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Histopathological and pathomorphological effects of 15 ppb mercuric chloride on Persian sturgeon, Acipenser persicus, were investigated using histological and electron microscopy observations. Light microscopy showed that the gill epithelial hypertrophy, wrinkling and hyperplasia in lamellar epithelia and lamellae fusion occurred after 48 h of exposure. Gill epithelia also showed occasional necrosis, which had almost been completed and blood emerged from the capillaries. However, occasional necrosis in some regions of the filament, both with blood emerging and with no bleeding, was observed by using electron microscopy. These injuries were well observed in inter-lamellar regions of the filament and also wrinkling of the lamellar epithelium. Ultrastructural observations showed some cellular disorders in gill epithelium of the Persian sturgeon, A. persicus, fry. In addition, increase in apical vesicles of the chloride cells and necrosis in apical surfaces of some chloride cells, hypertrophy and necrosis of the chloride cells’ mitochondrion and endoplasmic reticulum also were some of the other cellular disorders observed through transmission electron microscopy. In conclusion, the gills of A. persicus fry were sensitive to low concentrations of inorganic mercury (HgCl2).

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Bacterial soft rot causes severe damage to potatoes and is responsible for considerable economic losses in potato crop during both growing season and storage period. The most common causal agent of potato soft rot worldwide is Pectobacterium carotovorum (Pc); however in Iran, two other species: P. atrosepticum and P. wasabiae have been reported. Identification and assessment of genetic variation in pathogen populations are very important to understanding taxonomy, epidemiology, and management of a pathogen. In this study, potato stems and tubers showing soft rot symptoms along with their surrounding soil were collected from fields and seed storages of Ardabil province. A total of 33 pectolytic bacterial strains were isolated on nutrient agar and eosin methylene blue culture media. The isolated strains and five standard strains belonging to P. atrosepticum, P. carotovorum and Dickeya dianthicola were studied. The strains were identified as P. carotovorum subsp. carotovorum on the basis of phenotypic characteristics including: gram-negative, facultative anaerobic, soft rot production on potato slices, growth at 37 °C, and inability to produce acid from α-methyl-D-glucoside and also molecular identification using species-specific primers. Based on Y1/Y2 and ExpccF/ExpccR primers, the expected amplicons (434 and 550 bp fragments, respectively) were obtained for all strains and the standard strains belonging to P. carotovorum. According to rep-PCR and cluster analysis using UPGMA and NTSYS 2.1 software, the selected strains were categorized into two main groups and four subgroups. Rep-PCR indicated different levels of genetic heterogeneity among Pcc strains, however, no clear correlation was found between clustering and the geographical origin of the strains. 

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 Tomato bacterial wilt and canker caused by Clavibacter michiganensis subsp. michiganensis (Cmm) is an economically important seed-borne disease in the major tomato growing regions all over the world. Also, this disease is present in northern, northwestern, and central provinces of Iran. This study aimed to isolate fluorescent pseudomonads with efficient antagonistic activity against Cmm from tomato rhizosphere and rhizoplane. In the present study, ninety six fluorescent pseudomonads were isolated from rhizosphere and rhizoplane of tomato plants using King’s medium B agar and tested for antagonistic activity against Cmm by co-inoculation culture in vitro. Seed and roots of tomato transplants were inoculated with representative antagonistic strains and planted in the soil infected by Cmm in greenhouse. The incidence and severity of the disease were assessed on tomato as well as growth parameters. Nineteen strains exhibited inhibitory activity against Cmm in vitro and two selected strains (M1R1 and H1R1) were identified as Pseudomonas putida based on their phenotypic characteristics and partial 16S rRNA gene sequences. These two strains produced siderophore and hydrogen cyanide. In greenhouse, strain M1R1 reduced the disease incidence by 30% and 40% in Superluna and Falat cultivars, respectively. Strain H1R1 reduced the disease incidence by 20% only in Falat cultivar. Strains M1R1 and H1R1 decreased the disease severity by 52.93 % and 10.60 % in Superluna and 47.90 % and 42.88 % in Falat cultivars, respectively. Strain M1R1 increased the growth parameters, including fresh and dry weight, and height of the inoculated plants significantly in comparison with control. These results indicated that rhizospheric fluorescent pseudomonads could be effective agents in the biocontrol of tomato bacterial wilt and canker disease.
 

