Genetic characterization of Lactococcus garvieae isolated from farmed rainbow trout by random amplified polymorphic DNA-PCR in Iran

Lactococcosis is one of the main bacterial infections of fish around the world. Lactococcus garvieae has been a major cause of rainbow trout losses in freshwater farming. This study aimed to genotype and determine the variability of L. garvieae isolated from infected farmed rainbow trout in Iran by the RAPD-PCR method. Bacterial samples were collected from 12 farms located in the western part of Iran and suspected to carry Lactococcus infection. Two hundred bacterial cultures containing cocci shaped bacteria were cultured in Trypticase soy agar (TSA) and blood agar mediums. All bacterial cultures were tested by conventional microbiological and biochemical tests, and PCR assay to identify L. garvieae by 16S rDNA genes. The RAPD-PCR method was used to determine the genetic pattern of all isolates. The sample strain pattern of the isolates was analyzed in the NTSYS program. According to a similarity coefficient index of 70%, all L. garvieae isolates were separated into two groups with four RAPD profile types. The highest and the lowest genetic pairwise similarity among the isolates were 98% and 54%, respectively. The results of the present study revealed that RAPD-PCR is an applicable method to describe the genetic diversity of different strains of L. garvieae among farmed fish

Genetic characterization of Lactococcus garvieae isolated from farmed rainbow trout by random amplified polymorphic DNA-PCR in Iran

ΔΕΝ ΔΙΑΤΙΘΕΤΑΙ ΠΕΡΙΛΗΨΗLactococcosis is one of the main bacterial infections of fish around the world. Lactococcus garvieae has been a major cause of rainbow trout losses in freshwater farming. This study aimed to genotype and determine the variability of L. garvieae isolated from infected farmed rainbow trout in Iran by the RAPD-PCR method. Bacterial samples were collected from 12 farms located in the western part of Iran and suspect ted to carry Lactococcus infection. Two hundred bacterial cultures containing cocci shaped bacteria were cultured in Trypticase soy agar (TSA) and blood agar mediums. All bacterial cultures were tested by conventional microbiological and biochemical tests, and PCR assay to identify L. garvieae by 16S rDNA genes. The RAPD-PCR method was used to determine the genetic patternof all isolates. The sample strain pattern of the isolates was analyzed in the NTSYS program. According to a similarity coefficient index of 70%, all L. garvieae isolates were separated into two groups with four RAPD profile types. The highest and the lowest genetic pairwise similarity among the isolates were 98% and 54%, respectively. The results of the present study revealed that RAPD-PCR is an applicable method to describe the genetic diversity of different strains of L .garvieae among farmed fish

Visual Evoked Potential Recording in a Fatigued and Drowsy Patient under Anti-Seizure Medicine Treatment

The visual evoked potential is an electrophysiological technique to screen visual pathway disturbances. A quite fatigued and drowsy patient due to anti-epileptic drug therapy suffering from diplopia was tested for visual evoked potential with pattern reversal stimulation. The result was not reliable; thus, flash stimulation was applied. The optimal result was obtained considering both types of stimulations

Mechanical and structural evaluation of friction stir welded 6061 aluminium alloy lap joints at different welding speeds

Lap joints of 6061-T6 aluminium alloy were produced by friction stir welding, and the influence of welding speed on their weld quality was investigated in terms of welding defects, micro- and macrostructures, hardness distribution, and tensile properties as well as effective plate thickness (EPT) by applying the welding speed in the range 20–60 mm min–1 at constant rotation speed of 1000 rpm. The results showed that although tensile shear strength, joint efficiency, and microhardness of the weld nugget zone (WNZ) rather than the heat affected zone (HAZ), and the EPT increased with an increase in welding speed, the average grain size in the WNZ rather than the HAZ decreased. Due to increasing welding speed, the hooking and thinning defects were gradually restricted from the WNZ to the WNZ/TMAZ interface. The fracture mode within the highest tensile shear strength joints was denoted as plate separation along the hook throughout the stir zone

Dual-wavelength generation with terahertz spacing using GaAs–AlGaAs microring resonator waveguides

In this research, we present the demonstration of GaAs–AlGaAs waveguide resonators. Two microring resonators (MRRs) have the same radius of 6.36 μm are coupled and used to generate dual-wavelength with terahertz (THz) spacing. We have shown that such resonators can be used to generate ultra-wide free spectral range (FSR) pulses with THz spacing, providing THz photonics communication signals. A Gaussian laser beam with power of 1 W is used as input. The MRRs are modeled by using GaAs–AlGaAs with GaAs core having refractive index of 3.368 surrounded by AlGaAs (n = 3.135). The drop port outputs of the MRRs system contains a dual-wavelength generated within 33 nm wavelength range, having a linewidth of 1.48 (185.320 GHz) and FSR of 3.95 nm (500 GHz) which varies slightly along the wavelength. Results were generated using the time-domain travelling wave (TDTW) method and capable of modeling both active and passive photonic circuits

Investigation of microstructure and mechanical properties of friction stir lap welded AA6061-T6 in various welding speeds

