scholarly journals Influence of Fibrosis Amount and Patterns on Ventricular Arrhythmogenesis and Pumping Efficacy: Computational Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Aulia Khamas Heikhmakhtiar ◽  
Abrha Abebe Tekle ◽  
Ki Moo Lim
Keyword(s):  
Spatial Distribution ◽  
Mechanical Performance ◽  
Computational Study ◽  
Diffuse Fibrosis ◽  
Computational Studies ◽  
Diffuse Type ◽  
Compact Type ◽  
Phase Singularities ◽  
The Mean ◽  
Ventricular Arrhythmogenesis

Myocardial fibrosis is an integral component of most forms of heart failure. Clinical and computational studies have reported that spatial fibrosis pattern and fibrosis amount play a significant role in ventricular arrhythmogenicity. This study investigated the effect of the spatial distribution of fibrosis and fibrosis amount on the electrophysiology and mechanical performance of the human ventricles. Seventy-five fibrosis distributions comprising diffuse, patchy, and compact fibrosis types that contain 10–50% fibrosis amount were generated. The spatial fibrosis distribution was quantified using the fibrosis entropy (FE) metric. Electrical simulations under reentry conditions induced using the S1–S2 protocol were conducted to investigate the fibrosis arrhythmogenicity. We also performed mechanical simulations to examine the influence of the fibrosis amount and the spatial distribution of fibrosis on the pumping efficacy of the LV. We observed that the mean FE of the compact type is the largest among the three types. The electrical simulation results revealed that the ventricular arrhythmogenicity of diffuse fibrosis depends on the fibrosis amount and marginally on the spatial distribution of fibrosis. Meanwhile, the ventricular arrhythmogenicity of the compact and patchy fibrosis pattern is more reliant on the spatial distribution of fibrosis than on the fibrosis amount. The average number of phase singularities (PSs) in the compact fibrosis pattern was the highest among the three patterns of fibrosis. The diffuse type of fibrosis has the lowest average number of PSs than that in the patchy and compact fibrosis. The reduction in the stroke volume (SV) showed high influence from the electrical instabilities induced by the fibrosis amount and pattern. The compact fibrosis exhibited the lowest SV among the three patterns except in the 40% fibrosis amount. In conclusion, the fibrosis pattern is as crucial as the fibrosis amount for sustaining and aggravating ventricular arrhythmogenesis.

scholarly journals Influence of Fibrosis Amount and Patterns on Ventricular Arrythmogenesis and Pumping Efficacy:  Computational Study

2020 ◽  
Author(s):  
Abrha Abebe Tekle ◽  
Ki Moo Lim
Keyword(s):  
Spatial Distribution ◽  
Stroke Volume ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Computational Study ◽  
Cardiac Response ◽  
Diffuse Fibrosis ◽  
Conduction Model ◽  
Wide Range ◽  
Simulation Results

Abstract Background and aims: Clinical and computational studies have reported that spatial fibrosis pattern and fibrosis amount play a significant role in ventricular arrhythmogenicity. Nonetheless, the underlying mechanisms of arrhythmogenicity of fibrosis are not known accurately. In addition, we believe that the effect of different fibrosis types and fibrosis amount on the cardiac mechanical performance requires a further investigation. Therefore, this study investigated the effect of spatial distribution of fibrosis and fibrosis amount on the electrical and mechanical performance of the left ventricle (LV). Methods: We employed a human ventricular model that simulates both the electrophysiological and the mechanical contraction characteristics of the ventricle. The electrophysiological conduction model mimics the exchange of ions through the plasma membrane of myocardial cells whereas the mechanical contraction model simulates the mechanical cardiac response. Seventy-five fibrosis distributions comprising diffuse, patchy, and compact fibrosis types that contain 10%–50% fibrosis amount were generated to cover a wide range of fibrosis cases. The spatial fibrosis distribution in the human ventricular model was quantified using fibrosis entropy (FE) metric. Then, electrophysiological simulations under reentry conditions induced using the S1-S2 protocol were conducted to investigate the correlation between different patterns of fibrosis and ventricular arrhythmogenicity. Finally, we compared the mechanical response by conducting mechanical simulations to examine the influence of the fibrosis amount and spatial distribution of fibrosis on the pumping efficacy of the LV by extracting the calcium information from the electrophysiological simulation. Results: We observed that the spatial patchy fibrosis distribution was more chaotic (higher mean FE) than those of the compact and diffuse types. The electrical simulation results revealed that the ventricular arrhythmogenicity of diffuse fibrosis depends on the fibrosis amount and marginally on the spatial distribution of fibrosis. Meanwhile, the ventricular arrhythmogenicity of the compact and patchy fibrosis types is reliant on the spatial distribution of fibrosis than on the fibrosis amount. The average number of phase singularities in the electrical simulations with compact fibrosis was higher than those with patchy and diffuse fibrosis. As a result, compact fibrosis resulted a lower stroke volume (SV) of the LV, whereas the diffuse fibrosis resulted in a higher SV of the LV. The reduction in the stroke volume (SV) of the LV was linearly correlated to the electrical instabilities induced by the fibrosis amount and spatial distribution of fibrosis. Conclusion: The increase in the amount of diffuse, patchy and compact fibrosis in the myocardium increased the electrical instability and likely decreased the pumping efficacy of LV. Moreover, the effect fibrosis pattern on ventricular arrhythmogenesis was more significant in compact and patchy fibrosis types than in diffuse fibrosis.

