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One of the problems for use of rubber in various industries is the surface tension at the surface of rubbers, which results in the crack on the surface, fracture of the rubber and reduces its service life. These tensions are caused by contacting the rubber component with the metal surface and the friction between two surfaces. Roughness of the surface, the composition of the rubber compound, the environmental factors, test conditions and etc. affect the friction between rubbers – metal. Surface roughness plays an important role in sliding between two surfaces and mainly controls friction behavior. On the other hand, roughness effect on the coefficient of friction is controllable using a suitable lubricant. In the present study regarding to the application of JP4 as an aviation fuel, the effect of JP4 fuel as a lubricant was investigated in the reduction of the sliding friction coefficient between the NBR and aluminum surfaces with different roughness. Experimental studies showed, friction coefficient has a good correlation with the mean surface roughness (Ra). By applying JP4 lubricant, the coefficient of friction decreased by about 75%. JP4 fuel as lubricant has changed the trend of varying friction coefficient from decreasing to increasing regard to the surface roughness.

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Background: Aureobasidin A is known as a cyclic depsipeptide antibiotic with toxic effects against yeasts such as Candida spp at low concentration. Combination therapy is used as a conventional treatment for fungal infections, especially drug-resistant cases. The current study aimed to investigate the combined effects of fluconazole and Aureobasidin A on fluconazole-resistant C. albicans isolates using broth microdilution method.
Materials & Methods: Antifungal activity of Aureobasidin A (AbA) compared to fluconazole against C. albicans ATCC 76615 strain was determined using the standardized broth microdilution method according to the Clinical and Laboratory Standards Institute (CLSI, document M27-Ed4) guidelines. The checkerboard method was used to test the combined effects of Aureobasidin A and fluconazole. The synergy, indifference, and antagonism were defined based on the fractional inhibitory concentration values below 0.5, 0.5-4, and more than 4 μg/mL, respectively.
Findings: MIC50 and MIC90 evaluations of Aureobasidin A and fluconazole were done at concentrations of 0.25-2 and 32-64 μg/mL against C. glabrata isolates, respectively. The synergy between fluconazole and Aureobasidin A was observed against Candida isolate. A reduced MIC was demonstrated against C. albicans isolate when fluconazole was combined with Aureobasidin A at 4 to 0.12 μg/mL concentrations.
Conclusion: The present study findings revealed that Aureobasidin A combined with fluconazole exhibited potent inhibitory effects against fluconazole-resistant C. albicans isolates. Further studies is recommended to investigate the synergistic effects of Aureobasidin A and other antifungal drugs.

 

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Backgrounds: Aspergillus fumigatus is a pathogen responsible for invasive aspergillosis and the main leading cause of death in immunosuppressed individuals. The present study aimed to evaluate the impact of eugenol-loaded chitosan nanoparticles on the expression of CYP51a and CYP51b, two well-known genes responsible for triazole drug resistance in A. fumigatus.
Materials & Methods: The minimum inhibitory concentration (MIC) of eugenol-loaded chitosan nanoparticles, chitosan, eugenol, and itraconazole was determined based on the Clinical and Laboratory Standards Institute M38-E3 method at concentrations of 4.6-2400, 11.7-12000, 2-2048, and 1-256 μg/mL, respectively. The expression of CYP51A and CYP51B was evaluated in A. fumigatus exposed to 0.5, 1, and 2× of MIC concentration of NPs and itraconazole using the real-time polymerase chain reaction.
Findings: The obtained results showed that eugenol-loaded chitosan nanoparticles sucessfully reduced A. fumigatus fungal growth at 300 μg/mL concentration. MIC of chitosan, eugenol, and itraconazole was measured to be 6000, 256, and 4 μg/mL, respectively. The results of real-time PCR also revealed that eugenol-loaded chitosan nanoparticles increased the expression of both CYP51A and CYP51B in a dose-dependent manner. The expression of fungal CYP51A and CYP51B at mRNA level was significantly increased 1.26, 1.93, and 3.1-fold as well as 1.2, 2.1, and 2.4-fold at concentrations of 150, 300, and 600 μg/mL, respectively (p<.05). However, it seems that the prepared nanoparticles had a lower impact on the expression of these genes compared to itraconazole.
Conclusion: Overall, these findings suggest that the treatment of A. fumigatus with eugenol-chitosan nanoparticles could increase the expression of the CYP51 gene, suggesting the anti-fungal property of these nanoparticles.

