Nanocomposite particles with core‐shell morphology. I. Preparation and characterization of Fe3O4–poly(butyl acrylate‐styrene) particles via miniemulsion polymerization

Colloidal particles with magnetic properties have become increasingly important both technologically and for fundamental studies. Here, chemical initiator‐free miniemulsion polymerization of styrene and butyl acrylate has been performed for preparation of magnetic nanocomposite particles with the diameter of 81–150 nm in the presence of sodium dodecyl sulfate as surfactant, span 80 as stabilizer, and hexadecane as hydrophobe. The polymerization reaction was initiated and progressed under ultrasonic irradiation, generated by immersed probe into the latex. The key point in achievement of encapsulation of modified Fe₃O₄ nanoparticles was preparation of a stable colloidal dispersion at the end of the reaction. The obtained products in each step were characterized by FTIR spectroscopy. Dynamic light scattering analysis was used to follow particle size diameter of the samples. Morphology of the particles and formation of core‐shell structure were analyzed by SEM and TEM micrographs, respectively. TGA and magnetometry of the polymeric films confirmed the extent of insertion of used magnetite and their corresponding behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Collocation with ‘adaptive’ finite elements in Buckley-Leverett problem

In solving the Buckley-Leverett problem, the use of higher order Hermitian polynomials at the frontal location and lower order ones elsewhere in the solution domain yields an enhanced frontal definition. This improvement is achieved without a significant increase in computational effort.     

Effect of pH on Properties of Poly(Vinyl Pyrrolidone) + Tri-Sodium Citrate + Guanidine Hydrochloride Aqueous Two-Phase Systems

The experimental results for liquid–liquid equilibrium of poly(vinyl pyrrolidone) (K30) + tri-sodium citrate + guanidine hydrochloride (5 and 10 w/w%) aqueous two-phase system at 25°C and different pH values (6.2, 7.4, and 10.0) were studied. The partition behavior of guanidine hydrochloride is known to be a function of several factors. Some of them such as guanidine hydrochloride concentration, pH, polymer/salt ratio (w/w), size, and slant of the tie-lines (STLs) are investigated in this study. At higher guanidine hydrochloride concentrations, the binodal was observed to displace. The behavior of the tie-line size (TLS) seems to be somehow different from the influence of the polymeric phase. The increase of GuHCl concentration decreased the STLs, but the slant and size of the equilibrium tie-lines increased with the pH of the two-phase system. The viscosity (η), density (ρ), electrical conductivity (k), and refractive index (n_D) of the poly(vinyl pyrrolidone) (K30) + tri-sodium citrate + guanidine hydrochloride + water two-phase systems versus pH were investigated. It was observed that the viscosity and density of the aqueous two-phase system is influenced by the TLS. The density changes between the phases (Δρ) and viscosity changes of the phases (Δη) increased with the increase of the TLS. It was found that linear relations exist between the TLS and the interphase density and viscosity changes.     

Flaxseed Oil Supplementation Improve Gene Expression Levels of PPAR-γ, LP(a), IL-1 and TNF-α in Type 2 Diabetic Patients with Coronary Heart Disease

This study was carried out to determine the effects of flaxseed oil administration on gene expression levels related to insulin, lipid and inflammation in overweight diabetic patients with coronary heart disease (CHD). This randomized double‐blind, placebo‐controlled trial was conducted among 60 diabetic patients with CHD. Subjects were randomly allocated into two groups to intake either 1000 mg n‐3 fatty acid from flaxseed oil containing 400 mg α‐Linolenic acid [ALA (18:3n‐3)] (n = 30) or placebo (n = 30) twice a day for 12 weeks. Gene expression related to insulin, lipid and inflammation were quantified in peripheral blood mononuclear cells (PBMC) of diabetic patients with CHD with RT‐PCR method. Results of RT‐PCR demonstrated that after the 12‐week intervention, compared with the placebo, flaxseed oil supplementation could up‐regulate gene expression of peroxisome proliferator‐activated receptor gamma (PPAR‐γ) (P = 0.02) in PBMC of diabetic patients with CHD. In addition, compared with the placebo, taking flaxseed oil supplements down‐regulated gene expression levels of lipoprotein(a) [LP(a)] (P = 0.001), interleukin‐1 (IL‐1) (P = 0.001) and tumor necrosis factor alpha (TNF‐α) (P = 0.02) in PBMC of diabetic patients with CHD. We did not observe any significant effect of flaxseed oil supplementation on gene expression levels of low‐density lipoprotein receptor (LDLR), IL‐8 and transforming growth factor beta (TGF‐β) in PBMC of diabetic patients with CHD. Overall, flaxseed oil supplementation for 12 weeks in diabetic patients with CHD significantly improved gene expression levels of PPAR‐γ, LP(a), IL‐1 and TNF‐α, but did not influence LDLR, IL‐8 and TGF‐β.     

Acidic Heavy Oil Recovery Using a New Formulated Surfactant Accompanying Alkali–Polymer in High Salinity Brines

The strength of a newly formulated surfactant with an alkali and polymer (AS/ASP) to improve an acidic heavy oil recovery was laboratory evaluated by various flooding experiments. The comparative role of the parameters like chemical nature, surface wettability, salinity, temperature and injection scheme were explored at high temperature and pressure on Berea sandstone rocks. According to the results the anionic surfactant is capable of providing proper oil displacement under high salinity conditions around 15 wt%. Continuous monitoring of differential pressure response and effluents’ state clearly represented the formation of an emulsified oil in high saline solutions with both alkali and surfactant. Adding sodium metaborate to the surfactant solution reduced the interfacial tension (IFT) to ultra low values and decreased the surfactant emulsion generation capability at higher salinities. Besides, adding Flopaam AN113SH to the chemical slug increased the residual oil removal owing to lower mobility ratios. So, while high capillary number and an emulsion phase were generated by the A/S slug phases, adding polymer could further enhance the performance of these chemicals. On the other hand, chemical flooding through the oil-wet medium resulted in shorter break through time, lower differential pressure, finer emulsion formation, and lower oil recovery in comparison to the similar water-wet cases.     

