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51.
Phoevos Koukouvinis Manolis Gavaises Anastasios Georgoulas Marco Marengo 《International Journal of Computational Fluid Dynamics》2016,30(2):129-140
This paper discusses the implementation of an explicit density-based solver, that utilises the central-upwind schemes for the simulation of cavitating bubble dynamic flows. It is highlighted that, in conjunction with the Monotonic Upstream-Centered Scheme for Conservation Laws (MUSCL) scheme they are of second order in spatial accuracy; essentially they are high-order extensions of the Lax–Friedrichs method and are linked to the Harten Lax and van Leer (HLL) solver family. Basic comparison with the predicted wave pattern of the central-upwind schemes is performed with the exact solution of the Riemann problem, for an equation of state used in cavitating flows, showing excellent agreement. Next, the solver is used to predict a fundamental bubble dynamics case, the Rayleigh collapse, in which results are in accordance to theory. Then several different bubble configurations were tested. The methodology is able to handle the large pressure and density ratios appearing in cavitating flows, giving similar predictions in the evolution of the bubble shape, as the reference. 相似文献
52.
Kizas CM Manos MJ Nastopoulos V Boudalis AK Sanakis Y Tasiopoulos AJ 《Dalton transactions (Cambridge, England : 2003)》2012,41(5):1544-1552
Five novel pentanuclear Fe(3+) clusters with the aliphatic amino-alcohol ligands 3-amino-1-propanol (Hap) and 2-(hydroxymethyl)piperidine (Hhmpip) [Fe(5)(μ(3)-Ο)(2)(L)(4)(O(2)CR)(7)] [L = ap(-), R = Ph (1); L = ap(-), R = C(CH(3))(3) (2); L = hmpip(-), R = Ph (3); L = hmpip(-), R = C(CH(3))(3) (4)] and [Fe(5)(μ(4)-Ο)(μ(3)-Ο)(O(2)CC(CH(3))(3))(8)(ap)(2)Cl(HO(2)CC(CH(3))(3))] (5) are reported. Compounds 1-4 were prepared from reactions of preformed trinuclear Fe(3+) clusters with the ligands in a molar ratio 1 : 5 in MeCN (1, 3, 4) or DMF (2), whereas compound 5 was prepared from the reaction of FeCl(3) with Hap in the presence of HO(2)CC(CH(3))(3) in a molar ratio 1 : 3 : 2 in MeCN. To the best of our knowledge, 1-5 are the first examples of Fe(3+) complexes with the ligands Hap and Hhmpip. The structures of 1-4 are composed of a quasi-planar [Fe(5)(μ(3)-O)(2)](11+) core which consists of two vertex-sharing [Fe(3)(μ(3)-O)](7+) triangles. The structure of 5 is based on the [Fe(5)(μ(4)-O)(μ(3)-O)](11+) core, in which the five Fe(3+) ions adopt a monocapped trigonal pyramidal topology. Variable-temperature magnetic susceptibility measurements on powdered microcrystalline samples of 1 and 5 revealed the existence of antiferromagnetic interactions which led to an S = 5/2 ground state. M?ssbauer spectroscopy studies on powdered microcrystalline samples of 1 and 5 confirmed that all iron ions of both complexes are in the Fe(3+) (S = 5/2) state. The variation of the ligand environment in the various iron sites was reflected in their different quadruple splitting parameters. At T < 50 K the M?ssbauer spectra indicated the onset of spin relaxation effects in the time scale of the technique (10(-7)-10(-8) s). 相似文献
53.
