Study of bound phospholipase activities of fungal mycelia using an organic solvent system

It has been possible to demonstrate and characterize high phospholipase activities in mycelia of Rhizopus arrhizus and Mucor javanicus by use of a system in which substrates were dissolved in diisopropyl ether. Such activities were associated with bound enzymes and would have been difficult to detect using aqueous assay systems. In both cases, phosphatidylcholine hydrolysis was by phospholipase A1 (EC 3.1.1.32) activity followed by the action of lysophospholipase (EC 3.1.1.5). Phospholipase D (EC 3.1.4.4) activity was also detected. The methods used appear to be of general applicability for the detection and study of insoluble phospholipases.     

Friendly interfacing to simple speech recognizers

We describe improvements to the recognition performance of a simple commercial speech recognizer. Topics include the selection of acoustically distinct words; a method of 'training' (storing utterances for later use as templates) which mimics the real task, and therefore reduces the difference in diction between training and task; the representation of variability in diction by storing repeated examples of each utterance separately, instead of using a simple statistical average; and the construction of an adaptive algorithm which updates its templates at appropriate moments. The results of empirical investigations with the adaptive algorithm show a very considerable improvement in performance. We argue that the development of speech recognizers has given the hardware undue attention, and that a rigorous attack on adaptive recognition, treated as a problem in control theory, would lead to a sophisticated interface to complement sophisticated hardware. The system we describe has.been successfully used in an experimental voice-operated text-editing system (Morrison and Green 1982).     

Magnetoplumbite related barium aluminates

Yet new complexities are indicated in the structural details of the barium “hexa”-aluminates, in a burgeoning family of magnetoplumbites with many different types of possible defect structures.     

High-bandwidth control of a piezoelectric nanopositioning stage in the presence of plant uncertainties

Inversion-based feedforward techniques have been known to deliver accurate tracking performance in the absence of plant parameter uncertainties. Piezoelectric stack actuated nanopositioning platforms are prone to variations in their system parameters such as resonance frequencies, due to changes in operating conditions like ambient temperature, humidity and loading. They also suffer from nonlinear effects of hysteresis, an inherent property of a piezoelectric actuator; charge actuation is applied to reduce the effects of hysteresis. In this work, we propose and test a technique that integrates a suitable feedback controller to reduce the effects of parameter uncertainties with the inversion-based feedforward technique. It is shown experimentally that the combination of damping, feedforward and charge actuation increases the tracking bandwidth of the platform from 310 to 1320?Hz.     

BE-SONOS flash memory along with metal gate and high-k dielectrics in tunnel barrier and its impact on charge retention dynamics

We investigate the effect of a high-k dielectric in the tunnel layer to improve the erase speed-retention trade-off. Here, the proposed stack in the tunnel layer is AlLaO₃/HfAlO/SiO₂. These proposed materials possess low valence band offset with high permittivity to improve both the erase speed and retention time in barrier engineered silicon-oxide-nitride-oxide-silicon(BE-SONOS). In the proposed structure HfAlO and AlLaO₃ replace Si₃N₄ and the top SiO₂ layer in a conventional oxide/nitride/oxide(ONO) tunnel stack. Due to the lower conduction band offset(CBO) and high permittivity of the proposed material in the tunnel layer, it offers better program/erase(P/E) speed and retention time. In this work the gate length is also scaled down from 220 to 55 nm to observe the effect of high-k materials while scaling, for the same equivalent oxide thickness(EOT). We found that the scaling down of the gate length has a negligible impact on the memory window of the devices. Hence, various investigated tunnel oxide stacks possess a good memory window with a charge retained up to 87.4%(at room temperature) after a period of ten years. We also examine the use of a metal gate instead of a polysilicon gate, which shows improved P/E speed and retention time.     

