Two‐dimensional anisotropic Cartesian mesh adaptation for the compressible Euler equations

Simulating transient compressible flows involving shock waves presents challenges to the CFD practitioner in terms of the mesh quality required to resolve discontinuities and prevent smearing. This paper discusses a novel two‐dimensional Cartesian anisotropic mesh adaptation technique implemented for transient compressible flow. This technique, originally developed for laminar incompressible flow, is efficient because it refines and coarsens cells using criteria that consider the solution in each of the cardinal directions separately. In this paper, the method will be applied to compressible flow. The procedure shows promise in its ability to deliver good quality solutions while achieving computational savings. Transient shock wave diffraction over a backward step and shock reflection over a forward step are considered as test cases because they demonstrate that the quality of the solution can be maintained as the mesh is refined and coarsened in time. The data structure is explained in relation to the computational mesh, and the object‐oriented design and implementation of the code is presented. Refinement and coarsening algorithms are outlined. Computational savings over uniform and isotropic mesh approaches are shown to be significant. Copyright © 2004 John Wiley & Sons, Ltd.     

Risk aversion and optimal forest replanting: A stochastic efficiency study

A new stochastic efficiency analysis approach, called stochastic efficiency with respect to a function (SERF), is applied to analyse optimal tree replanting on an area of recently harvested forest land. SERF partitions a set of risky alternative tree replanting strategies in terms of certainty equivalents (CEs) for a specified range of attitudes to risk. Both the entailed risk and the forest owner’s risk aversion are taken into account. The forest owner’s degree of risk aversion affects both the optimal tree replacement strategy and the reinvestment decision. The degree of risk aversion also needs to be taken into account when designing policy measures to affect forest investment.     

一个机器服务模型的可靠性分析

本文讨论了由Ｎ个同型部件和一个服务设备组成的机器服务模型，在服务设备绝对可靠，或服务设备具有指数寿命，修理工对其修理的时间为ＰＨ分布，这两种情况下求得了系统的平稳概率分布，从而求得机器系统和服务设备的稳态可靠性指标，并证明了它们的首次失效时间均服从ＰＨ分布，服务设备和修理工的忙期亦服从ＰＨ分布．     

Direct method for surface silyl functionalization of mesoporous silica

A direct method of surface silyl modification and simultaneous surfactant removal of mesoporous silica is investigated in its physicochemical details. Twelve different silanes of various functionalities are studied. The method employs an alcohol solution of silanes to allow the simultaneous surfactant/silyl exchange process, which results in a more uniform monolayer coverage of the surface and a higher amount of surface attachments of silane. We vary the solution concentration of silanes to study the effect on loadings. It is found that the variation of the surface loading of the silyl group follows a Langmuir adsorption model closely. The method gives one a well-controlled monolayer coverage of the surface. The loadings are determined by the exchange equilibrium. Fittings of the loading data to Langmuir adsorption isotherms give one the adsorption equilibrium constants and maximum surface loadings. We categorize the silanes into three different groups according to the values of the equilibrium constants and discuss them with respect to molecular structures. We also report on the extensive characterizations of the surface-functionalized mesoporous materials, such as nitrogen adsorptions, X-ray diffraction, 29Si magic-angle spinning NMR, 13C magic-angle spinning NMR, and IR spectroscopy. The method provides one with a convenient and highly controllable approach to the surface functionalization of mesoporous silica.     

Identification and quantification of tamoxifen and four metabolites in serum by liquid chromatography-tandem mass spectrometry

We have developed a method for the determination of tamoxifen (tam) and its metabolites 4-hydroxytamoxifen (4OHtam), N-demethyltamoxifen (NDtam), N-dedimethyltamoxifen (NDDtam), tamoxifen-N-oxide (tamNox), and 4-hydroxy-N-demethyltamoxifen (4OHNDtam) in 50 microl human serum. Serum proteins were precipitated with acetonitrile. Deuterated-tamoxifen (D5 tam) was added as internal standard. Sample supernatant was injected into an on-line reversed-phase extraction column coupled with a C18 analytical column and analytes were detected by tandem mass spectrometry. The lower limits of quantification were 0.25 ng/mL for 4OHtam, NDtam and tam, 1.0 ng/mL for NDDtam and tamNox. Ranges of within- and between-day variation were 2.9-15.4% and 4.4-12.9%, respectively.     

