Hasil untuk "math.AG"

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CrossRef Open Access 2020
Regional Gray Matter Density Associated With Fast-Paced Walking in Older Adults: A Voxel-Based Morphometry Study

Nemin Chen, Caterina Rosano, Helmet T Karim et al.

Abstract Background Walking speed during fast-paced walking task has been associated with cognitive function. It is unclear what underlying brain structures are related to fast-paced walking. We investigated the association of gray matter (GM) density with fast-paced walking speed and usual-paced walking speed. Methods We collected data from 284 older adults from a subset of the Health, Aging, and Body composition study (mean age = 83 [SD = 2.8], 58% women, 41% black). Voxel-wise analyses on magnetic resonance imaging data identified regions of the brain where GM density was associated with fast-paced walking speed. We then extracted GM density for all identified regions and modeled the association with fast-paced walking speed after adjusting for demographic factors, clinical factors, and cognitive function. Analyses were repeated for usual-paced walking. Regions with beta coefficients ≥0.3 m/s were considered to be meaningfully correlated. Results GM density of clusters from cortical regions in the right middle and superior frontal gyrus, right postcentral gyrus, and left superior temporal gyrus were positively correlated with fast-paced walking speed in adjusted models. Adjustment for cognitive function had little impact on the findings. Caudate was correlated with usual paced walking speed at coefficient ≥0.3 m/s after adjustment of demographic factors and clinical factors, but not after further adjustment of cognitive function. Conclusions Fast-paced walking speed was correlated with GM density of right middle and superior frontal gyrus, right postcentral gyrus, and left superior temporal gyrus, and could potentially provide evidence about subclinical structural change of brain related to aging.

10 sitasi en
CrossRef Open Access 2019
Through‐Space Spin Coupling in a Silver(II) Porphyrin Dimer upon Stepwise Oxidations: Ag<sup>II</sup>⋅⋅⋅Ag<sup>II</sup>, Ag<sup>II</sup>⋅⋅⋅Ag<sup>III</sup>, and Ag<sup>III</sup>⋅⋅⋅Ag<sup>III</sup> Metallophilic Interactions

Akhil Kumar Singh, Mohammad Usman, Giuseppe Sciortino et al.

AbstractInvited for the cover of this issue are Sankar Prasad Rath and co‐workers at the Indian Institute of Technology (IIT Kanpur) and the University of Sassari. The image depicts through space interactions in a cofacial AgII porphyrin dimer upon stepwise oxidations, which allow the estimation of the structure and energy characteristics of metallophilic interactions between AgII/AgII (d9/d9), AgIII/AgIII (d8/d8) and also mixed‐valent AgII/AgIII (d9/d8) complexes. Read the full text of the article at 10.1002/chem.201901731.

1 sitasi en
CrossRef 2025
SIMULATION-BASED ANALYSIS OF TOOL WEAR PROGRESSION AND MECHANISMS IN TITANIUM ALLOY MACHINING

inspire AG, N. Zhang, F. Kneubühler et al.

This study presents a simulation-based approach for analyzing tool wear progression in Ti6Al4V machining using an in-house developed hybrid Smoothed Particle Hydrodynamics–Finite Element Method (SPH-FEM) solver. Cutting experiments are used to examine key wear indicators including crater depth and flank wear land width along with SEM analysis to understand underlying wear mechanisms. Despite the dominance of diffusion-accelerated attritious wear in titanium machining, the phenomenological Usui model is selected for wear simulation. Within a two-dimensional chip formation framework, the wear algorithm is integrated at the end of each time increment to predict wear progression based on tool–chip and tool–workpiece contact conditions. A correlation between relative wear rates and the Arrhenius law coefficient across varying cutting speeds is identified through simulation, providing the foundation for a new calibration method tailored to the Usui wear model. The calibrated models are then applied back within the same simulation framework for validation, demonstrating good predictive accuracy and strong agreement with experimental trends, particularly for crater wear.

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