Extracellular Iron-Sulfur Precipitates From Growth ofDesulfovibrio desulfuricans

1999 ◽  
Vol 590 ◽  
Author(s):  
Mark R. Antonio ◽  
Monica Lee Tischler ◽  
Dana Witzcak
Keyword(s):  
Ferrous Sulfate ◽  
Spectroscopic Data ◽  
Room Temperature ◽  
Average Distance ◽  
Basal Medium ◽  
X Ray Diffraction ◽  
X Ray ◽  
Iron Sulfur ◽  
X Ray Absorption ◽  
Iron Bearing

ABSTRACTWe have examined extracellular iron-bearing precipitates resulting from the growth ofDesulfovibrio desuyfuricansin a basal medium with lactate as the carbon source and ferrous sulfate. Black precipitates were obtained whenD. desulfuricanswas grown with an excess of FeSO4. WhenD. desulfuricanswas grown under conditions with low amounts of FeSO4, brown precipitates were obtained. The precipitates were characterized by iron K-edge XAFS (x-ray absorption fine structure),57Fe Mössbauer-effect spectroscopy, and powder x-ray diffraction. Both were noncrystalline and nonmagnetic (at room temperature) solids containing high-spin Fe(III). The spectroscopic data for the black precipitates indicate the formation of an iron-sulfur phase with 6 nearest S neighbors about Fe at an average distance of 2.24(1) Å, whereas the brown precipitates are an iron-oxygen-sulfur phase with 6 nearest O neighbors about Fe at an average distance of 1.95(1) Å.

scholarly journals Experimental Investigations of the Interaction of SO2 with MgO

1999 ◽  
Vol 590 ◽  
Author(s):  
Andrea Freitag ◽  
J. A. Rodriguez ◽  
J. Z. Larese
Keyword(s):  
High Resolution ◽  
Film Thickness ◽  
Room Temperature ◽  
Temperature Programmed Desorption ◽  
Experimental Investigations ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Temperature Programmed ◽  
X Ray Absorption

ABSTRACTHigh resolution adsorption isotherms, temperature programmed desorption (TPD), x-ray diffraction (XRD) and x-ray absorption near edge spectroscopy (XANES) methods were used to investigate the interaction of SO2 with high quality MgO powders. The results of these investigations indicate that when SO2 is deposited on MgO in monolayer quantities at temperatures near 100K both SO3 and SO4 species form that are not removed by simply pumping on the pre-dosed samples at room temperature. TPD and XANES studies indicate that heating of pre-dosed MgO samples to temperatures above 350 °C is required for full removal of the SO3/SO4 species. XANES measurements made as a function of film thickness indicate for coverages near monolayer completion that the SO4 species form first.

Local Structure of Molten CdCl2 Systems

2004 ◽  
Vol 59 (11) ◽  
pp. 819-824 ◽  
Author(s):  
Y. Okamoto ◽  
H. Shiwaku ◽  
T. Yaita ◽  
S. Suzuki ◽  
K. Minato ◽  
...  
Keyword(s):  
Fine Structure ◽  
Solid State ◽  
Local Structure ◽  
Room Temperature ◽  
Structural Parameters ◽  
Molten State ◽  
Tetrahedral Coordination ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Absorption

The local structure of molten CdCl2 was investigated by X-ray absorption fine structure (XAFS) and X-ray diffraction(XRD) analyses. The nearest Cd2+-Cl− distance decreases from 2.61 Å in the room temperature solid state to 2.47 - 2.50 Å in the molten state. The coordination number decreases from 6 in the solid to 4 in the melt. The obtained structural parameters from the XAFS and the XRD analyses suggest that a tetrahedral coordination (CdCl4)2− is predominant in molten CdCl2. The XAFS result of a molten 50%CdCl2-KCl mixture shows that the 4-fold (CdCl4)2− structure holds also in the mixture

Epitaxy of Thin Ternary Co1−xFexSi2 Silicide Films on SI(111)

1998 ◽  
Vol 528 ◽  
Author(s):  
L. Khouchaf ◽  
D. Berling ◽  
V. Pierron-Bohnes ◽  
C. Pirri ◽  
S. Hong ◽  
...  
Keyword(s):  
Room Temperature ◽  
Local Environment ◽  
Type Structure ◽  
Appreciable Amount ◽  
Silicide Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cscl Type ◽  
Cubic Structure ◽  
X Ray Absorption

