The electronic structure of organometallic complexes of the f elements XXVIII: Interpretation of the optical and magnetochemical data of a cyclohexylisocyanide adduct derived from Tris(η-cyclopentadienyl)samarium(III)

The absorption spectrum of Cp₃Sm·CNC₆H₁₁ has been measured at room temperature and at low temperatures in a hydrocarbon glass and in a KBr pellet. Electron paramagnetic resonance and magnetic susceptibility measurements are also reported in this paper. The observed optical bands were assigned on the basis of calculations which assumed that the crystal field parameters of the samarium complex were the same as for the previously analyzed Cp₃Pr·CNC₆H₁₃. The parameters of an empirical Hamiltonian were fitted to the energies of 39 levels to give an r.m.s. deviation of 21 cm⁻. On the basis of the wavefunctions of the crystal field ground state obtained from the fit, the ground state g values and the temperature-dependent magnetic susceptibility were calculated and compared with the experimental values.     

Korrosionsverhalten von Plasma- Heißdraht-Auftrag-Schweißungen. Teil I: Beständigkeit von auftraggeschweißten Nickelbasislegierungen gegen Loch- und interkristalline Korrosion

The corrosion properties of Plasma-Hot-Wire-Surfacing Part one: resistance of Nickel-base-alloy claddings against pitting and intergranular attack This paper describes measurements at claddings of nickel-based-alloys C 276, C 4 and C 22 on the St 52-3 steel substrat produced by Plasma-Hot-Wire-Surfacing (PHS). The correct heat control during the welding process is a crucial factor for the preparation of nearly precipitate-free claddings. For this reason it was necessary to optimize all the process data. The claddings itself as well as the rolled reference material (both of nearly the same chemical composition) were examined by means of metallografical and microanalytical techniques. Corrosion measurements show, that the composite materials exhibit high resistance both against pitting and intergranular corrosion and comparable to the properties of the rolled reference material. This was shown by determination of the critical pitting temperature in quinary salt solution, by electrochemical techniques in acidic chloride solution and by investigation in iron-(III)-sulfate-sulphuric acid solution.     

Electrochemical properties of anodic gold oxide layers—I: Potentiostatic oxide growth and double layer capacity

The potentiostatic growth of gold oxide layers was investigated at pH = 0, 2, and 6.2 in the potential range 1.4 V ? ? ? 2.3 V (vs hess) and for polarization times between 10^?4 and 10³ s. At ? < 2.0 V the growth of monomolecular oxide layers (oxide 1) with a thickness up to 10 Å was observed. This process takes place according to a high field mechanism. In this range, the double layer capacity decreases with increasing thickness d. With increasing ? there is a continuous change of oxide growth.At ? > 2.0 V a potential dependent linear growth law is observed with the formation of thick layers (oxide 2) up to 600 Å or more. In this range, further peaks arise in the cathodic charging curves, and the double layer capacity becomes independent of d.It follows that on the monomolecular boundary layer (oxide 1) the bulk oxide 2 is formed, which has a good ionic and electronic conductivity. Hence, the potential drop is small in oxide 2, but large in oxide 1. Even at high potentials the rate-determining step is the field dependent ionic migration in oxide 1.     

Structures of the N-Terminal Domain of PqsA in Complex with Anthraniloyl- and 6-Fluoroanthraniloyl-AMP: Substrate Activation in Pseudomonas Quinolone Signal (PQS) Biosynthesis

Pseudomonas aeruginosa, a prevalent pathogen in nosocomial infections and a major burden in cystic fibrosis, uses three interconnected quorum-sensing systems to coordinate virulence processes. At variance with other Gram-negative bacteria, one of these systems relies on 2-alkyl-4(1H)-quinolones (Pseudomonas quinolone signal, PQS) and might hence be an attractive target for new anti-infective agents. Here we report crystal structures of the N-terminal domain of anthranilate-CoA ligase PqsA, the first enzyme of PQS biosynthesis, in complex with anthraniloyl-AMP and with 6-fluoroanthraniloyl-AMP (6FABA-AMP) at 1.4 and 1.7 Å resolution. We find that PqsA belongs to an unrecognized subfamily of anthranilate-CoA ligases that recognize the amino group of anthranilate through a water-mediated hydrogen bond. The complex with 6FABA-AMP explains why 6FABA, an inhibitor of PQS biosynthesis, is a good substrate of PqsA. Together, our data might pave a way to new pathoblockers in P. aeruginosa infections.     

Do phosphoric acid esters affect the immediate enamel bond strengths?

Purpose: To investigate the effects of phosphoric acid esters (PAEs)-containing primers on the micro-tensile bond strengths (MTBS) of etched enamel, the micro-morphologies of the resin–enamel interfaces, and the enamel surfaces.

Materials and Methods: Thirty-three bovine incisors were used in this study. After the labial enamel surfaces were highly polished, they were etched, water sprayed, and air-dried. Afterward, the enamel surfaces were treated with or without (control) one of three PAEs-containing primers (40%MDP, Ivoclar Vivadent; Resulcin AquaPrime A + B, DMG; Xeno V, Dentsply), water sprayed, and air-dried. Subsequently, an adhesive Heliobond (Ivoclar Vivadent) was applied and resin composite (Core Build-up, Bisco) was placed incrementally. They were prepared into multiple beams of about 1 × 1 × 8 mm for MTBS tests. The enamel surfaces and resin–enamel interfaces were analyzed by SEM and TEM. The data were analyzed by two-way ANOVA and LSD test.

Results: Using PAEs-containing primers could increase the enamel MTBS (p < 0.05). The primer MDP produced higher MTBS than the primer Resulcin AquaPrime A + B and Xeno V. The SEM findings revealed the primed enamel surfaces were covered with a thin or glue-like layer of monomer-calcium salts of PAEs and the residual enamel crystallites, and various micro-porosities were detected within the hybrid layers. The TEM findings revealed the hydroxyapatite crystallites were tightly covered by the adhesive, the adhesive mixed with resin composite, or sparse irregular enamel crystallites.

Conclusion: The application of PAEs-containing primers on the etched enamel substrate could significantly increase the immediate enamel bond strengths. However, this effect was dependent on the individual PAEs-containing primer used.     

Tuning the colour of white polymer light emitting diodes

Colour tuning of white polymer light emitting diode (LED) light sources can be attained by various methods at various stages in the production process of the lamps and/or by the design of the active material incorporated in the LEDs. In this contribution we will describe the methods and discuss the physical background of colour tuning. Furthermore, the material design has led to polymers which are more stable during electrical stress, so that colour shift during lifetime can be excluded for white polymer LEDs.     

The European project trust—reconfigurable terminals and supporting networks

To date, research into reconfigurable mobile communications has predominantly focussed on the software radio concept, and specifically on the hardware technologies required to move physical layer processing into a programmable environment [1, 2, 3]. Although an interesting and necessary challenge, this only represents a fraction of the overall support and technology required to realise the potential of the concept. Other necessary developments include network/terminal cooperation for seamless inter-standard handoff, QoS management for software download and reconfiguration, a secure software download mechanism, terminal software and mobile radio network architecture supporting terminal reconfiguration, management for software downloads, configuration management, capability negotiation, radio resource management and spectrum allocation policies etc… This paper describes results from the EuropeanIst Trust (Transparently Reconfigurable UbiquitouS Terminal) [4] project concerning user and operator requirements, the proposed overall system environment, security issues, concerted radio resource management, and expected time frame for the development of reconfigurable terminals.