Montmorilonit – usporedba metoda za njegovo određivanje u ljevaoničkim bentonitima

A comparison and estimation of usefulness of a quantitative analysis of montmorillonite in foundry bentonites, was the aim of this research. The investigations were made by means of three different techniques: methylene blue (MB) adsorption method, Cu(II)-triethylenetetramine complex (Cu(II)-TET) adsorption method, and infrared spectroscopy (FTIR) method. Tests were performed for 9 kinds of bentonites originated from various producers. The achieved results indicated that, the results obtained by the FTIR method were, in general, even 10% lower than the ones obtained by other methods. The best correlation with the data given by the producers were obtained for the Cu(II)-TET method. In addition, this method was characterised by the smallest value of standard deviations. A very essential advantage of the Cu(II)-TET method is a much shorter time needed for the analysis and its easier execution, which is important under production conditions.Cilj ovog istraživanja je bila procjena upotrebljivosti kvantitativne analize montmorilonita u ljevaoničkim bentonitima. Istraživanja su provedena pomoću tri različite tehnike: adsorpcija metilenskog modrila (MB), adsorpcija Cu(II)-trietilentetramin kompleksa (CU(II)-TET), i infracrvena spektroskopija (FTIR). Ispitivanja su provedena na 9 vrsta bentonita koji potječu od različitih proizvođača. Rezultati dobiveni FTIR metodom u prosjeku su za čak 10,0% niži od rezultata dobivenih ostalim metodama. Najbolja korelacija s podatcima od proizvođača dobivena je primjenom Cu(II)-TET metode. Osim toga, kod te metode najmanje su vrijednosti standardnih devijacija. Vrlo važna prednost Cu(II)-TET metode je znatno kraće vrijeme potrebno za anaalizu i lakše provođenje, što je značajno u proizvodnim uvjetima

Sign problems, noise, and chiral symmetry breaking in a QCD-like theory

The Nambu-Jona-Lasinio model reduced to 2+1 dimensions has two different path integral formulations: at finite chemical potential one formulation has a severe sign problem similar to that found in QCD, while the other does not. At large N, where N is the number of flavors, one can compute the probability distributions of fermion correlators analytically in both formulations. In the former case one finds a broad distribution with small mean; in the latter one finds a heavy tailed positive distribution amenable to the cumulant expansion techniques developed in earlier work. We speculate on the implications of this model for QCD.Comment: 16 pages, 5 figures; Published version with minor changes from the origina

Translational regulation in mycobacteria and its implications for pathogenicity.

Protein synthesis is a fundamental requirement of all cells for survival and replication. To date, vast numbers of genetic and biochemical studies have been performed to address the mechanisms of translation and its regulation in Escherichia coli, but only a limited number of studies have investigated these processes in other bacteria, particularly in slow growing bacteria like Mycobacterium tuberculosis, the causative agent of human tuberculosis. In this Review, we highlight important differences in the translational machinery of M. tuberculosis compared with E. coli, specifically the presence of two additional proteins and subunit stabilizing elements such as the B9 bridge. We also consider the role of leaderless translation in the ability of M. tuberculosis to establish latent infection and look at the experimental evidence that translational regulatory mechanisms operate in mycobacteria during stress adaptation, particularly focussing on differences in toxin-antitoxin systems between E. coli and M. tuberculosis and on the role of tuneable translational fidelity in conferring phenotypic antibiotic resistance. Finally, we consider the implications of these differences in the context of the biological adaptation of M. tuberculosis and discuss how these regulatory mechanisms could aid in the development of novel therapeutics for tuberculosis