فهرست مطالب m. aali

The present work aims to investigate the effect of the parameters of the laser machining process and laser line angle to injection direction of sample plastics on the electrical resistance of Polymethyl Methyl Methacrylate (PMMA)/Multi-Wall Carbon Nanotubes (MWCNT) Nano-composite. The laser machining process was performed on the samples considering a combination of power, feed rate, and laser line angle with respect to to the direction of melted flow parameters. According to the obtained results from electrical resistance and magnetic properties measurements, this was demonstrated that the laser line angle to the direction of melted flow does not statistically, and physically affect the electrical resistance of the composite. And increasing laser machining power leads to electrical resistance reduction. On another hand, feed rate enhancement (with fixed lasering power) causes increasing the electrical resistance. Moreover, this is found out that laser machining does not significantly affect the magnetic properties of the samples.

The aim of this study is to find the effect of the Parallel Tubular Channel Angular Pressing (PTCAP) technic as a Severe Plastic Deformation (SPD) method on microstructure and mechanical properties of as-extruded AZ61 magnesium alloy. The main reason to accomplish this research is to achieve certainty while this process could enhance the mechanical characteristics of magnesium alloy. To this end, the initial material was processed for one, two and three passes at 350 °C. Afterward, the microstructure was studied by optical microscope (OM) and scanning electron microscope (SEM). Next, to verify the mechanical properties alterations, tensile tests were performed for each specimen. Then, in order to investigate stress and strain status during the process, process simulations were fulfilled by employing the software Abaqus. Microstructure investigations revealed the fact that after just one pass, great grain refinement occurred within the material. Al4Mn as a secondary phase was noted for 1-pass, 2-pass and 3-pass processed specimens via scanning electron microscopy images and Energy Dispersive X-ray Spectroscopy (EDS) patterns. Finite elements method results illustrated the highest value of stress for the second half-cycle of the third pass. The maximum amount of strain tolerated by material belonged to the second half-cycles of the second and third pass. Finally, it could be reasoned that the best properties achieved for the 2-pass processed specimen possessed the best strength and deformability values.

Oxylipins the products of fatty acid oxidation, to acclimate biotic and abiotic stresses. In this study, we evaluate the effects of cold stress by measuring manlodialdehyde (as membrane damage index), the activity of lipoxygenase (LOX) and allene oxide synthase (AOS) enzymes, the levels of transcript LOX, AOS and allene oxide cyclase (AOC) genes using quantitative reverse-transcriptase polymerase chain reaction (qPCR) under cold stress (4 C) in tolerant (Sel96Th11439) and susceptible (ILC533) chickpea (Cicer arietinum L.) genotypes. The data analysis revealed that under cold stress, MDA content significantly increased in both genotypes so that MDA content in susceptible plants was maximum on day 6 of cold stress ( by 57%) whereas in tolerant genotype, after an increase on day 1 of cold stress its content did not significantly change. Such increase in MDA content showed signaling role and induction of defense mechanisms in tolerant genotype. Under cold stress, the activity of LOX and AOS significantly increased in susceptible genotype compared to tolerant one. Therefore, the activity of AOS pathway, as main pathway of oxylipin was considered in chickpea under cold stress, indicating probably its role in creating jasmonates and induction of defense genes. The analysis of transcription level of LOX, AOS and AOC genes with REST software confirmed changes in oxylipin components. Thus degree of cold tolerance in tolerant plants was related with cell damages content and the activity of oxylipin pathway under cold stress.

The study of physiological and biochemical processes involved in cold tolerance can help breeders to produce tolerant varieties. In this study, H2O2, carotenoid, chlorophyll and ascorbic acid contents and antioxidative activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX), and some their isozymic patterns in two chickpea (Cicer arietinum L.) genotypes, Kabuli Sel96Th11439 and Desi 4322 during control (23°C), acclimation phase (10°C), cold stress phase (4°C) in acclimated plants after two and four days, cold stress phase (4°C) in non-acclimated plants after two and four days were investigated. Analysis of variance showed that there were a significant difference between genotypes and thermal treatments in most studied traits. By transferring acclimated plants to cold stress phase (4°C), the activity of SOD, CAT, APX and GPX increased whereas in non-acclimated plants, the activity of this enzymes decreased. Such results were confirmed by molecular indices like number, migration and intensity of isozymic bands. Cold stress phase (4°C) caused an increase of chlorophyll and carotenoid contents and a decrease of H2O2 content in acclimated plants compared to non-acclimated plants. Therefore, decreased levels of damage indices and increased capacity of defence systems can considered as main factors of cold tolerance in Kabuli plants compared to Desi plants.

In this study, accumulation of H2O2, malondialdehyde (MDA) (as cold-induced oxidative stress indicators), the transcript levels of dehydrin and beta-glucosidase genes (involved in metabolic responses) was evaluated in chickpea cv. Jam, using qRT-PCR during control, cold acclimation (CA), cold stress (CS), recovery, and freezing phases. Results showed the existence of wide range of genetic capacity in the cultivar to increase cold tolerance when environmental conditions change. Significant increase in H2O2 and MDA content during CA phase indicated that seedlings perceived cold signaling that resulted in remarkable increase in the transcript levels of dehydrin and beta-glucosidase genes as part of defense responses of plants. Balancing the expression of these genes and oxidative stress indicators showed the interplay between two major defense and injury pathways. During freezing phase, the higher transcript levels of these genes in acclimated plants compared to non-acclimated plants showed a more active role for plant cells. An incapability of defense machine in non-acclimated plants was a limiting factor determining the low potential of chickpea plants to freezing phase. It was suggested that adjustment and metabolic alterations like dehydrin and beta-glucosidase genes, especially after CA phase and, thereby, decrease in oxidative stress indicators, could be a reason for relative cold tolerance in chickpea.

