排序方式: 共有52条查询结果,搜索用时 31 毫秒
11.
Chiotellis A Tsoukalas C Pelecanou M Papadopoulos A Raptopoulou C Terzis A Pirmettis I Papadopoulos M Chiotellis E 《Inorganic chemistry》2006,45(14):5635-5640
The present paper deals with the synthesis and structural characterization of novel neutral oxorhenium(V) complexes of the general formula ReO[SNO][NN]. The simultaneous action of the tridentate SNO ligand, N-(2-mercaptoacetyl)glycine (1), and the bidentate NN ligand, N-phenylpyridine-2-aldimine (2), on ReOCl3(PPh3)2 leads to the formation of two isomers 4a and 4b of the general formula ReO[SNO][NN], as a result of the different orientations of the NN ligand. In both cases, the SNO donor atoms of the tridentate ligand occupy the three positions in the equatorial plane of the distorted octahedron, whereas the oxo group is always directed toward one of the apical positions. In the first isomer, 4a, the imino nitrogen of the NN ligand occupies the fourth equatorial position and the pyridine type nitrogen is directed trans to the oxo group, while in the second isomer, 4b, the imino nitrogen of the NN ligand occupies the apical position trans to the oxo group and the pyridine type nitrogen completes the equatorial plane of the distorted octahedron. The [SNO][NN] mixed-ligand system was applied in the synthesis of the oxorhenium complex 5 in which the 1-(2-methoxyphenyl)piperazine moiety, a fragment of the true 5-HT1A antagonist WAY 100635, has been incorporated in the NN bidentate ligand (NN is N-{3-[4-(2-methoxyphenyl)piperazin-1-yl]propyl}pyridine-2-aldimine). In this case, high-performance liquid chromatography and NMR showed the existence of one isomer, 5, in which the pyridine nitrogen is trans to the oxo core, as demonstrated by crystal structure analysis. 相似文献
12.
Efstratios N. Pistikopoulos Luis Dominguez Christos Panos Konstantinos Kouramas Altannar Chinchuluun 《Computational Management Science》2012,9(2):183-203
This paper presents an overview of recent theoretical and algorithmic advances, and applications in the areas of multi-parametric
programming and explicit/multi-parametric model predictive control (mp-MPC). In multi-parametric programming, advances include
areas such as nonlinear multi-parametric programming (mp-NLP), bi-level programming, dynamic programming and global optimization
for multi-parametric mixed-integer linear programming problems (mp-MILPs). In multi-parametric/explicit MPC (mp-MPC), advances
include areas such as robust multi-parametric control, multi-parametric nonlinear MPC (mp-NMPC) and model reduction in mp-MPC.
A comprehensive framework for multi-parametric programming and control is also presented. Recent applications include a hydrogen
storage device, a fuel cell power generation system, an unmanned autonomous vehicle (UAV) and a hybrid pressure swing adsorption
(PSA) system. 相似文献
13.
Katerina P. Papalexandri Efstratios N. Pistikopoulos 《Annals of Operations Research》1993,42(1):119-168
A mixed integer nonlinear programming (MINLP) model for the retrofit of heat exchanger networks (HENs) in order to improve their flexibility is presented in this paper. As stream flowrates and inlet temperatures and/or heat transfer coefficients are allowed to vary within either specified ranges or discrete sets, a multiperiod hyperstructure network representation is developed based on critical operating conditions (i.e. periods of operation) that limit the network's flexibility. This multiperiod hyperstructure includes all possible network configurations. Structural modifications, such as new stream matches, exchanger reassignments, splitting and mixing of streams are explicitly modeled either considering one-to-one or one-to-many assignment of heat exchangers to stream matches. Energy recovery and utility consumption are not predetermined but are optimized as part of a total annualized cost along with the structural modification cost in the objective function. Thus, trade-offs between operating and retrofit investment costs to improve the flexibility of a HEN are accounted for. The resulting large scale MINLP is solved with the application of the Generalized Benders Decomposition. The proposed multiperiod retrofit model can be included in a general framework to improve the operability of heat exchanger networks. 相似文献
14.
Bernadó P Mylonas E Petoukhov MV Blackledge M Svergun DI 《Journal of the American Chemical Society》2007,129(17):5656-5664
Structural analysis of flexible macromolecular systems such as intrinsically disordered or multidomain proteins with flexible linkers is a difficult task as high-resolution techniques are barely applicable. A new approach, ensemble optimization method (EOM), is proposed to quantitatively characterize flexible proteins in solution using small-angle X-ray scattering (SAXS). The flexibility is taken into account by allowing for the coexistence of different conformations of the protein contributing to the experimental scattering pattern. These conformers are selected using a genetic algorithm from a pool containing a large number of randomly generated models covering the protein configurational space. Quantitative criteria are developed to analyze the EOM selected models and to determine the optimum number of conformers in the ensemble. Simultaneous fitting of multiple scattering patterns from deletion mutants, if available, provides yet more detailed local information about the structure. The efficiency of EOM is demonstrated in model and practical examples on completely or partially unfolded proteins and on multidomain proteins interconnected by linkers. In the latter case, EOM is able to distinguish between rigid and flexible proteins and to directly assess the interdomain contacts. 相似文献
15.
Experimental Techniques - The mechanical behaviour of a 7 series high-strength aluminium alloy that is mainly used by the aerospace industry is under investigation. Aluminium alloy AA7449-T7651 is... 相似文献
16.
