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The drying of human whole blood pools has been studied experimentally to improve the understanding of drops and pools of human whole blood. Here blood is assimilated to a complex fluid made of several bio-colloids. The blood pools were created inside a glove box under controlled conditions. We performed experiments at temperatures of 21 °C, 29 °C, and 37 °C, and relative humidity ranging from 20 % to 70 %. The air inside the glove box was still, and the evaporation process was mainly purely diffusive. A human blood diffusion coefficient of (1.08 ± 0.02) × 10 −9 m 2 /s was obtained. This value is in agreement with literature values for polymers and colloidal films. Moreover, we elaborated an updated model using Page's model to describe the drying kinetics of human blood pools. The effect of the surface area of pools was considered using a diffusive characteristics time. These findings are of interest for biomedical and forensic applications.

Maximizing the fixing ability of polyselenides to reduce the shuttle effect in Li-Se batteries remains highly challenging. Single crystal metal-organic framework (MOF)-derived N-doped ordered hierarchically porous carbon (S-NOHPC) synthesized by a confined crystal growth and template-assisted method demonstrates excellent electrochemical performance as a host material for Li-Se battery. The large number of micropores inherited from the MOF structure provides large space and surface for Se loading and reaction sites, ensuring the high energy density of the battery. The in-situ X-ray diffraction (XRD) technique is used to understand the reaction mechanism. The synergy of the interconnected three-scale-level micro-meso-macroporous structure and N-doped polar sites can buffer the volume expansion, shorten the ion transportation with a very high diffusion coefficient of 4.44 × 10 −10 cm 2 s −1 and accelerate the lithiation/delithiation reaction. Selenium is sufficiently reactive and the polyselenide intermediates are tightly fixed inside the carbon host material, thereby achieving excellent specific capacity, stability, and rate capability. Such a cathode exhibits a very high 2 nd discharge/charge capacity of 658 and 683 mA h g −1, respectively, and retains a very high capacity of 367 mA h g −1 after 200 cycles at the current of 0.2 C. Even at the high current of 5 C, a very high discharge capacity of 230 mA h g −1 is obtained. This work provides a new kind of high-performance porous materials with rational pore arrangement applicable for highly efficient energy storage. [Figure not available: see fulltext.]

International audience; Yttrium mono- and di-silicates are excellent candidate materials for Environmental Barrier Coatings (EBC), to protect Ceramic-Matrix Composites (CMC). A large distribution of microstructures can be generated by varying the duration of sintering, the particle size distribution of the precursor and/or the deposition method. In the present work, investigations of the corrosion resistance of yttrium silicate coatings with various microstructures in the high temperature range, under different oxidizing environments are reported. An original experimental methodology has allowed quantifying the influence of the microstructure (especially grain size and grain boundary surface area) on properties such as ionic conductivity, resistance to oxygen diffusion, volatilization rate and surface recession, and showing that they directly affect their protection efficiency against oxidation. Based on these results, guidelines for the design of an optimized yttrium silicate EBC featuring microstructural and compositional variations are proposed.

Agricultural soils are a major source of the potent greenhouse gas and ozone depleting substance, N2O. To implement management practices that minimise microbial N2O production and maximise its consumption (i.e. complete denitrification) we must understand the interplay between simultaneously occurring biological and physical processes, especially how this changes with soil depth. Meaningfully disentangling these processes is challenging and typical N2O flux measurement techniques provide little insight into subsurface mechanisms. Additionally, denitrification studies are often conducted on sieved soil in altered O2 environments which relate poorly to in situ field conditions. Here, we use a novel dual headspace system with field-relevant O2 concentrations to incubate intact sandy clay loam textured agricultural topsoil (0-10 cm) and subsoil (50-60 cm) cores for 3-4 d at 50 and 70% water filled pore space (WFPS), respectively. 15N-N2O pool dilution and an SF6 tracer were used to determine the relative diffusivity (Ds/D0) and the net N2O emission and gross N2O emission and consumption rates. The relationship between calculated fluxes from the below- and above- soil core headspaces confirmed that the system performed well. We found no difference in Ds/D0 between soil depth fractions, which was probably because of the preservation of preferential flow pathways in intact cores. Both gross N2O emissions and uptake were not different with depth but were higher in the 50% WFPS, contrary to expectation. We attribute this to aerobic denitrification and simultaneously occurring denitrification and nitrification for the gross consumption and emission of N2O, respectively. Here, we developed a novel system that allows careful control of conditions and, with a headspace below and above a soil core, a more realistic reconstruction of in situ gas dynamics. We provide further evidence of substantial N2O consumption in drier soil and without net negative N2O emissions. The results from this study are important for the future application of the 15N-N2O pool dilution method and N budgeting and modelling, as required for improving management to minimise N2O losses.

Made available in DSpace on 2022-04-29T08:38:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Hydrogen embrittlement can occur when atomic hydrogen is absorbed by steel during the acid cleaning process. In the literature, studies of corrosion inhibition by organic compounds in acid solutions have not given attention to the inhibition of hydrogen permeation in the steel. In this work, we show that the best corrosion inhibition does not always indicate the best hydrogen permeation inhibition. For the first time, imidazole-based compounds were studied as hydrogen permeation inhibitors during carbon steel pickling in hydrochloric acid at high concentration (5.4 mol L−1). The immersion of steel in solutions containing 250 mg L−1 of the inhibitors 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) resulted in low corrosion inhibition efficiency of approximately 18% in both cases. On the other hand, the hydrogen permeation inhibition efficiency was 59%. The addition of 2-(nitromethylene) imidazolidine (IMD) and 2-(nitromethylene) oxazolidine (OXA) to HCl solutions provided corrosion inhibition efficiencies of 46.7% and 24.4%, respectively. However, these compounds did not present hydrogen permeation inhibition effects. Programa de Pós-Graduação em Engenharia Metalúrgica (PPGEM) Universidade Federal Fluminense, Volta Redonda Instituto de Ciências Exatas Universidade Federal Fluminense, Volta Redonda Programa de Pós-Graduação em Engenharia Mecânica Universidade Estadual Paulista, Guaratinguetá Companhia Siderúrgica Nacional (CSN), 27260-390, Volta Redonda Departamento de Ciências Exatas Escola de Engenharia Industrial e Metalurgia de Volta Redonda, Volta Redonda Programa de Pós-Graduação em Engenharia Mecânica Universidade Estadual Paulista, Guaratinguetá FAPERJ: -26/010.101125/2018 FAPERJ: E-26/010.002199/2019 FAPERJ: E-26/010.100639/2018

В соответствии с последними научными теориями процесс кристаллизации рассматривается как диффузионный процесс, т. е. в растворе перераспределение молекул сахарозы за счёт возникновения градиента концентраций между объёмами раствора с более высокой и более низкой концентрациями. В сахарсодержащем растворе вакуум-аппарата вследствие развития в нём процесса кристаллообразования отмечается повышение температуры раствора из-за фазового перехода жидкости в твёрдое, а также вследствие обеднения раствора сахарозой повышается и концентрация сухого вещества в нём. Оба этих фактора развиваются одновременно и существенно влияют на величину коэффициента диффузии. В работе на базе количественного анализа диффузионной модели процесса кристаллообразования приводится количественный анализ зависимости от результирующего воздействия на протекание этого процесса – температуры раствора и содержания в нём сухих веществ – при кристаллизации сахарозы в вакуум-аппарате, не освещённого ранее вопроса в технологии получения кристаллического белого сахара., In accordance with the latest scientific theories, the crystallization process is considered as a diffusion process, i. e., the redistribution of sucrose molecules in solution due to the occurrence of a concentration gradient between the volumes of the solution with higher and lower concentrations. In the sugar-containing solution of the vacuum apparatus, due to the development of the crystallization process in it, there is an increase in the temperature of the solution due to the phase transition of the liquid to the solid, as well as due to the depletion of the solution by sucrose, the concentration of dry matter in the solution also increases. Both of these factors develop simultaneously and significantly affect the value of the diffusion coefficient. In the work, the authors, based on the quantitative analysis of the diffusion model of the crystal formation process, provide a quantitative analysis of the dependence on the resulting effect on the course of this process – the temperature of the solution and the content of dry substances in it – during the crystallization of sucrose in a vacuum apparatus, an issue not previously covered in the technology of obtaining crystalline white sugar.

