Calculated Diffusion Coefficients Research Articles

Maximum likelihood-based estimation of diffusion coefficient is quick and reliable method for analyzing estradiol actions on surface receptor movements.

The rapid effects of estradiol on membrane receptors are in the focus of the estradiol research field, however, the molecular mechanisms of these non-classical estradiol actions are poorly understood. Since the lateral diffusion of membrane receptors is an important indicator of their function, a deeper understanding of the underlying mechanisms of non-classical estradiol actions can be achieved by investigating receptor dynamics. Diffusion coefficient is a crucial and widely used parameter to characterize the movement of receptors in the cell membrane. The aim of this study was to investigate the differences between maximum likelihood-based estimation (MLE) and mean square displacement (MSD) based calculation of diffusion coefficients. In this work we applied both MSD and MLE to calculate diffusion coefficients. Single particle trajectories were extracted from simulation as well as from α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor tracking in live estradiol-treated differentiated PC12 (dPC12) cells. The comparison of the obtained diffusion coefficients revealed the superiority of MLE over the generally used MSD analysis. Our results suggest the use of the MLE of diffusion coefficients because as it has a better performance, especially for large localization errors or slow receptor movements.

On the calculation of chloride diffusion coefficient from the multispecies transference numbers in the standard migration test

In order to better exploit the chloride migration test on cementitious materials and the movement of ion in the migration cell and to calculate the ion diffusion coefficients from the measured currents, knowledge of the transference numbers is required. In this paper, calculations of transference numbers of the ions involved in the standard migration test are proposed. This has been achieved from a global mass balance of the ion moving in the three zones of the migration test (catholyte, anolyte and sample). The leached ions from the sample and those generated from the electrode processes were considered. The transference numbers obtained in the catholyte are 0.35; 0.25; 0.05; 0.02; 0.33 for Cl−, Na+, K+, Ca++, OH− and 0.23 for H+ in the anolyte. Those in the sample tested are 0.23; 0.11; 0.41; 0.14 and 0.11 for Cl−, Na+, K+, Ca++ and OH−, respectively. Results of ion diffusion coefficients obtained from the transference numbers varied depending on the interpretation method used; possible causes are discussed.

Elucidation of diffusion blocking effect during anomalous structural change of L12 + D022 → L12 in Ni3Al1−xVx (0.4 < x < 0.55) alloys by a first-principles calculation

The mechanical properties of Ni3Al1−xVx alloys (0.4 < x < 0.55) at elevated temperatures are deteriorated by the disappearance of D022-Ni3V regions even though two-phase equilibrium of L12-Ni3(Al, V) and D022-Ni3V is predicted from the phase diagram. This anomalous structural change of L12 + D022 → L12 stems from the stagnation of V diffusion in the L12 matrix, but the mechanism of such a “diffusion blocking effect” has not been elucidated. In this study, a first-principles calculation was employed to quantify diffusion coefficients of Al and V in stoichiometric Ni3Al and V-doped Ni3Al from the intrinsic formation energies, migration energies and activation energies required for their diffusion. The calculated diffusion coefficient of V was three orders of magnitude smaller than that of Al, and thus the shorter diffusion distance of V than the requisite diffusion length for the retention of D022 was found to be responsible for the diffusion blocking effect observed in the Ni3Al1−xVx alloys.

Evaluation of transport properties of deteriorated concrete due to calcium leaching with coupled CT image analysis and random walk simulation

Concrete may deteriorate when chronically in contact with water due to the leaching of calcium ions. This study conducted a natural diffusion test for calcium ions with a minute cylindrical specimen of 3 mm in diameter and 6 mm in height to determine leaching at 20 and 80 °C in 33 days. One piece of limestone as aggregate was inserted inside each specimen to investigate the effect of the interfacial transition zone (ITZ). Changes in mass transfer in the leaching and non-leaching regions in bulk cement paste were evaluated using synchrotron X-ray computed tomography (CT) in a micrometer order. A deeper dissolution front of Ca(OH)2 inside the specimen was observed for a higher temperature leaching test. Random walk simulation was performed to obtain diffusion parameters. Results showed that the calcium diffusion coefficient of non-deteriorated ITZ is about ten times as high as that of the non-leaching region. For the leaching region, the diffusion coefficient is about 50 times and 100 times as high as that of the non-leaching region at 20 °C and 80 °C, respectively. In addition, the Ca(OH)2 dissolution front appeared deeper inside the specimen in the direction where aggregate is close or exposed to the dissolution front because of ITZ.

