فهرست مطالب n. valaie

Cropping history can affect our knowledge about the compositions and diversity of weed communities in the soil. Weed Species composition and density are influenced by farming practices and vary from field to field and among areas within fields. Plants that escape control and produce seeds within the field can be considered as a major source of seed entering the soil. Crop rotation is an effective weed management tool which can change weed distribution pattern by increasing selection pressures. Two types of rotation including corn-winter wheat and fallow-winter wheat are the most common cropping systems in arid and semi-arid areas of Iran. The multiple tillage operations can affect the vertical distribution, germination and emergence of weed seeds in the soil. Weed seed bank density, species composition and diversity will change when crop management practices are altered.

A field experiment was conducted to evaluate the effects of corn-wheat and fallow-wheat crop rotations on weed seed bank dynamics and seedling population during 2016-2018 growing season at Shiraz University. The fields divided into 10 by 10 meter grids. Soil samples were taken from 0-15 and 15-30 cm depths by soil sampler (auger) with 10 cm diameter. These samples collected after seedbed preparation and before crop sowing from 144 points. The samples of each depth were mixed together, placed in black plastic bags, and transferred to the laboratory. Then, 250g of the total soil was weighed and separated. These samples was placed in silk bags and washed with low water pressure. Finally, weed seeds dried, identified and counted to the level of species using a binocular stereomicroscope. Those seeds that were resistant to forceps pressure assumed as healthy seeds. Weed seedling population were calculated using a quadrat before and after application of herbicide at the same points were seed bank was carried out. Geostatistics technique was used to investigate density and spatial distribution of weed seedlings in two different crop rotations.

The highest frequency of weed seed bank belongs to Portalaca oleracea, Amaranthus retroflexus, Chenopodium album and Lamium amplexicaule. Relative density of P. oleracea and A. retroflexus seeds increased in corn-wheat rotation compared with fallow-wheat. The results showed that weed seed frequency was significantly affected by crop rotation and depth of plowing. As corn-wheat rotation had 33% increasing and fallow-wheat 19.44% decreasing of weed seed in 15-30 cm soil depth. The size of the total weed seed bank in corn-wheat caused a greater seed accumulation in the surface layer of the soil (0-15 cm). Weed seed density in corn-wheat rotation increased 89.79% and 62.85% in 0-15 and 15-30 cm, respectively during two years. Shannon diversity index increased by 12% in corn-wheat and decreased by 5.4% in fallow-wheat compared with the first year. Margalf index of corn-wheat rotation at 0-15 and 15-30 cm of soil depths decreased 33.70% and 38.25%, respectively, compared to the fallow-wheat rotation in the first year. Sorenson similarity index of corn-wheat and fallow-wheat at 0-15 and 15-30 soil depths was 0.82% and 0.80% during two years. The slope of linear regression also indicates that fallow-wheat weed seed bank (0.79) decreased more than corn-wheat rotation (0.47). Spatial distribution of weed seedlings showed that there is a large similarity in distribution patterns of total weed population between before and after herbicide application in two different rotations during the second year. However, distribution pattern of seedlings in corn-wheat rotation at the first year herbicide application was different after application of herbicide. Therefore, herbicide application can affect spatial distribution and number of weed seedling species.

Corn-wheat rotation as a high input level cropping system with deep tillage increases the size of the weed seed bank, especially in the soil surface layer (0-15 cm). While fallow-wheat rotation as a low input level cropping system causes a decreasing in weed seed bank dynamics, increasing in the diversity and richness of the seed bank and improving the soil structure by wheat residual on the soil during fallow system. The results of this study will be valuable in aiding the prediction of likely weed infestations in rotation systems. This ability to predict the size of weed seed bank, pouplation, diversity and emergence would also provide valuable input to population dynamics models that can be used in weed management.

Soil is one of the most important components of production, food security, self-sufficiency and national economy. Soil of semi-arid regions, which most of Iran's agricultural lands are located in these areas, are poor in terms of organic matter. The soil tillage operations are carried out by means of moldboard plow and removal of plant residue in most of the agricultural systems. This operation, called conventional tillage, requires not only high energy but also damages to soil physical properties and erosion in the long-term. Conventional tillage does not provide good environmental conditions to maintain moisture in the soil due to the impossibility of managing plant residue in the soil surface. In addition this tillage increases the evaporation and losses of soil water content and reduces the soil organic carbon as a result conventional tillage reduces the physical, chemical and biological characteristics of the soil. The objective of this study was investigation of effect of conventional and reduced tillage systems and management of tomato residue on soil water content, yield and yield components of wheat.

The experiment was conducted as split plot based on randomized complete block design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, during growth season 2017-18. Tillage system (in two levels i.e. conventional and minimum tillage) and tomato residue retention (0, 30 and 60%) were in main plots and sub plots, respectively. The sowing date was 11th November in 2017.Sampling was done at harvest time and included plant height, spike number.m-2, spike length, grain number per spike, 1000 grain weight, grain yield, biological yield and harvest index. During the growing season, soil water content in 0-20 and 20-40 cm depth was measured by the soil moisture meter (PMS-714 model) two days after irrigation. Data were analyzed with R software; obtained averages compared with Duncan’s multiple range test at the 5% probability level.

