Showing 3 results for Environmental Factors
Volume 9, Issue 3 (10-2010)
Abstract
A study of flora and population changes in a sample paddy field in Kalat (Mashhad) were done from May to September 2007 in four stages. Physical and chemical factors such as EC, pH and temperature were measured. Totally, 23 species, 8 genera and 5 families were identified. The identified species were: Chroococcaceae: Chroococcus, Gloeothece, Aphanothece Oscillatoriaceae: Oscillatoria Rivulariaceae: Calothrix Nostocaceae: Cylindrospermum, Nostoc, Anabaena Scytonemataceae: Scytonema. Regarding the heterocystous species, the most abundant cyanobacteria belong to genus Nostoc. pH in 4 collection were alkaline and did not show significant difference. Colony number did not indicate direct relation with pH despite of EC. Maximum colony number was seen in minimum temperature.
Saeed Afsharzadeh, Shabnam Abbasi,
Volume 11, Issue 1 (10-2011)
Abstract
Abstract
Introduction of plant groups of Yahya Abad region and their relationship with environmental factors
The region of Yahya Abad is located at Southern slops of Karkas mountains with about 6000 hectare area, at 35 kilometer-SW of Natanz in Isfahan, is one of arid mountain ecosystems in Iran. The aim of the study is grouping the plant species and their relationship with various environmental factors such as elevation and soil characteristics. sampling carried out in systematic-random method with 1.5×2m quadrates and percentage of plants cover estimated. In this research different methods of Cluster Analysis and Ordination were performed in order to study of plant groups and their relationship with environmental factors. Cluster Analysis demonstrated eight plant groups and Different methods of ordination indicated the altitude factor as the main factor in the separation of plant groups. Due to relatively uniform topography and livestock's grazing in this region there wasn’t clear relationship between altitude and diversity indeces.
Keywords: Vegetation, Environmental factors, Cluster Analysis, Ordination, Diversity indeces
Rajabali Ebrahimi,
Volume 14, Issue 1 (4-2014)
Abstract
The present work was an attempt to investigate the parameters which can affect the process of hydrogel formation in the presence of ultrasound. These parameters were concentration of the reactants (monomers and cross linker), the reaction medium (solvent, ionic strength, and pH), and acoustic parameters (power and pulse). The monomers were acrylic acid and acrylamide, and the cross linker was methylene bis acrylamide. The experiments were performed at a constant temperature of 37 °C. Pulsed power ultrasound was irradiated to the reaction mixture from the tip of a probe system. The results showthatultrasonic irradiation significantly reduces the reaction time and increases efficiency. Additionally, increasing glycerol in the solution changes the viscosity of the reaction for the better and increases the reaction rate. However, ionic strength and pH were not significantly effective in this respect. Results showed that ultrasonic acrylic hydrogel are sensitive to pH and temperature. Therefore, these hydrogels is capable for rapid drug absorption and release according to porosity in their structure. These findings provide a better understanding of hydrogel synthesis and enable us to control the pertinent parameters.
