bluuebunny/crossref_metadata_2025 huggingface dataset:
Biosensor based on two‐dimensional photonic lattice
Authors: Irawan Rudi , Zhang Dianwen , Tjin Swee Chuan , Yuan Xiaocong
Published: March 2007

A nanotechnology technique for biophotonics applications is proposed and simulated. The comparison of transmittance spectra of the two‐dimensional photonics lattices with different dielectric constant of the circular rods or holes, which show slab structures of two‐dimensional photonic lattices composed of a triangular or square array of circular rods or holes, are obviously feasible to be applied for biosensing in lab‐on‐chip applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1171–1175, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22372
Q and bandwidth of electrically small antennas
Authors: Hansen R. C.
Published: March 2007

The relation of Q and half‐power bandwidth for antennas, Q = 1/BW, is well known. Here it is shown that 1/Q gives an accurate bandwidth for electrically small dipoles and loops. Bandwidths from 1/Q are compared with exact bandwidths, using a sinusoidal current computer model for dipoles, and a constant current model for loops. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1170–1171, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22373
A new derivation for the coefficients of the scattering dyadic Green′s function in spherically layered media
Authors: Kim Yonghoon , Chae Heeduck , Nam Sangwook
Published: March 2007

The dyadic Green's function in spherically layered media is considered by assuming that source and field points can be located anywhere. After manipulations from the expression of the dyadic Green's function based on the reflections and transmissions of the scalar waves, the dyadic Green's function in terms of the spherical vector wave functions is newly constructed and also the coefficients of the scattering dyadic Green's function are derived in a simple form. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1142–1143, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22374
Time‐domain integral equation solvers using quadratic B‐spline temporal basis functions
Authors: Wang P. , Xia M. Y. , Jin J. M. , Zhou L. Z.
Published: March 2007

A novel numerical scheme that employs quadratic B‐spline functions as temporal basis functions is proposed for solving time‐domain integral equations (TDIE) of electromagnetic scattering. Because of the compact support of these new temporal basis functions, the resulting time‐domain integral equations solution is efficient in terms of memory usage and computation time. Numerical examples of scattering by both conducting and dielectric objects show that the solution is also stable and accurate. Compared with the Lagrange interpolating functions of the same order, the quadratic B‐spline functions, being complete to the second order, yield a better accuracy in the time‐domain integral equations solution of scattering problems. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1154–1159, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22385
Novel switched sector beam planar UWB antenna
Authors: Yao Yuan , Feng Zhenghe
Published: March 2007

A planar Vivaldi array antenna that can achieve four sector radiation patterns in the azimuth plane is presented. Prototypes of the proposed antenna operating within 3.1–10.6 GHz for ultrawideband applications were designed and constructed. Measured and simulated results are used to demonstrate the performance of the antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1185–1187, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22388
Four‐wave mixing characteristics in SOAs with optimum time‐delays between pump and probe pulses
Authors: Das Narottam Kumar , Karmakar Nemai Chandra , Yamayoshi Yasuhiro , Kawaguchi Hitoshi
Published: March 2007

We have analyzed the four‐wave mixing (FWM) characteristics in semiconductor optical amplifiers (SOAs) with optimum time‐delays between pump and probe pulses by the finite‐difference beam propagation method. This study is very important to achieve the high FWM conversion efficiency and to clarify the timing jitter. From the simulations, we have clarified that the FWM conversion efficiency increases with optimum time‐delays between pump and probe pulses in SOA for short optical pulses. In the experiment, we have found the similar tendency. Therefore, we have obtained an excellent agreement between the simulation and experimental results of high FWM conversion efficiency in SOAs with optimum time‐delays between pulses. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1182–1185, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22389
Analysis and design of AlGaN/GaN HEMT resistive mixers
Authors: Chang Tienyu , Wu Wenhsing , Lin Jenshan , Jang Soohwan , Ren Fan , Pearton Stephen , Fitch Robert , Gillespie James
Published: March 2007