scholarly journals Experimental and Computational Studies on N-alkylation Reaction of N-Benzoyl 5-(Aminomethyl)Tetrazole

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 704-713
Author(s):  
Younas Aouine ◽  
Aaziz Jmiai ◽  
Anouar Alami ◽  
Abdallah El Asri ◽  
Souad El Issami ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Nmr Spectroscopy ◽  
Density Functional ◽  
Computational Study ◽  
Benzyl Bromide ◽  
13C Nmr Spectroscopy ◽  
Alkylation Reaction ◽  
Computational Studies ◽  
Functional Theory ◽  
1H And 13C Nmr

The N-alkylation reaction of N-benzoyl 5-(aminomethyl)tetrazole (5-AMT) with benzyl bromide was carried out in the presence of K2CO3 as a base. Two separable regioisomers were obtained, thus their purification led to determine the proportion of each of them, and their structures were attributed essentially based on 1H and 13C NMR spectroscopy in addition to the elemental analysis and MS data. In order to confirm the results obtained at the synthesis level, a computational study was carried out by application of density functional theory (DFT) using the Becke three-parameter hybrid exchange functional and the Lee-Yang-Parr correlation functional (B3LYP).

Intracellular oxygen diffusion: the roles of myoglobin and lipid at cold body temperature.

1998 ◽  
Vol 201 (8) ◽  
pp. 1119-1128 ◽  
Author(s):  
B D Sidell
Keyword(s):  
Body Temperature ◽  
Fish Species ◽  
Oxygen Diffusion ◽  
Mechanical Performance ◽  
Muscle Cells ◽  
Cold Temperature ◽  
Oxygen Binding ◽  
Mitochondrial Density ◽  
Polar Fish ◽  
The Mean

Cold temperature can constrain the rate of oxygen movement through muscle cells of ectothermic animals because the kinetic energy of the solvent-solute system decreases and the viscosity of the aqueous cytoplasm increases during cooling within the physiological range of body temperatures. These factors affect the movement of both dissolved oxygen and oxymyoglobin, the two predominant routes of intracellular oxygen diffusion in vertebrate oxidative muscles. In addition, reductions in temperature have been shown to increase the affinity of myoglobin for oxygen and to slow the rate of Mb O2-dissociation, compromising the ability of this oxygen-binding protein to facilitate intracellular oxygen diffusion. Experiments with both seasonally cold-bodied fishes and polar fish species suggest that several factors combine to overcome these limitations in delivery of oxygen from the blood to the mitochondria. First, reductions in body temperature induce increases in mitochondrial density of oxidative muscle cells, reducing the mean diffusional pathlength for oxygen between capillaries and mitochondria. Second, cold body temperature in both temperate-zone and polar fishes is frequently correlated with a high content of neutral lipid in oxidative muscles, providing an enhanced diffusional pathway for oxygen through the tissue. Third, recent data indicate that myoglobins from fish species bind and release oxygen more rapidly at cold temperature than do those from mammals. Data from both oxidative skeletal muscle and cardiac muscle of fishes suggest that these factors in various combinations contribute to enhance the aerobically supported mechanical performance of the tissues at cold cellular temperatures.

