Change in molecular weight distribution by elution of polymers from PVA cast gel

Poly(vinyl alcohol) (PVA) cast gels with high degrees of polymerization and hydrolysis were prepared at room temperature. After sufficient exchange of the outer solvent by fresh pure water, the gel was re-dissolved in pure water at a high temperature. Using this solution, the cast gel was prepared again. This re-dissolution process was repeated again, and a third cast gel was prepared. During each swelling process after each cast-drying process, the amount of elution from the gel was measured and the molecular weight distributions of PVA in the gel as well as in the outer solvent were quantitatively evaluated. The molecular weight distribution of the eluted PVA was found to depend on that of the PVA in the gel; the average molecular weight gradually increased as the re-dissolution process was repeated, while the polydispersity indices of both the PVA from the gel and the eluted PVA decreased.     

Equilibrium of one-pot polymerization of polyimide

One-pot polymerization of polyimide from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) was examined. The equilibrium in the polyimide with water was examined in detail in p-chlorophenol solution during the polymerization. The equilibrium constant was expressed by log K = 1.50 + 1433 (1/T). The polymerization reaction is exothermic. The molecular weight increased with decrease of temperature. © 1996 John Wiley & Sons, Inc.     

Creep recovery of acrylate urethane oligomer/acrylate networks

Creep recovery of acrylate urethane/acrylate networks was investigated as a function of time and temperature. An important outcome was the capacity for superimposition of experimental data obtained at various temperatures. Arrhenius type temperature dependence of the creep recovery was also observed. The master curve obtained did not significantly depend on the measuring mode of creep recovery or the crosslink density, and the response could be approximated by the Bueche theory. The dynamic mechanical properties of the systems were also investigated. Retardation spectrum L obtained from the dynamic mechanical data overlapped with that obtained from the creep recovery data. The activation energy obtained from the temperature dependence of the shift factor a_T also agreed with that obtained from the temperature dependence of the creep recovery. © 1996 John Wiley & Sons, Inc.     

Properties of copolyimides prepared from different tetracarboxylic dianhydrides and diamines

Various copolymides were prepared from two acid dianhydrides (BPDA, 3,3′,4,4′-biphenyl tetracarboxylic dianhydride; PMDA, pyromelitic dianhydride) and two diamines (PPD, p-phenylene diamine; ODA, 4,4′-oxydianiline). The thermal and mechanical properties of these polyimides were examined in detail. By appropriately selecting the ratios of the acid dianhydride component and the diamine component, polyimide films having desirable mechanical and thermal characteristics can be obtained. Further, it was proved that there is a correlation between the properties and the compositions of the copolyimides and that the properties could be estimated from the compositions by the use of multiple regression analysis. © 1996 John Wiley & Sons, Inc.     

新一代超小型DIP-IPM

为了满足空调、洗衣机、冰箱等白色家电对高效、高性能的需要,三菱电机开发了新一代超小型第四代(Ver.4)双列直插封装的智能功率模块(Dual-In-linePackageIntelligentPowerModule,简称DIP-IPM)。本文首先分析了第四代超小型DIP-IPM内部电路的构成和功能,然后详细介绍了第四代DIP-IPM生产过程中的关键技术,包括无铅化、高热传导性绝缘片、chip-to-chip导线直接连接以及ASIC技术,最后与第三代(Ver.3)DIP-IPM进行了比较。     

Rewired Cellular Metabolic Profiles in Response to Metformin under Different Oxygen and Nutrient Conditions

Metformin is a metabolic disruptor, and its efficacy and effects on metabolic profiles under different oxygen and nutrient conditions remain unclear. Therefore, the present study examined the effects of metformin on cell growth, the metabolic activities and consumption of glucose, glutamine, and pyruvate, and the intracellular ratio of nicotinamide adenine dinucleotide (NAD⁺) and reduced nicotinamide adenine dinucleotide (NADH) under normoxic (21% O₂) and hypoxic (1% O₂) conditions. The efficacy of metformin with nutrient removal from culture media was also investigated. The results obtained show that the efficacy of metformin was closely associated with cell types and environmental factors. Acute exposure to metformin had no effect on lactate production from glucose, glutamine, or pyruvate, whereas long-term exposure to metformin increased the consumption of glucose and pyruvate and the production of lactate in the culture media of HeLa and HaCaT cells as well as the metabolic activity of glucose. The NAD⁺/NADH ratio decreased during growth with metformin regardless of its efficacy. Furthermore, the inhibitory effects of metformin were enhanced in all cell lines following the removal of glucose or pyruvate from culture media. Collectively, the present results reveal that metformin efficacy may be regulated by oxygen conditions and nutrient availability, and indicate the potential of the metabolic switch induced by metformin as combinational therapy.     

