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Showing 2 results for Bazrgar
Mohammad Javad Bazrgar, Mojtaba Dehghan Menshadi,
Volume 17, Issue 4 (6-2017)
Abstract
In during take-off and landing phases, flow structures and aerodynamics forces differ from the unbounded flow field. Computational fluid dynamics were used to study the flow field of a cranked kite wing with the focus on studying vortices treatment. Different Angles of attack and heights at free stream equal to 70 m/s were investigated at Mach number 0.2. Q-criteria shows that in ground effect, vortices treatment is at angles of attack 2° similar to 0° and angle of attack 8° similar to angles 4° and 6°.According to the topology of pressure gradient vectors at the angle of attack 2°, the center of all vortices in ground effect is fixed approximately. Axial residual vorticity, axial velocity and induced suction of all vortices increase and isosurfaces of Q-criteria become thicker. At the angle of attack 8° with height decreasing, axial residual vorticity of the primary vortex and the wing kink location vortex increase and decrease respectively. Also, the kink location vortex approach to the primary vortex and it takes away from the wing surface. At the angle of attack 8°, the coherent structure of vortex between leading edge and the kink location vortex breakdown in ground effect and recirculation bubble form on the wing surface. With height decreasing, the most drag and the lift coefficients increment occur on the lower surface.
Volume 23, Issue 2 (Spring 2020)
Abstract
Aims: Vitrification affects intracellular calcium, fertilization ability, and developmental competence of mammalian oocytes. This effect may be more closely associated with an intracellular calcium rise induced by cryoprotectants. The present study aimed to assess whether reducing calcium of vitrification solution could improve the fertilization and developmental competence of ovine oocytes.
Materials & Methods: COCs were collected from the ovine ovary. MII oocytes were divided into 5 groups, one non-vitrified (control) and four vitrified groups 24 hours after COC culture. Vitrified groups were designed according to the presence or absence of EGTA (a calcium chelator) and/or calcium in base media, including mPB1+ (modified PBS with Ca2+), mPB1- (modified PBS without Ca2+), mPB1+/EGTA (mPB1+ containing EGTA), mPB1-/EGTA (mPB1- containing EGTA). Fertilization rate and in vitro development were evaluated after embryo thawing. Also, blastocyst quality was assessed using differential staining. Data analysis was carried out using one-way analysis variance.
Findings: There was no significant difference in the viability rate between vitrified groups. Fertilization and the developmental rate decreased in the presence of calcium (p<0.05) but in the calcium-free medium with the EGTA supplementation group, the developmental rate obviously increased. On the other hand, blastocyst cell count in the control group was similar to vitrified groups.
Conclusion: Using a calcium-free cryoprotectant by adding EGTA can improve the quality of vitrified-thawed ovine MII oocyte and also a higher developmental rate in obtained embryos.
