Background: Two common acquisition strategies in MRI are Centre out Phase-Encoding (COPE) and Linear Phase-Encoding (LPE).Purpose: The objectives of this study were to (1) to investigate the effect of concentrations (0.8 and 1.2mmol/L) and different velocities on signal intensity (SI) strength, (2) to find the inflow effect at different velocities at the two concentrations using the LPE and COPE acquisitions, and (3) to recommend the best acquisition for measuring perfusion with MRI using inversion recovery T1-weighted images.Methods: A flow phantom was designed to produce four different steady state flows at the same time. The stationary state can be obtained when the water flow was stopped. All studies were carried out using a 1.5T clinical MR scanner. Mean SI was obtained in ROIs. The inflow correction factor can be calculated from the SI of the steady state flow divided by the SI of the stationary state at the same position in the image.Results: The results show that an increase in concentration and the velocity is associated with increase in the inflow correction factor for the both acquisitions. But the inflow has less effect on SI with the COPE than the LPE acquisition. In addition, the correction value depends on concentration.Conclusion: For measuring the absolute perfusion, the velocity and concentration of contrast agent of the arterial input function should be known to find the inflow correction factor using the two acquisitions. Otherwise, the COPE is the better acquisition for measuring perfusion, because inflow has less effect on SI.

Background: It is needed to minimize the effect of flow direction on the desired area, such as arterial input function (AIF) in magnetic resonance imaging (MRI). Objective: The current study aimed to investigate the effect of flow direction on different velocities (0–, 80. 39 cm/s) for the strength of the signal intensity (SI) at the linear phase-encoding (LPE) and the center out phase-encoding (COPE) schemes and to recommend the best flow direction in a selected slice and scheme for absolute perfusion measurement by inversion recovery T1-weighted turbo fast low-angle shot (TurboFLASH) MR images. Material and Methods: In this experimental study, the flow rates were measured using a flow phantom, and the signal intensity (SI) was measured at the two opposite flow directions in the Z-axis perpendicular to the coronal image at a concentration of 0. 8 mmol/L of gadolinium-diethylenetriaminepantaacetic acid (Gd-DTPA) by using the LPE and COPE schemes. Results: The increase in velocity along with the growth in SI and inflow affected the use of LPE and COPE acquisitions in both directions. The velocity of the arterial input function is needed to calculate the inflow correction factor by using two schemes in two opposite flow directions to investigate perfusion. Conclusion: The COPE scheme was better than the LPE scheme in measuring perfusion since the velocity and direction of blood flow affect SI less.

Introduction: According to the cumulative evidence, genes encoding GABA receptors inhibit neurotransmitters in CNS and are intricately involved in the pathogenesis of mood disorders. Based on this hypothesis, these genes may be expressed in bipolar patients. As a result, we evaluated the gene expressions of GABA-b3 and HT1D receptors to assess their associations with bipolar mood disorder.Methods: In this study, 22 patients with bipolar I disorder (single manic episode) and 22 healthy individuals were enrolled. All participants were older than 15 years and had referred to Farshchian Hospital, Hamadan, Iran. They were diagnosed based on DSM IV–TR criteria and young mania rating scale in order to determine the severity of mania by a psychiatrist as bipolar Type 1 disorder in manic episode. We evaluated the expression of GABA–b3 and HT1D receptor genes in peripheral blood mononuclear cells, using real-time RT-PCR analysis.Results: In our study, a reduction in the gene expression of GABA–β3 and HT1D receptors was observed in peripheral blood mononuclear cells of the patients with bipolar disorders compared to the healthy controls.Conclusion: The results of this study supports the hypothesis that the gene expression for serotonin and GABA receptors can be employed in elucidating the pathogenesis of bipolar disorders.

Introduction: Echo-planar imaging (EPI) is a group of fast data acquisition methods commonly used in fMRI studies. It acquires multiple image lines in k-space after a single excitation, which leads to a very short scan time. A well-known problem with EPI is that it is more sensitive to distortions due to the used encoding scheme.Source of distortion is inhomogeneity in the static B0 field that causes more geometric distortion in phase encoding direction. This inhomogeneity is induced mainly by the magnetic susceptibility differences between various structures within the object placed inside the scanner, often at air-tissue or bone-tissue interfaces. Methods of reducing EPI distortion are mainly based on decreasing steps of the phase encoding.Reducing steps of phase encoding can be applied by reducing field of view, slice thickness, and/or the use of parallel acquisition technique.Materials and Methods: We obtained three data acquisitions with different FOVs including: conventional low resolution, conventional high resolution, and zoomed high resolution EPIs. Moreover we used SENSE technique for phase encoding reduction. All experiments were carried out on three Tesla scanners (Siemens, TIM, and Germany) equipped with 12 channel head coil. Ten subjects participated in the experiments.Results: The data were processed by FSL software and were evaluated by ANOVA. Distortion was assessed by obtaining low displacement voxels map, and calculated from a field map image.Conclusion: We showed that image distortion can be reduced by decreasing slice thickness and phase encoding steps.Distortion reduction in zoomed technique resulted the lowest level, but at the cost of signal-to-noise loss.Moreover, the SENSE technique was shown to decrease the amount of image distortion, efficiently.

The aim is to characterize the role of symmetry pattern on the flow control induced by dielectric barrier discharge plasma actuators. Two DBD actuators are employed for in-phase excitation with duty cycle 50% leading to symmetric wake pattern and out-phase excitation for two pulsing frequencies St=0.2 and St=1 at Re=1000 which forms quasi-symmetric and asymmetric flow structures respectively. The modes deduced from POD and DMD methods represent the competition between symmetric (S) and asymmetric mode (K) in all cases. The harmonic in-phase plasma actuation with 50% duty cycle is the most effective flow control method with lowest power consumption. The harmonic out-phase excitation is not much effective; however adjustment of the actuator position can form the symmetric pattern with minimum power consumption. The superharmonic out-phase plasma actuation reduces the wake region however is not effective in lift reduction significantly and consumes high amount of energy. This indicates that phase difference and plasma location influence on the size and symmetry of the vortical structure. Then, based on the symmetry properties of the designed wake pattern created by frequency and phase difference of the plasma actuator, the effective active flow control can be performed. The numerical results are validated with experiments.

The objective of this paper is to evaluate the validity of commonly used multi axial fatigue criteria for different multiaxial loading conditions. The best criterion is identified through comparative analysis. The assessment is based on the experimental research findings of the SAE notched shaft, which is used as a benchmark. The relative performance of the three existing multiaxial fatigue theories based on the strain criteria and the critical plane approaches are investigated. There is no fixed strain life criterion that can predict the fatigue life best for different loading cases. Among all the critical plane models considered, Fatemi and Socie model gives best fatigue life prediction for both multiaxial in phase and 90° out of phase loading cases.