Fickian diffusion

We present a two-dimensional model for sedimentation of well-mixed weak plumes, accounting for lateral spreading of the cloud, downwind advection, increase of volumetric flux in the rising stage, and particle transport during fallout. The 17 June 1996 subplinian eruption of Ruapehu produced a bent-over plume that rose to a height of 8.5 km in a wind field with an average velocity of 24 m s À1 and generated a narrow deposit on land extending up to 200 km from vent. The sedimentation from the Ruapehu plume was dominated by coarse ash, with all the blocks and most of the lapilli falling while the plume was still rising. Particles with diameter <125 mm show three accumulation maxima, one coincident with a secondary maximum in the total tephra deposit about 150 km from the vent. Numerical modeling shows that the plume started spreading horizontally beyond about 30 km from vent. Investigations also show that Fickian diffusion can be a good approximation to the crosswind spreading of both ''vigorous'' and ''low-energy'' weak plumes, but a wide range of diffusion coefficients is to be expected, with the largest values necessary to describe the most vigorous weak plumes such as Ruapehu. One-dimensional and two-dimensional simulations show that tephra sedimentation must have been subvertical. This feature, also supported by direct observations, can be the result of the turbulence structure of the local wind field and convective instabilities, which could also have played an important role in the generation of the pronounced sinuosity shown by the Ruapehu deposit.

Nuclear magnetic resonance (n.m.r.) imaging was used to study the ingress of water into poly(tetrahydrofurfuryl methacrylate-co-hydroxyethyl methacrylate). The study offers strong evidence that the diffusion is Fickian in nature. The diffusion coefficient, D, obtained by fitting the underlying diffusion profile, attainable from the images, according to the equation for Fickian diffusion, is 1.5 x 10-11m2s-1, which is in good correlation with the value of 2.1 x 10-11 m 2 s-1, obtained from mass uptake measurements. Additionally, from the T2-weighted images, superimposed features observed in addition to the underlying Fickian diffusion profiles were shown tb h~ve a longer spin-spin relaxation time, T2. This suggests the presence of two types of water within the polymer matrix; a less mobile phase of absorbed water that is interacting strongly with the polymer matrix and a more mobile phase of absorbed water residing within the cracks observed in the environmental scanning electron micrograph.

DUMITRU NEDELCU*, LOREDANA SANTO, ANTONIO GABRIEL SANTOS , SIMONA PLAVANESCU (MAZURCHEVICI) “Gheorghe Asachi” Technical Univeristy of Iasi, Department of Machine Manufacturing and Indutrial Management,59A Mangeron Blvd., 700050, Iasi, Romania “Tor Vergata” University of Rome, Department of Industrial Engineering, Rome, Italy 3 Nova de Lisboa University, Faculty of Science and Technology, Lisbon, Portugal

We present a two-dimensional model for sedimentation of well-mixed weak plumes, accounting for lateral spreading of the cloud, downwind advection, increase of volumetric flux in the rising stage, and particle transport during fallout. The 17 June 1996 subplinian eruption of Ruapehu produced a bent-over plume that rose to a height of 8.5 km in a wind field with an average velocity of 24 m s À1 and generated a narrow deposit on land extending up to 200 km from vent. The sedimentation from the Ruapehu plume was dominated by coarse ash, with all the blocks and most of the lapilli falling while the plume was still rising. Particles with diameter <125 mm show three accumulation maxima, one coincident with a secondary maximum in the total tephra deposit about 150 km from the vent. Numerical modeling shows that the plume started spreading horizontally beyond about 30 km from vent. Investigations also show that Fickian diffusion can be a good approximation to the crosswind spreading of both ''vigorous'' and ''low-energy'' weak plumes, but a wide range of diffusion coefficients is to be expected, with the largest values necessary to describe the most vigorous weak plumes such as Ruapehu. One-dimensional and two-dimensional simulations show that tephra sedimentation must have been subvertical. This feature, also supported by direct observations, can be the result of the turbulence structure of the local wind field and convective instabilities, which could also have played an important role in the generation of the pronounced sinuosity shown by the Ruapehu deposit.

