Polyvinyl Alcohol (polyvinyl + alcohol)

Distribution by Scientific Domains

Selected Abstracts

Preparation and Characterization of a Large-Scale YBa2Cu3O7,x Superconductor Prepared by Plastic Forming without a High-Pressure Molding: Effect of Polyvinyl Alcohol (PVA) Addition on the Superconducting Properties

Makoto Takahashi
The preparation of large-scale YBa2Cu3O7,x superconductor samples was investigated. This method is based on plastic forming using a slurry consisting of YBa2Cu3O7,x particles and a sol solution made up of multimetallic hydroxide particles (YBa2Cu3(OH)x colloidal particles) and poly(vinyl) alcohol (PVA). The effects of adding PVA on the product, the crystallinity, and the superconducting properties of the sample were investigated. It was found that PVA acted as a protective colloid in the sol solution and stabilized YBa2Cu3(OH)x colloidal particles, and that the role of PVA changed from a thickener to a flocculant during drying so that the formability/workability of the green sheet sample was improved and large samples (about 80 mm × 80 mm × 3 mm) without large cracks were obtained after firing. The samples became superconducting at 91.5±0.5 K (Tcon) and the full transition temperature (Tcoff) was 88.5±1.5 K. The critical current density (Jc) of the sample prepared from the slurry containing 1 wt% PVA was 713±150 A/cm2 at 77 K. This Jc value was improved to 2300 A/cm2 by heat treatment at 773 K under an oxygen atmosphere. [source]

Cross-linked Polyvinyl Alcohol as a Binder for Gelcasting and Green Machining

France Chabert
Submicrometer alumina suspensions, dispersed in aqueous acidic solutions of polyvinyl alcohol (PVA) and 2,5-dimethoxy-2,5-dihydrofuran, have been evaluated for suitability as a cross-linkable binder system for casting complex-shaped ceramic components. Suspensions of up to 50 vol% solids have rheological behavior, which is suitable for pouring and filling molds. Complex-shaped green bodies are then formed by heating the suspension in the mold for a period of time (typically 15,60 min) at moderate temperature (60°,80°C) to gel the suspension. High green densities (58%,62% of full density) can be obtained. The dried green bodies have strength in excess of 1 MPa and may be readily machined. No more than 1,3 wt% PVA per weight of alumina is necessary, ensuring burnout that minimizes generation of flaws. The ceramic components can be fired to >96% of full density when fired for 2 h at 1400°,1450°C. Cross-linkable PVA may receive more widespread acceptance in ceramic processing than previous gelcasting formulations because PVA is already a common processing additive. [source]

Physically crosslinked composite hydrogels of PVA with natural macromolecules: Structure, mechanical properties, and endothelial cell compatibility

Y. Liu
Abstract Polyvinyl alcohol (PVA) hydrogels have been considered potentially suitable for applications as engineered blood vessels because of their structure and mechanical properties. However, PVA's hydrophilicity hinders its capacity to act as a substrate for cell attachment. As a remedy, PVA was blended with chitosan, gelatin, or starch, and hydrogels were formed by subjecting the solutions to freeze-thaw cycles followed by coagulation bath immersion. The structure-property relationships for these hydrogels were examined by measurement of their swelling, rehydration, degradation, and mechanical properties. For the case of pure PVA hydrogels, the equilibrium swelling ratio was used to predict the effect of freeze thaw cycles and coagulation bath on average molecular weights between crosslinks and on mesh size. For all hydrogels, trends for the reswelling ratio, which is indicative of the crosslinked polymer fraction, were consistent with relative tensile properties. The coagulation bath treatment increased the degradation resistance of the hydrogels significantly. The suitability of each hydrogel for cell attachment and proliferation was examined by protein adsorption and bovine vascular endothelial cell culture experiments. Protein adsorption and cell proliferation was highest on the PVA/gelatin hydrogels. This study demonstrates that the potential of PVA hydrogels for artificial blood vessel applications can be improved by the addition of natural polymers, and that freeze-thawing and coagulation bath treatment can be utilized for fine adjustment of the physical characteristics. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source]

Sensitive analysis of donepezil in plasma by capillary electrophoresis combining on-column field-amplified sample stacking and its application in Alzheimer's disease,