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Backgrounds: Allium cepa L. as a traditional medicine is a rich source of beneficial bioactive metabolites. In the present study, the effect of A. cepa ethanolic extract (EAC) was studied on Aspergillus fumigatus growth, ergosterol synthesis, gliotoxin production, and gliP gene expression.
Materials & Methods: The minimum inhibitory concentration (MIC) of EAC (125-4000 µg/mL) was determined against A. fumigatus isolates according to Clinical and Laboratory Standards Institute (CLSI) guidelines (M-38). Protease activity, gliotoxin production, cell membrane ergosterol content, ultrastructure, and gliP gene expression were evaluated in the fungus exposed to 0.5× MIC concentrations of EAC (1000 μg/mL) and fluconazole (FCZ: 64 μg/mL).
Findings: Ergosterol content was significantly reduced to 0.53 and 0.45 µg/mg in FCZ- and EAC-treated fungal cells, respectively (p< .001). The protease activity was significantly inhibited in both EAC- and FCZ-treated groups. The gliotoxin production was inhibited by 51.55 and 68.75% in the treated groups with FCZ and EAC, respectively. The expression of gliP in both EAC- and FCZ-treated A. fumigatus groups was significantly reduced by 0.40 and 0.53-fold, respectively (p< .05).
Conclusion: This study finding revealed that A. cepa ethanolic extract (EAC) effectively suppressed the growth and virulence factors of A. fumigatus, which could be attributed in part to its bioactive metabolites. Further studies are recommended to isolate and identify these metabolites as potential candidates for the development of antifungal drugs.

 

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Building structures begin to deteriorate once they are built due to harsh environment such as earthquake. To inspect present buildings and bridges following major disastrous events, such as earthquakes and hurricanes is often time-consuming and of high expense. This is also the case in regular operating conditions. Indeed critical members and connections are hidden under cladding and other architectural surface covers. This study aims to propose a novel method for identification of damages occurred in beams based on deflection under static loading. In this paper damage location on a beam is determined using statistical hypothesis testing applied on the deflection of the beam. It is worth mentioning that the statistical hypothesis testing is an appropriate method for statistical inference which can be used to judge a claim concerning an event in regards to different scenarios and possibilities. The statistical claim which would be analyzed is that damage is present among elements of the beam. Deflection of beam as a derivation of stiffness will be utilized here. Hence the basic idea in this study; to locate damages, is behind of calculating the difference between measured and estimated deflection of nodes of each element in both intact and damaged structures. Elements damage can be specified by applying damage index which is defined as D(x). Element’s damages can be judged through the damage index sign in two nodes of every element: The element will be considered damaged if the index is positive for both nodes of middle element or it is positive in only one node of element leading edges of fulcrums. To illustrate the efficiency and robustness of proposed method three different examples are considered. First example is a simple beam with five different scenarios including single and multiple damages. Second example is also presented to show comparison of the proposed method with the study by Abdo [18] and finally third instant is considered for showing reliability of the method in different beam types. For all of the examples, the deflection of damaged beams is recorded via sensors under only one state of static loading and the statistical parameters of the undamaged beams are generated under several static loading. Then by calculation of damage index, we can decide about damage locations. All examples show good performance of the novel method in damage localization. The most important result obtained from these examples is that, the more fine mesh, the better and the more accurate performance of the method. Of course this assertion is more important in the elements leading edges of fulcrums. Further, the performance of this method is demonstrated through damage simulation where the measured data are contaminated with noise and hence to evaluate the stability of the proposed method against various noise levels, scenarios are considered with different such levels.

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The aims of this study were evaluating the effect of Mellis herb (Melissa officinalis) powder and extract addition on the microbiological, chemical, rheological and sensorial attributes of pasteurized Doogh. In this study, 72 different Doogh samples were produced with Mellis extract and powder. On days 1, 10, 20, and 30, the physicochemical, microbial, rheological and sensory properties of Doogh samples were measured with three replications. pH, acidity, dry matter and SNF of Doogh samples containing Mellis powder and extract were significantly different (p<0.05). In the case of all of parameters the mean value of powder were greater than extract and there were no significant differences in syneresis and viscosity of Doogh samples. The rheological pattern of Doogh samples were as pseudoplastic fluid. In the case of sensorial properties, the flavor of mellis containing Doogh samples with powder and extract were not significantly different, but the about the texture, appearance and general acceptability, the extract and powder were significantly different and the scores of taste, texture, appearance and general acceptability of extract was higher than powder. Mellis addition inhibited the overall growth of moulds and yeasts until the 20th day. In the case of syneresis, at the first days, extract containing samples had lower syneresis but it increases with acidity development during the shelflife. As a result, using Mellis in Doogh production have beneficial effect on chemical, microbiological and sensorial properties of the product.

