Equivalence in Harmonics Between Cycloconverters and Bridge Converters

The similarity between a six-pulse three-phase cycloconverter operating in the circulating current-free mode and a six-pulse three-phase bridge converter is discussed analytically with regard to the rms value and the harmonics of the respective output voltages. A method is presented for calculating the rms voltage of a family of sideband frequencies which are generated in the output voltage of the cycloconverter. The results obtained from the analysis help to predict the amplitudes of subharmonics and beat frequencies with the cycloconverter and are essential for the design of the output filters. Analytical results are verified by comparison with those of experiment and digital computer simulation.     

Synthesis of highly purified and crystallized h-BN using calcium-assisted carbothermal reduction nitridation

Highly purified and crystallized hexagonal boron nitride (h-BN) powder is suitable as thermally conductive filler in resins. To obtain h-BN powder with large particle size, as well as high purity and crystallinity, high-temperature heat treatment over 1800°C in a N₂ gas atmosphere is effective. The carbothermal reduction nitridation (CRN) involves the carbothermic reduction of boric oxide in a N₂ gas atmosphere. In CRN using a CaO promoter, h-BN particles with high crystallinity can be obtained by a simple heat treatment process. CaO prevents the evaporation of boron oxide and aids in h-BN particle growth at high temperatures. However, CaB₆ is formed as byproduct or impurity when CRN using the CaO promoter is performed at temperatures higher than 1800°C. In this study, the relationship between the products and the reaction temperature was clarified via thermodynamic considerations and experimentation. The results clarified the ideal reaction process of CRN using a CaO promoter to obtain highly purified and crystallized h-BN powder.     

A Phenylfurocoumarin Derivative Reverses ABCG2-Mediated Multidrug Resistance In Vitro and In Vivo

The ATP-binding cassette subfamily G member 2 (ABCG2) transporter is involved in the development of multidrug resistance in cancer patients. Many inhibitors of ABCG2 have been reported to enhance the chemosensitivity of cancer cells. However, none of these inhibitors are being used clinically. The aim of this study was to identify novel ABCG2 inhibitors by high-throughput screening of a chemical library. Among the 5812 compounds in the library, 23 compounds were selected in the first screening, using a fluorescent plate reader-based pheophorbide a (PhA) efflux assay. Thereafter, to validate these compounds, a flow cytometry-based PhA efflux assay was performed and 16 compounds were identified as potential inhibitors. A cytotoxic assay was then performed to assess the effect these 16 compounds had on ABCG2-mediated chemosensitivity. We found that the phenylfurocoumarin derivative (R)-9-(3,4-dimethoxyphenyl)-4-((3,3-dimethyloxiran-2-yl)methoxy)-7H-furo [3,2-g]chromen-7-one (PFC) significantly decreased the IC₅₀ of SN-38 in HCT-116/BCRP colon cancer cells. In addition, PFC stimulated ABCG2-mediated ATP hydrolysis, suggesting that this compound interacts with the substrate-binding site of ABCG2. Furthermore, PFC reversed the resistance to irinotecan without causing toxicity in the ABCG2-overexpressing HCT-116/BCRP cell xenograft mouse model. In conclusion, PFC is a novel inhibitor of ABCG2 and has promise as a therapeutic to overcome ABCG2-mediated MDR, to improve the efficiency of cancer chemotherapy.     

Fundamental characteristics of electrostatic wafer chuck withinsulating sealant

The electrostatic wafer chuck is the most preferable handling method in advanced semiconductor manufacture. Even in a vacuum environment, it enables not only the ability to retain a wafer flat, but also to enhance heat transfer through the whole surface area because of firm contact. We have investigated the fundamental characteristics of an electrostatic chuck consisting of a pair of comb-type electrodes and a thin polymer film as a dielectric layer. In order to prevent breakdown between electrodes, the air gap between electrodes was filled with sealing material. The electrostatic force acting on the 4-inch silicon wafer is measured. Several types of insulating sealants and dielectric films were examined. The attractive force increased with the square of the applied voltage in the region of lower applied voltage and gradually saturated at higher voltage. The maximum force obtained in our experiments was approximately 30 N. These experimental results proved the high potentiality in actual use of the electrostatic chuck for silicon wafer handling. However, a few problems have to be overcome. Although the higher electrostatic force can be gained with the thinner dielectric layer, the thin polymer film is easily deformed and torn by tension when the object starts moving     

Effects of thermal treatment on the CO2 sorption of triblockcopolymers derived from polyimide and poly(methylmethacrylate)

