Quantum heuristic algorithm for traveling salesman problem

We propose a quantum heuristic algorithm to solve a traveling salesman problem by generalizing Grover search. Sufficient conditions are derived to greatly enhance the probability of finding the tours with extremal costs, reaching almost to unity and they are shown characterized by statistical properties of tour costs. In particular for a Gaussian distribution of the tours along the cost we show that the quantum algorithm exhibits the quadratic speedup of its classical counterpart, similarly to Grover search.Comment: Published versio

Effects of Deposit Insurance Reform on Moral Hazard in US Banking

In cross sections of US banks before the deposit-insurance system was reformed in the early 1990s, bank risk-taking was positively associated with bank size and negatively associated with the value of bank charters and bank capital. These empirical associations have an easy theoretical interpretation. Bank size is positively related, while charter value and capital are negatively related, to the moral hazard associated with flat insurance premiums and other aspects of a laxly administered system. Hence the observed associations of risk-taking with size, charter value, and capital reflected the expected positive relation between moral hazard and risk-taking. We test the hypothesis that the three associations became weaker after reform. In the case of unsystematic risk, we find no evidence of significant changes for any of the three. In the case of systematic risk, we find that risk-taking associated with lower charter values and larger size is indeed significantly weaker after reform. Risk-taking associated with capital ratios is also weaker after reform, though not significantly so. Since systematic risk is undoubtedly the more appropriate measure, reform seems to have reduced moral hazard. Copyright Blackwell Publishers Ltd 2001.

Surface Characterization of <i>Populus</i> during <i>Caldicellulosiruptor bescii</i> Growth by TOF-SIMS Analysis

<i>Caldicellulosiruptor bescii</i> is a thermophilic, anaerobic bacterium that is capable of utilizing unpretreated biomass in addition to breaking down cellulose and hemicellulose into simple sugars. Despite the fact that <i>C. bescii</i> must first bind to the surface of the biomass, there has been no analysis of the morphological or chemical changes to the biomass surface as a result of incubation with the micro-organism. To understand more about <i>C. bescii</i> growth, juvenile poplar stems were sectioned (80 μm thick) and incubated with <i>C. bescii</i> beyond the typical 24 h experiment length. Monitoring the cell counts during incubation revealed a biphasic growth pattern. The impact the micro-organism had on the surface was determined by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), which showed physical crevices in the cell wall caused by the <i>C. bescii</i> along with a decrease of polysaccharide ions and an increase in lignin ions on the poplar surface. Employing infrared microspectroscopy, the decreasing trend was corroborated

In vitro antimicrobial activity of total extracts of the leaves of Petiveria alliacea L. (Anamu)

The antimicrobial activity of 13 total extracts was evaluated, 10 soft extracts (B) and 3 blended extracts (E) prepared from dry and fresh leaves of Petiveria alliacea L. Various solvents were used for their preparation: hydroalcoholic solution at 30%, 80% and isopropyl alcohol. The antimicrobial effect of the extracts was tested by means of the method of Kirby-Bauer, using four bacterial strains from the ATCC collection (Escherichia coli, Staphylococcus aureus, Enterococcus faecalis and Pseudomonas aeruginosa) and a leveduriform fungus (Candida albicans). The following quality control parameters were determined for most active extracts: physical, physical-chemical and chemical parameters. The results were: nine extracts showed antibacterial activity, being the most concentrated (B8 and E3), the ones with the highest activity in the presence of the bacteria tested; the effect of blended extracts (E1, E2 and E3) was greater in the presence of P. aeruginosa. Blended extracts are considered more potent and active than soft extracts. No antifungal activity was obtained for both types of extracts. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined for both extracts, with the following results: MIC-soft extracts (>100 mg/mL), blended extracts (>50 mg/mL); MBC-soft extracts (≥400 mg/mL), blended extracts (≥200 mg/mL) based on fresh leaves