The results showed that the effect of tillage system was significant on soil water content in 0-20 cm depth two days after forth irrigation, soil water content in 20-40 cm two days after fifth, sixth and seventh irrigation, spike number.m-2, grain number per spike, grain and biological yield. Maximum of this traits were obtained in reduced tillage due to increased soil nutrition, improved physical condition of the soil and soil water status. However, the effect of management of tomato residue on any of the studied traits was not significant. This could be due to reducing microbial activity, in complete decomposition of plant residues and reducing available nitrogen.
The interaction effect between tillage system and tomato residue was significant on soil water content in 0-20 and 20-40 cm depth two days after forth and third irrigation, respectively, grain number per spike, 1000 grain weight and grain yield. Reduced tillage and 60% of tomato residue showed that maximum of soil water content and 1000 grain weight (38.4 g).Maximum of grain number per spike (61.9) and grain yield (7120. 7 kg.ha-1) were obtained in treatment of reduced tillage and 30% of tomato residue.
Conclusions  
The results of this study indicate that in order to achieve maximum grain yield and less damage to the physical and chemical properties of soil, the implementation of reduced tillage and maintenance of 30% of tomato residue is recommended in the studied area. In general, due to climate change and water resource constraints in the country, conservation tillage and residue management practices are a good way to maintain resources and sustainability.

Formation of microgaps between the fixture and abutment surfaces is still one of the major problems that may lead to mechanical and biological failure and inflammation around the implant. In this study, the effect of GapSeal on the prevention of liquid leakage and microgap in internal hex connection was investigated.

In this experimental study, sixteen internal hex implants (BioHorizons) were used in two groups. All implant-abutment assemblies were mounted in acrylic molds. GapSeal was inserted into the implants in the case group. All specimens were given a torque of 30 Ncm. Then, 1,200,000 cycles with a 100-N force and frequency of 1 Hz were applied to all samples. The samples were immersed in a methylene blue solution for microleakage evaluation. Microgap was randomly measured at six areas using scanning electron microscopy (SEM). Data were analyzed by SPSS 22 software using t-test.

The size of microgap was 3.04±0.54 µm in the control group and 0.99±0.39 µm in the case group, which was three times larger in the control group; the t-test showed that this difference was significant (P<0.000). In the control group, all samples (100%) showed leakage in the internal hex connection while in the case group, none of the samples (0%) showed leakage; Fischer's exact test showed that the difference was statistically significant (P<0.0001).

According to the results of this study, it can be concluded that GapSeal reduces microgap and microleakage in the case group compared to the control group.

Side effects of cigarette smoking are among the major concerns. These complications can adversely affect the oral environment. Since reduced salivary flow rate increases the incidence of tooth decay and other dental and oral problems, the present research aimed to investigate the relationship between cigarette smoking and salivary flow rate. In this historical cohort study, 50 cigarette smokers (case) and 50 non-smokers (control) were involved, who were matched according to age and gender. Non-stimulated whole saliva was measured by using the modified Schirmer test (MST) performed between 9 a.m. and 12 p.m. by a trained examiner. All the participants refrained from eating, drinking and smoking for 2 hours prior to the study. The subjects were asked to sit in an upright position and to raise and slowly retract their tongue, to avoid unintentional wetting of the Schirmer test's strip. The strip was kept vertically with the help of cotton pliers, while the bottom of the paper was in contact with the floor of the mouth. The length of the wet area on the strip was recorded at the intervals of 1, 2 and 3 minutes. Data were analyzed with Mann-U-Whitney and Chi-square tests. The quantitative value of salivary flow rate was equal to 24.8±2.4mm in controls, and 15.8±2.1mm in case group (P<0.001). 30% of non-smokers and 90% of smokers exhibited reduced salivary flow rate (P<0.000). It seems that reduced salivary flow rate is more significant in cigarette smokers than in non-smokers.

The ability of plants to reduce the negative effects of leaf removal or simulated herbivory on their growth is defined as their tolerance. Tragopogon graminifolius is a herbaceous perennial weed distributed around the world. To investigate the effect of leaf removals like 100% leaf removal, no damage (control), 50 % leaf removal at ten- leaf stage, 50 % leaf removal at twenty- leaf stage and 100 % leaf removal at twenty- leaf stage on its survival and final biomass of this plant, a greenhouse study was conducted during 2011 in completely randomized design. The results showed that the number of active leaves, number of flowers and seeds, number of branches and final height of T. graminifolius were significantly lower in “100% leaf removal at twenty-leaf stage” (P

Primary dysmenorrhea is a frequent entity with known side effects on life quality. Ginger has been shown to inhibit prostaglandins, thus, the present study was designed to compare ginger with mefenamic acid and ibubrofen for the treatment of primary dysmenorrhea in a group of students in dormitories affiliated to Isfahan and Shahid Beheshti University of Medical Sciences.

For this double-blinded clinical trial, 150 students with primary dysmenorrhea were enrolled. Subjects were matched according to dysmenorrheal severity, then, assigned in 3 equal groups of ginger (250mg), mefenamic acid (250mg), and ibubrofen (400mg) that were all prescribed 4 times a day for 3 days. Groups were matched according to the following criteria: age, age of menarche onset, weight, height, BMI, father’s position, maternal occupation and level of education, regular exercise, and duration, interval and amount of menses’ bleeding. Finally, verbal multidimensional scoring system was used to assess the efficacy of drugs on dysmenorrhea. ANOVA and chi square were used for data analysis.

Dysmenorrheal improvement did not differ significantly among ginger (64%), mefenamic acid (58%) and ibubrofen (66%) groups. Thus, ginger is as effective as mefenamic acid and ibubrofen in alleviating dysmenorrheal symptoms.

Ginger is an effective drug for alleviating primary dysmenorrheal symptoms.