Support Pressure Acting on the Epicardial Surface of a Rat Left Ventricle-A Computational Study.

The present computational study investigates the effects of an epicardial support pressure mimicking a heart support system without direct blood contact. We chose restrictive cardiomyopathy as a model for a diseased heart. By changing one parameter representing the amount of fibrosis, this model allows us to investigate the impairment in a diseased left ventricle, both during diastole and systole. The aim of the study is to determine the temporal course and value of the support pressure that leads to a normalization of the cardiac parameters in diseased hearts. These are quantified via the end-diastolic pressure, end-diastolic volume, end-systolic volume, and ejection fraction. First, the amount of fibrosis is increased to model diseased hearts at different stages. Second, we determine the difference in the left ventricular pressure between a healthy and diseased heart during a cardiac cycle and apply for the epicardial support as the respective pressure difference. Third, an epicardial support pressure is applied in form of a piecewise constant step function. The support is provided only during diastole, only during systole, or during both phases. Finally, the support pressure is adjusted to reach the corresponding parameters in a healthy rat. Parameter normalization is not possible to achieve with solely diastolic or solely systolic support; for the modeled case with 50% fibrosis, the ejection fraction can be increased by 5% with purely diastolic support and 14% with purely systolic support. However, the ejection fraction reaches the value of the modeled healthy left ventricle (65.6%) using a combination of diastolic and systolic support. The end-diastolic pressure of 13.5 mmHg cannot be decreased with purely systolic support. However, the end-diastolic pressure reaches the value of the modeled healthy left ventricle (7.5 mmHg) with diastolic support as well as with the combination of the diastolic and systolic support. The resulting negative diastolic support pressure is -4.5 mmHg, and the positive systolic support pressure is 90 mmHg. We, thereby, conclude that ventricular support during both diastole and systole is beneficial for normalizing the left ventricular ejection fraction and the end-diastolic pressure, and thus it is a potentially interesting therapy for cardiac insufficiency.

Transformation performance and subsystem coupling of resource-based cities in China: An analysis based on the support-pressure framework.

The sustainable development of resource-based cities is vital to China's high-quality development. Based on the support-pressure framework, this study simplifies the city system into an economy-society subsystem (ESS) and a resource-environment subsystem (RES), and measures the economy social developmental level (ESDL) and resource environmental carrying capacity (RECC) of China's 116 resource-based cities using the improved entropy-TOPSIS model. Then, it applies the coupling coordination degree (CCD) and relative development models to explore their coupling coordination relationships and relative developmental types. The results are as follows. (1) The ESDL and RECC of China's resource-based cities have improved significantly, and there is a large divergence between cities in different regions, development stages, and dominant resource types. (2) The CCD between the ESDL and RECC of China's resource-based cities is still not ideal, and no city qualifies for the high coordination category. (3) Overall, the RECC lags behind the ESDL, and the cities with a lagging ESDL are concentrated in the western and northeastern regions. Based on these conclusions, three specific suggestions are put forth. This study may provide a scientific reference for the Chinese government to formulate a sustainable development plan for resource-based cities. Integr Environ Assess Manag 2022;18:770-783. © 2021 SETAC.

Spatiotemporal Heterogeneity and Driving Factors of Water Resource and Environment Carrying Capacity under High-Quality Economic Development in China.

