On the relationship betweenT 1 andT 2 for stochastic relaxation models

We consider the relaxation dynamics of two quantum levels coupled to a stochastic bath. We emphasize that even if the matrix elements of the fluctuating Hamiltonian are Gaussian, a second-order cumulant truncation is not exact. For various stochastic models, including the case of a spin-1/2 particle in a fluctuating magnetic field, we calculate 1/T ₁, the population relaxation rate, and 1/T ₂, the phase relaxation rate, up to fourth order in perturbation theory. We show that unlike the commonly accepted second-order result that 1/T ₂1/2T ₁, when fourth-order terms are included, in some instances 1/T ₂<1/2T ₁.     

Thermal Analysis of Fe(III) Complexes with Salicylaldehyde Semi-, Thiosemi- and S-methylisothiosemi-carbazones

The paper describes the results of differential thermal analysis of the octahedral Fe(III) complexes of the general formula [Fe(HLⁿ)₂]Cl and Fe(HL³)L³, as well as of the corresponding ligands H₂Lⁿ (H₂Lⁿ — tridentate salicylaldehyde semi thiosemi- and S-methylisothiosemi-carabazones with n=1, 2 and 3 respectively). The decomposition of the complexes involving sulphur-containing ligands (H₂L² and H₂L³) starts with sulphur elimination. In case of the complexes [Fe(HL²)]Cl and [Fe(HL³)]Cl sulphur evolves independently, whereas with Fe(HL³)L³ it is eliminated within the SCH₃ group. In the former case, sulphur elimination takes place at the same temperature for both complexes. The change in the coordination mode, being a consequence of the replacement of O by S, has no essential effect on thermal stability of the coordination polyhedron. The complexes involving ONN coordination, realized with the H₂L³ ligand, exhibit a comparatively highest thermal stability of the coordination polyhedron.This revised version was published online in November 2005 with corrections to the Cover Date.     

Study of metal complexes of a tripodal hydroxypyridinone ligand by electrospray tandem mass spectrometry

The tripodal ligand N,N,N-tris[(1,hydroxy-2-pyridinon-6-yl)amide]propylamine was synthesized. It is composed of an anchor (nitrogen atom), a functional group (hydroxamate), and also a spacer of variable length defined by the number of methylene groups linking the anchor and the functional group. The characterization of this ligand in the presence of several divalent metal cations (Fe(II), Mn(II), Co(II) and Cu(II)), performed by electrospray ionization mass spectrometry (ESI-MS and ESI-MS/MS), allowed elucidation of oxidation states and also of different fragmentation patterns. The importance of the spacer length was studied in the case of the iron binary complex by comparing this ligand with another with a shorter spacer. In this way the stabilizing conditions, in which hydrogen bonds are implicated, were clarified.     

Desorption/ionization on porous silicon mass spectrometry (DIOS) of model cationized fatty acids

Desorption/ionization on porous silicon (DIOS) is a very useful technique in the case of small molecular weight compounds, compared to the matrix-assisted laser desorption ionization (MALDI). This is because MALDI generates matrix-related ions that overlap with the mass range of interest. The aim of our work was to investigate the suitability of the DIOS technique in the case of fatty acids in negative ion mode. The analysis of the chosen fatty acid models, nonadecanoic acid (C(19)H(38)O(2)) and heneicosanoic acid (C(21)H(42)O(2)), gave rise to the observation of the deprotonated monomeric species and selective cationized multimeric species. This cation selectivity was further elucidated by complementary studies based on the addition of various metals such as Ag(I), Zn(II), Fe(II), and also Cu(II). Specific behavior, depending upon the introduced metal, was highlighted by different redox reaction processes and also metastable decompositions (in PSD mode).     

Hydrolysis and Extraction Properties of Aroylhydrazones Derived from Nicotinic Acid Hydrazide

The kinetics of hydrolysis of N′-salicylidene-3-pyridinecarbohydrazide (1) and N′-(2-hydroxy-3-methoxyphenylmethylidene)-3-pyridinecarbohydrazide (2) were investigated in the dioxane/water (1/1, volume ratio) solvent system in acidic and basic media, and the corresponding reaction mechanisms were proposed. The kinetic results suggest that in the acidic solutions the rate-determining step of the hydrolysis reaction is the attack of a water molecule on the protonated azomethine group, whereas in the basic medium it is the attack of water on the completely deprotonated hydrazone. By analyzing the temperature dependence of the reaction rates, the thermodynamic activation parameters, i.e. activation enthalpy and entropy, were also evaluated and discussed. The complexation reactions of vanadium(V) with aroylhydrazones 1 and 2 as well as the extraction of V(V) from aqueous to an organic phase were studied spectrophotometrically. The optimum conditions for complex formation and extraction of vanadium(V) into chloroform solutions of compounds 1 or 2 have been evaluated. Based on the results obtained by Job’s method and the equilibrium shift method, the stoichiometries of the complexes were determined to be 1:1. The effect of foreign ions on V(V) extraction by compound 2 has been determined as well.     