Inducing Elasticity through Oligo‐Siloxane Crosslinks for Intrinsically Stretchable Semiconducting Polymers

The promise of wearable and implantable devices has made stretchable organic semiconductors highly desirable. Though there are increasing attempts to design intrinsically stretchable conjugated polymers, their performance in terms of charge carrier mobility and maximum fracture strain is still lacking behind extrinsic approaches (i.e., buckling, Kirigami interconnects). Here, polymer crosslinking with flexible oligomers is applied as a strategy to reduce the tensile modulus and improve fracture strain, as well as fatigue resistance for a high mobility diketopyrrolopyrrole polymer. These polymers are crosslinked with siloxane oligomers to give stretchable films stable up to a strain ε = 150% and 500 strain‐and‐release cycles of 100% strain without the formation of nanocracks. Organic field‐effect transistors are prepared to assess the electrical properties of the crosslinked film under cyclic strain loading. An initial average mobility (μ^avg) of 0.66 cm² V^?1 s^?1 is measured at 0% strain. A steady μ^avg above 0.40 cm² V^?1 s^?1 is obtained in the direction perpendicular to the strain direction after 500 strain‐and‐release cycles of 20% strain. The μ^avg in the direction parallel to strain, however, is compromised due to the formation of wrinkles.     

Variations of Cd/Pb and Zn/Pb ratios in Taipei aerosols reflecting long-range transport or local pollution emissions

Along with windblown dust, large quantities of pollutants are annually brought out of continental China by the westerlies in winter and spring; thereafter, they are partly subjected to transport by northeastern monsoon winds to Taiwan. To characterize the heavy metal composition differences between long-range transported and local aerosols and to evaluate metal contributions from long-range transported aerosols during the northeastern monsoon season, both PM(10) and PM(2.5) aerosols collected from Taipei, Taiwan from February 2002 to March 2003 were analyzed for three selected heavy metals, namely Pb, Cd and Zn using ICP-MS. Monthly patterns show that Pb concentrations in winter (62 ng/m(3)) were over two times higher than those in the other seasons, which is attributed to long-range transport from areas under development in China. Low Cd/Pb (0.017) and Zn/Pb (1.82) ratios were measured in aerosols collected during the Asian dust period, in which the ambient aerosols consisted predominantly of long-range transported pollutants. By contrast, high Cd/Pb (0.030) and Zn/Pb (3.44) ratios were observed during the summer monsoon season, in which aerosols were dominated by local pollutant emissions. Cd/Pb and Zn/Pb ratios appear to be successfully applied to identify the pollutants originating principally from the long-range transport or from local emissions. In addition, by assuming that a significant fraction of heavy metals associated with coarse airborne dust have settled to the sea prior to reaching Taiwan in spring, a mechanism is suggested to explain why higher anthropogenic metal concentrations occurred in winter than those in dust-rich spring.     

Crystallization of poly(butylene terephthalate)/poly(ethylene octene) blends: Nonisothermal crystallization

Poly(ethylene octene) (POE), maleic anhydride grafted poly(ethylene octene) (mPOE), and a mixture of POE and mPOE were added to poly(butylene terephthalate) (PBT) to prepare PBT/POE (20 wt % POE), PBT/mPOE (20 wt % mPOE), and PBT/mPOE/POE (10 wt % mPOE and 10 wt % POE) blends with an extruder. The melting behavior of neat PBT and its blends nonisothermally crystallized from the melt was investigated with differential scanning calorimetry (DSC). Subsequent DSC scans exhibited two melting endotherms (T_mI and T_mII). T_mI was attributed to the melting of the crystals grown by normal primary crystallization, and T_mII was due to the melting of the more perfect crystals after reorganization during the DSC heating scan. The better dispersed second phases and higher cooling rate made the crystals that grew in normal primary crystallization less perfect and relatively prone to be organized during the DSC scan. The effects of POE and mPOE on the nonisothermal crystallization process were delineated by kinetic models. The dispersed phase hindered the crystallization; however, the well‐ dispersed phases of an even smaller size enhanced crystallization because of the higher nucleation density. The nucleation parameter, estimated from the modified Lauritzen–Hoffman equation, showed the same results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008