Rms Fluctuations Research Articles

Engineering a novel immunogenic chimera protein utilizing bacterial infections associated with atherosclerosis to induce a deviation in adaptive immune responses via Immunoinformatics approaches.

Recent studies have established the role of bacteria including Streptococcus pneumoniae, Helicobacter pylori, Chlamydia pneumonia, Mycobacterium tuberculosis, and Porphyromonas gingivalis in the development of atherosclerosis. These bacteria contribute to plaque formation via promoting Th1 immune responses and speeding up ox-LDL formation. Hence, we employed computational reverse vaccinology (RV) approaches to deviate immune response toward Th2 via engineering a novel immunogenic chimera protein. Prominent atherogenic antigens from related bacteria were identified. Then, machine learning-based servers were employed for predicting CTL and HTL epitopes. We selected epitopes from a wide variety of HLAs. Then, a chimeric protein sequence containing TAT peptide, adjuvant, IL-10 inducer, and linker-separated epitopes was designed. The conformational structure of the vaccine was built via multiple-template homology modelling using MODELLER. The initial structure was refined and validated by Ramachandran plot. The vaccine was also docked with TLR4. After that, molecular dynamics (MD) simulation of the docked vaccine-TLR4 was conducted. Finally, the immune simulation of the vaccine was conducted via the C-ImmSim server. A chimera protein with 629 amino acids was built and, classified as a non-allergenic probable antigen. An improved ERRAT score of 80.95 for the refined structure verified its stability. Additionally, validation via the Ramachandran plot showed 98.09% of the residues were located in the most favorable and permitted regions. MD simulations showed the vaccine-TLR4 complex reached a stable conformation. Also, RMS fluctuations analysis revealed no sign of protein denaturation or unfolding. Finally, immune response simulations indicated a promising response by innate and adaptive immunity. In summary, we built an immunogenic vaccine against atherosclerosis and demonstrated its favorable properties via advanced Immunoinformatics analyses. This study may pave the path for combat against atherosclerosis.

Droplets Evaporation In Turbulent Flow: Statistical Study Based On Lagrangian Tracking And In Line Holography

Turbulence has long been suspected to increase the evaporation rate of droplets via the convective effects it generates. The experimental data reported in this paper provides evidence of this increase and statistically quantify these effects. Measurements was performed following a Lagrangian approach, using Digital in-line holography based on a high speed camera and an inverse problem reconstruction algorithm. Ether droplets was released in a quasi isotropic and homogeneous turbulence generated by synthetic jets. Their Schmidt number is typically of the order of 2 and their Reynolds number is moderate (≤ 3). Results are based on a large number of droplets trajectories for various turbulence conditions. The Lagrangian statistics computed from these trajectories, totaling 1.3 million samples, show that the relative mean motion and turbulence seen by the droplets on average increases their evaporation rate. Within the parameter range investigated, this increase is not well predicted when estimating the convective effect in the Sherwood number with the norm of the instantaneous relative velocity seen by the droplets. In contrast, this increase is very well predicted when the Sherwood number is calculated using a Reynolds number based on the norm of the mean relative velocity plus its RMS fluctuation.

Flame stability and equivalence ratio assessment of turbulent partially premixed flames

This study is geared toward generating highly stabilized partially premixed flames at various levels of turbulence and partially premixing. Therefore, with the help of the laser-induced breakdown spectroscopy (LIBS) technique, a new burner was constructed and employed to quantitatively estimate the mixture equivalence ratio (Φ) within the flame. Two turbulence generator disks, five degrees of partial premixing, and two fuels were used to assess the flame stability. Natural gas (NG) and liquefied petroleum gas (LPG) were used as fuels. The LIBS spectrum's most common atomic emission lines which include hydrogen, nitrogen, oxygen, and carbon, were chosen to establish the correlation between emission lines' intensity and the flame's mixture equivalence ratio. The results showed that the stability of NG flame was less sensitive to the variation of the partially premixing levels. In contrast, the LPG flames were more susceptible to the variation of the mixing degree. At a lower level of partially premixing, NG flames were more stable, and as the mixing degree increased, the stability of NG flames was reduced compared to LPG flames. In addition, the results showed that the equivalence ratio radial profiles are more homogeneous and have lower RMS fluctuation for the wider slot of the turbulence generator disc. Furthermore, the larger turbulence generator disk's higher turbulent intensity contributed in posting the mixing process and enhancing mixture homogeneity over even shorter recess distances than the smaller disk generator.

