Perfluoroalkyl substances (PFASs) are anthropogenic compounds that have been classed as persistent organic pollutants (POPs) and are found in both commercial and industrial products. PFASs have been detected in different environmental matrices and have been found to bioaccumulate in all trophic levels. The adverse effects that are associated with PFAS exposure include reduced body weight, increased liver weight, hepatocellular hypertrophy, a decrease in serum cholesterol and triglycerides. This project aims to characterize the metabolic changes in lipid metabolism in the liver after exposure to one of the well-studied PFASs, the perfluorooctane sulfonate (PFOS), during the embryo development using the domestic chicken as a model organism. The characterization of the metabolic changes was done by conducting both quantitative lipidomic analysis and semi-quantitative global profiling on extracted lipids from liver homogenates from a former related project looking at fatty acid profiles. The extracted lipids were analyzed using UHPLC/Q-TOF-MS. In the quantitative analysis, the PFOS-treated groups (0.1 ug/g and 1.0 ug/g)exhibited higher lipid concentrations when compared with the solvent control group (5% DMSO) and the untreated group leading to the conclusion that PFOS exposure disrupts the lipid metabolism. When comparing the lipid concentrations between the two PFOS-treated groups (0.1 ug/g and 1.0 ug/g), the majority of the lipids exhibited higher lipid concentrations in the 1.0 ug/g PFOS-treated groups leading to the conclusion that the effect PFOS has on the lipid metabolism is dose dependent. In the global profiling analysis, 63 lipids showed significant differences when comparing the solvent control group with samples either treated with 0.1 ug/g PFOS or 1.0 ug/g PFOS.

PFCs are used in a wide variety of industrial and commercial applications for more than 50 years. Among variation of PFCs, Perfluorooctane sulfonate (PFOS) (CF3(CF2)7SO3-) and perfluorooctanoic acid (PFOA) (CF3(CF2)6COO-) are the most dominant PFCs. In May 2009, PFOS, its salts and perfluorooctane sulfonyl fluoride (PFOSF) are designated as new Persistent Organic Compounds (POPs) which are resistant, bio-accumulating, and having potential of causing adverse effects to humans and environment (IISD, 2009). However, products containing PFCs are still being manufactured and used, which could be the main reason why they are still observed in the environment and biota (Berger et al., 2004; Saito et al., 2003; Sinclair et al., 2004). The study is focused on the PFCs contamination in water and industrial wastewater around the Central and Eastern Thailand, where is one of the major industrialized areas in the country. The samplings were conducted in major rivers, Chao Phraya, Bangpakong and Tachin River. PFCs were contaminated in all rivers. The average total PFCs were 15.10 ng/L, 18.29 ng/L and 7.40 ng/L in Chao Phraya, Bangpakong and Tachin River, respectively. PFOS and PFOA were the predominant PFCs in all samples. The total of 118.6 g/d PFOS and 323.6 g/d PFOA were released from the three rivers to the Gulf of Thailand. The survey was also conducted in small rivers, reservoirs, and coastal water around Eastern Thailand, where many industrial zones (IZ) are located. The geometric mean (GM) concentration of each PFC was ranged from 2.3 to 107.7 ng/L in small rivers, 2.2 to 212.2 ng/L in reservoirs, and 0.8 to 41.1 ng/L in coastal water samples. The higher PFCs contaminations were detected in the surface water around the industrial zones, where might be the sources of these compounds. Field surveys were also conducted in ten industrial zones (IZ1 – IZ10) to identify the occurrences of PFCs from in industries. The recovery rates of PFCs in the samples indicated that the matrix interference or enhancement was an important problem in PFCs analysis. The elevated concentrations were detected in electronics, textile, chemicals and glass making industries. Total PFCs concentrations in the influent of WWTP were ranged from 39.6 to 3, 344.1 ng/L. Ten industrial zones released 188.41 g/d of PFCs. All of the treatment processes inside industrial zones were biological processes, which were reported that they were not effective to remove PFCs. The influence of industrial discharges was affected not only the rivers and reservoirs but also in the coastal water. The PFCs in rivers and reservoirs were discharged to the Gulf of Thailand, which is the important food source for Thai people and exports. Due to the problems in industrial wastewater analysis, several optimizing options were applied in PFCs analytical method especially in Solid Phase Extraction (SPE) procedure. The combination of PresepC-Agri and Oasis®HLB was the better option for analyzing