Hsin-Hua Yeh
Abstract Field-amplified sample stacking (FASS) in capillary electrophoresis (CE) was used to determine the concentration of donepezil, an acetylcholinesterase inhibitor, in human plasma. A sample pretreatment by liquid,liquid extraction with isopropanol/n -hexane (v/v 3:97) and subsequent quantification by FASS-CE was used. Before sample loading, a water plug (0.5,psi, 6,s) was injected to permit FASS. Electrokinetic injection (7,kV, 90,s) was used to introduce sample cations. The separation condition for donepezil was performed in electrolyte solutions containing Tris buffer (60,mM, pH 4.0) with sodium octanesulfonate 40,mM and 0.01% polyvinyl alcohol as a dynamic coating to reduce analytes' interaction with capillary wall. The separation was performed at 28,kV and detected at 200,nm. Using atenolol as an internal standard, the linear ranges of the method for the determination of donepezil in human plasma were over a range of 1,50,ng/mL. The limit of detection was 0.1,ng/mL (S/N=3, sampling 90,s at 7,kV). One female volunteer (54 years old) was orally administered a single dose of 10,mg donepezil (Aricept®, Eisai), and blood samples were drawn over a 60,h period for pharmacokinetic study. The method was also applied successfully to monitor donepezil in sixteen Alzheimer's disease patients' plasmas. [source]

Preparation and Characterization of Uniformly Sized Sub-micrometer Spherical Silica/Organic Polymer Hybrid Particles

X.-s. Xing
Hybrid particles with a core-shell structure, consisting of a silica core and a polyvinyl alcohol (PVA) shell, (see Figure for an SEM image of a particle material of this type), were fabricated via a two-step sol-gel process. The PVA molecular chains are probably physically adsorbed onto the surface of silica cores by hydrogen bonds and van der Waals forces. [source]

Polyethylene glycol and polyvinyl alcohol as corrosion inhibitors for aluminium in acidic medium

S. A. Umoren
Abstract The corrosion inhibition of aluminum in H2SO4 in the presence of polyethylene glycol (PEG) and polyvinyl alcohol (PVA) as inhibitors at 30,60 °C was studied using gravimetric, gasometric, and thermometric techniques. The inhibition efficiency (%I) increased with increase in concentration of the inhibitors. Increase in temperature increased the corrosion rate in the absence and presence of inhibitors but decreased the inhibition efficiency. Both PEG and PVA were found to obey Temkin adsorption isotherm at all concentrations and temperatures studied. Phenomenon of physical adsorption is proposed from the activation parameters obtained. Thermodynamic parameters reveal that the adsorption process is spontaneous. PEG was found to be a better inhibitor than PVA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

The new adhesion prophylaxis membrane A-part®,From in vitro testing to first in vivo results

Bernd Martin Jaenigen
Abstract Introduction: Formation of postoperative intra-abdominal adhesions is a severe problem in surgery. Apart from standard surgical procedures, a variety of different substances is available to prevent adhesions, but no universal method has been developed so far. A membrane consisting of polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC) has been demonstrated to be antiadhesive. Here, the in vitro testing and first in vivo results in a rabbit sidewall model are reported. Materials and Methods: A-part® membrane contains a PVA/CMC mixture in a thickness of 40 ,m. The composition, dissolution, tensile strength, and elasticity were examined to characterize the membrane in vitro. Experiments in vivo were carried out using a ,rabbit sidewall model' in which a standardized peritoneal trauma was covered with a 5 × 6 cm A-part® membrane. Adhesion formation in A-part®-treated animals was compared with that in Adept® (15 mL/kg body weight) and untreated controls. Results: An 80/20 PVA/CMC mixture forms a stable, elastic, transparent membrane, which can easily be placed intraoperatively. The dissolution shows a half-life of about 2 weeks [day 15: (45.1 ± 4.9)% SD], which affords good adhesion protection during the initial critical phase of adhesion formation. In wet conditions, the membrane follows abdominal movements without tearing (tensile strength 5.0 ± 4.2 N/cm SD; elasticity 29.5%). In a rabbit sidewall model, A-part® membrane significantly reduced adhesion development by (83.1 ± 31.5)% SD compared with the control and the Adept group (p < 0.001). Conclusion: The properties of the A-part® membrane suggest that it may be useful as an antiadhesive in surgery. A-part® is effective in invivo testing as determined in a rabbit sidewall model. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source]

