Abstract: A combination of synchrotron radiation-based elementalimaging, in vivo redox status analysis, histology, and toxic responses was usedto investigate the uptake, biodistribution, and adverse effects of Cenanoparticles (CeO2NP; 10 nm; 0.5-34.96 mg Ce L-1) or Ce(NO3)3(2.3-26 mg Ce L-1)inCaenorhabditis elegans. Elemental mapping of theexposed nematodes revealed Ce uptake in the alimentary canal prior todepuration. Retention of CeO2NPs was low compared to that of Ce(NO3)3in depurated individuals. X-rayfluorescence (XRF) mapping showed that Cetranslocation was confined to the pharyngeal valve and foregut. Ce(NO3)3exposure significantly decreased growth, fertility, and reproduction, causedslightly reduced fecundity. XRF mapping and histological analysis revealedsevere tissue deformities colocalized with retained Ce surrounding thepharyngeal valve. Both forms of Ce activated the sod-1 antioxidant defense,particularly in the pharynx, whereas no significant effects on the cellular redox balance were identified. The CeO2NP-induceddeformities did not appear to impair the pharyngeal function or feeding ability as growth effects were restricted to Ce(NO3)3exposure. The results demonstrate the utility of integrated submicron-resolution SR-based XRF elemental mapping of tissue-specificdistribution and adverse effect analysis to obtain robust toxicological evaluations of metal-containing contaminants.

Abstract: A combined experimental and first-principles study is performed to study the origin of conductivity in
ZnO:Al nanoparticles synthesized under controlled conditions via a reflux route using benzylamine as a
solvent. The experimental characterization of the samples by Raman, nuclear magnetic resonance (NMR)
and conductivity measurements indicates that upon annealing in nitrogen, the Al atoms at interstitial
positions migrate to the substitutional positions, creating at the same time Zn interstitials. We provide
evidence for the fact that the formed complex of AlZn and Zni corresponds to the origin of the Knight
shifted peak (KS) we observe in 27Al NMR. As far as we know, the role of this complex has not been
discussed in the literature to date. However, our first-principles calculations show that such a complex is
indeed energetically favoured over the isolated Al interstitial positions. In our calculations we also
address the charge state of the Al interstitials. Further, Zn interstitials can migrate from Al_Zn and possibly
also form Zn clusters, leading to the observed increased conductivity.

Abstract: A combined Raman and electrochemical study of natural orpiment (As2S3), an arsenic sulfide pigment, was used to assess the quick formation of oxidized species such as arsenic oxide (As2O3) upon exposing the pigment to 405 nm or 532 nm monochromatic light while simultaneously recording the Raman spectra of the exposed sample. During this process, a distortion of the main band at 355 cm−1, associated with the stretching of the AsS3/2 pyramids of natural orpiment, was observed as well as an increased intensity of the 359 cm−1 band, corresponding to covalent AsAs bonds in natural orpiment. The distortion was accompanied by an overall decrease of the global Raman signal for natural orpiment, which could be explained by a loss in the crystal structure. The same phenomena were recorded in reference natural orpiment model paint samples stored for a long time together with verdigris (Cu(OH)2·(CH3COO)2·5H2O) and minium (Pb3O4) paints, the latter two appearing darkened on their sides closest to the orpiment sample as well as in several historical samples containing natural orpiment mixed with various blue pigments. By SEM-EDX and XRPD analysis, respectively on loose material and cast thin-sections of model paint samples, the darkening was identified as dark sulfide species such as chalcocite (Cu2S) and galena (PbS), suggesting the release of volatile sulfide or related species by the natural orpiment paint. XANES analyses of paint samples presenting AsAs bond increase indicated the presence of sulfur species most likely identified as organosulfur compounds formed upon the AsAs bond formation and explained the darkening of the Cu- and Pb-based pigments. To the best of our knowledge, this article reports for the first time the light-induced formation of AsAs bonds in natural orpiment used as an artists' pigment and objectively demonstrates the incompatibility between orpiment and (arsenic) sulfide-sensitive pigments.

Abstract: A comparative study is made of the propagation of wave packets and fronts in three different meta-media, i.e. graphene, left-handed media (LHM) and transmission lines, using one-dimensional models. It is shown that a potential step in graphene influences only the frequency of the electronic wave, i.e., the particular spectrum branch (electron or hole) to which the wave belongs to, while the envelop function (the wave front or packet form) remains unchanged. Although the model for a vacuum and LHM interface is similar to that of the potential step in graphene, the solutions are quite different due to differences in the chirality of the waves. Comparing the propagation of wave fronts and packets in a standard transmission line and its meta-analog we demonstrate that the propagating packets in the meta-line are much more deformed as compared to the standard one, including broadening, asymmetry and even the appearance of fast moving precursors. This influence is seen not only in the case of packets with steep fronts but in soft Gaussian packets as well.

