNA probe. None of the panel of 40 oral bacteria hybridized with the P. endodontalis probe, whereas the blot of the homologous organism showed a strong positive reaction. To determine the sensitivity of the probe, dilutions of a P. endodontalis suspension of known concentration were blotted onto a nylon membrane and reacted with the probe. The results of our investigation indicate that the DNA probe that we have prepared specifically detects only P. endodontalis and can detect at least 3 x 10(4) cells.

  4. Wearable probes for service design

    DEFF Research Database (Denmark)

    Mullane, Aaron; Laaksolahti, Jarmo Matti; Svanæs, Dag

    2014-01-01

    Probes are used as a design method in user-centred design to allow end-users to inform design by collecting data from their lives. Probes are potentially useful in service innovation, but current probing methods require users to interrupt their activity and are consequently not ideal for use...... by service employees in reflecting on the delivery of a service. In this paper, we present the ‘wearable probe’, a probe concept that captures sensor data without distracting service employees. Data captured by the probe can be used by the service employees to reflect and co-reflect on the service journey......, helping to identify opportunities for service evolution and innovation....

  5. Probing the pomeron structure with quasi-real photons

    International Nuclear Information System (INIS)

    Arteaga-Romero, N.; Kessler, P.

    1986-03-01

    Following a recent suggestion of Ingelman and Schlein, we here consider the possibility of probing the gluonic structure of the pomeron with quasi-real photons, i.e. in reactions e p → e p + 2 jets + X taking place at an ep collider such as HERA

  6. Gravity Probe B Gyroscope Rotor

    Science.gov (United States)

    2003-01-01

    The Gravity Probe B (GP-B) is the relativity experiment developed at Stanford University to test two extraordinary predictions of Albert Einstein's general theory of relativity. The experiment will measure, very precisely, the expected tiny changes in the direction of the spin axes of four gyroscopes contained in an Earth-orbiting satellite at a 400-mile altitude. So free are the gyroscopes from disturbance that they will provide an almost perfect space-time reference system. They will measure how space and time are very slightly warped by the presence of the Earth, and, more profoundly, how the Earth's rotation very slightly drags space-time around with it. These effects, though small for the Earth, have far-reaching implications for the nature of matter and the structure of the Universe. This photograph is a close up of a niobium-coated gyroscope motor and its housing halves. GP-B is among the most thoroughly researched programs ever undertaken by NASA. This is the story of a scientific quest in which physicists and engineers have collaborated closely over many years. Inspired by their quest, they have invented a whole range of technologies that are already enlivening other branches of science and engineering. Launched April 20, 2004 , the GP-B program was managed for NASA by the Marshall Space Flight Center. Development of the GP-B is the responsibility of Stanford University along with major subcontractor Lockheed Martin Corporation. (Image credit to Don Harley.)

  7. Gravity Probe B Space Vehicle

    Science.gov (United States)

    2003-01-01

    The space vehicle for Gravity Probe B (GP-B) arrives at the launch site at Vandenburg Air Force Base. GP-B is the relativity experiment being developed at Stanford University to test two extraordinary predictions of Albert Einstein's general theory of relativity. The experiment will measure, very precisely, the expected tiny changes in the direction of the spin axes of four gyroscopes contained in an Earth-orbiting satellite at a 400-mile altitude. So free are the gyroscopes from disturbance that they will provide an almost perfect space-time reference system. They will measure how space and time are very slightly warped by the presence of the Earth, and, more profoundly, how the Earth's rotation very slightly drags space-time around with it. These effects, though small for the Earth, have far-reaching implications for the nature of matter and the structure of the Universe. GP-B is among the most thoroughly researched programs ever undertaken by NASA. This is the story of a scientific quest in which physicists and engineers have collaborated closely over many years. Inspired by their quest, they have invented a whole range of technologies that are already enlivening other branches of science and engineering. Scheduled for launch in 2003 and managed for NASA by the Marshall Space Flight Center, development of the GP-B is the responsibility of Stanford University, with major subcontractor Lockheed Martin Corporation.

  8. The solar probe mission

    International Nuclear Information System (INIS)

    Feldman, W.C.; Anderson, J.; Bohlin, J.D.; Burlaga, L.F.; Farquhar, R.; Gloeckler, G.; Goldstein, B.E.; Harvey, J.W.; Holzer, T.E.; Jones, W.V.; Kellogg, P.J.; Krimigis, S.M.; Kundu, M.R.; Lazarus, A.J.; Mellott, M.M.; Parker, E.N.; Rosner, R.; Rottman, G.J.; Slavin, J.A.; Suess, S.T.; Tsurutani, B.T.; Woo, R.T.; Zwickl, R.D.

    1990-01-01

    The Solar Probe will deliver a 133.5 kg science payload into a 4 R s perihelion solar polar orbit (with the first perihelion passage in 2004) to explore in situ one of the last frontiers in the solar system---the solar corona. This mission is both affordable and technologically feasible. Using a payload of 12 (predominantly particles and fields) scientific experiments, it will be possible to answer many long-standing, fundamental problems concerning the structure and dynamics of the outer solar atmosphere, including the acceleration, storage, and transport of energetic particles near the Sun and in the inner ( s ) heliosphere

  9. Mobile Probing Kit

    DEFF Research Database (Denmark)

    Larsen, Jakob Eg; Sørensen, Lene Tolstrup; Sørensen, J.K.

    2007-01-01

    Mobile Probing Kit is a low tech and low cost methodology for obtaining inspiration and insights into user needs, requirements and ideas in the early phases of a system's development process. The methodology is developed to identify user needs, requirements and ideas among knowledge workers...... characterized as being highly nomadic and thus potential users of mobile and ubiquitous technologies. The methodology has been applied in the 1ST MAGNET Beyond project in order to obtain user needs and requirements in the process of developing pilot services. We report on the initial findings from applying...

  10. Usage Center

    DEFF Research Database (Denmark)

    Kleinaltenkamp, Michael; Plewa, Carolin; Gudergan, Siegfried

    2017-01-01

    Purpose: The purpose of this paper is to advance extant theorizing around resourceintegration by conceptualizing and delineating the notion of a usage center. Ausage center consists of a combination of interdependent actors that draw onresources across their individual usage processes to create v...

  11. Salience Is Only Briefly Represented: Evidence from Probe-Detection Performance

    Science.gov (United States)

    Donk, Mieke; Soesman, Leroy

    2010-01-01

    Salient objects in the visual field tend to capture attention. The present study aimed to examine the time-course of salience effects using a probe-detection task. Eight experiments investigated how the salience of different orientation singletons affected probe reaction time as a function of stimulus onset asynchrony (SOA) between the…

  12. Spin probes of chemistry in zeolites

    International Nuclear Information System (INIS)

    Werst, D.W.; Trifunac, A.D.

    1997-09-01

    Electron spin resonance (EPR) studies in zeolites are reviewed in which radiolysis was used to ionize the zeolite lattice, create reactive intermediates, spin label reaction products and to provide a window onto chemistry and transport of adsorbates and matrix control of chemistry. The review examines reactions of radical cations and the influence of the geometry constraints inside the zeolite, explores how zeolite model systems can be used to learn about energy and charge transfer in solids and illustrates the use of radiolysis and EPR for in situ spectroscopic studies of solid-acid catalysis. The various spin probes created inside the zeolite pores report on properties of the zeolites as well as shed light on radiolytic processes

  13. Neutral helium beam probe

    Science.gov (United States)

    Karim, Rezwanul

    1999-10-01

    This article discusses the development of a code where diagnostic neutral helium beam can be used as a probe. The code solves numerically the evolution of the population densities of helium atoms at their several different energy levels as the beam propagates through the plasma. The collisional radiative model has been utilized in this numerical calculation. The spatial dependence of the metastable states of neutral helium atom, as obtained in this numerical analysis, offers a possible diagnostic tool for tokamak plasma. The spatial evolution for several hypothetical plasma conditions was tested. Simulation routines were also run with the plasma parameters (density and temperature profiles) similar to a shot in the Princeton beta experiment modified (PBX-M) tokamak and a shot in Tokamak Fusion Test Reactor tokamak. A comparison between the simulation result and the experimentally obtained data (for each of these two shots) is presented. A good correlation in such comparisons for a number of such shots can establish the accurateness and usefulness of this probe. The result can possibly be extended for other plasma machines and for various plasma conditions in those machines.

  14. Unlabeled probes for the detection and typing of herpes simplex virus.

    Science.gov (United States)

    Dames, Shale; Pattison, David C; Bromley, L Kathryn; Wittwer, Carl T; Voelkerding, Karl V

    2007-10-01

    Unlabeled probe detection with a double-stranded DNA (dsDNA) binding dye is one method to detect and confirm target amplification after PCR. Unlabeled probes and amplicon melting have been used to detect small deletions and single-nucleotide polymorphisms in assays where template is in abundance. Unlabeled probes have not been applied to low-level target detection, however. Herpes simplex virus (HSV) was chosen as a model to compare the unlabeled probe method to an in-house reference assay using dual-labeled, minor groove binding probes. A saturating dsDNA dye (LCGreen Plus) was used for real-time PCR. HSV-1, HSV-2, and an internal control were differentiated by PCR amplicon and unlabeled probe melting analysis after PCR. The unlabeled probe technique displayed 98% concordance with the reference assay for the detection of HSV from a variety of archived clinical samples (n = 182). HSV typing using unlabeled probes was 99% concordant (n = 104) to sequenced clinical samples and allowed for the detection of sequence polymorphisms in the amplicon and under the probe. Unlabeled probes and amplicon melting can be used to detect and genotype as few as 10 copies of target per reaction, restricted only by stochastic limitations. The use of unlabeled probes provides an attractive alternative to conventional fluorescence-labeled, probe-based assays for genotyping and detection of HSV and might be useful for other low-copy targets where typing is informative.

  15. Dr. Harry Whelan With the Light Emitting Diode Probe

    Science.gov (United States)

    1999-01-01

    The red light from the Light Emitting Diode (LED) probe shines through the fingers of Dr. Harry Whelan, a pediatric neurologist at the Children's Hospital of Wisconsin in Milwaukee. Dr. Whelan uses the long waves of light from the LED surgical probe to activate special drugs that kill brain tumors. Laser light previously has been used for this type of surgery, but the LED light illuminates through all nearby tissues, reaching parts of tumors that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. Also, it can be used for hours at a time while still remaining cool to the touch. The probe was developed for photodynamic cancer therapy under a NASA Small Business Innovative Research Program grant. The program is part of NASA's Technology Transfer Department at the Marshall Space Flight Center.

  16. A complex probe for tokamak plasma edge conditions

    International Nuclear Information System (INIS)

    Castro, R.M. de; Silva, R.P. da; Heller, M.V.A.P.; Caldas, I.L.; Nascimento, I.C.; Degasperi, F.T.

