Magnetic properties of transition metal substituted MnP

The magnetic properties of polycrystalline samples of Mn_1?tT_tP (T = V, Cr, Fe and Co for 0.00 ≦ t ≦ 0.50) are studied by magnetic susceptibility, magnetization and neutron diffraction measurements. The magnetic phase diagrams of the Mn_1?tT_tP phases exhibit paramagnetic, ferromagnetic, helimagnetic and spin glass regions depending on temperature and substitution (T, t). The concentrated spin glass regions observed in Mn_1?tV_tP and Mn_1?tCo_tP (0.30 ≦ t ≦ 0.50) are believed to result from the disorder in the metal sublattice. The variation of the magnetic moment of the ordered Mn_1?tT_tP phases with the substitution (T, t) is discussed.     

Zwei kurze Beweise der isoperimetrischen Ungleichung

Ohne Zusammenfassung     

Efficient upconversion fluorescence in a blue-emitting spirobifluorene-anthracene copolymer doped with low concentrations of Pt(II)octaethylporphyrin

Upconversion-induced fluorescence in platinum-octaethylporphyrin (PtOEP)-doped thin films of a spirobifluorene-anthracene copolymer has been investigated. Upon exciting in the range of the absorption band (2.31 eV, 537 nm) of the guest molecules, blue fluorescence (2.75 eV, 450 nm) from the spirobifluorene host was observed. The intensity of the upconverted emission was found to be one order of magnitude higher than from a PtOEP doped but anthracene-free spirobifluorene copolymer and than previously reported for metallated porphyrin-doped polyfluorene samples. It is argued that the efficient upconversion originates from the triplet energy transfer from the phosphorescent dopant to the sensitive unit of the host polymer, followed by triplet-triplet annihilation and finally blue emission from the spirobifluorene host polymer backbone.     

Synthesis of α,β-epoxy diazomethyl ketones

The preparation of eighteen epoxy diazomethyl ketones 1 is described. Two general methods were developed. Firstly, treatment of the mixed anhydrides of glycidic acids and carbonic acid ester with diazomethane led to the title compounds in yields ranging from 17–74%. Secondly, glycidyl chlorides which were obtained from sodium glycidates and oxalyl chloride, gave the desired products upon treatment with diazomethane (yields 60–74%). The required α,β-epoxy carboxylic esters were prepared by Darzens condensation and epoxidation of α,β-unsaturated esters, but in some cases also by reaction of α-oxo carboxylic esters with diazomethane.     

Estimate of the wavelengths for the first and second resonance lines in the francium I spectra

Relativistic self-consistent-field wavefunctions have been used to calculate one-electron eigenvalues for the ground s-state, the first and the second excited p-states of Sr II, Cs I, Ba II, Fr I and Ra II. When knowing the difference between the experimental energies and the theoretical ones for Sr II, Cs I, Ba II and Ra II the wavelengths for the first and second resonance lines in Fr I have been estimated with the following result: λ(7²P_1/2? 7²S_1/2)=812±10) nm λ(7²P_3/2? 7²S_1/2)=719±10) nm λ(8²P_1/2? 7²S_1/2)=433±5) nm λ(8²P_3/2? 7²S_1/2)=423±5) nm     

Progressive hedging and tabu search applied to mixed integer (0,1) multistage stochastic programming

Many problems faced by decision makers are characterized by a multistage decision process with uncertainty about the future and some decisions constrained to take on values of either zero or one (for example, either open a facility at a location or do not open it). Although some mathematical theory exists concerning such problems, no general-purpose algorithms have been available to address them. In this article, we introduce the first implementation of general purpose methods for finding good solutions to multistage, stochastic mixed-integer (0, 1) programming problems. The solution method makes use of Rockafellar and Wets' progressive hedging algorithm that averages solutions rather than data. Solutions to the induced quadratic (0,1) mixed-integer subproblems are obtained using a tabu search algorithm. We introduce the notion of integer convergence for progressive hedging. Computational experiments verify that the method is effective. The software that we have developed reads standard (SMPS) data files.     

A modified surface forces apparatus for single molecule tracking

To unravel molecular motion within confined liquids, we have combined a surface forces apparatus (SFA) with a highly sensitive fluorescence microscope. Details of our setup including important modifactions to enable the tracking of single dye molecules within nanometer thin confined liquid films are presented. The mechanical and optical performance of our setup is discussed in detail. For a load of 20 mN we observed a circular-shaped contact region (d approximately 300 microm), which results in a confining pressure of about 280 kPa. First experiments on liquid films of tetrakis(2-ethylhexoxy)silane (TEHOS) doped with rhodamine B demonstrated the ability to track single dye molecules within the confining gap of a SFA. The mean diffusion constant was independent of the liquid film thickness of approximately 3x10(-8) cm2/s and thus 10 times smaller than the diffusion constant of rhodamine B in bulk TEHOS. This points to the existence of a thin interface layer with slower molecular dynamics and an attractive potential parallel to the solid surface trapping molecules in this interface region.