Rapid economic growth and social development in China have led to serious water pollution problems and water resource shortages, limiting the sustainable development that could support both the socio-economy and water resources carrying capacity (WRECC). However, the spatial heterogeneity and evolutionary characteristics of the coordination between the WRECC and economic development have not been adequately explored in China. In this study, we developed the support and pressure indicators of China's 30 provinces and then analyzed the spatiotemporal distribution and evolution characteristics of their WRECC by using the geographically and temporally weighted regression (GTWR) model. The main findings are shown in the following: (i) From a temporal perspective, there has been an overall upward trend in the WRECC to support human activities; however, the WRECC level is not high. Approximately 63.7% of provinces remain in an overloaded state, indicating that the support indicator of most provinces is smaller than the pressure indicator imposed by human social activities. (ii) There are significant spatial differences in the WRECC indicators across provinces. Provinces with low-level WRECCs are concentrated in central China but decrease significantly from the country's borders to its center. Eastern regions have a medium-level of WRECC with the greatest degree of regional difference, while western regions have a high-level of WRECC with the smallest degree of regional difference. The variation of WRECC is attributed to within-group differences in the three geographical regions in China. (iii) The factors that significantly impact the WRECC include population density, gross domestic product (GDP), temperature, urbanization, the added value of tertiary industry within the GDP, and R&D expenditures. GDP and R&D expenditures positively impact the WRECC, while the other four factors have different influences on the WRECC. (iv) The spatial distributions of driving factors show significant aggregation characteristics, with decreasing trends from the eastern to western regions and from the southern to northern regions. These findings present a comprehensive understanding of the current WRECC in China's provinces which can be used as a reference for realizing environmentally sustainable water development strategies under high-quality economic development.

Stability Analysis of the Horseshoe Tunnel Face in Rock Masses.

Accurately estimating the stability of horseshoe tunnel faces remains a challenge, especially when excavating in rock masses. This study aims to propose an analytical model to analyze the stability of the horseshoe tunnel face in rock masses. Based on discretization and "point-by-point" techniques, a rotational failure model for horseshoe tunnel faces is first proposed. Based on the proposed failure model, the upper-bound limit analysis method is then adopted to determine the limit support pressure of the tunnel face under the nonlinear Hoek-Brown failure criterion, and the calculated results are validated by comparisons with the numerical results. Finally, the effects of the rock properties on the limit support pressure and the 3D failure surface are discussed. The results show that (1) compared with the numerical simulation method, the proposed method is an efficient and accurate approach to evaluating the face stability of the horseshoe tunnel; (2) from the parametric analysis, it can be seen that the normalized limit support pressure of the tunnel face decreases with the increasing of geological strength index, GSI, Hoek-Brown coefficient, mi, and uniaxial compressive strength, σci, and with the decreasing of the disturbance coefficient of rock, Di; and (3) a larger 3D failure surface is associated with a high value of the normalized limit support pressure.

Evaluation of resources and environmental carrying capacity of 36 large cities in China based on a support-pressure coupling mechanism.

Resource and environmental carrying capacity (RECC) is an important foundation for the long-term development of cities. The accurate evaluation of the RECC of cities is of great significance to China, which is rapidly urbanizing. This paper constructs a support index and pressure index to calculate the level of support resources and the level of environmental pressure that human activities induce in 36 municipalities, provincial capitals and subprovincial cities in China from 2010 to 2016; in addition, this paper analyzes the factors affecting RECC. The results show that (1) the support index of most cities (32) is greater than the pressure index, demonstrating that the resource and environmental carrying capacity of most cities is stronger than the pressure of human social activities. (2) The RECC of first-line, super large cities is of concern; the RECCs of Beijing, Shanghai, Guangzhou and Shenzhen have already been exceeded. (3) The resources, the environmental services and the pressure of human activities on those services in most cities are average, while the resource, the environmental services and the pressure of human activities on those services are greater in a few developed cities (such as Beijing, Shanghai, Guangzhou, Shenzhen, etc.). (4) The ability of resources and the environment to support human activities in China's large cities exhibited a downward trend. The pressure of human social activities on urban resources and the environment is increasing, but the growth rate of that pressure has slowed. (5) Area of land used for urban construction, the area of urban green space and length of city sewage pipes and other resource indicators are common obstacles to the improvement of most cities' pressure indexes. Water shortage is a common problem faced by first-tier cities in China. This study supports a comprehensive understanding of China's large-scale RECC status and provides a reference for the formulation of a scientific and pragmatic urban development strategy.