ABSTRACT
We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 1^{3}S-2^{3}P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 2^{3}P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud's temperature from 380(20) to 170(20) K. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v_{1D}<3.7×10^{4} ms^{-1}.
ABSTRACT
The authors present the way of using the allogenic, frozen, radio-sterilized, spongy bone grafts in operational filling of defects after infra-articular fracture of proximal tibia. Fifteen patients (11 men and 4 women) classified between 30 and 66 years old were evaluated. These patients were operated from 1996 to 1998. The operational treatment with using frozen spongy bone grafts was performed on patients with comminuted split fracture of lateral condyle and depression of tibial plateau. In each case after elevating depressed fragment of tibial plateau bone grafts and screws were used to create a stable joint surface. In the same time other injured structures of the joint (ligaments, meniscus) were being reconstructed. To evaluate the stage of grafts incorporation, radiological examinations were made in; 4 weeks, 8 weeks, 6 months, 1 year from the date of the operation. We observed the process of calcification and forming trabeculac in bone grafts. The mechanical abilities of the reconstructed joint were evaluated according to the IKDS and Lysholm score. In all cases the spongy bone grafts in the joint were reconstructed and rebuild successfully. Thirteen patients had good and very good results in further clinical examinations. We claim that frozen, allogenic grafts of the spongy bone are very useful in filing detects of that bone caused by complicated injuries. This method of treatment with its good results is recommended.
