22 research outputs found
Early growth of Scots pine, European larch and common oak at the young age on post-fire area located in the SĆawa ĆlÄ ska Forest District (SW Poland)
The long-term forecasts predict that global warming will increase frequency and area of forest fires. Apart from economic losses resulting from a reduction of wood volume and annual increments of trees, the post-fire areas requiring the reforestation are enlarging considerably.           The present study aimed at the comparison of growth parameters of Scots pine, European larch and common oak seedlings growing on post-fire forest area with those growing in the control forest site established after clear cutting which was not enveloped by fire. We hypothesized that differences in growth traits of seedlings growing on post-fire area or in the control would depend on the species-specific ecological requirements. Among three study species Scots pine was selected to be the most suitable for planting on burnt area taking into account its growth traits and reforestation success.           Scots pine and European larch seedlings showed a greater thickness at root collar and pine had also a greater height on burnt area than in the control. Common oak responded inversely, it grew better in the control conditions compared with the burnt area. The pine grade of slenderness was similar in both treatments. Larch and oak reduced their grade of slenderness growing on post-fire area.Our results supported the hypothesis that the responses of the study trees to the burnt area conditions were determined by the species-dependent traits. The post-fire environment was the most favourable for light-demanding, pioneer pine and larch, but it was disadvantageous for late-successional, more conservative oak. Scots pine together with European larch are recommended to be planted on the burnt area to restore relatively fast the forest ecosystem. At the beginning of reforestation these species can play a role of pioneer crop and later will be able to become the dominant species together with less flammable broadleaved trees in the converted stands
nanocomposites obtained by ultrasonic DC electrodeposition
Composite coatings consisting of a nanocrystalline NiâW alloy matrix reinforced with ZrO2 particles (average size of 50 nm) were synthesized by electrochemical deposition assisted by an external ultrasonic field. The NiâW/ZrO2 coatings were deposited from aqueous sulphateâcitrate 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, Youngâs modulus) and microstructural (morphology, phase composition, crystallite size) properties of the coatings, the conditions for electrodeposition of crack-free, homogeneous NiâW/ZrO2 nanocomposites with enhanced functional properties have been developed
Elektroosadzanie i wĆaĆciwoĆci nanokrystalicznych stopĂłw na osnowie niklu z trudnotopliwym metalem z kÄ pieli cytrynianowych
GĆĂłwnym celem pracy byĆo ustalenie optymalnych warunkĂłw procesu elektroosadzania metalicznych powĆok Ni-Mo o podwyĆŒszonych wĆaĆciwoĆciach mikromechanicznych. Charakteryzowane stopy zostaĆy osadzone na podĆoĆŒu ze stali ferrytycznej, w warunkach galwanostatycznych, w modelowym ukĆadzie z wirujaca elektroda dyskowa (WED), z wodnych kompleksowych roztworĂłw cytrynianowych zawierajÄ
cych sole niklu i molibdenu. OkreĆlono wpĆyw pH elektrolitu (regulowanego przez dodatek kwasu siarkowego lub amoniaku) na zawartoĆÄ molibdenu w stopie, jakoĆÄ osadĂłw, jak rĂłwnieĆŒ wydajnosc pradowa procesu elektroosadzania. Stwierdzono, ĆŒe wzrost pH jest zwiÄ
zany ze stopniowym zwiÄkszaniem zawartoĆci molibdenu w powĆokach. Maksymalna zawartoĆÄ molibdenu uzyskano w stopach wydzielonych z kÄ
pieli galwanicznej o pH 7, gdzie jednoczeĆnie zaobserwowano najwyĆŒsze stÄĆŒenie cytrynianowych, elektroaktywnych kompleksĂłw molibdenu typu [MoO4(Cit)H]4?-(Cit=C6H5O3-7 ). Dla wybranej kÄ
pieli galwanicznej o optymalnym pH badano wpĆyw gÄstoĆci prÄ
du katodowego (kluczowego parametru operacyjnego, kontrolujÄ
cego miÄdzy innymi skĆad chemiczny oraz mikrostrukturÄ, w tym skĆad fazowy i rozmiar krystalitĂłw) na wĆaĆciwoĆci mechaniczne i tribologiczne wytworzonych powĆok. Wykazano, ĆŒe w caĆym analizowanym zakresie gÄstoĆci prÄ
du, otrzymano powĆoki Ni-Mo bez siatki mikropÄkniÄÄ, o dobrej adhezji do stalowego podĆoĆŒa, charakteryzujÄ
ce siÄ podwyĆŒszonÄ
twardoĆciÄ
w zakresie 6.5 do 7.8 GPa. Ponadto, powĆoki osadzane przy wyĆŒszych gÄstoĆciach prÄ
du (powyĆŒej 3.5 A/dm2) odznaczajÄ
siÄ zwartÄ
i jednorodnÄ
mikrostrukturÄ
, a tym samym najwyĆŒszÄ
odpornoĆciÄ
na zuĆŒycie 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
Assessment of quality of life among patients after lung transplantation: a single-center study
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
Comparison of phenyldibenzothiophene distributions predicted from molecular modelling with relevant experimental and geological data
Corrosion of Alumina-Spinel Refractory by Secondary Metallurgical Slag Using Coating Corrosion Test
International audienceIn this paper, the corrosion mechanism of commercial alumina-spinel refractory was investigated at 1350 and 1450 °C. Disc samples were coated with shells of two different slags containing 4 and 10 wt.% SiO2. The after-corrosion refractory was investigated in view of changes in its microstructure and phase composition by SEM/EDS and XRD techniques, respectively. At 1350 °C slags slightly infiltrated the microstructure, whereas at 1450 °C slags infiltrated the alumina-spinel refractory causing its significant corrosion. As a result of corrosion, new phases were formed, including calcium dialuminate (Ca2Al4O7), calcium hexaluminate (CaAl12O19), and gehlenite (Ca2AlSi2O7). Formation of calcium aluminate layers in the microstructure of the refractory inhibited further dissolution of alumina aggregates; however, expansive behavior of CaAl12O19 raised the microstructure porosity. The additional SiO2 in the slag doubled the amount of low melting gehlenite in the matrix, accelerating the corrosion process of alumina-spinel brick at high temperatures