Spreading Code Design Using a Global Optimization Method

The performance of a code division multiple access system depends on the correlation properties of the employed spreading code. Low cross-correlation values between spreading sequences are desired to suppress multiple access interference and to improve bit error performance. An auto-correlation function with a distinct peak enables proper synchronization and suppresses intersymbol interference. However, these requirements contradict each other and a trade-off needs to be established. In this paper, a global two dimensional optimization method is proposed to minimize the out-of-phase average mean-square aperiodic auto-correlation with average mean-square aperiodic cross-correlation being allowed to lie within a fixed region. This approach is applied to design sets of complex spreading sequences. A design example is presented to illustrate the relation between various correlation characteristics. The correlations of the obtained sets are compared with correlations of other known sequences.     

Improved measurement of Vub with inclusive semileptonic B decays

We report a new measurement of the Cabibbo-Kobayashi-Maskawa parameter Vub made with a sample of 9.7 x 10(6) BB- events collected with the CLEO II detector. Using heavy quark theory, we combine the observed yield of leptons from semileptonic B decay in the end-point momentum interval 2.2-2.6 GeV/c with recent CLEO II data on B-->X(s)gamma to find Vub = (4.08+/-0.34+/-0.44+/-0.16+/-0.24)x10(-3), where the first two uncertainties are experimental and the last two are from theory.     

Palladium-catalyzed 1,4-acetoxy-trifluoroacetoxylation of 1,3-dienes

Palladium-catalyzed oxidation of conjugated dienes in acetic acid containing CF₃COOH/LiOOCCF₃ results in the formation of 1-acetoxy-4-trifluoroacetoxy-2-alkenes.     

Database for trace element concentrations in biological samples

Summary Numerous methods have been published for the determination of the concentration of elements such as arsenic, cadmium, chromium, mercury and nickel in biological samples as blood, tissues and urine. It is not easy but highly desirable to assess the reliability of such methods. Several publications present values of trace element levels in samples from apparently healthy subjects as well as from persons with different diseases and after various exposures. Very often published normal values for unexposed subjects differ much — even up to one order of magnitude. There are major problems related to sampling, definition of the reference groups and analysis. Values for such groups can be called reference values rather than normal values.Therefore it is difficult even for experts to find such accurate and typical values to be used for comparative purposes e.g. in toxicology and occupational medicine. Knowledge is desirable of an average value and also of the respective frequency distribution. In this paper factors are discussed influencing the values such as selection of the reference groups and how to get typical reference intervals. We have worked for several years with developing methods for trace element determination and with evaluating data for use in e.g. occupational health. Therefore we felt a need for systematic evaluation accessible through a database.The original publications are retrieved by careful literature data search in e.g. Medline and Chemical Abstracts. We plan to offer discettes with evaluated typical concentrations of elements, specified details of sampling and analysis, reliability as well as references to the original publications. These discettes are very easy to use. A frequently updated and easily accessible database system should be very useful. Cooperation is planned with e.g. International Commission on Occupational Health, International Atomic Energy Agency (IAEA), International Labour Organization (ILO), International Union of Pure and Applied Chemistry (IUPAC), National Institute of Occupational Safety and Health (NIOSH in USA) and the World Health Organization (WHO).

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Datenbasis für Spurenelementkonzentrationen in biologischen Proben