Search results for "shear"
showing 10 items of 804 documents
Biometrical and Biological Considerations on the Cory’s Shearwater Calonectris Diomedea
1986
Today the Mediterranean distribution of Cory’s Shearwaters is believed to be well known. New colonies may be discovered, but certainly the largest ones are known. Many data were published during the last ten years and we believe to have a satisfactory knowledge of their biology, though some problems, as the winter movements of each population, the first breeding age and the ratio immatures/adults are still to be examined carefully.
Deformation history during chain building deduced by outcrop structural analysis: The case of the Sicilian fold-and-thrust belt (Central Mediterranea…
2015
Abstract The Sicilian fold-and-thrust belt is located in the central Mediterranean area, and it represents the south-eastern arcuate segment of the Apennine-Maghrebide orogen. The tectonic evolution of the Sicilian belt is documented after outcrop analysis of small-scale structural features carried out throughout the region. Results are consistent with the following four main deformation stages having affected the study area, from the oldest to the youngest: (i) multilayer weakening; (ii) folding-and-thrusting, (iii) extension, and (iv) renewed thrusting. The first deformation stage included three different substages (layer-parallel shortening, bed-parallel simple shear and fold nucleation)…
Polymer solutions: Equilibrium clusters versus shear clusters
2021
Abstract Polymer solutions are inhomogeneous on mesoscopic scales as a result of chemical bonds linking their monomeric units. This situation leads to polymer clusters within which the polymer concentration c cluster is only a small fraction of the overall concentration c. The ratio c/ c cluster (overlap parameters Ω ) quantifies the number of clusters that need to overlap to yield c. Equilibrium clusters (minimization of Gibbs energy) and shear clusters (minimization of entropy production) differ fundamentally where Ω equil ≥ Ω shear . Only in the vicinity of the glass transition temperature and at high concentration the opposite is the case. Experimental information on Ω equil as a functi…
Geometric aspects of synkinematic granite intrusion into a ductile shear zone — an example from the Yunmengshan core complex, northern China
2005
The Cretaceous Yungmengshan core complex in northern China contains a large syntectonic granodiorite batholith that intrudes a slightly older diorite intrusion. A major gently dipping ductile decollement shear zone is developed along the contact of the diorite and granodiorite. The shear zone is invaded by a large volume of granitic and pegmatite veins associated with the main granodiorite batholith during activity of the shear zone under high-grade metamorphic conditions. Progressively older veins are more strongly deformed into tight cylindrical fold structures rotated into parallelism with the lineation and foliation in the shear zone. Parallelism of veins to the foliation is partly due …
Exhumation of the lower crust during crustal shortening: an Alice Springs (380 Ma) age for a prograde amphibolite facies shear zone in the Strangways…
2000
Foliated garnet-bearing amphibolites occur within the West Bore Shear Zone, cutting through granulite facies gneisses of the Strangways Metamorphic Complex. In the amphibolites, large euhedral garnet (up to 3 cm) occurs within fine-grained recrystallized leucocratic diffusion haloes of plagioclase–quartz. The garnet and their haloes include a well-developed vertical foliation, also present in the matrix. This foliation is the same as that cutting through the unconformably overlying Neoproterozoic Heavitree Quartzite. The textures indicate syn- to late kinematic growth of the amphibolite facies mineral assemblages. All mineral assemblages record an arrested prograde reaction history. Notewor…
Metamorphic History of Gneiss Terrains
1990
The local metamorphic history is an essential topic in the study of high-grade gneiss terrains. This chapter only deals with those aspects of the metamorphic history that can be studied in the field. We will briefly outline terminology, the methods which can be applied, and the difficulties involved. For more information we refer to textbooks such as Miyashiro (1975), Winkler (1976), Mason (1981), Best (1982), Vernon (1983), Spry (1986), Yardley (1989) and to the references given in the text.
Strain analysis and vorticity of flow in the Northern Sardinian Variscan Belt: Recognition of a partitioned oblique deformation event
2008
Abstract A field example of strain partitioning has been analysed along the Nurra–Asinara transect of the NW Sardinian Variscan chain (Italy). The section in the Nurra–Asinara area is in a continuous sequence of tectono-metamorphic complexes made of low- to high-grade metamorphic rocks affected by a polyphase tectonic history. The principal fabric of the area is controlled by a D2 progressive deformation phase in which the strain is partitioned into folds and shear zone domains. The D2 stretching lineation and shear sense show a clear change from south to north. The principal meso- and micro-structures, vorticity gauges and a quantitative kinematic analysis of local strain suggest that the …
Experimental analysis of cross-sectional flow motion in a large amplitude meandering bend
2010
Flow in meandering bends is characterized by the formation of a large cross-sectional central-region circulation cell. The width-to-depth ratio is one of the most important parameters affecting the entity of the cross-circulation motion. In steep outside bends, beside the central-region cell, a counter-rotating circulation cell often forms in the upper part of the outer-bank. In spite of its practical importance, the evolving mechanisms of both the circulation cells and their role on boundary shear stress distribution in bends are not yet fully understood. The aim of the present paper is to gain some insight into how cross-sectional flow motion evolves along meandering bends. Experiments ha…
Sheared colloidal crystals in confined geometry: a real space study on stationary structures under shear.
2003
We constructed an optical plate-plate shear cell suitable for the study of aqueous suspensions of charged colloidal spheres under low electrolyte concentrations (10(-6) M). The variable gap height was adjusted to 30 microm corresponding to 15-30 interparticle distances. The concentration of 300 microm diameter polystyrene spheres was chosen around 1 microm(-1) where previous studies had revealed the equilibrium structure to be fluid or body centred cubic. Under shear, layer structures of hexagonal symmetry form, often coexistent with a fluid phase. We used an adapted high resolution video microscope to perform a detailed study of the structure. The central ray of light was prevented from en…
Shear bond strengths of composite resin and giomer to mineral trioxide aggregate at different time intervals
2017
Background The efficacy of the bond between the restorative materials and the pulp capping materials has an important role in the success of vital pulp therapy. Therefore, the aim of this study was to evaluate the shear bond strength of composite resin and giomer to MTA at different time intervals after mixing of MTA. Material and methods Ninety cylindrical MTA samples were prepared and assigned to two groups (n=45) based on the restorative materials used (composite resin or giomer). Each group was subdivided into 3 subgroups (n=15) based on the evaluation intervals (immediately, 2.45 hours and 3 days after mixing MTA). After the bonding procedures, the shear bond strengths of the samples w…