Fast enumeration algorithm for words with given constraints on run lengths of ones

We propose an algorithm for enumeration and denumeration of words with given constraints on run lengths of ones (dklr-sequences). For large n, operation time of the algorithm (per symbol of a sequence) is at most O(log³ n log log n), where n is the length of enumerated words, whereas for the best known methods it is at least cn, c > 0.     

E.p.r. spectroscopy of spin-labelled macromolecules as a tool for determining chain conformations in amorphous solid polymers

The feasibility of using e.p.r. spectrscopy in studying conformations of spin-labelled macromolecules in the amorphous solid state is examined. The algorithm for e.p.r. spectra computation is developed. It was assumed that molecular weights of labelled linear chains are high and their solid solution is diluted. It is shown that the scaling exponent which determines the dependence of mean-square end-to-end distance on molecular weight and stiffness parameter (mean-square length of monomer unit) may be extracted from the spectra. Computed spectra are compared with experimental ones, measured at 77 K, of diluted solutions of spin-labelled poly(4-vinyl pyridine) [P(4-VP)] of different molecular weights in methanol and non-labelled P(4-VP). The conformational state (Gaussian coil), parameter of stiffness, and radius of gyration of spin-labelled P(4-VP) macromolecule in frozen solutions are determined. A conclusion is drawn that e.p.r. spectroscopy may become a new tool for studying chain conformatin in solid polymers.     

Implantation of Various Cell-Free Matrixes Does Not Contribute to the Restoration of Hyaline Cartilage within Full-Thickness Focal Defects

Articular cartilage is a highly organized tissue that has a limited ability to heal. Tissue engineering is actively exploited for joint tissue reconstruction in numerous cases of articular cartilage degeneration associated with trauma, arthrosis, rheumatoid arthritis, and osteoarthritis. However, the optimal scaffolds for cartilage repair are not yet identified. Here we have directly compared five various scaffolds, namely collagen-I membrane, collagen-II membrane, decellularized cartilage, a cellulose-based implant, and commercially available Chondro-Gide^® (Geistlich Pharma AG, Wolhusen, Switzerland) collagen membrane. The scaffolds were implanted in osteochondral full-thickness defects, formed on adult Wistar rats using a hand-held cutter with a diameter of 2.0 mm and a depth of up to the subchondral bone. The congruence of the articular surface was almost fully restored by decellularized cartilage and collagen type II-based scaffold. The most vivid restoration was observed 4 months after the implantation. The formation of hyaline cartilage was not detected in any of the groups. Despite cellular infiltration into scaffolds being observed in each group except cellulose, neither chondrocytes nor chondro-progenitors were detected. We concluded that for restoration of hyaline cartilage, scaffolds have to be combined either with cellular therapy or morphogens promoting chondrogenic differentiation.     

Preparation of sulfide ceramic materials based on BaSm<Subscript>2</Subscript>S<Subscript>4</Subscript>and CaGd<Subscript>2</Subscript>S<Subscript>4</Subscript> with the use of sol-gel and cryochemical technologies

Solid solutions in the MeLn₂S₄?x (mol %) MeS (Ln₂S₃) (Me = Ca, Ba; Ln = Sm, Gd) systems are prepared. The regions of solid solution formation are determined, the unit cell parameters of the crystal lattice are calculated, the total conductivity is investigated, and the activation energies for electrical conduction are calculated for samples with different prehistories. The electrolytic properties of phases based on calcium and barium thiolanthanates are studied, and the mechanism of defect formation is proposed.