Study Of Precentral-Postcentral Connections On Hcp Data Using Probabilistic Tractography And Fiber Clustering

Fiber networks encompass a wide range of natural and manmade materials. The threads or filaments from which they are formed span a wide range of length scales: from nanometers, as in biological tissues and bundles of carbon nanotubes, to millimeters, as in paper and insulation materials. The mechanical and thermal behavior of these complex structures depends on both the individual response of the constituent fibers and the density and degree of entanglement of the network. A question of paramount importance is how to control the formation of a given fiber network to optimize a desired function. The study of fiber clustering of natural flocs could be useful for improving fabrication processes, such as in the paper and textile industries. Here, we use the example of aegagropilae that are the remains of a seagrass (Posidonia oceanica) found on Mediterranean beaches. First, we characterize different aspects of their structure and mechanical response, and second, we draw conclusions on their formation process. We show that these natural aggregates are formed in open sea by random aggregation and compaction of fibers held together by friction forces. Although formed in a natural environment, thus under relatively unconstrained conditions, the geometrical and mechanical properties of the resulting fiber aggregates are quite robust. This study opens perspectives for manufacturing complex fiber network materials.

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Tensile Mechanical Properties and Failure Modes of a Basalt Fiber/Epoxy Resin Composite Material

Advances in Civil Engineering ◽

10.1155/2018/7914727 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Jingjing He ◽

Junping Shi ◽

Xiaoshan Cao ◽

Yifeng Hu

Keyword(s):

Tensile Strength ◽

Composite Material ◽

Fiber Volume Fraction ◽

Failure Modes ◽

Volume Fraction ◽

Basalt Fiber ◽

Orientation Angle ◽

Fiber Volume ◽

Fiber Clustering ◽

Fiber Orientation Angle

Uniaxial tensile tests of basalt fiber/epoxy (BF/EP) composite material with four different fiber orientations were conducted under four different fiber volume fractions, and the variations of BF/EP composite material failure modes and tensile mechanical properties were analyzed. The results show that when the fiber volume fraction is constant, the tensile strength, elastic modulus, and limiting strain of BF/EP composite material all decrease with increasing fiber orientation angle. When the fiber orientation angle is constant, the tensile strength, elastic modulus, and limiting strain of BF/EP composite material all increase with increasing fiber volume fraction. A certain degree of fiber clustering appears in the epoxy resin when the basalt fiber volume fraction is >1.2%. The fiber equidistribution coefficient and clustering fiber content were used to characterize the basalt fiber clustering effect. With the increase of fiber volume fraction, the clustering fiber content gradually increased, but the fiber equidistribution coefficient decreased. Meanwhile, based on Tsai theory, a geometric model and a tensile mechanical model of the clustering fiber are established. By considering the fiber clustering effect, the BF/EP composite material tensile strength is calculated, and the calculated values are close to the experimental results.

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Clinically Weighted Probabilistic Tractography Mapping of Therapeutic Thalamic Deep Brain Stimulation for Essential Tremor

Neurosurgery ◽

10.1093/neuros/nyz310_364 ◽

2019 ◽

Vol 66 (Supplement_1) ◽

Author(s):

Evangelia Tsolaki ◽

Alon Kashanian ◽

Nader Pouratian

Keyword(s):

Deep Brain Stimulation ◽

Clinical Outcome ◽

Essential Tremor ◽

Clinical Improvement ◽

Brain Stimulation ◽

Structural Connectivity ◽

Precentral Gyrus ◽

Probabilistic Tractography ◽

Whole Brain ◽

Deep Brain

Abstract INTRODUCTION Traditional targeting methods rely on indirect targeting with atlas-defined coordinates that induce interpatient anatomical and functional variability. Precise targeting is crucial for successful surgical intervention associated with improved surgical outcomes. Here, we use clinically weighted probabilistic tractography to investigate the connectivity from volume of tissue activated (VTA) to whole brain in order to evaluate the relationship between structural connectivity and clinical outcome of patients that underwent thalamic deep brain stimulation (DBS). METHODS Magnetic resonance imaging and clinical outcomes from 10 essential tremor (ET) patients who were treated by VIM-DBS at the University of California Los Angeles were evaluated. LeadBDS was used for the VTA calculation and FSL was used to evaluate the whole brain probabilistic tractography of VTA. Tractography maps were binarized and weighted based on the percent of clinical improvement using the Fahn-Tolosa-Martin Tremor Rating Score. The resulting clinically weighted maps were non-linearly fused to MNI space and averaged. These population maps provide a voxel-by-voxel map of the average clinical improvement observed when the VTA demonstrates structural connectivity to the whole brain. RESULTS The VTA connectivity to the whole brain was delineated. Superior clinical improvement was associated with connectivity to voxels connecting the thalamus to the precentral gyrus and to the brainstem/cerebellum. Also, the clinical efficacy map showed that patients with higher clinical improvement (>70%) presented stronger structural connectivity to the precentral gyrus and to the caudal projection to the cerebellum. CONCLUSION Stronger connectivity to the precentral gyrus and to brainstem/cerebellum is associated with superior clinical outcome in thalamic DBS for ET. In the future, rather than focusing on connectivity to predetermined targets, these clinically weighted tractography maps can be used with a reverse algorithm to identify the optimal region of the thalamus to provide clinically superior results.

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