Effect of spraying parameters on the microstructural and corrosion properties of HVAF-sprayed Fe-Cr-Ni-B-C coatings

Thermally sprayed Fe-based coatings have been extensively studied as future solution in order to replace more expensive, harmful and environmentally dangerous Ni- and WC-based coatings for several industrial applications where high corrosion and wear resistance are required. The aim of the present study is to investigate the effect of spraying parameters on the microstructure and the corrosion resistance of Fe-based coatings manufactured with the High Velocity Air Fuel (HVAF) thermal spray process. Six sets of thermal spraying parameters have been chosen and their effect on the overall quality of coatings was investigated. All HVAF coatings showed comparably dense microstructure with near-zero oxidation, proving the high quality of the deposition process. However, higher anti-corrosion and mechanical properties were achieved by increasing the spraying air pressure and decreasing the particle feeding rate without altering the thickness and the overall deposition rate. Powder feeding rate was reported to have a remarkable effect on microstructure and corrosion properties. Coatings with beneficial compressive residual stresses were successfully obtained by increasing air pressure during spraying which resulted in improved microstructural and corrosion properties

Sliding and abrasive wear behaviour of HVOF- and HVAF-sprayed Cr3C2-NiCr hardmetal coatings

This paper provides a comprehensive characterisation of HVOF- and HVAF-sprayed Cr3C2-25 wt.% NiCr hardmetal coatings. One commercial powder composition with two different particle size distributions was processed using five HVOF and HVAF thermal spray systems. All coatings contain less Cr3C2 than the feedstock powder, possibly due to the rebound of some Cr3C2-rich particles during high-velocity impact onto the substrate. Dry sand-rubber wheel abrasive wear testing causes both grooving and pull-out of splat fragments. Mass losses depend on inter- and intra-lamellar cohesion, being higher (≥70 mg after a wear distance of 5904 m) for the coatings deposited with the coarser feedstock powder or with one type of HVAF torch. Sliding wear at room temperature against alumina involves shallower abrasive grooving, small-scale delamination and carbide pull-outs, and it is controlled by intra-lamellar cohesion. The coatings obtained from the fine feedstock powder exhibit the lowest wear rates (≈5×10-6 mm3/(Nm)). At 400 °C, abrasive grooving dominates the sliding wear behaviour; wear rates increase by one order of magnitude but friction coefficients decrease from ≈0.7 to ≈0.5. The thermal expansion coefficient of the coatings (11.08×10-6 °C-1 in the 30-400 °C range) is sufficiently close to that of the steel substrate (14.23×10-6 °C-1) to avoid macro-cracking

Tribology of HVOF- and HVAF-sprayed WC-10Co4Cr hardmetal coatings: A comparative assessment

This paper provides a comprehensive assessment of the sliding and abrasive wear behaviour of WC-10Co4Cr hardmetal coatings, representative of the existing state-of-the-art. A commercial feedstock powder with two different particle size distributions was sprayed onto carbon steel substrates using two HVOF and two HVAF spray processes. Mild wear rates of <10-7mm3/(Nm) and friction coefficients of 480.5 were obtained for all samples in ball-on-disk sliding wear tests at room temperature against Al2O3 counterparts. WC-10Co4Cr coatings definitely outperform a reference electrolytic hard chromium coating under these test conditions. Their wear mechanisms include extrusion and removal of the binder matrix, with the formation of a wavy surface morphology, and brittle cracking. The balance of such phenomena is closely related to intra-lamellar features, and rather independent of those properties (e.g. indentation fracture toughness, elastic modulus) which mainly reflect large-scale inter-lamellar cohesion, as quantitatively confirmed by a principal component analysis. Intra-lamellar dissolution of WC into the matrix indeed increases the incidence of brittle cracking, resulting in slightly higher wear rates. At 400\ub0C, some of the hardmetal coatings fail because of the superposition between tensile residual stresses and thermal expansion mismatch stresses (due to the difference between the thermal expansion coefficients of the steel substrate and of the hardmetal coating). Those which do not fail, on account of lower residual stresses, exhibit higher wear rates than at room temperature, due to oxidation of the WC grains.The resistance of the coatings against abrasive wear, assessed by dry sand-rubber wheel testing, is related to inter-lamellar cohesion, as proven by a principal component analysis of the collected dataset. Therefore, coatings deposited from coarse feedstock powders suffer higher wear loss than those obtained from fine powders, as brittle inter-lamellar detachment is caused by their weaker interparticle cohesion, witnessed by their systematically lower fracture toughness as well

In utero exposure to cigarette smoke dysregulates human fetal ovarian developmental signalling

