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排序方式: 共有288条查询结果,搜索用时 78 毫秒
71.
Tooru Kitagawa 《Journal of Macromolecular Science: Physics》2015,54(11):1323-1340
This article is concerned with describing novel structural features of the water vapor coagulated Poly-p-phenylenebenzobisoxazole fiber in comparison with other PBO fibers made with hot liquid water and non-aqueous coagulation. Micro-focus X-ray diffraction was adopted to see the skin-core difference of molecular orientation and crystal size along the fiber-radius direction. Low temperature differential scanning calorimetry (DSC) was performed to elucidate the structural features of never-dried fibers made with the different coagulation techniques. Comparison of micro-focus X-ray diffraction profiles from the different positions on the fiber suggests less anisotropy of preferential orientation for the water vapor coagulated fiber. The fiber made through water vapor coagulation showed a large skin-core difference in molecular orientation with structural inhomogeneity along the fiber axis. 相似文献
72.
High‐performance a‐Si1–xOx:H/c‐Si heterojunction solar cells realized by the a‐Si:H/a‐Si1–xOx:H stack buffer layer 下载免费PDF全文
We used amorphous silicon oxide (a‐Si1–xOx:H) and microcrystalline silicon oxide (µc‐Si1–xOx:H) as buffer layer and p‐type emitter layer, respectively, in n‐type silicon hetero‐junction (SHJ) solar cells. We proposed to insert a thin (2 nm) intrinsic amorphous silicon (a‐Si:H) thin film between the thin (2.5 nm) a‐Si1–xOx:H buffer layer and the p‐layer to form a stack buffer layer of a‐Si:H/a‐Si1–xOx:H. As a result, a high open‐circuit voltage (VOC) and a high fill factor (FF) were obtained at the same time. Finally, a high efficiency of 19.0% (JSC = 33.46 mA/cm2, VOC = 738 mV, FF = 77.0%) was achieved on a 100 μm thick polished wafer using the stack buffer layer.
73.
Akutsu M Koyasu K Atobe J Hosoya N Miyajima K Mitsui M Nakajima A 《The journal of physical chemistry. A》2006,110(44):12073-12076
The geometric and electronic structures of aluminum binary clusters, AlnX (X = Si and P), have been investigated, using mass spectrometry, anion photoelectron spectroscopy, photoionization spectroscopy, and theoretical calculations. Both experimental and theoretical results show that Al12Si has a high ionization energy and low electron affinity and Al12P has a low ionization energy, both with the icosahedral structure having a central Si or P atom, revealing that Al12Si and Al12P exhibit rare-gas-like and alkali superatoms, respectively. Experiments confirmed the possibility that the change in the total number of valence electrons on substitution could produce ionically bound binary superatom complexes, the binary cluster salts Al12P+ F- and Al12B- Cs+. 相似文献
74.
A functional polyrotaxane of a PEI-b-PEG-b-PEI copolymer is synthesized in aqueous solution in a one-pot sequence. To obtain a polyrotaxane with PEG-block-selective inclusion complexes, the solution pH of the polypseudorotaxane is lowered to 4.4 in the presence of 9-anthraldehyde (AN), which triggers the expulsion of the alpha-cyclodextrins (alpha-CDs) from the flank PEI chains. Synthetic strategy of a block-selective polyrotaxane between a PEI-b-PEG-b-PEI copolymer and alpha-cyclodextrins. 相似文献
75.
Shinya Miyajima 《Journal of Computational and Applied Mathematics》2010,234(12):3436-3444
Fast algorithms for enclosing minimal 2-norm solutions in underdetermined systems are proposed. For developing these algorithms, theory for computing error bounds for numerical solutions is established. Moreover techniques for accelerating the enclosure and obtaining smaller error bounds are introduced. Numerical results show the properties of the proposed algorithms. 相似文献
76.
Poly(ethylene glycol) (PEG)‐interlocked hydrogels were prepared by linking the PEG with α‐cyclodextrins (α‐CDs) threaded onto a PEG chain having ester linkages at the terminals (hydrolyzable polyrotaxane). These hydrogels were examined to clarify the effect of ionic strength of phosphate buffers, pH, and the addition of ethanol on erosion time in relation to inclusion states of α‐CDs with the ester linkages. The most characteristic phenomenon of the hydrogel erosion was observed in an ethanol/PBS cosolvent system: the time to reach the complete erosion time was shortened with decreasing water content. NMR analysis revealed that the ester linkages were exposed to the aqueous environment due to the aggregation of α‐CDs. These results suggest that the movement of α‐CDs in the polyrotaxanes from the terminal ester region to the another region gives the ester linkages a chance to interact with water.
77.
We disclosed a novel ‘racemization-free segment condensation’ based on the ‘O-acyl isopeptide method’ in which an N-segment including C-terminal O-acyl isopeptide structure with urethane-protected Ser/Thr residue was employed for the segment condensation, suggesting that the use of this method contributes to the effective convergent synthesis of long peptides/proteins. 相似文献
78.
Seiji Yamaguchi Mika Yoshida Izumi Miyajima Toshikatsu Araki Yoshiro Hirai 《Journal of heterocyclic chemistry》1995,32(5):1517-1519
Condensation of salicylonitrile with ethyl α-bromo-α-(o-ethoxycarbonylphenyl)acetate (4) effectively gave 5 (6H)-benzofuro[3,2-c]isoquinolinone (2) , which was converted to some 5-substituted benzofuro-[3,2-c]isoquinoline derivatives 1a-g. 相似文献
79.
A palladium-catalyzed CO(2)-recycling reaction has been developed. Reaction of 4-methoxycarbonyloxy-2-butyn-1-ols with phenols, carried out in the presence of a palladium catalyst, produces phenoxy-substituted cyclic carbonates by way of a pathway involving a CO(2) elimination-fixation. A variety of propargylic alcohols and phenols participate in these reactions which yield cyclic carbonates with high efficiencies. Stereoselective construction of trans-cyclic carbonates is achieved by using nonsymmetric substrates. Highly enantioselective reactions occur when (S)-BINAP is used as a ligand. Reaction of 4-phenoxycarbonyloxy-2-butyn-1-ol in the presence of the palladium catalyst yields the corresponding cyclic carbonates via a three-component decomposition-reconstruction process. 相似文献
80.
A beta-CD-based biodegradable polyrotaxane was prepared by capping both terminals of polypseudorotaxane consisting of hydrazide-terminated PEG-block-PPG-block-PEG (Pluronic P-105) and beta-CD-succinates with mono-aldehyde alpha-CDs. By decreasing pH, the fluorescent intensity of TNS was increased with time, indicating cleavage of the terminal hydrazone bonds followed by beta-CD-succinate release. The terminal alpha-CD moieties of the polyrotaxane are useful for self-assembled formation with some guest molecules. [Diagram: see text] 相似文献