Messung der Korrelation zwischen Beta- und zirkularpolarisierter Gammastrahlung im Zusammenhang mit der Nichterhaltung der Parität

Parity violation in beta decay was investigated by measuring the (beta, gamma) circular polarization correlation. The asymmetry coefficients were redetermined with higher accuracy for Co 60 (A=? 0,33±0,01) and Na 22 (A=+0,36±0,08). The cosΘ-dependence of the polarizationP was verified for the allowed beta transition of Co 60. Measurements on Zr 95 indicated a large GT-F-mixture and allowed to determine the relative magnitude of the matrix elements. For the first forbidden 2,3 MeV transition of Sb 124 the results are in agreement with the assumtion of an anomalously large value of the matrix elementB _ij compared to all other nuclear matrix elements.     

Phospha-alkene durch thermische,basen- oder metall-induzierte eliminierung

Thermal, base- and metal- induced 1,2-elimination reactions at P-halogen phosphanes of the type RP(Hal)-C(X)R¹R² were used for the preparation of phospha-alkenes with a new-type pattern of substitution at the (PC)-double-bond. The different methods are discussed in more detail.     

Direct top-quark width measurement at CDF

We present a measurement of the top-quark width in the lepton+jets decay channel of tt events produced in p p collisions at Fermilab's Tevatron collider and collected by the CDF II detector. From a data sample corresponding to 4.3 fb(-1) of integrated luminosity, we identify 756 candidate events. The top-quark mass and the mass of the hadronically decaying W boson that comes from the top-quark decay are reconstructed for each event and compared with templates of different top-quark widths (Γ(t)) and deviations from nominal jet energy scale (Δ(JES)) to perform a simultaneous fit for both parameters, where Δ(JES) is used for the in situ calibration of the jet energy scale. By applying a Feldman-Cousins approach, we establish an upper limit at 95% confidence level (CL) of Γ(t) <7.6 GeV and a two-sided 68% CL interval of 0.3 GeV <Γ(t) <4.4 GeV for a top-quark mass of 172.5 GeV/c(2), which are consistent with the standard model prediction.     

Automatic Symmetrization and Energy Estimates Using Local Operators for Partial Differential Equations

We develop a method for automatically symmetrizing Petrowsky well-posed Cauchy problems for constant coefficient linear partial differential equations. The method is rooted in the Sturm sequence technique for establishing the location of the roots of a complex polynomial and can be automated using standard symbolic computation tools. In the special case of homogeneous strictly hyperbolic scalar equations, we show that the resulting estimates are strong enough to control all principal order derivatives and thus can be used in place of the Leray energies. We also illustrate the method by applying it to various problems of mixed type.     

Vocal fold nodules in adult singers: Regional opinions about etiologic factors, career impact, and treatment. A survey of otolaryngologists, speech pathologists, and teachers of singing

This study was undertaken to better understand current regional opinions regarding vocal fold nodules in adult singers. A questionnaire was sent to 298 persons representing the 3 professional groups most involved with the care of singers with vocal nodules: otolaryngologists, speech pathologists, and teachers of singing. The questionnaire queried respondents about their level of experience with this problem, and their beliefs about causative factors, career impact, and optimum treatment. Responses within and between groups were similar, with differences between groups primarily in the magnitude of positive or negative responses, rather than in the polarity of the responses. Prevailing opinions included: recognition of causative factors in both singing and speaking voice practices, optimism about responsiveness to appropriate treatment, enthusiasm for coordinated voice therapy and voice training as first-line treatment, and acceptance of microsurgical management as appropriate treatment if behavioral management fails.     

On the benefits of acquiring peptide fragment ions at high measured mass accuracy

The advantages and disadvantages of acquiring tandem mass spectra by collision-induced dissociation (CID) of peptides in linear ion trap Fourier-transform hybrid instruments are described. These instruments offer the possibility to transfer fragment ions from the linear ion trap to the FT-based analyzer for analysis with both high resolution and high mass accuracy. In addition, performing CID during the transfer of ions from the linear ion trap (LTQ) to the FT analyzer is also possible in instruments containing an additional collision cell (i.e., the "C-trap" in the LTQ-Orbitrap), resulting in tandem mass spectra over the full m/z range and not limited by the ejection q value of the LTQ. Our results show that these scan modes have lower duty cycles than tandem mass spectra acquired in the LTQ with nominal mass resolution, and typically result in fewer peptide identifications during data-dependent analysis of complex samples. However, the higher measured mass accuracy and resolution provides more specificity and hence provides a lower false positive ratio for the same number of true positives during database search of peptide tandem mass spectra. In addition, the search for modified and unexpected peptides is greatly facilitated with this data acquisition mode. It is therefore concluded that acquisition of tandem mass spectral data with high measured mass accuracy and resolution is a competitive alternative to "classical" data acquisition strategies, especially in situations of complex searches from large databases, searches for modified peptides, or for peptides resulting from unspecific cleavages.     

High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications

The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.