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Search Results: 1 - 10 of 53402 matches for " polymer A "
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Assessment of Biological Properties of Mouse Embryonic Stem Cells Characteristics Prior To Differentiation  [PDF]
Gary Adams, Lee Buttery, Snow Stolnik, Stephen E. Harding, Nan Wang
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2011, DOI: 10.4236/jbnb.2011.24047
Abstract: Mouse embryonic stem (ES) cells are continuous cell lines derived directly from the fetal founder tissue of the pre-im- plantation embryo and can be expanded in vitro and give rise to cells from ectodermal, mesodermal and endodermal layers. Mouse ES cells can be maintained and their numbers expanded by culture on feeder layer cells with LIF present in the culture medium. This study shows that changes in seeding density can significantly influence cell number expansion rates. Culturing ES cells in the absence of feeder layer cells and LIF stimulates EB formation when cultured in non-adherent culture plates. Formation of EBs particularly numbers, size of EBs formed, rates of cell proliferation within EBs and viability of cells can also be controlled based on seeding density. All these factors are important for optimizing approaches to co-ordinate differentiation towards a specific cell type. A key goal of ES cell research is to develop specific functional cell types which can be potentially used to study mechanisms of tissue development and as a therapy to repair or replace damaged or diseased tissues.
Preparation and evaluation of transdermal drug delivery system of etoricoxib using modified chitosan
Wahid A,Sridhar B,Shivakumar S
Indian Journal of Pharmaceutical Sciences , 2008,
Abstract: In the present investigation chitosan has been chemically modified by treating with two different aldehydes like acetaldehyde and propionaldehyde to form Schiff′s bases. Schiff′s bases of chitosan with acetaldehyde and propionaldehyde were named as polymer A and polymer B, respectively. Fourier Transform Infra Red (FTIR) spectral data have confirmed the reaction carried out on chitosan. Drug free polymeric films of chitosan, chemically modified chitosan and chitosan/hydroxypropylmethylcellulose blend were prepared and evaluated for various physicochemical characters. Further, the films were incorporated with anti-inflammatory drug, etoricoxib using glycerol as plasticizer. The drug loaded films were cross-linked with sodium citrate and studied for permeation characteristics across dialysis membrane and rat skin. All the films were evaluated for bursting strength, swelling index, moisture uptake, thickness uniformity, drug content uniformity, tensile strength, percent elongation at break, percent flatness, water vapour transmission rate and in vitro drug permeation study.
Microscopic Characterization of Ecological Concrete Polymeric  [PDF]
A. D. Rodríguez, M. L. Domínguez, R. M. Melgoza
Microscopy Research (MR) , 2014, DOI: 10.4236/mr.2014.21003

The Scanning Electron Microscopy (SEM) and Optical Microscopy (OM) with integrated digital camera are techniques that are used in the present investigation, for the morphological characterization of a new composite material called “organic polymer concrete” in which microparticles added fibers and polyethylene terephthalate (PET) recycling mechanically (RM). Polymer concrete (PC) is a new composite material (MC) in the application considered as an alternative material of construction in which reinforcement particles are recycled polymers which have approximately the same dimensions in all directions. Therefore, the particles can be rods, spheres, chips and many other shapes whose appearance reasons are about 10 microns. These MC, the size, shape and distribution and the ratio and the modulus of the particles affect the properties of the material.

Influence of Prepackaged Polymer-Modified Mortar as a Modifier on Strength of Concrete
Abdullah Saand,Mohammad Ismail,Salihuddin Radin Sumadi
Journal of Applied Sciences , 2007,
Abstract: This study introduce a new trend of utilising Prepackaged Polymer-Modified Mortar (PPMM) as a modifier to ordinary concrete for producing Polymer-Modified Concrete (PMC). The experimental study articulates the strength development of proposed polymer-modified concrete. A range of quantities of PPMM, as 5 to 50%, were mixed with ordinary concrete of 30 N mm-2 characteristic strength to produce polymer-modified concrete and to evaluate for compressive strength, tensile strength, density and workability. The material behaviour in terms of compressive strength and tensile strength, together with density and slump was investigated by casting and testing cubes of 100 mm size, cylinders 100 mm dia and 200 mm height. This Preliminary study shows that compressive strength and tensile strength is improved significantly by inclusion of various quantities as percentages of PPMM to ordinary concrete and curing regime as specified by JIS. PPMM dosages of 5 to 20% resulted considerably higher compressive and tensile strength than that of ordinary concrete, on the other hand further increase in percentage of PPMM gave less strengths. Results demonstrated more prominent percentage increase in tensile strength than compressive strength of produced polymer-modified concrete. Polymer-modified concrete mixes with all percentage dosages of PPMM were found cohesive and workable.
