On the Mach number and temperature dependence of jet noise: Results from a simplified numerical model

Numerical simulations of sound radiation from perturbed round jets are used, firstly to explore the structure of the sound sources and then to carry out a parametric study of the effect of jet Mach number and jet temperature. The simplified model problem includes a steady base jet flow, maintained in the absence of disturbances, superimposed with instability waves that are free to interact nonlinearly. Simulations over a range of subsonic jet Mach numbers show that a nonlinear mechanism dominates over a linear mechanism for low-frequency sound radiation, while for supersonic Mach numbers the linear mechanism is dominant. Additional insight is gained from a frequency-wavenumber analysis, including a transformation in the radial direction. With this decomposition, the acoustic field is located by the arc of a circle in plots of radial against streamwise wavenumber for discrete frequencies. The transformation is applied to both the pressure field, showing the sound directivity, and to selected source terms, showing characteristic directivity patterns for the streamwise and radial quadrupole terms. Decreasing the Mach number leads to a reduction in amplitude of the sources and of the sound radiation. Simulations with broadband forcing show that the qualitative effects of Mach number and jet heating are captured by this approach, which requires less resolution than a direct numerical simulation. A significant increase in the strength of the acoustic radiation for cold jets is observed, which is worthy of further investigation.     

On sufficiency and duality for a class of interval-valued programming problems

In this paper, we are concerned with an interval-valued programming problem. Sufficient optimality conditions are established under generalized convex functions for a feasible solution to be an efficient solution. Appropriate duality theorems for Mond-Weir and Wolfe type duals are discussed in order to relate the efficient solutions of primal and dual programs.     

Unsymmetrical diimine chelation to M(II) (M=Zn, Cd, Pd): atropisomerism, pi-pi stacking and photoluminescence

Three types of atropisomeric unsymmetrical diimine complexes, tetrahedral (L(R)(Φ))MX(2) (M = Zn, Cd; X = Cl, Br; R = Me, CMe(3), OH, OMe, Cl; 1a-k, type-I), tetrahedral (L(Me2)(Φ))ZnBr(2) (2, type-II) and square planar (L(OH)(?))PdCl(2) (3, type-III) with different photoluminescence properties, have been reported (L(R)(Φ) = (E)-4-R-N-(pyridine-2-ylmethylene)aniline; Φ = dihedral angle between the diimine unit including the pyridine ring and the phenyl ring planes). In crystals, Φ = 0° for type-I, 90° for type-II and 63° for type-III atropisomers have been confirmed by single crystal X-ray structure determinations of 1c, 1e, 2 and 3·H(2)O isomers. Optimizations of geometries in methanol have established Φ = 28-32° for type-I, 90.83° for type-II and 43.44° for type-III isomers. In solids, type-I atropisomers with Φ = 0, behave as conjugated 14πe systems facilitating π-π stacking and are brightly luminescent at room temperature while type-II and type-III isomers in solid and type-I isomers in solutions are more like non-conjugated 8πe + 6πe systems and non-emissive. Frozen glasses of acetonitrile, methanol and dichloromethane-toluene mixture at 77 K of type-I isomers are emissive and display structured excitation and emission spectra for R = Me, CMe(3), OMe species. Excitation and emission maxima of frozen glasses (λ(ex) = 320-380 nm; λ(em) = 440-485 nm) are red shifted in the solid (λ(ex) = 390-455 nm; λ(em) = 470-550 nm). TD-DFT calculations on 1b, 1d, 1f and stacked (1b)(2) isomers and luminescence lifetime measurements have elucidated that an excited (1)ILCT state has been the origin of emission of the type-I isomers and delocalizations of the photoactive π(diimine) and π(diimine)(*) orbitals of the L(R)(Φ) over the stacked layers shift the λ(ext) and λ(em) of solids to lower energies than those in frozen glasses. The trends of diimine ligand based electron transfer events of the complexes in DMF have been investigated by cyclic voltammetry at 298 K.     

A Study on Spectro-Analytical Aspects,DNA – Interaction,Photo-Cleavage,Radical Scavenging,Cytotoxic Activities,Antibacterial and Docking Properties of 3 – (1 – (6 – methoxybenzo [d] thiazol – 2 – ylimino) ethyl) – 6 – methyl – 3H – pyran - 2, 4 – dione and its Metal Complexes

The focus of the present work is on the design, synthesis, characterization, DNA-interaction, photo-cleavage, radical scavenging, in-vitro cytotoxicity, antimicrobial, docking and kinetic studies of Cu (II), Cd (II), Ce (IV) and Zr (IV) metal complexes of an imine derivative, 3 – (1 – (6 – methoxybenzo [d] thiazol – 2 – ylimino) ethyl) – 6 – methyl – 3H – pyran – 2, 4 – dione. The investigation of metal ligand interactions for the determination of composition of metal complexes, corresponding kinetic studies and antioxidant activity in solution was carried out by spectrophotometric methods. The synthesized metal complexes were characterized by EDX analysis, Mass, IR, ¹H-NMR, ¹³C-NMR and UV–Visible spectra. DNA binding studies of metal complexes with Calf thymus (CT) DNA were carried out at room temperature by employing UV-Vis electron absorption, fluorescence emission and viscosity measurement techniques. The results revealed that these complexes interact with DNA through intercalation. The results of in vitro antibacterial studies showed the enhanced activity of chelating agent in metal chelated form and thus inferring scope for further development of new therapeutic drugs. Cell viability experiments indicated that all complexes showed significant dose dependent cytotoxicity in selected cell lines. The molecular modeling and docking studies were carried out with energy minimized structures of metal complexes to identify the receptor to metal interactions.     

