Micropore-free surface-activated carbon for the analysis of polychlorinated dibenzo-p-dioxins-dibenzofurans and non-ortho-substituted polychlorinated biphenyls in environmental samples

2,3,7,8-Substituted polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and non-ortho-substituted polychlorinated biphenyls (PCBs) account for almost all of the total toxic equivalents (TEQ) in environmental samples. Activated carbon columns are used to fractionate the samples for GC-MS analysis or bioassay. Micropore-free surface-activated carbon is highly selective for PCDD/Fs and non-ortho-PCBs and can improve the conventional activated carbon column clean-up. Along with sulfuric acid-coated diatomaceous earth columns, micropore-free surface-activated carbon provides a rapid, robust, and high-throughput sample preparation method for PCDD/Fs and non-ortho-PCBs analysis.     

Scalar auxiliary variable approach for conservative/dissipative partial differential equations with unbounded energy functionals

BIT Numerical Mathematics - In this paper, we present a novel investigation of the so-called SAV approach, which is a framework to construct linearly implicit geometric numerical integrators for...     

A Structure-Preserving Numerical Method for the Fourth-Order Geometric Evolution Equations for Planar Curves

For fourth-order geometric evolution equations for planar curves with the dissipation of the bending energy, including the Willmore and the Helfrich flows, we consider a numerical approach. In this study, we construct a structure-preserving method based on a discrete variational derivative method. Furthermore, to prevent the vertex concentration that may lead to numerical instability, we discretely introduce Deckelnick’s tangential velocity. Here, a modification term is introduced in the process of adding tangential velocity. This modified term enables the method to reproduce the equations’ properties while preventing vertex concentration. Numerical experiments demonstrate that the proposed approach captures the equations’ properties with high accuracy and avoids the concentration of vertices.     

Measurement of stress distribution in sandwich beams under four-point bending

The bending-stress distributions through thickness in sandwich-composite beams are different from those obtained by conventional composite-beam theory because of the shear effect of the core, especially when the ratio of elastic moduli of face to core (k=E _f /E _c ) is large. Accordingly, the stress distributions in sandwich beams of composite materials with various combinations of face and core materials subjected to four-point bending are analyzed by introducing the multilayer-buitup theory. The bending stiffnesses of face and core, and the relative displacement between both faces are taken into consideration in the analysis. Photoelastic measurements were carried out on model specimens having four differentk-values and the applicable ranges of the two theories are discussed on the basis of the experimental results. It is shown that the experimental-stress distributions in sandwich-composite beams havingk-values larger than 120 can be well explained by the multilayer-builtup theory. The ratio of the coupling moment due to the axial forces in the two faces to the applied total moment, which denotes the sandwich structural efficiency, can be well estimated by the multilayer-builtup theory. The availability of this simple onedimensional theory should be useful in the structural design of sandwich beams with a small-core rigidity.     

Enhanced mass resolution tandem mass spectrometry method for 2,3,7,8-tetrachlorodibenzo-p-dioxin detection with ion trap mass spectrometry using high damping gas pressure

Damping gas flow was optimized for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) determination using ion trap mass spectrometer. A tandem mass spectrometry (MS-MS) method with better than unit-mass resolution (mass width, 0.3 u) was developed at a damping gas flow of 1.5 ml/min and a collision-induced dissociation (CID) voltage of 3.30 V. The relative standard deviation (R.S.D.) at the enhanced resolution was 2.9% in 24 h of consecutive injections. The detection limit was significantly improved because the efficiency of both precursor ion trapping and fragmentation increased with the damping gas flow. Product ion yield was 4.5 times higher and limit of detection was 3.2 times lower than at the default flow (0.3 ml/min and 1.65 V).     

Synthesis of single-walled carbon nanotubes in mesoporous silica film and their field emission property

We have succeeded in direct synthesis of single-walled carbon nanotubes (SWNTs) on a conductive substrate coated with a 3D mesoporous silica film, and observed the field emission. Co catalysts for the growth of SWNTs are deposited on the substrate by electroplating. The particle size of the catalyst is well-controlled inside defined space of the mesoporous silica film. Furthermore, the location of Co particles can be controlled in the mesopores by the electroplating method. Mono-dispersed SWNTs are grown along with the mesopores that are normal to the substrate, because Co particles are deposited at the bottom of the mesopores. It is also found that the mesoporous silica film prevents the aggregation of Co catalysts and the distortion of Au layer as the conductive substrate. The field emission measurement shows that the turn-on field is 4.2 V/μm at 10 μA/cm². The field enhancement factor is about 1500. This approach provides an efficient methodology for fabricating an SWNTs-based field emitters. PACS 73.63.Fg; 78.55.Mb     

Centrifugal concentrator for the substitution of nitrogen blow-down micro-concentration in dioxin/polychlorinated biphenyl sample preparation

A centrifugal concentrator was applied for the substitution of nitrogen blow-down micro-concentration in dioxin/PCB sample preparation. Automation was achieved through this apparatus and resulted in significant improvements in sample preparation productivity, along with excellent reproducibility and recovery rate of dioxin/PCB. Mean recoveries of dioxin congeners were 90-106%, respectively.     

Development and evaluation of novel hydrogel for preventing postoperative pancreatic fistula

Pancreatic fistula is a complication that frequently occurs after pancreatic surgery. Although various attempts have been made to prevent pancreatic fistula after pancreatic surgery, no effective methods have been developed thus far. In this study, to prevent the pancreatic fistula, we attempted to prepare the hydrogels consisting of two types of polyvinyl alcohol (PVAs), Poval® and Exceval® by the freezing–thawing (F/T) method. As the concentration and the number of F/T cycles increased, it was revealed that the swelling degree tended to decrease, and tensile strength tended to increase. Especially, Exceval® formed more robust hydrogels than that of Poval® hydrogel prepared by the same conditions. Furthermore, the release behavior of tartrazine from 10% Exceval® hydrogels differed depending on the number of F/T cycles. It was also revealed that the diffusion pattern of the drug in the hydrogel differed along with the release, and the entire amount of tartrazine in the hydrogel was released by 120 min. As nafamostat mesylate was loaded, in vivo study, Pancreatic enzyme values were obtained after 48 h, which allowed comparison of the preventive effects against pancreatic fistula between the untreated group, the Exceval® hydrogel group, and nafamostat mesylate-containing Exceval®-applied group. Furthermore, there was a significant difference between the untreated group and the hydrogel-applied group. Besides, PVA hydrogels prepared by the F/T method could probably absorb pancreatic enzymes. This study found that Exceval® hydrogel prepared by the F/T method was considered a novel hydrogel formulation to prevent pancreatic fistula.     

Shear-lag effect in CFRP I-beams under three-point bending

Shear-lag effect in CFRP (carbon-fiberreinforced plastic) I-beams is investigated by applying Reissner's method concerning box beams to CFRP I-beams. This modified beam theory (MBT) assumes that the flanges are orthotropic and includes the effect of the shearing rigidity of the web and the deformation of the flanges themselves. The anisotropy of the flanges causes the decrease of the flexural rigidity of I-beams. The decrease, however, is restrained by a preventive action on the shear-lag effect in the flanges with a decrease of the anisotropy ratio due to the selection of fiber orientation. In order to verify this MBT, I-beam structures were fabricated from carbon fiber and epoxy resin using three different lay-up schemes: unidirectional, quasi-isotropic, and a ±45-deg angle-ply. The stiffness and shear-lag effect of these I-beams were measured and compared with results from the composite beam theory and MBT. The theoretical load-deflection curves and the strain distributions agreed well with the corresponding experimental results.