Synchrotron SAX and WAX diffraction study of a hydrated very long-chain, dendritic amphiphile + DPPC mixture

The tri-headed anionic dendritic amphiphile, 4-(2-carboxyethyl)-4-[(icosyloxycarbonyl)amino]heptanedioic acid (3CCb20), forms mixed aggregates with dipalmitoylphosphatidylcholine (DPPC) in excess water at 3CCb20:DPPC = 0.91:1 molar ratio. On heating, these mixed aggregates transform into fluid bilayers stacked in the liquid crystalline lamellar L phase at about 40 °C. This phase transition and the microstructure of 3CCb20 + DPPC aggregates were studied with small- and wide-angle synchrotron X-ray diffraction. The ability of 3CCb20 to solubilize solidlike lipid bilayers could contribute to the antimicrobial activities of 3CCb20, including its anti-HIV activity.     

Infrared emission spectrum of hot D2O

An emission spectrum of hot D₂O (1500 °C) has been analyzed in the 2077-4323 cm⁻¹ region. A considerable number of new vibration-rotation energy levels have been determined and two new vibrational levels identified. The new (0 4 1) and (0 2 2) vibrational levels have estimated band origins of 7343.93 ± 0.01 and 7826.38 ± 0.02 cm⁻¹, respectively.     

A Flux Correction Multigrid for Compressible Flow

A finite-volume based linear multigrid algorithm is proposed and used within an implicit linearized scheme to solve Navier–Stokes equations for compressible laminar flows. Coarse level problems are constructed algebraically based on convective and diffusive fluxes, without the knowledge of coarse geometry. Numerical results for complex 2D geometries such as airfoils, including stretched meshes, show mesh size independent convergence and efficiency of the method compared to other finite-volume-based multigrid method.     

Clay pigment structure characterisation as a guide for provenance determination—a comparison between laboratory powder micro-XRD and synchrotron radiation XRD

Application of X-ray diffraction (XRD)-based techniques in the analysis of painted artworks is not only beneficial for indisputable identification of crystal constituents in colour layers, but it can also bring insight in material crystal structure, which can be affected by their geological formation, manufacturing procedure or secondary changes. This knowledge might be helpful for art historic evaluation of an artwork as well as for its conservation. By way of example of kaolinite, we show that classification of its crystal structure order based on XRD data is useful for estimation of its provenance. We found kaolinite in the preparation layer of a Gothic wall painting in a Czech church situated near Karlovy Vary, where there are important kaolin deposits. Comparing reference kaolin materials from eight various Czech deposits, we found that these can be differentiated just according to the kaolinite crystallinity. Within this study, we compared laboratory powder X-ray micro-diffraction (micro-XRD) with synchrotron radiation X-ray diffraction analysing the same real sample. We found that both techniques led to the same results.     

Chemical states of nitrogen in ZnO studied by near-edge X-ray absorption fine structure and core-level photoemission spectroscopies

Interaction of low-energy nitrogen ions with ZnO surface has been studied by photoemission spectroscopy (PES) around N 1s core-level and near-edge X-ray absorption fine structure (NEXAFS) around N K-edge. Nitrogen can break Zn-O bonds at the surface and form N-O, Zn-N or Zn-N-O bonds, characterised by specific chemical shifts in PES or absorption peaks in NEXAFS. A distinctive signal from molecular nitrogen has also been observed in ion-bombarded samples in both NEXAFS and PES.     

