Determination of polarity parameters for liquid crystals using solvatochromic method in anisotropic and isotropic phases

The use of liquid crystals (LCs) as anisotropic solvents is desired for various potential applications and usually for other organic and inorganic compounds. In this work, solvent polarity parameters are obtained using a spectroscopic method for four LCs with a range of high and low dielectric anisotropy (?ε). Solvatochromic polarity parameters for these LCs were defined via Kamlet–Abboud–Taft polarity functions characterizing different temperatures and phases, isotropic and anisotropic, and using the Reichardt’s dye and 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinio) phenolate standard probe. The investigated polarity parameters reveal the effects of LC media on the photo-physical behaviour of solute molecules in isotropic and anisotropic media. Subsequently, a new LC polarity parameter (Z_o) is introduced as an overall matrix anisotropy polarity parameter to characterize variation between isotropic and anisotropic phases. The values of Z_o are sorted from higher to lower dielectric anisotropies (?ε).     

Mixed biopolymer systems based on starch

A binary mixture of starch-starch or starch with other biopolymers such as protein and non-starch polysaccharides could provide a new approach in producing starch-based food products. In the context of food processing, a specific adjustment in the rheological properties plays an important role in regulating production processing and optimizing the applicability, stability, and sensory of the final food products. This review examines various biopolymer mixtures based on starch and the influence of their interaction on physicochemical and rheological properties of the starch-based foods. It is evident that the physicochemical and rheological characteristics of the biopolymers mixture are highly dependent on the type of starch and other biopolymers that make them up mixing ratios, mixing procedure and presence of other food ingredients in the mixture. Understanding these properties will lead to improve the formulation of starch-based foods and minimize the need to resort to chemically modified starch.     

Effect of Different Purification Techniques on the Characteristics of Heteropolysaccharide-Protein Biopolymer from Durian (<em>Durio zibethinus</em>) Seed

Natural biopolymers from plant sources contain many impurities (e.g., fat, protein, fiber, natural pigment and endogenous enzymes), therefore, an efficient purification process is recommended to minimize these impurities and consequently improve the functional properties of the biopolymer. The main objective of the present study was to investigate the effect of different purification techniques on the yield, protein content, solubility, water- and oil-holding capacity of a heteropolysaccharide-protein biopolymer obtained from durian seed. Four different purification methods using different chemicals and solvents (i.e., A (isopropanol and ethanol), B (isopropanol and acetone), C (saturated barium hydroxide), and D (Fehling solution)] to liberate the purified biopolymer from its crude form were compared. In most cases, the purification process significantly (p < 0.05) improved the physicochemical properties of heteropolysaccharide-protein biopolymer from durian fruit seed. The present work showed that the precipitation using isopropanol and acetone (Method B) resulted in the highest purification yield among all the tested purification techniques. The precipitation using saturated barium hydroxide (Method C) led to induce the highest solubility and relatively high capacity of water absorption. The current study reveals that the precipitation using Fehling solution (Method D) most efficiently eliminates the protein fraction, thus providing more pure biopolymer suitable for biological applications.     

Kinetic Studies of Substitution Reactions of Uranyl(VI) Schiff Base Complexes with Tributylphosphine

The kinetics of the substitution reaction of uranyl Schiff base complexes with tributylphosphine was studied spectrophotometrically in acetonitrile. Uranyl complexes have a pentagonal bipyramidal structure with a trans‐UO₂ moiety at the axial positions. In uranyl tetradentate Schiff base complexes, the fifth position of the equatorial plane is occupied by the solvent molecule, which weakly coordinates to the U center. In a substitution reaction, tributylphosphine can easily replace the solvent molecule. By considering the excellent linearity of k_obs versus the molar concentration of tributylphosphine, the large negative values of Δ S^#, and the small values of Δ H^#, an associative (A) mechanism has been suggested. By comparing the rate constants (k₂) and the activation parameters, it is obvious that two parameters are effective in the rate of substitution reactions; The first parameter is the steric effect that the rate of reaction has been decreased by increasing this factor, and the other parameter is the electronic property that the electron‐withdrawing group leads to increase the rate of reaction and the electron donor group decreases it. © 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 168–174, 2013     

Hemorrhage control in arteries using high-intensity focused ultrasound: a survival study

