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  • 1
    Digitale Medien
    Digitale Medien
    The Compounds Contributing to the Greenness of Green Tea (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 69 (2004), S. 0 
    Details
    ISSN: 1750-3841
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: : Color is one of the determinant sensory qualities for green tea. As cold tea beverages in clear bottles are getting more popular, the traditional evaluation methods are gradually being altered to attach more importance to the tea infusion color. For quality control, experiments were carried out on 10 green tea samples to investigate the compounds influencing the colors of dry tea leaves and infusions. By calculating the coefficients of determination between the greenness (expressed in tristimulus data) and chemical composition, chlorophylls proved to be the influential compounds for the color of dry tea leaves; water-insoluble chlorophylls were also released from the fragile tea leaves during infusion and increased both the greenness and turbidity of tea infusions. Among the flavonoids (catechins and flavonols) detected in green tea infusions, quercetin was shown to be the most important phenolic compound contributing to the greenness of tea infusion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2621.2004.tb09894.x
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  • 2
    Digitale Medien
    Digitale Medien
    The penetration enhancement and the lipolytic effects of TAT–GKH, both in in vitro, ex vivo, and in vivo (2004)
    Oxford, UK : Blackwell Science Ltd
    International journal of cosmetic science 26 (2004), S. 0 
    Details
    ISSN: 1468-2494
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: It was demonstrated that the trans-activating transcriptional activator (TAT) protein from HIV-1 could enter cells when added to the surrounding media. TAT peptide chemically attached to various proteins was able to deliver these proteins to various cells and even at high levels in heart and spleen tissues in mice. In this study, the tri-peptide GKH (glycine–lysine–histidine) derived from the parathyroid hormone, which is known as a lipolytic peptide, was attached to 9-poly lysine (TAT) to be used as a cosmetic ingredient for eye-bag care product. When glycerol is released, expressed as the extracellular glycerol concentration (the so-called lipolysis index), TAT–GKH at 10−5m induces a maximal lipolytic effect of approximately 41.5% in epididymal adipocytes isolated from rats, compared with basal lipolysis. In a microdialysis study, TAT–GKH was perfused into epididymal adipose tissues of anaesthetized rats in increasing concentrations in a Ringer solution. The glycerol concentration in each dialysate was measured using an ultra-sensitive radiometric method. The perfusion of TAT–GKH induced a lipolytic effect. A penetration study showed that TAT–GKH resulted in a sevenfold higher penetration into excised hairless mice skin than GKH. An in vivo study showed that a TAT–GKH containing emulsion had a better effect upon the relative volume reduction of eye bag after 28 days of application on 22 healthy female volunteers than the placebo.It was therefore concluded that TAT–GKH increased skin penetration, which resulted in enhanced lipolytic effects in in vitro, ex vivo and in volume reduction of eye-bags in in vivo studies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1467-2494.2004.00230_1.x
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  • 3
    Digitale Medien
    Digitale Medien
    Development of effects of plant extracts on the activity and expression of UVA-induced MMPs (matrix metalloproteases) (2004)
    Oxford, UK : Blackwell Science Ltd
    International journal of cosmetic science 26 (2004), S. 0 
    Details
    ISSN: 1468-2494
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The effects of several natural products on in vitro MMP-1 activity and UVA-induced MMP-1 synthesis in human dermal fibroblast (HDF) cultures were studied with the aim of developing novel anti-aging agents from natural sources. We measured MMP-1 activities by fluorescence assay using gelatin as substrates. In addition, UVA-induced MMP-1 expression was analyzed by enzyme-linked immunosorbent assay (ELISA) and gelatin-based zymography in HDF cultures, and RT-PCR techniques were used. The results showed a strong inhibitory effect of the extracts of Dicentra spectabilis and of the flower buds of Tussilago farfara. In a concentration of 0.05% (w/v), the extracts of the flower buds of Tussilago farfara and of Dicentra spectabilis inhibited MMP-1 activity by 92 and 87% respectively. At 0.1% (w/v), the extracts of the flower buds of Tussilago farfara and of Dicentra spectabilis suppressed the UVA-induced expression of MMP-1 by an amount similar to that with Vitamin C 200 μm. These results suggest that the extracts of Dicentra spectabilis and of the flower buds of Tussilago farfara effectively protect skin from UV-induced photoaging. Therefore, the extracts are thought to have potential as effective raw materials for anti-aging cosmetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1467-2494.2004.00244_6.x
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  • 4
    Digitale Medien
    Digitale Medien
