scholarly journals Resolved Hyperfine at L-band for High-Spin CoEDTA, A Model for Co Sites in Proteins

2019 ◽  
Vol 20 (10) ◽  
pp. 2385
Author(s):  
William E. Antholine
Keyword(s):  
Accurate Determination ◽  
Cobalt Complex ◽  
Low Frequency ◽  
Paramagnetic Resonance ◽  
X Band ◽  
Epr Parameters ◽  
L Band ◽  
Band Spectra

Low-frequency electron paramagnetic resonance (EPR) spectra were obtained for the Co complex of ethylene diamine tetraacetic acid (CoEDTA). It was found that the cobalt hyperfine at geff-mid is better resolved at a low frequency, L-band (1.37 GHz), and not resolved at X-band (9.631 GHz), which is the conventional frequency used for most spectra for metal complexes. Resolved cobalt hyperfine lines lead to additional EPR parameters like A-mid for cobalt and a more-accurate determination of g-mid. Resolved hyperfine lines in the L-band, but not the S-band, spectra were obtained at a concentration of 1 mM. Knowing these additional EPR parameters provides a means to better determine the electron density in the ground state orbital for each cobalt complex, as well as to determine differences upon a change of ligation. If zinc sites can be replaced by cobalt, the cobalt spectra for these sites will enhance the characterization of the zinc sites.

scholarly journals Better Resolution of High-Spin Cobalt Hyperfine at Low Frequency: Co-Doped Ba(Zn1/3Ta2/3)O3 as a Model Complex

2018 ◽  
Vol 19 (11) ◽  
pp. 3532 ◽  
Author(s):  
William Antholine ◽  
Shengke Zhang ◽  
Justin Gonzales ◽  
Nathan Newman
Keyword(s):  
Binding Sites ◽  
Low Frequency ◽  
Zinc Binding ◽  
Paramagnetic Resonance ◽  
X Band ◽  
Model Complex ◽  
Epr Parameters ◽  
Electron Paramagnetic ◽  
Insight Into ◽  
Co Doped

Low-frequency electron paramagnetic resonance (EPR) is used to extract the EPR parameter A-mid and support the approximate X-band value of g-mid for Ba(CoyZn1/3−yTa2/3)O3. Although the cobalt hyperfine structure for the |±1/2⟩ state is often unresolved at X-band or S-band, it is resolved in measurements on this compound. This allows for detailed analysis of the molecular orbital for the |±1/2⟩ state, which is often the ground state. Moreover, this work shows that the EPR parameters for Co substituted into Zn compounds give important insight into the properties of zinc binding sites.

scholarly journals Better Resolution of High-Spin Cobalt Hyperfine at Low Frequency: Co-Doped Ba(Zn1/3Ta2/3)O3 as a Model Complex

2018 ◽  
Author(s):  
William E. Antholine ◽  
Shengke Zhang ◽  
Justin Gonzales ◽  
Nathan Newman
Keyword(s):  
Binding Sites ◽  
Low Frequency ◽  
Zinc Binding ◽  
Paramagnetic Resonance ◽  
X Band ◽  
Model Complex ◽  
Epr Parameters ◽  
Electron Paramagnetic ◽  
Insight Into ◽  
Co Doped

Low-frequency electron paramagnetic resonance (EPR) is used to extract the EPR parameter A-mid and support the approximate X-band value of g-mid for Ba(CoyZn1/3-yTa2/3)O3. Although cobalt hyperfine structure for the [+/−1/2> state is often unresolved at X-band or S-band, it is resolved in measurements on this compound. This allows for detailed analysis of the molecular orbital for the [+/−1/2> state, which is often the ground state. Moreover, this work shows that the EPR parameters for Co substituted into Zn compounds gives important insight into the properties of zinc binding sites.

scholarly journals Comparison of Elemental Analysis Techniques for the Characterization of Commercial Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 736
Author(s):  
Peter Seidel ◽  
Doreen Ebert ◽  
Robert Schinke ◽  
Robert Möckel ◽  
Simone Raatz ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Analytical Techniques ◽  
Optical Emission ◽  
Breakdown Spectroscopy ◽  
General Evaluation ◽  
Sample Composition ◽  
Laser Induced Breakdown ◽  
Copper Aluminum

