Concentration Profiles Research Articles

The use of R code for modeling and simulation of 2-D contaminant migration through a soil for the pulse source

<p>In this study, based on an existing analytical solution for the two-dimensional transport of contaminants in a saturated soil layer, for the pulse source, the R program code was developed. The simulation is used to obtain the profiles of contaminant concentration, for a steady groundwater velocity, as a function of distance from the source and time. The problem is analytically solved by leveraging the similarity between the Gaussian (normal) distribution and contaminant concentration distribution, the development of the analytical model (i.e., solution of partial differential equation) by using this similarity is explained step by step since it may be of interest to researchers. Contaminant propagation is modeled using R software, which helps to understand how contaminants migrate through a saturated soil layer. This approach aids in comprehending the mechanisms and spatial dynamics of contaminant dispersion, facilitating the prediction and management of soil and groundwater contamination. The provided R code can be altered for different parameters and time intervals.</p>

The use of R code for modeling and simulation of 2-D contaminant migration through a soil for the pulse source

<p>In this study, based on an existing analytical solution for the two-dimensional transport of contaminants in a saturated soil layer, for the pulse source, the R program code was developed. The simulation is used to obtain the profiles of contaminant concentration, for a steady groundwater velocity, as a function of distance from the source and time. The problem is analytically solved by leveraging the similarity between the Gaussian (normal) distribution and contaminant concentration distribution, the development of the analytical model (i.e., solution of partial differential equation) by using this similarity is explained step by step since it may be of interest to researchers. Contaminant propagation is modeled using R software, which helps to understand how contaminants migrate through a saturated soil layer. This approach aids in comprehending the mechanisms and spatial dynamics of contaminant dispersion, facilitating the prediction and management of soil and groundwater contamination. The provided R code can be altered for different parameters and time intervals.</p>

Comparative analysis of non‐newtonian fluids over an exponentially stretching sheet with convective boundaries

AbstractThe primary objective of this research is to explore the behavior of several non‐Newtonian fluids, including Casson, Williamson, and Maxwell fluids, over an exponentially stretching sheet considering an inclined magnetic field into account. Non‐Newtonian fluids can be encountered in many industrial and biological applications. They differentiate themselves by their sophisticated viscosity and flow properties. For the purpose of optimizing applications like coating technologies, bioengineering, and polymer processing, it is essential to comprehend their flow dynamics. This work illuminates these fluids' behaviors under convective boundary conditions, which is important for numerous industrial processes. Due to the convective boundary conditions, heat transfer at the sheet is affected by the surrounding fluid. The dominating flow field's nonlinear partial differential equations (PDEs) are synthesized into a system of coupled nonlinear ordinary differential equations (ODEs) using appropriate similarity transformations, and the resulting equations are then numerically solved using the BVP4C solver in MATLAB software. To demonstrate the behaviors of velocity, temperature, and concentration, a parametric research has been attempted. Significant parameter's effect on velocity, temperature, concentration, skin friction coefficient, Nusselt number, and Sherwood number have been investigated, and numerical findings are shown graphically. The numerical data is validated to previously published results on a variety of particular instances and found to be in great agreement. For varying values of the porosity parameter, Darcy‐Forchheimer parameter, and magnetic field, the fluid velocity falls. It is claimed that as the Forchheimer number and the porosity parameter expands, the momentum boundary layer thickness and the velocity profile diminishes. Furthermore, at the maximum levels of Schmidt number, the temperature profile rises synchronously, although the concentration profile reflects the flip pattern.

Heat and mass transfer in tri‐layer ependymal ciliary transport with diverse viscosity

