Electrospun salicylic acid/polyurethane composite nanofibers for biomedical applications

Salicylic acid (SA)/polyurethane (PU) composite nanofiber mats were fabricated by introducing SA in PU solution during the electrospinning process. Cell viability assays showed that the as-prepared composite nanofibers had a good biocompatibility. Further, the composite mats showed good antibacterial performance against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. Easy fabrication, good mechanical properties, good biocompatibility as well as the antibacterial activity of PU nanofibers containing SA indicated their significant promise for a variety of potential medical applications such as tissue engineering, wound healing, and drug delivery system.     

Reliability analysis for systems with large hydro resources in a deregulated electric power market

This work describes a procedure that determines the optimal allocation for the yearly energy resulting from random water inflows to the different subperiods of a year so that the expected benefits are maximized. Its main idea is to distribute the energy stored in reservoirs in each period into two parts: one is directly sold in the energy market, while the other is made available to cover any unplanned outages of thermal units. The method proposed fulfills two objectives, to distribute the hydro energy optimally according to economic criteria and to assess the impact of new market rules on the reliability of an electric system. The procedure will be illustrated by an example based on the Spanish generating system.     

Investigation of ceramic boron nitride by terahertz time-domain spectroscopy

Four grades of hexagonal boron nitride are investigated by terahertz time-domain spectroscopy. The refractive indices and loss coefficients at terahertz frequencies are measured and are related to aspects of material fabrication and properties.     

How Individuals Explain Social Problems: The Influences of Media Use

This study examined the role of media use in individuals' explanations of crime and welfare. Attribution theory and the information-processing approach to media effects provided a theoretical framework for this research. Media effects on explanations of social problems are enhanced by individuals' patterns of information processing. Specifically, active processing of national television public affairs content increased while active processing of newspaper public affairs content decreased the likelihood of individualistic explanations. The study also showed that individualistic explanations of crime and welfare are related to support for the death penalty and to opposition toward welfare programs.     

Simple Approximation to Bottom Friction for Bingham Fluid Depth Integrated Models

Catastrophic gravity driven flows such as debris flows, mud flows, and flow slides cause major economic damage and loss of human life. Numerical models are important prediction tools which can help to design contention, channeling, and routing structures. Their accuracy is limited by that of the rheological model they implement. Bingham models provide a reasonable good compromise between accuracy and simplicity, and they have been frequently used to describe the rheology of hyperconcentrated flows, mudflows, and debris flows. Their use in depth integrated models presents a difficulty. In order to obtain the bottom friction term, one has to obtain the roots of a third order polynomial. This paper describes a depth integrated model for flows of Bingham fluids. Bottom friction is obtained using an approximation which provides good accuracy and saves 20% of CPU time.     

Poincare's index for double points of a second-order autonomous recurrence

Using Neimark's result, Poincare's index is defined for different types of double points of an autonomous second-order recurrence, in the absence of a critical case. A necessary condition is given for the existence of a closed trajectory surrounding a number of double points.     

Transverse chemotactic migration of bacteria from high to low permeability regions in a dual permeability microfluidic device

Low permeability regions such as clay lenses are difficult to remediate using conventional treatment methods. Bacterial chemotaxis (directed migration toward a contaminant source) may be helpful in enhancing bioremediation of such contaminated sites. This study experimentally simulates a two-dimensional dual-permeability groundwater contamination scenario using a microfluidic device (MFD) and evaluates transverse chemotactic migration of bacteria from high to low permeability regions under various flow velocities. Chemotaxis of Escherichia coli (E. coli) HCB33 to the chemoattractant dl-aspartic acid was quantified in terms of change in total bacterial counts in pore throats in low permeability regions containing attractant. An increase in total bacterial counts, ranging from 1.09 to 1.74 times, was observed in low permeability regions in experiments under chemotactic conditions. Experiments with no attractant showed no increase in total bacterial counts in low permeability regions. A large increase in bacterial counts in the pore throats just outside the low permeability region was also observed in chemotaxis experiments. The bacterial chemotactic response was observed to decrease linearly with increase in flow velocity, with no observed response at the highest flow velocity (Darcy velocity = 0.22 mm/s), where chemotaxis was offset by advective flow.     

Investigation of dilution effects on partially premixed swirling syngas flames using a LES-LEM approach

The dilution effects of CO₂ and H₂O on partially premixed swirling syngas flames are investigated with the large eddy simulation (LES) method. The linear-eddy model (LEM) is employed to directly resolve the unclosed molecular diffusion, scalar mixing and chemical reaction processes occurring at subgrid scale level using their specific length and time scales instead of modelling, which makes the LES-LEM approach quite attractive for hydrogen fuel combustion as the obviously different diffusion and reaction characteristics of H₂ and H compared to other species in the syngas mixture. Firstly, adding CO₂ into the fuel stream can significantly decrease the flame temperature during the partially premixed combustion. The concentration of H and OH radicals decreases upon CO₂ dilution and thus the chemical reaction processes are modified. Compared with CO₂, H₂O is less effective in changing the temperature field because of the chemical effects of H₂O. The simultaneous addition of H₂O and CO₂ as dilution gases with volume ratio 1:1 into the fuel stream is also conducted to identify the effects of H₂O and CO₂ on partially premixed combustion dynamics by comparing with single H₂O and CO₂ cases. The obtained results are expected to provide helpful information for the design and operation of gas turbine combustion systems with syngas fuels.