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  • 1
    Digitale Medien
    Digitale Medien
    A new class of collective excitations: Exciton strings (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9283-9291 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Optical excitation in a strongly neutral quasi-one-dimensional mixed-stack charge-transfer solid results in an exciton state, in which the electron and the hole are bound by electrostatic Coulomb interactions that are large compared to the one-electron hopping. We present a joint theoretical–experimental demonstration of a new class of collective excitations, multiexcitons or exciton strings, consisting of a string of several (more than two) bound excitons, in a prototype neutral charge-transfer solid. The stability of the multiexciton states arise from the combined effects of one dimensionality and strong Coulomb interactions. Theoretically, we show that in narrow band one-dimensional semiconductors with long range Coulomb interactions, the occurrence of stable 2-exciton string (biexciton) necessarily implies stable higher multiexcitons. Experimentally, evidence for the multiexciton strings is demonstrated by femtosecond pump–probe spectroscopy of anthracene pyromellitic acid dianhydride. Excellent qualitative agreement is found between the calculated and the measured differential transmission spectra. Photoinduced absorptions to the 2-exciton string at low pump intensity and to the 3-exciton string at high pump intensity are observed, in agreement with the theory of excited state absorption. The 2-exciton string is confirmed also by a direct two-photon absorption measurement. The binding energies of the 2-exciton and the 3-exciton strings are obtained from the experimental data. The larger binding energy of the 3-exciton is in agreement with theory. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.471710
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  • 2
    Digitale Medien
    Digitale Medien
    Observation of three resonances in the third harmonic generation spectrum of conjugated polymers: Evidence for the four-level essential states model (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 1665-1672 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Much of the theoretical effort to understand the mechanism of optical nonlinearity in π-conjugated polymers has been focused towards explaining the early observation of only two resonances in the third harmonic generation spectrum of trans-polyacetylene. A recent theory of third order optical nonlinearity predicts three, instead of two, resonances, with their intensities decreasing with increasing frequencies. This is a fundamental difference between the band and the exciton pictures of π-conjugated polymers. Very recent experimental results obtained with cis-polyacetylene, as well as earlier experiments on two blue forms of polydiacetylenes, are in complete agreement with this prediction. An isolated single strand of cis-polyacetylene should exhibit exciton behavior. We briefly discuss the latest experimental results for trans-polyacetylene.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.466594
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  • 3
    Digitale Medien
    Digitale Medien
    Exciton-to-biexciton transition in quasi-one-dimensional organics (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9292-9296 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: In the previous paper we demonstrated novel multiexcitons in a neutral mixed-stack charge-transfer solid. The lowest multiexciton, the biexciton, has recently been of interest also in the context of quasi-one-dimensional organic materials that are different from the mixed-stack solids. The nature and strength of the optical transition from the exciton to the two-exciton states is of importance in understanding photoinduced absorption as well as two-photon absorption. We show that within the diverse theoretical models that describe these different classes of materials, the excited state absorption from the optical exciton to the two-exciton states changes in a fundamental way upon the formation of the biexciton. The identical nature of the exciton absorption within these models is a consequence of one dimensionality. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.471707
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  • 4
    Digitale Medien
    Digitale Medien
    Effects of anaesthetics on the oxygen consumption rates of platyfish Xiphophorus maculatus (Günther) (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 26 (1995), S. 0 
    Details
    ISSN: 1365-2109
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: This study was carried out to find out the effects of anaesthetics, 2-phenoxyethanol. quinaldine sulphate. MS-222 and metomidate. at various dosages, on the oxygen consumption rates of two size groups of platyfish. Xiphophorus maculatus (Günther) at three temperatures. The results show that the oxygen consumption by the platyfish of both size groups was temperature dependent, being higher at higher temperature, but not size dependent. The effects of anaesthetics on the oxygen consumption rates of platyfish were dosage dependent and temperature dependent, especially for 2-phenoxyethanol, the effect always being significantly greater at lower temperature. Small and large fish did not show much difference in their responses to anaesthetic treatments. However, with 2-phenoxyethanol, the effect on the large platyfish was always better than on the small ones at 20-25°C. At 220-440 ppm and at 20°C, 2-phenoxyethanol was more effective than the other anaesthetics in suppressing oxygen consumption by the platyfish.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2109.1995.tb00883.x
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  • 5
    Digitale Medien
    Digitale Medien
    Effects of anaesthetics on the water parameters in a simulated transport experiment of platyfish, Xiphophorus maculatus (Günther) (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 26 (1995), S. 0 
