Arterial mechanics considering structural inhomogeneity in the extracellular matrix

Elastin and collagen fibers are the major extracellular matrix (ECM) constituents of the arterial wall. Elastic fibers in the medial layer form concentric layers of elastic lamella, together with smooth muscles cells and collagen fibers, organizing into a lamellar unit that is considered as a functional unit of the arterial wall. The lamellar unit is designed to support and evenly distribute the mechanical loading in the arterial wall. The ECM fiber networks in the arterial wall are highly inhomogeneous in structure with varying fiber diameters, density, orientation distribution, etc. The objective of this work is to advance the current understanding of the multi-scale ECM mechanics and the role of structural inhomogeneity in the arterial wall using a coupled experimental and modeling approach that integrates mechanical characterization, advanced optical imaging, and computational modeling. Our study on the micromechanics of elastic lamellae shows that structural inhomogeneity is important in maintaining tissue homeostasis. The higher lamellae unfolding in the inner lamellae layer compensates the larger strain experienced at the inner surface of the arterial wall, and plays an important role in maintaining a more evenly distributed stretching/stress in the lamellar layers. Studies on elastin fiber organization reveal that there is a transmural variation in the orientation distribution of elastin fibers through the arterial wall, which is closely correlated with the anisotropic behavior of elastin network. The study of power-law behavior in the arterial wall revealed the structural inhomogeneity in the inter-lamellar ECM network in the form of a nonuniform spatial distribution of interlamellar fibers, in terms of the fiber density along the axial direction, as well as their orientation with respect to lamellar layers. We found that this structural inhomogeneity is the underlying mechanism of the avalanche behavior in the propagation of aortic dissection. In the study of a discrete fiber network model, we proposed a finite element based framework considering the interfiber crosslinking properties of ECM network that successfully predicts the mechanical behavior of arterial elastin network. Our results suggest that rotational stiffness of the crosslinks plays more important role in local fiber-level than in tissue-level responses in the ECM network.2020-03-28T00:00:00

A survey on energy justice: a critical review of the literature

The increasing scarcity of resources and the escalating complexity of reality make the fairness ensuring in energy activities even more difficult. In this context, energy justice, as an emerging cross-field, tries to provide solutions based on practical problems. In the face of the surge of energy justice publications, it is necessary to review them in time, so that we can comprehend the significant achievements and the research directions worthy of further exploration. With the help of visualization tools, this paper conducts a comprehensive quantitative analysis of 1,910 energy justice publications. Based on the results, we reach the following main conclusions: (1) The energy justice publications have only emerged rapidly in recent years; (2) The research hotspots are closely related to the renewable energy transition; (3) The distribution of prominent contributors in this field is relatively concentrated. The main contribution of this study is to comprehensively display the essential characteristics of the literature in this field, such as the evolutions of research themes and the performances of research contributors in different dimensions, so as to provide readers with an effective way to understand the knowledge structure in this field, and help related researchers rationally examine the existing results

Avalanches and power law behavior in aortic dissection progression

Aortic dissection is a devastating cardiovascular disease known for its rapid propagation and high morbidity and mortality. The mechanisms underlying the propagation of aortic dissection are not well understood. Our study reports the discovery of avalanche-like failure of the aorta during dissection propagation that results from the local buildup of strain energy followed by a cascade failure of inhomogeneously distributed interlamellar collagen fibers. An innovative computational model was developed that successfully describes the failure mechanics of dissection propagation. Our study provides the first quantitative agreement between experiment and model prediction of the dissection propagation within the complex extracellular matrix (ECM). Our results may lead to the possibility of predicting such catastrophic events based on microscopic features of the ECM.Published versio

Vascular smooth muscle Sirtuin-1 protects against aortic dissection during Angiotensin II-induced hypertension

