Investigation of novel cuprates of the TlCa1-xLnxSr2Cu2O7- δ (Ln=rare earth) series showing electron- or hole-superconductivity depending on the composition

Superconductivity in cuprates of the general formula TlCa1-xLnxSr2Cu2O7+ delta has been investigated as a function of Ln and x. Compositions with 0.250.25. Thus, these cuprates exhibit a composition-dependent electron- or hole-superconductivity. In the normal state, most of the members of the series traverse compositionally determined metal-insulator transitions. High-energy spectroscopies show the presence of Cu in the 1+ and 2+ states. The Raman frequency around 525 cm-1 characteristic of the Tl-O2-Cu linkage is sensitive to both Ln and x, indicating a possible involvement in the mechanism of superconductivity.

An alpha-aminomethyl carbanion equivalent via a novel Barbier reaction: (1H-naphtho[1,8-de]-1,2,3-triazin-2-yl)methyl anion

A novel sonication-promoted Barbier reaction putatively generated the titled species from the corresponding naphthotriazinylmethyl chloride and magnesium in THF: its formal addition to a variety of carbonyl compounds in situ occurred in excellent yields. Subsequent catalytic hydrogenolysis of the triazine moiety demasked the amine, thus defining a route to various phenylethylamines (including the alkaloid 'mescaline'), or ethanolamines (in two cases), in excellent overall yields. (C) 2000 Elsevier Science Ltd. All rights reserved.

A Novel Construction of Complex Orthogonal Designs with Maximal Rate and Low-PAPR

Space-time block codes based on orthogonal designs are used for wireless communications with multiple transmit antennas which can achieve full transmit diversity and have low decoding complexity. However, the rate of the square real/complex orthogonal designs tends to zero with increase in number of antennas, while it is possible to have a rate-1 real orthogonal design (ROD) for any number of antennas.In case of complex orthogonal designs (CODs), rate-1 codes exist only for 1 and 2 antennas. In general, For a transmit antennas, the maximal rate of a COD is 1/2 + l/n or 1/2 + 1/n+1 for n even or odd respectively. In this paper, we present a simple construction for maximal-rate CODs for any number of antennas from square CODs which resembles the construction of rate-1 RODs from square RODs. These designs are shown to be amenable for construction of a class of generalized CODs (called Coordinate-Interleaved Scaled CODs) with low peak-to-average power ratio (PAPR) having the same parameters as the maximal-rate codes. Simulation results indicate that these codes perform better than the existing maximal rate codes under peak power constraint while performing the same under average power constraint.

Novel phase-transition behavior in an aqueous electrolyte solution

We have investigated the near-critical behavior of the susceptibility of a ternary liquid mixture of 3-methylpyridine. water, and sodium bromide as a function of the salt concentration. The susceptibility was determined from light-scattering measurements performed at a scattering angle of 90 degrees in the one-phase region near the locus of lower consolute points. A sharp crossover from asymptotic Ising behavior to mean-field behavior has been observed at concentrations ranging from 8 to 16.5 mass% NaBr. The range of asymptotic Ising behavior shrinks with increasing salt concentration and vanishes at a NaBr concentration of about 17 mass%. where complete mean-field-like behavior of the susceptibility is observed. A simultaneous pronounced increase in the background scattering at concentrations above 15 mass%, as well as a dip in the critical locus at 17 mass % NaBr, suggests that this phenomenon can be interpreted as mean-field tricritical behavior associated with the formation of a microheterogeneous phase due to clustering of the molecules and ions. An analogy with tri critical behavior observed in polymer solutions as well as the possibility of a charge-density-wave phase is also discussed. In addition, we, have observed a third soap-like phase an the liquid-liquid interface in several binary and ternary liquid mixtures.

