Elliptic jets, part 2. Dynamics of coherent structures: Pairing

The dynamics of the jet column mode of vortex pairing in the near field of an elliptic jet was investigated. Hot-wire measurements and flow visualization were used to examine the details of the pairing mechanism of nonplanar vortical elliptic structures and its effect on such turbulence measures as coherent velocities, incoherent turbulence intensities, incoherent and coherent Reynolds, stresses, turbulence production, and mass entrainment. It was found that pairing of elliptic vortices in the jet column does not occur uniformly around the entire perimeter, unlike in a circular jet. Merger occurs only in the initial major-axis plane. In the initial minor-axis plane, the trailing vortex rushes through the leading vortex without pairing and then breaks down violently, producing considerably greater entrainment and mixing than in circular or plane jets

Selecting the number and values of the CPWI steering angles and the effect of that on imaging quality

Compounded Plane-Wave Imaging (CPWI) has the ability to provide ultrafast imaging for many applications like colour flow imaging, microbubble imaging and elastography. The compounding operation improves the imaging quality at the expense of reducing the frame rate. Due to the importance of frame rate in ultrafast imaging, selecting the number and value of the compounded angles is a critical step to achieve the best possible imaging quality using the minimum number of angles whilst preserving the frame rate. This paper produces a new method for selecting the angular range and the number of angles in CPWI depending on the characteristics of the transducer and medium using Field II program. Experiments were performed on a wire phantom to show the efficiency of the produced method. The results show a comparative imaging quality of CPWI at the selected parameters when compared with linear imaging

Kaempferol Treatment after Traumatic Brain Injury during Early Development Mitigates Brain Parenchymal Microstructure and Neural Functional Connectivity Deterioration at Adolescence.

Targeting mitochondrial ion homeostasis using Kaempferol, a mitochondrial Ca2+ uniporter channel activator, improves energy metabolism and behavior soon after a traumatic brain injury (TBI) in developing rats. Because of broad TBI pathophysiology and brain mitochondrial heterogeneity, Kaempferol-mediated early-stage behavioral and brain metabolic benefits may accrue from diverse sources within the brain. We hypothesized that Kaempferol influences TBI outcome by differentially impacting the neural, vascular, and synaptic/axonal compartments. After TBI at early development (P31), functional magnetic resonance imaging and diffusion tensor imaging (DTI) were applied to determine imaging outcomes at adolescence (2 months post-injury). Vehicle and Kaempferol treatments were made at 1, 24, and 48 h post-TBI, and their effects were assessed at adolescence. A significant increase in neural connectivity was observed after Kaempferol treatment as assessed by the spatial extent and strength of the somatosensory cortical and hippocampal resting-state functional connectivity (RSFC) networks. However, no significant RSFC changes were observed in the thalamus. DTI measures of fractional anisotropy (FA) and apparent diffusion coefficient, representing synaptic/axonal and microstructural integrity, showed significant improvements after Kaempferol treatment, with highest changes in the frontal and parietal cortices and hippocampus. Kaempferol treatment also increased corpus callosal FA, indicating measurable improvement in the interhemispheric structural connectivity. TBI prognosis was significantly altered at adolescence by early Kaempferol treatment, with improved neural connectivity, neurovascular coupling, and parenchymal microstructure in select brain regions. However, Kaempferol failed to improve vasomotive function across the whole brain, as measured by cerebrovascular reactivity. The differential effects of Kaempferol treatment on various brain functional compartments support diverse cellular-level mitochondrial functional outcomes in vivo

Two-way Quality Assessment Approach for Tumour Detection using Free-hand Strain Imaging

A novel two-way image quality assessment method is proposed for free-hand strain imaging. In elasticity imaging, tissue with different stiffness exhibit varying contrast in the strain images and detectability of a lesion is measured using elastographic contrast-to-noise ratio (CNRe). Representing quality of strain images quantitatively is vital for improving imaging techniques and also for clinical diagnosis. It avoids the subjective approach of interpreting strain images. Conventionally, contrast between stiff lesion and surrounding soft tissue is measured using contrast-to-noise ratio and strain image with the highest CNRe amplitude is considered an optimal strain image. However experimental results have suggested that merely CNRe metric is often misleading and does not always represent the true elastic modulus contrast as the correlation coefficient falls below an acceptable levels and accuracy is compromised. Therefore in this study, the objective is to propose a comprehensive strain image quality assessment method which is reliable for clinical examinations and research

Improved shear wave-front reconstruction method by aligning imaging beam angles with shear-wave polarization: Applied for shear compounding application

In shear compounding, shear waves are generated at various angles and individual elasticity maps are averaged to reduce noise and improve accuracy. The steered shear waves tilt the tissue motion direction therefore conventional plane wave tracking is not capable of capturing true shear wave amplitude and direction. The proposed method aligns the tracking beams with the shear wave angles, enables beam-axis in the direction of tissue motion to estimate true shear wave motion vector. In this experimental work, shear waves are produced at five different angles and motion is captured using proposed and conventional method. All the experiments are conducted using inclusion-based elasticity phantom. In the results, the displacement maps show that proposed method accurately captured the steered push-beam wave-fronts while conventional method produced push-beam direction artefacts. In the final compounded elasticity maps, the proposed method slightly improved background-to-inclusion elasticity ratio, CNR by 2 dB, and produced inclusion boundary shape sharper than the conventional tracking