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91.
This paper consists of two results dealing with balanced metrics (in Donaldson terminology) on noncompact complex manifolds. In the first one we describe all balanced metrics on Cartan domains. In the second one we show that the only Cartan–Hartogs domain which admits a balanced metric is the complex hyperbolic space. By combining these results with those obtained in Loi and Zedda (Mathematische Annalen, 2011, to appear) we also provide the first example of complete, Kähler-Einstein and projectively induced metric g such that α g is not balanced for all α > 0. 相似文献
92.
In this paper we are concerned with the optimal control problem consisting in minimizing the time for reaching (visiting)
a fixed number of target sets, in particular more than one target. Such a problem is of course reminiscent of the famous “Traveling
Salesman Problem” and brings all its computational difficulties. Our aim is to apply the dynamic programming technique in
order to characterize the value function of the problem as the unique viscosity solution of a suitable Hamilton–Jacobi equation.
We introduce some “external” variables, one per target, which keep in memory whether the corresponding target is already visited
or not, and we transform the visiting problem in a suitable Mayer problem. This fact allows us to overcome the lacking of
the Dynamic Programming Principle for the originary problem. The external variables evolve with a hysteresis law and the Hamilton–Jacobi
equation turns out to be discontinuous 相似文献
93.
Local branching is a general purpose heuristic method which searches locally around the best known solution by employing tree
search. It has been successfully used in Mixed-Integer Programming where local branching constraints are used to model the
neighborhood of an incumbent solution and improve the bound. We propose the integration of local branching in Constraint Programming
(CP). This integration is not simply a matter of implementation, but requires a number of significant extensions. The original
contributions of this paper are: the definition of an efficient and incremental bound computation for the neighborhood, a
cost-based filtering algorithm for the local branching constraint and a novel diversification strategy that can explore arbitrarily
far regions of the search tree w.r.t. the already found solutions. We demonstrate the practical value of local branching in
CP by providing an extensive experimental evaluation on the hard instances of the Asymmetric Traveling Salesman Problem with
Time Windows. 相似文献
94.
Claudio Bianchini Pierluigi Barbaro Michela Macchi Andrea Meli Francesco Vizza 《Helvetica chimica acta》2001,84(10):2895-2923
As part of our modelling studies of the hydrodenitrogenation of N‐heterocycles contained in raw oil materials, we investigated the selective hydrogenation of quinoline to 1,2,3,4‐tetrahydroquinoline by rhodium catalysts modified with the tripodal polyphosphane ligand MeC(CH2PPh2)3. Experiments in standard autoclaves and in high‐pressure sapphire NMR tubes, kinetic and isotope labelling studies, and independent reactions with isolated compounds have contributed to the elucidation of the catalytic mechanism as well as identification of the electronic requisites of the metal catalyst for selective and efficient hydrogenation. 相似文献
95.
Raluca Maria Pop Ioana Corina Bocsan Anca Dana Buzoianu Veronica Sanda Chedea Sonia Ancua Socaci Michela Pecoraro Ada Popolo 《Molecules (Basel, Switzerland)》2020,25(22)
Natural products black cumin—Nigella sativa (N. sativa) and wild garlic—Allium ursinum (AU) are known for their potential role in reducing cardiovascular risk factors, including antracycline chemotherapy. Therefore, this study investigates the effect of N. sativa and AU water and methanolic extracts in a cellular model of doxorubicin (doxo)-induced cardiotoxicity. The extracts were characterized using Ultraviolet-visible (UV-VIS) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, Liquid Chromatography coupled with Mass Spectrometry (LC-MS) and Gas Chromatography coupled with Mass Spectrometry (GC-MS) techniques. Antioxidant activity was evaluated on H9c2 cells. Cytosolic and mitochondrial reactive oxygen species (ROS) release was evaluated using 2′,7′-dichlorofluorescin-diacetate (DHCF-DA) and mitochondria-targeted superoxide indicator (MitoSOX red), respectively. Mitochondrial membrane depolarization was evaluated by flow cytometry. LC-MS analysis identified 12 and 10 phenolic compounds in NSS and AU extracts, respectively, with flavonols as predominant compounds. FT-IR analysis identified the presence of carbohydrates, amino acids and lipids in both plants. GC-MS identified the sulfur compounds in the AU water extract. N. sativa seeds (NSS) methanolic extract had the highest antioxidant activity reducing both intracellular and mitochondrial ROS release. All extracts (excepting AU methanolic extract) preserved H9c2 cells viability. None of the investigated plants affected the mitochondrial membrane depolarization. N. sativa and AU are important sources of bioactive compounds with increased antioxidant activities, requiring different extraction solvents to obtain the pharmacological effects. 相似文献
96.
