Diffusion Of Chemical Species Research Articles

Diffusion in Porous Rock Is Anomalous.

Molecular diffusion of chemical species in subsurface environments─rock formations, soil sediments, marine, river, and lake sediments─plays a critical role in a variety of dynamic processes, many of which affect water chemistry. We investigate and demonstrate the occurrence of anomalous (non-Fickian) diffusion behavior, distinct from classically assumed Fickian diffusion. We measured molecular diffusion through a series of five chalk and dolomite rock samples over a period of about two months. We demonstrate that in all cases, diffusion behavior is significantly different than Fickian. We then analyze the results using a continuous time random walk framework that can describe anomalous diffusion in heterogeneous porous materials such as rock. This methodology shows extreme long-time tailing of tracer advance as compared to conventional Fickian diffusion processes. The finding that distinct anomalous diffusion occurs ubiquitously implies that diffusion-driven processes in subsurface zones should be analyzed using tools that account for non-Fickian diffusion.

Controlling the europium oxidation state in diopside through flux concentration.

This paper explores the connection between the H3BO3 flux concentration and the co-existence of Eu2+ and Eu3+ dopants within CaMgSi2O6 crystals (diopside). The samples were synthesised using a solid-state synthesis method under varying atmospheric conditions, including oxidative (air), neutral (N2), and reductive (H2/N2 mixture) environments. Additionally, some materials underwent chemical modification by partially substituting Si4+ with Al3+ ions acting as charge compensation defects stabilizing Eu3+ luminescence. Depending on the specific synthesis conditions, the materials predominantly displayed either the orange-red luminescence of Eu3+ (under oxidising conditions) or the blue luminescence of Eu2+; however, the comprehensive results confirmed the co-existence of Eu3+/Eu2+ luminescence in both cases. This work shows that varying flux concentrations added during synthesis significantly affect the relative strength of Eu2+ and Eu3+ emissions in a manner dependent on the synthesis atmosphere. The emission of Eu2+ increases with a higher flux concentration in materials synthesised under oxidative and neutral atmospheres independent of the chemical modification. In contrast, for materials obtained under a reductive atmosphere, the changes in the Eu3+ emission intensity depended on the presence or absence of Al3+ ions namely the increase of flux increased the Eu3+ intensity in the case of unmodified materials and decreased in the Al-modified ones. All observed effects were qualitatively explained considering the double role of the flux in the studied system, which besides facilitating the diffusion of chemical species during synthesis acts as a charge compensating agent by creating B'Si centres stabilizing Eu3+ emission.

Thermal and diffusion conditions for delta ferrite formation in partially melted and heat-affected zones of multipass SAW joint performed in martensitic stainless steel 12Cr–1Mo

It is widely known the harmful delta ferrite effect on the mechanical properties of martensitic stainless steel (MSS), especially in the partially melted (PMZ) and heat-affected (HAZ) regions brought about the welding thermal cycle. Therefore, this research studied the cooling and diffusion conditions responsible for delta ferrite formation, distribution, and morphology. A finite element numerical model helped to estimate the welding thermal cycle and then was correlated with delta ferrite formation. The numerical analysis considered the application of the submerged arc welding (SAW) process in multipass mode to obtain a coupon test fabricated of MSS 12Cr–1Mo. Heat diffusion and convection processes were strongly related to ferritic phase formation in the PMZ, which affected heat dissipation. Meanwhile, solid-state diffusion of chemical species C, Cr and Mo was analyzed in the HAZ to quantify its effect on delta ferrite grains formation derived from the carbide dissolution process. There was a significant fall in mechanical strength and corrosion resistance (pitting formation) in the HAZ, where some vermicular delta ferrite chains were detected.

A Kinetic Study on the Preparation of Al-Mn Alloys by Aluminothermic Reduction of Mn3O4 and MnO Powders

The study of aluminothermic reduction in manganese compounds is a complex challenge in preparing Al-Mn alloys. The primary objective of this study was to ascertain the activation energy values for the aluminothermic reduction of MnO and Mn3O4 oxides derived from alkaline batteries. The study melted aluminum found in beverage cans and utilized the technique of powder addition with mechanical agitation. The kinetics of the reaction were studied under the effects of temperature (750, 800, and 850 °C), degree of agitation (200, 250, and 300 rpm), and the initial concentration of magnesium in molten aluminum (1, 2, 3, and 4% by weight). Kinetic measurements for Mn3O4 particles suggest a reaction mechanism that occurs in stages, where manganese undergoes oxidation states [Mn+3] to [Mn+2] until it reaches the oxidation state Mn0, which allows it to dissolve in the molten aluminum, forming alloys with up to 1.5 wt.% of Mn. Therefore, the kinetic of the aluminothermic reduction of MnO is described by the geometric contraction model, while the mechanism of Mn3O4 reduction occurs in two stages: geometric contraction, followed by an additional stage involving the diffusion of chemical species to the boundary layer. In addition, this stage can be considered a competition between the formation of MnO and the chemical reaction itself.

