Self-assembling of phenothiazine compounds investigated by small-angle X-ray scattering and electron paramagnetic resonance spectroscopy

Small-angle X-ray scattering (SAXS) and electron paramagnetic resonance (EPR) have been carried out to investigate the structure of the self-aggregates of two phenothiazine drugs, chlorpromazine (CPZ) and trifluoperazine (TFP), in aqueous solution. In the SAXS studies, drug solutions of 20 and 60 mM, at pH 4.0 and 7.0, were investigated and the best data fittings were achieved assuming several different particle form factors with a homogeneous electron density distribution in respect to the water environment. Because of the limitation of scattering intensity in the q range above 0.15 angstrom(-1), precise determination of the aggregate shape was not possible and all of the tested models for ellipsoids, cylinders, or parallelepipeds fitted the experimental data equally well. The SAXS data allows inferring, however, that CPZ molecules might self-assemble in a basis set of an orthorhombic cell, remaining as nanocrystallites in solution. Such nanocrystals are composed of a small number of unit cells (up to 10, in c-direction), with CPZ aggregation numbers of 60-80. EPR spectra of 5- and 16-doxyl stearic acids bound to the aggregates were analyzed through simulation, and the dynamic and magnetic parameters were obtained. The phenothiazine concentration in EPR experiments was in the range of 5-60 mM. Critical aggregation concentration of TFP is lower than that for CPZ, consistent with a higher hydrophobicity of TFP. At acidic pH 4.0 a significant residual motion of the nitroxide relative to the aggregate is observed, and the EPR spectra and corresponding parameters are similar to those reported for aqueous surfactant micelles. However, at pH 6.5 a significant motional restriction is observed, and the nitroxide rotational correlation times correlate very well with those estimated for the whole aggregated particle from SAXS data. This implies that the aggregate is densely packed at this pH and that the nitroxide is tightly bound to it producing a strongly immobilized EPR spectrum. Besides that, at pH 6.5 the differences in motional restriction observed between 5- and 16-DSA are small, which is different from that observed for aqueous surfactant micelles.

X-ray photoelectron spectroscopy analysis of zirconium nitride-like films prepared on Si(100) substrates by ion beam assisted deposition

Thin zirconium nitride films were prepared on Si(l 00) substrates at room temperature by ion beam assisted deposition with a 2 keV nitrogen ion beam. Arrival rate ratios ARR(N/Zr) used were 0.19, 0.39, 0.92, and 1.86. The chemical composition and bonding structure of the films were analyzed with X-ray photoelectron spectroscopy (XPS). Deconvolution results for Zr 3d, Zr 3p(3/2), N 1s, O 1s, and C 1s XPS spectra indicated self-consistently the presence of metal Zr-0, nitride ZrN, oxide ZrO2, oxymnide Zr2N2O, and carbide ZrC phases, and the amounts of these compounds were influenced by ARR(N/Zr). The chemical composition ratio N/Zr in the film increased with increasing ARR(N/Zr) until ARR(N/Zr) reached 0.92, reflecting the high reactivity of nitrogen in the ion beam, and stayed almost constant for ARR(N/Zr) >= 1, the excess nitrogen being rejected from the growing film. A considerable incorporation of contaminant oxygen and carbon into the depositing film was attributed to the getter effect of zirconium. (C) 2007 Elsevier B.V. All rights reserved.

MAGNETIC RESONANT X-RAY DIFFRACTION APPLIED TO THE STUDY OF EuTe FILMS AND MULTILAYERS

In this work we use magnetic resonant x-ray diffraction to study the magnetic properties of a 1.5 mu m EuTe film and an EuTe/PbTe superlattice (SL). The samples were grown by molecular beam epitaxy on (111) oriented BaF(2) substrates. The measurements were made at the Eu L(2) absorption edge, taking profit of the resonant enhancement of more than two orders in the magnetically diffracted intensity. At resonance, high counting rates above 11000 cps were obtained for the 1.5 gm EuTe film, allowing to check for the type II antiferromagnetic order of EuTe. An equal population of the three possible in-plane magnetic domains was found. The EuTe/PbTe SL magnetic peak showed a satellite structure, indicating the presence of magnetic correlations among the 5 ML (monolayers) EuTe layers across the 15 ML PbTe non-magnetic spacers. The temperature dependence of the integrated intensities of the film and the SL yielded different Neel temperatures T(N). The lower T(N) for the SL is explained considering the higher influence of the surface atoms, with partial bonds lost.

