Scattering of Heavy Charged Particles on Hydrogen Atoms

 Low-energy scattering of heavy positively charged particles on hydrogen atoms (H) is investigated by solving Faddeev equations in configuration space. A resonant value of the pH scattering length, a = 750 ± 5 a.u., in the pp antisymmetric state was found. This large value indicates the existence of a first excited state with a binding energy B = 1.14 × 10⁻⁹ a.u. below the H ground state. Resonances for non-zero angular-momenta states are predicted. Received November 4, 2001; accepted for publication November 12, 2001     

ISAC-I and ISAC-II: Present status and future perspectives

The ISAC facility at TRIUMF utilizes up to 100 μA from the 500 MeV H^- cyclotron to produce the RIB using the Isotopic Separation On Line (ISOL) method. The ISAC-I facility comprised the RNB production target stations, the mass separator and the beam delivery to low energy area and to a room temperature linear accelerator composed of a 4-rod RFQ and an inter-digital H type structure Drift Tube LINAC. ISAC-I linear accelerator can provide beam from A = 3 to 30 amu with an energy range from 0.15 to 1.5 A MeV. Since the beginning of operations target development program has been to increase proton beam currents on targets. Now we routinely operate our target at 50 to 85 μA and recently we have operated our target at 100 μA. Other developments are in place to add other ion sources, laser, FEBIAD and ECRIS to the actual surface ion source. The last two five year plans were mainly devoted to the construction of a heavy ion superconducting LINAC (ISAC-II), that will upgrade the mass and the energy range from 30 to 150 and 1.5 to 6.5 A MeV, respectively. We are now commissioning the medium β section and first experiment is scheduled for the fall 2006.     

Spectrofluorimetric Determination of 3-hidroxy-2-naphthoic Acid by Use of Its Ternary Complex with Zirconium (IV) and Beta-Cyclodextrin: Application to Determination in River Water

A spectrofluorimetric method has been developed for the determination of 3-hydroxy-2-naphthoic acid (3H2NA) by formation of a ternary complex with zirconium (IV) and β-cyclodextrin (β-CD). It has been observed that the fluorescence intensity of 3H2NA is greatly enhanced when the ternary complex is formed and is accompanied with shifts in the excitation and emission wavelengths. The conditions for the formation of the ternary complex have been optimized and the stoichiometry has been calculated, resulting a 1:2:1 complex (3H2NA:Zr: β-CD). The linear range was 20–2000 ng mL⁻¹ and the detection and quantification limits calculated were 17 and 58 ng mL⁻¹, respectively. The proposed method was applied to the determination of 3H2NA in river water. To eliminate interferences an off-line solid phase extraction (SPE) procedure using C18 cartridges was used. The extraction procedure was optimized and good recoveries were obtained (around 100%) with relative standard deviations (RSDs) of less than 5%.     

XPS study of the chemical bonding in hydrogenated amorphous germanium–carbon alloys

A systematic study of the chemical bonding in hydrogenated amorphous germanium–carbon (a-Ge_1-xC_x:H)alloys using X-ray photoelectron spectroscopy (XPS) is presented. The films, with carbon content ranging from 0 at. % to 100 at. %, were prepared by the rf co-sputtering technique. Raman spectroscopy was used to investigate the carbon hybridization. Rutherford backscattering spectroscopy (RBS) and XPS were used to determine the film stoichiometry. The Ge 3d and C 1s core levels were used for investigating the bonding properties of germanium and carbon atoms, respectively. The relative concentrations of C–Ge, C–C, and C–H bonds were calculated using the intensities of the chemically shifted C 1s components. It was observed that the carbon atoms enter the germanium network with different hybridization, which depends on the carbon concentration. For concentrations lower than 20 at. %, the carbon atoms are preferentially sp³ hybridized, and approximately randomly distributed. As the carbon content increases the concentration of sp² sites also increases and the films are more graphitic-like. Received: 4 May 1999 / Accepted: 24 November 1999 / Published online: 24 March 2000     

Neutron excess nuclei of hydrogen and helium at ACCULINNA

Attempt to observe a ⁷H resonance produced in the reaction ²H(⁸He,³He)⁷H resulted only in setting a limit dσ/dΩ≤ 20 μb/sr for the reaction exit channel which could populate a resonance lying between 0 and 3 MeV above the ⁷H decay threshold. The quasi-free scattering of the α core bound in ⁶He was explored keeping in mind the possible study of the cluster structure of this halo nucleus. For the first time coincident particles emitted in the ⁴He(⁶He, 2α)nn reaction were detected in wide angular ranges giving a wide kinematical range of the measured angular and momentum distributions. The contribution of processes, competing with QFS in the α+ α+n+n output channel, was considerably suppressed by the selection of events with E_α1(2)-nn>10 MeV. A number of experimental distributions, relevant to the reaction mechanism and to the ⁶He structure, were compared with the results of MC simulations based on the PWIA formalism. The PWIA predictions showed consistency with the experimental data.     

