Search

A simple algorithm to find logarithms in a finite field of characteristic two is described. It uses the Euclidean algorithm for polynomials in attempting to reduce an element to a product of factors all of whose logarithms are stored in a database. The algorithm, which is similar to one of Adleman, has a random runtime and constant storage requirements. It is analyzed and problems associated with the construction of the database are considered. The aim of the work is to show that the algorithm is feasible for the field with $2^{127} $ elements on which several proposed public key distribution systems have been based. For such application it is felt that the discrete logarithm is still a viable technique for sufficiently large fields.

A study was made of the cecal microflora isolated from broilers (5-week-old) reared under typical commercial husbandry conditions. Three hundred and twenty-five bacterial strains (randomly isolated from colonies representing 49 to 81% of the microscopic count) were isolated from cecal digesta of six animals on a rumen fluid roll tube medium (M98-5). Seventy-seven percent of these strains consisted of strict anaerobes: gram-negative, pleomorphic cocci (5.2%), Peptostreptococcus(1.5%), gram-positive rods (36.1% as Propionibacterium acnesand Eubacteriumsp.), gram-negative rods (18.6% as Bacteroides clostridiiformis, B. hypermegasand B. fragilis) and sporeforming rods (15.7% as Clostridiumsp.). Two types of facultatively anaerobic bacteria (gram-positive cocci and Escherichia coli) were also isolated and constituted 17.5% of the remaining flora. The distribution of the bacterial groups isolated from six cecal samples varied considerably. Data on the growth requirements of anaerobic strains indicated that many could be cultured in a simple medium consisting of an energy source, minerals, reducing agent, Trypticase, and yeast extract (or a vitamin mixture in place of yeast extract). The growth of some of these bacteria was also enhanced by CO2and rumen fluid. These preliminary data suggest that some of the more numerous anaerobes isolated from the chicken cecum may not require complex nutrients for growth and, in fact, may be nutritionally similar to rumen anaerobes.

The mechanism by which cryosolvents such as alcohols modify and penetrate cell membranes as a function of their concentration and hydration state remains poorly understood. We conducted molecular dynamics simulations of 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayers in the presence of aqueous solutions of four common penetrating hydroxylated cryosolvents (methanol, ethylene glycol, propylene glycol, and glycerol) at varying concentration ranges and across three different hydration states. All cryosolvents were found to preferentially replace water at the bilayer interface, and a reduction in hydration state correlates with a higher proportion of cryosolvent at the interface for relative concentrations. Minor differences in chemical structure had a profound effect on cryosolvent–membrane interactions, as the lone methyl groups of methanol and propylene glycol enhanced their membrane localization and penetration, but with increasing concentrations acted to destabilize the membrane structure in a process heightened at higher hydration states. By contrast, ethylene glycol and glycerol promoted and retained membrane structural integrity by forming hydrogen-bonded lipid bridges via distally located hydroxyl groups. Glycerol exhibited the highest capacity to cross-link lipids at relative concentrations, as well as promoted a bilayer structure consistent with a fully hydrated bilayer in the absence of cryosolvent for all hydration states investigated.

Photoexcitation of a zinc imidazoporphyrin-fullerene dyad with a short linkage results in formation of the charge-separated state by photoinduced electron transfer. The charge-separated state has a lifetime of 310 μs in benzonitrile at 278 K, which is the longest lifetime in solution ever reported for electron donor−acceptor-linked dyads.