In this article, resistive mixers using AlGaN/GaN high electron‐mobility transistor (HEMT) devices are examined. Models of the GaN devices in linear region were created. Behavior of conversion loss with LO power is well predicted using the developed model. Three down‐conversion mixers were designed for RF frequency of 1.7 GHz and IF frequency of 200 MHz using LO frequency of 1.9 GHz. GaN HEMT devices with gate width of 300 μm, and gate lengths of 1.2, 1.0, and 0.75 μm were used in the mixers. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1152–1154, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22390
The design and fabrication of multitransmission‐band optical FBG filter with ultranarrow wavelength spacing
Authors: Xia Li , Shum Ping , Cheng Teehiang
Published: March 2007

Optical filters with ultranarrow wavelength spacing of 0.068, 0.052, and 0.032 nm, are designed and fabricated on uniform fiber Bragg grating (FBG). Moreover, triple‐, and quadruple‐transmission bands with wavelength spacing of 0.050, 0.046 nm, respectively, are achieved through introducing three and four phase shifts along the fiber Bragg grating. These filters can be applied in the ultranarrow wavelength spacing filtering, photonic generation of microwave signal, multiwavelength distributed feedback Bragg lasing, etc. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1122–1125, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22392
High‐gain high‐isolation CMFB stacked‐LO subharmonic gilbert mixer using SiGe BiCMOS technology
Authors: Wu T. H. , Meng C. C. , Huang G. W.
Published: March 2007

A 5.2‐GHz SiGe BiCMOS stacked‐LO‐stage CMFB (common mode feedback) subharmonic mixer is demonstrated in this article. The stacked‐LO‐stage and the active loads are used to improve the 2LO‐RF isolation and the conversion gain, respectively. The SiGe mixer includes five levels of transistors stacked together at the supply voltage of 3.3 V because of the low knee‐voltage characteristic of the SiGe HBTs (heterojunction bipolar transistors). The mixer demonstrated achieves 23 dB conversion gain and −78 dB 2LO‐RF isolation. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1214–1216, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22398
Microstrip antennas with loaded trapezoidal slots for broadband tactical wireless communications
Authors: Rao Qinjiang , Denidni Tayeb A.
Published: March 2007

In this letter, a broadband microstrip antenna suitable for tactical wireless communication at 1.35–1.75 GHz was proposed by loading trapezoidal slots. Compared with rectangular slotted patch antennas, the proposed design achieved a smaller size and a larger bandwidth. In addition, due to more design parameters, better antenna performances can be obtained by optimizing these parameters. Simulated and measured results validate the proposed design. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1210–1212, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22400
Erratum: Algorithm study of the space transformation factor in the transformed‐space nonuniform pseudo‐spectral time‐domain scheme
Authors: Liu Xiaoping , Chen Yinchao , Wu Xian , Tong Ming‐Sze , Huray Paul G.
Published: March 2007

Originally published Microwave Opt Technol Lett 48: 2367–2372, 2006. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1225, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22478
Functional imaging with Turbo‐CASL: Transit time and multislice imaging considerations
Authors: Lee Gregory R. , Hernandez‐Garcia Luis , Noll Douglas C.
Published: March 2007

The optimal use of turbo continuous arterial spin labeling (Turbo‐CASL) for functional imaging in the presence of activation‐induced transit time (TT) changes was investigated. Functional imaging of a bilateral finger‐tapping task showed improved sensitivity for Turbo‐CASL as compared to traditional CASL techniques for four of six subjects when scanned at an appropriate repetition time (TR). Both experimental and simulation results suggest that for optimal functional sensitivity with Turbo‐CASL, the pulse TR should be set to a value that is 100–200 ms less than the resting‐state TT. Simulations were also run to demonstrate the differences in TT sensitivity of different slices within a multislice acquisition, and the signal loss that is expected as the number of slices is increased. Despite the lower baseline ASL signal provided by the Turbo‐CASL acquisition, one can achieve equal or improved functional sensitivity due in part to the signal enhancement that accompanies the decrease in TT upon activation. Turbo‐CASL is thus a promising technique for functional ASL at higher temporal resolution. Magn Reson Med 57:661–669, 2007. © 2007 Wiley‐Liss, Inc.
Rapid quantitation of cardiovascular flow using slice‐selective fourier velocity encoding with spiral readouts
Authors: Carvalho Joao L. A. , Nayak Krishna S.
Published: March 2007