Experimental validation of numerical two-phase flow in a horizontal separator

Multiphase flows have been a significant problem in the oil and gas industry, with many recent reports of failures in industrial piping and equipment due to erosion either from long-term liquid impingements or solid particles. One of the most efficient horizontal sand separators is the product developed by Specialized Desanders Inc., which is called the “Horizontal Desander.” It is a gravity-based separator, and the associated multiphase flow physics has been investigated in this research. This study analyzes the phase separation by applying multiphase numerical analysis using Star CCM + software. Experimental testing with the two-phase flow (air and water) was performed and compared to the numerical results. The Particle Image Velocimetry measurements applied to the two-phase experiment showed that the time-averaged, RMS of velocity fluctuations and the frequency analysis of the air-liquid interface are in an acceptable agreement with the simulation results. Knowledge of the different phase interactions and behavior of multiphase flow is essential in developing and optimizing gravity separators. The results from this study will be the steppingstone to simulate multiphase flows with more than two phases.

Self-regulation in electroencephalographic signals during an arithmetic performance test: an approach with an rms fluctuation function

Self-regulation in electroencephalographic signals during an arithmetic performance test: an approach with an rms fluctuation function

The explicit filtering method for large eddy simulations of a turbulent premixed flame

This paper reports large eddy simulations (LES) of a premixed turbulent round methane-air jet flame at an equivalence ratio of 0.8 and unburnt gas temperature of 800 K using the explicit filtering LES (EFLES) method. The nominal 1D premixed flame speed, sL=2.05ms−1 and thermal thickness, δL=300μm. EFLES is formally derived from the approximate deconvolution method for LES computations. The nominal turbulent Reynolds number Ret=34 and the turbulent Karlovitz number Ka=25 places the present flame in the thin reaction zones regime of turbulent premixed combustion. LES and DNS results are obtained by solving species transport equations using a reduced 13-species chemical mechanism. Chemical source terms in the LES are computed using resolved species and temperature fields in all simulations. Conditional means of net heat release rate predicted by the LES and DNS show excellent agreement. The LES results show a marginally thicker flame brush and a shorter mean flame height when compared to the DNS results. Good agreement between LES and DNS for mean quantities is seen upstream of the tip. Larger quantitative differences are seen at the tip due to the difference in flame height between LES and DNS cases, as may be expected. Even at these positions, qualitative features of the DNS results and peak mean values are recovered correctly. Agreement between conditional mean statistics from both LES and DNS is good. RMS fluctuation amplitudes show larger quantitative differences between LES and DNS when compared to mean statistics while still capturing the correct qualitative features of the DNS profiles. The radial profiles of unconditioned RMS fluctuations are broader by O(δL) in the LES results, with increasing downstream distance. The smaller range of resolved scales in the LES causes the resolved flow motions to be more energetic resulting in increased turbulent transport rates for mean and RMS quantities. This results in the observed broadening of flow statistics in the LES when compared to the DNS. With mesh refinement, differences between LES and DNS results for all statistics are found to diminish smoothly.

A MeerKAT 1.28 GHz Atlas of Southern Sources in the IRAS Revised Bright Galaxy Sample

Abstract The IRAS Revised Bright Galaxy Sample (RBGS) comprises galaxies and unresolved mergers stronger than S = 5.24 Jy at λ = 60 μm with Galactic latitudes ∣b∣ > 5°. Nearly all are dusty star-forming galaxies whose radio continuum and far-infrared luminosities are proportional to their current rates of star formation. We used the MeerKAT array of 64 dishes to make 5 × 3 minutes snapshot observations at ν = 1.28 GHz covering all 298 southern (J2000 δ < 0°) RBGS sources identified with external galaxies. The resulting images have θ ≈ 7.″5 FWHM resolution and rms fluctuations σ ≈ 20 μJy beam−1 ≈ 0.26 K low enough to reveal even faint disk emission. The rms position uncertainties are σ α ≈ σ δ ≈ 1″ relative to accurate near-infrared positions, and the image dynamic ranges are DR ≳ 104: 1. Cropped MeerKAT images of all 298 southern RBGS sources are available in FITS format from 10.48479/dnt7-6q05.