An Investigation of Flow Fields Over Multi-Element Aerofoils

2001 ◽  
Vol 124 (1) ◽  
pp. 154-165 ◽  
Author(s):  
S. R. Maddah ◽  
H. H. Bruun
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Separated Flow ◽  
Mean Flow ◽  
Model Configuration ◽  
Attached Flow ◽  
The Mean ◽  
Flap Deflection ◽  
Comparative Results ◽  
Lift And Drag

This paper presents results obtained from a combined experimental and computational study of the flow field over a multi-element aerofoil with and without an advanced slat. Detailed measurements of the mean flow and turbulent quantities over a multi-element aerofoil model in a wind tunnel have been carried out using stationary and flying hot-wire (FHW) probes. The model configuration which spans the test section 600mm×600mm, is made of three parts: 1) an advanced (heel-less) slat, 2) a NACA 4412 main aerofoil and 3) a NACA 4415 flap. The chord lengths of the elements were 38, 250 and 83 mm, respectively. The results were obtained at a chord Reynolds number of 3×105 and a free Mach number of less than 0.1. The variations in the flow field are explained with reference to three distinct flow field regimes: attached flow, intermittent separated flow, and separated flow. Initial comparative results are presented for the single main aerofoil and the main aerofoil with a nondeflected flap at angles of attacks of 5, 10, and 15 deg. This is followed by the results for the three-element aerofoil with emphasis on the slat performance at angles of attack α=10, 15, 20, and 25 deg. Results are discussed both for a nondeflected flap δf=0deg and a deflected flap δf=25deg. The measurements presented are combined with other related aerofoil measurements to explain the main interaction of the slat/main aerofoil and main aerofoil/flap both for nondeflected and deflected flap conditions. These results are linked to numerically calculated variations in lift and drag coefficients with angle of attack and flap deflection angle.

scholarly journals Finding the pattern: online extraction of spatial structure during virtual navigation

2019 ◽  
Author(s):  
Kathryn Nicole Graves ◽  
James Antony ◽  
Nicholas Turk-Browne
Keyword(s):  
Spatial Distribution ◽  
Animal Behavior ◽  
Virtual Water ◽  
Single Session ◽  
Statistical Knowledge ◽  
Navigation Patterns ◽  
The Mean ◽  
Online Extraction ◽  
Human Participants ◽  
The Individual

While navigating the world, we pick up on patterns of where things tend to appear. According to theories of memory and studies of animal behavior, knowledge of these patterns emerges gradually over days or weeks, via consolidation of individual navigation episodes. Here we discover that navigation patterns can also be extracted online, prior to the opportunity for offline consolidation, as a result of rapid statistical learning. Human participants navigated a virtual water maze in which platform locations were drawn from a spatial distribution. Within a single session, participants increasingly navigated through the mean of the distribution. This behavior was better simulated by random walks from a model with only an explicit representation of the current mean, compared to a model with only memory for the individual platform locations. These results suggest that participants rapidly summarized the underlying spatial distribution and used this statistical knowledge to guide future navigation.

scholarly journals Crystal structure, computational study and Hirshfeld surface analysis of ethyl (2S,3R)-3-(3-amino-1H-1,2,4-triazol-1-yl)-2-hydroxy-3-phenylpropanoate

2019 ◽  
Vol 75 (12) ◽  
pp. 1919-1924
Author(s):  
Abdelkader Ben Ali ◽  
Youness El Bakri ◽  
Chin-Hung Lai ◽  
Jihad Sebhaoui ◽  
Lhoussaine El Ghayati ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Gas Phase ◽  
Surface Analysis ◽  
Computational Study ◽  
Hirshfeld Surface ◽  
Hirshfeld Surface Analysis ◽  
Dft Methods ◽  
Important Interaction ◽  
The Mean ◽  
Title Molecule

In the title molecule, C13H16N4O3, the mean planes of the phenyl and triazole rings are nearly perpendicular to one another as a result of the intramolecular C—H...O and C—H...π(ring) interactions. In the crystal, layers parallel to (101) are generated by O—H...N, N—H...O and N—H...N hydrogen bonds. The layers are connected by inversion-related pairs of C—H...O hydrogen bonds. The experimental molecular structure is close to the gas-phase geometry-optimized structure calculated by DFT methods. Hirshfeld surface analysis indicates that the most important interaction involving hydrogen in the title compound is the H...H contact. The contribution of the H...O, H...N, and H...H contacts are 13.6, 16.1, and 54.6%, respectively.