Accurate flow visualization and quantitation is important for the assessment of many cardiovascular conditions such as valvular stenosis and regurgitation. Phase contrast based methods experience partial volume artifacts when flow is highly localized, complex and/or turbulent. Fourier velocity encoding (FVE) avoids such problems by resolving the full velocity distribution within each voxel. This work proposes the use of slice selective FVE with spiral readouts to acquire fully localized velocity distributions in a short breath‐hold. Scan‐plane prescription is performed using classic protocols, and an automatic algorithm is used for in‐plane localization of the flow. Time and spatially‐resolved aortic valve velocity distributions with 26‐msec temporal resolution and 25 cm/sec velocity resolution over a 600 cm/sec field‐of‐view were acquired in a 12‐heartbeat breath‐hold. In carotid studies, scan time was extended to achieve higher spatial resolution. The method was demonstrated in healthy volunteers and patients, and the results compared qualitatively well with Doppler ultrasound. Acquisition time could be reduced to 7 heartbeats (a 42% reduction) using partial Fourier reconstruction along the velocity dimension. Magn Reson Med 57:639–646, 2007. © 2007 Wiley‐Liss, Inc.
Advantageous application of a surface coil to EPR irradiation in overhauser‐enhanced MRI
Authors: Matsumoto Shingo , Yamada Kenichi , Hirata Hiroshi , Yasukawa Keiji , Hyodo Fuminori , Ichikawa Kazuhiro , Utsumi Hideo
Published: March 2007

The present study describes the advantageous application of a surface coil to electron paramagnetic resonance (EPR) irradiation in Overhauser‐enhanced MRI (OMRI). OMRI is a double‐resonance method for imaging free radicals based on the Overhauser effect. Proton NMR images are recorded without and with EPR irradiation of the free radical resonance, which results in a difference proton image that shows signal enhancement in spatial regions that contain the free radical. To obtain good signal enhancement in OMRI, very high RF power and a long EPR irradiation time are required. To improve sensitivity and shorten the image acquisition time, especially for localized (and topical) applications, we developed and tested a surface‐coil‐type EPR irradiation coil. Theoretical calculations and experimental data showed that EPR irradiation through the surface coil could ameliorate the localized Overhauser enhancement, which was related to the ratio of B1 surface coil/B1 volume coil in the region of interest (ROI), as expected. The increased sensitivity could also be converted into a shortened EPR irradiation time, resulting in fast data acquisition. For biomedical applications, the use of a surface coil (as opposed to a conventional volume coil) could decrease the total RF power deposition in the sample required to obtain the same Overhauser enhancement in the ROI. Magn Reson Med 57:806–811, 2007. © 2007 Wiley‐Liss, Inc.
Studies on polymers and composites from lignin and fiber derived from sugar cane
Authors: Doherty William , Halley Peter , Edye Les , Rogers David , Cardona Francisco , Park Yoosup , Woo Tim
Published: March 2007

Sugarcane fiber (i.e. bagasse) lignin has a larger fraction of aromatics unsubstitution in the ortho position than hardwood or softwood lignin and hence has the greater ability to be derivatized. Furthermore, organosolv lignin has a higher purity than sulfonated and kraft lignins. This work examines the purification of organosolv lignin derived from bagasse and the physico‐chemical properties of the lignin and lignin‐phenol formaldehyde (PF) resin coatings, and composites.

