A characterization of Hering's plane of order 27

Hering's translation plane of order 27 has been characterized by its order and the fact that it admits SL(2, 13) in its translation complement (see [1]). We show that, aside from the Desarguian plane and a Generalized, André plane, it is the only plane of order 27 which admits a subgroup of SL(2, 13) of order 13×12.Partially supported by FONDECYT 0343 and ANDES FOUNDATION.     

Experimental and theoretical study of the photophysics and structures of europium cryptates incorporating 3,3'-bi-isoquinoline-2,2'-dioxide.

A detailed photophysical study of [Eu within (biqO2.2.2)(CF3SO3)](CF3SO3)2. CH3CN.H2O (Eu within 1) and two other types of cryptates incorporating three 3,3'-biisoquinoline-2,2'-dioxide units has been performed. Structural crystallographic data of Eu within 1, electronic structure calculations and theoretical models were used to obtain the intramolecular energy transfer rates and the appropriate set of rate equations, which was solved numerically. Quantum yields and decay lifetimes were obtained from these results and compared to the experimental data. The role of the ligand-to-metal charge transfer (LMCT) states was ascertained. A theoretical ligand field and intensity analysis was carried out and the results agree very well with the emission spectra. The molecular structures of the lanthanide cryptates were successfully modelled by the YIII ion using the restricted Hartree-Fock (RHF) method, with the advantage of dealing with closed-shell systems. These molecular structures were used to explain the drastic differences in the photophysics of the three EuIII cryptates.     

Spherical chen surfaces which are mass-symmetric and of 2-type

The main purpose is to classify spherical Chen surfaces which are mass-symmetric and of 2-type. We prove that these surfaces are either pseudoumbilical or flat,moreover,in the later case,they lie fully in a 3-sphere,a 5-sphere,or a 7-sphere. Our result divides the family of such surfaces into four classes. In the last section, we give examples of surfaces which belong to each of these four classes.     

Selective transformation of light olefins into aromatic hydrocarbons over pentasil zeolites

1-Pentene and 1-hexene transformation into aromatic hydrocarbons over H-ZSM-5, H-ZBS-11 and H-ZSM-11 modified with Zn(II), Ga(III), Mn(II) and Fe(III) has been studied. Aluminosilicate zeolites exhibited higher activity than borosilicate zeolites. Zn-species are effective in dehydrogenation, generating allylic intermediates from olefins used as feed.     

Topologically inseparable functions I: Finitary case

Given a finite set A and a distinguished function f: A → A, we study the set of all functions g: A → A that are continuous for all topologies for which f is continuous. The main result is a characterization of the functions f such that this set is trivial, that is, contains only the constant functions and the iterates of f.     

General M-estimates for contaminated p th-order autoregressive processes: Consistency and asymptotic normality

Summary This work is concerned with simultaneous estimation of coefficients and a scale parameter of a p th-order autoregressive process (X _t ). The observations are Y _t =V _t Z _t +(1-V _t )X _t where (Z _t) is a contaminating process and (V _t ) represents the proportion of contamination. If (X _t ) or (Z _t ) have heavy tails both least squares estimates and ordinary M-estimates are seriously affected. Under general conditions we prove consistency and asymptotic normality of a general class of M-estimates which contains some M-estimates studied by Denby and Martin [6].     

Effect of rf cold plasmas on polysaccharides

Low temperature-low pressure argon, nitrogen, and air plasmas generated with rf radiation have been used to treat cotton cellulose and other saccharides. The physical and chemical nature of each substrate was altered by the cold plasma. Although no gross topographical changes of the cotton surface were visible even under the electron microscope, plasma-treated cotton wetted more rapidly and more uniformly than its control, and other saccharides were more soluble in water and other chemical reagents (such as ammonium hydroxide) after plasma treatment. Free radicals were created within the cellulose matrix and structures of all other saccharides. ESR signals, which indicate presence of carbon radicals, degenerated asymmetrically, implying that other types of radicals also existed. ESCA spectra of cotton cellulose showed that some carbon atoms had been oxidized and some oxygen atoms reduced during plasma activation. Activated cottons displayed chemiluminescence and had redox powers that varied with their environments. When cotton and organic monomers were simultaneously present in cold plasma, reactive centers initiated polymerization ofthin films upon the cotton surface. Plasmaactivated cottons exhibited the same chemical reactions as a-hydroxyperoxides or their precursors from living organisms.     

The stereochemistry of the reaction of 2-norbornylmagnesium bromide with formaldehyde

Diastereomeric $\text{endo}$-2-norbornylmagnesium bromide and mixtures of $\text{endo}$- and $\text{exo}$-2-norbornylmagnesium bromide react stereospecifically with retention of configuration at the carbon-magnesium bond with formaldehyde to form the expected primary alcohol. This stereochemical result, which is comparable to that observed previously in electrophilic substitutions of stereoisomeric organomagnesium reagents, is observed even when 5 mole % ferric chloride is added. The stereospecificity observed both with and without added metal salts suggests that single electron transfer is not important in 1,2 addition of $\text{sec}$-alkylmagnesium reagents to simple aliphatic aldehydes.     

Phase plates for laser beam compensation

A phase plate inserted in the output beam of a multimode laser oscillator can yield a substantial improvement in the beam characteristics. Experiments with helium-neon and carbon-dioxide lasers are in agreement with the theoretical considerations.     

Ab initio study of substituent effect on the addition of hydrogen fluoride to fluoroethylenes

An ab initio 3-21G study of the direct addition of HF to C₂H_nF_(4–n), with n = 0 to 4, has been performed to investigate the effect of the substituent on the reaction. Geometry optimization of all charge-transfer complexes and transition states has been done. Standard analysis of activation energies of addition reactions, vibrational and thermodynamical analysis, as well as Morokuma energy decomposition, BSSE correction, PMO analysis, and Pauling bond orders were used to explain the results. A subset of the reactions, including that of C₂H₄ as reference one and the two most favorable cases, was also studied at the MP2/6–31G(d,p)//HF/6–31G(d,p) level. The barriers so obtained are in agreement with the indirectly found from experimental data. It was found that the effect of the substituent is not monotonic for the additions. Decomposition of the interaction energy is shown to be adequate to explain this nonmonotonic behavior. The implications for laser chemistry of the addition of hydrogen halides to fluorosubstituted olefins is briefly discussed.