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Pyramiding genes related to grain quality and resistance through marker assisted selection (MAS) is an important approach in rice breeding programs. Marker-assisted selection can be used for monitoring the presence or absence of these genes in breeding populations and can be combined with conventional breeding approaches. This study is a part of cultivar development program in Iran through integration of conventional breeding with marker assisted selection. Crosses between two high yielding transgenic lines carrying an insect resistance gene (cry1Ab, from Bacillus thuringiensis) with a local aromatic variety were made followed by selection for incorporation of insect resistance and aroma (fgr) genes in desirable single F2 plants. Finally, plants homozygous for aroma and carrying cry1Ab genes with good agronomic performance were identified. Further analyses are underway on these plants in F3 generation. These plants promise to develop new aromatic Bt rice lines through integration of classical and molecular breeding in the near future in Iran

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Reactive powder concrete (RPC) represents a new generation of cement-based materials composed of cement, reactive ultrafine powders, siliceous fine aggregates, super plasticizers and fibers. Due to its microstructural properties, this concrete demonstrates specific properties including high compressive and flexural strength, superb durability. Since this is a novel type of concrete, a single design code containing multiple experimental results of high quality, together with reliable stress-strain models for the nonlinear analysis of the structural members made of this concrete type is lacking. Although some experimental equations to predict the strength of the RPC members can be found in the literature, note that there are shortcomings in the information provided specifically regarding the RPC containing synthetic and hybrid fibers. Hence, in this study, ten different mix designs of RPC, containing steel fibers at the volume fractions of 1, 2, and 3%, polyvinyl alcohol fibers at the volume fractions of 0.25, 0.5, and 0.75%, together with hybridizations of the two fiber types at the total fiber volume fraction of 1% were prepared, and then tested to obtain accurate and applicable equations as well as the compressive stress-strain curve with the purpose of estimating the mechanical properties and better predicting the behavior of this type of concrete. Then, the effect of the type and volume fraction of fibers, together with curing regime on the properties of RPC including the compressive strength, strain at peak stress, modulus of elasticity, and the shape of stress-strain curve was investigated. The obtained results indicate that as the volume fraction of steel and polyvinyl alcohol fibers increases, the compressive strength and strain at peak stress of the RPC specimens decreases; a trend which is also observed as the volume fraction of synthetic fibers in the concrete mix containing hybrid fibers increases.. The trend which is observed for the strain at peak stress in the RPC is very close to that for its compressive strength. The secant and tangential modulus of elasticity values of the RPC also demonstrate trends similar to each other, and the tangential modulus of elasticity in all the specimens has values higher than the corresponding secant modulus of elasticity. The RPC containing high volume fractions of steel fibers shows high modulus of elasticity values, due to the crimped shape of fibers as well as the strong cohesion they provide in the concrete. Heat treatment has a positive effect on the compressive strength and strain at peak stress of the RPC specimens, due to the acceleration of the hydration process of cementitious materials at high temperatures as well as the formation of a dense matrix. By using the nonlinear regression analysis of the data, experimental equations were developed for the parameters affecting the stress-strain curve of RPC. Finally, based on the experimental parameters obtained for all the RPC specimens, a model was proposed to predict the compressive stress-strain curve. By comparing the proposed model with the experimental results of the stress-strain curve of RPC, it can be said that the proposed model is capable of predicting the experimental results with a very good accuracy.

