Duquesne University

About: Duquesne University is a education organization based out in Pittsburgh, Pennsylvania, United States. It is known for research contribution in the topics: Population & Health care. The organization has 3615 authors who have published 7169 publications receiving 180066 citations. The organization is also known as: Duquesne University of the Holy Spirit.

Light-dependant biostabilisation of sediments by stromatolite assemblages.

Abstract: For the first time we have investigated the natural ecosystem engineering capacity of stromatolitic microbial assemblages. Stromatolites are laminated sedimentary structures formed by microbial activity and are considered to have dominated the shallows of the Precambrian oceans. Their fossilised remains are the most ancient unambiguous record of early life on earth. Stromatolites can therefore be considered as the first recognisable ecosystems on the planet. However, while many discussions have taken place over their structure and form, we have very little information on their functional ecology and how such assemblages persisted despite strong eternal forcing from wind and waves. The capture and binding of sediment is clearly a critical feature for the formation and persistence of stromatolite assemblages. Here, we investigated the ecosystem engineering capacity of stromatolitic microbial assemblages with respect to their ability to stabilise sediment using material from one of the few remaining living stromatolite systems (Highborne Cay, Bahamas). It was shown that the most effective assemblages could produce a rapid (12–24 h) and significant increase in sediment stability that continued in a linear fashion over the period of the experimentation (228 h). Importantly, it was also found that light was required for the assemblages to produce this stabilisation effect and that removal of assemblage into darkness could lead to a partial reversal of the stabilisation. This was attributed to the breakdown of extracellular polymeric substances under anaerobic conditions. These data were supported by microelectrode profiling of oxygen and calcium. The structure of the assemblages as they formed was visualised by low-temperature scanning electron microscopy and confocal laser microscopy. These results have implications for the understanding of early stromatolite development and highlight the potential importance of the evolution of photosynthesis in the mat forming process. The evolution of photosynthesis may have provided an important advance for the niche construction activity of microbial systems and the formation and persistence of the stromatolites which came to dominate shallow coastal environments for 80% of the biotic history of the earth.

Inhibiting bacterial cooperation is an evolutionarily robust anti-biofilm strategy.

Abstract: Bacteria commonly form dense biofilms encased in extracellular polymeric substances (EPS). Biofilms are often extremely tolerant to antimicrobials but their reliance on shared EPS may also be a weakness as social evolution theory predicts that inhibiting shared traits can select against resistance. Here we show that EPS of Salmonella biofilms is a cooperative trait whose benefit is shared among cells, and that EPS inhibition reduces both cell attachment and antimicrobial tolerance. We then compare an EPS inhibitor to conventional antimicrobials in an evolutionary experiment. While resistance against conventional antimicrobials rapidly evolves, we see no evolution of resistance to EPS inhibition. We further show that a resistant strain is outcompeted by a susceptible strain under EPS inhibitor treatment, explaining why resistance does not evolve. Our work suggests that targeting cooperative traits is a viable solution to the problem of antimicrobial resistance.

The finite horizon nonstationary stochastic inventory problem: near-myopic bounds, heuristics, testing

Abstract: Nonstationary stochastic periodic review inventory problems with proportional costs occur in a number of industrial settings with seasonal patterns, trends, business cycles, and limited life items. Myopic policies for such problems order as if the salvage value in the current period for ending inventory were the full purchase price, so that information about the future would not be needed. They have been shown in the literature to be optimal when demand "is increasing over time," and to provide upper bounds for the stationary finite horizon problem and in some other situations. Some results are also known, given special salvaging assumptions, about lower bounds on the optimal policy which are near-myopic. Here analogous but stronger bounds are derived for the general finite horizon problem, without such special assumptions. The best upper bound is an extension of the heuristic used by industry for some years for end of season EOS problems; the lower bound is an extension of earlier analytic methods. Four heuristics were tested against the optimal obtained by stochastic dynamic programming for 969 problems. The simplest heuristic is the myopic heuristic itself: it is good especially for moderately varying problems without heavy end of season salvage costs and averages only 2.75% in cost over the optimal. However, the best of the heuristics exceeds the optimal in cost by an average of only 0.02%, at about 0.5% of the computational cost of dynamic programming.

Construction and Validation of the 4-Item Dynamic Gait Index

Abstract: Background and Purpose. People with balance disorders often have difficulty walking. The purpose of this study was to develop and test the psychometric properties of a short form of the Dynamic Gait Index (DGI) for the clinical measurement of walking function in people with balance and vestibular disorders. Subjects. A total of 123 subjects with such disorders (test subjects) and 103 control subjects were included in this study. Methods. Rasch and factor analyses were used to create a short form of the DGI. Internal consistency and discriminative validity for test subjects versus control subjects and for falling versus nonfalling test subjects were evaluated. Results. Four items were selected for the shorter version of the test: gait on level surfaces, changes in gait speed, and horizontal and vertical head turns. Discussion and Conclusion. The clinical psychometric properties of the 4-item DGI were equivalent or superior to those of the 8-item test. The 4-item DGI can be used by clinicians to measure gait in people with balance and vestibular disorders without compromising important clinical measurement characteristics.