Study of antimicrobial properties of cotton medical textiles treated with citric acid and dried/cured by microwaves

The purpose of this study was to examine antibacterial and antifungal activity of antibacterial finish based on Citric acid on cotton medical textiles. The ability to effectively reduce the number of gram-negative, gram-positive bacteria and yeast was evaluated, specifically comparing the antibacterial activity after two different drying/curing methods. Citric acid (CA) and diethyl–tetradecyl–[3–(trimethoxysilyl)-propyl] ammonium chloride (Quat) were used for hygiene and disinfection purposes of medical textiles in this study. It was applied by pad-dry process and its fixation to cellulose hydroxyls was enhanced either by high curing temperatures or microwaves (MW). Determination of antibacterial activity of finished products was performed according to ISO 20743:2007 standard before the washing and after the 10 washing cycles. Antibacterial activity was tested against gram-negative bacteria, Escherichia coli, gram-positive-Staphylococcus aureus and yeast, Candida albicans. Obtained results are confirming the possibility of eco-friendly CA application, for the purpose of antimicrobial finishing of cotton medical textiles. Prevention of nosocomial infections with the Citric acid is possible using both curing methods (convection and microwave) and furthermore, the treatment is durable up to 10 washing cycles. Citric acid, as one of the suitable active substances is crosslinked to the cellulose hydroxyls by the formation of ester linkages. Its antimicrobial effectiveness against the chosen microorganisms proved to be the best against S. aureus. Applied finish bath has additional crease proof effectiveness providing sufficient both antimicrobial and crease proof effectiveness, so as the durability against 10 washing cycles.     

Do multi-use cellulosic textiles provide safe protection against the contamination of sterilized items?

The aim of this study was to determine whether multiple use cellulosic medical textiles (cotton blends, Tencel^®) could provide protection against contamination after sterilization, regardless of the barrier system of only qualified materials, as per EN 868-2, used in the process. New methods for testing permeability and durability of the microbial barrier cellulosic textiles were developed. The most resistant endospores of two apathogenic bacteria of the Bacilllus genus (Geobacillus stearothermophilus and Bacillus atrophaeus) were used. Testing was conducted after 1, 10, 20, 30 and 50 washing and sterilization cycles under real hospital conditions of the University Hospital Centre Zagreb. The retention period of the microbial barrier of the diagonally packaged packages (one layer; EN ISO 11607-1:2009) after sterilization was tested after the time period of 1, 2 and 3 months of storage under controlled conditions. Bacterial permeability occurred in cellulosic medical textiles when they were contaminated with an extremely high quantity of aerobe bacterial spores. During the testing of microbial barrier durability, the package remained uncontaminated after 1, 2 and 3 months of storage. Medical cellulose textiles used under real hospital conditions functioned properly as a microbial barrier system after 50 cycles of washing and sterilization and 3 months of storage, as the sterilized content was not contaminated at all; they could be used as a microbe barrier system for packing in sterilization, regardless of the fact that they did not meet the standard EN 868-02:2009 Packaging materials for terminally sterilized medical devices. Part 2: sterilization wrap—requirements and test methods or the International standard, for example EN ISO 11607-1:2009 Packaging for terminally sterilized medical devices, part 1: requirements for materials, sterile barrier systems and packaging systems.     

Antioxidative responses to seasonal changes and chemiluminescence assay of Astragalus onobrychis leaves extract

The aim of this study was to research the seasonal changes of antioxidant enzyme activity and total antioxidant capacity in leaves of Astragalus onobrychis L. subsp. chlorocarpus (Griseb.) S. Kozuharov et D.K. Pavlova. Leaves of A. onobrychis were collected during the different stages of growth and analyzed for antioxidant enzyme activity: superoxide dismutase, catalase, guaiacol peroxidase, glutathione peroxidase. Quantities of malonyldialdehyde, superoxide radicals, and hydroxyl radicals were measured as well as the content of soluble proteins. Furthermore, total antioxidant capacity was determined by the inhibition of chemiluminescence activity of blood phagocytes by leaf extracts. Stages of vegetation significantly affected the accumulation of superoxide radicals, but there were no significant differences in hydroxyl radical quantity and lipid peroxidation levels during vegetation. Soluble proteins vary greatly between different stages of growth. Seasonal changes were found to have an effect on enzymatic activities. During the spring season, guaiacol peroxidase showed the highest levels. Catalase and glutathione peroxidase increased their activities in summer, while, during the autumn season, superoxide dismutase showed maximum activity. On the basis of chemiluminescence assay, it can be concluded that leaf extract of A. onobrychis possesses a significant antioxidant capacity thus protecting plants during environmental stress.