The competing roles of extensional viscosity and normal stress differences in complex flows of elastic liquids

Walters, K.,Tamaddon-Jahromi, H.R.,Webster, M.F.,Tome, M.F.,McKee, S. The Korean Society of Rheology 2009 Korea-Australia rheology journal Vol.21 No.4

In various attempts to relate the behaviour of highly-elastic liquids in complex flows to their rheometrical behaviour, obvious candidates for study have been the variation of shear viscosity with shear rate, the two normal stress differences $N_1$ and $N_2$, especially $N_1$, and the extensional viscosity $\eta_E$. In this paper, we shall be mainly interested in 'constant-viscosity' Boger fluids, and, accordingly, we shall limit attention to $N_1$ and $\eta_E$. We shall concentrate on two important flows - axisymmetric contraction flow and "splashing" (particularly that which arises when a liquid drop falls onto the tree surface of the same liquid). Modern numerical techniques are employed to provide the theoretical predictions. It is shown that the two obvious manifestations of viscoelastic rheometrical behaviour can sometimes be opposing influences in determining flow characteristics. Specifically, in an axisymmetric contraction flow, high $\eta_E$ can retard the flow, whereas high $N_1$ can have the opposite effect. In the splashing experiment, high $\eta_E$ can certainly reduce the height of the so-called Worthington jet, thus confirming some early suggestions, but, again, other rheometrical influences can also have a role to play and the overall picture may not be as clear as it was once envisaged.

Serum Resistant and Enhanced Transfection of Plasmid DNA by PEG-Stabilized Polyplex Nanoparticles of L-Histidine Substituted Polyethyleneimine

Haniye Najafi,Ali Mohammad Tamaddon,Samira Sadat Abolmaali,Bahareh Owrangi,Younes Ghasemi 한국고분자학회 2015 Macromolecular Research Vol.23 No.7

To improve transfection of plasmid DNA as well as serum protein stability of polyionic complex nanoparticles of branched polyethyleneimine (bPEI), poly(ethylene glycol) (PEG)-stabilized nanoparticles were made from L-histidine substituted bPEI (PEI-Histidine) synthesized by Fmoc chemistry. The polymer was characterized by TNBS assay, 1H NMR, GFC, potentiometric titration and elemental analysis of carbon and nitrogen, DNA condensation, and the stability against extracellular matrix (heparin sulfate) was investigated by dye exclusion and agarose gel retardation assays. The nanoparticles were characterized by dynamic light scattering-zeta potential analyzer. Cytotoxicity and expression of enhanced green fluorescent protein (EGFP) were determined in hepatocellular carcinoma by MTT assay and fluorescent techniques. PEI-Histidine showed a reduced pKa without any significant loss of total primary amines. Plasmid DNA was condensed almost thoroughly with PEGylated polymers, either bPEI or PEI-Histidine, at lower critical N/P ratios. PEGylated PEI-Histidine showed the better resistance to heparin induced displacement and the lower cytotoxicity when it was compared to bPEI. Interestingly unlike bPEI, smaller and less positively charged nanoparticles were obtained from PEGylated PEI-Histidine at N/P ratio=2 that resulted in about 4 folds higher EGFP expression than bPEI without any significant cytotoxicity. These properties are consistent with the higher serum protein resistance and buffer capacity of PEGylated PEI-Histidine at endosomal acidic pH.

The competing roles of extensional viscosity and normal stress differences in complex flows of elastic liquids

K. Walters,H.R. Tamaddon-Jahromi,M.F. Webster,M.F. Tomé,S. McKee 한국유변학회 2009 Korea-Australia rheology journal Vol.21 No.4

In various attempts to relate the behaviour of highly-elastic liquids in complex flows to their rheometrical behaviour, obvious candidates for study have been the variation of shear viscosity with shear rate, the two normal stress differences N1 and N2, especially N1, and the extensional viscosity ηE. In this paper, we shall be mainly interested in ‘constant-viscosity’ Boger fluids, and, accordingly, we shall limit attention to N1 and ηE. We shall concentrate on two important flows - axisymmetric contraction flow and “splashing” (particularly that which arises when a liquid drop falls onto the free surface of the same liquid). Modern numerical techniques are employed to provide the theoretical predictions. It is shown that the two obvious manifestations of viscoelastic rheometrical behaviour can sometimes be opposing influences in determining flow characteristics. Specifically, in an axisymmetric contraction flow, high ηE can retard the flow, whereas high N1 can have the opposite effect. In the splashing experiment, high ηE can certainly reduce the height of the so-called Worthington jet, thus confirming some early suggestions, but, again, other rheometrical influences can also have a role to play and the overall picture may not be as clear as it was once envisaged.

Novel Tm(III) Membrane Sensor Based on 2,2'-Dianiline Disulfide and Its Application for the Fluoride Monitoring of Mouth Wash Preparations

Ganjali, Mohammad Reza,Norouzi, Parviz,Tamaddon, Atefeh,Husain, Syed Waqif Korean Chemical Society 2006 Bulletin of the Korean Chemical Society Vol.27 No.9

In this work the construction of a novel poly(vinyl chloride) membrane sensor based on 2,2'-dianiline disulfide (DADS) as a neutral carrier, o-nitrophenyloctyl ether (NPOE) as a plasticizer and sodium tetraphenyl borate (NaTPB) as an anionic site with unique selectivity towards Tm(III) ions is reported. The electrode has a linear dynamic range between $1.0\;{\times}\;10^{-6}$ and $1.0\;{\times}\;10^{-2}$ M, with a nice Nernstian slope of 19.5 ${\pm}$ 0.3 mV per decade and a detection limit of $4.0\;{\times}\;10^{-7}$ M at the pH range of 4.8-8.5. It has a very fast response time (<15 s) in the whole concentration range, and can be used for at least 4 weeks without any considerable divergence in the electrode potentials. The proposed sensor revealed comparatively good selectivity with respect to most common metal ions, and especially lanthanide ions. It was used as an indicator electrode in the potentiometric titration of Tm(III) ions with EDTA and in direct determination of concentration of Tm(III) ions in binary mixtures. It was also applied in determination of fluoride ions in mouth wash preparations.