AbstractSpecialized cilia known as ependymal cilia help the cerebrospinal fluid, which is important for nutrient delivery and waste elimination, to circulate in the brain. Many species rely on cilia and flagella for fluid movement and motility. Cilia and flagella, for instance, produce propulsive forces that allow unicellular creatures like Paramecium and Euglena to move through their surroundings. Ciliary transport plays a role in the flow of egg cells, or oocytes, via the fallopian tubes in the female reproductive system. The transfer of the egg towards the uterus is facilitated by the synchronized wave‐like motion produced by the cilia lining the fallopian tubes. Like this, ciliary transport in men aids in the passage of sperm cells via the epididymis. Many scientists and researchers are studying the mechanics of cilia motion and the properties of the viscoelastic fluid layer to develop new treatments and applications in biomedical engineering and for some diseases. Motivated by a wide range of biological applications, the objective of this study is to investigate the heat and mass transfer flow of tri‐layered Newtonian fluids flowing with the help of ciliary beating in a Cartesian coordinate. The fluid is incompressible, and fluid layers are not intermixed. The fluid flow with heat and mass transfer is first modelled in wave and then transmuted into fixed. Solutions for temperature profile, velocity distribution, stresses and concentration distribution are obtained. The influence of incipient parameters is displayed with graphs and plotted with the computational software MATHEMATICA 13.0 in the results section. The key findings obtained from graphs show that the maximum magnitude for temperature and velocity is achieved in the middle layer of fluid whereas in the outer layer concentration profile is maximum. It is predicted that this approach will make an essential contribution to the progress and enhancement of various types of drug delivery systems in the biomedical industry and biomechanics.

Experimental and modeling approaches to determine drug diffusion coefficients in artificial mucus

Asthma, usually characterized by inflammation and mucus accumulation, causes restricted airflow and impaired lung function. The physiological and biochemical characteristics of mucus pose a strong barrier for drugs administered orally or via the pulmonary route for asthma treatment. In this study, two drugs commonly employed in the treatment of asthma, theophylline and albuterol, were placed in contact with an artificial mucus layer, measuring their interface concentrations, and modeling the concentration profiles to determine their diffusion coefficients. To monitor the diffusion process, the upper surface of a mucus layer was placed in contact with the drug solutions and the lower mucus surface was in contact with a zinc selenide crystal to allow for time-resolved Fourier transform infrared spectroscopy (FTIR) measurements. FTIR spectra were collected at constant time intervals and monitored for quantitative changes in spectral peaks corresponding to functional groups specific to each of these drugs. Changes in peak heights were correlated to concentration via Beer's Law. Fick's 2nd Law of Diffusion was used along with Crank's trigonometric series solution for a planar semi-infinite sheet to analyze the concentration data and determine diffusion coefficients. Using this method, fitting the experimental data resulted in diffusivity coefficients of D = 6.56 x 10−6 cm2/s for theophylline and D = 4.66 x 10−6 cm2/s for albuterol through artificial mucus. The drug diffusivity coefficients align closely with literature reports, wherein, diffusivity data was obtained experimentally using a rotating-disk apparatus and intrinsic dissolution technique. By coupling analytical and experimentally determined drug diffusion data, this approach provides a fast, non-invasive method for quickly assessing drug diffusion profiles through complex media.

Tailoring Crystallization Kinetics in Thin Sucrose Films during Convective Drying: Impact of Temperature and Humidity on Onset, Growth, and Nucleation Rate.

Drying experiments with varying air temperature and humidity were conducted to investigate the influence of the drying process on the crystallization of thin sucrose films. For the first time, the effects of the nucleation onset, nucleation rate, and growth rate were investigated in situ and their differentiated influence on product crystallinity could be assessed. The growth rate was not influenced by air humidity but showed a strong dependence on temperature. It increased with drying temperature; however, at high temperatures, growth was inhibited when the water content falls below a critical level. Noticeable differences in nucleation behavior could be observed with regard to air humidity. Dry air led to crystallization onsets at lower levels of supersaturation, while moderately humid air retarded it. At higher temperatures, nucleation onset commenced at lower water contents but at a constant supersaturation level. The nucleation rate doubled in experiments with moderately humid air (15% RH), while an elevated drying temperature showed generally lower nucleation rates. The observed differences in the nucleation onset and rate could be explained by the film-internal concentration profile, which is strongly influenced by drying parameters. The insights therefore provide a differentiated understanding of the formation of the physical state and how it can be influenced during convective drying.