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Concrete -filled steel tube are widely used today in many civil engineering structures. The advantage of steel members is their high tensile strength and ductility and, on the other hand, concrete members have high compressive strength. Composite members combine steel and concrete, which have positive properties of both materials. In members under compressive loading, circular tube columns, for a given cross section area, have the large uniform bending strength in all directions in comparison to other cross-sections. Filling the pipe with concrete will increase the ultimate strength of the member without significantly increasing costs. On the other hand, the concrete in the tube delays the local buckling of the pipe wall. In this type of section, the outward buckling will reduce the amount of confinement, ductility and ultimate strength.
Subsea and offshore marine structures are mainly made of hollow steel circular sections, where water pressure reduces their load carrying capacity. By converting these sections to concrete filled tube, external pressure can improve the behavior by increasing the confinement. This paper tries to investigate the effect of external pressure on the ultimate strength of CFT, so that the use of this kind of composite sections in construction and retrofitting of marine structures would be investigated. This paper tried to evaluate the effect of lateral pressure on improving the behavior of concrete-filled steel tubes (CFT) by conducting laboratory studies. For this purpose, tri-axial testing set up, with capability of 400 bars pressure, was designed and constructed by the authors. Parameters such as lateral pressure, concrete strength and diameter to thickness ratio (D/t) of steel tube were tested.
Concrete with strength of 15 to 45 MPa was cast in pipes of 0.5 to 2 mm thickness and subjected to axial loading under external pressure between 0 and 150 bars. All specimens have a constant diameter of 100 mm and a height of 250 mm and are filled with ordinary concrete. All specimens have a diameter of 100 mm and a height of 250 mm and are filled with normal concrete. To evaluate effect of lateral pressure on the final strength, the ratio of d Parameters such as ultimate strength and failure mode of specimens along with their displacement load diagrams were investigated. Diameter to thickness in some samples was considered higher than the values proposed in the standards. Experimental tests results were compared with the relationships presented in the Eurocode 4 and AISC standards.
According to the calculations, the AISC standard result in conservative numbers compared to the EC4 standard for the ultimate strength of the specimen. External pressure has increased the loading capacity, as well as the ductility of the specimens by preventing the buckling and sudden crushing of the core concrete. Increase in load carrying capacity due to external pressure was up to 91% in some specimen. The effect of increasing on ultimate strength on the lower thickness specimens was significant. In conclusion, results of the experiments showed a significant effect of lateral pressure on the final strength of the CFT with normal concrete.

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An undesirable failure mode of a reinforced concrete beam is shear mode. Low tensile strength of conventional concrete and brittle crushing due to shear failure in reinforced concrete beams can be improved by adding adequate percentage of steel fibers. The combination of high and low elasticity fibers is capable of arresting macro- and micro-cracks. In fact, the bridging action of fibers on crack faces causes a strong limitation on opening of the crack. This phenomenon improves the aggregate interlock on the crack faces which results in increasing the shear strength of the cracked section. In order to accurately study the pull-out characteristics of crimped-steel fibers with end hook and to compare the results with the behavior of hooked steel fibers and crimped steel fibers alone, an experimental study was conducted. Pull-out load versus slip was thoroughly investigated in 25 specimens and parameters such as maximum pull-out force and its associated slip were taken into account for comparison purposes. The results indicated that the crimped-steel fibers with end hook have better performance in pull out test. In fact, the post-peak behavior of this type of fiber shows a slight drop in carried load. This increases the area under the load-displacement curve in comparison with the others. It can be predicted that cementitious composites reinforced with crimped-steel fibers with end hook would be more ductile than those reinforced with other fibers. In addition, the effect of modified polymer fibers along with different amounts of crimped end hook steel fibers on the mechanical properties of conventional concrete such as compressive strength and indirect tensile strength was studied. The modified polymer fibers were added into the mixes for arresting micro-cracks. 45 specimens were made in 5 groups and the volume fraction of polypropylene fiber was kept constant (0.25%). The volume fraction of steel fibers were selected in three ranges of 0.5%, 0.75%, 1.0%. Also a mix was cast without any fibers to be used for comparison purposes. The results of this study showed that by adding 0.25% polypropylene fibers and 1.00% crimped end hook steel fibers, 27.5% and 66.7% increase in compressive strength and indirect tensile strength are observed compared to conventional concrete. In all cases, by adding steel fibers with polypropylene fiber in the mentioned percentages, the fibers can show desirable performance in post-cracking behavior. Finally, the criteria of ACI 318-2011 for using this fiber reinforced concrete (without shear reinforcement) as the minimum shear reinforcement was investigated. The test is based on ASTM C1609 and it is applicable to the sections of a beam when the applied shear is less than the concrete strength from one hand but, on the other hand, it is greater than the half of that. It was found that this requirements is met in all proposed fiber reinforced concretes. It can be concluded that in such sections the cementitious composites studied in this paper can be utilized without accompanying any stirrups. In fact, the ductility required by ACI 318-2011 in this area can be provided with steel fibers, rather than stirrups.

