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91.
Takeshi Suwa Terutaka Watanabe Jiro Okamoto Sueo Machi 《Journal of polymer science. Part A, Polymer chemistry》1979,17(1):129-138
Simultaneous formation of hydrofluoric acid (HF) in the radiation-induced polymerization of tetrafluoroethylene (TFE) was investigated. HF concentration in PTFE latex was determined mainly by conductometric titration with 0.01 and 0.001N NaOH. The amount of HF formed is almost independent of agitation speed and the amount of n-hexadecane added and is maximal at ca. 70°C corresponding to the rate of polymerization. The rate of HF formation increases with the initial pressure of TFE monomer and dose rate and decreases with polymerization or TFE consumption. This fact suggests that HF is formed mainly by TFE reactions and not by the degradation of PTFE. The mechanism of HF formation in this reaction system in the absence of oxygen is shown in the following two schemes: scheme I is the reaction of TFE with primary radicals (OH·, H·, e) from the radiolysis of water; scheme II is the reaction of water with the species from the radiolysis of TFE. On the assumption that HF is formed only according to scheme I, the G value of HF formation G(HF)calc can be calculated as 11.25. All observed G values G(HF)obs are larger than G(HF)calc. When the polymerization is carried out at 20 kg/cm2 under various dose rates, G(HF)obs increases with the dose rate. When the polymerization is carried out at 3.0 × 104 rad/hr under various pressures, G(HF)obs decreases with the decrease in pressure from 20 to 2 kg/cm2 and is fairly close to G(HG)calc at 2 kg/cm2. This indicates that HF formation is due mainly to scheme II at high pressure (in the presence of enough TFE) and to scheme I as the pressure is lowered. 相似文献
92.
Kana Kobayashi-Taguchi Takashi Saitou Yoshiaki Kamei Akari Murakami Kanako Nishiyama Reina Aoki Erina Kusakabe Haruna Noda Michiko Yamashita Riko Kitazawa Takeshi Imamura Yasutsugu Takada 《Molecules (Basel, Switzerland)》2022,27(10)
Fibroadenomas (FAs) and phyllodes tumors (PTs) are major benign breast tumors, pathologically classified as fibroepithelial tumors. Although the clinical management of PTs differs from FAs, distinction by core needle biopsy diagnoses is still challenging. Here, a combined technique of label-free imaging with multi-photon microscopy and artificial intelligence was applied to detect quantitative signatures that differentiate fibroepithelial lesions. Multi-photon excited autofluorescence and second harmonic generation (SHG) signals were detected in tissue sections. A pixel-wise semantic segmentation method using a deep learning framework was used to separate epithelial and stromal regions automatically. The epithelial to stromal area ratio and the collagen SHG signal strength were investigated for their ability to distinguish fibroepithelial lesions. An image segmentation analysis with a pixel-wise semantic segmentation framework using a deep convolutional neural network showed the accurate separation of epithelial and stromal regions. A further investigation, to determine if scoring the epithelial to stromal area ratio and the SHG signal strength within the stromal area could be a marker for differentiating fibroepithelial tumors, showed accurate classification. Therefore, molecular and morphological changes, detected through the assistance of computational and label-free multi-photon imaging techniques, enable us to propose quantitative signatures for epithelial and stromal alterations in breast tissues. 相似文献
93.
94.
Keiichiro Shiraga Yuichi Ogawa Shojiro Kikuchi Masayuki Amagai Takeshi Matsui 《Molecules (Basel, Switzerland)》2022,27(9)
While bulk water and hydration water coexist in cells to support the expression of biological macromolecules, how the dynamics of water molecules, which have long been only a minor role in molecular biology research, relate to changes in cellular states such as cell death has hardly been explored so far due to the lack of evaluation techniques. In this study, we developed a high-precision measurement system that can discriminate bulk water content changes of ±0.02% (0.2 mg/cm3) with single-cell-level spatial resolution based on a near-field CMOS dielectric sensor operating at 65 GHz. We applied this system to evaluate the temporal changes in the bulk water content during the cell death process of keratinocytes, called corneoptosis, using isolated SG1 (first layer of stratum granulosum) cells in vitro. A significant irreversible increase in the bulk water content was observed approximately 1 h before membrane disruption during corneoptosis, which starts with cytoplasmic high Ca2+ signal. These findings suggest that the calcium flux may have a role in triggering the increase in the bulk water content in SG1 cells. Thus, our near-field CMOS dielectric sensor provides a valuable tool to dissect the involvement of water molecules in the various events that occur in the cell. 相似文献
95.