“On-water” synthesis of 3-substituted indoles via Knoevenagel/Michael addition sequence catalyzed by Cu doped ZnS NPs

Cu doped ZnS NPs represent a green catalyst for an ‘on-water’ one-pot rapid synthesis of 3-substituted indole derivatives via Knoevenagel/Michael addition reaction of indane-1,3-dione, aromatic aldehydes, and indole. The catalytic activity of Cu doped ZnS NPs was about sevenfold higher as compared to the ZnS NPs. The Cu doped ZnS NPs catalyst could be recovered and reused for five reaction cycles, giving a total TOF = 201 h⁻¹.     

Convenient,One-Step Syntheses of 2-Fluoroveratrole And 2-Fluoroveratraldehyde

Metalated veratraldehyde and veratrole were quenched with perchloryl fluoride to provide one-step syntheses of 2-fluoroveratraldehyde and 2-fluoroveratrole, respectively. Previous syntheses of these precursors to 2-fluorodopamine and 5-fluoronorepinephrine are multi-step processess which involve introduction of fluorine at an early stage. Perchloryl fluoride is a potentially hazardous reagent, and should be used only on an appropriate (millimolar) scale with precautions.     

Critical in vitro evaluation of responsive MRI contrast agents for calcium and zinc

The synthesis of two gadolinium(III) complexes that exhibit an increase in proton relaxivity in the presence of added Ca(2+) or Zn(2+) ions is reported. The complexes increase their hydration state from zero to one following metal-ion binding, confirmed by spectral measurements on the corresponding Eu(III) complexes. At a field of 1.4 T and 310 K, modulation of relaxivity of the order of 30-40% was observed in mouse serum in each case. The dissociation constants for Ca(2+) and Zn(2+) binding were sensitive to the presence of added bicarbonate, and were 450 μM (Ca(2+)) and 200 μM (Zn(2+)) in serum. Such systems may, therefore, be considered for use as magnetic resonance imaging (MRI) contrast agents to track the restoration of changes in metal-ion concentration in the cerebrospinal fluid of the brain, following neural stimulation.     

Altering protein surface charge with chemical modification modulates protein–gold nanoparticle aggregation

Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas significant attention has focused on modifying the nanoparticle surface to regulate protein–AuNP assembly or influence the formation of the protein “corona,” modification of the protein surface as a mechanism to modulate protein–AuNP interaction has been less explored. Here, we examine this possibility utilizing three small globular proteins—lysozyme with high isoelectric point (pI) and established interactions with AuNP; α-lactalbumin with similar tertiary fold to lysozyme but low pI; and myoglobin with a different globular fold and an intermediate pI. We first chemically modified these proteins to alter their charged surface functionalities, and thereby shift protein pI, and then applied multiple methods to assess protein–AuNP assembly. At pH values lower than the anticipated pI of the modified protein, AuNP exposure elicits changes in the optical absorbance of the protein–NP solutions and other properties due to aggregate formation. Above the expected pI, however, protein–AuNP interaction is minimal, and both components remain isolated, presumably because both species are negatively charged. These data demonstrate that protein modification provides a powerful tool for modulating whether nanoparticle–protein interactions result in material aggregation. The results also underscore that naturally occurring protein modifications found in vivo may be critical in defining nanoparticle–protein corona compositions.     

Separable integral extensions and plus closure

We show that an excellent local domain of characteristic p has a separable big Cohen–Macaulay algebra. In the course of our work we prove that an element which is in the Frobenius closure of an ideal can be forced into the expansion of the ideal to a module-finite separable extension ring. Received: 28 May 1998 / Revised version: 30 November 1998     

When SF5 outplays CF3: effects of pentafluorosulfanyl decorated scorpionates on copper

Polyfluorinated, electron-withdrawing, and sterically demanding supporting ligands are of significant value in chemistry. Here we report the assembly and use of a bis(pyrazolyl)borate, [Ph₂B(3-(SF₅)Pz)₂]⁻ that combines all such features, and involves underutilized pentafluorosulfanyl substituents. The ethylene and carbonyl chemistry of copper(i) supported by [Ph₂B(3-(SF₅)Pz)₂]⁻, a comparison to the trifluoromethylated counterparts involving [Ph₂B(3-(CF₃)Pz)₂]⁻, as well as copper catalyzed cyclopropanation of styrene with ethyl diazoacetate and CF₃CHN₂ are presented. The results from cyclopropanation show that SF₅ groups dramatically improved the yields and stereoselectivity compared to the CF₃.

Copper–ethylene and carbonyl complexes of the newly developed [Ph₂B(3-(SF₅)Pz)₂]⁻ enable the study of ligand steric and electronic effects caused by the –SF₅ group (dubbed “super CF₃”), and a comparison to the –CF₃ bearing analogs.