Achieving clean production with nanostructured coated milling tools dry machining low carbon steel

The advancement of clean production using nanostructured materials in subtractive manufacturing processes has focused on replacing the use of liquid lubrication with solid lubricants coated to conventional cutting tools machining low carbon steel (∼0.2 wt % carbon). However, little is known about the wear mechanisms that dominate such tools when coated with functional graded nanostructured coatings. The present study follows an international standard for characterizing such wear (ISO 8688) but uses advanced measurement techniques such as x-ray fluorescence technology to measure the diffusion of chemical species from tool to workpiece and vice versa, that contributes to tool wear with the view to enhance the principles of cleaner production. The results show that when commercially-available tools coated with the appropriate functionally graded industrial coating, diffusion does not take place and creates an effective chemical barrier during machining. The experimental methods used in the study include machining workpieces using a CNC milling machine, tachometer for measuring spindle speed, dynamometer for measuring cutting forces, infra-red camera for measuring cutting temperatures, chemical species diffusion wear using x-ray fluorescence detector, and an optical microscope for measuring tool wear. Coupled with the physical measurement of wear, it is concluded that mechanical wear dominates the milling of a low carbon steel and that thermal properties of the coatings do not correlate with such wear. It is also concluded that flank wear as a function of volume of workpiece removed and machining duration (machining index) is a sound method for assessing the transition of the stages of wear during clean machining operations. The present study not only has implications for the design of better cutting tools, but also advances dry machining processes that eliminate the use of liquid lubricants making subtractive production processes cleaner. The main conclusions drawn from this study show that coated tools have a longer life under dry conditions compared to uncoated tools and that there is no correlation between coating properties and tool wear. Diffusion of chemical species into the cut chips did not occur because of the lack of thermally induced chemical wear of the cutting tool and that wear is caused by the gradual erosion of the flank face due to the chip abrading the cutting tool.

Nanofluidic osmotic power generation from CO2 with cellulose membranes

The diffusion of chemical species down concentration gradient is a ubiquitous phenomenon that releases Gibbs free energy. Nanofluidic materials have shown great promise in harvesting the energy from ionic diffusion via the reverse electrodialysis process. In principle, any chemicals that can be converted to ions can be used for nanofluidic power generation. In this work, we demonstrate the power generation from the diffusion of CO2 into air using nanofluidic cellulose membranes. By dissolving CO2 in water, a power density of 87 mW/m2 can be achieved. Using monoethanolamine solutions to dissolve CO2, the power density can be increased to 2.6 W/m2. We further demonstrate that the waste heat released in industrial and carbon capture processes, can be simultaneously harvested with our nanofluidic membranes, increasing the power density up to 16 W/m2 under a temperature difference of 30 °C. Therefore, our work should expand the application scope of nanofluidic osmotic power generation and contribute to carbon utilization and capture technologies.

Surface Severe Plastic Deformation for Improved Mechanical/Corrosion Properties and Further Applications in the Bio-Medical and Hydrogen Sectors

Various techniques enabling surface severe plastic deformation (SSPD) have been developed or optimised over the past years. This manuscript presents a broad overview of recent developments in the field of SSPD and its application that take advantages of having a deformed gradient surface with both (i) higher strength and (ii) an improved "reactivity". First, the principle and technological advantages/disadvantages of several SSPD technologies, involving either guided or non-directional mechanical impacts, are recalled. Then, after a short recall on the nature of the structure the modified surface formed under SSPD, the effects of the processing parameters and temperature of deformation on the surface roughness and subsurface microstructure modifications are illustrated with a particular emphasis on the surface mechanical attrition treatment (SMAT) and ultrasonic shot peening (USP) techniques deriving from the traditional pre-strain shot peening. The effect of these surface and sub-surface modifications on the mechanical properties, and in particular the fatigue response, are recalled with a special emphasis on the surface integrity and potential over shot peening. Then, the manuscript concentrates on the effect of the surface enhanced diffusion of chemical species induced by the presence of structural defects to modify the corrosion behaviour and enhance the potential assisted SSPD + thermo-chemically “duplex” treatments. In these cases, in addition to induce grain refinement and dislocations, the importance of controlling some potential surface contamination is stressed. Finally, the manuscript terminates by illustrating some new research studies on potential applications for the challenges in the hydrogen sector for its solid-state storage and the protection of mechanical infrastructures as well as for bio-medical applications with biocompatible Ti-based alloys and biodegradable Mg-based ones.