Abstract: A comparative study of NH3-sensing performance of blank and modified nanocrystal line SnO2 was performed. Tin dioxide modified by ruthenium displayed the highest ammonia sensitivity with a maximum signal at 200 degrees C. The modifier was shown by XPS and EPR to occur in a mixed valence state of oxidized ruthenium distributed between the surface and bulk of tin dioxide nanocrystals. RuOx clustering on SnO2 surface was detected by means of electron microscopy assisted EDX-mapping. The effect of RuOx on tin dioxide interaction with ammonia was studied by temperature-programmed NH3 desorption, simultaneous Kelvin probe and DC-resistance measurements, EPR spectroscopy and analyses of the gas-solid interaction products. The modifier was shown to promote the materials reactivity to NH3 due to the catalytic activity of RuOx. The interaction with ammonia resulted in dipoles formation on the oxide surface along with reducing the grains net surface charge, established from the electron affinity increase and resistance decrease during NH3 exposure. The RuOx-catalyzed gas-solid interaction was deduced to proceed deeper than in the case of non-modified SnO2 and to yield nitrogen oxides (e.g. NO2), as was suggested by the oxidative character of gaseous products of NH3 interaction with RuOx-modified tin dioxide at 200 degrees C. (C) 2012 Elsevier B.V. All rights reserved.

Abstract: A comparison of four methods for the determination of barium, lanthanum, cerium and neodymium in lateritic materials from Brazil is presented. Three of the methods were based on x-ray fluorescence (XRF) spectroscopy: two by radioisotope excitation (Co-57 and Am-241) and one by secondary target XRF (a molybdenum target with a tungsten anode). The other method was based on neutron activation analysis employing both a Ge(Li) coaxial detector and a high-purity germanium detector. The results from these four methods were similar for lanthanum, cerium and neodymium, but for barium at low concentrations (<500 ppm) the neutron activation and the secondary target XRF methods were not suitable. Data on the precision and accuracy of these methods using a series of standard reference rocks are given. The advantages and limitations of each of these methods with respect to the analysis of lateritic materials are discussed.

Abstract: A computational method is presented for angle-resolved photoemission spectra (ARPES) and photoelectron diffraction (PED) in the ultraviolet regime. The one-step model is employed and both initial valence and final continuum states are calculated using the finite-cluster, real-space multiple scattering method. Thereby the approach is versatile and provides a natural link to core-level PED. The method is applied to the Cu(111) valence band and good agreement with experiment is found for both ARPES spectra and PED patterns. When the PED patterns are integrated over a filled band of a single-orbital symmetry, such as Cu-3d, we show, both numerically and analytically, that the exact theory with delocalized initial states can be replaced by the much simpler, core-level-type theory where the initial states are taken as localized.

Abstract: A computer routine was developed for qualitative and quantitative analysis of photographically recorded spark-source mass spectra. Particular attention is given to the case of a graphite matrix. The program starts from the line intensities (expressed as Seidel values) and isotope masses calculated from the densitometer readings by a commercially available routine. From the intensities in the different exposures (typically 15 stages), it computes the parameters for the linear parts of the density curves for each ion. Taking into account mutual interferences of multivalent ions, isotope or C-clusters, oxide, carbide and dicarbide ions, the program automatically identifies and then quantifies the elements present. The precision of the results is around 5%. Reading and complete processing of one photoplate is achieved within 23 h.

Abstract: A copper(II) hexafluoroacetylacetonate (1,1,1,5,5,5-hexafluoro-2,4-pentanedionate, hfa) adduct with N,N,N¡ä,N¡ä-tetramethylethylenediamine (TMEDA) [Cu(hfa)2¡¤TMEDA] is used for the first time as precursor for the chemical vapor deposition (CVD) of copper oxide nanosystems. The syntheses are carried out under both O2 and O2+H2O reaction atmospheres on Si(100) substrates, at temperatures ranging between 250 and 550 ¡ãC. Subsequently, the interrelations between the preparative conditions and the system composition, nanostructure, and morphology are elucidated by means of complementary analytical techniques [Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron and X-ray excited auger electron spectroscopies (XPS and XE-AES), glancing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM)]. The obtained data revealed a gradual transformation from Cu2O, to Cu2O + CuO, to CuO nanosystems upon increasing the deposition temperature from 250 to 550 ¡ãC under both growth atmospheres. Such a phenomenon was accompanied by a progressive morphological evolution from continuous films to 1D hyperbranched nanostructures. Water vapor introduction in the deposition environment enabled to lower the deposition temperature and resulted in a higher aggregate interconnection, attributed to a higher density of nucleation centers.

Abstract: A crucial step, which is still not well understood in the destruction of volatile organic compounds (VOCs) with low temperature plasmas, is the initiation of the process. Here, we present a kinetic model for the destruction of ethylene in low temperature plasmas that allows us to calculate the relative importance of all plasma species and their related reactions. Modifying the ethylene concentration and/or the SED had a major impact on the relative importance of the radicals (i.e., mainly atomic oxygen) and the metastable nitrogen (i.e., more specifically N2(equation image)) in the destruction process. Our results show that the direct destruction by electron impact reactions for ethylene can be neglected; however, we can certainly not neglect the influence of N2(equation image)).

