Oxidation behaviour and strength of B4C-30 wt% SiC composite materials

The oxidation behaviour and the effect of oxidation on the room-temperature flexural strength of B₄C-30 wt% SiC composite material were investigated. The weight changes of the samples exposed to air at temperatures between 500 and 1000 °C were continuously monitored with a microbalance. At temperatures below 800 °C, the weight change of the specimen was negligible. As the temperature was increased to 800 °C, parabolic weight gain was observed. The rate of the weight gain increased with exposure temperature. The oxidation product formed on the surface was found to be a crystalline boric oxide (B₂O₃) by X-ray analyses. The oxide layer was severely cracked due to the thermal expansion mismatch between the oxide layer and the substrate. However, the room-temperature flexural strength was increased when the samples were exposed at temperature between 700 and 900 °C, apparently due to the blunting of strength-limiting defects at the surface. When the temperature was higher than 1000 °C, a severe reduction in strength was observed. The reliability of the composite material was also improved significantly by such exposures.     

A spectral domain method for multiple scattering in discrete randommedia

In an earlier paper (see ibid., vol.36, p.1114-28, 1988) a spectral-domain method was developed for analyzing multiply scattered scalar wavefields propagating in continuous random media. This method is extended to accommodate vector wavefields propagating in discrete random media. The two-dimensional Fourier spectra of vector wavefields propagating in the forward and backward directions are characterized by a pair of coupled first-order differential equations. Dyadic scattering functions characterize the local interaction of the wavefields with the random medium. The results are restricted to sparse distributions whereby the dyadic scattering functions are easily computed. The first- and second-order moments of the vector wavefields can be computed by invoking an assumption essentially equivalent to the Markov approximation as it is applied to scalar wavefields propagating in continuous random media. A complete solution for the coherent wavefield is derived and compared to known results. The results are essentially equivalent to those obtained by using the effective field approximation     

The picture superiority effect in categorization: Visual or semantic?

Two experiments are reported whose aim was to replicate and generalize the results presented by J. G. Snodgrass and B. McCullough (1986) on the effect of visual similarity in the categorization process. For pictures, Snodgrass and McCullough's results were replicated because Ss took longer to discriminate elements from 2 categories when they were visually similar than when they were visually dissimilar. However, unlike Snodgrass and McCullough, an analogous increase was also observed for word stimuli. The pattern of results obtained here can be explained most parsimoniously with reference to the effect of semantic similarity, or semantic and visual relatedness, rather than to visual similarity alone. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gastric emptying after gastric interposition for esophageal carcinoma: comparison between the anterior and posterior mediastinal approaches

BACKGROUND/AIMS: Close observation and evaluation of the function of the transposed stomach after esophagectomy is essential. The present study uses the sulfamethizole capsule meal test to evaluate differences in gastric emptying between the anterior and posterior mediastinal approaches in patients undergoing esophagectomy. METHODOLOGY: Thirty-eight patients who underwent the esophagectomy and esophagogastrostomy for esophageal cancer were randomly divided into 2 groups: Group 1: anterior mediastinal approach, and Group 2: posterior mediastinal approach. Gastric emptying was studied using the sulfamethizole capsule meal test. Patients received sulfamethizole food capsules, 65 g of bread, and 150 ml of water. Plasma sulfamethizole levels were determined by high performance liquid chromatography (HPLC). RESULTS: Gastric emptying in both groups was significantly accelerated compared to healthy volunteers. Gastric emptying did not differ significantly between groups 1 and 2. CONCLUSIONS: The present data show that the sulfamethizole capsule meal test is an effective means of evaluating the emptying of the transposed stomach. Furthermore, when the stomach is used as an esophageal substitute following esophagectomy, gastric emptying does not differ according to the access route.     

Insights into Polymerization of Vegetable Oil: Oligomerization of Oleic Acid

Viscous gel-like species form in vegetable oils during frying. After fatty acid formation, thermal oxidation of unsaturated chains causes polymerization. Heat treatment of oleic acid was employed to produce and identify the initial polymerization products. Spectroscopic studies revealed that heating oleic acid (210 °C, open to air) causes the formation of oligomers cross-linked by ester groups. The absence of esters, before thermal treatment, facilitated observation of cross-links (ester groups) that propagate to produce heavier insoluble products.     

Aging effect of atmospheric pressure plasma jet treated polycaprolactone polymer solutions on electrospinning properties

In previous work, an atmospheric pressure plasma jet was applied to successfully improve the electrospinnability of poly-ε-caprolactone (PCL) which enabled the fabrication of beadless nanofibers. In this paper, we report the aging effect of the plasma treatment to evaluate the robustness of the developed process. For this purpose, plasma-treated PCL polymer solutions with different exposure time were stored for 1 and 8 days and the aged solutions were analyzed in terms of conductivity, viscosity, surface tension, pH, and polymer molecular weight. During storage, the surface tension and acidity of the plasma-treated solutions were maintained constant. However, the viscosity was found to be significantly lower after 8 days which was attributed to PCL degradation. Electrospinning of all stored PCL solutions resulted in the generation of beadless PCL nanofibers. The plasma treatment effects were thus found to be highly stable over time and capable of producing high-quality PCL nanofibers up to 8 days. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48914.     

