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31.
A reverse-phase high-performance liquid chromatographic method for the determination of trans-resveratrol with spectrophotometric detection (306 nm) and amperometric detection at carbon paste electrode (E = + 1,2 V) was developed and tested on real samples of grains, hulls and leaves of six varieties of common buckwheat (Fagopyrum esculentum Möench) and two varieties of tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.). Optimal conditions for the determination of trans-resveratrol were as follows: column Kromasil C-18 (7 μm), 125 × 4 mm; mobile phase acetonitrile: diluted BR buffer pH 7 (50:50, 30:70 for grains and hulls and 20:80 for leaves); flow rate 1 ml min−1. Under these conditions, the limit of detection of trans-resveratrol (LD) was 3.5 × 10−8 mol l−1 (R2 = 0.9986) for electrochemical detection and 3.2 × 10−8 mol l−1 (R2 = 0.9993) for spectrophotometric detection. 相似文献
32.
Lana-Simone Unger Rian Ruhl Matthias Meffert Christian Niedrig Wolfgang Menesklou Stefan F. Wagner Dagmar Gerthsen Henny J.M. Bouwmeester Ellen Ivers-Tiffée 《Journal of the European Ceramic Society》2018,38(5):2388-2395
Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) in its cubic perovskite phase has attracted much interest for potential use as oxygen transport membrane (OTM) due to its very high oxygen permeability at high temperatures. However, performance degradation due to a sluggish phase decomposition occurs when BSCF is operated below 840?°C. Partial B-site substitution of the transition metal cations in BSCF by larger and redox-stable cations has emerged as a potential strategy to improve the structural stability of cubic BSCF. In this study, the influence of yttrium doping (0…10?mol-%) on oxygen transport properties and stability of the cubic BSCF phase is assessed by in situ electrical conductivity relaxation (ECR) and electrical conductivity measurements during long-term thermal annealing both at 700?°C and 800?°C. Detailed phase analysis is performed by scanning electron microscopy (SEM) after long-term annealing of the samples in air at different temperatures. 相似文献
33.
Guzanová Anna Draganovská Dagmar Ižaríková Gabriela Brezinová Janette Rajt’úková Viktória Živčák Jozef Hudák Radovan Janoško Erik Moro Róbert 《Journal of Mechanical Science and Technology》2021,35(10):4389-4404
Journal of Mechanical Science and Technology - The article deals with selective laser melting process using CoCrW powder. Our aim was to identify the influence of product position on the building... 相似文献
34.
35.
Maláková Silvia Guzanová Anna Draganovská Dagmar Fedorko Gabriel Molnár Vieroslav 《Journal of Mechanical Science and Technology》2019,33(12):5817-5827
Journal of Mechanical Science and Technology - The paper is focused on the influence of gearing material and thermal or chemical-thermal processing of wheels on the results of the strength... 相似文献
36.
Lode Daelemans Wim Van Paepegem Dagmar R. D'hooge Karen De Clerck 《Advanced functional materials》2019,29(8)
One of the challenges for multiphase materials is the improvement of the interconnectivity of their separate phases. A promising route toward excellent adhesion is molecular interdiffusion, in which molecules are transferred to enable physical interaction. In the present work, a novel straightforward and direct method is developed to tune the adhesion between electrospun nanofibers and their matrix, starting from fundamental insights on molecular diffusion and considering in situ chemical formation of one of the polymer phases to effectively regulate interdiffusion. Proof‐of‐concept is provided for the adhesion of a thermoplastic phase (poly(ε‐caprolactone)) to a thermoset matrix (epoxy) during the cured‐induced formation of the latter. For isothermal curing, only an intermediate temperature (50 °C) allows the production of nanofiber hybrid materials with good adhesion between the constituents and preservation of the nanomorphology. Moreover, excellent adhesion properties are obtained in case a two‐step curing (25 °C/80 °C), or coaxial electrospinning (polyamide 6/poly(ε‐caprolactone)) toward core–shell nanomorphologies is applied. Improvements in toughness of the optimized interdiffused materials with G values over 600 J m?2 (up to 65% improvement) are recorded due to excellent bonding of the thermoplastic nanofibers with the matrix. 相似文献
37.
Stella Gries Manuel Brinker Berit Zeller-Plumhoff Dagmar Rings Tobias Krekeler Elena Longo Imke Greving Patrick Huber 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(22):2370157
Many biological materials exhibit a multiscale porosity with small, mostly nanoscale pores as well as large, macroscopic capillaries to simultaneously achieve optimized mass transport capabilities and lightweight structures with large inner surfaces. Realizing such a hierarchical porosity in artificial materials necessitates often sophisticated and expensive top-down processing that limits scalability. Here, an approach that combines self-organized porosity based on metal-assisted chemical etching (MACE) with photolithographically induced macroporosity for the synthesis of single-crystalline silicon with a bimodal pore-size distribution is presented, i.e., hexagonally arranged cylindrical macropores with 1 µm diameter separated by walls that are traversed by pores 60 nm across. The MACE process is mainly guided by a metal-catalyzed reduction–oxidation reaction, where silver nanoparticles (AgNPs) serve as the catalyst. In this process, the AgNPs act as self-propelled particles that are constantly removing silicon along their trajectories. High-resolution X-ray imaging and electron tomography reveal a resulting large open porosity and inner surface for potential applications in high-performance energy storage, harvesting and conversion or for on-chip sensorics and actuorics. Finally, the hierarchically porous silicon membranes can be transformed structure-conserving by thermal oxidation into hierarchically porous amorphous silica, a material that could be of particular interest for opto-fluidic and (bio-)photonic applications due to its multiscale artificial vascularization. 相似文献
38.
Gómez Núñez Jersain García Martínez Magdalena Mompremier Rojacques González Beltrán Beatriz A. Barceló Quintal Icela Dagmar 《Water Resources Management》2022,36(13):5191-5205
Water Resources Management - The behavior of a rainwater harvesting system depends on some variables that cannot be controlled, such as rainfall, building roof size and water consumption. The... 相似文献
39.
Extensive damage to the vegetation cover in arctic and alpine landscapes has raised the question of restoration as a possible management strategy. Restoration is a goal-oriented activity, a technological undertaking wider than its parent science of ecology. Social science and planning concepts and methods are necessary to handle the value judgements implicit in restoration. It is argued that the notion of 'desired state' is a better reference point in defining restoration goals than the notion of 'original state'. Using qualitative methods, two areas with vulnerable arctic/alpine vegetation are investigated. Based on participants' statements, four possible scenarios or desired states for future management are constructed. The main focus in the scenarios is on participants' attitudes to restoration activity, and it is shown how these are influenced by participants' attachment to the area and their view of nature. 相似文献
40.
It has been postulated that males of a number of scorpionfly species produce sex pheromones. This is based on the observation
that females often respond only to conspecific males when they evert their genital pouch, the proposed site of pheromone release.
In this study, we prove that in Panorpa germanica (Mecoptera, Panorpidae), the eversion of a male’s genital pouch is associated with the release of a volatile sex pheromone.
In dual choice situations, females showed a high preference for ‘calling’ (males with everted genital pouch) over noncalling
individuals. Volatiles emitted by males and females were collected and identified by coupled gas chromatography–mass spectrometry.
Two aldehydes [(2E,6Z)-nona-2,6-dienal and (E)-non-2-enal] were characteristic of calling males but not of noncalling or immature males or females. Bioassays with synthetic
compounds confirmed that the identified substances are attractive to females. To the best of our knowledge, this is the first
identification of a sex pheromone in scorpionflies. 相似文献