In order to analyze the effect induced by encapsulating the drug in liposomes, comparative studies were performed for control hydrogels and complex systems (the same hydrogels containing liposomes). The results showed that the use of liposomes entrapped within chitosan hydrogels allows a strong decrease of burst effect and, moreover, the mechanism of drug release is a complex Fickian diffusion, consisting of drug diffusion through the swollen hydrogel and/or water filled pores, being continuously fed by calcein loaded in liposomes.

Controlled drug release is a promising pathway of biomedicine, meant to suppress side effects with the aim of increasing patient`s comfort. A route to achieve this goal represents the encapsulation of drugs into matrixes, capable to develop physical forces, which further can control the drugs release. To this purpose, mathematical modeling is an important tool, which offers the possibility to understand the drug release mechanisms and to further design new performant systems. In this paper, a theoretical model for drug release from an amphiphilic matrix is presented. This is achieved using a conservation multifractal law of probability density followed by validation of the model. Moreover, because nonsteroidal anti-inflammatory drugs (NSAIDs), such as diclofenac, are widely used in endometriosis as painkillers for dysmenorrhea management or Asherman syndrome for reducing the endometrial inflammation, some implications of our model for drug delivery systems applied in the field of gy...

The paper describes the preparation of chitosan/gelatin hydrogels, obtained by double crosslinking with glutaraldehyde and sodium sulphate/sodium tripolyphosphate that may be used as matrices for the inclusion of drug loaded liposomes composed of phosphatidylcholine. The main objective was to create a protective layer to stabilize the liposomal surface and to prolong/control the release of drugs from such systems. Therefore, complex systems capable of prolonged drug release and controlled release kinetics were obtained. Samples consisting of different chitosan/gelatin ratios and type/amount of ionic crosslinker have been prepared and characterized. The present study shows that calcein (used as a model hydrophilic drug) release from polymeric hydrogels has been retarded from several days to weeks after calcein inclusion in small unilamellar vesicles (SUVs) and multilamellar vesicles (MLVs) entrapped subsequently in hydrogels with variable composition. The calcein release kinetics of complex systems were compared to simple systems (control hydrogels) and important changes were observed thus proving that the mechanism of the process increases in complexity. Also, it is demonstrated that liposomes' stability can be greatly improved by inclusion in polymeric matrices. Multilamellar liposomes showed a better release behaviour, which indicates that these calcein loaded vesicles remained intact to some extent after release from the matrix, due to their improved stability provided by the multiple layers. When small unilamellar liposomes were tested, calcein have been released from hydrogels predominantly in a free form (due to their unilamellarity related instability even inside the hydrogel) but in a sustained and controllable manner. The main applications of the systems obtained are in the area of drug release for tissue engineering/tissue repair (topical administration of drugs for wound therapyburns, for example). Hydrogels capable of delivering drugs over prolonged periods of time represent a step forward in wound management and many diseases that request long term and sustained delivery of drugs. These hydrogels could be used as tissue replacement or injectable depot systems in many high risk diseases including cancer.

The paper describes the preparation of chitosan/gelatin hydrogels, obtained by double crosslinking with glutaraldehyde and sodium sulphate/sodium tripolyphosphate that may be used as matrices for the inclusion of drug loaded liposomes composed of phosphatidylcholine. The main objective was to create a protective layer to stabilize the liposomal surface and to prolong/control the release of drugs from such systems. Therefore, complex systems capable of prolonged drug release and controlled release kinetics were obtained. Samples consisting of different chitosan/gelatin ratios and type/amount of ionic crosslinker have been prepared and characterized. The present study shows that calcein (used as a model hydrophilic drug) release from polymeric hydrogels has been retarded from several days to weeks after calcein inclusion in small unilamellar vesicles (SUVs) and multilamellar vesicles (MLVs) entrapped subsequently in hydrogels with variable composition. The calcein release kinetics of complex systems were compared to simple systems (control hydrogels) and important changes were observed thus proving that the mechanism of the process increases in complexity. Also, it is demonstrated that liposomes' stability can be greatly improved by inclusion in polymeric matrices. Multilamellar liposomes showed a better release behaviour, which indicates that these calcein loaded vesicles remained intact to some extent after release from the matrix, due to their improved stability provided by the multiple layers. When small unilamellar liposomes were tested, calcein have been released from hydrogels predominantly in a free form (due to their unilamellarity related instability even inside the hydrogel) but in a sustained and controllable manner. The main applications of the systems obtained are in the area of drug release for tissue engineering/tissue repair (topical administration of drugs for wound therapyburns, for example). Hydrogels capable of delivering drugs over prolonged periods of time represent a step forward in wound management and many diseases that request long term and sustained delivery of drugs. These hydrogels could be used as tissue replacement or injectable depot systems in many high risk diseases including cancer.