Optical and structural investigations of annealing impact on phase separation of Erbium-doped Al2O3 layers

We report on the effect of annealing treatment on the structural and optical properties of Er-doped Al2O3 thin films elaborated by atomic layer deposition. The properties of the films were studied using ellipsometry and Fourier-transform infrared (FTIR) spectroscopies, cathodoluminescence (CL) versus annealing temperature varied in the 650-1100 °C range. Spatial location and diffusion of chemical species were investigated at the atomic scale by atom probe tomography (APT). The CL measurements evidence Er3+ light emission over the visible-infrared spectral range. The CL spectra evolution showed non-monotonic variation with annealing temperature and a CL quenching occurring at 1000 °C. The CL signal evolution as a function of the annealing treatment is discussed regarding to the evolution of structural properties.

Synchrotron Radiation μ-XRF Imaging Reveals Mn Zoning in Freshwater Pearls

Chemical zoning is commonly seen in inorganic minerals, and it holds implications for magmatic processes, hydrothermal evolution, or metal mineralization. However, few studies are available on oscillatory zoning in biominerals, which carries the most direct and unique information on the biomineralization mechanism. This study investigates spatial and temporal resolution of trace element distributions in pearls that were cultivated in the Hyriopsis cumingii mantle (non-nucleated pearls and nucleated Akoya pearls) or visceral mass (nucleated Edison pearls) for 1–5 years. Using synchrotron radiation micro-X-ray fluorescence imaging, we find a variety of trace elements such as Sc, Cr, Mn, Cu, Zn, Ge, and Ba. The types of trace elements are slightly different for individuals. For the first time, submillimeter-scale Mn zoning is identified ubiquitously, concentric with the pearl, and exhibits increased concentrations toward the pearl margin. In non-nucleated pearls and nucleated Akoya pearls, the Mn zones are superposed with a spatially damped pattern with a decrease in the interzones. In contrast, no damped trends are observed in the Mn zones in nucleated Edison pearls. This difference may be due to different cultivation sites within mollusks that have different requirements for Mn during pearl growth. We suggest a growth model of dissipative structure for the Mn zoning in pearls, which depends upon the coupling between the interface kinetics and the diffusion of chemical species in the environment. The trace elements (including Mn) substitute Ca in aragonite isomorphically, based on Raman imaging. The scanning electron microscopy images show a periodic structure of aragonite platelets and organic matter of pearls. Locally in the Mn zones, there are minor defects on platelets, which may arise from the enrichment of trace elements. This study would develop a new research field for chemical zoning in minerals and introduce a new angle in understanding trace element incorporation in biominerals and the biomineralization processes.

Outcrop scale mixing enhanced by permeability variations: the role of stationary and travelling waves of high saturation indices

AbstractTo study the ore mineralization at the outcrop scale we merge an advection–diffusion simulation with the geochemical software iphreeqc to model the mixing of two realistic fluids. We simulate the infiltration of a metal-rich fluid into a rock that is saturated with pore fluid. We test the feedback effects with a number of scenarios based on an outcrop-scale 5 × 5 m model consisting of two high-permeable vertical faults within a low-permeable host rock that lead into a permeable layer. The hot metal-rich fluid enters the model through the faults from below. We solve the advection–diffusion equation for 12 chemical species and temperature, and use iphreeqc to determine the resulting properties of local fluid domains as well as related saturation indices for minerals. The faults in the model act as pathways for the metal-rich fluid, with the infiltrating fluid displacing the pore fluid. Mixing in the model takes place as a function of advection along permeable faults coupled with diffusion of chemical species at the interface between two fluids, while heat diffusion is fast enough (103 times faster) to equilibrate temperature. Simulations show a high saturation index of mixing-derived minerals such as barite at the interface between the two fluids as a result of fluid mixing. Fast fluid pathways (i.e. faults) show travelling waves of high saturation indices of barite, while low-permeability zones such as fault walls and areas below less permeable layers experience stationary waves of high saturation indices. Our results show that, depending on the dominant transport process (advection or diffusion), mineralization will localize next to permeability contrasts in zones where local diffusion dominates.

