Wear-Resistant composite coatings with increased chemical resistance,produced by electrodeposition on a cathode

The formation and properties of coatings produced by electrodeposition on a cathode on the basis of an amine-containing oligomeric film-forming?ent modified with highly dispersed polytetrafluoroethylene, polyphenylene sulfide, and fluorine rubber were studied. A procedure is suggested for introduction of powdered polyphenylene sulfide into a formulation for cathodic electrodeposition. It was found that polyphenylene sulfide and polytetrafluoroethylene form a separate phase in a coating; during electrodeposition on a cathode, fluorine rubber SKF-264B enters into a chemical interaction with the amine-containing oligomeric film-forming agent; a scheme of this interaction is suggested. A formulation was created with a triple modification of the amine-containing oligomeric film-forming agent with polytetrafluoroethylene, polyphenylene sulfide, and fluorine rubber. This formulation forms a wear-resistant coating with increased chemical and corrosion resistance.     

Interfacial Activity of Phosphonated-PEG Functionalized Cerium Oxide Nanoparticles

In a recent publication, we have highlighted the potential of phosphonic acid terminated PEG oligomers to functionalize strong UV absorption cerium oxide nanoparticles, (1) which yield suspensions that are stable in aqueous or organic solvents and are redispersible in different solvents after freeze-drying. In the present work, we highlight the interfacial activity of the functional ceria nanoparticles and their potential to modify hydrophobic surfaces. We first investigated the phosphonated-PEG amphiphilic oligomers behavior as strong surface active species forming irreversibly adsorbed layers. We then show that the oligomers interfacial properties translate to the functional nanoparticles. In particular, the addition of a small fraction of phosphonated-PEG oligomers with an extra C16 aliphatic chain (stickers) into the formulation enabled the tuning of (i) the nanoparticles adsorption at the air/water, polystyrene/water, oil/water interfaces and (ii) the particle/particle interaction in aqueous solutions. We also found that dense and closely packed two-dimensional monolayers of nanoceria can be formed by spontaneous adsorption or surface compression using a Langmuir trough. A hexagonal organization controlled by reversible and repulsive interaction has been characterized by GISAXS. Mono- or multilayers can also be stably formed or transferred on solid surfaces. Our results are key features in the field of polymer surface modification, solid-stabilized emulsions (Pickering), or supracolloidal assemblies.     

Poly(ether ester amide) microspheres for protein delivery: influence of copolymer composition on technological and biological properties

The production of PEEA microspheres with potential as carriers for protein oral delivery is described. PEEAs with different hydrophilicity were synthesized and characterized. Experiments showed that an increase in copolymer hydrophilicity gave particles less prone to cell interaction. BSA release profiles from PEEA microspheres demonstrated that an increase in polymer hydrophilicity was useful in limiting protein burst and modulating drug delivery rate by increasing PEEA degradability. These results show that fine-tuning of the hydrophilic/hydrophobic properties of PCL is essential for the formulation protein-loaded microspheres with specific properties.     

Transport of biomolecules in asymmetric nanofilter arrays

We propose a theoretical model for describing the electric-field-driven migration of rod-like biomolecules in nanofilters comprising a periodic array of shallow passages connecting deep wells. The electrophoretic migration of the biomolecules is modeled as transport of point-sized Brownian particles, with the orientational degree of freedom captured by an entropy term. Using appropriate projections, the formulation dimensionality is reduced to one physical dimension, requiring minimal computation and making it ideal for device design and optimization. Our formulation is used to assess the effect of slanted well walls on the energy landscape and resulting molecule mobility. Using this approach, we show that asymmetry in the well shape, such as a well with one slanted and one vertical wall, may be used for separation using low-frequency alternating-current fields because the mobility of a biomolecule is different in the two directions of travel. Our results show that, compared to methods using direct-current fields, the proposed method remains effective at higher field strengths and can achieve comparable separation using a significantly shorter device.     

