Electrostriction of lead zirconate titanate/polyurethane composites

Author name used in this publication: K. S. LamAuthor name used in this publication: Y. ZhouAuthor name used in this publication: Y. W. WongAuthor name used in this publication: F. G. Shin2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Photonic ultrawideband pulse generation with HNL-DSF-based phase and intensity modulator

We propose and experimentally demonstrate a photonic ultrawideband (UWB) pulse (monocycle and doublet) generator based on a highly nonlinear dispersion-shifted fiber (HNL-DSF). The pulsed pump, located in the anomalous group-velocity dispersion regime of the HNL-DSF, performs as both an intensity and a phase modulator in our scheme. We experimentally prove, for the first time to the best of our knowledge, that the UWB doublet pulse can be generated when the optical carrier is located at the center of a narrow tunable filter's passband. Furthermore, the encoded doublet signal, fully compliant with the Federal Communications Commission (FCC) regulations, is transmitted at 950 Mb/s through a 25-km single-mode fiber without introducing any obvious pulse distortion. © 2006 IEEE.published_or_final_versio

A power-efficient ultra-wideband pulse generator based on multiple PM-IM conversions

A novel photonic generation of power-efficient ultra-wideband (UWB) pulse by incoherent summation of two asymmetric monocycle pulses with inverted polarities is experimentally demonstrated. The principles of multiple cross-phase modulations in a highly nonlinear fiber and multiple phase modulation to intensity modulation conversions in a commercially available arrayed-waveguide grating are used. The combined UWB pulse exploiting spectral efficiency of 50.59% in experiment is fully compliant with the Federal Communications Commission (FCC) spectral mask without power attenuation. The FCC-compliant UWB pulse gains larger than 11.5- and 6-dB improvement against monocycle and doublet pulses after power attenuation to respect the FCC spectral mask, respectively. Such a power-efficient UWB pulse with pulse duration of approximately 320 ps has potential to achieve high-speed transmission without pulse overlapping and obvious distortion. © 2010 IEEE.published_or_final_versio

A power-efficient ultra-wideband pulse generator based on multiple PM-IM conversions

A novel photonic generation of power-efficient ultra-wideband (UWB) pulse by incoherent summation of two asymmetric monocycle pulses with inverted polarities is experimentally demonstrated. The principles of multiple cross-phase modulations in a highly nonlinear fiber and multiple phase modulation to intensity modulation conversions in a commercially available arrayed-waveguide grating are used. The combined UWB pulse exploiting spectral efficiency of 50.59% in experiment is fully compliant with the Federal Communications Commission (FCC) spectral mask without power attenuation. The FCC-compliant UWB pulse gains larger than 11.5- and 6-dB improvement against monocycle and doublet pulses after power attenuation to respect the FCC spectral mask, respectively. Such a power-efficient UWB pulse with pulse duration of approximately 320 ps has potential to achieve high-speed transmission without pulse overlapping and obvious distortion. © 2010 IEEE.published_or_final_versio

High-speed photonic power-efficient ultra-wideband transceiver based on multiple PM-IM conversions

We experimentally demonstrate a novel photonic ultra-wideband (UWB) transceiver with pulse spectral efficiency of 50.97% and transmission speed up to 3.125 Gb/s. The UWB generator only consists of a highly nonlinear fiber (HNLF) and a commercial arrayed-waveguide grating (AWG). By using the concept of multiple cross-phase modulation in the HNLF and multiple phase modulation to intensity modulation conversions in the AWG, a power-efficient UWB pulse is combined with incoherent summation of two asymmetric monocycle pulses with inverted polarities. Benefiting from the ultra-fast response of fiber nonlinearities in the HNLF, onoff keying encoded UWB signals generated at 781.25 Mb/s, 1.5625 Gb/s, and 3.125 Gb/s are all error-free transmitted through a 22.5-km single-mode fiber (SMF) with power penalties lower than 1 dB. The bit-error rate is directly measured on down-converted baseband signals by using optical full rectification and electrical low-pass filtering technologies. The measured electrical spectra before and after 22.5-km SMF link transmission both fully comply with the spectral mask specified by the U.S. Federal Communications Commission (FCC) without power attenuation. © 2006 IEEE.published_or_final_versio

