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781.
Velimir Popsavin Sanja Grabe? Ivana Krsti? Gordana Bogdanovi? 《Tetrahedron letters》2004,45(51):9409-9413
A new approach to the dephenyl goniofufurone analogue 2 and the corresponding (3S,4R)-stereoisomer 3 is reported. The resulting furanolactones 2 and 3 have shown a potent and selective in vitro cytotoxicity against certain human tumour cell lines. 相似文献
782.
Christopher D. Thompson Evan G. Robertson Ivana Aleksic Don McNaughton 《Journal of Molecular Spectroscopy》2005,230(2):81
The FTIR spectrum of pentafluoroethane (R125) was measured in the mid infrared region from 900 to 4000 cm−1. Vibrational assignments for R125 are revised by comparison of previous and current experimental data with ab initio calculations at both the MP2/6-311+(d,p) and B3LYP/TZV+(3df,3p) levels of theory. High resolution FTIR spectra were recorded at room temperature and in an enclosive flow cell at a rotational temperature of 140 K. The cold spectrum was sufficiently resolved to enable rovibrational analyses of the overlapping ν4 (1200.7341 cm−1) and ν13 (1223.3 cm−1) bands, which have a/c hybrid and b-type character, respectively. Ground state combination differences were used to confirm assignment of 2375 lines to ν4 (Jmax = 86, Ka max = 50) and 2921 lines to ν13 (Jmax = 60, Ka max = 54). Effective rotational and centrifugal distortion constants were determined for ν4, and the polarization ratio was found to be . Severe Coriolis perturbations prevent any satisfactory fit to the ν13 band. 相似文献
783.
IvanaCarrizo SergioFavier 《分析论及其应用》2003,19(3):238-254
In this work two aspects of theory of frames are presented: a side necessary condition on irregular wavelet frames is obtained, another perturbation of wavelet and Gabor frames is considered. Specifically,we present the results obtained on frame stability when one disturbs the mother of wavelet frame, or the parameter of dilatation, and in Gabor frames when the generating function or the parameter of translation are perturbed. In all cases we work without demanding compactness of the support, neither on the generating function, nor on its Fourier transform. 相似文献
784.
Ivana Alexandrova 《偏微分方程通讯》2013,38(10):1505-1535
ABSTRACT We consider scattering by general compactly supported semi-classical perturbations of the Euclidean Laplace-Beltrami operator. We show that if the suitably cut-off resolvent quantizes a Lagrangian relation on the product cotangent bundle, the scattering amplitude quantizes the natural scattering relation. In the case when the resolvent is tempered, which is true at non-trapping energies or at trapping energies under some non-resonance assumptions, and when we work microlocally near a non-trapped ray, our result implies that the scattering amplitude defines a semiclassical Fourier integral operator associated to the scattering relation in a neighborhood of that ray. Compared to previous work, we allow this relation to have more general geometric structure. 相似文献
785.
Stefan Gollowitzer Bernard Gendron Ivana Ljubić 《Computational Optimization and Applications》2013,55(3):647-674
We consider a network design problem that arises in the cost-optimal design of last mile telecommunication networks. It extends the Connected Facility Location problem by introducing capacities on the facilities and links of the networks. It combines aspects of the capacitated network design problem and the single-source capacitated facility location problem. We refer to it as the Capacitated Connected Facility Location Problem. We develop a basic integer programming model based on single-commodity flows. Based on valid inequalities for the capacitated network design problem and the single-source capacitated facility location problem we derive several (new) classes of valid inequalities for the Capacitated Connected Facility Location Problem including cut set inequalities, cover inequalities and combinations thereof. We use them in a branch-and-cut framework and show their applicability and efficacy on a set of real-world instances. 相似文献
786.
We consider a new combinatorial optimization problem that combines network design and facility location aspects. Given a graph with two types of customers and two technologies that can be installed on the edges, the objective is to find a minimum cost subtree connecting all customers while the primary customers are served by a primary subtree that is embedded into the secondary subtree. In addition, besides fixed link installation costs, facility opening costs, associated to each node where primary and secondary subtree connect, have to be paid. The problem is called the Two Level Network Design Problem with Transition Facilities (TLNDF). 相似文献
787.