PFCs in water samples. The optimum flow rate for loading the samples was 5 mL/min. Methanol (2 mL) plus Acetronitrile (2 mL) was the effective way to elute PFCs from the cartridges. The specific solvent percentages to elute each PFCs were identified for both water and industrial wastewater samples. The matrix removal methods by using Envi-Carb and Ultrafilter were effective for different types of industrial wastewater samples. PFCs were detected in surface waters, which are the sources of tap and drinking water for the people in Central and Eastern Thailand. The surveys were conducted in Bangkok city. Samples were collected from water treatment plants (WTPs), tap water, and drinking water. PFCs were detected in all tap water and drinking water samples. PFOS and PFOA concentrations in raw water of WTP were found 4.29 ng/L and 16.54 ng/L, respectively. The average PFOS and PFOA concentrations in tap water were detected 0.17 and 3.58 ng/L, respectively. The tap water results also showed that PFOS and PFOA concentrations were not similarly detected in all area in the city. PFOA were detected higher in the western area, while PFOS concentration was quite similar in all areas. Overall, it can be concluded that the current treatment processes were not completely remove PFCs. Nevertheless, PFCs in particulate phase were effectively removed by the primary sedimentation and rapid sand filtration. Elevated PFCs were found in the industrial zones (IZ2 and IZ5). To understand the distribution and fate of PFCs during industrial wastewater process, PFCs mass flows were studied. Higher PFCs in adsorbed phase were detected only in activated sludge and some influent samples. In IZ2, PFOA loading in the dissolved phase increased after activated sludge process by 5%. There was no degradation of PFOA inside the polishing pond. The highest loading to the treatment plant was PFOS with the loading of 2, 382 mg/d and 1, 529 mg/d in dissolved and adsorbed phase, respectively. Unlike PFCAs that showed no removal in the treatment process, PFOS were decreased during the treatment processes with 36% in the activated sludge process and 36% in the polishing pond. The predominant in this IZ5 was PFOS. The increasing of PFOS was also found in this treatment plant dissimilar to IZ2. PFOS was increasing by 45% in dissolved phase and 47% in adsorbed phase. All of PFCs in this industrial zone were detected higher in the effluent, indicated that PFCs’ precursors should be the major effects of this contamination. / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14930号 / 工博第3157号 / 新制||工||1473(附属図書館) / 27368 / UT51-2009-M844 / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 田中 宏明, 教授 清水 芳久, 教授 藤井 滋穂 / 学位規則第4条第1項該当

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15659号 / 工博第3317号 / 新制||工||1501(附属図書館) / 28196 / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 田中 宏明, 教授 清水 芳久, 教授 藤井 滋穂 / 学位規則第4条第1項該当

First, this study examined the association of perfluorinated chemicals with 1) cardio-metabolic health outcomes and 2) the association of phthalates with cardiometabolic health outcomes, and 3) cardio-metabolic health outcomes while assessing the possibility of additive interactions between perfluorinated chemicals (PFCs) and phthalates. Second, association with markers of chronic inflammation and oxidative stress were explored. Finally, this study examined the association of these chemicals with estrogenic cancers- Breast cancer, prostate cancer, uterine cancer and ovarian cancer. Using data from the National Health and Nutrition Examination Survey (NHANES), logistic regression models were used to investigate the relationship between PFCs and the cardio-metabolic health outcomes adjusting for covariates. An interaction term between PFCs and phthalates was added to the main effect model to assess the possibility of effect modification. Generalized linear models were used to examine associations between PFCs and inflammatory and oxidative stress markers per unit increase in exposure to PFCs while adjusting for covariates. Binomial logistic regression was used in investigating the association between quartiles of PFCs and presence or absence of cancer while also adjusting for covariates. Discriminant analysis was used to assess the correlation between individual PFCs compounds and individual cancer categories. Perfluorononanoic acid (PFNA) was associated with increased odds of central obesity in females, odds ratio (OR): 1.10; 95% confidence interval (CI): (1.01, 1.21). Perfluorohexane sulfonic acid (PFHS), Perfluorononanoic acid (PFNA), Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonic acid (PFOS), and Perfluorodecanoic acid (PFDE) were all significantly associated with lymphocyte counts. Beta (95% CI); 0.03(0.02,0.05), 0.04(0.02,0.05), 0.05(0.03, 0.07), 0.04(0.03,0.05), 0.03(0.01,0.04) and with serum iron 0.07(0.05,0.09), 0.04(0.02,0.07), 0.10(0.07,0.12), 0.05(0.03,0.07), 0.04(0.02,0.06) and serum albumin 0.02(0.02,0.02), 0.02(0.02,0.03), 0.03(0.03,0.04), 0.02(0.02, 0.023), 0.01 (0.01, 0.05). Only PFHS, PFNA, PFOA and PFOS were associated with serum total bilirubin 0.04(0.03,0.05), 0.02(0.00,0.03), 0.06(0.04,0.08), 0.03(0.02,0.05). PFCs studied were associated with increased odds of breast, prostate, uterine and ovarian cancers, p