    1995-01-01

    The study of the physical processes that occur in the plasma edge of tokamak machines has recently grown due to the evidence that these processes influence those that occur in the center of the plasma column. Experimental studies show the existence of a strong level of fluctuations in the plasma edge. The results of these studies indicate that these fluctuations enhance particle and energy transport and degrade the confinement. In order to investigate these processes in the plasma edge of the TBR-1 Tokamak, a Langmuir probe array, a triple and a set of magnetic probes have been designed and constructed. With this set probes the mean and fluctuation values of the magnetic field were detected and correlated with the fluctuating parameters obtained with the electrostatic probes. (author). 7 refs., 5 figs

  17. A selected ion flow tube study of the reactions of H3O+, NO+ and O-2(+center dot) with seven isomers of hexanol in support of SIFT-MS

    Czech Academy of Sciences Publication Activity Database

    Smith, D.; Sovová, Kristýna; Španěl, Patrik

    2012-01-01

    Roč. 319, MAY 1 2012 (2012), s. 25-30 ISSN 1387-3806 R&D Projects: GA ČR GA203/09/0256 Institutional support: RVO:61388955 Keywords : selected ion flow tube mass spectrometry * proton transfer * ion molecule reaction Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.142, year: 2012

  18. Quasielastic reactions

    International Nuclear Information System (INIS)

    Hansen, O.

    1983-01-01

    A brief review is presented of the experimental and theoretical situation regarding transfer reactions and inelastic scattering. In the first category there is little (very little) precision data for heavy projectiles and consequently almost no experience with quantitative theoretical analysis. For the inelastic scattering the rather extensive data strongly supports the coupled channels models with collective formfactors. At the most back angles, at intensities about 10 -5 of Rutherford scattering, a second, compound-like mechanism becomes dominant. The description of the interplay of these two opposite mechanisms provides a new challenge for our understanding

  19. The Antartic Ice Borehole Probe

    Science.gov (United States)

    Behar, A.; Carsey, F.; Lane, A.; Engelhardt, H.

    2000-01-01

    The Antartic Ice Borehole Probe mission is a glaciological investigation, scheduled for November 2000-2001, that will place a probe in a hot-water drilled hole in the West Antartic ice sheet. The objectives of the probe are to observe ice-bed interactions with a downward looking camera, and ice inclusions and structure, including hypothesized ice accretion, with a side-looking camera.

  20. The Galaxy Evolution Probe

    Science.gov (United States)

    Glenn, Jason; Galaxy Evolution Probe Team

    2018-01-01

    The Galaxy Evolution Probe (GEP) is a concept for a far-infrared observatory to survey large regions of sky for star-forming galaxies from z = 0 to beyond z = 3. Our knowledge of galaxy formation is incomplete and requires uniform surveys over a large range of redshifts and environments to accurately describe mass assembly, star formation, supermassive black hole growth, interactions between these processes, and what led to their decline from z ~ 2 to the present day. Infrared observations are sensitive to dusty, star-forming galaxies, which have bright polycyclic aromatic hydrocarbon (PAH) emission features and warm dust continuum in the rest-frame mid infrared and cooler thermal dust emission in the far infrared. Unlike previous far-infrared continuum surveys, the GEP will measure photometric redshifts commensurate with galaxy detections from PAH emission and Si absorption features, without the need for obtaining spectroscopic redshifts of faint counterparts at other wavelengths.The GEP design includes a 2 m diameter telescope actively cooled to 4 K and two instruments: (1) An imager covering 10 to 300 um with 25 spectral resolution R ~ 8 bands (with lower R at the longest wavelengths) to detect star-forming galaxies and measure their redshifts photometrically. (2) A 23 – 190 um, R ~ 250 dispersive spectrometer for redshift confirmation and identification of obscured AGN using atomic fine-structure lines. Lines including [Ne V], [O IV], [O III], [O I], and [C II] will probe gas physical conditions, radiation field hardness, and metallicity. Notionally, the GEP will have a two-year mission: galaxy surveys with photometric redshifts in the first year and a second year devoted to follow-up spectroscopy. A comprehensive picture of star formation in galaxies over the last 10 billion years will be assembled from cosmologically relevant volumes, spanning environments from field galaxies and groups, to protoclusters, to dense galaxy clusters.Commissioned by NASA, the

  1. Nuclear reactions

    International Nuclear Information System (INIS)

    Corner, J.; Richardson, K.; Fenton, N.

    1990-01-01

    Nuclear reactions' marks a new development in the study of television as an agency of public policy debate. During the Eighties, nuclear energy became a major international issue. The disasters at Three-mile Island and Chernobyl created a global anxiety about its risks and a new sensitivity to it among politicians and journalists. This book is a case-study into documentary depictions of nuclear energy in television and video programmes and into the interpretations and responses of viewers drawn from many different occupational groupings. How are the complex and specialist arguments about benefit, risk and proof conveyed through the different conventions of commentary, interview and film sequence? What symbolic associations does the visual language of television bring to portrayals of the issue? And how do viewers make sense of various and conflicting accounts, connecting what they see and hear on the screen with their pre-existing knowledge, experience and 'civic' expectations. The authors examine some of the contrasting forms and themes which have been used by programme makers to explain and persuade, and then give a sustained analysis of the nature and sources of viewers' own accounts. 'Nuclear Reactions' inquires into the public meanings surrounding energy and the environment, spelling out in its conclusion some of the implications for future media treatments of this issue. It is also a key contribution to the international literature on 'television knowledge' and the processes of active viewing. (author)

  2. Probing the Terrain

    DEFF Research Database (Denmark)

    Johannessen, Runa

    2016-01-01

    Whether manifest in built structures or invisible infrastructures, architectures of control in the occupied Palestinian West Bank is structurally defined by endemic uncertainty. Shifting lines and frontiers are recorded on the terrain, creating elastic zones of uncertainty necessitating navigatio...... to the territory through its lines and laws, and how the very structure of the occupation has changed over the years, I seek to make visible the ways in which architectures of uncertainty compensate for the fleeting terrain that HH is probing.......Whether manifest in built structures or invisible infrastructures, architectures of control in the occupied Palestinian West Bank is structurally defined by endemic uncertainty. Shifting lines and frontiers are recorded on the terrain, creating elastic zones of uncertainty necessitating...

  3. Heat transfer probe

    Science.gov (United States)

    Frank, Jeffrey I.; Rosengart, Axel J.; Kasza, Ken; Yu, Wenhua; Chien, Tai-Hsin; Franklin, Jeff

    2006-10-10

    Apparatuses, systems, methods, and computer code for, among other things, monitoring the health of samples such as the brain while providing local cooling or heating. A representative device is a heat transfer probe, which includes an inner channel, a tip, a concentric outer channel, a first temperature sensor, and a second temperature sensor. The inner channel is configured to transport working fluid from an inner inlet to an inner outlet. The tip is configured to receive at least a portion of the working fluid from the inner outlet. The concentric outer channel is configured to transport the working fluid from the inner outlet to an outer outlet. The first temperature sensor is coupled to the tip, and the second temperature sensor spaced apart from the first temperature sensor.

  4. Solar Probe Plus

    Science.gov (United States)

    Szabo, Adam

    2011-01-01

    The NASA Solar Probe Plus mission is planned to be launched in 2018 to study the upper solar corona with both.in-situ and remote sensing instrumentation. The mission will utilize 6 Venus gravity assist maneuver to gradually lower its perihelion to 9.5 Rs below the expected Alfven pOint to study the sub-alfvenic solar wind that is still at least partially co-rotates with the Sun. The detailed science objectives of this mission will be discussed. SPP will have a strong synergy with The ESA/NASA Solar orbiter mission to be launched a year ahead. Both missions will focus on the inner heliosphere and will have complimentary instrumentations. Strategies to exploit this synergy will be also presented.

  5. Cosmological Probes for Supersymmetry

    Directory of Open Access Journals (Sweden)

    Maxim Khlopov

    2015-05-01

    Full Text Available The multi-parameter character of supersymmetric dark-matter models implies the combination of their experimental studies with astrophysical and cosmological probes. The physics of the early Universe provides nontrivial effects of non-equilibrium particles and primordial cosmological structures. Primordial black holes (PBHs are a profound signature of such structures that may arise as a cosmological consequence of supersymmetric (SUSY models. SUSY-based mechanisms of baryosynthesis can lead to the possibility of antimatter domains in a baryon asymmetric Universe. In the context of cosmoparticle physics, which studies the fundamental relationship of the micro- and macro-worlds, the development of SUSY illustrates the main principles of this approach, as the physical basis of the modern cosmology provides cross-disciplinary tests in physical and astronomical studies.

  6. Trapping and Probing Antihydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Wurtele, Jonathan [UC Berkeley and LBNL

    2013-03-27

    Precision spectroscopy of antihydrogen is a promising path to sensitive tests of CPT symmetry. The most direct route to achieve this goal is to create and probe antihydrogen in a magnetic minimum trap. Antihydrogen has been synthesized and trapped for 1000s at CERN by the ALPHA Collaboration. Some of the challenges associated with achieving these milestones will be discussed, including mixing cryogenic positron and antiproton plasmas to synthesize antihydrogen with kinetic energy less than the trap potential of .5K. Recent experiments in which hyperfine transitions were resonantly induced with microwaves will be presented. The opportunity for gravitational measurements in traps based on detailed studies of antihydrogen dynamics will be described. The talk will conclude with a discussion future antihydrogen research that will use a new experimental apparatus, ALPHA-I.

  7. Traversing incore probe device

    International Nuclear Information System (INIS)

    Yoshioka, Michiko.

    1985-01-01

    Purpose: To measure the neutron flux distribution in the reactor core always at a high accuracy. Constitution: A nuclear fission ionizing chamber type detector is disposed at the end of a cable for sending a detection signal of a traversing incore probe device and, further, a gamma-ray ionizing chamber type detector is connected in adjacent therewith and a selection circuit for selecting both of the detection signals and inputting them to a display device is disposed. Then, compensation for the neutron monitors is conducted by the gamma-ray ionizing chamber type detector during normal operation in which control rods are not driven and the positioning is carried out by the nuclear fission ionizing chamber type detector. Furthermore, both of the compensation for the neutron detector and the positioning are carried out by the nuclear fission ionizing chamber type detector upon starting where the control rods are driven. (Sekiya, K.)

  8. Impact of Probe Placement Error on MIMO OTA Test Zone Performance

    DEFF Research Database (Denmark)

    Fan, Wei; Nielsen, Jesper Ødum; Carreño, Xavier

    2012-01-01

    Standardization work for MIMO OTA testing methods is currently ongoing, where a multi-probe anechoic chamber based solution is an important candidate. In this paper, the probes located on an OTA ring are used to synthesize a plane wave field in the center of the OTA ring, and the EM field for each...

  9. Measurement Verification of Plane Wave Synthesis Technique Based on Multi-probe MIMO-OTA Setup

    DEFF Research Database (Denmark)

    Fan, Wei; Carreño, Xavier; Nielsen, Jesper Ødum

    2012-01-01

    Standardization work for MIMO OTA testing methods is currently ongoing, where a multi-probe anechoic chamber based solution is an important candidate. In this paper, the probes located on an OTA ring are used to synthesize a plane wave field in the center of the OTA ring. This paper investigates...

