Vortex sound due to a flexible boundary backed by a cavity in a low mach number mean flow

Low frequency sound radiated due to the unsteady motion of an inviscid vortex in the proximity of a flexible membrane backed by an airtight cavity on an otherwise rigid plane is investigated theoretically. Results show that both monopole and dipole are created but the latter is important only when the vortex is traversing over the membrane. The monopole results from the membrane vibration and the dipole from the transverse motion of the vortex. It is also found that these sound fields tend to counteract each other. The increase in the mean flow speed in general results in a stronger acoustic power radiation, but sound attenuation may be possible if the membrane-cavity system is weak compared with the mean flow momentum.     

Syntheses,structures, and optical properties of heteroselenometallic W–Se–Ag polymer compounds {[Et4N][(μ-WSe4)Ag]}n and {[Ln(Me2SO)8][(μ3-WSe4)3Ag3]}n (Ln = Pr,Er)

The one-dimensional linear polymer W–Se–Ag compound {[Et₄N][(μ-WSe₄)Ag]}_n (1) was obtained from the reaction of [Et₄N]₂[WSe₄] and AgNO₃ in a mixed solvent, MeCN/DMF (1:10). Treatment of a solution of 1 in Me₂SO with Ln(NO₃)₃ · 6H₂O resulted in the formation of a helical chain polymer compound {[Ln(Me₂SO)₈][(μ₃-WSe₄)₃Ag₃]}_n (Ln = Pr 2, Er 3). The solid-state structures of the three polymer compounds 1, 2, and 3 have been established by X-ray crystallography. The third-order non-linear optical properties of the linear polymer compound 1 were determined by z-scan techniques with 7 ns pulses at 532 nm.     

Tunable stabilization of gold nanoparticles in aqueous solutions by mononucleotides

Gold nanoparticles are one of the popular nanomaterials, widely used in biosensor applications as well as nanostructure construction. An essential attribute of these gold nanoparticles (Au-nps) is their stabilization against salt-induced aggregation. In this work, utilization of deoxyribonucleotides (dNTPs) as a tunable surface-stabilization agent for Au-nps was investigated. It was found that surfaces of Au-nps are covered by a layer of dNTPs after an adequate incubation with dNTPs solutions. Electrostatic repulsion among dNTP-coated Au-nps could prevent aggregation of Au-nps at a high salt concentration. The strength of dNTP-based protection can be manipulated by changing preparation protocols (e.g., incubation temperature, ionic strength, and ratio of Au-nps to dNTPs). Four different types of dNTPs exhibit different binding affinity to Au-nps and thus various stabilization efficiency in the order of dATP > dCTP > dGTP approximately dTTP. Moreover, this salt-induced aggregation can be reinitiated by the increase of solution temperature, which leads to a partial removal of the protective dNTP layer on Au-nps. The advantage of thermally tunable aggregation/dispersion of Au-nps mediated by dNTP adsorption offers a useful approach for the preparation of biomolecule (oligonucleotides and oligopeptides) modified nanoparticles in applications of bioassay and nanobiotechnology.     

Metabolic studies of turinabol in horses

Turinabol (4-chloro-17alpha-methyl-17beta-hydroxy-1,4-androstadien-3-one) is a synthetic oral anabolic androgenic steroid. As in the case of other anabolic steroids, it is a prohibited substance in equine sports. The metabolism of turinabol in human has been reported previously; however, little is known about its metabolic fate in horses. This paper describes the studies of both the in vitro and in vivo metabolism of turinabol in racehorses with an objective to identify the most appropriate target metabolites for detecting turinabol administration. For the in vitro studies, turinabol was incubated with fresh horse liver microsomes. Metabolites in the incubation mixture were isolated by liquid-liquid extraction and analysed by gas chromatography-mass spectrometry (GC-MS) after trimethylsilylation. The results showed that the major biotransformation of turinabol was hydroxylation at the C6, C16 and C20 sites to give metabolites 6beta-hydroxyturinabol (M1), 20-hydroxyturinabol (M2), two stereoisomers of 6beta,16-dihydroxyturinabol (M3a, M3b) and 6beta,20-dihydroxyturinabol (M4). The metabolite 6beta-hydroxyturinabol was confirmed using an authentic reference standard. The structures of all other turinabol metabolites were tentatively identified by mass spectral interpretation. For the in vivo studies, two horses were administered orally with turinabol. Pre- and post-administration urine samples were collected for analysis. Free and conjugated metabolites were isolated using solid-phase extraction and analysed by GC-MS as described for the in vitro studies. The results revealed that turinabol was extensively metabolised and the parent drug was not detected in urine. Two metabolites detected in the in vitro studies, namely 20-hydroxyturinabol and 6beta,20-dihydroxyturinabol, these were also detected in post-administration urine samples. In addition, 17-epi-turinabol (M5) and six other metabolites (M6a-M6c and M7a-M7c), derived from D-ring hydroxylation and A-ring reduction, were also detected. Except for 17-epi-turinabol, none of these metabolites has ever been reported in any species. All in vivo metabolites were detected within 48 h after administration.     

