Concentration-distance Profiles Research Articles

Using 1H and 23Na NMR relaxometry as a novel tool to monitor the moisture and salt distribution in commercial low-moisture part skim mozzarella

Zonal variations in 1H or 23Na content in commercial low-moisture part-skim mozzarella with a uniform salt distribution, obtained by dry-salting, or with a salt gradient, obtained by dry-salting and brining, were profiled using a combined 1H and 23Na NMR relaxometry procedure. 1D concentration–distance profiles were constructed in all cheeses from the surface to the core. Rapid, non-invasive, (∼21 min) distinction between dry-salted and brined cheese was enabled. Uptake of salt in cheese brined for 0–24 h was determined, and the derived effective diffusion coefficient of 23Na (3.23 × 10−10 m2 s−1) compared favourably with values reported for other semi-hard cheeses during brining; the 23Na concentration–distance profiles of brined cheese stored for 2–44 d at 4 °C corresponded to an effective diffusion coefficient of about 5.21 × 10−10 m2 s−1. Small variations in moisture content in the cheese could not be distinguished from the random fluctuations in 1H signal intensity.

Hydrogen defects in feldspars: kinetics of D/H isotope exchange and diffusion of hydrogen species in alkali feldspars

Diffusion of hydrogen in natural alkali feldspars (Eifel sanidine and adularia from unknown locality) containing strongly bonded OH defects was investigated by D/H isotope exchange in the T range 600–1050 °C at ambient pressure and at elevated pressures up to 8 kbar. Runs at 1 atm were performed in a fused silica tube connected to a liquid D2O reservoir at room temperature. In the high- pressure experiments samples were sealed with D2O in gold capsules and processed up to 4 kbar in externally heated pressure vessels using Ar/D2O as the pressure medium. Experiments at 6–8 kbar were performed in an internally heated gas pressure vessel using the double capsule technique to minimize isotopic contamination by the pressure medium. Diffusion coefficients were determined either by measuring concentration-distance profiles of OH and OD with an IR microscope or by measuring the total exchange of oriented plates after various run durations using a macroscopic IR technique. Both methods gave consistent data. D/H interdiffusion, DD/H, is almost identical in the adularia and in the sanidine implying that the chemical composition and the degree of Al/Si disorder have minor influence on the hydrogen isotope exchange in alkali feldspars. Furthermore, no effect of crystallographic orientation was found for DD/H in both feldspars. DD/H in sanidine, however, depends on the thermal pre-treatment. Heating for several days at 900 °C leads to a lowering of D by a factor of 2.3, indicating a corresponding decrease in mobile hydrogen species. Data for sanidine pre-annealed at 900 °C are well described in the T range 600–1050 °C by DD/Hm2/s=6.9·10-6exp-162kJ/molR·T\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$~D_{{{\\text{D/H}}}} \\left( {{\\text{m}}^{2} {\\text{/s}}} \\right) = 6.9 \\cdot 10^{{ - 6}} \\exp \\left( {\\frac{{ - 162{\\text{~kJ}}/{\\text{mol}}}}{{R \\cdot T}}} \\right)$$\\end{document}The diffusivity is strongly enhanced by water pressures (PH2O), i.e., in the range of 0–2 kbar. At PH2O = 2 kbar the following equation applies in the T-range of 645–800 °C: DD/Hm2/s=1.2·10-6exp-131kJ/molR·T\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$~D_{{D/H}} \\left( {{\\text{m}}^{2} /{\\text{s}}} \\right) = 1.2 \\cdot 10^{{ - 6}} \\exp \\left( {\\frac{{ - 131~{\\text{kJ}}/{\\text{mol}}}}{{R \\cdot T}}} \\right)$$\\end{document}Experiments with D2O/CO2 mixture of ratio 1:1 gave smaller exchange rates compared to pure D2O fluids, confirming that that not the pressure but the water fugacity leads to the increase in the mobility of hydrogen species. At 720 °C and pressures of 4–8 kbar, chemical diffusivities of H2O, tilde{D}_{{{text{H}}_{2} {text{O}}}}, were determined by fitting the weighted sum of the absorbances of the OH and the OD band vs. distance. The tilde{D}_{{{text{H}}_{2} {text{O}}}} values are similar to those reported by Kronenberg et al. (Geochim Cosmochim Acta 60:4075–4094, 1996) for dehydration of Kristallina adularia at ambient pressure. It is concluded that in both cases high concentrations of H2O molecules on interstitial sites govern the transport of hydrogen. Comparison of D/H interdiffusion to O diffusion in sanidine (Freer et al. in Phil Mag A75:485–503, 1997) implies that not only interstitial H2O but also protons contribute to the transport of hydrogen under hydrothermal conditions. On the other hand, the high DD/H at ambient pressure is attributed to an interdiffusion of protons and Na+, which is supported by Na tracerdiffusion data for sanidine (Wilangowski et al. in Defect Diffus Forum 363:79–84, 2015). A basic conclusion of this research is that hydrogen storage capacity and hydrogen diffusion in feldspars are largely determined by extrinsic defects, such as substitutional defects (i.e., Al3+ + H+ for Si4+) and associates of water molecules with vacancies. The bonding of hydrogen species to the defects can vary greatly, depending on the genesis of the feldspars, so that quantitative predictions are difficult.

