ROOM-TEMPERATURE PHOSPHORESCENCE FROM AZURIN DERIVATIVES. PHOSPHORESCENCE QUENCHING IN OXIDIZED NATIVE AZURIN

The tryptophan phosphorescence from a series of derivatives of Pseudomonas aeruginosa azurin has been monitored at 30 degrees C in pH 8.5 buffer solution. The phosphorescence lifetimes fall in the range of 230-270 ms for deoxygenated solutions of derivatives containing Cd(II), Cu(I), Co(II), Ni(II), Hg(II) or apoazurin. A weak signal with a lifetime of ca 130 ms is observed from solutions of oxidized native azurin, but this component is ascribed to a modified form of azurin in solution, i.e. protein heterogeneity, on the basis of the unique sensitivity to quenching by dioxygen. Aside from this minor component, the tryptophan phosphorescence in the Cu(II) protein appears to be fully quenched. The quenching is assigned an electron-transfer mechanism involving transient reduction of the metal center. The same mechanism is deemed to be responsible for fluorescence quenching in oxidized native azurin as well. These observations are of interest because aromatic groups like tryptophan may be conduits for physiological electron-transfer processes involving the copper center.     

Carbazole compounds as host materials for triplet emitters in organic light-emitting diodes: tuning the HOMO level without influencing the triplet energy in small molecules

A series of novel carbazole compounds was synthesized and tested for their suitability as host for triplet emitters in an organic-light emitting diode (OLED). In these compounds, a carbazole unit is either connected to other carbazole units to form carbazole dimers and trimers or to fluorene and oxadiazole derivatives to form mixed compounds. The HOMO level of carbazole compounds can be tuned by substitution at the 3, 6, and/or 9 positions. Making oligomers by connecting carbazole molecules via their 3 (3') positions shifts the HOMO level to higher energy, while replacing alkyl groups at the 9 (9') positions by aryl groups shifts the HOMO level to lower energy. Furthermore, it has been found that the triplet energy of these compounds is determined by the presence of poly(p-phenyl) chains in the molecular structure. By identifying the longest poly(p-phenyl) chain, one can predict whether a compound will be a suitable host for a high-energy triplet emitter. An overview of HOMO levels, singlet and triplet levels, and exchange energies is given for all carbazole compounds synthesized. Finally, OLEDs employing two selected carbazole compounds as host and fac-tris(2-phenylpyridine)-iridium (Ir(ppy)(3)) as guest were constructed and characterized electrically.     

Classification of Equilibrium Solutions of the Cometary Flow Equation and Explicit Solutions of the Euler Equations for Monatomic Ideal Gases

The set of smooth equilibrium solutions of a kinetic model for cometary flows is split into equivalence classes according to similarity transformations. For each equivalence class in the two- and three-dimensional cases a normal form is computed. Each such equilibrium solution gives rise to an explicit solution of the compressible Euler equations for monatomic gases. The set of these solutions is discussed with special emphasis on solutions containing vacuum regions.     

Experimental and numerical investigation into the dynamics of dust lifting up from the layer behind the propagating shock wave

In a number of industrial facilities and factory buildings dust layers cover floors, walls, ceilings and various installations. The dust can be easily dispersed by pressure waves generated by weak explosions or as a result of damage of a compressed gas systems. If the obtained explosive dust-air mixture is ignited, a devastating explosion may occur. The aim of the work was to study the dust lifting process from the layer behind the propagating shock wave and to determine some important parameters, which later could be used for development and validation of the numerical model of the process. The experiments were conducted with the use of a shock tube. For measuring the dust concentration in the mixture with air, a special five-channel optical device was constructed, enabling measurements at five positions located in one vertical plane along the height of the tube. The delay in lifting of the dust from the layer and the vertical velocity of the dust cloud were calculated from the dust concentration measurements. The research was carried out for various initial conditions and for various types of dusts. The results obtained in tests with black coal dust are presented in the paper. Three shock wave velocities: 450, 490 and 518 m/s and three dust layer thicknesses, equal to 1.0, 1.5 and 2.0 mm, were taken into consideration. Measurements results of the mean vertical component of the dust cloud velocity between the layer and the first laser beam were used in a new model, where the dust dispersing process is modeled as an injection of the dust from the layer. The numerical simulations were based on the Euler or Lagrange model of the dust phase. In case of Euler model, the dust layer was replaced by injection of dust from the bottom of the channel. The calculations were performed for two models of the investigated process. In the first model, correlation was worked out for all tested dusts and in the new model, the individual correlations for every tested dust were prepared. The results obtained with use of the second model proved to be closer to the experimental results. It appeared, however, that lifting up of the dust from the thick layers, thicker than 1 mm, is a more complex process than that from a thin layers and still requires more research. Probably the problem is, that the shock wave action upon the thick layer causes its aggregation in the first stage of the dispersing process, what makes the dust lifting process more difficult.     

(Bio)sensors based on manganese dioxide-modified carbon substrates: retrospections, further improvements and applications

An overview is presented which summarizes our accomplishment in the development of sensors and biosensors based on heterogenous carbon electrodes modified with manganese dioxide. Brief account of each sensor and biosensor has been given and example of real sample applications provided where appropriate.     

Synthesis of borondipyrromethene (BODIPY)-labeled sphingosine derivatives by cross-metathesis reaction

A new efficient and flexible synthesis of fluorescently labeled sphingosine derivatives from commercially available Garner aldehyde (8) is described. For this, appropriate alkenylated borondipyrromethene (BODIPY) dyes were synthesized and used for the first time in a cross-metathesis reaction, the key step of the approach. The labeled sphingosines with appropriate chain length were accepted as substrates by sphingosine kinases (SPHKs), yielding the corresponding phosphorylated products. One of these derivatives (11d) was identified as the first reported selective substrate for SPHK-1.     

Time Optimal Path Planning for Industrial Robots: A Dynamic Programming Approach Considering Torque Derivative and Jerk Constraints

This paper presents a dynamic programming approach for calculating time optimal trajectories for industrial robots, subject to various physical constraints. In addition to path velocity, motor torque, joint velocity and acceleration constraints, the present contribution also shows how to deal with torque derivative and joint jerk limitations. First a Cartesian path for the endeffector is defined by splines using Bernstein polynomials as basis functions and is parameterized via a scalar path parameter. In order to compute the belonging quantities in configuration space, inverse kinematics is solved numerically. Using this and in combination with the dynamical model, joint torques as well as their derivatives can be constrained. For that purpose the equations of motion are calculated with the help of the Projection Equation. As a consequence of the used optimization problem formulation, the dynamical model as well as the restrictions have to be transformed to path parameter space. Due to the additional consideration of jerk and torque derivative constraints, the phase plane is expanded to a phase space. The parameterized restrictions lead to feasible regions in this space, in which the optimal solution is sought. Result of the optimization is the time behavior of the path parameter and subsequently the feed forward torques for the optimal motion on the spatial path defined by previously mentioned splines. Simulation results as well as experimental results for a three axes industrial robot are presented. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)