Search

Hydrodechlorination reaction of 3-(benzo-1,3-dioxol-5-yl)-3-chloro-2-methylacrylaldehyde in the presence of different low metal content heterogeneous mono- or bimetallic catalysts was tested for the synthesis of the fragrance Helional® (3-[3,4-methylendioxyphenyl]-2-methyl-propionaldehyde). In particular, mono Pd/Al2O3, Rh/Al2O3 or bimetallic Pd-Cu/Al2O3, Rh-Cu/Al2O3 catalysts were tested in different reaction conditions from which it emerged that mono-Rh/Al2O3 was the best performing catalyst, allowing achievement of 100% substrate conversion and 99% selectivity towards Helional® in 24 h at 80 °C, p(H2) 1.0 MPa in the presence of a base. To establish correlations between atomic structure and catalytic activity, catalysts were characterized by Cu, Rh and Pd K-edge XANES, EXAFS analysis. These characterizations allowed verification that the formation of Pd-Cu alloys and the presence of Cu oxide/hydroxide species on the surface of the Al2O3 support are responsible for the very low catalytic efficiency of bimetallic species tested. [ABSTRACT FROM AUTHOR]

The β phase of tungsten has attracted great interest for spintronic applications due to its higher spin Hall angle compared to other elemental solids and large spin–orbit torque, but the stability of this phase is yet to be well understood as many different results are there in the literature mainly based on the film thickness, temperature, and overall growth conditions. The growth of films by sputter deposition has emerged as a promising technique to achieve β-W owing to its compatibility with current spintronic technology. We demonstrate here the efficient ability of dc magnetron sputtering to grow stable β-W films up to a thickness of ∼180 nm at room temperature by varying a set of deposition parameters like pressure, power, and deposition time and discuss the various underlying mechanisms. From these results, the optimized set of deposition parameters for growing β-W films is given. A clear understanding of the influence of oxygen in the atomic structure of β-W is obtained by varying the thickness of the films. This is confirmed from the ab initio molecular dynamics (MD) simulations, where the atomic structure is influenced by the oxygen doping concentration. A stable polycrystalline β phase can be achieved by controlled doping of oxygen. Additionally, a phase transformation from α to β with the doping of oxygen is also evident by MD simulations. [ABSTRACT FROM AUTHOR]

HoCrO3, a member of the rare-earth chromate family, is known to exhibit an orthorhombic structure with Pbnm space group in bulk at room temperature. We have employed the pressure driven powder consolidation technique, spark plasma sintering, for synthesizing HoCrO3 powder-compact, which exhibits a superior quality with fewer defects over that synthesized by conventional solid-state sintering (resulting in a large reduction of charge carrier mediated extrinsic dielectric contribution). The powder compact shows magneto-dielectric coupling but does not exhibit a detectable ferroelectric phase in the range of 50 K to 300 K. Low temperature Raman spectra show structural distortions below 250 cm−1, indicating Ho ion displacements. Temperature evolution of the crystal structure using synchrotron x-ray diffraction reveals a probable structural phase transition below 240 K. Pyrocurrent measurement, together with synchrotron x-ray diffraction analysis, further points to a magneto-structural transition at 100 K. [ABSTRACT FROM AUTHOR]

FeGa3 is a well known intermetallic semiconductor with a band gap, which is induced by d-p hybridization. In this work, we present the results of experimental and theoretical studies on the effect of Al substitution in FeGa3, obtained by X-ray diffraction (XRD) study, temperature dependent resistivity measurement, room temperature Mössbauer measurement, and density functional theory based electronic structure calculations. It is observed that up to x=0.178 in Fe(AlxGa1-x)3, which is the maximum range studied in this work, Al substitution reduces the lattice parameters a and c, preserving the parent tetragonal P42/mnm crystal structure of FeGa3. Rietveld refinement of the XRD data shows that Al atoms replace Ga atoms located at the 8j sites in FeGa3. A comparison of the trends of the lattice parameters and energy band gap obtained from the calculations and experimental measurements also confirms that Al atoms primarily replace the Ga atoms in the 8j site. The band gap of Fe(AlxGa1-x)3 for x=0.178 is reduced by ≈24% as compared to FeGa3. The system thus has a lot of promise for applications in band gap engineering in infra-red devices. [ABSTRACT FROM AUTHOR]

