A low‐complexity companding technique using Padé approximation for PAPR reduction of an OFDM system

Orthogonal Frequency Division Multiplexing (OFDM) systems have become the most promising wireless communication systems in the recent years. For OFDM systems, there is one major drawback, which is the high peak‐to‐average power ratio (PAPR). Companding techniques have been frequently proposed to reduce PAPR. Exponential companding technique offers efficient PAPR reduction with a low bit error rate (BER). However, the exponential companding technique is difficult to implement. This paper utilizes the Padé approximation to simplify the exponential companding technique. The simulation results demonstrate that the proposed companding technique offers the same performance results as those of the exponential companding technique, while Additive White Gaussian Noise (AWGN) or multipath fading channel is considered. Further, the hardware implementation results show that the complexity of the proposed companding technique is less than that of the exponential companding technique. Copyright © 2011 John Wiley & Sons, Ltd.     

Enhancing electron field emission of carbon nanoflakes by hydrogen post-annealing process

In this study, the carbon nanoflakes (CNFs) fabricated by sputtering were chosen as the field emission emitters because of their very sharp and thin edges which are potentially good electron field emission sites. The as-deposited CNFs were annealed in the furnace under hydrogen atmosphere. The results showed that the optimum field emission properties with smaller turn-on field and larger current density were obtained at annealing temperature of 600 °C for 10 min. The hydrogen thermal annealing has chemical etching on the surface of the CNFs and produces appropriate emission site density to increase the emission current density. The turn-on field was reduced from 6.7 to 5.8 V/μm and electric current density was increased from 22 to 187 μA/cm² under 8 V/μm after hydrogen thermal annealing.     

Control strategies for flexible operation of power plant with CO2 capture plant

About 20% power output penalties will be incurred for implementing CO₂ capture from power plant. This loss can be partially compensated by flexible operation of capture plant. However, daily large variations of liquid and gas flows may cause operation problems to packed columns. Control schemes were proposed to improve the flexibility of power output without causing substantial hydraulic disturbances in capture plant is presented. Simulations were implemented using ASPEN Plus. In varying lean solvent flow strategy, the flow rate of recycling solvent was manipulated to control the CO₂ capture rate. The liquid flow of the absorber and gas flow of the stripper will vary substantially. In an alternative strategy, the lean solvent loading will be varied. Variation of gas throughput in the stripper is avoided by recycling part of CO₂ vapor to stripper. This strategy provided more stable hydraulics condition in both columns and is recommended for flexible operation. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

A new method for Stokes problems with circular boundaries using degenerate kernel and Fourier series

This study is concerned with the Stokes flow of an incompressible fluid of constant density and viscosity with circular boundaries. To fully capture the circular boundary, the boundary densities in the direct and indirect boundary integral equations (BIEs) are expanded in terms of Fourier series. The kernel functions in either the direct BIE or the indirect BIE are expanded to degenerate kernels by using the separation of field and source points. Consequently, the improper integrals are transformed to series sum and are easily calculated. The linear algebraic system can be established by matching the boundary conditions at the collocation points. Then, the unknown Fourier coefficients can be easily determined. Finally, several examples including circular and eccentric domains are presented to demonstrate the validity of the present method. Five gains were obtained: (1) meshless approach; (2) free of boundary‐layer effect; (3) singularity free; (4) exponential convergence; and (5) well‐posed model. Copyright © 2007 John Wiley & Sons, Ltd.     

From enzyme to zymogen: engineering Vip2, an ADP-ribosyltransferase from Bacillus cereus, for conditional toxicity

The adenosine diphosphate (ADP)-ribosyltransferase, Vip2 (vegetative insecticidal protein), from Bacillus cereus in combination with another protein from the same organism, Vip1, has insecticidal activity against western corn rootworm larvae. The Vip2 protein exerts its intracellular poisoning effect by modifying actin and preventing actin polymerization. Due to the nature of this toxin, expression of Vip2 in planta is lethal. In this work, we attempted to build an enzyme precursor (proenzyme, zymogen) that would silently reside in one biological system (e.g. plants or yeast) and be activated in the other (insect larvae). Our approach involved engineering a random propeptide library at the C-terminal end of Vip2 and selecting for malfunctional enzyme variants in yeast. A selected proenzyme (proVip2) possesses reduced enzymatic activity as compared with the wild-type Vip2 protein, but remains a potent toxin toward rootworm larvae. In addition, upon analysis of the digestive fate of the engineered enzyme precursor in rootworm larvae, we demonstrated that 'zymogenized' Vip2 can be proteolytically activated by rootworm digestive enzyme machinery. This report represents an example of applying a protein engineering strategy for the creation of a plant-tolerated, zymogen-like form of an otherwise toxic protein. This approach may outline a novel path to address challenges associated with utilizing toxic proteins in certain biotechnological applications.     

