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111.
To any compact hyperbolic Riemann surface X, we associate a new type of automorphism group — called its commensurability automorphism group, ComAut(X). The members of ComAut(X) arise from closed circuits, starting and ending at X, where the edges represent holomorphic covering maps amongst compact connected Riemann surfaces (and the vertices represent
the covering surfaces). This group turns out to be the isotropy subgroup, at the point represented by X (in $ T_\infty $), for the action of the universal commensurability modular group on the universal direct limit of Teichmüller
spaces, $ T_\infty $. Now, each point of $ T_\infty $ represents a complex structure on the universal hyperbolic solenoid.
We notice that ComAut(X) acts by holomorphic automorphisms on that complex solenoid. Interestingly, this action turns out to be ergodic (with respect
to the natural measure on the solenoid) if and only if the Fuchsian group uniformizing X is arithmetic. Furthermore, the action of the commensurability modular group, and of its isotropy subgroups, on some natural vector bundles
over $ T_\infty $, are studied by us. 相似文献
112.
The vector recursion method is generalized to a multichannel scattering formalism and used to study the transmittance in a one-dimensional model with an s-d hybridized Hamiltonian. The transmittance and wavefunctions of the s and d channels are studied. 相似文献
113.
Palladium acetate catalyzed Mizoroki-Heck reactions of arylboronic acids with diethyl vinylphosphonates afford α,β-unsaturated phosphonates in good yields. 相似文献
114.
In many industries the pricing of a product over time can be used to manage demand for the product. Lead time, or promised
delivery time is often a significant factor in price negotiations. However, the production planning literature has largely
treated pricing decisions as exogeneous while focusing on the allocation of production capacity between products over time.
On the other hand, the marketing literature has generally ignored the effects of capacity constraints and focused on the effects
of pricing.
In this paper, we begin by reviewing the existing literature on integrative production-marketing research, focusing on those
models that consider lead times and capacity. We suggest a number of directions for future research that take advantage of
recent developments in production planning models, as well as explicit modeling of feedback loops governing key parameters,
which suggest a broader view of the problem. 相似文献
115.
Senjuti De Michael G. B. Drew David W. Price Samik Nag Dipankar Datta 《International journal of quantum chemistry》2007,107(1):182-188
G3B3 and G2MP2 calculations using Gaussian 03 have been carried out to investigate the protonation preferences for phenylboronic acid. All nine heavy atoms have been protonated in turn. With both methodologies, the two lowest protonation energies are obtained with the proton located either at the ipso carbon atom or at a hydroxyl oxygen atom. Within the G3B3 formalism, the lowest‐energy configuration by 4.3 kcal · mol?1 is found when the proton is located at the ipso carbon, rather than at the electronegative oxygen atom. In the resulting structure, the phenyl ring has lost a significant amount of aromaticity. By contrast, calculations with G2MP2 show that protonation at the hydroxyl oxygen atom is favored by 7.7 kcal · mol?1. Calculations using the polarizable continuum model (PCM) solvent method also give preference to protonation at the oxygen atom when water is used as the solvent. The preference for protonation at the ipso carbon found by the more accurate G3B3 method is unexpected and its implications in Suzuki coupling are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
116.
Summary Nickel(II), palladium(II), cobalt(II) and copper(II) complexes of the ligandN,N-1,2-propane-bis(methyl 2-amino-cyclopent-1-ene-dithiocarboxylate) (H2L1),N,N-1,3-propane-bis(methyl 2-aminocyclopent-1-ene-dithiocarboxylate) (H2L2) andN,N-[bis(methyl 2-aminocyclopent-1-ene-dithiocarboxylate)] diethylenetriamine (H2L3) have been synthesised. Both H2L1 and H2L2 form complexes of the type ML, and all but the copper(II) complexes, are square planar. In the copper(II) complexes tetrahedral distortion is significantly more with CuL2. From H2L3 square planar complexes of the type [M(HL3)X] (M=Ni, X=Cl, Br, I or SCN; M=Pd, X=Cl or Br) have been obtained in which the donor unit involved is N2SX. The composition of the cobalt(II) and copper(II) complexes is [M(H2L3)X2] (X=Cl or Br) which contain the chromophore [MN3X2]. 相似文献
117.
Nag Purnima Bohra Rakesh Mehrotra Ram C. Ratnani Raju 《Transition Metal Chemistry》2002,27(3):321-325
Reactions of an acidified aqueous solution of Na2MoO4 · 2H2O with 3-mercaptopropionic acid, 2-mercaptomethylethanoate and 3-mercaptomethyl propanate yield blue oxo-bridged MoV complexes of the type [Mo2O3L4], whereas corresponding reactions with 2-aminophenol, 2-aminobenzyl alcohol, salicylaldehyde and 2-methyl-8-hydroxyquinoline, yield yellow dioxomolybdenum(VI) complexes, [MoO2L′2]. All these coloured solids are sparingly soluble, even in coordinating solvents. They have been characterized by elemental and spectroscopic analysis. 相似文献
118.