X-ray and gamma irradiation effects on dipole defects in CaF2 : La, Yb, Al

Impurity-interstitial dipoles in calcium fluoride solutions with Al3+, Yb3+ and La3+ fluorides were studied using the thermally stimulated depolarization current (TSDC) technique. The dipolar complexes are formed by substitutional trivalent ions in Ca2+ sites and interstitial fluorine in nearest neighbor sites. The relaxations observed at 150 K are assigned to dipoles nnR(S)(3+)- F-i(-) (R-S = La or Yb). The purpose of this work is to study the processes of energy storage in the fluorides following X-ray and gamma irradiation. Computer modelling techniques are used to obtain the formation energy of dipole defects. (C) 2007 Elsevier Ltd. All rights reserved.

X-ray transmission through nanostructured and microstructured CuO materials

This study presents a comparison of the X-ray transmission through microsized and nanosized materials. For this purpose CuO nanoparticles, with 13.4 nm average grain size, and CuO microparticles, with a mean particle size of 56 mu m, were incorporated separately to beeswax in a concentration of 5%. Results show that the transmission through the above material plates with microsized and nanosized CuO was almost the same for X-ray beams generated at 60 and 102 kV tube voltages. However, for the radiation beams generated at 26 and 30 kV tube voltages the X-rays are more attenuated by the nanostructured CuO plates by a factor of at least 14%. Results suggest that the difference in the low energy range may be due to the higher number of particles/gram in the plates designed with CuO nanoparticles and due to the grain size effect on the X-ray transmission. (C) 2010 Elsevier Ltd. All rights reserved.

Energy-dispersive X-ray fluorescence analysis of a pre-Columbian funerary gold mask from the Museum of Sican, Peru

A funerary gold mask from the Museum of Sican, Ferranafe, Peru was analyzed in 30 different areas using a portable equipment using energy-dispersive X-ray fluorescence. It was deduced from the measurements that the main sheet of the mask and the majority of the pendants have a similar composition and are made of tumbaga, which means a poor gold alloy enriched at the surface by depletion gilding, and have a similar `equivalent` gilding thickness of about 5 mu m. The nose, also on tumbaga, has different composition and a thickness of about 8 mu m. The clamps are on gilded or on silvered copper. The red pigment dispersed on the surface of the mask is cinnabar. Copyright (C) 2009 John Wiley & Sons, Ltd.

Root uptake and reduction of hexavalent chromium by aquatic macrophytes as assessed by high-resolution X-ray emission

Aquatic macrophytes Salvinia auriculata, Pistia stratiotes and Eichhornia crassipes were chosen to investigate the Cr(VI) reduced by root-based biosorption in a chromium uptake experiment, using a high-resolution XRF technique. These plants were grown in hydroponics medium supplied with non-toxic Cr concentrations during a 27-day metal uptake experiment. The high-resolution Cr-K beta fluorescence spectra for dried root tissues and Cr reference material (100% Cr, Cr(2)O(3), and CrO(3)) were measured using an XRF spectrometer. For all species of aquatic plant treated with Cr(VI), the energy of the Cr-K beta(2,5) line was shifted around 8 eV below the same spectral line identified for the Cr(VI) reference, but it was also near to the line identified for the Cr(III) reference. Moreover, there was a lack of the strong Cr-K beta"" line assigned to the Cr(VI) reference material within the Cr(VI)-treated plant spectra, suggesting the reduction of Cr(VI) for other less toxic oxidation states of Cr. As all Cr-K beta spectra of root tissue species were compared, the peak energies and lineshape patterns of the Cr-K beta(2,5) line are coincident for the same aquatic plant species, when they were treated with Cr(III) and Cr(VI). Based on the experimental evidence, the Cr(VI) reduction process has happened during metal biosorption by these plants. (C) 2009 Elsevier Ltd. All rights reserved.

Metal location and thickness in a multilayered sheet by measuring K alpha/K beta, L alpha/L beta and L alpha/L gamma X-ray ratios

When a multilayered material is analyzed by means of energy-dispersive X-ray fluorescence analysis, then the X-ray ratios of K alpha/K beta, or L alpha/L beta and L alpha/L gamma, for an element in the multilayered material, depend on the composition and thickness of the layer in which the element is situated, and on the composition and thickness of the superimposed layer (or layers). Multilayered samples are common in archaeometry, for example, in the case of pigment layers in paintings, or in the case of gilded or silvered alloys. The latter situation is examined in detail in the present paper, with a specific reference to pre-Columbian alloys from various museums in the north of Peru. (C) 2009 Elsevier B.V. All rights reserved.

