Hg(II) Coordination Studies in Penicillamine Enantiomers by 199mHg-TDPAC

In order to study the binding of the toxic heavy metal ion Hg²⁺ to penicillamine, complexes with the D- and L-enantiomers of penicillamine were investigated by the nuclear quadrupole interaction of ¹⁹⁹Hg monitored by time differential perturbed angular correlation spectroscopy. It was found that bound Hg(II) occurs in two-fold, three-fold and four-fold coordinations. This revised version was published online in September 2006 with corrections to the Cover Date.     

Evidence of Hg-chain formation in Hg x TiS2: a199mHg-TDPAC study

We determined the^199mHg nuclear quadrupole interaction in the misfit or superstoichiometric compound Hg _x TiS₂ by time differential perturbed angular correlation. A unique Hg-site withv _Q =511(1) MHz and =0.410(4) was observed, irrespective of the Hg-uptake (2/3x4/3). We propose a model of Hg-Hg zig-zag chains which accounts for these observations as well as for the X-ray diffraction data.     

Hg 199(n,ce) Hg200 studies

The conversion-electron spectrum from slow neutron capture in Hg 199 has been measured with the beta spectrometer at the reactor FRM. Approximately 100 conversion-electron lines with energies between 200 and 2300 keV were observed. The multipolarities and mixing ratios of about 50 transitions were determined. Branching and mixing ratios are compared with theoretical predictions.     

Electron spin resonance studies of 199HgH, 201HgH, 199HgD and 201HgD isolated in neon and argon matrices at 4K: an electronic structure investigation

Various isotopomers of the mercury hydride radical (HgH) have been generated in a microwave discharge and trapped in neon and argon matrices at 4 K for electron spin resonance (ESR) investigations. Both the dipolar (A_dip) and isotropic (A_iso) components of the nuclear hyperfine interactions have been directly measured for ¹⁹⁹Hg, ²⁰¹Hg, H and D. Electronic structure information for HgH in its X²Σ ground state obtained from the hyperfine data is compared with theoretical results from several different computational methods. The hyperfine interactions in HgH are unusually large with A_iso(¹⁹⁹Hg) = 6859(3), A_dip(¹⁹⁹Hg) = 446(3), A_iso(H) = 730(2) and A_dip(H) = 0(2) MHz. A standard analysis of the hyperfine interactions demonstrates the need for a more in-depth theoretical treatment of HgH that should include relativistic effects. An interesting shift in spin density is observed when deuterium replaces hydrogen in HgH. The decreased spin density on deuterium, which was demonstrated in earlier studies, can now be more fully investigated since these new measurements confirm an associated increase in spin density on mercury     

Analytical TEM studies of Nd-Fe-B containing V,Co and Dy

Microstructural changes resulting from the addition of V, Co and Dy to Nd-Fe-B to yield the composition Nd_14.4Dy_1.6Fe₆₇Co₅V₄B₈ have been studied using transmission electron microscopy (TEM). Two types of precipitates ranging in size from ≈ 0.1 μm to several micrometers in diameter were observed embedded in the intergranular Nd-rich region and within the hard magnetic matrix grains. These two types of precipitates were round and lamellar, respectively. They were both borides (V boride and V-Fe boride) as shown by electron energy loss spectroscopy (EELS). TEM diffraction patterns revealed that the lamellar phase could be indexed as an orthorhombic structure with a = 0.291 nm, b = 0.278 nm and c = 0.7837 nm, which is close to VB and has not been reported before in V containing Nd-Fe-B material. The round particles have a tetragonal structure with a = 0.53 nm and b = 0.30 nm, which is similar to that of the V_2-x Fe_xB₂ phase reported previously. Co was found to form Nd₃Co precipitates in the Nd-rich boundary regions. The Co dissolved in the matrix phase is responsible for the increase of Curie temperature ( ≈ 354°C).     

Alpha decay properties of199Rn and199mRn

Theα-decays of¹⁹⁹Rn (E _α = (6.989±0.010) MeV,T _1/2>300ms) and of^199m Rn (E _α = (7.060±0.015) MeVT _1/2=(61 _?2 ⁺³² ) ms) were identified by anα-α-correlation method. They proceed via separated decay paths to¹⁹⁵Po and^195m Po, respectively. The spins of the involved states are discussed by aid of the shell model, and a tentative spin assignment is given.     