Turbulent Flow over Confined Backward-Facing Step: PIV vs. DNS

Particle Image Velocimetry measurements of the liquid velocity fields in the flow over the backward-facing step were performed in the same flow configuration as in the existing Direct Numerical Simulation (DNS). The experiment and the simulation were performed in an identical cross-section geometry with step expansion rate 2.25 and the square shape of the outlet duct at the Reynolds number in an inlet part of the section 7100. The experiment was performed in transparent test section, 1.2 m long, with 20 × 45 mm2 cross-section upstream and 45 × 45 mm2 downstream, while a domain that was three times shorter was used in the DNS. A 2D-2C PIV system with a single high-speed camera and a pulse laser was used for a series of two-dimensional measurements of the velocity field at several cross-sections from two different perspectives. Variables analyzed in the experiment are time-averaged fluid velocities, velocity RMS fluctuations and two components of the Reynolds stress tensor. The key novelty is the comparison of two very accurate approaches, PIV and DNS, in the same cross-section geometry. Comparison of the similarities, and especially the differences between the two approaches, elucidates uncertainties of both studies and answers the question on what kind of agreement is expected when two very accurate approaches are compared.

A computational study of a new design configuration for a turbulence tunnel

A new kind of turbulence tunnel, the pure coherent shear source turbulence tunnel, proposed to produce high Reynolds number, approximately homogeneous isotropic turbulence is studied computationally. The Reynolds-averaged Navier–Stokes equations, along with the standard k − ϵ model for closure, are solved in the computations. The tunnel design studied here consists of a duct of square cross section with a plane at one end consisting of an array of round jets and suction vents. This plane, referred to as the momentum source plane (MSP), also a zero net-mass flux plane, forces the flow into the tunnel. The flow field inside consists of an advection-dominated region where the jets merge to form a combined flow, and an advection-free near-homogeneous turbulence region. Turbulence statistics in the advection-dominated and advection-free regions of the flow field, and the effect of parameters associated with the forcing that affects these statistics are studied. A plateau of turbulence statistics with rms of fluctuations as high as 0.8 times the mean advective velocity scale for the tunnel section, U T , is obtained in a region with negligible mean advection. The effect of geometrical configuration at the MSP on the turbulence quantities in the advection free region is studied. The Reynolds number based on Taylor length scale of the turbulence produced is estimated to be of the order of 350 in a tunnel of size 0.5 × 0.5 m2.

Field-emission electron gun for a MEMS electron microscope

This article presents a field-emission electron gun intended for use in a MEMS (microelectromechanical system) electron microscope. Its fabrication process follows the technology of a miniature device under development built from silicon electrodes and glass spacers. The electron gun contains a silicon cathode with a single very sharp protrusion and a bundle of disordered CNTs deposited on its end (called a sharp silicon/CNT cathode). It was tested in diode and triode configurations. For the diode configuration, a low threshold voltage <1000 V and a high emission current that reached 90 µA were obtained. After 30 min of operation at 900 V, the emission current decreased to 1.6 µA and was stable for at least 40 min, with RMS fluctuation in the anode current lower than 10%. The electron beam spot of the source was observed on the phosphor screen. In the diode configuration, the spot size was the same as the emission area (~10 µm), which is a satisfactory result. In the triode configuration, an extraction electrode (gate) control function was reported. The gate limited the emission current and elongated the lifetime of the gun when the current limit was set. Moreover, the electron beam current fluctuations at the anode could be reduced to ~1% by using a feedback loop circuit that controls the gate voltage, regulating the anode current. The developed sharp silicon/CNT cathodes were used to test the MEMS electron source demonstrator, a key component of the MEMS electron microscope, operating under atmospheric pressure conditions. Cathodoluminescence of the phosphor layer (ZnS:Ag) deposited on the thin silicon nitride membrane (anode) was observed.

Investigations of Gas–Particle Two-Phase Flow in Swirling Combustor by the Particle Stokes Numbers

Gas turbulence modulations and particle dispersions of swirling gas–particle two-phase flow in the combustor is investigated under the large spans of the particle Stokes numbers. To fully consider the preferential concentrations and anisotropic dispersions of a particle, a kinetic frictional stress model coupled with a second-order moment two-phase turbulent model and granular temperature equation is improved. The proposed modeling and simulations are in good agreement with the experimental validations. Results show turbulent modulations and particle dispersions exhibit strongly anisotropic characteristics, keeping a close relationship with flow structure. The axial gas velocity and RMS fluctuation velocity of 45.0-μm EGP was approximately 5.0 times and 3.0 times greater than 1000.0 μm Copper particles, and their axial particle velocity was 0.25 times and twice greater than those of 45.0 μm EGP. The degree of modulation in the axial–radial direction is larger than those of radial–tangential and axial–tangential direction. Particle dispersions are sensitive to particle diameter parameters and intensified by higher Stokes number.