学位授与年月日: 2007-07-23 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2837号 / Perfluorochemicals (PFCs) were produced by industries and consumed “safely” as surfactants, repellents, additives, fire-fighting foams, polymer emulsifiers and insecticides for almost fifty years. However they are now considered as persistent, bioaccumulated and toxic (PBT) chemicals, and ubiquitously distributed in waster, air, human body and biota. Although some efforts were contributed to reduce PFCs in environment, such as development of alternatives and recycling processes, huge amount of persisted PFCs have already been discharged in environment and accumulated in biota including humans. In some industrialized areas, such as Yodo river basin in Japan, water environment and human blood were polluted by some PFCs, and thus reduction and control of PFCs were urgently required for the purpose of environmental safety and human health in these areas. Unfortunately, some studies implied that current water and wastewater treatment processes seemed ineffective to remove PFCs in trace levels. Therefore, this study will try to develop some proper technologies to treat trace level of PFCs in wastewater. In order to achieve this main objective, several works have been accomplished as follows. 　Current available literature has been reviewed to obtain a solid background for this study. Basic information of PFCs was summarized in physiochemical properties, PBT properties, productions and applications, regulations and etc.. Analytical methods for PFCs, especially of LC-ESI-MS/MS, were reviewed including pretreatment processes in diverse matrices, which derived objectives of chapter III. Distributions and behavior of PFCs were briefly discussed in water environments, biota sphere and human bloods. Available control strategies were shown in detail about alternatives, industrial recycling processes, and newly developed treatment processes. Current wastewater treatment processes showed inefficient removal for some PFCs, deriving objectives of chapter IV on the PFC behavior in treatment process. Newly developed treatment technologies seemed able to decompose PFCs completely but unsuitable for application in WWTP. Therefore, granular activated carbon (GAC) adsorption and ultra violet (UV) photolysis were developed in chapter V and VI as removal and degradation processes respectively. 　Fifteen kinds of PFCs were included in this study, consisting of twelve kinds of perfluorocarboxylic acids (PFCAs) with 4~18 carbons and three kinds of perfluoroalkyl sulfonates (PFASs) with 4~8 carbons. An integral procedure was developed in chapter III to pretreat wastewater samples. LC-ESI-MS/MS was applied to quantify all PFCs in trace level. Pretreatment methods were optimized between C18 and WAX-SPE processes for aqueous samples, and between IPE, AD-WAX and ASE-WAX processes for particulate samples. Standard spiking experiments were regularly conducted for each wastewater sample to calculate recovery rate and control analytical quality. As the result, WAX-SPE showed better performance on samples with very high organics concentrations, and C18-SPE performed better for long-chained PFCs. ASE-WAX was proposed as the optimum method to pretreat particulate samples because of the simple and time saving operations. 9H-PFNA was used as internal standard to estimate matrix effect in wastewater. 　Behavior of PFCs in a municipal WWTP has been studied in chapter IV by periodical surveys for six times in half a year. All PFCs used in this study were detected in WWTP influent and effluent. According to their carbon chain lengths, all PFCs can be classified into “Medium”, “Long” and “Short” patterns to simplify behavior analysis. PFCs in same pattern showed similar properties and behavior in wastewater treatment facilities. Very high concentrations of PFCs existed in WWTP influent, indicating some point sources of industrial discharge in this area. “Medium” PFCs, such as PFOA(8), PFNA(9) and PFOS(8), were primary contaminants in the WWTP and poorly removed by overall process. Performances of individual facilities were estimated for removal of each PFC. Primary clarification and secondary clarification were helpful to remove all PFCs in both aqueous phase and particulate phase. “Medium” PFCs in aqueous phase were increased after activated sludge process, but other PFCs can be effectively removed. Ozone seemed ineffective to decompose PFCs because of the strong stability of PFC molecules. Sand filtration and biological activated carbon (BAC) filtration in this WWTP can not remove PFCs effectively too, which required further studies. Performances of combined processes were estimated by integrating individual facilities along the wastewater flow. Activated sludge process coupled with clarifiers showed satisfied removal of most PFCs in the investigated WWTP except “Medium” PFCs. 　