Abstract: A current method for the protection of cretaceous limestone present in various monuments consists of performing a passivating treatment with ammonium oxalate (AmOx). A calcium oxalate protective layer is formed on the surface and enhances the acid resistance of the stone. The in-depth formation of the calcium oxalate layer was investigated on cross sections by using combined micro X-ray fluorescence and micro X-ray powder diffraction (mu XRF/mu XRPD). XRPD showed the presence of both whewellite and weddellite in the calcite stone matrix. A correction was made for sample misalignment, which was visible in both the fluorescence and the diffraction line measurements. A semi-quantitative analysis was performed on the basis of Klug's equation for a two-phase mixture (the presence of weddellite was neglected) without the need for a known reference sample. By assuming two extreme compositions for a reference weight fraction (1 and 99wt%), it was possible to obtain whewellite concentration profiles, which can be used for comparing the effectiveness of different methods for the application of AmOx to the stone surface and the effect of treatment time and AmOx concentration used. It is shown that for the relative amounts of whewellite formed, the differences due to the assumed weight fractions are smaller than the errors due to sample heterogeneity and preferred orientation. Copyright (c) 2013 John Wiley & Sons, Ltd.

Abstract: A database-driven approach combined with ab initio density functional theory (DFT) simulations is used to identify and simulate alternative ferroelectric materials beyond Hf(Zr)O-2. The database-driven screening method identifies a class of wurtzite ferroelectric materials. DFT simulations of wurtzite magnesium chalcogenides, including MgS, MgSe, and MgTe, show their potential to achieve improved ferroelectric (FE) stability, simple atomistic unit cell structure, and large FE polarization. Strain engineering can effectively modulate the FE switching barrier height for facilitating FE switching. The effect of the piezoelectric property on the FE switching barrier heights is also examined.

Abstract: A deep understanding of the fine structure at the atomic scale of halide perovskite materials has been limited by their sensitivity to the electron beam that is widely used for structural characterization. The sensitivity of a gamma-CsPbIBr2 perovskite thin film under electron beam irradiation is revealed by scanning transmission electron microscopy (STEM) through a universal large-range electron dose measurement, which is based on discrete single-electron events in the STEM mode. Our research indicates that the gamma-CsPbIBr2 thin film undergoes structural changes with increasing electron overall dose (e(-).A(-2)) rather than dose rate (e(-).A(-2).s(-1)), which suggests that overall dose is the key operative parameter. The electron beam-induced structural evolution of gamma-CsPbIBr2 is monitored by fine control of the electron beam dose, together with the analysis of high-resolution (S)TEM, diffraction, and energy-dispersive X-ray spectroscopy. Our results show that the gamma-CsPbIBr2 phase first forms an intermediate phase [e.g., CsPb(1-x)(IBr)((3-y))] with a superstructure of ordered vacancies in the pristine unit cell, while a fraction of Pb2+ is reduced to Pb-0. As the electron dose increases, Pb nanoparticles precipitate, while the remaining framework forms the Cs2IBr phase, accompanied by some amorphization. This work provides guidelines to minimize electron beam irradiation artifacts for atomic-resolution imaging on CsPbIBr2 thin films.

Abstract: A detailed account is given of neutron and γ-ray attenuation effects in 14-MeV neutron activation analysis of oxygen. Appropriate neutron cross-section values have been determined in two different ways and compared with literature values. It appears that the attenuation process is best described in terms of nonelastic scattering cross-sections. It is also shown that the narrow beam total γ-ray attenuation coefficients at 6 MeV, given in the literature are suitable for correction purposes if 16N γ-rays are counted with a window of 4.56.5 MeV. Attention was paid to the contribution of β-rays when the 16N activity is counted in this energy interval with a NaI(Tl) detector.

Abstract: A detailed microstructural examination endeavoring to understand the interfacial phenomena yielding to cohesion
in solid-state assembling processes was performed. This study focuses on the transition zone of a dissimilar
titanium alloy joint obtained by Linear Friction Welding (LFW) the β-metastable Ti17 to the near-α
Ti6242. The transition zone delimitating both alloys is characterized by a sharp microstructure change from
acicular HCP (Hexagonal Close-Packed) α′ martensitic laths in the Ti6242 to equiaxed BCC β (Body-Centered
Cubic) subgrains in the Ti17; these α′ plates were shown to precipitate within prior-β subgrains remarkably more
rotated than the ones formed in the Ti17. Both α′ and β microstructures were found to be intermingled within
transitional subgrains demarcating a limited gradient from one chemical composition to the other. These peculiar
interfacial grains revealed that the cohesive mechanisms between the rubbing surfaces occurred in the
single-phase β domain under severe strain and high-temperature conditions. During the hot deformation process,
the mutual migration of the crystalline interfaces from one material to another assisted by a continuous dynamic
recrystallization process was identified as the main adhesive mechanism at the junction zone. The latter led to
successful cohesion between the rubbing surfaces. Once the reciprocating motion stopped, fast cooling caused
both materials to experience either a βlean→α′ or βlean→βmetastable transformation in the interfacial zone depending
on their local chemical composition. The limited process time and the subsequent hindered chemical
homogenization at the transition zone led to retaining the so-called intermingled α’/βm subgrains constituting
the border between both Ti-alloys.