Performance of GEANT4 in dosimetry applications: Calculation of X-ray spectra and kerma-to-dose equivalent conversion coefficients

In order to validate the Geant4 toolkit for dosimetry applications, simulations were performed to calculate conversion coefficients h(10, alpha) from air kerma free-in-air to personal dose equivalent Hp(10, a). The simulations consisted of two parts: the production of X-rays with radiation qualities of narrow and wide spectra, and the interaction of radiation with ICRU tissue-equivalent and ISO water slab phantoms. The half-value layers of the X-ray spectra obtained by simulation were compared with experimental results. Mean energy, spectral resolution, half-value layers and conversion coefficients were compared with ISO reference values. The good agreement between results from simulation and reference data shows that the Geant4 is suitable for dosimetry applications which involve photons with energies in the range of ten to a few hundreds of keV. (C) 2008 Elsevier Ltd. All rights reserved.

X-ray spectrometry: a powerful tool for the measurement of complete fusion of weakly bound nuclei

We describe how the method of detection of delayed K x-rays produced by the electron capture decay of the residual nuclei can be a powerful tool in the investigation of the effect of the breakup process on the complete fusion (CF) cross-section of weakly bound nuclei at energies close to the Coulomb barrier. This is presently one of the most interesting subjects under investigation in the field of low-energy nuclear reactions, and the difficult experimental task of separating CF from the incomplete fusion (ICF) of one of the breakup fragments can be achieved by the x-ray spectrometry method. We present results for the fusion of the (9)Be + (144)Sm system. Copyright (c) 2008 John Wiley & Sons, Ltd.

X-ray spectroscopy applied to radiation shielding calculation in mammography

The protective shielding design of a mammography facility requires the knowledge of the scattered radiation by the patient and image receptor components. The shape and intensity of secondary x-ray beams depend on the kVp applied to the x-ray tube, target/filter combination, primary x-ray field size, and scattering angle. Currently, shielding calculations for mammography facilities are performed based on scatter fraction data for Mo/Mo target/filter, even though modern mammography equipment is designed with different anode/filter combinations. In this work we present scatter fraction data evaluated based on the x-ray spectra produced by a Mo/Mo, Mo/Rh and W/Rh target/filter, for 25, 30 and 35 kV tube voltages and scattering angles between 30 and 165 degrees. Three mammography phantoms were irradiated and the scattered radiation was measured with a CdZnTe detector. The primary x-ray spectra were computed with a semiempirical model based on the air kerma and HVL measured with an ionization chamber. The results point out that the scatter fraction values are higher for W/Rh than for Mo/Mo and Mo/Rh, although the primary and scattered air kerma are lower for W/Rh than for Mo/Mo and Mo/Rh target/filter combinations. The scatter fractions computed in this work were applied in a shielding design calculation in order to evaluate shielding requirements for each of these target/filter combinations. Besides, shielding requirements have been evaluated converting the scattered air kerma from mGy/week to mSv/week adopting initially a conversion coefficient from air kerma to effective dose as 1 Sv/Gy and then a mean conversion coefficient specific for the x-ray beam considered. Results show that the thickest barrier should be provided for Mo/Mo target/filter combination. They also point out that the use of the conversion coefficient from air kerma to effective dose as 1 Sv/Gy is conservatively high in the mammography energy range and overestimate the barrier thickness. (c) 2008 American Association of Physicists in Medicine.

In situ X-ray diffraction studies of phase transition in Pb1-x La x Zr0.40Ti0.60O3 ferroelectric ceramics

The temperature dependence of the crystalline structure and the lattice parameters of Pb1-xLaxZr0.40Ti0.60O3 ferroelectric ceramic system with 0.00 x 0.21 was determined. The samples with x 0.11 show a cubic-to-tetragonal phase transition at the maximum dielectric permittivity, Tmax. Above this amount and especially for the x = 0.12 sample, a spontaneous phase transition from a relaxor ferroelectric state (cubic phase) to a ferroelectric state (tetragonal phase) is observed upon cooling below the Tmax. Unlike what has been reported in other studies, the x = 0.13, 0.14, and 0.15 samples, which present a more pronounced relaxor behavior, also presents a spontaneous normal-to-relaxor transition, indicated by a cubic to tetragonal symmetry below the Tmax. The origin of this anomaly has been associated with an increase in the degree of tetragonality, confirmed by the measurements of the X-ray diffraction patterns. The differential thermal analysis (DSC) measurements also confirm the existence of these phase transitions.