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This study examines the chemical composition of the essential oil of Xanthium strumarium fruits, and evaluates its antioxidant and antimicrobial activities on various plant pathogens that commonly cause irreparable damages to agricultural crops. The essential oil of X. strumarium fruitswas analyzed by Gas Chromatography coupled to Mass Spectrometry (GC/MS). Antimicrobial activity was tested against 14 microorganisms, including three gram-positive, five gram-negative bacteria and six fungi, using disk diffusion method and the Minimum Inhibitory Concentration (MIC) technique. The X. strumarium fruitswere also subjected to screening for possible antioxidant activity by using catalase, guaiacol peroxidase, superoxide dismutase enzymes and 2, 2-DiPhenyl-1-Picryl Hydrazyl (DPPH) assay. Thirty six components were identified, representing 97.89% of the total oil, with methyl linoleate (40.64%), methyl oleate (13.12%), and methyl palmitate (12.43%) being the major ingredients. The essential oil showed significant activity against Rathayibacter toxicus (MIC= 25 µg mL^-1), and Pyricularia oryzae (MIC= 12.5 µg mL^-1). In addition, the analysis of free radical scavenging activities of the X. strumarium fruitsrevealed antiradical activity of 138.87 µg mL^-1 in DPPH, 32.766 µmole activity/mg protein in catalase, 5.567 mmol activity/mg protein in guaiacol peroxidase and 1.714 U mg^-1 protein in superoxide dismutase. Furthermore, the phytochemical analysis showed moderate to good amounts of alkaloid (0.54 mg g^-1), phenolic (54.44 mg g^-1) and flavonoid (20.11 mg g^-1) compounds in X. strumarium fruits. Our results suggest that this plant may be a potential source of biocide, for economical and environmentally friendly disease control strategies. It may also be a good candidate for further biological and pharmacological investigations.

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In Iran, thousands of tons of plastic and rubber materials are discarded as wastes each year. The accumulation of these wastes around metropolitan areas has become a major environmental problem for cities and countries across the globe. Thus, many efforts have been made in recent years to find ways to recycle waste plastic materials and eliminate them from the environment. In this regard, reusing recycled materials is a strategy to deal with this problem. Since these waste materials do not have a proper quality to be used for usual life purposes such as household items, thus the best application for these materials is to use them as aggregates in the construction industry. Furthermore, using waste rubber materials such as scrap tires in the concrete mix is regarded as one of the efficient ways to recycle these waste materials. In addition, substituting a fraction of natural aggregates in the concrete mix by waste materials is a promising strategy to deal with environmental problems associated with these materials. Given that the presence of waste aggregate in concrete degrades its properties, adding fibers to the concrete mix has been shown to improve the mechanical performance. Therefore, in the present study, the compressive strength of the concrete reinforced with steel fibers and containing recycled scrap tire rubber aggregate was evaluated after exposure to high temperatures through an experimental program. Here, a total of nine mix designs were prepared for the experimental phase, with the test variables being the volume percentage of tire rubber aggregate as a replacement for natural sand (0, 5, and 10%), the volume fraction of steel fibers (0, 0.5, and 1%), and temperature (20, 200, 400, and 600 °C). Moreover, the compressive strength values were compared with those predicted by the ACI 216 and EN 1994-1-2 codes. The results showed that adding steel fibers together with tire rubber aggregate in the concrete mix led to a decrease in the compressive strength of the heated and unheated concrete specimens. In addition, as temperature increased, the compressive strength of all the concrete specimens saw a considerable reduction. In this regard, after exposure to 600 °C, the compressive strength loss rate was higher compared to that after exposure to other temperatures, such that the compressive strength of the reference specimen and those containing tire aggregate and fibers decreased by 59.5-76.9% relative to that of the corresponding specimens at ambient temperature. ACI 216 and EN 1994-1-2 provide a relatively good estimation for the normalized compressive strength of all the concrete specimens containing tire rubber and steel fibers at 200 and 400 °C; however, they give an overestimation for the reference concrete. In addition, the above codes give a relatively good prediction for the normalized compressive strength of the specimens exposed to 600 °C (except for specimens ST0TR10, ST0.5TR10, and ST1.0TR5). Finally, by employing the response surface method (RSM), an optimum solution was proposed for the design parameters in which the compressive strength of the fiber-reinforced concrete containing recycled tire aggregate was maximized at different temperatures.
 