The wetability tests have shown that lignin and lignin‐PF resin films are effective water barrier coatings, though the contact angles of lignin‐PF resin films were considerably less than the wax films. The overall mechanical properties (i.e. peak stress, peak strain and modulus) of the bagasse fiber composites were lower than the values obtained with the composites without the inclusion of bagasse fiber. Copyright © 2007 John Wiley & Sons, Ltd.
Rapid prenatal diagnosis of Duchenne muscular dystrophy with gene duplications by ion‐pair reversed‐phase high‐performance liquid chromatography coupled with competitive multiplex polymerase chain reaction strategy
Authors: Huang Wan‐Yi , Hung Chia‐Cheng , Lee Chien‐Nan , Su Yi‐Ning , Chen Chih‐Ping
Published: March 2007

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are caused by various mutations in the dystrophin gene. Rapid prenatal diagnosis of DMD with gene duplications is difficult due to limitation in gene dosage determination and the requirement for a known disease‐causing mutation in the pedigree to achieve a rapid and accurate diagnosis. We report, here, a case with rapid prenatal diagnosis of DMD‐affected male with gene duplications in the absence of a known disease‐causing variation in the pedigree by using ion‐pair reversed‐phase high‐performance liquid chromatography (IP‐RP‐HPLC) coupled with competitive multiplex polymerase chain reaction (PCR) protocol. In cases with clinical diagnosis of DMD/BMD, this test should identify greater than 92% of disease‐causing DNA variants. The postnatal genetic diagnosis of this case and the same disease‐causing mutations subsequently identified in other members of the pedigree confirmed the accuracy of competitive multiplex PCR/IP‐RP‐HPLC assay in direct prenatal diagnosis of DMD. Copyright © 2007 John Wiley & Sons, Ltd.
Infrared spectrum of polymethyl acrylate
Authors: Haken J. K. , Werner R. L.
Published: March 2007

The infrared spectrum of polymethyl acrylate has been studied in the region 4000 to 150 cm−1 and a detailed assignment made.
Interfacial and diffusion phenomena in emulsion polymerisation
Authors: Brooks B. W.
Published: March 2007

Evidence is presented which shows that both free‐radical and monomer species can be subject to mass transfer resistances in an emulsion polymerisation. The possible causes of these resistances are analysed. In most cases, simple diffusional resistances will not affect the course of an emulsion polymerisation appreciably. However, interfacial resistance to mass transfer which occurs at the water‐particle boundary can have noticeable effects on the polymerisation.

The practical consequences of these phenomena are discussed. These can be of particular importance in emulsion copolymerisation.
The coloration of synthetic polymers: A review of the chemistry of dyeing of hydrophobic fibres
Authors: Giles C. H.
Published: March 2007

The dyeing methods of anionic dyes on nylon, cationic dyes on polyacrylonitrile fibres, and non‐ionic (disperse) dyes on nylon, cellulose acetate, polyethylene terephthalate, and polypropylene are surveyed and their chemical mechanism outlined.

The mass coloration of plastics, and the state of disperse dyes in the fibre are also briefly discussed. Dyeing of the polar hydrophobic fibres with disperse dyes differs from all other types of dyeing in that the dye—fibre bonding is overwhelmingly hydrogen bonding, and van der Waals or hydrophobic bonding seems to have a negligible influence. All the polar groups and aromatic nuclei in the dye and the fibre can take part in the bonding, and the fibre can act as proton acceptor or donor. Because of these facts disperse dyeing has special features, including: linearity of adsorption isotherms; direct relation between water solubility and fibre solubility of dye and between number of hydrogen‐bonding groups in a dye and its solubility in the fibre; constancy of dye diffusion coefficient in the fibre, and additivity of solubility in the fibre of certain disperse dyes; and the possibility of dry dyeing, either from the vapour phase or from non‐aqueous solvents.

The size, shape, and number and nature of polar substituent groups of the disperse dye molecule influence its diffusion coefficient in the fibre.