Giuseppe Romanazzi Valentina Petrelli Ambra Maria Fiore Piero Mastrorilli Maria Michela DellAnna 《Molecules (Basel, Switzerland)》2021,26(4)
Recently, N-substituted anilines have been the object of increasing research interest in the field of organic chemistry due to their role as key intermediates for the synthesis of important compounds such as polymers, dyes, drugs, agrochemicals and pharmaceutical products. Among the various methods reported in literature for the formation of C–N bonds to access secondary anilines, the one-pot reductive amination of aldehydes with nitroarenes is the most interesting procedure, because it allows to obtain diverse N-substituted aryl amines by simple reduction of nitro compounds followed by condensation with aldehydes and subsequent reduction of the imine intermediates. These kinds of tandem reactions are generally catalyzed by transition metal-based catalysts, mainly potentially reusable metal nanoparticles. The rapid growth in the last years in the field of metal-based heterogeneous catalysts for the one-pot reductive amination of aldehydes with nitroarenes demands for a review on the state of the art with a special emphasis on the different kinds of metals used as catalysts and their recyclability features. 相似文献
97.
This paper presents constraint programming (CP) as a natural formalism for modelling problems, and as a flexible platform for solving them. CP has a range of techniques for handling constraints including several forms of propagation and tailored algorithms for global constraints. It also allows linear programming to be combined with propagation and novel and varied search techniques which can be easily expressed in CP. The paper describes how CP can be used to exploit linear programming within different kinds of hybrid algorithm. In particular it can enhance techniques such as Lagrangian relaxation, Benders decomposition and column generation. 相似文献
98.
Michela Begala Pierluigi Caboni Maria João Matos Giovanna Lucia Delogu 《Tetrahedron letters》2018,59(18):1711-1714
The reaction of 2-hydroxybenzyltriphenylphosphonium bromide with substituted benzoyl chlorides under Wittig conditions, led to 2-phenylbenzofuran derivatives 4a–p and the unexpected formation of 3-benzoyl-2-phenylbenzofuran derivatives 5a–p. Benzoyl chlorides possessing electron-withdrawing groups afforded 3-benzoyl-2-phenylbenzofuran derivatives in higher yields than those with electron-donating groups. This reaction represents a simple and regioselective, one-pot route towards the preparation of deactivated 3-benzoyl-2-phenylbenzofuran compounds which are difficult to obtain by the direct acylation of 2-phenylbenzofurans. 相似文献
99.
The reactivity of 2,2-dimethyl-5-methoxyindan-1-ol (1) and 2,2-dimethyl-6-methoxytetral-1-ol (2) radical cations has been studied both in acidic and basic solution. At pH≤4 both 1+ and 2+ undergo CαH deprotonation as the exclusive reaction with k=4.6×104 and 3.2×104 s−1, respectively. In basic solution 1+ and 2+ behave as oxygen acids undergoing −OH-induced αOH deprotonation in a diffusion controlled process (k−OH≈1010 M−1 s−1). An intermediate alkoxyl radical is formed which undergoes a 1,2-hydrogen atom shift in competition with CC β-scission (with 1+) or as the exclusive pathway (with 2+). A behavior which is interpreted in terms of the greater ease of ring-opening of a five membered ring as compared to a six-membered one. 相似文献
100.
Ottaviani P Giuliano M Velino B Caminati W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):538-543
The 1:1 molecular complex between oxetane and water has been investigated by using free-jet millimeter-wave spectroscopy. The rotational spectra of five isotopomers (with H(2)O, D(2)O, DOH, HOD and H(2) (18)O) have been assigned. Partial r(0) and r(s) structures of the complex have been derived. The water moiety lies in the plane of symmetry of oxetane, with the "free" hydrogen E with respect to the ring. The oxetane ring appears to be slightly nonplanar, with the C(beta) carbon tilted on the opposite side of the water unity. The three atoms involved in the hydrogen bond adopt a linear arrangement with an O(ring).H distance of about 1.86 A, and the angle between the COC bisector and the O(ring).H bond being congruent with 106 degrees. Additionally, quantum-chemical calculations for the complex were performed and were found to be in agreement with the experimental results. 相似文献