Development of the shields for tendon injury repair using polyvinyl alcohol , hydrogel ( PVA-H)

Masanori Kobayashi
Abstract In recent years, marked advances have been made in repair techniques for tendon injury, but the treatment of finger flexor tendon injury is still one of the most difficult and important problems in the orthopedic field. The main problem in tendon repair is adhesion between the tendon and surrounding tissue. To prevent this adhesion and achieve tendon union, we developed adhesion preventive shields for tendon repair using polyvinyl alcohol hydrogel ( PVA-H) with 90% water content, and carried out an implant experiment using the deep flexor tendon of the third toe of domestic fowl. Injured tendons shielded with PVA-H showed union at about 3 weeks after the operation without adhesion to the surrounding tissue and good function such as gliding and range of motion. Neither breakage of the PVA-H shield itself nor infection, nor degeneration in the surrounding tissue were observed. These results confirmed that the tendon itself has repair ability, and the tendon is regenerated by synovial nutrition through PVA-H. High water content PVA-H may have clinically potential and be applicable to adhesion-preventive shields for tendon repair. However, re-rupture was observed, probably due to accidental tendon injury at an early period after the operation. In some cases, tendon immobilization methods to prevent re-rupture might be necessary. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 344,351, 2001 [source]

Feasibility study of aerosolized prostaglandin E1 microspheres as a noninvasive therapy for pulmonary arterial hypertension

Vivek Gupta
Abstract This study was designed to test the feasibility of polymeric microspheres as an inhalable carrier for prostaglandin E1 (PGE1) for treatment of pulmonary arterial hypertension. Poly(lactic- co -glycolic acid) (PLGA) microspheres were prepared by a double emulsion,solvent evaporation method. Six different microspheric formulations were prepared using two different blends of PLGA (50:50 and 85:15) and varying concentrations of polyvinyl alcohol (PVA) in the external aqueous phase (EAP). The particles were characterized for morphology, size, aerodynamic diameter, entrapment efficiency, release patterns, and metabolic stability. Pulmonary absorption was studied in a rat model, and safety of the formulations was evaluated by measuring cytotoxicity in Calu-3 cells and assessing injury markers in bronchoalveolar lavage (BAL) fluid. Both actual particle size and aerodynamic diameter of the formulations decreased with increasing PVA concentration. The mass median aerodynamic diameter of the particles was within the respirable range. Entrapment efficiency increased with increasing PVA concentration; PLGA 85:15 showed better entrapment due to hydrophobic interactions with the drug. Compared to intravenously administered PGE1, microspheres prepared with PLGA 85:15 produced a 160-fold increase in the half-life of PGE1 following pulmonary administration. Although plain PGE1 showed rapid degradation in rat lung homogenate, PGE1 entrapped in the particles remained intact for about 8,h. Optimized formulations were demonstrated to be safe, based on analysis of cytotoxicity and lung-injury markers in BAL fluid. Overall, the data suggest that microspheric PGE1 formulations have the potential to be used as a noninvasive and controlled-release alternative to the current medications used for treatment of pulmonary arterial hypertension that are administered by continuous infusion or require multiple inhalations. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1774,1789, 2010 [source]

Sumatriptan succinate transdermal delivery systems for the treatment of migraine

C. Balaguer-Fernández
Abstract We have successfully obtained sumatriptan transdermal systems with different polymer compositions: methyl cellulose (MC), polyvinyl pyrrolidone (PVP) and a polyvinyl pyrrolidone (PVP)-polyvinyl alcohol (PVA) mixture. The systems contained 1,2-propilenglycol (MC) or sorbitol as a plasticizer (PVP and PVP-PVA), methacrylate copolymer as an adhesive agent, and an occlusive liner. Azone® (5%, w/w) was incorporated into all the systems as a percutaneous enhancer. Transdermal systems are thin, transparent and non-adhesive when in a dry state. The permeation of sumatriptan succinate across pig ear skin was studied using the systems prepared. The formulation with MC polymer produced a statistically significant increment with respect to the PVP and PVP-PVA formulations (p,<,0.05). Azone® incorporation into the systems produced an increment in the sumatriptan flux values of all three transdermal systems with respect to those of the controls (p,<,0.05). In addition, the application of iontophoresis to the wet methyl cellulose-Azone® formulation produced a much higher increase of sumatriptan transdermal flux. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2102,2109, 2008 [source]

