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151.
This paper studies the geometric decay property of the joint queue-length distribution {p(n
1,n
2)} of a two-node Markovian queueing system in the steady state. For arbitrarily given positive integers c
1,c
2,d
1 and d
2, an upper bound
of the decay rate is derived in the sense
It is shown that the upper bound coincides with the exact decay rate in most systems for which the exact decay rate is known.
Moreover, as a function of c
1 and c
2,
takes one of eight types, and the types explain some curious properties reported in Fujimoto and Takahashi (J. Oper. Res.
Soc. Jpn. 39:525–540 [1996]).
相似文献
152.
153.
Pharaonis halorhodopsin (pHR) functions as a light-driven inward chloride ion pump in Natoronomonas pharaonis, while pharaonis phoborhodopsin (ppR; also called pharaonis sensory rhodopsin II, pSRII), is a light sensor for negative phototaxis. ppR forms a 2:2 complex with its cognate transducer protein (pHtrII) through intramembranous hydrogen bonds: Tyr199(ppR)-Asn74(pHtrII) and Thr189(ppR)-Glu43 (pHtrII), Ser62(pHtrII). It was reported that a pHR mutant (P240T/F250Y), which possesses the hydrogen-bonding sites, impairs its pumping activity upon complexation with pHtrII. In this study, effect of the complexation with pHtrII on the structural changes upon formation of the K, L(1) and L(2) intermediates of pHR was investigated by use of Fourier-transform infrared spectroscopy. The vibrational changes of Tyr250(pHR) and Asn74(pHtrII) were detected for the L(1) and L(2) intermediates, supporting that Tyr250(pHR) forms a hydrogen bond with Asn74(pHtrII) as similarly to Tyr199(ppR). The conformational changes of the retinal chromophore were never affected by complexation with pHtrII, but amide-I vibrations were clearly different in the absence and presence of pHtrII. The molecular environment around Asp156(pHR) in helix D is also slightly affected. These additional structural changes are probably related to blocking of translocation of a chloride ion from the extracellular to the cytoplasmic side during the photocycle. 相似文献
154.
The combination of 5 mol % Cu(OTf)2 and CuCl in the presence of DMAP effectively catalyzed a three-component coupling reaction involving an alkynylsilane, an o-hydroxybenzaldehyde derivative, and a secondary amine. The reaction proceeded via intramolecular 5-exo-dig cyclization, resulting in direct synthesis of the corresponding benzofuran derivatives in moderate to excellent yields. 相似文献
155.
Naoki Tsuchiya Tetsuhiro Yamamoto Hiroki Akagawa Prof. Dr. Takashi Nishikata 《Angewandte Chemie (International ed. in English)》2023,62(21):e202301343
Herein, we report a copper-catalyzed stereospecific fluorination involving CsF and α-bromocarboxamides as tertiary alkyl sources that, unlike traditional stereospecific routes involving stereoinversive SN2 reactions, proceeds with retention of stereochemistry. The developed stereospecific Cu-catalyzed reaction is among the most efficient methods for synthesizing fluorinated molecules that possess highly congested stereogenic carbon centers. Mechanistic studies revealed that the combined reactivity of CuF2 and Cs salt is essential for completing the catalytic cycle. Our catalytic system underwent fluorination exclusively with tertiary alkyl bromides and did not react with primary alkyl bromides, indicating that this stereospecific fluorination methodology is suitable for synthesizing fluorinated building blocks possessing stereo-defined F-containing tertiary carbon stereogenic center. 相似文献
156.
Naoki Komatsu 《Journal of inclusion phenomena and macrocyclic chemistry》2008,61(3-4):195-216
This review article surveys the author’s work during the last ten years. The research works have been carried out in the interdisciplinary fields of supramolecular, synthetic organic and materials chemistry. This review consists of the following 5 topics; (1) novel synthetic methodology for constructing benzyl ether-linked oxacyclophanes and oxacalixarenes by reductive coupling reactions, (2) preferential precipitation of C70 over C60 with p-halohomooxacalix[3]arenes prepared by the above reductive coupling reactions, (3) highly practical purification of fullerenes by filtration through activated carbon thin layer, (4) host-guest chemistry of C60 and C70 with porphyrin monomers and dimers in solution, and (5) optical resolution of carbon nanotubes through preferential complexation with chiral diporphyrin nanotweezers. New terminology is also proposed in the definition of the structures and stereochemistry of carbon nanotubes. 相似文献
157.
Cover Picture: Nucleobase‐Modified PNA Suppresses Translation by Forming a Triple Helix with a Hairpin Structure in mRNA In Vitro and in Cells (Angew. Chem. Int. Ed. 3/2016) 下载免费PDF全文
158.
159.
Bhattacharya S Ujihashi N Aonuma S Kimura T Komatsu N 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(3):495-503
The host-guest interaction of zinc(II) 5,10,15,20-tetrahexylporphyrin (Zn-THP) and its free base (H2-THP) with fullerenes (C60 and C70) has been studied in toluene medium. Binding constants (K) for H2- and Zn-THP complexes of fullerenes were determined by UV-vis, fluorescence and NMR spectroscopic techniques. Large K values of C70/THP complexes (KC70 ) were obtained in the range of 1.4-2.5 x 10(4)M(-1), while those of C60/THP complexes (KC60) were smaller (1.0-3.2 x10(3)M(-1)). These results show that the KC70 is about 10 times as large as KC60 in both THPs (KC70/KC60 = 10). Enthalpies of formation (DeltaHf degrees) for various fullerene/THP complexes were estimated by ab initio calculations; DeltaHf degrees for C60/H2-THP, C70/H2-THP, C60/Zn-THP and C70/Zn-THP complexes are 5.82, 2.80, 2.31 and 1.54 kcal mol(-1), respectively. The trends in DeltaHf degrees support the experimental results of selective complexation of THPs towards C70 over C60 and fullerenes towards Zn-THP over H2-THP. 相似文献
160.