199Hg and63,65Cu NMR studies of mercury based high-T c superconductors

Hg-oxide ceramic high temperature superconductors were studied by¹⁹⁹Hg and^63,65Cu NMR spectroscopy. Room temperature spectra, spin-spin and spin-lattice relaxation times of samples with different superconducting transition temperatures are presented. A spin-lattice relaxation time ofT ₁=35 msec and a spin-spin relaxation time ofT ₂=1.6 msec were found for the¹⁹⁹Hg NMR. All samples exhibit similar characteristic powder spectra caused by an axially symmetric¹⁹⁹Hg spin interaction. The isotropic value and the anisotropy of the tensor relative to solid HgCl₂ as a standard substance is estimated. Furthermore, results of^63,65Cu NMR measurements at a temperature of 4.2 K which exhibit a typical powder line shape (forI=3/2) are presented.     

Interactions between oligopeptides and oxidised titanium surfaces detected by vibrational spectroscopy

Five alternating polar/hydrophobic oligopeptides derived from EAK 16 (AEAEAKAKAEAEAKAK) were examined in comparison with EAK 16 (peptide 1) both after solubilisation/lyophilisation and deposition on oxidised titanium surfaces. The peptides were synthesised for their possible use as biomimetic materials due to their self‐assembling properties and the presence, in one of them, of the arginine‐glycine‐aspartic (RGD) sequence, an active modulator of cell adhesion. Infrared (IR) and Raman spectroscopies were used to investigate the influence of the amino acid substitution on the self‐assembling properties of the peptides under both experimental conditions. In the lyophilised peptides, β‐sheet was the prevailing conformation (65–69%) as in EAK 16, irrespective of acid substitution (E→D, peptide 2), basic substitution (K→O, peptide 3), hydrophobic spacer substitution (A→Abu, peptide 4 and A→Y, peptide 5) and RGD insertion (peptide 6). After deposition on oxidised titanium, the main conformation remained β‐sheet. The side‐chain shortening of the acidic amino acid residue (peptide 2) or the insertion of a rigid and bulky residue such as Y (peptide 5) decreased the self‐assembling ability more than the side‐chain shortening of the basic amino acid residue (peptide 3) or the insertion of the RGD head (peptide 6). The interaction with the oxidised titanium surface was mainly due to carboxylate groups with a bidentate bridging coordination and C  O peptidic groups. Copyright © 2010 John Wiley & Sons, Ltd.     

Conductivity, FTIR studies, and thermal behavior of PMMA-based proton conducting polymer gel electrolytes containing triflic acid

The addition of polymer to liquid electrolytes containing trifluoromethanesulfonic acid (HCF₃SO₃) in propylene carbonate (PC) has been found to result in an increase in conductivity of gel electrolytes. The increase in conductivity has been observed to be due to the dissociation of ion aggregates present in the electrolytes which has also been supported by Fourier transform infrared studies. The maximum ionic conductivity (at 25 °C) of 7.55?×?10^?3 S/cm has been observed for polymer gel electrolytes containing 1.5 wt% polymethylmethacrylate in 0.5 M solution of HCF₃SO₃ in PC. Polymer gel electrolytes have been found to be thermally stable up to a temperature of 125 °C by simultaneous differential scanning calorimetry/thermogravimetric analysis studies. The conductivity of polymer gel electrolytes does not show any appreciable change over a limited period of time.     

Production of the Hg-199 isotope by the photochemical method

Researchers at the Russian Research Center Kurchatov Institute are developing a photochemical method of mercury isotope extraction. The method is based on oxidation of selectively excited mercury atoms in the presence of 1,3-butadiene. Along with the Hg-198, Hg-196, Hg-200, and Hg-202 isotopes, a Hg-199 isotope with a concentration as high as 90% has been produced for the first time.     

