On the explicit analytic solutions of an Oldroyd 6-constant fluid

This paper deals with some steady unidirectional flows of an Oldroyd 6-constant fluid. The modelled differential equation is non-linear and proposes some new mathematical difficulties. The governing non-linear equation for the steady flow of an Oldroyd 6-constant fluid is different than from the Newtonian fluid and involves the non-Newtonian features. Moreover, the exact analytic solutions are obtained for Couette, Poiseuille and generalized Couette flows for all values of non-Newtonian parameters. The homotopy analysis method (HAM) is used to construct the solutions.     

Dynamics and the single spike

Responses of vestibular primary afferent neurons to head rotation exhibit fractional-order dynamics. As a consequence, the head tends to be in a localized region of its state-space at spike times of a particular neuron during arbitrary head movements, and single spikes can be interpreted as state measurements. We are developing a model of neural computations underlying trajectory prediction and control tasks, based on this experimental observation. This is a step toward a formal neural calculus in which single spikes are modeled realistically as the operands of neural computation.     

The nature of the gregarizing signal responsible for maternal transfer of phase to the offspring in the desert locust Schistocerca gregaria

We examined aggregative behavior of hatchlings of the desert locust Schistocerca gregaria emerging from solitaria egg pods that had been incubated in sand previously used for consecutive ovipositions by gregarious females. Hatchlings derived from such eggs were significantly more gregarious than those derived from pods laid in clean sand. The gregarizing effect of the sand-associated factor originating from 3, 5, or 10 ovipositions by gregarious females increased in a dose-dependent fashion. Washing the sand with organic solvents following such ovipositions, or flushing it with nitrogen gas, led to substantial loss of its gregarizing effect, showing that the active signal is volatile and of medium polarity. The gregarizing activity of the exposed sand correlated with the presence of C-8 unsaturated ketones, (Z)-6-octen-3-one and (E,E)-3,5-octadiene-2-one and its E,Z isomer, previously shown by us to form part of the releaser pheromone system that mediates group oviposition in S. gregaria. These ketones were present in relatively large amounts in the eggs obtained from egg pods of gregarious females and were also detected in the extracts of accessory glands of gregarious females, a candidate source of the gregarization factor. It is proposed that the pheromone is secreted at the onset of oviposition. This would account for its distribution predominantly within the eggs and surrounding sand at the site of oviposition. The study sheds new light on the pheromonal mechanism associated with transgenerational transmission of gregarious characters in crowded S. gregaria populations and provides yet another case in this insect of dual releaser and primer roles played by the same pheromone blend.     

Kinetics of thermal inactivation of transglutaminase from a newly isolated Bacillus circulans BL32

BACKGROUND: This paper describes the modeling of the kinetics of thermal inactivation of transglutaminase (TGase) from a newly isolated Bacillus circulans BL32, isolated from the Amazon environment. The purified enzyme was incubated at temperatures ranging from 30 to 70 °C and values of the thermodynamic inactivation parameters, such as activation energy (ΔE), activation enthalpy (ΔH), activation entropy (ΔS), and free energy (ΔG) for thermal inactivation, were calculated. RESULTS: The kinetics of TGase thermo‐inactivation followed a Lumry–Eyring model. The enzyme was very stable up to 50 °C, with approximately 50% of activity remaining after heating for 12 h. It was completely inactivated by incubation at 70 °C for 2 min. ΔE for TGase was 350.5 kJ mol^?1. ΔH and ΔS for thermo‐inactivation of the TGase were 347.8 kJ mol^?1 and 744 J mol^?1 K^?1 at 50 °C, respectively. Dynamic light scattering measurements suggest that the thermal inactivation of this microbial TGase can be partially attributed to the formation of aggregates. CONCLUSION: These results provide useful information about the thermal characteristics of the microbial TGase from B. circulans BL32 and indicate that this enzyme could be a good candidate for industrial applications. Copyright © 2009 Society of Chemical Industry     