В настоящее время в сахарной промышленности при анализе кристаллизационных процессов обычно исходят из условий постоянства коэффициента диффузии в растворе и изотермического характера процесса. В то же время экспериментальные работы показывают наличие быстрого снижения коэффициента диффузии вместе с убыванием значения концентрации раствора при обессахаривании межкристального раствора в процессе кристаллизации сахарозы. Данный факт снижает достоверность теоретических результатов расчёта эффективности процесса кристаллизации, если в них не учитывается условие изменения коэффициента диффузии. В работе предлагается новая схема расчёта размера кристаллов и массы получаемого продукта в зависимости от времени кристаллизации с учётом динамики изменения коэффициента диффузии по содержанию сухого вещества в межкристальном растворе в течение всего процесса кристаллизации. Теоретический эксперимент, представленный в работе, подтверждён экспериментальными данными, отражающими особенности кристаллообразования сахарозы в вакуум-аппарате. В данной работе с учётом фактора зависимости характеризующего интенсивность молекулярного массопереноса коэффициента диффузии обоснована постановка задачи, аналитическая формализация и численный расчёт, проверка адекватности полученных теоретических результатов опытным наблюдениям и физическому смыслу предмета исследования, применение полученных расчётных зависимостей для оценки эффективности работы вакуум-аппарата., Currently, in the sugar industry, when analyzing crystallization processes, they usually proceed from the conditions of constancy of the diffusion coefficient in solution and the isothermal nature of the process. At the same time, experimental work shows the presence of a rapid decrease in the diffusion coefficient along with a decrease in the concentration of the solution during desaccharification of the intercrystal solution during the crystallization of sucrose. This fact reduces the reliability of the theoretical results of calculating the efficiency of the crystallization process, if they do not take into account the condition for changing the diffusion coefficient. In this paper, the authors propose a new scheme for calculating the size of crystals and the mass of the resulting product depending on the crystallization time, taking into account the dynamics of the diffusion coefficient change in the dry matter content in the intercrystal solution during the entire crystallization process. The theoretical experiment presented in the paper is confirmed by experimental data reflecting the features of sucrose crystal formation in a vacuum apparatus. In this paper, taking into account the dependence factor characterizing the intensity of molecular mass transfer of the diffusion coefficient, the formulation of the problem, analytical formalization and numerical calculation, verification of the adequacy of the obtained theoretical results to experimental observations and the physical meaning of the subject of the study, the use of the obtained calculated dependencies to evaluate the efficiency of the vacuum apparatus are justified.

Original chemical composition datafor diffusion profiles in garnets measured by EPMA.

International audience; Aggregation mechanisms of amyloid β peptides depend on multiple intrinsic and extrinsic physicochemical factors (e.g., peptide chain length, truncation, peptide concentration, pH, ionic strength, temperature, metal concentration, etc.). Due to this high number of parameters, the formation of oligomers and their propensity to aggregate make the elucidation of this physiopathological mechanism a challenging task. From the analytical point of view, up to our knowledge, few techniques are able to quantify, in real time, the proportion and the size of the different soluble species during the aggregation process. This work aims at demonstrating the efficacy of the modern Taylor dispersion analysis (TDA) performed in capillaries (50 μm i.d.) to unravel the speciation of β-amyloid peptides in low-volume peptide samples (∼100 μL) with an analysis time of ∼3 min per run. TDA was applied to study the aggregation process of Aβ(1-40) and Aβ(1-42) peptides at physiological pH and temperature, where more than 140 data points were generated with a total volume of ∼1 μL over the whole aggregation study (about 0.5 μg of peptides). TDA was able to give a complete and quantitative picture of the Aβ speciation during the aggregation process, including the sizing of the oligomers and protofibrils, the consumption of the monomer, and the quantification of different early- and late-formed aggregated species.

The new chalcone, 1-(PYRIDIN-2-YL)-3-(THIOPHEN-2-YL)PROPENONE, has been synthesized and its crystal and molecular structure determined. An electrochemical characterization of the molecule disclosed some reversible and irreversible processes in its cathodic/anodic reactions. A density functional study was carried out in order to calculate the frontier molecular orbitals and the diffusion coefficient, which showed very good agreement with the experimental data.

Measurements of the carbon dioxide (CO2) diffusion in graphene oxide (GO) and reduced graphene oxide (rGO) vs. temperature have been performed using uniform GO thin foils with15 mu m thickness. Regarding rGO, its foils have been obtained by submitting GO at a temperature of 130 degrees C in vacuum for 30 min. The CO2 diffusion has been controlled by the gas pressure gradient applied to two faces of the thin foils versus the time and the temperature. The calculated CO2 coefficient diffusions have been compared with those relative to the nitrogen (N-2) and argon (Ar) gases obtained in previous measurements. The deduced diffusion coefficients are different for the three investigated gases, but remain of the order of 10(-3) cm(2)/s. At room temperature in GO the minimum value is obtained for nitrogen, while the highest one for Ar. Indeed, at 100 degrees C in rGO the minimum value is deduced for nitrogen and the maximum one for the carbon dioxide. The different diffusion coefficients can be attributed not only to the different size, shape and atomic mass of the investigated gases, but also to the inner lattice structure of the GO and rGO foils. GO contains water and oxygen functional groups which obstacle the diffusion process. rGO is poorer of oxygen functional groups and of water, partially enhancing the diffusion, but it has a high compactness and density which may reduce the total diffusivity. The obtained results, their correlation with the inner structure of the graphene sheets and the comparison between measurements and the literature data are presented and discussed.

Измеренные скорости уплотнения порошка кальцита под действием одноосной нагрузки в присутствии насыщенного раствора CaCO, содержащего катионы магния или гумат-анионы, сопоставлены с расчетами скорости деформации, проведенными с учетом растворимости, кинетики растворения и скорости массопереноса вещества матрицы в поровой жидкости. Адекватность предложенной схемы расчета подтверждается незначительным различием экспериментальных и вычисленных значений (в пределах 20 %). Показано, что скорость деформации кальцита в растворах, содержащих ионы магния, лимитируется скоростью растворения материала из-за доломитизации поверхности. Замедление скорости уплотнения в присутствии гумат-анионов также происходит из-за частичного блокирования поверхности в результате адсорбции гумата. The rates of calcite powder compaction under uniaxial stress in CaCO saturated aqueous solutions containing magnesium cations or humate anions have been compared with computed rate estimations. The interplay of calcite solubility, dissolution kinetics, and mass transfer rate of solid matter through the liquid bulk controls the overall process kinetics. A not significant difference between the experimental and calculated datasets (within 20%) confirms the adequacy of the model proposed. The calcite creep rate in magnesium-containing media is limited by the material dissolution stage as a result of the surface dolomitization. The creep hindering by humate anions is likely to be due to the partial surface coverage with adsorbed matter.

As is known, boriding is carried out to increase the wear resistance and corrosion resistance of iron-carbon alloys. Along with high hardness, borides, unfortunately, have very high fragility and high refractoriness. An effective way to counter the fragility of boride layers is to form a composite structure consisting of inclusions of solid borides in a more plastic matrix. Such coatings can be obtained by volumetric heating in a muffle furnace using a boron paste that besides a mixture of iron and boron powders contained ammonium hydroxide and activated carbon with or without liquid glass. Boriding of a surface is carried out at high temperatures =1000 °С for 5 minutes. It is experimentally found that the microhardness of the surface layer increased by about 30% compared with the microhardness of the substrate, and that the thickness of the boride layer depends on the presence of liquid glass in the coating. It has been established that specially calculated proportions of ammonia, liquid glass, and charcoal contribute to the formation of an extensive diffusion zone of iron borides, the formation of which is due to the anomalously high diffusion mass transfer of boron into the matrix., Как известно, борирование проводят с целью повышения износостойкости, коррозионной стойкости железоуглеродистых сплавов. Наряду с высокой твердостью бориды, к сожалению, обладают очень большой хрупкостью и высокой тугоплавкостью. Эффективным способом борьбы с хрупкостью боридных слоев является формирование композиционной структуры, состоящей из включений твердых боридов в более пластичной матрице. Такие покрытия можно получить методом объемного нагрева в муфельной печи с применением пасты для борирования, которая, помимо смеси порошков железа и бора, содержала: гидроксид аммония, активированный уголь с добавлением жидкого стекла или без него. Борирование поверхности осуществлялось при высоких температуре = 1000 °С в течение 5 минут. Экспериментальным путем выявлено, что микротвердость поверхностного слоя повысилась примерно на 30 % по сравнению с микротвердостью подложки, а толщина боридного слоя зависит от наличия в обмазке жидкого стекла. Установлено, что использование аммиака, жидкого стекла и древесного угля в специально рассчитанных пропорциях способствует формированию обширной диффузионной зоны боридов железа, формирование которой осуществляется за счет аномально высокого диффузионного массопереноса бора в матрицу.