Adsorption characteristics of PFCs onto GAC have been studied by batch experiments in chapter V. Freundlich equation and homogenous surface diffusion model (HSDM) were applied to interpret experimental data. Isothermal and kinetics experiments implied that PFC adsorption on GAC was directly related with their carbon chain lengths. By ascendant carbon chain length, adsorption capacity for specific PFC was increased, and diffusion coefficient (Ds) was decreased. Ds of GAC adsorption was also decreased gradually in smaller GAC diameters. Coexisted natural organic matters (NOMs) reduced adsorption capacities by mechanism of competition and carbon fouling. Carbon fouling was found reducing adsorption capacity much more intensively than competition by organics. Acidic bulk solution was slightly helpful for adsorption of PFCs. However adsorption velocity or kinetics was not affected by NOM and pH significantly. GAC from Wako Company showed the best performance among four kinds of GACs, and Filtra 400 from Calgon Company was considered more suitable to removal all PFCs among the commercial GACs. Preliminary RSSCT and SBA results implied that background organics broke through fixed GAC bed much earlier than trace level of PFCs. Medium-chained PFCs can be effectively removed by fixed bed filtration without concerning biological processes. 　Direct photolysis process has been developed in chapter VI to decompose PFCAs in river water. Irradiation at UV254 nm and UV254+185 nm can both degrade PFCAs. Stepwise decomposition mechanism of PFCAs was confirmed by mass spectra analysis, and consecutive kinetics was proposed to simulate experimental data. PFASs can also be degraded by UV254+185 photolysis, although the products have not been identified yet. Coexisted NOMs reduced performance of UV photolysis for PFCAs by competition for UV photons. Sample volume or irradiation intensity showed significant influence on degradation of PFCAs. Local river water polluted by PFOA can be cleaned up by UV254+185 photolysis effectively. Ozone-related processes were also studied but ineffective to degrade PFC molecules. However, PFCs could be removed in aeration flow by another mechanism. / 京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第13340号 / 工博第2837号 / 新制||工||1417(附属図書館) / UT51-2007-M963 / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 田中 宏明, 教授 藤井 滋穂, 教授 伊藤 禎彦 / 学位規則第4条第1項該当 / Doctor of Engineering / Kyoto University / DFAM

The presence of emerging contaminants (ECs) in water and wastewater systems has become a subject of significant concern worldwide. These emerging contaminants are complex organic molecules which potentially affect human health and environment. Conventional wastewater treatment plants are unable to completely remove these contaminants from water and therefore can discharge them into environment. The need to develop effective methods for ECs removal is essential. This study assess the potential of ozone based advanced oxidation processes (AOP) to oxidize number of emerging contaminants. Different combinations of ozone with hydrogen peroxide and sodium persulfate were tested. For this study 1-4, dioxane, perfluorinated compounds (PFCs), N,N-Diethyl-metatoluamide, and three pharmaceuticals sulfamethoxazole, trimethoprim and carbamazepine have been selected. The effect of different process parameters such as chemical dosages, ozone weight percent, ozone flow rates, etc. on destruction of ECs were examined. It was observed that 1, 4-dioxane were persistent to direct ozone reaction, however were easily oxidized by hydroxyl radical. However, ozonation was solely very effective (> 99 %) in removing pharmaceuticals such as sulfamethoxaole, trimethoprim and carbamazepine. It was not very efficient for the removal of perfluorinated compound and N,N-Diethylmeta-toluamide. The operational conditions were optimized for maximum removal of every compound and their influence on the degradation process is discussed. / Civil Engineering