Production of organic solvent tolerant lipase by Staphylococcus caseolyticus EX17 using raw glycerol as substrate

BACKGROUND: In this work we used Plackett–Burman statistical design and central composite design in order to optimize culture conditions for lipase production by Staphylococcus caseolyticus strain EX17 growing on raw glycerol, which was obtained as a by‐product of the enzymatic synthesis of biodiesel. The stability of lipase was verified over several organic solvents, such as methanol, ethanol and n‐hexane. RESULTS: Optimal culture conditions for lipase production were found to be 36 °C, initial pH 8.12, glycerol 30 g L^?1, olive oil 3.0 g L^?1, and soybean oil 2.5 g L^?1, with 145.8 U L^?1 of enzyme activity. When commercial glycerol was substituted by the raw glycerol from biodiesel synthesis, lipolytic activity was 127.3 U L^?1. Experimental validation of enzyme production matched values predicted by the mathematical model, which was 138.3 U L^?1. Stability tests showed that lipase from S. caseolyticus EX17 was stable in methanol, ethanol, and n‐hexane. CONCLUSIONS: Results obtained in this work suggest that raw glycerol can be used for lipase production by S. caseolyticus EX17 and that this enzyme has a potential application in the synthesis of biodiesel. Copyright © 2008 Society of Chemical Industry     

Book Reviews

Applied Network Optimization, Christoph Mandl, Academic Press London, 1979, 175 pages

Studies in Management Sciences, Vol. 12, Forecasting, S. Makridakis and S. C. Wheelwright, Elsevier North-Holland Publishing Co., 52 Vanderbilt Ave., New York, NY 10017 (373 pages; $29.95) 1979.     

The X-Y chart: A tool for systems designers

The X-Y Chart is a tool developed to improve user participation in information system specification and design as one of the Bottom-Up alternatives. It is extremely simple to use and offers a framework for extremely easy to use and develop procedures manuals. Its simplicity in system analysis and design aids in bridging the communication gap that exists between system designers and user staff, and it also reduces the time taken to design an overall information system architecture.     

Tailoring the properties of leno woven fabrics by varying the structure

Abstract

This study focused on the development of woven structures based on leno weave with tailored performance properties. To achieve this objective, pure leno and hybrid leno weaves were used to produce woven fabrics. In hybrid weaves, leno weave was combined with 1/1 plain, 3/1 twill, and 2/2 matt weaves, and 12 samples were produced with three different weft thread densities. The multifilament polyester yarn was used as warp and weft material. The characterization of physical and mechanical properties showed that comparable tensile properties were achieved by leno and hybrid weave fabrics, but the hybrid structures offered lower resistance to puncture as compared to pure leno fabrics. A multi-response optimization technique was used to determine the best sample under a particular set of conditions.     

Comparative production of xylanase and the liberation of xylooligosaccharides from lignocellulosic biomass by Aspergillus brasiliensis BLf1 and recombinant Aspergillus nidulans XynC A773

We investigated the simultaneous production of xylanase and the liberation of xylooligosaccharides in rice husk solid‐state cultivations of Aspergillus brasiliensis BLf1 and by the recombinant Aspergillus nidulans XynC A773 strain. The bioprocess was optimised by experimental fractional design and response surface analysis. Results show that both fungi strains produced xylanases and their activities were dependent on the addition of basal medium, moisture content and the interactions between particle size and inoculum size, producing maximum xylanase activities of 230.7 U g^?1 substrate for A. brasiliensis, and 187.9 U g^?1 substrate for A. nidulans XynC. Xylooligosaccharides were liberated in the same cultures, with concentrations up to 17.6 mg g^?1 and 23.9 mg g^?1 of substrate for A. brasiliensis and A. nidulans XynC, respectively, both strains presenting similar profiles, with xylose residues varying from X3 to X6. These results suggest the possibility of lowering production costs of enzymes for food applications and oligosaccharides.