Temperature dependence of molecular dynamics and supramolecular aggregation in MEH-PPV films: A solid-state NMR, X-ray and fluorescence spectroscopy study

This article presents an investigation of the temperature induced modification in the microstructure and dynamics of poly[2-methoxy-5-(2`-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) cast films using Wide-Angle X-ray Scattering (WAXS), solid-state Nuclear Magnetic Resonance (NMR), and Fluorescence Spectroscopy (PL). MEH-PPV chain motions were characterized as a function of temperature by NMR. The results indicated that the solvent used to cast the films influences the activation energy of the side-chain motions. This was concluded from the comparison of the activation energy of the toluene cast film, E(a) = (54 +/- 8) kJ/mol, and chloroform cast film, E(a) = (69 +/- 5) kJ/mol, and could be attributed to the higher side-chain packing provided by chloroform, that preferentially solvates the side chain in contrast to toluene that solvates mainly the backbone. Concerning the backbone mobility, it was observed that the torsional motions in the MEH-PPV have average amplitude of similar to 10 degrees at 300 K, which was found to be independent of the solvent used to cast the films. In order to correlate the molecular dynamics processes with the changes in the microstructure of the polymer, in situ WAXS experiments as a function of temperature were performed and revealed that the interchain spacing in the MEH-PPV molecular aggregates increases as a function of temperature, particularly at temperatures where molecular relaxations occur. It was also observed that the WAXS peak associated with the bilayer spacing becomes narrower and its intensity increases whereas the peak associated with the inter-backbone planes reduces its intensity for higher temperatures. This last result Could be interpreted as a decrease in the number of aggregates and the reduction of the interchain species during the MEH-PPV relaxation processes. These WAXS results were correlated with PL spectra modifications observed upon temperature treatments. (C) 2008 Elsevier Ltd. All rights reserved.

Synthesis, characterization, X-ray structure and in vitro anti mycobacterial and antitumoral activities of Ru(II) phosphine/diimine complexes containing the ""SpymMe(2)"" ligand, SpymMe(2)=4,6-dimethyl-2-mercaptopyrimidine

The reaction of cis-[RuCl2(dppb)(N-N)], dppb = 1,4-bis(diphenylphosphino)butane, complexes with the ligand HSpymMe(2), 4,6-dimethyl-2-mercaptopyrimidine, yielded the cationic complexes [Ru(SpymMe(2))(dppb)(N-N)]PF6, N-N = bipy (1) and Me-bipy (2), bipy = 2,2`-bipyridine and Me-bipy = 4,4`dimethyl-2,2`-bipyridine, which were characterized by spectroscopic and electrochemical techniques and X-ray crystallography and elemental analysis. Additionally, preliminary in vitro tests for antimycobacterial activity against Mycobacterium tuberculosis H37Rv ATCC 27264 and antitumor activity against the MDA-MB-231 human breast tumor cell line were carried out on the new complexes and also on the precursors cis-[RuCl2(dppb)(N-N)], N-N = bipy (3) and Me-bipy (4) and the free ligands dppb, bipy, Me-bipy and SpymMe(2). The minimal inhibitory concentration (MIC) of compounds needed to kill 90% of mycobacterial cells and the IC50 values for the antitumor activity were determined. Compounds 1-4 exhibited good in vitro activity against M. tuberculosis, with MIC values ranging between 0.78 and 6.25 mu g/mL, compared to the free ligands (MIC of 25 to >50 mu g/mL) and the drugs used to treat tuberculosis. Complexes I and 2 also showed promising antitumor activity, with IC50 values of 0.46 +/- 0.02 and 0.43 +/- 0.08 mu M, respectively, against MDA-MB-231 breast tumor cells. (C) 2008 Elsevier Inc. All rights reserved.

Study of the phenanthroline-Mn-imidazole bonding in Mn(I) triscarbonyl complex: A X-ray and DFT computational analysis

355 nm light irradiation of fac-[Mn(CO)(3)(phen)(imH)](+) (fac-1) produces the mer-1 isomer and a long lived radical which can be efficiently trapped by electron acceptor molecules. EPR experiments shows that when excited, the manganese(I) complex can be readily oxidized by one-electron process to produce Mn(II) and phen(.-). In the present study, DFT calculations have been used to investigated the photochemical isomerization of the parent Mn(I) complex and to characterize the electronic structures of the long lived radical. The theoretical calculations have been performed on both the fac-1 and mer-1 species as well as on their one electron oxidized species fac-1+ and mer-1+ for the lowest spin configurations (S = 1/2) and fac-6 and mer-6 (S = 5/2) for the highest one to characterize these complexes. In particular, we used a charge decomposition analysis (CDA) and a natural bonding orbital (NBO) to have a better understanding of the chemical bonding in terms of the nature of electronic interactions. The observed variations in geometry and bond energies with an increasing oxidation state in the central metal ion are interpreted in terms of changes in the nature of metal-ligand bonding interactions. The X-ray structure of fac-1 is also described. (C) 2011 Elsevier B.V. All rights reserved.