Impact of Decreased Transmural Conduction Velocity on the Function of the Human Left Ventricle: A Simulation Study

BioMed Research International ◽

10.1155/2020/2867865 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Jiří Vaverka ◽

Jiří Moudr ◽

Petr Lokaj ◽

Jiří Burša ◽

Michal Pásek

Keyword(s):

Energy Consumption ◽

Left Ventricle ◽

Conduction Velocity ◽

Heart Function ◽

Pressure Rise ◽

Shortening Velocity ◽

Electromechanical Delay ◽

Windkessel Model ◽

Isovolumic Contraction ◽

The Impact

This study investigates the impact of reduced transmural conduction velocity (TCV) on output parameters of the human heart. In a healthy heart, the TCV contributes to synchronization of the onset of contraction in individual layers of the left ventricle (LV). However, it is unclear whether the clinically observed decrease of TCV contributes significantly to a reduction of LV contractility. The applied three-dimensional finite element model of isovolumic contraction of the human LV incorporates transmural gradients in electromechanical delay and myocyte shortening velocity and evaluates the impact of TCV reduction on pressure rise (namely, dP/dtmax) and on isovolumic contraction duration (IVCD) in a healthy LV. The model outputs are further exploited in the lumped “Windkessel” model of the human cardiovascular system (based on electrohydrodynamic analogy of respective differential equations) to simulate the impact of changes of dP/dtmax and IVCD on chosen systemic parameters (ejection fraction, LV power, cardiac output, and blood pressure). The simulations have shown that a 50% decrease in TCV prolongs substantially the isovolumic contraction, decelerates slightly the LV pressure rise, increases the LV energy consumption, and reduces the LV power. These negative effects increase progressively with further reduction of TCV. In conclusion, these results suggest that the pumping efficacy of the human LV decreases with lower TCV due to a higher energy consumption and lower LV power. Although the changes induced by the clinically relevant reduction of TCV are not critical for a healthy heart, they may represent an important factor limiting the heart function under disease conditions.

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Effect of Transmural Differences in Excitation-Contraction Delay and Contraction Velocity on Left Ventricle Isovolumic Contraction: A Simulation Study

BioMed Research International ◽

10.1155/2018/4798512 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

J. Vaverka ◽

J. Burša ◽

J. Šumbera ◽

M. Pásek

Keyword(s):

Heart Failure ◽

Left Ventricle ◽

Wall Stress ◽

Element Model ◽

Ventricular Wall ◽

Shortening Velocity ◽

Electromechanical Delay ◽

Contraction Coupling ◽

Physiological Importance ◽

Isovolumic Contraction

Recent studies have shown that left ventricle (LV) exhibits considerable transmural differences in active mechanical properties induced by transmural differences in electrical activity, excitation-contraction coupling, and contractile properties of individual myocytes. It was shown that the time between electrical and mechanical activation of myocytes (electromechanical delay: EMD) decreases from subendocardium to subepicardium and, on the contrary, the myocyte shortening velocity (MSV) increases in the same direction. To investigate the physiological importance of this inhomogeneity, we developed a new finite element model of LV incorporating the observed transmural gradients in EMD and MSV. Comparative simulations with the model showed that when EMD or MSV or both were set constant across the LV wall, the LV contractility during isovolumic contraction (IVC) decreased significantly (dp/dtmax⁡ was reduced by 2 to 38% and IVC was prolonged by 18 to 73%). This was accompanied by an increase of transmural differences in wall stress. These results suggest that the transmural differences in EMD and MSV play an important role in physiological contractility of LV by synchronising the contraction of individual layers of ventricular wall during the systole. Reduction or enhancement of these differences may therefore impair the function of LV and contribute to heart failure.

