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91.
Parameter-study on the influence of steel fibers and coarse aggregate content on the fresh properties of self-compacting concrete 总被引:7,自引:0,他引:7
Self-compacting concrete (SCC) offers several economic and technical benefits; the use of steel fibers extends its possibilities. Steel fibers bridge cracks, retard their propagation, and improve several characteristics and properties of the concrete. Fibers are known to significantly affect the workability of concrete. Therefore, an investigation was performed to compare the properties of plain SCC and SCC reinforced with steel fibers. Two mixtures of SCC with different aggregate contents were used as reference. Each of the concretes was tested with four types of steel fibers at different contents in order to answer the question to what extent the workability of SCC is influenced. The slump flow, a fiber funnel and the J-ring test were used to evaluate the material characteristics of the fresh concrete. This paper discusses the suitability of the applied test methods and the effect of the coarse aggregate content, the content and type of steel fibers on the workability of SCC. 相似文献
92.
93.
Object
Delta relaxation enhanced magnetic resonance (dreMR) is a new imaging technique based on the idea of cycling the magnetic field B 0 during an imaging sequence. The method determines the field dependency of the relaxation rate (relaxation dispersion dR 1/dB). This quantity is of particular interest in contrast agent imaging because the parameter can be used to determine contrast agent concentrations and increases the ability to localize the contrast agent.Materials and methods
In this paper dreMR imaging was implemented on a clinical 1.5?T MR scanner combining conventional MR imaging with fast field-cycling. Two improvements to dreMR theory are presented describing the quantification of contrast agent concentrations from dreMR data and a correction for field-cycling with finite ramp times.Results
Experiments demonstrate the use of the extended theory and show the measurement of contrast agent concentrations with the dreMR method. A second experiment performs localization of a contrast agent with a significant improvement in comparison to conventional imaging.Conclusion
dreMR imaging has been extended by a method to quantify contrast agent concentrations and improved for field-cycling with finite ramp times. Robust localization of contrast agents using dreMR imaging has been performed in a sample where conventional imaging delivers inconclusive results. 相似文献94.
Steffen Uhlig Dr. Petra Gowik 《Journal für Verbraucherschutz und Lebensmittelsicherheit》2010,5(1):35-46
This paper presents a validation approach for microbiological methods based on a combination of interlaboratory tests and factorial experiments. It requires not more than 4 participants but is achieving comparable statistical confidence as in method validation studies with 8–12 participants, if properly designed. The approach is illustrated by a comprehensive validation of the Arxula adeninivorans yeast estrogen screen (A-YES) assay for the detection of estrogenic activity in mineral water. 相似文献
95.
René-Maxime Gracien Sarah C. Reitz Marlies Wagner Christoph Mayer Steffen Volz Stephanie-Michelle Hof Vinzenz Fleischer Amgad Droby Helmuth Steinmetz Sergiu Groppa Elke Hattingen Johannes C. Klein Ralf Deichmann 《Magma (New York, N.Y.)》2017,30(1):75-83
Objective
Proton density (PD) mapping requires correction for the receive profile (RP), which is frequently performed via bias-field correction. An alternative RP-mapping method utilizes a comparison of uncorrected PD-maps and a value ρ(T1) directly derived from T1-maps via the Fatouros equation. This may be problematic in multiple sclerosis (MS), if respective parameters are only valid for healthy brain tissue. We aimed to investigate whether the alternative method yields correct PD values in MS patients.Materials/methods
PD mapping was performed on 27 patients with relapsing-remitting MS and 27 healthy controls, utilizing both methods, yielding reference PD values (PDref, bias-field method) and PDalt (alternative method).Results
PDalt-values closely matched PDref, both for patients and controls. In contrast, ρ(T1) differed by up to 3 % from PDref, and the voxel-wise correlation between PDref and ρ(T1) was reduced in a patient subgroup with a higher degree of disability. Still, discrepancies between ρ(T1) and PDref were almost identical across different tissue types, thus translating into a scaling factor, which cancelled out during normalization to 100 % in CSF, yielding a good agreement between PDalt and PDref.Conclusion
RP correction utilizing the auxiliary parameter ρ(T1) derived via the Fatouros equation provides accurate PD results in MS patients, in spite of discrepancies between ρ(T1) and actual PD values.96.
Steffen Vojacek Lukas Schulig Nathalie Wössner Norman Geist Prof. Dr. Walter Langel Prof. Dr. Manfred Jung Prof. Dr. Dennis Schade Prof. Dr. Andreas Link 《ChemMedChem》2019,14(8):853-864
Indoles are privileged structures in medicinal and bioorganic chemistry that are particularly well suited to serve as platforms for diversity. Among many other therapeutic areas, the indole scaffold has been used to design aromatic compounds useful to interfere with enzymes engaged in the regulation of substrate acylation status, such as sirtuins. However, the planarity of the indole ring is not necessarily optimal for all target enzymes, especially when functionalization with aromatic side chains is required. Replacement of flat scaffolds by nonplanar molecular cores dominated by sp3 hybridization is a common strategy to avoid the disadvantages associated with poor solubility and high promiscuity, while covering less-well-explored areas of chemical space. Thus, we synthesized fragment-like tetrahydroindoles suitable for fragment-based drug discovery as well as a well-characterized small library intended as multipurpose screening compounds. For proof of principle, these compounds were screened against sirtuins 1–3, enzymes known to be addressable by indoles. We found that 2,6,6-trimethyl-4-oxo-4,5,6,7-tetrahydro-1H-indole-3-carboxamides are potent and selective SIRT2 inhibitors. Compound 16 t displayed an IC50 value of 0.98 μm and could serve as exquisite starting point for hit-to-lead profiling. 相似文献
97.