Naturally irradiated fluorite as a historic violet pigment: Raman spectroscopic and X‐ray diffraction study

Naturally irradiated violet fluorite, a cubic CaF₂ mineral, is a rare historic pigment. Its documented usage in Europe stretches from ca. 1450 to ca. 1550. The intensely coloured violetish black naturally irradiated fluorite is commonly called antozonite, which is only vaguely defined based on its dark colour and specific odour emanated during grinding. In the published literature, there have been some discrepancies about its Raman spectrum. Therefore, sixteen samples of antozonite were analysed by Raman (micro‐)spectroscopy using five different excitation laser wavelengths (445, 532, 633, 780 and 1064 nm), which revealed specific bands located below 500 cm⁻¹ probably related to radiation‐caused defects. Their intensity increased with increasing violet colour saturation, thus providing a specification for antozonite's definition. Spectra excited at 445 and 780 nm contained also numerous broad bands above 500 cm⁻¹, which seem to be caused by the presence of rare earth elements. The structural damage of antozonite samples has been assessed by X‐ray diffraction and related to their lightness using analysis of image histograms. The obtained results have been applied in the analysis of micro‐samples of a Late Gothic altarpiece located in an Italian Court in UNESCO city Kutná Hora, Czech Republic, which contained exceptionally large grains of deep violet fluorite identified as antozonite. Copyright © 2015 John Wiley & Sons, Ltd.     

Open‐Shell 3d Transition Metal Nitridophosphates MIIP8N14 (MII=Fe,Co, Ni) by High‐Pressure Metathesis

3d transition metal nitridophosphates M^IIP₈N₁₄ (M^II=Fe, Co, Ni) were prepared by high‐pressure metathesis indicating that this route might give a systematic access to a structurally rich family of M‐P‐N compounds. Their structures, which are stable in air up to at least 1273 K, were determined through powder X‐ray diffraction and consist of highly condensed tetra‐layers of PN₄ tetrahedra and MN₆ octahedra. Magnetic measurements revealed paramagnetic behavior of CoP₈N₁₄ and NiP₈N₁₄ down to low temperatures while, FeP₈N₁₄ exhibits an antiferromagnetic transition at T_N=3.5(1) K. Curie–Weiss fits of the paramagnetic regime indicate that the transition metal cations are in a oxidation state +II, which was corroborated by Mössbauer spectroscopy for FeP₈N₁₄. The ligand field exerted by the nitride ions in CoP₈N₁₄ and NiP₈N₁₄ was determined from UV/Vis/NIR data and is comparable to that of aqua‐ligands and oxophosphates.     

Open‐Shell 3d Transition Metal Nitridophosphates MIIP8N14 (MII=Fe,Co, Ni) by High‐Pressure Metathesis

3d transition metal nitridophosphates M^IIP₈N₁₄ (M^II=Fe, Co, Ni) were prepared by high‐pressure metathesis indicating that this route might give a systematic access to a structurally rich family of M‐P‐N compounds. Their structures, which are stable in air up to at least 1273 K, were determined through powder X‐ray diffraction and consist of highly condensed tetra‐layers of PN₄ tetrahedra and MN₆ octahedra. Magnetic measurements revealed paramagnetic behavior of CoP₈N₁₄ and NiP₈N₁₄ down to low temperatures while, FeP₈N₁₄ exhibits an antiferromagnetic transition at T_N=3.5(1) K. Curie–Weiss fits of the paramagnetic regime indicate that the transition metal cations are in a oxidation state +II, which was corroborated by Mössbauer spectroscopy for FeP₈N₁₄. The ligand field exerted by the nitride ions in CoP₈N₁₄ and NiP₈N₁₄ was determined from UV/Vis/NIR data and is comparable to that of aqua‐ligands and oxophosphates.     

Effects of inelastic neutrino-nucleus scattering on supernova dynamics and radiated neutrino spectra

Based on the shell model for Gamow-Teller and the random phase approximation for forbidden transitions, we calculate cross sections for inelastic neutrino-nucleus scattering (INNS) under supernova (SN) conditions, assuming a matter composition given by nuclear statistical equilibrium. The cross sections are incorporated into state-of-the-art stellar core-collapse simulations with detailed energy-dependent neutrino transport. While no significant effect on the SN dynamics is observed, INNS increases the neutrino opacities noticeably and strongly reduces the high-energy tail of the neutrino spectrum emitted in the neutrino burst at shock breakout. Relatedly the expected event rates for the observation of such neutrinos by earthbound detectors are reduced by up to about 60%.