Crosslinked poly(ethylene oxide) for drug release systems

Three types of poly(ethylene oxide) (PEO)- based hydrogels have been synthesized and studied for drug release applications: γ-irradiated high molecular weight PEO, biodegradable polyether-polyester networks with malic acid as crosslinker of poly(ethylene glycol)s and amphiphilic PEO-based polyureas crosslinked with multifunctional isocyanates. Varying the length of the PEO chain and the type of the crosslinker, hydrogels with different swelling properties, loading capacities and release characteristics were obtained. A large number of pharmaceuticals (acebutolol. HCl, diclofenac. Na, procaine. HCl, phenobarbital.a, propranolol, etc.) were tested for a sustained release in different media (pH=1.2, 6.5, 7.4). Most of them # gave reasonable retarded release profiles for 8 hours when incorporated before the γ-irradiation crosslinking of PEO. While amphiphilic hydrogels were found to be suitable for hydrophobic solutes, the biodegradable PEO-based polyester ones affected predominantly the release of water-soluble drugs. No pH effect was found for the γ-irradiated PEO as a carrier in contrast to the strong pH dependence for the degradable polyester networks.     

Presenting Powers Of Augmentation Ideals and Pfister Forms Dedicated to Professor Daniel Quillen on his Sixtieth Birthday

The article proposes a solution to the fundamental question of finding all additive relations among n-fold Pfister classes in the Witt ring and provides evidence for the solution by presenting the nth power of the augmentation ideal of an integral group ring of a group of exponent 2. The proposed solution generalizes Milnor's conjecture for quadratic forms, whose proof has been announced by V. Voevodsky.     

Structure,energy spectra and magnetic properties of poly(m-aniline)s

The energy spectra and magnetic properties of a large class of one-dimensional poly(m-aniline)s (PMA) and further model polymers are investigated theoretically. The band structure of those PMA's which are aza-analogs of the alternant non-classical (non-Kekulé) hydrocarbons (polymers) is characterized by a wide gap in which there is a narrow half-filled band (HFB). The different contributions to the effective spin exchange between the unpaired electrons in the HFB: Coulomb (Hund), kinetic and indirect exchange interactions are calculated. While it has been shown earlier that PMA exhibits a net spin exchange of ferromagnetic nature, this approach enables a detailed understanding of the influence of substituents on the nitrogen centers and changes in the aromatic bridging unit. The ferromagnetic nature of the spin coupling in the singly bridged PMA models therebye prevails independent of the structural changes. The HFB width of those PMA's which are derivatives (aza-analogs) of ladder-type non-alternant hydrocarbons is very large and the Wannier functions are delocalized. For this group of polymers the delocalized, non-magnetic state is favored and, therefore, they may be good candidates for testing electrical conduction.     

Role of Mono- and Disaccharide Combination in Cryoprotective Medium for Rooster Semen to Ensure Cryoresistance of Spermatozoa

The combination of saccharides in the composition of a cryopreservation medium may represent a promising method for the preservation of the reproductive cells of male birds. In the current study, cryoprotective media with a combined composition of mono- and di-saccharides were developed. The degree of penetration of reducing saccharide molecules (maltose—Mal20 medium) and non-reducing disaccharide molecules (trehalose—Treh20 medium) from the cryoprotective medium into the cytosol of rooster spermatozoa was studied. LCM control media without disaccharides were used as the control. The number of maltose molecules penetrating from the outside into the cytosol of the spermatozoon was 1.06 × 10⁴, and the number of trehalose molecules was 3.98 × 10⁴. Using a combination of maltose and fructose, the progressive motility of frozen/thawed semen and the fertility rates of eggs were significantly higher ((p < 0.05) 40.2% and 68.5%, respectively) than when using a combination of trehalose and fructose in a cryoprotective diluent (33.4% and 62.4%, respectively). A higher rate of chromatin integrity at the level of 92.4% was obtained when using Treh20 versus 74.5% Mal20 (p < 0.05). Maltose positively affected the preservation of frozen/thawed sperm in the genital tract of hens. On the seventh day from the last insemination when using Mal20, the fertilization of eggs was 42.6% and only 27.3% when using Treh20. Despite the same molecular weight, maltose and trehalose have different physicochemical and biological properties that determine their function and effectiveness as components of cryoprotective media.     

Modeling General Relativistic Perfect Fluids in Field-Theoretic Language

Skew-symmetric massless fields, their potentialsbeing r-forms, are close analogues of Maxwell's field(though the nonlinear cases also should be considered).We observe that only two of them (r = 2 and 3) automatically yield stress-energy tensorscharacteristic of normal perfect fluids. It is shownthat they naturally describe both nonrotating (r = 2)and rotating general relativistic perfect fluids (then a combination of r = 2 and r = 3 fields isindispensable) and possess every type of equation ofstate. Meanwhile, a free r = 3 field is completelyequivalent to the appearance of the cosmological term inEinstein's equations. Sound waves represent perturbationspropagating on the background of the r = 2 field. Someexotic properties of these two fields areoutlined.