Sensitivity of AERMOD (V21112) RLINEXT dispersion model outputs by source type to variability in single noise barrier height and separation distance

The U.S. Environmental Protection Agency (USEPA) introduced the RLINEXT modeling feature in the latest versions of AERMOD (since version v21112) to predict traffic-induced pollutant concentration when noise barriers are present. The research presented in this paper explores the impacts of noise barrier characteristics on AERMOD-predicted concentrations. The research finds that because AERMOD can currently only attach one barrier to each road side, and because that barrier only impacts the source to which it is attached, it is also important to split links so that they properly pair with barriers. Given the sensitivity of AERMOD-predicted concentrations to barrier characteristics (i.e., barrier heights and distances to roadway), the research also concludes that barriers must be appropriately matched with input links. This study investigated the sensitivity of CO concentration predicted by the latest AERMOD under various noise barrier conditions (barrier heights and distances between road and barrier) and meteorological conditions (wind directions and wind speeds). The results indicate that ground-level concentration of downwind receptors decreases with increased barrier heights, and that distant barriers have less of an impact on predicted concentrations. This study also explored the impact of noise barrier on both horizontal and vertical concentration profiles, indicating that concentrations rise behind the barrier as plumes are predicted to loft over the barrier. The sensitivity analysis associated with splitting roadway links to match with barriers indicated an impact on predicted concentration for certain receptors of up to 10%, but the overall the impact on maximum concentrations was marginal.

Numerical Simulation and Neural Network Model for Hydromagnetic Nanofluid Convection in a Porous Wavy Channel with Thermal Non-Equilibrium Model

Abstract The present study aims to analyze the nonfluid MHD convective heat transfer in a porous wavy channel with a local thermal non-equilibrium (LTNE) model. Such a model finds applications related to enhancement in thermal performance, increasing the heat transfer coefficient in the compact design of heat exchangers for the aerospace and automotive industries and elevation in the efficiency of the solar collector. A sinusoidal porous wavy LTNE channel containing nanofluid and subjected to the induced and applied magnetic fields is considered. A uniform magnetic field is applied orthogonal to the channel and the induced magnetic field effects are considered due to the large magnetic Reynolds number. The momentum, continuity, energy, and nanoparticle volume fraction equations constitute the coupled nonlinear system of differential equations and are solved using the Galerkin finite element method. The reliability of the technique is assessed by comparing the proposed procedure with the results from earlier sources. A detailed analysis is presented to determine the effects of different physical parameters arising in the system on temperature, nanoparticle concentration, and velocity profiles. As an illustration, the findings exhibit that increasing the modified diffusivity ratio increases the values of the nanoparticle volume fraction whereas, reducing the modified diffusivity ratio enhances the temperature distribution. A higher value of thermal Rayleigh number presents a significant involvement of buoyancy forces, potentially resulting in the development of convective currents. A higher Nield number indicates more effective heat transport from the solid surface to the nanofluid. Consequently, there is a minimal thermal difference between the solid surface and the bulk nanofluid. Effective heat transmission enhances the nanofluid ability to absorb heat and generates a more consistent dispersion of temperature inside the fluid. The performance of the designed algorithms of the artificial neural network, namely, the Levenberg – Marquardt algorithm, in the problem under consideration is evaluated and the methodology is found reasonably precise with the matching of order around 6 to 7 decimal places of accuracy.

Impact of non-uniform heat flux, Arrhenius activation energy on gyrotactic microorganisms in conducting a nanofluid flow

ABSTRACT The primitive focus of this article is to examine the consequences of unsteady electrically conducting non-Newtonian magnetised tangent hyperbolic hybrid nanofluid flow which slides along the extensible surface with a porous medium along with Darcy–Forchheimer in a flow. Here we have taken into account the thermophoresis and Brownian movement for single- and multi-wall CNT dispersed in water. The temperature profile is accompanied by non-linear heat flux and viscous dissipation. The aftermath of activation energy on the concentration and the flow of gyrotactic microorganisms are taken into consideration. Differential equations after introducing various parameters are converted into ODE with the help of similarity transformations, which are later on, are solved using the bvp4c solver in the MATLAB software. For the range 0 ≤ Sq ≤ 4 there is an upsurge in the picture profiles of concentration and temperature obtained. However, the velocity of the flow gets diminished when the range of MHD and porosity parameter is confined between 0 ≤ M , K p ≤ 6 .

