Search results for "meat"

Chemical and acidic composition of Longissimus dorsi muscle of Comisana lambs fed with Trifolium subterraneum and Lolium multiflorum

2010

Aim of this study was to evaluate the effects of grazing on Trifolium subterraneum and Lolium multiflorum, as pure or associated crops, on the chemical composition and on the fatty acid profile of the intramuscular lipids of the meat of lambs. Forty Comisana male lambs, on average weighing 13.75±1.90 kg, were divided into four homogenous groups of ten and called, in relation to the diet: group T those grazing on T. subterraneum; Group L on L. multiflorum; Group TL on adjacent monocultures of T. subterraneum and L. multiflorum (66.6 and 33.3% of surface, respectively); Group LT on adjacent monocultures of T. subterraneum and L. multiflorum (33.3 and 66.6% of surface, respectively). Every 10 …

The mechanism of polymer permeation through polymer gel membranes

2007

Polymer gels are capable of producing separation effects on polymers. Applications for fractionation and for osmotic measurements are possible. Investigations are reported concerning the separation properties of polystyrene layers grafted onto a supporting cellulose basis. The permeation for pure solvents and the separating molecular limit for different solvents are tested. Their size depends uniquely on the interaction between the grafted polystyrene and the solvent.

Simulations of Polymers in Confined Geometries

1991

The properties of flexible polymers moving inside porous structures are believed to be relevant to practical problems such as filtration, gel permeation chromatography, heterogeneous catalysis, oil recuperation, etc.1. Similarly the adsorption of macromolecules on interfaces plays an important role for problems such as adhesion, flocculation and stabilisation of colloid particles, biological membrane function, artificial organs in medicine, etc. 2. Aside from this eventual practical application, the configurational statistics of polymers in such confined geometries is a challenging problem of theoretical physics. The present brief review will be concerned with the study of a single long fle…

Solution Properties of Polysarcosine: From Absolute and Relative Molar Mass Determinations to Complement Activation

2018

Polysarcosine (pSar) was one of the first polymers synthesized in a controlled living manner, but it was only recently when it was reconsidered as a promising alternative for poly(ethylene glycol) (PEG) in biomedical applications. Despite receiving more and more attention, very little is known about the solution properties of pSar, such as coil dimensions and thermodynamic interactions. In this article, we report on these properties of pSar with degrees of polymerization 50 < X-n < 400 that were prepared by controlled living ring-opening polymerization. The polymers are characterized by gel permeation chromatography (GPC), MALDI-TOF mass spectrometry, dynamic and static light scattering (SL…

Synthesis and Characterization of Syndiotactic Polystyrene-Polyethylene Block Copolymer

2019

The direct synthesis of syndiotactic polystyrene-block-polyethylene copolymer (sPS-b-PE) with a diblock structure has been achieved. The synthetic strategy consists of the sequential stereocontrolled polymerization of styrene and ethylene in the presence of a single catalytic system: cyclopentadienyltitanium(IV) trichloride activated by modified methylaluminoxane (CpTiCl3/MMAO). The reaction conditions suitable for affording the partially living polymerization of these monomers were identified, and the resulting copolymer, purified from contaminant homopolymers, was fully characterized. Gel permeation chromatography coupled with two-dimensional NMR spectroscopy COSY, HSQC, and DOSY confirme…

The fractal calibration method applied to the characterization of polymers in solvent mixtures and in mixed gel packings by SEC.

2007

The size-exclusion chromatographic (SEC) behaviour of different solvent/polymer systems in three packing sets has been analysed from fractal considerations. The three-column sets studied are specifically formed by: (i) 'pure' micro-styragel, (ii) 'mixed' TSK Gel H(HR + XL + HR) and (iii) mixed TSK Gel H(XL + HR + XL). The experimental data reveals that in most of the systems assayed the classical universal calibration (UC) is not fulfilled, denoting the existence of secondary effects accompanying the main SEC mechanism. In order to obtain an accurate characterization of different polymers eluted in solvent mixtures and/or mixed packings, the use of a reliable and trusted calibration curve i…

Star poly(2-ethyl-2-oxazoline)s-synthesis and thermosensitivity

2011

A series of star-shaped poly(2-ethyl-2-oxazoline)s was prepared by cationic polymerization. The polymerization was initiated by dipentaerythrityl hexakis(4-nitrobenzene sulfonate) and a tosylated hyperbranched polymer of glycidol. The polymerization proceeded in a controlled manner. The star structure of the products was determined by nuclear magnetic resonance. The molar mass distributions that were measured by gel permeation chromatography with multiangle laser light scattering were narrow, and the experimental values of the molar masses were close to those predicted. The very compact structure of the polymers obtained (compared with the linear counterparts) confirmed the star formation. …

1996

An iterative, approximative procedure is presented, to calibrate the determination of molar masses of polymers with gel-permeation chromatography, additionally using viscometry, and transformations, according to Benoit's concept of universal calibration, even if only polymers with broad molar mass distribution are available. The calculated (intermediate) values of the average molar masses from each step of iteration converge to final values. With at least two fractions of the polymers to be analyzed, and with measured intrinsic viscosities of the fractions, a calibration curve of gel-permeation chromatography and Mark-Houwink's constants can be determined. Assumptions for the use of the cal…

Continuous polymer fractionation of polysaccharides using highly substituted trimethylsilylcellulose

1998

Trimethylsilylcellulose (TMSC) was prepared from commercial cellulose with a mixture of hexamethyldisilazane and chlorotrimethylsilane in the solvent system N,N-dimethylacetamide/lithium chloride. The soluble, highly silylated polymer (degree of substitution, DS 2.9) had a molar mass M, of 500 kg/mol and a molecular non-uniformity U = (M w /M n )- 1 of 2.9. In order to investigate the principal suitability of a continuous polymer fractionation for polysaccharides like cellulose derivatives and to obtain TMSC with different molecular weights and lower non-uniformity TMSC was fractionated by means of CPF (Continuous Polymer Fractionation), well-established in the field of synthetic polymers. …

Fractal calibration in size-exclusion chromatography

2003

Abstract The elution behaviour of different polymer–solvent systems in three types of organic columns for SEC has been compared and interpreted. The experimental data show that the classical universal calibration is not accomplished. Deviations from a unique curve are observed due to the binary and ternary interactions between the components of the system (solvent, polymer and gel) which results on secondary mechanisms accompanying the main pure or “ideal” SEC separation mechanism. Both, enthalpic and entropic effects are interpreted in terms of the swelling and crosslinking degrees of the gel packings, and are also related with the fractal characteristics of their surfaces, such as the fra…