Flux trapping in a macroscopic cylinderical hole drilled in Bi-Sr-Ca-Cu-O

The flux dynamics in a polycrystalline sample of Bi_1.7Pb_0.3Sr₂Ca₂Cu₃O_x with a macroscopic cylindrical hole (CH) drilled was investigated by slow transport relaxation (V-t curves) and magnetovoltage measurements (V-H curves). It was monitored that there are several discontinuities in the time evolution of quenched state in V-t curves, which was attributed to the leaving of quantized flux lines trapped through CH together with surface superconducting effects. We observed that asymmetric V-H curves demonstrate unusual remarkable counter clockwise hysteresis effects upon cycling of field. This interesting result was correlated mainly to the flux trapping inside the CH that acts as a macroscopic attractive pinning center for flux lines. Further, the hysteresis effects in V-H curves for a fixed transport current provide a direct evidence that the number of flux lines, measured dissipation and relative decrease/increase in irreversibilities could be determined by sweeping rate of external magnetic field (dH/dt) which leads also to peculiar time effects.     

The cytotoxic activities of imidazole derivatives prepared from various guanylhydrazone and phenylglyoxal monohydrate

Abstract

A series of imidazole derivatives were synthesized from two-component condensation reaction of phenylgloxal monohydrate with guanylhydrazone. They were characterized by spectroscopic and analytical techniques. The in vitro anticancer evaluation of these compounds was done on human breast cancer (MCF-7) and human liver cancer (HepG2) cell lines using the MTT assay method. Most of the newly synthesized compounds displayed cytotoxic activity against these cancerous cells. In fact, compounds 3a, 3e, and 3?h exhibited more cytotoxic activities than the positive control drugs, fluro-5, and irinocam, against the MCF-7 cell line. Almost all the compounds, except for three, 3b, 3d, and 3f, gave more cytotoxic results than cisplatin. Therefore, these compounds could be considered for further development as anticancer drug candidates.     

Spectroscopy and X-ray studies of {{6,6′-dimethoxy-2,2′-[ethane-1,2-diyl-bis-(nitrilomethylidyne)]diphenolato}(aqua)-dioxouranium(VI)} dehydrate

The C₁₈H₂₀N₂O₇U · 2H₂O (I) complex has been prepared and characterized by single crystal X-ray diffraction properties (CIF file CCDC no. 913243). The title compound crystallizes in the orthorhombic system, space group Pbca with a = 19.542(5), b = 9.916(5), c = 21.940(5) Å, V = 4252(3) ų and Z = 8. In complex I, the U atom has a distorted pentagonal-bipyramidal geometry with a tetradentate Schiff base ligand and water molecule in the equatorial plane and oxo atoms in the axial positions. The crystal packing occurs intra-inter molecular hydrogen bonds.     

Unitary quantum groups,quantum projective spaces andq-oscillators

We discuss the parametrization of quantum groups in terms of independent operators. We find that this consideration leads to the parametrization ofSU _q(2) in terms of aq-oscillator plus a commuting phase. The commuting phase is naturally identified with the subgroupU(1) and the remaining cosetSU _q(2)/U(1)=CP _q(1) consists of aq-oscillator. For unitary quantum groupsSU _q (n), the analogous construction results in the quantum projective spaceSU _q(n+1)/U _q (n)=CP _q (n) being identified with then-dimensionalq-oscillator. This yields a nonlinear action of the quantum groupSU _q(n+1) on then-dimensionalq-oscillator.     

Dynamic pricing and scheduling in a multi-class single-server queueing system

This paper investigates an optimal sequencing and dynamic pricing problem for a two-class queueing system. Using a Markov Decision Process based model, we obtain structural characterizations of optimal policies. In particular, it is shown that the optimal pricing policy depends on the entire queue length vector but some monotonicity results prevail as the composition of this vector changes. A numerical study finds that static pricing policies may have significant suboptimality but simple dynamic pricing policies perform well in most situations.     

Determination of Na, Mg, Al, Si, K, Cl, Ca and Fe in cigarette tobacco by fast neutron activation analysis

FNAA has been, for many years, a technique for the non-destructive analysis of a wide variety of sample materials-liquids, solids and powders. The important advantages of fast neutron activation analysis are good analytical sensitivity without sample preparation, accuracy and total analysis in a short time. In our work, the concentrations of the elements Na, Mg, Al, Si, K, Cl, Ca and Fe, were determined in cigarette tobacco of two brands commercially available in, Turkey using 14.6 MeV neutron activation analysis.     

