Search

Transportation facility and automotive service enterprise location is an interesting and important issue. In practice, such factors as customer demand, allocations, even locations of customers and facilities are usually changing, thus making facility location problematic with uncertainty. To account for it, some researchers have addressed stochastic/fuzzy models for locating an automotive service enterprise. However, probabilistic/fuzzy models are not suitable to describe all kinds of uncertainty, but only randomness or fuzziness. In fact, the uncertain environment of locating an automotive service enterprise is a mixed one with both randomness and fuzziness. To handle this issue in a practical manner, this work proposes fuzzy random tradeoff issues for it. Moreover, some regional constraints can greatly influence its location. By taking the vehicle inspection station as a typical example, this work presents new fuzzy random cost–profit tradeoff models of its location problem with regional constraints. A hybrid algorithm integrating fuzzy random simulation and genetic algorithms is adopted to solve the proposed models. Additionally, some risk factors have a great impact on decision making when faced with a location problem. This work thus conducts a risk performance analysis for locating an automotive service enterprise. Some numerical examples are given to illustrate the proposed models. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Many real-life stains have origins from biological matters including proteins, lipids, and carbohydrates that act as gluing agents binding along with other particulates or microbes to exposed surfaces of automobiles, furniture, and fabrics. Mimicking naturally occurring self-defensive processes, we demonstrate in this work that a solid surface carrying partially exposed enzyme granules protected the surface in situ from contamination by biological stains and fingerprints. Attributed to the activities of enzymes which can be made compatible with a wide range of materials, such anti-contamination and self-cleaning functionalities are highly selective and efficient toward sticky chemicals. This observation promises a new mechanism in developing smart materials with desired anti-microbial, self-reporting, self-cleaning, or self-healing functions.

Summary It has been previously noted that mixed communities typically produce more power in microbial fuel cells than pure cultures. If true, this has important implications for the design of microbial fuel cells and for studying the process of electron transfer on anode biofilms. To further evaluate this, Geobacter sulfurreducens was grown with acetate as fuel in a continuous flow ‘ministack’ system in which the carbon cloth anode and cathode were positioned in close proximity, and the cation-selective membrane surface area was maximized in order to overcome some of the electrochemical limitations that were inherent in fuel cells previously employed for the study of pure cultures. Reducing the size of the anode in order to eliminate cathode limitation resulted in maximum current and power densities per m 2

Hierarchically ordered mesocellular mesoporous silica materials (MMS) were synthesized using a single structure directing agent under neutral conditions for the first time. The mesocellular pores are synthesized without adding any pore expander, and the walls of cellular pores in MMS are composed of SBA-15 type mesopores. The small-angle X-ray scattering (SAXS) pattern of MMS revealed the presence of ordered pore structures with two different length scales. The current MMS possesses four different pore systems; complementary micro/mesopores, main 13 nm mesopores, 40 nm mesocellular spherical pores, and textural inter-particle macropores. Nanometer-scale enzyme reactors (NER) were developed in mesocellular mesoporous silica (MMS) via a ship-in-a-bottle approach, which employs adsorption of enzymes followed by cross-linking using glutaraldehyde (GA) treatment. The resulting NER show an impressive stability and activity with an extremely high loading of enzymes. For example, NER containing α-chymotrypsin (NER-CT) could hold 0.5 g CT in 1 g of silica, but the specific activity of NER-CT was 10.4 times higher than that of the adsorbed CT with a lower loading (0.07 g CT per 1 g of silica), which was further decreased by a continuous leaching of adsorbed CT. NER-CT showed excellent stability without any leaching, i.e. no activity decrease atmore » all in a rigorously-shaking condition for two weeks (a half-life with 3.8 years), while the conventional adsorption method resulted in a half-life of 3.6 days in the same condition.« less

Multistep reactions catalyzed by a covalently immobilized enzyme-cofactor-enzyme system were achieved. Lactate dehydrogenase (LDH), glucose dehydrogenase (GDH), and cofactor NADH were incorporated into two porous silica glass supports. One of the glass supports had pores of 30 nm in diameter, while the other was of 100-nm pore size. Effective shuttling of the covalently bound NADH between LDH and GDH was achieved, such that regeneration cycles of NADH/NAD(+) were observed. The glass of 30-nm pore size afforded enzyme activities that were about twice those observed for the glass of 100-nm pore size, indicating the former provided better enzyme-cofactor integration. The effect of the size of spacers was also examined. The use of longer spacers increased the reaction rates by approximately 18 times as compared to those achieved with glutaraldehyde linkage. It appeared that the concave configuration of the nanopores played an important role in enabling the multistep reactions. The same multienzyme system immobilized on nonporous polystyrene particles of 500-nm diameter was only approximately 2% active as the glass-supported system. It is believed that the nanoporous structure of the glass supports enhances the molecular interactions among the immobilized enzymes and cofactor, thus improving the catalytic efficiency of the system.

Nanoparticles provide an ideal remedy to the usually contradictory issues encountered in the optimization of immobilized enzymes: minimum diffusional limitation, maximum surface area per unit mass, and high effective enzyme loading. In addition to the promising performance features, the unique solution behaviors of the nanoparticles also point to a transitional region between the heterogeneous (with immobilized enzymes) and homogeneous (with soluble free enzymes) catalysis. The particle mobility, which is related to particle size and solution viscosity through Stokes-Einstein equation, may impact the reaction kinetics according to the collision theory. The mobility-activity relationship was examined through experimental studies and theoretical modeling in the present work. Polystyrene particles with diameters ranging from 110-1000 nm were prepared. A model enzyme, alpha-chymotrypsin, was covalently attached to the nanoparticles up to 6.6 wt%. The collision theory model was found feasible in correlating the catalytic activities of particles to particle size and solution viscosity. Changes in the size of particles and the viscosity of reaction media, which all affect the mobility of the enzyme catalyst, evidently altered the intrinsic activity of the particle-attached enzyme. Compared to K(M), k(cat) appeared to be less sensitive to particle size and viscosity.

Improvement of catalytic efficiency of immobilized enzymes via materials engineering was demonstrated through the preparation of bioactive nanofibers. Bioactive polystyrene (PS) nanofibers with a typical diameter of 120 nm were prepared and examined for catalytic efficiency for biotransformations. The nanofibers were produced by electrospinning functionalized PS, followed by the chemical attachment of a model enzyme, alpha-chymotrypsin. The observed enzyme loading as determined by active site titration was up to 1.4% (wt/wt), corresponding to over 27.4% monolayer coverage of the external surface of nanofibers. The apparent hydrolytic activity of the nanofibrous enzyme in aqueous solutions was over 65% of that of the native enzyme, indicating a high catalytic efficiency as compared to other forms of immobilized enzymes. Furthermore, nanofibrous alpha-chymotrypsin exhibited a much-improved nonaqueous activity that was over 3 orders of magnitude higher than that of its native counterpart suspended in organic solvents including hexane and isooctane. It appeared that the covalent binding also improved the enzyme's stability against structural denaturation, such that the half-life of the nanofibrous enzyme in methanol was 18-fold longer than that of the native enzyme.