Self-similar structure of a hot magnetized flow with thermal conduction

We have explored the structure of hot magnetized accretion flow with thermal conduction. The importance of thermal conduction in hot accretion flows has been confirmed by observations of the hot gas surrounding Sgr $A^*$ and a few other nearby galactic nuclei. For a steady state structure of such accretion flows a set of self similar solutions are presented. In this paper, we have actually tried to re-check the solution presented by Abbassi et al. (2008) using a physical constrain. In this study we find that Eq 29 places a new constrain that limits answers presented by Abbassi et al. 2008. In that paper the parameter space in which it is established in the new constrain was plotted. However, the new requirement makes up only a small parameter space with physically acceptable solutions. And now in this manuscript we have followed the idea with more effort, and tried to find out how thermal conduction influences the structur of the disks in a physical parameter space. We have found out that the existence of thermal conduction will lead to reduction of accretion and radial and azimuthal velocities as well as the vertical thickness of the disk, which is slightly reduced. Moreover, the surface density of the disk will increase when the thermal conduction becomes important in the hot magnetized flow.Comment: Accepted for publication, AP

Effect of Freezing Stress on Lipid Peroxidation and Antioxidant Enzyme Activities of Olive cvs. ‘Fishomi’ and ‘Roughani’

Changes in freezing injury percentage, lipid peroxidation (malonaldehyde formation), antioxidant enzymes activity and proline content were monitored in the leaves of olive cvs. ‘Fishomi’ and ‘Roughani’ under different freezing temperatures (-5, -10, -15 and -20°C for 10 h). The results showed that freezing injury (determined by electrolyte leakage analysis) and malonaldehyde (MDA) content of cv. ‘Fishomi’ were significantly lower than of cv. ‘Roughani’ ones. The activities of peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and polyphenol oxidase (PPO) enzymes of cv. ‘Fishomi’ were signifi cantly higher than those of cv. ‘Roughani’. However, superoxide dismutase (SOD) activity of cv. ‘Roughani’ was higher than of cv. ‘Fishomi’. The proline accumulated in leaves of cv. ‘Fishomi’ was significantly higher than of cv. ‘Roughani’ during freezing stress. The results demonstrated that freezing injury percentage was positively correlated with ion leakage percentage and MDA content in both cultivars. In contrast, SOD, APX and CAT activities and also proline content were negatively correlated with freezing injury percentage. There was a significant negative correlation between PPO activity and freezing injury in cv. ‘Fishomi’. It can be concluded that the lower freezing injury percentage, ion leakage, and MDA content followed by the higher antioxidant enzyme activates as well as proline content in cv. ‘Fishomi’ is a consequence of more effective protective mechanisms

Acer velutinum Bioss. (velvet maple) seedlings are more tolerant to water deficit than Alnus subcordata C.A. Mey. (Caucasian alder) seedlings

Drought stress is a major environmental factor limiting plant growth. Selection of drought-tolerant plants is of critical importance in vegetation restoration and forestation programs. Alnus subcordata and Acer velutinum are two valuable, dominant, and endemic species in the Hyrcanian forests. There are fast-growing species and significant diffuse-porous hardwood in afforestation and reforestation. One-year old seedlings of both species were exposed to four water shortage treatments (100, 75, 50 and 25% of field capacity (FC) chosen as control, mild, moderate, and severe) for 12 weeks. Thereafter, their morphological characteristics such as height and basal area, total and organs biomass (root, stem, and leaf), leaf area (LA), specific leaf area (SLA), leaf area ratio (LAR), as well as physiological and biochemical characteristics such as relative water content (RWC), content of chlorophyll, free proline and malondialdehyde (MDA), and superoxide dismutase (SOD) and peroxidase (POD) activity were measured. The results showed that when exposed to reduced water availability, plants’ height, basal diameter, total and organs biomass, LA, LAR, RWC and chlorophyll content decreased, but their proline concentration, MDA content, SOD, and POD activity increased in both species. The root to shoot ratio (R/S) and root mass ratio (RMR) increased at 50 and 25% FC treatments in A. subcordata, whereas no significant difference was found in A. velutinum under drought treatments. SLA increased significantly at 50% FC in A. velutinum and decreased in A. subcordata under drought treatments compared to control treatment. A. velutinum showed more proline content, RWC, POD, and lower increase in MDA content than A. subcordata under moderate treatment. Therefore, A. velutinum appears to possess a better mechanism to cope drought stress. The drought tolerance of A. velutinum may enhance its potential for climatic adaptations under drier conditions with the ongoing climatic change