Scaling laws for lattice distortions: Application to high entropy alloys

Lattice distortions are intrinsic features of all solid solution alloys associated with varying atomic radii; this phenomenon facilitates the formation of single-phase solid solutions. Using high-entropy alloys (HEAs), as an example, we investigate the influence of variations in inter-atomic separations for stabilizing and controlling their structural, mechanical, and thermodynamic properties. This is done through a combination of statistical mechanics analysis and molecular dynamics simulations on simplified 2D systems, as well as a 3D crystals with harmonic and anharmonic inter-atomic bonds with varying natural inter-atomic separations. We demonstrate that the impact of this inter-atomic length disorder (representing static lattice distortion) and temperature fluctuations (representing dynamic lattice distortion) on fundamental and universal thermodynamic, structural, and elastic characteristics are similar and can be unified through effective temperature; i.e. a scaling law for HEAs that establishes a relationship between these factors. This scaling law reveals that different HEAs (i.e. varying degrees of local lattice distortions) collapse onto a single curve when plotted against the effective temperature. We demonstrate that lattice distortion significantly enhances the stability of solid solution alloys (relative to phase separation or ordering by effectively increasing the temperature of the system; this stabilization effect is particularly pronounced in HEAs).

Sex-Specific Limitation of Cardiac Capacity During the Adult Life Span: Return to Fundamental Structure and Function

Physiology underlying reduced cardiac pumping capacity in women compared with men and its interaction with aging remains unresolved. Herein, the pressure gradient (PG) driving venous return was manipulated to evidence whether cardiac structure and/or function explain sex differences in cardiac capacity. Healthy women/men matched by age and physical activity were included within young (n = 40, age = 25 ± 4 years) and older (n = 55, age = 60 ± 8 years) groups. Cardiac volumes/output (Q) were assessed up-to-peak exercise under 2 hemodynamic conditions ("low"/"high" PG between lower/upper body). Main outcomes included sex differences in delta ("high" - "low" PG) left ventricular (LV) end-diastolic volume (∆LVEDV), stroke volume (∆SV), and Q (∆Q). In young individuals, "high"-PG increased exercise LVEDV and SV in men (p ≤ .002), but not in women (p ≥ .562), relative to "low"-PG (control condition). Accordingly, peak ∆LVEDV, ∆SV, and ∆Q were enhanced in young men versus young women (p ≤ .019). Notwithstanding, right/left atrial volumes during exercise were similarly increased by "high"-PG in both young sexes (p ≤ .007). "High"-PG exclusively prolonged moderate exercise LV filling time in young men (p ≤ .036). In older individuals, "high"-PG did not modify exercise cardiac volumes and reduced LV diastolic function (p ≤ .049). In conclusion, the female young heart is unrestrained by venous return or structural factors external to the myocardium. As determined during moderate exercise, impaired LV filling time lengthening limits female-specific cardiac capacity. With older age, cardiac chambers are not distended and LV relaxation is impaired with increased PG in both sexes. During early but not late adulthood, a functional LV limitation may explain sex differences in cardiac capacity.

Hemodynamic significance of intracranial atherosclerotic disease and ipsilateral imaging markers of cerebral small vessel disease

INTRODUCTION

Cerebral small vessel disease (CSVD) commonly exists in patients with symptomatic intracranial atherosclerotic disease (sICAD). We aimed to investigate the associations of hemodynamic features of sICAD lesions with imaging markers and overall burden of CSVD.

PATIENTS AND METHODS

Patients with anterior-circulation sICAD (50%-99% stenosis) were analyzed in this cross-sectional study. Hemodynamic features of a sICAD lesion were quantified by translesional pressure ratio (PR = Pressurepost-stenotic/Pressurepre-stenotic) and wall shear stress ratio (WSSR = WSSstenotic-throat/WSSpre-stenotic) via CT angiography-based computational fluid dynamics modeling. PR ⩽median was defined as low ("abnormal") PR, and WSSR ⩾ fourth quartile as high ("abnormal") WSSR. For primary analyses, white matter hyperintensities (WMHs), lacunes, and cortical microinfarcts (CMIs) were assessed in MRI and summed up as overall CSVD burden, respectively in ipsilateral and contralateral hemispheres to sICAD. Enlarged perivascular spaces (EPVSs) and cerebral microbleeds (CMBs) were assessed for secondary analyses.

RESULTS

Among 112 sICAD patients, there were more severe WMHs, more lacunes and CMIs, and more severe overall CSVD burden ipsilaterally than contralaterally (all p < 0.05). Abnormal PR and WSSR (vs normal PR and WSSR) was significantly associated with moderate-to-severe WMHs (adjusted odds ratio = 10.12, p = 0.018), CMI presence (5.25, p = 0.003), and moderate-to-severe CSVD burden (12.55; p = 0.033), ipsilaterally, respectively independent of contralateral WMHs, CMI(s), and CSVD burden. EPVSs and CMBs were comparable between the two hemispheres, with no association found with the hemodynamic metrics.

DISCUSSION AND CONCLUSION

There are more severe WMHs and CMI(s) in the hemisphere ipsilateral than contralateral to sICAD. The hemodynamic significance of sICAD lesions was independently associated with severities of WMHs and CMI(s) ipsilaterally.

Highly Conductive Covalent-Organic Framework Films

Chemically inert organic networks exhibiting electrical conductivity comparable to metals can advance organic electronics, catalysis, and energy storage systems. Covalent-organic frameworks (COFs) have emerged as promising materials for those applications due to their high crystallinity, porosity, and tunable functionality. However, their low conductivity has limited their practical utilization. In this study, copper-coordinated-fluorinated-phthalocyanine and 2,3,6,7-tetrahydroxy-9,10-anthraquinone-based COF (CuPc-AQ-COF) films with ultrahigh conductivity are developed. The COF films exhibit an electrical conductivity of 1.53 × 103 S m-1 and a Hall mobility of 6.02 × 102 cm2 V-1 s-1 at 298 K, reaching the level of metals. The films are constructed by linking phthalocyanines and anthraquinones through vapor-assisted synthesis. The high conductivity properties of the films are attributed to the molecular design of the CuPc-AQ-COFs and the generation of high-quality crystals via the vapor-assisted method. Density functional theory analysis reveals that an efficient donor-acceptor system between the copper-coordinated phthalocyanines and anthraquinones significantly promotes charge transfer. Overall, the CuPc-AQ-COF films set new records of COF conductivity and mobility and represent a significant step forward in the development of COFs for electronic, catalytic, and electrochemical applications.