Polypropylene fibre, if unmodified, has no polar or ionic groups and has no affinity for most disperse dyes; a very few however, have sufficient attraction by dispersion forces, to enable them to give weak shades on this fibre.
Report on meeting: Can computers help with polymer information?
Authors: Dilke M. H.
Published: March 2007

A review of four papers presented at a Symposium organised by the Plastics and Polymer Group of the Society of Chemical Industry on October 27, 1970. Two described the operation of established systems while a third dealt with lessons learned from them. The fourth dealt with a system not yet operational and prospects for the future.
Hot melt adhesives: An outline scheme for the separation and identification of their components
Authors: Finch C. A. , Kidman D. H.
Published: March 2007

Methods are described for identifying polyamides, polyurethanes, ethylene–vinyl acetate resins, polyesters, rosins and their esters, polyisobutenes and paraffin waxes in “hot‐melt” adhesives, by a combination of chemical tests and infrared spectrophotometry. Mixtures are separated quantitatively into their components by selective solvent extraction before testing.
An extension of polymer crystallisation kinetics to a branching mechanism for spherulitic growth
Authors: Booth A. , Hay J. N.
Published: March 2007

The initial stages in the development of spherulites from primary nuclei to spherical arrays of branching fibrils are included in the kinetics of polymer crystallisation. Since most of the experimental isotherms exhibit the required time dependence only over a limited range it is considered that the model has little use, and these initial stages in the development of spherulites have little effect on the degree of fit of the experimental isotherms to the Avrami rate equation.

The general time dependences of crystallisations developing as a branching process is outlined and compared with that of the Avrami equations for growth of spherical particles.
Nitrogen‐containing products from the thermal decomposition of flexible polyurethane foams
Authors: Woolley W. D.
Published: March 2007

The thermal decomposition of a polyester and a polyether flexible foam in a nitrogen atmosphere has been studied by gas chromatography, mass spec‐trometry and elemental ultramicroanalysis. It is shown that the decomposition behaviours of the two foams are similar. At low temperatures (200 to 300 °C) there is a rapid and complete loss of the tolylene diisocyanate unit of each foam as a volatile yellow smoke leaving a polyol residue. The smoke has been isolated as a yellow solid (common to both foams) which contains virtually all of the nitrogen of the original foams and, under the conditions of test, is stable at temperatures up to 750 °C. Nitrogen‐containing products of low molecular weight (mainly hydrogen cyanide, acetonitrile, acrylonitrile, pyridine and benzonitrile) observed during the high temperature decomposition (over 800 °C) of the foams are shown to be derived from the yellow smokes. At 1000 °C, approximately 70% of the available nitrogen has been recovered as hydrogen cyanide.
The effectiveness of ultraviolet absorbers in PVC
Authors: Martin K. G.
Published: March 2007

The influence of some benzophenone‐type ultraviolet absorbers in a general PVC formulation has been studied by determining rates of photo‐oxidation when specimens were exposed to xenon‐arc irradiation under controlled conditions. Replicates of the formulation but without the absorbers were similarly photo‐oxidised behind a series of glass filters to provide a basis for assessing the effectiveness of the absorbers. Some changes in appearance of the specimens have also been measured and discussed in relation to the data on photo‐oxidation rate.
Sequence length and crystallinity in alpha‐olefin terpolymers
Authors: Davison S. , Taylor G. L.
Published: March 2007

The minimum sequence length for crystallisation in a polymer was determined by a novel kinetic approach using sequence analysis of a series of blocky terpolymers.

Copolymers and terpolymers of ethylene, propylene, and but‐l‐ene were prepared with a Ziegler–Natta catalyst system. Compositions of feeds and polymers were analysed, and kinetic reactivity parameters were calculated using both the Fineman–Ross and Alfrey–Goldfinger approaches. The parameters were then applied to determine the sequence length distribution of each component in the terpolymers. Also, deliberate control of sequence lengths enabled synthesis of heptane‐soluble, rubbery polymers even using a catalyst system which normally produced blocky materials.

