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#32746370   2020/07/22 To Up

Simulation of blood as fluid: A review from rheological aspects.

Blood flow in the human vascular system is a complex to understand example of fluid dynamics in a closed conduit. Any irregularities in the hemodynamics may lead to lethal cardiovascular disease like heart attack, heart failure and ischemia. Numerical simulation of hemodynamics in the blood vessel can facilitate a thorough understanding of blood flow and its interaction with the adjacent vessel wall. A good simulation approach for blood flow can be helpful in early prediction and diagnosis of the mentioned disease. The simulation outcomes may also provide decision support for surgical planning and medical implants. This study reports an extensive review of various approaches adopted to analyze the influence of blood rheological characteristics in a different class of blood vessels. In particular, emphasis was given on the identification of best possible rheological model to effectively solve the hemodynamics inside different blood vessels. The performance capability of different rheological models was discussed for different classes and conditions of vessels and the best/poor performing models are listed out. The Carreau, Casson and generalized power-law models were appeared to be superior for solving the blood flow at all shear rates. In contrast, power law, Walburn-Scheck and Herchel-Bulkley model lacks behind in the purpose.
Vikas Kannojiya, Arup Das, Prasanta Kumar Das

1589 related Products with: Simulation of blood as fluid: A review from rheological aspects.

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#32746324   2020/07/20 To Up

Evaluating reachable workspace and user control over prehensor aperture for a body-powered prosthesis.

Using a shoulder harness and control cable, a person can control the opening and closing of a body-powered prosthesis prehensor. In many setups the cable does not pass adjacent to the shoulder joint center allowing shoulder flexion on the prosthetic side to be used for prehensor control. However, this makes cable setup a difficult compromise as prosthesis control is dependent on arm posture; too short and the space within which a person can reach may be unduly restricted, too long and the user may not be able to move their shoulder sufficiently to take up the inevitable slack at some postures and hence have no control over prehensor movement. Despite the fundamental importance of reachable workspace to users, to date there have been no studies in prosthetics on this aspect. Here, a methodology is presented to quantify the reduction in the reachable volume due to the harness, and to record the range-of-motion of the prehensor at a series of locations within the reachable workspace. Ten anatomically intact participants were assessed using a body-powered prosthesis simulator. Data was collected using a 3D motion capture system and an electronic goniometer. The harnessed reachable workspace was 38-85% the size of the unharnessed volume with participants struggling to reach across the body and above the head. Across all arm postures assessed, participants were only able to achieve full prehensor range-of-motion in 9%. The methodologies presented could be used to evaluate future designs of both body-powered and myoelectric prostheses.
Alix Chadwell, Laurence P J Kenney, David Howard, Robert T Ssekitoleko, Brenda T Nakandi, John Head

1995 related Products with: Evaluating reachable workspace and user control over prehensor aperture for a body-powered prosthesis.

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#32746254   2020/05/18 To Up

Top-Down Shape Abstraction Based on Greedy Pole Selection.

Motivated by the fact that the medial axis transform is able to encode the shape completely, we propose to use as few medial balls as possible to approximate the original enclosed volume by the boundary surface. We progressively select new medial balls, in a top-down style, to enlarge the region spanned by the existing medial balls. The key spirit of the selection strategy is to encourage large medial balls while imposing given geometric constraints. We further propose a speedup technique based on a provable observation that the intersection of medial balls implies the adjacency of power cells (in the sense of the power crust). We further elaborate the selection rules in combination with two closely related applications. One application is to develop an easy-to use ball-stick modeling system that helps non-professional users to quickly build a shape with only balls and wires, but any penetration between two medial balls must be suppressed. The other application is to generate porous structures with convex, compact (with a high isoperimetric quotient) and shape-aware pores where two adjacent spherical pores may have penetration as long as the mechanical rigidity can be well preserved.
Zhiyang Dou, Shiqing Xin, Rui Xu, Jian Xu, Yuanfeng Zhou, Shuang-Min Chen, Wenping Wang, Xiuyang Zhao, Changhe Tu

2712 related Products with: Top-Down Shape Abstraction Based on Greedy Pole Selection.