The extraction of red pigment and conductive matters from individual red beet tissue slices following pulsed electric field pretreatment of different durations was compared with a two dimensional bimodal Fickian diffusion model. The process appeared to be governed by two apparent diffusion coefficients, one slow and one fast. The values of these coefficients were independent of the duration of treatment, but the yield associated with each coefficient varied. Following the treatment of longest duration and treatment by freezing and thawing of the tissue, the yield from the faster diffusion coefficient accounted completely for the mass transport. The faster apparent diffusion coefficient was 2-5 times smaller than the diffusion coefficients in dilute solution.

In this paper, we propose an analyzis method for the dynamics of polymer chains, based on a Ricatti procedure induced by possible correlations through the compatibility of the thermal radiation-classical damped oscillator dynamics. Then, the quantification (radiation frecquency is directly proportional to the color temperature) and the erasure of one bit of information becomes a natural processes induced by the system structure itself. The theory has implications in the dynamics of biological structures (arhitecture of tumors, information on tumor growth and angiogenesis, etc.) in the form of Resonant Recognition Model.

titled ‘Diffusion of fluorescent insulin from an acrylic derivatised dextranconcanavalin A gel in an implantable closed loop insulin delivery device’ for poster presentation at the 41st Annual Meeting & Exposition of the Controlled Release Society, July 13 – 16, 2014, Chicago, USA Diffusion of fluorescent insulin from an acrylic derivatised dextran-concanavalin A gel in an implantable closed loop insulin delivery device D. Jacob 1 , M J Taylor, P Tomlins, T S Sahota and E Jaroszkiewicz 1 Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, the Gateway, Leicester, LE1 9BH, United Kingdom P09050910@myemail.dmu.ac.uk ABSTRACT SUMMARY The drug delivery mechanism of fluorescently labelled insulin (FITC-Insulin) from a glucose sensitive gel held in an implantable closed loop insulin delivery device was found to be diffusion controlled. The diffusion coefficient of FITC-Insulin in the gel was determined and response to glucose triggers assessed.SUMMARY...

Amoxicillin and clavulanic acid are two of the most commonly prescribed antibacterial worldwide for treating oral infectious diseases. Oral health is of big importance for well-being and general health. A few novel drug delivery systems were designed for oral treatment and prophylaxis of different diseases in the oral cavity. This work focused on the latest drug delivery development of the most common oral pathologies, namely, periodontitis, oral mucosal infections, dental caries and oral cancer. Herein we reveal the synthesis, characterization and application of chitosan nanoparticles for intracellular transport of the weakly cell-penetrating amoxicillin and clavulanic acid in order to improve their efficacy on bacterial infections.

A series of four drug release formulations based on 5-fluorouracil encapsulated into a chitosan-based matrix were prepared by in situ hydrogelation with 3,7-dimethyl-2,6-octadienal. The formulations were investigated from structural and morphological aspects by FTIR spectroscopy, polarized light microscopy and scanning electron microscopy. It was established that 5-fluorouracil was anchored into the matrix as crystals, whose dimension varied as a function of the crosslinking density. The in vitro drug release simulated into a media mimicking the physiological environment revealed a progressive release of the 5-fluorouracil, in close interdependence with the crosslinking density. In the context of Pharmacokinetics behavioral analysis, a new mathematical procedure for describing drug release dynamics in polymer-drug complex system is proposed. Assuming that the dynamics of polymer-drug system�s structural units take place on continuous and nondifferentiable curves (multifractal curves...

Controlled drug release is a promising pathway of biomedicine, meant to suppress side effects with the aim of increasing patient`s comfort. A route to achieve this goal represents the encapsulation of drugs into matrixes, capable to develop physical forces, which further can control the drugs release. To this purpose, mathematical modeling is an important tool, which offers the possibility to understand the drug release mechanisms and to further design new performant systems. In this paper, a theoretical model for drug release from an amphiphilic matrix is presented. This is achieved using a conservation multifractal law of probability density followed by validation of the model. Moreover, because nonsteroidal anti-inflammatory drugs (NSAIDs), such as diclofenac, are widely used in endometriosis as painkillers for dysmenorrhea management or Asherman syndrome for reducing the endometrial inflammation, some implications of our model for drug delivery systems applied in the field of gy...