On the capability of the curvilinear immersed boundary method in predicting near-wall turbulence of turbulent channel flows

The immersed boundary method has been widely used for simulating flows over complex geometries. However, its accuracy in predicting the statistics of near-wall turbulence has not been fully tested. In this work, we evaluate the capability of the curvilinear immersed boundary (CURVIB) method in predicting near-wall velocity and pressure fluctuations in turbulent channel flows. Simulation results show that quantities including the time-averaged streamwise velocity, the rms (root-mean-square) of velocity fluctuations, the rms of vorticity fluctuations, the shear stresses, and the correlation coefficients of u′ and v′ computed from the CURVIB simulations are in good agreement with those from the body-fitted simulations. More importantly, it is found that the time-averaged pressure, the rms and wavenumber-frequency spectra of pressure fluctuations computed using the CURVIB method agree well with the body-fitted results.

Correlation between electronic micro-roughness and surface topography in two-dimensional surface conducting hydrogen-terminated diamond

The influence of surface topography on phase coherent transport in the two-dimensional (2D) hole band of surface transfer doped hydrogen-terminated (100) diamond is investigated. Low-temperature magneto-conductance measurements were carried out with an applied in-plane magnetic field to quantify the effect of electronic micro-roughness on spin dephasing in the 2D hole band for Hall bar devices with similar transport characteristics, but significantly different topographic roughness. The electronic micro-roughness of the 2D hole band, described by the parameter d2L, where d is the root-mean-square (rms) fluctuation in the width of the quantum well and L is the correlation length of the fluctuations, is found to increase for surfaces with increased roughness. Fluctuations in the well width likely arise from a locally varying hole carrier density, arising for example from a local variation in the concentration of ionic components in the surface water layer.

Generation and sustenance of electric fields in sandstorms

Sandstorms are frequently accompanied by the generation of intense electric fields and lightning. In a very narrow region close to the ground level, sand particles undergo a charge exchange mechanism whereby larger (resp. smaller) sized sand grains become positively (resp. negatively) charged are then entrained by the turbulent fluid motion. Our central hypothesis is that differently sized sand particles get differentially transported by the turbulent flow resulting in a large-scale charge separation, and hence a large-scale electric field. We utilize our simulation framework, comprising of large-eddy simulation of the turbulent atmospheric boundary layer along with sand particle transport and an electrostatic Poisson solver, to investigate the physics of electric fields in sandstorms and thus, to confirm our hypothesis. We utilize the simulation framework to investigate electric fields in weak to strong sandstorms that are characterized by the number density of the sand particles. Our simulations reproduce observational measurements of both mean and RMS fluctuation values of the electric field. We propose a scaling law in which the electric field scales as the two-thirds power of the number density that holds for weak-to-medium sandstorms.

BGV theorem, geodesic deviation, and quantum fluctuations

I point out a simple expression for the ‘Hubble’ parameter , defined by Borde, Guth and Vilenkin in their proof of past incompleteness of inflationary spacetimes. I show that the parameter which an observer O with four-velocity v will associate with a congruence u is equal to the fractional rate of change of the magnitude ξ of the Jacobi field ξ associated with u , measured along the points of intersection of O with u , with its direction determined by v . I then analyse the time dependence of and ξ using the geodesic deviation equation, computing these exactly for some simple spacetimes, and perturbatively for spacetimes close to maximally symmetric ones. The perturbative solutions are used to characterise the rms fluctuations in these quantities arising due to possible fluctuations in the curvature tensor.

Statistical analysis of deformation of a shock wave propagating in a local turbulent region

Direct numerical simulation is performed for analyzing the interaction between a normal shock wave and turbulence. The shock wave is initially located in a quiescent fluid and propagates into a local turbulent region. This flow setup allows investigation of the initial transition and statistically steady stages of the interaction. Shock deformation is quantified using the local shock wave position. The root-mean-square (rms) fluctuation in the shock wave position increases during the initial stage of the interaction, for which the time interval divided by the integral time scale increases with Mt2/(Ms2−1), where Mt is a turbulent Mach number and Ms is a shock Mach number. In late time, the rms fluctuation in the shock wave position hardly depends on the propagation time and follows a power law, [Mt2/(Ms2−1)]0.46, whose exponent is similar to the power law exponent of the rms pressure-jump fluctuation reported in experimental studies. Fluctuations in the shock wave position have a Gaussian probability density function. The spectral analysis confirms that the length scale that characterizes shock wave deformation is the integral length scale of turbulence. The fluctuating shock wave position is correlated with dilatation of the shock wave, where the correlation coefficient increases with Mt/(Ms − 1). In addition, the shock wave that deforms backward tends to be stronger than average and vice versa. Mean pressure jumps across the shock wave are different between areas with forward and backward deformations. This difference increases with the rms fluctuation in the shock wave position and is well-represented as a function of Mt2/(Ms2−1).