3 x 3 reactionsOne 96-Well Microplate Ki 100ul 2 ml Two 96-Well Microplate Ki 25 ml Ready-to-use 1 mg 25 MGOne 96-Well Microplate Ki 6 ml

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#32746230   2020/07/27 To Up

Optimum speckle tracking based on ultrafast ultrasound for improving blood flow velocimetry.

Speckle tracking using optimum comparison frames (STO) is proposed to improve the blood flow velocity profile (BFVP) estimation based on ultrafast ultrasound with coherent plane-wave compounding. The optimum comparison frames are as far as possible from the reference frame image while possessing a speckle correlation above a given threshold. The correlation thresholds for different kernel sizes are determined via an experiment based on a vascular-mimicking phantom. In in vitro experiments with different peak velocities of the flow ranging from 0.38 to 1.18 m/s, the proposed STO method with three kernel sizes (0.46 × 0.46 mm2, 0.31 × 0.69 mm2, and 0.92 × 0.92 mm2) is used for the BFVP estimations. The normalized root mean square errors (NRMSEs) between the estimated and theoretical BFVPs are calculated and compared with the results based on the speckle tracking using adjacent-frame images. For the three kernel sizes, the mean relative decrements in the STO-based NRMSEs are 46.6%, 44.7%, and 52.9%, and the standard deviations are 36.8%, 37.6%, and 35.9%, respectively. The STO method is also validated by in vivo experiments using rabbit iliac arteries with contrast agents. With parabolic curves fitting to the mean velocity estimates, the average relative increments for the STO-based R2 (coefficients of determination) are 7.22% and 6.25% for kernel sizes of 0.46 × 0.46 mm2 and 0.31 × 0.69 mm2, respectively. In conclusion, the STO method improves the BFVP measurement accuracy, whereby accurate diagnosis information can be acquired for clinical applications.
Bingbing He, Yufeng Zhang, Kexin Zhang, Jianhua Chen, Junhua Zhang, Hong Liang

1263 related Products with: Optimum speckle tracking based on ultrafast ultrasound for improving blood flow velocimetry.

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#32746098   2020/05/27 To Up

Multivariate Statistical Modeling of Retinal Optical Coherence Tomography.

In this paper a new statistical multivariate model for retinal Optical Coherence Tomography (OCT) Bscans is proposed. Due to the layered structure of OCT images, there is a horizontal dependency between adjacent pixels at specific distances, which led us to propose a more accurate multivariate statistical model to be employed in OCT processing applications such as denoising. Due to the asymmetric form of the probability density function (pdf) in each retinal layer, a generalized version of multivariate Gaussian Scale Mixture (GSM) model, which we refer to as GM-GSM model, is proposed for each retinal layer. In this model, the pixel intensities in each retinal layer are modeled with an asymmetric Bessel K Form (BKF) distribution as a specific form of the GM-GSM model. Then, by combining some layers together, a mixture of GM-GSM model with eight components is proposed. The proposed model is then easily converted to a multivariate Gaussian Mixture model (GMM) to be employed in the spatially constrained GMM denoising algorithm. The Q-Q plot is utilized to evaluate goodness of fit of each component of the final mixture model. The improvement in the noise reduction results based on the GM-GSM model, indicates that the proposed statistical model describes the OCT data more accurately than other competing methods that do not consider spatial dependencies between neighboring pixels.
Maryam Samieinasab, Zahra Amini, Hossein Rabbani

2421 related Products with: Multivariate Statistical Modeling of Retinal Optical Coherence Tomography.

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#32745807   2020/07/03 To Up

An epigenome-wide association study of Alzheimer's disease blood highlights robust DNA hypermethylation in the HOXB6 gene.