    Experimental characterization of the dynamic failure behavior of mortar under impact loading (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2115-2123 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The failure behavior of mortar under dynamic impact loading is characterized through a series of plate impact experiments. The analysis focuses on the spall strength and the shear stress carrying capacity in different regions of the specimen under normal impact loading. Special attention is paid to the possible existence of a failure wave phenomenon that has been widely recognized as an important failure mechanism for glasses during plate impact. The experiments are designed to allow the strengths of the medium at locations behind and ahead of a possible failure wave front to be analyzed. The diagnostics used include velocity interferometer system for any reflector (VISAR) recording of the free surface velocities of targets and monitoring of the internal stresses via polyvinylidene fluoride (PVDF) gauges embedded in the specimen. Experiments conducted do not provide evidence for the existence of a failure wave phenomenon for mortar under plate normal impact loading. While the study suggests that a threshold impact stress must be exceeded for failure to occur, a clearly defined failure wave that propagates behind the loading wave is not observed. Instead, a gradual failure process that initiates upon the arrival of the loading wave and progresses thereafter is observed. This gradual failure process in mortar is in contrast to the well-defined failure front and complete loss of tensile strength associated with the failure wave phenomenon reported for glasses. The study also indicates that, under impact involving high levels of input stresses, attenuation of the loading wave occurs as it propagates through the failed medium. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1340005
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  • 5
    Digitale Medien
    Digitale Medien
    C lattice site distributions in metastable Ge1−yCy alloys grown on Ge(001) by molecular-beam epitaxy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3644-3652 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Epitaxial metastable Ge1−yCy alloy layers with y≤0.045 were grown on Ge(001) by solid-source molecular-beam epitaxy (MBE) at temperatures Ts=200–400 °C. Using calculated strain coefficients and measured layer strains obtained from high-resolution reciprocal lattice maps (HR-RLMs), we determine C lattice site distributions as a function of Ts and total C concentration y. HR-RLMs show that all as-deposited alloys are fully coherent with their substrates. Ge1−yCy(001) layers grown at Ts≤350 °C are in a state of in-plane tension and contain C in substitutional sites, giving rise to tensile strain, as well as in nanocluster sites which induce negligible lattice strain. Ts=400 °C layers are strain neutral with negligible substitutional C incorporation. Increasing y and/or Ts leads to a decrease in substitutional C concentration, consistent with Raman spectroscopy results, with a corresponding increase in the C fraction incorporated in nanocluster sites. The latter suggests that nanocluster formation is kinetically limited during film deposition by the C–C adatom encounter probability at the growth surface. Overall, the results show that it is not possible by MBE to obtain fully substitutional C incorporation in Ge1−yCy(001) alloys, irrespective of y and Ts. This is consistent with ab initio density functional calculations results showing that C incorporation in nanoclusters sites is energetically favored over incorporation in substitutional Ge lattice sites. Annealing the Ge1−yCy(001) layers at Ta=550 °C leads to a significant decrease in the substitutional C fraction and, hence, lower tensile strain. Layers annealed at 650 °C are strain free as all substitutional C has migrated to lower-energy nanocluster sites. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1448677
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  • 6
    Digitale Medien
    Digitale Medien
    Carbon incorporation pathways and lattice sites in Si1−yCy alloys grown on Si(001) by molecular-beam epitaxy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5716-5727 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We use a combination of in situ and postdeposition experimental probes together with ab initio calculations of strain coefficients and formation energies associated with specific C configurations in the Si lattice to determine C incorporation pathways and lattice site distributions in fully coherent Si1−yCy alloy layers grown by molecular-beam epitaxy on Si(001) as a function of deposition temperature Ts (380 °C–680 °C) and C fraction y (0–0.026). Lattice strain and Raman spectroscopy measurements demonstrate that all C, irrespective of y, is incorporated into substitutional lattice sites in Si1−yCy(001) layers grown at Ts≤480 °C. Increasing Ts≥580 °C leads to strong C surface segregation, as shown by in situ angle-resolved x-ray photoelectron spectroscopy, yielding additional pathways for C incorporation. Photoluminescence measurements indicate that an increasing fraction of the incorporated C in the higher-temperature layers resides in dicarbon complexes. Reflection high-energy electron diffraction and cross sectional transmission electron microscopy reveal surface roughening at Ts≥580 °C with the formation of bulk planar structures, interconnected by {113} segments, that are periodic along [001] with a periodicity which decreases with increasing Ts. We interpret the planar structures as layers of C-rich Si1−yCy which form in the presence of excess surface C resulting from segregation. Our ab initio density functional calculations show that substitutional C arranged in an ordered Si4C phase is 0.34 eV per C atom more stable than isolated substitutional C atoms. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1465122
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  • 7
    Digitale Medien
    Digitale Medien
