Relative Diffusion Coefficient Research Articles

Effect of mechanical stresses on epoxy coating ageing approached by Electrochemical Impedance Spectroscopy measurements

The present work is a new illustration of the interest to use electrochemical analysis to investigate polymer coating degradation. We focus our attention on specific effect of visco-elastic (VE) stress on the hygrothermal ageing of a model polymer DGEBA/TETA coating applied on steel panels. Two different VE stress values (stretched and compressed modes) were applied on the coated panels and these samples were hygrothermally aged in NaCl 3wt.% solution at different temperatures. Electrochemical Impedance Spectroscopy was used in order to determine the solubility, the diffusion coefficient and the initial relative permittivity of the coating. The obtained results suggested that all of these parameters appeared as thermo-activated functions of the absolute value of the applied stress and that the stress, independent of its sign, leads to a decrease of the initial relative permittivity, solubility and diffusion coefficient. A thermodynamic approach was used to separate the enthalpy and entropic contributions of each property. It is shown that the entropic contribution plays a major role on the modification of these parameters. It means that the VE applied stress modifies the polymer chain spatial distribution. Finally, the VE stress allows a better barrier effect of the coating and then to delay the corrosion process of the metallic substrates.

Spatially dependent relative diffusion of nanoparticles in polymer melts

We formulate and apply a microscopic statistical-mechanical theory for the non-hydrodynamic relative diffusion coefficient of a pair of spherical nanoparticles in entangled polymer melts based on a combination of Brownian motion, mode-coupling, and polymer physics ideas. The focus is on the mesoscopic regime where particles are larger than the entanglement spacing. The dependence of the non-hydrodynamic friction on interparticle separation, degree of entanglement, and tube diameter is systematically studied. The overall magnitude of the relative diffusivity is controlled by the ratio of the particle to tube diameter and the number of entanglements in a manner reminiscent of single-particle self-diffusion and Stokes-Einstein violations. A rich spatial separation dependence of mobility enhancement relative to the hydrodynamic behavior is predicted even for very large particles, and the asymptotic dependence is derived analytically in the small and large separation limits. Particle separations in excess of 100 nm are sometimes required to recover the hydrodynamic limit. The effects of local polymer-particle packing correlations are found to be weak, and the non-hydrodynamic effects are also small for unentangled melts.

Evaluation of placenta with relative apparent diffusion coefficient and relative T2 signal intensity analysis

We aimed to test the null hypothesis that relative apparent diffusion coefficient (rADC) and relative signal intensity values (rSI(HASTE)) do not change in the evaluation of placental maturation with advancing gestational age. Fifty-six fetuses with diffusion-weighted magnetic resonance imaging (DW-MRI) data were enrolled in this retrospective study. Fetuses were analyzed in three different gestational age groups: group 1, 18-23 weeks; group 2, 24-28 weeks; and group 3, 29-38 weeks. The rADC (mean ADC/ADC(globe)) and rSI(HASTE) values (mean SI(HASTE)/SI(globe)) were obtained. Two radiologists experienced in fetal MRI who were blinded to the patient information reviewed MRI images independently. Kruskal-Wallis Test was used to compare the rADC and rSI(HASTE) with gestational age groups. The agreement between the two blinded readers was tested using Krippendorff's alpha ratio. Both placental rADC values and placental rSI(HASTE) values were not significantly different between the gestational age groups (P = 0.688 and P = 0.280, respectively). rADC and rSI(HASTE) measurements were reproducible with a good agreement between the two readers (Krippendorff's alpha ratio was 0.613 and 0.778, respectively). The rADC and rSI(HASTE) values do not change with advancing gestational age.

Findings and Patterns on MRI and MR Spectroscopy in Neonates after Therapeutic Hypothermia for Hypoxic Ischemic Encephalopathy Treatment

The purpose of this study is to describe the findings and patterns of injury on magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) after whole-body hypothermia treatment for neonatal hypoxic ischemic encephalopathy. A retrospective review of consecutive term neonates treated with whole-body hypothermia was performed. Data recorded included demographics and MRI and MRS findings, and day of life (DOL) studies were performed. Injury patterns were classified on MRI as deep, cortical, mixed, or diffuse. The relative apparent diffusion coefficient (rADC) was plotted against DOL scanned and the presence of lactate was recorded. MRI was performed in 44 infants, 34 of whom also underwent MRS. MRI was abnormal in 32% of neonates, 29.5% of whom were imaged at DOL 4 to 8. rADC values were lowest in neonates scanned on DOL 4 and 5 and remained low up to DOL 8. The deep brain nuclei were involved in hypoxic ischemic encephalopathy in 93% of neonates with abnormal MRIs and lactate was identified on MRS in 18% of neonates between DOL 4 and 8. MRI performed after therapeutic cooling was abnormal in 29.5% of neonates scanned on DOL 4 to 8. Deep nuclear injury was identified in 93% of neonates. Lactate was present on MRS in 18% of neonates, and rADC values were most reduced on MRI between DOL 4 and 8.

