The 24Mg(α, α')24Mg reaction; statistical analysis

The ²⁴Mg(α, α')²⁴Mg reaction to the 1.37 MeV state has been studied over an α-energy range of 9.625–13.825 MeV, in ≈40 keV steps, and over a 25°–160° angular interval. These cross sections have been analysed in terms of statistical theory and a number of deviations from its predictions are found. These deviations point to the importance of non-statistical processes, such as intermediate structure, to the α-scattering. The average compound nuclear width o₁ 62±7 keV is found for ²⁸Si over the 18–22 MeV excitation.     

Numerical solution of exterior Maxwell problems by Galerkin BEM and Runge–Kutta convolution quadrature

In this paper we consider time-dependent electromagnetic scattering problems from conducting objects. We discretize the time-domain electric field integral equation using Runge–Kutta convolution quadrature in time and a Galerkin method in space. We analyze the involved operators in the Laplace domain and obtain convergence results for the fully discrete scheme. Numerical experiments indicate the sharpness of the theoretical estimates.     

Improving the signal intensity and sensitivity of MALDI mass spectrometry by using nanoliter spots deposited by induction-based fluidics

A new contact-free, small droplet deposition method using an induction-based fluidics (IBF) technique to dispense nanoliter drops is described and evaluated for sample preparation in matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). The signal intensities available when using nanoliter spots are greater than those obtained with normal, microliter spots when the same amount of analyte is used. When using an ionic-liquid matrix, the improvement in sensitivity is equal to the concentration enhancement that was achieved by using smaller quantities of matrix. When using a conventional solid matrix, however, the increase in signal intensity shows a more complicated relationship to concentration. The approach of nanoliter deposition also supports multiple spotting to increase sample concentration and, thus, sample signal intensity. Nanoliter spotting not only improves the signal intensity and sensitivity achieved by MALDI-MS but also allows a major fraction of trace samples to be saved for other experiments, thus expanding the application of MALDI-MS to biological studies where sample quantity is limited.     

Formation and stability of a suspended biomimetic lipid bilayer on silicon submicrometer-sized pores

We report the fabrication of a thin silicon membrane with an array of micrometer and submicrometer pores that acts as a scaffold for suspending a lipid bilayer. We successfully deposited a lipid bilayer by the Langmuir-Blodgett method on a synthetic silicon membrane bearing arrays of pores with sizes of 1000, 650, and 300 nm. Topographic images obtained by AFM showed a suspended lipid film spanning the pores, whatever the pore size. Higher stability of bilayers supported on smaller pores was shown by AFM characterization. These results represent an important first step to creating a biomimetic environment to study cell membrane dynamics and/or in developing a biosensor.     

A Posteriori Control of Dimension Reduction Errors on Long Domains

In this work, we consider linear elliptic problems posed in long domains, i.e. the domains whose size in one coordinate direction is much greater than the size in the other directions. If the variation of the coefficients and right‐hand side along the emphasized direction is small, the original problem can be reduced to a lower‐dimensional one that is supposed to be much easier to solve. The a‐posteriori estimation of the error stemming from the model reduction constitutes the goal of the present work. For general coefficient matrix and right‐hand side of the equation, the reliable and efficient error estimator is derived that provides a guaranteed upper bound for the modelling error, exhibits the optimal asymptotics as the size of the domain tends to infinity and correctly indicates the local error distribution. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sparse convolution quadrature for time domain boundary integral formulations of the wave equation

S. A. Sauter Institut für Mathematik, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland ^{Many important physical applications are governed by the waveequation. The formulation as time domain boundary integral equationsinvolves retarded potentials. For the numerical solution ofthis problem, we employ the convolution quadrature method forthe discretization in time and the Galerkin boundary elementmethod for the space discretization. We introduce a simple apriori cut-off strategy where small entries of the system matricesare replaced by zero. The threshold for the cut-off is determinedby an a priori analysis which will be developed in this paper.This analysis will also allow to estimate the effect of additionalperturbations such as panel clustering and numerical integrationon the overall discretization error. This method reduces thestorage complexity for time domain integral equations from O(M2N)to O(M2N logM), where N denotes the number of time steps andM is the dimension of the boundary element space.}     

31P-spectroscopy of head and neck tumors--surface coil technique

Comparative phosphorus-31 magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) of 15 patients with superficial masses such as sarcoma, carcinoma, lymphoma, adenoma, and tuberculosis revealed significant increased concentrations of phosphomonoester, phosphodiester, and inorganic phosphorus in the lesion, whereas the concentration of the phosphocreatine was lower in comparison to muscle tissue. In nearly all masses, pH showed a slight alkaline shift. Existence of necrotic regions detected by MRI was marked by an increase of inorganic phosphorous in the spectra. Tumor growth was characterized by raised concentrations of phosphomonoester. Follow-up studies in a case of lymphoma showed a six-fold decrease of the tumor, while the spectra indicated a gradual transition of tumor values to muscle values. A follow-up study during irradiation of a squamous cell carcinoma revealed a considerable decrease of inorganic phosphate and a subsequent increase of phosphodiester.     

Fungizide Pyridinderivate, 2. Mitt.: Derivatisierung von α-Trichlormethyl-3-pyridinmethanol

Summary The antifungal lead structure -trichloromethyl-3-pyridinemethanol (1 a) was modified and esters, (thio-)carbamates, and sulfonates as well as other derivatives incorporating the pyridylcarbinol structure were prepared. The optical resolution as well as the N-oxidation of1 a are described.