Iron(III) chelating resins. VI. Stability constants of iron(III)–ligand complexes on insoluble polymeric matrices

A method is presented for the determination of stability constants of iron(III)–ligand complexes on insoluble polymeric matrices based on a competition chelation reaction for iron(III) of the resin with a soluble chelator. Stability constants (K') were calculated for iron(III)–ligand complexes on DFO–Sepharose gel, HMP–Sepharose gel, AHMP–HEMA resin, and AHMP–DMAA resin. In these resins, desferrioxamine B (DFO, hexadentate ligand) or the 3-hydroxy-2methyl-4(1H)-pyridinone (HMP, bidentate ligand) was bound on insoluble polymeric matrices. The average values (log K') were: 26.6 (DFO–Sepharose); 37.9 (HMP–Sepharose); 27.2 (AHMP–HEMA); and 39.9 (AHMP–DMAA). The stability constants of the insoluble iron(III) complexes on the resins were compared with those of the corresponding soluble iron(III) complexes. The effect of immobilization on the constants was discussed, and it was found that a higher hydrophilicity and stability of a resin resulted in an increase of the stability constant, whereas steric hindrance decreased the stability constant. © 1995 John Wiley & Sons, Inc.     

NORMAL MODES OF FLUID-STRUCTURE INTERACTION IN INTERNAL FLOWS

As an important cornerstone, the methodology of normal modal analysis plays a quite important role in dynamic analyses of linear vibrating systems, and makes much easy to access an understanding of frequency-domain characteristics of the systems. However, most reported work on fluid-structure interaction (FSI) in liquid-filled pipes has been directly carried out in the time domain. When needed, information in the frequency domain has been deduced by the discrete Fourier transforms. In this paper, an analysis is undertaken directly to get modal information of FSI in internal flows and has the advantage of enabling dispersive and dissipative terms to be included in a fully coupled manner. The development used herein highlights common features of the analysis in the frequency domain. The method is validated by comparison with an exact analytical solution, with the results obtained by the discrete Fourier transform from an analysis using the method of characteristics and by comparison with measured data fr     

Substructure-based virtual screening for adenosine A2A receptor ligands

A virtual ligand-based screening approach was designed and evaluated for the discovery of new A(2A) adenosine receptor (AR) ligands. For comparison and evaluation, the procedures from a recently published virtual screening study that used the A(2A) AR X-ray crystal structure for the target-based discovery of new A(2A) ligands were largely followed. Several screening models were constructed by deriving the distinguishing structural features from selected sets of A(2A) AR antagonists, so-called frequent substructure mining. The best model in statistical terms was subsequently applied to large-scale virtual screens of a commercial vendor library. This resulted in the selection of 36 candidates for acquisition and testing. Of the selected candidates, eight compounds significantly inhibited radioligand binding at A(2A) AR (>30%) at 10 μM, corresponding to a "hit rate" of 22%. This hit rate is quite similar to that of the referenced target-based virtual screening study, while both approaches yield new, non-overlapping sets of ligands.     

Toward implantable devices for angle-sensitive,lens-less,multifluorescent, single-photon lifetime imaging in the brain using Fabry–Perot and absorptive color filters

Implantable image sensors have the potential to revolutionize neuroscience. Due to their small form factor requirements;however, conventional filters and optics...     

The Global Biogeochemical Silicon Cycle

Silicon is one of the most important elements in the current age of the anthropocene. It has numerous industrial applications, and supports a high-tech multi-billion Euro industry. Silicon has a fascinating biological and geological cycle, interacting with other globally important biogeochemical cycles. In this review, we bring together both biological and geological aspects of the silicon cycle to provide a general, comprehensive review of the cycling of silicon in the environment. We hope this review will provide inspiration for researchers to study this fascinating element, as well as providing a background environmental context to those interested in silicon.     

