Search results for "Molar"
showing 10 items of 1069 documents
Thermodynamic study on phase equilibrium of epoxy resin/thermoplastic blends
2008
Abstract The experimental phase diagrams (cloud point curves) of three series of epoxy/thermoplastic blends, namely, epoxy/polystyrene (PS), epoxy/poly(ether sulfone) (PES), and epoxy/poly(ether imide) (PEI) as a function of molar mass and composition have been analysed from a thermodynamic point of view. A model based on the Flory–Huggins lattice theory considering the concentration dependence of the interaction parameter as predicted by Koningsveld was employed to determine the equilibrium compositions, and concentration and temperature dependent interaction parameters. Binodal, spinodal, and critical point data have been computed and show good agreement with experimental data.
Polymer Incompatibility Caused by Different Molecular Architectures: Modeling via Chain Connectivity and Conformational Relaxation
2009
The calculation of phase diagrams for blends of linear and branched polymers made up of identical monomeric units is modeled using an approach that subdivides the mixing process into two steps: i) contact formation between the different components, keeping their chain conformations and the volume of the system constant; and, ii) relaxation of the macromolecules into their equilibrium state by molecular rearrangements. It is assumed that step (ii) causes shape-induced polymer incompatibility and that the degree of branching can be quantified in terms of the volumes the isolated coils of the branched polymer occupy in relation to the volume the linear product with the same molecular weight oc…
Biocompatibility of alginates for grafting: impact of alginate molecular weight.
2003
Optimising microencapsulation technology towards the effective clinical transplantation has created the need for highly biocompatible alginates. Therefore, in this study the biocompatibility of different beads prepared from alginates with varying average molecular weight was examined. In some experiments the beads were covered with a multilayer membrane surrounded by an alginate layer. First of all, we found that beads made of a lower weight average alginate elicted a much stronger fibrotic response compared to beads made of a higher weight average alginate (LV-alginate > MV-alginate). The results were confirmed by the observation that the extent of tissue fibrosis was significantly increas…
Quantification of hydrolysis of toxic organophosphates and organophosphonates by diisopropyl fluorophosphatase from Loligo vulgaris by in situ Fourie…
2008
Abstract The enzyme diisopropyl fluorophosphatase (DFPase) from the squid Loligo vulgaris effectively catalyzes the hydrolysis of diisopropyl fluorophosphate (DFP) and a number of organophosphorus nerve agents, including sarin, soman, cyclosarin, and tabun. Up to now, the determination of kinetic data has been achieved by techniques such as pH-stat titration, ion-selective electrodes, and fluorogenic substrate analogs. We report a new assaying method using in situ Fourier transform infrared (FTIR) spectroscopy with attenuated total reflection (ATR) for the real-time determination of reaction rates. The method employs changes in the P–O–R stretching vibration of DFP and nerve agent substrate…
Performance of polyester-based electrospun scaffolds under in vitro hydrolytic conditions: From short-term to long-term applications
2019
The evaluation of the performance of polyesters under in vitro physiologic conditions is essential to design scaffolds with an adequate lifespan for a given application. In this line, the degradation-durability patterns of poly(lactide-co-glycolide) (PLGA), polydioxanone (PDO), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) scaffolds were monitored and compared giving, as a result, a basis for the specific design of scaffolds from short-term to long-term applications. For this purpose, they were immersed in ultra-pure water and phosphate buffer solution (PBS) at 37 °
Ionic self-complementarity induces amyloid-like fibril formation in an isolated domain of a plant copper metallochaperone protein
2004
This article is available from: http://www.biomedcentral.com/1472-6807/4/7
Characterization of melt-polymerized polycarbonate: preparative fractionation, branching distribution and simulation
2001
Melt-polymerized bisphenol-A polycarbonate materials characterized by a low degree of branching were fractionated according to molecular weight by the continuous polymer fractionation (CPF) method. The distribution of two types of end-groups and in-chain salicylate moieties arising from thermal rearrangement reactions were assessed across the molecular weight distribution by analysis of the fractions. Experimentally determined branching densities of the fractions agreed well with a molecular simulation based on a random sampling polycondensation model. Both simulation and experiments showed that the branching density increases with molecular weight in the experimentally accessible range. (C…
Physiological and agonistic behavioural response of Procambarus clarkii to an acoustic stimulus
2012
Summary This study examined the effects of an acoustic stimulus on the haemolymph and agonistic behaviour of the red swamp crayfish Procambarus clarkii. The experiment was conducted in a tank equipped with a video recording system using 6 groups (3 control and 3 test groups) of five adult crayfish (30 specimens in total). After one hour of habituation, the behaviour of the crayfish was monitored for two hours. During the second hour, the animals in the test groups were exposed to a linear sweep (frequency range 0.1-25 kHz; peak amplitude 148 dBrms re 1 µPa at 12 kHz) acoustic stimulus for 30 minutes. Exposure to the noise produced significant variations in haemato-immunological parameters a…
Acute changes of systemic parameters in tumour-bearing rats, and of tumour glucose, lactate, and ATP levels upon local hyperthermia and/or hyperglyca…
1991
Arterial blood pressure and relevant parameters of the arterial blood (O2 and CO2 tensions, pH, haematocrit, serum electrolytes and osmolality) were determined in tumour-bearing rats upon local hyperthermia (HT) and/or hyperglycaemia (HG). Tumour heating was performed in a saline bath (44 degrees C) for 120 min; hyperglycaemia was induced by i.v. infusion of 40% glucose solution for 150 min [blood glucose levels: 35-40 mM during heating; total amount of glucose: 1.19 g/100 g body wt.; infusion rates: 0.31 ml (100 g body wt.)-1 min-1 for 2 min, 0.02 ml (100 g body wt.)-1 min-1 for 88 min, and 0.01 ml (100 g body wt.)-1 min-1 for 60 min]. Immediately after treatment, glucose, lactate and ATP …
Filmability and properties of compatibilized PA6/LDPE blends
2005
Blends of low density polyethylene (LDPE) and polyamide 6 (PA6), compatibilized with an ethylene-acrylic acid copolymer (EAA), either alone or combined with a low molar mass bis-oxazoline compound (PBO), have been processed in film blowing operations and the properties of the films have been investigated. Without of compatibilization, the filmability of the blend was very poor and no significant specimen was collected. As a result of the reactive compatibilization, the blends with EAA and even more with the EAA-PBO, were processed successfully in film blowing. The films of the quaternary blends were shown to possess satisfactory mechanical properties as a result of fine and stable morpholog…