Chemo-mechanical model for degradation of oil paintings by amorphous and crystalline metal soaps

Metal soap formation is recognised as a critical degradation mechanism in historical oil paintings, which threatens the preservation of museum collections worldwide. Metal soaps form via a complex sequence of chemical reactions between metal ions released by the pigments and saturated fatty acids originating from the drying oil. The latest advances in chemistry research suggest that metal ions and saturated fatty acids may initially react by means of a reversible reaction, which leads to the formation of metal soaps in an amorphous state. Metal soaps may subsequently crystallise via an irreversible reaction into large aggregates that deform the paint layers, potentially triggering delamination, cracking, and ultimately flaking of the paint. This paper proposes a chemo-mechanical model to predict metal soap formation and the consequent mechanical damage in historical oil paintings. The chemical process is described in terms of a set of diffusion–reaction equations, which account for both the reversible reaction between free saturated fatty acids and metal ions forming amorphous metal soap, and the subsequent irreversible reaction to crystalline metal soap. The chemical model is two-way coupled with a mechanical model that effectively describes the cracking processes caused by metal soap formation and growth. The coupling is generated from the mechanical model by accounting for the development of a chemically-induced growth strain in the crystalline metal soap. In addition, the presence of cracks locally hampers the diffusion of chemical species, which is taken into account in the chemical model through a dependency of the diffusion parameter at the crack faces on the amount of mechanical damage generated. The spatial development of the crystalline metal soap phase is simulated by using a tailor-made scanning algorithm that identifies the reaction zone in which metal soap formation takes place. The proposed model is calibrated on experimental data presented in the literature. The model is subsequently applied to analyse two numerical examples that are representative of typical metal soap-related degradation processes observed in historical oil paintings, revealing that the growth process of crystalline metal soap, the deformation of the paint surface, and the consequent cracking and delamination patterns are predicted in a realistic fashion.

Significance of nanoparticles aggregation and Coriolis force on the dynamics of Prandtl nanofluid: The case of rotating flow

A comparative study is provided by this article with rotational Prandtl host fluid flux of aggregated nano particles and non aggregated nano particles on linear stretching surface. Along with the chemical species diffusion, Arrhenius activation energy is examined. The nano particles thats are playing vital role in modern technology like heat exchange, electronics and material sciences are incorporated because of enhancing heat transmission. The current analysis has significant applications in rolling and manufacturing of polymer sheet, lubrication processes, crystal growing, polymer industry, biomedical and polymer industry. By applying similarity transformation to mathematical formulation based upon conservation laws yielded a related set of differential equations. For obtaining the numerical solution of non linear problem, Runge Kutta technique is employed and listed in platform of MATLAB. The goal of this study is to illustrate the comprehensive analysis of repercussions of parameters on heat, velocity and nanoparticles concentration via graphical and numerical outcomes is computed. Both velocities (f1′ and f2) reduced against amplified value of β, λ and Fr but, have increasing behavior for α1 and α2. Heat distribution is rise with growing values of Fr and λ but, reduce in case of α1 (Prandtl fluid parameter) and α2 (elastic parameter) and concentration of nano particles is higher for λ and E but, lessen for δ. It is observed that the increment and decrement in values of f1′, f2, θ, ϕ by impact of variation in values of parameters is slightly fast in non aggregated phase as compared to aggregated phase. On linearly extending surface, Nu and friction factor variational patterns are numerically calculated.

Consistent lattice Boltzmann model for reactive mixtures

A new lattice Boltzmann model (LBM) for chemically reactive mixtures is presented. The approach capitalizes on the recently introduced thermodynamically consistent LBM for multicomponent mixtures of ideal gases. Similar to the non-reactive case, the present LBM features Stefan–Maxwell diffusion of chemical species and a fully on-lattice mean-field realization of the momentum and energy of the flow. Besides introducing the reaction mechanism into the kinetic equations for the species, the proposed LBM also features a new realization of the compressible flow by using a concept of extended equilibrium on a standard lattice in three dimensions. The full thermodynamic consistency of the original non-reactive multicomponent LBM enables us to extend the temperature dynamics to the reactive mixtures by merely including the enthalpy of formation in addition to the sensible energy considered previously. Furthermore, we describe in detail the boundary conditions to be used for reactive flows of practical interest. The model is validated against a direct numerical simulation of various burning regimes of a hydrogen/air mixture in a microchannel, in two and three dimensions. Excellent comparison in these demanding benchmarks indicates that the proposed LBM can be a valuable and universal model for complex reactive flows.