  10. Verification of Emulated Channels in Multi-Probe Based MIMO OTA Testing Setup

    DEFF Research Database (Denmark)

    Fan, Wei; Carreño, Xavier; Nielsen, Jesper Ødum

    2013-01-01

    Standardization work for MIMO OTA testing methods is currently ongoing, where a multi-probe anechoic chamber based solution is an important candidate. In this paper, the probes located on an OTA ring are used to synthesize a plane wave field in the center of the OTA ring. This paper investigates...

  11. Spallation reactions; Reactions de spallation

    Energy Technology Data Exchange (ETDEWEB)

    Cugon, J.

    1996-12-31

    Spallation reactions dominate the interactions of hadrons with nuclei in the GeV range (from {approx} 0.1 to {approx} 10 GeV). They correspond to a sometimes important ejection of light particles leaving most of the time a residue of mass commensurate with the target mass. The main features of the experimental data are briefly reviewed. The most successful theoretical model, namely the intranuclear cascade + evaporation model, is presented. Its physical content, results and possible improvements are critically discussed. Alternative approaches are shortly reviewed. (author). 84 refs.

  12. Synthesis and electroplating of high resolution insulated carbon nanotube scanning probes for imaging in liquid solutions.

    Science.gov (United States)

    Roberts, N A; Noh, J H; Lassiter, M G; Guo, S; Kalinin, S V; Rack, P D

    2012-04-13

    High resolution and isolated scanning probe microscopy (SPM) is in demand for continued development of energy storage and conversion systems involving chemical reactions at the nanoscale as well as an improved understanding of biological systems. Carbon nanotubes (CNTs) have large aspect ratios and, if leveraged properly, can be used to develop high resolution SPM probes. Isolation of SPM probes can be achieved by depositing a dielectric film and selectively etching at the apex of the probe. In this paper the fabrication of a high resolution and isolated SPM tip is demonstrated using electron beam induced etching of a dielectric film deposited onto an SPM tip with an attached CNT at the apex.

  13. Measuring reactive oxygen and nitrogen species with fluorescent probes: challenges and limitations

    Science.gov (United States)

    Kalyanaraman, Balaraman; Darley-Usmar, Victor; Davies, Kelvin J.A.; Dennery, Phyllis A.; Forman, Henry Jay; Grisham, Matthew B.; Mann, Giovanni E.; Moore, Kevin; Roberts, L. Jackson; Ischiropoulos, Harry

    2013-01-01

    The purpose of this position paper is to present a critical analysis of the challenges and limitations of the most widely used fluorescent probes for detecting and measuring reactive oxygen and nitrogen species. Where feasible, we have made recommendations for the use of alternate probes and appropriate analytical techniques that measure the specific products formed from the reactions between fluorescent probes and reactive oxygen and nitrogen species. We have proposed guidelines that will help present and future researchers with regard to the optimal use of selected fluorescent probes and interpretation of results. PMID:22027063

  14. Nanobits: customizable scanning probe tips

    DEFF Research Database (Denmark)

    Kumar, Rajendra; Shaik, Hassan Uddin; Sardan Sukas, Özlem

    2009-01-01

    We present here a proof-of-principle study of scanning probe tips defined by planar nanolithography and integrated with AFM probes using nanomanipulation. The so-called 'nanobits' are 2-4 mu m long and 120-150 nm thin flakes of Si3N4 or SiO2, fabricated by electron beam lithography and standard s...

  15. Gene probes: principles and protocols

    National Research Council Canada - National Science Library

    Aquino de Muro, Marilena; Rapley, Ralph

    2002-01-01

    ... of labeled DNA has allowed genes to be mapped to single chromosomes and in many cases to a single chromosome band, promoting significant advance in human genome mapping. Gene Probes: Principles and Protocols presents the principles for gene probe design, labeling, detection, target format, and hybridization conditions together with detailed protocols, accom...

  16. Non-inductive current probe

    DEFF Research Database (Denmark)

    Bak, Christen Kjeldahl

    1977-01-01

    The current probe described is a low-cost, shunt resistor for monitoring current pulses in e.g., pulsed lasers. Rise time is......The current probe described is a low-cost, shunt resistor for monitoring current pulses in e.g., pulsed lasers. Rise time is...

  17. Kinematical coincidence method in transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Acosta, L.; Amorini, F. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Auditore, L. [INFN Gruppo Collegato di Messina and Dipartimento di Fisica, Università di Messina (Italy); Berceanu, I. [Institute for Physics and Nuclear Engineering, Bucharest (Romania); Cardella, G., E-mail: cardella@ct.infn.it [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Chatterjiee, M.B. [Saha Institute for Nuclear Physics, Kolkata (India); De Filippo, E. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Francalanza, L.; Gianì, R. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia, Catania (Italy); Grassi, L. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Rudjer Boskovic Institute, Zagreb (Croatia); Grzeszczuk, A. [Institut of Physics, University of Silesia, Katowice (Poland); La Guidara, E. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania (Italy); Lanzalone, G. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Facoltà di Ingegneria e Architettura, Università Kore, Enna (Italy); Lombardo, I. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Scienze Fisiche, Università Federico II and INFN Sezione di Napoli (Italy); Loria, D.; Minniti, T. [INFN Gruppo Collegato di Messina and Dipartimento di Fisica, Università di Messina (Italy); Pagano, E.V. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia, Catania (Italy); and others

    2013-07-01

    A new method to extract high resolution angular distributions from kinematical coincidence measurements in binary reactions is presented. Kinematics is used to extract the center of mass angular distribution from the measured energy spectrum of light particles. Results obtained in the case of {sup 10}Be+p→{sup 9}Be+d reaction measured with the CHIMERA detector are shown. An angular resolution of few degrees in the center of mass is obtained. The range of applicability of the method is discussed.

  18. Mobile Probes in Mobile Learning

    DEFF Research Database (Denmark)

    Ørngreen, Rikke; Blomhøj, Ulla; Duvaa, Uffe

    In this paper experiences from using mobile probes in educational design of a mobile learning application is presented. The probing process stems from the cultural probe method, and was influenced by qualitative interview and inquiry approaches. In the project, the mobile phone was not only acting...... as an agent for acquiring empirical data (as the situation in hitherto mobile probe settings) but was also the technological medium for which data should say something about (mobile learning). Consequently, not only the content of the data but also the ways in which data was delivered and handled, provided...... a valuable dimension for investigating mobile use. The data was collected at the same time as design activities took place and the collective data was analysed based on user experience goals and cognitive processes from interaction design and mobile learning. The mobile probe increased the knowledge base...

  19. Water cooled static pressure probe

    Science.gov (United States)

    Lagen, Nicholas T. (Inventor); Eves, John W. (Inventor); Reece, Garland D. (Inventor); Geissinger, Steve L. (Inventor)

    1991-01-01

    An improved static pressure probe containing a water cooling mechanism is disclosed. This probe has a hollow interior containing a central coolant tube and multiple individual pressure measurement tubes connected to holes placed on the exterior. Coolant from the central tube symmetrically immerses the interior of the probe, allowing it to sustain high temperature (in the region of 2500 F) supersonic jet flow indefinitely, while still recording accurate pressure data. The coolant exits the probe body by way of a reservoir attached to the aft of the probe. The pressure measurement tubes are joined to a single, larger manifold in the reservoir. This manifold is attached to a pressure transducer that records the average static pressure.

  20. Development of a neutron probe for soil humidity measurements using 6 LiI(Eu) detector

    International Nuclear Information System (INIS)

    Silva, Iran Jose Oliveira da; Khoury, Helen; Carneiro, Clemente J.G.

    2002-01-01

    A prototype of soil moisture probe was build using a crystal of 6 LiI(Eu) as a thermal neutron detector. Light pulses are produced by the exoergic nuclear reaction 6 Li (n,α) 3 He and transmitted through the light guide to a photomultiplier tube on the soil surface. Liquid light guides have several advantages when compared with bundle of glass fibers. First, liquid guides do not suffer from packing fraction losses spaces between fibers that cause reduced coupling efficiency. Second, repeated handling of liquid light guides does not result in the breakage typical of glass bundles, which reduces efficiency over time. Third, liquid guides have excellent UV transmission properties with a cut off the near infrared spectrum yielding an optimum transmission for visible applications. The major advantage of this prototype is the elimination of the electromagnetic interference inside of the soil. Tests were carried out aiming the improvement of electronic and technical viability aspects of neutrons probes. The soil moisture probe calibration curve was carried out in a drum of 60 cm diameter and 42 cm height. This drum was completely filled with an air dry soil. Counts in the center of the drum with the dry and saturated soils make possible to obtain the curves of the soil water content versus the normalized counts for two thermal neutron detectors. The medium value of the counts, the standard deviation and the number of counts were obtained for 6 LiI(Eu) and 3 He detectors, respectively for water, air dry, and saturated soil. From those measurements, a linear calibration curve was obtained for each of detectors. (author)

  1. Steerable Doppler transducer probes

    International Nuclear Information System (INIS)

    Fidel, H.F.; Greenwood, D.L.

    1986-01-01

    An ultrasonic diagnostic probe is described which is capable of performing ultrasonic imaging and Doppler measurement consisting of: a hollow case having an acoustic window which passes ultrasonic energy and including chamber means for containing fluid located within the hollow case and adjacent to a portion of the acoustic window; imaging transducer means, located in the hollow case and outside the fluid chamber means, and oriented to direct ultrasonic energy through the acoustic window toward an area which is to be imaged; Doppler transducer means, located in the hollow case within the fluid chamber means, and movably oriented to direct Doppler signals through the acoustic window toward the imaged area; means located within the fluid chamber means and externally controlled for controllably moving the Doppler transducer means to select one of a plurality of axes in the imaged area along which the Doppler signals are to be directed; and means, located external to the fluid chamber means and responsive to the means for moving, for providing an indication signal for identifying the selected axis

  2. Chain reaction

    International Nuclear Information System (INIS)

    Balogh, Brian.

    1991-01-01

    Chain Reaction is a work of recent American political history. It seeks to explain how and why America came to depend so heavily on its experts after World War II, how those experts translated that authority into political clout, and why that authority and political discretion declined in the 1970s. The author's research into the internal memoranda of the Atomic Energy Commission substantiates his argument in historical detail. It was not the ravages of American anti-intellectualism, as so many scholars have argued, that brought the experts back down to earth. Rather, their decline can be traced to the very roots of their success after World War II. The need to over-state anticipated results in order to garner public support, incessant professional and bureaucratic specialization, and the sheer proliferation of expertise pushed arcane and insulated debates between experts into public forums at the same time that a broad cross section of political participants found it easier to gain access to their own expertise. These tendencies ultimately undermined the political influence of all experts. (author)

  3. Design of fiber optic probes for laser light scattering

    Science.gov (United States)

    Dhadwal, Harbans S.; Chu, Benjamin

    1989-01-01

    A quantitative analysis is presented of the role of optical fibers in laser light scattering. Design of a general fiber optic/microlens probe by means of ray tracing is described. Several different geometries employing an optical fiber of the type used in lightwave communications and a graded index microlens are considered. Experimental results using a nonimaging fiber optic detector probe show that due to geometrical limitations of single mode fibers, a probe using a multimode optical fiber has better performance, for both static and dynamic measurements of the scattered light intensity, compared with a probe using a single mode fiber. Fiber optic detector probes are shown to be more efficient at data collection when compared with conventional approaches to measurements of the scattered laser light. Integration of fiber optic detector probes into a fiber optic spectrometer offers considerable miniaturization of conventional light scattering spectrometers, which can be made arbitrarily small. In addition static and dynamic measurements of scattered light can be made within the scattering cell and consequently very close to the scattering center.

