Linear Viscoelastic Characteristics of Poly(trimethylene terephthalate)/Polycarbonate Blends in the Melt State

Summary: Blends of poly(trimethylene terephthalate) (PTT) and polycarbonate (PC) over full composition range were prepared using a twin‐screw extruder. A glycidyl methacrylate‐based terpolymer was used to modify the interface of the blends. Morphological examinations were carried out using transmission electron microscopy (TEM) and confirmed the biphasic structure of the blends. Dynamic rheological response of the blends was recorded in the linear viscoelastic region. It was observed that addition of the terpolymer to the system increases the dynamic shear moduli and complex viscosity of the blends, which is attributed to interactions of the terpolymer at the interface of two phases leading to a restricted chain mobility of the blend components. The Veenstra model was found to be able to describe dynamic shear modulus of the PTT/PC 50/50 blend; however, for the compatibilized blend of PTT/PC 50/50, the fit is not as good as that of uncompatibilized system, which is believed to be due to formation of micelles in this system.

Dynamic storage modulus of the compatibilized and uncompatibilized PTT/PC blends.     

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.     

Modeling and closed‐loop control of particle size and initial burst of PLGA biodegradable nanoparticles for targeted drug delivery

An in‐house computer code based on artificial intelligence has been developed and applied in modeling and closed‐loop optimization of release behavior of Poly(lactic‐co‐glycolic acid) (PLGA) biodegradable particles. A series of micro‐ and nanoparticles were prepared via water‐in‐oil‐in‐water double emulsion to be loaded with albumin–fluorescein isothiocyanate conjugate as a typical drug. The interrelationship between input variables (molecular weight of polymer and stabilizer, polymer concentration, and sonication rate) and outputs (PLGA particle size and percentage of initial burst) was uncovered with the aid of artificial neural network modeling. The regression analysis confirmed acceptable correlation coefficients for the aforementioned responses, where the PLGA molecular weight played the most important role among the studied variables. Input variables needed to minimize PLGA size and PLGA initial burst were then obtained via multiobjective optimization performed by a genetic algorithm. PLGA nanoparticles were checked for particle size and particle size distribution using scanning electron micrographs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45145.     

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.     

Morphological and phase evaluation of Al/15 wt.% BN nanocomposite synthesized by planetary ball mill and sintering

In this study, Al/15 wt.% BN nanocomposite was fabricated by high energy ball milling, cold compaction, and sintering process. Then the effect of milling process on the morphology change and phase evaluation was studied. The Aluminum (45 µm) and hexagonal boron nitride (70 nm) powders were milled using planetary ball mill under a pure argon atmosphere for various times of 75, 150, 300 and 600 min. The as-milled powders were consolidated at 400 MPa pressure and sintered at 600 °C for 60 min. The morphology change evaluation studied by using scanning electron microscopy (SEM) showed that the equiaxed composite powders were obtained after a short time milling process of 150 min. The steady state condition between welding and fracturing occurred by continuous milling up to 600 min. The results of X-ray diffraction patterns and differential scanning calorimetric (DSC) revealed that the BN particles completely decomposed to boron and nitrogen and dissolved in the Al matrix after 300 min of ball milling and the AlN and AlB₂ as in-situ phases were formed after sintering at temperatures above 580 °C.