Better quality control for alloy manufacturing and sorting of post-consumer scraps relies heavily on the accurate determination of their chemical composition. In recent decades, analytical techniques, such as X-ray fluorescence spectroscopy (XRF), laser-induced breakdown spectroscopy (LIBS), and spark optical emission spectroscopy (spark-OES), found widespread use in the metal industry, though only a few studies were published about the comparison of these techniques for commercially available alloys. Hence, we conducted a study on the evaluation of four analytical techniques (energy-dispersive XRF, wavelength-dispersive XRF, LIBS, and spark-OES) for the determination of metal sample composition. It focuses on the quantitative analysis of nine commercial alloys, representing the three most important alloy classes: copper, aluminum, and steel. First, spark-OES is proven to serve as a validation technique in the use of certified alloy reference samples. Following an examination of the lateral homogeneity by XRF, the results of the techniques are compared, and reasons for deviations are discussed. Finally, a more general evaluation of each technique with its capabilities and limitations is given, taking operation-relevant parameters, such as measurement speed and calibration effort, into account. This study shall serve as a guide for the routine use of these methods in metal producing and recycling industries.

Development and Characterization of a Multimycotoxin Reference Material

2019 ◽  
Vol 102 (6) ◽  
pp. 1642-1650 ◽  
Author(s):  
Melissa M. Phillips ◽  
Tomás M. López Seal ◽  
Jennifer M. Ness ◽  
Kai Zhang
Keyword(s):  
Interlaboratory Comparison ◽  
Accurate Determination ◽  
Data Sets ◽  
Mass Fractions ◽  
Adequate Quality ◽  
Multiple Sample ◽  
Lc Tandem Ms ◽  
The U.S

Background: Matrix-matched reference materials (RMs) are critical for adequate quality assurance of extraction, digestion, separation, and/or detection processes for analytes of interest in foods and dietary supplements. The accurate determination of mycotoxins in foods is an international concern. While RMs for mycotoxins are available from a variety of RM producers, these mainly address a single mycotoxin or group of mycotoxins and therefore require the use of multiple RMs for multitarget methods. Objective: To address the increasing needs of laboratories moving toward LC-MS-based multimycotoxin analysis, the U.S. National Institute of Standards and Technology (NIST) collaborated with the U.S. Food and Drug Administration (FDA) to produce a naturally incurred RM for multiple mycotoxins in corn. Methods: Homogeneity of the RM has been assessed using a stratified random sampling of the final product based on mycotoxin mass fractions measured by the FDA and NIST. Multiple sample sizes were evaluated to maximize homogeneity in the obtained results. The mycotoxin levels in the final materials have been evaluated via interlaboratory comparison and isotope dilution LC–tandem MS measurements made at the FDA and NIST. The final value assignment combined results from these data sets. Conclusions: The study successfully developed a certified RM, SRM 1565 Mycotoxins in Corn, and a workflow for the future development of multimycotoxin RMs in different matrices.

scholarly journals Softening of Shear Elastic Coefficients in Shape Memory Alloys Near the Martensitic Transition: A Study by Laser-Based Resonant Ultrasound Spectroscopy

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1383
Author(s):  
Petr Sedlák ◽  
Michaela Janovská ◽  
Lucie Bodnárová ◽  
Oleg Heczko ◽  
Hanuš Seiner
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Single Crystals ◽  
Accurate Determination ◽  
Martensitic Transition ◽  
Elastic Coefficient ◽  
Resonant Ultrasound Spectroscopy ◽  
Resonant Ultrasound

We discuss the suitability of laser-based resonant ultrasound spectroscopy (RUS) for the characterization of soft shearing modes in single crystals of shape memory alloys that are close to the transition temperatures. We show, using a numerical simulation, that the RUS method enables the accurate determination of the c′ shear elastic coefficient, even for very strong anisotropy, and without being sensitive to misorientations of the used single crystal. Subsequently, we apply the RUS method to single crystals of three typical examples of shape memory alloys (Cu-Al-Ni, Ni-Mn-Ga, and NiTi), and discuss the advantages of using the laser-based contactless RUS arrangement for temperature-resolved measurements of elastic constants.

Local bond order parameters for accurate determination of crystal structures in two and three dimensions

2018 ◽  
Vol 20 (42) ◽  
pp. 27059-27068 ◽  
Author(s):  
Hossein Eslami ◽  
Parvin Sedaghat ◽  
Florian Müller-Plathe
Keyword(s):  
Crystal Structures ◽  
Bond Order ◽  
Accurate Determination ◽  
Three Dimensional ◽  
Order Parameters ◽  
Three Dimensions ◽  
Local Order ◽  
Crystalline Structures

Local order parameters for the characterization of liquid and different two- and three-dimensional crystalline structures are presented.

