Toxic Effects of Lead on Growth and Some Biochemical and Ionic Parameters of Sunflower (Helianthus annuus L.) Seedlings

Abstract: Lead (Pb) is one of the non essential and toxic heavy metals which can cause oxidative stress in plants. The effects of Pb(NO 3 ) 2 toxicity on growth and some biochemical parameters of record cultivars of Helianthus annuus L. were studied under hydroponic condition. Different treatments of Pb(NO 3 ) 2 [control (0), 200, 400, 600 and 800 :M] were used in order to consider changes in dry weight, proline and Pb accumulation in roots and shoots; Total chlorophyll, enzyme activity (catalase and peroxidase) and K + , Ca 2+ amounts of leaves. Compared with the control, Pb treatment caused a significant decrease in roots and shoots dry weight, leaves chlorophyll, catalase activity and K + , Ca 2+ amounts. In contrast, a significant increase in proline and Pb accumulation of roots and shoots and peroxidase activity of leaves was observed in Pb treatments

The Effects of NaCl Stress on the Physiological and Oxidative Situation of Maize (Zea mayz L.) Plants in Hydroponic Culture

Abstract: The effects of NaCl salinity on biomass, Malondialdehyde (MDA), peroxidase (POD), Catalase (CAT), Na + , K + , Ca 2+ and proline in Zea mays L. seedlings were investigated under hydroponic condition. Seedlings were subjected to NaCl stress (0, 50, 100, 150 and 200 mM) for 14 days. A completely randomized design with four replicates for each treatment was used. Salinity stress affected on the growth and caused a reduction in root and shoot biomass. NaCl treatment caused a significant increase in root MDA content. NaCl at 100 mM and higher increased also the shoot MDA content significantly. Catalase activity of leaf was significantly increased at 100, 150 and 200 mM NaCl in comparison with the control. Peroxidase activity in leaf started to significant increase with the rise of NaCl content at 150 and 200 mM. The leaf Na + content, root and shoot proline concentrations increased with the increase in salinity stress. The leaf K + and Ca 2+ amounts were significantly decreased with the rise of salinity stress in comparison with control

Particle-laden Turbulent Wall-bounded Flows in Moderately Complex Geometries

Wall-bounded turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. The complex nature of the carrier and the particulate phase is elevated to a higher level when introducing geometrical complexities such as curved walls. Realising such flows and dispersed phases poses challenging problems both from computational and also physical point of view. The present thesis addresses some of these issues by studying a coupled Eulerian–Lagrangian computational framework. The content of the thesis addresses both turbulent wall flows and coupled particle motion. In the first part, turbulent flow in straight pipes is simulated by means of direct numerical simulation (DNS) with the spectrally accurate code nek5000  to examine the Reynolds-number effect on turbulence statistics. The effect of the curvature to these canonical turbulent pipe flows is then added to generate Prandtl’s secondary motion of first kind. These configurations, as primary complex geometries in this study, are examined by means of statistical analysis to unfold the evolution of turbulence characteristics from a straight pipe. A fundamentally different Prandtl’s secondary motion of the second kind is also put to test by adding side-walls to a canonical turbulent channel flow and analysing the evolution of various statistical quantities with varying the duct width-to-height aspect ratios. Having obtained a characterisation of the turbulent flow in the geometries of bent pipes and ducts, the dispersion of small heavy particles is modelled in these configurations by means of point particles which are one-way coupled to the flow. For this purpose a parallel Lagrangian Particle Tracking (LPT) scheme is implemented in the spectral-element code nek5000 . Its numerical accuracy, parallel scalability and general performance in realistic situations is scrutinised. The analysis of the resulting particle fields shows that even a small amount of secondary motion has a profound impact on the particle phase dynamics and its concentration maps. For each of the aforementioned turbulent flow cases new and challenging questions have arisen to be addressed in the present research works. The goal of extending understanding of the particle dispersion in turbulent bent pipes and rectangular ducts are also achieved.QC 20151118</p

Particle-laden Turbulent Wall-bounded Flows in Moderately Complex Geometries

Wall-bounded turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. The complex nature of the carrier and the particulate phase is elevated to a higher level when introducing geometrical complexities such as curved walls. Realising such flows and dispersed phases poses challenging problems both from computational and also physical point of view. The present thesis addresses some of these issues by studying a coupled Eulerian–Lagrangian computational framework. The content of the thesis addresses both turbulent wall flows and coupled particle motion. In the first part, turbulent flow in straight pipes is simulated by means of direct numerical simulation (DNS) with the spectrally accurate code nek5000  to examine the Reynolds-number effect on turbulence statistics. The effect of the curvature to these canonical turbulent pipe flows is then added to generate Prandtl’s secondary motion of first kind. These configurations, as primary complex geometries in this study, are examined by means of statistical analysis to unfold the evolution of turbulence characteristics from a straight pipe. A fundamentally different Prandtl’s secondary motion of the second kind is also put to test by adding side-walls to a canonical turbulent channel flow and analysing the evolution of various statistical quantities with varying the duct width-to-height aspect ratios. Having obtained a characterisation of the turbulent flow in the geometries of bent pipes and ducts, the dispersion of small heavy particles is modelled in these configurations by means of point particles which are one-way coupled to the flow. For this purpose a parallel Lagrangian Particle Tracking (LPT) scheme is implemented in the spectral-element code nek5000 . Its numerical accuracy, parallel scalability and general performance in realistic situations is scrutinised. The analysis of the resulting particle fields shows that even a small amount of secondary motion has a profound impact on the particle phase dynamics and its concentration maps. For each of the aforementioned turbulent flow cases new and challenging questions have arisen to be addressed in the present research works. The goal of extending understanding of the particle dispersion in turbulent bent pipes and rectangular ducts are also achieved.QC 20151118</p