Preparation and characterization of a customized cellulose acetate butyrate dispersion for controlled drug delivery

Siva Vaithiyalingam
Abstract The purpose of the present experiment was to prepare and characterize the aqueous-based pseudolatex system of cellulose acetate butyrate (CAB) for controlled drug delivery. Aqueous pseudolatex systems are advantageous over organic-based coating systems because these systems are devoid of criteria pollutants such as carbon monoxide, nitrogen oxides, nonmethane volatile organic compounds, and sulfur dioxide. Pseudolatex was prepared with CAB and polyvinyl alcohol (stabilizer) by a polymer emulsification technique. The stability of pseudolatex was evaluated. Particle size was measured and rheological experiments were conducted. The glass transition temperature, microscopic free volume, permeation coefficient, and mechanical properties of plasticized pseudolatex films were estimated. Surface roughness of coating on inert Nu-Pareil® beads (Ingredient Technology Corp., Mahwah, NJ) was measured as a function of coating weight gain. The CAB Pseudolatex was found to be stabilized by steric forces. From intrinsic viscosity, the thickness of the stabilization layer was estimated. An increase in polymeric particles proportionately decreased the thickness of the stabilization layer. All the essential properties of a coating membrane such as microscopic free-volume fraction, permeability coefficient, mechanical properties, and glass transition temperature were fairly controllable as a function of plasticizer concentration. The pseudolatex dispersion of CAB was stable with negligible sedimentation volume and a particle size of 300 nm. Because CAB is water insoluble and non-ionizable, this pseudolatex can be used for pH-independent coating. The films obtained were strong and flexible for controlled drug delivery applications. Coating with the CAB dispersion reduced the surface roughness of beads but it remained stable as a function of increase in coating weight gain. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:1512,1522, 2002 [source]

Effect of surfactant on fabrication and characterization of paclitaxel-loaded polybutylcyanoacrylate nanoparticulate delivery systems

Amitava Mitra
ABSTRACT The feasibility of applying biodegradable polybutylcyanoacrylate (PBCA) nanoparticulate delivery systems (NDSs) for the controlled release of paclitaxel was investigated. Paclitaxel-loaded and unloaded PBCA-NDSs containing various surfactants (dextran 70, cholesterol, polyvinyl alcohol and lecithin) were prepared by anionic polymerization. The effects of surfactant (1% w/v), surfactant combination (1% w/v each), and surfactant concentration (0.05, 1.0 and 2.5% w/v) on PBCA-NDSs were evaluated and characterized by particle size, zeta potential, entrapment efficiency, and in-vitro paclitaxel release kinetics. The physicochemical characteristics of PBCA-NDSs incorporated with various surfactants were significantly improved compared with PBCA-NDS without any surfactant, by decreasing particle size at least 3-fold as well as by increasing the zeta potential up to 18-fold to minimize the agglomeration of nanoparticles. Moreover, PBCA-NDSs incorporated with various surfactants demonstrated higher entrapment efficiency of paclitaxel. Results from the in-vitro release kinetic studies indicated that a more controlled biphasic zero-order release pattern of paclitaxel was observed for PBCA-NDSs incorporated with various surfactants. Compared with dextran 70 and polyvinyl alcohol, the naturally occurring lipids, lecithin and cholesterol, indicated greater advantages in improving the physicochemical properties of PBCA-NDSs, in terms of smaller particle size, higher zeta potential and better drug entrapment efficiency, and better controlled release of paclitaxel, in terms of lower release rate and prolonged action from PBCA-NDSs. [source]

Synthesis of biocompatible and biodegradable block copolymers of polyvinyl alcohol- block -poly(,-caprolactone) using metal-free living cationic polymerization

