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| 312. |
- Nabavi, Seyed Tohid, et al.
(författare)
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Inclined transpression in the Neka Valley, eastern Alborz, Iran
- 2017
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Ingår i: International journal of earth sciences. - : SPRINGER. - 1437-3254 .- 1437-3262. ; 106:5, s. 1815-1840
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Tidskriftsartikel (refereegranskat)abstract
- Three major nappes in the Neka Valley in the eastern Alborz Mountains of Iran allow the Cimmerian to present convergence following the oblique collision between Iran and the southern margin of Eurasia. This work reports the identification of an inclined transpression zone recognized by field investigations and strain analyses of the geometries of formations and detailed mesoscopic structural analyses of multiple faults, folds and a cleavage. The main structures encountered include refolded recumbent asymmetric fold nappes, highly curved fold hinges, in a transpression zone that dips 37 degrees to the NW between boundaries thrusts striking from N050 degrees to N060 degrees. The beta angle (the angle between the zone boundary and direction of horizontal far-field shortening) is about 80 degrees. The north-west and south-east boundaries of this zone coincide with the Haji-abad thrust and the Shah-Kuh thrust, respectively. Fold axes generally trend NE-SW and step to both right and left as a result of strike-slip components of fault displacements. Strain analyses using Fry's method on macroscopic ooids and fusulina deformed into oblate ellipsoids indicate that the natural strain varies between 2.1 and 3.14. The estimated angle between the maximum instantaneous strain axis (ISA(max)) and the transpression zone boundary (theta') is between 6 degrees and 20 degrees. The estimated oblique convergence angle (alpha), therefore, ranges between 31 degrees and 43 degrees. The average kinematic vorticity number (W-k) is 0.6, in a zone of sinistral pure shear-dominated inclined triclinic transpression. These results support the applicability of kinematic models of triclinic transpression to natural brittle-ductile shear zones.
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| 313. |
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| 314. |
- Pereyra, Ricardo T., 1974, et al.
(författare)
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Parallel speciation or long-distance dispersal? : Lessons from seaweeds (Fucus) in the Baltic Sea
- 2013
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 26:8, s. 1727-1737
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Tidskriftsartikel (refereegranskat)abstract
- Parallel evolution has been invoked as a forceful mechanism of ecotype and species formation in many animal taxa. However, parallelism may be difficult to separate from recently monophyletically diverged species that are likely to show complex genetic relationships as a result of considerable shared ancestral variation and secondary hybridization in local areas. Thus, species' degrees of reproductive isolation, barriers to dispersal and, in particular, limited capacities for long-distance dispersal will affect demographical structures underlying mechanisms of divergent evolution. Here, we used nine microsatellite DNA markers to study intra- and interspecific genetic diversity of two recently diverged species of brown macroalgae, Fucus radicans (L. Bergstrom & L. Kautsky) and F.vesiculosus (Linnaeus), in the Baltic Sea. We further performed biophysical modelling to identify likely connectivity patterns influencing the species' genetic structures. For each species, we found intraspecific contrasting patterns of clonality incidence and population structure. In addition, strong genetic differentiation between the two species within each locality supported the existence of two distinct evolutionary lineages (F-ST=0.15-0.41). However, overall genetic clustering analyses across both species' populations revealed that all populations from one region (Estonia) were more genetically similar to each other than to their own taxon from the other two regions (Sweden and Finland). Our data support a hypothesis of parallel speciation. Alternatively, Estonia may be the ancestral source of both species, but is presently isolated by oceanographic barriers to dispersal. Thus, a limited gene flow in combination with genetic drift could have shaped the seemingly parallel structure.
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| 315. |
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| 319. |
- Suchorzewski, Jan, et al.
(författare)
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Size effect at aggregate level in microCT scans and DEM simulation – Splitting tensile test of concrete
- 2022
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Ingår i: Engineering Fracture Mechanics. - : Elsevier Ltd. - 0013-7944 .- 1873-7315. ; 264
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes an experimental and numerical study of size effect on concrete cylindrical specimens in splitting tensile test. Own experimental campaign was performed on specimens with 5 various diameters from D = 74, 105, 150, 192 and 250 mm with hardboard loading strips (distributed load according to standard methods) scaled proportionally to the specimen diameter. The crack opening-control system was applied to obtain the post-peak behaviour of all tested specimens including catastrophic behaviour (snap-back). The tested specimens at a certain point were unloaded and scanned with novel high-resolution micro tomography to analyse the macro cracks and phenomena like aggregate breakage, crack branching etc. at the aggregate level. Based on realistic mesostructure the discrete element method (DEM) 2D model of 3 specimens with diameters of D = 74, 150 and 250 mm were constructed and tested. The fracture was analysed at macro and micro-level in DEM and directly compared with microCT scans. DEM simulations revealed additional information related to the loss of material strength and ductility with increasing specimen size (size effect). The simulation and experimental results were in good agreement. © 2022 The Authors
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