Angelos Tsoukalas Berç Rustem Efstratios N. Pistikopoulos 《Journal of Global Optimization》2009,44(2):235-250
We propose an algorithm for the global optimization of three problem classes: generalized semi-infinite, continuous coupled
minimax and bi-level problems. We make no convexity assumptions. For each problem class, we construct an oracle that decides
whether a given objective value is achievable or not. If a given value is achievable, the oracle returns a point with a value
better than or equal to the target. A binary search is then performed until the global optimum is obtained with the desired
accuracy. This is achieved by solving a series of appropriate finite minimax and min-max-min problems to global optimality.
We use Laplace’s smoothing technique and a simulated annealing approach for the solution of these problems. We present computational
examples for all three problem classes. 相似文献
17.
Gordana Klaric Felic Feras Al-Dirini Faruque M. Hossain Thanh Cong Nguyen Efstratios Skafidas 《Applied Physics A: Materials Science & Processing》2014,115(2):491-493
Properties of surface plasmon polaritons can be exploited for the miniaturisation of photonic circuits below the optical wavelength scale. Smaller and more sensitive photodetectors can be made by using sub-wavelength semiconductor elements such as germanium or silicon nanowires in combination with nanometer-scale antennas. The proposed nanowire photodetector enables on-chip optical sensing applications with increased sensitivity and reduced size. 相似文献
18.
Chryssou K Pelecanou M Pirmettis IC Papadopoulos MS Raptopoulou C Terzis A Chiotellis E Stassinopoulou CI 《Inorganic chemistry》2002,41(18):4653-4663
Synthesis of the 2,9-dimethyl-4,7-diaza-4-alkyl-2,9-decanedithiol (1, alkyl = morpholinylethyl in a, and alkyl = pyrrolidinylethyl in b), following a widely used synthetic scheme for diaminedithiol (DADT) ligands, led to the isolation of 1-alkyl-2-(1'-methyl-1'-sulfanylethyl)-3-(2' '-methyl-2' '-sulfanylpropyl)diazolidine (3) as the major product. Both ligands 1 and 2 gave complexes with the oxorhenium ReO(V) core. Ligand 1 gave the expected ReO[SNNS] complex (2) with the side chain on nitrogen in the syn configuration. Ligand 3 gave, in the presence of a monodentate aromatic thiol, complexes of the ReO[SNN][S][S] (4) and ReO[SNN][S] type (5), respectively, in which the diazolidine ring has rearranged to a thiazolidine ring. Crystallographic analysis showed that in 4 the coordination geometry about the metal is distorted octahedral where the equatorial plane is defined by the sulfur and one of the nitrogen atoms of the ligand and the two sulfurs of the aromatic thiols, while the axial positions are occupied by the oxygen of the ReO core and the second nitrogen of the ligand. Specifically, complex 4a crystallizes in space group P2(1)/c, a = 15.63(1) A, b = 15.28(2) A, c = 16.07(1) A, beta = 113.78(2) degrees, V = 3512(5) A(3), Z = 4. Complex 4b crystallizes in space group P2(1)/n, a = 14.560(9) A, b = 14.804(9) A, c = 19.85(1) A, beta = 90.94(2) degrees, V = 4278(1) A(3), Z = 4. In 5b, the coordination geometry is distorted square pyramidal with the SNN donor atom of the ligand and the aromatic thiol defining the equatorial plane and the doubly bonded oxygen occupying the apex of the pyramid. Complex 5b crystallizes in space group P(-)1, a = 9.387(5) A, b = 11.306(5) A, c = 14.040(6) A, alpha = 84.51(1) degrees, beta = 84.45(2) degrees, gamma = 87.17(1) degrees, V = 1475(1) A(3), Z = 2. All isolated complexes are neutral and lipophilic. Complete assignments of (1)H and (13)C NMR resonances are reported. 相似文献
19.
I.K. Mylonas A.K. Rossides V.M. Rothos 《The European physical journal. Special topics》2016,225(6-7):1187-1197
In this work, we study the stability and internal modes of one-dimensional gap solitons employing the modified nonlinear Schrödinger equation with a sinusoidal potential together with the presence of a weak nonlocality. Using an analytical theory, it is proved that two soliton families bifurcate out from every Bloch-band edge under self-focusing or self-defocusing nonlinearity, and one of these is always unstable. Also we study the oscillatory instabilities and internal modes of the modified nonlinear Schrödinger equation. 相似文献
20.
Bertini I Calderone V Fragai M Jaiswal R Luchinat C Melikian M Mylonas E Svergun DI 《Journal of the American Chemical Society》2008,130(22):7011-7021
The proteolytic activity of matrix metalloproteinases toward extracellular matrix components (ECM), cytokines, chemokines, and membrane receptors is crucial for several homeostatic and pathological processes. Active MMPs are a family of single-chain enzymes (23 family members in the human genome), most of which constituted by a catalytic domain and by a hemopexin-like domain connected by a linker. The X-ray structures of MMP-1 and MMP-2 suggest a conserved and well-defined spatial relationship between the two domains. Here we present structural data for MMP-12, suitably stabilized against self-hydrolysis, both in solution (NMR and SAXS) and in the solid state (X-ray), showing that the hemopexin-like and the catalytic domains experience conformational freedom with respect to each other on a time scale shorter than 10(-8) s. Hints on the probable conformations are also obtained. This experimental finding opens new perspectives for the often hypothesized active role of the hemopexin-like domain in the enzymatic activity of MMPs. 相似文献