scholarly journals Mechanism of Consistent Gyrus Formation: an Experimental and Computational Study

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Tuo Zhang ◽  
Mir Jalil Razavi ◽  
Xiao Li ◽  
Hanbo Chen ◽  
Tianming Liu ◽  
...  
Keyword(s):  
Experimental Data ◽  
Computational Modeling ◽  
Computational Study ◽  
Regional Growth ◽  
Cortical Plate ◽  
Joint Analysis ◽  
Growth Speed ◽  
Differential Growth ◽  
Analysis Scheme ◽  
Special Area

Abstract As a significant type of cerebral cortical convolution pattern, the gyrus is widely preserved across species. Although many hypotheses have been proposed to study the underlying mechanisms of gyrus formation, it is currently still far from clear which factors contribute to the regulation of consistent gyrus formation. In this paper, we employ a joint analysis scheme of experimental data and computational modeling to investigate the fundamental mechanism of gyrus formation. Experimental data on mature human brains and fetal brains show that thicker cortices are consistently found in gyral regions and gyral cortices have higher growth rates. We hypothesize that gyral convolution patterns might stem from heterogeneous regional growth in the cortex. Our computational simulations show that gyral convex patterns may occur in locations where the cortical plate grows faster than the cortex of the brain. Global differential growth can only produce a random gyrification pattern, but it cannot guarantee gyrus formation at certain locations. Based on extensive computational modeling and simulations, it is suggested that a special area in the cerebral cortex with a relatively faster growth speed could consistently engender gyri.

scholarly journals Two and three pseudoscalar production in e+e− annihilation and their contributions to (g − 2)μ

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Wen Qin ◽  
Ling-Yun Dai ◽  
Jorge Portolés
Keyword(s):  
Experimental Data ◽  
Theoretical Prediction ◽  
Pseudoscalar Meson ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Vacuum Polarization ◽  
Meson Production ◽  
The Other ◽  
Joint Analysis ◽  
The Standard Model

Abstract A coherent study of e+e− annihilation into two (π+π−, K+K−) and three (π+π−π0, π+π−η) pseudoscalar meson production is carried out within the framework of resonance chiral theory in energy region E ≲ 2 GeV. The work of [L.Y. Dai, J. Portolés, and O. Shekhovtsova, Phys. Rev. D88 (2013) 056001] is revisited with the latest experimental data and a joint analysis of two pseudoscalar meson production. Hence, we evaluate the lowest order hadronic vacuum polarization contributions of those two and three pseudoscalar processes to the anomalous magnetic moment of the muon. We also estimate some higher-order additions led by the same hadronic vacuum polarization. Combined with the other contributions from the standard model, the theoretical prediction differs still by (21.6 ± 7.4) × 10−10 (2.9σ) from the experimental value.

scholarly journals Sliding Blocks Revisited: A Simulational Study

1998 ◽  
Vol 09 (06) ◽  
pp. 875-880 ◽  
Author(s):  
A. R. de Lima ◽  
C. Moukarzel ◽  
T. J. P. Penna
Keyword(s):  
Experimental Data ◽  
Friction Coefficient ◽  
Power Law ◽  
Computational Study ◽  
Recent Experimental Data ◽  
Power Law Distribution ◽  
Inclined Surfaces ◽  
Wide Range

A computational study of sliding blocks on inclined surfaces is presented. Assuming that the friction coefficient μ is a function of position, the probability P(λ) for the block to slide down over a length λ is numerically calculated. Our results are consistent with recent experimental data suggesting a power-law distribution of events over a wide range of displacements when the chute angle is close to the critical one, and suggest that the variation of μ along the surface is responsible for this.