A novel two sources ultrasound modulated optical tomographic system for screening breast cancer through elasticity characterization

The study of non-invasive characterization of elastic properties of soft biological tissues has been a focus of active researches since recent years. Light is highly scattered by biological tissues and hence, sophisticated reconstruction algorithms are required to achieve good imaging depth and a reasonable resolution. Ultrasound (US), on the otherhand, is less scattered by soft tissues and it has been in use for imaging in biomedical ultrasound systems. Combination of the contrast sensitivity of light and good localization of ultrasound provides a challenging technique for characterization of thicker tissues deep inside the body non-invasively. The elasticity of the tissues is characterized by studying the response of tissues to mechanical excitation induced by an acoustic radiation force (remotely) using an optical laser. The US modulated optical signals which traverse the tissue are detected by using a CCD camera as detector array and the pixel map formed on the CCD is used to characterize the embedded inhomogeneities. The use of CCD camera improves the signal-noise-ratio (SNR) by averaging the signals from all of the CCD pixels.

A novel fiber-coated strong base-type anion exchanger with superfast kinetics. Removal and recovery of silver thiosulfate from aqueous solutions

A commercial acrylic fiber with 92% (w/w) acrylonitrile content was partially hydrolyzed converting a fraction of the nitrile (-CN) groups to carboxylic acid (-COOH) groups, to coat the fiber with polyethylenimine (PEI) resin, which was then crosslinked with glutaraldehyde and further quaternized with ethyl chloroacetate to produce a novel strong-base anionic exchanger in the form of fiber. Designated as PAN(QPEI.XG)(Cl-), the fibrous sorbent was compared with a commercial bead-form resin Amberlite IRA-458(Cl-) in respect of sorption capacity, selectivity, and kinetics for removal of silver thiosulfate complexes from aqueous solutions. Though the saturation level of [Ag(S2O3)(2)](3-) on PAN(QPEI.XG)(Cl-) is considerably less than that on IRA-458(Cl-), the gel-coated fibrous sorbent exhibits, as compared to the bead-form sorbent, a significantly higher sorption selectivity for the silver thiosulfate complex in the presence of excess of other anions Such as S2O32-, SO42-, and Cl-, and a remarkably faster rate of both sorption and stripping. The initial uptake of the sorbate by the fibrous sorbent is nearly instantaneous, reaching up to similar to 80% of the saturation capacity within 10 s, as compared to only similar to 12% on the bead-form sorbent. The high initial rate of uptake fits a shell-core kinetic model for sorption on fiber of cylindrical geometry. With 4M HCl, the stripping of the sorbed silver complex from the fibrous sorbent is clean and nearly instantaneous, while, in contrast, a much slower rate of stripping on the bead-form sorbent leads to its fouling due to a slow decomposition of the silver thiosulfate complex in the acidic medium.

Structural and spectral perspectives of a novel thiosemicarbazone synthesized from di-2-pyridyl ketone and 4-phenyl-3-thiosemicarbazide

A new thiosemicarbazone, HL is synthesized from di-2-pyridyl ketone and 4-phenyl-3-thiosemicarbazide and structurally and spectrochemically characterized. H-1 NMR, C-13 NMR, COSY, HMQC and IR spectra of the compound are studied and the proton magnetic resonance spectrum reveals some unprecedented observations. The thione form is predominant in the solid state, as supported by the crystal structure and IR data, while a thiol-thione equilibrium is proposed in the solution state by NMR studies. The compound crystallizes into a monoclinic lattice with space group C2/c and the ZE conformation is exhibited by the thiosemicarbazone. Intra- and intermolecular hydrogen-bonding interactions give rise to a two-dimensional packing in the crystal lattice

A Novel Synthetic Route For The Preparation Of Ammonium And Alkali-Metal Tetrafluoroborates And Alkyl Substituted Ammonium Tetrafluoroborates Using Pyridinium Tetrafluoroborate As The Precursor

Ammonium and alkali metal tetrafluoroborates have been prepared by the cation exchange reaction of pyridinium tetrafluoroborate with the corresponding hydroxides/halides. The reaction of pyridinium tetrafluoroborate with primary, secondary and tertiary alkyl amines at room temperature gives rise to mono-, di- and tri-alkylammonium tetrafluoroborates, respectively. The yields are good and the samples are of high purity. The products have been characterised by elemental analysis, IR and PMR spectroscopy. The spectral data for most of the compounds are reported for the first time.