A growing number of epigenome-wide association studies have demonstrated a role for DNA methylation in the brain in Alzheimer's disease. With the aim of exploring peripheral biomarker potential, we have examined DNA methylation patterns in whole blood collected from 284 individuals in the AddNeuroMed study, which included 89 nondemented controls, 86 patients with Alzheimer's disease, and 109 individuals with mild cognitive impairment, including 38 individuals who progressed to Alzheimer's disease within 1 year. We identified significant differentially methylated regions, including 12 adjacent hypermethylated probes in the HOXB6 gene in Alzheimer's disease, which we validated using pyrosequencing. Using weighted gene correlation network analysis, we identified comethylated modules of genes that were associated with key variables such as APOE genotype and diagnosis. In summary, this study represents the first large-scale epigenome-wide association study of Alzheimer's disease and mild cognitive impairment using blood. We highlight the differences in various loci and pathways in early disease, suggesting that these patterns relate to cognitive decline at an early stage.
Janou A Y Roubroeks, Adam R Smith, Rebecca G Smith, Ehsan Pishva, Zina Ibrahim, Martina Sattlecker, Eilis J Hannon, Iwona Kłoszewska, Patrizia Mecocci, Hilkka Soininen, Magda Tsolaki, Bruno Vellas, Lars-Olof Wahlund, Dag Aarsland, Petroula Proitsi, Angela Hodges, Simon Lovestone, Stephen J Newhouse, Richard J B Dobson, Jonathan Mill, Daniël L A van den Hove, Katie Lunnon

2077 related Products with: An epigenome-wide association study of Alzheimer's disease blood highlights robust DNA hypermethylation in the HOXB6 gene.

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#32745667   2020/07/31 To Up

Relationships between rectal and perirectal doses and rectal bleeding or tenesmus in pooled voxel-based analysis of 3 randomised phase III trials.

This study aimed to identify anatomically-localised regions where planned radiotherapy dose is associated with gastrointestinal toxicities in healthy tissues throughout the pelvic anatomy.
M Marcello, J W Denham, A Kennedy, A Haworth, A Steigler, P B Greer, L C Holloway, J A Dowling, M G Jameson, D Roach, D J Joseph, S L Gulliford, D P Dearnaley, M R Sydes, E Hall, M A Ebert

2413 related Products with: Relationships between rectal and perirectal doses and rectal bleeding or tenesmus in pooled voxel-based analysis of 3 randomised phase III trials.

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#32745662   2020/07/31 To Up

Cortical reorganization processes in meditation naïve participants induced by 7 weeks focused attention meditation training.

Based on the evidence that meditation is associated with numerous beneficial effects on well-being and reduced stress-related symptoms, mindfulness-based techniques were increasingly implemented into psychotherapeutic programs. However, different meditation styles and the cross-sectional nature of most previous analyses resulted in a great variety of morphometric findings. The present study aims to elucidate cortical reorganization processes and altered axonal integrity caused by short-term meditation training, and benefits from solely using focused attention meditation (FAM).
Lukas Lenhart, Ruth Steiger, Michaela Waibel, Stephanie Mangesius, Astrid E Grams, Nicolas Singewald, Elke R Gizewski

2891 related Products with: Cortical reorganization processes in meditation naïve participants induced by 7 weeks focused attention meditation training.

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#32745405   // To Up

Observation of Non-Abelian Nodal Links in Photonics.

In crystals, two bands may cross each other and form degeneracies along a closed loop in the three-dimensional momentum space, which is called nodal line. Nodal line degeneracy can be designed to exhibit various configurations such as nodal rings, chains, links, and knots. Very recently, non-Abelian band topology was proposed in nodal link systems, where the nodal lines formed by consecutive pairs of bands exhibit interesting braiding structures and the underlying topological charges are described by quaternions. Here, we experimentally demonstrate non-Abelian nodal links in a biaxial hyperbolic metamaterial. The linked nodal lines threading through each other are formed by the crossings between three adjacent bands. Based on the non-Abelian charges, we further analyze various admissible nodal link configurations for the three-band system. On the interface between the metamaterial and air, surface bound states in the continuum are observed, which serves as the symmetry-enforced derivative of drumhead surface states from the linked nodal lines. Our work serves as a direct observation of the global topological structures of nodal links, and provides a platform for studying non-Abelian topological charge in the momentum space.
Erchan Yang, Biao Yang, Oubo You, Hsun-Chi Chan, Peng Mao, Qinghua Guo, Shaojie Ma, Lingbo Xia, Dianyuan Fan, Yuanjiang Xiang, Shuang Zhang

2355 related Products with: Observation of Non-Abelian Nodal Links in Photonics.

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