Effect of the Drug–Excipient Ratio in Matrix-Type-Controlled Release Systems: Computer Simulation Study

The main objective of this work is to study the drug release behavior from inert matrix systems by using computer simulation. This study allowed us to propose a new statistical method to evaluate the drug percolation threshold as a function of the exposed surface area of the device. The matrix system was simulated as a simple cubic lattice. The sites of the lattice were randomly occupied at various drug–excipient ratios. By simulating a diffusive process, the drug was delivered from the matrix system. The obtained release profiles were fitted to two different models: near the excipient percolation threshold, the square root of the time was well fitted, whereas close to (but above) the drug percolation threshold, the power law described accurately the release data. A relationship between the initial drug load and the amount of drug trapped inside the matrix system at infinite time was found. This relationship was conveniently described by an error function. Percolation thresholds in the matrix systems were determined from the latter relationship by using a nonlinear regression method. The assessment of percolation thresholds depends on the exposed surface area of the matrix systems. Moreover, estimated percolation thresholds were in agreement with the predicted values stated in the percolation theory.     

Adsorption of anionic textile dye Acid Green 9 from aqueous solution onto weak or strong base anion exchangers

The aim of this work is to study the thermodynamic and kinetic studies with regard to the adsorption of Acid Green 9 (AG9) on the most efficient resin, namely, acrylic weak base anion exchange resin with ethylenediamine‐functional groups (A1) selected from several anion exchange resins. The influence of the various experimental parameters such as, pH, initial dye concentration, contact time, temperature, and adsorbent dose was investigated by batch experiments. The extent of the dye adsorption increased with the decrease of the initial dye concentration and the increase of the contact time, temperature, and amount of the adsorbent. Adsorption process was quantitative and very fast at low concentrations of the dye. To investigate the mechanism of the adsorption and potential rate‐controlling steps, pseudo first‐ and second‐order, as well as intraparticle diffusion kinetic equations have been used. The adsorption kinetic of AG9 dye from aqueous solution onto A1 could be described by the pseudo second‐order reaction model. The obtained results are in agreement with the Langmuir and Freundlich models. In the optimum conditions established, an adsorption capacity of 500 mg textile dye (72% purity) g^?1 adsorbent (at 293 K) was reached. Desorption experiments by batch and dynamic methods were performed using a solution of 0.05 mol L^?1 NaOH. A series of 13 adsorption–desorption cycles were carried out by the dynamic method with a quantitative adsorption and the desorption efficiency higher than 95%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sunflower Protein Concentrates and Isolates Prepared from Oil Cakes Have High Water Solubility and Antioxidant Capacity

Increasing the applications of industrial by-products is of great interest. Therefore, in the present study, sunflower oil cake from a local oil manufacturing company was used to obtain soluble protein concentrates and isolates with different content of phenolic compounds. All the extraction procedures evaluated resulted in concentrates and isolates with water solubility higher than 75% but with different chemical composition, color and physicochemical properties (i.e. surface hydrophobicity, thermal stability, and polypeptide composition). Since no extraction process led to a complete extraction of phenolic compounds, all the products exhibited antioxidant activity, which depended on the concentration of such compounds. Phenolic compounds give a dark color to sunflower protein concentrates and isolates; nevertheless their final color tone was more dependent on the conditions used in the preparation process than on the amount of phenolic compounds in the product. The results demonstrate the value of sunflower industrial oil cake as a source of proteins with high water solubility, good physicochemical properties and antioxidant activity.     

The study of the performance of Ni supported on gadolinium doped ceria SOFC anode on the steam reforming of ethanol

The catalytic performance of Ni/CeGd SOFC anodes prepared by co-precipitation for steam reforming of ethanol at different reaction temperatures was evaluated. The Ni/CeGd SOFC anode calcined at 1073 K exhibited the highest activity and the lowest by-products formation rates during SR at 773 K. The TG and SEM analyses of the used catalysts showed that the deactivation observed for SR at 773 K was associated with the formation of carbon filaments. It was also observed that the increase of reaction temperature from 773 to 1073 K decreased coke formation, which was no longer detected at 1073 K. This result was attributed to the reverse of the Boudouard reaction and the promoting effect of the support on carbon gasification.     

The kinetics of Maillard reaction in lactose-hydrolysed milk powder and related systems containing carbohydrate mixtures

The kinetics of Maillard reaction in lactose-hydrolysed skim milk powder and related systems containing carbohydrate mixtures were analysed. The effect of the increase of water activity and temperature during storage of the commercial product was also evaluated. In systems with two and three carbohydrates, a marked decrease of the reaction rate was observed when monosaccharides were partially replaced by lactose, notwithstanding the fact that the former still remained in a higher proportion than lysine. The rate of available lysine loss in lactose-hydrolysed milk was mostly affected by the presence of galactose. The reaction rate constants at a_w 0.52 and at 37 and 50 °C were higher than at a_w 0.33. However, no significant differences were observed at 60 °C. Temperature is the most important factor to be controlled in order to minimise nutritional deterioration during storage.     