    Effect of the band-tail states on the exciton peaks in GaN epilayers grown on sapphire substrates (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 790-793 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photoluminescence (PL) measurements have been carried out to investigate the effects of the band-tail states on the exciton lines in unintentionally doped and Mg-doped GaN epilayers grown on sapphire substrates by using plasma-assisted molecular beam epitaxy. The results of the PL spectra for the Mg-doped epilayers show that the peak positions of the bound exciton lines shift to higher energy with increasing temperature within the low-temperature region. The radiative recombinations of the carriers are related to the band-tail states, and the temperature-dependent blueshifts are analyzed by using a Gaussian distribution of charged impurities. The calculated thermal activation energies of the band-edge emission lines show that those lines in Mg-doped GaN epilayers are related to ionized donor bound exciton recombinations. These results indicate that the positions and the intensities of the exciton peaks observed in Mg-doped GaN films are significantly affected by the concentration of the magnesium dopant. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.373738
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  • 8
    Digitale Medien
    Digitale Medien
    Solid-phase crystallization of Si1−xGex alloy layers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2091-2095 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Solid-phase crystallization of Si1−xGex (x=0–1.0) alloy layers deposited on a Si (100) substrate was investigated by ellipsometric spectroscopy. From a dispersion analysis of dielectric spectra, we deduced a crystallinity corresponding to the degree of average lattice alignment of the composed polycrystalline Si1−xGex layers and investigated the dynamical change in crystallinity during crystallization. We found that the crystallinity and crystallization temperature (TC) rapidly decreased with increasing Ge concentration (x). When x was small (=0–0.3), the highest crystallinity was ∼0.8 of that for single crystals while the lowest one was considerably below 0.6 when x〉0.8. Moreover, the crystallinity decreased with increasing temperature above TC. We investigated the nucleation rate during crystallization and found that the decrease in crystallinity at both large Ge concentration and high temperature can be explained by a trade-off between the nucleation and crystallization rates; nucleation was dominant under these conditions. An overview of the crystallinity of solid-phase crystallized Si1−xGex alloy layers is provided. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1344215
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  • 9
    Digitale Medien
    Digitale Medien
    Three-dimensional magnetohydrodynamic simulations on the interaction of interplanetary density pulses with the bow shock (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1764-1774 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Three-dimensional magnetohydrodynamic (MHD) simulations are carried out in order to study the interaction of upstream density pulses with the planetary bow shock. In this work, three distinguished types of the density pulse have been simulated: (1) Pure density pulse with no variations in all other variables, (2) density pulse in fast/slow mode-like type, and (3) another pure density pulse with a much stronger peak. For the first case, where the peak density is two times the background value, its interaction with the bow shock results in various MHD waves and a shock in the magnetosheath, including the fast mode wave which evolves into a fast shock, the entropy wave, and the slow mode wave. For the second case, the amplitude of the transmitted density pulse in the magnetosheath is reduced overall as compared to that in the first case. This is due to the generation of the stronger fast mode wave in the magnetosheath, and the effect is more pronounced for the fast mode-like pulse than for the slow mode-like pulse. When the third type pulse is incident with the peak density being five times the background value, the magnetosheath is more strongly compressed, which is followed by an expansion due to the sunward repulsion and then a second compression again. This still results in similar MHD waves and a shock in the magnetosheath, but they are generated in manners well-distinguished from the previous two cases. Based on the results from all three cases, it is suggested that the density amplitude and the properties of its related waves/shock in the magnetosheath can appear quite different depending on the observing spacecraft's position, and thus necessitating a multispacecraft measurement for a reliable monitor. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1461847
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  • 10
    Digitale Medien
    Digitale Medien
    Bunch stability during high-gradient wakefield generation in a dielectric-lined waveguide : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2461-2465 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A recently developed analytic theory for wakefields generated when a charge bunch, or train of bunches, passes along a dielectric-lined waveguide is applied to examine stability issues for this system. Such a configuration could be the key element in a two-beam accelerator to create colliding TeV-range electron and positron beams. It is shown that a 587 MV/m peak acceleration gradient can be achieved when a train of five 2 nC, 1.0 GeV, 0.20 mm long drive bunches passes along the axis of an alumina-lined waveguide (ε=9.5) with inner and outer radii 0.50 and 5.0 mm. The energy gain of a 0.2 nC test bunch in a 4 m long stage under these conditions is shown to be 1.48 GeV, for an average acceleration gradient of 370 MV/m. However, when a drive bunch is injected parallel to, but displaced from, the waveguide axis, transverse (mainly dipole) forces cause the tail of the bunch to swerve sharply toward the waveguide wall (head-to-tail instability), and to intersect the wall after traversing a relatively short distance. These results suggest that successful exploitation of the appealing strong wakefields generated by a train of drive bunches will require some means of transverse stabilization, such as an array of externally applied focusing and defocusing quadrupoles. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1343886
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