Low-temperature thermal conductivity of GexAs40−xS60 glasses

Thermal conductivity, k, of Ge_xAs_40−xS₆₀ glasses has been measured between 4.5 and 300 K. A variation of k with the composition is found and dependences of its parameters on the mean coordination numbers are established. Analyses have been made within but also independently of the soft-potential model. Some correlations and scaling laws are proposed.     

Constructions Over Tournaments

We investigate tournaments that are projective in the variety that they generate, and free algebras over partial tournaments in that variety. We prove that the variety determined by three-variable equations of tournaments is not locally finite. We also construct infinitely many finite, pairwise incomparable simple tournaments.     

Zur Bestimmung der Feuchtigkeit von Ru?

Ohne Zusammenfassung     

Singular covers in free lattices

A covering a>b in a lattice is called a singular cover if a is join irreducible and b is meet irreducible. A classification of the singular covers which occur in free lattices is given.     

A Note on Idempotent Modifications of Groups

The idempotent modification of a group is always a subdirectly irreducible algebra.     

Chaotic properties of multipoint correlation functions of an Ising model with long-range interactions on the Sierpiński—Gasket lattice

A class of multispin correlation functions of an Ising model with ferromagnetic nearest neighbor interactionsK and constant (distance-independent) long-range interactionsQ ₁=Q,l=1,2,..., on the Sierpiski-gasket lattice is considered. Using an exact method for calculating thermodynamic functions of hierarchically constructed Ising systems, it is shown that, for a set of values ofQ and for almost all values ofK, someM _k-spin correlation functions, whereM _k=3 ^k +3 withk=1,2,...,n andn=1,2,... being the order of lattice construction, change chaotically asn, k, and therebyM _k increase to infinity. Accordingly, in the thermodynamic limit, these correlation functions prove to be nonanalytic for appropriate values ofQ andK. SinceM _k-point correlation functions withk being finite, i.e., correlation functions involving finite numbers of spins, remain analytic asn tends to infinity, there is a smooth crossover between analytic properties of correlation functions of the two types.     

Infrared spectroscopy of oxygen bond systems

The vibrational spectra of various types of oxygen-bonded systems with other elements are interpreted in terms of factor group analysis and normal vibration analysis. The stereochemical structures of pseudo-octahedral (MO_nL_6-n) and pseudo-tetrahedral (MO_nL_4-n) compounds with terminal oxygen atoms and of M₂OL_n compounds with oxygen bridge bonding are discussed on the basis of our own data and those from the literature.The present work also contains certain general statements concerning p_π-d_π interactions in oxy compounds of metals having d and p electrons.     

Hydrolysis and Solvolysis of Methyltriethoxysilane Catalyzed with HCl or Trifluoroacetic Acid: IR Spectroscopic and Surface Energy Studies

The aim of this study was, at first, to re-consider the IR spectra of methyltriethoxysilane (MTEOS) catalysed with HCl (hydrolysis) and to compare them with IR spectra of MTEOS catalysed with trifluoroacetic acid (TFAcOH). TFAcOH as a strong carboxylic acid performs non-hydrolytic sol-gel process based on the condensation between the alkoxide and the acid function, liberating ester molecules (solvolysis). We assessed from the time-dependent IR attenuated reflection spectroscopic (IR ATR) measurements the solvolysis and hydrolysis reactions, formation of the oligomeric species and final condensation products. Additional evidence for the formation of these species was obtained from the spectra of films dip-coated from sols aged to different extent. The results of the IR spectral analysis showed that the structure of both xerogels consisted of irregular T_n (n = 8, 10, 12) cube-like species bridged via the ladder-like oligomers (in the case of MTEOS/TFAcOH) and open-chain trisiloxane species (for MTEOS/HCl). ²⁹Si NMR spectra of MTEOS/TFAcOH showed only signals of T³ while MTEOS/HCl spectra showed beside T³ also T² signals, in agreement with IR spectra results. From the XRD peaks at low Bragg angles (∼ 9–10°) we inferred that both xerogels consisted of nanocrystalline CH₃-SiO_3/2 species. In addition, the surface energy values of the films deposited from the corresponding sols were measured and the dispersive and polar portions correlated with the spectral features noted in the films.     

Solvent and pH effects on fast and ultrasensitive 1,1'-oxalyldi(4-methyl)imidazole chemiluminescence

Solvent and pH effects on fast and ultrasensitive 1,1'-oxalyldi(4-methyl)imidazole chemiluminescence (OD4MI-CL) were studied. The influences of these two factors on the complex OD4MI-CL reaction are discussed within a conceptual prototype for developing aqueous and non-aqueous capillary electrophoresis (ACE and NACE) devices with OD4MI-CL detection. The reaction channel length and OD4MI yield from the reaction between bis(2,4,6-trichlorophenyl) oxalate (TCPO) and 4-methylimidazole in the channel will be influenced by pH, water volume fraction, and cosolvent properties of the solution. Optimum OD4MI-CL efficiency is observed at pH 6.5 when 1-propanol, which has a low dielectric constant (epsilon = 20.8), is used as the NACE solvent in the separation channel. Water (epsilon = 80.1), the solvent in the ACE separation channel, acts similarly to a high dielectric constant organic solvent in NACE because the disadvantages normally associated with TCPO-CL reactions in water disappear due to the faster OD4MI-CL reaction versus OD4MI decomposition in aqueous solution. Therefore, it is expected that the OD4MI-CL detection system can be used in both NACE and ACE devices without requiring detector modifications. We also conclude that OD4MI-CL detection in NACE and ACE devices will be much more sensitive than the TCPO-CL detection used in current NACE devices.