Dispersion of metal nanoparticles on flat surfaces has attracted considerable interest in many technological applications. Numerous advantages of functionalized patterned nanostructures especially in medical physics, chemistry, biology, and semiconductor quantum dot applications have rapidly driven the growth of this field in the last two decades. In particular, for applications involving biomedical imaging, the nanoparticles have attracted perhaps the greatest attention as these materials provide a direct interface at the subcellular length scale. Reliable characterization methods are thus often needed to infer their detailed structural properties such as average particle size, particle shape, internal structure, surface morphology, distribution of particles, and their chemical composition. As a nondestructive probe, X-ray fluorescence measurements at grazing incidence provide sensitive information about the physical and chemical nature of the nanoparticles over the large surface area of a substrate. Herein, we demonstrate the potential capabilities of the X-ray fluorescence technique for reliable and precise determination of surface morphology of metal nanoparticles, dispersed on a flat surface. Our results show that X-ray standing wave assisted fluorescence measurements are markedly sensitive to the nature of dispersion of nanoparticles on a substrate surface. We have analyzed different types of nanostructured materials; e.g. a W thin film structure and Au nanoparticles deposited on a Si surface. The average size of the Au nanoparticles estimated, using X-ray standing wave fluorescence analysis, was found to closely agree with the atomic force microscopy measurements. The inherent features of the X-ray fluorescence technique permit us to analyze distribution of all kinds of metal and metalloid nanoparticles on a flat surface. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper is a continuation and extension of our earlier work ( X-ray Spectrom. 2010, 39, 127-134, DOI:10.1002/xrs.1215) on the development of a software platform CATGIXRF, as a solution to provide non-destructive evaluation of nanostructured materials. Here, we describe an interactive graphical user interface (GUI) for the CATGIXRF program. The newly developed GUI interface facilitates determination of microstructural parameters on angstrom length scale for the nanostructured thin layered materials using synchrotron as well as laboratory X-ray sources. It allows combined analysis capabilities for both the X-ray reflectivity and grazing incidence X-ray fluorescence (GIXRF) data simultaneously, thus enabling us a greater sensitivity for the determination of microstructural parameters such as thickness, interface mixing, and roughness of a thin film medium with improved accuracies. The utility and various newly added salient features of the GUI-CATGIXRF program are described by providing example calculations as well as by analyzing experimentally a few thin film structures with different surface-interface properties. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Long-term durability of a thin film device is strongly correlated with the nature of interface structure associated between different constituent layers. Synthetic periodic multilayer structures are primarily employed as artificial X-ray Bragg reflectors in many applications, and their reflection efficiency is predominantly dictated by the nature of the buried interfaces between the different layers. Herein, we demonstrate the applicability of the combined analysis approach of the X-ray reflectivity and grazing incidence X-ray fluorescence measurements for the reliable and precise determination of a buried interface structure inside periodic X-ray multilayer structures. X-ray standing wave field (XSW) generated under Bragg reflection condition is used to probe the different constituent layers of the W-B4C multilayer structure at 10 keV and 12 keV incident X-ray energies. Our results show that the XSW assisted fluorescence measurements are markedly sensitive to the location and interface morphology of a buried layer structure inside a periodic multilayer structure. The cross sectional transmission electron microscopy results obtained on the W-B4C multilayer structure provide a deeper look on the overall reliability and accuracy of the XSW method. The method described here would also be applicable for nondestructive characterization of a wide range of thin film based semiconductor and optical devices. [ABSTRACT FROM AUTHOR]

