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  • 1
    Digitale Medien
    Digitale Medien
    Self-regulation of iron ion concentration in hydrated porous glasses (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5861-5865 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The water proton spin-lattice relaxation rate was measured in Fe contaminated water filled porous glasses with pore diameters of 548 and 2917 A(ring) at 0.65T at room temperature as a function of pore hydration. Two distinct regimes could be defined. A "wet'' pores regime (0.6〈V0/V〈1) and a regime with water only within the pores (1〈V0/V〈4), where V0 is the pore volume and V the water volume. In both regimes, the proton relaxation rate varies linearly with V0/V. A small Fe ion concentration in porous silica glass water remains constant while the hydration of pores is changed by a factor of ≈4, which is a necessary assumption to model the observed proton spin-lattice relaxation rate. Such a constant small concentration premise agrees with the Langmuir isotherm, which for systems with large surface to volume ratios (S/V0), predicts a constant small volume concentration. In the two studied porous glasses with S/V0 of 9.2×106 and 42×106 m−1, the condition for large S/V0 was satisfied, while the Fe volume concentration which was ∼1 mM was small, as required. An analysis of the paramagnetically enhanced proton relaxation is presented. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.363579
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  • 2
    Digitale Medien
    Digitale Medien
    Continuum percolation and depletion flocculation (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 6026-6032 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Using Brownian dynamics simulations, we investigate continuum percolation in a system of colloid particles aggregating due to depletion flocculation. For all values of aggregating potential, there is a lower threshold volume fraction of colloid particles at which a percolating cluster appears. This threshold defines a percolation "phase" boundary that crosses the phase boundary between the colloid fluid phase and colloid fluid+crystal coexistence. In the two-phase coexistence regime, the lifetime of percolated clusters increases dramatically, and therefore the percolation threshold may be related to a transient gel threshold reported from experiment. In the phase coexistence regime, there is evidence of aging due to the thermal restructuring of clusters, implying a finite lifetime for percolating structures. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.476015
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  • 3
    Digitale Medien
    Digitale Medien
    Metastable states and the kinetics of colloid phase separation (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 2280-2288 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We report on the results of extensive Brownian dynamics simulations of colloid phase separation due to depletion flocculation. We study in detail the effect of potential variation at fixed volume fraction of colloid and fixed range of interaction. We find a variety of nonequilibrium behaviors for quenches into the colloid fluid+crystal phase coexistence regime. We present clear evidence of metastability, of homogeneous nucleation, and of a kinetically arrested gel state. We also find evidence that suggests a density instability in the metastable colloid fluid preceding crystal nucleation. Our findings are consistent with a previous proposal that nonequilibrium behavior is determined by a metastable vapor+liquid binodal hidden in the fluid+crystal phase coexistence regime. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.477881
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  • 4
    Digitale Medien
    Digitale Medien
    Effect of Yb3+ doping on upconversion emission intensity and mechanism in Er3+/Yb3+-codoped fluorozirconate glasses under 800 nm excitation (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6143-6149 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Er3+ singly- and Er3+/Yb3+-codoped fluorozirconate glasses were prepared. The upconversion emission intensities of the Er3+ ion around both 550 and 660 nm were measured under 800 nm excitation. The absorption band of the Yb3+ ion is located around 980 nm. Though the absorption band of Yb3+ does not interact directly with the incident light at 800 nm, both upconversion intensities around 550 and 660 nm emission increased with the increasing YbF3 concentration. We calculated the upconversion intensities around 550 and 660 nm by using rate equations and evaluated the principal upconversion mechanism in Er3+ singly- and Er3+/Yb3+-codoped samples quantitatively. We also investigated the reason for the increase of the upconversion emission intensities with the codoping of Yb3+ under 800 nm excitation. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.371666
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  • 5
    Digitale Medien
    Digitale Medien