Optimization of Sandwich Composites Fuselages Under Flight Loads

The sandwich composites fuselages appear to be a promising choice for the future aircrafts because of their structural efficiency and functional integration advantages. However, the design of sandwich composites is more complex than other structures because of many involved variables. In this paper, the fuselage is designed as a sandwich composites cylinder, and its structural optimization using the finite element method (FEM) is outlined to obtain the minimum weight. The constraints include structural stability and the composites failure criteria. In order to get a verification baseline for the FEM analysis, the stability of sandwich structures is studied and the optimal design is performed based on the analytical formulae. Then, the predicted buckling loads and the optimization results obtained from a FEM model are compared with that from the analytical formulas, and a good agreement is achieved. A detailed parametric optimal design for the sandwich composites cylinder is conducted. The optimization method used here includes two steps: the minimization of the layer thickness followed by tailoring of the fiber orientation. The factors comprise layer number, fiber orientation, core thickness, frame dimension and spacing. Results show that the two-step optimization is an effective method for the sandwich composites and the foam sandwich cylinder with core thickness of 5 mm and frame pitch of 0.5 m exhibits the minimum weight.     

Estimation of a human capital model of migration

"The main deficiency of the current literature on the determinants of migration is the large gap between theoretical analyses and empirical applications. If no direct link is established between a theoretical model and its empirical specification, the empirical results cannot validate the model. This paper develops a version of the human capital model of migration which permits empirical specification. The human capital model presented incorporates two important concepts from migration theory: (1) an index of characteristics that uniquely define a specific location; and (2) location-specific human capital. The empirical model is estimated with a data set consisting of a number of cases from the Michigan [United States] Panel Study of Income Dynamics (PSID) survey."     

A Dynamic Risk Assessment Methodology for Maintenance Decision Support

The failure mode and effect analysis (FMEA) is a widely applied technique for prioritizing equipment failures in the maintenance decision‐making domain. Recent improvements on the FMEA have largely focussed on addressing the shortcomings of the conventional FMEA of which the risk priority number is incorporated as a measure for prioritizing failure modes. In this regard, considerable research effort has been directed towards addressing uncertainties associated with the risk priority number metrics, that is occurrence, severity and detection. Despite these improvements, assigning these metrics remains largely subjective and mostly relies on expert elicitations, more so in instances where empirical data are sparse. Moreover, the FMEA results remain static and are seldom updated with the availability of new failure information. In this paper, a dynamic risk assessment methodology is proposed and based on the hierarchical Bayes theory. In the methodology, posterior distribution functions are derived for risk metrics associated with equipment failure of which the posterior function combines both prior functions elicited from experts and observed evidences based on empirical data. Thereafter, the posterior functions are incorporated as input to a Monte Carlo simulation model from which the expected cost of failure is generated and failure modes prioritized on this basis. A decision scheme for selecting appropriate maintenance strategy is proposed, and its applicability is demonstrated in the case study of thermal power plant equipment failures. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal and thermomechanical properties of poly(butylene succinate) nanocomposites

This article describes the thermal and thermomechanical properties of poly(butylene succinate) (PBS) and its nanocomposites. PBS nanocomposites with three different weight ratios of organically modified synthetic fluorine mica (OMSFM) have been prepared by melt-mixing in a batch mixer at 140 degrees C. The structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD) analyses and transmission electron microscopy (TEM) observations that reveal the homogeneous dispersion of the intercalated silicate layers into the PBS matrix. The thermal properties of pure PBS and the nanocomposite samples were studied by both conventional and temperature modulated differential scanning calorimetry (DSC) analyses, which show multiple melting behavior of the PBS matrix. The investigation of the thermomechanical properties was performed by dynamic mechanical analysis. Results reveal significant improvement in the storage modulus of neat PBS upon addition of OMSFM. The tensile modulus of neat PBS is also increased substantially with the addition of OMSFM, however, the strength at yield and elongation at break of neat PBS systematically decreases with the loading of OMSFM. The thermal stability of the nanocomposites compared to that of the pure polymer sample was examined under both pyrolytic and thermo-oxidative environments. It is shown that the thermal stability of PBS is increased moderately in the presence of 3 wt% of OMSFM, but there is no significant effect on further silicate loading in the oxidative environment. In the nitrogen environment, however, the thermal stability systematically decreases with increasing clay loading.