Stellar occultations enable milliarcsecond astrometry for Trans-Neptunian objects and Centaurs

Context. Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Stellar occultation is a ground-based method for studying these distant small bodies and has presented exciting results. These observations can provide precise profiles of the involved body, allowing an accurate determination of its size and shape. Aims. The goal is to show that even single-chord detections of TNOs allow us to measure their milliarcsecond astrometric positions in the reference frame of the Gaia second data release (DR2). Accurate ephemerides can then be generated, allowing predictions of stellar occultations with much higher reliability. Methods. We analyzed data from various stellar occultation detections to obtain astrometric positions of the involved bodies. The events published before the Gaia era were updated so that the Gaia DR2 stellar catalog is the reference, thus providing accurate positions. Events with detection from one or two different sites (single or double chord) were analyzed to determine the event duration. Previously determined sizes were used to calculate the position of the object center and its corresponding error with respectto the detected chord and the International Celestial Reference System propagated Gaia DR2 star position. Results. We derive 37 precise astrometric positions for 19 TNOs and four Centaurs. Twenty-one of these events are presented here for the first time. Although about 68% of our results are based on single-chord detection, most have intrinsic precision at the submilliarcsecond level. Lower limits on the diameter of bodies such as Sedna, 2002 KX14, and Echeclus, and also shape constraints on 2002 VE95, 2003 FF128, and 2005 TV189 are presented as valuable byproducts. Conclusions. Using the Gaia DR2 catalog, we show that even a single detection of a stellar occultation allows improving the object ephemeris significantly, which in turn enables predicting a future stellar occultation with high accuracy. Observational campaigns can be efficiently organized with this help, and may provide a full physical characterization of the involved object, or even the study of topographic features such as satellites or rings.

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Comparison of Elemental Analysis Techniques for the Characterization of Commercial Alloys

Metals ◽

10.3390/met11050736 ◽

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.

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Sulfur dioxide layer height retrieval from Sentinel-5 Precursor/TROPOMI using FP_ILM

Atmospheric Measurement Techniques ◽

10.5194/amt-12-5503-2019 ◽

2019 ◽

Vol 12 (10) ◽

pp. 5503-5517 ◽

Cited By ~ 7

Author(s):

Pascal Hedelt ◽

Dmitry S. Efremenko ◽

Diego G. Loyola ◽

Robert Spurr ◽

Lieven Clarisse

Keyword(s):

Sulfur Dioxide ◽

Accurate Determination ◽

Volcanic Eruptions ◽

Critical Parameters ◽

Layer Height ◽

Learning Machine ◽

The Impact ◽

First Time ◽

Better Than

Abstract. The accurate determination of the location, height, and loading of sulfur dioxide (SO2) plumes emitted by volcanic eruptions is essential for aviation safety. The SO2 layer height is also one of the most critical parameters with respect to determining the impact on the climate. Retrievals of SO2 plume height have been carried out using satellite UV backscatter measurements, but, until now, such algorithms are very time-consuming. We have developed an extremely fast yet accurate SO2 layer height retrieval using the Full-Physics Inverse Learning Machine (FP_ILM) algorithm. This is the first time the algorithm has been applied to measurements from the TROPOMI instrument onboard the Sentinel-5 Precursor platform. In this paper, we demonstrate the ability of the FP_ILM algorithm to retrieve SO2 plume layer heights in near-real-time applications with an accuracy of better than 2 km for SO2 total columns larger than 20 DU. We present SO2 layer height results for the volcanic eruptions of Sinabung in February 2018, Sierra Negra in June 2018, and Raikoke in June 2019, observed by TROPOMI.

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Development and Characterization of a Multimycotoxin Reference Material

Journal of AOAC International ◽

10.5740/jaoacint.19-0109 ◽

2019 ◽

Vol 102 (6) ◽

pp. 1642-1650 ◽

Cited By ~ 1

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.

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

Metals ◽

10.3390/met10101383 ◽

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.

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

Physical Chemistry Chemical Physics ◽

10.1039/c8cp05248d ◽

2018 ◽

Vol 20 (42) ◽

pp. 27059-27068 ◽

Cited By ~ 8

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.