Discrimination between defective and non-defective roasted coffees by diffuse reflectance infrared Fourier transform spectroscopy

The objective of this work was to evaluate the feasibility of employing Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for discrimination between defective and non-defective coffees after roasting and grinding. Defective (black, immature and sour) and non-defective Arabica coffee beans were submitted to light, medium and dark roasts at 220, 235 and 250 °C. Principal Components Analysis of the DRIFTS spectra (normalized or not) and of the first derivatives of the spectra provided separation of the samples into four groups: non-defective, black, dark sour and light sour, with immature beans scattered among the sour samples. Classification models were developed based on Linear Discriminant Analysis and recognition and prediction abilities of these models ranged from 95 to 100%. Such results indicate that DRIFTS presents potential for the development of a fast and reliable analytical methodology for discrimination between defective and non-defective coffee after roasting and grinding.     

Optimal design of reverse osmosis‐based water treatment systems

We address the problem of optimal design of reverse osmosis (RO)‐based water treatment systems. A superstructure optimization method is proposed to solve the problem, where the superstructure for a RO system is structurally enhanced with additional features. We formulate the problem as mixed‐integer nonlinear program which is solved to yield optimal results. A case study on desalination is considered in this work, and the numerical results obtained using our approach are validated using a commercial simulation tool. We further extend the problem by considering the effects of degradation of membrane performance over time and solve it by representing the problem as a two‐stage stochastic program. This new approach is highly useful for identifying minimum cost robust designs for membrane‐based water purification systems, which are especially important in desalination applications. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Electrodeposition of pristine and composite poly(3,4-ethylenedioxythiophene) layers studied by electro-acoustic impedance measurements

Composite layers of poly(3,4-ethylenedioxythiophene) and diamond nanoparticles were prepared by an electrocodeposition procedure from an electrolyte containing the monomer 3,4-ethylenedioxythiophene and a suspension of diamond nanoparticles in acetonitrile/water mixtures. For the in situ monitoring of the deposition process we used piezoelectric quartz crystals with gold electrodes as substrates (electrochemical quartz crystal microbalance, EQCM). The inclusion of the diamond particles increases the stiffness of the layers. This effect can be directly quantified via the electroacoustic impedance of the quartz crystal. We use a mean field model for the interpretation of our EQCM data which yields the complex shear modulus of the composite layers. The volume fraction of diamond (as determined by ex situ XPS) enters as a parameter in the evaluation procedure. Finally, we could estimate the solvent content of the composite layers and the shear moduli of the pure dry PEDOT matrix.     

Field-Synergy and Figure-of-Merit Analysis of Two Oxide–Water-Based Nanofluids' Flow in Heated Tubes

Field-synergy analysis is performed on the water–oxide nanofluid flow in circular heat sinks to examine the synergetic relation between the flow and temperature fields for heating processes. By varying the Reynolds number and the nanoparticle volume fraction, the convective heat transfer of nanofluid is investigated based on the field synergy number. For heating, the degree of synergy between the velocity and temperature fields of nanofluid flow deteriorates with the Reynolds number increase, leading to a decreased heat transfer performance of the nanofluid. By increasing the particle volume fraction, the degree of synergy between the velocity and temperature fields of the nanofluid flow can be intensified, thus going to convection heat transfer enhancement. After generating results, one can notice that the heat transfer enhancement is strongly dependent on nanoparticle type, Reynolds number, and volume fraction. The results are similar, even if the thermal conductivity of the two considered oxide nanoparticles are quite different. Additionally, a convenient figure of merit that is known as the Mouromtseff number was used as base of comparison, and the results indicated that the considered nanofluids can successfully replace water in specific applications for single-phase forced convection flow in a tube.     

Selective Enhancement of the Cell-Permeabilizing Activity of Adenylate Cyclase Toxin Does Not Increase Virulence of Bordetella pertussis

The whooping cough agent, Bordetella pertussis, secretes an adenylate cyclase toxin–hemolysin (CyaA, ACT, or AC-Hly) that catalyzes the conversion of intracellular ATP to cAMP and through its signaling annihilates the bactericidal activities of host sentinel phagocytes. In parallel, CyaA permeabilizes host cells by the formation of cation-selective membrane pores that account for the hemolytic activity of CyaA. The pore-forming activity contributes to the overall cytotoxic effect of CyaA in vitro, and it has previously been proposed to synergize with the cAMP-elevating activity in conferring full virulence on B. pertussis in the mouse model of pneumonic infection. CyaA primarily targets myeloid phagocytes through binding of their complement receptor 3 (CR3, integrin α_Mβ₂, or CD11b/CD18). However, with a reduced efficacy, the toxin can promiscuously penetrate and permeabilize the cell membrane of a variety of non-myeloid cells that lack CR3 on the cell surface, including airway epithelial cells or erythrocytes, and detectably intoxicates them by cAMP. Here, we used CyaA variants with strongly and selectively enhanced or reduced pore-forming activity that, at the same time, exhibited a full capacity to elevate cAMP concentrations in both CR3-expressing and CR3-non-expressing target cells. Using B. pertussis mutants secreting such CyaA variants, we show that a selective enhancement of the cell-permeabilizing activity of CyaA does not increase the overall virulence and lethality of pneumonic B. pertussis infection of mice any further. In turn, a reduction of the cell-permeabilizing activity of CyaA did not reduce B. pertussis virulence any importantly. These results suggest that the phagocyte-paralyzing cAMP-elevating capacity of CyaA prevails over the cell-permeabilizing activity of CyaA that appears to play an auxiliary role in the biological activity of the CyaA toxin in the course of B. pertussis infections in vivo.