Book review

Ohne Zusammenfassung

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Book review

     

An implementation of a discretization method for semi-infinite programming

For linear semi-infinite programming problems a discretization method is presented. A first coarse grid is successively refined in such a way that the solution on the foregoing grids can be used on the one hand as starting points for the subsequent grids and on the other hand to considerably reduce the number of constraints which have to be considered in the subsequent problems. This enables an efficient treatment of large problems with moderate storage requirements. A numerically stable Simplex-algorithm is used to solve the LP-subproblems. Numerical examples from bivariate Chebyshev approximation are presented.     

Measuring the quantum efficiency of the optical emission of single radiating dipoles using a scanning mirror

Using scanning probe techniques, we show the controlled manipulation of the radiation from single dipoles. In one experiment we study the modification of the fluorescence lifetime of a single molecular dipole in front of a movable silver mirror. A second experiment demonstrates the changing plasmon spectrum of a gold nanoparticle in front of a dielectric mirror. Comparison of our data with theoretical models allows determination of the quantum efficiency of each radiating dipole.     

Kristall- und Molekülstruktur von Bis[N-(diethylaminothiocarbonyl)-benzamidin]silber(l)-nitrat

Crystal and Molecular Structure of Bis[N-(diethylaminothiocarbonyl)-benzamidine]-silver(I) Nitrate The crystal structure of bis[N-(diethylaminothiocarbonyl)-benzamidine]silver(I) nitrate has been determined by X-ray structure analysis on a single crystal. The compound is monoclinic, space group P2₁/n with a = 12.541, b = 43.470, c = 11.096 Å, β = 106.27° and 8 formula units per unit cell. The structure was solved by application of direct methods to difference structure factors (DIRDIF) and refined for 5242 observed reflections to a final R value of R = 0.070. There are two symmetrically independent molecules of the title compound in the asymmetric unit. The central Ag ion is coordinated by the S atoms of two ligands. The nitrate ions do not coordinate. The coordination geometry is slightly bent.     

A single molecule as a probe of optical intensity distribution

Single terrylene molecules embedded in microscopic p-terphenyl crystals are identified with the technique of fluorescence excitation spectroscopy. By use of the architecture of a scanning-probe microscope at T = 1.4 K , a single molecule is scanned through an excitation laser beam while the fluorescence signal is recorded. In this manner we have mapped the intensity distribution in a one-dimensional optical standing wave, demonstrating the potential of a single molecule as a nanometric probe. We discuss future experiments aimed at combining the high spatial and spectral sensitivity of a single molecule.     

Investigation of UV matrix-assisted laser desorption fourier transform mass spectrometry for peptides

Analytical Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA Ultraviolet matrix-assisted laser desorption can be used to enhance formation of [M + H]⁺, [M + Na]⁺, and [M + K)⁺ ions from small peptides for Fourier transform mass spectrometry (FTMS). In accord with laser desorption (LD) time-of-flight experiments, matrices such as nicotinic acid and 2-pyrazinecarboxylic acid exhibit strong enhancement effects (i.e., formation of abundant protonated and cationized molecules for the analyte with virtually no fragment ions) for 266 nm LD/FTMS, whereas pyrazinedicarboxylic acid provides no matrix enhancement at this wavelength. Both sinapinic acid and coumarin-120 provide strong matrix enhancement effects for the 355-nm LD of peptides. For the small peptides examined in this study, no significant differences in the abundance of fragment ions were observed between the 266- and 355-nm wavelengths. Matrix-assisted LD/FTMS is useful for the generation and characterization of ions corresponding to protonated and cationized molecules from virtually all biological compounds with molecular weights up to 2000. The lack of observation of biological ions with m/ z > 2500 may be related to inefficient trapping of these laser-desorbed ions or instrumental detection limitations of FTMS and is under further investigation.     

Perfluorinated tert‐Butoxides of Tin(II): The Dimeric Alkoxide and Its Monomeric Ate Complex

Surprisingly little is known about fluorinated tin(II) alkoxides. Here the synthesis and characterization of Sn(OR^F)₂ [OR^F = OC(CF₃)₃] and the crystal structures of its adducts with phenanthroline and dppe are reported. In addition, its ate complex [Sn(OR^F)₃]^– was synthesized with lithium or sodium as cation and as acetonitrile adduct. The thermolytic behavior of both, the alkoxide and the lithium stannate(II), was investigated together with first electrochemical measurements of Li[Sn(OR^F)₃].