One of the main challenges in designing a release system is the possibility to control the release rate in order to maintain it at a constant value below a defined limit, to avoid exceeding the toxicity threshold. We propose a method of overcoming this difficulty by introducing the drug into liposomes, prior to its inclusion in the hydrogel. Furthermore, a natural cross linker (as is tannic acid) is used, instead of the toxic cross linkers commonly used, thus reducing the toxicity of the release system as a whole.

Endometriosis is considered a serious public health issue because of the large number of females affected by this illness. Chronic pain management in patients with endometriosis demands new strategies to increase the life quality of these patients. The development of drug delivery systems represents a new approach in pain treatment among endometriosis patients. Diclofenac sodium, one of the most utilized nonsteroidal anti-inflammatory drugs (NSAID), has its own limitations when being used in formulas such as oral, parental, or local applications. In this paper, a series of four drug release formulations based on chitosan, 2-hydroxy-5-nitrobenzaldehyde, and diclofenac sodium salt were prepared in view of the investigation of the drug release ability. The formulations were analyzed from a morphological and supramolecular point of view by scanning electron microscopy and polarized light microscopy. The in vitro drug release ability was investigated by mimicking a physiologic environmen...

A series of four drug release formulations based on 5-fluorouracil encapsulated into a chitosan-based matrix were prepared by in situ hydrogelation with 3,7-dimethyl-2,6-octadienal. The formulations were investigated from structural and morphological aspects by FTIR spectroscopy, polarized light microscopy and scanning electron microscopy. It was established that 5-fluorouracil was anchored into the matrix as crystals, whose dimension varied as a function of the crosslinking density. The in vitro drug release simulated into a media mimicking the physiological environment revealed a progressive release of the 5-fluorouracil, in close interdependence with the crosslinking density. In the context of Pharmacokinetics behavioral analysis, a new mathematical procedure for describing drug release dynamics in polymer-drug complex system is proposed. Assuming that the dynamics of polymer-drug system�s structural units take place on continuous and nondifferentiable curves (multifractal curves...

A series of four drug release formulations based on 5-fluorouracil encapsulated into a chitosan-based matrix were prepared by in situ hydrogelation with 3,7-dimethyl-2,6-octadienal. The formulations were investigated from structural and morphological aspects by FTIR spectroscopy, polarized light microscopy and scanning electron microscopy. It was established that 5-fluorouracil was anchored into the matrix as crystals, whose dimension varied as a function of the crosslinking density. The in vitro drug release simulated into a media mimicking the physiological environment revealed a progressive release of the 5-fluorouracil, in close interdependence with the crosslinking density. In the context of Pharmacokinetics behavioral analysis, a new mathematical procedure for describing drug release dynamics in polymer-drug complex system is proposed. Assuming that the dynamics of polymer-drug system�s structural units take place on continuous and nondifferentiable curves (multifractal curves...

Endometriosis is considered a serious public health issue because of the large number of females affected by this illness. Chronic pain management in patients with endometriosis demands new strategies to increase the life quality of these patients. The development of drug delivery systems represents a new approach in pain treatment among endometriosis patients. Diclofenac sodium, one of the most utilized nonsteroidal anti-inflammatory drugs (NSAID), has its own limitations when being used in formulas such as oral, parental, or local applications. In this paper, a series of four drug release formulations based on chitosan, 2-hydroxy-5-nitrobenzaldehyde, and diclofenac sodium salt were prepared in view of the investigation of the drug release ability. The formulations were analyzed from a morphological and supramolecular point of view by scanning electron microscopy and polarized light microscopy. The in vitro drug release ability was investigated by mimicking a physiologic environment. A mathematical model, using the fractal paradigm of motion, is utilized to explain the behaviors of the drug delivery system presented in this paper. These results suggest a great potential of the proposed drug delivery system, based on chitosan and 2-hydroxy-5-nitrobenzaldehyde to improve the diclofenac sodium salt bioavailability, and it may represent a future treatment formula for endometriosis pain.