Nanocrystals and amorphous matrix phase studies of Finemet-like alloys containing Ge

Two simple models were developed in order to determine the chemical composition of both nanocrystals and intergranular amorphous phases in nanocrystallized Fe_73.5Si_13.5B₉Nb₃Cu₁ containing Ge using data from X-ray diffraction and Mössbauer spectroscopy techniques. Saturation magnetization of the amorphous intergranular matrix (M_s^am) was calculated considering the contribution of the α-Fe(Si,Ge) nanocrystals and saturation magnetization of the alloys. The behavior of M_s^am with the iron content of the matrix was obtained and discussed. The exchange stiffness constant for the nanograins and for the amorphous phases was determined. The increment in the coercive field (H_c) with increasing Ge content was evaluated using two theoretical models for the random magnetocrystalline anisotropy constant (〈K₁〉). Results show that the magnetic hardening observed could not be attributed to an increase in 〈K₁〉 but mainly to an important increment of the magnetostriction constant of the α-Fe(Si,Ge) nanocrystals (λ_s^cr). Values for λ_s^cr are proposed.     

99Ru,61Ni,57Fe,and119Sn Mössbauer studies of Heusler alloys containing ruthenium

⁹⁹Ru,⁶¹Ni,⁵⁷Fe and¹¹⁹Sn Mössbauer spectroscopic studies were made on ternary intermetallic compounds containing ruthenium, Ru_xY_3?xZ (Y=Fe, Ni; Z=Si, Sn). In the system of Ru_xFe_3?xSi, two different hyperfine magnetic fields were observed at the⁹⁹Ru nuclei (H _hf[Ru]) in the range ofx≤1.0 and the magnitude of eachH _hf[Ru] was found to decrease with an increase in the ruthenium concentrationx. Both the⁹⁹Ru and¹¹⁹Sn Mössbauer spectra of Ru₂FeSn could be analyzed with two sets of magnetically split lines. The⁶¹Ni Mössbauer spectra of Ru₂NiSn were obtained at 5 and 77 K.     

Proton NMR relaxation studies of solid tyrosine derivatives and their mixtures with L-leucinamide.

Proton NMR relaxation time measurements were carried out on solid tyrosine derivatives: acetyl-L-tyrosine ethyl ester (Ac-Tyroet), N-carbobenzyloxy-L-tyrosine ethyl ester (CBZ-Tyroet), N-trifluoroacetyl-L-tyrosine ethyl ester (TFAc-Tyroet) and their mixtures with L-leucinamide. It was found that spin-lattice relaxation was driven mainly by methyl group rotation it low temperature for the pure solids and the mixtures. Benzene ring flipping motion and a third motion (possibly whole molecule tumbling) were found to be responsible for relaxing Ac-Tyroet and CBZ-Tyroet at high temperature. However, these motions were highly hindered in TFAc-Tyroet. Molecular tumbling motion was detected in the supercooled liquid mixtures of L-leuNH/CBZ-Tyroet and L-leuNH/Ac-Tyroet, while this motion is absent in the mixture L-leuNH/TFAc-Tyroet. The hindered motion in TFAc-Tyroet may be one of the factors affecting its ability to form a supercooled liquid with L-leucinamide.     

ESR spectral studies of a Cu(II) salicylidene tyrosine complex

A novel Schiff base derived from salicylidene and tyrosine and its copper(II) complex have been synthesized and characterized. The composition of the complex is K[CuL(Ac)] · H₂O, where L = H₁₃C₁₆NO₄. Electron spin resonance (ESR) spectra of the copper(II) complex were investigated at different temperatures and in various solvents. The second-order effect and the relaxation effect were observed in the solution spectrum at room temperature and satisfactorily explained by the spin Hamiltonian. The bonding parameters of the Cu(II) complex were calculated with spectral parameters from ESR spectra at low temperature. Its bonding characterization and stability were discussed. The result shows that both the in-plane σ-bond and the in-plane π-bond in the complex play an important role.     

