Improving Quantitative EDS Chemical Analysis of Alloy Nanoparticles by PCA Denoising: Part I, Reducing Reconstruction Bias

Scanning transmission electron microscopy is a crucial tool for nanoscience, achieving sub-nanometric spatial resolution in both image and spectroscopic studies. This generates large datasets that cannot be analyzed without computational assistance. The so-called machine learning procedures can exploit redundancies and find hidden correlations. Principal component analysis (PCA) is the most popular approach to denoise data by reducing data dimensionality and extracting meaningful information; however, there are many open questions on the accuracy of reconstructions. We have used experiments and simulations to analyze the effect of PCA on quantitative chemical analysis of binary alloy (AuAg) nanoparticles using energy-dispersive X-ray spectroscopy. Our results demonstrate that it is possible to obtain very good fidelity of chemical composition distribution when the signal-to-noise ratio exceeds a certain minimal level. Accurate denoising derives from a complex interplay between redundancy (data matrix size), counting noise, and noiseless data intensity variance (associated with sample chemical composition dispersion). We have suggested several quantitative bias estimators and noise evaluation procedures to help in the analysis and design of experiments. This work demonstrates the high potential of PCA denoising, but it also highlights the limitations and pitfalls that need to be avoided to minimize artifacts and perform reliable quantification.

STATE OF BOTTOM SEDIMENTS OF THE VORONEZH RESERVOIR IN THE PLACES OF WATER DISCHARGE FROM THE TREATMENT FACILITIES OF THE CITY OF VORONEZH

Рассмотрена проблема загрязнения Воронежского водохранилища в пределах Воронежской городской агломерации, в местах сброса вод с очистных сооружений предприятий левого берега. В работе использованы результаты количественного химического анализа донных отложений, выполненных на базе эколого-аналитической лаборатории факультета географии, геоэкологии и туризма Воронежского госуниверситета, а также данные мониторинга, предоставленных Федеральной службой по надзору в сфере природопользования и Департаментом природных ресурсов и экологии Воронежской области. База данных включает результаты наблюдений с 2000 по 2021 год. По составу осадков прослежена история аккумуляции загрязнителей, выделены проблемные зоны водоема в каждом исследуемом периоде. Выполнен пространственно-временной анализ содержаний загрязняющих веществ, рассчитаны «кларки концентрации» тяжелых металлов, по которым для каждой точки наблюдения в порядке возрастания значения признака построен ранжированный ряд. На основании лабораторных исследований и результатов их статистической обработки с применением корреляционного анализа сделаны выводы о перспективах существования и развития Воронежского водохранилища. Проверены корреляционные связи между «кларками концентрации» и суммой выпавших осадков за календарный и за гидрологический год. По содержаниям сероводорода в различные годы, сделаны выводы о диапазоне колебания концентраций и формировании цикличного процесса. Выделена зона устойчивой деградации водоема. Ее формирование происходит выше и ниже сброса с городских очистных сооружений левого берега города. Результаты многолетних наблюдений за качеством донных отложений указывают на значительную техногенную нагрузку со стороны Воронежской городской агломерации. Недостаточная очистка воды, медленная скорость течения и турбулентность природной воды ускоряет процесс естественного эвтрофирования водоема. The author considers the problem of pollution of the Voronezh water reservoir within the Voronezh urban agglomeration, in places of discharge of water from the treatment facilities of enterprises of the left bank. The paper uses the results of quantitative chemical analysis of bottom sediments performed on the basis of the ecological and analytical laboratory of the Faculty of Geography, Geoecology and Tourism of Voronezh State University, as well as monitoring data provided by the Federal Service for Supervision of Nature Management and the Department of Natural Resources and Ecology of the Voronezh Region. The database includes the results of monitoring from 2000 till 2021. On the basis of the composition of precipitation the author detected the history of accumulation of pollutants; as well she identified problem areas of the water reservoir in every study period. The author performed a spatio-temporal analysis of the contents of pollutants, calculated the "concentration clarkes" of heavy metals, according to which she created an ordered series for each observation point in ascending order of the attribute value. Based on laboratory studies and results of their statistical processing using correlation analysis the author draws some conclusions concerning the prospects for the Voronezh water reservoir existence and development. The correlations between the "concentration clarkes" and the amount of precipitation for the calendar and hydrological year have been verified. Based on the hydrogen sulfide content in different years, the author concludes about the range of concentration fluctuations and the formation of a cyclic process. She identified the zone of stable degradation of the water reservoir. Its formation occurs above and below the discharge from the municipal sewage treatment plants of the left bank of the city. The results of long-term observations of the quality of bottom sediments indicate a significant anthropogenic load on the part of the Voronezh urban agglomeration. Insufficient water purification, slow flow velocity and turbulence of natural water accelerate the process of natural eutrophication of the water reservoir.