The aim of this study was to determine the thickness of the hydrodynamic diffusion layer (h(HDL)) of three poor water-soluble compounds under laminar fluid flow using a single particle dissolution technique. The single particle dissolution experiments were performed in a flowing aqueous medium using four different fluid velocities (v), ranging from 46 to 103 mm/s. The particles used had an initial radius (r) of 18.8 to 52.3 mu m. The determined h(HDL) values were calculated from both dissolution experiments and computational fluid dynamics (CFD) simulation. In this study, single particle dissolution experiments gave, with one exception, h(HDL) values in the range of 2.09 to 8.85 mu m and corresponding simulations gave h(HDL) values in the range of 2.53 to 4.38 mu m. Hence, we found a semi-quantitative concordance between experimental and simulated determined h(HDL) values. Also, a theoretical relation between the dependence of hHDL on particle radius and flow velocity of the medium was established by a series of CFD simulations in a fluid velocity range of 10-100 mm/s and particle size (radius) range of 5-40 mu m. The outcome suggests a power law relation of the form h(HDL)alpha r(3/5)v(-2/5). In addition, the h(HDL) seems to be independent of the solubility, while it has a diffusion coefficient dependence. In conclusion, the hHDL values were determined under well-defined conditions; hence, this approach can be used to estimate the h(HDL) under different conditions to increase the understanding of the mass transfer mechanisms during the dissolution process.

Actin filament’s polyelectrolyte and hydrodynamic properties, their interactions with the biological environment, and external force fields play an essential role in their biological activities in eukaryotic cellular processes. In this article, we introduce a unique approach that combines dynamics and electrophoresis light scattering experiments, an extended semiflexible worm-like chain model, and an asymmetric polymer length distribution theory to characterize the polyelectrolyte and hydrodynamic properties of actin filaments in aqueous electrolyte solutions. A fitting approach was used to optimize the theories and filament models for hydrodynamic conditions. We used the same sample and experimental conditions and considered several g-actin and polymerization buffers to elucidate the impact of their chemical composition, reducing agents, pH values, and ionic strengths on the filament translational diffusion coefficient, electrophoretic mobility, structure factor, asymmetric length distribution, effective filament diameter, electric charge, zeta potential, and semiflexibility. Compared to those values obtained from molecular structure models, our results revealed a lower value of the effective G-actin charge and a more significant value of the effective filament diameter due to the formation of the double layer of the electrolyte surrounding the filaments. Contrary to the data usually reported from electron micrographs, the lower values of our results for the persistence length and average contour filament length agree with the significant difference in the association rates at the filament ends that shift to sub-micro lengths, the maximum of the length distribution.

This paper is concerned with the stability issue in determining absorption and diffusion coefficients in quantitative photoacoustic imaging. Assuming that the optical wave is generated by point sources in a region where the optical coefficients are known, we derive pointwise H{\"o}lder stability estimate of the inversion. This result shows that the reconstruction of the optical coefficients is stable in the region close to the optical illumination sources and deteriorate exponentially far away. Our stability estimate is therefore in accordance with known experimental observations. Mathematics subject classification : 35R30.

The interconnection of ionogenic channel structure, cation hydration, water and ionic translational mobility was revealed in Nafion and MSC membranes based on polyethylene and grafted sulfonated polystyrene. A local mobility of Li+, Na+ and Cs+ cations and water molecules was estimated via the 1H, 7Li, 23Na and 133Cs spin relaxation technique. The calculated cation and water molecule self-diffusion coefficients were compared with experimental values measured using pulsed field gradient NMR. It was shown that macroscopic mass transfer is controlled by molecule and ion motion near sulfonate groups. Lithium and sodium cations whose hydrated energy is higher than water hydrogen bond energy move together with water molecules. Cesium cations in possession of low hydrated energy are directly jumping between neighboring sulfonate groups. Cation Li+, Na+ and Cs+ hydration numbers (h) in membranes were calculated from 1H chemical shift water molecule temperature dependences. The values calculated from the Nernst–Einstein equation and the experimental conductivity values were close to each other in Nafion membranes. In MSC membranes, calculated conductivities were one order of magnitude more compared to the experimental ones, which is explained by the heterogeneity of the membrane pore and channel system.

A computational strategy based on molecular dynamics (MD) simulations is proposed for the 14 prediction of tracer diffusion coefficients of bioactive compounds in CO2 ( ) and CO 𝐷12 2 modified 15 with ethanol ( ), in both supercritical and subcritical regions. Three systems were used for its 𝐷m,i 16 validation, namely, β-carotene and ibuprofen in supercritical CO2, and gallic acid in CO2 modified 17 with 16 mol.% of ethanol. The MD diffusivities were assessed with experimental data, with 18 average absolute relative deviations (AARD) between 3.82 % and 7.36 %, and average relative 19 deviations (ARD) between -6.18 % and 5.75 %. The dependency of the diffusion coefficient on 20 temperature, pressure, and Stoke-Einstein coordinate ( ) was also evaluated. All data followed 𝑇 𝜇 21 the expected trends apart from gallic acid in CO2 modified with 16 mol.% of ethanol, for which 22 the computed showed a weak linear dependency with . 𝐷m,i 𝑇 𝜇 23 The validated MD strategy was then employed to calculate diffusivities of eucalyptol in 24 sub/supercritical CO2, and in sub/supercritical CO2 modified with 8 mol.% and 16 mol.% of 25 ethanol. The computational strategy was re-evaluated upon comparison with experimental 26 diffusivities of eucalyptol in sub/supercritical mixtures of CO2 with 8 mol.% ethanol. The 27 expected dependencies on pressure, temperature, and Stoke-Einstein coordinate were obeyed, and 28 it was also found that the diffusion coefficient decreased with increasing ethanol content. Four 29 phenomenological models from the literature were adopted to represent MD data, with AARD 30 values between 1.21 % and 4.40 %, suggesting they can be used for diffusivity estimations over 31 wider ranges of operating conditions. published

According to actual literature data, hyaluronic acid (HA) that is presented in the extracellular matrix can interact with proteins and thereby affect several important functions of the cell membrane. The purpose of this work was to reveal the features of the interaction of HA with proteins using the PFG NMR method by sampling two systems: aqueous solutions of HA with bovine serum albumin (BSA) and aqueous solutions of HA with hen egg-white lysozyme (HEWL). It was found that the presence of BSA in the HA aqueous solution initiates a certain additional mechanism; as a result, the population of HA molecules in the gel structure increases to almost 100%. At the same time, for an aqueous solution of HA/HEWL, even in the range of low (0.01–0.2%) HEWL contents, strong signs of degradation (depolymerization) of some HA macromolecules were observed such that they lost the ability to form a gel. Moreover, lysozyme molecules form a strong complex with degraded HA molecules and lose their enzymatic function. Thus, the presence of HA molecules in the intercellular matrix, as well as in the state associated with the surface of the cell membrane, can, in addition to the known ones, perform one more important function: the function of protecting the cell membrane from the destructive action of lysozymes. The obtained results are important for understanding the mechanism and features of the interaction of extracellular matrix glycosaminoglycan with cell membrane proteins.