The nucleation and evolution of Ni nanoparticles during reduction of a Ni(NO3)2.6H2O precursor supported on a commercial titania substrate have been studied in situ at atomic resolution using environmental transmission electron microscopy. An incipient wetness technique was used to prepare the starting unreduced material (10 wt % Ni precursor on titania). The Ni precursor, before reduction, shows a nonuniform distribution over the titania support. It is observed that upon reduction, the initial Ni "seed" crystal nucleates within the precursor patch. The distribution and size of the Ni nanoparticles thus generated are influenced by the distribution and size of the precursor patches. In this system, we see no evidence of preferential nucleation of Ni particles on anatase or rutile. At 350 degrees C with CO as the reducing agent, the {111} surface facets of the Ni nanoparticles are predominant during the initial stage of nucleation and growth. However, the {111} facets are partially consumed with time, indicating that they are not thermodynamically favored in the CO atmosphere. In CO and H2 atmospheres, Ni particles show a nonwetting morphology on titania, while in a mild oxidizing environment, a thin layer of NiOx is formed, thus giving rise to a morphology that is indicative of wetting of the support. This work provides fundamental information on understanding and controlling the important parameters involved in the preparation of a well-designed supported Ni catalyst using the incipient wetness technique. 相似文献
119.
Rate constants for the attachment of DABCO (1,4-diazabicyclo[2.2.2]octane) to Fischer carbene complexes of the type (CO)(5)Cr=C(XR)C(6)H(4)Z (X = O and S) in dry MeCN at 25 degrees C are reported. Hammett rho values are 2.18 +/- 0.13 and 0.89 +/- 0.07 for DABCO reactions with (CO)(5)Cr=C(OMe)C(6)H(4)Z (10-Cr-Z) and (CO)(5)Cr=C(SMe)C(6)H(4)Z (11-Cr-Z), respectively. The rho values for the reaction of 10-Cr-Z and 11-Cr-Z with CH(CN)(2)(-) in 50% MeCN-50% H(2)O (v/v) are comparable to the present reactions. The reaction of DABCO with 10-Cr-Z is more closely related to the reaction of (n-Bu)(3)P with (CO)(5)W=C(OMe)C(6)H(5)-Z (23) which also provided a rho value 2.22. The much higher rho values and hence much higher reactivity of methoxy carbene complexes over the corresponding thiomethyl derivatives fit a pattern observed previously for alkoxide ion, OH(-), amine, and thiolate ion nucleophiles, and a rational explanation comes from the consideration of the substituent effects not only on the transition state but also on the reactant. A major difference between 10-Cr-Z and 11-Cr-Z is that the pi-donor effect of the methoxy group is much stronger than that of thiomethyl group. This leads to a substantial contribution of the zwitterionic form to the structure of 10-Cr-Z with much more localized positive charge on the methoxy group than the negative charge on the (CO)(5)Cr moiety. This leads to overall destabilization by an electron-withdrawing phenyl substituents resulting an increase in reactivity. The ethoxycarbene complexes are somewhat less reactive than their methoxy counterparts due to the somewhat more ground state stabilization through its stronger pi donor effect and partly due to steric crowding exerted by the slightly larger ethoxy group in the transition state. Higher k(1)(W)/k(1)(Cr) ratios for (thiomethyl)carbene complexes than methoxy or ethoxycarbene complexes are related to the intrinsic rate constant which is higher for ((thiomethyl)carbene)tungsten complexes than the corresponding Cr ones resulting in an enhanced ratio. 相似文献
120.
Efficient White‐Light Generation from Ionically Self‐Assembled Triply‐Fluorescent Organic Nanoparticles
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Dr. Susmita Das Tanay Debnath Amrita Basu Dr. Deepanwita Ghosh Prof. Abhijit Kumar Das Dr. Gary A. Baker Prof. Amitava Patra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(26):8855-8863
Low cost, simple, and environmentally friendly strategies for white‐light generation which do not require rare‐earth phosphors or other toxic or elementally scare species remain an essentially unmet challenge. Progress in the area of all‐organic approaches is highly sought, single molecular systems remaining a particular challenge. Taking inspiration from the designer nature of ionic‐liquid chemistry, we now introduce a new strategy toward white‐light emission based on the facile generation of nanoparticles comprising three different fluorophores assembled in a well‐defined stoichiometry purely through electrostatic interactions. The building blocks consist of the fluorophores aminopyrene, fluorescein, and rhodamine 6G which represent blue, green, and red‐emitting species, respectively. Spherical nanoparticles 16(±5) nm in size were prepared which display bright white‐light emission with high fluorescence quantum efficiency (26 %) and color coordinate at (0.29, 0.38) which lie in close proximity to pure white light (0.33, 0.33). It is noteworthy that this same fluorophore mixture in free solution yields only blue emission. Density functional theory calculations reveal H‐bond and ground‐state proton transfer mediated absolute non‐parallel orientation of the constituent units which result in frustrated energy transfer, giving rise to emission from the individual centers and concomitant white‐light emission. 相似文献