Theoretical and experimental investigation of selective gas permeability in polystyrene/polyolefin elastomer/nanoclay nanocomposite films

Nanoclay (NC) has gas barrier properties that, when used in food packaging, protects food against spoilage. Moreover, food packaging frequently makes use of rigid and foamed polystyrene (PS). In this work, reactive blending in a co-rotating twin-screw extruder was used to process PS, polyolefin elastomer (POE), and NC blends, leading to microphase-separated PS/POE/NC nanocomposite films. The structural and CO2 and N2 barrier properties of the resulting films were determined. The distribution of the NC platelets in the blends was theoretically predicted using the wetting coefficients. Nearly all NC platelets were found in the PS phase, in agreement with the theoretical predictions. Moreover, the NC platelets were found to be concentrated at the interfacial zones between the polymer phases when a compatibilizer was added to the blend. Scanning electron microscopy, wide-angle X-ray scattering, and transmission electron microscopy were used to examine the microstructure of the PS/POE/NC nanocomposites. Adding NCs as a gas barrier component to the PS/POE blend resulted in a decrease in CO2 and N2 permeability. For a better understanding of the gas diffusion in the pure PS and POE, as well as PS/POE blend, molecular dynamics simulations were performed to enable the calculation of gas diffusion coefficients in the different systems. The simulation results confirmed the experimental trends observed in this work.

Phosphate aggregation, diffusion, and adsorption on kaolinite in saline solutions by molecular dynamics simulation

Large amounts of phosphates are required for the survival of cells. However, undesirable algae overgrowth requires phosphorus levels to be kept under control. For large bodies of water, cost-effective and ecosystem-friendly ways to export phosphate are needed. The use of clays appears to be the most promising method in seawater. However, for a broader application, the mechanisms of phosphate adsorption on kaolinite, the conditions for effective flocculation, and the impact of salt must first be addressed. In this study, molecular dynamics simulations are used to determine the adsorption and anchoring mechanisms of two species of phosphates that predominate at neutral pH, the dihydrogen phosphate ion H2PO4− and the hydrogen phosphate ion HPO42−, in a 1:1 ratio, on each of the three kaolinite principal planes, the basal surfaces, octahedral gibbsite (001) and tetrahedral siloxane (001¯), and the edge sites (010), in aqueous NaCl at a concentration of 0.6 M to mimic seawater. Phosphate aggregation is enhanced by Na bridges, although at very high concentrations, the number of aggregates and the size of the largest cluster decrease. Calculated diffusion coefficients for both phosphate species drop sharply in hypersaline solutions, although the decay rate is higher for the HPO42− species. Diffusion results are in close agreement with experimental data. Phosphate adsorption on kaolinite occurs in clusters. The hydrophilic surface (001) adsorbs increasing amounts of each of the phosphate species as the salt concentration increases, more HPO42− than H2PO4−. The hydrophobic (001¯) surface remains non-reactive to any species. The hydrophilic (010) edge surface increases adsorption of H2PO4− and drastically decreases that of HPO42− as salt concentration increases. Bidentate adsorption of HPO42− on the much rougher edge surface, even if saturated with adsorbed Na ions, is sterically impeded. The dominant adsorption mechanism is through cationic bridges on the gibbsite surface and at the edges. The adsorption capacity of kaolinite, including all its surfaces, increases with salt concentration, reaching its highest value in synthetic seawater. The values are of the order, although lower than the experimental ones obtained with less-accessible clays with atomic substitutions. The use of clays to control phosphate content in coastal waters is expected to contribute to public health and sustainability of marine industrial activities.

Universal approach for diffusion quantification applied to lead halide perovskite single crystals

A universal approach to calculating diffusion coefficients in lead halide perovskite single crystals, which have ionic and mixed ionic–electronic conductivity, is proposed. Using impedance spectroscopy, it is demonstrated how to model a non-ideal Warburg element and transmission line equivalent circuit to identify ionic diffusion in the material. The proposed method is applicable to samples of any thickness and electrical properties. Additionally, it is shown how to overcome the challenges of low-frequency impedance measurement and the non-ideal behavior of the elements through extrapolative modeling and approximation.