AbstractLow-energy electron diffraction, x-ray diffraction, and x-ray absorption techniques are used to investigate the atomic structure of ternary silicides (MSi2, M = Co, Fe). 100 Å thick Co1−xFexSi2 films (with 0 ≤ × ≤ 1) were grown by codeposition onto a Si(111) substrate held at room temperature. The as-deposited films are metallic and adopt an ordered cubic structure of CsCl-type with essentially random vacancies, very similar to that of room-temperature grown FeSi2 and CoSi2 silicides. Upon annealing at 650°C, Fe-rich (x ≥ 0.85) films invariably convert into a semiconducting phase with a structure similar to the orthorhombic β-FeSi2 one. Yet, most interestingly, an almost cubic structure is preserved for x ≤ 0.85. Nevertheless, x-ray diffraction reveals a demixion into a Co rich CaF2-type silicide and a Fe-rich phase with a nearly cubic α-FeSi2 type structure. Extended x-ray absorption fine structure measurements indicate a local environment of Fe atoms similar to that in CsCl-type or α-FeSi2-type structure over the whole 0 < x < 0.85 composition range, showing that Fe does not merely substitute for Co atoms in a perfect CaF2-type CoSi2 structure, even for very low Fe content. In contrast, the local environment of Co atoms is similar to that in CoSi2 for Co-rich ternary compounds. Substantial modifications around Co sites are although observed in Fe richer silicides, suggesting that for x < 0.5, an appreciable amount of Co is incorporated in the α-FeSi2-type silicide phase.

Differential anomalous wide-angle X-ray scattering and X-ray absorption experiments to investigate the formation of glass ceramics in the CaO–SiO2–ZrO2system

1999 ◽  
Vol 32 (6) ◽  
pp. 1090-1099 ◽  
Author(s):  
Carlo Meneghini ◽  
Alessandro F. Gualtieri ◽  
Cristina Siligardi
Keyword(s):  
Glass Ceramic ◽  
Room Temperature ◽  
Glass Ceramics ◽  
Anomalous Scattering ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Two Samples ◽  
Devitrification Process ◽  
X Ray Absorption

The structure of a CaO–SiO2–ZrO2-based glass ceramic has been investigated by X-ray diffraction, X-ray absorption spectroscopy and differential anomalous scattering techniques as a function of the thermal treatment of the sample. The microstructure of the glass has been investigated at room temperature, before the recrystallization of the glass ceramic, and on two samples annealed at 1073 and 1273 K for 1 h to follow the early stages of nucleation of the quartz and wollastonite crystalline phases. Indications on the roles of Ca, Si and Zr during the devitrification process are given.

Early Instability Phenomena of IN792 DS Superalloy

2016 ◽  
Vol 879 ◽  
pp. 2026-2031 ◽  
Author(s):  
Roberto Montanari ◽  
Oriana Tassa ◽  
Alessandra Varone
Keyword(s):  
Electron Microscopy ◽  
Dynamic Modulus ◽  
Room Temperature ◽  
Average Distance ◽  
Directionally Solidified ◽  
X Ray Diffraction ◽  
Mechanical Spectroscopy ◽  
X Ray ◽  
Microstructure Stability ◽  
Transmission Electron

Microstructure stability of the directionally solidified Ni base IN792 superalloy has been investigated by Mechanical Spectroscopy (MS), i.e. internal friction (IF) and dynamic modulus measurements. Repeated IF test runs from room temperature to 1173 K have been carried out on the same samples and a Q-1 maximum has been always observed above 700 K. Its position does not depend on the resonance frequency. After each run the values of modulus and Q-1 at room temperature change indicating that a progressive irreversible transformation occurs. Damping phenomena have been attributed to the rearrangement of dislocation structures in disordered matrix which modifies dislocation density and average distance of pinning points. The results are supported by X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations.