High-intensity focused ultrasound (HIFU) has been shown to provide an effective method for hemorrhage control of blood vessels in acute animal studies. The objective of the current study was to investigate the long-term effects of HIFU-induced hemostasis in punctured arteries. The femoral arteries ( approximately 2mm in diameter) of 25 adult anesthetized rabbits were surgically exposed, and either punctured and treated with HIFU (n=15), served as control (no puncture and no HIFU application: n=7), or were punctured and left untreated (n=3). Treated animals were allowed to recover, and examined and/or sacrificed on days 0, 1, 3, 7, 14, 28, and 60 after treatment to obtain ultrasound images and samples of blood and tissue. Hemostasis (arrest of bleeding) was achieved in all 15 of the HIFU-treated arteries. Eleven of the arteries were patent after HIFU treatment, and four arteries were occluded, as determined by Doppler ultrasound. The median HIFU application time to achieve hemostasis was 20s (range 7-55 s) for the patent arteries and 110 s (range 50-134 s) for the occluded arteries. In untreated animals, bleeding had not stopped after 120 s. One of the occluded arteries had reopened by day 14. No immediate or delayed re-bleeding was observed after HIFU treatment. Maximal blood flow velocities were similar in HIFU-treated patent vessels and control vessels. No significant difference in hematocrits was found between HIFU-treated and control groups at different time points after the procedure. Light microscopy observations of the HIFU-treated arteries showed disorganization of adventitia, and coagulation and thinning of the tunica media. The general organization of the adventitia and tunica media recovered to normal appearance within 28 days, with some thinning of the tunica media observed up to day 60. Neointimal hyperplasia was observed on days 14 and 28. The results show that HIFU can produce effective and long-term (up to 60 days) hemostasis of punctured femoral arteries while preserving normal blood flow and vessel wall structure in the majority of vessels.     

Analysis of particle contact using frustrated total internal reflection

Meccanica - Within the field of soil mechanics a continuum assumption is generally adopted in order to avoid the complications of modelling micro-mechanical behaviour. However, certain constitutive...     

Direct purification of pectinase from mango (Mangifera Indica Cv. Chokanan) peel using a PEG/salt-based Aqueous Two Phase System

An Aqueous Two-Phase System (ATPS) was employed for the first time for the separation and purification of pectinase from mango (Mangifera Indica Cv. Chokanan) peel. The effects of different parameters such as molecular weight of the polymer (polyethylene glycol, 2,000-10,000), potassium phosphate composition (12-20%, w/w), system pH (6-9), and addition of different concentrations of neutral salts (0-8%, w/w) on partition behavior of pectinase were investigated. The partition coefficient of the enzyme was decreased by increasing the PEG molecular weight. Additionally, the phase composition showed a significant effect on purification factor and yield of the enzyme. Optimum conditions for purification of pectinase from mango peel were achieved in a 14% PEG 4000-14% potassium phosphate system using 3% (w/w) NaCl addition at pH 7.0. Based on this system, the purification factor of pectinase was increased to 13.2 with a high yield of (97.6%). Thus, this study proves that ATPS can be an inexpensive and effective method for partitioning of pectinase from mango peel.     

Phase and structural order in mixture of nematic liquid crystals and anisotropic nanoparticles

We studied the structural order in randomly perturbed nematic liquid crystals using a random anisotropic nematic-type lattice model. Simulations were carried out at zero temperature and at various other temperatures, for which we varied the concentration of impurities p, anchoring strength W and imposed external strength fields B at two different histories: temperature-quenched history (TQH) and field-quenched history. The Haller approximation method utilized the temperature dependence of the order parameter to determine the pseudo-critical exponent β at different values of p and W. Consequently, the values of β increased when p and W were increased. Additionally, applying an external field B for investigating the parameters revealed that the TQH established long-range order for high magnitudes of B at zero temperature (T* = 0) and T* = 0.5.     

Integrated fuzzy AHP and fuzzy VIKOR model for supplier selection in an agile and modular virtual enterprise

In this ever-changing world, organizations need to outsource parts of their processes for having agile response to market’s needs and varying demands. Because of temporal nature of virtual enterprises (VE’s), the situation of outsourcing process in this kind of organizations is a vital situation. The main idea of this paper aims to present a decision-making framework for specific area that is appropriated for complex states. Its contribution is developing a fuzzy VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method and combining it with fuzzy analytic hierarchy process (AHP). This extension suitable for decision-making situations which is faced with mixture appraisement that simultaneously regarded to both “group utility” or majority and “individual regret” of the opponent. The Integrated and developed model suits to inconsistent conditions that we face to collection of criteria and subcriteria that should satisfy some of them collectively and simultaneously and in other attainment of some individual criteria is desirable. This framework then extended to a case study with varied criteria for outsourcing process.