Development of optically transparent ZnS/poly(vinylpyrrolidone) nanocomposite films with high refractive indices and high Abbe numbers

A series of optically transparent ZnS‐poly(vinylpyrrolidone) (PVP) nanocomposite films with high refractive indices and high Abbe numbers have been prepared. Mercaptoethanol (ME) capped ZnS nanoparticles (NPs) were introduced into the PVP polymer matrix via simple blending with high nanophase contents. ME‐ZnS NPs of around 3 nm were prepared from zinc acetate and thiourea precursors in N,N‐dimethylformamide using ME as a capping agent. Transparent nanocomposite films with high refractive indices and high Abbe numbers can be easily prepared by a conventional film casting method. TGA results indicated that the ZnS/PVP nanocomposite films exhibit good thermal stability and the measured contents of ZnS NPs in the films agree well with the theoretical values. The refractive indices and the Abbe numbers of the ZnS/PVP nanocomposite films range from 1.5061 to 1.7523 and 55.6 to 20.4 with the content of ME‐ZnS NPs varied between 0 and 80 wt %, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of conjugated linoleic acid, fish oil and soybean oil on PPARs (α & γ) mRNA expression in broiler chickens and their relation to body fat deposits

An experiment was conducted on broiler chickens to study the effects of different dietary fats (Conjugated linoleic acid (CLA), fish oil, soybean oil, or their mixtures, as well as palm oil, as a more saturated fat), with a as fed dose of 7% for single fat and 3.5 + 3.5% for the mixtures, on Peroxisome Proliferator-Activated Receptors (PPARs) gene expression and its relation with body fat deposits. The CLA used in this experiment was CLA LUTA60 which contained 60% CLA, so 7% and 3.5% dietary inclusions of CLA LUTA60 were equal to 4.2% and 2.1% CLA, respectively. Higher abdominal fat pad was found in broiler chickens fed with a diet containing palm oil compared to chickens in the other experimental groups (P ≤ 0.05). The diets containing CLA resulted in an increased fat deposition in the liver of broiler chickens (P ≤ 0.05). The only exception was related to the birds fed with diets containing palm oil or fish oil + soybean oil, where contents of liver fat were compared to the CLA + fish oil treatment. PPARγ gene in adipose tissue of chickens fed with palm oil diet was up-regulated compared to other treatments (P ≤ 0.001), whereas no significant differences were found in adipose PPARγ gene expression between chickens fed with diets containing CLA, fish oil, soybean oil or the mixture of these fats. On the other hand, the PPARα gene expression in liver tissue was up-regulated in response to the dietary fish oil inclusion and the differences were also significant for both fish oil and CLA + fish oil diets compared to the diets with palm oil, soybean oil or CLA as the only oil source (P ≤ 0.001). In conclusion, the results of present study showed that there was a relationship between the adipose PPARγ gene up-regulation and abdominal fat pad deposition for birds fed with palm oil diet, while no deference was detected in n-3 and n-6 fatty acids, as well as CLA on PPARγ down regulation in comparison to a more saturated fat. When used on its own, fish oil was found to be a more effective fat in up-regulating hepatic PPARα gene expression and this effect was related to a less fat deposition in liver tissue. A negative correlation coefficient (-0.3) between PPARα relative gene expression and liver tissue fat content confirm the anti-lipogenic effect of PPARα, however, the change in these parameters was not completely parallel.     

Interactions in miscible blends and complexes of poly(N-acryloylmorpholine) with poly(p-vinylphenol)

Poly(p-vinylphenol) (PVPh) and poly(N-acryloylmorpholine) (PAcM) form interpolymer complexes in ethanol/water (1:1) solution. However, only ordinary blends are obtained from dimethylformamide solution. Each of the complexes and ordinary blends shows one composition-dependent glass transition temperature, indicating its single-phase nature. Fourier transform infrared spectroscopy and ¹³C solid-state nuclear magnetic resonance spectroscopy reveal the existence of hydrogen-bonding interactions between the hydroxyl groups of PVPh and the carbonyl groups as well as the ether oxygen of PAcM in the blends and complexes. In addition, X-ray photoelectron spectroscopy shows that the nitrogen atoms in PAcM are also involved in hydrogen-bonding interactions. Measurements of proton spin-lattice relaxation time in the rotating frame, T_1ρ(H), reveal that each of the complexes and ordinary miscible blends has one composition-dependent T_1ρ(H), indicating an intimate mixing on a scale of about 1.5 nm. The blends show a higher degree of surface enrichment of PVPh than the complexes.     

A mathematical model of polymer electrolyte fuel cell with anode CO kinetics

We develop a mathematical model of solid polymer electrolyte fuel cell with anode CO kinetics, which is essentially a model that marrying the work of Bernardi and Verbrugge (J. Electrochem. Soc. 139 (1992) 2477) with that of Springer et al. (J. Electrochem. Soc. 148 (2001) A11). Two cases of study were carried out. First, the water self-sufficiency of fuel cell operation was conducted under different current density, temperature, pressure differential across the membrane-electrode-assembly (MEA), hydraulic permeability and electro-kinetic permeability. Comparison of superficial water velocities in the MEA under the effect of different current density with those from Bernardi and Verbrugge was conducted. Results showed that, treating the catalyst layers as interfaces instead of regions as simplified by Bernardi and Verbrugge, would significantly underestimate the water velocities in the MEA and the error is particularly large at high current density operations. Second, the effect of CO poisoning of fuel cell was presented in terms on cell polarization. The prediction covered 0, 25, 50, 100 and 250 ppm of CO concentration in hydrogen feedstock and results were validated by experimental data obtained from Springer et al. The trends of anode polarization curve due to CO poisoning were explained.     