Response surface methodology (RSM) of chicken skin gelatin based composite films with rice starch and curcumin incorporation

This study aims to optimize the formulation of composite films based on chicken skin gelatin with incorporation of rice starch (10–20%, w/w) and curcumin (0.03–0.10%, w/v). The effect of their interaction on film's tensile strength (TS), elongation at break (EAB), water vapor permeability (WVP) and antioxidant properties (DPPH%) were investigated using a response surface methodology-central composite design (RSM-CCD). The optimized film formulation was further validated to indicate the validity of the prediction model. The optimum conditions of the film were selected with incorporation of rice starch at 20% (w/w) and curcumin at 0.03% (w/v). The optimized film formulation has revealed better mechanical properties with low WVP value and good antioxidant activity. The results showed that optimized composite films formulation based on chicken skin gelatin with the incorporation of rice starch and curcumin has proving good validation of model prediction and can be effectively utilized in food packaging industry.     

A residue-pairwise generalized born scheme suitable for protein design calculations

We describe an efficient generalized Born (GB) approximation for proteins, in which the interaction energy between two amino acids depends on the whole protein structure, but can be accurately computed from residue-pairwise information. Two results make the scheme pairwise. First, an accurate expression exists for the interaction energy between two residues R and R' that depends on the product B = BRBR' of their residue Born solvation radii. Second, this expression is accurately fitted by a parabolic function of B; the (three) fitting coefficients depend only on the pair RR', not on its environment. In effect, the quantity B captures all the information that is relevant about the pair's dielectric environment. The method is tested with calculations on several hundred structures of the proteins trpcage, BPTI, ubiqutin, and thoredoxin. It yields solvation energies in better agreement with Poisson calculations than a traditional GB formulation. We also compute the effect of the protein/solvent environment on the interactions between pairs of charged residues in the active site of the enzyme aspartyl-tRNA synthetase. Our method captures this effect as accurately as traditional GB. Because it is residue-pairwise, the method can be incorporated into efficient protocols for rotamer placement and computational protein design.     

Role of surface-exposed charged basic amino acids (Lys,Arg) and guanidination in insulin on the interaction and stability of insulin–insulin receptor complex

Naturally occurring proteins are emerging as novel therapeutics in the protein-based biopharmaceutical industry for the treatment of diabetes and obesity. However, proteins are not suitable for oral delivery due to short half-life, reduced physical and chemical stability and low permeability across the membrane. Chemical modification has been identified as a formulation strategy to enhance the stability and bioavailability of protein drugs. The present study aims to study the effect of charge-specific modification of basic amino acids (Lys, Arg) and guanidination on the interaction of insulin with its receptor using molecular modelling. Our investigation revealed that the guanidination of insulin (Lys-NHC = NHNH₂) enhanced and exerted stronger binding of the protein to its receptor through electrostatic interaction than native insulin (Lys-NH₃⁺). Point mutations of Lys and Arg (R22, K29; R22K, K29; R22, K29R; R22K, K29R) were attempted and the effects on the interaction and stability between insulin/modified insulins and insulin receptor were also analyzed in this study. The findings from the study are expected to provide a better understanding of the possible mechanism of action of the modified protein at a molecular level before advancing to real experiments.     

Polymeric eye films based on polyvinyl alcohol and arabinogalactan with levofloxacin

Physicochemical methods were used to study the interaction of arabinogalactan from Siberian larch with the antibacterial preparation levofloxacin. Polymeric eye films with controllable output of the medicinal preparation were produced on the basis of an arabinogalactan-polyvinyl alcohol formulation. A high pharmaceutical activity of the new eye films was demonstrated.     

Stearic Acid and Glyceryl Monostearate Based Self-Assembled Vesicles: Preparation and In vitro Evaluation

The objective of the present investigation was to study the spontaneous self-assembling behavior of stearic acid in the presence of its monoglyceride and to evaluate its potential to be used as drug delivery vehicle. The interesting feature of this system lies in spontaneous formation of vesicles on hydration of molten mixture of stearic acid (SA) and glyceryl monostearate (GMS) without using any solvent. The 1H NMR spectrum of a sample was devoid of signals from fatty acid side chain protons, suggesting that upon interaction between SA and GMS, it adopts an orientation in which fatty acid side chains exists in hydrophobic domains separated from hydrophilic headgroup. A single endothermic event of optimized formulation was obtained as the inflection point of the jump heat capacity at 57°C. To evaluate its feasibility to be used as drug delivery vehicle, ciprofloxacin HCl (CFn) was chosen as a model drug. The entrapment efficiency of CFn was found to be 13 ± 3% and 32 ± 4.2% when the formulation was prepared at pH 5.5 and 9.5, respectively. When viewed through polarizing filter, discernible Maltese cross was observed describing bilayer structure. The viscosity profile demonstrates that the both of the formulation follow Newtonian flow. The size of the vesicles was found to be in the range of 1–3 µm. In a 24 hours study period the VES-1c and VES-2c formulation released 95.8% and 82.3% of the drug, respectively. The formulation was found to be resistant towards osmotic stress. These formulations were found to be biocompatible when studied against J774 macrophages.     