Swelling of <Emphasis Type="Italic">N</Emphasis>-vinylcaprolactam-dodecyl methacrylate gel in {heptane + toluene} mixtures

A copolymer gel has been synthesized from N-vinylcaprolactam and dodecyl methacrylate in ethanol using the free radical cross-linking polymerization method. Characterizations of the gel were performed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) techniques. Swelling behavior of the gel was investigated in heptane, toluene, and their binary mixtures with different compositions. Swelling value in toluene is higher than that in heptane and swelling value increases with the increasing initial content of toluene in the binary mixture with heptane. The swelling values are correlated by the first- and second-order differential equations, and the best model correlating the experimental results is a second-order one. Diffusion coefficients have also been calculated for heptane and toluene at each concentration by power-law and first-order equations. While the diffusion mechanism of the gel in heptane is a Fickian one, the gel swelled in toluene exhibits a non-Fickian character. Diffusion mechanisms of the gels in binary mixtures are much more complicated. Because of the higher swelling degree in toluene compared to that in heptane, selectivity of the gel in different {heptane + toluene} mixtures with selectivity close to 1 has also been taken into consideration.     

Synthesis, characterization and aggregation behaviour of novel peripherally tetra-substituted octacationic water soluble metal-free and metallophthalocyanines

In this study, a new phthalonitrile derivative 3 bearing 1,3-bis[3(dimethylamino)phenoxy]propan-2-ol 1, metal-free phthalocyanine (Pc) 4, metallophthalocyanines (MPcs) 5–7 and their quaternized derivatives 4a–7a were synthesized. Metal-free Pc 4 was prepared by cyclotetramerization of phthalonitrile derivate 3 and MPcs 5–7 were synthesized by heating 3 with NiCl₂, CoCl₂ and CuCl₂ in n-pentanol in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, respectively. Quaternization of the dimethylamino functionality produced quaternized octacationic water soluble metal-free, Ni, Co and Cu Pcs which were soluble in water, DMF, DMSO. The aggregation behaviour of these compounds were investigated in different concentrations of chloroform for metal-free, Ni, Co and Cu Pcs. The effect of solvents on absorption spectra were studied in various organic solvents. The novel compounds were characterized using IR, ¹H-, ¹³C NMR, UV–vis and MS spectral data.     

Peptide anchored Langmuir–Blodgett films of a fullerene amphiphile

A new amphiphilic derivative of fullerene C₆₀ bearing an oligoglycyl tail (C₆₀CHCOgly₂OEt, 2) formed stable Langmuir floating films at the air–water interface. This occurred when the molecular assembly was stabilized by anchoring the amphiphilic C₆₀'s to the aqueous subphase, via hydrogen bonding interactions between a dipeptide (Gly–L–Leu) dissolved in the water subphase, and the oligoglycyl chain. The compression (π−A) isotherm of the Langmuir floating film constructed in such a way showed no hysteresis, was steep, and evidenced that the monolayer collapsed at a surface pressure π65 mN m⁻¹, thus confirming that the film was tightly packed, extremely stable, and rigid. A limiting area per molecule of 89.1 Ų was extrapolated, in agreement with the calculated cross-section area of the C₆₀ fullerene. On the contrary, when the dipeptide was absent and pure water was used as the subphase, the π−A isotherm yielded a limiting area <55 Ų which indicated the formation of multiple layers; moreover it showed significant hysteresis, the film was fragile, and it collapsed at π≈50 mN m⁻¹. Once anchored by the dipeptide, the floating monolayer of 2 could be transferred onto hydrophobic quartz, glass and silicon substrates, by successive vertical dipping cycles, each cycle made up of two down-strokes and two up-strokes, to yield the Langmuir–Blodgett film. Up to 200 down- and up-strokes could be repeated reproducibly, a noteworthy result for non-covalently assembled LB films of fullerenes. The transfer ratio was 1.0, except for the second down-stroke of each cycle that gave a transfer ratio of zero, making the sequence of successful transfers: D, U, U, (cleaning and spreading), D, U, U, (cleaning and spreading), and so on (D=down-stroke, U=up-stroke). The total number of deposited layers was therefore 150. X-ray diffraction spectra were registered and exhibited a peak, which was fitted by a Montecarlo method of simulation to obtain the distribution of the repeat unit responsible for scattering; such distribution, with thickness between 20 and 60 Å, was consistent with the size of the amphiphile and the transfer sequence. The UV–Vis spectra of the LB film exhibited the characteristic C₆₀ bands, and the absorption peaks in the 200–400 nm range were proportional to the number of layers, indicating that the deposition was reproducible and that the molecular environment of C₆₀ in each layer remained constant.