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Concrete-encased concrete-filled steel tube (CFST) has been presented to integrate reinforced concrete (RC) and CFSTs that have been used increasingly in high-rise buildings and bridges in the world. Concrete-encased CFST exhibits higher confinement of the concrete core, high stiffness and strength, better durability and ductility, small sectional size, higher fire resistance due to the protection of the outer RC encasement compared to CFST, avoidance of local buckling and corrosion of steel tube, and easier connection with steel RC beams. On account of the insufficient research and the unknown behavior of these beam types, in this research, prestressed concrete-encased CFST (PCE-CFST) beams that incorporate CFST in the compression zone to improve the strength of concrete, and prestressed strands in the tension zone to control cracks in reinforced concrete (RC) beams are numerically investigated. The objective of this study is the finite element analysis of parameters that are not feasible to be examined through experimental specimens. Hence, the experimental study has been done to validate the nonlinear finite element modeling and a full-scale model is constructed to explore the flexural behavior of the cross-section. The model is then developed to include parameters such as the longitudinal rebar ratio, prestressed strand ratio, core concrete ratio, and the steel tube ratio indices. Based on findings, a good agreement was observed in the moment-deflection diagrams and the failure modes between the experimental and numerical results. Then the model was developed and 9 PCE-CFST beams is modeled by finite element software of ABAQUS to investigation of longitudinal rebar ratio (0.0257, 0.00856, 0.00286), prestressed strand ratio (0.00228, 0.00912, 0.000569), core concrete ratio (0.0206, 0.07799, 0.0281), and the steel tube ratio (0.01385, 0.00615, 0.000385) indices. The beam specimens were subjected to four-point loading and the parameters of bearing capacity, moment-deflection curve, energy absorption, ductility, failure mode, bending stiffness were investigated. Examination of indices revealed that as the prestressed strand ratio increases, displacement ductility, flexural stiffness and ultimate moment increase by 1.47, 1.06 and 3.22 times, respectively. Further, the elastic and entire absorbed energy of cross-section escalate by 1.04 and 3.22 times respectively, with increasing prestressed strand ratio. Likewise, by increasing the index of longitudinal rebar ratio, flexural stiffness and ultimate moment are 1.18 and 1.22 folded, respectively. In addition, the elastic absorbed energy is increased by 2.85 times as the longitudinal rebar ratio increased. As the ratios of core concrete and steel tube increase, the flexural stiffness is reduced by 5% and 6%, respectively. While, by increasing the core concrete and steel tube ratios, the ultimate moment grow by 1.05 and 1.29 times, respectively. The only effective index on the cross-section ductility and the entire absorbed energy is the prestressed strand ratio. The longitudinal rebar ratio has also the greatest increasing impact on the flexural stiffness and the elastic absorbed energy. Moreover, the core concrete ratio has the least effect (less than 10%) on the flexural stiffness. The prestressed strand and core concrete indices have respectively the highest and lowest escalating effects on the ultimate moment. As a consequence, an increase in the prestressed strand and longitudinal rebar ratios lead to a rise in the flexural stiffness and ultimate moment. On the contrary, an increase in the steel tube and core concrete ratios, decrease the flexural stiffness and gives a marginal increase to the ultimate moment. It was also unveiled that the failure mode of full-scale beams is flexural, and shear crack and shear capacity govern the behavior of PCE-CFST beams with shear span-to-depth ratios of less than 2. As shear span-to-depth ratio increases, that is, the shear failure mode shifts to flexural, flexural stiffness decreases, yet the ultimate bending moment increases. Additionally, a strut-and-tie model was proposed to describe the load transfer mechanism of PCE-CFST beams.