Three-dimensional solute transport in finite and curved porous media with surface input sources

In this paper, an analytical solution for three-dimensional solute transport in porous media between two curved surfaces is investigated. It is assumed that the groundwater velocity and dispersion coefficient vary with time and position. Groundwater velocity is not considered to be horizontal. The components of dispersion coefficient along the axes are considered to be proportional to the square of corresponding the position variable. The dispersion coefficient components along axes are proportional to the corresponding component of groundwater velocity in temporal aspects while former is squarely proportional to letter one in position components. It is assumed that the sources originate from two curved surfaces. The nature of the source on the two surfaces is the same, but there may be a variation in potential. Initially, the aquifer's domain is supposed to be uniformly polluted. The Laplace Integral Transformation Technique (LITT) is used to obtain analytical solutions. Numerical examples are given to demonstrate the effects of various factors on the solute concentration profile in a system where advection and dispersion play important roles.In addition, the sub-case of horizontal flow is also discussed. The model is extremely useful in analyzing and dealing with widespread surface sources of groundwater pollution in simulated agricultural fields or urban dumping areas.

A DEM study on the criteria for particle movement over a granular bed

The collision of a spherical particle onto a granular bed, generating a splash of ejected grains, is a crucial process in the study of wind-blown sand. Previous research has faced challenges in clearly distinguishing between particles in saltation, reptation, and creep motion. This study employs the Discrete Element Method (DEM) to simulate particle trajectories during sand-bed collisions, providing a systematic analysis of the vertical mass concentration profiles and the probability density functions (PDFs) for splash velocity, splash angle, and the number of splashed particles associated with saltation, reptation, and creep particles. Our results reveal that reptation motion predominantly occurs within a vertical height range of 0.064 mm to 8 mm above the surface, creep motion occurs below 0.032 mm, and saltation occurs at heights greater than 8 mm.

A new three-dimensional modeling of fluorescence excitation-emission measurements to explore the interaction of hydroxychloroquine and DNA, and to quantify their binding constant

A new three-dimensional chemometric approach was introduced to explore the interaction of hydroxychloroquine (HCQ)-calf thymus deoxyribonucleic acid (DNA) and quantify binding constant using fluorescence excitation and emission measurements. The fluorescence excitation-emission spectra were recorded after gradual titration of HCQ with DNA. Then, the excitation and emission curves and relative concentrations of the drug and drug-DNA complex were quantitatively estimated using a three-dimensional model called Parallel Factor Analysis (PARAFAC) to a cubic fluorescence data array. The interaction of HCQ and DNA was predicted by applying newly modified Stern-Volmer equations to the relationship between the actual DNA concentration, and the HCQ concentration in the relative concentration profile of the PARAFAC model. In the PARAFAC application, the binding constants of the HCQ-DNA complex at 288, 298, and 310 K were found as 6.78 × 103, 5.07 × 103, and 3.74 × 103 L mol−1, respectively. From the temperature studies, the thermodynamic parameters (ΔS0= 3.528 J mol−1 K−1, ΔH0= −20.099 kJ mol−1 and ΔG0=-21.11, −21.12, and −21.19 kJ mol−1 at 288, 298, and 310 K, respectively) were calculated. The drug-DNA interaction is spontaneous due to negative ΔG0 values. The positive ΔS0 and negative ΔH0 values revealed the major role of the electrostatic force on the binding of HCQ to DNA. Assay results obtained from the proposed three-way modeling were compared to those provided by the traditional spectrofluorimetric method.

A Highly Atom-Efficient Prodrug Approach to Generate Synergy between H2S and Nonsteroidal Anti-inflammatory Drugs and Improve Safety.

Efforts to synergize hydrogen sulfide (H2S) with NSAIDs have faced challenges due to complex structural entities and independent release kinetics. This study presents a highly atom-efficient approach of using a thiocarboxylic acid (thioacid) as a novel H2S releasing precursor and successfully employs it to modify NSAIDs, which offers several critical advantages. First, thioacid-modified NSAID is active in inhibiting cyclooxygenase, sometimes with improved potency. Second, this prodrug approach avoids introducing extra structural moieties, allowing for the release of only the intended active principals. Third, the release of H2S and NSAID is concomitant, thus optimally synchronizing the concentration profiles of the two active principals. The design is based on our discovery that esterases can directly and efficiently hydrolyze thiocarboxylic acids, enabling controlled release H2S. This study demonstrates the proof of principle through synthesizing analogs, assesses release kinetics, enzyme inhibition, and pharmacological efficacy, and evaluates toxicity and gut microbiota regulation in animal models.

