Multivariate hyperspectral data analytics across length scales to probe compositional, phase, and strain heterogeneities in electrode materials.

The origins of performance degradation in batteries can be traced to atomistic phenomena, accumulated at mesoscale dimensions, and compounded up to the level of electrode architectures. Hyperspectral X-ray spectromicroscopy techniques allow for the mapping of compositional variations, and phase separation across length scales with high spatial and energy resolution. We demonstrate the design of workflows combining singular value decomposition, principal-component analysis, k-means clustering, and linear combination fitting, in conjunction with a curated spectral database, to develop high-accuracy quantitative compositional maps of the effective depth of discharge across individual positive electrode particles and ensembles of particles. Using curated reference spectra, accurate and quantitative mapping of inter- and intraparticle compositional heterogeneities, phase separation, and stress gradients is achieved for a canonical phase-transforming positive electrode material, α-V2O5. Phase maps from single-particle measurements are used to reconstruct directional stress profiles showcasing the distinctive insights accessible from a standards-informed application of high-dimensional chemical imaging.

Exercise Hypertension in Athletes.

Background: An exaggerated blood pressure response (EBPR) during exercise testing is not well defined, and several blood pressure thresholds are used in different studies and recommended in different guidelines. Methods: Competitive athletes of any age without known arterial hypertension who presented for preparticipation screening were included in the present study and categorized for EBPR according to American Heart Association (AHA), European Society of Cardiology (ESC), and American College of Sports Medicine (ACSM) guidelines as well as the systolic blood pressure/MET slope method. Results: Overall, 1137 athletes (mean age 21 years; 34.7% females) without known arterial hypertension were included April 2020−October 2021. Among them, 19.6%, 15.0%, and 6.8% were diagnosed EBPR according to ESC, AHA, and ACSM guidelines, respectively. Left ventricular hypertrophy (LVH) was detected in 20.5% of the athletes and was approximately two-fold more frequent in athletes with EBPR than in those without. While EBPR according to AHA (OR 2.35 [95%CI 1.66−3.33], p < 0.001) and ACSM guidelines (OR 1.81 [95%CI 1.05−3.09], p = 0.031) was independently (of age and sex) associated with LVH, EBPR defined according to ESC guidelines (OR 1.49 [95%CI 1.00−2.23], p = 0.051) was not. In adult athletes, only AHA guidelines (OR 1.96 [95%CI 1.32−2.90], p = 0.001) and systolic blood pressure/MET slope method (OR 1.73 [95%CI 1.08−2.78], p = 0.023) were independently predictive for LVH. Conclusions: Diverging guidelines exist for the screening regarding EBPR. In competitive athletes, the prevalence of EBPR was highest when applying the ESC (19.6%) and lowest using the ACSM guidelines (6.8%). An association of EBPR with LVH in adult athletes, independently of age and sex, was only found when the AHA guideline or the systolic blood pressure/MET slope method was applied.