Diffusion study in BCC Zr–Nb–Ti ternary alloys

Analyzing diffusion behaviors can help in predicting the relevant properties of Zr alloy materials. In this work, the diffusion behaviors of the BCC Zr–Ti–Nb system were studied via the diffusion couple method. Based on the concentration-distance profiles analytically represented by the error function expansion (ERFEX), the ternary inter-diffusion coefficients and impurity diffusion coefficients of Zr–Ti–Nb alloys were extracted using the Whittle–Green method and Hall methods. By comparing the average of different diffusion coefficients, it was found that the diffusion rate of Ti in the Zr–Ti–Nb alloys was generally faster than that of Nb and that the diffusion rate increased as the temperature increased. The main diffusion coefficients D˜TiTiZr and D˜NbNbZr decreased as the concentration of Ti or Nb increased, and the rate of decrease was affected by the x (Ti)/x (Nb) ratio in the Zr alloys. A high x (Ti)/x (Nb) ratio could slow down the reduction trend of the main diffusion coefficients. The impurity diffusion coefficients of Ti in Zr–Nb binary alloys decreased as the concentration of Nb increased, while the impurity diffusivities of Nb in Zr–Ti alloys exhibited an opposite trend.

Interdiffusion and Atomic Mobilities in fcc Ni-Mo-Ta Alloys

Ternary fcc Ni-Mo-Ta diffusion couples annealed at 1473 and 1573 K have been studied by using electron probe microanalysis. Based on the measured concentration-distance profiles and Whittle–Green method, the interdiffusion coefficients were calculated to critically assess the atomic mobilities by means of DICTRA software package. Comprehensive comparisons between calculated and experimental diffusion coefficients show that the atomic mobilities obtained in this work could well reproduce the experimental data. Reasonable agreements between model-predicted diffusion properties and the experimental data indicated that present mobility database can be used to study the diffusion behavior, such as diffusion paths and concentration-distance profiles in the ternary fcc Ni-Mo-Ta alloys.