Izabela Magdalena Zaleska
Abstract Applications of metal-free living cationic polymerization of vinyl ethers using HCl·Et2O are reported. Product of poly(vinyl ether)s possessing functional end groups such as hydroxyethyl groups with predicted molecular weights was used as a macroinitiator in activated monomer cationic polymerization of ,-caprolactone (CL) with HCl·Et2O as a ring-opening polymerization. This combination method is a metal-free polymerization using HCl·Et2O. The formation of poly(isobutyl vinyl ether)- b -poly(,-caprolactone) (PIBVE- b -PCL) and poly(tert -butyl vinyl ether)- b -poly(,-caprolactone) (PTBVE- b -PCL) from two vinyl ethers and CL was successful. Therefore, we synthesized novel amphiphilic, biocompatible, and biodegradable block copolymers comprised polyvinyl alcohol and PCL, namely PVA- b -PCL by transformation of acid hydrolysis of tert -butoxy moiety of PTBVE in PTBVE- b -PCL. The synthesized copolymers showed well-defined structure and narrow molecular weight distribution. The structure of resulting block copolymers was confirmed by 1H NMR, size exclusion chromatography, and differential scanning calorimetry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5169,5179, 2009 [source]

Orientation-Control Synthesis of KTa0.25Nb0.75O3 Nanorods

Yong-Ming Hu
Single-crystalline KTa0.25Nb0.75O3 (KTN) nanorods with an orthorhombic perovskite structure were synthesized via a polymer-assisted hydrothermal method. The preferred crystallographic orientation of the nanorods were found to be controllable by using different types of polymers in the process; that is, [001]-oriented KTN were obtained upon the use of polyvinyl alcohol (PVA) and [110]-oriented ones were formed with the use of a combination of polyacrylic acid and PVA. The two types of nanorods showed different properties. The [110]-oriented nanorods exhibited a better photocatalytic decolorization efficiency but very likely a lower thermal conductivity (as indicated by the Raman spectrum measurements) than the [001] nanorods. [source]

Cross-linked Polyvinyl Alcohol as a Binder for Gelcasting and Green Machining

France Chabert
Submicrometer alumina suspensions, dispersed in aqueous acidic solutions of polyvinyl alcohol (PVA) and 2,5-dimethoxy-2,5-dihydrofuran, have been evaluated for suitability as a cross-linkable binder system for casting complex-shaped ceramic components. Suspensions of up to 50 vol% solids have rheological behavior, which is suitable for pouring and filling molds. Complex-shaped green bodies are then formed by heating the suspension in the mold for a period of time (typically 15,60 min) at moderate temperature (60°,80°C) to gel the suspension. High green densities (58%,62% of full density) can be obtained. The dried green bodies have strength in excess of 1 MPa and may be readily machined. No more than 1,3 wt% PVA per weight of alumina is necessary, ensuring burnout that minimizes generation of flaws. The ceramic components can be fired to >96% of full density when fired for 2 h at 1400°,1450°C. Cross-linkable PVA may receive more widespread acceptance in ceramic processing than previous gelcasting formulations because PVA is already a common processing additive. [source]

Aqueous Processing of Titanium Carbide Green Sheets

Jing-Xian Zhang
TiC sheets were prepared by an aqueous tape-casting process. The zeta potential measurement showed that the isoelectric point for TiC powders in the absence of dispersant had a pH value of ,3.3. According to the surface properties of TiC powders, a cationic polymer PEI was selected as dispersant. In the presence of dispersant, the isoelectric point increased to a pH value of ,10.4. The slip stability was determined by visual observation of the fluidity of the slip as well as the settling of the powders. Results showed that the amount of dispersant required to achieve a minimum of viscosity for 50 vol% suspensions was equal to 1.2 wt%. In the absence and presence of dispersant, stable slips could be obtained in the pH ranges 7,9 and 11,12, respectively. The rheological measurements showed that with PEI as dispersant, TiC suspensions exhibited a small time dependent behavior. With polyvinyl alcohol as binder and glycerol as plasticizer, suspensions showed a thixotropic feature. As-cast tapes were dried in air at room temperature. The results showed that it was possible to fabricate homogeneous green tapes with smooth surfaces from these suspensions. [source]

Comparison of the Effects of an Ionic Liquid and Other Salts on the Properties of Electrospun Fibers, 2 , Poly(vinyl alcohol)

