Optical Sensing of Cesium Using 1,3-Alternate Calix[4]-mono- and Di(anthrylmethyl)aza-crown-6

We have synthesized two derivatives of alkylanthracene covalently bonded to 1,3-alternate calix[4]aza-crown-6 at the nitrogen position to study the effect of alkali metal ion complexation on the emission properties of anthracene fluorophore. The mono- and dianthryl-substituted probes are weakly fluorescent because their emission is partially quenched by photoinduced electron transfer (PET) from the nitrogen lone pair to the excited singlet state of anthracene. Upon complexation of alkali metal ions (e.g. K⁺, Cs⁺) by the crown moiety, the nitrogen lone pair can no longer participate in the PET process causing an enhancement in the emission of anthracene fluorophore (fluorescent turn on). The maximum fluorescence enhancement observed upon complexation of cesium ions by mono- and dianthryl-substituted calix[4]aza-crown-6 relative to the uncomplexed form was 8.5- and 11.6-fold, respectively.     

Ultrasensitive pulsed, balanced homodyne detector: application to time-domain quantum measurements

A pulsed, balanced homodyne detector has been developed for precise measurement of the electric field quadratures of pulsed optical quantum states. A high level of common mode suppression (>85 dB) and low electronic noise (730 electrons per pulse) provide a signal-to-noise ratio of 14 dB for measurement of the quantum noise of individual pulses. Measurements at repetition rates as high as 1 MHz are possible. As a test, quantum tomography of the coherent state was performed, and the Wigner function and the density matrix were reconstructed with 99.5% fidelity. The detection system can be used for ultrarsensitive balanced detection in cw mode, e.g., for weak absorption measurements.     

Connections between generalized,inexact and semi-infinite linear programming

This paper presents duality results between generalized and inexact linear programs and describes a special type of linear semi-infinite programs in connection with the programs above mentioned. In order to solve inexact linear programs a corresponding auxiliary problem can be formulated which is explicitly solvable. However, this auxiliary problem is a reformulation of the reduced semi-infinite problem. Therefore, all the numerical methods for solving semi-infinite linear programs can be used for the numerical treatment of inexact and generalized linear programs.

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Zusammenfassung Die vorliegende Arbeit zeigt Dualitätsergebnisse zwischen verallgemeinerten und inexakten linearen Programmen auf und beschreibt einen speziellen Typ linear-semi-infiniter Programme in Zusammenhang mit den oben erwähnten Optimierungsaufgaben. Um inexakte lineare Programme zu lösen wird ein Hilfsproblem aufgestellt, das explizit lösbar ist. Dieses Hilfsproblem ist eine Reformulierung des reduzierten semi-infiniten Problems. Daher können alle numerischen Methoden zur Lösung semi-infiniter linearer Programme auch zur numerischen Behandlung von inexakten und verallgemeinerten lineraren Programmen herangezogen werden.

     

Structural Characterization of Normal and Modified Oligonucleotides by Matrix-assisted Laser Desorption Fourier Transform Mass Spectrometry

Matrix-assisted UV laser desorption Fourier transform mass spectrometry (266 nm, nicotinic acid matrix) can be used for the detailed structural characterization of normal and modified oligonucleotides. The negative ion spectra for these compounds revealed abundant (M ? H) ^- ions as well as fragment ions that provided the information necessary to determine oligomer sequence and to differentiate isomers. The nicotinic acid matrix was required for the production of (M ? H) ^- ions for the oligonucleotide dimers, trimers, tetramers, and hexamers examined in this study. Elimination of the nicotinic acid matrix resulted in complete loss of the (M ?H) ^- ions as well as most of the larger fragment ions for the oligomers. The primary fragmentation pathway was observed to be phosphate ester bond cleavage with the resulting charge retained on the 3’ end of the oligomer and enabled isomeric differentiation of compounds such as d(S’-CGCG-3’) and d(S’-CCGG-3’). Collisioninduced dissociation experiments of the (M ? H) ^- ions for these compounds confirmed the preferential loss of nucleotides from the 5’ end of the oligomers. The presence and location of modifications such as methyl and ethyl alkyl groups to the oligonucleotides could also be identified.