Molecular dynamics simulations employing the all-atom optimized potential for liquid simulations (OPLS-AA) force field were performed for determining self-diffusion coefficients (D11) of ethanol and tracer diffusion coefficients (D12) of solutes in ethanol at several temperature and pressure conditions. For simulations employing the original OPLS-AA diameter of ethanol’s oxygen atom (σOH), calculated and experimental diffusivities of protic solutes differed by more than 25%. To correct this behavior, the σOH was reoptimized using the experimental D12 of quercetin and of gallic acid in liquid ethanol as benchmarks. A substantial improvement of the calculated diffusivities was found by changing σOH from its original value (0.312 nm) to 0.306 nm, with average absolute relative deviations (AARD) of 3.71% and 4.59% for quercetin and gallic acid, respectively. The new σOH value was further tested by computing D12 of ibuprofen and butan-1-ol in liquid ethanol with AARDs of 1.55% and 4.81%, respectively. A significant improvement was also obtained for the D11 of ethanol with AARD = 3.51%. It was also demonstrated that in the case of diffusion coefficients of non-polar solutes in ethanol, the original σOH=0.312 nm should be used for better agreement with experiment. If equilibrium properties such as enthalpy of vaporization and density are estimated, the original diameter should be once again adopted.

Cosmic-ray transport in astrophysical environments is often dominated by the diffusion of particles in a magnetic field composed of both a turbulent and a mean component. This process, which is two-fold turbulent mixing in that the particle motion is stochastic with respect to the field lines, needs to be understood in order to properly model cosmic-ray signatures. One of the most important aspects in the modeling of cosmic-ray diffusion is that fully resonant scattering, the most effective such process, is only possible if the wave spectrum covers the entire range of propagation angles. By taking the wave spectrum boundaries into account, we quantify cosmic-ray diffusion parallel and perpendicular to the guide field direction at turbulence levels above 5% of the total magnetic field. We apply our results of the parallel and perpendicular diffusion coefficient to the Milky Way. We show that simple purely diffusive transport is in conflict with observations of the inner Galaxy, but that just by taking a Galactic wind into account, data can be matched in the central 5 kpc zone. Further comparison shows that the outer Galaxy at $>5\,$kpc, on the other hand, should be dominated by perpendicular diffusion, likely changing to parallel diffusion at the outermost radii of the Milky Way., Published in Springer Nature Applied Sciences

The effect of the communication channel size on the transport and subsequent detection of chemical messengers is investigated on millimetric and micrometric channels. The transport of the information carriers, being characterized by an advective and a diffusive contribution, was simulated by varying the flow velocity and the diffusion coefficient. Then, to evaluate the information quality, the Intersymbol Interference (ISI) between two consecutive signals at a specific release delay was estimated. This allowed us to verify that operating under micrometric channel conditions has a larger flow velocity range to obtain completely separated successive signals and smaller release delays can be used between signals. The theoretical results were confirmed by developing a prototype molecular communication platform operating under microfluidic conditions, which enables communication through fluorescent nanoparticles, namely Carbon Quantum Dots (CQDs).

Non-Hermitian topological edge states have many intriguing properties, however, to date, they have mainly been discussed in terms of bulk–boundary correspondence. Here, we propose using a bulk property of diffusion coefficients for probing the topological states and exploring their dynamics. The diffusion coefficient was found to show unique features with the topological phase transitions driven by parity–time (PT)-symmetric non-Hermitian discrete-time quantum walks as well as by Hermitian ones, despite the fact that artificial boundaries are not constructed by an inhomogeneous quantum walk. For a Hermitian system, a turning point and abrupt change appears in the diffusion coefficient when the system is approaching the topological phase transition, while it remains stable in the trivial topological state. For a non-Hermitian system, except for the feature associated with the topological transition, the diffusion coefficient in the PT-symmetric-broken phase demonstrates an abrupt change with a peak structure. In addition, the Shannon entropy of the quantum walk is found to exhibit a direct correlation with the diffusion coefficient. The numerical results presented herein may open up a new avenue for studying the topological state in non-Hermitian quantum walk systems.

Agricultural soil emissions are a balance between sinks and sources of greenhouse gases (GHGs). The fluxes of GHGs from soils are complex and spatially and temporally heterogenous. While the soil surface is the exchange site with the atmosphere and is commonly where GHG fluxes are measured, it is important to consider processes occurring throughout the soil profile. To reduce emissions and improve agricultural sustainability we need to better understand the drivers and dynamics (production, consumption, diffusion) of these gases within the soil profile. Due to the heterogeneous nature of GHG processes at small to large scales, it is important to test how these processes differ with depth in different systems. In this study, we measured in situ CO2, N2O and CH4 concentration gradients as a function of soil depth over subsequent maize and wheat growing seasons with active gas samplers inserted into an arable field at 10, 20, 30 and 50 cm depths. We found N2O and CH4 concentrations increased with depth, but only CO2 concentrations differed with depth between growing seasons due likely to differences in soil diffusivity driven by soil conditions. Using the concentration gradient method (GM), the CO2 fluxes at each depth and their contribution to the surface flux were calculated and validated against a chamber method (CM) measured surface flux. We found the GM estimated surface CO2 flux was only 6 % different in the wheat, but 28 % lower than the surface measured flux in the maize growing season, due to drought conditions reducing the accuracy of the GM. Finally, we measured fluxes of CO2, N2O and CH4 in ambient and highly concentrated headspaces in laboratory mesocosms over a 72 h incubation period. We provide evidence of depth dependent CH4 oxidation and N2O consumption and possibly CO2 fixation. In conclusion, our study provides valuable information on the applicability of the GM and further evidence of the GHG production, consumption and diffusion mechanisms that occur deeper in the soil in a temperate arable context.

Concrete structures such as rigid pavements, tunnels, and runways at airports are usually subject to fatigue traffic loading during their service life. Research on the aftereffects of drying–wetting cycles coupled with alternating loads on concrete erosion in saline–alkali and coastal areas is of considerable practical importance. For this study, we utilized specimens of dimensions 100 mm × 100 mm × 400 mm with strength ratios of C30, C40, and C50. We incubated the concrete samples in a 24 h/24 h drying–wetting cycle with sodium sulfate solutions of different concentrations as we applied alternating loads. We conducted ultrasonic wave velocity tests every 30 days from the 60th day of the experiment to determine the change in the sound velocity of the concrete over the course of 360 days. In addition, we examined the invasion depth of SO42− with time. Based on the change in sound velocity, we developed the damage degree function, and we modified the diffusion coefficient of SO42− in concrete in accordance with the coupling of drying–wetting cycles and alternating loads. We conducted a simulation on SO42− penetration depth, and the results were in reasonable agreement with those obtained by experimental testing.

The metrological analysis of non-destructive methods determined the diffusion coefficient in block products formed from porous materials is considered. The methods are based on both various types of pulsed effects on the products flat surface and their reaction monitoring in terms of electromotive force changes of an electrochemical converter. The developed technique obviates long transducer calibration stage for each new porous material and diffusing polar solvent, increasing the analysis efficiency. The analyzed methods application areas are substantiated in the context of ensuring acceptable accuracy including in the presence of pronounced anisotropy of properties.

The possibility to assess diffusion coefficients of small molecules in packaging polymer films directly on the shelf, or even along the fabrication line, without the use laboratory equipment commonly employed for gravimetric methods would represent a paradigm changer in the evaluation of barrier properties and byproduct formation in goods packaging and device encapsulation. In this work, we demonstrate a simple, effective and versatile method for the determination of the molecular diffusion coefficients that exploits simple UV-Vis spectroscopy and is suitable for any polymer film. This simple method also allows the direct identification of the intercalating molecule without the need for chemical targeting or of complex laboratory equipment. For this purpose, we report on the assessment of diffusion coefficients of both polar and non-polar molecules including water, ammonia, methanol, ethanol, toluene, and even hexafluorobenzene into polyvinyl chloride wrap commercialized for food packaging.

