Hydrogen-assisted laser-induced resonant transitions between metastable states of antiprotonic helium atoms

Laser resonance transitions between normally metastable states of antiprotonic helium atoms were observed making use of state dependent quenching effects caused by small admixtures of \htwo\ molecules. By selectively shortening the lifetimes of states with higher principal quantum number $n$ as compared to those of lower $n$, this method for the first time provides access to all initially populated metastable states of \pbar\hep\ atoms. This was demonstrated by observing the transitions $(n,l)=(38,l)\rightarrow (39,l+1),\ l=35,36,37$ and $(n,l)=(37,l)\rightarrow (38,l+1),\ l=34,35,36$

Quenching of metastable states of antiprotonic helium atoms by collisions with H2_2 molecules

Laser resonance transitions between normally metastable states of antiprotonic helium atoms were induced making use of state dependent quenching effects caused by trace admixtures of \mbox{H$_2$}\ to the target helium gas. With this method of ``\mbox{H$_2$}-assisted inverse resonances'' the decay rates of the states $(n,l)=(39,l),\ l=36,37,38$ and $(38,l),\ l=35,36,37$ of \mbox{$\overline{\mathrm{p}}$}\mbox{He$^{+}$}\ were determined as a function of the \mbox{H$_2$}\ admixture. The quenching cross sections at 30~K deduced therefrom for the states with $n=39$ were found to be of the order of the geometrical cross section for \mbox{$\overline{\mathrm{p}}$}\mbox{He$^{+}$}-\mbox{H$_2$}\ collisions ($2\cdot 10^{-15}$~cm$^2$), with a moderate decrease with increasing $l$. Within a given cascade with constant $v=n-l-1$, the quenching cross sections for states with $n=38$ are smaller by a factor of 4--6 than those for states with $n=39$

Transrectal color Doppler sonography of the A-uterina in cyclic mares

Color Doppler ultrasound was used transrectally in 6 mares to locate both the left and right Aa uterniae and to obtain flow velocity waveforms at defined times (Days 0, 5, 10, 15 and 20) during 4 estrous cycles. Blood flow reflected by the resistance index (RI) was determined for both arteries on 120 occasions. As there was no significant difference and a high correlation in the RI values between the left and right arteries (paired Student's t-test, correlation coefficient r > 0.94 ; P 0.05) could be measured. The results suggest that transrectal Color Doppler sonography is a noninvasive method for examining differences in impedance to uterine blood flow between different mares and cycle periods