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81.
82.
High-density polyethylene (HDPE)/clay nanocomposites were prepared via water-assisted and conventional melt blending. The influence of exfoliated/intercalated domains on crystallinity of nanocomposites was then investigated. X-ray diffraction and electron microscopy evidenced for enhanced intercalation and partial exfoliation of clay platelets pursuing rheological measurements. The methane permeability of water-injected nanocomposites was lower compared to melt-blended specimens implying the influence of intercalated domains. A theoretical/experimental analysis was performed to roughly determine the lamellar thickness distribution of the crystalline regions. Contribution of clay platelets to crystallization mechanisms was indicative of clay impact as heterogeneous nucleating agent, whereas mechanical properties were dependent on interface situation.  相似文献   
83.
Acute transplant rejection is the leading cause of graft loss in the first months after kidney transplantation. Lipoxygenase products mediate pro- and anti-inflammatory actions and thus we aimed to correlate the histological reports of renal transplant biopsies with urinary lipoxygenase products concentrations to evaluate their role as a diagnostic marker. This study included a total of 34 kidney transplant recipients: 17 with an acute transplant rejection and 17 controls. LTE4, LTB4, 12-HETE and 15-HETE concentrations were measured by enzyme immunoassay. Urinary lipoxygenase product concentrations were not significantly changed during an acute allograft rejection. Nevertheless, LTB4 concentrations correlated significantly with the body temperature (P ≤ 0.05) 3 months after transplantation, and 12- and 15-HETE concentrations correlated significantly with renal function (P ≤ 0.05) 2 weeks after transplantation. In conclusion, our data show a correlation for LTB4 with the body temperature 3 months after transplantation and urinary 12- and 15-HETE concentrations correlate positively with elevated serum creatinine concentrations but do not predict acute allograft rejection.  相似文献   
84.
This paper describes a rapid and reliable method for dopamine (DA), ascorbic acid (AA), and uric acid (UA) determination in human urine using a cathodically pretreated poly(1-aminoanthraquinone) (PAAQ)-modified electrode. By applying a simple cathodic pretreatment to the PAAQ electrode well-defined voltammetric peaks for AA, DA, and UA were obtained. The pretreated PAAQ showed good selectivity, sensitivity, and repeatability for measuring AA, DA, and UA with detection limits of 2.50 × 10?5, 3.05 × 10?6, and 1.15 × 10?5 M, respectively. The practical applicability of the modified electrode is illustrated by selective measurements of AA and UA in human urine without any preliminary treatment. Recovery values between 94.8 and 102 % for AA and between 77.8 and 100 % for UA were obtained with a relative standard deviation of 2.74 and 2.98 %, respectively.  相似文献   
85.
Phase inversion is a very flexible technique to obtain membranes with a large sort of morphologies. Membrane properties can vary greatly depending on the kind of polymer system used. Bisphenol A polycarbonate (PC) could be used as a phase inversion membrane base polymer, and presents very good properties. Nevertheless, very little information on membrane preparation using PC and the phase inversion process can be found in the literature. In this work flat‐sheet microporous membranes were obtained by the phase inversion process using the immersion precipitation technique. A new polymer system was studied, consisting of polycarbonate, N‐methyl‐2‐pyrrolidone as solvent, water as the nonsolvent, and an additive. The influence of some parameters on membrane morphology, such as polymer solution composition, exposition time before immersion into the precipitation bath, and the kind of additive was investigated. Precipitation was followed using light transmission experiments and membrane morphology was observed through Scanning Electron Microscopy (SEM). The viscosity and cloud points of all polymer solutions were also determined. The results were related to the studied synthesis parameters, using the basic principles of membrane formation by the phase inversion technique, looking forward to establishing criteria to control the morphology of flat‐sheet membranes using polycarbonate as the base polymer. The results showed that both additives were able to increase pore interconnectivity and even suppress macrovoid formation. The decrease in the miscibility region of the polymer system and increase in mass transfer resistance are found to be the determining factors during polymer solution precipitation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3085–3096, 2002  相似文献   
86.
Silicon nitride bulk ceramics with varying compositions of the grain boundary phase but similar grain sizes were developed, which allows to analyze the influence of the grain boundary chemistry on mechanical properties. Micrographs of the crack path reveal a much weaker interface when the rare-earth element in the grain boundary phase changes from a small to a large rare-earth cation (RE3+). Room temperature measurements of toughness and bending strength show that weaker grain boundaries result in a higher toughness, but in a decreased strength of the bulk material. This investigation demonstrates that the mechanical behavior of silicon nitride can be readily tuned by chemical composition changes of the grain boundary phase, but that a compromise between toughness and strength has to be found when designing the material.  相似文献   
87.
Journal of Applied Electrochemistry - The present work reports the development of screen-printed electrode (SPE) using flexible polyester sheets modified with nanodiamond (ND), Au nanoparticles...  相似文献   
88.
Overexpression of the histone lysine demethylase KDM4A, which regulates H3K9 and H3K36 methylation states, has been related to the pathology of several human cancers. We found that a previously reported hydroxamate‐based histone deacetylase (HDAC) inhibitor (SW55) was also able to weakly inhibit this demethylase with an IC50 value of 25.4 μm . Herein we report the synthesis and biochemical evaluations, with two orthogonal in vitro assays, of a series of derivatives of this lead structure. With extensive chemical modifications on the lead structure, also by exploiting the versatility of the radical arylation with aryldiazonium salts, we were able to increase the potency of the derivatives against KDM4A to the low‐micromolar range and, more importantly, to obtain demethylase selectivity with respect to HDACs. Cell‐permeable derivatives clearly showed a demethylase‐inhibition‐dependent antiproliferative effect against HL‐60 human promyelocytic leukemia cells.  相似文献   
89.
In the present study, the incongruent dissolution of barium from barium titanate (BaTiO3) has been studied as a function of dispersion pH and powder volume fraction for two different BaTiO3 powders. In alkaline dispersions, the barium solubility strongly increases as the pH increases, as suggested by thermodynamic considerations. At pH <7, the barium solubility reaches a plateau, the height of which is dependent on the surface area of the powder and the solids loading of the slip. The BaTiO3 surface is completely depleted of barium in this region.  相似文献   
90.
因热处理时发生畸变,加之精度要求较高,零件热处理后通常都要进行机加工。由于通过机加工修正变形的成本太高,所以应尽可能减小零件的热处理畸变。本文研究结果证明,零件的热处理畸变与其几何形状有关。首先概述使零件几何形状成为畸变倾向重要载体的物理效应。其次,以复杂的汽车零件为例说明零件几何形状影响畸变的程度。最后介绍一种能更有效控制系统畸变的新途径。  相似文献   
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