The focus of this thesis was to investigate developmental neurotoxic effects of different persistent and non-persistent environmental pollutants, alone or in binary mixtures, when exposure occurs during a critical period of brain development, in mice. The compounds investigated included a perfluorinated compound, perfluorohexane sulphonate (PFHxS), and four different pesticides, endosulfan, cypermethrin, chlorpyrifos and carbaryl. Both persistent and non-persistent pollutants are detected in the environment and in humans, which shows that exposure to these compounds is occurring in real life. Humans can therefore be exposed to various pollutants during their whole lifetime, starting from the gestational period to adulthood. Furthermore, exposure to environmental pollutants is rarely exclusive to a single compound, but rather occurs through combinations of various pollutants present in the environment. Exposure to environmental pollutants during human brain development have been suggested to be a possible cause for neuropsychiatric disorders, such as autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). Previous studies have shown that chemicals can induce irreversible disorders in brain function when exposure to these chemicals occurs during a critical defined period of the brain development known as the brain growth spurt (BGS). The BGS is characterized by a rapid growth and development of the immature brain. In humans, and mice, this period also overlaps the lactation period indicating that newborns and toddlers can be exposed via mothers’ milk as well. This thesis has shown that a single oral exposure to PFHxS, endosulfan, cypermethrin, chlorpyrifos or carbaryl can induce developmental neurotoxic effects in mice, when exposure occurs during a critical period of brain development. These effects are manifested as persistent altered adult spontaneous behavior in a novel home environment, modified habituation, altered susceptibility of the cholinergic system and changed levels of neuroproteins in the mouse brain. Furthermore, a single neonatal co-exposure to a binary mixture of carbaryl/chlorpyrifos or PFHxS/endosulfan can interact and exacerbate the adult behavioral effects. These effects were seen at dosages were the single compound did not elicit a response or induced a much weaker behavioral effect. This indicates that risk assessments conducted on single compounds might underestimate interaction effects of mixtures when co-exposed.

BACKGROUND: Perfluorinated compounds (PFCs) have been used as durable water and oil repellent treatments in clothing for more than 50 years. The reason for its popularity is related to the chemical structure, which also makes these compounds persistent in the environment. Numerous studies have shown negative environmental and health effects related to high concentrations of perfluorinated compounds in blood serum. Due to these studies, this paper aimed to find out if perfluorinated compounds could be replaced by non-perfluorinated without compromising performance related to water and oil repellency. METHODOLOGY: A reference sample impregnated with fluorocarbons was compared with the following non-perfluorinated treatments, aliphatic polyurethane (comb polymer) organic silicone and acid (comb polymer) and hydrocarbon (dendrimer). Impregnations were subjected to abrasion, UV-radiation and washing and after each destructive treatment; oil and water repellency tests were conducted. The environmental and health effect of all treatments were examined in a theoretical study. RESULTS: Due to difficulties with the impregnation process, comparable results could only be concluded with the perfluorinated and the hydrocarbon compound. The hydrocarbon was superior the perfluorinated compound to abrasion but for usage simulation methods that allowed chemical reactions, hence UV-radiation and washing, the fluorocarbons showed better resistance. CONCLUSION: Results show that the hydrocarbon treatment could replace perfluorinated treatments commercially when only water and not oil repellency is required. The alternative treatments in this study are not yet sufficiently examined with respect to environmental and health and can therefore not be called greener with certainty. / Program: Textilingenjörsutbildningen