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Objective: The prevalence of respiratory allergies, especially those induced by fungi such as Alternaria alternata, has dramatically increased over the past decade. This increase has caused major health problems worldwide. This study aimed to investigate the role of A. alternata in the etiology of allergic asthma, by using the skin prick test and assessment of IgE specific to the fungus in the patient's sera. Methods: This study enrolled 202 patients with allergic asthma, aged 12 to 83 years. Participants included 40.1% males and 59.9% females who were enrolled after recording demographic information. A skin prick test with the whole cellextract of A. alternata was performed on the epidermis of the patients' forearms. Histamine and normal saline were used as positive and negative controls, respectively. Serum levels of IgE specific for A. alternata were measured for all patients using the ImmunoCAP Phadiatop method in which the specific A. alternata allergen cocktail that connected to the solid phase reacted to IgE antibodies in each patient's sera. Data were analyzed by analysis of variance and chi-square tests. Results: Among 202 patients with allergic asthma, 14 (6.93%) had mild asthma, 73 (36.10%) were moderate asthmatics and 115 (56.90%) had severe asthma. In total, 14 (6.93%) patients were positive for both the skin test and IgE specific to A. alternata, 35 (17.33%) had negative specific IgE and positive skin test results, and 36 (17.82%) had a positive specific IgE and negative skin test. A total of 117 (57.92%) patients were negative for both tests. Conclusion: The results of this study showed the presence of IgE specific for A. alternata in 50 of 202 (24.75%) patients diagnosed with allergic asthma. The skin prick test was successfully used as a screening test. The results were further confirmed by solid-phase immunoassay of the IgE specific for A. alternata crude allergenic extract.

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Objective: Fusarium species are prevalent contaminants of foodstuffs and agricultural crops.  They produce fumonisins, which are carcinogenic mycotoxins. The present study has evaluated maize and wheat samples from ten provinces in Iran that were contaminated with Fusarium species. Special attention was paid to the ability of the isolates to produce fumonisin B₁ (FB₁) as a public health hazard. Methods: We collected 32 maize and 15 wheat samples from ten provinces that were major cultivation areas. Samples surface disinfected with a 1% sodium hypochlorite solution for 2 minutes. Fusarium species were isolated by the flotation method on malachite green agar. Pure cultures on potato dextrose agar (PDA) were identified using a combination of macroscopic and microscopic morphological criteria. The ability of the isolates to produce FB₁ was evaluated by thin layer chromatography (TLC) and the amounts of fumonisin B₁ produced were assessed by high performance liquid chromatography (HPLC). Results: A total of 55 Fusarium isolates that belonged to five species were isolated. There were 27 of the 32 maize samples (84.4%) and 11 of 15 wheat samples (73.3%) that were contaminated with Fusarium species. Species consisted of F. verticillioides (23 isolates), F. proliferatum (22 isolates), F. subglutinans (5 isolates), F. nygamai (4 isolates) and F. redolens (1 isolate) based on morphological criteria. Twenty-two of the 55 (40%) Fusarium isolates produced FB₁ in a total range from 230.4 to 9565 µg/ml. The highest amounts of FB₁ production were related to toxigenic isolates of F. verticillioides and F. proliferatum. Conclusion: Results of the present work indicates a high degree of contamination of maize and wheat with Fusarium strains that belong to the Gibberella fujikuroi species complex وparticularly F. verticillioides and F. proliferatum. This contamination is a potential public health threat due to food spoilage and subsequent production of high levels of carcinogenic FB₁.

