Adiabatic Quantum Computing for Random Satisfiability Problems

The discrete formulation of adiabatic quantum computing is compared with other search methods, classical and quantum, for random satisfiability (SAT) problems. With the number of steps growing only as the cube of the number of variables, the adiabatic method gives solution probabilities close to 1 for problem sizes feasible to evaluate via simulation on current computers. However, for these sizes the minimum energy gaps of most instances are fairly large, so the good performance scaling seen for small problems may not reflect asymptotic behavior where costs are dominated by tiny gaps. Moreover, the resulting search costs are much higher than for other methods. Variants of the quantum algorithm that do not match the adiabatic limit give lower costs, on average, and slower growth than the conventional GSAT heuristic method.Comment: added discussion of discrete adiabatic method, and simulations with 30 bits 8 pages, 8 figure

Inter-cluster reactivity of Metallo-aromatic and anti-aromatic Compounds and Their Applications in Molecular Electronics: A Theoretical Investigation

Local reactivity descriptors such as the condensed local softness and Fukui function have been employed to investigate the inter-cluster reactivity of the metallo-aromatic (Al4Li- and Al4Na-) and anti-aromatic (Al4Li4 and Al4Na4) compounds. We use the concept of group softness and group Fukui function to study the strength of the nucleophilicity of the Al4 unit in these compounds. Our analysis shows that the trend of nucleophilicity of the Al4 unit in the above clusters is as follows; Al4Li- > Al4Na- > Al4Li4 > Al4Na 4 For the first time we have used the reactivity descriptors to show that these clusters can act as electron donating systems and thus can be used as a molecular cathode.Comment: 23 pages, 1 figure and 1 table of conten

Bose-Einstein condensation of correlated atoms in a trap

The Bose-Einstein condensation of correlated atoms in a trap is studied by examining the effect of inter-particle correlations to one-body properties of atomic systems at zero temperature using a simplified formula for the correlated two body density distribution. Analytical expressions for the density distribution and rms radius of the atomic systems are derived using four different expressions of Jastrow type correlation function. In one case, in addition, the one-body density matrix, momentum distribution and kinetic energy are calculated analytically, while the natural orbitals and natural occupation numbers are also predicted in this case. Simple approximate expressions for the mean square radius and kinetic energy are also given.Comment: 14 pages, 19 figures, 1 Table, RevTe

Postantibiotic and sub-MIC effects of benzylpenicillin against Streptococcus pneumoniae with different susceptibilities for penicillin

Background: The purpose of the study was to examine whether penicillin-susceptible and nonsusceptible strains of Streptococcus pneumoniae exhibited different pharmacodynamic responses to benzylpenicillin. Methods: The postantibiotic effects (PAEs) and the postantibiotic sub-MIC effects (PA SMEs) were investigated by optical density against strains of S. pneumoniae with different susceptibilities to benzylpenicillin. To validate the data, the PAE and PA SME of one susceptible and one resistant strain were also tested with the viable count method. The post-MIC effects (PMEs) were studied in an in vitro kinetic model, simulating human pharmacokinetics with a half-life of 1 h and a time above MIC of approximately 20% of 24 h. Results: There were no differences with respect to the PAEs, PA SMEs and PMEs of benzylpenicillin for the various strains of S. pneumoniae, irrespective of their susceptibility to penicillin. For both some of the susceptible and resistant strains investigated, longer PA SMEs at 0.2 and 0.3 x MIC were noted, indicating that these parameters might be more dependent on the type of strain rather than on the susceptibility status. Conclusion: No differences in the pharmacodynamic response after similar drug exposure were seen for S. pneumoniae strains with different penicillin susceptibility. Copyright (C) 2003 S. Karger AG, Basel

Pharmacodynamic studies of amoxicillin against Streptococcus pneumoniae: comparison of a new pharmacokinetically enhanced formulation (2000 mg twice daily) with standard dosage regimens

Objectives: To compare the pharmacodynamic effects of a pharmacokinetically enhanced formulation of amoxicillin 2000 mg twice daily, with amoxicillin 875 mg twice daily, 875 mg three times daily and 500 mg three times daily against Streptococcus pneumoniae with different susceptibility to amoxicillin in an in vitro kinetic model. Methods: Strains of S. pneumoniae with amoxicillin MICs of 1, 2, 4 and 8 mg/L at an initial inoculum of approximately 10(5) cfu/mL were exposed to amoxicillin in an in vitro kinetic model simulating the human serum concentration-time profile of the pharmacokinetically enhanced formulation twice daily (C-max 17 mg/L after 1.5 h). All isolates were also exposed to amoxicillin with concentration-time profiles correlating to the human dosage of 875 mg twice daily (C-max 15 mg/L after 1 h), 875 mg three times daily and 500 mg (C-max 8 mg/L after 1 h) three times daily with simulated half-life of 1 h. Repeated samples were taken regularly during 24 h and viable counts were carried out. Results: Overall, the pharmacokinetically enhanced formulation was more effective at reducing bacterial counts than any of the other formulations evaluated. Eradication was achieved with the enhanced formulation for strains with a MIC of less than or equal to2 mg/L, however, regrowth occurred with the other dosing regimens. In the experiments with the strain with a MIC of 4 mg/L, the enhanced formulation kept the bacterial counts less than or equal to10(2) cfu/mL for at least 14 out of 24 h tested. In contrast, none of the other formulations reduced the bacterial counts down to less than or equal to10(2) cfu/mL at any point. None of the regimens was able to eradicate the strain with an MIC of 8 mg/L, even though an initial substantial kill was noted with the enhanced formulation after both doses. The least effective dosage regimen for all strains was 875 mg twice daily