The Methodology for inventory of contaminated sites (MIFO) is a method designed by the Swedish Environmental Protection Agency with an aim to facilitate agents and consultants during inventory of contaminated areas. It is structured into two stages, the first phase comprises oriented studies of the area while the second one consists of conceptual studies, such as field testing and analysis. After each phase the object is assigned a risk class that describes the degree of contamination and the risk associated with it. At Sundsvall-Timrå airport, the soil, surface- and groundwater at two fire drilling sites are contaminated with the anthropogenic substance PFOS, a former supplement in extinguishing foam. As a result of this, a number of environmental investigations have occurred over the past seven years which has led to a substantial amount of data in regards to the degree and dispersion of the contamination. However, prior to this date no risk classification according to MIFO phase 2 has been done. In order to appropriately remediate the site, it is essential that this step of the process is completed. Thus the County Administrative Board of Västernorrland in Sweden commissioned this thesis for the purpose of risk classifying Sundsvall-Timrå Airport. This was done by analysing the results from previous environmental investigations made by WSP Environmental and comparing them to the Swedish Geological Institute’s preliminary benchmark value for PFOS. The fact that Sundsvall-Timrå airport is situated in close approximation to a nature reserve and due to the high degree of contamination together with the substance distribution capabilities and high toxicity, the study resulted in the object being assigned risk class 1, very high risk. / Syftet med detta självständiga arbete var att på uppdrag av Länsstyrelsen i Västernorrland göra en MIFO fas 2 riskklassning av ett förorenat område vid Sundsvall-Timrå flygplats. MIFO (Metodik för inventering av förorenade områden) är en metodik framtagen av Naturvårdsverket med ändamålet att vägleda ombud och konsulter vid inventeringar av förorenade områden. Metoden är uppdelad i två steg, fas 1 och fas 2. Den första fasen involverar orienterade studier av området och den andra består av översiktliga studier, som till exempel fältundersökningar och analyser. Efter var fas tilldelas objektet en riskklass utifrån hur allvarlig föroreningssituationen bedöms vara. På Sundsvall-Timrå flygplats är marken, yt- och grundvattnet vid två brandövningsplatser förorenat med det antropogena ämnet PFOS som brukade ingå i släckskum. Som följd till detta har ett flertal miljötekniska mark- och grundvattenundersökningar gjorts i området under de senaste sju åren. Detta har lett till ett betydande underlag av data beträffande halt och spridning av föroreningen men fram tills nu har ingen fas 2 riskklassning av brandövningsplatserna med avseende på PFOS gjorts. Avsikten med arbetet var således att med hjälp av resultaten från tidigare miljötekniska undersökningar och SGIs preliminära riktvärden för PFOS, tilldela objektet en riskklass. Då Sundsvall-Timrå flygplats ligger intill Indalsälvens naturreservat, föroreningsnivån vid brandövningsplatserna anses vara mycket stor samt det faktum att PFOS har höga spridningsförutsättningar och toxicitet, resulterade studien i att området tilldelades riskklass 1, vilket innebär mycket stor risk.

This thesis describes the design, manufacture and characterisation of thick vacuum plasma sprayed tungsten (W) coatings on steel substrates. Fusion is a potentially clean, sustainable, energy source in which nuclear energy is generated via the release of internal energy from nuclei. In order to fuse nuclei the Coulomb barrier must be breached - requiring extreme temperatures or pressures – akin to creating a ‘star in a box’. Tungsten is a promising candidate material for future fusion reactors due to a high sputtering threshold and melting temperature. However, the large coefficient of thermal expansion mismatch with reactor structural steels such as the low activation steel Eurofer’97 is a major manufacturing and in-service problem. A vacuum plasma spraying approach for the manufacture of tungsten and tungsten/steel graded coatings has been developed successfully. The use of graded coatings and highly textured 3D interface surfi-sculpt substrates has been investigated to allow the deposition of thick plasma sprayed tungsten coatings on steel substrates. Finite element models have been developed to understand the residual stresses that develop in W/steel systems and made use of experimental measurements of coating thermal history during manufacture and elastic moduli measured by nano-indentation. For both the graded and surfi-sculpt coating, the models have been used to understand the mechanism of residual stress redistribution and relief in comparison with simple W on steel coatings, particularly by consideration of stored strain energy. In the case of surfi-sculpt W coatings, the patterned substrate gave rise to regular stress concentrating features, and allowed 2mm thick W coatings to be produced reproducibly without delamination. Preliminary through thickness residual stress measurements were compared to model predictions and provided tentative evidence of significant W coating stress relief by regulated coating segmentation.