Millimetre-wave fibre–wireless transmission systems with reduced effects of fibre chromatic dispersion

This paper describes two techniques for the implementation of millimetre-wave (mm-wave) wireless communication systems incorporating optical fibre distribution networks. Fibre chromatic dispersion can exhibit severe effects on the transportation of mm-wave frequencies over fibre, resulting in greatly reduced post-detection rf powers. Each mm-wave fibre–wireless system demonstrated here incorporates a method for the generation and modulation of an optical mm-wave carrier, which enables the effect of fibre dispersion to be significantly reduced. One set-up is a direct-detection scheme where optical single-sideband (SSB) with carrier modulation is used to overcome fibre dispersion effects. The other system employs a self-heterodyne arrangement in which a dual-frequency optical source generates a low phase-noise mm-wave beat signal. Data transmission is achieved by externally modulating the dual-mode signal and reduced effects of fibre dispersion are observed.     

Synthesis and photopolymerization of novel multifunctional vinyl esters

Novel mono‐ and multifunctional vinyl ester monomers containing thioether groups were synthesized via an amine‐catalyzed Michael addition reaction between vinyl acrylate and multifunctional thiols. Using photo‐differential scanning calorimetry and real‐time Fourier transform infrared (RTIR) spectroscopy, the polymerization kinetics and oxygen inhibition of the homopolymerizations of the vinyl ester monomers were investigated. The effect of the vinyl ester and thioether group on acrylate/vinyl ester and thiol/vinyl ester copolymerizations was determined using real‐time IR spectroscopy to monitor polymerization rates of acrylate, vinyl, and thiol groups simultaneously. Polymerization of the vinyl esters used was found to be relatively insensitive to oxygen inhibition. We propose that the thioether group is responsible for reducing oxygen inhibition by a series of chain transfer/oxygen‐scavenging reactions. In polymerization of a acrylate/vinyl ester mixture both in nitrogen and in air, the vinyl ester monomer significantly enhances the polymerization rates and the conversion of the acrylate double bonds via plasticization of the crosslinked matrix and reduction of inhibition by oxygen. Ultimately, the vinyl ester monomer is incorporated into the polymer network. Thiol/vinyl ester free‐radical copolymerization is much faster than either thiol/allylether copolymerization or vinyl ester homopolymerization. The electron‐rich vinyl ester double bonds ensure rapid copolymerization with thiol. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4424–4436, 2004     

A Comparative Study of the Phospholipid Profiles of Guinea Pig Cardiac Muscle and Bullfrog Cardiac and Thigh Skeletal Muscle,and their In-Vitro Differential Deacylation by Endogenous Phospholipases. Thin Layer Chromatographic and Densitometric Analysis

JPC – Journal of Planar Chromatography – Modern TLC - The phospholipid profiles of guinea pig and bullfrog cardiac muscle and of bullfrog thigh skeletal muscle before and after in-vitro...     

Pilot-based cross-phase modulation compensation for coherent optical orthogonal frequency division multiplexing long-haul optical communications systems

A pilot-based nonlinearity compensator (PB-NLC) is shown in this Letter to be an effective method for compensating cross-phase modulation (XPM) in coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. An unmodulated pilot tone is transmitted at the center of each OFDM channel to detect phase errors caused by the Kerr effect, which converts intensity fluctuations from all channels to phase errors. The pilots are then used to cancel the XPM phase errors for each OFDM channel at the receiver after each channel's self-phase modulation (SPM) has been compensated, using its intensity waveform to determine its SPM. Numerical simulations of a 58 Gb/s single polarization 2375 km system with inline dispersion compensation show that the signal quality, Q, at the optimal launch power is increased by 2.4 dB if SPM compensation is used before the PB-NLC. This contrasts with only a 0.9 dB improvement if the PB-NLC is used without an SPM compensator for the same link. This shows the PB-NLC can effectively mitigate XPM but not SPM.     

Xenon biosensor amplification via dendrimer-cage supramolecular constructs

Polyamidoamine dendrimers were synthesized with a single biotin moiety and used with cryptophane-A cages to form supramolecular biosensor constructs. These new biosensors amplified the NMR signals obtained from polarized xenon 8 times more than the original Xe biosensor.     

Palladium-catalyzed [3+2] cycloaddition of carbon dioxide and trimethylenemethane under mild conditions

Carbon dioxide undergoes a Pd-catalyzed [3+2] cycloaddition with trimethylenemethane (TMM) under mild conditions (1 atm, 75 degrees C, 30 min) to produce a gamma-butyrolactone product in 63% yield, when the Pd-TMM complex is generated from 2-(acetoxymethyl)-3-(trimethylsilyl)propene. The reaction reported here is more rapid than the all-carbon [3+2] cycloaddition, and only the gamma-butyrolactone is produced in a competition experiment. With substituted substrates, the reaction is completely regioselective, producing the product derived from the kinetic Pd-TMM complex.     

A coupled chemical-genetic and bioinformatic approach to Polo-like kinase pathway exploration

Protein phosphorylation is a ubiquitous mechanism for cellular signal propagation, and signaling network complexity presents a challenge to protein kinase substrate identification. Few targets of Polo-like kinases are known, despite their significant role in coordinating cell-cycle progression. Here, we combine chemical-genetic, bioinformatic, and proteomic tools for Polo-like kinase substrate identification. Specific pharmacological inhibition of budding yeast Polo-like kinase, Cdc5, resulted in a misaligned preanaphase spindle and subsequently delayed anaphase nuclear migration, revealing a Cdc5 function. A cellular screen for Cdc5 substrates identified Spc72, a spindle pole body (SPB) component and microtubule anchor required for nuclear positioning. Spc72 bound to the Cdc5 PBD in a mitosis-specific manner, was phosphorylated by Cdc5 in vitro, and demonstrated a loss of mitotic phosphorylation in vivo upon Cdc5 inhibition. Finally, an examination of Cdc5 binding by SPB-localized proteins expanded our knowledge of Cdc5 function at the SPB.     

Construction of Teacher Knowledge in Context: Preparing Elementary Teachers to Teach Mathematics and Science

The purpose of this study was to further the understanding of how preservice teachers construct teacher knowledge and pedagogical content knowledge of elementary mathematics and science in a school‐based setting and the extent of knowledge construction. Evidence of knowledge construction (its acquisition, its dimensions, and the social context) was collected through the use of a qualitative methodology. The methods course was content‐specific with instruction in elementary mathematics and science. Learning experiences were based on national standards with a constructivist instructional approach and immediate access to field experiences. Analysis and synthesis of data revealed an extensive acquisition of teacher knowledge and pedagogical content knowledge. Learning venues were discovered to be the conduits of learning in a situated learning context. As in this study, content‐specific, school‐based experiences may afford preservice teachers greater opportunities to focus on content and instructional strategies at deeper levels; to address anxieties typically associated with the teaching of elementary mathematics and science; and to become more confident and competent teachers. Gains in positive attitudes and confidence in teaching mathematics and science were identified as direct results of this experience.