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Zone Formation (zone + formation)
Selected AbstractsFracture of poly(vinylidene fluoride): a combined synchrotron and laboratory in-situ X-ray scattering studyJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Günther A. Maier Semi-crystalline polymers show a complex fracture mechanism, which is controlled by the micro-mechanisms associated with formation and breakdown of a plastic deformation region. Such regions develop at notches, cracks or other stress-raising defects. In the present paper, we use time-resolved synchrotron X-ray scattering techniques during the deformation process in poly(vinylidene fluoride) to study the plastic zone formation and fracture processes at different strain rates. This gives new insight into the micro-mechanisms of cavitation, lamellae separation and fibril formation in this particular material. [source] Age determination and growth of turbot and brill in the Adriatic Sea: reversal of the seasonal pattern of otolith zone formationJOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2001E. Arneri The growth of two commercially important flatfish, turbot (Psetta maxima) (L.) and brill (Scophthalmus rhombus) (L.), was investigated in the Adriatic using whole otoliths (sagittae) and stained otolith sections. At variance with the pattern usually observed in temperate seas, the opaque zone was found to be laid down in autumn and winter, and the translucent zone in spring and summer. Growth rates differed according to sex, with the females attaining greater body lengths. The von Bertalanffy growth parameters were: L,=66.2 cm, K=0.31 years,1, and t0=,0.14 years for turbot males, L,=81.5 cm, K=0.21 years,1, and t0=,0.48 years for turbot females; L,=40.2 cm, K=0.49 years,1, and t0=,1.03 years for brill males; L,=50.1 cm, K=0.27 years,1, and t0=,1.75 years for brill females. Growth rates and maximum age recorded for turbot were comparable to those reported in the North Sea. [source] Estimating the timing of growth rings in Atlantic cod otoliths using stable oxygen isotopesJOURNAL OF FISH BIOLOGY, Issue 3 2006H. Høie A technique involving micro-scale sampling of otolith carbonate and analyses of stable oxygen isotope composition was used to relate the zone appearance of the otolith to the seasonal temperature cycle. Otolith opacity could then be related to the timing of zone formation. Otoliths from two groups of Atlantic cod Gadus morhua held under known temperature conditions over a period of 4 and 6 years were examined. The otolith translucency followed the same pattern as the estimated temperature (from otolith ,18O values) in the yearly increments three and four, meaning that the translucent zones were deposited at the seasonal highest temperature in late summer and early autumn. The relative light intensities of otolith yearly increments five and six of older fish (deposited in the same years), however, were not significantly correlated to the estimated temperatures since increased otolith translucency also occurred at low temperatures. This might have been caused by stress in connection with gonad development or starvation during the spawning period. The results showed that this method of coupling otolith opacity and stable oxygen isotope composition can be used to estimate the timing of zone formations in otoliths. [source] Timing and nature of fluid flow and alteration during Mesoproterozoic shear zone formation, Olary Domain, South AustraliaJOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2005C. CLARK Abstract The development of shear zones at mid-crustal levels in the Proterozoic Willyama Supergroup was synchronous with widespread fluid flow resulting in albitization and calcsilicate alteration. Monazite dating of shear zone fabrics reveal that they formed at 1582 ± 22 Ma, at the end of the Olarian D3 deformational event and immediately prior to the emplacement of regional S-type granites. Two stages of fluid flow are identified in the area: first an albitizing event which involved the addition of Na and loss of Si, K and Fe; and a second phase of calcsilicate alteration with additions of Ca, Fe, Mg and Si and removal of Na. Fluid fluxes calculated for albitization and calcsilicate alteration were 5.56 × 109 to 1.02 × 1010 mol m,2 and 2.57 × 108,5.20 × 109 mol m,2 respectively. These fluxes are consistent with estimates for fluid flow through mid-crustal shear zones in other terranes. The fluids associated with shearing and alteration are calculated to have ,18O and ,D values ranging between +8 and +11,, and ,33 and ,42,, respectively, and ,Nd values between ,2.24 and ,8.11. Our