Showing 128 results for Char
Davar Khalili, Abolghassem Yousefi,
Volume 2, Issue 3 (10-1998)
Abstract
Physiographic characteristics of Atrak Watershed described by a number of parameters were used in regression models to estimate maximum daily discharges. These parameters were sub-watershed area, main waterway length, mean waterway slope, mean watershed elevation and mean watershed slope. Based on the results of correlation between the above parameters and their suitability for discharge estimation, three regression models were developed for further analysis. Model 1 applied area as the independent variable to estimate maximum daily discharge. In model 2 area and mean watershed elevation were the independent variables. Model 3 used area and mean waterway slope as the independent variables. Even though the results of testing did identified all three models as appropriate for application, further testing selected model 1 as the most appropriate. Recommendations were made for model application to similar watersheds lacking the necessary data.
G.h. Tahmasebi, D. Qujeq, R. Ebadi, M. Akhoundi,
Volume 3, Issue 4 (1-2000)
Abstract
An important and fundamental step in breeding honeybees is the separation of honeybee populations in Iran. During the years 1992-1996, several research works were directed towards the investigation of genetic populations of the Iranian honeybee (Apis mellifera L.), using biochemical methods. For this purpose, samples of worker bees were taken from 251 colonies of 115 apiaries in 84 cities in 21 provinces. The biochemical studies were conducted on thoracic proteins of worker bees using the horizontal electrophoresis.
The thoracic proteins of worker bees from the north and east populations isolated by electrophoretic techniques lacked a protein band having molecular weight of about 100,000 daltons. The results obtained from morphological and biochemical techniques and segregation of populations, indicate that breeding centers can be established in northern as well as western and central regions of Iran to improve genetic potentials of Iranian honeybee population.
M. Mostajeran, M. A. Edriss, R. Ebadi, G. H. Tahmasebi,
Volume 4, Issue 1 (4-2000)
Abstract
In order to estimate the heritability of morphological characters of worker honey bee and honey yield, 30 queen-mothers were selected randomly from the apiary of Research Center of Animal Science and Natural Resources in Isfahan Province. From each queen-mother, five queen-daughters were reared and introduced to equalize colonies after natural mating of queens. Summer honey yield was measured, while fall honey production was calculated from area of sealed honey combs. The total honey was calculated by adding summer honey production to fall honey production. Morphological characters were measured under a stereo-dissecting microscope fitted with a calibrated micrometer reticle according to Ruttners method (1985).
Heritabilities were estimated by intraclass correlation method. Heritabilities of summer, fall and total yearly honey yields were estimated to be 0.64, 0.51 and 0.30, respectively. Estimates of heritability of morphological characters for probscis length, tibia length, femur length, metatarsus length, metatarsus width, forewing length, forewing width, cubital index, hindwing length and number of hamuli were 0.64±0.08, 0.45±0.07, 0.50±0.07, 0.47±0.07, 0.33±0.06, 0.42±0.06, 0.89±0.10, 0.5±0.07, 0.94±0.10 and 0.45±0.07, respectively. It could be concluded that in order to increase honey yield in either season (summer or fall), selection must be based on the amount of honey yield in the corresponding season. Thus, heritabilities of forewing and hindwing lengths were high selection according to these morphological characters would, therefore, change the size of these characters.
S.s. Eslamian, V. Salimi, S. Chavoshi,
Volume 4, Issue 2 (7-2000)
Abstract
Peak discharge is one of the basic parameters in the design of hydraulic structures. There are various methods for peak discharge determination. Regional flood frequency analysis is based on physical, climatological and hydrological characteristics of basins. The objective of this study is to examine different models for the estimation of quantiles for some catchments in western Iran (namely: Gharehsoo, Gamasiab, Kashkan, Seimareh, Sezar and Abshineh) for which only maximum daily mean discharge data exist. In this research, peak and maximum daily mean discharges for 11 stream gauging stations were collected for a 21-year period. The ratio of these two discharges (R) and mean and standard deviations of peak discharges and maximum daily mean discharges were computed. Catchment characteristics including catchment area, catchment perimeter, main channel length, mean elevation, mean slope equivalent rectangle length, circular ratio, Gravelius coefficient, drainage density, time of concentration, relief ratio and diameter of the circle having equal area with the catchment were computed. Linear regression analysis was performed between independent variables of the catchments and mean standard deviation of the parameter “R” to develop a relation. The results of this study can be applied to the estimation of extreme flow values for non-recording stream gauging stations (daily reading sites).