Lagrangian Particles in Turbulence and Complex Geometries

Wall-dominated turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. The complex nature of the  arrier and the dispersed phase is elevated to a higher level introducing geometrical complexities such as curved walls. Realising such flows and particulate phases poses challenging problems both from computational and also physical point of view. The present thesis tries to address some of these issues Lagrangian computational frame. In the first step, turbulent flow in straight pipes is simulated by means ofdirect numerical simulation with a spectrally accurate code nek5000 to examine the Reynolds number effect on turbulent statistics. Adding the effect of the curvature to these canonical turbulent pipe flows generates Prandtl’s secondary motion of first kind. These configurations, as primary complex geometries in this study, are examined by means of statistical analysis to unfold the evolutionof turbulent characteristics from a straight pipe configuration. A fundamentally different Prandtl’s secondary motion of second kind is also put to test by means of adding the side-walls to a canonical turbulent channel flow and the evolution of various statistical quantities with varying the duct aspect ratios is discussed. After having obtained a characterisation of the turbulent flow in the geometries of bent pipes and ducts, the dispersion of small heavy particles is modelled in the bent pipe by means of point particles which are one-way coupled to the flow. For this purpose a parallel Lagrangian Particle Tracking (LPT) scheme is implemented in the spectral-element code nek5000. Its numerical accuracy, parallel scalability and general performance in realistic situations are scrutinised in various situations. Also, the resulting particle fields are analysed, showing that even a small degree of geometrical curvature has a profound impact on the particle concentration maps. For each of the aforementioned turbulent flow cases new and challenging questions have arisen to be addressed in the present and upcoming research works. Along with an improved understanding of the particle dispersion in the considered complex geometries, the current project is particularly intended to improve the numerical aspects of the current LPT module suitable for largescale computations.QC 20140226</p

Particle-laden Turbulent Wall-bounded Flows in Moderately Complex Geometries

Wall-bounded turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. The complex nature of the carrier and the particulate phase is elevated to a higher level when introducing geometrical complexities such as curved walls. Realising such flows and dispersed phases poses challenging problems both from computational and also physical point of view. The present thesis addresses some of these issues by studying a coupled Eulerian–Lagrangian computational framework. The content of the thesis addresses both turbulent wall flows and coupled particle motion. In the first part, turbulent flow in straight pipes is simulated by means of direct numerical simulation (DNS) with the spectrally accurate code nek5000  to examine the Reynolds-number effect on turbulence statistics. The effect of the curvature to these canonical turbulent pipe flows is then added to generate Prandtl’s secondary motion of first kind. These configurations, as primary complex geometries in this study, are examined by means of statistical analysis to unfold the evolution of turbulence characteristics from a straight pipe. A fundamentally different Prandtl’s secondary motion of the second kind is also put to test by adding side-walls to a canonical turbulent channel flow and analysing the evolution of various statistical quantities with varying the duct width-to-height aspect ratios. Having obtained a characterisation of the turbulent flow in the geometries of bent pipes and ducts, the dispersion of small heavy particles is modelled in these configurations by means of point particles which are one-way coupled to the flow. For this purpose a parallel Lagrangian Particle Tracking (LPT) scheme is implemented in the spectral-element code nek5000 . Its numerical accuracy, parallel scalability and general performance in realistic situations is scrutinised. The analysis of the resulting particle fields shows that even a small amount of secondary motion has a profound impact on the particle phase dynamics and its concentration maps. For each of the aforementioned turbulent flow cases new and challenging questions have arisen to be addressed in the present research works. The goal of extending understanding of the particle dispersion in turbulent bent pipes and rectangular ducts are also achieved.QC 20151118</p

Combined upper bound and slab method, finite element and experimental study of optimal die profile in extrusion

In this paper, a new combined upper bound and slab method is proposed for estimating the deformation load for cold rod extrusion of aluminum and lead in an optimum curved die profile. For the purpose of comparison, an optimum conical die that was already obtained by the authors, has also been selected and studied. The corresponding results have also been determined experimentally and by using the finite element software, ABAQUS. It is illustrated that the extrusion load in the optimum curved die during the deformation is considerably less than that in the optimum conical die.Peer reviewed: YesNRC publication: Ye

Experimental and numerical study of energy consumption in forward and backward rod extrusion

The primary concern in any metal forming operation is to produce the desired product with maximum die life and minimum die wear. These requirements are achieved when the required load and energy is minimised. In this paper, the extrusion energy is determined for the two optimal conical and curved dies, for aluminum and lead billets, in forward and backward extrusion, using FEM and by performing experiments. It is illustrated that the energy required to deform aluminum and lead billets in the optimum curved die is considerably less than that in the optimum conical die.Peer reviewed: YesNRC publication: Ye