  4. Systematic uncertainties in direct reaction theories

    International Nuclear Information System (INIS)

    Lovell, A E; Nunes, F M

    2015-01-01

    Nuclear reactions are common probes to study nuclei and in particular, nuclei at the limits of stability. The data from reaction measurements depend strongly on theory for a reliable interpretation. Even when using state-of-the-art reaction theories, there are a number of sources of systematic uncertainties. These uncertainties are often unquantified or estimated in a very crude manner. It is clear that for theory to be useful, a quantitative understanding of the uncertainties is critical. Here, we discuss major sources of uncertainties in a variety of reaction theories used to analyze (d,p) nuclear reactions in the energy range E d = 10–20 MeV, and we provide a critical view on how these have been handled in the past and how estimates can be improved. (paper)

  5. A Common Probe Design for Multiple Planetary Destinations

    Science.gov (United States)

    Hwang, H. H.; Allen, G. A., Jr.; Alunni, A. I.; Amato, M. J.; Atkinson, D. H.; Bienstock, B. J.; Cruz, J. R.; Dillman, R. A.; Cianciolo, A. D.; Elliott, J. O.; hide

    2018-01-01

    Atmospheric probes have been successfully flown to planets and moons in the solar system to conduct in situ measurements. They include the Pioneer Venus multi-probes, the Galileo Jupiter probe, and Huygens probe. Probe mission concepts to five destinations, including Venus, Jupiter, Saturn, Uranus, and Neptune, have all utilized similar-shaped aeroshells and concept of operations, namely a 45-degree sphere cone shape with high density heatshield material and parachute system for extracting the descent vehicle from the aeroshell. Each concept designed its probe to meet specific mission requirements and to optimize mass, volume, and cost. At the 2017 International Planetary Probe Workshop (IPPW), NASA Headquarters postulated that a common aeroshell design could be used successfully for multiple destinations and missions. This "common probe"� design could even be assembled with multiple copies, properly stored, and made available for future NASA missions, potentially realizing savings in cost and schedule and reducing the risk of losing technologies and skills difficult to sustain over decades. Thus the NASA Planetary Science Division funded a study to investigate whether a common probe design could meet most, if not all, mission needs to the five planetary destinations with extreme entry environments. The Common Probe study involved four NASA Centers and addressed these issues, including constraints and inefficiencies that occur in specifying a common design. Study methodology: First, a notional payload of instruments for each destination was defined based on priority measurements from the Planetary Science Decadal Survey. Steep and shallow entry flight path angles (EFPA) were defined for each planet based on qualification and operational g-load limits for current, state-of-the-art instruments. Interplanetary trajectories were then identified for a bounding range of EFPA. Next, 3-degrees-of-freedom simulations for entry trajectories were run using the entry state

  6. STM-SQUID probe microscope

    International Nuclear Information System (INIS)

    Hayashi, Tadayuki; Tachiki, Minoru; Itozaki, Hideo

    2007-01-01

    We have developed a STM-SQUID probe microscope. A high T C SQUID probe microscope was combined with a scanning tunneling microscope for investigation of samples at room temperature in air. A high permeability probe needle was used as a magnetic flux guide to improve the spatial resolution. The probe with tip radius of less than 100 nm was prepared by microelectropolishing. The probe was also used as a scanning tunneling microscope tip. Topography of the sample surface could be measured by the scanning tunneling microscope with high spatial resolution prior to observation by SQUID microscopy. The SQUID probe microscope image could be observed while keeping the distance from the sample surface to the probe tip constant. We observed a topographic image and a magnetic image of Ni fine pattern and also a magnetically recorded hard disk. Furthermore we have investigated a sample vibration method of the static magnetic field emanating from a sample with the aim of achieving a higher signal-to-noise (S/N) ratio

  7. The AMEMIYA probe. Theoretical background

    International Nuclear Information System (INIS)

    Belitz, Hans Joahim; Althausen, Bernhard; Uehara, Kazuya; Amemiya, Hiroshi

    2010-01-01

    The present probe was developed in order to measure the temperature T i of positive ions in the scrape-off layer (SOL) of tokamak where T i is usually larger than the electron temperature Ti so that the presheath in front of the probe need not be considered and the ions reach the probe with the thermal velocity. The axis of the cylindrical probe is placed parallel to the magnetic field. The important parameter are L/a, the ratio of the length to the radius of the cylindrical probe and κ, the ratio of the probe radius to (π/4) 1/2 , where is the mean ion Larmor radius. The ion current densities to the side and the end surfaces are expressed by the double integral, which can give an analytical formula with respect to the value of κ. If two electrodes with different lengths are placed parallel to the magnetic field, the difference of current densities can be reduced to κ and hence to Ti. Some examples of the application of the probe to tokamaks, JFT-2M and Textor, are demonstrated. (author)

  8. Flexible poly(methyl methacrylate)-based neural probe: An affordable implementation

    Science.gov (United States)

    Gasemi, Pejman; Veladi, Hadi; Shahabi, Parviz; Khalilzadeh, Emad

    2018-03-01

    This research presents a novel technique used to fabricate a deep brain stimulation probe based on a commercial poly(methyl methacrylate) (PMMA) polymer. This technique is developed to overcome the high cost of available probes crucial for chronic stimulation and recording in neural disorders such as Parkinson’s disease and epilepsy. The probe is made of PMMA and its mechanical properties have been customized by controlling the reaction conditions. The polymer is adjusted to be stiff enough to be easily inserted and, on the other hand, soft enough to perform required movements. As cost is one of the issues in the use of neural probes, a simple process is proposed for the production of PMMA neural probes without using expensive equipment and operations, and without compromising performance and quality. An in vivo animal test was conducted to observe the recording capability of a PMMA probe.

  9. Short recovery time NMR probe

    International Nuclear Information System (INIS)

    Ramia, M.E.; Martin, C.A.; Jeandrevin, S.

    2011-01-01

    A NMR probe for low frequency and short recovery time is presented in this work. The probe contains the tuning circuit, diode expanders and quarter wavelength networks to protect the receiver from both the amplifier noise and the coil ringing following the transmitter power pulse. It also possesses a coil damper which is activated by of non active components. The probe performance shows a recovery time of about of 15μs a sensitive Q factor reduction and an increase of the signal to noise ratio of about 68% during the reception at a work frequency of 2 MHz. (author)

  10. Studies of nuclear structure in antinucleon charge-exchange reactions

    International Nuclear Information System (INIS)

    Auerbach, N.

    1986-01-01

    The antinucleon-nucleus charge exchange reaction is discussed an its use as a probe of isovector excitations in nuclei is described. Attention is drawn to the fact that the (anti p,anti n) reaction will predominantly excite ''pionic'' (i.e., longitudinal spin) modes in nuclei. Comparison between (anti p,anti n) and (n,p) reactions is made. Plans for (anti p,anti n) experiments in the near future are mentioned. 21 refs., 3 figs

  11. Center for Adaptive Optics | Center

    Science.gov (United States)

    Astronomy, UCSC's CfAO and ISEE, and Maui Community College, runs education and internship programs in / Jacobs Retina Center Department of Psychology University of California, San Francisco Department of University School of Optometry Maui Community College Maui Community College Space Grant Program Montana

  12. Lepton probes in nuclear physics

    Energy Technology Data Exchange (ETDEWEB)

    Arvieux, J. [Laboratoire National Saturne, Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1994-12-31

    Facilities are overviewed which use the lepton probe to learn about nuclear physics. The lepton accelerating methods out some existing facilities are considered. The ELFE project is discussed in detail. (K.A.). 43 refs., 15 figs., 4 tabs.

  13. Probing of flowing electron plasmas

    International Nuclear Information System (INIS)

    Himura, H.; Nakashima, C.; Saito, H.; Yoshida, Z.

    2001-01-01

    Probing of streaming electron plasmas with finite temperature is studied. For the first time, a current-voltage characteristic of an electric probe is measured in electron plasmas. Due to the fast flow of the electron plasmas, the characteristic curve spreads out significantly and exhibits a long tail. This feature can be explained calculating the currents collected to the probe. In flowing electron plasmas, the distribution function observed in the laboratory frame is non-Maxwellian even if the plasmas come to a state of thermal equilibrium. Another significant feature of the characteristic is that it determines a floating potential where the current equals zero, despite there being very few ions in the electron plasma. A high impedance probe, which is popularly used to determine the space potential of electron plasmas, outputs the potential. The method is available only for plasmas with density much smaller than the Brillouin limit

  14. Monitoring probe for groundwater flow

    Science.gov (United States)

    Looney, B.B.; Ballard, S.

    1994-08-23

    A monitoring probe for detecting groundwater migration is disclosed. The monitor features a cylinder made of a permeable membrane carrying an array of electrical conductivity sensors on its outer surface. The cylinder is filled with a fluid that has a conductivity different than the groundwater. The probe is placed in the ground at an area of interest to be monitored. The fluid, typically saltwater, diffuses through the permeable membrane into the groundwater. The flow of groundwater passing around the permeable membrane walls of the cylinder carries the conductive fluid in the same general direction and distorts the conductivity field measured by the sensors. The degree of distortion from top to bottom and around the probe is precisely related to the vertical and horizontal flow rates, respectively. The electrical conductivities measured by the sensors about the outer surface of the probe are analyzed to determine the rate and direction of the groundwater flow. 4 figs.

  15. Pneumatic probe with laser interferometer

    International Nuclear Information System (INIS)

    Wilkens, P.H.

    1978-01-01

    Improvements to upgrade the accuracy of Rotacon probes by a complete redesign of probe to include a Michelson interferometer to replace the existing long-range capacity transducer are described. This has resulted in a compact and interchangeable probe cartridge with a 3 μin. resolution and accuracy; the cartridge can be installed and replaced in the Rotacon gauge with the minimum of realignment, which should reduce our dependence on operator skill. In addition, the stylus contact force can be reduced to 750 mg for the contacting types, but an alternative feature, which we are still developing, will use a gas jet cushion in place of the stylus to provide a noncontacting version of the same basic probe cartridge. This device is very sensitive to external vibration effects because it is virtually frictionless

  16. Lepton probes in nuclear physics

    International Nuclear Information System (INIS)

    Arvieux, J.