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Impact of roof shading on building energy performance in warm & humid climatic places of India

iCRBE Procedia ◽

10.32438/icrbe.202037 ◽

2020 ◽

pp. 50-64

Author(s):

Kuladeep Kumar Sadevi ◽

Avlokita Agrawal

Keyword(s):

Energy Consumption ◽

Energy Conservation ◽

Energy Performance ◽

General Assumption ◽

Climatic Conditions ◽

Building Envelope ◽

Passive Cooling ◽

Base Case ◽

U Value ◽

The Impact

With the rise in awareness of energy efficient buildings and adoption of mandatory energy conservation codes across the globe, significant change is being observed in the way the buildings are designed. With the launch of Energy Conservation Building Code (ECBC) in India, climate responsive designs and passive cooling techniques are being explored increasingly in building designs. Of all the building envelope components, roof surface has been identified as the most significant with respect to the heat gain due to the incident solar radiation on buildings, especially in tropical climatic conditions. Since ECBC specifies stringent U-Values for roof assembly, use of insulating materials is becoming popular. Along with insulation, the shading of the roof is also observed to be an important strategy for improving thermal performance of the building, especially in Warm and humid climatic conditions. This study intends to assess the impact of roof shading on building’s energy performance in comparison to that of exposed roof with insulation. A typical office building with specific geometry and schedules has been identified as base case model for this study. This building is simulated using energy modelling software ‘Design Builder’ with base case parameters as prescribed in ECBC. Further, the same building has been simulated parametrically adjusting the amount of roof insulation and roof shading simultaneously. The overall energy consumption and the envelope performance of the top floor are extracted for analysis. The results indicate that the roof shading is an effective passive cooling strategy for both naturally ventilated and air conditioned buildings in Warm and humid climates of India. It is also observed that a fully shaded roof outperforms the insulated roof as per ECBC prescription. Provision of shading over roof reduces the annual energy consumption of building in case of both insulated and uninsulated roofs. However, the impact is higher for uninsulated roofs (U-Value of 3.933 W/m2K), being 4.18% as compared to 0.59% for insulated roofs (U-Value of 0.33 W/m2K).While the general assumption is that roof insulation helps in reducing the energy consumption in tropical buildings, it is observed to be the other way when insulation is provided with roof shading. It is due to restricted heat loss during night.

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ANALISIS DETERMINAN KUALITAS LINGKUNGAN PERIODE 1999-2013

Jurnal Ekonomi dan Bisnis ◽

10.24123/jeb.v21i1.1632 ◽

2016 ◽

Vol 21 (1) ◽

pp. 9-20

Author(s):

Ersalina Tang

Keyword(s):

Foreign Direct Investment ◽

Energy Consumption ◽

Gross Domestic Product ◽

Co2 Emissions ◽

Direct Investment ◽

Meat Consumption ◽

Domestic Product ◽

World Data ◽

The World ◽

The Impact

The purpose of this study is to analyze the impact of Foreign Direct Investment, Gross Domestic Product, Energy Consumption, Electric Consumption, and Meat Consumption on CO2 emissions of 41 countries in the world using panel data from 1999 to 2013. After analyzing 41 countries in the world data, furthermore 17 countries in Asia was analyzed with the same period. This study utilized quantitative approach with Ordinary Least Square (OLS) regression method. The results of 41 countries in the world data indicates that Foreign Direct Investment, Gross Domestic Product, Energy Consumption, and Meat Consumption significantlyaffect Environmental Qualities which measured by CO2 emissions. Whilst the results of 17 countries in Asia data implies that Foreign Direct Investment, Energy Consumption, and Electric Consumption significantlyaffect Environmental Qualities. However, Gross Domestic Product and Meat Consumption does not affect Environmental Qualities.

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The Nexus between Financial Development, Economic Growth and Energy Consumption in India: A VECM Technique

Indian Journal of Economics and Development ◽

10.35716/ijed/20131 ◽

2020 ◽

pp. 602-612

Keyword(s):

Economic Growth ◽

Energy Consumption ◽

Financial Development ◽

Consumer Price Index ◽

Development Economic ◽

Energy Prices ◽

Vector Error Correction ◽

Percent Increase ◽

Growth Energy ◽

The Impact

The demand for energy consumption requires efficient financial development in terms of bank credit. Therefore, this study examines the nexus between Financial Development, Economic Growth, Energy Prices and Energy Consumption in India, utilizing Vector Error Correction Model (VECM) technique to determine the nature of short and long term relationships from 2010 to 2019. The estimation of results indicates that a one percent increase in bank credits to private sector results in 0.10 percent increase in energy consumption and 0.28 percent increase in energy consumption responses to 1 percent increase in economic growth. It is also observed that the impact of energy price proxied by consumer price index is statistically significant with a negative sign indicating the consistency with the theory.

