水锤诱发弱约束管道流固耦合振动频谱分析

本文在充分利用现有ＭＯＣ法优点的基础上,提出一种与其十分相似的频谱分析法。该方法能解析分析水锤诱发作用下输流管道流固耦合振动的频谱特性,并能直接考虑色散和能量耗散对系统运动的影响。使用该方法能在任意激源和各种边界条件下得到管道频谱和色散曲线。文中以英国丹迪大学流体力学实验室的标准试验装置为例,说明了该方法的应用。     

An automated HPLC determination of meticlorpindol in eggs with UV absorbance detection, using on-line dialysis and pre-concentration as sample clean-up; occurrence in and carry over to eggs

Summary A fully automated HPLC determination of the coccidiostat meticlorpindol in whole egg, egg white and yolk is described. The sample homogenate is dialysed online against water. The dialysate is concentrated on-line on a short reversed-phase (RP) column. The contents of this column are transferred to the reversed-phase analytical column by means of the mobile phase. Meticlorpindol is detected using an absorbance detector at 270 nm. Linear calibration graphs are obtained in the range 40–900 ng/g in whole egg and egg white (detection limit 10 ng/g) and 80–1800 ng/g in yolk (detection limit 20 ng/g). Out of 111 commercially obtained egg samples 12 contained meticlorpindol with levels varying from 10 to 433 ng/g. A group of laying hens, kept in cages, received 10 mg/kg of Lerbek (meticlorpindol and methylbenzoquate; Dow Chemical) in the feed for 10 days. Meticlorpindol residues in the eggs rose to a level of 622 ng/g. Meticlorpindol was found in the eggs until 6 days after withdrawal of the medicated feed. Another group received 110 mg/kg in the feed. Meticlorpindol residues rose to levels of 4480 ng/g in the eggs, 5880 ng/g in the egg white and 2660 ng/g in the yolk. Meticlorpindol was found in the eggs and the egg white until 14 days and in the yolk until 8 days after withdrawal of the medicated feed.

---

Eine automatisierte HPLC-Methode zur Bestimmung von Meticlorpindol in Eiern mit UV-Detektion und Probenaufarbeitung mit direkter Dialyse und direkter Vorkonzentrierung; Übertragung (Carry-over) und Vorkommen in Eiern

Zusammenfassung Mit dem beschriebenen Verfahren können Rückstände von Meticlorpindol in Eiern, Eiklar und Dotter automatisch bestimmt werden. Homogenisierte Proben werden gegen Wasser dialysiert. Das Dialysat wird an einer Vorkonzentrierungssäule konzentriert. Mit der mobilen Phase wird das Konzentrat auf die analytische Säule gebracht. Der Nachweis wird mit einem UV-Absorption-Detektor ausgeführt (Wellenlänge 270 nm). Der Zusammenhang zwischen Meßwert und Meticlorpindolgehalt ist linear in dem Bereich von 40 bis 900 ng/g Meticlorpindol in Vollei und Eiklar (Nachweisgrenze etwa 10 ng/g) und von 80 bis 1800 ng/g in Dotter (Nachweisgrenze etwa 20 ng/g). Bei der Untersuchung von 111 Handelsproben wurden in 12 Proben Rückstände von Meticlorpindol nachgewiesen mit Konzentrationen zwischen 10 und 433 ng/g. Eine Gruppe von Legehennen erhielt 10 mg/kg Lerbek (Meticlorpindol und Methylbenzoquate; Dow Chemical) im Futter während 10 Tagen. Die Eier wiesen bis zum 6. Tag nach dem Absetzen des Futterzusatzes nachweisbare Meticlorpindol-Rückstände auf (Höchstgehalt 622 ng/g in Vollei). Eine zweite Gruppe erhielt 110 mg/kg im Futter. In den Volleiproben und Eiklarproben dieser Gruppe konnten bis zum 14. Tag nach dem Absetzen Rückstände von Meticlorpindol nachgewiesen werden (Höchstgehalte 4480 und 5880 ng/g), in den Dotterproben bis zum 8. Tag (Höchstgehalt 2660 ng/g).