Uranium diffusion and time‐dependent adsorption–desorption in soil: A model and experimental testing of the model

AbstractMost past research on uranium (U) transport and reaction in the environment has been concerned with groundwater contamination and not with uptake by plants or soil biota, both of which operate over much smaller time and distance scales. We developed and tested a model of U diffusion and reaction in soil at scales appropriate for uptake by plant roots, based on a model we developed in an earlier paper. The model allows for the speciation of U with hydroxyl, carbonate and organic ligands in the soil solution, and the nature and kinetics of sorption reactions with the soil solid. The model predictions were compared with experimentally measured concentration–distance profiles of U in soil adjusted to different pHs and CO2 pressures. Excellent agreement between observed and predicted profiles was obtained using model input parameters measured or otherwise estimated independently of the concentration–distance profiles, showing that the model was a correct description of the system and all important processes were allowed for. The importance of the kinetics of U adsorption and desorption for the timescale of diffusion through the soil is highlighted. The results are discussed in terms of the uptake of U by plant root systems, as modelled in the earlier paper.Highlights We developed a model of U diffusion and reaction in soil on scales relevant to uptake by plant roots. We tested the model against measured diffusion profiles and obtained excellent agreement. The kinetics of U adsorption–desorption reactions are important. Reaction kinetics measured in shaken suspensions or flow‐through systems are likely to be misleading.

Interdiffusion and Atomic Mobilities in Co-rich fcc Co-Cr-V Alloys

Diffusion couples for Co-rich fcc Co-Cr-V alloys were prepared, all of which were annealed at 1473 K for 259 200 s. The interdiffusion coefficients in fcc Co-Cr-V ternary systems were investigated by means of Whittle and Green method with the help of electronic-probe microanalysis (EPMA). On the basis of the thermodynamic parameters available in the literature, the interdiffusion data were critically assessed to develop the atomic mobilities of the fcc Co-Cr-V alloys via the DICTRA software. Comprehensive comparisons between the calculated and experimental diffusion coefficients show that the experimental data can be well reproduced by the atomic mobilities obtained in this work. And the validity of the diffusion mobilities was tested by simulating the concentration-distance profiles and diffusion paths in diffusion couples.

Interdiffusion and Atomic Mobilities in fcc Co-Cr-Mo Alloys

The diffusion couples of Co-Cr-Mo ternary alloys were prepared and annealed at 1473 K for 72 h in order to determine the interdiffusion coefficients by using the electron probe microanalysis combined with Whittle and Green method. The experimental interdiffusion coefficients were critically assessed to the atomic mobilities by means of DICTRA software package. Good agreements were obtained from comprehensive comparison between the model-predicted diffusion properties and the experimental data, meanwhile, considered that the calculated diffusion coefficients were within the acceptable uncertainty of the experimentally measured diffusion coefficients, which verified the reliability of the atomic mobilities. The diffusion phenomena, such as diffusion paths and the concentration-distance profiles in the Co-Cr-Mo ternary system can be reasonably described by the presently obtained atomic mobilities.

Diffusive exchange of trace elements between alkaline melts: Implications for element fractionation and timescale estimations during magma mixing

The diffusive exchange of 30 trace elements (Cs, Rb, Ba, Sr, Co, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ta, V, Cr, Pb, Th, U, Zr, Hf, Sn and Nb) during the interaction of natural mafic and silicic alkaline melts was experimentally studied at conditions relevant to shallow magmatic systems. In detail, a set of 12 diffusion couple experiments have been performed between natural shoshonitic and rhyolitic melts from the Vulcano Island (Aeolian archipelago, Italy) at a temperature of 1200 °C, pressures from 50 to 500 MPa, and water contents ranging from nominally dry to ca. 2 wt.%. Concentration-distance profiles, measured by Laser Ablation ICP-MS, highlight different behaviours, and trace elements were divided into two groups: (1) elements with normal diffusion profiles (13 elements, mainly low field strength and transition elements), and (2) elements showing uphill diffusion (17 elements including Y, Zr, Nb, Pb and rare earth elements, except Eu). For the elements showing normal diffusion profiles, chemical diffusion coefficients were estimated using a concentration-dependent evaluation method, and values are given at four intermediate compositions (SiO2 equal to 58, 62, 66 and 70 wt.%, respectively). A general coupling of diffusion coefficients to silica diffusivity is observed, and variations in systematics are observed between mafic and silicic compositions. Results show that water plays a decisive role on diffusive rates in the studied conditions, producing an enhancement between 0.4 and 0.7 log units per 1 wt.% of added H2O. Particularly notable is the behaviour of the trivalent-only REEs (La to Nd and Gd to Lu), with strong uphill diffusion minima, diminishing from light to heavy REEs. Modelling of REE profiles by a modified effective binary diffusion model indicates that activity gradients induced by the SiO2 concentration contrast are responsible for their development, inducing a transient partitioning of REEs towards the shoshonitic melt. These results indicate that diffusive fractionation of trace elements is possible during magma mixing events, especially in the more silicic melts, and that the presence of water in such events can lead to enhanced chemical diffusive mixing efficiency, affecting also the estimation of mixing to eruption timescales.