Four-Nucleon States in the Continuum: A Means to Probe the Nucleon-Nucleon Interaction

 Four-nucleon states in the continuum are studied through exact microscopic calculations based on the solution of the AGS equations for four nonrelativistic quantum particles. Our studies include calculations of cross sections and analyzing powers for all two-body reactions of interest, but here we only show results for n ³He → n ³He. The NN interactions we use are Bonn-CD, Nijmegen II, and Bonn-B. Compared to existing quality data, one finds large discrepancies and some sensitivity to the choice of NN force model. The calculated n + ³He elastic phase shifts show a very strong inelastic resonance at about 0.3 MeV which is not supported by the total cross-section data. This result is due to the existence of a ³ P ₀ (0⁻) resonance in isospin I = 0 at this energy and the undesirable coincidence of n + ³He and p + ³H thresholds in our calculation due to lack of Coulomb repulsion between protons. This interpretation is supported by R-matrix analyses of the data on the basis of coincident thresholds. Calculated 0⁺ and 0⁻ states are compared with modified R-matrix analyses. Received October 30, 2001; accepted for publication November 7, 2001     

Electric-field-enhanced metal-induced crystallization of hydrogenated amorphous silicon at room temperature

A novel simple method of crystallization of hydrogenated amorphous silicon (a-Si:H) thin films is described. Namely, we studied a metal-induced crystallization enhanced by a dc electric field in sandwich p⁺–i–n⁺structures. The samples were fabricated from wide-bandgap a-Si:H with high hydrogen content (13–51 at. % H). Macroscopic islands of a-Si:H (up to ∼1 mm in diameter) in the region between upper (CrNi) and lower (ITO) contacts crystallize instantaneously when a sufficiently high dc electric field (≳10⁵ V cm^-1) is applied. The crystallization sets in at room temperature and ambient atmosphere and is spatially selective. A proposed microscopic mechanism of such an easy macroscopic crystallization consists in easy diffusion of Ni and/or Ni silicides (representing nucleation sites) through a dense network of voids in hydrogen-rich a-Si:H. Received: 30 November 2000 / Accepted: 3 May 2001 / Published online: 27 June 2001     

Fluorescence Interaction and Determination of Calf Thymus DNA with Two Ethidium Derivatives

In this paper, we reported the syntheses and investigation of the modes of binding to DNA of the two new ethidium derivatives containing benzoyl and phenylacetyl groups of both amines at 3-and 8- positions. The interactions between calf thymus DNA (ct-DNA) and the two derivatives, 3,8-dibenzoylamino-5-ethyl-6-phenylphenantridinium cloride (E2) and 3,8-diphenylacetylamino-5-ethyl-6-phenylphenantridinium chloride (E3), were investigated by fluorescence quenching spectra and UV-vis absorption spectra. The Stern-Volmer quenching constants, binding constants, binding sites and the corresponding thermodynamic parameters ΔH, ΔS and ΔG were calculated at different temperatures. The results indicated the formation of E2 and E3-DNA complexes and van der Waals interactions as the predominant intermolecular forces in stabilizing for each complex. In addition, increasing nucleophilicity of the functional groups at 3- and 8- positions exhibited the respectable increment the DNA binding affinities of derivatives. The results of absorption, ionic strength and iodide ion quenching suggested that the interaction mode of E2 and E3 with ct-DNA was intercalative binding. The limit of detection (LOD) of ct-DNA were 7.49 × 10⁻⁸ (n = 4) and 4.18 × 10⁻⁸ mol/l (n = 7) in presence of E2 and E3, respectively.     

