RESUMO
We report on cyclotron frequency measurements on trapped 206,207Pb+ ions by means of the non-destructive Fourier-transform ion-cyclotron-resonance technique at room temperature. In a proof-of-principle experiment using a quartz crystal instead of a coil as a resonator, we have alternately carried out cyclotron frequency measurements for 206Pb+ and 207Pb+ with the sideband coupling method to obtain 21 cyclotron-frequency ratios with a statistical uncertainty of 6 × 10-7. The mean frequency ratio R¯ deviates by about 2σ from the value deduced from the masses reported in the latest Atomic Mass Evaluation. We anticipate that this shift is due to the ion-ion interaction between the simultaneously trapped ions (≈100) and will decrease to a negligible level once we reach single-ion sensitivity. The compactness of such a crystal makes this approach promising for direct Penning-trap mass measurements on heavy and superheavy elements.
RESUMO
OBJECTIVE: To determine if preconceptional screening for carriership of cystic fibrosis (CF) meets the requirements formulated by the Committee for Screening for Hereditary and Congenital Disorders of the Health Council. DESIGN: Theoretical evaluation. METHOD: Preconceptional screening for CF carriership by means of direct mutation analysis in a blood sample, cheek smear or mouth rinse sample of both partners of pairs desiring children was tested against the criteria of the Health Council. RESULTS: Preconceptional screening for CF carriership proves to meet most of the requirements for genetic screening. Current problems are the inadequate sensitivity of the screening (72% for pairs, 85% for individuals), the consequences of this for the meaning of the test results and reaching of the target group. Much attention is required for provision of information at all stages of the screening procedure. The desirability, feasibility and psychosocial effects of this type of screening have not yet been investigated sufficiently in the Netherlands.