M. Kalbasi, S.f. Mousavi,
Volume 4, Issue 3 (10-2000)
Abstract
Life in central Iran depends on the Zayandehrood river, making the preservation of its quality important. Salinization and pollution of the flow as a result of different organic and inorganic pollutants create serious threats to the environment and to the agricultural activities in the region. Although the role of the main drains discharged into the Zayandehrood in changing its quality is well known, little information is available on the volume and quality of the discharged drains. The purpose of this research was to study the quantity and quality of three main drains (Zoab-Ahan, Rudasht and Segzi) discharging into the Zayandehrood, Monthly samples were taken from each drain and their chemical properties were measured in 1998. The discharge rates were also measured simultaneously at sections near the discharge points.
The results showed that all three drains were alkaline and, therefore, had no negative effects on the pH of the river flow. Mean annual EC of Zoab-Ahan, Rudasht and Segzi drains were 5.56, 27.18 and 42.41 dS/m, respectively, and the salt loads discharged into the river by these drains were 39258.4, 37672.9 and 259781.2 ton/year, respectively. Annual mean N concentrations were 4.49, 3.92 and 4.18 mg/L and annual mean P concentrations were 0.26, 0.16 and 0.12 mg/L in the drains, respectively. The most important effect of the drains on the Zayandehrood was salinization, especially in the lower parts of the river. The increase in soluble salt contents of the river after Segzi drain discharge was so high that it made the water thereafter unusable for any purpose.
S.j. Khajeddin,
Volume 4, Issue 4 (1-2001)
Abstract
Astracantha adscendens is an endemic species in Iran growing on alpine and above alpine timberline habitats on the Zagross Mountain Range. These habitats are characterized by steep slopes, heavy snowfalls and long ice formation periods. The present study was carried out in Chelgerd, Bakhtiari, and Fereidan, Isfahan. Slopes, elevation above sea-level, and magnetic north azimuth were measured. The canopy cover was also measured along four radii in upward, downward, left and right directions. Regression analysis was performed for the measured values of plant and environmental factors.
The results revealed that the upward radius had a high negative correlation with slope changes while the downward radius showed no relationship with slope variations. The two left and right radii had a high and positive relationship with each other, both reducing in length as the slope steepness increased. Shrub volume decreases with increasing slope steepness. Plant shape was classified into seven groups using Sorenson similarity index and constructing the dendrogram. Snow pressure bends the stem toward the soil surface. Snow gliding pressure scratches stem and its base buds above the bent stem. Soil and debris move downward the slope as a result of snow gliding and rainfall runoff as well as wildlife and domestic animals. Snow gliding along with other natural factors have various effects on A. adscendens plant form which can be grouped under three categories: direct mechanical effect of snow, physiological effect of snow, and indirect effect of precipitation and wildlife. The environmental factors and plant physiological responses to them change the A. adscendens plant form from a funnel or ob-conical shape to a semi-funnel or semi ob-conical form.
M.a. Izadbakhsh, S.s. Eslamian, S.f. Mosavi,
Volume 5, Issue 2 (7-2001)
Abstract
Flood is one of the catastrophic events that has attracted the hydrologists’ attention. In this research one of the important flood indices, i.e. maximum-daily mean-discharge, was determined for several western Iran watersheds, namely, in the catchments of Gamasiab, Qarasou, Saimare, Kashkan, Sezar and Abshineh. Daily data were prepared from stream-gauging stations and a 30-year concurrent period was selected.