Multi-structural polymer composites are widely used in the mechanical engineering, automotive, aviation and oil refining industries, as well as in the printing industry as a shock-absorbing deckle on the offset cylinders of printing machines. During offset printing, composites come into contact with inks and washing solutions, the components of which penetrate the material and cause the polymers to swell. This process degrades the print quality, and for this reason the study of its features is relevant. The prerequisites for this work are the study of the fundamental laws of diffusion and sorption of liquids by polymers with different micro- and macro-structures in different physical states and in different forms (e.g., films, sheets, fibers and fabrics). The combination of polymer materials in the composition of multi-structural fabric blankets makes it possible to obtain materials with unique mechanical properties and high resistance to liquid penetrating media and to use them in high-tech processes of multi-color printing with high resolution and color rendering. This article reports for the first time the kinetics and thermodynamics results obtained from the swelling of multi-structural polymeric blankets in solvents used in printing, and the effect of sorption of different polar liquids on the viscoelastic strain under compression during the operation of the damping systems of printing machines. Using mathematical models of activated liquid diffusion in polymers and deformation of a viscoelastic body, the swelling rate constants, solvent diffusion coefficients (the kinetic characteristics of the swelling process) and Flory–Huggins parameters (the thermodynamic characteristics of the interaction of the solvent with the composite) for composite–solvent systems with several chemical composition variants were determined. The elastic modulus and the viscosity coefficient of the composite under liquid saturation were calculated based on the experimental cyclic compression data. The range of change in the compression and restoration times of the polymeric blankets (0.09 s ÷ 0.78 s) was determined. It was shown that the composite swelled to a limited extent in all the studied liquids. All solvents used were thermodynamically poor (χ > 0.5). It has been established that rubber–fabric blankets coated with nitrile rubber are the least resistant to the action of dichloroethane, and that blankets with layers of polyolefins are not resistant to ethyl acetate. Water significantly affects the physicochemical properties of rubber–fabric blankets with a large proportion of cotton fabric layers. The data obtained can serve as a basis for optimizing the compositions of inks and cleaning solutions, as well as a theoretical basis for the thermodynamics of composite–solvent systems.

A present summary is assigned to present the transport characteristics of the free randomly moving (RM) electrons in silicon at any doping level by phosphorous donors. The application of the Fermi-Dirac statistics and stochastic description of the free RM electrons lead to obtaining the general expressions of conductivity, the effective density of the free RM electrons, their diffusion coefficient and the drift mobility, which are valid for silicon with any doping level. It is shown that drift mobility of the free RM electrons considerably exceeds the Hall mobility at heavy doping, and that the Einstein relation is fundamental and is conserved at any level of degeneracy. It is estimated what part of electrons in the conduction band of heavily doped silicon is not free and is coupled with phosphorous ions. The main conclusions and formulations can be applicable for holes in acceptor-doped silicon, and other homogeneous materials with one type of the free RM charge carriers as well.

The block ratio of SBS is an important factor influencing the swelling effect of modified asphalt, but the effect of the block ratio in the swelling process cannot be accurately studied by macro testing. In order to solve this problem and screen out the optimal SBS block ratio, molecular models of asphalt and SBS with different block ratios were established by molecular simulation technology at the microscopic level, and an asphalt–SBS interaction layer system was established on this basis. The diffusion and adhesion effects of SBS with different block ratios were evaluated by calculating the immersion depth, diffusion coefficient, and adhesion work of SBS in asphalt. The results show that SBS has a physical cross-linking reaction with asphalt during swelling, and SBS with a higher butadiene block ratio exhibits a deeper immersion depth; thus, SBS with a 3/7 block ratio has the best performance in the modification process, which is superior to SBS with other block ratios, in terms of both the diffusion and adhesion effect. The performance of asphalt modified by SBS with different block ratios was tested using penetration, softening point, and ductility, and the results were consistent with the simulation results, which proved the reliability of the microscopic conclusions from a macro perspective.

Hydrogen is a main factor in cold cracking or hydrogen-induced cracking. The most crack susceptible region of a steel welded joint is the heat affected zone (HAZ). The formulation and functional-analytical solution of the one-dimensional problem of hydrogen diffusion in an inhomogeneous butt-welded joint considering weld and joint dimensions and initial hydrogen distribution as well as hydrogen diffusion coefficients and solubilities are presented. It is shown that the peak hydrogen concentration in the HAZ of inhomogeneous joints varies in direct proportion to the initial hydrogen concentration in the weld metal. It is inversely proportional to the ratio of hydrogen solubilities in the weld metal and the HAZ metal and is nonlinear in the diffusion coefficient ratio of these metals. The peak hydrogen concentration in the HAZ can exceed 170% of the average initial concentration in the joint if martensitic steel is welded using low-carbon low-alloy welding consumables. The utilization of austenitic consumables leads to a dramatic reduction in the hydrogen concentration in the HAZ in comparison with the non-austenitic consumables. No direct relationship was found between the hydrogen concentration in the HAZ and the hydrogen evolution from the joint surface.

The diffusion bonding method is one of the most essential manufacturing technologies for Ti-steel composite plates. In this paper, the atomic diffusion behavior at the Fe-Ti interface during the bonding process of Ti-steel composite plates is studied using classical diffusion theory and molecular dynamics (MD) simulation. Henceforth, the diffusion mechanism of Fe and Ti atoms at the bonding interface is obtained at the atomic scale. The results show that Fe and Ti atoms diffused deeply into each other during the diffusion process. This behavior consequently increased the thickness of the diffusion layer. Moreover, the diffusion quantity of Fe atoms to the Ti side was much greater than that of Ti atoms to the Fe side. Large plastic deformation and shear strain occurred at the diffusion interface during diffusion. The crystal structure of the diffusion zone was damaged and defects were generated, which was beneficial to the diffusion behavior of the interface atoms. As the diffusion time and temperature increased, the shear strain of the atoms at the interface also increased. Furthermore, there is a relationship between the mutual diffusion coefficient and the temperature. Subsequently, after the diffusion temperature was raised, the mutual diffusion coefficient and atomic disorder (Fe atom and Ti atom) increased accordingly.

The migration of radionuclides from radioactive waste into the environment poses a public safety concern. Thus, the long-term safety assessment for near-surface disposal sites for radioactive waste in South Korea entails providing reasonable assurance that the annual radiation dose exposure from radionuclide release from the waste repository into the biosphere will not exceed the regulatory limit of 0.1 mSv/yr. At the first near-surface disposal site in Gyeongju, concrete was a crucial component of the engineered barriers designed to contain radionuclides within the disposal site. The ability of concrete to retain radioactive waste within the disposal site is attributed to its high sorption capacity for radionuclides. However, research has shown that the degradation of concrete can affect its radionuclide retention capabilities, which are defined by sorption properties of distribution (Kd) and diffusion (Ds) coefficient parameters. As a result, changes in sorption properties may lead to radionuclides migrating out of the disposal vault. In light of the geochemical deterioration of engineered concrete barriers, this study assesses the long-term safety of near-surface disposal sites. To simulate the impact of concrete degradation on radionuclide migration, we employed RESRAD-OFFSITE’s extended source-term features, which can model the release of radionuclides from radioactive waste shielded by concrete barriers. Using carefully screened published sorption data of four radionuclides (14C, 137Cs, 90Sr and 99Tc) in different stages of concrete degradation, the results indicated that released radioactivity during the most degraded state of concrete will result in a maximum radiation exposure dose of 1.4 × 10−8 mSv/yr from 99Tc which is below the permissible limit of 0.1 mSv per year, thus demonstrating that concrete is a reliable component of the engineered designed barriers for near-surface disposal facilities.