Circadian clocks and phosphorylation: Insights from computational modeling

2009 ◽  
Vol 4 (3) ◽  
pp. 290-303 ◽  
Author(s):  
Jean-Christophe Leloup
Keyword(s):  
Experimental Data ◽  
Computational Modeling ◽  
Regulatory Mechanism ◽  
Circadian Clocks ◽  
Recent Experimental Data ◽  
Sleep Phase ◽  
Clock Proteins ◽  
High Degree ◽  
Clock Protein

AbstractCircadian clocks are based on a molecular mechanism regulated at the transcriptional, translational and post-translational levels. Recent experimental data unravel a complex role of the phosphorylations in these clocks. In mammals, several kinases play differential roles in the regulation of circadian rhythmicity. A dysfunction in the phosphorylation of one clock protein could lead to sleep disorders such as the Familial Advanced Sleep Phase Disorder, FASPS. Moreover, several drugs are targeting kinases of the circadian clocks and can be used in cancer chronotherapy or to treat mood disorders. In Drosophila, recent experimental observations also revealed a complex role of the phosphorylations. Because of its high degree of homology with mammals, the Drosophila system is of particular interest. In the circadian clock of cyanobacteria, an atypical regulatory mechanism is based only on three clock proteins (KaiA, KaiB, KaiC) and ATP and is sufficient to produce robust temperature-compensated circadian oscillations of KaiC phosphorylation. This review will show how computational modeling has become a powerful and useful tool in investigating the regulatory mechanism of circadian clocks, but also how models can give rise to testable predictions or reveal unexpected results.

CFD Studies on a Large Diameter Jet Impingement Flow

2004 ◽  
Author(s):  
Zhiguo Zhang ◽  
Mounir Ibrahim
Keyword(s):  
Experimental Data ◽  
Computational Study ◽  
Large Diameter ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
University Of Minnesota ◽  
Inlet Conditions ◽  
The University ◽  
The Impact

This paper presents computational study for a large diameter (216 mm) and small space ratios (S/D = 0.25 and 0.5) jet impingement flow. CFD-ACE code was used as the computational tools; the code was first validated by comparing its predictions with both CFD and experimental data from the literature. Then, the study was performed for two different Reynolds numbers: 7600, 17700 and two different space ratios: 0.25 and 0.5. Also two different turbulence models were utilized in this study: low Reynolds number turbulent k-ε and k-ω. The CFD results were compared with flow visualization results conducted at the University of Minnesota for the same configurations. The impact of choosing different inlet conditions on the CFD flow field was examined. The k-ε model showed greater sensitivity to the selection of the inlet conditions. Moreover, the k-ω model showed much better agreement with the experimental data than the k-ε model.

Experimental and Computational Study of Oscillating Turbine Cascade and Influence of Part-Span Shrouds

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
X. Q. Huang ◽  
L. He ◽  
David L. Bell
Keyword(s):  
Experimental Data ◽  
Computational Study ◽  
Three Dimensional ◽  
Unsteady Flows ◽  
Correction Method ◽  
Influence Coefficient ◽  
Turbine Cascade ◽  
Test Configuration ◽  
Practical Applications ◽  
Influence Coefficient Method

This paper presents a combined experimental and computational study of unsteady flows in a linear turbine cascade oscillating in a three-dimensional bending/flapping mode. Detailed experimental data are obtained on a seven-bladed turbine cascade rig. The middle blade is driven to oscillate and oscillating cascade data are obtained using an influence coefficient method. The numerical simulations are performed by using a 3D nonlinear time-marching Navier–Stokes flow solver. Single-passage domain computations for arbitrary interblade phase angles are achieved by using the Fourier shape correction method. Both measurements and predictions demonstrate a fully 3D behavior of the unsteady flows. The influence of the aerodynamic blockage introduced by part-span shrouds on turbine flutter has been investigated by introducing flat plate shaped shrouds at 75% span. In contrast to practical applications, in the present test configuration, the mode of vibration of the blades remains unchanged by the introduction of the part-span shroud. This allows the influence of the aerodynamic blockage introduced by the part-span shroud to be assessed in isolation from the change in mode shape. A simple shroud model has been developed in the computational solver. The computed unsteady pressures around the shrouds are in good agreement with the experimental data, demonstrating the validity of the simple shroud model. Despite of notable variations in local unsteady pressures around the shrouds, the present results show that the blade aerodynamic damping is largely unaffected by the aerodynamic blockage introduced by part-span shrouds.

