Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

scholarly journals On-line solid phase microextraction derivatization for the sensitive determination of multi-oxygenated volatile compounds in air

2021 ◽  
Vol 14 (7) ◽  
pp. 4989-4999
Author(s):  
Esther Borrás ◽  
Luis A. Tortajada-Genaro ◽  
Milagro Ródenas ◽  
Teresa Vera ◽  
Thomas Speak ◽  
...  
Keyword(s):  
Solid Phase ◽  
Accurate Determination ◽  
High Volume ◽  
Automated System ◽  
Gas Chromatography Mass Spectrometry ◽  
Oxygenated Compounds ◽  
On Line ◽  
Secondary Aerosols ◽  
Hydroxy Aldehydes

Abstract. Multi-oxygenated volatile organic compounds are important markers of air pollution and precursors of ozone and secondary aerosols in both polluted and remote environments. Herein, their accurate determination was enhanced. The approach was based on an automated system for active sampling and on-fibre derivatization coupled with the gas chromatography–mass spectrometry (GC–MS) technique. The method capability was determined for different compound families, such as aldehydes, ketones, α-dicarbonyls, hydroxy-aldehydes, hydroxy-ketones, and carboxylic acids. A good accuracy (<7 %) was demonstrated from the results compared to Fourier-transform infrared spectroscopy (FTIR). Limits of detection (LODs) of 6–100 pptV were achieved with a time resolution lower than 20 min. The developed method was successfully applied to the determination of multi-oxygenated compounds in air samples collected during an intercomparison campaign (EUROCHAMP-2020 project). Also, its capability and accuracy for atmospheric monitoring was demonstrated in an isoprene ozonolysis experiment. Both were carried out in the high-volume outdoor atmospheric simulation chambers (EUPHORE, 200 m3). In summary, our developed technique offers near-real-time monitoring with direct sampling, which is an advantage in terms of handling and labour time for a proper quantification of trace levels of atmospheric multi-oxygenated compounds.

scholarly journals Radiation attenuation by single-crystal diamond windows

2017 ◽  
Vol 50 (1) ◽  
pp. 76-86 ◽  
Author(s):  
M. Guthrie ◽  
C. G. Pruteanu ◽  
M.-E. Donnelly ◽  
J. J. Molaison ◽  
A. M. dos Santos ◽  
...  
Keyword(s):  
Single Crystal ◽  
Accurate Determination ◽  
Incident Beam ◽  
Neutron Radiation ◽  
Cost Effective ◽  
High Pressure Studies ◽  
Single Crystal Diamond ◽  
Diamond Anvil ◽  
Semi Empirical

As artificial diamond becomes more cost effective it is likely to see increasing use as a window for sample environment equipment used in diffraction experiments. Such windows are particularly useful as they exhibit exceptional mechanical properties in addition to being highly transparent to both X-ray and neutron radiation. A key application is in high-pressure studies, where diamond anvil cells (DACs) are used to access extreme sample conditions. However, despite their utility, an important consideration when using single-crystal diamond windows is their interaction with the incident beam. In particular, the Bragg condition will be satisfied for specific angles and wavelengths, leading to the appearance of diamond Bragg spots on the diffraction detectors but also, unavoidably, to loss of transmitted intensity of the beam that interacts with the sample. This effect can be particularly significant for energy-dispersive measurements, for example, in time-of-flight neutron diffraction work using DACs. This article presents a semi-empirical approach that can be used to correct for this effect, which is a prerequisite for the accurate determination of diffraction intensities.

On-line monitoring of anaerobic digestion: application of a device for continuous measurement of bicarbonate alkalinity

1994 ◽  
Vol 30 (12) ◽  
pp. 1-10 ◽  
Author(s):  
Freda R. Hawkes ◽  
Alan J. Guwy ◽  
Dennis L. Hawkes ◽  
Alberto G. Rozzi
Keyword(s):  
Anaerobic Digestion ◽  
Accurate Determination ◽  
Gas Production ◽  
Stable Operation ◽  
Anaerobic Digesters ◽  
Ph Buffering ◽  
Volatile Fatty Acid Concentration ◽  
On Line ◽  
Bicarbonate Alkalinity

Alkalinity or pH buffering capacity in anaerobic digesters is chiefly a function of bicarbonate levels, and should be within 10 to 50 mM for stable operation. A novel on-line instrument for measuring bicarbonate alkalinity has been developed, independent of titration techniques. Using a 10 litre anaerobic filter digester operating on ice-cream wastewater, on-line measurements were made of bicarbonate alkalinity, pH, gas production and % CO2 and hydrogen concentration in the biogas during periods of organic overload. The bicarbonate alkalinity monitor was shown to be an effective instrument for monitoring instability of anaerobic digestion, and a useful tool for early warning of overloading. Moreover, in digesters fed with wastewaters containing low potential alkalinity, it allows indirect on-line determination of variations in volatile fatty acid concentration. Finally, used in conjunction with a sensor that measures CO2 in the gas, it allows an indirect but accurate determination of pH in those solutions where fouling of electrodes is severe.

