scholarly journals Energy research with neutrons (ErwiN) and installation of a fast neutron powder diffraction option at the MLZ, Germany

2018 ◽  
Vol 51 (3) ◽  
pp. 591-595 ◽  
Author(s):  
Michael Heere ◽  
Martin J. Mühlbauer ◽  
Alexander Schökel ◽  
Michael Knapp ◽  
Helmut Ehrenberg ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Dynamic Range ◽  
Driving Forces ◽  
Neutron Powder Diffraction ◽  
Small Sample ◽  
Small Samples ◽  
Energy Research ◽  
Time Resolved ◽  
Spatially Resolved ◽  
Medium Resolution

The need for rapid data collection and studies of small sample volumes in the range of cubic millimetres are the main driving forces for the concept of a new high-throughput monochromatic diffraction instrument at the Heinz Maier-Leibnitz Zentrum (MLZ), Germany. A large region of reciprocal space will be accessed by a detector with sufficient dynamic range and microsecond time resolution, while allowing for a variety of complementary sample environments. The medium-resolution neutron powder diffraction option for `energy research with neutrons' (ErwiN) at the high-flux FRM II neutron source at the MLZ is foreseen to meet future demand. ErwiN will address studies of energy-related systems and materials with respect to their structure and uniformity by means of bulk and spatially resolved neutron powder diffraction. A set of experimental options will be implemented, enabling time-resolved studies, rapid parametric measurements as a function of external parameters and studies of small samples using an adapted radial collimator. The proposed powder diffraction option ErwiN will bridge the gap in functionality between the high-resolution powder diffractometer SPODI and the time-of-flight diffractometers POWTEX and SAPHiR at the MLZ.

Oxovanadium(IV) hydrogen phosphate hydrates: a time-resolved neutron powder diffraction study

1991 ◽  
Vol 3 (3) ◽  
pp. 407-413 ◽  
Author(s):  
Pedro Amoros ◽  
Rafael Ibanez ◽  
Aurelio Beltran ◽  
Daniel Beltran ◽  
Amparo Fuertes ◽  
...  
Keyword(s):  
Diffraction Study ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Hydrogen Phosphate ◽  
Time Resolved

ChemInform Abstract: Oxovanadium(IV) Hydrogen Phosphate Hydrates: A Time-Resolved Neutron Powder Diffraction Study.

ChemInform ◽  
2010 ◽  
Vol 22 (35) ◽  
pp. no-no
Author(s):  
P. AMOROS ◽  
R. IBANEZ ◽  
A. BELTRAN ◽  
D. BELTRAN ◽  
A. FUERTES ◽  
...  
Keyword(s):  
Diffraction Study ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Hydrogen Phosphate ◽  
Time Resolved

Phase development of Bi-2212 superconductor: A time-resolved neutron powder diffraction investigation

1996 ◽  
Vol 11 (2) ◽  
pp. 277-280 ◽  
Author(s):  
Dimitri N. Argyriou ◽  
Julie A. Garcia ◽  
John F. Mitchell ◽  
J. D. Jorgensen ◽  
D. G. Hinks
Keyword(s):  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Lattice Parameters ◽  
Time Resolved ◽  
Temperature Range ◽  
Phase Development

Time-resolved in situ neutron powder diffraction and Rietveld refinement have been used to study the synthesis of Bi-2212 from hydroxide precursors in a 2% O2 atmosphere. Bi-2212 was found to form within the temperature range 770–800 °C. Studies at 800 °C show that Bi-2212 grows rapidly at the expense of Bi-2201. Upon lowering the temperature to 500 °C and changing the atmosphere to Ar, a rapid increase in the lattice parameters was observed. We attribute this change to the loss of oxygen from the Bi-2212 lattice. The final material exhibited a Tc of 94 K.

scholarly journals Cation migrations and Bronsted site formation in NH4 form of zeolite omega: a combined in situ time-resolved synchrotron and neutron powder diffraction study

2018 ◽  
Vol 74 (a2) ◽  
pp. e49-e49
Author(s):  
Giada Beltrami ◽  
Annalisa Martucci ◽  
Francesco Di Renzo ◽  
Alberto Alberti ◽  
Maria de Lourdes Guzman-Castillo ◽  
...  
Keyword(s):  
Diffraction Study ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Site Formation ◽  
Time Resolved

Time-of-flight neutron powder diffraction with milligram samples: the crystal structures of NaCoF3and NaNiF3post-perovskites

