QN-spaces, wQN-spaces and covering properties

The main results of the paper are as follows: covering characterizations of wQN-spaces, covering characterizations of QN-spaces and a theorem saying that Cp(X) has the Arkhangel'ski?ˇ property (α₁) provided that X is a QN-space. The latter statement solves a problem posed by M. Scheepers [M. Scheepers, Cp(X) and Arhangel'ski?ˇ's αi-spaces, Topology Appl. 89 (1998) 265-275] and for Tychonoff spaces was independently proved by M. Sakai [M. Sakai, The sequence selection properties of Cp(X), Preprint, April 25, 2006]. As the most interesting result we consider the equivalence that a normal topological space X is a wQN-space if and only if X has the property S₁(Γshr,Γ). Moreover we show that X is a QN-space if and only if Cp(X) has the property (α₀), and for perfectly normal spaces, if and only if X has the covering property (β₃).     

External influence on magnetic properties of Fe-based nanocrystalline alloys

Amorphous and nanocrystalline ribbons of NANOPERM, FINEMET and HITPERM were studied by Mössbauer spectroscopy (MS) after the influence of external factors: different annealing atmospheres, tensile stress and several kinds of corrosion. MS is a suitable tool for such studies because the spectral parameters are very sensitive to changes in the vicinity of the probe — ⁵⁷Fe nuclei. The most sensitive parameters were hyperfine magnetic field in crystalline component, average hyperfine field in amorphous component and direction of net magnetic moments. Influence of external factors modified also the structure of the alloys, i.e. new or modified phases were identified by MS phase analysis.     

Approximating Clarke’s subgradients of semismooth functions by divided differences

We show that the algorithm presented in an earlier paper by Studniarski (Numer. Math., 55:685–693, 1989) can be applied, after only a small modification, to approximate numerically Clarke’s subgradients of semismooth functions of two variables. Results of computational testing of this modified algorithm are also reported.      

Investigation of the Separation of Higher Fatty Acid Methyl Esters by Reversed-Phase HPTLC

JPC – Journal of Planar Chromatography – Modern TLC - Separations of eight methyl esters of higher fatty acids on RP-18 stationary phase with methanol—water and...     

In vitro screening of the action of non-steroidal anti-inflammatory drugs on hypochlorous acid-induced hyaluronan degradation

The antioxidative effect of two non-steroidal anti-inflammatory drugs was studied in vitro by measuring the kinetics of degradation of high-molecular weight hyaluronan (HA) in a system comprising hypochlorous acid + CuCl₂ + ascorbic acid using a Brookfield rotational viscometer equipped with a Teflon cup and spindle of coaxial cylindrical geometry. The changes in HA chemical structure were investigated by chemiluminometry. When sodium naproxen was added to the system during a running degradative process its inhibitory effect was clearly shown. The inhibition was dependent on the drug concentration. However, when this drug was added to the system before the initiation of HA degradation, no inhibition was seen even at the highest drug concentration tested. The inhibitory effect of acetylsalicylic acid was achieved with a relatively low concentration of the drug and was independent of the experimental model used.     

A model for dynamic relaxations in amorphous polymers. I. Conceptual framework,formal implementation of simplest version,and application to poly(ester carbonates)

A new model for the dynamic relaxations occurring below the glass transition temperature in amorphous polymers is introduced. This model combines ideas from theoretical solidstate physics, thermodynamics, and statistical mechanics. Formal analogies are made between the dynamic relaxations and phase transitions. The concepts of percolation theory are briefly discussed. The molecular level motions which might be giving rise to each dynamic relaxation are incorporated within this framework. The simplest version of the model is then formally implemented within the context of bisphenol-A polycarbonate (BPAPC) and its poly (ester carbonates) (PEC). The following results are calculated: (1) Characteristic temperatures (T_c) for BPAPC, similar to γ₁, and γ₂ relaxation temperatures observed by dynamic mechanical spectroscopy (DMS) at commonly used measurement frequencies. (2) T_c for the β₂ relaxation in tetrabromo-BPAPC much higher than the T_c in BPAPC. (3) A slow and monotonic increase in both the intensity and the T_cof the γ₂ relaxation with an increasing fraction of terephthalate comonomer in PEC copolymers. It is hoped that this model, which is admittedly tentative at this time, will be useful as a working hypothesis. The next paper of this series will provide extensions and generalizations of the model, and its application to the poly (alkyl methacrylates).