Ganesh Kumar Arumugam
Abstract Understanding the effect of conductivity in electrospinning solutions is crucial in order to improve or control the electrospinning process. In this paper the effect of adding small amounts (0.039,0.259 mol,·,kg,1) of three different conductive additives to aqueous solutions of polyvinyl alcohol has been investigated. The salts were HMICl (a room temperature ionic liquid), TEBAC (a quaternary ammonium salt) and KCl. Addition of these salts caused a steady increase in the solution conductivity but the fiber diameter was typically greater than that of PVA alone, and exhibited an oscillatory trend. The oscillatory trend on the fiber diameter is attributed to fiber backbuilding and fusion that occurs prior to deposition on the collector. [source]

Study on Enzymatic Hydrolysis of Polylactic Acid by Endogenous Depolymerizaion Model

Masaji Watanabe
Abstract Enzymatic degradation of polylactic acid is studied experimentally and analytically. Gel permeation chromatography profiles obtained before and after the enzymatic degradation of polylactic acid (PLA) were introduced into the analysis based on a mathematical model. Previously developed techniques were successfully adapted to the analysis of an initial value problem consisting of an endogenous depolymerization model and an initial condition, and an inverse problem to determine the degradation rate for which the solution of the initial value problem also satisfies a final condition. Those problems were solved numerically and numerical results are introduced. Degradabilities of PLA and polyvinyl alcohol are compared. [source]

Preparation of smallest microparticles of poly- D,L -lactide by modified precipitation method: Influence of the process parameters

Ivana Jovanovi
Abstract Biodegradable microspheres such as those made of poly- D,L -lactide (PDLLA) are widely investigated delivery systems for drugs or antigens. The aim of this study was to examine experimental conditions in order to produce PDLLA microspheres with the best properties for controlled and sustained drug delivery by the modified precipitation method. For this purpose, the following parameters were varied: co-solvent (methanol or ethanol), the concentration of stabilizer polyvinyl alcohol (PVA), chloroform-to-water ratio and the speed and time of homogenization. Scanning electron microscopy (SEM) and stereological analysis were used to characterize the particles. The average size and morphology of the microspheres varied substantially with preparation conditions from 8.44,1.25 ,m. Results showed that the smallest particles were obtained with methanol, 1% PVA and with 10 min of homogenization at 21,000 rpm. Microsc. Res. Tech., 2008. © 2007 Wiley-Liss, Inc. [source]

Glutathione and adenosine triphosphate content of in vivo and in vitro matured porcine oocytes

A.M. Brad
Abstract Glutathione (GSH) content in mature porcine oocytes is correlated with subsequent fertilization and developmental success. Adenosine triphosphate (ATP) is an important energy source for maintaining cellular activities and protein synthesis. The objective of this study was to compare GSH and ATP concentrations of in vivo and in vitro matured porcine oocytes. Ovulated, in vivo matured oocytes were frozen at ,80°C in groups of 10,20 (GSH) or 5,10 (ATP). In vitro oocytes were matured in either tissue culture medium-199 (TCM199) supplemented with polyvinyl alcohol (PVA) or hyaluronic acid (MAP5), or North Carolina State University-23 (NCSU23) supplemented with porcine follicular fluid (pFF) and frozen as described, or fertilized and cultured. GSH content was determined by the dithionitrobenzoic acid,glutathione disulfide (DTNB,GSSG) reductase recycling assay. ATP content was determined by using the Bioluminescent Somatic Cell Assay Kit. Oocytes matured in vitro in defined TCM199 with PVA or hyaluronic acid, or NCSU23 with pFF had significantly lower concentrations (P,<,0.05) of GSH (n,=,207, 9.82,±,0.71 pmol/oocyte; n,=,104, 9.73,±, 0.81 pmol/oocyte; n,=,108, 7.89,±,0.66 pmol/oocyte, respectively) compared to in vivo matured oocytes (n,=,217, 36.26,±,11.00 pmol/oocyte). Concentrations of ATP were not different between treatments (in vivo, n,=,70, 0.97,±,0.07 pmol/oocyte; TCM,PVA, n,=,117, 0.81,±,0.13 pmol/oocyte; TCM,MAP, n,=,107, 1.02,±,0.18 pmol/oocyte; NCSU,pFF, n,=,134, 0.71,±,0.08 pmol/oocyte). Intracellular ATP content does not appear to be related to developmental potential in porcine oocytes. Low intracellular GSH may be responsible, in part, for lower developmental competence observed in in vitro matured porcine oocytes. Mol. Reprod. Dev. 64: 492,498, 2003. © 2003 Wiley-Liss, Inc. [source]