STUDY QUESTION How does maternal cigarette smoking disturb development of the human fetal ovary?&lt;p&gt;&lt;/p&gt; SUMMARY ANSWER Maternal smoking increases fetal estrogen titres and dysregulates several developmental processes in the fetal ovary.&lt;p&gt;&lt;/p&gt; WHAT IS KNOWN ALREADY Exposure to maternal cigarette smoking during gestation reduces human fetal ovarian cell numbers, germ cell proliferation and subsequent adult fecundity.&lt;p&gt;&lt;/p&gt; STUDY DESIGN, SIZE, DURATION The effects of maternal cigarette smoking on the second trimester human fetal ovary, fetal endocrine signalling and fetal chemical burden were studied. A total of 105 fetuses were studied, 56 from mothers who smoked during pregnancy and 49 from those who did not.&lt;p&gt;&lt;/p&gt; PARTICIPANTS/MATERIALS, SETTING METHODS Ovary, liver and plasma samples were collected from electively terminated, normally progressing, second trimester human fetuses. Circulating fetal hormones, levels of 73 fetal ovarian transcripts, protein localization, density of oocytes/primordial follicles and levels of 16 polycyclic aromatic hydrocarbons (PAHs) in the fetal liver were determined.&lt;p&gt;&lt;/p&gt; MAIN RESULTS AND THE ROLE OF CHANCE Circulating fetal estrogen levels were very high and were increased by maternal smoking (ANOVA, P = 0.055–0.004 versus control). Smoke exposure also dysregulated (two-way ANOVA, smoking versus gestation weeks interaction, P = 0.046–0.023) four fetal ovarian genes (cytochrome P450 scc [CYP11A1], NOBOX oogenesis homeobox [NOBOX], activator of apoptosis harakiri [HRK], nuclear receptor subfamily 2, group E, member 1 [NR2E1]), shifted the ovarian Inhibin βA/inhibin α ratio (NHBA/INHA) transcript ratio in favour of activin (ANOVA, P = 0.049 versus control) and reduced the proportion of dominant-negative estrogen receptor 2 (ERβ: ESR2) isoforms in half the exposed fetuses. PAHs, ligands for the aryl hydrocarbon receptor (AHR), were increased nearly 6-fold by maternal smoking (ANOVA, P = 0.011 versus control). A fifth transcript, COUP transcription factor 1 (nuclear receptor subfamily 2, group F, member 1: NR2F1, which contains multiple AHR-binding sites), was both significantly increased (ANOVA, P = 0.026 versus control) and dysregulated by (two-way ANOVA, smoking versus gestation weeks interaction, P = 0.021) maternal smoking. NR2F1 is associated with repression of FSHR expression and smoke-exposed ovaries failed to show the normal increase in FSHR expression during the second trimester. There was a significantly higher number of DEAD (Asp-Glu-Ala-Asp) box polypeptide 4 (DDX4) VASA-positive (ANOVA, P = 0.016 versus control), but not POU domain, class 1, transcription factor 1 (POU5F1) OCT3/4-positive, oocytes in smoke-exposed fetuses and this matched with a significantly higher number of primordial follicles (ANOVA, P = 0.024 versus control).&lt;p&gt;&lt;/p&gt; LIMITATIONS, REASONS FOR CAUTION The effects of maternal smoking on establishment of the maximum fetal primordial follicle pool cannot be reliably studied in our population since the process is not completed until 28 weeks of gestation and normal fetuses older than 21 weeks of gestation are not available for study. Our data suggest that some fetal ovaries are affected by smoke exposure while others are not, indicating that additional studies, with larger numbers, may show more significant effects.&lt;p&gt;&lt;/p&gt; WIDER IMPLICATIONS OF THE FINDINGS Fetal exposure to chemicals in cigarette smoke is known to lead to reduced fecundity in women. Our study suggests, for the first time, that this occurs via mechanisms involving activation of AHR, disruption of inhibin/activin and estrogen signalling, increased exposure to estrogen and dysregulation of multiple molecular pathways in the exposed human fetal ovary. Our data also suggest that alterations in the ESR2 positive and dominant negative isoforms may be associated with reduced sensitivity of some fetuses to increased estrogens and maternal smoking

Interrelationships Between the Kinetics of VLDL Subspecies and HDL Catabolism in Abdominal Obesity: A Multicenter Tracer Kinetic Study

Context: Low plasma high-density lipoprotein (HDL) cholesterol is a major abnormality in abdominal obesity. This relates due to accelerated HDL catabolism, but the underlying mechanism requires further elucidation. The relationships between HDL catabolism and other variables that may be modified in abdominal obesity, such as very low-density lipoprotein (VLDL) subspecies (VLDL1, VLDL2) kinetics, liver fat, or visceral adiposity, remain to be investigated. Objectives: Our aim was to study the associations between HDL apolipoprotein (apo)-A-I fractional catabolic rate (FCR) and the kinetics of VLDL subspecies and estimates of liver and visceral and sc fat. Design: We carried out a multicenter in vivo kinetic study using stable isotopes (deuterated leucine and glycerol) in 62 individuals with abdominal obesity. Results: In a multivariate analysis, among the morphological and biological parameters that may predict apoA-I FCR, liver fat (beta = .400, P = .003), and VLDL1-apoB (beta = .307, P = .020) were independently associated with apoA-I FCR. In a multivariate analysis, among the kinetic parameters, VLDL1-triglycerides (TGs) indirect FCR (beta = .357, P = .001), VLDL1-TG production rate (beta = 0.213, P = .048), and apoA-II FCR (beta = .667, P < .0001) were independently associated with apoA-I FCR. After adjustment for VLDL1-TG production rate, liver fat was no more correlated with apoA-I FCR. No association between apoA-I FCR and visceral fat was observed. Conclusions: We show that VLDL1 is an important independent determinant of apoA-I FCR and more precisely that apoA-I FCR is independently associated with both catabolism and the production of VLDL1-TG. In addition, we show an association between liver fat and apoA-I FCR that is mostly mediated by VLDL1-TG production. These data indicate that, in abdominal obesity, dysfunctional VLDL1 metabolism is an important modulator of HDL apoA-I catabolism

