Epidemiology of Leishmania infantum, Toxoplasma gondii, and Neospora caninum in Rattus rattus in absence of domestic reservoir and definitive hosts.

Isolated environments are privileged settings to study transmission of infection. Montecristo is a small island where no wild or domestic carnivores are present. Invasive Black rats Rattus rattus (n=78) were captured and tested by PCR for Leishmania infantum, Toxoplasma gondii and Neospora caninum. We wanted to test, for these parasites, the existence of a sylvatic cycle independent of reservoir or definitive hosts. None of the rats tested positive by PCR for either T. gondii or N. caninum. We recorded a 15.5% prevalence (CI95% 8-26%) of L. infantum in the rats and Phlebotomus mascittii was captured in Montecristo, leading us to identify it as possible vector of the parasite.

Methanol Laser Line Assignments: Evidence of Four-Level Laser Systems

The "Ritz" computer program, developed for facilitating the assignment of molecular Fourier transform absorption spectra and described in a previous work, determines the energy level values involved in the assigned transitions by the Rydberg-Ritz combination principle. Combining the data obtained from the analyses of high-resolution infrared (IR) and far-infrared (FIR) spectra, it is possible to predict possible FIR laser emissions of molecules. In the present work we have applied this method to the common isotopomer methanol, 12CH3 16OH, and obtained 14 proposed assignments for previously unassigned FIR laser lines. We also predict 15 possible new FIR laser emissions. For the first time, an assignment involving a four-level laser system with collisional population transfer to a slightly higher energy level is reported. Copyright 1998 Academic Press.

Evidence for laser cooling in a magnesium atomic beam.

Laser cooling in a Mg atomic beam is reported for the first time to our knowledge. Previous cooling experiments were performed by using visible or infrared lasers. The Mg atoms were cooled by using an intracavity frequency-doubled dye laser at 285 nm to reach the resonant (1)S(0)-(1)P(1) transition. Evidence of laser cooling was obtained even with the limited available laser power ( approximately 1-2 mW).

Ramsey fringes in the nonlinear Hanle effect in a metastable atomic beam.

Evidence of coherence effects has been observed in the Zeeman sublevels by means of nonlinear level crossing in a metastable Ca beam with resonance width 3 orders of magnitude less than the radiative linewidth of the investigated transitions. By using two separate traveling waves, Ramsey-like fringes have been observed. The final measured widths are determined by the transit time, are weakly dependent on the magnetic-field inhomogeneities, and are independent of the natural width of the optical transitions and the laser bandwidth.

Subnatural coherence effects in saturation spectroscopy using a single traveling wave.

We have performed zero-field level-crossing resonance measurements (nonlinear Hanle effect) in a metastable Ca atomic beam. By saturating the optical transitions (3)P(1,2) ? (3)S(1), for which the radiative linewidth is 10.5 MHz, we have recorded resonances corresponding to widths of about 31 kHz. The effect has been investigated as a function of the saturating-radiation intensity. The frequency jitter of the laser used in the measurements is about 40 times wider than the recorded widths.

Triple-resonance spectroscopy on CH3OH far-infared laser lines.

Intracavity triple-resonance spectroscopy in CH(3)OH far-infrared lasers has been extended to the microwave region. A triple-resonance signal at 13410.45(10) MHz was observed on the 224.5-microm CH(3)OH laser line optically pumped by a waveguide CO(2) laser. The results confirm the assignment proposed for this line and improve the knowledge of A-state splitting in the = 5 vibrational state.

Intracavity double resonance on optically pumped submillimeter lasers.

The double resonance on the active medium of a far-infrared laser is discussed, and experimental results on methanol are presented. The intensity and polarization-selection rules are presented. The K doubling in the K = 4 levels of the first-excited-CO stretch state is measured for the first reported time.

High speed frequency modulation of far infrared lasers using the Stark effect.

Electronic frequency tuning of an optically pumped far infrared waveguide laser has been achieved by using the Stark effect. Frequency modulation with a 50-kHz modulation frequency and an index greater than 1 has been observed as well as a maximum modulation frequency of 300 kHz.