Investigation of Zohr Hydraulic Flying Lead Reaction Drive Shafts

The HFLs for the Zohr Phase 1 project contains a cobra head at each end that incorporates the female couplers and the locking mechanism. Beginning in February 2020, and with the most recent incident recorded in September 2020, a total of 4 supplied HFL reaction drive shafts (RDS) failed subsea, resulting in partial separation of the HFL cobra heads from their respective fixed stabplates with a loss of hydraulic supply pressure and subsequent automatic well shut ins. HFL failures occurred on both the XT and HIPPS side of the HFLs on 3 different well sites. A further RDS tested at the laboratory from the UTA end of an HFL showed signs of microscopic cracking consistent with the failed specimens suggesting it may have had the potential to lead to a failure in the future. The failed HFLs were retrieved and returned onshore, the HFL locking mechanism was stripped down to gain access to the failed ends of the RDS and a visual inspection was performed. The initial inspection after partial disassembly to reveal the inside of the HFL locking mechanism identified that the RDS had completely failed at a location on the threaded portion of the RDS. Surface deposits were collected from each probe surfaces and analysed using scanning electron microscopy (SEM), together with energy- dispersive X-ray (EDX). A piece 10mm long was taken from each of the four probes for quantitative chemical analysis. Standard tensile and Charpy V-notch impact and Vickers hardness surveys have been conducted. Each of the failed probe exhibited an intergranular fracture surface morphology. This was confirmed through metallography/EBSD. No single initiation site was located on fracture surfaces, although some regions showed a mixed fractographic morphology, with some small areas of micro-void coalescence. Secondary intergranular cracking and corrosion was apparent at various locations, in each of the failed probes, including in thread roots, in samples 183 and 188, and just above the thread, in sample 052. These observations points towards an environmentally assisted cracking mechanism (i.e. stress corrosion cracking). Metallography revealed two layers within surface films, both in cracks and on the fracture surface: an inner layer, rich in nickel, sulphur and aluminium, and an outer, rich in copper and sulphur. Mechanical testing and chemical analysis revealed consistent results across the probes. The probe material was specified as Nibron Special (CuNi14Al3/DIN 2.1504) with a size of 2inch. Would be challenging to get the full root cause of using this material for subsea applications as it is resistant to seawater. Another factor contributed allows risk of material failure which should be eliminated for all subsea industry or taken into consideration to avoid further failures.

Application of robust parameter design in the development of a quantitative chemical analysis procedures in metallurgy

The paper presents the results of experimental research for the quantitative chemical analysis procedures using the robust parameter design methodology. There is an example of the parameter design in development of the measurement procedure for the mass fraction of chlorine in dusty waste in the ferronickel production. Results of experiment analysis has provided an information about the optimal conditions for sample preparation procedure.

IMPACT DAMAGE AND INJECTION REPAIR STRENGTH RESTORATION

Impact damage to composite structures can lead to a range of damage modes. Of interest is modest damage composed of delaminations less than 50 mm in size, and no visible impact-side fiber breakage. While resin injection is a current-practice repair technique that can be used to address these damage modes in a manner that is much less invasive than bonded scarf patch repair, the injection technique is not currently credited as one restoring strength back to laminate. Issues of quantifying the removal of any internal contamination, assessing degree of resin fill, and demonstration of how much strength is restored are being addressed within the scope of this research activity. Resin injection will be conducted and the resulting strength restoration assessed in local fracture tests (end-notch flexure). The formation of actual impact damage morphologies, namely multiple planes of delamination interconnected with matrix cracks, is a critical aspect of this problem. Three 25-ply composite panel types having varying percentage of 0o fiber content have been impacted under low velocity at a range of energy levels. Resulting force vs. time and ultrasonic mapping of damage extent. Damage produced by such impacts will be used in subsequent injection repair studies. Intentional contamination will be introduced, and then removal will be achieved via injected solvents and atmospheric plasma, with monitoring of contaminant presence achieved by in-line quantitative chemical analysis.

Olivine as an indicator of polygenic assemblage of inclusions from Late Cenozoic volcanic rocks in the Tunka Valley, Baikal Rift Zone