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Here, the efficiency of the non-destructive Break-Off (BO) test was investigated for assessing the in-place compressive strength of steel fiber reinforced concrete (SFRC). SFRC was studied due to its advantages in increasing toughness and tensile and flexural strength in particular. To provide a through and comprehensive database, 24 mix designs were selected with cement contents of 400, 450 and 500 kg/m3 with constant water/cement ratio of 0.4 for all mixes, two maximum aggregate sizes of 12.5 and 25 mm along with steel fiber volume fractions of 0%, 0.33%, 0.67% and 1% for ages of 14, 28 and 90 days. A total of 360 BO tests and 216 standard cube tests were carried out in this investigation.Then, effective parameters of SFRC and BO test results were evaluated. In the BO method, the force required to break off an in-place concrete cylinder of 55 mm in diameter and 70 mm long, is related to the compressive strength of the concrete from a predetermined calibration curve developed for concrete mix.The studies showed that volumetric percentage and features of steel fibers had a significant influence on concrete properties as well as BO test results. According to the experimental results it could be generally concluded that the influencing factors, namely, SFRC properties due to presence of steel fibers and BO test significantly affect the results as follows: Generally, for a constant W/C ratio, it can be concluded that raising the cement content increase the mean values of BO strength. It can be stated that the maximum aggregate size within the range of 12.5–25 mm has a negligible effect on the BO test results for SFRC with 1% steel fiber volume fractions as the average value of BO strength for 25 mm aggregate concrete was significantly more than the corresponding value for 12.5 mm aggregate size for plain concrete. Moreover, the improving trend the BO strength with age is observed to be similar for all different concretes. Furthermore, increase of BO strength of SFR concretes respect to corresponding plain value is observed as concrete grows older. In addition, results showed that strength estimation based on a single general calibration curve is not feasible. Therefore, a specific calibration curve for each SFRC should be represented for a realistic assessment and interpretation of results. The coefficient of variation of the BO strength was in range of 4– 11%. The higher values are for concretes with higher amounts of fibers, especially at early ages. The reliability of the method seems to be good in which the coefficient of variation for each group of BO tests are below 11%. It should be noted that even under ideal conditions with a specific calibration it is unlikely that 95% confidence limits of better than ±15% can be achieved for an absolute prediction of concrete compressive strength. The findings show that higher values are not only due to the lack of precision of the test procedure, but also due to the intrinsic heterogeneity of granular materials like concrete, particularly in presence of higher amounts of fibers.

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In the last decades, the development of nanotechnology has been rising and nanomaterials have been widely used in combination with many traditional materials. The prominent chemical and physical properties of nanomaterials enable them to play an important role in various applications such as modifying the structure of materials, improving the properties of composites, and manufacturing new multifunctional products. The building industry has not been exempted from this rule. Many studies have been carried out on the effect of nanoparticles on concrete performance and most of them demonstrated the improvement of concrete properties. There are a lot of studies on the effect of nanoclay on cement composites. However, there are little researches on the halloysite nanotube (HNT) effect, as subcategories of nanoclay, on the properties of cement composites. Halloysites are a kind of mineral clay which are often produced by air-induced erosion or by thermal transformation of ultramafic rocks, volcanic glasses, and pumice. They are chemically similar to kaolinite but, unit layers in halloysites are separated by a monolayer of water molecules. In general, halloysites have different shapes and exist in the plate, spherical, and tubular forms. The tubular structure is the dominant form of halloysite in nature. Chemically, the outer surface of the HNTs has properties similar to SiO2 while the inner cylinder core is related to Al2O3. Due to the tubular geometry, HNTs like carbon nanotubes could be classified as one-dimensional nanoparticles. Halloysite can grow into long multi-walled tubules, which morphologically resemble to multi-walled carbon nanotubes. In terms of dimensional characteristics, HNTs have an external diameter of about 30 to 190 nm, an inner diameter of about 10 to 100 nm and a length between 3 to 30 µm. Halloysite characteristics could be sum up as high length to diameter (L/D) ratio, high specific surface, large pore volume, low density in surface, and pozzolanic properties. Mechanical properties of HNTs could make them an ideal reinforcing additive to improve the mechanical properties of cement composites. In addition, due to the nano scale size of HNTs, they can play the role of filler and make a denser and stronger microstructure. Therefore, in this research, the effect of HNTs on the performance of cement mortar was evaluated and the workability and permeability of mortar samples containing 3% halloysite nanotubes were presented. The results indicated an increase of more than 28% of electrical resistance, a decrease of approximately 26% of water absorption rate, 23% reduction in water repellent, a decrease in the workability, and an increment in the rate of hydration of cement mortar due to the incorporation of 3% halloysite nanotube. These results indicate that halloysite nanotubes can be used as an appropriate nanoparticle to improve the properties of cementitious composites. The pozzolanic properties of HNTs enable them to decrease the permeability of cementitious matrices. Silicate of HNTs react with calcium ions of hydrated cement and increase the calcium silicate hydrate gel. This could lead to an enhancement in the durability of cementitious matrices. This paper can provide more insights on the application of nanoparticles with cementitious composites.