Dopant-profile independent electron transport has been observed through a combined study of temperature dependent electrical resistivity and magnetoresistance measurements on a series of Ti incorporated ZnO thin films with varying degree of static-disorder. These films were grown by atomic layer deposition through in-situ vertical stacking of multiple sub-monolayers of TiOx in ZnO. Upon decreasing ZnO spacer layer thickness, electron transport smoothly evolved from a good metallic to an incipient non-metallic regime due to the intricate interplay of screening of spatial potential fluctuations and strength of static-disorder in the films. Temperature dependent phase-coherence length as extracted from the magnetotransport measurement revealed insignificant role of inter sub-monolayer scattering as an additional channel for electron dephasing, indicating that films were homogeneously disordered three-dimensional electronic systems irrespective of their dopant-profiles. Results of this study are worthy enough for both fundamental physics perspective and efficient applications of multi-stacked ZnO/TiOx structures in the emerging field of transparent oxide electronics. [ABSTRACT FROM AUTHOR]

The effect of longitudinal (or temporal) coherence on total reflection assisted x-ray standing wave (TR-XSW) analysis of nanoscale materials is quantitatively demonstrated by showing how the XSW fringe visibility can be strongly damped by decreasing the spectral resolution of the incident x-ray beam. The correction for nonzero wavelength dispersion (δλ ≠ 0) of the incident x-ray wave field is accounted for in the model computations of TR-XSW assisted angle dependent fluorescence yields of the nanostructure coatings on x-ray mirror surfaces. Given examples include 90 nm diameter Au nanospheres deposited on a Si(100) surface and a 3 nm thick Zn layer trapped on top a 100 nm Langmuir-Blodgett film coating on a Au mirror surface. Present method opens up important applications, such as enabling XSW studies of large dimensioned nanostructures using conventional laboratory based partially coherent x-ray sources. [ABSTRACT FROM AUTHOR]

A new multipurpose x-ray reflectometer station has been developed and augmented at the microfocus beamline (BL-16) of Indus-2 synchrotron radiation source to facilitate synchronous measurements of specular x-ray reflectivity and grazing incidence x-ray fluorescence emission from thin layered structures. The design and various salient features of the x-ray reflectometer are discussed. The performance of the reflectometer has been evaluated by analyzing several thin layered structures having different surface interface properties. The results reveal in-depth information for precise determination of surface and interface properties of thin layered materials demonstrating the immense potential of the combined measurements of x-ray reflectivity and grazing incidence fluorescence on a single reflectometer. [ABSTRACT FROM AUTHOR]

Total reflection X-ray fluorescence (TXRF) spectroscopy has seen remarkable progress over the past years. Numerous applications in basic and applied sciences prove its importance. The large spectral background, which is a major detrimental factor in the conventional X-ray fluorescence technique, limits the element detection sensitivities of the technique to the µg g-1 (ppm) range. This spectral background is reduced to a great extent in the TXRF technique due to the low extinction depth of the primary incident X-ray beam. In synchrotron radiation (SR) based TXRF measurements the spectral background is reduced further because of the polarization of the synchrotron X-ray beam. Here, we show in detail the influence of synchrotron polarization on the spectral background in a fluorescence spectrum and its significance towards TXRF detection sensitivities. We have performed TXRF measurements on standard reference materials to show that one obtains approximately one order of magnitude enhancement in the spectral signal strength by utilizing the anisotropic nature of the scattered synchrotron radiation in the horizontal detection geometry. [ABSTRACT FROM AUTHOR]

Nanocrystalline La0.15Ca0.85MnO3 samples of various grain sizes ranging from ∼17 to 42 nm have been prepared by sol-gel technique. Phase purity and composition were verified by room temperature x-ray diffraction and SEM-EDAX analysis. The bulk La0.15Ca0.85MnO3 is known to order antiferromagnetically around 170 K and to undergo a simultaneous crystal structural transition. DC magnetization measurements on 17 nm size La0.15Ca0.85MnO3 show a peak at ∼130 K (TN) in zero-field-cooled (ZFC) state. Field-cooled magnetization bifurcates from ZFC data around 200 K hinting a weak ferromagnetic component near room temperature due to surface moments of the nanoparticle sample. Low temperature powder neutron diffraction experiments reveal that the incomplete structural transition from room temperature orthorhombic to low temperature orthorhombic-monoclinic state also occurs in the nanoparticle sample as in the bulk. Magnetization in the ordered state decreases as particle size increases, thus indicating the reduction of the competing ferromagnetic surface moments. [ABSTRACT FROM AUTHOR]

