Eine neue Schnellmethode zur Bestimmung des Cadmiums

Ohne Zusammenfassung     

Time resolved molecular spectroscopy using high power solid state lasers in pulse transmission mode. A re-examination of the Sn← S1 spectra of naphthalene and anthracene

A nanosecond laser spectrometer consisting of a 3nsec ruby/Nd PTM laser, fast detection system and high brightness analysing source is described. An analysis of the geometry considerations is given for crossed beam and collinear arrangement. The excited-state absorption spectra of naphthalene in 3MP at 85°K and 293°K from 14000 to 30000 cm^?1 are given. The results provide a direct method to evaluate the quantum yields for fluorescence φ_f and intersystem crossing φ_T. Also the excited-state absorption spectra of anthracene in PMM from 16000 to 26000 cm^?1 and in 3MP from 26000 to 36000 cm^?1 are reported.     

Synthesis, characterization, antibacterial and cytotoxic activity of new palladium(II) complexes with dithiocarbamate ligands: X-ray structure of bis(dibenzyl-1-S:S′-dithiocarbamato)Pd(II)

Six palladium(II) dithiocarbamates of general formula Pd(AmDTC)₂, where HAmDTC = aminedithiocarbamic acid, [Pd(II) piperidinedithiocarbamate (1), Pd(II) 4-methylpiperidinedithiocarbamate (2), Pd(II) N-methylbenzyldithiocarbamate (3), Pd(II) dibenzyldithiocarbamate (4), Pd(II) dicyclohexyldithiocarbamate (5), Pd(II) N-cyclohexyl-N-methyldithiocarbamate (6)] have been synthesized and characterized by elemental analyses, FT-IR, ¹H and ¹³C NMR. The X-ray structure of Pd(II), compounds 3 and 4, showed that the ligands are chelated by both sulfur atoms with bond angles S1-Pd-S4 = 179.24(2)° and S2-Pd-S3 = 179.09(5)°, with a distorted square planar geometry around Pd. All these complexes were screened for cytotoxic and antibacterial effects and showed significant antibacterial activity and no substantial in vitro cytotoxicity indicating specificity of the compounds.     

Reversible intersystem crossing,fluorescence lifetime lengthening and collisionally induced phosphorescence in biacetyl

The emissions of biacetyl excited at 4200 Å were studied at pressures down to 10^?3 torr. Apart from the well-known nanosecond fluorescence, a new emission of the same spectral composition was found with a non-exponential decay in the microsecond range. Furthermore the phosphorescence, as defined by its spectral composition, was found to be collisionally induced.The results imply that after excitation, the molecule rapidly transfers (rate constant k_S→T) to the triplet state, giving rise to the nanosecond decay time; and can then transfer back to the singlet state (rate constant k_T→S), giving rise to the microsecond emission. At the same time internal conversion can occur (k_S→S0). From an analysis of the data we find for k_S→S0 = 2.4 × 10⁷ sec^?1, k_S→T = 7.6 × 10⁷ sec^?1, k_T→S = 1.9 × 10⁵ sec^?1. The kinetic treatment can be transformed to a quantum mechanical one, yielding values for the triplet level density (?_T), the coupling element V_ST and the number of triplet states (N) coupled to the singlet excited. At 4200 Å we find ?_T = 6.3 × 10⁵cm, V_ST = 1.0 × 10^?5 cm^?1, N = 400.Phosphorescence occurs only when the molecule is deactivated by collisions to a vibronic triplet state below the vibrationless excited singlet state. The efficiency of biacetyl collisions is 0.54.     

Good Lattice Rules in Weighted Korobov Spaces with General Weights

We study the problem of multivariate integration and the construction of good lattice rules in weighted Korobov spaces with general weights. These spaces are not necessarily tensor products of spaces of univariate functions. Sufficient conditions for tractability and strong tractability of multivariate integration in such weighted function spaces are found. These conditions are also necessary if the weights are such that the reproducing kernel of the weighted Korobov space is pointwise non-negative. The existence of a lattice rule which achieves the nearly optimal convergence order is proven. A component-by-component (CBC) algorithm that constructs good lattice rules is presented. The resulting lattice rules achieve tractability or strong tractability error bounds and achieve nearly optimal convergence order for suitably decaying weights. We also study special weights such as finite-order and order-dependent weights. For these special weights, the cost of the CBC algorithm is polynomial. Numerical computations show that the lattice rules constructed by the CBC algorithm give much smaller worst-case errors than the mean worst-case errors over all quasi-Monte Carlo rules or over all lattice rules, and generally smaller worst-case errors than the best Korobov lattice rules in dimensions up to hundreds. Numerical results are provided to illustrate the efficiency of CBC lattice rules and Korobov lattice rules (with suitably chosen weights), in particular for high-dimensional finance problems.     

Relations Between Seepage Velocities in Immiscible,Incompressible Two-Phase Flow in Porous Media

Based on thermodynamic considerations, we derive a set of equations relating the seepage velocities of the fluid components in immiscible and incompressible two-phase flow in porous media. They necessitate the introduction of a new velocity function, the co-moving velocity. This velocity function is a characteristic of the porous medium. Together with a constitutive relation between the velocities and the driving forces, such as the pressure gradient, these equations form a closed set. We solve four versions of the capillary tube model analytically using this theory. We test the theory numerically on a network model.     

Modelling of Unsteady Transition in Low-Pressure Turbine Blade Flows with Two Dynamic Intermittency Equations

A transition model for describing wake-induced transition is presented based on the SST turbulence model by Menter and two dynamic equations for intermittency: one for near-wall intermittency and one for free-stream intermittency. In the Navier-Stokes equations, the total intermittency factor, which is the sum of the two, multiplies the turbulent viscosity computed by the turbulence model. The quality of the transition model is illustrated on the T106A test cascade for two Reynolds numbers, using experimental results by Stieger and Hodson for transition mainly due to kinematic wake impact on a separation bubble. The quality of the model is also revealed on the T106D test cascade using experimental results from Hilgenfeld, Stadtmuller and Fottner for wake turbulence induced transition. The test cases differ in pitch to chord ratio, Reynolds number and inlet free-stream turbulence intensity, causing different transition mechanisms. The unsteady results are presented in space-time diagrams of shape factor and wall shear stress on the suction side. The results show the capability of the model to capture the physics of unsteady transition in separated state. Inevitable shortcomings are revealed as well.