A water isotope (2H, 17O, and 18O) spectrometer based on optical feedback cavity-enhanced absorption for in situ airborne applications

Measurements of the isotopic composition of water are thought to help explain stratospheric aridity and related issues in atmospheric sciences. Simultaneous in situ measurements of ²H/¹H, ¹⁷O/¹⁶O, and ¹⁸O/¹⁶O at high spatial resolution are required for this purpose. We present the design and laboratory performance of a device that will be used on high-altitude research aircraft. It is based on optical feedback cavity-enhanced spectroscopy (OF-CEAS), with better sensitivity than traditional multi-pass arrangements. It utilizes a near-infrared laser source, avoiding the need for cryogens. We demonstrate an airborne precision during tropospheric flight conditions of 1 ‰, 3 ‰, and 9 ‰ for δ¹⁸O, δ¹⁷O, and δ²H, respectively, for 30-s averaged data and a water concentration of about 200 ppm. With recent improvements we expect to remain within a factor of about three of these values under true stratospheric conditions (water mixing ratio ∼10 ppmv). PACS 07.88.+y; 42.55.Px; 42.62.Fi; 92.60.Hd; 92.60.Jq     

IR Spectroscopic signs of malignant neoplasms in the thyroid gland

We use Fourier transform IR spectroscopy to study thyroid tumor tissues which were removed during surgery. The IR spectra of the tissues with pathological foci are compared with data from histologic examination. In the region of N–H, C–H, and C = O stretching vibrations, the IR spectra of the tissues for thyroid cancer are different from the IR spectra of tissues without malignant formations. We identify the spectral signs of thyroid cancer. We show that IR analysis is promising for identification of thyroid pathology at the molecular level.     

Isolated lepton events at HERA: SUSY R-parity violation?

Events with an isolated high p_T lepton, a hadron jet and missing energy as observed in the H1 experiment at HERA, are potentially associated with R-parity violation in supersymmetric theories. However, stringent kinematic constraints must be fulfilled if the production of supersymmetric particles in R-parity violating scenarios were the correct path for explaining these puzzling events. A reference point ℝ/   is specified for which these constraints are illustrated and implications of the supersymmetric interpretation for new classes of multi-lepton events are indicated.     

Study of the 3He(4He,γ)7Be and 3H(4He,γ)7Li Reactions in an Extended Two-Cluster Model

 The ³He(⁴He, γ)⁷Be and ³H(⁴He, γ)⁷Li reactions are studied in an extended two-cluster model which contains α + h/t and ⁶Li + p/n clusterizations. We show that the inclusion of the ⁶Li + p/n channels can significantly change the zero-energy reaction cross sections, S(0), and other properties of the ⁷Be and ⁷Li nuclei, like the quadrupole moments Q. However, the results agree with the known correlation trend between S(0) and Q. Moreover, we demonstrate that the value of the zero-energy derivatives of the astrophysical S-factors are more uncertain than currently believed. Received June 17, 1999; revised February 22, 2000; accepted for publication April 17, 2000     

On the Uniqueness of Gravitational Centre

The dual volume of order α of a convex body A in R ⁿ is a function which assigns to every a ∈ A the mean value of α-power of distances of a from the boundary of A with respect to all directions. We prove that this function is strictly convex for α > n or α < 0 and strictly concave for 0 < α < n (for α = 0 and for α = n the function is constant). It implies that the dual volume of a convex body has the unique minimizer for α > n or α < 0 and has the unique maximizer for 0 < α < n. The gravitational centre of a convex body in R³ coincides with the maximizer of dual volume of order 2, thus it is unique.      

Intramolecular Proton Transfer Effects on 2,6-diaminopyridine

The photophysical behaviour of 2,6-diaminopyridine (DAP) has been studied in solvents of different polarity, pH, β-cyclodextrin (β-CD) and compared with 2-amino pyridine (2AP). The inclusion complex of both molecules with β-CD are analysed by UV-visible, fluorimetry, FT-IR, ¹H NMR, SEM and AM1 methods. The solvent studies shows i) DAP gives more red shifted absorption and emission maxima than 2AP molecule and ii) addition of amino group in 2AP effectively increase the resonance interaction in the pyridine ring. A regular red shift observed in acidic pH solutions suggests intramolecular proton transfer (IPT) present in both molecules. β-CD studies indicates i) in pH  ~ 7, a regular red shifted absorption and emission maxima observed in AP molecules suggests pyridine ring encapsulated in to the β-CD cavity (1:1 inclusion complex formed) and ii) in pH ~ 1, a blue shifted absorption maxima noticed in 2AP, is due to protonated amino group deeply encapsulated in to the hydrophobic part of the β-CD cavity.     