Aim: Early Intervention in Psychosis teams (EITs) are a growing entity internationally, yet they remain under‐researched given challenges facing their delivery. Model adaptations include stand‐alone services, a hub‐and‐spoke model with various bases and integrating specialist staff into existing mental health teams. The present critical review focuses on reviewing the evidence base for the delivery of EITs in rural areas, first pertaining to evidence for model adherence and second to clinically outcomes. Method: A systematic literature search was undertaken, finding 53 papers of interest. Nine papers met the inclusion criteria. A critical appraisal tool was used to consider the quality of the evidence and a narrative review of their findings is presented. Results: The five studies reporting clinical outcomes of rural EITs demonstrate positive outcomes of a hub‐and‐spoke and stand‐alone EIT on reducing hospital admissions, psychotic symptoms and improving quality of life. One study directly comparing hub‐and‐spoke to stand‐alone EIT found that hub‐and‐spoke EIT had more positive outcomes than a stand‐alone service. Of the studies attempting to promote adherence to EIT model in rural areas, services show low overall adherence and report issues pertaining to funding and managerial support for practical barriers to implementation. Conclusions: EIT services in rural areas may show similar positive outcomes to urban areas and adaptations to suit rural populations appear acceptable, such as using a hub‐and‐spoke model, though further research is required. Adherence to EIT service models in rural areas may be limited and training programmes to promote adherence benefit from managerial and financial support. [ABSTRACT FROM AUTHOR]

Joubert syndrome is a genetically heterogeneous disorder that belongs to the group of cerebello-oculo-renal syndromes. It is characterised by neurodevelopmental abnormalities and complex midbrain-hindbrain malformation, visible on brain imaging as a molar tooth sign. It is classified as a ciliopathy and has variable renal involvement. Herein, we report a case of a 9-year-old boy with developmental delay, presented as chronic kidney disease and evaluation showed features of Joubert syndrome. Recognition of specific clinical and radiological findings will help in early diagnosis and appropriate care. [ABSTRACT FROM AUTHOR]

Background: Quantum dots (QDs) are crystalline nanoparticles that are compatible with biological systems to provide a chemically and photochemically stable fluorescent label. New ligand probes with fluorescent reporter groups are needed for detection and characterization of G protein-coupled receptors (GPCRs). Results: Synthetic strategies for coupling the A2A adenosine receptor (AR) agonist CGS21680 (2-[4-(2- carboxyethyl)phenylethylamino]-5'-N-ethylcarboxamidoadenosine) to functionalized QDs were explored. Conjugates tethered through amide-linked chains and poly(ethyleneglycol) (PEG) displayed low solubility and lacked receptor affinity. The anchor to the dendron was either through two thiol groups of (R)-thioctic acid or through amide formation to a commercial carboxy-derivatized QD. The most effective approach was to use polyamidoamine (PAMAM) D5 dendrons as multivalent spacer groups, grafted on the QD surface through a thioctic acid moiety. In radioligand binding assays, dendron nucleoside conjugate 11 displayed a moderate affinity at the human A2AAR (Kiapp 1.02 ± 0.15 μM). The QD conjugate of increased water solubility 13, resulting from the anchoring of this dendron derivative, interacted with the receptor with Kiapp of 118 ± 54 nM. The fluorescence emission of 13 occurred at 565 nm, and the presence of the pendant nucleoside did not appreciably quench the fluorescence. Conclusions: This is a feasibility study to demonstrate a means of conjugating to a QD a small molecular pharmacophore of a GPCR that is relatively hydrophobic. Further enhancement of affinity by altering the pharmacophore or the linking structures will be needed to make useful affinity probes. [ABSTRACT FROM AUTHOR]

Presents a list of information resources in finance and accounting. "Integrating Managerial and Tax Objectives in Transfer Pricing," by Tim Baldenius, Nahim D. Melumad and Stefan Reichelstein; "Managerial and Investor Responses to Disclosure Regulation," by Brian J. Bushee, Dawn A. Matsumoto and Gregory S. Miller; "Permanently Reinvested Foreign Earnings, Taxes, and Earnings Management," by Linda K. Krull.