Fraser SJ Mulet X Martin L Praporski S Mechler A Hartley PG Polyzos A Separovic F 《Langmuir : the ACS journal of surfaces and colloids》2012,28(1):620-627
A strategy for tethering lipid liquid crystalline submicrometer particles (cubosomes) to a gold surface for the detection of proteins is reported. Time-resolved quartz crystal microbalance (QCM-D) was used to monitor the cubosome-protein interaction in real time. To achieve specific binding, cubosomes were prepared from the nonionic surfactant phytantriol, block-copolymer, Pluronic F-127, and a secondary biotinylated lipid, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[biotinyl(polyethyleneglycol)-2000], which enabled attachment of the particles to a neutravidin (NAv)-alkanethiol monolayer at the gold surface of the QCM sensor chip. A second set of cubosomes was further functionalized with addition of the glycolipid (G(M1)) to facilitate a specific binding uptake of the protein, cholera toxin B subunit (CT(B)), from solution. QCM-D confirmed the specificity of the cubosome-NAv binding. The analysis of titration experiments, also performed with QCM, suggests that an optimal concentration of cubosomes is required for the efficient packing of the particles at the surface: high cubosome concentrations lead to chaotic cubosome binding onto the surface, sterically inhibiting surface attachment, or require significant reorganization to permit uniform cubosome coverage. The methodology enabled the straightforward preparation of a complex nanostructured edifice, which was then used to specifically capture analyte proteins (cholera toxin B subunit or free NAv) from solution, supporting the potential for development of this approach as a biosensing platform. 相似文献
54.
Complex networks have been studied across many fields of science
in recent years. In this paper, we give a brief introduction of
networks, then follow the original works by Tsonis et al
(2004, 2006) starting with data of the surface temperature from 160
Chinese weather observations to investigate the topology of
Chinese climate networks. Results show that the Chinese climate network
exhibits a characteristic of regular, almost fully connected
networks, which means that most nodes in this case have the same number
of links, and so-called super nodes with a very large number of
links do not exist there. In other words, though former results show
that nodes in the extratropical region provide a property of
scale-free networks, they still have other different local fine
structures inside. We also detect the community of the Chinese
climate network by using a Bayesian technique; the effective number
of communities of the Chinese climate network is about four in this
network. More importantly, this technique approaches results in
divisions which have connections with physics and dynamics; the
division into communities may highlight the aspects of the dynamics
of climate variability. 相似文献
55.
56.
57.
Reaction of [UO(2)(NO(3))(2)] with the hydroxy ketones 3-hydroxy-2-methyl-4-pyrone (Hma) and 3-hydroxy-1,2-dimethyl-4(1H)-pyridone (Hdpp) in aqueous acidic solutions (pH approximately 3) yields the compounds [UO(2)(ma)(2)(H(2)O)].H(2)O (1.H(2)O) and [UO(2)(dpp)(Hdpp)(2)(H(2)O)]ClO(4) (2), respectively. X-ray diffraction shows that the geometry around the metal ion in both complexes is pentagonal bipyramid. Uranium ion in the crystal structure of 1 were found to be ligated with two chelate ma(-) groups and one unidentate H(2)O molecule (C coordination mode) at the equatorial plane, while in 2 with two single-bonded Hdpp there were one chelate dpp(-) and one H(2)O molecule (P coordination mode). Crystal data (Mo Kalpha; 293(2) K) are as follows: (1) monoclinic space group C2/c, a = 14.561(7) A, b = 14.871(9) A, c = 7.250(4) A, beta = 95.40(4) degrees , Z = 4; (2) monoclinic space group P2(1)/c, a = 19.080(2) A, b = 9.834(1) A, c = 15.156(2) A, beta = 104.62(1) degrees , Z = 4. (1)H NMR measurements indicate that complex 2 retains its structure in CD(3)CN solution; however, in DMSO-d(6) both complexes adopt the C structure. Line-shape analysis for the (1)H NMR peaks of 2 at various temperatures shows a fast intramolecular exchange process between the chelate dpp(-) and one of the single bonded Hdpp ligands and one slower exchange between all three ligands. The activation parameters and the decrease of the exchange rate by replacing unidentate ligand with DMSO indicate the dissociation of the unidentate ligand as the rate-determining step for the former exchange. Density functional calculations (DFT) support this mechanism and give a quantitative interpretation of the electronic structure of the two ligands and the geometries adopted by the complexes. 相似文献
58.