BACKGROUND: Sirtuin-1 (SirT1), a nicotinamide adenine dinucleotide(+)-dependent deacetylase, is a key enzyme in the cellular response to metabolic, inflammatory, and oxidative stresses; however, the role of endogenous SirT1 in the vasculature has not been fully elucidated. Our goal was to evaluate the role of vascular smooth muscle SirT1 in the physiological response of the aortic wall to angiotensin II, a potent hypertrophic, oxidant, and inflammatory stimulus. METHODS AND RESULTS: Mice lacking SirT1 in vascular smooth muscle (ie, smooth muscle SirT1 knockout) had drastically high mortality (70%) caused by aortic dissection after angiotensin II infusion (1 mg/kg per day) but not after an equipotent dose of norepinephrine, despite comparable blood pressure increases. Smooth muscle SirT1 knockout mice did not show any abnormal aortic morphology or blood pressure compared with wild-type littermates. Nonetheless, in response to angiotensin II, aortas from smooth muscle SirT1 knockout mice had severely disorganized elastic lamellae with frequent elastin breaks, increased oxidant production, and aortic stiffness compared with angiotensin II-treated wild-type mice. Matrix metalloproteinase expression and activity were increased in the aortas of angiotensin II-treated smooth muscle SirT1 knockout mice and were prevented in mice overexpressing SirT1 in vascular smooth muscle or with use of the oxidant scavenger tempol. CONCLUSIONS: Endogenous SirT1 in aortic smooth muscle is required to maintain the structural integrity of the aortic wall in response to oxidant and inflammatory stimuli, at least in part, by suppressing oxidant-induced matrix metalloproteinase activity. SirT1 activators could potentially be a novel therapeutic approach to prevent aortic dissection and rupture in patients at risk, such as those with hypertension or genetic disorders, such as Marfan's syndrome.R01 HL098028 - NHLBI NIH HHS; HL098028 - NHLBI NIH HHS; HL105287 - NHLBI NIH HHS; T32 HL07224 - NHLBI NIH HH

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Computed tomographic manifestations of celiac ganglia between hypertensive and non‐hypertensive population

Abstract The celiac ganglion (CG) is associated with the sympathetic nervous system (SNS) and plays an important role in the pathogenesis of hypertension. The characteristics of the CG in patients with hypertension remain unknown. The aim of our study was to explore the differences in celiac ganglia (CGs) characteristics between hypertensive and non‐hypertensive populations using computed tomography (CT). CGs manifestations on multidetector row CT in 1003 patients with and without hypertension were retrospectively analyzed. The morphological characteristics and CT values of the left CGs were recorded. The CT values of the ipsilateral adrenal gland (AG) and crus of the diaphragm (CD) were also measured. The left CG was located between the left AG and CD, and most CGs were long strips. The frequency of visualization of the left CGs was higher in the hypertension group than in the non‐hypertension group (p  .05). Except for the left CG in the arterial phase, the CT values of the left CG and AG in the non‐hypertensive group were higher than those in the hypertension group (p < .05). The venous phase enhancement of the left CG in the non‐hypertension group was significantly higher than that in the hypertension group (p < .05). Our findings reveal that CGs have characteristic manifestations in the hypertensive population. As important targets of the SNS, CGs have the potential to regulate blood pressure

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

The core-collapse supernova (CCSN) is considered one of the most energetic astrophysical events in the universe. The early and prompt detection of neutrinos before (pre-SN) and during the supernova (SN) burst presents a unique opportunity for multi-messenger observations of CCSN events. In this study, we describe the monitoring concept and present the sensitivity of the system to pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton liquid scintillator detector currently under construction in South China. The real-time monitoring system is designed to ensure both prompt alert speed and comprehensive coverage of progenitor stars. It incorporates prompt monitors on the electronic board as well as online monitors at the data acquisition stage. Assuming a false alert rate of 1 per year, this monitoring system exhibits sensitivity to pre-SN neutrinos up to a distance of approximately 1.6 (0.9) kiloparsecs and SN neutrinos up to about 370 (360) kiloparsecs for a progenitor mass of 30 solar masses, considering both normal and inverted mass ordering scenarios. The pointing ability of the CCSN is evaluated by analyzing the accumulated event anisotropy of inverse beta decay interactions from pre-SN or SN neutrinos. This, along with the early alert, can play a crucial role in facilitating follow-up multi-messenger observations of the next galactic or nearby extragalactic CCSN