| 151. |
- Sohler, D, et al.
(författare)
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Neutron Excitations Across the N=50 Shell Gap in 102In
- 2002
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Ingår i: Nuclear Physics, Section A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 708:3-4, s. 181-189
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Tidskriftsartikel (refereegranskat)abstract
- The structure of In-102 has been investigated by in-beam gamma-spectroscopic methods. Knowledge on the excited states of this nucleus has significantly been extended. Three cascades of transitions were observed to exceed the spin-energy domain spanned by the pig(9/2)(-1)v(d(5/2),g(7/2))(3) configurations. The new high spin states at similar to 4 MeV excitation energy could be assigned to the pig(9/2)(-1)v(d(5/2), g(7/2))(2)h (11/2) configuration, while at least those at 4.733, 5.192 and 5.853 MeV most likely arise from the vg(9/2) --> vd(5/2), g(7/2) one-particle-one-hole excitation across the N = 50 shell closure.
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| 152. |
- Somesfalean, Gabriel, et al.
(författare)
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Violet diode laser in time-resolved stored-ion spectroscopy
- 2004
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; 69:2, s. 98-103
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Tidskriftsartikel (refereegranskat)abstract
- Lifetime measurements of the metastable 3d D-2(3/2) level in singly charged calcium were performed using the newly developed violet diode laser operated in an external cavity arrangement. The laser was employed on stored ions at the CRYRING facility to optically pump the resonance line at 397 nm. In combination with laser probing at 866 nm this detection scheme gave the possibility to record the lifetime of this level. which has a radiative lifetime of about 1 s.
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| 153. |
- Sun, Licheng C., et al.
(författare)
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Towards an artificial model for Photosystem II : a manganese(II,II) dimer covalently linked to ruthenium(II) tris-bipyridine via a tyrosine derivative
- 2000
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Ingår i: Journal of Inorganic Biochemistry. - 0162-0134 .- 1873-3344. ; 78:1, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- In order to model the individual electron transfer steps from the manganese cluster to the photooxidized sensitizer P-680(+) in Photosystem II (PS II) in green plants, the supramolecular complex 4 has been synthesized. In this complex, a ruthenium(II) tris-bipyridine type photosensitizer has been linked to a manganese(II) dimer via a substituted L-tyrosine, which bridges the manganese ions. The trinuclear complex 4 was characterized by electron paramagnetic resonance (EPR) and electrospray ionization mass spectrometry (ESI-MS). The excited state lifetime of the ruthenium tris-bipyridine moiety in 4 was found to be about 110 ns in acetonitrile, Using flash photolysis in the presence of an electron acceptor (methylviologen), it was demonstrated that in the supramolecular complex 4 an electron was transferred from the excited state of the ruthenium tris-bipyridine moiety to methylviologen, forming a methylviologen radical and a ruthenium(III) tris-bipyridine moiety. Next, the Ru(III) species retrieved the electron from the manganese(II/II) dimer in an intramolecular electron transfer reaction with a rate constant k(ET)>1.0X10(7) s(-1), generating a manganese(II/III) oxidation state and regenerating the ruthenium(II) photosensitizer. This is the first example of intramolecular electron transfer in a supramolecular complex, in which a manganese dimer is covalently linked to a photosensitizer via a tyrosine unit, in a process which mimics the electron transfer on the donor side of PS II.
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| 154. |
- Sun, Licheng C., et al.
(författare)
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Towards artificial photosynthesis : ruthenium-manganese chemistry for energy production
- 2001
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Ingår i: Chemical Society Reviews. - : Royal Society of Chemistry (RSC). - 0306-0012 .- 1460-4744. ; 30:1, s. 36-49
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Forskningsöversikt (refereegranskat)abstract
- The synthesis and characterisation of supramolecular model systems mimicking the light reactions on the donor side of Photosystem II (PSII) in green plants have been reviewed. In these systems, manganese complexes and tyrosine are electron donors, modelling the manganese cluster and tyrosine(Z) in PSII. The donors have been covalently linked to a photosensitizer, a ruthenium(ii) tris-bipyridyl complex, that plays the role of the P-680 chlorophylls in PSII. It has been demonstrated that, in the presence of an external electron acceptor in solution, the model systems can undergo an intermolecular electron transfer from the photoexcited state of Ru-II to an acceptor, followed by an intramolecular electron transfer from the coordinated Mn complexes or the tyrosine unit to the photogenerated Ru-III. This leads to regeneration of the Ru-II and oxidation of the Mn complexes or generation of a tyrosine radical. The process closely mimics the primary reaction steps on the donor side of PSII.
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| 155. |
- Söderman, Olle, et al.
(författare)
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NMR studies of surfactants
- 2004
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Ingår i: Concepts in magnetic resonance. Bridging education and research. - : Wiley. - 1546-6086 .- 1552-5023. ; 23A:2, s. 121-135
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Tidskriftsartikel (refereegranskat)abstract
- Surfactant molecules are amphipathic and posses complicated solution chemistry and self-assembly properties. In addition to being of enormous practical significance, the physical characterization of surfactant systems presents a rich area of condensed matter physics. This article focuses on the application and interpretation of the commonly used NMR approaches for probing these systems. In particular, the use of NMR relaxation, diffusometry and, more briefly, electrophoretic NMR to determine characteristics such as micellar size and structure, ion-binding and solubilization are considered. The application of these NMR techniques is illustrated by a number of pertinent examples.
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| 156. |
- Tinoco, José, et al.