Effect of О<sub>2</sub><sup>+</sup> Ion Implantation on the Elemental and Chemical Composition of the Si(111) Surface

Using the methods of secondary ion mass spectrometry, elastic peak electron spectroscopy and Auger electron spectroscopy, the elemental and chemical composition of the surface, concentration profiles of the distribution of atoms over the depth of silicon implanted with O2+ ions with energy E0 = 1 keV at a dose of D = 6 × 1016 cm–2 were studied. It was found that oxides and suboxides of Si (SiO2, Si2O and SiO0.5) were formed in the ion-doped layer, and it also contained unbound O and Si atoms. Post-implantation annealing at 850–900 K led to the formation of a stoichiometric SiO2 layer ~25–30 Å thick.

Thermal analysis in unsteady oscillatory Darcy blood flow through stenosed artery

This study aims to provide an extensive overview of the consequences of heat source and thermal radiation on blood flow in stenosed arteries through Casson fluid. We examine the behaviour of an unsteady non-Newtonian fluid under oscillatory Darcy flow. This analysis explores the impact of blood flow in the stenosed arteries on the momentum and energy profiles of the Casson fluid. In addition, this study examines a parametric analysis to illustrate the impact of the Nusselt number and Casson parameter. Higher values of the thermal radiation and Casson-Viscous parameters result in enhanced velocity fields. The Brinkman model accurately represents the resistance to flow caused by the porous material, known as Darcy resistance. The inner space of the coronary artery generates cholesterol-rich fatty plaques and blood clots that block the artery, simulating the diseased condition of blood circulation in this study. We employ a set of non-dimensional variables to convert the governing equations of the current flow into dimensionless partial differential equations. Analytical methods have derived a solution for the studied problem. The discovery is pertinent to the natural circulation of blood through coronary arteries, which are highly porous. A particular artery pathology creates a permeable structure within the arterial lumen. The current study demonstrates that blood flow may be manipulated by adjusting the intensity of the external magnetic field, while the temperature of the blood can be managed by either increasing or decreasing its thermal conductivity. The graphical representation demonstrates the impact of different physical parameters on velocity, temperature, and concentration profiles. The significant results of the current studies are that, the fluid velocity diminishes with rising magnetic and Biot numbers but exhibits an increase when considering the Darcy number and Hall parameter. There is a gentle increase in the wall shear stress as the Casson parameter (β) increases from 0.1 to 0.3. For β= 0.3, the percentage change along the axial direction (x) is more pronounced. This is because the wall shear stress is proportional to the number of Casson parameters.

Convective diffusive thermal flow over an inclined surface with viscous dissipation and aligned magnetic field applications

This investigation incorporating the fluctuation in heat and mass transfer associated to the mixed convection magnetized flow of viscous fluid due to inclined surface with porous media. The contribution of Soret effects and viscous dissipation appliances is addressed. Furthermore, the heat transfer improvement is also assessed by thermal radiation, heat source and joule heating effects. The chemical reaction enrollment is also studied for concentration phenomenon. The convection of problem into non-dimensional framework is based on implication of new variables. The perturbation technique is followed to tracking the analytical outcomes. Physical visualization and interpretation of results under the influence of perturbed parameters have been studied. It is observed that heat and mass transfer enhances due to Soret number. Presence of chemical reaction leads to decrement of concentration profile. Claimed results presents applications in heat and mass transfer processes, chemical reaction, manufacturing systems, chemical engineering, extrusion processes etc.

The nanoparticles aggregation aspects on the chemically reactive unsteady flow of alumina-water based nanofluid: A Keller box approach with applications of wavelet physics inspired neural networks

The present study explores the unsteady flow of a nanoliquid past a stretching cylinder with the consequence of heat source/sink and chemical reaction. Additionally, the effect of nanoparticle aggregation, convective boundary conditions, and magnetic field on the liquid flow is taken into consideration. Utilizing similarity variables, the modeled equations are transformed into dimensionless ordinary differential equations (ODEs). Further, the obtained ODEs are numerically solved by using the Keller box method. Moreover, the physics-informed neural network (PINN) is applied to analyze the flow, heat, and mass transport features. Graphical illustrations are used to display the influence of various parameters on the velocity, concentration, and temperature profiles for aggregation and without aggregation cases. As the value of the magnetic parameter increases, the temperature and concentration profile upsurge, but the reverse trend can be seen in the velocity profile. The concentration and temperature profiles rise as the unsteadiness parameter increases, but the velocity profile declines. The concentration, velocity, and temperature profiles are strengthened by an improvement in the curvature parameter value. The intensification in the values of the chemical reaction parameter declines the concentration.

