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101.
Stephanie Weiss Philipp M. Neu Christopher Ludwig Sigurd Schober Martin Mittelbach 《European Journal of Lipid Science and Technology》2018,120(6)
Steryl glucosides (SG) and acylated steryl glucosides (ASG) are natural components of plant cell membranes and present in different concentrations in various plant foods. Currently, their positive effects on human health are under investigation. The present work presents a new and efficient synthesis method for cholesteryl glucosides starting from disaccharides. A five‐step synthesis protocol is done to obtain the desired product in 35% overall yield. In the first step, the hydroxy groups of the starting material sucrose are protected using benzyl ethers. After the subsequent acidic hydrolysis the obtained pyranosyl moiety of the disaccharide is transformed to its trichloroacetimidate derivative. Next, the formation of the glycosidic bond to cholesterol is performed and catalytic transfer hydrogenation in order to remove the protecting groups leads to the desired product. In this context, APCI‐MS‐TOF has turned out to be an excellent analytical tool for the high sensitive analysis of SG as well as intermediates. Practical Applications: Due to the comparatively high amounts of SG and ASG in seeds and oils, not only the food industry but also in biodiesel production, these natural compounds are of increasing interest. However, analysis of the compounds is difficult, commercially available pure standard materials are costly and their synthesis often requires time‐consuming work‐up procedures. The described preparation method allows the synthesis of cholesteryl glucosides which can be used as reference or standard material for the quantitative analysis of phytosteryl glucosides in plant derived samples. The general synthesis method could be also applied to other SG and ASG derivatives. Cholesteryl glucosides are synthesized using a new and efficient five‐step synthesis protocol starting from disaccharides. The preparation method provides products with good overall yield and high purity and, therefore, the synthesized glucosides can be used as reference or standard material for the quantitative analysis of phytosteryl glucosides in plant derived samples. APCI‐MS‐TOF is extensively used as analytical tool for the sensitive analysis of cholesteryl glucosides as well as intermediates. 相似文献
102.
Phenolic compounds obtained from alkyl oleates as additives to improve the oxidative stability of methyl rapeseed biodiesel 下载免费PDF全文
103.
The main objective of the European Validation of the Integral Code ASTEC (EVITA) project is to distribute the severe accident integral code ASTEC to European partners in order to apply the validation strategy issued from the VASA project (4th EC FWP). Partners evaluate the code capability through validation on reference experiments and plant applications accounting for severe accident management measures, and compare results with reference codes.The basis version V0 of ASTEC (Accident Source Term Evaluation Code)—commonly developed and basically validated by GRS and IRSN—was made available in late 2000 for the EVITA partners on their individual platforms. Users’ training was performed by IRSN and GRS. The code portability on different computers was checked to be correct. A “hot line” assistance was installed continuously available for EVITA code users. The actual version V1 has been released to the EVITA partners end of June 2002. It allows to simulate the front-end phase by two new modules:
- • for reactor coolant system 2-phase simplified thermal hydraulics (5-equation approach) during both front-end and core degradation phases,
- • for core degradation, based on structure and main models of ICARE2 (IRSN) reference mechanistic code for core degradation and on other simplified models.
104.
Oxidized actinide species are often more mobile than reduced forms. Bioremediation strategies have been developed to exploit this chemistry and stabilize actinides in subsurface environments. We investigated the ability of metal-reducing bacteria Geobacter metallireducens and Shewanella oneidensis to enzymatically reduce Np(V) and Np(V) citrate, as well as the toxicity of Np(V) to these organisms. A toxic effect was observed for both bacteria at concentrations of > or = 4.0 mM Np(V) citrate. Below 2.0 mM Np(V) citrate, no toxic effect was observed and both Fe(III) and Np(V) were reduced. Cell suspensions of S. oneidensis were able to enzymatically reduce unchelated Np(V) to insoluble Np(IV)(s), but cell suspensions of G. metallireducens were unable to reduce Np(V). The addition of citrate enhanced the Np(V) reduction rate by S. oneidensisand enabled Np(V) reduction by G. metallireducens. The reduced form of neptunium remained soluble, presumably as a polycitrate complex. Growth was not observed for either organism when Np(V) or Np(V) citrate was provided as the sole terminal electron acceptor. Our results show that bacteria can enzymatically reduce Np(V) and Np(V) citrate, but that the immobilization of Np(IV) may be dependent on the abundance of complexing ligands. 相似文献
105.
