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Enzymes of marine organisms are ideal candidates for biomonitoring of pollution in marine environments. For the widespread use of enzymes in industrial processes, carried out under certain physico-chemical conditions, their stability must be improved. In this study, for the first time, chitosan nanoparticles were used as matrices for augmenting the stability of Penaeus vannamei (Whiteleg shrimp)-derived purified proteases against metallic ions. For the electrostatic binding of the enzyme to the chitosan nanoparticles, the protein solution at a concentration of 7mg/ml was added to the nanoparticles, and incubated for 4 hours at 10°C. After 3 times rinsing with phosphate buffer of pH=7.5, the nano-enzyme was dissolved in 1ml phosphate buffer, and used for further studies. The results of this study showed that Fe²⁺ and Mn²⁺ significantly increased the enzyme activity, whereas a strong inhibitory effect was observed in the presence of Cd²⁺, Hg²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺, and a weak inhibitory effect in the presence of Na⁺ and K⁺. The immobilized enzyme exhibited greater resistance to metal ions than its free counterpart. The free enzyme was susceptible to the presence of metal ions, and with the increment of their concentrations, enzyme activity declines. From this nexus, it could be inferred that the high stability of immobilized enzyme is due to the presence of chitosan nanoparticles. Stability retention of the immobilized enzyme at high concentrations of metal ions indicates the efficacy and utility of the immobilization method in industrial enzyme technology.

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Chitinases are essential enzymes in crustaceans that play an important role in the molting cycle and digestion of chitin. Based on the present study, the chitinase encoding cDNA of Penaeus mergueinsis with a length of 1440 bp containing 467 amino acids was sequenced by PCR and then its phylogenetic and bioinformatics analysis was performed. The new sequence was registered in the gene bank with the accessition number MT250539 and the molecular weight of the protein resulting from this sequence was predicted to be 51.84 KDa and the theoretical isoelectric point of 4.79. Comparison of amino acid sequences among penaeid chitinases showed the highest identification (about 97 to 92%) with P. mondon chi-3, F. chinensis, P. vannamei and P. japonicus chi-3, respectively. Phylogenetic studies showed that chitinase in the present study belongs to group 3 chitinases. Revealed protein pattern analyzes showed that chitinase from P. mergueinsis contained the catalytic domain Glyco-18 at position 2-347, a chitin-binding site of pritrophin A at position 403-456, a disulfide bridge formed by two cysteines at position 436-421 is a chitin-binding domain type 2, active site (¹¹7FDGLDMDWE¹²⁵), a proline / threonine-rich region at positions 376-412, and a putative N-glycosylation site at position 427-424 (NTSG). The present study shows that the P. mergueinsis sequence contains active chitinase motifs similar to previously sequenced chitinases, and in the case of cloning, expression and purification probably has functional and structural features similar to the enzymes of the above species.

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The aim of this study was to isolate and identify a-amylase-producing bacteria present in mangrove ecosystems on Qeshm Island, Hormozgan, Iran. Samples of mangrove leaves and roots were screened for a-amylase activity using Lugol’s solution. Crude extracts were prepared of positive samples, and their a-amylase activity was determined by the Bernfeld method. The two strains with the highest activity were identified by molecular analysis of their 16S rRNA genes. a-Amylase production and activity were optimized by varying temperature and pH. 46 bacterial strains were isolated from mangrove tree leaf and root samples. Of these, 28 strains were capable of producing a-amylase. 16S rRNA gene sequence analysis of two strains with the highest enzyme production identified them as Bacillus sp. strain HR10 and Bacillus sp. strain HR11. The optimum temperature for enzyme production was 35 and 30 °C for strains HR10 and HR11, respectively, and the optimum pH was pH 8 for both strains. The highest enzyme activity was observed at 70 °C and 60 °C for the HR10 and HR11 strains, respectively, and the optimum pH was pH 8 for both strains. In conclusion, we have shown that bacteria isolated from mangrove leaf and root samples are potential source of a-amylases, tolerating a wide range of temperature and pH. Such a-amylases may be of interest for use in environmentally friendly industries.