Translational diffusion in paramagnetic liquids by 1H NMR relaxometry: Nitroxide radicals in solution

For nitroxide radicals in solution one can identify three frequency regimes in which (1)H spin-lattice relaxation rate of solvent molecules depend linearly on square root of the (1)H resonance frequency. Combining a recently developed theory of nuclear (proton) spin-lattice relaxation in solutions of nitroxide radicals [D. Kruk et al., J. Chem. Phys. 137, 044512 (2012)] with properties of the spectral density function associated with translational dynamics, relationships between the corresponding linear changes of the relaxation rate (for (14)N spin probes) and relative translational diffusion coefficient of the solvent and solute molecules have been derived (in analogy to (15)N spin probes [E. Belorizky et al., J. Phys. Chem. A 102, 3674 (1998)]). This method allows a simple and straightforward determination of diffusion coefficients in spin-labeled systems, by means of (1)H nuclear magnetic resonance (NMR) relaxometry. The approach has thoroughly been tested by applying to a large set of experimental data-(1)H spin-lattice relaxation dispersion results for solutions of different viscosity (decalin, glycerol, propylene glycol) of (14)N and (15)N spin probes. The experiments have been performed versus temperature (to cover a broad range of translational diffusion coefficients) using field cycling spectrometer which covers three decades in (1)H resonance frequency, 10 kHz-20 MHz. The limitations of NMR relaxometry caused by the time scale of the translational dynamics as well as electron spin relaxation have been discussed. It has been shown that for spin-labeled systems NMR relaxometry gives access to considerably faster diffusion processes than for diamagnetic systems.

Magnetic Resonance Imaging of Mass Transport and Structure Inside a Phototrophic Biofilm

The aim of this study was to utilize magnetic resonance imaging (MRI) to image structural heterogeneity and mass transport inside a biofilm which was too thick for photon based imaging. MRI was used to map water diffusion and image the transport of the paramagnetically tagged macromolecule, Gd-DTPA, inside a 2.5mm thick cyanobacterial biofilm. The structural heterogeneity of the biofilm was imaged at resolutions down to 22×22μm, enabling the impact of biofilm architecture on the mass transport of both water and Gd-DTPA to be investigated. Higher density areas of the biofilm correlated with areas exhibiting lower relative water diffusion coefficients and slower transport of Gd-DTPA, highlighting the impact of biofilm structure on mass transport phenomena. This approach has potential for shedding light on heterogeneous mass transport of a range of molecular mass molecules in biofilms.

Ilościowa ocena stopnia zaniku oraz zaburzeń perfuzji i dyfuzji w obrębie hipokampów u pacjentów z chorobą Alzheimera i łagodnymi zaburzeniami poznawczymi.

BackgroundThe aim of this study was to evaluate atrophy rates, perfusion, and diffusion disturbances within the hippocampus, which is the site of characteristic changes in Alzheimer’s disease (AD) and mild cognitive impairment (MCI).Material/MethodsThirty patients with AD (mean age 71.2 yrs) – 34 with MCI (mean age 67.7 yrs) and 20 healthy controls (mean age 68.1 yrs) – underwent structural MR examination followed by perfusion and diffusion-weighted imaging on a 1.5 T scanner. Visual rating of hippocampal atrophy, planimetric measurements of hippocampal formation (HF) and perihippocampal fluid spaces (PFSs), and values of relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) were assessed. The results were correlated with the MMSE scores.ResultsIn AD we found decreased size of HF and increased diameters of PFSs and ADC values, compared to MCI and control group. Compared to normal controls, the MCI group showed decreased HF size and increased diameters of only medial PFS. There were no differences in rCBV values among all the subject groups. Planimetric measurements of hippocampal atrophy showed the highest accuracy in diagnosing AD and MCI. In all patients, the increased rates of hippocampal atrophy correlated with the increased ADC values. In MCI, MMSE scores correlated with the HF size and ADC values.ConclusionsIn AD and MCI, hippocampal atrophy is associated with decreased tissue integrity without coexisting perfusion disturbances. Of all evaluated hippocampal measurements, atrophy rates seem to be the most useful parameters in detecting changes among AD, MCI, and control subjects.