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Empirical evidence on the impact of urban overheating on building cooling and heating energy consumption

iScience ◽

10.1016/j.isci.2021.102495 ◽

2021 ◽

pp. 102495

Author(s):

Mi Aye Su ◽

Jack Ngarambe ◽

Mat Santamouris ◽

Geun Young Yun

Keyword(s):

Energy Consumption ◽

Empirical Evidence ◽

Heating Energy Consumption ◽

Building Cooling ◽

The Impact

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Graphene-based 3D XNOR-VRRAM with ternary precision for neuromorphic computing

npj 2D Materials and Applications ◽

10.1038/s41699-021-00236-x ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

Batyrbek Alimkhanuly ◽

Joon Sohn ◽

Ik-Joon Chang ◽

Seunghyun Lee

Keyword(s):

Neural Network ◽

Energy Consumption ◽

Recognition Accuracy ◽

Material Selection ◽

Weighted Sum ◽

Device Design ◽

Key Factors ◽

Neuromorphic Computing ◽

Device Scaling ◽

The Impact

AbstractRecent studies on neural network quantization have demonstrated a beneficial compromise between accuracy, computation rate, and architecture size. Implementing a 3D Vertical RRAM (VRRAM) array accompanied by device scaling may further improve such networks’ density and energy consumption. Individual device design, optimized interconnects, and careful material selection are key factors determining the overall computation performance. In this work, the impact of replacing conventional devices with microfabricated, graphene-based VRRAM is investigated for circuit and algorithmic levels. By exploiting a sub-nm thin 2D material, the VRRAM array demonstrates an improved read/write margins and read inaccuracy level for the weighted-sum procedure. Moreover, energy consumption is significantly reduced in array programming operations. Finally, an XNOR logic-inspired architecture designed to integrate 1-bit ternary precision synaptic weights into graphene-based VRRAM is introduced. Simulations on VRRAM with metal and graphene word-planes demonstrate 83.5 and 94.1% recognition accuracy, respectively, denoting the importance of material innovation in neuromorphic computing.

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Review on Urban Heat Island in China: Methods, Its Impact on Buildings Energy Demand and Mitigation Strategies

Sustainability ◽

10.3390/su13020762 ◽

2021 ◽

Vol 13 (2) ◽

pp. 762

Author(s):

Liu Tian ◽

Yongcai Li ◽

Jun Lu ◽

Jue Wang

Keyword(s):

Energy Consumption ◽

Urban Heat Island ◽

Building Energy ◽

Design Stage ◽

Heat Island ◽

Building Energy Consumption ◽

Rapid Urbanization ◽

Substantial Impact ◽

Urban Heat ◽

The Impact

High population density, dense high-rise buildings, and impervious pavements increase the vulnerability of cities, which aggravate the urban climate environment characterized by the urban heat island (UHI) effect. Cities in China provide unique information on the UHI phenomenon because they have experienced rapid urbanization and dramatic economic development, which have had a great influence on the climate in recent decades. This paper provides a review of recent research on the methods and impacts of UHI on building energy consumption, and the practical techniques that can be used to mitigate the adverse effects of UHI in China. The impact of UHI on building energy consumption depends largely on the local microclimate, the urban area features where the building is located, and the type and characteristics of the building. In the urban areas dominated by air conditioning, UHI could result in an approximately 10–16% increase in cooling energy consumption. Besides, the potential negative effects of UHI can be prevented from China in many ways, such as urban greening, cool material, water bodies, urban ventilation, etc. These strategies could have a substantial impact on the overall urban thermal environment if they can be used in the project design stage of urban planning and implemented on a large scale. Therefore, this study is useful to deepen the understanding of the physical mechanisms of UHI and provide practical approaches to fight the UHI for the urban planners, public health officials, and city decision-makers in China.