In this study, the induced responses of acclimated and non-acclimated genotypes of bread wheat (Triticum aestivum L.) (Norstar) and durum wheat (Triticum turgidum L.) (Gerdish and SRN) to cold stress have been assayed by detecting electrolyte leakage index (ELI), malondialdehyde content (MDA) and the activity of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and guiacol peroxidase). Wheat genotypes showed different responses to thermal treatments (23 and -5°C). After exposing plants into cold stress, along with decreasing of damage indices the antioxidative activities increased particularly in acclimated plants so that the maximum and minimum activity of enzymes belonged to Norstar and SRN plants. Acclimated plants showed more readiness in facing up cold stress in Norstar plants compared to durum wheat so that the minimum damage indices and the maximum enzyme activities were observed. The results have shown a potent variety in the level and speed of cell responses in these genotypes. Simultaneous changes of damage indices (ELI and MDA results) and antioxidative activities showed that these enzymes accompanied with other defense mechanisms increased cold tolerance and/ or enhance plant survive in wheat and can cause plant recovery even after sever cold stress. The short-term cold acclimation increased genetic capacity in wheat genotypes so that the degree of tolerance in Norstar was higher than that of durum genotypes. Such defense and damage indices may be used as cold tolerance marker in evaluation of genotypes in a short-term cold stress profitably in a short time and low cost.

Plant responses to low temperatures have been created through cold acclimation process using gene expression regulatory mechanisms. In this research, the quantitative gene expression ratio of rubisco, as an important enzyme participating in photosynthesis and cell energy production, the peroxidation of membrane fatty acids as a damage index, and the changes in proline content as one of the cell protecting mechanisms in normal, acclimation, cold stress and recovery temperatures have been assessed. Our results have shown meaningful differences between thermal treatments in studied characteristics. Increasing Rubisco gene expression accompanied by low damage index and high membrane proline has revealed the importance of Rubisco as one of the effective genes in cell response processes. At the end of cold stress situation and by starting recovery phase, Rubisco gene expression increased which is a sign of decreasing membrane damage, surveying plant cells and stabilizing a new homeostasis in chickpea. All in all, this study showed that the regulation of Rubisco gene expression related with cell protecting agents and membrane damage and can be assumed as one of the important processes in tolerant mechanisms.

uring the composing process, microorganisms involved in degradation of agricultural and municipal waste are of great importance. Therefore, identification of beneficial microorganisms could play an important role in improving the quality of the produced compost. Fungi play an effective role in degradation of organic matter, So the objective of the present study was to isolate and characterize effective fungal strains during composting process. The fungi were isolated from mature compost in Isfahan Compost manufacture using serial dilution method. The enzymatic activities (lipase, amylase, cellulose, xylanase and protease) of the isolates were measured by qualitative and quantitative methods. Three isolates with enzyme activity were isolated and used for more detailed studies. The isolated fungal strains showed a wide range of different enzymatic activities. Molecular identification of the selected strains was performed based on PCR amplification and sequencing of a 1100 bp fragment of fungal 18SrDNA using M13R and M13F primers. Phylogenic studies revealed that the isolated fungal strains belonged to Aspergillus fumigates which are commonly exist in composting process. According to Municipal Solid Waste enrich cellulosic, starchy and protein compounds and these three strains have high potential of producing degradation enzymes, application of these fungal strains as accelerator in composting process (microbial booster) with different enzyme activities can transform wastes rapidly, then the efficiency of compost.

Alfalfa is one of the most important forage crops in the world. The west and northwest parts of Iran are the important regions for Alfalfa planting. Because few studies are available on the genetic diversity of this crop in the regions, therefore, the objective of this study was to determine the genetic diversity in 34 populations of alfalfa from west and northwest of Iran.These were analyzed using 10 microsatellite markers. Totally, 51 bands were obtained from which 45 bands were polymorphic corresponding to an average of 5 alleles per locus. The percentage of polymorphism with an average of 0.55 varied from 0.29 for MAL369471 to \0.8 for ENOD20 and also for MI with an average of 2.1 from 0.29 for MAL369471 to 4.01 for ENOD20. Chaharmahal va Bakhtiari province had maximum of both gene diversity and Shannon's Information index (He=0.19, I=0.29), while the minimum amounts (He=0.13, I=0.13) were obtained in Tehran province. Dendrogram constructed based on dissimilarity matrix grouped populations in two main groups; the first group belongs to populations from Karaj, while in the other populations were located in second group. The result showed that microsatellite markers are effective tools for evaluation genetic diversity in Iranian alfalfa populations. The results of this study provided useful information for the future collection and for the of genetic resource management in the regions.

We present a new model and a new approach for solving fuzzy linear programming (FLP) problems with various utilities for the satisfaction of the fuzzy constraints. The model, constructed as a multi-objective linear programming problem, has the significance to provide flexibility for the decision maker (DM), allowing for the assignment of distinct weight corresponding to each constraint and the objective function. A DM’s desired solution is produced by solving a crisp problem controlled by a parameter. We establish the validity of the proposed model and show the effect of the control parameter over the solution. We also show the effectiveness of the model and present three algorithms for solving the FLP problem. One algorithm computes a desired solution by solving a single crisp problem. The other two algorithms, interacting with the decision maker, each time compute a solution achieving a new satisfaction level. Finally, we work out an illustrative example showing that the solutions obtained are often more satisfactory than desired.