Flood frequency analysis was performed using HYFA and TR computer programs and optimum distributions were chosen by goodness of fit tests. Extreme flow values having different return periods of 2, 5, 10, 25, 50, 100, 500 and 1000 years were calculated. Modeling was done with regional analysis using multiple regression technique between maximum-daily mean-discharge and physiographic characteristics of the basins. The most important parameter for the selection of the model was the adjusted coefficient of determination while significant level, standard error and observed discharger vs. computed discharge plot acted as controlling parameters. Finally, different models with different parameters were selected from power, exponential, linear and logarithmic forms. The results showed the power model to be the best among the four types. The main channel length, drainage density and time of concentration were the most effective parameters on flow. After analyzing the errors, it appeared that increasing the return period would cause an increase in the model error. At 1000-year return period, the error reached 32.2%.
A. Hosseinpur, M. Kalbasi,
Volume 5, Issue 3 (10-2001)
Abstract
Potassium fixation and release by phillosilicate clay minerals in soils are very important processes influencing the availability of K to plants. This investigation was conducted to determine the potassium fixation capacity and charge characteristics of soil clays of 15 surface soils (0-30 cm) from central and northern Iran. After clay particle separation, both total and tetrahedral cation exchange capacity of soil clays were determined. Tetrahedral CEC was measured after saturation with Li and heating at 300 C to reduce octahedral charge to near zero. Potassium fixation was obtained in both wet (1:10 soil:solution, 16 h on a shaker) and dry conditions (after drying for 24 h at 70°C) using three different levels of added K
The total CEC in soil clays of Isfahan, Char-Mahal and Gilan provinces ranged from 22.1-36.0, 33.0-55.8 and 31.3-47.9 cmol kg-1, respectively. Tetrahedral CEC in soil clays of Isfahan, Char-Mahal and Gilan provinces ranged from 17.9-4504, 26.2-32.5 and 8.3-23.8 cmol kg-1, respectively, which consisted of 81.0-98.4, 58.5-95.8 and 24.7-72.5% of their total charge, respectively. The amount of K fixation increased with drying and the level of k added. Mean potassium fixation in soil clays of Isfahan, Char-Mahal and Gilan ranged from 5.42-9.13, 6.63-14.67 and 8.87-10.36, respectively. Mean potassium fixation by soil clays (except for soil clays of Gilan) best correlated with total CEC. In the soil clays of Isfahan, mean potassium fixation correlated with tetrahedral CEC, whereas no correlation was observed in soil clays from other places. The average amount of potassium fixation in clay fractions was in the order: Gilan clays > Char-Mahal clays > Isfahan clays.
F. Noorbakhsh, S. Hajrasuliha, G. Emtiazy,
Volume 5, Issue 3 (10-2001)
Abstract
The urease enzyme plays an important role in the efficient use of urea fertilizer and some environmental risk assessment. Urease activities in 20 different soil samples of arid to semi-arid regions of Isfahan Province were determined and their correlations with some soil physical, chemical and biological characteristics were studied. Urease activities range from 5.3 to 79.2 µg NH4
+ g
-1 soil 2hr
-1.
Results indicated that soil organic carbon was significantly correlated with urease activity (r=0.899***). None of sand, silt and clay percentages were significantly correlated with urease activity. Total nitrogen was significantly correlated with urease activity (r=0.797***). Electrical conductivity of saturated paste extracts were also negatively correlated (r=-0.499*) but sodium adsorption ratio (SAR), pH, equivalent calcium carbonate and cation exchange capacity failed to be correlated significantly with urease activity. No significant correlations were found between urease activity and total bacteria (on nutrient agar) or total fungi (on potato dextrose agar), but the bacteria that could colonize urea-agar media were significantly correlated with urease activity (r=0.47*). Multiple stepwise regression analysis showed that organic carbon accounted for most of the variation in urease activity.