Molecular dynamics simulation of Cr-N clusters formation in high nitrogen austenitic stainless steel

The Cr2N precipitation has a prominent effect to high nitrogen austenitic stainless steel (HNASS) performance. The formation of Cr-N clusters as precursor of Cr2N phase based on a model of Cr and N along grain boundaries under aging at 1023 K were simulated using LAMMPS molecular dynamics (MD) approach. The Cr and N atoms at austenite grain boundary can aggregate into tightly structured Cr-N clusters with atomic number from 19 to 169. The variation of calculated diffusion coefficients with time suggests Cr-N clusters formation is controlled by the diffusion of Cr, N and Cr-N cluster. Furthermore, the calculated radius of pair gyration of Cr-N clusters indicates that the structural features of Cr-N clusters at grain boundaries are shifted from a chaotic distribution to more orderly structure. The mechanism on Cr-N clusters revealed by this study may be of guiding significance to the optimization design of controlling Cr2N precipitation.

Concentration and solvent effects on structural and thermodynamic properties of uranium (Ⅳ) fluoride by molecular dynamic simulation

The structural and thermodynamic properties of UF4-LiF, UF4-NaF and UF4-KF molten salts were systematically investigated by using molecular dynamic simulation with a polarizable force field, and the effects of UF4 concentration and solvent were discussed. The reliability of molecular dynamic simulation was verified by the reasonable agreements between the calculated and experimental density values of the molten salts. The calculated diffusion coefficients of U4+, Li+, Na+, K+ and F‒ in various systems all followed the form of Arrhenius equation. A linear relationship between the logarithm of viscosity and the reciprocal of temperature was observed. The association between U4+ and F‒ in UF4-KF was strongest, followed by UF4-NaF and UF4-LiF. A transition percentage of 0.3–0.4 for UF4 in mix salts should be paid attention to, which is generally used in nuclear fuel design. The enthalpy of mixing, diffusion coefficient, the radial distribution function and coordination number all showed some transition behaviors at such UF4 transition percentage.

Meningioma: Is apparent diffusion coefficient value of any importance? A study from the tertiary care center

Objectives: Meningiomas are one of the most common intracranial tumors accounting for 14–20% of all intracranial tumors. Diffusion-weighted imaging (DWI) along with the calculation of apparent diffusion coefficient (ADC) is a novel, non-invasive, and reliable technique of choice for the pre-operative assessment and the treatment planning of different types of meningiomas. Our study aimed to correlate the ADC values of meningiomas with their histopathological grade. Materials and Methods: We studied 21 patients with meningioma. These were initially diagnosed on imaging and confirmed on histopathology. We calculated the normalized ADC (NADC) values from the DWI of their lesion. NADC values and atypical morphological features were utilized to type the meningiomas as typical or atypical. These findings were correlated with histopathological reports of grading of meningioma. Results: There was no significant correlation between the grades of meningioma and the ADC values. The normalized ADC values varied from 0.14 to 1.37 × 10−3 mm2/s for Gr I meningioma in our series and most of our cases fell in this category of meningioma. We had a solitary case of Gr-II meningioma and the ADC value for this lesion was 1.26 × 10−3 mm2/s. Conclusion: Meningiomas are a common group of tumors in the brain with a quest to characterize the grades preoperatively on imaging. The NADC is a better method as compared to plain ADC values for this purpose. In our series, we did not find any correlation of NADC on pre-operative imaging to the grades of tumors.

Temporally and spatially resolved micro-rheometry of a transient viscous polymer formation

Real-time viscosity measurement techniques have been used to analyze the transition of hydrogels from a liquid state to a gel state. As viscosity is inversely proportional to diffusion coefficient, measuring real-time changes in viscosity can be done through passive rheometry with the addition of tracer particles. Particle diffusometry (PD) quantifies Brownian motion of sub-micron sized fluorescent particles by computing diffusion coefficients via statistical averaging. Herein, we demonstrate a method to study changes in diffusion coefficient as a function of time using PD for a temporally and spatially resolved rheometry measurement technique. We refined the PD algorithm using synthetic images of particles suspended in a liquid undergoing a sigmoidally decreasing diffusion trend to simulate the viscosity change of the solution during gelation. Then, the technique is applied to visualize the temporal and spatial gradients of diffusion coefficient during polyacrylamide hydrogel formation experiments. This work establishes the groundwork for quantifying over time changes in Brownian motion.