Christina Polasky Armin Steffen Kristin Loyal Christian Lange Karl-Ludwig Bruchhage Ralph Pries 《International journal of molecular sciences》2021,22(21)
Obstructive sleep apnea (OSA) is characterized by nocturnal breathing intermissions resulting in oxidative stress and eventually, a low-grade systemic inflammation. The study aimed to investigate the impact of positive airway pressure (PAP) therapy on the inflammatory milieu as measured by monocyte and T cell phenotypic alterations. Participants were assessed for their OSA severity before PAP therapy and about six months later, including patient-reported outcome and therapy usage by telemetry readout. The distributions of the CD14/CD16-characterized monocyte subsets as well as the CD4/CD8-characterized effector T cell subsets with regard to their PD-1 and PD-L1 expression were analyzed by flow cytometry from blood samples. Data of 25 patients revealed a significant reconstitution of the monocyte subset distribution and a decrease in PD-L1 expression on pan-monocytes and CD8+ T cells without an association to initial AHI and overweight. The PD-1 expression was still increased on T cell subsets, especially on CD4+ TH17/22 cells. We conclude that PAP therapy might have a rapid effect on the monocyte phenotype and overall PD-L1 expression levels. However, T cell immune alterations especially on TH17/22 cells persist longer, indicating an ongoing disturbance of the adaptive immune system. 相似文献
98.
Nicolai Szeliga Lando Helmrich von Elgott Daniel Bezecny Steffen Richter Marko Hoffmann Michael Schlüter 《化学,工程师,技术》2019,91(12):1802-1811
Experiments were carried out in a 50‐m3 cylindrical tank to determine the influence of strong momentum on the formation of large‐scale gas‐core vortices. Gas‐core lengths were measured for varying volume flow rates and submergence depths. The critical Froude numbers were also determined and the efficiency of different vortex suppressors on the gas‐core formation was investigated. The horizontal velocity field inside the vortex core region was additionally recorded using particle image velocimetry. The experimental results were used to verify numerical simulations and compared to vortex models and correlations from literature. 相似文献
99.
Doris Pospiech Andreas Korwitz Kathrin Eckstein Hartmut Komber Dieter Jehnichen Marcus Suckow Albena Lederer Kerstin Arnhold Michael Göbel Martina Bremer Anton Hoffmann Steffen Fischer Anett Werner Thomas Walther Harald Brünig Brigitte Voit 《应用聚合物科学杂志》2019,136(46):48257
Thermotropic liquid crystalline polyesters with varied chemical structure are synthesized by melt transesterification polycondensation. They are employed as matrix for blends with lignin materials to obtain melt-spinnable precursors for carbon fibers. The lignin samples are carefully purified by fractionation, enzymatic removal of reducing sugars, and subsequent modification of the terminal OH groups. Effective melt blending is achieved with liquid-crystalline aromatic–aliphatic polyesters having melting ranges that match the softening temperature of the lignin fractions, which is necessary to prevent thermal decomposition of the lignin. Polyester/lignin blends are partially compatibilized, phase-separated materials. The polyester/lignin materials are melt-spun successfully. The fiber properties depend on the lignin purification process. X-ray scattering reveals that orientation in lignin-containing fibers is maintained. First experiments show that the fibers can be converted successfully to carbon fibers by thermal annealing procedures. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48257. 相似文献
100.
Benjamin Bock Anne Schmidt Edyta Sniezek Steffen Dudczig Gert Schmidt Jacek Szczerba Christos G. Aneziris 《Ceramics International》2019,45(4):4499-4508
Since solid, non-metallic inclusions influence considerably the quality of casted steel products, carbon-bonded alumina foam filters are used in secondary metallurgical treatments to remove these particles from steel melts. In order to attain a significant improvement of the filtration process, five different carbonaceous spinel compounds from the Fe-/Mg-/Mn-Al-O systems are applied on carbon-bonded alumina filters in this study and investigated with regard of their filtration efficiency. However, these spinel compounds decompose partially during sintering at 1400?°C under reducing atmosphere, wherefore the resulting coatings contain not only spinel compounds, but also oxidic and metallic components. The subsequent interaction with molten steel leads to the development of multicrystal structures on the filter surface, which stem from interfacial reactions between coating materials, molten steel, and inclusions. As a result of this procedure, a reduction of almost 60% alumina inclusions is measured with the aid of an automatic SEM, whereby spinel compounds from the Fe-Mn-Al-O system achieve highest filtration efficiencies. 相似文献