Effective implementation of relationship orientation in new product launches

The critical role of relationships in business performance is widely recognized in the business marketing literature. However, to date, the prevailing new product launch research has concentrated on firms&#39; general customer and competitor focus on predicting launch performance, and mainly applied a product centered or marketing mix perspective on considering effective strategic and tactical launch activities. Consequently, there is only scant knowledge on the relevance of a relational perspective when launching new products. The study contributes to this gap by examining the impact of firms&#39; relationship orientation on launch performance and the key activities through which it is transformed into performance in the new product launch context. A set of hypotheses is developed and tested with data collected from 109 new product launches in pharmaceutical companies. The results show that sales force management and relationship leveraging mediate relationship orientation&#39;s impact on launch performance through complexly intertwined relationships. From a theoretical perspective, this study highlights the role of the relational perspective in new product launch and fosters our understanding on how relationship-focused culture is effectively implemented in practice. From a managerial perspective, the results offer insights on how firms can effectively enhance the successful commercialization of new products through relationship-oriented sales and marketing activities.</p

The LAGUNA design study- towards giant liquid based underground detectors for neutrino physics and astrophysics and proton decay searches

The feasibility of a next generation neutrino observatory in Europe is being considered within the LAGUNA design study. To accommodate giant neutrino detectors and shield them from cosmic rays, a new very large underground infrastructure is required. Seven potential candidate sites in different parts of Europe and at several distances from CERN are being studied: Boulby (UK), Canfranc (Spain), Fr\'ejus (France/Italy), Pyh\"asalmi (Finland), Polkowice-Sieroszowice (Poland), Slanic (Romania) and Umbria (Italy). The design study aims at the comprehensive and coordinated technical assessment of each site, at a coherent cost estimation, and at a prioritization of the sites within the summer 2010.Comment: 5 pages, contribution to the Workshop "European Strategy for Future Neutrino Physics", CERN, Oct. 200

Fostering transformational teacher agency in Finnish teacher education

In this article, we studied how well teacher education in Finland is able to answer the changing needs of the contemporary world. More precisely, we focussed on the question of how well an alternative teacher education model guides teacher students’ agency towards a transformational view of the teaching profession, making it possible for schools to enable social change. This question was studied in the framework of critical social pedagogy. The data for this article was collected ethnographically by observing meetings in the Critical Integrative Teacher Education (CITE) programme at the University of Jyväskylä in 2015–2017. The analysis is based on a theoretical background in which we outline two different discourses on the concept of teachers’ agency. The first promotes schools’ role in conservation; teachers are expected to educate obedient and uncritical citizens to maintain steady economic growth. The second discourse is defined as critical and emancipatory, where the education pursues transformation in students’ underlying attitudes and a deeper understanding of education and society. The results showed that the CITE model fosters teacher students’ critical self-reflection and understanding of group phenomena considering education. The students’ ability to understand schools in a social context also develops. However, CITE seems to struggle in transforming the students’ thinking and understanding into actions. According to the data, feelings of inability, cynicism and a lacklustre ability to understand concretely how teachers can have an impact on society through their profession prevent a more complete transformation in the students’ everyday modes of action. A stronger community perspective, collaboration with institutions outside teacher education, the enabling of group-oriented action and the provision of real-life experiences regarding the transformation could better help to develop future teachers’ agency towards transformational views

Slurry and dry particle erosion wear properties of WC-10Co4Cr and Cr3C2-25NiCr hardmetal coatings deposited by HVOF and HVAF spray processes

Thermally sprayed hardmetal coatings were produced to provide improved erosion wear compared to conventional cast GX4CrNi13-4 martensitic steel (CA6NM) used in hydro turbine components. Sprayed coatings and reference materials were tested with high-speed slurry pot tester using either fine or coarse quartz as the erosive media. Additional erosion tests were carried out with centrifugal dry erosion tester. Tungsten carbide based coatings provided the highest wear resistance due to the high hardness and even distribution of the fine carbide particles. The cast 13-4 steel samples experienced up to 180 times higher wear rates in fine quartz slurry and up to 36 times higher wear rates in coarse slurry compared to the sprayed coatings