DSC and elastic moduli studies on tellurite-vanadate glasses containing antimony oxide

xSb₂O₃-40TeO₂-(60 − x) V₂O₅ glasses with 0 ≤ x ≤ 10 (in mol%) have been prepared by rapid- melt quenching method. DSC curves of these ternary glasses have been investigated. The glass transition properties that have been measured and reported in this paper, include the glass transition temperature (T _g ), glass transition width (ΔT _g ), heat capacity change at glass transition (ΔC _P ) and fragility (F). Thermal stability, Poisson’s ratio, fragility and glass forming tendency of these glasses have been estimated, to determine relationship between chemical composition and the thermal stability or to interpret the structure of glass. In addition, Makishima and Makenzie’s theory was applied for determination of Young’s modulus, bulk modulus and shear modulus, indicating a strong relation between elastic properties and structure of glass. Generally, results of this work show that glass with x = 0 has the highest shear, bulk and Young’s moduli which make it as suitable candidate for the manufacture of strong glass fibers in technological applications; but it should be mentioned that glass with x = 8 has higher handling temperature and super resistance against thermal attack.     

Nonlinear optical studies of a newly synthesized copolymer containing oxadiazole and substituted thiophenes

We investigated the third-order nonlinear optical properties of a newly synthesized soluble copolymer containing oxadiazole and thiophene units using Z-scan and Degenerate Four Wave Mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of χ⁽³⁾ determined from both experiments. Z-scan results indicate a negative nonlinear refractive index, n₂, whose magnitude is of the order of 10⁻¹⁰ esu. The copolymer exhibits strong nonlinear absorption and good optical limiting properties at 532 nm, and hence may be a potential material for optical limiting applications.     

Absorption and fluorescence studies of Sm ions in lead containing sodium fluoroborate glasses

Lead containing calcium zinc sodium fluoroborate glasses (LCZSFB) with molar composition of 20PbO+5CaO+5ZnO+10NaF+(60−x) B₂O₃+x Sm₂O₃, (x=0.1, 0.25, 0.5, 1.0 and 2.0 mol%) were prepared and investigated by the XRD, FTIR, optical absorption, photoluminescence and decay curve analysis. Judd-Ofelt theory was applied to the experimental oscillator strengths to evaluate the phenomenological J-O intensity parameters Ω_λ (λ=2, 4 and 6). Using the J-O intensity parameters as well as from the emission and decay measurements, various radiative parameters such as transition probabilities (A_R), radiative lifetimes (τ_R), measured lifetimes (τ_m), calculated branching ratios (β_R), measured branching ratios (β_m), effective bandwidth (Δλ_eff) and stimulated emission cross sections σ(λ_p) have been calculated for the excited ⁴G_5/2 luminescent level. The nature of decay curves of ⁴G_5/2 level for different Sm³⁺ ion concentrations in all LCZSFB glasses has been analyzed and the lifetimes are noticed to decrease with increase of concentration. The concentration quenching has been attributed to the energy transfer through the cross-relaxation between Sm³⁺ ions. Based on these results, the utility of Sm³⁺ ions doped lead containing fluoroborate glasses as laser active materials in the visible region is discussed.     

Analysis of the generic singularity studies by Belinskii,Khalatnikov, and Lifschitz

We apply some modern mathematical methods of global analysis to a series of studies undertaken by Belinskii, Khalatnikov and Lifschitz (BKL) to elucidate the structure of space-time near a general cosmological singularity. A brief summary of BKL's large body of work on inhomogeneous cosmological models is given (their work on homogeneous models is not under discussion here). Various theorems are proven and analyses of a mathematical and physical nature are made to show that the constructions of BKL cannot be general and in some cases do not give Lorentz manifolds. We conclude that although the work of BKL has led to very significant advances in our understanding of the dynamics of homogeneous cosmological models, the local techniques they employ do not extend to give us reliable information about the global structure of generic space-times. A detailed discussion of stability, generality, function counting, linearization stability, physical singularities and fictitious singularities is given together with an outline of various physical considerations which might be useful in future studies of the structure of generic space-times.     

Conversion electron measurement of isomeric primary transitions in196, 198, 199, 200, 201Pb

The transition energies of nine low energy primary transitions from high spin isomers in^{196, 198, 199, 200, 201}Pb have been measured with conversion electron spectroscopy usinge ^? e ^? ande ^? γ coincidences.B(E2) values as deduced from the measured lifetimes and transition energies are discussed in terms of seniority shell model configurations and of a quasiparticle Tamm-Dancoff approach using the surface delta interaction. A revised discussion of the effectiveE2 charge in neutron deficient Pb isotopes is presented.