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synchrotron radiation

Zhen Wang, Jianzhu Ju, Lingpu Meng, Nan Tian, Jiarui Chang, Haoran Yang, Youxin Ji, Fengmei Su, Liangbin Li
Structural and morphological transitions of flow-induced crystallization (FIC) in poly(1-butene) (PB-1) melt have been studied by combining extensional rheology and in situ synchrotron radiation ultrafast wide- and small-angle X-ray scattering (WAXD/SAXS) measurements. Unexpectedly, metastable Form III is crystallized directly from the PB-1 melt by high-speed extension, which has a short lifetime of several tens of milliseconds and manifests the thermodynamic and kinetic competition among Form III, Form II and melt under flow...
April 27, 2017: Soft Matter
Pip C J Clark, Hanna Radtke, Atip Pengpad, Andrew I Williamson, Ben F Spencer, Samantha J O Hardman, Marina A Leontiadou, Darren C J Neo, Simon M Fairclough, Andrew A R Watt, Igor Pis, Silvia Nappini, Federica Bondino, Elena Magnano, Karsten Handrup, Karina Schulte, Mathieu G Silly, Fausto Sirotti, Wendy R Flavell
Achieving control of the surface chemistry of colloidal quantum dots (CQDs) is essential to fully exploit their properties in solar cells, but direct measurement of the chemistry and electronic structure in the outermost atomic layers is challenging. Here we probe the surface oxidation and passivation of cation-exchanged PbS/CdS core/shell CQDs with sub nm-scale precision using synchrotron-radiation-excited depth-profiling photoemission. We investigate the surface composition of the topmost 1-2.5 nm of the CQDs as a function of depth, for CQDs of varying CdS shell thickness, and examine how the surface changes after prolonged air exposure...
April 26, 2017: Nanoscale
Vinita J Ghosh, Charles Schaefer, Henry Kahnhauser
The National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory was shut down in September 2014. Lead bricks used as radiological shadow shielding within the accelerator were exposed to stray radiation fields during normal operations. The FLUKA code, a fully integrated Monte Carlo simulation package for the interaction and transport of particles and nuclei in matter, was used to estimate induced radioactivity in this shielding and stainless steel beam pipe from known beam losses. The FLUKA output was processed using MICROSHIELD® to estimate on-contact exposure rates with individually exposed bricks to help design and optimize the radiological survey process...
June 2017: Health Physics
Ashish Chhaganlal Gandhi, Jauyn Grace Lin
Finite sized Ni/NiO nanoparticles (NPs) are prepared by oxidizing pure Ni-NPs in an ambient atmosphere with varying annealing time (t A). A synchrotron radiation x-ray diffraction technique was used to estimate the grain size, weight fraction and lattice parameters of Ni and NiO. The temperature (T) dependencies of effective g-factor and line-width of ferromagnetic resonance (FMR) spectra for a series of Ni/NiO NPs are determined. Three T-regions with different FMR behaviors T  >  200 K, 200  >  T  >  130 K and T  <  130 K are identified...
April 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Shabnam Oghbaie, Mathieu Gisselbrecht, Erik P Månsson, Joakim Laksman, Christian Stråhlman, Anna Sankari, Stacey L Sorensen
Dissociative double photoionization of cyclopropane is studied in the inner-valence region using tunable synchrotron radiation. With the aid of ab initio quantum chemical calculations the energies of dication states and their favoured fragmentation pathways are determined. These are compared to the experimental appearance energies of two-body fragmentation processes and to the kinetic energy released upon dissociation. Photon energy dependent state-selective dissociation in the 25-35 eV range is found. Calculations of dissociation pathways suggest that cyclopropane ring-deformation is selectively triggered at certain photon energies...
April 24, 2017: Physical Chemistry Chemical Physics: PCCP
M Coduri, M Scavini, M Pani, M M Carnasciali, H Klein, C Artini
The evolution of the defect structure and microstructure of heavily Gd-doped ceria (Ce1-μREμO2-y, 0.313 ≤ μ ≤ 0.438) for different synthetic pathways is investigated here to explore the way defects interact with each other in a composition range known to effectively hamper the application of the material as an electrolyte. Synchrotron radiation powder diffraction is exploited by combining conventional Rietveld analysis with the Pair Distribution Function to get a multiscale picture of defect structures, and it is combined with Raman spectroscopy to assess local scale interactions...
April 21, 2017: Physical Chemistry Chemical Physics: PCCP
M Altissimo, M Kiskinova, R Mincigrucci, L Vaccari, C Guarnaccia, C Masciovecchio
Revealing the structure of complex biological macromolecules, such as proteins, is an essential step for understanding the chemical mechanisms that determine the diversity of their functions. Synchrotron based X-ray crystallography and cryo-electron microscopy have made major contributions in determining thousands of protein structures even from micro-sized crystals. They suffer from some limitations that have not been overcome, such as radiation damage, the natural inability to crystallize a number of proteins, and experimental conditions for structure determination that are incompatible with the physiological environment...