Miscibility and interactions in blends and complexes of poly(4-methyl-5-vinylthiazole) with proton-donating polymers

The miscibility and interactions in blends and complexes of poly(4-methyl-5-vinylthiazole) (PMVT) with poly(p-vinylphenol) (PVPh), poly(acrylic acid) (PAA) and poly(vinylphosphonic acid) (PVPA) were studied. PMVT formed complexes with PVPA but not with PVPh and PAA. Each of the blends of PMVT with PVPh and PAA showed a single glass transition temperature (T_g), indicating miscibility. Fourier-transform infrared spectroscopic and X-ray photoelectron spectroscopic studies provided the existence of interactions in the PMVT blends and complexes. The XPS studies indicated that the thiazole nitrogen atoms are involved in hydrogen-bonding interactions with PVPh and PAA, and ionic interactions with PVPA. The sulfur atoms of PMVT also interact with PVPh, PAA and PVPA.     

Rational design of green fluorescent protein mutants as biosensor for bacterial endotoxin

Enhanced green fluorescent protein (EGFP) was selected as asignalling scaffold protein for design of a fluorescent biosensorfor bacterial endotoxin [or lipopolysaccharide (LPS)]. Virtualmutagenesis was utilized to model EGFP variants containing bindingsites for LPS and lipid A (LA), the bioactive component of LPS.Cationic amphipathic sequences of five alternating basic andhydrophobic residues were introduced to ß-sheets locatedon the surface of EGFP barrel, in the vicinity of the chromophore.Computational methods were employed to predict binding affinityof Escherichia coli LA, to the models of virtual EGFP mutants.DNA mutant constructs of five predicted best binding EGFP variantswere expressed in COS-1 cells. The EGFP-mutant proteins exhibiteddifferential expression and variable degrees of fluorescenceyield at 508 nm. The EGFP mutants showed a range of LA bindingaffinities that corresponded to the computational predictions.LPS/LA binding to the mutants caused concentration-dependentfluorescence quenching. The EGFP mutant, G10 bearing LPS/LAamphipathic binding motif in the vicinity of the chromophore(YLSTQ_200–204     

HPLC analysis of desmosterol, 7-dehydrocholesterol,and cholesterol

A simple and sensitive method to analyzed mixtures of desmosterol, 7-dehydrocholesterol and cholesterol is described. The method involves the oxidative conversion of the sterols with cholesterol oxidase, followed by high performance liquid chromatographic (HPLC) analysis. A C₁₈ reversed phase column (3 μm, 75×4.6 mm) and a mixture of methanol and acetonitrile (1∶1, v/v) at a rate of 1 ml/min are used to separate the sterols. The eluted sterols are quantified by measuring UV absoprtion at 240 nm. As little as 10 pmoles of sterol can be quantified under these conditions.     

Miscibility of polysulfone and poly(ether sulfone) with tertiary amide polymers

The miscibility of polysulfone (PSf) and poly(ether sulfone) (PES) with three tertiary amide polymers has been studied. PES is miscible with poly(N-methyl-N-vinylacetamide) (PMVAc) and with poly(N,N-dimethylacrylamide) (PDMA) but not with poly(2-methyl-2-oxazoline) (PMOx). Miscible PES/PDMA blends show lower critical solution temperature behavior. However, PSf is immiscible with all the three tertiary amide polymers. Previous studies have shown that both PES and PSf are miscible with poly(N-vinyl-2-pyrrolidone). PES is also miscible with poly(2-ethyl-2-oxazoline) but PSf is not. Therefore, PES is more readily miscible with tertiary amide polymers as compared to PSf. Received: 23 October 1996/Revised: 11 November 1996/Accepted: 12 November 1996     

Fabrication of 3D Microfluidic Channels and In‐Channel Features Using 3D Printed,Water‐Soluble Sacrificial Mold

Recent advent of additive manufacturing potentiates the fabrication of microchannels, albeit with limitations in resolution of printed structures, freedom of geometry, and choice of printable materials. Herein, a method is developed by sacrificial molding to fabricate microchannels in various polymer matrices and geometries. This method allows for rapid fabrication of 3D microchannels and channels harboring intricate in‐channel features. The method uses commercially available fused deposition modeling 3D printer and filament made of polyvinyl alcohol (PVA). Mechanically stable molds are fabricated for 3D microchannels that can be completely removed in water. Importantly, the PVA mold is stable and resilient in hydrogels despite being hygroscopic. Perfusion channels are fabricated in biocompatible substrates such as gelatin and poly(ethylene glycol) diacrylate. Fabrication of the network of 3D multilayer microchannels is demonstrated by preassembling sacrificial molds from modular pieces of molds. Intricate staggered‐herringbones grooves (SHGs) are also fabricated within microchannels to produce micromixers. The versatility and resilience of the method developed here is advantageous for biological and chemical applications that require 3D configurations of microchannels in various matrices, which would not be compatible with fabrication by direct 3D printing and softlithography.