Hemostatic efficacy and tissue reaction of oxidized regenerated cellulose hemostats

Oxidized regenerated cellulose (ORC) has been used as an absorbable hemostat since World War II. In the present study, hemostasis time was determined in a spleen incision model in swine. The effect of mass on absorbable hemostat efficacy and hemostasis time was evaluated by standardizing the ORC materials on a mass basis. The median hemostasis time for a single layer of the new nonwoven ORC was as much as 51 % shorter than woven ORC (P < 0.001). The mean hemostasis time for nonwoven ORC was not affected by the mass of hemostat applied to the wound. The hemostatic efficacy of woven ORC increased with the mass (layers) of hemostat applied to the wound. Nonwoven ORC is significantly faster in achieving hemostasis than woven ORC, and its hemostatic efficacy is not influenced by the mass of material applied. Tissue reaction was minimal and the material was fully absorbed by 14 days.     

Identification of lipophilic bioproduct portfolio from bioreactor samples of extreme halophilic archaea with HPLC-MS/MS

Extreme halophilic archaea are a yet unexploited source of natural carotenoids. At elevated salinities, however, material corrosivity issues occur and the performance of analytical methods is strongly affected. The goal of this study was to develop a method for identification and downstream processing of potentially valuable bioproducts produced by archaea. To circumvent extreme salinities during analysis, a direct sample preparation method was established to selectively extract both the polar and the nonpolar lipid contents of extreme halophiles with hexane, acetone and the mixture of MeOH/MTBE/water, respectively. Halogenated solvents, as used in conventional extraction methods, were omitted because of environmental considerations and potential process scale-up. The HPLC-MS/MS method using atmospheric pressure chemical ionization was developed and tuned with three commercially available C₄₀ carotenoid standards, covering the wide polarity range of natural carotenoids, containing different number of OH-groups. The chromatographic separation was achieved on a C₃₀ RP-HPLC column with a MeOH/MTBE/water gradient. Polar lipids, the geometric isomers of the C₅₀ carotenoid bacterioruberin, and vitamin MK-8 were the most valuable products found in bioreactor samples. In contrast to literature on shake flask cultivations, no anhydrous analogues of bacterioruberin, as by-products of the carotenoid biosynthesis, were detected in bioreactor samples. This study demonstrates the importance of sample preparation and the applicability of HPLC-MS/MS methods on real samples from extreme halophilic strains. Furthermore, from a biotechnological point-of-view, this study would like to reveal the relevance of using controlled and defined bioreactor cultivations instead of shake flask cultures in the early stage of potential bioproduct profiling.     

<Emphasis Type="Italic">N</Emphasis>-Methyl-D-aspartic Acid (NMDA) in the nervous system of the amphioxus <Emphasis Type="Italic">Branchiostoma lanceolatum</Emphasis>

Background  

NMDA (N-methyl-D-aspartic acid) is a widely known agonist for a class of glutamate receptors, the NMDA type. Synthetic NMDA elicits very strong activity for the induction of hypothalamic factors and hypophyseal hormones in mammals. Moreover, endogenous NMDA has been found in rat, where it has a role in the induction of GnRH (Gonadotropin Releasing Hormone) in the hypothalamus, and of LH (Luteinizing Hormone) and PRL (Prolactin) in the pituitary gland.     

Markov chain model for the critical micelle concentration of surfactant mixtures

An extension of the Markov chain model (MC) for micellization is proposed, which allows the distribution of the surfactants between the monomer solution and the micelles in a mixed surfactant system to be predicted. The dependence of the critical micelle concentration (cmc) on the composition of the solution is investigated. The equilibrium thermodynamic relation between cmc and micelle composition is discussed. The case of ternary mixtures is analyzed, and theoretical triangular diagram is constructed according to MC. Available experimental data for binary and ternary mixtures agree well with the new MC theory. The dependence of MC parameters on the structure of the surfactants is discussed. Comparison of MC with the simple mixture (“regular solution”) model is presented. The parameters of the MC theory are related to the interaction parameter β _SM of the simple mixture model.     

An algorithm for determination of the copolymer molecular weight distribution by Markov chain simulation

A simple and general algorithm, convenient for computer implementation, for calculation of the copolymer molecular weight distribution (MWD), its moments, copolymer composition, etc. from standard data has been developed describing copolymerization as a Markovian process. The algorithm is applicable for simulations of multimonomer copolymerization with monomolecular, bimolecular and mixed termination. It can be used for calculating the MWD of copolymers prepared under non-stationary conditions. Explicit formulae have been derived for the above parameters. They are exact even for low-molecular-weight oligomers. The calculation procedure involves nothing but plain matrix operations as matrix multiplication and inversion. For high-molecular-weight copolymers, even simpler dependencies that resemble those used for homopolymers can be used. A very simple numerical test has been proposed for checking their correctness.     

A Molecular-Wide and Electron Density-Based Approach in Exploring Chemical Reactivity and Explicit Dimethyl Sulfoxide (DMSO) Solvent Molecule Effects in the Proline Catalyzed Aldol Reaction

Modelling of the proline (1) catalyzed aldol reaction (with acetone 2) in the presence of an explicit molecule of dimethyl sulfoxide (DMSO) (3) has showed that 3 is a major player in the aldol reaction as it plays a double role. Through strong interactions with 1 and acetone 2, it leads to a significant increase of energy barriers at transition states (TS) for the lowest energy conformer 1a of proline. Just the opposite holds for the higher energy conformer 1b. Both the ‘inhibitor’ and ‘catalyst’ mode of activity of DMSO eliminates 1a as a catalyst at the very beginning of the process and promotes the chemical reactivity, hence catalytic ability of 1b. Modelling using a Molecular-Wide and Electron Density-based concept of Chemical Bonding (MOWED-CB) and the Reaction Energy Profile–Fragment Attributed Molecular System Energy Change (REP-FAMSEC) protocol has shown that, due to strong intermolecular interactions, the HN-C-COOH (of 1), CO (of 2), and SO (of 3) fragments drive a chemical change throughout the catalytic reaction. We strongly advocate exploring the pre-organization of molecules from initially formed complexes, through local minima to the best structures suited for a catalytic process. In this regard, a unique combination of MOWED-CB with REP-FAMSEC provides an invaluable insight on the potential success of a catalytic process, or reaction mechanism in general. The protocol reported herein is suitable for explaining classical reaction energy profiles computed for many synthetic processes.     

Newtonian plane Couette flow with dynamic wall slip

Meccanica - The occurrence of slip complicates the estimation of the viscosity in rheometric flows. Thus, special analyses and experimental protocols are needed in order to obtain reliable...