Correlative electron microscopy of discontinuous precipitation

This paper presents a comprehensive study on discontinuous precipitation (DP) in Al-22 at.% Zn alloy, leveraging the correlative and synergic effects of advanced microscopy and modelling techniques. The study is structured into three pivotal steps: in-situ scanning electron microscopy combined with an energy backscattered diffraction analysis for real-time monitoring and an analysis of DP reaction kinetics and grain boundary misorientations; transmission electron microscopy and an energy X-ray dispersive microanalysis for detailed observation of solute-depleted α and solute-rich β lamellae, offering insights into the kinetics of the reaction front (RF) and solute concentration profiles; and a sophisticated modelling approach addressing the limitations of direct observation methods by simulating solute concentration changes within αphase lamellae during RF go-and-stop cycles. This multifaceted approach elucidates the nuances of DP mechanisms, from the nucleation and growth of precipitates to the estimation of instantaneous RF velocity and the impact of grain boundary misorientations. The integration of these methodologies enhances our understanding of DP kinetics and morphology at both meso- and nanoscales, highlighting the significant role of correlative microscopy in metallurgical research. The findings not only deepen our grasp of the fundamental mechanisms driving DP reactions but also provide a valuable comparison framework for experimental data, potentially guiding the development and optimization of metallurgical processes.

Optimizing β-lactam-containing antibiotic combination therapy for the treatment of Buruli ulcer.

The current treatment for Buruli ulcer is based on empirical evidence of efficacy. However, there is an opportunity for shortening its duration and improving response rates. Evolving understanding of the pharmacokinetic-pharmacodynamic relationships provides the basis for a stronger dose rationale for antibiotics. In conjunction with modelling and simulation, it is possible to identify dosing regimens with the highest probability of target attainment (PTA). This investigation aims to: (i) assess the dose rationale for a new combination therapy including amoxicillin/clavulanic acid (AMX/CLV) currently in clinical trials; and (ii) compare its performance with alternative dosing regimens including rifampicin, clarithromycin and AMX/CLV. In vitro estimates of the minimum inhibitory (MIC) concentration were selected as a measure of the antibacterial activity of different drug combinations. Clinical trial simulations were used to characterize the concentration vs. time profiles of rifampicin, clarithromycin and amoxicillin in a virtual cohort of adult and paediatric patients, considering the effect of baseline covariates on disposition parameters and interindividual variability in exposure. The PTA of each regimen was then assessed using different thresholds of the time above MIC. A weight-banded dosing regimen including 150-600 mg rifampicin once daily, 250-1000 mg clarithromycin and AMX/CLV 22.5mg/kg /1000 mg twice daily ensures higher PTA than the standard of care with AMX/CLV 45 mg/kg/2000 mg once daily. The higher PTA values support the proposed 4-drug combination (rifampicin, clarithromycin, AMX/CLV) currently under clinical investigation. Our findings also suggest that higher rifampicin doses might contribute to enhanced treatment efficacy.

Numerical study of Casson dusty hybrid nanofluid flow with volume fraction over a Darcy–Forchheimer porous medium

AbstractThis study develops a mathematical model for dusty Casson hybrid nanofluid flow over a vertical stretching sheet, considering the influence of volume fractions for the dust particles and nanoparticles, magnetic field and Darcy–Forchheimer penetrating medium. The nanoparticles used are TC4 (Ti‐6Al‐4V) and Nichrome (80% Ni and 20% Cr), suspended in unused engine oil (EO). The governing partial differential equations are transformed into ordinary ones using suitable transforms. Solutions are obtained numerically via the Matlab built‐in program Bvp4c technique and represent graphically the velocity, temperature, and concentration profiles for both the fluid and dust phases. Additionally, tabular forms present wall shear stress and heat transfer rate variations under different parameter values. It is found that the enhancing volume fraction parameter helps to boost the magnitude of shear stress, heat, and mass diffusivity.