The (14)C atoms naturally present in a piece of 19th-century wood have been detected directly by means of a tandem Van de Graaff accelerator used as a high-energy mass spectrometer. The (14)C ions were easily resolved from interfering ions with the use of a DeltaE-E detector telescope (this telescope consists of a pair of detectors; one of them measures the specific ionization, DeltaE, and the sum of the signals from both detectors gives the total energy for each ion, ET). The technique offers a number of practical advantages.

It has been shown that through the process of resonant excitation the fragmentation of ions confined in a low-pressure (Ͻ0.05 mTorr) linear ion trap (LIT) can be accomplished while maintaining both high fragmentation efficiency and high resolution of excitation. The ion reserpine, 609.23 Da, has been fragmented with efficiencies greater than 90% while a higher mass ion, a homogeneously substituted triazatriphosphorine of mass 2721.89 Da, has been fragmented with 48% efficiency. This was accomplished by extended resonant excitation by low-amplitude auxiliary RF signals. Computer modelling of ion trajectories and analysis of the trapping potentials have demonstrated that a reduction in neutralization of ions on the rods (or losses on the rods) and increased fragmentation is a consequence of higher order terms in the potential introduced by the round-rod geometry of the LIT. (LIT), leading to neutralization on the rods and/or fragmentation, has been demonstrated previously using both quadrupolar and dipolar auxiliary RF signals [1][2][3][4]. Typically, these experiments were carried out using nitrogen collision gas, at pressures ranging from 1.5 to 7 mTorr, with exposures to resonant excitation of a few milliseconds. At these pressures and exposures it was possible to obtain increased resolutions of excitation from 75 to 250 as the pressure in the LIT was decreased [3]. In those experiments, resolution decreased as the amplitude of the auxiliary signal was increased. However, the auxiliary amplitude required for either neutralization on the rods or fragmentation was dependent upon the pressure of the buffer gas. When the auxiliary amplitude was too low, thermalizing collisions reduced ion energies, both translational and internal, at a rate greater than energy was added by the auxiliary signal. In consequence, there existed a threshold for the auxiliary amplitude below which neutralization/fragmentation did not occur [5,6]. When the auxiliary amplitude was only slightly above this threshold, resolution of excitation was high, but the degree of neutralization/fragmentation was low [3]. In order to achieve a high degree of neutralization/fragmentation, it was necessary to increase the auxiliary amplitude and suffer the decreased resolution.The range of frequencies, about the secular frequency, to which ions respond (frequency response) increases with pressure. This behavior is predicted by the theory of a forced damped harmonic oscillator (FDHO). Models based on the FDHO theory have been used to describe the behavior of ions confined in a Paul trap at pressures in the mTorr regime [7,8]. However, when excited on-resonance at pressures below one mTorr, it has been assumed generally that ions would be lost on the rods before significant fragmentation occurred. In contrast, it is well known that effective fragmentation at low pressures (1 ϫ 10 Ϫ4 to 1 ϫ 10 Ϫ6 torr) can be achieved through the use of off-resonance excitation, as demonstrated in sustained off-resonance irradiation (SORI) experiments in FT-ICR [9 -11].In t...

Inheritance patterns of randomly amplified polymorphic DNA (RAPD) phenotypes were tested in 13 full-sib families of lake trout Salvelinus namaycush. Single-pair matings of parents with known phenotypes were made, and up to 20 progeny of each mating were used to test inheritance patterns. Seven RAPD primers amplified 13 polymorphic bands. With the exception of one family, expected segregation ratios for dominant Mendelian genetic traits were observed. Our results support previously reported findings that RAPD markers can be considered Mendelian traits and therefore could be used for analysis of genetic population structure.

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