    1994-01-01

    Facilities are overviewed which use the lepton probe to learn about nuclear physics. The lepton accelerating methods out some existing facilities are considered. The ELFE project is discussed in detail. (K.A.). 43 refs., 15 figs., 4 tabs

  17. TRIMOLECULAR REACTIONS OF URANIUM HEXAFLUORIDE WITH WATER

    Energy Technology Data Exchange (ETDEWEB)

    Westbrook, M.; Becnel, J.; Garrison, S.

    2010-02-25

    The hydrolysis reaction of uranium hexafluoride (UF{sub 6}) is a key step in the synthesis of uranium dioxide (UO{sub 2}) powder for nuclear fuels. Mechanisms for the hydrolysis reactions are studied here with density functional theory and the Stuttgart small-core scalar relativistic pseudopotential and associated basis set for uranium. The reaction of a single UF{sub 6} molecule with a water molecule in the gas phase has been previously predicted to proceed over a relatively sizeable barrier of 78.2 kJ {center_dot} mol{sup -1}, indicating this reaction is only feasible at elevated temperatures. Given the observed formation of a second morphology for the UO{sub 2} product coupled with the observations of rapid, spontaneous hydrolysis at ambient conditions, an alternate reaction pathway must exist. In the present work, two trimolecular hydrolysis mechanisms are studied with density functional theory: (1) the reaction between two UF{sub 6} molecules and one water molecule, and (2) the reaction of two water molecules with a single UF{sub 6} molecule. The predicted reaction of two UF{sub 6} molecules with one water molecule displays an interesting 'fluorine-shuttle' mechanism, a significant energy barrier of 69.0 kJ {center_dot} mol{sup -1} to the formation of UF{sub 5}OH, and an enthalpy of reaction ({Delta}H{sub 298}) of +17.9 kJ {center_dot} mol{sup -1}. The reaction of a single UF{sub 6} molecule with two water molecules displays a 'proton-shuttle' mechanism, and is more favorable, having a slightly lower computed energy barrier of 58.9 kJ {center_dot} mol{sup -1} and an exothermic enthalpy of reaction ({Delta}H{sub 298}) of -13.9 kJ {center_dot} mol{sup -1}. The exothermic nature of the overall UF{sub 6} + 2 {center_dot} H{sub 2}O trimolecular reaction and the lowering of the barrier height with respect to the bimolecular reaction are encouraging; however, the sizable energy barrier indicates further study of the UF{sub 6} hydrolysis reaction

  18. DNA probe for lactobacillus delbrueckii

    Energy Technology Data Exchange (ETDEWEB)

    Delley, M.; Mollet, B.; Hottinger, H. (Nestle Research Centre, Lausanne (Switzerland))

    1990-06-01

    From a genomic DNA library of Lactobacillus delbrueckii subsp. bulgaricus, a clone was isolated which complements a leucine auxotrophy of an Escherichia coli strain (GE891). Subsequent analysis of the clone indicated that it could serve as a specific DNA probe. Dot-blot hybridizations with over 40 different Lactobacillus strains showed that this clone specifically recognized L. delbrueckii subsp. delbrueckii, bulgaricus, and lactis. The sensitivity of the method was tested by using an {alpha}-{sup 32}P-labeled probe.

  19. DNA probe for lactobacillus delbrueckii

    International Nuclear Information System (INIS)

    Delley, M.; Mollet, B.; Hottinger, H.

    1990-01-01

    From a genomic DNA library of Lactobacillus delbrueckii subsp. bulgaricus, a clone was isolated which complements a leucine auxotrophy of an Escherichia coli strain (GE891). Subsequent analysis of the clone indicated that it could serve as a specific DNA probe. Dot-blot hybridizations with over 40 different Lactobacillus strains showed that this clone specifically recognized L. delbrueckii subsp. delbrueckii, bulgaricus, and lactis. The sensitivity of the method was tested by using an α- 32 P-labeled probe

  20. Wake of a blunt planetary probe model under hypervelocity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kastell, D.; Hannemann, D.; Eitelberg, G. [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Goettingen (Germany). Inst. fuer Stroemungsmechanik

    1998-12-31

    The flow in the wake of a planetary probe under hypervelocity re-entry conditions has two idiosyncrasies not present in the conventional (cold) hypersonic flows: the strong dissociation reaction occurring behind the bow shock wave, and the freezing of the chemical reactions of the flow by the rapid expansion at the shoulder of the probe. The aim of the present study was to both understand the relative importance of the two phenomena upon the total heat and pressure loads on a planetary probe and its possible payload as well as to provide experimental validation data for those developing numerical codes for planetary probe design and analysis. For the experimental study an instrumented blunted 140 cone was tested in the High Enthalpy Shock Tunnel in Goettingen (HEG). The numerical calculations were performed with a Thin-Layer Navier-Stokes code which is capable of simulating chemical and thermal nonequilibrium flows. For the forebody loads the prediction methods were very reliable and capable of accounting for the kinetic effects caused by the high specific enthalpy of the flow. On the other side considerable discrepancies between experimental and numerical results for the wake of the model have been observed. (orig.)

  1. Wake of a blunt planetary probe model under hypervelocity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kastell, D.; Hannemann, D.; Eitelberg, G. (DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Goettingen (Germany). Inst. fuer Stroemungsmechanik)

    1998-01-01

    The flow in the wake of a planetary probe under hypervelocity re-entry conditions has two idiosyncrasies not present in the conventional (cold) hypersonic flows: the strong dissociation reaction occurring behind the bow shock wave, and the freezing of the chemical reactions of the flow by the rapid expansion at the shoulder of the probe. The aim of the present study was to both understand the relative importance of the two phenomena upon the total heat and pressure loads on a planetary probe and its possible payload as well as to provide experimental validation data for those developing numerical codes for planetary probe design and analysis. For the experimental study an instrumented blunted 140 cone was tested in the High Enthalpy Shock Tunnel in Goettingen (HEG). The numerical calculations were performed with a Thin-Layer Navier-Stokes code which is capable of simulating chemical and thermal nonequilibrium flows. For the forebody loads the prediction methods were very reliable and capable of accounting for the kinetic effects caused by the high specific enthalpy of the flow. On the other side considerable discrepancies between experimental and numerical results for the wake of the model have been observed. (orig.)

  2. Chemical potential and reaction electronic flux in symmetry controlled reactions.

    Science.gov (United States)

    Vogt-Geisse, Stefan; Toro-Labbé, Alejandro

    2016-07-15

    In symmetry controlled reactions, orbital degeneracies among orbitals of different symmetries can occur along a reaction coordinate. In such case Koopmans' theorem and the finite difference approximation provide a chemical potential profile with nondifferentiable points. This results in an ill-defined reaction electronic flux (REF) profile, since it is defined as the derivative of the chemical potential with respect to the reaction coordinate. To overcome this deficiency, we propose a new way for the calculation of the chemical potential based on a many orbital approach, suitable for reactions in which symmetry is preserved. This new approach gives rise to a new descriptor: symmetry adapted chemical potential (SA-CP), which is the chemical potential corresponding to a given irreducible representation of a symmetry group. A corresponding symmetry adapted reaction electronic flux (SA-REF) is also obtained. Using this approach smooth chemical potential profiles and well defined REFs are achieved. An application of SA-CP and SA-REF is presented by studying the Cs enol-keto tautomerization of thioformic acid. Two SA-REFs are obtained, JA'(ξ) and JA'' (ξ). It is found that the tautomerization proceeds via an in-plane delocalized 3-center 4-electron O-H-S hypervalent bond which is predicted to exist only in the transition state (TS) region. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  3. Charge-exchange giant resonances as probes of nuclear structure

    International Nuclear Information System (INIS)

    Blomgren, J.

    2001-09-01

    Giant resonances populated in charge-exchange reactions can reveal detailed information about nuclear structure properties, in spite of their apparent featurelessness. The (p,n) and (n,p) reactions - as well as their analog reactions - proceed via the same nuclear matrix element as beta decay. Thereby, they are useful for probing electroweak properties in nuclei, especially for those not accessible to beta decay. The nuclear physics aspects of double beta decay might be investigated in double charge-exchange reactions. detailed nuclear structure information, such as the presence of ground-state correlations, can be revealed via identification of 'first-forbidden' transitions. In addition, astrophysics aspects and halo properties of nuclei have been investigated in charge exchange. Finally, these experiments have questioned our knowledge of the absolute strength of the strong interaction

  4. Design - manufacturing and characterization of specific ultrasonic probes

    International Nuclear Information System (INIS)

    Petit, J.

    1985-01-01

    Optimization of ultrasonic examinations requires essentially to determine precisely parameters used for manufacturing of probes and to check characteristics of beams used. The system presented permits an automatic determination of dimensions of beams in conditions which are totally representative of those of their use. In the field of ultrasonic examinations a good estimate or knowledge of sound beams is of great help to solve difficult examination problems. The FRAMATOME's Centre d'Etude et de Recherche en Essais Non Destructifs (CEREND) : (Study and Research Center in Non-Destructive Testing) has developed and elaborated various techniques in order to improve ultrasonic examinations with specific probes. These techniques concern design, manufacturing and characterization of these probes

  5. Chemical kinetics and reaction mechanism

    International Nuclear Information System (INIS)

    Jung, Ou Sik; Park, Youn Yeol

    1996-12-01

    This book is about chemical kinetics and reaction mechanism. It consists of eleven chapters, which deal with reaction and reaction speed on reaction mechanism, simple reaction by rate expression, reversible reaction and simultaneous reaction, successive reaction, complicated reaction mechanism, assumption for reaction mechanism, transition state theory, successive reaction and oscillating reaction, reaction by solution, research method high except kinetics on reaction mechanism, high reaction of kinetics like pulsed radiolysis.

  6. Pulsed-laser atom-probe field-ion microscopy

    International Nuclear Information System (INIS)

    Kellogg, G.L.; Tsong, T.T.

    1980-01-01

    A time-of-flight atom-probe field-ion microscope has been developed which uses nanosecond laser pulses to field evaporate surface species. The ability to operate an atom-probe without using high-voltage pulses is advantageous for several reasons. The spread in energy arising from the desorption of surface species prior to the voltage pulse attaining its maximum amplitude is eliminated, resulting in increased mass resolution. Semiconductor and insulator samples, for which the electrical resistivity is too high to transmit a short-duration voltage pulse, can be examined using pulsed-laser assisted field desorption. Since the electric field at the surface can be significantly smaller, the dissociation of molecular adsorbates by the field can be reduced or eliminated, permitting well-defined studies of surface chemical reactions. In addition to atom-probe operation, pulsed-laser heating of field emitters can be used to study surface diffusion of adatoms and vacancies over a wide range of temperatures. Examples demonstrating each of these advantages are presented, including the first pulsed-laser atom-probe (PLAP) mass spectra for both metals (W, Mo, Rh) and semiconductors (Si). Molecular hydrogen, which desorbs exclusively as atomic hydrogen in the conventional atom probe, is shown to desorb undissociatively in the PLAP. Field-ion microscope observations of the diffusion and dissociation of atomic clusters, the migration of adatoms, and the formation of vacancies resulting from heating with a 7-ns laser pulse are also presented

  7. Polymerase chain reaction and conventional DNA tests in detection of HPV DNA in cytologically normal and abnormal cervical scrapes

    DEFF Research Database (Denmark)

    Kalia, A.; Jalava, T.; Nieminen, P.

