Synthesis of 1,3-Bis(trialkylammonio)-2-propanol Dihalides Exhibiting Retardant Activity toward Rape

1,3-Bis(trialkylammonio)-2-propanol dihalides were prepared, and their retardant activity was studied in relation to the chemical structure.     

A remark on Lorentz algebras

We consider the class of Euclidean algebras associated to Minkowski light cones and called Lorentz algebras. We prove that in Lorentz algebras the estimate ∥P(a,b) ∥_∞≥(√2-1) ∥a∥_∞ ∥b∥_∞ is valid for the spectral norm and is therefore independent of the dimension of the Lorentz algebra.     

Model of free charge generation in polymers

A time solution of the excimer-ion pair system is presented here with a special attention to the time asymptote. Presented at the Czech-Israeli-German Symposium “Dynamical Processes in Condensed Molecular Systems”, Prague, Czech Republic, 26–30 May 1997. This work was supported by the grant No. C 1050601 of the Grant Agency of the Academy of Sciences of the Czech Republic.     

On a certain two-sided symmetric condition in magnetic field analysis and computations

A special two-sided condition for the incremental magnetic reluctivity is introduced which guarantees the unique existence of both the weak and the approximate solutions of the nonlinear stationary magnetic field distributed on a region composed of different media, as well as a certain estimate of the error between the two solutions. The condition, being discussed from the physical as well as the mathematical point of view, can be easily verified and is fulfilled for various magnetic reluctivity models used in electrotechnical practice.     

Magnetization and Specific Heat of UCo0.95T0.05Al (T = Fe, Ni) Single Crystals

We present the first single-crystal study of Fe and Ni doped U(Co_1-x T _x )Al compounds in comparison to the parent compound, the itinerant 5f-electron metamagnet UCoAl. Magnetization and specific-heat data measured in the temperature range of (1.8-300) K and in fields up to 10 T are analyzed and discussed. Both compounds exhibit a strong uniaxial anisotropy with the dominating magnetic response along the c-axis of the hexagonal ZrNiAl-type structure. Ni substitution yields an increase of the critical field for metamagnetism; UCo_0.95Fe_0.05Al is ferromagnetic below 30 K. Temperature evolution of the entropy change between 0 and 10 T points to involvement of magnetic correlations or spin fluctuations in the paramagnetic compounds UCoAl and UCo_0.95Ni_0.05Al.     

EPR investigation of cell membrane fluidity upon external oxidative stimulus

The perturbation of the physical state of cell membranes triggered by an external oxidative stimulus has been studied with sperm cells which were chosen as a model system. Electron paramagnetic resonance (EPR) spectroscopy was applied and three different nitroxides bearing a paramagnetic group on the 5th, 7th and 13th carbon of the stearic acid acyl chain were used to probe different regions of the membrane. The theoretical simulations of the experimental spectra indicate distinct domains in the intact cell plasma membrane where local steric constraints impose different degrees of motional averaging experienced by the reporter group. Upon the external oxidative stimulus the spectral changes were proportional to the accumulated oxidation products and were detected only for the reporter group residing close to the lipid-water interface. The EPR spectra reveal that the motion of the reporter group has slowed down in the oxidized cells and that the oxidatively modified membrane shows up as a more rigid structure as compared with the native state. The results also indicate that the oxidation-induced spectral changes are supressed in the presence of gangliosides.     

On the Seneta Sequences

In this paper, we prove some properties of the Seneta sequences and functions, and in particular we prove a representation theorem in the Karamata sense for the sequences from the Seneta class SOc.     

A census of semisymmetric cubic graphs on up to 768 vertices

A list is given of all semisymmetric (edge- but not vertex-transitive) connected finite cubic graphs of order up to 768. This list was determined by the authors using Goldschmidt's classification of finite primitive amalgams of index (3,3), and a computer algorithm for finding all normal subgroups of up to a given index in a finitely-presented group. The list includes several previously undiscovered graphs. For each graph in the list, a significant amount of information is provided, including its girth and diameter, the order of its automorphism group, the order and structure of a minimal edge-transitive group of automorphisms, its Goldschmidt type, stabiliser partitions, and other details about its quotients and covers. A summary of all known infinite families of semisymmetric cubic graphs is also given, together with explicit rules for their construction, and members of the list are identified with these. The special case of those graphs having K_1,3 as a normal quotient is investigated in detail. Supported in part by N.Z. Marsden Fund (grant no. UOA 124) and N.Z. Centres of Research Excellence Fund (grant no. UOA 201) Supported in part by “Ministrstvo za šolstvo, znanost in šport Slovenije”, research program no. 101-506. Supported in part by research projects no. Z1-4186-0101 and no. Z1-3124-0101. The fourth author would like to thank the University of Auckland for hospitality during his visit there in 2003.