Aroyl-pyrrolyl hydroxyamides: influence of pyrrole C4-phenylacetyl substitution on histone deacetylase inhibition

The novel aroyl-pyrrolyl hydroxyamides 4 a-a' are analogues of the lead compound 3-(1-methyl-4-phenylacetyl-1H-pyrrol-2-yl)-N-hydroxy-2-propenamide (2) and are active as HDAC inhibitors. The benzene ring of 2 was substituted with a wide range of electron-donating and electron-withdrawing groups, and the effect was evaluated on three HDACs from maize, namely HD2, HD1-B (a class I HDAC), and HD1-A (a class II HDAC). Inhibition studies show that the benzene 3' and, to a lesser extent, 4' positions of 2 were the most suitable for the introduction of substituents, with the 3'-chloro (in 4 b) and the 3'-methyl (in 4 k) derivatives being the most potent compounds, reaching the same activity as SAHA. Inhibition data for 4 b,k against mouse HDAC1 were consistent with those observed in the maize enzyme. The substituent insertion on the benzene ring of 2 (compounds 4 a-a') abated the slight (3-fold) selectivity for class II HDACs displayed by 2. Compound 4 b showed interesting, dose-dependent antiproliferative and cytodifferentiation properties against human acute promyelocytic leukemia HL-60 cells.     

Synthesis and Biological Studies of Pyrazolyl‐Diamine PtII Complexes Containing Polyaromatic DNA‐Binding Groups

New [PtCl(pz*NN)]ⁿ⁺ complexes anchored by pyrazolyl‐diamine (pz*NN) ligands incorporating anthracenyl or acridine orange DNA‐binding groups have been synthesized so as to obtain compounds that would display synergistic effects between platination and intercalation of DNA. Study of their interaction with supercoiled DNA indicated that the anthracenyl‐containing complex L²Pt displays a covalent type of binding, whereas the acridine orange counterpart L³Pt shows a combination of intercalative and covalent binding modes with a strong contribution from the former. L²Pt showed a very strong cytotoxic effect on ovarian carcinoma cell lines A2780 and A2780cisR, which are, respectively, sensitive to and resistant to cisplatin. In these cell lines, L²Pt is nine to 27 times more cytotoxic than cisplatin. In the sensitive cell line, L³Pt showed a cytotoxic activity similar to that of cisplatin, but like L²Pt was able significantly to overcome cisplatin cross‐resistance. Cell‐uptake studies showed that L²Pt accumulates preferentially in the cytoplasm, whereas L³Pt reaches the cell nucleus more easily, as clearly visualized by time‐lapse confocal imaging of live A2870 cells. Altogether, these findings seem to indicate that interaction with biological targets other than DNA might be involved in the mechanism of action of L²Pt because this compound, despite having a weaker ability to target the cell nucleus than L³Pt , as well as an inferior DNA affinity, is nevertheless more cytotoxic. Furthermore, ultrastructural studies of A2870 cells exposed to L²Pt and L³Pt revealed that these complexes induce different alterations in cell morphology, thus indicating the involvement of different modes of action in cell death.     

Ti-doped indium tin oxide thin films for transparent field-effect transistors: control of charge-carrier density and crystalline structure

Indium tin oxide (ITO) films are representative transparent conducting oxide media for organic light-emitting diodes, liquid crystal displays, and solar cell applications. Extending the utility of ITO films from passive electrodes to active channel layers in transparent field-effect transistors (FETs), however, has been largely limited because of the materials' high carrier density (>1 × 10(20) cm(-3)), wide band gap, and polycrystalline structure. Here, we demonstrate that control over the cation composition in ITO-based oxide films via solid doping of titanium (Ti) can optimize the carrier concentration and suppress film crystallization. On 120 nm thick SiO(2)/Mo (200 nm)/glass substrates, transparent n-type FETs prepared with 4 at % Ti-doped ITO films and fabricated via the cosputtering of ITO and TiO(2) exhibited high electron mobilities of 13.4 cm(2) V(-1) s(-1), a low subthreshold gate swing of 0.25 V decade(-1), and a high I(on/)I(off) ratio of >1 × 10(8).     

Sulfated Hyaluronan Binds to Heparanase and Blocks Its Enzymatic and Cellular Actions in Carcinoma Cells

We examined whether sulfated hyaluronan exerts inhibitory effects on enzymatic and biological actions of heparanase, a sole endo-beta-glucuronidase implicated in cancer malignancy and inflammation. Degradation of heparan sulfate by human and mouse heparanase was inhibited by sulfated hyaluronan. In particular, high-sulfated hyaluronan modified with approximately 2.5 sulfate groups per disaccharide unit effectively inhibited the enzymatic activity at a lower concentration than heparin. Human and mouse heparanase bound to immobilized sulfated hyaluronan. Invasion of heparanase-positive colon-26 cells and 4T1 cells under 3D culture conditions was significantly suppressed in the presence of high-sulfated hyaluronan. Heparanase-induced release of CCL2 from colon-26 cells was suppressed in the presence of sulfated hyaluronan via blocking of cell surface binding and subsequent intracellular NF-κB-dependent signaling. The inhibitory effect of sulfated hyaluronan is likely due to competitive binding to the heparanase molecule, which antagonizes the heparanase-substrate interaction. Fragment molecular orbital calculation revealed a strong binding of sulfated hyaluronan tetrasaccharide to the heparanase molecule based on electrostatic interactions, particularly characterized by interactions of (−1)- and (−2)-positioned sulfated sugar residues with basic amino acid residues composing the heparin-binding domain-1 of heparanase. These results propose a relevance for sulfated hyaluronan in the blocking of heparanase-mediated enzymatic and cellular actions.