Electron Microscopy of Human Gallstones

1971 ◽  
Vol 29 ◽  
pp. 296-297
Author(s):  
C. Wolpers ◽  
R. Blaschke
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Bile Pigment ◽  
X Ray Diffraction ◽  
Triclinic Crystal System ◽  
X Ray ◽  
Follow Up Study ◽  
Infra Red ◽  
Main Components

Scanning microscopy was used to study the surface of human gallstones and the surface of fractures. The specimens were obtained by operation, washed with water, dried at room temperature and shadowcasted with carbon and aluminum. Most of the specimens belong to patients from a series of X-ray follow-up study, examined during the last twenty years. So it was possible to evaluate approximately the age of these gallstones and to get information on the intensity of growing and solving.Cholesterol, a group of bile pigment substances and different salts of calcium, are the main components of human gallstones. By X-ray diffraction technique, infra-red spectroscopy and by chemical analysis it was demonstrated that all three components can be found in any gallstone. In the presence of water cholesterol crystallizes in pane-like plates of the triclinic crystal system.

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

Xenon Trioxide Adducts of O-Donor Ligands; [(CH3)2CO]3XeO3, [(CH3)2SO]3(XeO3)2, (C5H5NO)3(XeO3)2, and [(C6H5)3PO]2XeO3

2018 ◽  
Author(s):  
Katherine Marczenko ◽  
James Goettel ◽  
Gary Schrobilgen
Keyword(s):  
Room Temperature ◽  
Triphenylphosphine Oxide ◽  
Donor Ligands ◽  
Mechanical Shock ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Coordination ◽  
Xenon Trioxide ◽  
Distorted Octahedra ◽  
Coordination Spheres

Oxygen coordination to the Xe(VI) atom of XeO<sub>3</sub> was observed in its adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO<sub>3</sub>, which detonates when mechanically or thermally shocked, the solid [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub>, [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub>,<sub> </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> adducts are insensitive to mechanical shock, but undergo rapid deflagration when ignited by a flame. Both [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3 </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> are air-stable whereas [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> slowly decomposes over several days and [(CH<sub>3</sub>)<sub>2</sub>CO]<sub>3</sub>XeO<sub>3</sub> undergoes adduct dissociation at room temperature. The xenon coordination sphere of [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub> is a distorted square pyramid which provides the first example of a five-coordinate XeO<sub>3</sub> adduct. The xenon coordination spheres of the remaining adducts are distorted octahedra comprised of three Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO<sub>3</sub>. Quantum-chemical calculations were used to assess the Xe---O adduct bonds, which are predominantly electrostatic σ-hole bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the xenon atoms.

Effect of trytophan as dopant on potassium acid phthalate single crystals

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Visible Region ◽  
X Ray Diffraction ◽  
X Ray ◽  
Slow Evaporation Technique ◽  
Absorption Studies ◽  
Evaporation Technique ◽  
Potassium Acid Phthalate ◽  
Acid Phthalate

Optically transparent single crystals of potassium acid phthalate (KAP, 0.5 g) 0.05 g and 0.1 g (1 and 2 mol %) trytophan were grown in aqueous solution by slow evaporation technique at room temperature. Single crystal X- ray diffraction analysis confirmed the changes in the lattice parameters of the doped crystals. The presence of functional groups in the crystal lattice has been determined qualitatively by FTIR analysis. Optical absorption studies revealed that the doped crystals possess very low absorption in the entire visible region. The dielectric constant has been studied as a function of frequency for the doped crystals. The thermal stability was evaluated by TG-DSC analysis.

scholarly journals Structural and Enhanced Optical Properties of Stabilized γ‒Bi2O3 Nanoparticles: Effect of Oxygen Ion Vacancies

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1023 ◽  
Author(s):  
Ashish Chhaganlal Gandhi ◽  
Chia-Liang Cheng ◽  
Sheng Yun Wu
Keyword(s):  
Room Temperature ◽  
Excess Oxygen ◽  
Ambient Atmosphere ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Band Emission ◽  
Oxygen Ion ◽  
Integrated Intensity ◽  
Effect Of Oxygen

We report the synthesis of room temperature (RT) stabilized γ–Bi2O3 nanoparticles (NPs) at the expense of metallic Bi NPs through annealing in an ambient atmosphere. RT stability of the metastable γ–Bi2O3 NPs is confirmed using synchrotron radiation powder X-ray diffraction and Raman spectroscopy. γ–Bi2O3 NPs exhibited a strong red-band emission peaking at ~701 nm, covering 81% integrated intensity of photoluminescence spectra. Our findings suggest that the RT stabilization and enhanced red-band emission of γ‒Bi2O3 is mediated by excess oxygen ion vacancies generated at the octahedral O(2) sites during the annealing process.

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