Multi-component sorption of Pb2+, Cu2+ and Ni2+ on PEI modified chitosan-based hybrid membranes

Novel poly(ethylene imine) (PEI) modified chitosan-based hybrid membranes (PMCHMs) were created via a soft chemistry method, in which unmodified chitosan (CS) firstly reacted with PEI to produce a CS-PEI precursor. Later, such CS-PEI precursor was blended with silicone to create the membrane solution of PMCHMs. Finally, PMCHMs could be obtained via phase-inversion process. Multi-component sorption of Pb2+, Cu2+ and Ni2+ on PMCHMs in metal mixed solutions, such as, Pb2+&Cu2+ and Pb2+&Ni2+ binary, Pb2+, Cu2+ and Ni2+ ternary, as well as Pb2+, Cu2+, Ni2+, Cd 2+ and Cr3+ quintuple mixed solutions, was inspected. The calculation of effective diffusion coefficients, distribution coefficients and selectivity coefficients showed that Pb2+ sorption on PMCHMs had excellent selectivity in these mixed multi-metal solutions. While, the calculation of activation energy proved that Pb2+, Cu2+ and Ni2+ sorption on PMCHMs was a physic-sorption process Also, mechanism insight reveals that Pb2+ sorption on PMCHMs could be depicted via Lagergren pseudo-2nd-order kinetic model and Langmuir or Freundlich isotherm equation. Exclusively, intra-particle diffusion process was discussed in detail. Desorption testing verified that HCl is a good desorbent for metals sorption on PMCHMs and the cycle time of membranes can arrive at 6 times. These results demonstrate that PMCHMs can be used to preferentially eradicate Pb2+ from metal mixture solutions, showing prospective applications in the treatment of metal mixture wastewater from waste vehicle power-battery and other various metal-bearing polluted water.

Morphological Effect of Side Chain Length in Sulfonated Poly(arylene ether sulfone)s Polymer Electrolyte Membranes via Molecular Dynamics Simulation.

With the recognition of the multiple advantages of sulfonated hydrocarbon-based polymers that possess high chemical and mechanical stability with significant low cost, we employed molecular dynamics simulation to explore the morphological effects of side chain length in sulfonated polystyrene grafted poly(arylene ether sulfone)s (SPAES) proton exchange membranes. The calculated diffusion coefficients of hydronium ions (H3O+) are in range of 0.61-1.15 × 10-7 cm2/s, smaller than that of water molecules, due to the electrical attraction between the oppositely charged sulfonate group and H3O+. The investigation into the radial distribution functions suggests that phase segregation in the SPAES membrane is more probable with longer side chains. As the hydration level of the membranes in this study is relatively low (λ = 3), longer side chains correspond to more water molecules in the amorphous cell, which provides better solvent effects for the distribution of sulfonated side chains. The coordination number of water molecules and hydronium ions around the sulfonate group increases from 1.67 to 2.40 and from 2.45 to 5.66, respectively, with the increase in the side chain length. A significant proportion of the hydronium ions appear to be in bridging configurations coordinated by multiple sulfonate groups. The microscopic conformation of the SPAES membrane is basically unaffected by temperature during the evaluated temperature range. Thus, it can be revealed that the side chain length plays a key role in the configuration of the polymer chain and would contribute to the formation of the microphase separation morphology, which profits proton transport in the hydrophilic domains.

Electronic property and effective diffusion coefficient calculation model of hydrogen isotopes in multicomponent steel 2.25Cr1Mo from first-principles calculations

Chrome-molybdenum (2.25Cr1Mo) ferritic steel is one of the primary materials used in heat exchanger pipes in the steam generators of high-temperature gas-cooled reactors (HTGRs). Studying the tritium diffusion mechanism in 2.25Cr1Mo ferritic steel is of vital importance for the prediction and interpretation of tritium activity concentration in the reactor. However, the permeation of hydrogen isotopes in these alloys remains difficult to predict owing to the lack of understanding of the microscopic interactions between hydrogen isotopes and multicomponent alloys. In this study, the electronic and diffusion properties of the hydrogen isotopes in 2.25Cr1Mo alloy were investigated using first-principles calculations. Hydrogen preferentially intercalated into tetrahedral interstitial sites rather than octahedral ones in 2.25Cr1Mo alloy. The Cr and Mo dopants induced strong repulsion between H and the matrix. Interaction between H and 2.25Cr1Mo exhibited a combination of ionic and covalent bonds with electrons transferred from the steel to H atom. Dopants acted as scattering centers with local interaction with H and expanded the preventive effect of H diffusion to the second-nearest tetrahedral interstitials with a high energy barrier. The effective H diffusion coefficient in the alloy was calculated by an approximate model based on the volumetric ratio of the components for the first time. The obtained pre-exponential factor and activation energy agreed well with the experimental results. The current research provides a reliable way to determine the effective diffusion coefficient of hydrogen isotopes in multielement alloys, which can accelerate R&D of tritium-resistant materials in both fusion and fission reactors.