Gelation of an alginate film via spraying of calcium chloride droplets

External gelation process of Ca-alginate gel with a controlled supply of CaCl2 to alginate solution was experimentally and numerically investigated. A single Na-alginate solution film was prepared and suspended in a closed chamber of CaCl2 spray droplets. The collected mass of CaCl2 by the film increases as the spraying time increases. The collection efficiency (E) between the film and CaCl2 droplets was averagely 0.0015. The degree of gelation (P) of the film was found to be alginate and CaCl2 solution concentration dependent. The experimental results of the mass of CaCl2 droplets collected by the film and the E were in good agreement with the numerical results. The concentration-distance profiles of Ca2+ cation, alginate, and Ca-alginate gel in the film were determined using the one-dimensional diffusion–reaction model. The model is useful to determine the P of the Ca-alginate gel film produced using a limited supply of CaCl2.

Interdiffusion and Atomic Mobilities in fcc Co-Ga and Co-V Alloys

On the basis of Co/Co-10Ga, Co/Co-12Ga, and Co/Co-10V (at.%) diffusion couples, interdiffusion coefficients in the face-centered cubic (fcc) phase of the Co-Ga and Co-V binary systems were investigated in the temperature range between 1273 and 1573 K by means of the den Broeder method. Based on available thermodynamic information, the interdiffusion data were assessed to develop the atomic mobilities for the fcc Co-Ga and Co-V alloys using the DICTRA software package, and their validity was tested by simulating concentration–distance profiles.

Water-enhanced interdiffusion of major elements between natural shoshonite and high-K rhyolite melts

The interdiffusion of six major elements (Si, Ti, Fe, Mg, Ca, K) between natural shoshonite and a high-K rhyolite (Vulcano island, Aeolian archipelago, Italy) has been experimentally measured by the diffusion couple technique at 1200°C, pressures from 50 to 500MPa and water contents from 0.3 (‘nominally dry’) to 2wt%. The experiments were carried out in an internally heated pressure vessel, and major element profiles were later acquired by electron probe microanalysis. The concentration-distance profiles are evaluated using a concentration-dependent diffusivity approach. Effective binary diffusion coefficients for four intermediate silica contents are obtained by the Sauer-Freise modified Boltzmann-Matano method. At the experimental temperature and pressures, the diffusivity of all studied elements notably increases with dissolved H2O content. Particularly, diffusion is up to 1.4 orders of magnitude faster in a melt containing 2wt% H2O than in nominally dry melts. This effect is slightly enhanced in the more mafic compositions. Uphill diffusion was observed for Al, while all other elements can be described by the concept of effective binary interdiffusion. Ti is the slowest diffusing element through all experimental conditions and compositions, followed by Si. Fe, Mg, Ca and K diffuse at similar rates but always more rapidly than Si and Ti. This trend suggests a strong coupling between melt components. Since effects of composition (including water content) are dominant, a pressure effect on diffusion cannot be clearly resolved in the experimental pressure range.