Ivana Zrinski Sanja Martinez Astrid Ortner Anchalee Samphao Janez Zavašnik Kurt Kalcher Eda Mehmeti 《Electroanalysis》2021,33(5):1325-1332
The electrocatalytic oxidation of rapamycin, one of the most studied immunosuppressant, cancer-preventing drug, is investigated for the first time on the surface of the modified carbon paste electrode prepared by incorporating multi-walled carbon nanotubes (MWCNTs) and conductive polymer pyrrole using differential pulse voltammetry (DPV). Rapamycin exhibited a well-defined oxidation peak at +1.1 V (versus Ag/AgCl) in Briton Robinson buffer solution with a pH 4.0. Effect of the most important experimental parameters was optimized and obtained signals are linear to the concentration of rapamycin in the range from 0.1 to 20 μM with 0.06 μM limit of detection. The repeatability is calculated as ±2 % and the reproducibility as ±5 %. The possible interfering compounds were tested showing negligible effect and the sensor was successfully applied for the determination of rapamycin in commercial pharmaceutical formulations with obtained recoveries in the range from 98 % to 102 %. 相似文献
788.
Dijana Pešić Ivana Ozimec Landek Ana Čikoš Biserka Metelko Vesna Gabelica Barbara Stanić Mladen Merćep Milan Mesić 《Journal of heterocyclic chemistry》2007,44(5):1129-1133
789.
Pace A Pibiri I Piccionello AP Buscemi S Vivona N Barone G 《The Journal of organic chemistry》2007,72(20):7656-7666
The experimental investigation of the base-catalyzed rearrangements of 3-acylamino-1,2,4-oxadiazoles evidenced a new reaction pathway which competes with the well-known ring-degenerate Boulton-Katritzky rearrangement (BKR). The new reaction consists of a one-atom side-chain rearrangement that is base-activated, occurs at a higher temperature than the BKR, and irreversibly leads to the corresponding 2-acylamino-1,3,4-oxadiazoles. An extensive DFT study is reported to elucidate the proposed reaction mechanism and to compare the three possible inherent routes: (i) the reversible three-atom side-chain ring-degenerate BKR, (ii) the ring contraction-ring expansion route (RCRE), and (iii) the one-atom side-chain rearrangement. The results of the computational investigation point out that the latter route is kinetically preferred over the RCRE and can be considered as the ground-state analogue of a previously proposed C(3)-N(2) migration-nucleophilic attack-cyclization (MNAC) photochemically activated pathway. The MNAC consists of the formation of a diazirine intermediate, involving the exocyclic nitrogen, that eventually evolves into a carbodiimide intermediate (migration); the latter undergoes a single intramolecular nucleophilic attack-cyclization step leading to the final 2-acylamino-1,3,4-oxadiazole. 相似文献
790.
Marcelli A Foggi P Moroni L Gellini C Salvi PR Badovinac IJ 《The journal of physical chemistry. A》2007,111(12):2276-2282
The fluorescence spectra of unsubstituted porphyrin (H2P), diprotonated porphyrin (H4P2+), and isoelectronic tetraoxaporphyrin dication (TOxP2+) have been measured in solution at room temperature. The S2-->S0 fluorescence has been observed, much more intense for TOxP2+ than for H4P2+ and H2P. In the TOxP2+ case, the S2-->S0 fluorescence spectrum is remarkably sharp and shows an excellent mirror symmetry with respect to S0-->S2 absorption. On the contrary, the spectra of H4P2+ and H2P are shifted and more extended with respect to the absorption counterparts. The differences have been attributed primarily to the change of the equilibrium geometry upon excitation, larger in H2P and H4P2+ than in TOxP2+ and in the case of H4P2+ to the nonplanar conformation of the macrocycle. Also the S1-->S0 spectra of H2P, H4P2+, and TOxP2+ have been measured and more qualitatively discussed. The S1 and S2 fluorescence decays have been observed for H4P2+ and TOxP2+ exciting with ultrashort pulses. The S2 lifetime of TOxP2+ is of the order of the temporal resolution of our experimental apparatus, whereas that of H4P2+ is shorter. The S2-->S0 quantum yield of TOxP2+ has been estimated to be 0.035, approximately 3 orders of magnitude higher than that of H4P2+. It is proposed on the basis of ab initio model calculations that excited states of the H4P2+(CF3COO-)2 complex with charge-transfer character are responsible of the increased extension of the S2-->S0 spectrum with respect to that of H2P. 相似文献