    Details
    ISSN: 1365-2109
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: An experiment was carried out to study the effects of anaesthetics (2-phenoxyethanol, quinaldine sulphate, metomedate and MS-222) on water parameters during simulated air transport of platyfish. Xiphophorus maculatus (Günther). The platyfish were put in sealed plastic bags, one-quarter full of water, to which a required amount of anaesthetic was added. The rest of the bag was filled with oxygen. The water in the bag was tested for pH. total ammonia and carbon dioxide at intervals of 4 and 8 h for a period of 48 h. Mortality rates within this period and the post-packaging period were also noted. It was found that 2-phertoxyethanol was most effective, followed by quinaldine sulphate, in decreasing the excretion of metabolic wastes by the fish. Metomidate had no effect in the control of waste production. MS-222 reduced ammonia excretion but not carbon dioxide. None of the anaesthetics used had any effect on the pH of the water.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2109.1995.tb00911.x
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  • 6
    Digitale Medien
    Digitale Medien
    Creep behaviour of composite lead-free electronic solder joints (2003)
    Bradford : Emerald
    Soldering & surface mount technology 15 (2003), S. 39-42 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: In an attempt to improve service life of lead-free Sn-based electronic solder joints, compatible reinforcements were introduced by in-situ and mechanical mixing methods. The reinforcements affect the steady-state creep rate and the strain for the onset of tertiary creep of the solder joints. However, neither of these parameters, when considered alone, can be used for evaluating the reliability of solder joints. The Larson-Miller parameter, and a new parameter proposed in the paper, can incorporate test parameters to arrive at a reliability prediction methodology. The role of these reinforcements in homogenising creep strain within the joint is analysed. The observed creep behaviour of these composite solders is discussed on the basis of interfacial bonding strength between the reinforcement and the solder matrix.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540910310455716
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  • 7
    Digitale Medien
    Digitale Medien
    Intermetallic morphology around Ni particles in Sn-3.5Ag solder (2002)
    Bradford : Emerald
    Soldering & surface mount technology 14 (2002), S. 11-17 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The influence of the thermal reflow profile on the formation and resultant morphology of the intermetallic layer that developed at the Ni particle reinforcements within an eutectic Sn-Ag composite solder matrix was investigated. The composite solder was fabricated by mechanically dispersing 15 vol% Ni particles into eutectic Sn-3.5Ag solder paste. Two distinct intermetallic compound (IMC) morphological microstructures were observed around the Ni reinforcements. IMC morphological microstructure apparently varied depending on the amount of heat input and differences in heating rates used in the reflow profile. A "sunflower" IMC morphology was typically noted when the total amount of heat input was small. However, with sufficient heat input, a faceted "blocky" IMC morphology was consistently achieved. Multiple-reflow thermal profiling experiments were conducted to measure and compare the amount of heat input necessary to change the sunflower IMC morphology around Ni particle reinforcements to the blocky morphology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540910210427772
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  • 8
    Digitale Medien
    Digitale Medien
    Microstructural characterisation of reflowed and isothermally-aged Cu and Ag particulate reinforced Sn-3.5Ag composite solders (2001)
    Bradford : Emerald
    Soldering & surface mount technology 13 (2001), S. 7-18 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Composite solders were prepared by mechanically dispersing 15v% of Cu or Ag particles into the eutectic Sn-3.5Ag solder. The average sizes for the nominally spherical Cu and Ag particles were 6 and 4 microns, respectively. Two different processing methods were used to prepare the composite solders: blending the powdered particles with solder paste, and adding particles to the molten solder at 2808C. The composite solders were characterised by studying the morphology, size and distribution of the reinforcing phase. Particular interest and emphasis are given towards the modifications of the reinforcements during the reflow process. Microstructural features and chemical analysis of the composite solders were studied using optical and scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) analysis. The effect of reflow and isothermal ageing on the microstructure as well as the morphological changes in the interfacial IM layer of the composite solders were extensively analysed. A mechanism for IM layer growth is proposed for solid state isothermal ageing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540910110361668
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  • 9
    Digitale Medien
    Digitale Medien
    Potassium Cobalt Aluminium Mixed Phosphate, K(CoII,Al)2(PO4)2 (1997)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 53 (1997), S. 1754-1756 
    Details
    ISSN: 1600-5759
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0108270197009906
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  • 10
    Digitale Medien
    Digitale Medien
    Electrolyte induced vesiculation of MA"7"8"2 mice mammary adenocarcinoma ascites cells
    Amsterdam : Elsevier
    FEBS Letters 281 (1991), S. 97-100 
    Details
    ISSN: 0014-5793
    Schlagwort(e): Ascites cell ; Membrane vesicle ; Plasma membrane
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0014-5793(91)80367-C
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