    1992-01-01

    Med.mikrobiologi, polymerase chain reaction, DNA tests, human papillomavirus (HPV), cervical smear, hybridisation, cytologi, affiProbe HPV test, ViraType test......Med.mikrobiologi, polymerase chain reaction, DNA tests, human papillomavirus (HPV), cervical smear, hybridisation, cytologi, affiProbe HPV test, ViraType test...

  8. Gravity Probe B data system description

    International Nuclear Information System (INIS)

    Bennett, Norman R

    2015-01-01

    The Gravity Probe B data system, developed, integrated, and tested by Lockheed Missiles and Space Company, and later Lockheed Martin Corporation, included flight and ground command, control, and communications software. The development was greatly facilitated, conceptually and by the transfer of key personnel, through Lockheed’s earlier flight and ground test software development for the Hubble Space Telescope (HST). Key design challenges included the tight mission timeline (17 months, 9 days of on-orbit operation), the need to tune the system once on-orbit, and limited 2 Kbps real-time data rates and ground asset availability. The result was a completely integrated space vehicle and Stanford mission operations center, which successfully collected and archived 97% of the ‘guide star valid’ data to support the science analysis. Lessons learned and incorporated from the HST flight software development and on-orbit support experience, and Lockheed’s independent research and development effort, will be discussed. (paper)

  9. IVVS probe mechanical concept design

    Energy Technology Data Exchange (ETDEWEB)

    Rossi, Paolo, E-mail: paolo.rossi@enea.it; Neri, Carlo; De Collibus, Mario Ferri; Mugnaini, Giampiero; Pollastrone, Fabio; Crescenzi, Fabio

    2015-10-15

    Highlights: • ENEA designed, developed and tested a laser based In Vessel Viewing System (IVVS). • IVVS mechanical design has been revised from 2011 to 2013 to meet ITER requirements. • Main improvements are piezoceramic actuators and a step focus system. • Successful qualification activities validated the concept design for ITER environment. - Abstract: ENEA has been deeply involved in the design, development and testing of a laser based In Vessel Viewing System (IVVS) required for the inspection of ITER plasma-facing components. The IVVS probe shall be deployed into the vacuum vessel, providing high resolution images and metrology measurements to detect damages and possible erosion. ENEA already designed and manufactured an IVVS probe prototype based on a rad-hard concept and driven by commercial micro-step motors, which demonstrated satisfying viewing and metrology performances at room conditions. The probe sends a laser beam through a reflective rotating prism. By rotating the axes of the prism, the probe can scan all the environment points except those present in a shadow cone and the backscattered light signal is then processed to measure the intensity level (viewing) and the distance from the probe (metrology). During the last years, in order to meet all the ITER environmental conditions, such as high vacuum, gamma radiation lifetime dose up to 5 MGy, cumulative neutron fluence of about 2.3 × 10{sup 17} n/cm{sup 2}, temperature of 120 °C and magnetic field of 8 T, the probe mechanical design was significantly revised introducing a new actuating system based on piezo-ceramic actuators and improved with a new step focus system. The optical and mechanical schemes have been then modified and refined to meet also the geometrical constraints. The paper describes the mechanical concept design solutions adopted in order to fulfill IVVS probe functional performance requirements considering ITER working environment and geometrical constraints.

  10. Double displacement: An improved bioorthogonal reaction strategy for templated nucleic acid detection.

    Science.gov (United States)

    Kleinbaum, Daniel J; Miller, Gregory P; Kool, Eric T

    2010-06-16

    Quenched autoligation probes have been employed previously in a target-templated nonenzymatic ligation strategy for detecting nucleic acids in cells by fluorescence. A common source of background signal in such probes is the undesired reaction with water and other cellular nucleophiles. Here, we describe a new class of self-ligating probes, double displacement (DD) probes, that rely on two displacement reactions to fully unquench a nearby fluorophore. Three potential double displacement architectures, all possessing two fluorescence quencher/leaving groups (dabsylate groups), were synthesized and evaluated for templated reaction with nucleophile (phosphorothioate) probes both in vitro and in intact bacterial cells. All three DD probe designs provided substantially better initial quenching than a single-Dabsyl control. In isothermal templated reactions in vitro, double displacement probes yielded considerably lower background signal than previous single displacement probes; investigation into the mechanism revealed that one dabsylate acts as a sacrificial leaving group, reacting nonspecifically with water, but yielding little signal because another quencher group remains. Templated reaction with the specific nucleophile probe is required to activate a signal. The double displacement probes provided a ca. 80-fold turn-on signal and yielded a 2-4-fold improvement in signal/background over single Dabsyl probes. The best-performing probe architecture was demonstrated in a two-color, FRET-based two-allele discrimination system in vitro and was shown to be capable of discriminating between two closely related species of bacteria differing by a single nucleotide at an rRNA target site.

  11. Intermolecula transfer and elimination of molecular hydrogen in thermal reactions of unsaturated organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Suria, Sabartanty [Iowa State Univ., Ames, IA (United States)

    1995-02-10

    Two reactions which are important to coal liquefaction include intermolecular transfer and the elimination of two hydrogen atoms. We have designed several model reactions to probe the viability of several hydrogen transfer and elimination pathways. This report described studies on these reactions using organic model compounds.

  12. PROBES, POPULATIONS, SAMPLES, MEASUREMENTS AND RELATIONS IN STEREOLOGY

    Directory of Open Access Journals (Sweden)

    Robert T Dehoff

    2011-05-01

    Full Text Available This summary paper provides an overview of the content of stereology. The typical problem at hand centers around some three dimensional object that has an internal structure that determines its function, performance, or response. To understand and quantify the geometry of that structure it is necessary to probe it with geometric entities: points, lines, planes volumes, etc. Meaningful results are obtained only if the set of probes chosen for use in the assessment is drawn uniformly from the population of such probes for the structure as a whole. This requires an understanding of the population of each kind of probe. Interaction of the probes with the structure produce geometric events which are the focus of stereological measurements. In almost all applications the measurement that is made is a simple count of the number of these events. Rigorous application of these requirements for sample design produce unbiased estimates of geometric properties of features in the structure no matter how complex are the features or what their arrangement in space. It is this assumption-free characteristic of the methodology that makes it a powerful tool for characterizing the internal structure of three dimensional objects.

  13. Experimental facility and void fraction calibration methods for impedance probes

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Fernando L. de; Rocha, Marcelo S., E-mail: floliveira@ipen.br, E-mail: msrocha@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    An experimental facility was designed and constructed with aims of to calibrate a capacitance probe for gas-liquid flow void fraction measurements. The facility is composed of a metallic hack with a vertical 2,300 mm high glass tube with 38 mm ID with stagnant water and compressed air bubbling system simulating the gas phase (vapor). At the lower part, a mixing section with a porous media element releases the air bubbles into the water, and the compressed air flow is measured by two calibrated rotameters. At the upper part a stagnant water tank separates the liquid and gas. Two pressure taps are located near the lower and upper sides of the glass tube for pressure difference measurement. The pressure difference is used for low void fraction values (0-15%) calibration methods, as described in the work. Two electrically controlled quick closing valves are installed between the porous media element and the upward separation tank for high void fraction values measurement (15-50%) used to calibrate the capacitance probe. The experimental facility design, construction, capacitance probe calibration methods and results, as well as flow pattern visualization, are presented. Finally, the capacitance probe will be installed on a natural circulation circuit mounted at the Nuclear Engineering Center (CEN/IPEN/CNEN-SP) for measurement of the instantaneous bulk void. Instantaneous signals generated by the capacitance probe will allow the determination of natural circulation loop global energy balance. (author)

  14. Experimental facility and void fraction calibration methods for impedance probes

    International Nuclear Information System (INIS)

    Oliveira, Fernando L. de; Rocha, Marcelo S.

    2013-01-01

    An experimental facility was designed and constructed with aims of to calibrate a capacitance probe for gas-liquid flow void fraction measurements. The facility is composed of a metallic hack with a vertical 2,300 mm high glass tube with 38 mm ID with stagnant water and compressed air bubbling system simulating the gas phase (vapor). At the lower part, a mixing section with a porous media element releases the air bubbles into the water, and the compressed air flow is measured by two calibrated rotameters. At the upper part a stagnant water tank separates the liquid and gas. Two pressure taps are located near the lower and upper sides of the glass tube for pressure difference measurement. The pressure difference is used for low void fraction values (0-15%) calibration methods, as described in the work. Two electrically controlled quick closing valves are installed between the porous media element and the upward separation tank for high void fraction values measurement (15-50%) used to calibrate the capacitance probe. The experimental facility design, construction, capacitance probe calibration methods and results, as well as flow pattern visualization, are presented. Finally, the capacitance probe will be installed on a natural circulation circuit mounted at the Nuclear Engineering Center (CEN/IPEN/CNEN-SP) for measurement of the instantaneous bulk void. Instantaneous signals generated by the capacitance probe will allow the determination of natural circulation loop global energy balance. (author)

  15. NMR reaction monitoring in flow synthesis

    Directory of Open Access Journals (Sweden)

    M. Victoria Gomez

    2017-02-01

    Full Text Available Recent advances in the use of flow chemistry with in-line and on-line analysis by NMR are presented. The use of macro- and microreactors, coupled with standard and custom made NMR probes involving microcoils, incorporated into high resolution and benchtop NMR instruments is reviewed. Some recent selected applications have been collected, including synthetic applications, the determination of the kinetic and thermodynamic parameters and reaction optimization, even in single experiments and on the μL scale. Finally, software that allows automatic reaction monitoring and optimization is discussed.

  16. NMR reaction monitoring in flow synthesis.

    Science.gov (United States)

    Gomez, M Victoria; de la Hoz, Antonio

    2017-01-01

    Recent advances in the use of flow chemistry with in-line and on-line analysis by NMR are presented. The use of macro- and microreactors, coupled with standard and custom made NMR probes involving microcoils, incorporated into high resolution and benchtop NMR instruments is reviewed. Some recent selected applications have been collected, including synthetic applications, the determination of the kinetic and thermodynamic parameters and reaction optimization, even in single experiments and on the μL scale. Finally, software that allows automatic reaction monitoring and optimization is discussed.