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In this paper, the effect of soil-structure interaction is investigated on the maximum drift demand and probabilistic seismic confidence level of geometric vertically irregular steel buildings. A series of vertically irregular steel building with different setback ratios were designed based on the regulations in the earliest version of Iranian seismic design code. Foundation design of the structures was accomplished with the assumption of sandy soil with shear wave velocity of 200m/s under the strip footings. Three dimensional model of nonlinear soil-structure system was built in OpenSees. Concentrated plastic hinges were used at the end of frame members to model the nonlinear behavior of these elements. Soil-foundation system of the structures was modeled with Beam on Nonlinear Winkler Foundation (BNWF) approach. In this method, a series of nonlinear springs are used to model the soil behavior under the dynamic excitation. The seismic analysis of the structures was performed under the simultaneous action of orthogonal components of real ground motions. An ensemble of twenty ground motions that have a reasonable response spectrum matching with the design spectrum was chosen for the time history analysis. Incremental dynamic analysis (IDA) was accomplished to estimate the structural performance of the regular and vertically irregular setback buildings from the earlier linear behavior to the nonlinear phase and up to the global instability of the structures. Based on the results, the median IDA curve of fixed and flexible base buildings was evaluated. Four common performance objectives namely Immediate Occupancy (IO), Life Safety (LS), Collapse prevention (CP) and Global Instability (GI) were specified on the median IDA curve of each fixed and flexible base structure. Following the performance-based earthquake engineering framework, the confidence level of meeting a specific performance level was evaluated at each limit state. Based on the given results, curves were generated to specify the confidence level of meeting a specific performance level for a range of earthquake intensities and corresponding maximum inter story drift ratio. The performance based confidence level of flexible base setback buildings was compared to that of the fixed base structures at five seismic hazard levels. The seismic hazard of earthquakes was chosen to cover a wide range of return period from 25 years to 4975 years. It is observed that all the fixed and flexible base buildings have the ability to continue their immediate occupancy with the confidence level of 100% under the excitation of earthquakes with low to medium hazard levels (i.e. with the return period of 25 to 43 years that know as the service level). However, as the level of seismic hazard increases the difference between the confidence level of flexible base structure and the fixed base ones increases. Depend on the position and ratio of the setback, 40 to 60% of reduction is observed in the performance based confidence level of flexible base structures. Meanwhile, demand evaluation of structures at each hazard level shows that soil-structure interaction increases the maximum drift demand in structures. Based on the given results, it is observed that up to 35% increase of maximum drift happens in vertically irregular structures with flexible foundation.

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This paper presents a new Neuro-fuzzy control system to control rigid-flexible manipulators. Enhancing the performance of fuzzy controller and intelligence in fuzzy and non-fuzzy units are the goals of this research. Proposed control system includes a fuzzy controller in the feedback and a neural network is the feed-forward. The network has the responsibility of estimating the inverse dynamic of device and then, the production of control command. Updating weighting coefficients of network is done on line using the fuzzy controller output. On the other hand, two dynamic recurrent neural networks are used for making fuzzy unit intelligent. Networks are responsible for regulating the main factors of membership functions in the fuzzy controller. The input of these networks is error and error change rate and their weights are done by using an error back-propagation algorithm. To verify the effectiveness of the proposed method, simulation is conducted for skilled manipulators with three interfaces which the end interface is flexible. System responses to step input and sinusoidal input are separately obtained for fuzzy controllers and proposed controller and compared. Comparison and studies indicate the effectiveness of the provided method.