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Economic Development, CO2 Emissions and Energy Use Nexus-Evidence from the Danube Region Countries

Energies ◽

10.3390/en14113165 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3165

Author(s):

Eva Litavcová ◽

Jana Chovancová

Keyword(s):

Economic Growth ◽

Energy Consumption ◽

Co2 Emissions ◽

Carbon Emissions ◽

Bounds Testing ◽

Mutual Cooperation ◽

Long Run ◽

Short Run ◽

Danube Region ◽

The Impact

The aim of this study is to examine the empirical cointegration, long-run and short-run dynamics and causal relationships between carbon emissions, energy consumption and economic growth in 14 Danube region countries over the period of 1990–2019. The autoregressive distributed lag (ARDL) bounds testing methodology was applied for each of the examined variables as a dependent variable. Limited by the length of the time series, we excluded two countries from the analysis and obtained valid results for the others for 26 of 36 ARDL models. The ARDL bounds reliably confirmed long-run cointegration between carbon emissions, energy consumption and economic growth in Austria, Czechia, Slovakia, and Slovenia. Economic growth and energy consumption have a significant impact on carbon emissions in the long-run in all of these four countries; in the short-run, the impact of economic growth is significant in Austria. Likewise, when examining cointegration between energy consumption, carbon emissions, and economic growth in the short-run, a significant contribution of CO2 emissions on energy consumptions for seven countries was found as a result of nine valid models. The results contribute to the information base essential for making responsible and informed decisions by policymakers and other stakeholders in individual countries. Moreover, they can serve as a platform for mutual cooperation and cohesion among countries in this region.

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Left ventricular remodeling: is there a real impact of cardiac rehabilitation?

European Journal of Preventive Cardiology ◽

10.1093/eurjpc/zwab061.366 ◽

2021 ◽

Vol 28 (Supplement_1) ◽

Author(s):

NPD Cunha ◽

I Aguiar-Ricardo ◽

T Rodrigues ◽

P Silverio Antonio ◽

S Couto Pereira ◽

...

Keyword(s):

Exercise Training ◽

Left Ventricle ◽

Cardiac Rehabilitation ◽

Phase Ii ◽

Left Ventricular ◽

Cardiac Resynchronization ◽

Left Ventricular Ejection ◽

Ventricular Ejection Fraction ◽

Ischemic Disease ◽

The Impact

Abstract Funding Acknowledgements Type of funding sources: None. Introduction A number of randomized controlled trials have examined the effect of exercise training on left ventricle (LV) remodeling in individuals with cardiovascular disease. However, the results of these trials have been inconclusive. Purpose Evaluation of the impact of a cardiac rehabilitation program (CRP) on left ventricle remodelling evaluated by echocardiogram. Methods Observational single centre study including consecutive patients, undergoing structured CRP since June 2016 until February 2020. Phase II CRP included 3 months of exercise training, aerobic and strength exercise, individually prescribed, 3 times a week, 60 minutes sessions. All patients were submitted to a clinical evaluation, echocardiogram, and cardiopulmonary exercise test before and after the CRP. Results 205 patients (62.6 ± 11 years, 83.4% men, 82.3% ischemic disease) were included in a phase II CRP. Most patients had ischemic disease (82.3%) and 23.5% of patients had left ventricular ejection fraction (LVEF) <40%. Of the cardiovascular risk factors, hypertension was the most prevalent (76%), followed by dyslipidaemia (67.4%), active smoking (45.9%) and diabetes (26.9%). After the CRP, there was a significant improvement of LVEF (from 48.3 ± 13 to 52 ± 11.6 %, p = 0.001) and a significant reduction of LV volumes (LV end-diastolic volume, LVEDV , decreased from 140 ± 81 to 121 ± 57, p = 0.002; LV end-systolic volume , LVESV , reduced from 80 ± 75 to 64 ± 48, p = 0.004). Considering only the patients with LVEF < 40% (n = 38), the improvement was even greater: LVEF increased from 30 ± 8 to 39 ± 13 (p = 0.002); LVEDV reduced from 206 ± 107 to 159 ± 81 (p = 0.001) and LVESV reduced from 142 ± 99 to 101 ± 66 (p = 0.002). 63.6%(n = 14) of these patients improved at least 10% of LVEF and only 1 of them had a cardiac resynchronization therapy device. Conclusions A phase II CR program was associated with significant improvements in left ventricular reverse remodelling irrespective of baseline EF classification. Those with reduced baseline EF derived an even greater improvement, highlighting the great importance of CR in this subgroup of patients.

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