75,023 research outputs found
Cation-π Interaction in Complex Formation Between Tl+ Ion and Calix[4]crown-6 and Some Calix[4]biscrown-6 Derivatives: Thallium-203 NMR, Proton NMR and X-Ray Evidences
No full textMetallocapped complexation of the thallium(I) ion with calix[4]crown-6 (1) and three different calix[4]biscrown-6
derivatives (2-4) has been investigated by a combination of 203Tl and 1H NMR in a CD3CN/CDCl3 (4:1 v/v) solution.
The results clearly revealed the formation in solution of mono- and dithallium(I) complexes in which the metal cations
are held in the ligands’ cavities close to the calix[4]arene ring. In addition, a solid state mononuclear complex between
1,3-calix[4]bis-o-benzo-crown-6 (3) and TlClO4 was prepared, and its X-ray crystal structure was determined. The
results of the structural data in solution and the solid state suggested that the calix[4]crown-6 derivatives considered
provide π cavities as active sites for the complexation of thallium(I) ions
Selective Extraction of Cesium at Tracer Level Concentration From a Sodium Nitrate Solution with Calix Crowns: Molecular Modeling Study of the Cs+/Na+ Selectivity
No full textCalix[4]arene mono- and bis-crown6 in the 1,3 alternate conformation are highly selective extractants for cesium towards sodium in an acidic liquid waste. Extraction and selectivity are related to complexation properties which can be studied by Molecular Dynamics techniques. In this paper, we describe the results of Molecular Dynamics simulations in an explicit water phase for four complexes of 1,3-alternate mono- and bis-crown-calix[4]arenes. The structural features obtained are interpreted on the basis of cation/ligand complementarity and can explain the relative performances in Na+ and Cs+ extraction for the compounds simulated
The Benefits of Being Economics Professor A (and not Z)
No full textAlphabetic name ordering on multi-authored academic papers, which is the convention in the economics discipline and various other disciplines, is to the advantage of people whose last name initials are placed early in the alphabet. As it turns out, Professor A, who has been a first author more often than Professor Z, will have published more articles and experienced afaster growth rate over the course of her career as a result of reputation and visibility. Moreover, authors know that name ordering matters and indeed take ordering seriously: Several characteristics of an author group composition determine the decision to deviate from the default alphabetic name order to a significant extent.performance measurement, incentives, economists, name ordering
Final word on Jersey Dutch
No full textIn this article, William Z. Shetter compares and contrasts the dialects that developed between different Dutch colonies in the New World. He explores in-depth the nuances of Jersey Dutch, and provides theories to explain how Dutch and colonial languages blended. The article is reprinted from American Speech, December 1958, Volum XXXIII, No. 4
Lanthanide Complexes of Encapsulating Ligands: Luminescent Device at the Molecular Level
No full textLanthanide complexes of encapsulating ligands are studied as luminescent devices at the molecular level. The photophysical properties of the complexes which, up till now, showed the most intense luminescence are reported. The luminescence intensity of these complexes is discussed considering the efficiency of incident light-emitted light conversion, defined as the product of the absorption efficiency and the luminescence quantum yield. It is illustrated how the metal luminescence intensity can be enhanced by adapting the ligands on basis of previously obtained experimental results. The possible application of these complexes in fluoroimmunoassays is examined
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Statistics of the subgrid scales after the shock-turbulence interaction
No full textThe interaction of a normal shock with isotropic turbulence (IT) represents a basic problem for studying some of the phenomena associated with high speed flows, such as hypersonic flight, supersonic combustion and Inertial Confinement Fusion (ICF). In general, in practical applications, the shock width is much smaller than the turbulence scales and the upstream turbulent Mach number is modest. In this case, recent high resolution shock-resolved Direct Numerical Simulations (DNS) (Ryu and Livescu, J. Fluid Mech., 756, R1, 2014) show that the interaction can be described by the Linear Interaction Approximation (LIA). By using LIA to alleviate the need to solve the shock, DNS post-shock data can be generated at much higher Reynolds numbers than previously possible. Here, such results with Taylor Reynolds number around are used to investigate the properties of the subgrid scales (SGS). In particular, it is shown that the shock interaction decreases the asymmetry of the SGS dissipation PDF as the shock Mach number increases, with a significant enhancement in size of the regions and magnitude of backscatter
Transition to turbulence in a qblique shock-wave/boundary-layer interaction at M=15
No full textDirect numerical simulations are carried out for different forcing techniques to trigger transition during the interaction between an oblique shock-wave and a laminar boundary-layer at M = 1.5. Three forcing methods are used: a) forcing of oblique unstable modes, whose shape and behaviour are determined by the local linear stability theory, b) broadband free-stream acoustic disturbances, and c) a cold plasma flow control device. While the oblique-mode breakdown is dominant for low-amplitude forcing, long streaky structures drive the transition process in a high-amplitude disturbance environment. LES are also performed on the experimental setup by the Institute of Theoretical and Applied Mechanics (ITAM) from Novosibirsk State University with cold plasma actuation. As well as the disturbance type, the effect of Reynolds number and forcing amplitude will be investigated
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