John A. Mikroyannidis Anastasios P. Melissaris 《Journal of polymer science. Part A, Polymer chemistry》1988,26(5):1405-1418
Novel phosphorylated bismaleimides and nonphosphorylated tetramaleimides containing substituted s-triazine rings (chain-extended by imide, amide, or urea groups) were prepared and polymerized. These polymer precursors were prepared by reacting 2,4-bis(4-aminophenoxy)-6-diethoxyphosphinyl-s-triazine or 2,4,6-tris(4-aminophenoxy)-s-triazine with maleic anhydride in combination with a bridging agent such as pyromellitic or benzophenone tetracarboxylic dianhydride, terephthaloyl chloride, and tolylene diisocyanate. The structure of polymer precursors was confirmed by infrared (IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy and their curing behavior was investigated by differential thermal analysis (DTA). The phosphorylated bismaleimides were thermally polymerized at a lower temperature than did the corresponding nonphosphorylated tetramaleimides. Dynamic thermogravimetric analysis (TGA) showed that the nonphosphorylated and phosphorylated cured resins were stable up to 320–370 and 312–327°C, respectively, in nitrogen or air atmosphere. In addition, the latter afforded a relatively higher char yield. The relative thermal and thermooxidative stability of polymers with regard to the chemical structure of the bridging group was of the order imide > amide > urea. Upon isothermal aging the phosphorylated polymers exhibited a lower weight loss than did the corresponding nonphosphorylated polymers. 相似文献
59.
Spyros Nikas Nestor A. Rodios Anastasios Varvoglis Aristidis Terzis Catherine R. Raptopoulou 《Journal of heterocyclic chemistry》1996,33(3):997-999
The reaction between dimedone anion and trimethylsilylethynyl phenyliodonium triflate leads to the formation of 4,4-dimethyl-6-(1,5-bistrimethylsilylpentane-1,4-diyne-3-ylidene)-δ-valerolactone, whose crystal structure has been determined. 相似文献
60.
Anastasios I. Mitsionis Tiverios C. Vaimakis 《Journal of Thermal Analysis and Calorimetry》2010,99(3):785-789
The precipitation of calcium phosphate was studied using a heat flow twin calorimeter (C80, Setaram, France). The process
was carried out using two identical membrane vessels. In the lower parts of both vessels 2 mL of a supersaturated solution
(solution A) containing Ca(H2PO4)·2H2O (0.054 M) and CaCl2·H2O (0.125 M) with a molar ratio Ca/P = 1.67 were added. Then 0.05 mL of an ammonium solution (25% w/w) (solution B) and 0.05 mL
of distilled water were transferred in the upper parts of sample and reference vessels, respectively. After temperature had
been maintained at 303, 313, 323 and 333 K the membranes of both sample and reference vessels were broken simultaneously.
The precipitation process also repeated with the same conditions for periods of 15, 60 and 120 min in a bath. The first two
calorimetric curves (303, 313 K) show a single exothermic step during the process as a sharp peak in the initial stage. On
the contrary at the experimental temperature of 323 K except of the sharp peak in the initial stage, a steadily exothermic
tendency appears after 100 min time. In higher temperature (333 K) the sharp peak appears in the initial stage followed by
a broad exothermic step between 75 and 320 min time. The XRD analyses show that the solids in the initial experimental stages
are mainly consisted of dicalcium phosphate dihydrate (DCPD) for the lower temperature and a biphasic or triphasic system
consisted of hydroxyapatite (HA), dicalcium phosphate anhydrous (DCPA) and octacalcium phosphate (OCP) for the rest temperatures.
The XRD analyses show also that during the solution aging the initial products are transformed into the more stable thermal
forms of HA and octacalcium phosphate (OCP). 相似文献