Friction stir welding of Aluminum alloys has been increasingly used in the industry on the ground of higher welding quality in comparison with conventional methods. However, not enough studies have been done on a lap joint of AA 6061-T6 which widely been used in aerospace industries. In this article, friction stir lap welding of 6061-T6 aluminium alloy with 5 mm thickness was carried out by using various welding speeds. The effect of welding speed on microstructure, lap shear performance, micro hardness, failure mode and effective plate thickness was investigated. Results showed that tensile shear strength of weld increased by the rising welding speed. Rising welding speed caused hooking and thinning approaches to two plate interfaces which in turn concluding in higher tensile shear strength. The fracture surface of welds was analyzed by field emission scanning electron microscopy (FE-SEM). Study of the fracture surface of the nugget zone by EDX indicated the Fe compounds in that region

Effect of artificial aging on the microstructure and mechanical properties of aluminum alloy AA6061-T6

The properties of aluminum alloy AA6061-T6 after aging at 220°C for 0.5 – 8 h are studied by the methods of light and scanning electron microscopy and fractography. The mechanical characteristics of the alloy are determined by tensile tests

Determination of enrofloxacin residue in the muscle and liver of cultured rainbow trout in Chaharmahal-va-Bakhtiary province by ELISA

Enrofloxacin is one of the broad-spectrum antibiotics in veterinary medicine which in recent years its application has grown considerably for the control of infectious diseases in farmed fish. Alpha The aim of this study was to quantify enrofloxacin residue in muscle and liver of rainbow trout cultured in Chaharmahal-va-Bakhtiary province using ELISA method. For this, the samples were obtained from the farms located in Ardal and Koohrang areas during the spring and summer of 2011. Three farms were chosen from each area and 15 samples were taken from three weight categories including 150 g (5 samples from each category). Results revealed that maximum (58.33) and minimum (23.33) percentage of enrofloxacin residue was determined in 150 g categories, respectively. In Koohrang region, the quantity of enrofloxacin residues in muscle and liver samples was 13.84 ± 11.50 and 19.95 ± 18.06, respectively. Meanwhile in Ardal, the quantity of the residue was estimated at 12.83 ± 11.62 and 11.22 ± 11.09, respectively. Considering the sampling time, among spring samples the quantity of the residues in muscle and liver was estimated at 14.27 ± 13 and 22.06 ± 21.69, respectively. The quantity of enrofloxacin among the summer samples was 12.40 ± 10.29 and 8.86 ± 7.31, respectively. Moreover, mean value of enrofloxacin residue in the muscle and liver of Koohrang was higher than Ardal region. It was concluded that enrofloxacin residue was lower than the maximum acceptance limit determined by the European Union

Mechanical characterization of AA6061-T6 aluminum alloy friction stir and tungsten arc welded with and without post-weld heat treatment

Friction stir welding (FSW) process is a solid-state method in which is accepted as a favorable joining method for aluminum alloys and other engineering materials. The joining of metal plates in FSW is done at below their melting point temperature and based on a thermo-mechanical action used by a non-consumable welding tool onto metal plates. Despite the fast development in solid state welding, fusing welding such as Tungsten Inert Gas welding (TIG) is still vastly applied for thick joint design. Furthermore, solid state joining such as FSW is not applicable for positions such as overhead, horizontal and vertical. On the other hand, aluminum alloys have been increasingly applied in different industries, therefore, several research works on the manufacturing processes of these alloys have been developed over the time such as joining (welding) processes. The 6061-T6 aluminum alloy is an Al-Mg-Si precipitation hardening alloy from the 6XXX series which is often employed because it presents relatively good mechanical properties in relation to its light weight. Since the microstructure of 6061-T6 aluminium alloy and chemistry as well as dimension and distribution of the intermetallic particles in the matrix of aluminium alloy may be changed owing to heat generated and severe plastic deformation during the welding process. Accordingly, mechanical properties of weldments can be changed after welding as opposed to the base metal. However, the vast part of these changing can be recovered by doing post weld heat treatment (PWHT). Butt joints of 6061-T6 aluminum alloy were produced by FSW, and the influence of process parameters on their welds quality of weldments in terms of welding defects, microstructure, hardness distribution, and tensile properties by applying the shoulder angle and welding speed in the range of 0-10° and 63-110 mm/min, respectively, have been investigated using NDT, optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive x-ray (EDX) facilities, XRD, Electron backscatter diffraction (EBSD) and mechanical test such as microhardness test and the tensile test on the welded joints, as the first and second objective. The welding results obtained shown that among all the welding conditions, two welding parameters which is 10°– 89 mm/min and 10°-110 mm/min showed the highest tensile properties (184 MPa for UTS) and higher hardness. Consequently, one of them selected to perform post weld heat treatment (PWHT). In additional to above mentioned characterization, nanoindentation test was done to find local mechanical and nanomechanical properties in as-weld and PWHT of selected sample (as stated in third objective). The majority of properties were closed to the base metal condition by performing PWHT. The TIG welding process was performed on 60061-T6 aluminum alloy using ER5356 filler. All above mentioned characterization was performed to find mechanical and nanomechanical properties in as-weld and PWHT conditions. PWHT led to microstructural recovery of the Heat Affected Zone (HAZ) in addition to the appearance of β-phase (Al3Mg2) in the grain boundaries of weld zone. The ultimate tensile stress was improved to 204 MPa, even though the improvement in FSW sample (after PWHT) was better with almost 300 MPa. Final comparison between the effect of these two process on mechanical, metallurgical and nanomechanical properties of 6061-T6 aluminum alloy as well as the effect of PWHT in the properties studied shows better mechanical, metallurgical and metallurgical properties