Diffusion in biofilms respiring on electrodes

The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (D(e)) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed noninvasive, nondestructive, high spatial resolution in situ D(e) measurements in living biofilms respiring on electrodes. The electrodes were polarized so that they would act as the sole terminal electron acceptor for microbial metabolism. We present our results as both two-dimensional D(e) heat maps and surface-averaged relative effective diffusion coefficient (D(rs)) depth profiles. We found that 1) D(rs) decreases with depth in G. sulfurreducens biofilms, following a sigmoid shape; 2) D(rs) at a given location decreases with G. sulfurreducens biofilm age; 3) average D(e) and D(rs) profiles in G. sulfurreducens biofilms are lower than those in S. oneidensis biofilms-the G. sulfurreducens biofilms studied here were on average 10 times denser than the S. oneidensis biofilms; and 4) halting the respiration of a G. sulfurreducens biofilm decreases the D(e) values. Density, reflected by D(e), plays a major role in the extracellular electron transfer strategies of electrochemically active biofilms.

Concrete mix design for service life of RC structures exposed to chloride attack

The purpose of this research is to propose a design technique of concrete mix proportions satisfying service life through genetic algorithm (GA) and neural network (NN). For this, thirty mix proportions and the related diffusion coefficients in high performance concrete are analyzed and fitness function for diffusion coefficient is obtained considering mix components like w/b (water to binder ratio), cement content, mineral admixture (slag, flay ash and silica fume) content, sand and coarse aggregate content. Through averaging the results of 10 times GA simulations, relative errors to the previous data decrease lower than 5.0% and the simulated mix proportions are verified with the experimental results. Assuming the durability design parameters, intended diffusion coefficient for intended service life is derived and mix proportions satisfying the service life are obtained. Among the mix proportions, the most optimized case which satisfies required concrete strength and the lowest cost is selected through GA algorithm. The proposed technique would be improved with the enhancement of comprehensive data set including wider the range of diffusion coefficients.

Research on the effective gas diffusion coefficient in dry porous media embedded with a fractal-like tree network

A theoretical model for the relative gas diffusion coefficient in dry porous media embedded with a Y-shaped fractal-like tree network is presented under the combination of bulk diffusion and Knudsen diffusion. The proposed model is expressed as a function of the length ratio, the diameter ratio, the branching level, the branching angle and the relative areal porosity. The effect of the structural parameters of the medium and the tortuosity on gas diffusion is analyzed in detail. Model predictions are compared with available experimental data, and a fair agreement between them is found.

Long-Term Changes of Diffusion Tensor Imaging and Behavioural Status after Acupuncture Treatment in Rats with Transient Focal Cerebral Ischaemia

The effect of acupuncture treatment in cerebral ischaemia is controversial. A study was undertaken to assess its effects in rats with transient middle cerebral artery occlusion (tMCAO) and discuss its mechanisms. 21 Sprague-Dawley rats were divided into three groups. Group 1 underwent tMCAO and subsequently received acupuncture treatment, Group 2 underwent tMCAO without treatment and Group 3 only underwent sham operation. The evolution of diffusion tensor imaging (DTI) features in ischaemic lesions from acute to chronic periods was assessed and the correlations with behavioural tests and histopathological changes were examined. tMCAO rats displayed side-specific sensorimotor deficits after occlusion. Behavioural scores of rats in group 1 reduced gradually with acupuncture treatment. No significant difference in lesion size on T2-weighted imaging was found between the two tMCAO groups. Relative apparent diffusion coefficient (rADC) and relative fractional anisotropy (rFA) values in the centre and at the edge of the ischaemic lesions reduced at first and then increased to varying degrees. Only changes in the rFA value at the edge of the ischaemic lesions were significantly different between the two tMCAO groups. A more significant increase in growth-associated protein B-50 and synaptophysin protein expression was found in group 1 than in the other groups. No significant correlations were found between behavioural scores, DTI appearances and immunohistochemical results. The acupuncture points applied were effective, and improving neuronal regeneration may have a role in the mechanism of acupuncture treatment of post-stroke paralysis of the limbs in rats. MRI, particularly the fractional anisotropy value of DTI, is an appropriate parameter to evaluate the recovery status.

