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991.
We refine a well-known theorem of Auslander and Reiten about the extension closedness of nth syzygies over noether algebras. Applying it, we obtain the converse of a celebrated theorem of Evans and Griffith on Serre’s condition (S n ) and the local Gorensteiness of a commutative ring in height less than n. This especially extends a recent result of Araya and Iima concerning a Cohen–Macaulay local ring with canonical module to an arbitrary local ring. 相似文献
992.
Takae S Miyata K Oba M Ishii T Nishiyama N Itaka K Yamasaki Y Koyama H Kataoka K 《Journal of the American Chemical Society》2008,130(18):6001-6009
PEG-based polyplex micelles, which can detach the surrounding PEG chains responsive to the intracellular reducing environment, were developed as nonviral gene vectors. A novel block catiomer, PEG-SS-P[Asp(DET)], was designed as follows: (i) insertion of biocleavable disulfide linkage between PEG and polycation segment to trigger PEG detachment and (ii) a cationic segment based on poly(aspartamide) with a flanking N-(2-aminoethyl)-2-aminoethyl group, P[Asp(DET)], in which the Asp(DET) unit acts as a buffering moiety inducing endosomal escape with minimal cytotoxicity. The polyplex micelles from PEG-SS-P[Asp(DET)] and plasmid DNA (pDNA) stably dispersed in an aqueous medium with a narrowly distributed size range of approximately 80 nm due to the formation of hydrophilic PEG palisades while undergoing aggregation by the addition of 10 mM dithiothreitol (DTT) at the stoichiometric charge ratio, indicating the PEG detachment from the micelles through the disulfide cleavage. The PEG-SS-P[Asp(DET)] micelles showed both a 1-3 orders of magnitude higher gene transfection efficiency and a more rapid onset of gene expression than PEG-P[Asp(DET)] micelles without disulfide linkages, due to much more effective endosomal escape based on the PEG detachment in endosome. These findings suggest that the PEG-SS-P[Asp(DET)] micelle may have promising potential as a nonviral gene vector exerting high transfection with regulated timing and minimal cytotoxicity. 相似文献
993.
Yuta Sato Akito Osada Dr. Narihito Ogawa Dr. Yuichi Kobayashi 《European journal of organic chemistry》2023,26(28):e202300403
The Cu(OTf)2-catalyzed alkyl–alkyl coupling reaction of a secondary substrate MeCH(OSO2Py)CH2CH2C6H4(4-OMe) with a nBuLi-based reagent prepared by transmetalation with MgBr2 ⋅ THF3 in THF produced a coupling product in 74 % yield. The use of soluble MgBr2 ⋅ THF3 in THF was required for this reaction. This method was applied to sBuLi and Ph(CH2)4Li. In contrast, transmetalation of MeLi with soluble MgCl2 ⋅ THF2 in THF produced the Me reagent, which was reactive for the coupling reaction. The reaction proceeded with inversion of the stereogenic carbon. Furthermore, (S)-14-methyloctadecan-2-one, a sex pheromone produced by lichen moths, was synthesized. 相似文献
994.
Seki S Umebayashi Y Tsuzuki S Hayamizu K Kobayashi Y Ohno Y Kobayashi T Mita Y Miyashiro H Terada N Ishiguro S 《Chemical communications (Cambridge, England)》2008,(43):5541-5543
An unusual ionic conduction phenomenon related to the phase transition of a novel phosphonium-cation-based room-temperature ionic liquid (RTIL) is reported; we found that in the phase change upon cooling, a clear increase in ionic conductivity was seen as the temperature was lowered, which differs from widely known conventional RTILs; clearly, our finding of abnormality of the correlation between temperature change and ionic conduction is the first observation in the electrolyte field. 相似文献
995.
996.
997.
Imai Y Abe H Goto T Yoshimura Y Kushiyama S Matsumoto H 《The journal of physical chemistry. B》2008,112(32):9841-9846
By in situ observations using simultaneous X-ray diffraction and the DSC (differential scanning calorimetry) method, the effect of water, methanol, ethanol, and benzene on the crystallization has been observed in an ionic liquid (IL)-rich phase. The IL is a hydrophilic ionic liquid, N, N-diethyl-N-methyl-N-2-methoxyethyl ammonium tetrafluoroborate, [DEME][BF4]. At a small amount of the above additional molecules in the IL, the conventional preferred orientation on the Debye rings was seen by the X-ray diffraction. At 0.9 mol % H2O, twinlike crystal domains develop extraordinary on the microdomains. By the "crystal-growth enhancement effect" at a slight amount of water, a composite domain structure, which consists of the large domain and the weakly orientated microdomains, is formed without internal strains. Above 2.9 mol % H2O, the domain structure, however, disappears completely. It is remarkable that, in a thermal cycling experiment using pure [DEME][BF4], the similar composite domain structure appeared. This is also caused by an uptake of a slight amount of water. 相似文献
998.
Stereocontrolled synthesis of the A/B-ring fragment of the originally assigned structure of gambieric acid B and its possible diastereomers has been accomplished. Detailed comparison of their 1H and 13C NMR data with those of the corresponding moiety of the natural product culminated in a stereochemical reassignment of the absolute configuration of the polycyclic ether region of gambieric acid B. 相似文献
999.
The exfoliation-reduction of VOPO4·2H2O in l-butanol oriso-butanol alone, and in a l-butanol/ethanol oriso-butanol/ethanol mixture, were conducted. Although all precursors were composed of a lamellar compound with intercalated alcohol molecules, VOHPO4·0.5H2O was formed when the exfoliation-reduction process was carried out in the mixed alcohol. All precursors transformed to a single phase of (VO)2P2O7 under the reaction conditions forn-butane oxidation, but the crystallinity of (VO)2P2O7 was different. The catalyst synthesized iniso-butanol/ethanol was well crystalline (VO)2P2O7, and exhibited higher selectivity to maleic anhydride than that synthesized iniso-butanol alone for then-butane oxidation. 相似文献
1000.
Shimojima A Goto R Atsumi N Kuroda K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(28):8500-8506
Siloxane-organic hybrids with well-ordered mesostructures were synthesized through the self-assembly of novel amphiphilic molecules that consist of cubic siloxane heads and hydrophobic alkyl tails. The monoalkyl precursors functionalized with ethoxy groups (C(n)H(2n+1)Si(8)O(12)(OEt)(7), 1 Cn, n=16, 18, and 20) were hydrolyzed under acidic conditions with the retention of the siloxane cages, leading to the formation of two-dimensional hexagonal phases by evaporation-induced self-assembly processes. Analysis of the solid-state (29)Si MAS NMR spectra of these hybrid mesostructures confirmed that the cubic siloxane units were cross-linked to form siloxane networks. Calcination of these hybrids gave mesoporous silica, the pore diameter of which varied depending on the alkyl-chain length. We also found that the precursors that had two alkyl chains formed lamellar phases, thus confirming that the number of alkyl chains per cage had a strong influence on the mesostructures. These results expand the design possibility of novel nanohybrid and nanoporous materials through the self-assembly of well-defined oligosiloxane-based precursors. 相似文献