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排序方式: 共有442条查询结果,搜索用时 15 毫秒
101.
Samuel Owusu Yeboah Yulita Chebotip Mitei Jane Catherine Ngila Ludger Wessjohann Juergen Schmidt 《Journal of the American Oil Chemists' Society》2011,88(10):1539-1549
The lipid components of three Cameroonian seed oils, ke tchock (Aframomum arundinaceum), njangsa (Ricinodendron heudelotii) and calabash nutmeg (Monodora myristica), have been investigated. Gas chromatography (GC)–mass spectrometry (MS) fatty acid (FA) analysis showed M. myristica seed oil to be dominated by linoleic (49.29%) and oleic (37.17%) acids; R. heudelotii was mainly linoleic (58.73%), followed by stearic (15.00%) and oleic (14.21%) acids; A. arundinaceum was predominantly oleic (65.76%) and palmitic (20.36%) acids. Electrospray ionization (ESI)-Fourier transform ion cyclotron resonance (FTICR)-MS analysis showed seven major triacylglycerol (TAG) classes for M. myristica, with C54:5, C54:4 and C54:6 dominating. R. heudelotii had eight major TAG classes with C54:8, C54:7 and C54:6 being most abundant. A. arundinaceum also had eight major TAG classes with C52:2, C54:3 and C50:2 dominating. 13C nuclear magnetic resonance (NMR) analysis of the TAGs showed that both sn-1,3 and sn-2 positions were predominantly occupied by linoleoyl and oleoyl chains. High-performance liquid chromatography (HPLC) fluorescence detector (FLD) analysis showed that M. myristica contained only α- and β-tocopherols (195.40 and 73.95 μg/g, respectively), R. heudelotii contained mainly γ-tocopherol (289.40 μg/g), and A. arundinaceum had mainly γ- and β-tocopherols (236.78 and 124.93 μg/g, respectively). GC–MS analysis of the unsaponifiable matter showed that β-sitosterol was the most abundant phytosterol in all three seed oils. The absolute amounts of 4-desmethylsterols were 196.15, 608.71 and 362.15 μg/g for M. myristica, R. heudelotii and A. arundinaceum seed oils, respectively. These compositional and structural studies provide justification for the use of all three seed oils in food products. 相似文献
102.
Active control of ion transport plays important roles in chemical and biological analytical processes. Nanofluidic systems hold the promise for such control through electrostatic interaction between ions and channel surfaces. Most existing experiments rely on planar geometry where the nanochannels are generally very long and shallow with large aspect ratios. Based on this configuration the concepts of nanofluidic gating and rectification have been successfully demonstrated. However, device minimization and throughput scaling remain significant challenges. We report here an innovative and facile realization of hetero-structured Al(2)O(3)/SiO(2) (Si) nanopore array membranes by using pattern transfer of self-organized nanopore structures of anodic aluminum oxide (AAO). Thanks to the opposite surface charge states of Al(2)O(3) (positive) and SiO(2) (negative), the membrane exhibits clear rectification of ion current in electrolyte solutions with very low aspect ratios compared to previous approaches. Our hetero-structured nanopore arrays provide a valuable platform for high throughput applications such as molecular separation, chemical processors and energy conversion. 相似文献
103.
Holger Hoche Juergen Schmidt Stefan Groß Torsten Troßmann Christina Berger 《Surface & coatings technology》2011
Magnesium is a prospective material to save weight and fuel due to its low density and its high specific strength. Nevertheless corrosion and wear resistance are weak so that the surface has to be protected. Previous studies of the authors pointed out the potential of TiMgAlN PVD-coatings for surface protection of Mg-alloys. Within the presented study, the chemical, structural and electrochemical properties of TiMgAlN based PVD coating materials were examined entirely. Therefore, coatings of different compositions were deposited onto the magnesium alloy AZ31 and on glass substrates. Glass substrates were used to examine the electrochemical properties of the coating materials without any substrate influence. The magnesium content in the coatings varied between 1 at.% and 60 at.%. Increasing Mg content in the coatings improves mechanical and electrochemical properties, thus making TiMgAlN prospective candidates to protect magnesium against wear and corrosion. Beyond this, addition of magnesium leads to a densification of the coating microstructure. 相似文献
104.
Mechanical stress on suspended particles in two- and three-phase airlift loop reactors and bubble columns 总被引:1,自引:0,他引:1
Roman Daniel Pilz 《Chemical engineering science》2005,60(22):6004-6012
The effect of power input, fluid phase viscosity and solids loading on the mechanical stress on suspended particles was examined. Experiments were carried out in an airlift loop reactor and a bubble column operated in two- and three-phase mode. The disintegration of a shear sensitive floc system was observed with an optical in-line particle system analyser and information about the mechanical stress was obtained by means of mathematical analysis of the raw data. The volumetric power input has been derived to be the governing factor and a linear dependence between volumetric power input and resulting mechanical stress was observed. The addition of a solid phase leads to a drastical change of mechanical stress on the particles with a dominating increase of the stress at high solids loadings. Likewise higher fluid phase viscosity leads to higher mechanical stress on the floc system. 相似文献
105.