Use of a glucomannan polymer to reduce the effects of mycotoxin-contaminated diets in finishing pigs
G. Battacone,G. A. Carboni,P. Nicolussi,C. Ligios
Italian Journal of Animal Science , 2010, DOI: 10.4081/ijas.2007.1s.673
Abstract: The use of feed additives with mycotoxin adsorption capacity is a common strategy for controlling negative effects of mycotoxins in swine production systems. However, adsorbents that may results very effective under experimental conditions, i.e. when feed contamination level is rather high, do not necessarily retain their efficacy when tested under field conditions feed with generally low mycotoxin contamination. In this study, the effects of diets artificially contaminated with aflatoxin B1 or ochratoxin A on fattening performance and serum chemistry of fattening pigs are investigated. Moreover, the ability of a commercial glucomannan polymer (Gm polimer) to reduce or eliminate the effects of the contaminated feeds is tested. Thirty heavy pigs (BW = 110±10.6 kg) were fed 6 diets (n = 5 pigs/diet) for 4 weeks until slaughtering. Diets were: control without toxin added (C); added with 0.02 ppm of aflatoxin B1 (AFB1); added with 0.05 ppm of ochratoxin A (OTA); other three diets as the previous but the addition of 2.0 g/kg of Gm polymer (C-GM, AFB1-GM, OTA-GM). Daily weight gain (ADG) and Feed efficiency ratio (FE) were measured every two weeks. Data were analyzed with a two-way ANOVA that included the fixed effect of diet, time and their interaction. After the first 2 weeks the ADG did not differ significantly between the diets, even if the ADG of AFB1 diet was about 20% lower than AFB1-Gm or C. In the last 2 weeks the ADG of AFB1 diet was significantly lover than the other diets (P<0.01) and was about one-half of the values reported for the same group in the first period. The contamination with ochratoxin A did not affect fattening performance of pigs during the whole experimental period. No damages were found in kidneys of all diets. Moreover, no evidence of association between observed liver damages and different diets was found. Finally, no differences between experimental diets were evidenced for the haematological parameters.
On the adsorbed mass of polymers on surfaces (NOTE)
Journal of the Serbian Chemical Society , 2001,
Abstract: It is shown that for ideal polymers interacting with a surface via the pseudopotential of a delta function, the number of contacts between the monomer units and the surface as a function of concentration cb is a dependence of the form acb/(1 bcb). The architecture of the polymer, the degree of polymerization, the interaction energy between a monomer unit and the surface, the area of the surface and the monomer length are embodied in the parameters a and b. The above dependence of the adsorbed mass of a polymer on the concentration is confirmed by the experimental results of Takahashi and his collaborators. For linear polystyrene of molecular weight 134×105,interacting with a chrome plate, the parameters a and b are, respectively, about equal to (89938/273) ×10-6 m and ( 19300/273) m3 kg-1.
Journal of Science and Arts , 2012,
Abstract: The dielectric measurements have been done for the determination of real and imaginary part of permittivity of a monotropic Smectic sample alongwith its polymer doped sample. The samples have been investigated in the frequency range from 1 kHz to 1 MHz and temperature range 315 K to 340 K. The dielectric measurements in smectic phase indicate Debye-type dispersion with relaxation peak at 357.72 kHz and 354 .83 kHz for pure and polymer doped samples respectively at 333 K. Measurements have also been made for refractive indices, birefringence, optical transmittance in the above mentioned temperature range and order parameter have been calculated using birefringence data. The temperature dependence of these parameters has been discussed in detail.
Rheological Properties of Polymers: Structure and Morphology of Molten Polymer Blends  [PDF]
Oluranti Sadiku-Agboola, Emmauel Rotimi Sadiku, Adesola Taoreed Adegbola, Olusesan Frank Biotidara
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.21005
Abstract: The article reviews a brief literature on the rheological properties of polymer melts and blends. Experimental results on polymer blends are summarized. Technically, vital types of multi-phase polymers such as compounds and blends are discussed. The importance of the rheological properties of polymer mixtures in the development of the phase structure is discussed. And the importance of considering the stress and/or strain history of a material sample in a rheological investigation is discussed. Finally, the outlook on the past, present and future developments in the field of polymer rheology are given. The review concludes with a brief discussion on the opportunities and challenges in the field of polymer blends and blend rheology.
Preparation and Properties of Polyaniline in the Presence of Trehalose  [PDF]
Hirotsugu Kawashima, Hiromasa Goto
Soft Nanoscience Letters (SNL) , 2011, DOI: 10.4236/snl.2011.13013
Abstract: Oxidative polymerization of aniline in aqueous solution in the presence of trehalose was conducted. Fourier transform infrared spectroscopy confirmed successful preparation of polyaniline containing a trace amount of trehalose. Electron spin resonance spectroscopy revealed that electron spin concentration of the polyaniline increases with aniline/trehalose ratio in the polymerization. Scanning electron microscopy revealed that the polyaniline shows granular and porous morphology. Electrical conductivity of these polyanilines was in the order of 10-4 S/cm.
Effect of Concentration of Mica on Properties of Polyester Thermoplastic Elastomer Composites  [PDF]
M. S. Sreekanth, V. A. Bambole, S. T. Mhaske, P. A. Mahanwar
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2009, DOI: 10.4236/jmmce.2009.84024
Abstract: Particulate filled polymer composites are becoming attractive because of their wide applications and low cost. In this study the effects of mica with varying concentration on the mechanical, thermal, electrical, rheological and morphological properties of polyester thermoplastic elastomer (Hytrel?) was investigated. Composites of Hytrel? with varying concentrations (viz. 5 to 40 weight %) of mica were prepared by twin screw extrusion. Mechanical properties such as flexural strength and modulus were found to increase with mica concentration, whereas tensile strength was found to decrease at higher concentrations. Electrical and thermal properties of composite were found to increase with filler concentration. Morphological studies revealed that there is a good dispersion of filler in the polymer matrix at lower oncentrations.
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