An expeditious asymmetric synthesis of the pentacyclic core of the cortistatins by an intramolecular (4+3) cycloaddition

A concise, asymmetric synthesis of the pentacyclic framework of the cortistatins has been accomplished in 12 steps from commercially available starting materials, employing a highly diastereoselective intramolecular (4+3) cycloaddition of epoxy enolsilanes as the key step. © 2011 The Royal Society of Chemistry.postprin

Revisiting the subculture: understanding deviant students in China

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Bicriterion scheduling with equal processing times on a batch processing machine

Author name used in this publication: C. T. NgAuthor name used in this publication: T. C. E. Cheng2008-2009 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Culturally Relevant Protective and Risk Factors of Youth Risk Behaviors Among Pakistani and Indian Students in Hong Kong: A Focus Group Study

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Single-machine scheduling with a time-dependent learning effect

Author name used in this publication: J.-B. WangAuthor name used in this publication: C. T. NgAuthor name used in this publication: T. C. E. Cheng2007-2008 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Salt-induced osmotic stress for lipid overproduction in batch culture of Chlorella vulgaris

Effect of NaCl-induced osmotic stress on lipid production was investigated in batch culture of Chlorella vulgaris. Based on the facts that NaCl stress improved lipid production but inhibited cells growth at the same times, the novel strategies of multiple osmotic stresses with different NaCl additions (2 g/L at 80 h, 4 g/L at 100 h, and 6 g/L at 120 h) were adopted for lipid overproduction. Results show that after 180 h cultivation, lipid yield reached 3.16 g/L and intracellular lipid content was 58.6%, increased by 21.1 and 22.9%, respectively, compared to the control. Further applying the strategies to 5 L fermentor, lipid yield of 3.81 g/L was achieved at 180 h, which was 30.1% higher than the control, suggesting application of osmotic stress to lipid overproduction as being feasible.Key words: NaCl-induced osmotic stress, heterotrophic cultivation, lipid, glucose, Chlorella vulgaris

Two Nonlinear Lattice Problems in Materials

The interplay of spatial discreteness and nonlinearity plays an important role in the dynamics of nonlinear lattice systems, as illustrated by two problems considered in this thesis. The first problem concerns kinetics of a step propagating along a twin boundary in a cubic lattice undergoing an antiplane shear deformation. To model twinning, we consider a piecewise quadratic double-well interaction potential with respect to one component of the shear strain and harmonic interaction with respect to another. We construct semi-analytical traveling wave solutions that correspond to a steady step propagation and obtain the kinetic relation between the applied stress and the velocity of the step. We show that this relation strongly depends on the width of the spinodal region where the double-well potential is nonconvex and on the material anisotropy parameter. In the limiting case when the spinodal region degenerates to a point, we construct new solutions that extend the kinetic relation obtained in the earlier work of Celli, Flytzanis and Ishioka into the low-velocity regime. Numerical simulations suggest stability of some of the obtained solutions, including low-velocity step motion when the spinodal region is sufficiently wide. When the applied stress is above a certain threshold, nucleation and steady propagation of multiple steps are observed. In the second part of the thesis we explore a novel locally resonant granular material bearing harmonic internal resonators in a chain of beads interacting via Hertzian elastic contacts. Dynamics of the system can range from strongly to weakly nonlinear, depending on the solution amplitude and the amount of static precompression. We provide numerical and analytical evidence of the existence of discrete dark breathers solutions, exponentially localized, time-periodic states mounted on top of a non-vanishing background. Our results are obtained by means of an asymptotic reduction to suitably modified versions of the discrete p-Schr\"{o}dinger and nonlinear Schr\"{o}dinger modulation equations in the strongly and weakly nonlinear regime, respectively. Stability and bifurcation structure of numerically computed exact dark breathers are examined. In some parameter regimes we also find small-amplitude periodic traveling waves, long-lived standing and traveling bright breathers, i.e., localized time-periodic solutions with exponentially decaying tails

Purification and biochemical characterization of a serine alkaline protease TC4 from a new isolated Bacillus alcalophilus TCCC11004 in detergent formulations

An extracellular alkaline protease producing strain was isolated from alkaline soil and identified as Bacillus alcalophilus TCCC11004 on the basis of 16S rDNA gene sequencing and biochemical properties. The most appropriate medium for the protease production was composed of (g/l): maltodextrin 110, yeast extract 17.5, cotton seed meal 29.3, K2HPO4 18, trisodium citrate 3.3 and CaCl2 2.6. The alkaline protease TC4 was purified from the culture supernatant by ammonium sulfate precipitation, Sephadex G-75 gel filtration and SP-Sepharose HP ion exchange chromatography, with a 6.8 fold increase in specific activity and 15.2% recovery. The molecular weight was estimated to be 26 kDa on SDS-PAGE. The protease was highly active from pH 9.0-12.0 with an optimal at pH 11.0. It was active at 30 - 60°C and exhibited maximal activity at 50°C. The thermostability of the protease was increased by the addition of CaCl2. It retained 70 and 81% of its initial activity after heating for 2 h at 50°C, in the absence or presence of 2 mM CaCl2, respectively. The enzyme was inactivated by diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride, suggesting that it is a serine protease. The protease was stable in 0.5% SDS and retained 70.3% of its initial activity after 1 h of incubation. It was active in the presence of 3% Triton X-100 with 100% activity and stable towards oxidizing agent with 69.2% activity in the presence of 1% H2O2. The enzyme showed excellent compatibility with commercial detergents such as TaiZi, BiLang, DiaoPai and TianQing, retaining more than 90% of its initial activity in the tested detergents after 1 h of preincubation at 40°C.Keywords: Serine alkaline protease, Bacillus alcalophilus, stability, detergent compatibility

Tunneling magnetoresistance in Fe3Si/MgO/Fe3Si(001) magnetic tunnel junctions

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Biomechanical study of the funnel technique applied in thoracic pedicle screw replacement

Background: Funnel technique is a method used for the insertion of screw into thoracic pedicle.Aim: To evaluate the biomechanical characteristics of thoracic pedicle screw placement using the Funnel technique, trying to provide biomechanical basis for clinical application of this technology.Methods: 14 functional spinal units (T6 to T10) were selected from thoracic spine specimens of 14 fresh adult cadavers, and randomly divided into two groups, including Funnel technique group (n=7) and Magerl technique group (n=7). The displacement-stiffness and pull-out strength in all kinds of position were tested and compared.Results: Two fixed groups were significantly higher than that of the intact state (P<0.05) in the spinal central axial direction, compression, anterior flexion, posterior bending, lateral bending, axial torsion, but there were no significant differences between two fixed groups (P>0.05). The mean pull-out strength in Funnel technique group (789.09±27.33) was lower than that in Magerl technique group (P<0.05).Conclusions: The Funnel technique for the insertion point of posterior bone is a safe and accurate technique for pedicle screw placement. It exhibited no effects on the stiffness of spinal column, but decreased the pull-out strength of pedicle screw. Therefore, the funnel technique in the thoracic spine affords an alternative for the standard screw placement.Keywords: Thoracic; Pedicle screws; Biomechanics; Funnel techniqu