Searching the k-change neighborhood for TSP is W[1]-hard

We show that searching the k-change neighborhood is W[1]-hard for metric TSP, which means that finding the best tour in the k-change neighborhood essentially requires complete search (modulo some complexity-theoretic assumptions).     

Internet Technology in Magnetic Resonance: A Common Gateway Interface Program for the World-Wide Web NMR Spectrometer

A custom-written Common Gateway Interface (CGI) program for remote control of an NMR spectrometer using a World Wide Web browser has been described. The program, running on a UNIX workstation, uses multiple processes to handle concurrent tasks of interacting with the user and with the spectrometer. The program's parent process communicates with the browser and sends out commands to the spectrometer; the child process is mainly responsible for data acquisition. Communication between the processes is via the shared memory mechanism. The WWW pages that have been developed for the system make use of the frames feature of web browsers. The CGI program provides an intuitive user interface to the NMR spectrometer, making, in effect, a complex system an easy-to-use Web appliance.     

Hyperfine structure measurements in the 7S3 metastable finestructure level in stable and unstable Eu+ isotopes

Clouds of stable and unstable Eu⁺ isotopes have been confined in a Paul trap, each containing about 10⁵ particles. In a microwave-optical double resonance experiment several hyperfine separations in the 4f⁷ 6s ⁷S₃ exited level have been measured with the experimental uncertainties ranging between 10^-8 and 3×10^-6. These experiments have confirmed that also in the case of an excited level with a large number of hyperfine or Zeeman sublevels the microwave-optical double resonance technique in a Paul trap can be useful for precise hyperfine structure investigation. The hyperfine coupling constants A and B have been determined for the isotopes ¹⁵³Eu⁺, ¹⁵¹Eu⁺, ¹⁵⁰Eu⁺ and ¹⁴⁸Eu⁺. The results complement earlier measurements on the ground state of Eu⁺ and give additional information on the hyperfine anomaly in the Eu isotopic chain.     

Grazing incidence X-ray diffraction analysis of surface modified SiC layers

Thin films of silicon carbide with codeposited elemental silicon were prepared by chemical vapor deposition (CVD). In a second CVD-process a thin titanium layer was deposited on the SiC(Si) basic layer. The solid state reaction between titanium and the codeposited silicon can be observed by X-ray diffractometry. A helpful analytical method for the observation of the growth of the reaction products is grazing incidence X-ray diffractometry. Various diffraction patterns of titanium silicides can be obtained by decreasing incidence angles. Received: 24 June 1996 / Accepted: 5 December 1996