  17. Tissue reactions of abdominal integuments to surgical sutures in sonography

    Directory of Open Access Journals (Sweden)

    Andrzej Smereczyński

    2014-03-01

    Full Text Available Classical abdominal surgeries usually require long incisions of the abdominal integuments followed by tight closure with adequate suturing material. Nonabsorbable sutures may cause various reactions, including granuloma reactions, both sterile and inflammatory. The aim of the study was to analyze prospective ultrasound examinations of the abdominal integuments in order to detect tissue reactions to surgical sutures. Material and methods: For 10 years, ultrasound examinations of the abdominal integuments involved the assessment of surgical scars in all patients who underwent open or closed surgeries for various reasons (in total 2254 patients. Ultrasound examinations were performed only with the use of linear probes with the frequency ranging from 7 to 12 MHz. Each scar in the abdominal integuments was scanned in at least two planes. When a lesion was detected, the image was enlarged and the transducer was rotated by approximately 180° in order to capture the dimensions of the granuloma and the most characteristic image of the suture. Moreover, vascularization of the lesion was also assessed with the use of color Doppler mode set to detect the lowest flows. Results: All granulomas (19 lesions, two in one patient created hypoechoic oval or round nodules, were relatively well-circumscribed and their size ranged from 8 × 4 mm to 40 × 14 mm. In the center of the lesion, it was possible to notice a thread that was coiled to various degrees and presented itself as a double, curved hyperechoic line. In 9 out of 19 granulomas, slight peripheral vascularization was observed. The substantial majority of the lesions (n = 15 were in contact with the fascia. In seven patients, compression with the transducer induced known local pain (n = 4 or intensified pain that had already been present (n = 3; all of these granulomas infiltrated the fascia and showed slight peripheral vascularization. Cutaneous fistulae developed in two patients with purulent

  18. Development of Bioorthogonal Reactions and Their Applications in Bioconjugation

    Directory of Open Access Journals (Sweden)

    Mengmeng Zheng

    2015-02-01

    Full Text Available Biomolecule labeling using chemical probes with specific biological activities has played important roles for the elucidation of complicated biological processes. Selective bioconjugation strategies are highly-demanded in the construction of various small-molecule probes to explore complex biological systems. Bioorthogonal reactions that undergo fast and selective ligation under bio-compatible conditions have found diverse applications in the development of new bioconjugation strategies. The development of new bioorthogonal reactions in the past decade has been summarized with comments on their potentials as bioconjugation method in the construction of various biological probes for investigating their target biomolecules. For the applications of bioorthogonal reactions in the site-selective biomolecule conjugation, examples have been presented on the bioconjugation of protein, glycan, nucleic acids and lipids.

  19. Perceiving the vertical distances of surfaces by means of a hand-held probe.

    Science.gov (United States)

    Chan, T C; Turvey, M T

    1991-05-01

    Nine experiments were conducted on the haptic capacity of people to perceive the distances of horizontal surfaces solely on the basis of mechanical stimulation resulting from contacting the surfaces with a vertically held rod. Participants touched target surfaces with rods inside a wooden cabinet and reported the perceived surface location with an indicator outside the cabinet. The target surface, rod, and the participant's hand were occluded, and the sound produced in exploration was muffled. Properties of the probe (length, mass, moment of inertia, center of mass, and shape) were manipulated, along with surface distance and the method and angle of probing. Results suggest that for the most common method of probing, namely, tapping, perceived vertical distance is specific to a particular relation among the rotational inertia of the probe, the distance of the point of contact with the surface from the probe's center of percussion, and the inclination at contact of the probe to the surface. They also suggest that the probe length and the distance probed are independently perceivable. The results were discussed in terms of information specificity versus percept-percept coupling and parallels between selective attention in haptic and visual perception.

  20. Eddy-current probe design

    International Nuclear Information System (INIS)

    Kincaid, T.G.; McCary, R.O.

    1983-01-01

    This paper describes theoretical and experimental work directed toward finding the optimum probe dimensions and operating frequency for eddy current detection of half-penny surface cracks in nonmagnetic conducting materials. The study applies to probes which excite an approximately uniform spatial field over the length of the crack at the surface of the material. In practical terms, this means that the probe is not smaller than the crack length in any of its critical dimensions. The optimization of a simple coil probe is first analyzed in detail. It is shown that signal-to-noise ratio and lift-off discrimination are maximized by a pancake coil with mean radius not greater than the crack length, operated at a frequency which gives a skin depth equal to the crack depth. The results obtained for the simple coil are then used as a basis for discussion of the design of coils with ferrite cores and shields, and for the design of recording head type probes

  1. Nanomaterials and MRI molecular probe

    International Nuclear Information System (INIS)

    Inubushi, Toshiro

    2008-01-01

    This paper presents the current state and future prospect of enhancing probes in MRI which enable to image specific cells and molecules mainly from the aspect of cell trafficking. Although MRI requires such probes for specific imaging, it has an advantage that anatomical images are simultaneously available even during surgical operation without radiation exposure, differing from X-CT, -transillumination and positron emission tomography (PET). In the development of novel MRI molecular probes, the recent topic concerns the cell trafficking biology where cells related with transplantation and immunological therapy can be traced. Although superparamagnetic iron oxide (SPIO) has been used as a commercially available enhancer, this nanoparticle has problems like a difficulty to penetrate cell, cytotoxicity and others. For these, authors have developed the nanoparticle SPIO covered with silica shell, which can be chemically modified, e.g., by binding fluorescent pigments to possibly allow MR bimodal molecular imaging. For penetration of particles in cells, envelop of Sendai virus is used. PET-CT has been more popular these days; however, MRI is superior to CT for imaging soft tissues, and development of PET-MRI is actively under progress aiming the multi-modal imaging. At present, molecular probes for MRI are certainly not so many as those for PET and cooperative efforts to develop the probes are required in medical, technological and pharmaceutical fields. (R.T.)

  2. I. Use of m- and p-azidobenzamidines, 4-fluoro-3-nitro-phenylazide, and 3-azido-1,2,4-triazole as photoaffinity probes of tryptic binding site conformation. II. Analysis of tryptophan in proteins by an acidic reaction of 3-diazonium-1,2,4-triazole

    Energy Technology Data Exchange (ETDEWEB)

    DeTraglia, M.C.

    1979-01-01

    Meta- and para-azidobenzamidine have been prepared and evaluated as photoaffinity labels. The compounds inhibit trypsin reversibly in the dark and are competitive with substrate binding. Upon photolysis, irreversible noncompetitive inhibition is observed and is dependent upon concentration, photolysis time, and pH. Specificity of the probes is indicated by experiments in which p-tosyl-L-arginine methyl ester, a trypsin substrate, is used to protect against photoinactivation.

  3. Nuclear data services of the Nuclear Data Centers Network available at the National Nuclear Data Center

    International Nuclear Information System (INIS)

    McLane, V.

    1997-01-01

    The Nuclear Data Centers Network provides low and medium energy nuclear reaction data to users around the world. Online retrievals are available through the U.S. National Nuclear Data Center, the Nuclear Energy Agency Data Bank, and the IAEA Nuclear Data Section from these extensive bibliographic, experimental data, and evaluated data files. In addition to nuclear reaction data, the various databases also provide nuclear structure and decay data, and other information of interest to users. The WorldWideWeb sites at the National Nuclear Data Center and the NEA Data Bank provide access to some of the Centers' files. (orig.)

  4. Gamma-ray imaging probes

    International Nuclear Information System (INIS)

    Wild, W.J.

    1988-01-01

    External nuclear medicine diagnostic imaging of early primary and metastatic lung cancer tumors is difficult due to the poor sensitivity and resolution of existing gamma cameras. Nonimaging counting detectors used for internal tumor detection give ambiguous results because distant background variations are difficult to discriminate from neighboring tumor sites. This suggests that an internal imaging nuclear medicine probe, particularly an esophageal probe, may be advantageously used to detect small tumors because of the ability to discriminate against background variations and the capability to get close to sites neighboring the esophagus. The design, theory of operation, preliminary bench tests, characterization of noise behavior and optimization of such an imaging probe is the central theme of this work

  5. Scanning vector Hall probe microscopy

    International Nuclear Information System (INIS)

    Cambel, V.; Gregusova, D.; Fedor, J.; Kudela, R.; Bending, S.J.

    2004-01-01

    We have developed a scanning vector Hall probe microscope for mapping magnetic field vector over magnetic samples. The microscope is based on a micromachined Hall sensor and the cryostat with scanning system. The vector Hall sensor active area is ∼5x5 μm 2 . It is realized by patterning three Hall probes on the tilted faces of GaAs pyramids. Data from these 'tilted' Hall probes are used to reconstruct the full magnetic field vector. The scanning area of the microscope is 5x5 mm 2 , space resolution 2.5 μm, field resolution ∼1 μT Hz -1/2 at temperatures 10-300 K

  6. Spaser as a biological probe

    Science.gov (United States)

    Galanzha, Ekaterina I.; Weingold, Robert; Nedosekin, Dmitry A.; Sarimollaoglu, Mustafa; Nolan, Jacqueline; Harrington, Walter; Kuchyanov, Alexander S.; Parkhomenko, Roman G.; Watanabe, Fumiya; Nima, Zeid; Biris, Alexandru S.; Plekhanov, Alexander I.; Stockman, Mark I.; Zharov, Vladimir P.

    2017-06-01

    Understanding cell biology greatly benefits from the development of advanced diagnostic probes. Here we introduce a 22-nm spaser (plasmonic nanolaser) with the ability to serve as a super-bright, water-soluble, biocompatible probe capable of generating stimulated emission directly inside living cells and animal tissues. We have demonstrated a lasing regime associated with the formation of a dynamic vapour nanobubble around the spaser that leads to giant spasing with emission intensity and spectral width >100 times brighter and 30-fold narrower, respectively, than for quantum dots. The absorption losses in the spaser enhance its multifunctionality, allowing for nanobubble-amplified photothermal and photoacoustic imaging and therapy. Furthermore, the silica spaser surface has been covalently functionalized with folic acid for molecular targeting of cancer cells. All these properties make a nanobubble spaser a promising multimodal, super-contrast, ultrafast cellular probe with a single-pulse nanosecond excitation for a variety of in vitro and in vivo biomedical applications.