ABA‐type triblock copolymers were synthesized using 4,4‐(hexafluoroisopropylidene) diphthalic anhydride‐2,3,5,6‐tetramethyl‐1,4‐phenylenediamine (6FDA‐TeMPD) and poly(methyl methacrylate) (PMMA). The films were characterized by determining the effects of different content ratios and thermal decomposition of PMMA block on CO₂ sorption properties. TGA results showed that a thermal labile block can be completely decomposed under a previously reported thermal condition. SEM results presented that the asperity was micro‐phase separation caused by the PMMA block content rate. Numerous pores with sizes of approximately 10 to 50 nm were detected on Block(28/72) and Block(10/90). The isotherms of all films fitted the dual‐mode sorption model, and CO₂ sorption decreased with increased PMMA content rate. Infinite‐dilution CO₂ solubility depended on the Langmuir's site of each polymer because S_H0/S₀ of PI and Block(PI/PMMA) varied from 0.84 to 0.92 CO₂ affinity was increased by thermal treatment as indicated by the higher b and S₀ values of thermally treated films than those of nontreated films. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42208.     

Co-Application with Tannic Acid Prevents Transdermal Sensitization to Ovalbumin in Mice

Transdermal sensitization to allergens is of great concern as a sensitization route for food allergies. This skin-mediated invasion and sensitization to allergens is involved in skin barrier breakdown and inflammation, followed by the production of several kinds of cytokines. Cytokines such as thymic stromal lymphopoietin and thymus and activation-regulated chemokine are also involved. In this study, we investigated the suppressive effect of tannic acid (TA) on transdermal sensitization using ovalbumin (OVA), a major egg-white allergen. We also analyzed the mechanisms associated with the inhibitory effects of TA. The results showed that the co-application with TA prevents transdermal sensitization to OVA. As possible mechanisms, its anti-inflammatory and astringent effect on the skin and binding ability with the protein were considered. These results indicate that TA could be applied to cosmetics and lotions, which could suppress the transdermal sensitization to allergens.     

Hyperosmotic Stress Induces Phosphorylation of CERT and Enhances Its Tethering throughout the Endoplasmic Reticulum

The ceramide transport protein (CERT) delivers ceramide from the endoplasmic reticulum (ER) to the Golgi apparatus, where ceramide is converted to sphingomyelin (SM). The function of CERT is regulated in two distinct phosphorylation-dependent events: multiple phosphorylations in a serine-repeat motif (SRM) and phosphorylation of serine 315 residue (S315). Pharmacological inhibition of SM biosynthesis results in an increase in SRM-dephosphorylated CERT, which serves as an activated form, and an enhanced phosphorylation of S315, which augments the binding of CERT to ER-resident VAMP-associated protein (VAP), inducing the full activation of CERT to operate at the ER–Golgi membrane contact sites (MCSs). However, it remains unclear whether the two phosphorylation-dependent regulatory events always occur coordinately. Here, we describe that hyperosmotic stress induces S315 phosphorylation without affecting the SRM-phosphorylation state. Under hyperosmotic conditions, the binding of CERT with VAP-A is enhanced in an S315 phosphorylation-dependent manner, and this increased binding occurs throughout the ER rather than restrictedly at the ER–Golgi MCSs. Moreover, we found that de novo synthesis of SM with very-long acyl chains preferentially increases via a CERT-independent mechanism under hyperosmotic-stressed cells, providing an insight into a CERT-independent ceramide transport pathway for de novo synthesis of SM.     

Chemical Fingerprinting of Heat Stress Responses in the Leaves of Common Wheat by Fourier Transform Infrared Spectroscopy

Wheat (Triticum aestivum L.) is known to be negatively affected by heat stress, and its production is threatened by global warming, particularly in arid regions. Thus, efforts to better understand the molecular responses of wheat to heat stress are required. In the present study, Fourier transform infrared (FTIR) spectroscopy, coupled with chemometrics, was applied to develop a protocol that monitors chemical changes in common wheat under heat stress. Wheat plants at the three-leaf stage were subjected to heat stress at a 42 °C daily maximum temperature for 3 days, and this led to delayed growth in comparison to that of the control. Measurement of FTIR spectra and their principal component analysis showed partially overlapping features between heat-stressed and control leaves. In contrast, supervised machine learning through linear discriminant analysis (LDA) of the spectra demonstrated clear discrimination of heat-stressed leaves from the controls. Analysis of LDA loading suggested that several wavenumbers in the fingerprinting region (400–1800 cm⁻¹) contributed significantly to their discrimination. Novel spectrum-based biomarkers were developed using these discriminative wavenumbers that enabled the successful diagnosis of heat-stressed leaves. Overall, these observations demonstrate the versatility of FTIR-based chemical fingerprints for use in heat-stress profiling in wheat.