E. Rowghani Haghighi Fard, M.j. Zamiri,
Volume 5, Issue 3 (10-2001)
Abstract
Three levels of urea (0, 0.5 and 0.75% on fresh weight basis) were added to whole corn plants to investigate their effects on the chemical composition, and digestibility in 16 Ghezel male lambs using a completely randomized design. Rumen degradability and nutritive values were also evaluated.
pH, total nitrogen and ammonia-N concentration of silages increased (P<0.05) with the addition of urea. Total nitrogen apparent digestibility was higher (P<0.05) with the urea addition. Nitrogen balance in ruminal fluid increased (P<0.05) with the addition of 0.5% urea. pH and ammonia-N concentration increased (P<0.05) with the addition of urea until 1.5 hr post feeding. Blood serum urea nitrogen concentration was higher (P<0.05) with the addition of urea until 6 hr post feeding. Potential degradability of dry matter and organic matter was higher at 0.5% urea level. Average daily gain increased with the urea addition and was highest (212.88 gr) at 0.75% urea. Subcutaneous fat depth was significantly (P<0.0l) lower for the sheep fed with 0.5% urea-treated silage as compared to other treatments. The results indicated that feed efficiency may be improved by urea addition and that the addition of urea (0.5% on fresh weight basis) may be recommended in order to increase the feeding value of whole corn plants.
M. Heidarpour, H. Afzalimehr, E. Khorami,
Volume 6, Issue 3 (10-2002)
Abstract
Of the many hydraulic structures developed by man, the weir is perhaps the oldest. Weirs are used for the measurement of discharge and regulation of water flow. The most common types of weirs are broad-crested, sharp-crested, circular-crested and cylindrical, and ogee crest weirs. Advantage of the circular-crested and cylindrical weir compared to the other weirs include simplicity of design, stable overflow pattern, larger coefficient of discharge and the associated lower costs. In the present study, potential flow around a circular cylinder are adapted to determine the velocity distribution at the crest section and to develop a model for coefficient of discharge (Cd) for circular-crested weirs. These results were evaluated using present test data for three types of weir models, namely, cylindrical, semicylindrical and semicylindrical with different heights and also Dressler theory. The results of the study showed that the experimental velocity profile agree very well with the theoretical profiles for the range of the study. Also, the prediction of the velocity distribution over the weir crest using Dressler theory is always less than the proposed model and measured data. The predicted values of coefficient of discharge (Cd) based on the proposed model agree well with Cd determined from direct discharge measurements. For the cylindrical model, the coefficient of discharge can be predicted from the proposed model within an error of –7% and for the semicylindrical and semicylindrical with different heights within ± 5%.
T. Honar, M. Javan, A. Keshavarzi,
Volume 6, Issue 3 (10-2002)
Abstract
Side weirs as flow diversion devices are widely used in irrigation, land drainage and urban sewage systems. In the present study, the effects of the length and height of inclined side weir crest on discharge coefficient were investigated in prismatic and nonprismatic rectangular channels.. In this study, 675 laboratory tests were conducted.
Analysis of experimental tests showed that the discharge coefficient is strongly correlated with uptream Froude number, height of weir to depth ratio at upstream of weir, ratio of water depth on weir to length of weir, and with prismatic factor. Based on experimental results, a model is proposed. The model is capable of estimating the discharge coefficient under subcritical flow conditions. Finally, the data from the proposed model was compared with those obtained by other researchers under different side and bed slopes. There was a good agreement with a relative error of less than ten percent.
S. M. Taghavi, M. Ziaee,
Volume 7, Issue 1 (4-2003)
Abstract
In order to compare Pseudomonas syringae pv. syringae (Pss) isolates from cereals, citrus, stone fruits and weeds by phenotypic characteristics, serological properties and pathogenicity, samples were taken during 1998-1999 in Fars Province, Karaj, Fereidan, Aligudarz and Shahrekord regions. From 350 fluorescent isolates, 47 were negative with respect to oxidase, potato soft rot and arginine dihydrolase tests but positive in hypersensitive reaction (HR) on tobacco, pelargonium, or both. In complementary biochemical tests, these isolates were identified as Pss. Based on LOPAT (levan, oxidase, potato soft rot, arginine dihydrolase and HR on tobacco leaves) tests, the isolates were divided into two groups, but based on the results of GATTa tests alone, isolates were divided into nine groups. Isolates from different hosts showed differences in lipolysis, syringomycin production, ice nucleation activity, lecithinase, pathogenicity, serology and protein profiles.