Evaluation of thermal stability of enalapril maleate tablets using thermogravimetry and differential scanning calorimetry

Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used in order to evaluate the thermal stability of an enalapril maleate formulation packaged in two types of packaging, polyvinyl chloride/aluminum blister and aluminum strip. Enalapril and the excipients employed in the formulation were also evaluated by TG and DSC. Tablets were analyzed before and after storage in an acclimatized room at 40 °C and relative humidity of 75 % for 90 days. The DSC and TG results were compared with the results of dosage of enalapril and related compounds obtained by high-performance liquid chromatography. These results indicate an occurrence of chemical interaction between enalapril maleate and the excipients during its storage. After storage, it was observed that the enalapril content reduced and the predominant degradation product was diketopiperazine for both types of packaging. The predominance of diketopiperazine could be related to the absence of sodium bicarbonate in the tablets, alkalinizing agent employed in the thermal stabilization of the drug.     

A two-chromophore model for two-photon circular dichroism

A discussion of two-photon circular dichroism due to dissymmetrically placed chromophores is presented. Using quantum electrodynamics, expressions are derived for the differential rates or absorption associated with an electronic transition which is electric dipole forbidden to a one-photon interaction. A complex field formulation enables effective interaction operators to be derived which are formally equivalent to those arising in the theory of induced circular dichroism. For non-equivalent chromophores, it is shown that a coupling mechanism provides the necessary chiral discrimination, whilst for equivalent chromophores there is an additional contribution from an interference term which becomes more important as the chromophore separation is decreased.     

Exploration of the effects of chloride ions on the analysis of polar compounds at low concentrations by hydrophilic interaction liquid chromatography coupled to a charged aerosol detector: Application to tromethamine

In this study, we discuss the origin of the slightly increased response of the charged aerosol detector when low-concentration polar drugs formulated with sodium chloride are analyzed by hydrophilic interaction liquid chromatography coupled to the charged aerosol detector. In the case of tromethamine mixed with saline solutions, we investigated several levels including the mobile phase, sample matrix, and detection. We show that the analysis of the rich-salted sample results in both interactions with the mobile phase modifiers and the stationary phase during the run time. With 150 mM NaCl as a compounding solution, a slight increase in the tromethamine peak area was observed (<5.5%). Our study suggests that chloride ions in excess sequentially interact firstly with the counterions from the organic modifiers and secondly with the analyte via the stationary phase and the contribution of hydrophilic interaction liquid chromatography retention mechanisms. Because of these effects, the hydrophilic interaction liquid chromatography-charged aerosol detector analysis of drugs in saline solutions requires particular attention, and a correction factor for quantitative purposes that accounts for formulation ions remains appropriate.     

Symmetric group graphical approach to the direct configuration interaction method

An approach to the configuration interaction method based on symmetric groups (SGA ) is developed. The formalism is an alternative of the unitary group approach (UGA ). In many aspects the present formulation seems to be superior to UGA . In particular, in SGA the orbital and the spin parts of the configuration state functions may be processed separately. In consequence its graphical formulation is much simpler and the coupling constant expressions are more compact than the UGA analogs. A special emphasis is put on direct CI implementations. In addition to formulas for coupling constants, explicit expressions allowing for separation of external and internal space contributions are also presented.     

Dielectric dispersion interpretation of single enzyme dynamic disorder, spectral diffusion, and radiative fluorescence lifetime

A formulation based on measurable dielectric dispersion of enzymes is developed to estimate fluctuations in electrostatic interaction energy on time scales as long as milliseconds to seconds at a local site in enzymes. Several single molecule experimental obsevations occur on this time scale, currently unreachable by real time computational trajectory simulations. We compare the experimental results on the autocorrelation function of the fluctuations of catalysis rate with the calculations using the dielectric dispersion formulation. We also discuss the autocorrelation functions of the fluorescence lifetime and of spectral diffusion. We use a previously derived relation between the observables and the electric field fluctuations and calculate the latter using dielectric dispersion data for the proteins and the Onsager regression hypothesis.     

