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141.
Nina Pauline Holzapfel Boris Michael Holzapfel Simon Champ Jesper Feldthusen Judith Clements Dietmar Werner Hutmacher 《International journal of molecular sciences》2013,14(7):14620-14646
Lycopene is a phytochemical that belongs to a group of pigments known as carotenoids. It is red, lipophilic and naturally occurring in many fruits and vegetables, with tomatoes and tomato-based products containing the highest concentrations of bioavailable lycopene. Several epidemiological studies have linked increased lycopene consumption with decreased prostate cancer risk. These findings are supported by in vitro and in vivo experiments showing that lycopene not only enhances the antioxidant response of prostate cells, but that it is even able to inhibit proliferation, induce apoptosis and decrease the metastatic capacity of prostate cancer cells. However, there is still no clearly proven clinical evidence supporting the use of lycopene in the prevention or treatment of prostate cancer, due to the only limited number of published randomized clinical trials and the varying quality of existing studies. The scope of this article is to discuss the potential impact of lycopene on prostate cancer by giving an overview about its molecular mechanisms and clinical effects. 相似文献
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Kah-Yoong Chan Joachim Kirchhoff Aad Gordijn Dietmar Knipp Helmut Stiebig 《Thin solid films》2009,517(23):6383-1080
Hydrogenated microcrystalline silicon (µc-Si:H) has recently received significant attention as a promising material for thin-film transistors (TFTs) in large area electronics due to its high electron and hole charge carrier mobilities. We report on ambipolar TFTs based on microcrystalline silicon prepared by plasma-enhanced chemical vapor deposition at temperature of 160 °C with high electron and hole charge carrier mobilities of 40 cm2/Vs and 10 cm2/Vs, respectively. The ambipolar microcrystalline silicon TFTs provide a simple route in realizing large area integrated circuits at low cost. The electrical characteristics of the ambipolar microcrystalline silicon TFTs will be described and the first results on ambipolar inverters will be presented. The influence of the ambipolar TFT characteristics on the performance of the inverter will be also discussed. 相似文献
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A one-dimensional, two-phase, transient PEM fuel cell model including gas diffusion layer, cathode catalyst layer and membrane is developed. The electrode is assumed to consist of a network of dispersed Pt/C forming spherically shaped agglomerated zones that are filled with electrolyte. Water is modeled in all three phases: vapor, liquid and dissolved in the ionomer to capture the effect of dehydration of the ionomer as well as flooding of the porous media. The anode is modeled as a sophisticated spatially reduced interface. Motivated by environmental scanning electron microscope (ESEM) images of contact angles for microscopic water droplets on fibers of the gas diffusion layer, we introduce the feature of immobile saturation. A step change of the saturation between the catalyst layer and the gas diffusion layer is modeled based on the assumption of a continuous capillary pressure at the interface. The model is validated against voltammetry experiments under various humidification conditions which all show hysteresis effects in the mass transport limited region. The transient saturation profiles clearly show that insufficient liquid water removal causes pore flooding, which is responsible for the oxygen mass transport limitation at high current density values. The simulated and measured current responses from chronoamperometry experiments are compared and analyzed. 相似文献
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Peter Biedenkopf Thomas Karwath Dietmar Kobertz Manisha Rane Egbert Wessel Klaus Hilpert Lorenz Singheiser 《Journal of the American Ceramic Society》2001,84(7):1445-1452
The corrosion and vaporization behavior of eight commercial refractories containing Cr2 O3 were investigated under simulated pressurized pulverized coal combustion (PPCC) conditions at 1723 K in the presence of liquid slag. The corrosion resistance of the refractory materials decreased with increased content of free Cr2 O3 , because bursting (reaction of Fe3 O4 with Cr2 O3 ) occurred. Refractories containing MgCr2 O4 with dissolved Al2 O3 showed the highest corrosion resistance. Thermodynamic calculations showed that CrO3 and CrO2 (OH)2 were the most volatile species in air and in PPCC flue gas, whereas additions of A2 O (A = Na and K, minor slag component) increased the chromium vaporization significantly because of A2 CrO4 formation. Knudsen effusion mass spectrometry measurements showed that the chromium vaporization of refractories was directly correlated to the Cr2 O3 content of the material. In contrast, refractories containing MgCr2 O4 showed a significant decrease in chromium vaporization. 相似文献
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In connection with the analysis and the development of failure concepts in fracture mechanics for quasistatic loaded components and elastic-plastic behaviour of the material, tests are also carried out with welded and/or complex shaped specimens or structures. Thereby the difficulty arises of generating reproducible flaws in the form of fatigue precracks in definite positions in the components, respectively in the welded joint. It is reported exemplarily about experiments on different CT25 and CCT specimens and on a pressure vessel which contained a fatigue pre-crack, a 0.2 mm saw cut or notches with notch root radius ≤ ≥ 0.1 mm as flaws. The comparison of the results with regard to J-integral at initiation of stable crack, Ji, and JR curves shows that under certain conditions the 0.2 mm saw cut (notch root radius ≤ ≤ 0.02 mm) is a useful alternative, if reproducible generation of a fatigue pre-crack will not be successful or too expensive. The tests were carried out on StE 460 and on a welded joint of this steel at 25 ± 2°C. 相似文献
149.
Catalysis of an Essential Step in Vitamin B2 Biosynthesis by a Consortium of Broad Spectrum Hydrolases 下载免费PDF全文
Sonja Sarge Dr. Ilka Haase Dr. Boris Illarionov Dr. Dietmar Laudert Dr. Hans‐Peter Hohmann Prof. Adelbert Bacher Prof. Markus Fischer 《Chembiochem : a European journal of chemical biology》2015,16(17):2466-2469
An enzyme catalysing the essential dephosphorylation of the riboflavin precursor, 5‐amino‐6‐ribitylamino‐2,4(1H,3H)‐pyrimidinedione 5′‐phosphate ( 6 ), was purified about 800‐fold from a riboflavin‐producing Bacillus subtilis strain, and was assigned as the translation product of the ycsE gene by mass spectrometry. YcsE is a member of the large haloacid dehalogenase (HAD) superfamily. The recombinant protein was expressed in Escherichia coli. It catalyses the hydrolysis of 6 (vmax, 12 μmol mg?1 min?1; KM, 54 μm ) and of FMN (vmax, 25 μmol mg?1 min?1; KM, 135 μm ). A ycsE deletion mutant of B. subtilis was not riboflavin dependent. Two additional proteins (YwtE, YitU) that catalyse the hydrolysis of 6 at appreciable rates were identified by screening 13 putative HAD superfamily members from B. subtilis. The evolutionary processes that have resulted in the handling of an essential step in the biosynthesis of an essential cofactor by a consortium of promiscuous enzymes require further analysis. 相似文献
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