2014 ◽  
Vol 47 (6) ◽  
pp. 1939-1947 ◽  
Author(s):  
Alex Lindsay-Scott ◽  
David Dobson ◽  
Fabrizio Nestola ◽  
Matteo Alvaro ◽  
Nicola Casati ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Structural Parameters ◽  
Time Of Flight ◽  
Neutron Powder Diffraction ◽  
Small Sample ◽  
Unit Cell ◽  
X Ray

Using the recently upgraded Polaris diffractometer at the ISIS Spallation Neutron Source (Rutherford Appleton Laboratory), the crystal structures of the post-perovskite polymorphs of NaCoF3and NaNiF3have been determined by time-of-flight neutron powder diffraction from samples, of mass 56 and 16 mg, respectively, recovered after synthesis at ∼20 GPa in a multi-anvil press. The structure of post-perovskite NaNiF3has also been determined by single-crystal synchrotron X-ray diffraction for comparison. All measurements were made at atmospheric pressure and room temperature. Despite the extremely small sample size in the neutron diffraction study, there is very good agreement between the positional parameters for NaNiF3obtained from the refinements of the X-ray and neutron data. Relative to the commonly used oxide post-perovskite analogue phases having calcium as theAcation, the axial ratios and derived structural parameters of these fluoride post-perovskites are more consistent with those of Mg0.91Fe0.09SiO3at high pressure and temperature. The structures of NaCoF3and NaNiF3are very similar, but the unit-cell and CoF6octahedral volumes of NaCoF3are larger than the corresponding quantities in NaNiF3, which supports the hypothesis that the Co2+ion has a high-spin state in this compound. The anisotropic atomic displacement parameters of the Na ions in NaNiF3post-perovskite are of similar magnitude to those of the F ions. The probability ellipsoid of the F1 ion is a prolate spheroid with its largest component parallel to thebaxis of the unit cell, corresponding to rotational motion of the NiF6octahedra about theaaxis of the crystal. Although they must be synthesized at pressures above about 18 GPa, theseABF3compounds are strongly metastable at atmospheric pressure and room temperature and so are highly suitable for use as analogues for (Mg,Fe)SiO3post-perovskite in the deep Earth, with significant advantages over oxides such as CaIrO3or CaPtO3.

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

How to Correct for Chance Agreement in the Estimation of Sensitivity and Specificity of Diagnostic Tests

1994 ◽  
Vol 33 (02) ◽  
pp. 180-186 ◽  
Author(s):  
H. Brenner ◽  
O. Gefeller
Keyword(s):  
Sensitivity And Specificity ◽  
Disease Status ◽  
Disease Prevalence ◽  
Small Sample ◽  
Small Samples ◽  
Interval Estimate ◽  
Traditional Concept ◽  
Interval Estimates ◽  
Major Disadvantage ◽  
Test Result

Abstract:The traditional concept of describing the validity of a diagnostic test neglects the presence of chance agreement between test result and true (disease) status. Sensitivity and specificity, as the fundamental measures of validity, can thus only be considered in conjunction with each other to provide an appropriate basis for the evaluation of the capacity of the test to discriminate truly diseased from truly undiseased subjects. In this paper, chance-corrected analogues of sensitivity and specificity are presented as supplemental measures of validity, which pay attention to the problem of chance agreement and offer the opportunity to be interpreted separately. While recent proposals of chance-correction techniques, suggested by several authors in this context, lead to measures which are dependent on disease prevalence, our method does not share this major disadvantage. We discuss the extension of the conventional ROC-curve approach to chance-corrected measures of sensitivity and specificity. Furthermore, point and asymptotic interval estimates of the parameters of interest are derived under different sampling frameworks for validation studies. The small sample behavior of the estimates is investigated in a simulation study, leading to a logarithmic modification of the interval estimate in order to hold the nominal confidence level for small samples.

Monitoring Polymer-Assisted Mechanochemical Cocrystallisation Through in Situ X-Ray Powder Diffraction

2020 ◽  
Author(s):  
Luzia S. Germann ◽  
Sebastian T. Emmerling ◽  
Manuel Wilke ◽  
Robert E. Dinnebier ◽  
Mariarosa Moneghini ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Powder Diffraction ◽  
Reaction Rate ◽  
Polymer Additives ◽  
Time Resolved ◽  
X Ray

Time-resolved mechanochemical cocrystallisation studies have so-far focused solely on neat and liquid-assisted grinding. Here, we report the monitoring of polymer-assisted grinding reactions using <i>in situ</i> X-ray powder diffraction, revealing that reaction rate is almost double compared to neat grinding and independent of the molecular weight and amount of used polymer additives.<br>

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