A simplified thermodynamic modeling procedure for predicting asphaltene precipitation

In this work, a simplified thermodynamic modeling procedure for determination of the amount of asphaltene precipitation is presented. The onset of asphaltene precipitation in the presence of different solvents is predicted by applying the molecular solubility model. Since asphaltene molecular weight varies in different solvents, the molecular weight of asphaltene has been tuned by experimental data. The tuned molecular weight is used to predict the amount of precipitated asphaltene. The Flory–Huggins statistical thermodynamics theory is applied to derive the Gibbs free energy relationship. A necessary and sufficient condition is defined to minimize the Gibbs free energy relation. By solving the set of equations derived from the minimization, the weight percent of precipitated asphaltene has been determined. The advantage of this model is that one does not need to perform expensive and time consuming experiment in order to obtain molecular weight data. The other improvement of this model compared to the other models is the requirement of a minimum amount of experimental data to find the unknown parameters. It also has the advantage of obtaining solubility parameters through thermodynamics relationships rather than using the relation for regular solution when the asphaltene solution is a non-regular solution. The results of this model are in good agreement with the experimental data.     

On computational complexity of impossible differential cryptanalysis

Impossible differential cryptanalysis is one of the conventional methods in the field of cryptanalysis of block ciphers. In this paper, a general model of an impossible differential attack is introduced. Then, according to this model, the concept of an ideal impossible differential attack is defined and it is proven that the time complexity of an ideal attack only depends on the number of involved round key bits in the attack.     

Influence of dietary vitamin E,selenium and age on regional distribution of α-tocopherol in the rat brain

Concentrations of α-tocopherol (α-T) in plasma, cerebrum, cerebellum, midbrain and brain stem and activity of selenium (Se)-dependent glutathione peroxidase (GSH-Px) in plasma were measured in 1- and 15-month-old male F344 rats fed diets containing vitamin E (E, IU/kg) and Se (ppm) in the following combinations: 30 E, 0.1 Se (control diet, minimum requirements); 200E, 0.2 Se; 0.0 E, 0.2 Se; 200 E, 0.0 Se; 0.0 E, 0.0 Se for 8 or 20 weeks. α-T and GSH-Px levels in plasma were reflective of dietary treatment in young rats in which an interaction of the two nutrients was noted. A longer period of dietary vitamin E deficiency was necessary to deplete plasma α-T and depress GSP-Px activity significantly in the old rats. Among the brain regions of all ages, cerebrum and midbrain had the highest concentrations of α-T while cerebellum showed the lowest. However, cerebellum of young rats and cerebellum and brain stem of old rats had a greater α-T accumulation with doubly supplemented diets, whereas only cerebellum of young and old rats showed a marked increased of α-T with vitamin E supplementation. In old rats, vitamin E deficiency resulted in greater depletion of α-T in cerebellum and brain stem than cerebrum and midbrain regions. Se deficiency in brain stem of young and old rats significantly decreased α-T accumulation by vitamin E supplementation. Se supplementation marginally alleviates vitamin E depletion in brain. Cerebellum and brain stem of old rats fed the minimum requirements of vitamin E and Se for 20 weeks showed a significant decline in α-T. Therefore, cerebellum and brain stem appear, to have a higher turnover of α-T than cerebrum and midbrain, and older rats may require a higher level, of vitamin E in the diet to maintain steady state levels of α-T in these regions.     

Low‐power,latch‐based multistage time‐to‐digital converter in 65 nm CMOS technology

In this paper, a low‐power and high‐resolution latch‐based time‐to‐digital converter (TDC) based on a multistage scheme is proposed. The proposed multistage TDC includes coarse, middle, and fine stages. The coarse stage is a new design of the flash TDC that is implemented by latches without using the delay cell. Also, the middle stage is a new design of the Vernier TDC with employed latches. The fine stage comprises parallel latches with different input loads.     

Improved hepatoprotective activity of silymarin via encapsulation in the novel vesicular nanosystem bilosomes

The main objective of the present work was to formulate, characterize, and evaluate silymarin (SM)-loaded bilosomes, compared to conventional liposomes, aiming at increasing the hepatoprotective activity of the drug. SM-loaded bilosomes were prepared by thin film hydration technique employing soybean phosphatidyl choline (SPC) and different bile salts. After being subjected to different methods of characterization, SM-loaded bilosomes were investigated for their hepatoprotective activity, in CCl₄ hepatointoxicated rat model. The developed SM dispersions exhibited an entrapment efficiency ranging from 21.80?±?2.01 to 84.54?±?2.51% and a particle size diameter in the nanometric dimensions (413?±?96.9 to 686.9?±?62.38?nm), with a negative zeta potential values (<–45?mV). In vitro release study revealed a lower cumulative amount of drug released from the developed formulae, compared to free drug. Ex vivo intestinal uptake study, performed using confocal laser scanning calorimetry, revealed the superiority of bilosomal uptake compared to that of liposomes. In vivo studies revealed an enhanced hepatoprotective effect of SM-loaded bilosomes/liposomes compared to free drug. These results were in good correlation with histopathological examination. These findings support the potential use of bilosomes for improving the hepatoprotective activity of SM via oral administration.