     

Prospective Validation of a Comprehensive In silico hERG Model and its Applications to Commercial Compound and Drug Databases

Ligand‐based in silico hERG models were generated for 2 644 compounds using linear discriminant analysis (LDA) and support vector machines (SVM). As a result, the dataset used for the model generation is the largest publicly available (see Supporting Information). Extended connectivity fingerprints (ECFPs) and functional class fingerprints (FCFPs) were used to describe chemical space. All models showed area under curve (AUC) values ranging from 0.89 to 0.94 in a fivefold cross‐validation, indicating high model consistency. Models correctly predicted 80 % of an additional, external test set; Y‐scrambling was also performed to rule out chance correlation. Additionally models based on patch clamp data and radioligand binding data were generated separately to analyze their predictive ability when compared to combined models. To experimentally validate the models, 50 of the predicted hERG blockers from the Chembridge database and ten of the predicted non‐hERG blockers from an in‐house compound library were selected for biological evaluation. Out of those 50 predicted hERG blockers, tested at a concentration of 10 μM , 18 compounds showed more than 50 % displacement of [³H]astemizole binding to cell membranes expressing the hERG channel. K_i values of four of the selected binders were determined to be in the micromolar and high nanomolar range (K_i (VH 01 )=2.0 μM , K_i (VH 06 )=0.15 μM , K_i (VH 19 )=1.1 μM and K_i (VH 47 )=18 μM ). Of these four compounds, VH 01 and VH 47 showed also a second, even higher affinity binding site with K_i values of 7.4 nM and 36 nM , respectively. In the case of non‐hERG blockers, all ten compounds tested were found to be inactive, showing less than 50 % displacement of [³H]astemizole binding at 10 μM . These experimentally validated models were then used to virtually screen commercial compound databases to evaluate whether they contain hERG blockers. 109 784 (23 %) of Chembridge, 133 175 (38 %) of Chemdiv, 111 737 (31 %) of Asinex and 11 116 (18 %) of the Maybridge database were predicted to be hERG blockers by at least two of the models, a prediction which could, for example, be used as a pre‐filtering tool for compounds with potential hERG liabilities.     

Morphology and properties of NR/EPDM rubber blends filled with small amounts of titania nanoparticles

This article describes the results of an investigation on the influence of titania nanoparticles on the morphology and properties of vulcanized natural rubber (NR)/ethylene‐propylene‐diene monomer (EPDM) blends. The samples were prepared through roll‐milling and melt‐pressing and diphenyl guianidine was used as vulcanization accelerator. The transmission electron microscopy (TEM) and X‐ray diffraction (XRD) results show that the titania particles are concentrated in the NR phase, and that the presence of titania in EPDM seems to initiate the formation of crystals in the rubber phase. From the dynamic mechanical analysis (DMA) and tensile testing results it is clear that the presence of titania particles inhibited the vulcanization process in both the investigated rubbers, and that the mechanical properties of the nanocomposites were influenced by the interaction between the nanoparticles and the rubber, the reduced vulcanization of the two rubber phases, and the development of crystallinity in EPDM. The thermogravimetric (TGA) results show improved thermal stability of EPDM, and of the EPDM phase in the blend, for the samples containing titania nanoparticles. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Layered silicates nanocomposite matrix for improved fiber reinforced composites properties

Three-phase glass fiber reinforced composites (GFRP) consisting of traditional woven glass fiber and polyamide-6 (PA6) matrix dispersed with organically modified layered silicates were prepared and investigated in this study. The fabrication of GFRP with different weight percentages of layered silicates was successful when the matrix contains less than 5 wt% of the layered silicates. The improvement due to the high aspect ratio and high stiffness of the layered silicates is illustrated through the matrix-controlled properties of the GFRP. The results showed that the GFRP with 5 wt% layered silicates offer the largest improvement of approximately 30% increase in both flexural strength and compressive strength at elevated temperatures. On the other hand, the in-plane shear properties measured from [±45]_s laminates revealed that the layered silicates help improved both the in-plane shear strength and modulus appropriately. By utilizing a nanocomposite matrix, improvement of stiffness and strength, as well as thermal and barrier properties is obtained without any change in processing temperature of the fiber composites.     

The effect of expanded graphite on the physical properties of conductive EVA/wax phase change blends for thermal energy storage

A study of the morphology, dynamic mechanical, impact, and tensile properties of ethylene vinyl acetate copolymer (EVA)/expanded graphite (EG) and EVA/wax/EG composites is presented. The composites were prepared by melt blending. The EVA/EG composites showed ductile behavior, while brittle behavior was observed in the presence of wax. A finer dispersion of EG was observed in the matrix when wax was present. The storage modulus of the EVA/wax/EG composite was higher than that of the EVA/EG composite, which is ascribed to a better interaction between the EVA and the wax‐covered EG that significantly reduced the EVA chain mobility. The composites showed a decrease in impact strength with increasing EG and wax contents. There was a significant difference in the elongation at break between the EVA/EG and EVA/wax/EG composites, and little change in Young's modulus of EVA in the presence of EG and with increasing EG content. However, Young's modulus of the EVA/wax blends increased in the presence of and with increasing EG content. In all the investigated samples containing EVA and wax, irrespective of the EG content, the stress at break decreased with an increase in wax content. POLYM. COMPOS., 37:3025–3032, 2016. © 2015 Society of Plastics Engineers     