Schisandrin enhances dendrite outgrowth and synaptogenesis in primary cultured hippocampal neurons

BACKGROUND: Schisandra chinensis, commonly used in Asia for tea material and traditional Chinese medicine, is presumed to enhance mental and intellectual functions. In this study, the effects and signalling mechanisms of a purified compound schisandrin, one of the lignan of Schisandra chinensis, on primary cultured hippocampal neurons were investigated. RESULTS: Schisandrin treatment enhanced total dendritic length and branching complexity, both of which were significantly suppressed in the presence of specific blockers for calmodulin‐dependent kinase II (CaMKII), protein kinase C epsilon (PKCε), and mitogen activated protein kinase kinase (MEK). Moreover, schisandrin induced calcium influx, and phosphorylation of CaMKII, PKCε, and MEK. Inhibition of CAMKII and PKCε attenuated the schisandrin‐induced phosphorylation of PKCε and MEK, and the phosphorylation of MEK, respectively. Moreover, schisandrin also stimulated the phosphorylation of cyclic AMP responsive‐element binding protein (CREB) at Ser‐133, an effect that was blocked by KN93. In addition to its neuritogenic effects, schisandrin increased the numbers of postsynaptic density‐95‐positive and FM1‐43‐positive puncta in dendrites and synaptic boutons, respectively. CONCLUSION: In hippocampal neurons, schisandrin exhibits neurotrophic properties that are mediated by the CaMKII‐PKCε‐MEK pathway. Copyright © 2010 Society of Chemical Industry     

Expression of granule‐bound starch synthase in developing rice grain

The expression of granule‐bound starch synthase (GBSS) in rice (Oryza sativa) genotype Tainung 67 (200 g kg^?1 grain amylose content) and its two NaN₃‐induced mutants SA419 and SA418 were examined. G/T polymorphism analysis indicated that SA418 (300 g kg^?1 grain amylose content) carried Wx^a allele. The insertion of 23 base pairs sequence was found only in SA419 (80 g kg^?1 grain amylose content), suggesting that it was a waxy mutant. Microsatellite polymorphisms (CT)_n were also detected on the Wx gene encoding GBSS in the tested genotypes. The activities of several key enzymes involving starch biosynthesis in developing grains of field‐grown rice plants were also compared during grain filling period. Significant genotypic differences were only found in the expression of GBSS. The content of amylose in SA418 grain was higher than Tainung 67 and SA419 grains throughout the entire grain filling period, possibly due to its superiority to synthesize amylose through GBSS. The lowest amylose content of SA 419 grain was attributable to its extremely low activity of GBSS in comparison with the two other genotypes. The mutation effects on the expression of GBSS were confirmed by two‐dimensional electrophoresis and mass spectrometry. Copyright © 2007 Society of Chemical Industry     

Nitro‐blue tetrazolium staining of starch‐synthesizing enzymes in developing rice grains

An in situ nitro‐blue tetrazolium (NBT) staining method was used to locate the activities of enzymes involved in starch synthesis in developing grains of field grown rice (Oryza sativa L.) cultivar Tainung 67 and its early ripening mutant SA 419. The results indicated that all the tested enzymes, including sucrose synthase, invertase, hexokinase, ADP‐glucose pyrophosphorylase, UDP‐glucose pyrophosphorylase and starch synthase, were detectable in developing rice endosperms by using NBT staining. The activity of these enzymes was also measurable by using chemical assays. The expression of enzyme activity, as indicated by the formation of blue formazan precipitate, in growing grain of Tainung 67 were visualized in entire endosperm at 11 days after anthesis (DAA). However, NBT staining shifted from central to peripheral region of endosperm after 18 DAA, and the staining disappeared at 25 DAA. Similar staining patterns were also observed in the growing grains of mutant SA 419, but the shift of staining from central to peripheral endosperm occurred at 11 DAA. Electron microscopy examinations showed that the growing patterns of starch granules, sampled from central and peripheral regions of endosperm, varied between two cultivars, with SA 419 growing faster than Tainung 67. Both cultivars showed that the shifts of NBT staining pattern coincided with the changes in the growing pattern of starch granules located in central and peripheral regions of endosperms. The NBT staining results showed that the activities of sucrose to starch conversion enzymes in mutant SA 419 declined and disappeared earlier than its wild‐type Tainung 67 and therefore it ripened earlier than cultivar Tainung 67. Copyright © 2005 Society of Chemical Industry     

Mitigating large water ingresses into the New Yungchuen Tunnel,Taiwan

During the construction of New Yungchuen Tunnel, a major water inflow was encountered and the advance was abandoned. Further advances were attempted and again abandoned. Following detailed investigations, the problem area was determined as a very voided marble layer. The paper describes the use of hot bituminous grouting followed by cement and chemical grouting to both reduce the water inflow to acceptable volumes and pressures and also to reduce the convergence. In addition, the design of the tunnel was changed to include the construction of a larger circular tunnel through which the general horse-shoe shaped tunnel would subsequently pass.     

Efficient non-doped blue light emitting diodes based on novel carbazole-substituted anthracene derivatives

In this study, we synthesized three anthracene derivatives featuring carbazole moieties as side groups - 2-tert-butyl-9,10-bis[4-(9-carbazolyl)phenyl]anthracene (Cz⁹PhAnt), 2-tert-butyl-9,10-bis{4-[3,6-di-tert-butyl-(9-carbazolyl)]phenyl}anthracene (tCz⁹PhAnt), and 2-tert-butyl-9,10-bis{4′-[3,6-di-tert-butyl-(9-carbazolyl)]biphenyl-4-yl}anthracene (tCz⁹Ph₂Ant) - for use in blue organic light emitting devices (OLEDs). The anthracene derivatives presenting rigid and bulky tert-butyl-substituted carbazole units possessed high glass-transition temperatures (220 °C). Moreover, the three anthracene derivatives exhibited strong blue emissions in solution, with high quantum efficiencies (91%). We studied the electroluminescence (EL) properties of non-doped OLEDs incorporating these anthracene derivatives, with and without a hole-transporting layer (HTL). OLEDs incorporating an HTL provided superior EL performance than did those lacking the HTL. The highest brightness (6821 cd/m²) was that for the tCz⁹PhAnt-based device; the greatest current efficiency (2.1 cd/A) was that for the tCz⁹Ph₂Ant-based device. The devices based on these carbazole-substituted anthracene derivatives also exhibited high color purity.