Mutation Analysis of Radioresistant Early-Stage Cervical Cancer

Radiotherapy is a definitive treatment for early-stage cervical cancer; however, a subset of this disease recurs locally, necessitating establishment of predictive biomarkers and treatment strategies. To address this issue, we performed gene panel-based sequencing of 18 stage IB cervical cancers treated with definitive radiotherapy, including two cases of local recurrence, followed by in vitro and in silico analyses. Simultaneous mutations in KRAS and SMAD4 (KRAS^mt/SMAD4^mt) were detected only in a local recurrence case, indicating potential association of this mutation signature with radioresistance. In isogenic cell-based experiments, a combination of activating KRAS mutation and SMAD4 deficiency led to X-ray resistance, whereas either of these factors alone did not. Analysis of genomic data from 55,308 cancers showed a significant trend toward co-occurrence of mutations in KRAS and SMAD4. Gene Set Enrichment Analysis of the Cancer Cell Line Encyclopedia dataset suggested upregulation of the pathways involved in epithelial mesenchymal transition and inflammatory responses in KRAS^mt/SMAD4^mt cancer cells. Notably, irradiation with therapeutic carbon ions led to robust killing of X-ray-resistant KRAS^mt/SMAD4^mt cancer cells. These data indicate that the KRAS^mt/SMAD4^mt signature is a potential predictor of radioresistance, and that carbon ion radiotherapy is a potential option to treat early-stage cervical cancers with the KRAS^mt/SMAD4^mt signature.     

Direct Observation of Pure Cu and Cu-Ag Anode Passivation in H2SO4-CuSO4 Aqueous Solution by Channel Flow Double Electrode and Optical Microscopy

Metallurgical and Materials Transactions B - The dissolution and passivation of pure Cu and Cu-5 wt pct Ag anodes in H2SO4-CuSO4 electrolyte were investigated by a direct...     

Perfluorinated surfactants in surface, subsurface water and microlayer from Dalian Coastal waters in China

Two predominant perfluorinated compounds (PFCs), Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), in surface water (SW, 0-20 cm), subsurface water (SSW, > 30 cm depth), and sea surface microlayer (SML, 50 microm thickness) were measured from Dalian Coastal waters in China. The SML samples were collected using glass-plate dipping method. Analysis of the PFCs was conducted through solid-phase extraction, followed by LC/MS-SIM. The PFC's concentrations in SW samples were consistent with previously reported data in this region. Significantly higher concentrations of PFCs were found in SML samples than corresponding SSW samples. The enrichment factors (EF = C(SML)/C(SSW)) for PFOS were as high as 24-109 atthree near-shore sites. The concentration in SW was also generally higher than corresponding SSW samples, giving C(SW)/C(SSW) mean ratios of 1.5 and 1.4 for PFOS and PFOA, respectively. This apparent enrichment of PFCs in surface water, especially in the microlayer, has implications for designing measurement techniques, understanding their distributions, and sea spray-mediated transport in the environment.     

Contamination levels of PCDDs, PCDFs and Co-PCBs in commercial baby foods in Japan

To examine dioxin contamination in commercial baby foods in Japan, congener analyses of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) were performed on 102 varieties of baby foods obtained from supermarkets in 2001-2002. The toxic equivalent quantity (TEQ) levels for dioxins in samples ranged from < 0.001 to 0.135 pg-TEQ/g wet weight when undetected or trace levels of congeners were taken as zero. Among 102 samples tested, 26 samples exceeded 0.010 pg-TEQ/g. The highest TEQ value was for "sardine, vegetables" (0.135 pg-TEQ/g), followed by "Japanese radish (daikon), sardine" (0.080 pg-TEQ/g). Thus, dioxins were detected at low levels in baby foods containing animal products such as fishes and/or dairy products.