Limited drug solubility can be decisive even for freely soluble drugs in highly swollen matrix tablets

The aim of this study was to elucidate the importance of potential limited solubility effects for the control of drug release from hydrophilic matrix tablets loaded with a freely water-soluble drug. It is often assumed that the considerable amounts of water penetrating into this type of advanced drug delivery systems are sufficient to rapidly dissolve the entire drug loading, and that limited drug solubility is not playing a role for the control of drug release. Here, we show that this assumption can be erroneous. HPMC/lactose matrix tablets were loaded with 5 to 60% diprophylline (e.g. solubility in 0.1M HCl at 37°C: 235mg/mL), and drug release was measured at low and neutral pH, respectively. A mechanistically realistic mathematical theory was applied, considering drug diffusion in axial and radial direction in the cylindrical matrices and the potential co-existence of dissolved and non-dissolved drug. Importantly, only dissolved drug is available for diffusion. It is demonstrated that during major parts of the release periods, non-dissolved drug excess exists within tablets containing 30% or more diprophylline, despite of the substantial water contents of the systems. This leads to partially almost linear drug concentration distance profiles within the tablets, and reveals a major contribution of limited drug solubility effects to the control of drug release, even in the case of freely water-soluble diprophylline. It can be expected that also in other types of drug delivery systems, e.g. microparticles and implants (containing much less water), limited drug solubility effects play a much more important role than currently recognized.

Interdiffusion and Atomic Mobilities in bcc Ti-Ga and Ti-Cu Alloys

On the basis of three groups of Ti/Ti-10 at.% Ga and Ti/Ti-7 at.% Cu diffusion couples, respectively, interdiffusion coefficients in the bcc Ti-Ga and Ti-Cu binary alloys in the temperature range of 1273-1573 K were evaluated by means of the den Broeder method. Based on various reported experimental and the present measured diffusion coefficients as well as the available thermodynamic information, accurate atomic mobilities in the bcc Ti-Ga and Ti-Cu alloys were assessed via the DICTRA simulation package. A semi-empirical correlation was employed in the present work for the self-diffusivities in the hypothetical bcc Ga and Cu. Comparision between the calculated and measured diffusion coefficients indicated that most of the experimental information can be reasonably reproduced. The developed diffusion mobilities were further validated by the prediction of the concentration-distance profiles.

Hydrogen diffusion in Ti-doped forsterite and the preservation of metastable point defects

The effect of trace concentrations of Ti on the rate and mechanism of hydrogen diffusion in pure forsterite was investigated experimentally. Forsterite doped with 350–400 ppm Ti (predominantly octahedral Ti 3+ , minor tetrahedral Ti 4+ ) was prepared by diffusing Ti into pure synthetic forsterite at high temperature (1500 °C), very low oxygen fugacity (~QFM-5) at atmospheric pressure. The Ti-doped forsterite was then diffusively hydroxylated in a piston-cylinder apparatus at much lower temperatures (650–1000 °C) and higher oxygen fugacities, at 1.5–2.5 GPa, with chemical activities buffered by forsterite-enstatite or forsterite-periclase and partial pressure of H 2 O equal to total pressure. This produced hydrogen concentration-distance profiles of several hundred micrometers in length. Diffusion of hydrogen through the Ti-doped forsterite, even at very high f O 2 , does not lead to redox re-equilibration of the high Ti 3+ /ΣTi ratio set during the synthesis of the starting material at extremely reducing conditions—the metastable point defects are partially preserved. Three main hydroxylated point defects are observed; hydroxyl is associated with Ti 4+ (titano-clinohumite point defects), Ti 3+ (and possibly other trivalent cations), and M-site vacancies. Concentration-distance profiles represent an interplay between diffusion and reaction (i.e., site rearrangement) to form the observed point defects. In all experiments, the concentration-distance profiles of the hydroxylated Ti defects coincide with the concentration-distance profiles of the M-site vacancy substitution, with the same crystallographic anisotropy. This suggests that the macroscopic movement of hydrogen through the crystal is due to one diffusion mechanism (the diffusion of hydroxylated M-site vacancies). The net H diffusion coefficient [log D (ΣH)], between 650–1000 °C, is log D ( Σ H ) = log D 0 ( Σ H ) + ( − 223 ( ± 8 ) kJ / mol 2 . 3 R T ) where the values of log D 0 (ΣH) parallel to [100] and [001] directions are −3.0 ± 0.4 and −2.2 ± 0.4, respectively; diffusion is therefore around one order of magnitude faster along the c axis than along the a axis. The diffusion of hydrogen is slightly faster in Ti-doped forsterite than in pure forsterite. There is no effect of chemical activity or oxygen fugacity on the rate of diffusion. Hydrogen diffusion profiles represent a complex interplay between the movement of H through the crystal lattice and point-defect reactions to maintain charge balance.

