Comprehensive 4D velocity mapping of the heart and great vessels by cardiovascular magnetic resonance

<p>Abstract</p> <p>Background</p> <p>Phase contrast cardiovascular magnetic resonance (CMR) is able to measure all three directional components of the velocities of blood flow relative to the three spatial dimensions and the time course of the heart cycle. In this article, methods used for the acquisition, visualization, and quantification of such datasets are reviewed and illustrated.</p> <p>Methods</p> <p>Currently, the acquisition of 3D cine (4D) phase contrast velocity data, synchronized relative to both cardiac and respiratory movements takes about ten minutes or more, even when using parallel imaging and optimized pulse sequence design. The large resulting datasets need appropriate post processing for the visualization of multidirectional flow, for example as vector fields, pathlines or streamlines, or for retrospective volumetric quantification.</p> <p>Applications</p> <p>Multidirectional velocity acquisitions have provided 3D visualization of large scale flow features of the healthy heart and great vessels, and have shown altered patterns of flow in abnormal chambers and vessels. Clinically relevant examples include retrograde streams in atheromatous descending aortas as potential thrombo-embolic pathways in patients with cryptogenic stroke and marked variations of flow visualized in common aortic pathologies. Compared to standard clinical tools, 4D velocity mapping offers the potential for retrospective quantification of flow and other hemodynamic parameters.</p> <p>Conclusions</p> <p>Multidirectional, 3D cine velocity acquisitions are contributing to the understanding of normal and pathologically altered blood flow features. Although more rapid and user-friendly strategies for acquisition and analysis may be needed before 4D velocity acquisitions come to be adopted in routine clinical CMR, their capacity to measure multidirectional flows throughout a study volume has contributed novel insights into cardiovascular fluid dynamics in health and disease.</p

Effect of laser heating temperature on coating characteristics of Stellite 6 deposited by cold spray

Laser-assisted cold spray (LCS) is a new coating and fabrication process which combines some advantages of CS: solid-state deposition, retain their initial composition and high build rate with the ability to deposit materials which are either difficult or impossible to deposit using cold spray alone. Stellite 6 powder is deposited on medium carbon steels by LCS using N 2 as carrier gas pressure. The topography, cross section thickness, structure of the coatings is examined by SEM, optical microscopy, EDX. The results show that thickness and fluctuation of coating are improved with increased deposition site temperature. Porosity of coating is affected by N 2 and deposition site temperature. In this paper, it presents optimal coating using N 2 at a pressure of 3 MPa and temperature of 450°C and deposition site temperature of 1100°C

Enhanced light-harvesting by plasmonic hollow gold nanospheres for photovoltaic performance

A 'sandwich'-structured TiO2NR/HGN/CdS photoanode was successfully fabricated by the electrophoretic deposition of hollow gold nanospheres (HGNs) on the surface of TiO2 nanorods (NRs). The HGNs presented a wide surface plasmon resonance character in the visible region from 540 to 630 nm, and further acted as the scatter elements and light energy 'antennas' to trap the local-field light near the TiO2NR/CdS layer, resulting in the increase of the light harvesting. An outstanding enhancement in the photochemical behaviour of TiO2NR/HGN/CdS photoanodes was attained by the contribution of HGNs in increasing the light absorption and the number of electron-hole pairs of photosensitive semiconductors. The optimized photochemical performance of TiO2NR/HGN/CdS photoanodes by using plasmonic HGNs demonstrated their potential application in energy conversion devices

Influence of the interface on the magnetic properties of NiZn ferrite thin films treated by proton irradiation

In order to systematically investigate the influence of the interface on the magnetic properties, polycrystalline NiZn ferrite thin films were irradiated with 60 keV proton in the dose range from 5 x 10(12) to 5 x 10(16) ions/cm(2). A non-destructive approach by proton irradiation was found to finely adjust the magnetic properties of polycrystalline NiZn ferrite thin films such as coercivity, perpendicular magnetic anisotropy as well as the effective g value. The coercivity is about 725 Oe for high proton dose ferrite, which is twice larger than the unirradiated one. The ferromagnetic resonance measurements indicated that perpendicular magnetic anisotropy and the effective g value increase with the irradiation dose. Our finding indicates that all modifications of these magnetic properties were associated with the change of interface due to the diffusion and the stress induced by proton irradiation. The change of the effective g value is a result of lattice expansion and the decrease of the magnetic dipole interaction between the columnar grains. This work provides a feasible way to tailor the magnetic properties of thin films by ion irradiation and promotes investigations for the stability of magnetic thin film devices in space or unclear radiation environments. (C) 2015 Elsevier B.V. All rights reserved

Three-dimensional thermal weight function method for the interface crack problems in bimaterial structures under a transient thermal loading

Different from previous two-dimensional thermal weight function (TWF) method, a three-dimensional (3D) TWF method is proposed for solving elliptical interface crack problems in bimaterial structures under a transient thermal loading. The present 3D TWF method based on the Betti's reciprocal theorem is a powerful tool for dealing with the transient thermal loading due to the stress intensity factors (SIFs) of whole transient process obtained through the static finite element computation. Several representative examples demonstrate that the 3D TWF method can be used to predict the SIFs of elliptical interface crack subjected to transient thermal loading with high accuracy. Moreover, numerical results indicate that the computing efficiency can be enhanced when dealing with transient problems, especially for large amount of time instants