July 2017: Structural Dynamics (Melville, N.Y.)
Matthias Franke, Daniel Wechsler, Quratulain Tariq, Michael Röckert, Liang Zhang, Pardeep Kumar Thakur, Nataliya Tsud, Sofiia Bercha, Kevin Prince, Tien-Lin Lee, Hans-Peter Steinrück, Ole Lytken
We have investigated the interactions between cobalt(ii)-tetraphenylporphyrin (CoTPP) molecules and MgO(100) thin films on Ag(100) by means of Synchrotron Radiation X-Ray and Ultra-Violet Photoelectron Spectroscopy (SR-XPS and SR-UPS). At room temperature, the CoTPP monolayer consists of two different species. A minority of molecules exhibits a strong electronic interaction with the substrate, whereas for the majority a similar spectroscopic signature as for multilayer molecules is observed. Based on the lateral inhomogeneity of the surface electronic structure, we tentatively suggest that the strongly interacting molecules adsorb with their metal center directly above oxygen ions...
April 20, 2017: Physical Chemistry Chemical Physics: PCCP
Waed Ahmad, Cecile Coeur, Alexandre Tomas, Thomas Fagniez, Jean-Blaise Brubach, Arnaud Cuisset
Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) synchrotron analyses supplemented by density functional theory (DFT) anharmonic calculations have been undertaken to study the fundamental vibrational signatures of guaiacol and syringol, two methoxyphenol compounds found at the highest concentrations in fresh wood smoke and precursors of secondary organic aerosols (SOA) affecting the radiative balance and chemistry of the atmosphere. Nitroderivatives of these two compounds have also been studied experimentally for nitroguaiacol and theoretically for nitrosyringol...
April 10, 2017: Applied Optics
F Albert, N Lemos, J L Shaw, B B Pollock, C Goyon, W Schumaker, A M Saunders, K A Marsh, A Pak, J E Ralph, J L Martins, L D Amorim, R W Falcone, S H Glenzer, J D Moody, C Joshi
We investigate a new regime for betatron x-ray emission that utilizes kilojoule-class picosecond lasers to drive wakes in plasmas. When such laser pulses with intensities of ∼5×10^{18}  W/cm^{2} are focused into plasmas with electron densities of ∼1×10^{19}  cm^{-3}, they undergo self-modulation and channeling, which accelerates electrons up to 200 MeV energies and causes those electrons to emit x rays. The measured x-ray spectra are fit with a synchrotron spectrum with a critical energy of 10-20 keV, and 2D particle-in-cell simulations were used to model the acceleration and radiation of the electrons in our experimental conditions...
March 31, 2017: Physical Review Letters
Takashi Tanaka
A new method of coherent mode decomposition (CMD) is proposed that is based on a Wigner-function representation of Hermite-Gaussian beams. In contrast to the well-known method using the cross spectral density (CSD), it directly determines the mode functions and their weights without solving the eigenvalue problem. This facilitates the CMD of partially coherent light whose Wigner functions (and thus CSDs) are not separable, in which case the conventional CMD requires solving an eigenvalue problem with a large matrix and thus is numerically formidable...
April 15, 2017: Optics Letters
Sergey Y Bershitsky, Natalia A Koubassova, Michael A Ferenczi, Galina V Kopylova, Theyencheri Narayanan, Andrey K Tsaturyan
Muscle contraction is powered by actin-myosin interaction controlled by Ca(2+) via the regulatory proteins troponin (Tn) and tropomyosin (Tpm), which are associated with actin filaments. Tpm forms coiled-coil dimers, which assemble into a helical strand that runs along the whole ∼1 μm length of a thin filament. In the absence of Ca(2+), Tn that is tightly bound to Tpm binds actin and holds the Tpm strand in the blocked, or B, state, where Tpm shields actin from the binding of myosin heads. Ca(2+) binding to Tn releases the Tpm from actin so that it moves azimuthally around the filament axis to a closed, or C, state, where actin is partially available for weak binding of myosin heads...
April 11, 2017: Biophysical Journal
Yolanda Sadikin, Pascal Schouwink, Matteo Brighi, Zbigniew Łodziana, Radovan Černý
Three different types of anion packing, i.e., hexagonal close packed (hcp), cubic close packed (ccp), and body centered cubic (bcc), are investigated experimentally and with ab initio calculations in the model system Na2B12H12. Solvent free and water assisted mechanical grinding provide polycrystalline samples for temperature-dependent synchrotron radiation X-ray powder diffraction and electrochemical impedance spectroscopy. It is shown that among the common close packed lattices, the hcp anionic backbone creates very favorable conditions for three-dimensional ionic conduction pathways, comprised of O-O, T-T, and T-O-T (O for octahedral, T for tetrahedral) cation hops...