Extended hydrodynamic approach to quantum-classical nonequilibrium evolution. I. Theory

A mixed quantum-classical formulation is developed for a quantum subsystem in strong interaction with an N-particle environment, to be treated as classical in the framework of a hydrodynamic representation. Starting from the quantum Liouville equation for the N-particle distribution and the corresponding reduced single-particle distribution, exact quantum hydrodynamic equations are obtained for the momentum moments of the single-particle distribution coupled to a discretized quantum subsystem. The quantum-classical limit is subsequently taken and the resulting hierarchy of equations is further approximated by various closure schemes. These include, in particular, (i) a Grad-Hermite-type closure, (ii) a Gaussian closure at the level of a quantum-classical local Maxwellian distribution, and (iii) a dynamical density functional theory approximation by which the hydrodynamic pressure term is replaced by a free energy functional derivative. The latter limit yields a mixed quantum-classical formulation which has previously been introduced by I. Burghardt and B. Bagchi, Chem. Phys. 134, 343 (2006).     

Rotational excitation (J = 0 → J = 2) of polar molecules in the sudden approximation

The cross section for impact excitation of J = 2 rotational levels of polar molecules in the ground state is derived in an impact parameter formulation of the sudden approximation, assuming a dipole interaction. A simple expression for the rate coefficient is given and some results for excitation of CN by protons and electrons are presented.     

Van der Waals interactions in a dielectric with continuously varying dielectric function

We formulate and evaluate the van der Waals part of the free energy due to a dielectric profile that varies continuously throughout the space between two interacting bodies. Not considering the work needed to create the inhomogeneous dielectric profile, focusing only on that part of the free energy affected by the inhomogeneity, we compare the ensuing interaction free energy with that of the original Lifshitz formulation with its step function changes at material boundaries and uniform dielectric medium. Rather than the monotonically varying attraction between like bodies given by the original formulation, the inhomogeneous continuous dielectric function leads to attractions as well as repulsions. The Lifshitz result emerges naturally in the limit of separations much larger than the thickness of the interfaces.     

Stability studies on nifedipine tablets using thermogravimetry and differential scanning calorimetry

A new formulation of nifedipine tablets was prepared. The tablets were conditioned in amber-colored glass containers and placed in a climatized room at 40 °C and relative humidity of 75% for 180 days. Differential scanning calorimetry (DSC) and Thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two well-known nifedipine degradation products. There is no evidence of interaction between nifedipine and excipients or degradation products. High performance liquid chromatography (HPLC) was used in the dosage of nifedipine tablets before and after acclimatized exposure. Results show that DSC and TG offer important data for a more detailed assessment of the stability of a pharmaceutical formulation.     

Study of the polymer concentration and polymer/crosslinker ratio effect on gelation time of a novel grafted polymer gel for water shutoff using a central composite design method

In this research article, a hydrogel was prepared by crosslinking of carboxymethyl cellulose‐g‐polyacrylamide copolymer aqueous solution with chromium(III) acetate for the purpose of a water shutoff job in the oil reservoir. The experiments were conducted to investigate the main effects of copolymer concentration and crosslinker/copolymer ratio on gelation time of the hydrogel system. Then the effects of these two factors and their interactions on the gelation time were determined by using a central composite design (CCD) of the response surface method. CCD was used to generate the quadratic mathematical model for the gelation time response as a function of copolymer concentration, crosslinker/copolymer ratio, and their interaction. Furthermore, the analysis of variance (ANOVA) was used to evaluate the quality of the quadratic model. The ANOVA result of the developed model showed that the model was highly significant. The result also showed that the crosslinker/polymer ratio had more effects on the gelation time than did the polymer concentration and their interaction. A response surface method provides an optimum gel formulation. Core flooding experiments reveal that a significant permeability reduction on the sand pack cores can be achieved at reservoir conditions, when it is treated with an optimum gel formulation. Hence, this gel system may be suitable in the water shutoff job required for enhanced oil recovery from the oil fields. Copyright © 2015 John Wiley & Sons, Ltd.