Significance of hybrid nanoparticles, Lorentz and Coriolis forces on the dynamics of water based flow

This article addresses a comparative study with MHD effect on the rotational flux of hybrid nano liquid (Al2O3 -Cu/ water) and nano liquid (Al2O3/ water) over the linearly extending surface. Arrhenius activation energy is analyzed along with the chemical species diffusion. The three-dimensional leading equations (PDEs) for momentum, mass, concentration, and temperature are converted into ODEs by employing appropriate similarity conversion. Runge Kutta scheme is implemented and listed in MATLAB to acquire the non-linear differentiated problem's solution numerically. This study aims to explain the detailed examination of repercussions of parameters on velocity, concentration of nano particles and heat via graphical and numerical results. Both velocities (primary and secondary) decreased against the growing rotation value, but temperature distribution and concentration of nano particles are higher for hybrid-phase (Al2O3 - Cu/ water). It is determined that rising inputs of parameters like rotation, porosity factor, activation energy, magnetic effect and Forchheimer number made crucial enhancement in temperature. At linear extending surface, the variational patterns of Nusselt number and skin friction are conducted numerically. Al2O3 - Cu nano particles proved to be a better heat transformer as compared to Al2O3 nano particle.

Homogeneous and heterogeneous reactions in the mixed convection flow of hybrid nanofluid over a slender cylinder

AbstractThis article is about the study of homogeneous and heterogeneous reactions in the mixed convection flow of hybrid nanofluid over a moving vertical slender cylinder. It is based on the considerations of unequal diffusivity of chemical species and the numerical solutions from the nonsimilar approach. This study has found applications in many chemically reacting processes, including the processes in the biochemical systems, combustion, and catalysis. Numerically approximate solutions to a set of equations, which govern the flow, temperature, and concentrations of the chemical species with prescribed boundary constraints, are obtained by utilizing the implicit finite‐difference scheme aided by the quasi‐linearization technique. The impacts of several relevant parameters on various profiles and gradients are discussed with the aid of graphs and tables. From the results, the skin friction coefficient and rate of heat transport are pronounced to be more for hybrid nanofluid than nanofluid. The strength of homogeneous reaction on species concentration is found to be fewer than the heterogeneous reaction. The streamwise coordinate (nonsimilar variable) is more favorable to the concentration of autocatalyst than to the reactant concentration.

Instabilities during convection–diffusion of binary mixtures in a non-isothermal flow: A linear stability analysis

This paper reports a fully developed thermo–solutal mixed convection flow of the binary mixture of some important chemical species and its linear stability characteristics in a vertical channel. The flow is jointly driven by an external pressure gradient as well as simultaneous buoyancy effects of thermal and chemical species diffusion. A spectral collocation method is adopted to solve the governing equations numerically. The numerical calculation is performed for a wide range of the governing flow parameters. The main emphasis is given to examine the effect of the buoyancy ratio, which is defined as N, on basic flow characteristics and the instability mechanism for chemical species diffusion of interest in the air (Pr = 0.7) over a Schmidt number (Sc) range 0.2–2.01. A comprehensive investigation shows that when N≥−1, the heat and mass transfer rates increase monotonically on increasing the thermal buoyant force, whereas for N<−1 they are in a sinusoidal form. The velocity profiles contain the point of inflection for N>−1; however, both the point of inflection and flow separation are present when N<−1. The stability of the flow decreases on increasing the value of Sc, when the buoyant force from species diffusion acts in the same direction as the thermal buoyant force. The flow is also unstable under mild heating conditions for a relatively large magnitude of N. The disturbance kinetic energy analysis at the linear stability critical point shows that more contribution of the shear term in the production of disturbance kinetic energy effectively stabilizes the flow.

Study of cracking susceptibility in similar and dissimilar welds between carbon steel and austenitic stainless steel through finger test and FE numerical model