Optimal orientation in flows: providing a benchmark for animal movement strategies

Animal movements in air and water can be strongly affected by experienced flow. While various flow-orientation strategies have been proposed and observed, their performance in variable flow conditions remains unclear. We apply control theory to establish a benchmark for time-minimizing (optimal) orientation. We then define optimal orientation for movement in steady flow patterns and, using dynamic wind data, for short-distance mass movements of thrushes (Turdus sp.) and 6000 km non-stop migratory flights by great snipes, Gallinago media. Relative to the optimal benchmark, we assess the efficiency (travel speed) and reliability (success rate) of three generic orientation strategies: full compensation for lateral drift, vector orientation (single-heading movement) and goal orientation (continually heading towards the goal). Optimal orientation is characterized by detours to regions of high flow support, especially when flow speeds approach and exceed the animal''s self-propelled speed. In strong predictable flow (short distance thrush flights), vector orientation adjusted to flow on departure is nearly optimal, whereas for unpredictable flow (inter-continental snipe flights), only goal orientation was near-optimally reliable and efficient. Optimal orientation provides a benchmark for assessing efficiency of responses to complex flow conditions, thereby offering insight into adaptive flow-orientation across taxa in the light of flow strength, predictability and navigation capacity.     

Structure and properties of a β‐nucleated polypropylene impact copolymer

The effect of a β‐nucleating agent (β‐NA) on the properties and structure of a commercial impact polypropylene copolymer (IPC) was investigated. The effect of selected β‐NAs on the impact resistance, stress and strain behaviour of the IPC is reported. In addition, the IPC was fractionated according to crystallinity by preparative temperature rising elution fractionation. Fractions with varying chemical composition and crystallinity were treated with a two‐component β‐NA to investigate the effect of the β‐NA on the various fractions. The results indicate that the efficacy of the β‐NA is dependent on the chemical composition of the polymer that crystallises, more specifically on the sequence length of crystallisable propylene units. The effect of the addition of β‐NAs on the overall morphology of the IPC was also investigated, and in particular the size and distribution of the rubbery particles in these complex reactor blends were probed. © 2014 Society of Chemical Industry     

Dynamic mechanical and thermal properties of the composites of thermoplastic starch and lanthanum hydroxide nanoparticles

Nanostructured lanthanum (III)‐oxide (La₂O₃) particles were prepared by a polymer complex solution method and further used for the preparation of lanthanum hydroxide (La(OH)₃) nanoparticles. The La(OH)₃ nanopowder was mixed with glycerol‐plasticized maize starch and the effect of the filler on the thermal, mechanical, and viscoelastic properties of the matrix was investigated. It was expected that this nanofiller, which shows an affinity toward OH groups, would strongly affect the physical properties of thermoplastic starch (TPS). The pure TPS and the TPS‐La(OH)₃ nanocomposite films (with 1, 2, and 3 wt % filler) were conditioned at various relative humidities (RHs) (35, 57, 75, and 99% RH). After conditioning at 99% RH, the pure TPS films exhibited higher affinity toward water than the nanocomposites. Differential scanning calorimetric measurements showed that, due to retrogradation effects, the melting enthalpies of the films increased with increasing RH. Dynamic mechanical analysis revealed that the mechanical properties in the linear range strongly depend on both the humidity conditions and the concentration of the filler. The results also show that La(OH)₃ nanoparticles are good reinforcement for TPS films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dissolved Silicon and Its Origin in Belgian Beers—A Multivariate Analysis

Beer is a quintessential part of Belgian heritage. We performed a detailed analysis of factors controlling Si content in Belgian beers as a case study to coincide with the 2011 IBiS meeting in Antwerp (Belgium). Beer is one of the richest dietary sources of Si. Three decades of research have yielded evidence of a role for Si in human physiology: it plays an essential role in bone mineral density and reduces the biological availability of aluminium. We analysed 119 Belgian beers: highest dissolved Si concentrations were found in high fermentation, traditionally brewed ales. Concentrations ranged between 214 and 2,071 μmol L^???1. This is probably due to the complexity and length of the brewing procedure: longer, more complicated processing and presence of brewing sediment in the bottle allows more Si to dissolve out of the base products like hop, barley or even rice. As a side effect of fermentation, alcohol content was related to Si content.