K. Etebari, M. Fazilati,
Volume 7, Issue 1 (4-2003)
Abstract
In order to investigate the effects of mineral compounds as complementary nutrients for silkworm, Bombyx mori, an experiment was performed in CRD with five treatments including: 1%, 5% and10% concentrations of multi-mineral mixtures (nitrogen, phosphorus and potassium) with normal and distilled water treatments as controls. The larvae were fed by mulberry leaves from Shien Ichenoise variety up to the fourth instar. From the beginning of the fourth instar, the supplementary leaves were used once a day. The supplementation of the leaves was done by spraying the solution on them. The amount of total protein and uric acid in haemolymph of a 6-day 5th instar larva was measured. The value of total protein compared to controls had significantly increased in all mineral treatments. The larvae's weight on the third day of the fifth instar had significant difference from controls, but the weight of silk gland did not show such a difference. However, uric acid of insect's blood demonstrated little differences but it showed no statistical significant differences from that in controlled insects. Despite this, the weight of cocoon, cocoon shell and pupa also had significant differences compared to controls, where this enhancement was higher in females than in males. Due to increase of the number of eggs, statistically there was a significant difference between the 10% treatment and others. The compounds had decreased the hatching percentage.
M. Chorom, C. Jafari,
Volume 7, Issue 2 (7-2003)
Abstract
Environmental pollution is one of the major problems for humans and animals. Radioactive wastes and heavy metals are important sources of pollution. Recent studies suggest that soil and geomedia have a high potential for the disposal of radioactive wastes and heavy metals. The clay minerals in geomedia can act as a barrier against radioactive wastes and heavy metals. However, enough information and experimental evidence about the mechanisms involved in the fixation of metals by clays are not available. This study aimed to show the effect of clay type on the fixation of cobalt and cadmium as affected by thermal energy. Increasing the temperature from 25 to 400°C decreased the CEC of clays in Ahwaz and Darab soils saturated with cobalt from 35.6 and 50.1 cmolc+/kg to 28.8 and 4.5, respectively. In cadmium clays, however, reductions in CEC were minimal (from 34.3 and 51.2 at 25°C to 32.5 and 47.7 cmolc+/kg at 400°C, respectively) compared to cobalt saturated clays. Consequently, the bonding characteristics change according to the size of the cations upon thermal treatment. The small cation, cobalt with an ionic radius of 0.68 Å, apparently migrates to the octahedral vacant sites and forms covalent bonds after heating at 400°C to become non-exchangable (fixed). The larger cation, Cd with an ionic radius of 0.97Å, apparently does not migrate into lattice sites on thermal treatment and remains exchangeable.
R. Mohammadi, A. F. Mirlohi,
Volume 7, Issue 2 (7-2003)
Abstract
A symbiotic relationship exists between the endophytic fungi of the genus Neotyphodium and many cool-season grasses. Endophytes can alter the growth as well as morphological and physiological characteristics of the host plant, thereby influencing the persistence and survival rate of infected plants. This study was conducted to evaluate the effects of endophyte on phenotypic characteristics of Iranian tall fescue (Festuca arundinacea Schreb.) and meadow fescue (Festuca pratensis Huds.). The experiment was set up as a completely randomized design with three replications in a factorial arrangement. The first factor was the two plant accessions and the secondary factor was the endophyte-infected and noninfected plants. The results showed that most of phenotypic characteristics significantly altered as a result of endophyte infection in both tall fescue and meadow fescue plants. Results of analysis of variance showed that the influence of endophyte fungus was positive and significant on tiller number, herbage yield, dry crown weight, dry root weight per plant, and crown depth. Also between plant accessions, there were significant differences for dry herbage yield, crown weight, dry root weight per plant, crown depth, and dry matter percentage. Plant by endophyte interaction was highly significant for crown depth and dry root weight per plant. Therefore, eudophytic fungi can be used to improve phenotypic characteristics in these plants.