April 11, 2017: Inorganic Chemistry
Akinari Yokoya, Takashi Ito
PURPOSE: We review interesting findings reported in the studies of the biological effects induced by inner-shell ionization with the aim of interpreting them from a mechanistic viewpoint of Auger effect of in particular atoms on to the different biological systems. MATERIALS AND METHODS: Cited more than 70 published papers on the Auger effects ranging from DNA related elements (carbon, nitrogen, oxygen and phosphorus) to mammalian cells. Externally administrated bromine, iodine, and platinum have also been cited for the present endeavor...
April 11, 2017: International Journal of Radiation Biology
Dunfeng Gao, Yi Zhang, Zhiwen Zhou, Fan Cai, Xinfei Zhao, Wugen Huang, Yangsheng Li, Junfa Zhu, Ping Liu, Fan Yang, Guoxiong Wang, Xinhe Bao
The electrochemical CO2 reduction reaction (CO2RR) typically uses transition metals as the catalysts. To improve the efficiency, tremendous efforts have been dedicated to tuning the morphology, size, and structure of metal catalysts and employing electrolytes that enhance the adsorption of CO2. We report here a strategy to enhance CO2RR by constructing the metal-oxide interface. We demonstrate that Au-CeOx shows much higher activity and Faradaic efficiency than Au or CeOx alone for CO2RR. In situ scanning tunneling microscopy and synchrotron-radiation photoemission spectroscopy show that the Au-CeOx interface is dominant in enhancing CO2 adsorption and activation, which can be further promoted by the presence of hydroxyl groups...
April 14, 2017: Journal of the American Chemical Society
Andrew J Feola, Baptiste Coudrillier, John Mulvihill, Diogo M Geraldes, Nghia T Vo, Julie Albon, Richard L Abel, Brian C Samuels, C Ross Ethier
Purpose: Cerebrospinal fluid pressure (CSFp) changes are involved or implicated in various ocular conditions including glaucoma, idiopathic intracranial hypertension, and visual impairment and intracranial pressure syndrome. However, little is known about the effects of CSFp on lamina cribrosa and retrolaminar neural tissue (RLNT) biomechanics, potentially important in these conditions. Our goal was to use an experimental approach to visualize and quantify the deformation of these tissues as CSFp increased...
April 1, 2017: Investigative Ophthalmology & Visual Science
Shunbo Li, Johannes Ihli, William J Marchant, Muling Zeng, Li Chen, Katia Wehbe, Gianfelice Cinque, Oscar Cespedes, Nik Kapur, Fiona C Meldrum
Fourier transform infrared micro-spectroscopy provides an effective means of performing rapid, non-destructive, and label-free analysis of specimens according to their vibrational modes. However, as water absorbs very strongly in the infrared region, analysis of aqueous solutions in transmission mode can suffer from problems with signal saturation. We here describe the fabrication of a novel microfluidic device that overcomes this problem. Devices with channel depths of just 3 μm were constructed from calcium fluoride using photolithography and hot embossing bonding, where calcium fluoride was selected due to its transparency in the IR region...
April 7, 2017: Lab on a Chip
Simone Vadilonga, Ivo Zizak, Dmitry Roshchupkin, Emelin Evgenii, Andrei Petsiuk, Wolfram Leitenberger, Alexei Erko
X-ray Bragg diffraction in sagittal geometry on a Y-cut langasite crystal (La3Ga5SiO14) modulated by Λ = 3 µm Rayleigh surface acoustic waves was studied at the BESSY II synchrotron radiation facility. Owing to the crystal lattice modulation by the surface acoustic wave diffraction, satellites appear. Their intensity and angular separation depend on the amplitude and wavelength of the ultrasonic superlattice. Experimental results are compared with the corresponding theoretical model that exploits the kinematical diffraction theory...
April 1, 2017: Journal of Applied Crystallography
P Scardi, L Rebuffi, M Abdellatief, A Flor, A Leonardi
Synchrotron radiation X-ray diffraction (XRD) patterns from an extensively ball-milled iron alloy powder were collected at 100, 200 and 300 K. The results were analysed together with those using extended X-ray absorption fine structure, measured on the same sample at liquid nitrogen temperature (77 K) and at room temperature (300 K), to assess the contribution of static disorder to the Debye-Waller coefficient (Biso). Both techniques give an increase of ∼20% with respect to bulk reference iron, a noticeably smaller difference than reported by most of the literature for similar systems...
April 1, 2017: Journal of Applied Crystallography
Shuyu Liang, Patrick Hemberger, Joëlle Levalois-Grützmacher, Hansjörg Grützmacher, Sabyasachi Gaan
The thermal behavior of organophosphorus compounds is intricate and poorly understood but crucial for understanding gas-phase flame inhibition, syntheses of thermally active phosphorus-based reactive precursors, catalytic combustion, incineration of toxic nerve gases, and astrochemistry. In this work, the pyrolysis of dimethyl phosphoramidate was investigated using photoion photoelectron coincidence spectroscopy in combination with vacuum ultraviolet synchrotron radiation. This technique enables isomer-selective detection of reactive intermediates, which are crucial in the understanding of the decomposition process...
April 24, 2017: Chemistry: a European Journal
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