Quantitative Interpretation of Isotope Correlation Coefficient Ratios in Solid Diffusion

The correlation coefficient f is crucial in the calculation of the absolute diffusion coefficient D, especially for the vacancy mechanism. The current study for f is complex and contains many approximations and assumptions. However, f can be ignored when considering the isotope effect, which has only been stated qualitatively by previous authors and not explained from a quantitative perspective. In this paper, we will explain the reason why f can be neglected in the isotope diffusion effect by finding the most essential formula and source of f, as a way to save the most troublesome step in the calculation of the isotope diffusion effect.

Effect of layer charge density and cation concentration on sorption behaviors of heavy metal ions in the interlayer and nanopore of montmorillonite: A molecular dynamics simulation

Soil and ground water pollution by heavy metal is an identified global environment concern. Montmorillonite is widely adopted as an adsorbent used in retardation of heavy metals due to its excellent adsorption capacity, conveniency, and stability. However, the adsorption mechanism of heavy metal ions in the interlayer and nanopore of montmorillonite needs to be further studied. The classical grand canonical monte carlo (GCMC) and molecular dynamics (MD) simulations were performed to quantify the structural and dynamic properties of heavy metal ions in the interlayer and nanopore of montmorillonite (MMT). Two layer charge densities of MMT, two cation concentrations, and three typical heavy metal ions (Pb2+, Ba2+, and Cs+) were considered. With the increase of layer charge density, outer-sphere adsorption (OSA) was transformed into inner-sphere adsorption (ISA) for three heavy metal ions. The adsorption quantity increased with the increase of layer charge density and cation concentration. The calculated diffusion coefficients of three heavy metal caions in montmorillonite was bulk solution > nanopore > interlayer. The results and adsorption mechanism are helpful for understanding the natural processes of heavy metal ions in environment and developing more efficient remediation materials.

Calculation of diffusion coefficient of liquid less simple metals

Diffusion coefficient of liquid less simple metals has been studied using linear trajectory (LT) and small-step (SS) diffusion theories of liquid metals with Carnahan–Stirling (CS) approximation. Friction coefficients, the key ingredients of this study, are calculated using effective pair potentials, v(r), and static structure factors, S(q). For v(r), Brettonet–Silbert pseudopotential model has been chosen whereas for S(q), both variational modified hypernetted chain (VMHNC) integral equation and linearized Weeks–Chandler–Andersen (LWCA) perturbation theory have been employed. Calculated friction coefficients are found comparable to the available simulated data. Inclusion of CS approximation increases the value of friction coefficient obtained from hard part which dominates over rest of the coefficients. Applied LWCA theory provides slightly larger values of diffusion coefficients than those obtained from VMHNC. Comparing with literature values, calculated results suggest that the combination of LWCA theory along with LT and SS theories with CS approximation is excellent for calculation of diffusion coefficient.

Benzoylthiourea based polymers as new binding agents for diffusive gradients in thin films technique in labile mercury determination in freshwaters