results indicate that fluids were derived from metamorphic dehydration of the Willyama Supergroup metasediments. Fluid generation occurred during prograde metamorphism of deeper crustal rocks at or near peak pressure conditions. Shear zones acted as conduits for major crustal fluid flow to shallow levels where peak metamorphic conditions had been attained earlier leading to the apparent ,retrograde' fluid-flow event. Thus, the peak metamorphism conditions at upper and lower crustal levels were achieved at differing times, prior to regional granite formation, during the same orogenic cycle leading to the formation of retrograde mineral assemblages during shearing. [source] Deformation, mass transfer and mineral reactions in an eclogite facies shear zone in a polymetamorphic metapelite (Monte Rosa nappe, western Alps)JOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2004L. M. Keller Abstract This study analyses the mineralogical and chemical transformations associated with an Alpine shear zone in polymetamorphic metapelites from the Monte Rosa nappe in the upper Val Loranco (N-Italy). In the shear zone, the pre-Alpine assemblage plagioclase + biotite + kyanite is replaced by the assemblage garnet + phengite + paragonite at eclogite facies conditions of about 650 °C at 12.5 kbar. Outside the shear zone, only minute progress of the same metamorphic reaction was attained during the Alpine metamorphic overprint and the pre-Alpine mineral assemblage is largely preserved. Textures of incomplete reaction, such as garnet rims at former grain contacts between pre-existing plagioclase and biotite, are preserved in the country rocks of the shear zone. Reaction textures and phase relations indicate that the Alpine metamorphic overprint occurred under largely anhydrous conditions in low strain domains. In contrast, the mineralogical changes and phase equilibrium diagrams indicate water saturation within the Alpine shear zones. Shear zone formation occurred at approximately constant volume but was associated with substantial gains in silica and losses in aluminium and potassium. Changes in mineral modes associated with chemical alteration and progressive deformation indicate that plagioclase, biotite and kyanite were not only consumed in the course of the garnet-and phengite-producing reactions, but were also dissolved ,congruently' during shear zone formation. A large fraction of the silica liberated by plagioclase, biotite and kyanite dissolution was immediately re-precipitated to form quartz, but the dissolved aluminium- and potassium-bearing species appear to have been stable in solution and were removed via the pore fluid. The reaction causes the localization of deformation by producing fine-grained white mica, which forms a mechanically weak aggregate. [source] Effect of carbide volume fraction on the oxidation of austenitic Fe-Cr-C alloysMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2006L. B. Susanto Abstract A series of Fe-15Cr-(2-3)Mo alloys (compositions in weight percent) was produced with different carbon concentrations, to control the distribution of chromium between matrix metal and M23C6 precipitates. The alloys were oxidized in the austenitic state at 850°C in pure oxygen, with and without a pre-oxidation treatment at low oxygen potential, where no iron oxide could form. Protective, chromia-rich scaling took place if the chromium concentration at the metal-scale interface was high enough. This concentration was controlled by the original alloy matrix chromium concentration, and whether or not a high diffusivity ferrite zone developed at the surface by decarburization. Ferrite zone formation was assisted by pre-oxidation at low oxygen potentials. The value of the carbides as suppliers of additional chromium was demonstrated by comparison with the oxidation performance of carbide-free alloys of corresponding matrix chromium levels. However, because dissolution of the coarse carbides could be slow, alloys with high volume fractions of large carbides were unsuccessful. [source] Intracellular membrane trafficking in bone resorbing osteoclastsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2003Mika Mulari Abstract There is ample evidence now that the two major events in bone resorption, namely dissolution of hydroxyapatite and degradation of the organic matrix, are performed by osteoclasts. The resorption cycle involves several specific cellular activities, where intracellular vesicular trafficking plays a crucial role. Although details of these processes started to open up only recently, it is clear that vesicular trafficking is needed in several specific steps of