Carbonyl groups development on degraded cellulose. Correlation between spectroscopic and chemical results

Cellulose undergoing accelerated hydrothermal ageing gives a pattern of carbonyl groups whose vibrational modes were observed in UV/VI/NIR, FTIR and Raman spectra. Indirectly their presence in degraded samples was observed traced by the changes in the degree of polymerization (DP) and acidity (pH). Conjugated ketonic groups found in FTIR and Raman spectra after accelerated ageing were correlated to the chromophores detected by UV/VIS. A simple model describing the formation of chromophores was put forward and verified by experiments. PACS 81.05.-t; 82.20.Wt; 36.20.Kd; 36.20.Ng     

Analysis of temperature-programmed desorption spectra for NaY + butene-1 system

The curve fitting method for analyzing temperature-programmed desorption spectra has been developed. The method was applied to butene-1 desorption from the NaY zeolite and found to be useful for determining the surface coverage dependence of the apparent activation energy of desorption as well as the pre-exponential factor.     

Magnetic phase transition of Mn1.88Cr0.12Sb

The nature of the first order phase transition in Mn_1.88Cr_0.12Sb crystal is discussed. According to the magnetic susceptibility χ_⊥ and the specific heat measurements, there are two phase transitions, at 280 K and 315 K, respectively. They correspond to the vanishing of the “magnetic soft modes” for FIM and AF phases [4]. No change of the energy level positions was detected using the ESCA method.     

Investigations of Dy(FexAl1−x)2 laves phases by x-ray,magnetometric and Mössbauer effect methods

The crystal and magnetic properties of the Dy(Fe_xAl_1-x)₂ (0≤x≤1.0) system are investigated with the X-ray, magnetometric and Mössbauer effect methods. The system constitutes two cubic C15 structure regions separated by hexagonal C14 structure region. The X-ray investigations indicate the structure disorder of the C15 type phases. All compounds of the investigated system are ferrimagnets. Some of them exhibit a pronounced magnetic anisotropy. Substitution of Al for Fe decreases the Curie temperature and the Fe hyperfine magnetic field. The distribution of hyperfine magnetic field at iron sites is correlated with their nearest neighbours configurations. The Mössbauer effect data indicate the existence of the appreciable amount of the covalent apart from the long-range metallic bond in the investigated phases.     

The large-amplitude motions in quasi-symmetric top molecules with internal C3v rotors: The vibration-torsion-rotation Hamiltonian of a two-top molecule

An expression for the vibration-torsion-rotation Hamiltonian of a molecule with triatomic nonrigid frame and two internal C_3v rotors has been derived. Three large-amplitude motions, namely skeletal bending and two torsions, are removed from the vibrational problem and are considered together with the rotational problem. The Hamiltonian obtained is applicable to any two-C_3v-top molecule with triatomic linear or bent frame. The zeroth-order skeletal bending-torsion-rotation Hamiltonian is derived and the method of solving the corresponding Schrödinger equation is discussed. The Hamiltonian obtained with only slight modifications is shown to be applicable to any single-C_3v-top molecule with a quasi-linear tetratomic nonrigid frame or to the problem of the large-amplitude bending motion in a pentatomic quasi-linear molecule.     

The cluster blocking distribution function in the spin glass transition range of FexV2O5

The cluster blocking distribution function for the iron sublattice of the iron vanadium oxide bronzes Fe_xV₂O₅ /x = 0.33?0.37/ was experimentally established in a range 4 – 36 K by means of Wohlfarth method. It shows that the blocking process starts already in the paramagnetic phase and is most intense just below T_g.     

Spin glass phase in the iron vanadium oxide bronze θ − Fe0.35V2O5

Low temperature magnetic susceptibility measurements performed on Fe_0.35V₂O₅ and Al_0.35V₂O₅ indicate for the first time for vanadium oxide bronzes that the magnetically ordered spin glass phase occurs in the iron bronze below 8 K.     

Removal of Methylene Blue from Aging Water Solutions Treated by a Submerged Arc

Low voltage, low energy submerged pulsed arcs with a pulse repetition rate of 100 Hz, energies of 2.6–192 mJ and durations of 10–40 μs, followed by aging in the dark, were used to decompose 10 mg/l methylene blue (MB) dissolved in 40 ml of water, with the addition of 0.5 % H₂O₂. Electrode pairs composed of Fe/Fe, Ti/Ti, Cu/Cu, Cu/Fe, Fe/Cu, Ti/Fe, Fe/Ti, Cu/Ti and Ti/Cu were used. MB degraded during arc treatment, and during post arc treatment aging. The aging degraded MB faster (by a factor of ~2–3) when the MB solution was subjected to arcing with dissimilar electrodes when one of them was Cu, than for arcing with other used electrode pairs. The impact of the arc treatment time and the electrode materials on the MB removal ratio (C₀–C_ta)/C₀ was determined as a function of aging time t_a, where C₀ and C_ta are the MB concentrations initially and after t_a. For a pulse duration of 10 μs and pulse energies of 2–20 mJ, the MB removal rate increased linearly with treatment time and its growth rate increased with pulse energy. The linear dependence of the MB removal rate on treatment time was violated with pulse duration of 40 μs and pulse energies of 30–200 mJ. Kinetics of the MB degradation during aging of the arc treated solution was well described by the 1st order linear rate equation.     

Sharp weighted logarithmic bound for maximal operators

The paper contains the study of sharp weighted logarithmic estimates for maximal operators on probability spaces equipped with a tree-like structure. These inequalities can be regarded as LlogL versions of the classical estimates of Fefferman and Stein. The proof exploits the existence of a certain special function, enjoying appropriate majorization and concavity conditions.     

An asymptotic version of the Gowers dichotomy and a new proof of Wagner theorem

We present an asymptotic version of the Gowers dichotomy and a new proof of a generalized version of Wagner’s theorem. They both concern weaker forms of unconditionality in the context of the asymptotic theory of Banach spaces.