NOVEL ECHOCARDIOGRAM ANALYSIS OF CARDIAC DYSFUNCTION IS ASSOCIATED WITH MORTALITY IN PEDIATRIC SEPSIS.

ABSTRACT: Objectives: The objective of our study was to semiautomatically generate echocardiogram indices in pediatric sepsis using novel algorithms and determine which indices were associated with mortality. We hypothesized that strain and diastolic indices would be most associated with mortality. Design: Retrospective cohort study of children with sepsis from 2017 to 2022. Survivors and nonsurvivors were compared for echocardiogram indices. Multivariate Cox proportional hazard models were constructed for our primary outcome of in-hospital mortality. Linear regression was performed for secondary outcomes, which included multiple composite 28-day outcomes. Results: Of the 54 patients in the study, 9 (17%) died. Multiple echocardiogram indices of both right (RV) and left ventricles (LV) were associated with in-hospital mortality [RV GLS adjusted hazard ratio (aHR): 1.16 (1.03-1.29), P = 0.011; RV global longitudinal early diastolic strain rate (GLSre) aHR: 0.24 (0.07 to 0.75), P = 0.014; LV GLSre aHR: 0.33 (0.11-0.97), P = 0.044]. Impairment in GLS was associated with fewer ventilator-free days [RV GLS ß-coefficient: -0.47 (-0.84 to -0.10), P = 0.013; LV GLS ß-coefficient -0.62 (-1.07 to -0.17), P = 0.008], organ-support free days [RV GLS ß-coefficient: -0.49 (-0.87 to -0.11), P = 0.013; LV GLS ß-coefficient: -0.64 (-1.10 to -0.17), P = 0.008], and days free from ICU [RV GLS ß-coefficient: -0.42 (-0.79 to -0.05), P = 0.026; LV GLS ß-coefficient: -0.58 (-1.03 to -0.13), P = 0.012]. Systolic indices were not associated with mortality in this cohort. Conclusion: Our study demonstrates the feasibility of obtaining echocardiogram indices in a semiautomatic method using our algorithms. We showed that abnormal strain is associated with worse outcomes in a cohort of children with sepsis.

Characterization of the mechanical properties of van der Waals heterostructures of stanene adsorbed on graphene, hexagonal boron-nitride and silicon carbide.

Stanene has revealed a new horizon in the field of quantum condensed matter and energy conversion devices but its significantly lower tensile strength limits its further applications and effective operation in these nanodevices. Van der Waals heterostructures have given substantial flexibility to integrate different two-dimensional (2D) layered materials over the past few years and have proven highly functional with exceptional features, appealing applications, and innovative physics. Considerable efforts have been made for the preparation, thorough understanding, and applications of van der Waals heterostructures in the fields of electronics and optoelectronics. In this paper, we have executed Molecular Dynamics (MD) simulations to predict the tensile strength of van der Waals heterostructures of stanene (Sn) adsorbed on graphene (Gr), hexagonal boron nitride (hBN), and silicon carbide (SiC) (Sn/Gr, Sn/hBN, and Sn/SiC, respectively) subjected to both armchair and zigzag directional loading at different strain rates for the first time, which has enticing applications in electronic, optoelectronic, energy storage and bio-engineered devices. Among all the van der Waals heterostructures, the Sn/SiC heterostructure exhibits the lowest tensile strength and tensile strain. Furthermore, it has been found that zigzag directional loading could endure more tensile strain before fracture. Besides, it has been disclosed that though the rule of mixtures may accurately reproduce the Young's modulus of these heterostructures, it has limitations to predict the tensile strength. Fracture analysis suggests that for the Sn/hBN heterostructure the fracture initiates from the stanene layer while for the Sn/Gr and Sn/SiC heterostructures the fracture initiates from the Gr and SiC layer, respectively, for both armchair and zigzag directional loading. Overall, this study would aid in the design and efficient operation of Sn/Gr, Sn/hBN, and Sn/SiC heterostructures when subjected to mechanical force.

Tuning the mechanical properties of functionally graded nickel and aluminium alloy at the nanoscale.

In this article, Molecular Dynamics (MD) simulation is used to investigate the tensile mechanical properties of functional graded Ni-Al (Ni3Al) alloy with Ni coating. The grading profile, temperature, crystallographic direction, and concentration of vacancy defects have been varied and corresponding changes in the tensile properties are reported. In general, it has been revealed that functional grading may reduce the ultimate tensile strength (UTS) of this homogeneous alloy but increase Young's modulus (YM). Furthermore, MD simulations suggest that elliptically graded Ni-Al alloy has the highest UTS at low temperature while at high temperature, the largest UTS is recorded for the parabolic grading. Besides, at any temperature, the parabolically graded Ni-Al alloy shows the largest YM, followed by linear grading and elliptical grading. Moreover, it is also observed that the [111] crystallographic direction for this alloy demonstrates the highest UTS and YM. At extremely low temperatures, lattice mismatch is also observed to exert a significant impact on the failure characteristics of functional graded Ni-Al alloys. This investigation also suggests that the vacancy defects introduced via removing either Al or Ni atoms degrades the UTS and YM of FGM alloys remarkably. Besides, it is also found that the UTS and YM of Ni-Al FGM alloys are very sensitive to Ni vacancies compared to Al vacancies. Parabolic grading demonstrates more resilience against vacancy defects, followed by linear and elliptical grading. This paper provides a comprehensive understanding of the mechanical properties of Ni-Al FGM alloys at the atomic level as a potential substitute for homogeneous alloys.

Investigation on the mechanical properties and fracture phenomenon of silicon doped graphene by molecular dynamics simulation.

Silicon doping is an effective way to modulate the bandgap of graphene that might open the door for graphene to the semiconductor industries. However, the mechanical properties of silicon doped graphene (SiG) also plays an important role to realize its full potential application in the electronics industry. Electronic and optical properties of silicon doped graphene are well studied, but, our understanding of mechanical and fracture properties of the doped structure is still in its infancy. In this study, molecular dynamics (MD) simulations are conducted to investigate the tensile properties of SiG by varying the concentration of silicon. It is found that as the concentration of silicon increases, both fracture stress and strain of graphene reduces substantially. Our MD results also suggest that only 5% of silicon doping can reduce the Young's modulus of graphene by ∼15.5% along the armchair direction and ∼13.5% along the zigzag direction. Tensile properties of silicon doped graphene have been compared with boron and nitrogen doped graphene. The effect of temperature, defects and crack length on the stress-strain behavior of SiG has also been investigated. Temperature studies reveal that SiG is less sensitive to temperature compared to free stranding graphene, additionally, increasing temperature causes deterioration of both fracture stress and strain of SiG. Both defects and cracks reduce the fracture stress and fracture strain of SiG remarkably, but the sensitivity to defects and cracks for SiG is larger compared to graphene. Fracture toughness of pre-cracked SiG has been investigated and results from MD simulations are compared with Griffith's theory. It has been found that for nano-cracks, SiG with larger crack length deviates more from Griffith's criterion and the degree of deviation is larger compared to graphene. Fracture phenomenon of pre-cracked SiG and the effect of strain rate on the tensile properties of SiG have been reported as well. These results will aid the design of SiG based semiconducting nanodevices.