Katrin Mackenzie Juergen Battke Robert Koehler Frank-Dieter Kopinke 《Applied catalysis. B, Environmental》2005,59(3-4):171-179
The hydrolysis reaction of 1,1,2,2-tetrachloroethane (TeCA) is significantly enhanced by sorption on activated carbon. TeCA is quantitatively transformed into trichloroethene (TCE) at moderate pH values. This transformation is exploited as the basic step of a site-adapted groundwater-cleanup technology. The volatility of TCE is a factor of 23 higher than that of TeCA such that the partially dehydrochlorinated product can be easily stripped out of the groundwater flow. The base-mediated and the neutral dehydrochlorination of TeCA were studied as a function of temperature and pH value in batch and column experiments. Surprisingly, it was found that despite high loadings of the sorbent with TeCA and TCE (≥20 wt.%) the TeCA remains available for the hydrolysis reaction. 相似文献
106.
In this publication, several stainless steel microstructure reactors specially designed to obtain rapid and periodic temperature changes are presented. Different microstructure reactor designs have been manufactured and tested for their thermal behaviour and equally by running a test reaction under stationary and non-stationary temperature conditions. The devices were continuously electrically heated and periodically cooled by a deionized water flow. The objective of the experimental measurements was to demonstrate that non-stationary temperature conditions may lead to an increase in the reaction rate compared to the stationary conditions. The heterogeneously catalysed oxidation of CO was chosen as the test reaction. The catalyst used was a dispersion of platinum on a porous alumina support generated by sol-gel technology. The experiments realized under non-stationary temperature conditions with a temperature oscillation amplitude of 41 K and a period duration of 21 s show an increase in the mean CO2 concentration of a factor 1.72 compared to the mean concentration under quasi-stationary temperature conditions. The simulations of a simple monomolecular reaction under non-stationary temperature conditions indicate that the presence of a transitional surface coverage generated by the temperature oscillations may be a possible explanation for the observed phenomenon. 相似文献
107.
Torsten Henning Juergen J. Brandner Lutz Eichhorn Klaus Schubert Martin Schreiber Martin Güngerich Hermann Günther Peter J. Klar Vivian Rebbin Michael Fröba 《Microfluidics and nanofluidics》2007,3(3):299-305
We have incorporated microspheres, from 50 to 80 μm in diameter, of periodic mesoporous organosilica (inner surfaces up to
1,000 m2/g and pore sizes in the nanometre range) with two types of organic functionalities (benzene and ethane bridges, respectively)
inside microstructured channels (each 200 μm wide and 100 μm deep) and, exemplarily, monitored by Raman microscopy (Raman
spectroscopy through microscope optics) that the temperature characteristics of the adsorption–desorption equilibria of benzene
and ethanol vary significantly with the type of organic functionality of the microspheres and the pore morphology. The integration
of this class of nanostructured material into devices by means of microchannels is a promising novel approach to, among others,
substance separation in analytics, micro process engineering, and micro chemistry. 相似文献
108.
109.
110.
Beta Bdi Patrick M. Pilz Lilla Mrtha Miriam Lang Ouafa Hamza Mikls Fagyas Petra L. Szab Dietmar Abraham Attila Tth Bruno K. Podesser Attila Kiss Zoltn Papp 《International journal of molecular sciences》2021,22(20)
Post-ischemic left ventricular (LV) remodeling and its hypothetical prevention by repeated remote ischemic conditioning (rRIC) in male Sprague–Dawley rats were studied. Myocardial infarction (MI) was evoked by permanent ligation of the left anterior descending coronary artery (LAD), and myocardial characteristics were tested in the infarcted anterior and non-infarcted inferior LV regions four and/or six weeks later. rRIC was induced by three cycles of five-minute-long unilateral hind limb ischemia and five minutes of reperfusion on a daily basis for a period of two weeks starting four weeks after LAD occlusion. Sham operated animals served as controls. Echocardiographic examinations and invasive hemodynamic measurements revealed distinct changes in LV systolic function between four and six weeks after MI induction in the absence of rRIC (i.e., LV ejection fraction (LVEF) decreased from 52.8 ± 2.1% to 50 ± 1.6%, mean ± SEM, p < 0.05) and in the presence of rRIC (i.e., LVEF increased from 48.2 ± 4.8% to 55.2 ± 4.1%, p < 0.05). Angiotensin-converting enzyme (ACE) activity was about five times higher in the anterior LV wall at six weeks than that in sham animals. Angiotensin-converting enzyme 2 (ACE2) activity roughly doubled in post-ischemic LVs. These increases in ACE and ACE2 activities were effectively mitigated by rRIC. Ca2+-sensitivities of force production (pCa50) of LV permeabilized cardiomyocytes were increased at six weeks after MI induction together with hypophosphorylation of 1) cardiac troponin I (cTnI) in both LV regions, and 2) cardiac myosin-binding protein C (cMyBP-C) in the anterior wall. rRIC normalized pCa50, cTnI and cMyBP-C phosphorylations. Taken together, post-ischemic LV remodeling involves region-specific alterations in ACE and ACE2 activities together with changes in cardiomyocyte myofilament protein phosphorylation and function. rRIC has the potential to prevent these alterations and to improve LV performance following MI. 相似文献