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In this paper, cracking in the first mode (opening) is modelled for reinforced concrete beams with FRP sheets based on presenting a new method by using the principles and relations of fracture mechanics and finite element method. In this method, for modelling the relationships of determining the stress intensity factor is developed for reinforcement sheet. In the proposed method, elements of the beam are divided into two categories, including elements with and without the crack. In the elements without the crack, the relationships, equation, stiffness and mass matrices of the beam are established with considering the changes in the moment of inertia due to the reinforced FRP sheet. In the elements with the crack, a change in the cross-section of the reinforced concrete due to the crack and a discontinuity in the crack point leads to an improvement in the standard governing relationships. So that the reduction of the stiffness of the cracked element is equivalent to the change in the size of the discontinuity. Here, the variation of the stiffness of the cracked element is calculated and presented as a function of the stress intensity factor. In this approach, the simulation of the crack is done by dividing the element to two sub-elements into the two sides of the rotational spring. In which, The stiffness and mass matrices of the two sub-elements and the improved stiffness and mass matrix of the element are derived by satisfying the continuity equation at the crack point. This method is developed from a vibrating analysis. The effects of crack depth and location and the effect of crack expansion on the static and vibrational behaviour of a concrete beam are investigated. To ensure the accuracy of the proposed method, all analysis performed in Abacus software is implemented. Comparing the results of the proposed model with the results of comprehensive modelling in Abacus software is applied to verify. The comparison of the results shows that the proposed methods are suitable for the analysis of reinforced concrete structures resistant to cracking. So that it can be generalised and optimally desirable for other models. In this paper, cracking in the first mode (opening) is modelled for reinforced concrete beams with FRP sheets based on presenting a new method by using the principles and relations of fracture mechanics and finite element method. In this method, for modelling the relationships of determining the stress intensity factor is developed for reinforcement sheet. In the proposed method, elements of the beam are divided into two categories, including elements with and without the crack. In the elements without the crack, the relationships, equation, stiffness and mass matrices of the beam are established with considering the changes in the moment of inertia due to the reinforced FRP sheet. In the elements with the crack, a change in the cross-section of the reinforced concrete due to the crack and a discontinuity in the crack point leads to an improvement in the standard governing relationships. So that the reduction of the stiffness of the cracked element is equivalent to the change in the size of the discontinuity. Here, the variation of the stiffness of the cracked element is calculated and presented as a function of the stress intensity factor. In this approach, the simulation of the crack is done by dividing the element to two sub-elements into the two sides of the rotational spring.

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Objective: The concern about the presence of aflatoxin and its risk for human and animal health has resulted in the introduction of different methods to eliminate or reduce this toxin. One of these methods is biological control of the fungus by other microorganisms. Methods: We isolated a strain of Bacillus amyloliquefaciens from the soil of a pistachio orchard, Damghan, Iran. This strain was applied as a biological control to examine the inhibition of growth and toxin production by Aspergillus parasiticus NRRL2999. After 72 hours of incubation of the bacterium at 30°C, we separated the supernatant as a potential source for antifungal compounds. Different doses of the supernatant were co-cultured with the fungus suspension in glucose yeast extract broth (GYB) at 28°C for 4 days. After the incubation period, we measured the inhibition of fungal growth by dry weight assessment of the fungal mass. We performed qualitative and quantitative assessment to determine the amount of aflatoxin B₁ by TLC and HPLC, respectively. Results: Increased bacterial culture supernatant as the antagonist in fungal growth medium resulted in decreased fungal growth. AFB₁ production was 2.35 ppm in control samples, whereas the amount considerably decreased in samples treated by the bacterial supernatants. The toxin reduction was dose-dependent. Conclusion: The results of this study have shown that this bacterial strain, by taking into consideration its native origin, can be used as a biological control against aflatoxigenic fungi.

