Polymeric Multilayers that Contain Silver Nanoparticles can be Stamped onto Biological Tissues to Provide Antibacterial Activity

The design of polyelectrolyte multilayers (PEMs) that can be prefabricated on an elastomeric stamp and mechanically transferred onto biomedically‐relevant soft materials, including medical‐grade silicone elastomers (E’～450–1500 kPa; E’‐elastic modulus) and the dermis of cadaver skin (E’～200–600 kPa), is reported. Whereas initial attempts to stamp PEMs formed from poly(allylamine hydrochloride) and poly(acrylic acid) resulted in minimal transfer onto soft materials, we report that integration of micrometer‐sized beads into the PEMs (thicknesses of 6–160 nm) led to their quantitative transfer within 30 seconds of contact at a pressure of ～196 kPa. To demonstrate the utility of this approach, PEMs were impregnated with a range of loadings of silver‐nanoparticles and stamped onto the dermis of human cadaver skin (a wound‐simulant) that was subsequently incubated with bacterial cultures. Skin dermis stamped with PEMs that released 0.25 ± 0.01 μg cm^?2 of silver ions caused a 6 log₁₀ reduction in colony forming units of Staphylococcus epidermidis and Pseudomonas aeruginosa within 12 h. Significantly, this level of silver release is below that which is cytotoxic to NIH 3T3 mouse fibroblast cells. Overall, this study describes a general and facile approach for the functionalization of biomaterial surfaces without subjecting them to potentially deleterious processing conditions.     

Neural networks and fuzzy logic-based spark advance control of SI engines

In SI engines, spark advance (SA) needs to be controlled to get Maximum Brake Torque (MBT) timing. Spark advance can be controlled either by open loop or by closed loop controller. The open loop controller requires extensive testing and calibration of engine, to develop look up tables. In closed loop controller, empirical rules relating variables deduced from cylinder pressure are used. One of such empirical rules is to fix location of peak pressure (LPP) at a desired value of the crank angle. In the present work, a combined neural network and fuzzy logic-based control scheme is designed for SA control to get MBT timing. The fuzzy logic controller is designed to maintain LPP of SI engine close to 16° ATDC. The controller works in conjunction with Recurrent Neural Network model for cylinder pressure identification. LPP is estimated from cylinder pressure curve reconstructed using neural network model and is used as feedback signal to fuzzy logic controller. The simulations have been carried out to test the performance of the combined neural network and fuzzy logic-based control strategy. The simulation results show that the proposed strategy can quite satisfactorily control LPP to its desired value.     

COMPARISON AND VALIDATION OF OHM AND SCEM MEASUREMENTS FOR A FULL-SCALE COAL-FIRED POWER PLANT

Mercury emission measurements were performed at a 250 MW coal-fired power plant using the Ontario Hydro method (OHM) and semi-continuous emission monitors (SCEM). Flue gas sampling was performed at the inlet of the air preheater and at the outlet of the electrostatic precipitator. The results indicated that there is some agreement between the OHM and SCEM measurements on the total mercury species. However, the SCEM results were not always in good agreement with the OHM measurements on the elemental mercury species. These discrepancies in elemental mercury concentrations are probably the result of the differences in the location of the SCEM and OHM probes, the temperature difference between the SCEM sampling probe and the flue gas, and the nonuniformities in mercury concentration over the flue gas duct cross section. The other factor that contributed to the deviation between the SCEM and OHM measurement results is the sampling method: the SCEM measurements were performed at a single point while the OHM probe was traversed over multiple points over the duct cross section and the results were averaged. The effect of the SCEM sampling probe temperature was investigated by designing a sampling probe that could be heated to the sampled flue gas temperatures. This resulted in improvements in the accuracy of the elemental mercury measurements by the SCEM system.     

Biaxially oriented poly(propylene-g-maleic anhydride)/phosphate glass composite films for high gas barrier applications

The solid state structure and oxygen transport properties of biaxially oriented poly(propylene-graft-maleic anhydride) (PPgMA) reinforced with a low glass transition temperature (T_g) phosphate glass (Pglass) were investigated. Composites were prepared by melt blending PPgMA with up to 20 volume% Pglass. Melt blended composites were compression molded into monolayer structures and then biaxially stretched at a temperature above the T_g of the Pglass. Scanning electron microscopy confirmed that biaxial stretching transformed the spherical Pglass particles into platelets oriented in the plane of the film. Gas transport measurements revealed a reduction in the oxygen permeability by as much as 2 orders of magnitude compared to the unoriented PPgMA film. The permeability was analyzed according to performance models for dispersions of platelet-like fillers proposed by Cussler and Nielson. Aspect ratios ranging from 15 to 80 were obtained by fitting the experimental data to the models. Mechanical tests revealed that blending with Pglass increased the modulus of the stretched film but reduced the elongation at break only slightly.     

Preoperative sonographic diagnosis of acute appendicitis caused by Ascaris lumbricoides

Acute appendicitis caused by Ascaris lumbricoides is an uncommon variant of a common disease. We describe a case in which sonography was used for preoperative diagnosis of ascaris appendicitis.     

Catalytic hydrogenation for improvement of GaAs/Ge solar cell efficiency

Hydrogen passivation on MOCVD grown p-GaAs epilayers on Ge substrate have been studied by plasma and catalytic hydrogenation and the results were compared. The conversion efficiency of the GaAs/Ge solar cells was found to increase by 10% after catalytic hydrogenation at AM1.5. This increase in efficiency is probably due to passivation of surface dangling bonds.