Nodal diffusion codes have been successfully used for decades as a primary tool of commercial power reactor design, safety calculations and plant cycle simulations. The large-size, small-leakage property of these reactor cores and the appropriately generated and applied auxiliary parameters (such as albedos, discontinuity factors etc.) provide a calculation environment, where diffusion theory is fairly accurate, giving the industry the ultimate advantage of fast neutronic computation. Recently, several efforts have been made to extend this methodology to small-core, high-leakage research reactors, in which the validity of diffusion theory is not straightforward. In this paper, the appropriate generation of the diffusion coefficients and their effect on the overall performance of the simulations are investigated in light of recent developments. For the numerical analysis, the two-dimensional DIMPLE benchmarks and the BME TR core benchmark problems were chosen. Group constants were generated with the Serpent 2 Monte Carlo code, while nodal diffusion calculations were carried out with the PARCS code. The results were assessed in terms of multiplication factor, assembly level power and two-group flux distributions. (c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

In this work, we present a model, based on rough hard-sphere theory, for the tracer diffusion coefficients of gaseous solutes in non-polar liquids. This work extends an earlier model developed specifically for carbon dioxide in hydrocarbon liquids and establishes a general correlation for gaseous solutes in non-polar liquids. The solutes considered were light hydrocarbons, carbon dioxide, nitrogen and argon, while the solvents were all hydrocarbon liquids. Application of the model requires knowledge of the temperature-dependent molar core volumes of the solute and solvent, which can be determined from pure-component viscosity data, and a temperature-independent roughness factor which can be determined from a single diffusion coefficient measurement in the system of interest. The new model was found to correlate the experimental data with an average absolute relative deviation of 2.7 %. The model also successfully represents computer-simulation data for tracer diffusion coefficients of hard-sphere mixtures and reduces to the expected form for self-diffusion when the solute and solvent become identical.

Orientador: João Frederico da Costa Azevedo Meyer Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica Resumo: O objetivo cumprido por esta tese é a criação e validação de uma técnica de recuperação de coeficientes de difusão para problemas ecológicos. O trabalho consta de oito capítulos e três deles são dedicados às ferramentas necessárias para a geração de dados sabidamente difusivos ou para o ajuste dos dados. Para a geração de dados trabalha-se com a obtenção da solução numérica de um problema difusivo tipicamente ecológico, combinando Elementos Finitos, Método de Galerkin e Crank-Nicolson. A seguir embasado-se no conceito de função densidade de probabilidade e em função de distribuição acumulada, lança-se mão do Método da Transformada Inversa. O Capítulo dedicado aos ajustes figura do trabalho para apresentar, ao leitor que ainda não havia tido contato, uma aplicação de um Algoritmo Genético. Tal algoritmo é usado para obter a solução de Quadrados Mínimos não-lineares em três parâmetros. A Regressão Linear tradicional, contando com apenas um parâmetro a ser ajustado também é utilizada. O principal conteúdo, o desenvolvimento do modelo e os resultados, excelentes, compõem mais dois Capítulos, o quinto e o sétimo, que, somados à Introdução, discussão sobre a bibliografia e Conclusão, fecham o trabalho. Discorre-se amplamente sobre o tipo de dado relativo a problemas ecológicos, e dificuldades inerentes, e sobre como o conhecimento sobre esse tipo de dados é fundamental no {\itshape design} do modelo. A cada passo dado, ferramenta desenvolvida ou introduzida, sua qualidade é atestada a fim de que, ao fim, a estrutura tenha sido construída sobre uma base sólida. O método recupera com sucesso coeficientes de difusão dentro de todo o espectro analisado, entre 0.0001 e 1 unidades de espaço ao quadrado por tempo; sendo possível tratar os dados de modo que a possibilidade de erro seja direcionada para uma hiper-estimativa, o que pode ser uma atitude previdente a depender do problema Abstract: The goal attained by this thesis is the creation and validation of a diffusion coefficient, relative to ecological problems, recovery technique. Eight Chapters constitutes this work and three of them are dedicated to the tools needed for the diffusive related data generation or to the data fit. For the data generation, the numerical solution of a tipically ecological diffusive problem is obtained by combining Finite Elements, Galerkin's Method and Crank-Nicolson. Then, relying on the concepts of probability density function and cumulative distribution function, the Inverse Transform Method is applied. There is a Chapter dedicated to the fitting methods used here to introduce, to a reader who have not had the pleasure of meeting before, an application of a Genetic Algorithm. Such algorithm is used to obtain a non-linear Least Squares three parameter solution. The traditional Linear Regression is also used for fitting another version of the model. The main content, the development of the model and the excellent results compose two more Chapters, the fifth and the seventh that, when gathered to the Introduction, discussion about the bibliography and the Conclusion, closes the work. The kind of data related to ecological problems and the difficulties inherent to it are a main concern and deeply discussed. It is also focus of intense attention how the knowledge on this kind of data is fundamental for the method design. At each step, tool developed or introduced, its quality is attested with the purpose that, by the end of the work, the structure has been built on a solid basis. The method recovers succesfully diffusion coeficients with all the range analyzed, 0.0001 and 1 units of squared space over time; and it is also possible to determine the treatment for the data in such a way that error are directed to a hiper-estimative; that might be provident attitude depending on the problem Doutorado Matemática Aplicada Doutora em Matemática Aplicada

Orientador: Florencia Cecilia Menegalli Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos Resumo: No presente trabalho investigou-se a desidratação osmótica de maçãs (variedade Fuji), seguida ou não de secagem convectiva com ar quente. Foram determinados perfis de concentração de água e soluto(s) em amostras de maçãs cortadas ao meio e desidratadas osmoticamente em soluções aquosas binárias (30% e 50% de sacarose, p/p) e solução ternária (50% de sacarose e 10% de cloreto de sódio, m/m), sob agitação vigorosa e temperatura constante (27°C). As amostras imersas na solução osmótica durante 2, 4 e 8 h foram fatiadas a partir da superfície plana exposta. A densidade e os teores de água, açúcares totais e redutores e cloreto de sódio foram determinados em cada fatia. O modelo matemático que descreve o transporte de cada espécie estudada (água, sacarose e cloreto de sódio) se baseia na equação de continuidade e na Lei de Fick e considera o encolhimento do tecido. O modelo foi ajustado aos dados experimentais, através do método implícito de diferenças finitas de Crank-Nicolson para determinar os coeficientes efetivos de difusão como uma função da concentração, utilizando coordenadas materiais e integrando simultaneamente as equações diferenciais de cada componente (água e sacarose ou água, sacarose e cloreto de sódio). Imagens de microscopia ótica de tecidos tratados osmoticamente, previamente pigmentados com o corante vital vermelho neutro, foram obtidas variando-se a concentração das soluções e o tempo de exposição. Os registros fotográficos retratam alterações da estrutura celular, que variam de acordo com a intensidade do processo de desidratação. A secagem convectiva com ar quente foi realizada em amostras de maçãs cortadas ao meio, frescas e previamente tratadas em solução aquosa de sacarose a 50% p/p durante 4 horas (27°C). Os perfis de umidade foram determinados a partir da superfície, após a exposição da face plana das metades das maçãs ao fluxo de ar quente (60°C ) durante 3, 6, 10 e 24 horas de secagem. O modelo matemático que descreve o transporte da água se baseia nas equações de continuidade e na Lei de Fick e considera o encolhimento do tecido e a concentração inicial não homogênea para o tecido previamente tratado. De maneira similar à desidratação osmótica, a difusividade de água na secagem também foi determinada em função da concentração, utilizando-se o método implícito de diferenças finitas de Crank-Nicolson e coordenadas materiais. Obtevese um bom ajuste dos modelos matemáticos aos dados experimentais de desidratação osmótica e de secagem. A ordem de magnitude dos coeficientes obtidos para a desidratação osmótica foi uma ou duas vezes menor que de coeficientes de difusão binários de soluções puras de sacarose e de cloreto de sódio. No caso da secagem, o comportamento da difusividade mostrou dependência significativa com a concentração de água. O tecido fresco apresentou coeficientes superiores aos do tecido pré-tratado osmoticamente além de funcionalidades distintas para diferentes tempos de secagem (inferior e superior a 6 horas). O tecido tratado apresentou um comportamento mais estável da difusividade da água no material e foi descrito por uma única função. Este fato está relacionado com as mudanças estruturais ocorridas durante a secagem, mais severas para o tecido fresco em relação ao tecido tratado Abstract: In this study it was investigated the osmotic dehydration of apples (Fuji variety) followed or not by convective drying with hot air. Concentration profiles were determined for water and solute(s) in samples of apples cut in half and osmotically dehydrated in binary aqueous solutions (30% and 50% sucrose, w/w) and ternary solution (50% sucrose and 10% sodium chloride, w/w) under vigorous stirring and constant temperature (27°C). The samples immersed in the osmotic solution for 2, 4 and 8 h were sliced from the exposed flat surface. The density and water, total and reducing sugars and sodium chloride contents were determined in each slice. The mathematical model that describes the transport of each species studied (water, sucrose and sodium chloride) is based on the continuity equation and on the of Fick's diffusion law and considers the tissue shrinkage. The model was fitted to experimental data through the finite difference implicit method of Crank-Nicolson, to determine the effective diffusion coefficients as a function of concentration, using material coordinates and integrating simultaneously the differential equations of each component (water and sucrose or water, sucrose and sodium chloride). Light microscopy images of osmotically processed tissues previously pigmented with the vital dye neutral red, were obtained, varying the concentration of solutions and time of exposure. The photographic records show changes in cellular structure, which vary with the intensity of the dehydration process. The convective air drying was carried out on samples of apples cut in half, fresh and treated in aqueous solution of sucrose to 50% w/w for 4 hours (27°C). The moisture profiles were determined from the surface, after exposure of the flat face of half of the apples to the flow of hot air (60 ° C) during 3, 6, 10 and 24 hours of drying. The mathematical model that describes the water transport is based on the continuity equation, the Fick's diffusion law, the tissue shrinkage and the nonhomogeneous initial concentration of the previously treated tissue. Similarly to the osmotic dehydration, the water diffusivity in drying was also determined in terms of concentration, using the finite difference implicit method of Crank-Nicolson and coordinated materials. It was possible to obtained a good fit of mathematical models to experimental data of osmotic dehydration and drying. The order of magnitude of the coefficients obtained for the osmotic dehydration was one or two times lower than diffusion coefficients of pure binary solutions of sucrose and sodium chloride. For drying, the behavior of diffusivity showed significant dependence with the concentration of water. The fresh tissue showed coefficients greater than the osmotically pre-treated tissue than it needs distinct functions for different times of drying (and less than 6 hours). The treated tissue showed a more stable behavior of the water diffusivity in the material and was described by a single function. This fact is related to the structural changes during drying, more severe for the fresh tissue than for the treated tissue Doutorado Doutor em Engenharia de Alimentos