Polariscopic imaging and vibrational characterization of hybrid films for packaging

Iari-Gabriel Marino
Abstract Polymeric films (low-density polyethylene and oriented polypropylene) for packaging applications coated with organic,inorganic nanocomposite hybrids have been prepared by sol-gel process. Tetraethoxysilane and two different organic phases, polyvinyl alcohol and a diblock copolymer polyethylene-polyethylene glycol were used as precursors. Information about the hydrolysis and polycondensation degrees was obtained by investigating the vibrational features of the coatings by means of attenuated total reflectance-Fourier transform infrared and Raman spectroscopies. Through a new polariscopic imaging technique, the bi-dimensional maps of the optical anisotropy of the samples, both as-prepared and under mechanical strain, were obtained. The maps showed inhomogeneous retardation and nearly flat azimuth distributions. The anisotropy properties of the samples depended mainly on the substrates and were not influenced by the coatings, while the optical transmission was slightly better for the tetraethoxysilane-polyvinyl alcohol sample. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Response surface optimization of the feed compositions of biodegradable packaging foams

Jinchyau Peng
Abstract Response surface methodology (RSM) was used to analyse the effects of polyvinyl alcohol (PVOH) and calcium carbonate (CaCO3) on the physical and mechanical properties (radial expansion ratio, bulk density, compressibility and spring index) of a biodegradable cushioning extrudate. A rotatable central-composite design (CCD) was used to develop models for the objective responses. The experiments were run at 125°C with a feed rate of 27.8,l/h, screw speed of 215,r.p.m. and die diameter of 3.92,mm. Responses were most affected by changes in PVOH levels and to a lesser extent by CaCO3 levels. Individual contour plots of the different responses were overlaid. An optimum radial expansion ratio of 3.39, bulk density of 0.065 (g/cm3), compressibility of 32.27(N), and spring index of 0.906 were identified at 36% PVOH and 5% CaCO3. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Fiber-forming blend polypropylene-polyvinyl alcohol

Anton Marcin
Abstract The preparation of a fiber-forming blend consisting of polypropylene and polyvinyl alcohol mixed with glycerol and with polypropylene grafted with maleic anhydride were studied. The physical and mechanical properties of blend fibers were also studied. The rheological measurements for semiquantitative evaluation of technological compatibility of the components and for processing the polymeric material in extruding and spinning process were carried out. The experimental results revealed the technological compatibility of the polypropylene-polyvinyl alcohol blend in the presence of glycerol and polypropylene grafted with maleic anhydride. The colloidal structure of interface layer is assumed to be in a three- or four-component system. The mixture of polyvinyl alcohol with glycerol allows for the preparation of well spun fiber-forming polypropylene blends. Polypropylene-polyvinyl alcohol blend fibers consisting of up to 20% polyvinyl alcohol with sufficient mechanical properties, higher porosity and significantly higher sorption of water than polypropylene fibers alone were prepared. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Operational concept for the improved synthesis of (R)-3,3'-furoin and related hydrophobic compounds with benzaldehyde lyase

Marion B. Ansorge-Schumacher Dr.
Abstract Biphasic reaction systems for enzyme catalysis are an elegant way to overcome limited solubility and stability of reactants and facilitate continuous processes. However, many synthetically useful enzymes are not stable in biphasic systems of water and organic solvent. The entrapment in polymer beads of polyvinyl alcohol has been shown to enable the stable operation of enzymes unstable in conventional biphasic reaction systems. We report the extension of this concept to continuous operation in a fluidised bed reactor. The enzyme benzaldehyde lyase was used for the continuous synthesis of enantiopure (R)-3,3'-furoin. The results show enhanced stability with half-life times under operation conditions of more than 100 h, as well as superior enzyme utilisation in terms of productivity. Furthermore, racemisation and oxidation of the product could be successfully prevented under the non-aqueous and inert reaction conditions. [source]