Computational Modelling of Tip Heat Transfer to a Super-Scale Model of an Unshrouded Gas Turbine Blade

2008 ◽  
Author(s):  
Brian M. T. Tang ◽  
Pepe Palafox ◽  
David R. H. Gillespie ◽  
Martin L. G. Oldfield ◽  
Brian C. Y. Cheong
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Computational Study ◽  
Turbulence Models ◽  
Scale Model ◽  
Tip Leakage Flow ◽  
Blade Tip

Control of over-tip leakage flow between turbine blade tips and the stationary shroud is one of the major challenges facing gas turbine designers today. The flow imposes large thermal loads on unshrouded high pressure turbine blades and is significantly detrimental to turbine blade life. This paper presents results from a computational study performed to investigate the detailed blade tip heat transfer on a sharp-edged, flat tip HP turbine blade. The tip gap is engine representative at 1.5% of the blade chord. Nusselt number distributions on the blade tip surface have been obtained from steady flow simulations and are compared to experimental data carried out in a super-scale cascade, which allows detailed flow and heat transfer measurements in stationary and engine representative conditions. Fully structured, multiblock hexahedral meshes were used in the simulations, performed in the commercial solver Fluent. Seven industry-standard turbulence models, and a number of different tip gridding strategies are compared, varying in complexity from the one-equation Spalart-Allmaras model to a seven-equation Reynolds Stress model. Of the turbulence models examined, the standard k-ω model gave the closest agreement to the experimental data. The discrepancy in Nusselt number observed was just 5%. However, the size of the separation on the pressure side rim was underpredicted, causing the position of reattachment to occur too close to the edge. Other turbulence models tested typically underpredicted Nusselt numbers by around 35%, although locating the position of peak heat flux correctly. The effect of the blade to casing motion was also simulated successfully, qualitatively producing the same changes in secondary flow features as were previously observed experimentally, with associated changes in heat transfer to the blade tip.

scholarly journals Fixation durations in scene viewing: Experimental data and computational modeling

2010 ◽  
Vol 8 (6) ◽  
pp. 1107-1107 ◽  
Author(s):  
A. Nuthmann ◽  
T. J. Smith ◽  
J. M. Henderson
Keyword(s):  
Experimental Data ◽  
Computational Modeling ◽  
Fixation Durations ◽  
Scene Viewing

scholarly journals Computational study of the rovibrational spectrum of H2O-HF

2021 ◽  
Author(s):  
Dominika VIGLASKA ◽  
Xiao-Gang Wang ◽  
Tucker CARRINGTON ◽  
David Tew
Keyword(s):  
Experimental Data ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Energy Surface ◽  
Computational Study ◽  
Energy Levels ◽  
Dissociation Limit ◽  
Lanczos Algorithm ◽  
Vibrational States

In this paper we report rovibrational energy levels, transition frequencies, and intensities computed for H2O-HF using a new ab initio potential energy surface and compare with available experimental data. We use the rigid monomer approximation. A G4 symmetry-adapted Lanczos algorithm and an uncoupled product basis are employed. The rovibrational levels are computed up to J = 4. The new analytic 9-D potential is �t to 39771 counterpoise corrected CCSD(T)(F12*)/augcc- pVTZ energies and reduces to the sum of uncoupled H2O and HF potentials in the dissociation limit. On the new potential better agreement with experiment is obtained by re-assigning the R(1) transitions of two vibrational states.

Reversible Stepwise Motion by a Novel Symmetric Scratch Drive Actuator

2002 ◽  
Author(s):  
Shawn Chen ◽  
Wensyang Hsu
Keyword(s):  
Experimental Data ◽  
Material Properties ◽  
Previous Literature ◽  
Geometrical Parameters ◽  
Driving Voltage ◽  
Analysis Scheme ◽  
Simulation Results ◽  
Good Agreement

A novel symmetric scratch drive actuator (SSDA) capable of two-way motion is proposed here. An analysis scheme is presented, and also can be applied to the conventional scratch drive actuator (SDA). The analysis derived here is the first to be able to relate the step increment and driving voltage with given geometrical parameters and material properties for SSDA or SDA. In order to verify the analysis, the simulation results are compared to experimental data of SDA in previous literature [1], and it shows good agreement. In the analysis of SSDA, it is found that SSDA can provide the same order of step increment with the same driving voltage, and it may move in two directions by one device.

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