P45] Phase equilibria of Co-Ti-V ternary system and the mechanical property of γ + γʹ

Based on various experimentally measured diffusivities available in the literature together with the reported thermodynamic parameters, the atomic mobilities for disordered fcc and ordered L12 Ni–Al–W alloys were assessed on the basis of a recently developed phenomenological model incorporated in the DICTRA software. In order to provide the missing impurity diffusion coefficients of W in fcc_Al, first-principles calculations were utilized in the present work. Comprehensive comparisons between the calculated and experimental diffusion coefficients show that all the experimental data can be well reproduced by the atomic mobilities obtained in the present work. In order to further verify the reliability of the presently obtained atomic mobilities, two fcc/L12-type diffusion couples (i.e., Ni–5 at.% Al–5 at.% W/Ni–20 at.% Al–4 at.% W and Ni/Ni–22 at.% Al–2 at.% W) were prepared and the concentration-distance profiles after annealing at 1323 K for 86.4 ks were measured. The excellent agreement between the model-predicted concentration-distance profiles and the experimental data indicates that the presently obtained atomic mobilities in fcc/L12 Ni–Al–W alloys are reliable.

A simple reactive-transport model of calcite precipitation in soils and other porous media

Calcite formation in soils and other porous media generally occurs around a localised source of reactants, such as a plant root or soil macro-pore, and the rate depends on the transport of reactants to and from the precipitation zone as well as the kinetics of the precipitation reaction itself. However most studies are made in well mixed systems, in which such transport limitations are largely removed. We developed a mathematical model of calcite precipitation near a source of base in soil, allowing for transport limitations and precipitation kinetics. We tested the model against experimentally-determined rates of calcite precipitation and reactant concentration–distance profiles in columns of soil in contact with a layer of HCO3−-saturated exchange resin. The model parameter values were determined independently. The agreement between observed and predicted results was satisfactory given experimental limitations, indicating that the model correctly describes the important processes. A sensitivity analysis showed that all model parameters are important, indicating a simpler treatment would be inadequate. The sensitivity analysis showed that the amount of calcite precipitated and the spread of the precipitation zone were sensitive to parameters controlling rates of reactant transport (soil moisture content, salt content, pH, pH buffer power and CO2 pressure), as well as to the precipitation rate constant. We illustrate practical applications of the model with two examples: pH changes and CaCO3 precipitation in the soil around a plant root, and around a soil macro-pore containing a source of base such as urea.

Diffusivities and atomic mobilities in disordered fcc and ordered L12 Ni–Al–W alloys

Based on various experimentally measured diffusivities available in the literature together with the reported thermodynamic parameters, the atomic mobilities for disordered fcc and ordered L12 Ni–Al–W alloys were assessed on the basis of a recently developed phenomenological model incorporated in the DICTRA software. In order to provide the missing impurity diffusion coefficients of W in fcc_Al, first-principles calculations were utilized in the present work. Comprehensive comparisons between the calculated and experimental diffusion coefficients show that all the experimental data can be well reproduced by the atomic mobilities obtained in the present work. In order to further verify the reliability of the presently obtained atomic mobilities, two fcc/L12-type diffusion couples (i.e., Ni–5at.% Al–5at.% W/Ni–20at.% Al–4at.% W and Ni/Ni–22at.% Al–2at.% W) were prepared and the concentration-distance profiles after annealing at 1323K for 86.4ks were measured. The excellent agreement between the model-predicted concentration-distance profiles and the experimental data indicates that the presently obtained atomic mobilities in fcc/L12 Ni–Al–W alloys are reliable.