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

Applied Spectroscopy ◽

10.1366/0003702953965920 ◽

1995 ◽

Vol 49 (12) ◽

pp. 1826-1833 ◽

Cited By ~ 8

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.

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Characterization of Self-Heating Process in GaN-Based HEMTs

Electronics ◽

10.3390/electronics9081305 ◽

2020 ◽

Vol 9 (8) ◽

pp. 1305 ◽

Cited By ~ 1

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.

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Determination of Lead Traces by Stripping Voltammetry Using Ti(N,C) Working Electrodes

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.65.168 ◽

2010 ◽

Vol 65 ◽

pp. 168-173

Author(s):

Marta Ziemnicka ◽

Bogusław Baś ◽

Mateusz Jeż ◽

Ludosław Stobierski

Keyword(s):

Electron Microscopy ◽

Electrode Surface ◽

Stripping Voltammetry ◽

Electrochemical Activation ◽

Trace Metal Analysis ◽

Response Performance ◽

Disc Electrodes ◽

First Time

Electrochemical stripping techniques still attract considerable attention for trace metal analysis and for measuring several important organic compounds, due to their unique capabilities of pre-concentrating the analytes at the electrode surface and associated favourable low limits of detection. In this work it is reported for the first time that the Ti(N0,1C0,9), Ti(N0,4C0,6) and Ti(N0,5C0,5) working disc electrodes, a „mercury-free” sensors, offers surprisingly good analytical performance and some valuable properties. The analytical applicability of the Ti(N,C) electrode was confirmed in determination of lead(II) traces in synthetic solutions both with and without surfactants, in certified reference material and in natural water samples. The effects of dissolved oxygen, acids, anions and metal ions were investigated for the Ti(N,C) electrode. Newly prepared and not activated electrode usually cannot be polarized. Therefore, to use the electrode as a voltammetric sensor, its electrochemical activation is required. Composition of conditioning electrolyte and procedures of the electrodes activation were optimized. The fabrication and the response performance of the investigated electrodes were described in the paper. The voltammetric data were associated with the structural characterization of the electrode surface using scanning electron microscopy (SEM) and transmition electron microscopy (TEM).

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

MRS Proceedings ◽

10.1557/proc-420-45 ◽

1996 ◽

Vol 420 ◽

Cited By ~ 5

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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Endocranial Casts of Pre-Mammalian Therapsids Reveal an Unexpected Neurological Diversity at the Deep Evolutionary Root of Mammals

Brain Behavior and Evolution ◽

10.1159/000481525 ◽

2017 ◽

Vol 90 (4) ◽

pp. 311-333 ◽

Cited By ~ 9

Author(s):

Julien Benoit ◽

Vincent Fernandez ◽

Paul R. Manger ◽

Bruce S. Rubidge

Keyword(s):

Brain Size ◽

Accurate Determination ◽

Mammalian Brain ◽

Reliable Determination ◽

Origin And Evolution ◽

Show Evidence ◽

Size And Morphology ◽

First Time ◽

Linear Manner

The origin and evolution of the mammalian brain has long been the focus of scientific enquiry. Conversely, little research has focused on the palaeoneurology of the stem group of Mammaliaformes, the Permian and Triassic non-mammaliaform Therapsida (NMT). This is because the majority of the NMT have a non-ossified braincase, making the study of their endocranial cast (sometimes called the “fossil brain”) problematic. Thus, descriptions of the morphology and size of NMT endocranial casts have been based largely on approximations rather than reliable determination. Accordingly, here we use micro-CT scans of the skulls of 1 Dinocephalia and 3 Biarmosuchia, which are NMT with a fully ossified braincase and thus a complete endocast. For the first time, our work enables the accurate determination of endocranial shape and size in NMT. This study suggests that NMT brain size falls in the upper range of the reptilian and amphibian variation. Brain size in the dicynodont Kawingasaurus is equivalent to that of early Mammaliaformes, whereas the Dinocephalia show evidence of a secondary reduction of brain size. In addition, unlike other NMT in which the endocast has a tubular shape and its parts are arranged in a linear manner, the biarmosuchian endocast is strongly flexed at the level of the midbrain, creating a near right angle between the fore- and hindbrain. These data highlight an unexpected diversity of endocranial size and morphology in NMT, features that are usually considered conservative in this group.

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