Characterization of Matrix-Assisted Laser Desorption Based on Absorption and Acoustic Monitoring

1995 ◽  
Vol 49 (12) ◽  
pp. 1826-1833 ◽  
Author(s):  
Jan Preisler ◽  
Edward S. Yeung
Keyword(s):  
Atmospheric Pressure ◽  
Accurate Determination ◽  
Optimal Conditions ◽  
Plume Velocity ◽  
Ion Laser ◽  
Optical Probing ◽  
Argon Ion ◽  
Reduced Pressures

Conventional methods for studying matrix-assisted desorption-ionization rely on mass spectroscopy. In this study, a 488-nm argon-ion laser beam is deflected by two acoustooptic deflectors to image plumes desorbed at atmospheric pressure via absorption. All species, including neutral molecules, are monitored. Interesting features, e.g., differences between the initial plume and subsequent plumes desorbed from the same spot, or the formation of two plumes from one laser shot, are observed. Total plume absorbance can be correlated with the acoustic signal generated by the desorption event. A model equation for the plume velocity as a function of time is proposed. Optical probing also enables accurate determination of plume velocities at reduced pressures. These results define the optimal conditions for desorbing analytes from matrices, as opposed to achieving a compromise between efficient desorption and efficient ionization as is practiced in mass spectrometry.

scholarly journals Characterization of Self-Heating Process in GaN-Based HEMTs

Electronics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1305 ◽  
Author(s):  
Daniel Gryglewski ◽  
Wojciech Wojtasiak ◽  
Eliana Kamińska ◽  
Anna Piotrowska
Keyword(s):  
Communication Systems ◽  
Accurate Determination ◽  
Heating Process ◽  
Equivalent Circuits ◽  
High Electron ◽  
Thermal Impedance ◽  
Self Heating ◽  
Gan Hemt

Thermal characterization of modern microwave power transistors such as high electron-mobility transistors based on gallium nitride (GaN-based HEMTs) is a critical challenge for the development of high-performance new generation wireless communication systems (LTE-A, 5G) and advanced radars (active electronically scanned array (AESA)). This is especially true for systems operating with variable-envelope signals where accurate determination of self-heating effects resulting from strong- and fast-changing power dissipated inside transistor is crucial. In this work, we have developed an advanced measurement system based on DeltaVGS method with implemented software enabling accurate determination of device channel temperature and thermal resistance. The methodology accounts for MIL-STD-750-3 standard but takes into account appropriate specific bias and timing conditions. Three types of GaN-based HEMTs were taken into consideration, namely commercially available GaN-on-SiC (CGH27015F and TGF2023-2-01) and GaN-on-Si (NPT2022) devices, as well as model GaN-on-GaN HEMT (T8). Their characteristics of thermal impedance, thermal time constants and thermal equivalent circuits were presented. Knowledge of thermal equivalent circuits and electro–thermal models can lead to improved design of GaN HEMT high-power amplifiers with account of instantaneous temperature variations for systems using variable-envelope signals. It can also expand their range of application.

Study of a-Si:H / c-Si Heterojunctions for PV Applications

1996 ◽  
Vol 420 ◽  
Author(s):  
F. Zignani ◽  
R. Galloni ◽  
R. Rizzoli ◽  
M. Ruth ◽  
C. Summonte ◽  
...  
Keyword(s):  
Gas Phase ◽  
Open Circuit Voltage ◽  
Accurate Determination ◽  
Electrical Characterization ◽  
Silicon Layer ◽  
Open Circuit ◽  
Hydrogen Dilution ◽  
Intrinsic Efficiency

Abstracta-Si:H / c-Si heterojunction diodes were produced by PECVD with varying amorphous silicon layer thickness and hydrogen dilution of the gas phase. An accurate determination of the growth rate also in the initial stages of the deposition was made possible by an original chemical method based on the dissolution of the films followed by spectroscopical analysis of the obtained solution.The electrical characterization of the diodes confirms the generation - recombination - multitunneling nature of the transport. Although H2 dilution is important, however, beyond a certain level it is detrimental for the junction quality, probably due to the transition to a microcrystalline phase deposition. Solar cells were also produced, the best results being an open circuit voltage of 610 mV and an intrinsic efficiency of 14.2%.

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