Ni−W/ZrO2Ni-W/ZrO_2 nanocomposites obtained by ultrasonic DC electrodeposition

Composite coatings consisting of a nanocrystalline Ni–W alloy matrix reinforced with ZrO2 particles (average size of 50 nm) were synthesized by electrochemical deposition assisted by an external ultrasonic field. The Ni–W/ZrO2 coatings were deposited from aqueous sulphate–citrate electrolytes containing zirconia nanopowder in suspension on steel substrates in a system with a rotating disk electrode (RDE). The influence of relevant processing parameters (i.e., concentration of zirconia powder in plating bath, current density, hydrodynamic conditions, ultrasonic field frequency) on the composite characteristics was discussed. Based on micromechanical (microhardness, Young’s modulus) and microstructural (morphology, phase composition, crystallite size) properties of the coatings, the conditions for electrodeposition of crack-free, homogeneous Ni–W/ZrO2 nanocomposites with enhanced functional properties have been developed

Elektroosadzanie i właściwości nanokrystalicznych stopów na osnowie niklu z trudnotopliwym metalem z kąpieli cytrynianowych

Głównym celem pracy było ustalenie optymalnych warunków procesu elektroosadzania metalicznych powłok Ni-Mo o podwyższonych właściwościach mikromechanicznych. Charakteryzowane stopy zostały osadzone na podłożu ze stali ferrytycznej, w warunkach galwanostatycznych, w modelowym układzie z wirujaca elektroda dyskowa (WED), z wodnych kompleksowych roztworów cytrynianowych zawierających sole niklu i molibdenu. Określono wpływ pH elektrolitu (regulowanego przez dodatek kwasu siarkowego lub amoniaku) na zawartość molibdenu w stopie, jakość osadów, jak również wydajnosc pradowa procesu elektroosadzania. Stwierdzono, że wzrost pH jest związany ze stopniowym zwiększaniem zawartości molibdenu w powłokach. Maksymalna zawartość molibdenu uzyskano w stopach wydzielonych z kąpieli galwanicznej o pH 7, gdzie jednocześnie zaobserwowano najwyższe stężenie cytrynianowych, elektroaktywnych kompleksów molibdenu typu [MoO4(Cit)H]4?-(Cit=C6H5O3-7 ). Dla wybranej kąpieli galwanicznej o optymalnym pH badano wpływ gęstości prądu katodowego (kluczowego parametru operacyjnego, kontrolującego między innymi skład chemiczny oraz mikrostrukturę, w tym skład fazowy i rozmiar krystalitów) na właściwości mechaniczne i tribologiczne wytworzonych powłok. Wykazano, że w całym analizowanym zakresie gęstości prądu, otrzymano powłoki Ni-Mo bez siatki mikropęknięć, o dobrej adhezji do stalowego podłoża, charakteryzujące się podwyższoną twardością w zakresie 6.5 do 7.8 GPa. Ponadto, powłoki osadzane przy wyższych gęstościach prądu (powyżej 3.5 A/dm2) odznaczają się zwartą i jednorodną mikrostrukturą, a tym samym najwyższą odpornością na zużycie przez tarcie.The main aim of the present work was to determine the optimal conditions for electrodeposition of metallic Ni-Mo coatings of enhanced micromechanical properties. These alloys were electrodeposited on the ferritic steel substrate, under galvanostatic regime in a system with a rotating disk electrode (RDE), from an aqueous citrate complex solution containing nickel and molybdenum salts. The effect of the electrolyte solution pH (adjusted by sulphuric acid or ammonia) on the molybdenum content and on deposit quality as well as on the current efficiency of the electrodeposition process, has been studied. It was established that increase of bath pH is correlated with gradual increase of molybdenum content in deposits up to pH 7, where the maximum concentration of Mo(VI) electroactive citrate complex ions [MoO4(Cit)H]4- (Cit= C6H5O7-3 ) in plating bath was observed. In the selected bath of the optimum pH value, the effect of cathodic current density, as a crucial operating parameter which strongly controls the chemical composition and microstructure parameters (e.g. phase compositions, crystallite size), on the mechanical and tribological properties of the resulting coatings has been determined. It has been shown that - under all investigated current density range - crack-free, well adherent Ni-Mo coatings, characterized by microhardness of 6.5-7.8 GPa, were obtained. Alloys deposited at higher tested current densities (above 3.5 A/dm2) were characterized by compact and uniform microstructure, and thus had the highest wear and friction resistance

Low-temperature zircon growth related to hydrothermal alteration of siderite concretions in Mississippian shales, Scotland