  7. Exploring the dynamics of hydrogen atom release from the radical-radical reaction of O(3P) with C3H5

    International Nuclear Information System (INIS)

    Joo, Sun-Kyu; Kwon, Lee-Kyoung; Lee, Hohjai; Choi, Jong-Ho

    2004-01-01

    The gas-phase radical-radical reaction dynamics of O( 3 P)+C 3 H 5 →H( 2 S)+C 3 H 4 O was studied at an average collision energy of 6.4 kcal/mol in a crossed beam configuration. The ground-state atomic oxygen [O( 3 P)] and allyl radicals (C 3 H 5 ) were generated by the photolysis of NO 2 and the supersonic flash pyrolysis of allyl iodide, respectively. Nascent hydrogen atom products were probed by the vacuum-ultraviolet-laser induced fluorescence spectroscopy in the Lyman-α region centered at 121.6 nm. With the aid of the CBS-QB3 level of ab initio theory, it has been found that the barrierless addition of O( 3 P) to C 3 H 5 forms the energy-rich addition complexes on the lowest doublet potential energy surface, which are predicted to undergo a subsequent direct decomposition step leading to the reaction products H+C 3 H 4 O. The major counterpart C 3 H 4 O of the probed hydrogen atom is calculated to be acrolein after taking into account the factors of barrier height, reaction enthalpy, and the number of intermediates involved along the reaction pathway. The nascent H-atom Doppler profile analysis shows that the average center-of-mass translational energy of the H+C 3 H 4 O products and the fraction of the total available energy released as the translational energy were determined to be 3.83 kcal/mol and 0.054, respectively. On the basis of comparison with statistical calculations, the reaction proceeds through the formation of short-lived addition complexes rather than statistical, long-lived intermediates, and the polyatomic acrolein product is significantly internally excited at the moment of the decomposition

  8. Exploring the dynamics of hydrogen atom release from the radical-radical reaction of O(3P) with C3H5

    Science.gov (United States)

    Joo, Sun-Kyu; Kwon, Lee-Kyoung; Lee, Hohjai; Choi, Jong-Ho

    2004-05-01

    The gas-phase radical-radical reaction dynamics of O(3P)+C3H5→H(2S)+C3H4O was studied at an average collision energy of 6.4 kcal/mol in a crossed beam configuration. The ground-state atomic oxygen [O(3P)] and allyl radicals (C3H5) were generated by the photolysis of NO2 and the supersonic flash pyrolysis of allyl iodide, respectively. Nascent hydrogen atom products were probed by the vacuum-ultraviolet-laser induced fluorescence spectroscopy in the Lyman-α region centered at 121.6 nm. With the aid of the CBS-QB3 level of ab initio theory, it has been found that the barrierless addition of O(3P) to C3H5 forms the energy-rich addition complexes on the lowest doublet potential energy surface, which are predicted to undergo a subsequent direct decomposition step leading to the reaction products H+C3H4O. The major counterpart C3H4O of the probed hydrogen atom is calculated to be acrolein after taking into account the factors of barrier height, reaction enthalpy, and the number of intermediates involved along the reaction pathway. The nascent H-atom Doppler profile analysis shows that the average center-of-mass translational energy of the H+C3H4O products and the fraction of the total available energy released as the translational energy were determined to be 3.83 kcal/mol and 0.054, respectively. On the basis of comparison with statistical calculations, the reaction proceeds through the formation of short-lived addition complexes rather than statistical, long-lived intermediates, and the polyatomic acrolein product is significantly internally excited at the moment of the decomposition.

  9. DNA Probe for Lactobacillus delbrueckii

    Science.gov (United States)

    Delley, Michèle; Mollet, Beat; Hottinger, Herbert

    1990-01-01

    From a genomic DNA library of Lactobacillus delbrueckii subsp. bulgaricus, a clone was isolated which complements a leucine auxotrophy of an Escherichia coli strain (GE891). Subsequent analysis of the clone indicated that it could serve as a specific DNA probe. Dot-blot hybridizations with over 40 different Lactobacillus strains showed that this clone specifically recognizes L. delbrueckii subsp. delbrueckii, bulgaricus, and lactis. The sensitivity of the method was tested by using an α-32P-labeled DNA probe. Images PMID:16348233

  10. Radical probing of spliceosome assembly.

    Science.gov (United States)

    Grewal, Charnpal S; Kent, Oliver A; MacMillan, Andrew M

    2017-08-01

    Here we describe the synthesis and use of a directed hydroxyl radical probe, tethered to a pre-mRNA substrate, to map the structure of this substrate during the spliceosome assembly process. These studies indicate an early organization and proximation of conserved pre-mRNA sequences during spliceosome assembly. This methodology may be adapted to the synthesis of a wide variety of modified RNAs for use as probes of RNA structure and RNA-protein interaction. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Architectural Probes of the Infraordinary

    DEFF Research Database (Denmark)

    Lunde Nielsen, Espen

    2017-01-01

    of the city plays a vital role for the social coexistence of and the correlation between its inhabitants. In an era of explosive growth of our cities, it is crucial to critically examine the everyday social dimension, if our cities are to be liveable in the future. To enquire into the everyday topography...... approaches for probing into and interrogating the infraordinary: frameworks of perception and situated probes. Both are deployed in order to get at distance of the familiar and by-pass the usual hierarchies of perception to gain new knowledge. These critical spatial practices span an interdisciplinary...

  12. Detecting device of atomic probe

    International Nuclear Information System (INIS)

    Nikonenkov, N.V.

    1979-01-01

    Operation of an atomic-probe recording device is discussed in detail and its flowsheet is given. The basic elements of the atomic-probe recording device intented for microanalysis of metals and alloys in an atomic level are the storage oscillograph with a raster-sweep unit, a two-channel timer using frequency meters, a digital printer, and a control unit. The digital printer records information supplied by four digital devices (two frequency meters and two digital voltmeters) in a four-digit binary-decimal code. The described device provides simultaneous recording of two ions produced per one vaporation event

  13. Probing nuclear matter with dileptons

    International Nuclear Information System (INIS)

    Schroeder, L.S.

    1986-06-01

    Dileptons are shown to be of interest in helping probe extreme conditions of temperature and density in nuclear matter. The current state of experimental knowledge about dileptons is briefly described, and their use in upcoming experiments with light ions at CERN SPS are reviewed, including possible signatures of quark matter formation. Use of dileptons in an upcoming experiment with a new spectrometer at Berkeley is also discussed. This experiment will probe the nuclear matter equation of state at high temperature and density. 16 refs., 8 figs

  14. Radioactive Probes on Ferromagnetic Surfaces

    CERN Multimedia

    2002-01-01

    On the (broad) basis of our studies of nonmagnetic radioactive probe atoms on magnetic surfaces and at interfaces, we propose to investigate the magnetic interaction of magnetic probe atoms with their immediate environment, in particular of rare earth (RE) elements positioned on and in ferromagnetic surfaces. The preparation and analysis of the structural properties of such samples will be performed in the UHV chamber HYDRA at the HMI/Berlin. For the investigations of the magnetic properties of RE atoms on surfaces Perturbed Angular Correlation (PAC) measurements and Mössbauer Spectroscopy (MS) in the UHV chamber ASPIC (Apparatus for Surface Physics and Interfaces at CERN) are proposed.

  15. Labelling of HBV-DNA probe using reagent made in China

    International Nuclear Information System (INIS)

    Wang Quanshi

    1991-01-01

    The labelling hepatitis Bvirus DNA (HBV-DNA) probe was studied by using reagent made in China. The results showed that: (1) The dNTPs with high specific activity was necessary for the labelling of nigh specific activity HBV-DNA probe; (2) reaction of labelling HBV-DNA probe was completed in a few minutes; (3) 0.37 MBq 3 H dTTP (specific activity 1.554TBq/mmol) was enough to label 1 μg HBV-DNA and the specific activity of probe reached 3.4 x 10 cpm/μg; (4) 7 MBqα- 32 P dATP (specific activity > 111 TBq/mmol) can label HBV-DNA probe to specific activity 1.35 x 10 cpm/μg. It was concluded that the reagent made in China can be used for the study in molecular biology

  16. Detection of hepatitis A virus by hybridization with single-stranded RNA probes

    International Nuclear Information System (INIS)

    Xi, J.; Estes, M.K.; Metcalf, T.G.

    1987-01-01

    An improved method of dot-blot hybridization to detect hepatitis A virus (HAV) was developed with single-stranded RNA (ssRNA) probes. Radioactive and nonradioactive ssRNA probes were generated by in vitro transcription of HAV templates inserted into the plasmid pGEM-1. 32 P-labeled ssRNA probes were at least eightfold more sensitive than the 32 P-labeled double-stranded cDNA counterparts, whereas biotin-labeled ssRNA probes showed a sensitivity comparable with that of the 32 P-labeled double-stranded cDNA counterparts. Hybridization of HAV with the ssRNA probes at high stringency revealed specific reactions with a high signal-to-noise ratio. The differential hybridization reactions seen with probes of positive and negative sense (compared with HAV genomic RNA) were used to detect HAV in clinical and field samples. A positive/negative ratio was introduced as an indicator that permitted an semiquantitative expression of a positive HAV reaction. Good agreement of this indicator was observed with normal stool samples and with HAV-seeded samples. By using this system, HAV was detected in estuarine and freshwater samples collected from a sewage-polluted bayou in Houston and a saltwater tributary of Galveston Bay

  17. Analysis of conditional gene deletion using probe based Real-Time PCR

    Directory of Open Access Journals (Sweden)

    Lyko Frank

    2010-12-01

    Full Text Available Abstract Following publication of this article 1 the authors noticed that an incorrect probe reference was cited on page 3, 4, 5 and 6 ("UP #69, Roche Applied Science". The correct probe that was used for the 1lox/2lox allele ratio analysis in the paper is as follows Probe for 1lox/2lox allele quantification: 5'-6-FAM-atAaCtTCgtatagCATaCattatac-BHQ-1 -3' (uppercase letters = LNA bases Manufacturer: EUROGENTEC, Seraing, Belgium All other information and reaction conditions in the paper are correct as stated.

  18. Probing non nucleonic degrees of freedom with strong and electromagnetic interactions

    International Nuclear Information System (INIS)

    Frois, B.

    1985-10-01

    In this talk, I would like to examine our present view on non-nucleonic degrees of freedom with a few typical experimental results obtained recently both with hadronic and electromagnetic probes at intermediate energies. It is the first generation of experimental data which has probed mesonic degrees of freedom with a spatial resolution of the order of 0.5 fm. This has made possible for example the measurement of the size of the pion-nucleon interaction region. This is very stimulating progress and we begin to have a coherent overview on the various reaction mechanisms which are induced by hadronic and electromagnetic probes

  19. Direct reactions for nuclear structure and nuclear astrophysics

    International Nuclear Information System (INIS)

    Jones, Katherine Louise

    2014-01-01

    Direct reactions are powerful probes for studying the atomic nucleus. Modern direct reaction studies are illuminating both the fundamental nature of the nucleus and its role in nucleosynthetic processes occurring in the cosmos. This report covers experiments using knockout reactions on neutron-deficient fragmentation beams, transfer reactions on fission fragment beams, and theoretical sensitivity studies relating to the astrophysical r-process. Results from experiments on 108,106 Sn at the NSCL, and on 131 Sn at HRIBF are presented as well as the results from the nucleosynthesis study.

  20. Direct Reactions for Nuclear Structure and Nuclear Astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Katherine Louise [Univ. of Tennessee, Knoxville, TN (United States). Experimental Low-Energy Nuclear Physics Group

    2014-12-18

    Direct reactions are powerful probes for studying the atomic nucleus. Modern direct reaction studies are illuminating both the fundamental nature of the nucleus and its role in nucleosynthetic processes occurring in the cosmos. This report covers experiments using knockout reactions on neutron-deficient fragmentation beams, transfer reactions on fission fragment beams, and theoretical sensitivity studies relating to the astrophysical r-process. Results from experiments on 108,106Sn at the NSCL, and on 131Sn at HRIBF are presented as well as the results from the nucleosynthesis study.