Hyper-Lagrangian submanifolds of Hyperkähler manifolds and mean curvature flow

In this article, we define a new class of middle dimensional submanifolds of a Hyperkähler manifold which contains the class of complex Lagrangian submanifolds, and show that this larger class is invariant under the mean curvature flow. Along the flow, the complex phase map satisfies the generalized harmonic map heat equation. It is also related to the mean curvature vector via a first order differential equation. Moreover, we proved a result on nonexistence of Type I singularity.     

Fluorescent probes alter miscibility phase boundaries in ternary vesicles

We use 2H NMR to study the effects of probes on the miscibility transition in multilamellar vesicles of di(18:1) phosphatidylcholine (PC; DOPC), chain perdeuterated di(16:0)PC (DPPCd62), and cholesterol both with and without 0.5 mol % of the fluorescent probes DiIC12 and DiOC18. Both probes raise the miscibility transition temperature in dispersions of 1:1 DOPC/DPPCd62 + 30% cholesterol but to differing extents. In membranes containing the popular probe DiIC12, the fraction of DPPCd62 lipids in the liquid disordered phase is increased, and the ordering of that phase is reduced even at low temperatures. All findings are consistent with a probe-induced expansion of the entire miscibility phase boundary. We examine membranes with smaller DiIC12 fractions and find a significant increase in transition temperature for samples with 0.05 mol % DiIC12, demonstrating that trace components can dramatically alter membrane phase behavior.     

Exchange bias and blocking temperature in Co/FeMn/CuNi trilayers

Aspects of exchange bias between antiferromagnets and ferromagnets remain unclear despite recent research. An outstanding issue is the relationship between exchange bias and enhanced coercivity in the ferromagnetic layer. This Letter reports the unexpected finding that a substantial exchange bias can be generated between an antiferromagnet (FeMn) with a higher ordering temperature than that of the ferromagnet (CuNi). We interpret the result in terms of a temperature-dependent competition between interfacial exchange and antiferromagnet anisotropy energies. Crossover of these energies during cooling is responsible for the onset of exchange bias at the blocking temperature.     

Ruthenium complexes with tetraphenylimidodiphosphinate: syntheses, structures, and applications to catalytic organic oxidation

Treatment of Ru(PPh3)3Cl2 with K(tpip) (tpip(-)=[N(Ph2PO)2](-)) afforded Ru(tpip)(PPh3)2Cl (1), which reacted with 4- t-Bu-C6H4CN, SO2(g), and NH 3(g) to give Ru(tpip)(PPh3)2Cl(4- t-BuC6H4CN) (2), Ru(tpip)(PPh3)2Cl(SO2) (3), and fac-[Ru(NH3)3(PPh3)2Cl][tpip] (4), respectively. Reaction of [Ru(CO)2Cl2] x with K(tpip) in refluxing tetrahydrofuran (THF) led to isolation of the K/Ru bimetallic compound K 2Ru2(tpip)4(CO)4Cl2 (5). Photolysis of cis-Ru(tpip) 2(NO)Cl in MeCN and wet CH 2Cl 2 afforded cis-Ru(tpip) 2(MeCN)Cl ( 6) and cis-Ru(tpip)2(H2O)Cl (7), respectively. Refluxing 6 in neat THF yielded Ru(tpip) 2(THF)Cl (8). Treatment of Ru(CHR)Cl2(PCy3)2 (Cy=cyclohexyl) with [Ag(tpip)] 4 afforded cis-Ru(tpip)2(CHR)(PCy3) [R=Ph (9), OEt (10)]. Complex 9 is capable of catalyzing oxidation of alcohols and olefins with N-methylmorpholine N-oxide and iodosylbenzene, respectively. The crystal structures of 2-7 and 9 were determined.