Takeshi Nishii Fumiaki Miyamae Makoto Yoshizuka Hiroto Kaku Mitsuyo Horikawa Makoto Inai Tetsuto Tsunoda 《Tetrahedron: Asymmetry》2012,23(10):739-741
Excess lithium hexamethyldisilazide (LHMDS) with LiCl prompted the asymmetric aza-Claisen rearrangement of carboxamide and retarded the decomposition of its amide enolate. The addition of these two reagents was a key step that led to the total synthesis of (+)-α-cuparenone with a stereogenic quaternary center. 相似文献
96.
97.
Green organogelators with a sulfide linkage and free amino groups were synthesized via phase transfer catalysis using a N-benzylcinchonidinium bromide catalyst. Their self-assemblies in various common solvents were examined. These compounds exhibit high gelation ability especially in aromatic and highly polar solvents with a low critical gelation of 0.1 wt %. The organogels were analyzed by 1H nuclear magnetic resonance (1H NMR) and Fourier transfer-infrared spectroscopies (FT-IR), and their phase transition temperatures were determined by differential scanning calorimetry. The homogeneity of the gel networks was examined by field emission scanning electron microscopy and transmission electron microscopy (TEM). A lamellar structure was also confirmed by X-ray diffraction analysis. The organogels were employed as soft-templates for the in situ generation of stable gold nanoparticles dispersed in the gel matrix, and the resulting GNP dispersions were studied by 1H NMR and UV–vis absorption. Transmission electron microscopy showed that GNPs assemble into a thin membrane-like structure. 相似文献
98.
Takehito Dei Kazuhide Morino Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2012,50(13):2619-2625
Novel copolymers composed of a styrene (St) derivative bearing a vicinal tricarbonyl moiety and various vinyl monomers such as St, methyl methacrylate (MMA), and N‐vinylpyrrolidone (NVP) were synthesized by (1) radical copolymerization of a St derivative with a 1,3‐diketone structure with St, MMA, and NVP and (2) successive oxidation of the resulting copolymers with N‐bromosuccinimide in DMSO to convert their 1,3‐diketone moieties in the side chains into the corresponding vicinal tricarbonyl moieties. Their tricarbonyl moieties were readily hydrated in water‐containing acetone to generate the corresponding copolymers bearing geminal diol structures in the side chains. On the other hand, heating the resulting copolymers bearing the geminal diol structures in vacuo‐enabled successful recovery of the vicinal tricarbonyl moieties to demonstrate the reversible nature of this system. The hydration behavior in powdery state under air atmosphere saturated by water was also investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
99.
Synthesis of methacrylate polymer bearing cyanate groups and its chemoselective reaction with amines
Kousuke Tsuchiya Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2014,52(5):699-706
A novel reactive polymer containing cyanate groups in the side chain was prepared by free radical polymerization of a cyanate‐containing monomer, 2‐(4‐cyanatophenyl)ethyl methacrylate ( 1 ). The monomer 1 and its polymer, poly[2‐(4‐cyanatophenyl)ethyl methacrylate] (PCPMA), were stable under the air for a long period. The copolymerization of 1 and methyl methacrylate provided the corresponding copolymers with various cyanate contents. The availability of the cyanate‐containing polymers as a reactive polymer was investigated. Model reaction using 4‐cyanatotoluene revealed that a cyanate group reacted with aliphatic amines, whereas no reaction occurred in the presence of water, alcohols, and aromatic amines under mild conditions. Post‐functionalization of PCPMA was demonstrated using aliphatic amines or diamines. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 699–706 相似文献
100.
Bungo Ochiai Haruka Kojima Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2014,52(8):1113-1118
Polyhydroxyurethane bearing silicone backbone was prepared by polyaddition of silicone diamines with a bifunctional five‐membered cyclic carbonate prepared from the corresponding diepoxide and CO2. Polymerization in propylene glycol methyl ether acetate proceeded smoothly, and polymers could be obtained in high yields under appropriate conditions. The introduced silicone moieties improved the hydrophobicity and lowered the glass transition temperature keeping thermal stability. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1113–1118 相似文献