Zircon occurs in voids and cracks in phosphatic coprolites enclosed in siderite concretions in Mississippian shales near Edinburgh, Scotland. The zircon formed during hydrothermal alteration of early-diagenetic concretions and occurs as spherical aggregates of prismatic crystals, sometimes radiating. Vitrinite reflectance measurements indicate temperatures of ~270°C for the zircon-bearing concretions and the host shales. Molecular parameter values based on dibenzothiophene and phenanthrene distribution and occurrence of di- and tetra-hydro-products of polycyclic aromatic compounds suggest that the rocks experienced relatively high-temperature aqueous conditions related to hydrothermal fluids, perhaps associated with neighboring mafic intrusions. The zircon was dissolved from the concretions, transported in fluids, and reprecipitated in voids. This is the first record of the precipitation of authigenic zircon in sedimentary rock as a new phase, not as outgrowths

Adhesion Failures Determine the Pattern of Choroidal Neovascularization in the Eye: A Computer Simulation Study

Choroidal neovascularization (CNV) of the macular area of the retina is the major cause of severe vision loss in adults. In CNV, after choriocapillaries initially penetrate Bruch's membrane (BrM), invading vessels may regress or expand (CNV initiation). Next, during Early and Late CNV, the expanding vasculature usually spreads in one of three distinct patterns: in a layer between BrM and the retinal pigment epithelium (sub-RPE or Type 1 CNV), in a layer between the RPE and the photoreceptors (sub-retinal or Type 2 CNV) or in both loci simultaneously (combined pattern or Type 3 CNV). While most studies hypothesize that CNV primarily results from growth-factor effects or holes in BrM, our three-dimensional simulations of multi-cell model of the normal and pathological maculae recapitulate the three growth patterns, under the hypothesis that CNV results from combinations of impairment of: 1) RPE-RPE epithelial junctional adhesion, 2) Adhesion of the RPE basement membrane complex to BrM (RPE-BrM adhesion), and 3) Adhesion of the RPE to the photoreceptor outer segments (RPE-POS adhesion). Our key findings are that when an endothelial tip cell penetrates BrM: 1) RPE with normal epithelial junctions, basal attachment to BrM and apical attachment to POS resists CNV. 2) Small holes in BrM do not, by themselves, initiate CNV. 3) RPE with normal epithelial junctions and normal apical RPE-POS adhesion, but weak adhesion to BrM (e.g. due to lipid accumulation in BrM) results in Early sub-RPE CNV. 4) Normal adhesion of RBaM to BrM, but reduced apical RPE-POS or epithelial RPE-RPE adhesion (e.g. due to inflammation) results in Early sub-retinal CNV. 5) Simultaneous reduction in RPE-RPE epithelial binding and RPE-BrM adhesion results in either sub-RPE or sub-retinal CNV which often progresses to combined pattern CNV. These findings suggest that defects in adhesion dominate CNV initiation and progression

A census of young stellar objects in two line-of-sight star-forming regions toward IRAS 22147+5948 in the outer Galaxy

Context. Star formation in the outer Galaxy, namely, outside of the Solar circle, has not been extensively studied in part due to the low CO brightness of the molecular clouds linked with the negative metallicity gradient. Recent infrared surveys provide an overview of dust emission in large sections of the Galaxy, but they suffer from cloud confusion and poor spatial resolution at far-infrared wavelengths. Aims. We aim to develop a methodology to identify and classify young stellar objects (YSOs) in star-forming regions in the outer Galaxy and use it to resolve a long-standing disparity in terms of the distance and evolutionary status of IRAS 22147+5948. Methods. We used a support vector machine learning algorithm to complement standard color–color and color–magnitude diagrams in our search for YSOs in the IRAS 22147 region, based on publicly available data from the Spitzer Mapping of the Outer Galaxy survey. The agglomerative hierarchical clustering algorithm was used to identify clusters. Then the physical properties of individual YSOs were calculated. The distances were determined using CO 1–0 from the Five College Radio Astronomy Observatory survey. Results. We identified 13 Class I and 13 Class II YSO candidates using the color-color diagrams, along with an additional 2 and 21 sources, respectively, using the applied machine learning techniques. The spectral energy distributions of 23 sources were modeled with a star and a passive disk, corresponding to Class II objects. The models of three sources include envelopes that are typical for Class I objects. The objects were grouped into two clusters located at a distance of ~2.2 kpc and 5 clusters at ~5.6 kpc. The spatial extent of CO, radio continuum, and dust emission confirms the origin of YSOs in two distinct star-forming regions along a similar line of sight. Conclusions. The outer Galaxy may serve as a unique laboratory for exploring star formation across environments, on the condition that complementary methods and ancillary data are used to properly account for cloud confusion and distance uncertainties

Initial invasive or conservative strategy for stable coronary disease

BACKGROUND Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, 121.8 percentage points; 95% CI, 124.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used