Effect of initial conditions on interaction between a boundary layer and a wall-mounted finite-length-cylinder wake

Author name used in this publication: Y. ZhouAuthor name used in this publication: C. K. ChanAuthor name used in this publication: K. S. Lam2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

High-harmonic generation: taking control of polarization

The ability to control the polarization of short-wavelength radiation generated by high-harmonic generation is useful not only for applications but also for testing conservation laws in physics

Ultrasonic extraction of flavonoids and phenolics from loquat (Eriobotrya japonica Lindl.) flowers

Ethanol was used to extract flavonoids and phenolics from loquat (Eriobotrya japonica Lindl. cv. Ruantiaobaisha) flowers with ultrasonic pharmaceutical managing machine. Single-factor and orthogonal experiment were used to investigate the optimum extraction condition. The results showed that, the combination of 30°C, 80 min, 60% ethanol and 1:40 material ratio was optimum extraction condition with the highest yields of flavonoids and phenolics at 47 kHz/500 W. Under the optimum extraction condition, two consecutive extractions was enough, the extraction rates of flavonoids and phenolics were all more than 90%, with the contents of 10.59 and 102.02 mg/g dry weight, respectively.Key words: Eriobotrya japonica, flower, flavonoids, phenolics, ultrasonic extraction

Development of human single-chain antibodies against SARS-associated coronavirus.

The outbreak of severe acute respiratory syndrome (SARS), caused by a distinct coronavirus, in 2003 greatly threatened public health in China, Southeast Asia as well as North America. Over 1,000 patients died of the SARS virus, representing 10% of infected people. Like other coronaviruses, the SARS virus also utilizes a surface glycoprotein, namely the spike protein, to infect host cells. The spike protein of SARS virus consists of 1,255 amino acid residues and can be divided into two sub-domains, S1 and S2. The S1 domain mediates the binding of the virus to its receptor angiotensin-converting enzyme 2, which is abundantly distributed on the surface of human lung cells. The S2 domain mediates membrane fusion between the virus and the host cell. Hence two strategies can be used to block the infection of the SARS virus, either by interfering with the binding of the S1 domain to the receptor or by blocking the fusion of the virus with the cell membrane mediated by the S2 domain. Several antibodies against the S1 domain have been generated and all of them are able to neutralize the virus in vitro and in vivo using animal models. Unfortunately, point mutations have been identified in the S1 domain, so that the virus isolated in the future may not be recognized by these antibodies. As no mutation has been found in the S2 domain indicating that this region is more conserved than the S1 domain, it may be a better target for antibody binding. After predicting the immunogenicity of the epitopes of the S2 domain, we chemically synthesized two peptides and also expressed one of them using a recombinant DNA method. We screened a phage displaying library of human single-chain antibodies (ScFv) against the predicted epitopes and obtained a human ScFv which can recognize the SARS virus in vitro

Substrate-induced band gap opening in epitaxial graphene

Graphene has shown great application potentials as the host material for next generation electronic devices. However, despite its intriguing properties, one of the biggest hurdles for graphene to be useful as an electronic material is its lacking of an energy gap in the electronic spectra. This, for example, prevents the use of graphene in making transistors. Although several proposals have been made to open a gap in graphene's electronic spectra, they all require complex engineering of the graphene layer. Here we show that when graphene is epitaxially grown on the SiC substrate, a gap of ~ 0.26 is produced. This gap decreases as the sample thickness increases and eventually approaches zero when the number of layers exceeds four. We propose that the origin of this gap is the breaking of sublattice symmetry owing to the graphene-substrate interaction. We believe our results highlight a promising direction for band gap engineering of graphene.Comment: 10 pages, 4 figures; updated reference