Hot cracking susceptibility and the formation of brittle martensite phase are the main factors that limit the weldability of a dissimilar joint between carbon steel (CS) and austenitic stainless steel (SS). In this study, the self-constraint finger test was used to correlate the welding thermo-mechanical field with the crack susceptibility of a dissimilar weld between the CS ASTM A36 and SS AISI 304L. The finger test allowed to intercalate fingers (portions) of tested materials in the weld samples to produce dissimilar welds. The heat dissipation and the distortion behavior were related to the crack susceptibility, critical weld regions extension, and chemical species diffusion. Four samples were welded (two similar welds and two dissimilar welds) using the filler metals ER70S-6 and EC410NiMo. Welds were analyzed through light optical microscopy (LOM) and scanning electron microscopy (SEM) to characterize phases, detect cracks, microstructural changes, and element diffusion. A finite element (FE) numerical model was applied to simulate the welding thermo-mechanical field. FE estimations of distortion and residual stress helped to predict induced crack propagation (the initial gap between fingers) towards the fusion zone. Additionally, electrochemical tests were carried out to assess the corrosion susceptibility of the dissimilar welds. The observed cracks were produced due to different factors such as residual stress distribution, the formation of brittle and untempered martensitic phase in the fusion zone (FZ), and hot cracking associated with the weld sample distortion behavior. According to the FE estimations, the high thermal expansion of the SS was responsible for the bending curvature change in welds 2 and 4, which produced a gap between fingers and increased the crack extension in the FZ of weld 4. The dilution contributed to the formation of δ-ferrite in the FZ, which limited the growth of cold and hot cracks. The decarburization and sensitization were not observed in dissimilar welds due to the low element diffusion.

Sr and Co Vapor-Phase Transport from LSCF Cathodes

A series of tests were performed to differentiate between surface diffusion and vapor-phase diffusion of chemical species from LSCF cathode material at typical sintering temperatures (up to 1100°C) in SOFC production. A GDC source substrate was printed with LSCF and separated by an air gap from a YSZ target substrate. Various geometries with long surface paths were employed to reduce the possibility of surface transport. Sr and Co were detected on the target substrates via energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), including spatially resolved XPS. These results support a vapor-phase transport mechanism for Sr and Co. Sintering conditions and barrier layer requirements may need to be revisited to prevent the formation of undesired strontium zirconate at cathode/electrolyte interface due to vapor-phase transport.

The influence of turbulent transport in reactive processes: A combined numerical and experimental investigation in a Taylor-Couette reactor

Turbulent reactive flows are ubiquitous in industrial processes. Decoupling transport effects from intrinsic chemical reactions requires an in-depth understanding of fluid flow physics; computational fluid dynamics (CFD) methods have been widely used for this purpose. Most CFD simulations of reactive liquid-phase flows, where the Schmidt numbers are large, rely on isotropic eddy viscosity models. However, the assumption of turbulent isotropy in most stirred reactors and wall-bounded flows is fundamentally incorrect and leads to erroneous results. Here, we apply a systematic CFD approach to simulate liquid-phase diffusive and convective transport phenomena that occur in a Taylor-Couette (TC) reactor. We resolve the turbulent flow by extracting statistics from large eddy simulation which is used to tune the anisotropic Reynolds stress model. In addition, we conducted a series of turbulent precipitation and mixing studies in a TC reactor that was designed and fabricated in-house. The numerical model is successfully validated against a published torque correlation and it is found to accurately describe the advection and diffusion of chemical species. The validated model is then used to demonstrate key flow properties in the reactor. We define new local turbulent Peclét numbers to characterize the relative increase in diffusivity from turbulent advection and observe a 29% increase in the turbulent contribution as Reynolds number is doubled. Both reactive simulations and experiments show an increase in overall reaction rates with increased turbulence. The results from reactive simulations provide a deeper understanding of flow-kinetics interactions at turbulent conditions.

Theoretical evaluation of enhanced gold nanoparticle delivery to PC3 tumors due to increased hydraulic conductivity or recovered lymphatic function after mild whole body hyperthermia.

The objective of this study is to investigate the effect of hyperthermia-induced improvement of hydraulic conductivity and lymphatic function on both tumoral IFP reduction and nanoparticle delivery to PC3 tumors. We developed a theoretical model for nanoparticle transport in a tumor incorporating Starling's law, Darcy's law, transient convection, and diffusion of chemical species in porous media, and nanoparticle accumulation in tumors. Results have shown that both mechanisms were effective to decrease the IFP at the tumor center from 1600 Pa in the control without heating to 800 Pa in tumors with whole body heating. IFP reductions not only elevate the nanoparticle concentration in the tumor, but also result in a more uniform nanoparticle concentration in the tumor than that in the control without heating. Due to the IFP reductions at the tumor center and/or local blood perfusion increases, the final amount of accumulated nanoparticles in the tumor increased by more than 35-95% when compared to the control without heating. We conclude that increases in the hydraulic conductivity and recovery of lymphatic functions are possible mechanisms that lead to IFP reductions and enhancement in nanoparticle deposition in PC3 tumors observed in our in vivo experimental studies.