International audience; Short-chain chlorinated paraffins (SCCPs) are under regulation through the European Water Framework Directive and were recently classified as POPs. Consecutively, the increasing use of middle-chain chlorinated paraffins (MCCPs) becomes of growing concern. Knowledge on the occurrence of chlorinated paraffins (CPs) is still scarce particularly in water phase. To achieve sufficient method sensitivity, the passive sampling approach, acting as a relevant alternative to usual grab sampling, has been considered only very recently for the monitoring of CPs in water. The present work aimed at determining the diffusion coefficients in silicone (D s) and the silicone-water partition coefficients (K sw) of various CP groups, having different chlorine contents and carbon chain lengths, in four commercial CP mixtures. Log D s (-10.78 to-10.21) was found to vary little and to be high for the groups of CPs studied. Thus, their uptake in silicone is controlled by the water boundary layer, which allows to consider the release of performance and reference compounds for infield estimation of the sampling rate. Moreover, CPs partitioned strongly towards silicone rubbers. Both the chlorination degree and the carbon chain length of CPs cause large uncertainties in the partitioning between silicone and water (log K sw between 4.85 and 6.30), indicating that instead of an average value, differentiated K sw should be used to estimate aqueous CPs more accurately. Even so, the probable influence of chlorine atoms position on polarity and partitioning may be an argument for favoring sampling in the kinetic stage.

Orientador: João Frederico da Costa Azevedo Meyer Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica Resumo: Esta pesquisa busca obter aproximações para a solução da Equação Diferencial Parcial de Difusão-Advecção-Reação, utilizando para a simulação computacional o estudo de uma parte específica do rio Doce, que passa pela cidade de Colatina. O objetivo é considerar o coeficiente de difusibilidade variável espacialmente na equação do modelo clássico, devido à vegetação aquática e terrestre presente nas margens do rio. A discretização espacial foi feita pelo Método das Diferenças Finitas, e a discretização temporal através do Método de Crank-Nicolson. A condição de contorno usada foi a de Robin. E foi feita a análise de cada tipo de fronteira considerada no domínio. Nas simulações variamos o coeficiente de perda de poluentes para as margens e a difusibilidade, considerando cenários com e sem fontes de poluição. O objetivo secundário é o de criar um instrumental que sirva de apoio ao estabelecimento de políticas públicas de contenção de impacto, seja no trecho do Rio Doce estudado, seja em outras regiões de características de circulação mais baixa Abstract: This research seeks to obtain approximations for the solution of the Partial Differential-Diffusion-Advection-Reaction Equation, using for computational simulation the study of a specific part of the Doce River, which passes through the city of Colatina. The objective is to consider the coefficient of diffusibility variable spatially in the equation of the classical model, due to the aquatic and terrestrial vegetation present in the river banks. The spatial discretization was done by the Finite Differences Method, and the temporal discretization by the Crank-Nicolson Method. In order to generalize the model, boundary conditions were those of Robin in order to include phenomena along the margins of the river. And the analysis of each type of frontier considered in the domain was made. In the simulations we varied the coefficient of loss of pollutants for the margins and the diffusibility, considering scenarios with and without sources of pollution. A secondary objective is that of creating na auxiliary tool to support decisions and strategies for public environmental policies for Diminisshing impact, be it in the Rio Doce regions, be it elswhere in situations of low circulation characteristics Mestrado Matemática Aplicada Mestra em Matemática Aplicada CNPQ 143161/2015-6

We present a molecular dynamics and theoretical study on the diffusion of interacting particles embedded on the surface of a sphere. By proposing five different interaction potentials among particles, we perform molecular dynamics simulations and calculate the mean square displacement (MSD) of tracer particles under a crowded regime of high surface density. Results for all the potentials show four different behaviors passing from ballistic and transitory at very short times, to sub-diffusive and saturation behaviors at intermediary and long times. Making use of irreversible thermodynamics theory, we also model the last two stages showing that the crowding induces a sub-diffusion process similar to that caused by particles trapped in cages, and that the saturation of the MSD is due to the existence of an entropic potential that limits the number of accessible states to the particles. By discussing the convenience of projecting the motions of the particles over a plane of observation, consistent with experimental capabilities, we compare the predictions of our theoretical model with the simulations showing that these stages are remarkably well described in qualitative and quantitative terms.

In this article, we report the in-situ nanoscale experimental measurement of sublimation rates, activation energy of sublimation, and diffusion coefficients of 2,4,6-trinitrotoluene (TNT) single crystals in air using atomic force microscopy (AFM). The crystals were prepared by slow evaporation at 5 °C using acetone-dissolved TNT. The mass loss was calculated by monitoring the shrinkage of the surface area of layered islands formed on the surface of the TNT crystals due to sublimation upon isothermal heating at temperatures below the melting point. The results suggest the sublimation process occurs via two-dimensional detachment of TNT molecules from the non-prominent facets on the crystal surface which imitates the nucleation and crystal growth process. Sublimation rates are one order of magnitude smaller than previously reported values. However, the calculated activation energy (112.15 ± 3.2 kJ/mol) and temperature-dependent sublimation rates agree well with the reported values for TNT thin films and microcrystals determined by UV-vis absorbance spectroscopy and quartz crystal microscopy (QCM) (90–141 kJ/mol). The average diffusion coefficient is (4.35 × 10–6 m2/s) which is within the range of the reported theoretical values with an average of 5.59 × 10–6 m2/s, and about 25% less than that determined using thermogravimetric analysis for powder TNT.