Correlation between heat transfer and microstructure of turbulent flow in ribbed channel

Heat transfer and turbulence in channel flows past either a single rib or a rib array installed on the wall have been studied experimentally. It has been revealed that the local heat transfer coefficient behind a rib and a rib array is statistically closely related to RMS fluctuations of the vertical component of velocity in the near-wall region. This result points to a possible way to control the hydrodynamics aiming at heat transfer enhancement in turbulent flows in the channels with discrete roughness.

Experimental study of local solid volume fraction fluctuations in a liquid fluidized bed: Particles with a wide range of stokes numbers

In this study, the solid volume fraction fluctuations of different solid particles in a fluidized bed were measured using an Electrical Impedance Tomography system, which provides local fluctuation values. A wide range of particle Stokes numbers (122≤Stt≤3809) was tested by selecting specific particle sizes and densities. The results were compared with previous experimental studies. Since previous works measured only cross-sectional averages of the fluctuations, the local results of this study were spatially averaged for the comparison. The comparison showed an acceptable agreement in the level of RMS fluctuations. Importantly this study found that: (1) The strongest fluctuations always occurred at a narrow strip by the bed wall. Moving from the wall region towards the bed center, the magnitude of RMS fluctuations decreased. (2) The magnitude of local fluctuations was linked to the particle Stokes number (Stt), such that, at any given radial positions, the RMS fluctuations increased by increasing Stt. (3) Only limited agreement was observed among the trends of the measurements and the predictions of four existing mathematical and semiempirical models. The instantaneous local measurements conducted in this study are useful not only to examine currently available mathematical models, but they can also validate Computational Fluid Dynamics models of liquid fluidization.

Investigation of the interaction of a polyamine-modified flavonoid with bovine serum albumin (BSA) by spectroscopic methods and molecular simulation

The interaction between BSA and compound 1 was studied by UV–vis, fluorescence and circular dichroism spectroscopy under physiological conditions (pH = 7.4). Molecular docking and molecular dynamics analyses were also performed. The results showed that compound 1 could bind to BSA. When compound 1 bound to BSA, there were a series of changes in the spectral properties of BSA, which were an enhancement effect of the UV–Vis spectrum of BSA, fluorescence quenching and a weak conformational change in the CD spectrum. The results of the fluorescence experiments at 298, 303 and 310 K showed that fluorescence quenching caused by the addition of compound 1 to BSA was generally static quenching accompanied by a dynamic quenching process, which was shown by the quenching constants of 2.010 × 104 L∙M−1, 1.850 × 104 L∙M−1, and 1.970 × 104 L∙M−1 at the three different temperatures, respectively. From the obtained binding constants and thermodynamic parameters, it was found that hydrophobic forces played an important role in the binding process of 1 to BSA. The results of synchronous fluorescence and three-dimensional fluorescence showed that compound 1 caused a weak conformational change in BSA. Docking results showed that compound 1 was located at binding site II of bovine serum albumin protease. In addition, the flavonoid moiety of compound 1 contributes to the hydrophobic binding of compound 1 to BSA. The results of molecular dynamics, including the root-mean-square deviation (RMSD) and RMS fluctuation (RMSF) values, showed that the binding of compound 1 to BSA did not cause a significant conformational change in BSA.

Temperature measurement of a turbulent buoyant ethylene diffusion flame using a dual-thermocouple technique

High-frequency temperature measurements were carefully conducted for a 15 kW buoyant turbulent ethylene diffusion flame over a 15.2 cm diameter gas burner with air co-flow. A dual-thermocouple probe, consisting of two fine-wire thermocouples with 25 μm and 50 μm wire diameters, was used to determine a compensated turbulent gas temperature. A sensitivity analysis shows that temperatures resolved using this dual-thermocouple technique are less sensitive to changes in thermocouple bead size, therefore, uncertainty is greatly reduced even when soot deposition on the thermocouple bead occurs in sooty flames. Mean and root-mean square (rms) fluctuations of gas temperature were recorded in a two-dimensional plane across the flame centerline. The mean gas temperature monotonically decreases away from the flame centerline at most flame heights, except for 1 diameter above the burner, where a temperature dip is observed. The rms temperature peaks shift from the edge of the flame to the center as the height increases. This is due to the enhanced mixing between fuel and air, which is further shown using probability density functions of the local gas temperature. A systematic temperature dataset with high spatial resolution is established for sooty flames, which is valuable for future soot and radiation model validation.