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Progress in Agricultural Engineering Sciences
Authors:
Tamás Csurka
,
Klára Pásztor-Huszár
,
Adrienn Tóth
,
Richárd Pintér
, and
László Ferenc Friedrich

Abstract

Blood coagulation is a process, which is initiated by certain physico-chemical effects. This process results in a change in the blood from the sol state, that is well suited for further processing, to gel state. 13 blood clotting factors take part in the cascade system of blood coagulation. Trisodium-citrate affects factor IV, the calcium, and prevents the change in blood texture. The effect of different concentrations of trisodium-citrate (0, 0.48, 2.4, 4.8, 9.6, 14.4, 19.2, 24 w/w%) on the texture of blood is investigated. Porcine blood was collected in 20 cm3 test tubes in a slaughterhouse directly before trisodium-citrate addition and was stored for one day under refrigerated conditions. The samples without trisodium-citrate coagulated and the samples with high trisodium-citrate (4–5 g) became solid as well because of the protein salting-out. The viscosity of successfully treated samples and the shear stress were measured with a rotational viscometer (Physica MCR 51, Anton-Paar) with concentric cylinders and Couette type method. The flow behavior of all samples could be described by the Herschel-Bulkley model. The yield point, the consistency index and the power of law index, which are determined by the equation of the model, showed that the samples with lower trisodium-citrate content coagulated “better” and the sample with high trisodium-citrate were most similar to Newtonian fluid. The results are trend-likes, but significant differences may be expected in the case of higher sample amount. The yield point of the sample, which contained 14.4 w/w% trisodium-citrate, was by 37.3% less than the sample containing 0.48% trisodium-citrate, and the consistency index of the sample with 3 g trisodium-citrate was by 20.5% higher than that of the sample with 0.48% trisodium-citrate. Thanks to these results a cheaper concentration and drying of porcine blood and blood fractions are available because no surplus water is added to the blood.

Open access

Abstract  

The self-aggregation of two short ionic tetrapeptides (RWDW and RVDV, where R = arginine, V = valine, W = tryptophan, D = aspartic acid) was studied by different experimental techniques such as, atomic force microscopy (AFM), light scattering (LS), isothermal titration calorimetry (ITC) and viscosimetry. AFM was used to investigate the morphology of the aggregates; the AFM images showed the presence of fibrillar aggregates whose number and length increased with increasing oligopeptides concentration. On the other hand, the collected experimental calorimetric and physical chemical results consistently indicated a critical aggregation concentration (cac) around 0.5 and 2.0 mM for RWDW and RVDV respectively.

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Abstract  

The temperature influence (15–35 °C) on the adsorption mechanism and conformation of nonionic polymers (polyethylene glycol (PEG), polyethylene oxide (PEO) and polyvinyl alcohol (PVA)) on the zirconium dioxide surface was examined. The applied techniques (spectrophotometry, viscosimetry, potentiometric titration and microelectrophoresis) allowed characterization of the changes in structure and thickness of polymer adsorption layers with the increasing temperature. The rise of temperature favours more stretched conformation of polymer chains on the ZrO2 surface, which results in higher adsorption and thicker adsorption layer. Moreover, these conformational changes of adsorbed macromolecules affect the electric (solid surface charge density) and electrokinetic (zeta potential) properties of the zirconia–polymer interface. The obtained data indicate that the polyvinyl alcohol adsorption has a greater influence on zirconia properties in comparison to that of PEG and PEO. It is due to the presence of acetate groups in the PVA macromolecules (degree of hydrolysis 97.5%), which undergo dissociation.

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Abstract

The influence of solution pH on the structure of polyvinyl alcohol adsorption layer on the alumina surface was investigated. The spectrophotometry, viscosimetry, thermogravimetry, potentiometric titration and microelectrophoresis were applied in experiments. These methods enable determination of the following parameters: adsorbed amount of PVA, stability of suspension without and with polymer, thickness of its adsorption layers, changes in thermal characteristics of Al2O3 surface with the adsorbed polymer, surface charge density and zeta potential of solid particles in the presence and absence of PVA, respectively. All measurements were carried out in the pH range 3–9. The obtained results indicate that pH has a great influence on the conformation of PVA chains adsorbed on the alumina surface. It is due to incomplete hydrolysis of acetate groups of polyvinyl alcohol macromolecules (degree of hydrolysis 97.5%), which dissociate with the increasing pH. Moreover, the polymer adsorption on the alumina surface causes changes in the course of thermogravimetric curves. The effect of weight loss for Al2O3–PVA systems is smaller than that of Al2O3 without polymer. It is due to elimination of water molecules from the solid surface by adsorbed polymer.

Open access
Journal of Thermal Analysis and Calorimetry
Authors:
Javier A. Díaz-Ponce
,
Eugenio A. Flores
,
Alfonso Lopez-Ortega
,
Jose G. Hernández-Cortez
,
Arquimides Estrada
,
Laura V. Castro
, and
Flavio Vazquez

. Kök , M , Lettoffé , JM , Claudy , P , Martin , D , Garcin , M , Volle , J-L 1996 Comparison of wax appearance temperatures of crude oils by differential scanning calorimetry, thermomicroscopy and viscosimetry . Fuel 75 : 787 – 790 10

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