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These days the accurate estimation of seismic demand and capacity of structures are truly significant in the field of performance based earthquake engineering. Several methods exist to determine these parameters such as non-linear time history analysis and Incremental dynamic analysis (IDA). Because the history of seismic accelerogram records refers to the current century, in some areas there still exists no appropriate seismic record to perform the analyses; therefore in these cases we need to generate artificial accelerograms. In this paper a new combinational method is introduced to generate far-field artificial accelerograms using artificial neural network and wavelet packet transform (WPT) methods. In this method according to the geoseismic characteristics of the site and non-linear characteristics of the equivalent single degree of freedom (SDOF) system, several artificial accelerograms are generated. In order to consider the non-linear parameters to generate the accelerograms, IDA method is used. The values of intensity measure (IM) for all IDA curves are determined at specific levels of damage measure (DM) and are considered as the input data of the multilayer feed forward (MLFF) neural network. Accelerograms which are selected according to the geoseismic characteristics of the site are changed to standard forms and then decomposed using wavelet packet transform. The effective wavelet packet coefficients are selected according to an appropriate desired effective variance ratio of wavelet packet coefficient. Then, effective coefficient of each packet is considered as the output of a neural network. In order to enhance the efficiency of the network, principal components analysis (PCA) is used to reduce the number of the input data dimensions. In this paper neural network is trained by backpropagation algorithm as repetitive. After training the MLFF neural network, we should test the network for accelerograms not included in the training set. For this purpose we should use the IDA curve of each accelerogram out of the training set as the input of the neural network to generate the effective WPT coefficients. When a neural network is trained properly, we can now generate artificial accelerograms using a 50% fractile IDA curve as the input of the neural network. Adding a Gaussian random number to the output of each neuron in the neural network layers, we are able to generate several accelerograms according to 50% fractile IDA curve. In order to improve the condition of generated accelerograms according to 50% fractile IDA curve, a correction factor is used repeatedly for detail coefficients of discrete wavelet transform in jth level of generated accelerogram. Finally a SDOF system with perfectly elasto-plastic initial loading curve is used to show the efficiency of the proposed method to generate artificial accelerogram. The accuracy of this method depends on the accuracy of the trained neural networks. If the neural networks are trained appropriately with IDA curve, the generated accelerogram can estimate the IDA parameters of the SDOF system more properly. Also it is shown that suggested method can generate artificial accelerograms with frequency content almost close to the initial earthquake records.

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Bistable composites have gained increased attentions in industry, especially in the aerospace industry, due to their unique feature of shape-changing without the need for continuous energy. The advantage of using these structures is their ability to package in small size, whilst deploying in long lengths and high stiffness ratio along the length. This unique feature, along with the advantages of other fiber reinforced composites such as high strength, light weight and high rigidity, has made them a good choice for many applications such as deployable booms and antennas for satellites.
In this paper, the bistablility of shell structures at different time-temperature conditions are investigated. To explain the mechanical behavior of the Bistable Tape Springs (BiTSs) in different conditions, an analogous 2D model consist of rigid linkages, elastic springs and viscous dampers is proposed. The relationships between the force and energy through the transition path for the 2D model were established and the non-dimensional strain energy paths for different initial parameters were obtained, accordingly. As a case study, four BiTSs made of composite materials are fabricated and subjected to a particular thermo-viscoelastic condition to verify all stability behaviors of the 2D LSD model under thermo-viscoelastic conditions.

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Evaluation of probiotic properties of microorganisms isolated from stressful substrates has received considerable attention. Among probiotic microorganisms, yeasts are distinguished from lactic acid bacteria due to their bigger size, better adhesion ability, and resistance to antibiotics without the possibility of transferring resistance genes. In the present study, probiotic and antifungal properties of the predominant yeast isolated from natural honey were investigated. Sequencing results of the PCR products led to the identification of Saccharomyces cerevisiae as the predominant yeast isolated from honey. Moreover, the isolate had no hemolytic activity and showed the highest sensitivity towards natamycin among the studied antimycotic agents. In addition, although the yeast isolate had no proper survival under simulated gastrointestinal conditions, it had relatively high auto-aggregation (93.86%) and cell-surface hydrophobicity (76.36%). The highest co-aggregation ability of the isolate was also observed with Gram-positive bacteria Bacillus cereus and Staphylococcus aureus, and the inhibition activity of the isolate against B. cereus was significantly (p<0.05) higher than those of the other studied food-borne bacteria. The yeast isolate also showed 32.18% antifungal effect on Aspergillus flavus. Accordingly, the predominant yeast isolated from honey has suitable capabilities for application as a protective culture in fermentation industries.