MIRELA TEODORESCU1*, LAURENCE SCHACHER2, DOMINIQUE ADOLPHE2, IRINA GRADINARU3, IRINA ZETU3, SORIN STRATULAT3 1Institute of Macromolecular Chemistry Petru Poni Iasi, 41A Aleea Grigore Ghica Voda, 700487, Iasi, Romania 2Laboratoire de Physique et Mécanique Textiles EAC 7189 CNRS/UHA,ENSISA, 11 rue Alfred Werner F-68093 Mulhouse Cedex France 3„Gr. T. Popa” University of Medicine and Pharmacy of Iasi, Faculty of Dental Medicine, 16 Universitatii Str., 700115, Iasi, Romania

VLADIMIR ALEXANDRU PAUN1, LACRAMIOARA OCHIUZ2*, MANUELA HORTOLOMEI3, ANDREEA CRETEANU2, IULIAN STOlERIU4, CRISTINA MIHAELA GHICIUC5, GEORGIANA TANASE SERBAN6, GEORGETA ZEGAN7, GABRIELA CIOCA8 1Computer Science and Systems Engineering Department, ENSTA ParisTech, France 2 Grigore T. Popa University of Medicine and Pharmacy of Iasi, Faculty of Pharmacy, Department of Pharmaceutical Technology, 16 Universitatii Str., Iasi, 700115, Romania 3 S.C. ESTER FARM Ltd., 2E Grigore Ghica Voda Str., Iasi, 700575, Romania 4 Al. I. Cuza University, Faculty of Mathematics, 11 Blvd. Carol I, 700506, Iasi, Romania 5 Grigore T. Popa University of Medicine and Pharmacy of Iasi, Faculty of Medicine, Department of Pharmacology, 16 Universitatii Str., Iasi, 700115, Romania 6 Al. I. Cuza University of Iasi, Faculty of Physics, 11 Carol I Blvd., Iasi, 700506, Romania 7 Grigore T. Popa University of Medicine and Pharmacy, Faculty of Dental Medicine, Department of Surgery, 4 Agatha Barsescu Str., 700074, Iasi...

The purpose of this study was to develop and characterize the in vitro release kinetics of erythromycin from water-in-oil microemulsion preparations for dermal application. The results obtained confirm that the waterin-oil microemulsion systems based on avocado oil can be used as incorporation and delivery systems for the topical administration of ER in the treatment of skin disorders.

VLADIMIR ALEXANDRU PAUN1, LACRAMIOARA OCHIUZ2*, MANUELA HORTOLOMEI3, ANDREEA CRETEANU2, IULIAN STOlERIU4, CRISTINA MIHAELA GHICIUC5, GEORGIANA TANASE SERBAN6, GEORGETA ZEGAN7, GABRIELA CIOCA8 1Computer Science and Systems Engineering Department, ENSTA ParisTech, France 2 Grigore T. Popa University of Medicine and Pharmacy of Iasi, Faculty of Pharmacy, Department of Pharmaceutical Technology, 16 Universitatii Str., Iasi, 700115, Romania 3 S.C. ESTER FARM Ltd., 2E Grigore Ghica Voda Str., Iasi, 700575, Romania 4 Al. I. Cuza University, Faculty of Mathematics, 11 Blvd. Carol I, 700506, Iasi, Romania 5 Grigore T. Popa University of Medicine and Pharmacy of Iasi, Faculty of Medicine, Department of Pharmacology, 16 Universitatii Str., Iasi, 700115, Romania 6 Al. I. Cuza University of Iasi, Faculty of Physics, 11 Carol I Blvd., Iasi, 700506, Romania 7 Grigore T. Popa University of Medicine and Pharmacy, Faculty of Dental Medicine, Department of Surgery, 4 Agatha Barsescu Str., 700074, Iasi...

In order to analyze the effect induced by encapsulating the drug in liposomes, comparative studies were performed for control hydrogels and complex systems (the same hydrogels containing liposomes). The results showed that the use of liposomes entrapped within chitosan hydrogels allows a strong decrease of burst effect and, moreover, the mechanism of drug release is a complex Fickian diffusion, consisting of drug diffusion through the swollen hydrogel and/or water filled pores, being continuously fed by calcein loaded in liposomes.