D. Ataii, M. A. Sahari, M. Hamedi,
Volume 7, Issue 3 (10-2003)
Abstract
In this study, some physico-chemical characteristics of Iranian tea-seed oil (Lahijan variety) were compared with those of the oils from sunflower seed (Fars variety) and olive (Gilezeytoon variety) in terms of fatty acid contents, peroxide value, iodine value, saponification value, and oil shelf-life. Also the shelf-life of sunflower and olive oils containing 5% and 10% tea-seed oil were compared against control sample shelf-life. Tea-seed oil was found to be suitable and stable in nutritional properties. At a temeprature of 63oC, tea-seed and olive oils were found to have identical shelf-life values, which was higher than that of sunflower oil. Furthermore, the shelf-life of sunflower oil increased when mixed with tea-seed oil.
A. Ghazanfari-Moghaddam,
Volume 7, Issue 3 (10-2003)
Abstract
In order to increase the role of machine vision in agricultural research in Iran, especially for measuring physical attributes of seeds, a machine vision system was developed using a computer, a capture card, a video camera and a light box. All equipment was purchased from domestic markets. Computer programs were developed for hardware setup and for image processing applications. The programs perfomed tasks such as image acquisition and display, color conversion, image segmentation, object counting, and measurement of some physical attributes of the objects by analysing their images. The system was used to measure some physical attributes of pistachio nuts. The machine vision measurements were statistically compared with the measurements obtained by the conventional manual methods.
The results indicated that there was generally no significant difference between the two methods. However, the time consumed by the machine vision method was far less than the time taken by manual methods. The experimental results also showed that there were many sources of error and limiting factors in using machine vision for measuring physical attributes of seeds.
A. Kashi, S. Hosseinzadeh, M. Babalar, H. Lessani,
Volume 7, Issue 4 (1-2004)
Abstract
Watermelon (Citrullus Lanatus) cv. Charleston Gray is one of the most important cultivars grown in Iran. It has some good quantitative and qualitative characteristics but unfortunately is sensitive to Blossom End rot. To solve this problem, this experiment was conducted in a factorial manner in randomized complete block design with four replications in Research Station and Laboratories of Department of Horticulture, College of Agriculture, the University of Tehran, during 1997 & 1998. In this experiment, black polyethylene mulch was used and calcium nitrate was foliar sprayed at concentrations of 0, 4, and 6 g/L. Results indicated that mulch could increase yield by 85% over two years due to weed growth suppression and conserving soil moisture for a longer time. Foliage fresh weight, number and average weight of fruits per plant and precocity were also significantly affected by black polyethylene mulch. Furthermore, mulch reduced the number and weight of fruits affected by Blossom End rot by about 13% and 12.5% (average of two years), respectively. Calcium nitrate addition during both years had no significant effect on the measured fruit characteristics nor on Blossom End rot.
S. S. Eslamian, A. Zarei, A. Abrishamchi,
Volume 8, Issue 1 (4-2004)
Abstract
An approach for regional low flow frequency analysis is to use multiple regression techniques for obtaining relationships between low flows with specific return periods and catchments characteristics. In this paper, this method has been used. After single-site frequency analysis for 20 stream gauging stations, homogeneity test was performed. Regional relationships between low flows with return periods 2 , 5 , 10, and 20 years and catchments characteristics were derived.
For this purpose, catchment area, mean elevation, minimum elevation, shape factor, main channel length, length of main chanel from catchment centroid to outlet, forest area, mean annual rainfall, and mean catchment slope as model inputs were examined and cachment area, mean elevation, and mean catchment slope entered to the models. Finally, the mean relative error of models for different return period, 2, 5, 10, and 20 years, was computed 41.1, 41.3, 45.0, 47.2 percent, respectively that in comparison with other studies, it displays smaller errors.
