Search results for "Tributi"

Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 5. Bestimmung der Masse der Einzelm…

1977

A method is described for the determination of the molecular weight distribution (MWD) of various polymers from electron microscopy pictures of their molecules. It is shown, that the number of molecules needed to construct the distribution is between 200 and 300. Furthermore, with macroscopic density of the polymer and the volume determined by electron microscopy, the correct mass of a single molecule is obtained. The method is demonstrated for samples of polystyrene and poly(methyl methacrylate) and the results are compared with those of GPC-measurements.

Heterogeneous salt distribution in hot snacks enhances saltiness without loss of acceptability

2013

clef UT: 000318667000026; International audience; Abstract Health issues have led worldwide organisations to encourage the food industry to reduce salt in processed foods. Therefore, different strategies for salt reduction have been investigated. Here, the effect of heterogeneous salt distribution on saltiness perception intensity was assessed to compensate for salt reduction in snack foods. Two models of hot-served baked foods were developed. One model is made of two layers that vary in composition (cream-based and cereal-based layers) and salt (NaCl) concentration; the other one is made of four cream-based layers that vary in salt concentrations. Consumer panels rated the saltiness intens…

(Co)polymerisation Behaviour of Supported Metallocene Catalysts: Carrier Effect

2006

The polymerisation and copolymerisation of ethylene with 1-hexene over metallocene catalysts L 2 ZrCl 2 / MAO (L = Cp, n-BuCp, t-BuCp, i-PrCp, Me 5 Cp) supported on different types of carriers (MgCl 2 (MeOH) 6 or silica with CH 3 surface groups obtained in the sol-gel process) were studied. It was demonstrated that both the metallocene structure and the type of inorganic support affected catalyst activity and polymer properties such as melting point, molecular weight and molecular weight distribution. The metallocene structure also determined comonomer incorporation, both for homogeneous and supported catalytic systems. When a catalyst is anchored on a support, it becomes less effective at …

Milchsäure-Bildung und Verteilung in Erythrozytenkonzentraten

2001

1976

A radical mechanism is proposed for the formation of the 1,2-polymer 2 in the “spontaneous” polymerization of 4-vinylpyridinium salts 4-VP.HX (X=NO3, ClO4, HSO4, I) in aqueous solution on the basis of strong inhibition by oxygen and other radical inhibitors. Quantitative investigation of the influence of oxygen on the formation of the 1,2-polymer allowed the derivation of a formal kinetic scheme for the initiation and polymerization steps which is consistent with a free radical mechanism. Dependence of the average molecular weight of 2 on monomer concentration is in agreement with this model. Dependence of the inhibition time on the oxygen concentration as well as an acceleration of the fin…

Kristallisation und schmelzverhalten von fraktionen verzweigten polyethylens, 1. Darstellung und charakterisierung der fraktionen

1983

A branched polyethylene with broad molecular weight distribution was separated into a series of fractions by fractional precipitation from dilute solution. The fractions were characterized by viscometric and density measurements, IR-spectroscopy and calorimetry. The methyl group content and the density turned out as largely constant. Molecular weight effects show up in the melting behaviour. The main range of melting and the end of the melting curve shift to lower temperatures with decreasing molecular weight. Compared to the overall extension of the melting range these shifts are small. One has to conclude that polydispersity gives only a minor contribution to the broadening of the melting…

Kinetik und Molekulargewichtsverteilung eines anionischen Polymerisationsprozesses mit momentanem Start bei simultanem Monomerabbruch

1973

Die Kinetik und die Molekulargewichtsverteilung wird fur einen anionischen Polymerisationsprozes mit einem momentanen Startschritt und mit simultanem Monomerabbruch berechnet. Ein derartiger Polymerisationsablauf ist bei der anionischen Polymerisation von Methylmethacrylat in polaren Losungsmitteln zu erwarten. — Die Molekulargewichtsverteilung geht mit steigendem Monomerabbruch in eine SCHULZ-FLORY-Verteilung uber. The kinetics and the molecular weight distribution are calculated for an anionic polymerization with rapid initiation and simultaneous deactivation by the monomer. Such a process is to be expected for the anionic polymerization of methylmethacrylate in polar solvents. — The mole…

The Interaction of State Transitions and Chlororespiration in the Xanthophycean Alga Pleurochloris Meiringensis

1990

Wavelength dependent State I-State II-transitions have been shown to exist in chlorophytes and red algae. Little is known about the regulation of energy distribution between the photosystems of chlorophyll c-containing plants. Previously it was shown that in the xanthophycean alga Pleurochloris meiringensis two states of energy distribution could be established [l]: In state “D” light is preferentially transferred to PS II, whereas in state “L” PS I is favoured. These state regulations strictly depend on the intensity and not on the wavelength of prei1lumination. In this paper we give new evidence that chlororespiration is involved in the mechanism of state “L”-state “D”-transitions.

Some Aspects of the Influence of Particle Size on Properties and Behaviour of a Dielectric Material : Example of Barium Titanate

1989

Anybody agrees with the idea that particle size plays an important role in the behaviour of a polycrystalline material but very few studies are giving precise information about this role. In this paper some experimental results are presented succintly to illustrate the importance of this physico-chemical factor. They are related to barium titanate, the main component of the dielectric material in the type II ceramic capacitors.

Influence of molecular parameters on the elongational behaviour of different polyethylenes and their blends

1988

Elongational data on a large number of polyethylene samples with different structures and their blends are presented in order to evaluate the influence of the molecular weight and molecular weight distribution for a given degree of long chain branching. The elongational viscosity rises with the number of branch points and also with molecular weight and molecular weight distribution. Simple relationships between elongational viscosity at a given deformation and molecular parameters are presented.