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Structural damage not only changes the dynamic characteristics of the structure, but also it may lead to complete destruction of the structure in some cases. Since early identification of damage can prevent such catastrophic events, structural health monitoring and damage detection has absorbed the attention of the civil, mechanical and aerospace engineers in the last decades. An effective health monitoring methodology not only can provide information about the global serviceability of the monitored structure, but also it can help the engineers to prepare cost-effective rehabilitation programs based on the obtained details about the health of the structure and its members. Different methods have been proposed for structural damage identification and estimation. Vibration-based methods consider the changes in the structural modal parameters, like natural frequencies and associated mode shapes, and/or their derivatives, like modal flexibility and residual force vector, for damage identification and quantification. Considering their acceptable sensitivity to wide-range of structural damages, vibration-based methods are considered as one of the most practical approaches for structural fault prognosis. Employing vibration parameters to define the damage detection problem as a model updating problem, is one of the well-known strategies that can return both the damage location and extent in different types of engineering structures. Such methods can be solved with optimization algorithms to find and report the structural damage in terms of the global extremums of a damage-sensitive objective function.
In this paper a new model updating approach for health monitoring and damage localization and quantification in engineering structures is presented. At first, a damage-sensitive objective function, which is based on the error function between the modal data of the monitored structure and its analytical model, is proposed. This objective function is formulated by means of the point-by-point matching strategy to minimize the difference between two models. Modal natural frequencies and the associated mode shape vectors are directly fed to the objective function and this can result in an easy assessment methodology to check the convergence rate of the function. Moreover, in such a case, the objective function uses the sensitivity of both these parameters for damage identification. The proposed inverse problem is solved using Moth-Flame Optimization (MFO) algorithm which has been inspired form spiral convergence of moths toward artificial lights. From mathematical point of view, updating the position of the moths with respect to the flames –which are the best solutions obtained during iterations–, reduces the probability of being trapped in the local extremum points and also, ensures the convergence of the algorithm to its global optimal solution. The applicability of the method was evaluated by studying different damage patterns on three numerical examples of engineering structures: a seven-story shear frame, a simple beam with 10 elements, and a planar truss with 29 elements. In all these studies, damages were simulated as reduction in the stiffness matrix of the damaged elements. Different issues, like noise effects, were considered and their impacts on the performance of the proposed method were investigated. Furthermore, comparative studies were carried out to discuss the advantages and drawbacks of the introduced method as well as the employed techniques. The obtained results indicate that the method is an effective strategy for vibration-based damage detection and localization in engineering structures.

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Conventional construction cementitious composites typically contains cement, fine and gravel aggregate and additive in a specific ratio along with water. It is extensively used to bind the structural elements together like the bricks, stones, and concrete blocks, or end connection of the column and beam, and to develop a sufficient bond with the substrate as a repair cementitious composite, due to its several advantages, such as low cost, appropriate compressive strength, and easy access. However, some weaknesses of the cementitious mortar influence its performance under different conditions. For example, low tensile strength, brittle behavior, unacceptable performance against shrinkage cracks, and lack of resistance against stress concentration are some of these critical properties of the mortar, if not modified, the structures will be deteriorated in a short time. These deficiencies emerge from extravagance water, bleeding, plastic settlement, shrinkage stress and strain concentrations due to external limitations. When loads are applied and further increased, type of cracks grow and reach a critical condition, and catastrophic failure is precipitated. In this situation, the mortar will be exposed to severe damaging factors such as premature saturation, disadvantage of freeze-thaw, scaling, and corrosion of steel. In recent years, researchers in the field of concrete technology have focused on the using of a variety of fibers such as carbon, steel, glass, polypropylene and basalt fiber into the cementitious composites to improve their mechanical properties (especially their ductility behavior) and to some extent their durability. Accordingly, in the present study, the hybrid effect of different percentages of basalt and polypropylene fibers on the workability, mechanical behavior and durability properties of cementitious mortar was investigated. Polypropylene fibers are known in the field of reinforced concrete, but basalt fibers are a new potential additive in this field. In recent decades, researchers have studied more about basalt fibers because of their potential reinforcement properties in composite materials. The basalt fibers are an appropriate replacement for another fibers, including glass, steel, and carbon fibers in plenty of applications due to their excellent properties such as high mechanical properties specially tensile strength and flexural strength, good resistance to low and high temperature, low cost, durability, vibration resistance, high elasticity modules, great failure strain, acceptable persistence to chemical assault, impact load and fire with less toxic materials. Samples containing a hybrid composition of 0.05 and 0.125 percent (weight percent of total cement and aggregate) of the basalt and polypropylene fibers have been used in order to evaluate the effect of fibers so that a total of 4 types of mixed designs containing hybrids of basalt and polypropylene fibers were made and its results have been compared with a control sample. As expected, after analyzing the results, the fibers had no significant effect on the compressive strength of the cementitious composite, while the results of this study reported a favorable and remarkable performance of these fibers in increasing flexural and splitting tensile strength, as well as the water absorption of cementitious mortar is favorably decreased by the fiber. The sample containing 0.125% basalt and polypropylene fibers increased flexural and splitting tensile strengths by 28 and 23%, respectively. Also, the sample containing 0.125% basalt fiber and 0.05% polypropylene fibers resulted in 9.3% increase in compressive strength, 24% decrease in sorptivity and 15% water absorption. The results of the current study have shown that the simultaneous use of basalt and polypropylene fibers can improve significantly the mechanical behavior and durability properties of cementitious mortar, whereas according to the previous studies if each of these fibers is used separately, such a desirable result will not be obtained.

