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51.
52.
We reveal the existence of asymmetric vortex solitons in ideally symmetric periodic lattices and show how such nonlinear localized structures describing elementary circular flows can be analyzed systematically using the energy-balance relations. We present the examples of rhomboid, rectangular, and triangular vortex solitons on a square lattice and also describe novel coherent states where the populations of clockwise and anticlockwise vortex modes change periodically due to a nonlinearity-induced momentum exchange through the lattice. Asymmetric vortex solitons are expected to exist in different nonlinear lattice systems, including optically induced photonic lattices, nonlinear photonic crystals, and Bose-Einstein condensates in optical lattices. 相似文献
53.
Yunyan Qiu Jacob Mohin Chia‐Hua Tsai Stephanie Tristram‐Nagle Roberto R. Gil Tomasz Kowalewski Kevin J. T. Noonan 《Macromolecular rapid communications》2015,36(9):840-844
A commercially available palladium N‐heterocyclic carbene (Pd‐NHC) precatalyst is used to initiate chain‐growth polymerization of 2‐bromo‐3‐hexyl‐5‐trimethylstannylthiophene. The molecular weight of the resultant poly(3‐hexylthiophene) can be modulated (7 to 73 kDa, Đ = 1.14 to 1.53) by varying the catalyst concentration. Mass spectrometry data confirm control over the polymer end groups and 1H NMR spectroscopy reveals that the palladium catalyst is capable of “ring‐walking”. A linear relationship between Mn and monomer conversion is observed. Atomic force microscopy and X‐ray scattering verify the regioregular nature of the resultant polythiophene.
54.
Two-electron oxidation of the [C(PPh(2)S)(2)](2-) dianion with iodine afforded an unexpected mixture of a dimeric Li-I carbenoid [(Et(2)O)(mu-Li)][(mu(4)-Li){IC(PPh(2)S)(2)}(2)] and a novel, unsaturated six-membered C(2)P(2)S(2) ring in [(SPh(2)P)(2)C(2)(PPh(2))(2)S(2)]. 相似文献
55.
The reaction of R'NHLi (R = (t)Bu, (t)Oct) with Ph(2)P(NSiMe(3))(2)Te(Cl)NPPh(2)NSiMe(3) in toluene at -78 degrees C, followed by warming to 23 degrees C, produces the tellurium diimide dimers RNTe(&mgr;-NR')(2)TeNR (2a, R' = (t)Bu, R = NPPh(2)NSiMe(3); 2b, R' = (t)Oct, R = NPPh(2)NSiMe(3)) and Ph(2)P(NHSiMe(3))(NSiMe(3)). X-ray analyses revealed that 2a and 2b have centrosymmetric structures containing a planar four-membered Te(2)N(2) ring and short exocyclic tellurium-nitrogen bond lengths (d(Te-N) = 1.900(5) and 1.897(4) or 1.905(4) ? for 2a and 2b, respectively). The exocyclic imido substituents adopt a trans arrangement with respect to the Te(2)N(2) ring. By contrast, the reaction of 2,4,6-(t)Bu(3)C(6)H(2)NHLi with Ph(2)P(NSiMe(3))(2)Te(Cl)NPPh(2)NSiMe(3) in toluene under similar conditions produces the telluradiazole ((t)Bu(2)C(6)H(2)N(2)Te)(2) (3), which exists as a weakly associated dimer in the solid state with intramolecular Te-N distances of 2.628(4) ?. The tellurium diimide dimer (t)BuNTe(&mgr;-N(t)Bu)(2)TeN(t)Bu (2c'), prepared by the reaction of TeCl(4) with (t)BuNHLi in a 1:4 molar ratio, consists of a folded Te(2)N(2) ring with exocyclic N(t)Bu groups in a cis orientation. The (1)H, (31)P, and (125)Te NMR spectra of 2a and 2b indicate that the trans isomers slowly transform into the corresponding cis isomers in solution. Crystals of 2b are triclinic, space group P&onemacr; (No. 2), with a = 13.304(3) ?, b = 16.927(3) ?, c = 13.292(5) ?, alpha = 98.94(2), beta = 109.27(2), gamma = 69.04(2) degrees, V = 2636(1) ?(3), and Z = 4. The final R and R(w) values were 0.034 and 0.033, respectively. Crystals of 2c' are orthorhombic, space group Pnma (No. 62), with a = 9.535(3) ?, b = 14.264(3) ?, c = 16.963(4) ?, V = 2307.1(9) ?(3), and Z = 4. The final R and R(w) values were 0.040 and 0.040, respectively. Crystals of 3 are monoclinic, space group P2(1)/n (No. 14), with a = 9.117(3) ?, b = 11.481(4) ?, c = 16.550(4) ?, beta = 97.76(2) degrees, V = 1716.5(8) ?(3), and Z = 4. The final R and R(w) values were 0.031 and 0.034, respectively. 相似文献
56.
Chivers T Krahn M Parvez M Schatte G 《Chemical communications (Cambridge, England)》2001,(19):1922-1923
Lithiation of SP[N(H)R]3 with LiBun produces the dimers [(THF)LiSP(NR)(NHR)2]2 (R = Pri) or ([LiSP(NR)-(NHR)2][(THF)LiSP(NR)2(NHR)])2 (R = But) with central Li2N2 or Li2S2 rings, respectively; further lithiation yields the dianion [SP(NR)2(NHR)]2- (R = Pri) or leads to sulfur extrusion when R = But. 相似文献
57.
The reaction of BCl(3) with two equivalents of LiN(H)Dipp (Dipp = 2,6-diisopropylphenyl) in THF produces DippN(H)BO(CH(2))(4)NDipp, which contains a puckered seven-membered C(4)OBN ring. 相似文献
58.
We introduce a novel class of stable lattice solitons with a complex phase structure composed of many single-charge discrete vortices in a triangular photonic lattice. We demonstrate that such nonlinear self-trapped states are linked to the resonant Bloch modes, which bear a honeycomb pattern of phase dislocations. 相似文献
59.
We study the polytopes of affine maps between two polytopes—the hom-polytopes. The hom-polytope functor has a left adjoint—tensor product polytopes. The analogy with the category of vector spaces is limited, as we illustrate by a series of explicit examples exhibiting various extremal properties. The main challenge for hom-polytopes is to determine their vertices. A polytopal analogue of the rank-nullity theorem amounts to understanding how the vertex maps behave relative to their surjective and injective factors. This leads to interesting classes of surjective maps. In the last two sections we focus on two opposite extremal cases—when the source and target polytopes are both polygons and are either generic or regular. 相似文献
60.
Tristram Chivers 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):679-687
Abstract Several aspects of recent developments in the chemistry of multiply bonded selenium and tellurium compounds are surveyed in this article. These include (a) tellurium(IV)-nitrogen compounds, (b) complexes with two (or more) terminal Group 14–Group 16 linkages, and (c) a new approach to previously inaccessible ligands containing Group 15–Group 16 functionalities. 相似文献