Standard single-mode fibers as convenient means for the generation of ultrafast high-pulse-energy super-continua

High-pulse-energy super-continua featuring an M² of one were generated in standard single-mode fibers. The highest pulse energy achieved was ∼600 nJ and the pulse duration was ∼1 ps. The spectral width of the generated continua extended over up to 35% of the pump wavelength. PACS 42.65.-k; 42.81.-i; 42.79.Nv     

Classical solutions of quasilinear parabolic systems on two dimensional domains

Using results on abstract evolutions equations and recently obtained results on elliptic operators with discontinuous coefficients including mixed boundary conditions we prove that quasilinear parabolic systems admit a local, classical solution in the space of p–integrable functions, for some p greater than 1, over a bounded two dimensional space domain. The treatment of such equations in a space of integrable functions enables us to define the normal component of the current across the boundary of any Lipschitz subset. As applications we have in mind systems of reaction diffusion equations, e.g. van Roosbroeck’s system.     

Synthesis of analogs of D-Ala-D-Ala as potential inhibitors of bacterial cell wall biosynthesis

The syntheses of the L,L- and D,D-stereoisomers of N- phenoxyacetyl -X-alanine in which X = Ser, Ala( beta Cl ) or Arg, are described. The antibacterial activity of these peptides and some of their synthetic intermediates has been examined. Four of the intermediates in which X = Ala( beta Cl ) and Arg(NO2), which possess C-terminal benzyl ester groups, were active against viridans streptococci and Streptococcus agalactiae. The D,D-enantiomers were more active than the corresponding L,L-isomers. None of the compounds were active against beta-lactamase producing bacteria or acted as beta-lactamase inhibitors.     

Ueber die Best?ndigkeit einiger Explosivstoffe

Ohne Zusammenfassung     

Exceptional Modules for Tubular Canonical Algebras

Let Λ be a tubular canonical algebra of quiver type over a field. We show that each exceptional Λ-module can be exhibited by matrices involving as coefficients 0, 1 and –1 if Λ is of type (3,3,3), (2,4,4) or (2,3,6) and by matrices involving as coefficients 0, 1, –1, λ, –λ and λ–1 if Λ is of type (2,2,2,2) and defined by a parameter λ. Presented by Claus M. Ringel.     

Electrochemical properties of a proton conducting polymer

Electrochemical, optical and thermal characterisation of a proton conducting polymer system based on poly(2-acrylamido-2 methyl-propane-sulfonic acid) (Poly-AMPS) for use in electrochromic windows is reported. The polymer electrolyte has been obtained by cross-linking branched poly(ethylene imine) with the 2-acrylamido-2 methyl-propane-sulfonic acid. The conductivity of the poly-AMPS films is influenced by the water content in the membrane and can vary between 10⁻⁴ and 10⁻⁷ Ω⁻¹ cm⁻¹. A minimum activation energy of 17±3 kJ/mol is estimated by a simple Arrhenius model. Poly-AMPS is very sensitive to the humidity in the surroundings and electrochromic windows should be sealed if poly-AMPS is used. Temperatures above 45–50 °C give increasing cracks in the polymer and loss of adhesion to the electrode surface. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

Discovery of novel iron clusters in proteins by Mössbauer spectroscopy

Iron clusters are the catalytically active groups of many proteins. The basis building blocks of these clusters are few; they are all variants of three archetypal patterns: [Fe–O–Fe], [2Fe–2S], and [4Fe–4S]. Mössbauer spectroscopy, in conjunction with EPR spectroscopy, susceptometry and EXAFS, plays an important role in characterizing type, number, oxidation states and magnetic properties of such clusters in newly discovered proteins, and in detecting how valency and magnetism vary by passing through the catalytical cycle of these proteins. In this contribution we present the characterization of a novel iron cluster with unusual bridging and terminal ligands and metal coordinations.     

Infrared absorption of silane,ammonia, acetylene and diborane in the range of the CO2 laser emission lines: Measurements and modelling

Absorption spectra of the gases SiH₄, NH₃, C₂H₂ and of SiH₄/Ar and SiH₄/B₂H₆ mixtures have been measured in the spectral range of the CO₂ laser from 9.2 to 10.8 µm. In agreement with literature, silane shows the highest absorption (absorption coefficient = 3.3 × 10^–2 Pa^–1 m^–1). The deviation of the measured absorption behaviour of silane from literature, as far as the pressure dependence is concerned, can be explained by the enhanced spectral energy density in our experiment. This is confirmed by a rate-equation model involving the basic mechanisms of V-V and V-T energy transfer between vibrationally excited silane molecules. In contrast to silane, the absorption coefficient of NH₃ at the 10P(20) laser line is 4.5 × 10^–4 Pa^–1 m^–1 atp = 20 kPa and has its maximum of 4.5 × 10^–3 Pa^–1 m^–1 at the 10R(6) laser line. For C₂H₂ and B₂H₆, is even less ( 2.1 Ò 10^–5 Pa^–1 m^–1 for C₂H₂).