Showing 5 results for طوق
Z. Banihashemi, A. Sartipi,
Volume 8, Issue 3 (10-2004)
Abstract
Distribution of Phytophthora species associated with stone fruits decline in Fars was investigated. Of 36 isolates of Phytophthora recovered, 23 were identified as P. cactorum (mostly from infected crown) from almond, apricot, and peach and 13 isolates of P. nicorianae from crown and basal stem of almond and apricot from different environmental conditions. The reactions of crown and root of 6- month–old local almond cultivars, i. e., Mamaee, Moheb-Ali, Talkheh e- Najafabad (Isfahan Province), Talkheh Sadeh, and Sang Talkheh Riz from Neiriz (Fars Province), peach cultivar bitter pit and apricot cultivar Hallander from Isfahan to a virulent isolate of P. cactorum were evaluated under greenhouse conditions. The inoculum of the pathogen was obtained by growing on vermiculate – hemp seed extract for 4-6 weeks and positioned around either crown or root system. Plant height, root and total weight of plants, lesion size, plant mortality, and percentage colinization of the pathogen on root and stem base were determined. The results indicated that almond cv. Mamaee was the most susceptible and almond cv. Talkheh-e-Najfabad, peach cv. bitter pit and apricot cv. Hallander were the most resistant rootstocks to P.cactorum. Comparative reactions of root and crown of various rootstocks to P. cactorum showed that although inoculation site (root or crown) in most cultivars was not significant to most characters measured, the interaction of cultivars × site of inoculation became significant for certain characters such as plant height, lesion size, root and total plant weight and mortality, indicating different reactions by root and crown to P. cactorum in some cultivars.
D. Safaee, S.m. Okhovat, G.h. Hedjaroude , H. Younesi,
Volume 12, Issue 43 (4-2008)
Abstract
In order to diagnose form species of Bipolaris involving root and crown rot of wheat plants and determine their distribution, frequency and disease severity, 410 wheat fields (W. Fs.) in different regions of Kermanshah province were sampled at seedling, tillering and heading stages during three crop years (1997– 2000). Also 90 W. Fs. (30 per year) in different regions of the province were chosen randomly to estimate percentage of infected wheat plants. For the isolation of the fungi from tissues of root, subcrown internodes, crown and foot, the tissues were surface sterilized and placed on culture media. The results showed that there were some root and crown rots in the most regions of the province and the percentage of diseased plants was 0-24%, whose average was 3.2%. Forty three isolates belonging to form genus Bipolaris were isolated including form species B. sorokinina, B. cynodontis and B. spicifera. All three form species were pathogenic under greenhouse conditions. Disease severity and frequency of B. sorokinina were more than the others. Disease severity of B. cynodontis and B. spicifera was the same and their differences compared with the control were significant.
A. Masjedi, M. Gholamzadeh Mahmoodi,
Volume 15, Issue 55 (4-2011)
Abstract
Every year river flooding causes serious damage to the bridges at the time needed most. One of the most effective factors causing bridge failure is scouring around the piers in a river bend. One of the methods to decrease scouring around the bridge piers is fitting them with a coller on the piers. The collars protect the river bed against vortex flow in the vicinity of the pier base. An experiment was conducted to study lab flumes made of Plaxiglass with a 180 degree bend and 2.8 m central radius and a 0.6 m width. In this study, a 6cm diameter pier was placed with a circular collar with four different collar sizes in one position in bend with constant discharge and depth under clear-water conditions. The collar was placed at four different elevations. The soil material had a diameter of d50 = 2mm and geometric standard deviation of σg = 1.3. The results of the model study indicated that the maximum depth scouring was highly dependent on the experimental duration. It was observed that as the size of a collar plate increases, the scour decreases. So, minimum depth of scour is dependent on the 3D coller and -0.1D elevation. Circular collar results in maximum reduction in scour depth (93%) compared with no circular collar.
P. Shojaei, D. Farsadizadeh , A. Hoseinzadeh Dalir,
Volume 15, Issue 57 (10-2011)
Abstract
Submerged vanes are low aspect ratio flow-training structures mounted vertically on the river bed at an angle to the prevailing flow. The aim of application of vane is to generate a secondary circulation in the main flow, designed to modify the near-bed flow pattern and thus redistribute flow and sediment transport within the channel cross section. Collar is a flat sheet with low thickness fixed vertically on the pier at stream bed level or near it. Installation of a collar leads to protect the river bed against the direct impact of downflow produced at the upstream face of the pier and therefore reduces the scour depth. This research is a laboratory study that examines the effectiveness of submerged vanes and combination of submerged vanes and collar as a pier scour protection device. Experiments were conducted in an 8 m long and 0.8 m wide flume and a cylindrical pier used was 6 cm in diameter. Clear-water scour tests with u*/u*c = 0.9 were performed with a collar 3 times wider than the pier diameter at the stream bed level and submerged vanes 1.5 times longer than the pier diameter at the stream bed level (H=0). Different arrays of vanes with different angles to main flow direction were employed. The highest reduction in the depth of scour hole with four vanes and a collar showed 61% reduction in scour depth.
