Rb-Sr age of the riphean glauconites of the Kamov group (Baikit anteklise, Siberian platform)

A mineralogical and geochemical study was conducted and the Rb-Sr age of globular layered silicates (GPS) of the glauconite-illite series of the Dolgokta Formation from a parametric Chunkinskaya-282 drillcore was determined. The assessment of suitability of the mineral for geochronological purposes took into account the data of Mössbauer spectroscopy and modeling of the cation distribution in the GPS octahedral net. Mineralogical and crystalochemical characteristics indicate an epigenetic alteration of glauconite structure; therefore, its Rb-Sr isochronous age (1300 ± 7 Ma) is “rejuvenated” and reflects the stage of partial recrystallization. The 87Sr/86Sr ratio in dolomites of the Dolgokta and Kuyumba formations varies from 0.70602 to 0.72230, which confirms the epigenetic recrystallization. The model Rb-Sr age of glauconite, calculated taking into account the enrichment of radiogenic 87Sr, is within 1340-1400 Ma. The age estimate determines the upper limit of distribution of the Mesoproterozoic fossil Tappania, found in the Yurubchen and Dolgokta formations of the Baikit anteclise.

A New Parallel GA-Based Method for Constraint Satisfaction Problems

Despite some success of Genetic Algorithms (GAs) when tackling Constraint Satisfaction Problems (CSPs), they generally suffer from poor crossover operators. In order to overcome this limitation in practice, we propose a novel crossover specifically designed for solving CSPs including Temporal CSPs (TCSPs). Together with a variable ordering heuristic and an integration into a parallel architecture, this proposed crossover enables the solving of large and hard problem instances as demonstrated by the experimental tests conducted on randomly generated CSPs and TCSPs based on the model RB. We will indeed demonstrate, through these tests, that our proposed method is superior to the known GA-based techniques for CSPs. In addition, we will show that we are able to compete with the efficient MAC-based Abscon 109 solver for random problem instances as well as those instances taken from Lecoutre’s CSP library. Finally, we conducted additional tests on very large consistent and over constrained CSPs and TCSPs instances in order to show the ability of our method to deal with constraint problems in real time. This corresponds to solving the CSP or the TCSP by giving a solution with a quality (number of solved constraints) depending on the time allocated for computation.

99mTc-prulifloxacin in artificially infected animals

SummaryAim: The radiosynthesis of 99mTc-Prulifloxacin (99mTc-PRN) was assessed in terms of stability, binding with Staphylococcus aureus (S. aureus), biodistribution in rats (RT) and scintigraphic profile in rabbits (RB). Animals, material, methods: 99mTc-PRN was synthesized by mixing 25 μg of stannous fluoride (SnF2) with 18.5 MB of sodium pertechnetate. Thereafter, 0.5 mg of the prufloxacin (PRN) was added to the reaction mixture and the pH was set at 5.1 with 0.01 mol/l HCl. The reaction mixture was incubated at room temperature. The same process was repeated by increasing the concentration of the stannous fluoride from 25 to 250 μg, sodium pertechnetate from 18,5 to 185 MBq and the PRN from 0.5 to 5 mg. The radiochemical stability of the 99mTc-PRN was investigated in higher concentration of the cystein. In-vitro binding investigation was performed using living and heat killed S. aureus to verify specificity of the 99mTc-PRN. Biodistribution was evaluated in artificially infected rats and scintigraphic precision in rabbits at different interval. Results: The 99mTc-RPN prepared by mixing 2 mg of PRN, 74 MBq sodium pertechnetate, 100 μg stannous fluoride at pH 5.4, appeared to be more than 90% stable with a maximum radiochemical yield of 98.15 ± 0.25% at 30 min. The 99mTc-PRN showed higher stability in serum and satisfactory in-vitro binding to living as compared to heat killed S. aureus. 14.25 ± 0.15% of the injected dose was accumulated in the infected muscle of the model RT. Infected to normal muscle ratio was 5.12 and inflamed to normal muscle was 1.2. The biodistribution was validated by the scintigraphic localization of infection in rabbits. Conclusion: This investigation of 99mTc-PRN confirmed its momentous radiochemical immovability in saline, serum, preferential in-vitro binding to living bacteria, higher uptake in the infected muscle of model RT and precise localization in the infected muscle of model RB.

Exact Phase Transitions in Random Constraint Satisfaction Problems

In this paper we propose a new type of random CSP model, called Model RB, which is a revision to the standard Model B. It is proved that phase transitions from a region where almost all problems are satisfiable to a region where almost all problems are unsatisfiable do exist for Model RB as the number of variables approaches infinity. Moreover, the critical values at which the phase transitions occur are also known exactly. By relating the hardness of Model RB to Model B, it is shown that there exist a lot of hard instances in Model RB.