Microstructure and Mechanical Performance of AZ31-1.7 Wt.% Si Alloy Processed by Cyclic Channel Die Compression

2010 ◽  
Vol 667-669 ◽  
pp. 457-461
Author(s):  
Wei Guo ◽  
Qu Dong Wang ◽  
Man Ping Liu ◽  
Tao Peng ◽  
Xin Tao Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Mechanical Performance ◽  
Chinese Script ◽  
Cast State ◽  
Microstructure And Mechanical Properties ◽  
Mean Grain Size ◽  
The Matrix ◽  
The Mean

Cyclic channel die compression (CCDC) of AZ31-1.7 wt.% Si alloy was performed up to 5 passes at 623 K in order to investigate the microstructure and mechanical properties of compressed alloys. The results show that multi-pass CCDC is very effective to refine the matrix grain and Mg2Si phases. After the alloy is processed for 5 passes, the mean grain size decreases from 300 μm of as-cast to 8 μm. Both dendritic and Chinese script type Mg2Si phases break into small polygonal pieces and distribute uniformly in the matrix. The tensile strength increases prominently from 118 MPa to 216 MPa, whereas the hardness of alloy deformed 5 passes only increase by 8.4% compared with as-cast state.

Chemical Concentration and Spatial Uniformity of a Premixing In-Line Injection System Attached to a Variable-Rate Orchard Sprayer

2021 ◽  
Vol 64 (6) ◽  
pp. 1977-1987
Author(s):  
Zhihong Zhang ◽  
Heping Zhu ◽  
Zhiming Wei ◽  
Ramon Salcedo
Keyword(s):  
Spatial Distribution ◽  
Duty Cycle ◽  
Spray Deposition ◽  
Injection System ◽  
List Type ◽  
Variable Rate ◽  
Chemical Concentration ◽  
Fluorescent Tracer ◽  
Distribution Uniformity ◽  
The Mean

HighlightsA newly developed premixing in-line injection system attached to a variable-rate orchard sprayer was evaluated.Tests were conducted to verify the in-line injection system performance using a vertical spray patternator.Concentration accuracy and spatial distribution uniformity were determined with a fluorescent tracer.Uniform spray mixtures were obtained for different spray viscosities and duty cycle combinations.Abstract. Pesticide spray application efficiency is highly dependent on the chemical concentration accuracy and spatial distribution uniformity. In this study, the performance of a newly developed premixing in-line injection system was evaluated when it was attached to a laser-guided, pulse width modulated (PWM), variable-rate orchard sprayer. The chemical concentration accuracy was determined with respect to spray deposition with a fluorescent tracer, and the spatial distribution uniformity was determined with spray deposits at different heights on a vertical spray patternator. Outdoor tests were conducted with 27 combinations of target chemical concentration (1.0%, 1.5%, and 2.0%), viscosity of the simulated pesticide (1.0, 12.0, and 24.0 mPa·s), and various spray outputs manipulated with PWM duty cycles. For each injection loop, the amounts of the chemical concentrate and water discharged into the mixing line were measured separately in response to preset target concentrations. The results showed that the measured concentrations were consistent across the patternator heights, spray viscosities, and duty cycle combinations. For all treatments, the mean absolute percentage error (MAPE) of the measured concentration was 6.96%, indicating that the concentration accuracy of the system was acceptable. The mean coefficient of variation was 3.35%, indicating that the spatial distribution uniformity of the system was in the desirable range. In addition, there was little variation in chemical concentration for spray mixtures collected at different heights on the patternator. Thus, the premixing in-line injection system could adequately dispense chemical concentrate and water to produce accurate concentrations and uniform spray mixtures for variable-rate nozzles to discharge to targets. Keywords: Environment protection, Precision pesticide application, Laser-guided sprayer, Tank mixture disposal, Specialty crop.

