In Vivo Justification of Using Endobiliary Stents Made of Polyhydroxyalkanoates

Treatment of patients with mechanical jaundice (MJ) has been one of the topical problems of current medicine. The fraction of patients having MJ of oncologic character that can undergo radical surgery does not exceed 25–30%. A way out of such situation is to use minimally invasive endobiliary interventions, the main type of which is endoprosthesis replacement of bile duct lumens. The aim of the work was to study the biological properties of the experimental models of polymer stents made of PHA for endobiliary prosthetics and to investigate the biological properties of PHA suture material for forming of biliary-enteric anastomoses (cholecystoduodenostomy). Experiments were performed on 20 adult mongrel dogs, weighing 10–12 kg. The animals were divided to three groups: the negative control group (intact animals); the positive control group (the animals with implanted endobiliary silicon stents); and the experimental group (the animals with the PHA stents). The animals were monitored for 100 days. The clinical blood analysis was made before the operation, on day 7, 30, 60 and 100 days. During autopsy the presence of exudate, commissural process in the free abdominal cavity and subhepatic spatium, the appearance of choledoch where the prosthesis was located, as well as the appearance of cholecystoenterostomy, liver and duodenum. We did not found any signs of inflammation, cicatrical changes were estimated in the free abdominal cavity and subhepatic spatium. All implanted PHA stents were at their initial places of implantation. After the end of the experiment inflammatory reaction and anastomositis were absent. Macroscopic changes of liver and duodenum were also not detected. Liver function did not have any pathological deviations. These positive results give grounds to conclude that application of PHA as endobiliary stents in reconstructive surgery of bile passages and as suture material is a promising technology.     

Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−x Co x Si3 alloys

Recently, the solid solution Ce₂Au_{1− x Co} xSi₃ has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce₂AuSi₃, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce₂AuSi₃ lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.     

The growth of a single crystal of Sr3CuIrO6 and its magnetic behavior compared to polycrystals

We have grown single crystals of the psuedo-one-dimensional compound Sr₃CuIrO₆, a K₄CdCl₆-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence for at least two magnetic transitions, at 5 K (T ₁) and 19 K (T ₂), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of both the forms is found to be widely different, exhibiting unexpected time dependence.     

Cooperative catalysis approach to intramolecular hydroacylation

Prior examples of hydroacylation to form six- and seven-membered ring ketones require either embedded chelating groups or other substrate design strategies to circumvent competitive aldehyde decarbonylation. A cooperative catalysis strategy enabled intramolecular hydroacylation of disubstituted alkenes to form seven- and six-membered rings without requiring substrate-embedded chelating groups.