Potential of imaging analysis in establishing skin concentration-distance profiles for topically applied FITC-dextran 4 kDa

Quantitatively determining the skin concentration-distance profiles of topically applied drugs is important for evaluating their safety and efficacy. The aim of the present study was to quantitatively visualize the distribution of hydrophilic drugs through the skin using confocal laser scanning microscopy (CLSM) in order to obtain skin concentration-distance profiles. FITC-dextran with a molecular weight of approximately 4 kDa (FD-4) was selected as the model fluorescent drug in the present study, and excised pig ear skin was used. The skin concentration of FD-4 at each depth of a skin section was assessed by imaging analysis of the intensity of fluorescence. The FD-4 skin concentration-distance profile obtained was analyzed using Fick’s second law of diffusion, and was markedly similar to that using skin permeation parameters in the skin permeation study. These results suggest that the present CLSM method may be a promising tool for quantitatively visualizing the concentration-distance profiles of drugs through the skin.

Micro-FTIR imaging: an advanced method for the determination of CO2 and H2O concentration gradients in silicate glasses

Glass samples of diffusion couple experiments with rhyolitic to hawaiitic melts were analyzed by FTIR microscopy with a common single element and a 64 × 64 element focal plane array detector to obtain total CO 2 and H 2 O concentration distance profiles. In contrast to the single element detector, the array detector facilitates mid-infrared spectral imaging with a resolution on a micrometer scale. The imaged sample information was converted to multiple parallel concentration distance profiles, using the absorption band areas of the dissolved volatile species. The bulk CO 2 and H 2 O diffusivities from measurements with different array resolutions range from log D = −11.03 to −11.33 m 2 ·s −1 at 500 MPa and 1523–1623 K. All determined diffusion coefficients are within the error identical to single element detector analysis. Further test measurements were performed on a partially degassed, vesiculated phonolite in order to visualize the concentration of H 2 O around bubbles. Both applications confirm that FTIR imaging is a convenient tool to investigate the spatial distribution of CO 2 and H 2 O in silicate glasses, especially in terms of diffusion-related studies.

A new technique for tracing the concentration-distance variations in the cross section of polyamide rods by using a conventional scanner

A new method for determining the dye distribution in the cross section of polyamide rods from the scanner data is presented. Three commercial disperse dyes are used for dyeing purposes and two series of dyed samples are prepared. The first set is the samples with the full diffusion of dyes within the cross section of rods that used as the reference samples while the second set includes samples with different depths of penetrations, hence they benefit from non homogenous dye distribution in their cross sections. A conventional scanner is characterized with the ColorChecker SG and the transformation matrix is computed to convert the RGB values of samples to the CIEXYZ data. The spectral reflectances as well as the RGB values of the cross sections of the full diffused dyed samples are measured and the classical version and the weighted version of principal component analysis technique are employed to estimate the spectral behaviors of homogenous dyed samples from the CIEXYZ values obtained from the corresponding RGB data. Finally, the well known Kubelka Munk equation is employed to estimate the concentration of dyes in the cross sections of samples. The work is extended to non homogenous dyed samples to find the spatial distributions of dyes over the cross sections of rods. Similar to full diffused dyed samples, the spatial reflectance spectra of the cross sections are firstly estimated from the measured RGB values and then the spatial concentrations are computed. The plotted concentration-distance profiles confirm the classical variations of dye concentrations over the cross sections of dyed rods similar to those that are obtainable by conventional methods such as multiple membranes and Boltzmann-Matano as well as laser scanning confocal microscopy methods.