(författare)
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Modeling the in-flight events during metal spray forming
- 2004
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 365:1-2, s. 302-310
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the in-flight events occurring during deposition over a rotating substrate were modeled. The calculations were performed by solving the momentum and enthalpy equations for the gas. A Lagrangian approach was used to obtain the trajectories and thermal history of the droplets. A modified heat capacity model was used to simulate the release of latent heat due to the solidification of the droplets. Turbulent particle dispersion was not considered. The results showed that the droplet temperature strongly depends on the droplet diameter and on its location in the spray since the relative velocity between the gas and the droplets varies largely depending on the location. An estimation of the state of the spray is presented in terms of mass and thermal averages. The results showed that the average fraction of solid obtained in the spray depends on the initial conditions, such as gas temperature and particle size distribution parameters.
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| 157. |
- Tollmar, Konrad, et al.
(författare)
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IDeixis - Searching the Web with mobile images for location-based information
- 2004
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Ingår i: MOBILE HUMAN-COMPUTER INTERACTION - MOBILEHCI 2004, PROCEEDINGS. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 3540230866 ; 3160, s. 288-299
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Konferensbidrag (refereegranskat)abstract
- In this paper we describe an image-based approach to finding location-based information from camera-equipped mobile devices. We introduce a point-by-photograph paradigm, where users can specify a location simply by taking pictures. Our technique uses content-based image retrieval methods to search the web or other databases for matching images and their source pages to find relevant location-based information. In contrast to conventional approaches to location detection, our method can refer to distant locations and does not require any physical infrastructure beyond mobile internet service. We have developed a prototype on a camera phone and conducted user studies to demonstrate the efficacy of our approach.
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| 158. |
- Torto, N., et al.
(författare)
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In situ poly(ethylene imine) coating of hollow fiber membranes used for microdialysis sampling
- 2004
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Ingår i: Pure and Applied Chemistry. - : Walter de Gruyter GmbH. - 0033-4545 .- 1365-3075. ; 76:4, s. 879-888
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Tidskriftsartikel (refereegranskat)abstract
- A method for the in situ modification of hollow fiber membranes used as sampling units for microdialysis probes is presented. The method consists of adsorption-coating, high-molecular-weight poly(ethylene imine), PEI, onto membranes, already fitted on microdialysis probes. Modification of membranes was designed to specifically explore the so-called Andrade effects and thus enhance the interaction of membranes with enzyme. The performances of polysulfone, polyethersulfone, and polyamide membranes modified with PEI-enzyrne complex were evaluated based on the membrane extraction fraction for maltose and maltotriose and membrane morphology as examined by scanning electron microscopy. Of the membranes tested, the PEI-enzyme complex least affected the performance of the polysulfone membranes. Conversion of maltoheptaose to maltotriose and maltose was increased reproducibly (within a 5 % relative standard deviation) by 50 % for modified membranes compared to the native hollow fiber membranes. The results demonstrate the potential to effectively modify membranes already fitted on a microdialysis probe. Such a procedure can be modified and employed to either promote or reduce membrane-protein interaction for hollow fibers used as microdialysis sampling units or other similar membrane applications.
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| 159. |
- Vressner, Andreas, et al.
(författare)
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Multiple Point Ion Current Diagnostics in an HCCI Engine
- 2004
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Ingår i: SAE Transactions, Journal of Engines. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0096-736X. ; 113:3, s. 544-550
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Tidskriftsartikel (refereegranskat)abstract
- Interest in ion current sensing for HCCI combustion arises when a feedback signal from some sort of combustion sensor is needed in order to determine the state of the combustion process. A previous study has revealed that ion current sensors in the form of spark plugs can be used instead of expensive piezoelectric transducers for HCCI combustion sensing. Sufficiently high ion current levels were achieved when using relatively rich mixtures diluted with EGR. The study also shows that it is not the actual dilution per se but the actual air/fuel equivalence ratio which is important for the signal level. Conclusions were made that it is possible to obtain information on combustion timing and oscillating wave phenomena from the measurements. However, the study showed that the ion current is local compared to the pressure which is global in the combustion chamber. This observation triggered the present study where the aim is to investigate the ion current at different locations in the combustion chamber. The ion current was measured simultaneously at seven locations in the combustion chamber. In order to achieve this, 6 spark plugs were fitted circumferentially in a spacer placed between the cylinder block and the head. The seventh spark plug was placed in the cylinder head. Individual DC sources of 85 volts were applied across the spark plug gaps. The present study indicates that the combustion timing seems to be dependent on the wall temperature at the different spark plug locations. The largest difference in timing between different locations in the combustion chamber was 2 CAD. The ion current amplitude varies with different spark plug locations up to 1.5 μA. The signal strength increases with decreasing air/fuel ratio and is also affected by dilution.
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| 160. |
- Weissenrieder, Jonas, et al.
(författare)
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Experimental evidence for a partially dissociated water bilayer on Ru{0001}
- 2004
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 93:19
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Tidskriftsartikel (refereegranskat)abstract
- Core-level photoelectron spectra, in excellent agreement with ab initio calculations, confirm that the stable wetting layer of water on Ru{0001} contains O-H and H2O in roughly 3:5 proportion, for OHx coverages between 0.25 and 0.7 ML, and T<170 K. Proton disorder explains why the wetting structure looks to low energy electron diffraction (LEED) to be an ordered p(root3xroot3)R30degrees adlayer, even though approximate to3/8 of its molecules are dissociated. Complete dissociation to atomic oxygen starts near 190 K. Low photon flux in the synchrotron experiments ensured that the diagnosis of the nature of the wetting structure quantified by LEED is free of beam-induced damage.
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