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Cementitious composites are mainly used in the construction industry due to their good characteristics such as low cost, acceptable compressive strength, and easy access. However, there are many weaknesses in these materials, including low tensile strength, brittle behavior, and unacceptable durability (service life), which need to be improved to achieve more sustainable constructions. Nowadays, the using of nanotechnology have been growing and nanomaterials have been widely used in compound with a multitude of conventional materials. The outstanding chemical and physical properties of nanomaterials enable them to play a key role in various applications, such as modifying the material structure, ameliorating the properties of the material, and manufacturing modern multifunctional products. Recent advances in nanotechnology have led to produce nano-sized particles that can improve the durability performance of construction materials. Nanoparticles such as nano-silica, nano-Fe₂O₃, nano-clay, carbon nanotube (CNT), nano-Al₂O₃, nano-TiO₂, and graphene oxide have been used to enhance the properties of cementitious composites. The performance of halloysite nanotube on the characteristics of cementitious composites has been studied less than other nanomaterials. Although the positive effects of nanomaterials such as halloysite nanotube (HNT) on the properties of cementitious composites have been proven, the very important issue of the correct and proper dispersion of nanomaterials in the cementitious environment has not been studied acceptably. The high surface energy and interparticle forces, including van der Waals, hydrogen bonding, and electrostatic interactions, make the nanomaterials highly susceptible to agglomeration. The aggregates of nanomaterials not only decrease their benefit but also act as potential weak spots in cementitious composites that can cause stress concentration, therewith diminishing the mechanical properties of cementitious composites. In this regard, the current paper investigated the effective factors on the agglomeration of halloysite nanotube (HNT) in the cementitious alkaline environment. Finally, this paper presented an approach for solving the problem of HNT agglomeration. Results showed that Ca²⁺, K⁺, and Na⁺ ions as alkaline agents of cement environment are the main factors to provide a state for HNT agglomeration. Among them, Ca²⁺ has more effect in agglomeration of halloysite nanotube due to the bridging effect between halloysite particles. From the results, the dispersion of HNT made better with increasing the alkalinity of cement environment until pH=11, while after this pH, the agglomeration of HNT started and the intense of agglomeration raised with the increase of pH, where it reached a maximum value at pH=13.5. Common approaches to nanoparticle dispersion are through physical methods (e.g., ultrasonic, high shear mixing, ball milling, etc.) and chemical methods (e.g., chemical modification of nanoparticle surfaces, use of dispersants such as surfactants, etc.). For the cementitious systems, a combination of ultrasonic and surfactant is mostly suggested. In this research, the effect of various surfactants on overcoming the agglomeration of halloysite nanotube in the cementitious environment was studied. The results indicated that the Polycarboxylate-based surfactant has better performance on improving the dispersion of HNT compared to that of other surfactants. Furthermore, incorporation of 3 wt% HNT enhanced the compressive, flexural and sorptivity of plain mortar up to 26, 22, and approximately 28%, respectively. The outcomes of the current paper display the fact that it is necessary to have special attention on the subject of the proper dispersion of nanomaterials in the cementitious environment for achieving the maximum efficiency of nanomaterials.