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Seismic design codes provide different equations for estimating displacement demands in various buildings and structures. Such equations were usually obtained by performing regression analysis over the obtained data from numerical models under different nonlinear analyzes. On the other hand, the application of artificial earthquakes is allowed to be considered for design and demand assessment in structures when there is a lack of suitable ground motions for a specific region and site. Since the accuracy of such relations affects the reliability of demand estimating in structures, it is required to assess the efficiency of such predictive relations. Moreover, it is essential to assess the efficiency of those relations for artificially generated earthquakes. Hence, in this study, the estimated demands from the design and assessment codes relations are evaluated for artificially generated ground motions. In this regard, regulations in the fourth edition of the Iranian seismic design code (also known as Standard 2800) and the last revision of the Iranian seismic evaluation code of practice (also known as Code-360) are considered. Estimated demands from these codes are compared to the results from the nonlinear time-history analysis of a group of single degree of freedom (SDOF) systems. Although an SDOF system can not represent the complete behavior of a complex building, for the low to medium-rise buildings with a fundamental vibration first mode, such an idealization is acceptable. In this regard, a group of SDOF systems with the elastic-perfectly-plastic (EPP) nonlinear behavior was considered. SDOF systems have vibration periods between 0.1s to 2.0s (as low to medium-rise buildings) with strength reduction factors (R_μ) of 2 to 8 to cover most of the common lateral resisting systems. These systems were analyzed under the action of 24 artificially generated ground motion records. Earthquake records were generated based on three different envelop shapes including compound shape, exponential shape, and Saragoni and Hart shape. These envelop shapes are representing the general form of an earthquake accelerogram and try to impose the real characteristics of an earthquake on the generated record. After employing the time-history analysis on each SDOF system, the mean of the maximum displacement demands of SDOF systems was obtained and compared to those from the estimating equations in Standard 2800 and Code-360. It is observed that estimated demands from Standard 2800 are closer to those from time-history analysis when compared with the obtained results from Code-360. Among the considered strength reduction factors, it was observed that SDOF systems with larger R_μ lead to a higher difference between the time-history results and those from codes. This is more predominant over the period range of 0.1s to 0.8s. So, relations in both codes are required to be modified for better demand estimating. In this regard, a method is proposed for modifying the available equations in the prementioned codes to accurately predict the displacement demands in systems under the action of artificially generated ground motions. A comparison between the results from the modified equations and those from the nonlinear time-history analysis shows the efficiency of the proposed method.

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In today's, the preservation and maintenance of masonry structures in historical areas have become very important. A significant part of this issue is rooted in the use of non-reinforced construction materials in the building of such structures. In Iran, most of the historical buildings were built using masonry materials. The buildings were designed according to the special architecture of this region. The existing structures mostly consist of masonry walls as well as some openings with arched configurations. In these types of walls, the wall consists of two piers and an arch on top of them. Since Iran is located in a highly seismic zone, investigating the performance of these types of structures is essential under the action of earthquakes and lateral loadings. Therefore, in this paper, a numerical investigation is accomplished on the in-plane behavior of traditional brick arches under the action of lateral loads. To this end, the numerical model of a sample of an existing arch (in Kerman’s Mesgari bazaar) was considered. The model was developed on STKO software. In this regard, the nonlinear response of bricks and mortar joints was simulated by using the DamageTC3D material. As well, the geometry of the wall was constructed with four-node plane-stress elements. The lateral capacity of the wall was assessed under the action of gravity loads. To this end, the wall was analyzed under gravity loads with intensities of 0.0 to 0.2 MPa. Next, it was pushed laterally through the pushover analysis and the shear force-displacement capacity curve of the wall was obtained. Through a specific procedure, the obtained capacity curves were estimated with a bilinear graph. By using this graph, the performance points corresponding to the wall’s capacity were extracted and a complete discussion was made regarding the shear capacity and the corresponding displacement to each performance point. Based on the obtained results from the analysis, it was observed that with an increase in the intensity of the applied gravity load, the maximum shear capacity of the walls increases. However, a higher increase in gravity load intensity (over a specific limit) would cause more damage to the arch which leads to a smaller shear capacity. Also, it is observed that the distribution of cracks and their pattern along the walls follow a similar outline. However, crack widths are affected strongly by the intensity of the applied gravity load on the wall.