Effects of vacuum UV and UVC radiation on dry Escherichia coli plasmid pUC19 II. Mutational specificity at the lacZ gene

The mutational spectra at the lacZ gene, induced either by vacuum UV at 160 nm or UVC at 254 nm in vacuum-dried preparations of Escherichia coli plasmid pUC19 DNA, have been characterized from 72 E. coli-propagated mutants by DNA sequencing. In plasmids irradiated in vacuum, vacuum UV is five times more mutagenic than UVC. In the UV-induced mutants, base substitutions largely predominate, with GC → AT (G, guanine; C, cytosine; A, adenine; T, thymine) transitions being the most abundant type of base change for vacuum UV (61%) and UVC (47%). Most of the GC → AT transitions appear to occur at dipyrimidine sites, which are located at the non-transcribed DNA strand. Some, but not all, hot spots for GC → AT transitions are identical for vacuum UV and UVC. Frameshifts, resulting from a loss of the thymine residue, are specific for UVC (22%), and were not detected after treatent with vacuum UV. They occur predominantly at thymine runs of the transcribed DNA strand. Only a few deletions were detected following irradiation with vacuum UV (7.5%) and UVC (2%); however, their frequency is not enhanced compared with the spontaneous mutation spectrum. The data confirm the important role of base substitution mutations in UV-induced mutagenesis, which is not only valid for the UVC range, but extends towards the vacuum UV range.     

Systems of PDEs Obtained from Factorization in Loop Groups

We propose a generalization of a Drinfeld–Sokolov scheme of attaching integrable systems of PDEs to affine Kac–Moody algebras. With every affine Kac–Moody algebra and a parabolic subalgebra , we associate two hierarchies of PDEs. One, called positive, is a generalization of the KdV hierarchy, the other, called negative, generalizes the Toda hierarchy. We prove a coordinatization theorem which establishes that the number of functions needed to express all PDEs of the the total hierarchy equals the rank of . The choice of functions, however, is shown to depend in a noncanonical way on . We employ a version of the Birkhoff decomposition and a 2-loop formulation which allows us to incorporate geometrically meaningful solutions to those hierarchies. We illustrate our formalism for positive hierarchies with a generalization of the Boussinesq system and for the negative hierarchies with the stationary Bogoyavlenskii equation.     

Construction of constant mean curvature <Emphasis Type="Italic">n</Emphasis>-noids from holomorphic potentials

Using a Weierstrass type representation of constant mean curvature surfaces, we give a general method for constructing constant mean curvature n-noids (of genus 0) from holomorphic potentials, where n ≥ 3. The ends of these surfaces are embedded and asymptotically approach Delaunay surfaces, while the surfaces are in general not even almost embedded. In particular, a 3-parameter family of constant mean curvature trinoids is constructed. Part of this work was done, while the first named author held a Lehrstuhlvertretung at the University of Augsburg. He would like to thank the University of Augsburg for its hospitality. He would also like to acknowledge partial support by DFG-grant DO 776.     

Recovery of iodide ions from geothermal water with silica with grafted alkylammonium groups

Effect of a number of factors (time of contact and mass ratio of phases, acidity and temperature of the medium, concentrations of macrocomponents of geothermal water) on the sorption recovery of iodide ions with 3-(octadecyldimethylammonio)propylsilica and 3-(trimethylammonio)propylsilica from aqueous solutions was studied. Sorption isotherms were discussed. The possibility of using 3-(octadecyldimethylammonio)-propylsilica for recovery of iodide ions from highly mineralized geothermal water was analyzed.     

Dressing preserving the fundamental group

In this note we consider the relationship between the dressing action and the holonomy representation in the context of constant mean curvature surfaces. We characterize dressing elements that preserve the topology of a surface and discuss dressing by simple factors as a means of adding bubbles to a class of non-finite type cylinders.     

Solid phase synthesis of substituted quinolin-2(1H)-one-3-carboxylic acids via an intramolecular Knoevenagel condensation

A solid phase synthesis of substituted quinolin-2(1H)-one-3-carboxylic acids is described. The products are formed in a two-step synthesis in which ortho-aminophenones are first coupled to malonic acid bound to the Wang Resin followed by ring closure via an intramolecular Knoevenagel condensation.     

Billion‐Fold Enhancement in Sensitivity of Nuclear Magnetic Resonance Spectroscopy for Magnesium Ions in Solution

β‐nuclear magnetic resonance (NMR) spectroscopy is highly sensitive compared to conventional NMR spectroscopy, and may be applied for several elements across the periodic table. β‐NMR has previously been successfully applied in the fields of nuclear and solid‐state physics. In this work, β‐NMR is applied, for the first time, to record an NMR spectrum for a species in solution. ³¹Mg β‐NMR spectra are measured for as few as 10⁷ magnesium ions in ionic liquid (EMIM‐Ac) within minutes, as a prototypical test case. Resonances are observed at 3882.9 and 3887.2 kHz in an external field of 0.3 T. The key achievement of the current work is to demonstrate that β‐NMR is applicable for the analysis of species in solution, and thus represents a novel spectroscopic technique for use in general chemistry and potentially in biochemistry.     

Predicting time-to-churn of prepaid mobile telephone customers using social network analysis

Mobile phone carriers in a saturated market must focus on customer retention to maintain profitability. This study investigates the incorporation of social network information into churn prediction models to improve accuracy, timeliness, and profitability. Traditional models are built using customer attributes, however these data are often incomplete for prepaid customers. Alternatively, call record graphs that are current and complete for all customers can be analysed. A procedure was developed to build the call graph and extract relevant features from it to be used in classification models. The scalability and applicability of this technique are demonstrated on a telecommunications data set containing 1.4 million customers and over 30 million calls each month. The models are evaluated based on ROC plots, lift curves, and expected profitability. The results show how using network features can improve performance over local features while retaining high interpretability and usability.