Multifractal properties of porosity as calculated from computed tomography (CT) images of a sandy soil, in relation to soil gas diffusion and linked soil physical properties

Relationships between soil porosity and diffusive gas flux are poorly understood, partly because of a difference in measurement scales between the two. The complexity of soil pore systems can be described by multifractal analysis at the microscopic scale, whereas relative soil gas diffusion coefficients (Ds/Do) are usually evaluated at the core scale. The objectives of this study were to (i) define a quantitative ‘pseudo‐macroporositygas’ from high‐resolution X‐ray computed tomography (CT) scanning images and characterize it for 10 intact soil cores, (ii) analyse the frequency distribution of pseudo‐macroporesgas in the columns with a multifractal approach and (iii) assess relationships between Ds/Do measured at the core scale and multifractal parameters describing the pore system heterogeneity within a core. The shape and symmetry of the singularity spectra and the degree of curvilinearity of the Rényi spectra show that the multifractal behaviour of the pseudo‐macroporositygas distribution for a given CT image thresholding varied among soil columns. Correlations found between Ds/Do and some parameter estimates of the singularity spectrum suggest that the distribution of pseudo‐macroporesgas, depending on the CT image thresholding, influenced Ds/Do. In particular, a strong correlation between Ds/Do and the entropy dimension (Dq = 1) indicates that Ds/Do was influenced by the degree of spatial heterogeneity of the pseudo‐macroporositygas distribution. The correlation dimension (Dq = 2) was also linked to Ds/Do, suggesting that a second‐order power law might describe the scaling relationship between pseudo‐macroporositygas distribution and Ds/Do. In conclusion, the multifractal description of soil porosity as calculated from CT images may be regarded as a way to improve our understanding of gas movement in soils at the core scale.

Diffusion-weighted MRI for detection and differentiation of musculoskeletal tumorous and tumor-like lesions in pediatric patients

MRI is the diagnostic mainstay for detection and differentiation of musculoskeletal tumors. However, a projection regarding the biological dignity of lesions based on standard MRI sequences remains difficult and uncertain. This study was undertaken to analyse whether diffusion-weighted MRI (DWI) can distinguish between benign and malignant musculoskeletal tumorous and tumor-like lesions in pediatric patients. MR examinations of 44 consecutive pediatric patients (26 girls, mean age 11±6 years) including standard sequences and DWI (b=50/800 s/mm(2)) at 1.5 or 3 Tesla were retrospectively evaluated. The study group contained 10 patients with non-treated malignant tumors and 34 patients with benign lesions. Size, relative signal intensity and apparent diffusion coefficient (ADC, unit ×10(-3) mm(2)/s) were determined in one lesion per patient. Mean ADC was 0.78±0.45×10(-3) mm(2)/s in patients with malignant tumors and 1.71±0.75 ×10(-3) mm(2)/s in patients with benign lesions (P<0.001). Relative operating characteristics (ROC) analysis showed a sensitivity of 90% and a specificity of 91% for malignancy, based on an ADC cut-off value of ≤1.03. On logistic regression, mean ADC and lesion size accounted for 62% of variability in benign vs. malignant tumors. For malignant tumors, the signal intensity ratio was higher on DWI than on T1w post-contrast images (P<0.002). Two cases of local tumor recurrence were diagnosed by DWI only. DWI shows promising results for determination of biological dignity in musculoskeletal tumors. Mean ADC ≤1.03×10(-3) mm(2)/s is a strong indicator of malignancy at the first diagnosis. The use of DWI for early diagnosis of tumor recurrence in comparison with standard MRI sequences should be evaluated in prospective studies.