    Comparison between the calculated and measured energy transfer rates of the 4S3/2 state in Er3+-doped fluorozirconate glasses (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1900-1906 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The dependence of the fluorescence lifetime of the 4S3/2 state of the Er3+ ion on the ErF3 concentration was measured in fluorozirconate glasses at room temperature. Energy transfer rates were calculated from optical parameters assuming that the Er3+ ions in fluorozirconate glasses were dispersed as the cubic, bcc, or fcc structure, and were inserted into the rate equation. The dependence of the total transition rate of the 4S3/2 state of the Er3+ ion on the ErF3 concentration was calculated by using the rate equation and compared with the total transition rate measured by the lifetime experiment. Although many studies have reported the energy transfer rates in various rare-earth ions, the reliability of the calculated energy transfer rates has been hardly discussed. The energy transfer rate can be derived from the total transition rate. The energy transfer rate estimated from the rate equation calculation was compared with the energy transfer rate obtained from the lifetime measurement. It could be shown that the calculated energy transfer rate assuming that the Er3+ ions were dispersed as the cubic structure was closer to the measured energy transfer rate than that as the bcc and fcc structures. With increasing the ErF3 concentration, the calculated energy transfer rate when the Er3+ ions were dispersed as the cubic structure was comparable to the measured energy transfer rate. It was suggested that at the lower concentration of ErF3 (≤2 mol %), we needed to use the distance between Er3+ ions which was shorter than that as the cubic structure in the calculation of the energy transfer rate. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1303742
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  • 6
    Digitale Medien
    Digitale Medien
    Hydrogenation of ethylene over lanthanum-nickel (LaNi5) alloy (1977)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 81 (1977), S. 1762-1766 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100533a010
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  • 7
    Digitale Medien
    Digitale Medien
    TRANSCRIPTION OF REPEATED AND UNIQUE DNA SEQUENCES IN BRAIN NUCLEI (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 26 (1976), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: —Transcription of repeated and unique DNA in rat brain nuclei was examined using a RNA-DNA hybridization technique. Saturation hybridization experiments with a membrane filter showed that there were differences in the base sequence complements between labelled brain and labelled liver nuclear RNA. In competition hybridization experiments using a membrane filter, brain nuclear labelled RNA was in competition most effectively with unlabelled brain nuclear RNA, but less effectively with kidney or liver nuclear RNA. Experiments using a membrane filter loaded with isolated unique or repeated DNA fragments gave similar results. Furthermore, competition hybridization with a DNA excess also showed similar results at Cot 10,000. These results indicate the existence of tissue-specificity in the transcription of unique and repeated DNA sequences in brain nuclei. Subsequently, rat brain nuclei were separated into neuronal and glial nuclear fractions for the purpose of detecting the cell-specificity of RNA. The results of these experiments give evidence of significant differences in the transcription of unique DNA sequences, but indicate no differences in that of repeated DNA sequences between the two nuclear classes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1976.tb04440.x
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  • 8
    Digitale Medien
    Digitale Medien
    Hydrogenation of ethylene and isomerization of 1-butene over lanthanum cobalt nitride (LaCo5Nn) (1979)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 83 (1979), S. 2259-2263 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100480a016
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  • 9
    Digitale Medien
    Digitale Medien
    Upconversion mechanism in Er3+-doped fluorozirconate glasses under 800 nm excitation (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 29-37 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The upconversion emission intensities of Er3+ ion around 550 and 660 nm in fluorozirconate glasses were measured under 800 nm excitation. Though energy transfer processes played an important role in upconversion mechanism at high concentration of ErF3, those have not been treated quantitatively. The energy transfer rates were calculated from the optical parameters assuming some distribution of Er3+ ions. We calculated the upconversion intensities around 550 and 660 nm by using rate equations. It was found that the dependence of upconversion emission intensities on the ErF3 concentration could be reproducible and the principal upconversion mechanism could be evaluated. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.369445
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  • 10
    Digitale Medien
    Digitale Medien
    Fluorescence properties of fluorozirconate glasses containing Eu^3^+ ions
    Amsterdam : Elsevier
    Journal of Luminescence 55 (1993), S. 17-24 
    Details
    ISSN: 0022-2313
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-2313(93)90079-3
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