The synthesis and structural characterization of N-para-ferrocenyl benzoyl dipeptide esters: The X-ray crystal structure of N-{para-(ferrocenyl)benzoyl}-l-alanine-glycine ethyl ester

A series ofN-para-ferrocenyl benzoyl dipeptide esters 2-5 were prepared by coupling para-ferrocenyl benzoic acid (1) to the dipeptide ethyl esters using the conventional 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) protocol. The dipeptides employed in the synthesis were Ala-Gly(OEt) (2), Ala-Ala(OEt) (3), Ala-Leu(OEt) (4) and Ala-Phe(OEt) (5). The compounds were fully characterized by a range of NMR spectroscopic techniques, electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). In addition the X-ray crystal structure of the l-alanine-glycine derivative 2 has been determined.     

Acetyltrimethylsilane: a novel reagent for the transformation of 2H-pyran-2-ones to unsymmetrical biaryls

[reaction: see text] An expeditious synthesis of unsymmetrical biaryls functionalized with electron-withdrawing or -donating substituents is described and illustrated by carbanion-induced ring transformation of 2H-pyran-2-one using acetyltrimethylsilane (ATMS) as a novel reagent in good yield. The novelty of the reaction lies in the creation of an aromatic ring from 2H-pyran-2-ones via two-carbon insertion from ATMS used as a source of carbanion.     

Structural and dielectric properties of phosphorous-doped PLZT ceramics

In the present work we have reported the unique effects of P₂O₅-doped PLZT ceramics with composition (Pb_0.92La_0.08)(Zr_0.65Ti_0.35)O₃ +x wt% of P₂O₅ (wherex = 1, 3 and 5) prepared chemically by co-precipitation method. X-ray diffraction studies suggest that the prepared compound was very fine (10–25 nm), homogeneous and of rhombohedral symmetry. The apparent density of samples decreased with the P⁵⁺ additions. Studies of dielectric constant and dielectric loss as a function of frequency (10–1000 kHz) and temperature suggest that the compound undergoes diffuse type of phase transition without any sign of relaxor behaviour. With increasingx, dielectric constant was found to decrease appreciably, whereas Curie temperature (T_C) was found to increase     

Development of a new soft ferrite core for power applications

Manganese-substituted nickel–zinc ferrites have been investigated as power core materials for applications in switched-mode-power supplies. High frequency operation of these power supplies requires high performance cores with low power losses. The main contributors to the power loss are eddy current loss, hysteresis loss and residual loss. The ferrites have been synthesized by the citrate precursor technique and their electromagnetic properties such as resistivity, permeability, saturation magnetization and Curie temperature studied. A power loss of 500 mW/cc could be obtained at a frequency of 500 kHz, flux density of 50 mT and temperature 100 °C.     

Viscoelastic properties of silica‐grafted poly(styrene–acrylonitrile) nanocomposites

The melt state viscoelastic properties of styrene–acrylonitrile random copolymers grafted to silica nanoparticles and prepared by in situ atom transfer radical polymerization are examined. Linear dynamic oscillatory viscoelastic measurements indicate that nanocomposites with silica contents as low as 1.2 vol % exhibit solid‐like response. Steady shear results in considerable alteration to the mesoscale structure and results in the failure of the Cox‐Merz rule. Flow reversal studies confirm the elastic nature of the mesoscale structure and demonstrate that the relaxation of the flow altered structure is slow, non‐Brownian, and possibly cooperative. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2014–2023, 2006     

Effect of annealing temperature on microstructure of chemically deposited calcium modified lead titanate thin films

Thin ferroelectric films of calcium modified lead titanate Pb_1−xCa_xTiO₃(PCT) have been prepared by chemical deposition process. The as deposited amorphous films were thermally treated for crystallization and formation of perovskite structure. Characterization of these films by X-ray diffraction (XRD) have been carried out for various amounts of calcium (Ca)-doping (0.20, 0.24, and 0.28) on indium tin oxide (ITO) coated corning glass substrates. For a better understanding of the crystallization mechanism, the investigations were carried out at various annealing temperatures (450, 550, and 650 °C). Characterization of these films by XRD shows that the films exhibit tetragonal phase with perovskite structure. Atomic force microscope images (AFM) are characterized by slight surface roughness with a uniform crack-free, densely-packed structure. Also, Fourier transform infrared spectra (FT-IR) of the as deposited film and annealed thin films (x=0.24) at 650 °C on silicon (Si) substrates were taken to get more information about the film formation. Dielectric studies of the films were carried out and reported.     

Spin effects in InSb quantum wells

Among the III–V semiconductors, InSb has the smallest electron effective mass and the largest g-factor. We make use of these properties to explore some aspects of electron spin in InSb quantum wells with far-infrared magneto-spectroscopy. We observe the clear signature of spin-resolved cyclotron resonance caused by the non-parabolicity of the conduction band. We observe avoided-level crossings at magnetic fields where Landau levels of the same spin are predicted to intersect. We also study electron spin resonance in the far infrared over a wide range of magnetic field. In samples with symmetrically designed quantum wells we find cyclotron masses and observed g-factors in good agreement with a Pidgeon–Brown analysis adapted to the two-dimensional band structure. However, the spin splitting approaches 3 meV as the magnetic field approaches zero in samples intentionally asymmetrically doped.     

Muon catalyzed fusion of deuterium-tritium at elevated densities

Calculations of the number of deuterium-tritium fusions a muon might catalyze in temperature and density conditions found in moderate fuel compressions are examined. Analytic models of muon catalyzed fusion reactions including muon sticking suggest that a deuterium-tritium fuel target with injected muons achieves an energetically viable number of fusions per muon only at fuel temperatures less than about 5 eV and fuel densities greater than 100 times LHD.     

Some Conditions Implying Continuity of Maps

In this note, we study continuity of maps, in topological spaces, in terms of cluster points of images of convergent sequences and nets, and obtain some analogues of two results of Fuller [1].     

New lower rim looped calix[4]arene for ratiometric and chromogenic recognition of Cu2+

A new calix[4]arene derivative in its cone conformation and bearing Schiff base loop at the lower rim has been synthesized and evaluated as a specific molecular probe for copper ions. The new molecular receptor 4 shows a selective visible change in color from colorless to yellow only in the presence of Cu²⁺ ions which was confirmed by a significant bathochromic shift (?λ_max = 76 nm) in its absorption spectrum. The stoichiometry of the copper complex was calculated to be 1:1. These results may help to design more efficient chemical sensors for determining copper in biological systems.