Novel Tm(III) Membrane Sensor Based on 2,2'-Dianiline Disulfide and Its Application for the Fluoride Monitoring of Mouth Wash Preparations

Mohammad Reza Ganjali*,Parviz Norouzi,Atefeh Tamaddon,Syed Waqif Husain 대한화학회 2006 Bulletin of the Korean Chemical Society Vol.27 No.9

In this work the construction of a novel poly(vinyl chloride) membrane sensor based on 2,2'-dianiline disulfide (DADS) as a neutral carrier, o-nitrophenyloctyl ether (NPOE) as a plasticizer and sodium tetraphenyl borate (NaTPB) as an anionic site with unique selectivity towards Tm(III) ions is reported. The electrode has a linear dynamic range between 1.0 10-6 and 1.0 10-2 M, with a nice Nernstian slope of 19.5 0.3 mV per decade and a detection limit of 4.0 10-7 M at the pH range of 4.8-8.5. It has a very fast response time (<15 s) in the whole concentration range, and can be used for at least 4 weeks without any considerable divergence in the electrode potentials. The proposed sensor revealed comparatively good selectivity with respect to most common metal ions, and especially lanthanide ions. It was used as an indicator electrode in the potentiometric titration of Tm(III) ions with EDTA and in direct determination of concentration of Tm(III) ions in binary mixtures. It was also applied in determination of fluoride ions in mouth wash preparations.

Numerical simulation of tube-tooling cable-coating with polymer melts

A. Al-Muslimawi,H.R. Tamaddon-Jahromi,M.F. Webster 한국유변학회 2013 Korea-Australia rheology journal Vol.25 No.4

This study investigates the numerical solution of viscous and viscoelastic flows for tube-tooling die-extrusion coating using a hybrid nite element/nite volume discretisation (fe/fv). Such a complex polymer melt extrusion-draw-coating flow displays a dynamic contact line, slip, die-swell and two separate free-surfaces, presenting an inner and outer conduit surface to the melt-coating. The practical interest lies in determining efficient windows for process control over variation in material properties, stressing levels generated and vacuum pressure levels imposed. The impact of shear-thinning is also considered. Extensive reference is made throughout to viscous inelastic counterpart solutions. Attention is paid to the influence and variation in relevant parameters of Weissenberg number (We), solvent-fraction (β) and second normal difference (N2) (ξ parameter for EPTT). The impact of model choice and parameters upon field response is described in situ through, pressure-drops, rates of deformation and stress. Various numerical alternative strategies, their stability and convergence issues are also addressed. The numerical scheme solves the momentum-continuity-surface equations by a semi-implicit time-stepping Taylor-Galerkin/pressure-correction (TGPC) finite element (parent-cell) method, whilst invoking a sub-cell cell-vertex fluctuation distribution finite volume scheme for the constitutive stress equation. The hyperbolic aspects of the constitutive equation are addressed discretely through upwind Fluctuation Distribution techniques, whilst temporal and source terms are consistently accommodated through medium-dual-cell schemes. The dynamic solution of the moving boundary problem may be resolved by either separating the solution process for each free-surface section (decoupling), or coupling both sections and solving simultaneously. Each involves a surface height location method, with dependency on surface nodal velocities and surface element sections; two such schemes are investigated. Dedicated and localised shock-capturing techniques are introduced to handle solution singularities as disclosed by die-swell, slip and moving contact lines.

In-situ nanomicelle forming microneedles of poly NIPAAm-b-poly glutamic acid for trans-scleral delivery of dexamethasone

Vahid Alimardani,Samira Sadat Abolmaali,Gholamhossein Yousefi,Mohammad Hossein Nowroozzadeh,Ali Mohammad Tamaddon 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.119 No.-

Dissolving microneedles (dMNs) are proving to be attractive minimally invasive ophthalmic delivery systemsowing to their superior ability to deliver a variety of therapeutic agents through the cornea or sclera. Nevertheless, dMN formulation is most often complicated when poorly water-soluble drugs are used,because dMNs usually contain water-soluble polymers that dissolve quickly in ocular tissues. Here, wesynthesized the thermosensitive in-situ micelle-forming poly (N-isopropyl acrylamide)-b-poly (lglutamicacid) (PNIPAAm-b-PGA) copolymer which was soluble in organic and aqueous solvents, makingit possible to prepare MNs containing hydrophilic drugs. After full characterization of the copolymer, itwas successfully used to fabricate dMNs using the micro-molding technique. Remarkably, they generatedin-situ nanomicelles (NMCs) with sizes below 100 nm allowing for efficient dexamethasone (DEX) encapsulation. In this regard, the concentration of PNIPAAm-b-PGA copolymer was optimized to producemicroneedles with acceptable properties. A series of characteristics were assessed for microneedles,including mechanical and insertion properties, drug loading, in vitro release behavior, and in vitro permeation. Overall, the findings indicated that poly PNIPAAm-b-PGA copolymer is capable of self-assemblinginto NMCs and can significantly incorporate DEX as a hydrophobic drug, improving the trans-scleral DEX)permeation across the sclera, making it a promising system for treating posterior ocular diseases.