In this study, the diffusive gradient in thin film (DGT) has been developed using three new materials derived from benzoylthiourea (PBTU, BTP1 and BTP2) for the determination of bioavailable mercury (Hg). The efficiency of these DGT devices was compared with the well-established 3-mercaptopropyl functionalized silica gel (3MFS) in laboratory and field conditions. It was found that PBTU lacked of consistency for handling and assembling in the DGT device, whereas the other two polymers provided mechanically stable binding gels and extracted satisfactorily Hg. However, BTP2 showed no correlation between Hg uptake and Hg present in the aqueous solution, and therefore, BTP1 gels was chosen as the binding layer used for DGT technique. The calculated diffusion coefficient of DGT-BTP1 was 4.0 × 10 −6 cm 2 s −1 at 25 °C in 0.8 mm thick diffusion layer and 2.3% w/v of material in gel, whereas for DGT-3MFS, the D value was 9.1 × 10 −6 cm 2 s −1 . Moreover, it was found that neither the pH (range 4.5 – 9.5) nor the ionic strength (range 0.005–0.1 mol L −1 ) significantly affected the binding behavior of Hg (p > 0.05). Finally, the DGT-BTP1 devices were successfully used for in-situ measurements of Hg in Quito River (Colombia), impacted by artisanal gold mining, and were compared with DGT-3MFS. Results showed a good performance with values of the labile Hg concentration between 5 to 8% of the total Hg in water. This study demonstrates that benzoylthiourea based DGT is a useful tool for in situ monitoring of Hg in freshwaters. • Three new materials derived from benzoylthiourea were used for DGT technique. • BTP1 extracted satisfactorily Hg, with a diffusion coefficient of 4.0 × 10 −6 cm 2 s −1 . • DGT-BTP1 was suitable for aqueous solutions with a wide pH and ionic strength range. • These devices were successfully used in a Colombian river highly impacted by Hg. • Benzoylthiourea based DGT was a useful tool for in situ monitoring of Hg in freshwaters.

The N-body interatomic potentials for molecular dynamics simulations of diffusion in C15 Cr[formula omitted]Ta Laves phase

In this work, the interatomic potentials for modeling diffusion in the C15 Cr2Ta Laves phase were constructed within the N-body approach. The potential for Ta–Ta interactions reproduces the lattice parameter, cohesive energy, elastic constants, equation of state, thermal expansion, point defect energies, and phonon dispersion of body-centered cubic Ta in qualitative agreement with density functional theory (DFT) data and almost quantitative agreement with available experimental data in the temperature range of stability of C15 Cr2Ta Laves phase. The potential for Cr–Ta interactions reproduces the elastic constants, point defect properties, equilibrium volumes, and formation enthalpies of Cr–Ta structures in qualitative agreement with DFT data. Also, it reproduces the lattice stability and high-temperature formation enthalpy of C15 Cr2Ta Laves phase in very close agreement with the available experimental data. The calculations of diffusion coefficients with constructed potentials showed that diffusion in C15 Cr2Ta lattice is governed by Cr atoms which cannot move without creation of vacancies. The constructed potentials can be used in further investigations of diffusion processes in Cr–Ta phases at temperatures up to 2000 K, while the obtained results on diffusion coefficients in C15 Cr2Ta Laves phase would be useful in the rational design of Cr–Ta based alloys.

Supramolecular structure organization and rheological properties modulate the performance of hyaluronic acid-loaded thermosensitive hydrogels as drug-delivery systems

The challenges for developing new pharmaceutical formulations based on natural and synthetic polymers has led to innovation into the design of systems responsive environmental stimuli such as temperature. However, the presence of hydrophilic or hydrophobic molecules, charged groups, or metallic elements can affect their structural behavior and their biopharmaceutical performance This work aims to study and characterize the morphology and structure of polymeric formulations based on Poloxamer (PL) 407 (15 % and 30 % m/v) and its binary with PL 338 (15 % PL 407 + 15 % PL 338) and hyaluronic acid (0.5 % m/v), as drug delivery systems of local anesthetic bupivacaine (0.5 % m/v) and ropivacaine (0.5 % m/v) hydrochloride. For this, it was performed SANS analysis for determination of supramolecular organization and lattice parameters; calorimetry was done to characterize their thermodynamic parameters; rheological analysis flow curve, consistency and adhesion calculation, Maxwell model study. Also, it was performed drug release profiles and calculation of diffusion coefficients. It was identified lamellar structures in PL 407 15 % formulations, and coexistence of cubic and hexagonal phases in PL 407 30 % and binary formulations, however hyaluronic acid, bupivacaine or ropivacaine seem do not affect the type of supramolecular structure. In addition, these additives can modulate viscosity among poloxamers chains, increasing micelle-micelle interactions as it happens in presence of bupivacaine. On the other hand, addition of hyaluronic acid can promote increased structural stabilization by hydrophilic interactions between hyaluronic and micellar corona. It reflects the ability how to control the drug release, as in case of binary system that retained bupivacaine for longer time than other systems, as well it happens when hyaluronic acid is added in PL 407 15 % and PL 407 30 %.