Search results for "Diffraction"
showing 10 items of 1584 documents
Preparation and structural characterization of Ph3Sn(IV)+ complexes with pyridinecarboxylic acids or hydroxypyridene, -pyrimidine and –quinoline.
2006
A number of [Ph3Sn(IV)](+) complexes formed with ligands containing -OH (-C=O), or -COOH group(s) and aromatic IN) donor atom have been prepared. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. In the complexes containing hydroxy and carboxylate functions, the carboxylato group is coordinated to the organotin(IV) centres in monodentate or bridging bidentate manner. It was also found that in the hydroxypyridine and -pyrimidine complexes the [Ph3Sn(IV)]+ moiety in most cases reacts with the phenolic form of the ligands. The rationalisation of the experimental Sn-119 Mossbauer nuclear quadrupole splittings, vertical bar Delta(exp)vertical bar - according t…
Preparation and structural studies on the tBu2Sn(IV) complexes with aromatic mono- and dicarboxylic acids containing hetero {N} donor atom
2004
Nine complexes of 'Bu2Sn(IV)(2+) were obtained in the solid state with ligands containing -COOH group(s) and aromatic (N) donor atom. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. It was found that in most cases the -COO- groups are co-ordinated in monodentate manner. Nevertheless, in some of our complexes, the -COO- group forms bridges between two central {Sn} atoms resulting in the formation of an oligomeric structure, a motif that is characteristic only to the nicotinate compound. These pieces of information and the rationalisation of the experimental Sn-119 Mossbauer nuclear quadrupole splittings, Delta, - according to the point charge model forma…
Validation of Powder X-Ray Diffraction Following EN ISO/IEC 17025
2012
: Powder X-ray diffraction (PXRD) is used widely in forensic science laboratories with the main focus of qualitative phase identification. Little is found in literature referring to the topic of validation of PXRD in the field of forensic sciences. According to EN ISO/IEC 17025, the method has to be tested for several parameters. Trueness, specificity, and selectivity of PXRD were tested using certified reference materials or a combination thereof. All three tested parameters showed the secure performance of the method. Sample preparation errors were simulated to evaluate the robustness of the method. These errors were either easily detected by the operator or nonsignificant for phase iden…
Optimization of sample preparation conditions for detecting trace amounts of β-tegafur in α- and β-tegafur mixture.
2012
We report a semiquantitative method for determining trace amounts (<1%) of thermodynamically stable forms in polymorphic mixtures, focusing on sample preparation ef- fects on solid phase transitions. Tegafur (5-fluoro-1-(oxolan-2-yl)-1,2,3,4-tetrahydropyrimidine- 2,4-dione) was used as a model material in this study. The amounts of the thermodynamically stable $ tegafur were increased to levels detectable by powder X-ray diffractometry by grind- ing the samples in a ball mill in the presence of water. The limit of detection for this method was as low as 0.0005% of $ tegafur in " and $ tegafur mixtures. The amount of $ tegafur after sample preparation was found to be proportional to the init…
Inhibition of skin inflammation in mice by diclofenac in vesicular carriers: Liposomes, ethosomes and PEVs
2013
Diclofenac-loaded phospholipid vesicles, namely conventional liposomes, ethosomes and PEVs (penetration enhancer-containing vesicles) were developed and their efficacy in TPA (phorbol ester) induced skin inflammation was examined. Vesicles were made from a cheap and unpurified mixture of phospholipids and diclofenac sodium; Transcutol P and propylene glycol were added to obtain PEVs, and ethanol to produce ethosomes. The structure and lamellar organization of the vesicle bilayer were investigated by transmission electron microscopy and small and wide angle X-ray scattering, as well as the main physico-chemical features. The formulations, along with a diclofenac solution and commercial Volta…
Automated Diffraction Tomography: A New Era for Electron Crystallography
2011
Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.
Advances in automated diffraction tomography
2009
Crystal structure solution by means of electron diffraction or investigation of special structural features needs high quality data acquisition followed by data processing which delivers cell parameters, space group and in the end a 3D data set. The final step is the structure analysis itself including structure solution and subsequent refinement.
Automated Electron Diffraction Tomography
2012
Ab-initio structure analysis by electron diffraction is hampered by two major problems: insufficient number of reflections sampled and an intensity alteration by dynamical scattering contribution or beam damage. Thus, in recent years the principles of automated diffraction tomography (ADT) allowing systematic reciprocal space sampling and automated data analysis were developed. Here the basic ideas of ADT and its general applicability will be discussed along with some examples of solved structures.
Precise Characterization of the Rich Structural Landscape Induced by Pressure in Multifunctional FeVO4
2020
We have studied the high-pressure behavior of FeVO4 by means of single-crystal X-ray diffraction (XRD) and density functional theory (DFT) calculations. We have found that the structural sequence o...
Spin-Crossover Modification through Selective CO2 Sorption
2013
[EN] We present a spin-crossover Fe-II coordination polymer with no permanent channels that selectively sorbs CO2 over N-2. The one-dimensional chains display internal voids of similar to 9 angstrom diameter, each being capable to accept one molecule of CO2 at 1 bar and 273 K. X-ray diffraction provides direct structural evidence of the location of the gas molecules and reveals the formation of O=C=O(delta(-))center dot center dot center dot pi interactions. This physisorption modifies the spin transition, producing a 9 K increase in T-1/2.