osteoclast functioning. Several plasma membrane domains are formed during the polarization of the resorbing cells. Multinucleated osteoclasts create a tight sealing to the extracellular matrix as a first indicator of their resorption activity. Initial steps of the sealing zone formation are ,v,3 -integrin mediated, but the final molecular interaction(s) between the plasma membrane and mineralized bone matrix is still unknown. A large number of acidic intracellular vesicles then fuse with the bone-facing plasma membrane to form a ruffled border membrane, which is the actual resorbing organelle. The formation of a ruffled border is regulated by a small GTP-binding protein, rab7, which indicates the late endosomal character of the ruffled border membrane. Details of specific membrane transport processes in the osteoclasts, e.g., the formation of the sealing zone and transcytosis of bone degradation products from the resorption lacuna to the functional secretory domain remain to be clarified. It is tempting to speculate that specific features of vesicular trafficking may offer several potential new targets for drug therapy of bone diseases. Microsc. Res. Tech. 61:496,503, 2003. © 2003 Wiley-Liss, Inc. [source] Estimating the timing of growth rings in Atlantic cod otoliths using stable oxygen isotopesJOURNAL OF FISH BIOLOGY, Issue 3 2006H. Høie A technique involving micro-scale sampling of otolith carbonate and analyses of stable oxygen isotope composition was used to relate the zone appearance of the otolith to the seasonal temperature cycle. Otolith opacity could then be related to the timing of zone formation. Otoliths from two groups of Atlantic cod Gadus morhua held under known temperature conditions over a period of 4 and 6 years were examined. The otolith translucency followed the same pattern as the estimated temperature (from otolith ,18O values) in the yearly increments three and four, meaning that the translucent zones were deposited at the seasonal highest temperature in late summer and early autumn. The relative light intensities of otolith yearly increments five and six of older fish (deposited in the same years), however, were not significantly correlated to the estimated temperatures since increased otolith translucency also occurred at low temperatures. This might have been caused by stress in connection with gonad development or starvation during the spawning period. The results showed that this method of coupling otolith opacity and stable oxygen isotope composition can be used to estimate the timing of zone formations in otoliths. [source] Atom Probe Tomography I. Early Stages of Precipitation of NbC and NbN in Ferritic Steels,ADVANCED ENGINEERING MATERIALS, Issue 12 2006F. Danoix Abstract The results reported in this paper give new information regarding the early stages of precipitation in model low niobium steels. It clearly appears that the kinetic paths for carbides and nitrides precipitation in the investigated model alloys are very different, more continuous in the case of carbides, and through GP zones formation in the case of nitrides. [source] A Method for the Detection of Defluidized Zones in Slurry Bubble ColumnsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003Ahad Emami Abstract The formation of defluidized zones was studied in a laboratory slurry bubble column equipped with heat transfer probes. The probes were small thermistors 2.4 mm in diameter. Dionized water and air were used as a liquid and gas phase, respectively. Solids were fine ceramic particles with mean size of 19.2 ,m and density of 2244 kg/m3. The effects of solids holdup (up to 30 wt% on gas free basis), gas superficial velocity (0.01-0.09 m/s), sparger height (0.01-0.09 m) on defluidized zones formation was studied. Cycle analysis of the local heat transfer fluctuations reliably detected the local formation of defluidized zones for each condition. La formation de zones défluidisées a été étudiée dans une colonne à bulles avec bouillie, équipée de sondes de transfert de chaleur. Les sondes étaient des petits thermistors de 2.4 mm de diamètre. De l'eau déionisée et de l'air constituaient les phases liquide et gazeuse. Les solides étaient des fines particules en céramique avec une taille moyenne de 19.2 µm et une densité de 2244 kg/m3. Les effets de la rétention solide (jusqu'à 30 % en masses sur base sans gaz), de la vitesse superficielle du gaz (0.01-0.09 m/s) et de la hauteur du distributeur de gaz ont été étudiés. L'analyse de cycle du transfert de local de chaleur a détecté de façon fiable la formation locale de zones défluidisées pour chaque condition. [source] | ||||||||||||||||