신경망 이론을 이용한 염소이온 겉보기 확산계수 추정 및 이를 이용한 염화물 해석

염화물 이온은 콘크리트 내부로 유입되어 철근부식을 야기하므로 염화물 침투 평가는 매우 중요하다. 전기영동실험을 통한 촉진확산계수가 현실적으로 많이 쓰이고 있지만, 이는 자유염화물 이온에 대한 전기장 내의 이온속도를 나타낼 뿐이므로 염화물량에 대한 명확한 해를 제공하지 못한다. 겉보기 확산계수는 단순한 Fick의 이론을 배경으로 엔지니어에게 전염화물의 확산을 명확하게 제공할 수가 있다. 이 연구는 인공신경망이론을 이용하여 최적의 확산계수를 도출하고 시간의존성 확산계수를 이용하여 염화물 침투를 평가할 수 있는 기법을 제시하는 것이다. 이를 위해 기존의 연구에서 30개의 배합 및 염소이온 겉보기 염화물 확산계수를 인용하였으며, 배합인자(물결합재비, 단위시멘트량, 슬래그, 플라이애쉬, 실리카퓸, 단위 잔골재 및 굵은 골재)를 뉴런으로 선택하여 확산계수에 대한 학습을 훈련하였다. 또한 시간의존성 확산계수를 고려하여 단순한 Fick 법칙으로 염화물 침투를 평가할 수 있는 기법을 제시하였다. 장기침지실험 및 실태조사 결과를 이용하여 제안된 기법의 결과와 비교를 수행하였으며, 그 적용성을 평가하였다. 이 기법은 다양한 배합 및 관련 확산계수의 입수 및 학습을 통하여 더욱 합리적인 기법으로 발전할 수 있다.

Calculation of effective diffusion coefficient in a colloidal crystal by the finite-element method

The work is devoted to the calculation of effective diffusion coefficient of ions from the bulk solution to the electrode through a mask and the calculation of the distribution of the limiting current density over the electrode surface. A colloidal crystal, which is formed by orderly arranged monodispersed spherical particles, serves as a mask. It is shown that the diffusion of electroactive ions in the pores between spherical particles can be simulated by unit cells with rhombic, rectangular, or triangular cross-section. In the latter case, the cell side surface has no periodical boundaries. This simplifies significantly the numerical solution of the Laplace’s equation by the finite-element method. The effective diffusion coefficient in the bulk colloidal crystal is calculated at various values of its porosity. The calculated results agree well with the literature data. It is found that, for close-packed spherical particles, the relative effective diffusion coefficient in the bulk colloidal crystal is 0.16. The thicknesses of transient zones adjacent to the electrode surface and outer boundary of colloidal crystal and the effective diffusion coefficients for these zones are determined. The dependence of effective diffusion coefficient on the number of spherical particle layers in the colloidal crystal is obtained. The distribution of the limiting current density over the electrode surface is analyzed at various numbers of particle layers.

Gene interference regulates aquaporin-4 expression in swollen tissue of rats with cerebral ischemic edema: Correlation with variation in apparent diffusion coefficient.

To investigate the effects of mRNA interference on aquaporin-4 expression in swollen tissue of rats with ischemic cerebral edema, and diagnose the significance of diffusion-weighted MRI, we injected 5 μL shRNA- aquaporin-4 (control group) or siRNA- aquaporin-4 solution (1:800) (RNA interference group) into the rat right basal ganglia immediately before occlusion of the middle cerebral artery. At 0.25 hours after occlusion of the middle cerebral artery, diffusion-weighted MRI displayed a high signal; within 2 hours, the relative apparent diffusion coefficient decreased markedly, aquaporin-4 expression increased rapidly, and intracellular edema was obviously aggravated; at 4 and 6 hours, the relative apparent diffusion coefficient slowly returned to control levels, aquaporin-4 expression slightly increased, and angioedema was observed. In the RNA interference group, during 0.25–6 hours after injection of siRNA- aquaporin-4 solution, the relative apparent diffusion coefficient slightly fluctuated and aquaporin-4 expression was upregulated; during 0.5–4 hours, the relative apparent diffusion coefficient was significantly higher, while aquaporin-4 expression was significantly lower when compared with the control group, and intracellular edema was markedly reduced; at 0.25 and 6 hours, the relative apparent diffusion coefficient and aquaporin-4 expression were similar when compared with the control group; obvious angioedema remained at 6 hours. Pearson's correlation test results showed that aquaporin-4 expression was negatively correlated with the apparent diffusion coefficient (r = −0.806, P < 0.01). These findings suggest that upregulated aquaporin-4 expression is likely to be the main molecular mechanism of intracellular edema and may be the molecular basis for decreased relative apparent diffusion coefficient. Aquaporin-4 gene interference can effectively inhibit the upregulation of aquaporin-4 expression during the stage of intracellular edema with time-effectiveness. Moreover, diffusion-weighted MRI can accurately detect intracellular edema.