Diffractometer alignment and polarization determination of X-ray beams by means of the Borrmann effect

1989 ◽  
Vol 22 (2) ◽  
pp. 162-172 ◽  
Author(s):  
J.-L. Staudenmann ◽  
L. D. Chapman
Keyword(s):  
Incident Beam ◽  
Precise Determination ◽  
Beam Polarization ◽  
Transmitted Beam ◽  
Rocking Curve ◽  
X Ray ◽  
Practical Applications ◽  
Integrated Intensities ◽  
Laue Geometry

The Borrmann effect, that is, the anomalous transmission of X-ray beams through sufficiently thick perfect crystals in Laue geometry, is a sensitive diffraction tool which has many fundamental and practical applications: the accurate alignment of any full four-circle instrument (equipped with a cradle in asymmetric design) with respect to the incident beam, measurement of the divergence of any X-ray beam, and the precise determination of the beam polarization, incident or diffracted. For these applications, it is shown that no modifications to the diffractometer are required. The measurements simply consist of measuring φ and χ rocking curves of the anomalous transmitted beam where the ω angle is used as a parameter. The analyses require the findings of the peak centroid positions, the full widths at half maximum and the rocking-curve integrated intensities. Some results are presented as illustrations of the method. These Borrmann-effect applications promise to be more helpful for diffractometers installed at synchrotrons than for in-house laboratories.

scholarly journals On-line SPME derivatization for the sensitive determination of multi-oxygenated volatile compounds in air

2021 ◽  
Author(s):  
Esther Borrás ◽  
Luis A. Tortajada-Genaro ◽  
Milagros Ródenas ◽  
Teresa Vera ◽  
Thomas Speak ◽  
...  
Keyword(s):  
Good Accuracy ◽  
Accurate Determination ◽  
Automated System ◽  
Oxygenated Volatile Organic Compounds ◽  
Volatile Organic ◽  
On Line ◽  
Sensitive Determination ◽  
Secondary Aerosols ◽  
Hydroxy Aldehydes

Abstract. Multi-oxygenated volatile organic compounds are important markers of air pollution and precursors of ozone and secondary aerosols in both polluted and remote environments. Herein, their accurate determination was enhanced. The approach was based on an automated system for active sampling and on-fiber derivatization coupled with GC-MS technique. The method capability was determined for different compound families, such as aldehydes, ketones, α-dicarbonyls, hydroxy-aldehydes, hydroxy-ketones and, carboxylic acids. A good accuracy (

Accurate Determination of Foil Surface Normal in a Material with Stacking Faults

1980 ◽  
Vol 38 ◽  
pp. 378-379
Author(s):  
Samuel M. Allen
Keyword(s):  
Dihedral Angle ◽  
Accurate Determination ◽  
Stacking Faults ◽  
Optical Metallography ◽  
Dihedral Angles ◽  
Foil Surface ◽  
Beam Direction ◽  
Surface Normal ◽  
Transmission Electron

This paper describes a method for determining the foil surface normal in a transmission electron microscopy (TEM) sample containing stacking faults. The method makes use of observed dihedral angles at stacking fault intersections to compute the foil normal, when the beam direction is known. Dihedral angles are angles formed at the intersections of surfaces. The true dihedral angle is observed when viewed parallel to the line of intersection of the surfaces. For optical metallography, where observations are made by viewing normal to a plane of polish, the observed dihedral angle is the angle formed by thetraces of the intersecting surfaces on the plane of polish. The geometry of this problem was considered by Harker and Parker, who demonstrated that the observed angle could be either greater or less than the true angle.

scholarly journals Determining On-Axis Crystal Thickness with Quantitative Position-Averaged Incoherent Bright-Field Signal in an Aberration-Corrected STEM

2012 ◽  
Vol 18 (4) ◽  
pp. 720-727 ◽  
Author(s):  
Huolin L. Xin ◽  
Ye Zhu ◽  
David A. Muller
Keyword(s):  
Accurate Determination ◽  
Analytical Electron Microscopy ◽  
Mean Free Path ◽  
Specimen Thickness ◽  
Crystal Thickness ◽  
Bright Field ◽  
Analytical Electron ◽  
Inelastic Mean Free Path ◽  
Electron Energy Loss

AbstractAn accurate determination of specimen thickness is essential for quantitative analytical electron microscopy. Here we demonstrate that a position-averaged incoherent bright-field signal recorded on an absolute scale can be used to determine the thickness of on-axis crystals with a precision of ±1.6 nm. This method measures both the crystalline and the noncrystalline parts (surface amorphous layers) of the sample. However, it avoids the systematic error resulting from surface plasmon contributions to the inelastic mean-free-path thickness estimated by electron energy loss spectroscopy.

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