Spectrofluorimetric Study and Detection of Ketoconazole in the Presence of β-cyclodextrin

The formation of a complex between ketoconazole and β-cyclodextrin was followed by spectrofluorimety. The inclusion of ketoconazole in β-cyclodextrin cavity enhanced the native fluorescence of the drug. The stoichiometry of the complex was 1:1 β-cyclodextrin to ketoconazole and the stability constant of the complex (log K _f) was determined to be 4.3 ± 0.01 at pH = 7.9 and 3.7 ± 0.04 at pH = 2.6. A sensitive spectrofluorimetric method for the detection of ketoconazole is presented. At optimized experimental conditions, a linear relationship between the fluorescence intensity of the solution and concentration of ketoconazole is observed in the range of 0.01–10 μg ml⁻¹ (5 × 10⁻⁸ M–1.88 × 10⁻⁵ M). The method was applied to the detection of ketoconazole in pharmaceutical products and the results were satisfactory in comparison to the official method (relative error = 2.8% and standard deviation = 0.06 for tablets of ketoconazole). The recovery of ketoconazole from a blood serum sample, determined by the proposed method, was 97.1 ± 2.4%.     

Optical spectra and spin-Hamiltonian parameters of trivalent ytterbium in lead tungstate

By using crystal-field theory, the optical spectra and spin-Hamiltonian parameters (abbr. SH parameters, i.e. the anisotropic g factors g _∥, g _⊥, and hyperfine structure constants A _∥, A _⊥) of ¹⁷¹Yb^3 + and ¹⁷³Yb^3 + isotopes in the tetragonal PbWO₄ are calculated. The theoretical results agree well with the experimental values. The crystal-field parameters and the signs of the hyperfine structure constants for both ¹⁷¹Yb^3 + and ¹⁷³Yb^3 + isotopes are determined. The validities of the theoretical results are discussed.     

Spectrofluorimetric Assessment of Chlorzoxazone and Ibuprofen in Pharmaceutical Formulations by using Eu-Tetracycline HCl Optical Sensor Doped in Sol–Gel Matrix

A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol–gel matrix. The chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol–gel matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λ_ex = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10⁻⁹–1 × 10⁻⁴ and 1 × 10⁻⁸–7 × 10⁻⁵ mol L⁻¹, and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10⁻¹⁰ , 9.6 × 10⁻¹⁰ and 5.6 × 10⁻¹⁰, 1.7 × 10⁻⁹ mol L⁻¹, respectively.     

The effect of fast neutrons on the electrophysical properties of nuclear-doped <Emphasis Type="Italic">p</Emphasis>-silicon

The influence of the defects induced by fast-neutron irradiation on the rate of charge-carrier removal in nuclear-doped silicon (p-Si < B, P>) and a test p-Si < B > sample is studied by measuring the Hall coefficient and resistivity at room temperature. It is shown that the rate of removal of charge carriers in p-Si < B, P > is higher than that in p-Si < B>. A barrier model is developed to explain the observed effect.     

Effect of inorganic salts on the crystallinity of polyvinyl alcohol

We use IR spectroscopy to study the crystallinity of polyvinyl alcohol films cast from aqueous solutions containing inorganic salts. We have established that adding salt leads to an increase in the degree of crystallinity of the polymer. The crystallizing effect of the studied salts increases in the series Na₂CO₃ = Na₂SO₄ < NH₄Cl < CsCl = NaCl < KCl.     

Synthesis, Characterization, DNA-Binding Properties of the Ln(III) Complexes with 6-Hydroxy Chromone-3-Carbaldehyde-(4′-Hydroxy) Benzoyl Hydrazone

6-Hydroxy chromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazone (L) and its Ln (III) complexes, [Ln = La, Nd, Eu and Tb] have been prepared and characterized on the basis of elemental analyses, molar conductivities, mass spectra, ¹H NMR, thermogravimety/differential thermal analysis (TG-DTA), UV-vis spectra, fluorescence spectra and IR spectra. The formula of the complex is [Ln L·(NO₃)₂]·NO₃. Spectrometric titration, ethidium bromide displacement experiments and viscosity measurements indicate that Eu (III) complex bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constant of Eu (III) with DNA was 2.48 × 10⁵ M⁻¹ through fluorescence titration data.