COLLISION EFFICIENCY OF BROWNIAN COAGULATION FOR NANOPARTICLES TAKING INTO ACCOUNT THE SLIP BOUNDARY CONDITION ON THE PARTICLE SURFACE

The collision efficiency of Brownian coagulation for monodisperse nanoparticles is considered. A new expression for friction coefficient of particle pair is proposed based on an assumption from a statistical point of view and the relative diffusion coefficient is thus be modified in order to take into account this influence as well as the effects of slip. The modified diffusion coefficient increases the collision efficiency to some extent as expected whether van der Waals interparticle potential is considered or not. A comparison with experimental measurements shows the accuracy of the results predicted by modified theory and the necessity of considering the decrease of friction coefficient due to the random motion of nanoparticles as well as the slip effects arising from the finite mean free path of gas molecules.

Gas transport properties of compost–woodchip and green waste for landfill biocovers and biofilters

Because methane is a potent greenhouse gas emitted from landfills, there is considerable interest in landfill cover materials and biofilters for methane oxidation. Compost and green waste are used as biocovers and biofilters, but the gas transport properties of these materials are not well understood. Large wood particles and high organic matter content are typical for compost and green waste, which will affect air-filled porosity (ɛ), relative gas diffusion coefficient (Dp/D0) and air permeability (ka).Gas transport properties were measured for compost with wood particles >4mm (compost–woodchip) and green waste using repacked samples and intact cores, collected from a landfill biocover and biofilters. The widely used Millington–Quirk model predicted Dp/D0 poorly, particularly for dry conditions (ɛ>0.60). Models that assumed an inactive air-filled pore space through which gases cannot diffuse fitted Dp/D0 data much better: the Troeh model was best with root mean square error three to four times smaller than the Millington–Quirk model. Several models were evaluated for describing ka data, but none were able to match the highly variable data trends well. In some intact cores the relationships between Dp/D0 and ɛ, and ka and ɛ suggested the existence of dual-domain porous media with macropores. By examining gas transport properties of compost samples with and without wood particles, wood particles >4mm were found to increase the total porosity from 0.49 to 0.79 and ka by as much as two orders of magnitude, while Dp/D0 were altered by less than 40%.

An integrated approach to optimizing skin delivery of cosmetic and pharmaceutical actives

The academic literature on skin delivery provides countless examples of scientific insights into specific aspects of the overall process. For the practical formulator, however, it is difficult to know how to combine such insights in a way that fits into the realities of commercial formulations. In this study, five key principles are combined into an integrated approach that can be applied to real-world formulations. Given the complexities of skin science, the integrated approach cannot be expected to be highly precise. Instead, it is intended as a way for a formulation team to balance the many conflicting issues. The predictions are sufficiently specific to be examined by those with the appropriate analytical resources and data on formulation efficacy. It is hoped that such challenges will allow the approach to be refined for the future.

Computational Modeling of Protein Dynamics in Eukaryotic Cells

Proteins have important functions inside the cell, traveling diffusively or being actively transported to various cellular sites where their activity is needed. Protein motion in the cellular environment is therefore an important topic to understand. However, the cell provides a very complex environment for that motion, which poses problems especially for any modeling effort designed to interpret experimentally observed features. So as to gain a realistic picture of protein dynamics inside the cell, we have recently introduced advanced numerical methods for describing that dynamics [1]. The starting point is an accurate numerical duplicate of the cell determined by LSCM, which can be used as a simulation geometry. Interpreting the internal cellular structures that obstruct the protein motion as the solid component of a porous structure, and treating the motion in the same way as in the case of a porous medium (distinction between effective and apparent diffusion), we can rather accurately take into account the cellular environment in which the motion takes place. The numerical simulations of protein motion in the model cell are based on the lattice-Boltzmann method. Here we use these methods to exactly reproduce photobleaching experiments on the diffusion of Enhanced Yellow Fluorescent Protein (EYFP) in HeLa cells. Comparison of simulated and real experiments can be used to characterize protein motion and the related diffusion coefficients. We pay particular attention to the nuclear translocation of EYFP in these cells.[1] Kuhn T., Ihalainen T. O., Hyvaluoma J., Dross N., Willman S. F., Langovski J., Vihinen-Ranta M. and Timonen J. 2011 Protein Diffusion in Mammalian Cell Cytoplasm. PLoS ONE 6(8): e22962.