scholarly journals Occurrence and Spatial Distribution of Dibothriocephalus Latus (Cestoda: Diphyllobothriidea) in Lake Iseo (Northern Italy): An Update

2020 ◽  
Vol 17 (14) ◽  
pp. 5070
Author(s):  
Vasco Menconi ◽  
Paolo Pastorino ◽  
Ivana Momo ◽  
Davide Mugetti ◽  
Maria Cristina Bona ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Perca Fluviatilis ◽  
Northern Italy ◽  
Commercial Fishing ◽  
European Perch ◽  
Chi Square ◽  
Mean Intensity ◽  
Southern Area ◽  
Total Prevalence ◽  
The Mean

Dibothriocephalus latus (Linnaeus, 1758) (Cestoda: Diphyllobothriidea; syn. Diphyllobothrium latum), is a fish-borne zoonotic parasite responsible for diphyllobothriasis in humans. Although D. latus has long been studied, many aspects of its epidemiology and distribution remain unknown. The aim of this study was to investigate the prevalence, mean intensity of infestation, and mean abundance of plerocercoid larvae of D. latus in European perch (Perca fluviatilis) and its spatial distribution in three commercial fishing areas in Lake Iseo (Northern Italy). A total of 598 specimens of P. fluviatilis were caught in 2019. The total prevalence of D. latus was 6.5%. However, there were significant differences between areas (10.2% North; 7.3% Center; 1.5% South) (Chi-square test, p = 0.0018). The mean intensity of infestation ranged from 1 larva in southern area to 1.2 larvae in both the central and northern (Pisogne) areas. In addition, the mean abundance ranged from 0.02 in the southern area to 0.26 in the northern area (Pisogne). The total number of larvae (anterior dorsal—AD = 21; anterior ventral—AV = 1; posterior dorsal—PD = 15; posterior ventral—PV = 5) differed significantly between the four anatomical quadrants (Kruskal–Wallis test; p = 0.0001). The prevalence of D. latus plerocercoid larvae in European perch from Lake Iseo has long been investigated, but without an appropriate sampling design. With the present study, a broader analysis in spatial distribution has been added to the existing literature, revealing new information about D. latus distribution and occurrence in Lake Iseo, with new data that will be useful for health authorities and future studies.

Numerical Experiments for Flow Around a Ducted Tip Hydrofoil

2002 ◽  
Author(s):  
Hildur Ingvarsdo´ttir ◽  
Carl Ollivier-Gooch ◽  
Sheldon I. Green
Keyword(s):  
Turbulence Model ◽  
Vortex Core ◽  
Vortex Flow ◽  
Computational Study ◽  
Near Field ◽  
Vortex Formation ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Computational Studies ◽  
Tip Vortices

The performance and cavitation characteristics of marine propellers and hydrofoils are strongly affected by tip vortex behavior. A number of previous computational studies have been done on tip vortices, both in aerodynamic and marine applications. The focus, however, has primarily been on validating methods for prediction and advancing the understanding of tip-vortex formation in general, rather than showing effects of tip modifications on tip vortices. Studies of the most relevance to the current work include computational studies by Dacles-Mariani et al. (1995) and Hsiao and Pauley (1998, 1999). Daeles-Mariani et al. carried out interactively a computational and experimental study of the wingtip vortex in the near field using a full Navier-Stokes simulation, accompanied with the Baldwin-Barth turbulence model. Although they showed improvement over numerical results obtained by previous researchers, the tip vortex strength was underpredicted. Hsiao and Pauley (1998) studied the steady-state tip vortex flow over a finite-span hydrofoil, also using the Baldwin-Barth turbulence model. They were able to achieve good agreement in pressure distribution and oil flow pattern with experimental data and accurately predict vertical and axial velocities of the tip vortex core within the near-field region. Far downstream, however, the computed flow field was overly diffused within the tip vortex core. Hsiao and Pauley (1999) also carried out a computational study of the tip vortex flow generated by a marine propeller. The general characteristics of the flow were well predicted but the vortex core was again overly diffused.

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