A Novel Synthetic Route for the Preparation of Silver Salts of Hexafluorophosphate, Tetrafluoroborate and Hexafluorosilicate

Silver salts of hexafluorophosphates, tetrafluoro-borates and hexafluorosilicates have been prepared by a metathetic reaction between the respective ammonium salts and silver nitrate in acetonitrile medium. This one step procedure at room temperature offers salts of high purity in good yields. The salts (AgpF6, AgBF4 and Ag2SiF6) have been characterised by IR spectral data analysis and chemical analysis.

High contrast laser writing in insitu textured germanium films via a novel chemical oxide formation

A high contrast laser writing technique based on laser induced efficient chemical oxidation in insitu textured Ge films is demonstrated. Free running Nd-YAG laser pulses are used for irradiating the films. The irradiation effects have been characterised using optical microscopy, electron spectroscopy and microdensitometry. The mechanism for the observed contrast has been identified as due to formation of GeO2 phase upon laser irradiation using X-ray initiated Auger spectroscopy (XAES) and X-ray photoelectron spectroscopy (XPS). The contrast in the present films is found to be nearly five times more than that known due to GeO phase formation in similar films.

HNbWO6 and HTaWO6: Novel layered oxides related to the rutile structure. Synthesis and investigation of ion-exchange and intercalation behaviour

New protonated layered oxides, HMWO6·1.5H2O (M=Nb or Ta), have been synthesized by topotactic exchange of lithium in trirutile LiMWO6 with protons by treatment with dilute HNO3. The tetragonal cell constants are a=4.71 (2) and c=25.70 (8)Å for HNbWO6·1.5H2O and a=4.70 (2) and c=25.75 (9) Å for HTaWO6·1.5H2O. Partially hydrated compounds, HMWO6·0.5H2O and anhydrous compounds, HMWO6 retain the layered structure. The structure of these oxides consists of MWO6 sheets built up of M/W-oxygen octahedra with rutile type corner- and edge-sharing. Interlayer protons in HMWO6 are exchanged with Li+, Na+, K+ and Tl+. HMWO6 exhibit Brønsted acidity intercalating n-alkylamines and pyridine.

Low-temperature synthesis of novel layered alkali metal-MoO3 bronzes and hexagonal bronzes of the type KyW1−xMoxO3

A new class of layered alkali metal-MoO3 bronzes,AxMoO3 (A =Li, Na, K, Rb), with nearly the same unit cell parameters as the host oxide has been synthesized by the solid-state reaction of MoO3 with alkali metal iodides around 575 K; LixMoO3 absorbs H2O causing an increase in theb parameter of the unit cell. Hexagonal potassium bronzes of W1−xMoxO3 are synthesized for the first time.

Structural and spectral perspectives of a novel thiosemicarbazone synthesized from di-2-pyridyl ketone and 4-phenyl-3-thiosemicarbazide

A new thiosemicarbazone, HL is synthesized from di-2-pyridyl ketone and 4-phenyl-3-thiosemicarbazide and structurally and spectrochemically characterized. H-1 NMR, C-13 NMR, COSY, HMQC and IR spectra of the compound are studied and the proton magnetic resonance spectrum reveals some unprecedented observations. The thione form is predominant in the solid state, as supported by the crystal structure and IR data, while a thiol-thione equilibrium is proposed in the solution state by NMR studies. The compound crystallizes into a monoclinic lattice with space group C2/c and the ZE conformation is exhibited by the thiosemicarbazone. Intra- and intermolecular hydrogen-bonding interactions give rise to a two-dimensional packing in the crystal lattice. (c) 2005 Elsevier B.V. All rights reserved.