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Concrete and steel are materials with extensive use in human construction activities. Concrete is a material with high stiffness which is less expensive than other available construction materials, and steel is a material with high strength and ductility. Steel-concrete composite structural systems have been utilized in the construction of high-rise buildings due to their superior structural behavior. Fibrous concrete-encased steel columns are one of the most important composite structural members in which the axial load is carried by the steel and concrete at the same time. These columns are attracting the interest of many researchers due to their excellent structural performance under both static and seismic loading conditions. The steel-concrete interaction enhances the performance when carrying monotonous and earthquake loading. Reinforcing steel fibers help control crack propagation and prevent brittle failure in concrete through improving aggregate interlocking and thus enhance the properties of concrete including the tensile strength and ductility. This paper aims to investigate the axial capacity of fibrous concrete-encased steel composite stub columns. A total of 36 specimens with different cross-sectional shapes of steel profiles, including H-shaped and C-shaped, were tested, and axial parameters and compressive behavior were investigated. The variables of the research included the shape of the steel profile (H-shaped and C-shaped), steel fiber volume ratio (0%, 0.75%, and 1.25%), and the stirrup spacing (40, 65, and 130 mm). The results showed that the loading capacity of fibrous concrete-encased steel columns was affected by the shape of the steel profile inside. In this regard, the use of the H-shaped steel profile in the columns led to a higher axial loading capacity than the use of the C-shaped steel profile, due to greater confinement provided by concrete in columns with this section type (H-shape). Moreover, the addition of fibers significantly increased the ductility of these columns in comparison with those without fibers, and also, the addition of fibers increased the axial capacity of the steel-concrete composite columns by 6%. On the other hand, given the results, it is found that the stirrup spacing had a considerable effect on the load-carrying capacity of these columns, in that by increasing the stirrup spacing, due to the lower confinement of the column, the axial load-carrying capacity declined. In this regard, as the stirrup spacing increased, the decline in this parameter reached up to 11% for the columns with the H-shaped profile and 9% for the columns with the C-shaped profiles. Furthermore, the results of this study showed that the specimen with the H-shaped steel sections, 1.25% fibers, and the stirrup spacing of 40 mm generally were the optimal specimens in terms of the axial load-carrying capacity and ductility in comparison with the other specimens under study. All the specimens had almost similar damage patterns up to their failure. The difference was that the specimens containing fibers experienced failure mainly in the form of the crushing of concrete cover and its breakage from the middle of the column height, due to greater integrity of the concrete structure in these specimens. However, in the specimens without fibers, a considerable portion of the concrete cover was completely detached from the column.

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Nowadays, the use of composite sections has become a common practice in the construction industry. Concrete is inherently a brittle material, with high stiffness and compressive strength. On the other hand, steel is a material with high tensile strength and ductility. The simultaneous use of steel and concrete in composite sections improves the performance and leads to optimum exploitation of the properties of both steel and concrete materials. Concrete-filled steel tube (CFST) is a type of section often used in high-rise buildings. In addition, the composite action of steel and concrete in CFST columns gives some advantages to these sections during fire incidents. On the one hand, the concrete core prevents the local buckling of the steel tube, and on the other, the steel tube prevents the spalling of concrete at elevated temperatures. The behavior of CFST sections at elevated temperatures is complicated due to interactions between the steel tube and concrete core. Therefore, achieving a correct understanding of the behavior and material properties in CFST columns is required for design and strengthening purposes.

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In this paper, a finite element analysis of the behavior of embedded CFST columns to the foundation under axial-lateral combined loading. First, the proposed finite element model is compared and analyzed by the experimental results of previous research, which showed that the local damage, failure patterns and hysteresis curves were consistent. A detailed parametric study to evaluate the cyclic behavior of embedded CFST columns to the foundation with the characteristics, the ration diameter to thickness, embedded length, compressive strength and connection conditions CFST column to the foundation. Based on the parametric study, the values of stiffness, strength, ductility and energy for the studied specimen have been calculated. The results showed that using the proposed finite element model, weak cyclic behavior for CFST connection to the foundation in the conditions of connection with the base plate and better cyclic behavior for the CFST column and its connection to the foundation in the embedded conditions is obtained. In addition, the hysteresis behavior of the CFST column connection with the embedded stiffener plate is much better than the embedded connection without the stiffener. The rings stiffener of the hysteresis diagram changes compact condition with increasing concrete strength. In addition, lateral strength, lateral stiffness, ductility performance and cumulative energy dissipation also increased in compact specimens with increasing confine concrete. The failure modes of the CFST connection to the foundation with the base plate are the same as the embedded connection mode without the stiffener and with the ring stiffener. The failure modes in these three modes are from the connection as a tearing steel pipe at the end of the column. In the case of an embedded connection with a longitudinal stiffener, it is a diagonal crack of the concrete on the foundation. Lateral strength, lateral stiffness, ductility performance, and cumulative energy also increase with increasing steel pipe thickness. CFST column burial conditions with hardeners have a positive effect on the hysteresis rings of CFST connection to the foundation, and this type of connection has been able to significantly improve lateral strength, lateral stiffness, ductility and dissipative cumulative dissipation energy.