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Reduced Beam Section (RBS) connections are extensively used within seismic resistant steel moment frames in order to deal with the risk of brittle fractures in the connections, absorbing seismic energy through yielding and protect columns from damage. In this connection, at specific locations the beams flanges are trimmed back to provide weakened sections, in order to shift the plastic deformations away from beam-column connections and into the beam. Consequently, adequate ductility is provided by the frame to absorb the seismic energy and avoid the risk of brittle fractures occurring. The seismic performance of steel structures has been studied widely by many researchers. In general, the results of these studies indicate the good capability of RBS connections achieving these targets. In a reduced beam section (RBS) moment connection, in the region adjacent to the beam-to-column connection, a part of the beam flanges is trimmed selectively. Yielding and hinge formation are intended to take place primarily in the reduced section of the beam. Currently, in the design of RBS connections, the effect of RBS cutting parameters on the cyclic performance of the beam elements are not taken into account. However, using different RBS geometries for any beam with different sections can have different results in cyclic performance of the connections. In order to evaluate the effects of geometric parameters of RBS connection on the cyclic behavior of these connections, a parametric study is carried out on forty different European I-shaped steel cross-section specimens. These specimens are analyzed using ABAQUS finite element software under cyclic loading and the moment-rotation hysteresis curve was extracted for each of the specimens. In order to validate the FE model, a full-scale beam–column sub-assemblies were modelled in the general finite element (FE) software ABAQUS. An ideal curve was extracted from each of the hysteresis curves and using the curves, five parameters including Yield Moment (My), Peak Moment (Mc), Ultimate Rotation (θu), Ductility (μ) and Energy Dissipated Capacity (EDC) were extracted as the key design parameters for each sample. variation of the above-mentioned seismic design parameters in respect to the changes of RBS dimensions are analyzed. The results clearly illustrate that geometric features c do have most effect on the moment parameters. the parameters a and b have very little influence on moments which can be considered negligible, whereas these parameters have a small effect on the ultimate rotation, ductility and energy dissipated capacity. Increasing the value of c between its lower and upper limits, reduces the My more than 20% and Mc more than 17%. The effect of the distance of the cut area from the column face (a) and the length of the cut area (b) on the moment is close to zero and can be ignored. The effect of a and b on the ultimate rotation, ductility and energy dissipated capacity is less than five percent. However, the parameter c has significant influence over all the five seismic design parameters considered. Investigating the graphs of the variation of the key seismic design parameters respect to the changes of RBS dimensions shows that there is not enough correlation between the RBS parameters and the key seismic design parameters to propose a single equation between the key seismic design parameters and RBS parameters. Investigating the relationship between RBS dimensions, moment of inertia of RBS and full section characteristics showed that a relationship can be established between these parameters and the key seismic design parameters. At the end, the results of the investigation and relationships for calculating the key seismic design parameters were presented. This relationship was presented as a single equation, which includes the effect of all the above parameters. Using the obtained equation, the value of each of the key seismic design parameters can be calculated based on the dimensions and geometric characteristics of the section and the beam cutting dimensions.

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This research was carried out to provide suitable cotton seed for seed propagation in dryland. In this study, the potential of cotton seeds that have been stressed for the third-consecutive year was investigated to evaluate water stress memory responses. The experiment was arranged in split-plot factorial design with four irrigation levels of W₀ (No- irrigation), W₁ (33% FC), W₂ (66% FC), and W₃ (100% FC), as the main factor, and five seed treatments (four third-stressed seeds, i.e. S₂₁ to S₂₄, and registered seed), as a sub-plot. Seeds of cotton were grown under different levels of water-stress exposure for three crop-seasons. As results showed, S₃₂ received water stress signal in both W₀ and W₃ conditions through physiological mechanisms change. Seeds of S₃₂ accumulated the lowest ABA and the highest calcium in exposure to W₀ and W₃. Enhancement to superoxide dismutase and Aspartate peroxidase activity in leaves of S₃₂ in exposure to W₀ and W₁ is another memorial stress mechanism for scarce water acclimation. The highest-potential thirty-boll weight, thirty-fiber weight, and first-harvesting yield were obtained from S₃₂ against W₀, W₁, and W_2.. Also, the seeds of S₃₂ had the most seedling vigor and germination percentage in exposure to W₀, W₁, and W₂. It can be concluded that stress memory, via modification of physiology and morphology of plant behavior, helps plants to tolerate water deficiency when subjected to recurrent drought.