Chemical Profile and Antioxidant Capacity of Propolis from Tetragonula,Lepidotrigona, Lisotrigona and Homotrigona Stingless Bee Species in Vietnam

The present study aimed to analyze and compare the chemical profile and antioxidant capacity of propolis from different bee species and different regions. The chemical profiles of propolis from six stingless bee species (Tetragonula iridipennis, T. laeviceps, Lepidotrigona terminata, L. ventralis, Lisotrigona carpenteri and Homotrigona apicalis) collected from a total of eight locations in Vietnam were investigated by gas chromatography–mass spectrometry (GC-MS). More than 70 compounds were identified, amongst which phenolic lipids (cardanols, resorcinols and anacardic acids), aromatic acids, triterpenes and xanthones. Taxonomic markers for Mangifera indica (phenolic lipids and cycloartane triterpenes) were detected in propolis from bees of the genera Tetragonula and Lepidotrigona, although in different amounts, whereas propolis from H. apicalis was characterized by triterpenes of the amyrine type, typical of dipterocarp trees. A clear discrimination between both groups was observed by principal component analysis (PCA) and partial least squares–discriminant analysis (PLS-DA). Propolis from Tetragonula and Lepidotrigona spp. and from Lisotrigona carpenteri, which is rich in xanthones, possesses higher radical scavenging and ferric-reducing capacity than that from H. apicalis. Propolis produced by all six stingless bee species in Vietnam was analyzed for the first time. In addition, this is the first report on L. carpenteri propolis.     

New Benzil and Isoflavone Derivatives with Cytotoxic and NO Production Inhibitory Activities from Placolobium vietnamense

The phytochemical investigation of Placolobium vietnamense stems led to the isolation of a new isoflavone derivative (1) and three new benzil derivatives (2–4), together with four known pyranoisoflavones (5–8). The structures of all isolated compounds were determined on the basis of extensive spectroscopic analyses, including NMR and HRMS spectral data, as well as comparison of their spectroscopic data with those reported in the literature. The cytotoxicity of all isolated compounds was assessed against the human liver hepatocellular carcinoma (Hep G2) cell line, and compound 1 displayed the most significant cytotoxicity with an IC₅₀ value of 8.0 μM. Furthermore, all isolated compounds were also tested for their inhibitory activity against NO production in RAW 264.7 macrophages. Of these, compound 1 exhibited the strongest inhibitory efficacy against the LPS-induced NO production with the IC₅₀ value of 13.7 μM.     

New Flavonoid Derivatives from Melodorum fruticosum and Their α-Glucosidase Inhibitory and Cytotoxic Activities

Three new flavonoid derivatives, melodorones A–C (1–3), together with four known compounds, tectochrysin (4), chrysin (5), onysilin (6), and pinocembrin (7), were isolated from the stem bark of Melodorum fruticosum. Their structures were determined on the basis of extensive spectroscopic methods, including NMR and HRESIMS, and by comparison with the literature. Compounds 1–7 were evaluated for their in vitro α-glucosidase inhibition and cytotoxicity against KB, Hep G2, and MCF7 cell lines. Among them, compound 1 exhibited the best activity against α-glucosidase and was superior to the positive control with an IC₅₀ value of 2.59 μM. On the other hand, compound 1 showed moderate cytotoxicity toward KB, Hep G2, and MCF7 cell lines with the IC₅₀ values of 23.5, 19.8, and 23.7 μM, respectively. These findings provided new evidence that the stem bark of M. fruticosum is a source of bioactive flavonoid derivatives that are highly valuable for medicinal development.     

Effect of Indole‐3‐Acetic Acid Analogs on the Differentiation of HL‐60 Cells

In continuing search for novel cell differentiation agents, a series of derivatives of indole‐3‐acetic acid and indole‐3‐carboxylic acid were prepared and tested against HL‐60 cells for their differentiation and antiproliferation activities. Among them, N‐ethyl‐1‐benzylindole‐3‐carboxamide ( 14 ) was the most potent, whereas N‐methyl 1‐benzylindole‐3‐acetamide ( 5 ) and N‐methyl 1‐benzylindole‐3‐carboxamide ( 13 ) synergistically potentiated with all‐trans‐retinoic acid to induce cell differentiation as well as antiproliferation. Our results indicate that these compounds are effective cell differentiation and antiproliferation agents in combination with retinoic acid.