Research subject. Olivine of deep-seated inclusions from Late Cenozoic volcanic rocks of the Tunka valley.Materials and methods. Electron probe microanalysis of minerals with determination of calcium in olivine by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). A complex of methods of quantitative chemical analysis for determination of major oxides in rocks.Results. Deep-seated nodules from Late Cenozoic volcanic rocks in the Tunka Valley characterize the root part of the Slyudyanka metamorphic subterrane, formed during collisional accretion of the Khamar-Daban terrane to the Siberian paleocontinent in the Early Paleozoic and reactivated in the Late Cenozoic. From bulk compositions of deep-seated nodules, groups of xenoliths (restites, rocks closed to the primitive mantle composition, and metasomatites) and cognate rocks (magmatic and magmatic-metasomatic genesis) were distinguished. The polygenetic character of this assemblage is designated by variations of major and trace-element abundances in olivine. In olivine of xenoliths, forsterite (Fo) ranges from 86 to 91% under abundances of NiO – 0.2–0.5, MnO – 0.1–0.2, and CaO < 0.16 wt %. In olivine of magmatic rocks and those of mixed (magmatic-metasomatic) genesis, Fo decreases to 64% with a decrease in NiO (Ni/Mg ratio) and an increase in MnO and CaO. Magmatic olivine shows 0.16–0.21 wt % MnO and about 0.1 wt % CaO, in contrast to olivine of magmatic-metasomatic genesis, enriched in these oxides to 0.5 wt % and 0.45 wt %, respectively, with an increase in the Mn/Fe and Ca/Fe ratios. Olivine trends of the shallow polygenetic assemblage of inclusions are emphasized when compared with those of the deeper ones from volcanic rocks of the Vitim and Oka plateaus that represent a transition from the garnet to the spinel-pyroxene facies in mantle peridotites.Conclusion. Olivine compositions are indicative of the shallow origin of peridotite and pyroxenite nodules from the crust and crust–mantle transition in the root part of the Slyudyanka collision zone reactivated in the Late Cenozoic.

Technological characteristics of sulfide-magnetite ore washability at the magnetite skarn Peschanskoe deposit

Introduction. In the magnetite lime-skarn Peschanskoe deposit, the Zapadno-Peschanskaya ore deposit is distinguished, which differs from other ore bodies by an increased content of copper and precious metals. Due to the fact that the technology of processing magnetite ores of the Peschanskoe deposit at the enterprise of the subsurface user is configured to receive only iron concentrate, the development of a comprehensive technology for processing sulfide-magnetite ores is an urgent task. Research aim is to study the material composition and sulfide-magnetite ore concentration of the ZapadnoPeschanskaya ore deposit and to develop a comprehensive technology for its processing. The technology should ensure gold-containing, copper and iron concentrates production. Research methods consisted in studying the material composition of sulfide-magnetite ore by means of quantitative chemical analysis using Arcos emission spectrometer with inductively coupled plasma, Solaar atomic absorption spectrometer, CS-800sulfur analyzer, Titration Excellence T-70 automatic titration system, and Specord 250 Plus scanning spectrophotometer; chemical phase analysis for the forms of iron, copper, gold, silver and sulfur compounds; mineralogical analysis using the Axio Imager A1m optical microscope and Mineral C7 automated analyzer. Technological research was carried out by various concentration methods: X-ray radiometric separation on the SRF1-100L separator; dry magnetic separation on the PBS-90/25 magnetic separator; gravity on the KC-MD3 centrifugal concentrator and the SKL-0.2 concentration table; flotation on the FMP-L series flotation machines; wet magnetic separation on the electromagnetic separator EBM-32/20. Scope of results. The present research result can be used at complex sulfide-magnetite ores processing. Conclusions. The results of the material composition research and technological properties of the sulfidemagnetite ore of the Zapadno-Peschanskaya deposit of the Peschanskoe skarnovo-magnetite deposit are presented. It is established that the researched ore can be efficiently processed using a complex gravityflotation-magnetic technology, which allows to obtain: gravity gold-containing concentrate with a mass fraction of gold of 50 g/t at recovery of 27%; copper concentrate with a mass fraction of 23.71%, gold – 18.9 g/t and silver – 60.0 g/t when extracted, respectively, 93.6%, 42.9% and 54.6%; magnetite concentrate with a mass fraction of iron 66.5%, sulfur 0.7% with the recovery of total iron 76.6%.

Methodological approaches to the assessment of health risks associated with the use of repellent and insecticide agents

Introduction. The study’s relevance is due to the demand for repellent and insecticidal agents in the consumer market and their widespread use as protection against mosquitoes. At the same time, the problem of the impact on the human health of these funds has not been sufficiently studied. In this regard, analyzing the safety of repellents and insecticides for human health is of scientific interest. The aim of the study is to substantiate methodological approaches to assessing the risk to human health associated with the use of insecticides and repellents. Materials and methods. Authors used methods of analysis of scientific literature, toxicological methods for the study of health safety, methods of quantitative chemical analysis, biochemical methods for the study of blood serum, methods of mathematical modeling, health risk assessment methodology. Results. The assessment of the risk of negative responses from organs and systems of the body when exposed to repellents and insecticides has been carried out. Methodological approaches to assessing health risks under various scenarios for repellents and insecticides have been developed and tested. Conclusion. A feature of the proposed methodological approaches is the ability to take into account dose loads for various routes of entry of active substances into the body, the duration of exposure to a repellent or insecticide during regular use, and possible use in regimes exceeding normal use. As a result of the experiment, it was found that with the inhalation of an insecticide with 1% transfluthrin, the level of acceptable risk is observed at a level of exposure of transfluthrin in the air up to 0.0272 mg/m3. Under a percutaneous intake of the 50% DEET repellent, the acceptable risk level was noted at exposure less than 1200 mg/kg/day. In case of percutaneous arrival of the DETA repellent 7.5%, the level of acceptable risk is established under exposure up to 250 mg/kg/day.