Abstract simplicity of complete Kac-Moody groups over finite fields

Let G be a Kac-Moody group over a finite field corresponding to a generalized Cartan matrix A, as constructed by Tits. It is known that G admits the structure of a BN-pair, and acts on its corresponding building. We study the complete Kac-Moody group which is defined to be the closure of G in the automorphism group of its building. Our main goal is to determine when complete Kac-Moody groups are abstractly simple, that is have no proper non-trivial normal subgroups. Abstract simplicity of was previously known to hold when A is of affine type. We extend this result to many indefinite cases, including all hyperbolic generalized Cartan matrices A of rank at least four. Our proof uses Tits’ simplicity theorem for groups with a BN-pair and methods from the theory of pro-p groups.     

Hypercontractivity for a quantum Ornstein–Uhlenbeck semigroup

We prove hypercontractivity for a quantum Ornstein–Uhlenbeck semigroup on the entire algebra of bounded operators on a separable Hilbert space h. We exploit the particular structure of the spectrum together with hypercontractivity of the corresponding birth and death process and a proper decomposition of the domain. Then we deduce a logarithmic Sobolev inequality for the semigroup and gain an elementary estimate of the best constant.     

Synthesis, characterization, and use of asymmetric pyrenyl-gemini surfactants as emissive components in DNA-lipoplex systems

Gemini surfactants are potential candidates as synthetic vectors for the delivery of genes into cells to induce protein expression. With the ultimate objective of obtaining a better understanding of the mechanism of DNA transfection, two new asymmetric gemini surfactants (py-3-12 and py-6-12) have been synthesized as fluorescence probes. The physicochemical properties and morphologies of the self-assembled aggregates formed in aqueous solution have been studied using surface tension, specific conductance, dynamic light scattering (DLS), isothermal titration calorimetry (ITC), and fluorescence techniques. The interaction between pyrene-based gemini surfactants and DNA was investigated by using UV-vis and fluorescence spectroscopy. Binding constants for the DNA (salmon sperm)-gemini lipoplexes were measured. Fluorescence studies show that excimer emission occurs upon complexation with DNA.     

Tails and Ties

The study of behavioural and social phenomena has experienced a surge of interest over the last decade. One reason for this great attention is the huge amount of high quality data made available by the internet technologies. The many studies spanning concepts and problems belonging to economics, biology, ecology, physics and computer science, clearly indicates increasing interdisciplinary cross-fertilization, commonalities in the different approaches and communication across these disciplines. This issue of The European Physical Journal B is devoted to the interdisciplinary field of Sociophysics. The papers have been selected from the contributions presented at the 5th International Conference on “Applications of Physics in Financial Analysis" (APFA5) held in Torino from June 29th to July 1st 2006 (http://www.polito.it/apfa5). The synergy and richness of results obtained from the investigation of problems belonging to the area of complexity science from different perspectives clearly indicates future directions and research methodologies in this field.     

Formate ester synthesis via reaction of 2-bromoethylamines with dimethylformamide

2-Bromoethylamines are converted to the corresponding formate esters in the presence of DMF. Both primary and secondary bromides are smoothly transformed to the esters in satisfactory yields. The reaction mechanism involves the formation of an aziridinium ion, which upon reaction with DMF forms a Vilsmeier-type intermediate that is further hydrolyzed to the corresponding formates. Participation of the β-amino group appears to control not only the regioselectivity but also the stereoselectivity of the reaction. Application of the reaction conditions to chiral substrates indicated that non-rearranged products are formed with retention of configuration at the reacting center.     

Direct NMR detection of the binding of functional ligands to the human sweet receptor, a heterodimeric family 3 GPCR

We present a robust method for monitoring the binding of ligands to the heterodimeric (T1R2+T1R3) human sweet receptor (a family 3 GPCR receptor). The approach utilizes saturation transfer difference (STD) NMR spectroscopy with receptor proteins expressed on the surface of human epithelial kidney cells. The preparation investigated by NMR can contain either live cells or membranes isolated from these cells containing the receptor. We have used this approach to confirm the noncompetitive binding of alitame and cyclamate to the receptor and to determine that greatly reduced receptor binding affinity compared to wild-type brazzein explains the lack of sweetness of brazzein mutant A16C17. This approach opens new avenues for research on the mechanism of action of the sweet receptor and for the design of new noncalorigenic sweeteners.     

UV light induced photodegradation of liposome encapsulated fluoroquinolones: An MS study

Fluoroquinolone antibacterial agents are among the drugs most commonly causing phototoxic side effects. The phototoxicity may be originated in formation of reactive oxygen species upon ultraviolet exposure. Researches aiming the liposomal encapsulation of fluoroquinolones, expecting an increase in their therapeutic index, enhance the importance of studies on physicochemical properties and photostability of liposomal preparations. We studied the photodegradation of ciprofloxacin, ofloxacin and lomefloxacin by mass spectrometry upon various doses of UV irradiation. Lomefloxacin, the most phototoxic fluoroquinolone among them, was encapsulated into small unilamellar and multilamellar liposomes. Impact of vesicle structure and lipid composition – the presence of unsaturated fatty acid containing dioleoyl-phosphatidylcholine in dipalmitoyl-phosphatidylcholine liposomes – on the lomefloxacin photolysis was investigated; the structure of the main photoproducts was identified by mass spectrometry. It was found that the presence and type of lipids influence the ways of photodegradation process.     

Magnetic linear dichroism studies of in situ grown NiO thin films

We report thickness dependence of magnetic linear dichroism (MLD) of in situ grown NiO(0 0 1) films on Ag(0 0 1) substrate at the Ni L₂ absorption edge. Antiferromagnetic domains at the surface of NiO(0 0 1) films are found to be preferentially aligned in-plane. For films thinner than a critical thickness _tc$t_{\mathrm{c}}$ (20–40ML), we observe a softening of the in-plane magnetic domain alignments with increasing film thickness, arising from the strain-relaxation effects. Films thicker than _tc$t_{\mathrm{c}}$ exhibits a residual in-plane anisotropy, possibly related to the finite-thickness effects.     

Detrending moving average algorithm: A closed-form approximation of the scaling law

The Hurst exponent H of long range correlated series can be estimated by means of the detrending moving average (DMA) method. The computational tool, on which the algorithm is based, is the generalized variance , with being the average over the moving window n and N the dimension of the stochastic series y(i). The ability to yield H relies on the property of to vary as n^2H over a wide range of scales [E. Alessio, A. Carbone, G. Castelli, V. Frappietro, Eur. J. Phys. B 27 (2002) 197]. Here, we give a closed form proof that is equivalent to C_Hn^2H and provide an explicit expression for C_H. We furthermore compare the values of C_H with those obtained by applying the DMA algorithm to artificial self-similar signals.