Titanium alloys have become the material of choice for marine parts manufacturing due to their high specific strength and excellent resistance to seawater corrosion. However, it is still challenging for a single titanium alloy to meet the comprehensive specifications of a structural component. In this study, we have applied a molecular dynamics approach to simulate the aging phase transformation, K-TIG welding process, and mechanical properties of the TC4-TA17 (Ti6Al4V-Ti4Al2V) alloy. The results show that during the aging phase transformation process, changes in the structure of the titanium alloys are mainly manifested in the precipitation of a new phase from the sub-stable β-phase, and after the state stabilization, the α-phase content reaches 45%. Moreover, during the melting and diffusion process of TC4-TA17, aluminum atoms near the interface diffuse, followed by titanium atoms, while relatively few vanadium atoms are involved in the diffusion. Finally, the results of tensile simulations of the TC4-TA17 alloy after welding showed that stress values can reach up to 9.07 GPa and that the mechanical properties of the alloy in the weld zone are better than those of the single alloys under the same conditions. This study will provide theoretical support for the optimization of process parameters for TC4-TA17 alloy welding.

Pramipexole (PMXL) belongs to the benzothiazole class of aromatic compounds and is used in treating Parkinson’s disease; however, overdosage leads to some abnormal effects that could trigger severe side effects. Therefore, it demands a sensitive analytical tool for trace level detection. In this work, we successfully developed an electrochemical sensor for the trace level detection of PMXL, using the voltammetric method. For the analysis, graphitic carbon nitride (gCN) was opted and synthesized by using a high-temperature thermal condensation method. The synthesized nanoparticles were employed for surface characterization, using transmission electron microscopy (TEM), X-ray diffraction (XRD), and atomic force microscopy (AFM) techniques. The electrochemical characterization of the material was evaluated by using the electrochemical impedance spectroscopy (EIS) technique to evaluate the solution–electrode interface property. The cyclic voltammetry (CV) behavior of PMXL displayed an anodic peak in the forward scan, indicating that PMXL underwent electrooxidation, and an enhanced detection peak with lower detection potential was achieved for gCN-modified carbon paste electrode (gCN·CPE). The influence of different parameters on the electrochemical behavior was analyzed, revealing the diffusion governing the electrode process with an equal number of hydronium ions and electron involvement. For the fabricated gCN·CPE, good linearity range was noticed from 0.05 to 500 µM, and a lower detection limit (LD) of 0.012 µM was achieved for the selected concentration range (0.5 to 30 µM). Selectivity of the electrode in PMXL detection was investigated by conducting an interference study, while the tablet sample analysis demonstrates the sensitive and real-time application of the electrode. The good recovery values for the analysis illustrate the efficiency of the electrode for PMXL analysis.

International audience; Polymeric materials play a vital role in our daily life, but the growing concern for the environment demands economical and natural biopolymers that can be cross-linked to create technologically innovative lightweight materials. Their cellular matrix with extreme flexibility makes them highly acceptable for application prospects in material science, engineering, and biomedical applications. Furthermore, their biocompatibility, mechanical properties, and structural diversity provide a gateway to research them to form technologically important materials. In the light of the same, the review covers cellulose derivatives. The first section of the study covers the general properties and applications of cellulose and its derivatives. Then, the biopolymers are characterised based on their dielectric properties, crystallinity, rheology, and mechanical properties. An in-depth analysis of the diffuse process of swelling and dissolution followed by a brief discussion on diffusion and diffusion of crosslinking has been done. The review also covers a section on swelling and swelling kinetics of carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC). The examination of all the aforementioned parameters gives an insight into the future aspects of the biopolymers. Lastly, the study briefly covers some preferred choices of cross-linking agents and their effect on the biopolymers.

This study evaluated moisture loss, oil gain and porosity when frying pieces of yam (Dioscorea rotundata). The parallelepiped-shaped samples, approximately 1 × 1 × 4 cm, were subjected to frying temperatures of 145, 165 and 185 °C for 50, 150, 300, 450, or 600 s. Fick's law was used to determine the diffusion coefficient from the experiment data for the varieties 153 traditional Espino and 125 Brazilian Espino. The moisture loss in 153 traditional Espino was greater than in 125 Brazilian Espino. The diffusion coefficient and the activation energy were determined for both varieties, which were higher in the 153 traditional Espino variety. The porosity was expressed as a percentage and was also higher in the 153 traditional Espino variety., Dioscorea rotundata, Fick's law, diffusion coefficient, porosity, Deep fat frying.

Bone tissue is composed at the nanoscale of apatite minerals, collagen molecules and water that form the mineralized collagen fibril (MCF). Water has a crucial role in bone biomineralization. We developed a 3D random walk model to investigate the water diffusion process within the MCF for three different scenarios, namely low, intermediate and high mineral volume fraction. The MCF geometric model is obtained after applying 6·106 translational and rotational perturbations to an ordered arrangement of mineral. Subsequently, we compute 300 random trajectories of water molecules within the MCF for each mineral volume fraction. Every trajectory is constituted of up to 500 k positions of the water particle. We determined the diffusion coefficient from the linear fit of the mean squared displacement of water molecules as a function of time. We investigate changes in the diffusivity values in relation to variation of bone mineral content. The analysis performed on the random walk data, for all mineralization conditions, leads to diffusion coefficients in good agreement with the diffusivity outcomes achieved from previous experimental studies. Thus, the 3D geometrical configuration adopted in this numerical study appears suitable for modelling the MCF with different volume fractions, from hypo- to hyper-mineralized conditions. We observed that low mineral content is associated with an increase of the water diffusion, while lower values of diffusivity are determined in hypermineralized conditions. In agreement with experimental data, our results highlight the influence of the structural alterations on the mass transport properties.

Patients undergoing standard chemoradiation post-resection had MRIs at radiation planning and fractions 10 and 20 of chemoradiation. MRIs were 1.5T and 3D T2-FLAIR, pre- and post-contrast 3D T1-weighted (T1) and echo planar DWI with three b-values (0, 500, and 1000s/mm2) were acquired. T2-FLAIR was coregistered to T1C images. Non-overlapping T1 contrast-enhancing (T1C) and nonenhancing T2-FLAIR hyperintense regions were segmented, with necrotic/cystic regions, the surgical cavity, and large vessels excluded. The simplified IVIM model was used to calculate voxelwise diffusion coefficient (D) and perfusion fraction (f) maps; ADC was calculated using the natural logarithm of b = 1000 over b = 0 images. T1C and T2-FLAIR segmentations were brought into this space, and medians calculated. MGMT promoter methylation status (MGMTPMS), age at diagnosis, and Eastern Cooperative Oncology Group (ECOG) performance status were extracted from electronic medical records. The data were presented, analyzed, and described in the article, “Intravoxel incoherent motion (IVIM) modeling of diffusion MRI during chemoradiation predicts therapeutic response in IDH wildtype Glioblastoma”, published in Radiotherapy and Oncology [1] .

A novel form-stable phase-change material (PCM) based on facing bricks was developed by incorporating thermoregulating PEG-SiO2, synthetized by sol-gel method and based on polyethylene glycol as phase-change material and silica as stabilizer compound. The PEG-SiO2 in its liquid form (sol) is firstly adsorbed inside the porous brick and lastly stabilized (gel) by controlling its gelation time, obtaining form-stable PCMs with PEG-SiO2 contents within 15–110 wt.%. Kinetic adsorption curves of the sol into bricks having different porosities as well as maximum adsorption capacities were obtained. The effective diffusion coefficients (Deff) were estimated by means of Fick’s second law, it being possible to predict the adsorption of sol PEG-SiO2 by the brick as function of its porosity and the free diffusion coefficient. Finally, form-stable PCMs demonstrated an improvement in their thermal energy storage capacity (up to 338%), these materials being capable of buffering the indoor temperature during an entire operational day

In the current regulations there is no clear indication about what is the limit of crack opening that can produce a decrease in the service life of reinforced concrete structures, in terms of the arrival of chlorides to the reinforcement and the initiation of corrosion. The crack becomes a preferential way of entry of aggressive agents, especially chlorides in solution. In this work, the transport of chlorides in cracked concrete is studied, obtaining the coefficients of stationary and non-stationary diffusion, the period of initiation of the corrosion, as well as the decrease of this according to the width of the crack. Concrete samples have been manufactured with different cement compositions that, after their conditioning, have been cracked by indirect traction test. The method includes natural and accelerated chloride transport tests, the latter by applying an electric current, according to current Spanish regulations.