Search results for "Anisotropy"

The impact of the volumetric swelling behavior on the water uptake of gas shale

2018

Abstract Water uptake of gas shales is commonly considered one of the most important factors responsible for fluid loss during flowback operations after hydraulic fracturing. Imbibition experiments cover a key role in this context to analyze the impact of several factors (such as mineralogical composition, fluids composition, anisotropic structure, volumetric swelling) that contribute to the water uptake in these unconventional reservoirs. The aim of this study is the quantification of the impact of the volumetric response (swelling and shrinkage) of gas shales on the water uptake during imbibition and desiccation processes. An experimental methodology to quantify the volumetric response du…

2016

Focal demyelinated lesions, diffuse white matter (WM) damage and grey matter (GM) atrophy influence directly the disease progression in patients with multiple sclerosis. The aim of this study was to identify specific characteristics of GM and WM structural networks in subjects with clinically isolated syndrome (CIS) in comparison to patients with early relapsing-remitting multiple sclerosis (RRMS). Twenty patients with CIS, thirty three with RRMS and forty healthy subjects were investigated using 3 T-MRI. Diffusion tensor imaging was applied, together with probabilistic tractography and fractional anisotropy (FA) maps for WM and cortical thickness correlation analysis for GM, to determine t…

Comparison between iMSD and 2D-pCF analysis for molecular motion studies on in vivo cells: The case of the epidermal growth factor receptor.

2018

Image correlation analysis has evolved to become a valuable method of analysis of the diffusional motion of molecules in every points of a live cell. Here we compare the iMSD and the 2D-pCF approaches that provide complementary information. The iMSD method provides the law of diffusion and it requires spatial averaging over a small region of the cell. The 2D-pCF does not require spatial averaging and it gives information about obstacles for diffusion at pixel resolution. We show the analysis of the same set of data by the two methods to emphasize that both methods could be needed to have a comprehensive understanding of the molecular diffusional flow in a live cell.

Early silent microstructural degeneration and atrophy of the thalamocortical network in multiple sclerosis

2016

Recent studies on patients with clinically isolated syndrome (CIS) and multiple sclerosis (MS) demonstrated thalamic atrophy. Here we addressed the following question: Is early thalamic atrophy in patients with CIS and relapsing-remitting MS (RRMS) mainly a direct consequence of white matter (WM) lesions-as frequently claimed-or is the atrophy stronger correlated to "silent" (nonlesional) microstructural thalamic alterations? One-hundred and ten patients with RRMS, 12 with CIS, and 30 healthy controls were admitted to 3 T magnetic resonance imaging. Fractional anisotropy (FA) was computed from diffusion tensor imaging (DTI) to assess thalamic and WM microstructure. The relative thalamic vol…

Characterizing microstructural tissue properties in multiple sclerosis with diffusion MRI at 7 T and 3 T: The impact of the experimental design

2019

The recent introduction of advanced magnetic resonance (MR) imaging techniques to characterize focal and global degeneration in multiple sclerosis (MS), like the Composite Hindered and Restricted Model of Diffusion, or CHARMED, diffusional kurtosis imaging (DKI) and Neurite Orientation Dispersion and Density Imaging (NODDI) made available new tools to image axonal pathology non-invasively in vivo. These methods already showed greater sensitivity and specificity compared to conventional diffusion tensor-based metrics (e.g., fractional anisotropy), overcoming some of its limitations. While previous studies uncovered global and focal axonal degeneration in MS patients compared to healthy contr…

Corticospinal Tract Integrity and Long-Term Hand Function Prognosis in Patients With Stroke

2019

Background: The restoration of hand function is an important goal for patients with stroke. This study investigated the relationship between corticospinal tract (CST) integrity and the functional status of the hand in patients with stroke 6 months after onset and evaluated which of the following values would be useful for predicting hand function: fiber number (FN), fractional anisotropy (FA) at the mid-pons, and FA at the pontomedullary junction. Methods: The present retrospective cross-sectional observational study assessed 44 patients with stroke who were able to walk without using a walking aid or orthosis. The final hand function results were classified into three groups: no recovery (…

Angular Trapping of Anisometric Nano-Objects in a Fluid

2012

We demonstrate the ability to trap, levitate, and orient single anisometric nanoscale objects with high angular precision in a fluid. An electrostatic fluidic trap confines a spherical object at a spatial location defined by the minimum of the electrostatic system free energy. For an anisometric object and a potential well lacking angular symmetry, the system free energy can further strongly depend on the object's orientation in the trap. Engineering the morphology of the trap thus enables precise spatial and angular confinement of a single levitating nano-object, and the process can be massively parallelized. Since the physics of the trap depends strongly on the surface charge of the objec…

Characterizing the initial conditions of heavy-ion collisions at the LHC with mean transverse momentum and anisotropic flow correlations

2022

Physics letters / B 834, 137393 (2022). doi:10.1016/j.physletb.2022.137393

Multiple scattering approach for two-electron resonant emission studied by angle-resolved coincidence spectroscopy.

2008

International audience; We have developed a generalization of the multiple-scattering formalism to deal with Auger-photoelectron coincidence spectroscopy APECS in the solid state. We have merged the exact atomic treatment of the angular correlations between the two electrons and the single-particle approach, on which the multiplescattering description of condensed matter relies. This allows the recovering, even in extended systems, of the entangled form of the electron-pair wave function characterizing the coincidence angular diffraction pattern. In the atomic limit our formalism correctly reproduces the cross section, as calculated within the statistical-tensors approach, usually employed …

Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

2011

The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies $E>E_{th}=5.5\times 10^{19}$ eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at $E>E_{th}$ are heavy nuclei with charge $Z$, the proton component of the sources should lead to excesses in the same regions at energies $E/Z$. We here report the lack of anisotropies in these directions at energies above $E_{th}/Z$ (for illustrative values of $Z=6,\ 13,\ 26$). If the anisotropies above $E_{th}$ are du…