Trying to catch the elusive A and more. Reactions initiated by b-quarks and the Higgs sector of the MSSM

We study the cross sections for the production of neneural, intermediate mass Higgs boson in the process pp→ tq′φ, pp→tW⁻φ and pp→bZ⁰φ in the Minimal Supersymmetric Standard Model (φ = H⁰, h⁰ and A⁰) at Supercollider energies. The additional heavy particles (t, W, Z) in the final state can be used for tagging purposes, increasing the signal to background ratio. These reactions are dominated by bg and bg fusion. Their relevance for Higgs particle searches is discussed taking into account the expected efficiencies and purities for b-tagging. We find that, for tan β = 30, the cross sections for pp → bZ⁰φ are larger than 14 pb, over the whole intemediate range of M_A⁰, for A⁰ and at least one of the other two Higgses. Therefore this reaction is an excellent candidate for the discovery of one or more MSSM Higgs particles.     

Numerical Burniat and Irregular Surfaces

In this paper, we construct three numerical Burniat surfaces as desingularizations of double planes of degree >10. Two are surfaces having the bigenus P ₂=4 and the third is a surface having the bigenus P ₂=5. In addition, another surface of general type is constructed as a desingularization of a double plane of degree 12 having the birational invariants: q=p _g =1, P ₂=4. One of the numerical Burniat surfaces with P ₂=4 is obtained as a desingularization of a double plane of degree 22 with an irreducible branch locus, so it is a good candidate for having torsion zero. Moreover, its bicanonical transformation seems to be birational.     

Synthesis,Surface Activity and Micelle Formation of Novel Cyanine Dyes

The synthesis, surface activity and micelle formation of three novel cyanine dyes with amphiphilic character is described. It is illustrated by combined surface tension and absorption measurements that in one case self-assembly is highly cooperative leading to aggregates with unique absorption properties.     

Solvent effects on electron transfer reactions. The system iron(III)-phenothiazine in water-alcohol mixtures

Summary The effect of solvent composition (aqueous mixtures of methanol, ethanol, propan-1-ol and propan-2-ol) on the rate constants and activation parameters of the electron transfer between iron(III) and phenothiazine has been investigated. The dependence of the kinetic parameters on the solvent composition is discussed with reference to previously investigated systems.     

Effect of a proximal substituent on the triruthenium dodecacarbonyl-catalyzed reductive carbonylation of nitroarenes

Three nitroarenes were submitted to Ru₃(CO)₁₂-catalyzed reductive carbonylation in acetonitrile and in cis-cyclooctene. The main reaction products were the corresponding amines, ureas and six- or five-membered cyclization products. Optimization of the reaction varying the temperature, the CO pressure, the catalyst/substrate ratio and the reaction time and a statistical analysis of conversion and selectivity data allow to suggest a reaction mechanism in some reaction conditions.     

The photoprotector mechanism of mycosporine-like amino acids. Excited-state properties and photostability of porphyra-334 in aqueous solution

The photostability and photophysical parameters of an aqueous solution of the mycosporine-like amino acid (MAA) porphyra-334 have been determined. The excited-singlet state lifetime, measured by time-correlated single photon counting, was 0.4 ns. Laser flash photolysis experiments at 355 nm did not show any transient species. The triplet state of porphyra-334 was sensitized by triplet-triplet energy transfer. The T-T absorption spectrum was determined and the maximal absorption coefficient at 440 nm was estimated to be 1 x 10(4) M(-1) cm(-1). In this way an upper limit for the intersystem crossing quantum yield was determined. The very low quantum yield of fluorescence (phiF = 0.0016) and triplet formation (phiT < 0.05) together with a photodecomposition quantum yield of 2-4 x 10(-4), in the absence and the presence of oxygen respectively, can be explained by a very fast internal conversion process. These results support the photoprotective role assigned to this MAA in living systems.     

Methylpyridylbenzimidazoles. Part II. Bridged mono and bis-quaternary salts

The reaction of 2-(4-methyl-2-pyridyl)benzimidazole and of its N long alkyl chain derivatives with 1,3-dibromopropane led to cyclic bis-charged salts. Their spectroscopic (nmr and uv) and surface properties are briefly discussed. It turned out to be interesting to compare the similar behaviour of these salts and the corresponding well known derivatives of 2,2′-bipyridyl.     

MICELLAR EFFECT ON THE FLUORESCENCE QUENCHING OF INDOLIC COMPOUNDS BY AMINOACIDS

Abstract— The photolysis in aqueous neutral solutions of 5-nitrofurfural (NFA), an important metabolite of nitrofurans used as medicines, was investigated. Upon UV-A irradiation NFA loses up to 70 mol % nitrite, with formation of 5-hydroxymethylene-2(5H)-furanone, a new substance. When Cl⁻¹ is present 5-chlorofurfural is an important photoproduct. Photo-induced addition of either OH or CI⁻¹, followed by thermochemical elimination of NO₂⁻¹, is the proposed mechanism. Furthermore, NFA reacts with nitrite yielding nifuroxim. The possible role of the NFA photolysis in the occurrence of (photo)biological effects of NFA is discussed.     

Acid-base titrations of substituted benzoic acids in micellar systems

The dissociation equilibria of substituted benzoic acids in cationic and anionic micellar systems, investigated potentiometrically, show pK shifts of less than 1.0 in cationic and 0.5–3 in anionic micelles. Visual titrations of otherwise insoluble acids in cationic micelles give satisfactory results.