106.
The growth of small fatigue cracks in PH 13-8 Mo (H1050) stainless steel under constant amplitude loading at different mean
stresses (R=0.1 and −1) under generally high cycle fatigue conditions was investigated. Small cracks were allowed to initiate naturally
at the root of a single edge notch specimen and were monitored using a surface replicating technique. It was found that the
initiation and growth of surface cracks up to 100 μm encompassed 70 to 90 pct of the total fatigue life at stress amplitudes just above the fatigue limit. Cracks of length less
than 100 μm were subject to strong influences of the microstructure and exhibited stage I (shear-dominated) growth, which was manifested
in oscillatory crack growth rates. The oscillations diminished as the crack transitioned to stage II growth. The higher stress
ratio (R=0.1) resulted in a more rapid transition from stage I to stage II growth in comparison to R=−1. After transitioning to stage II, the crack growth could be well characterized by conventional long crack tools even when
the crack was still physically small. The small crack growth behavior is shown to be similar to that of a quenched and tempered
AISI 4340 steel having a comparable strength. 相似文献
107.
Influence of coefficient of friction on fretting fatigue crack nucleation prediction 总被引:1,自引:0,他引:1
The role of coefficient of friction (COF) on fretting fatigue damage prediction is studied using an elastic/plastic finite element analysis (FEA) of an experimental fretting fatigue test. At a scale on the order of tens of microns, the COF has a large impact on fretting fatigue damage prediction. By using a higher COF than that determined from conventional gross sliding tests, along with critical plane multiaxial fatigue damage models, the life and experimentally observed damage at this scale appear to be better predicted. Potential origins of this higher effective COF are discussed. 相似文献
108.
Rafael Stratmann Dipl.-Ing. Veit Birtel Dipl.-Ing. Peter Mark Priv. Doz. Dr.-Ing. habil. Helmut Neuß Dipl.-Ing. Wolfgang Niemeier Prof. Dr.-Ing. habil. Björn Riedel Dr.-Ing. Eberhard Ziem Dipl.-Ing. 《Beton- und Stahlbetonbau》2008,103(4):252-261
A Digital System to Record and Analyse Cracks A digital system – ready for its practical use – is presented to precisely record and analyse cracks at concrete or masonry structures. It uses a standard digital camera and a specific cylindrical attachment to photographically record crack pattern at surfaces. Crack parameters like medium widths, width variations or width profiles are analysed from several dozen measurement points per centimetre of a crack using a developed software tool. Applications on site – like bridge evaluations acc. DIN 1076 – and in the lab – like monitorings of shear crack developments – illustrate handling, precision and data extent of the system in comparison to standard methods. 相似文献
109.
110.
Francisco García-Moreno Tillmann Robert Neu Paul Hans Kamm John Banhart 《Advanced Engineering Materials》2023,25(8):2201355
X-ray tomography is a versatile tool in materials research and engineering since it allows for a non-destructive and three-dimensional mapping of the constituents of a heterogeneous material as long as they differ in their interactions with X-rays. Recent developments of the technique have brought down the time needed for the acquisition of a single tomogram by many orders of magnitude compared to what was needed 25 years ago. Nowadays, up to 1000 full tomograms can be recorded in a second, which enables real-time studies of changes in samples caused by reactions or by applied processing operations. The term tomoscopy has been coined for such sequences of 3D images. We review the application of X-ray tomography and tomoscopy on metals and describe each step required and the associated challenges. A selection of representative investigations is presented with a focus on time-resolved phenomena in metals and alloys ranging from mechanical deformation, solidification to metals processing processes such as welding and additive manufacturing. Finally likely future developments are discussed. 相似文献