Crystalline contents of the terpolymers were determined experimentally by nitric acid digestion. A critical comparison of the measured crystallinities with the calculated sequence length distributions was thereby made possible. From this comparison a minimum sequence length of monomer below which crystallisation did not occur was estimated; this length was approximately 20 backbone carbon atoms.
Calibration procedures in gel permeation chromatography
Authors: Dawkins J. V.
Published: March 2007

Procedures for the determination of the log molecular weight vs. elution volume calibration relation are reviewed for linear homopolymers. The calibration curve is readily established with narrow molecular weight distribution fractions. For broad molecular weight distribution fractions the peak molecular weight at the peak elution volume of a fraction's gel permeation chromatogram has to be calculated from average molecular weights. When well‐characterised fractions of the polymer requiring analysis are unavailable, a calibration curve can be established by procedures which assume that the hydrodynamic volume of a polymer molecule in solution controls fractionation in gel permeation chromatography. These universal calibration procedures require information on Mark‐Houwink viscosity constants or polymer unperturbed dimensions. The validity of hydrodynamic volume as the universal calibration parameter is discussed with special reference to the goodness of the solvent for a polymer and polymer polarity. Examples are given of the various calibration procedures which are employed in the determination of molecular weight distribution and average molecular weights for poly(methylmethacrylate), polyethylene and polyisoprene.
Reaction of disulphides with cyclic phosphoramidites
Authors: Jarvie A. W. P. , Moore C. G. , Skelton D.
Published: March 2007

It has been observed that cyclic phosphoramidites react more slowly than triphenylphosphine with diallyldisulphide and do not give a quantitative yield of monosulphide. Therefore, contrary to expectation, these reagents are unsuitable for use as chemical probes for determining the structure of sulphurvulcanised rubber. It appears that, like triphenylphosphine, the cyclic phosphoramidites react with allylic disulphides by a SNi' mechanism.
The effect of boiling water on an amorphous aromatic polyamide
Authors: Buckley A. , Curnuck P. A. , Jones M. E. B. , Thomas I.
Published: March 2007

Amorphous poly(sulphonyldi‐p‐phenylene‐α,ω‐alkylene dicarboxamides) undergo marked changes during immersion in boiling water. This treatment produces opacity, softening and ultimately blistering and embrittlement of moulded or cast specimens produced from these polyamides. These changes have been shown to be due to a lowering of the glass‐transition temperature (Tg) to below 100 °C, and to the acid catalysed, hydrolytic scission of in‐chain amide bonds. The stability to boiling water is improved by copolymerisation to raise the Tg and by minimising the total acid content of the polymers. An n.m.r. method for the determination of terminal amine groups in these polyamides is described.
Polymers for the industrial water user
Authors: Stafford A. E.
Published: March 2007

This paper deals with the roles played by synthetic polymers in industrial water treatment practice. Other contributors have covered the use of polymers in such fields as water purification, sewage treatment and mineral separation, and this contribution is mainly confined to the use of polymers in boiler feed water and cooling water treatment.
Parameters affecting the performance of polyelectrolytes as aids to water clarification
Authors: Wilde P. F. , Dexter R. W.
Published: March 2007

An investigation of the flocculation of silica and alumina suspensions by a series of synthetic flocculants of a wide range of charge density both anionic and cationic in nature has been carried out. The extent of flocculation was determined by measurements of settling rate, sediment volume and supernatant clarity. The effect of the pH of the suspension on the performance of a number of selected polymers has been investigated. In the systems examined, flocculation was largely controlled by the charge carried by the suspended particles and polymer molecules.

The dosage/settling rate characteristics of kaolin suspensions flocculated with non‐ionic polymers of varying molecular weight are reported.

The dosages of non‐ionic polymers required for optimum flocculation of kaolin suspensions of varying solids content have been measured. At low particle concentrations bridging is less effective, and is probably reduced due to the adsorption of polymer molecules on to single particles.
Siloxane modification of polyamides
Authors: Owen M. J. , Thompson J.
Published: March 2007

Polyamide–polydimethylsiloxane block copolymers were made by the BuLi or LiOSi(CH3)2OSi(CH3)2OLi catalysed polymerisation of hexamethylcyclotrisiloxane terminated by and using this substituted siloxane to initiate the polymerisation of lauryllactam or caprolactam in toluene solvent in the presence of lithium aluminium hydride as the catalyst.

One or 2% of the polycaprolactam‐polydimethylsiloxane block copolymers were mixed with nylon 6 and discs moulded. The presence of silicone in the surface was demonstrated by determining the critical surface tensions of wetting using ethanol–water mixtures as the contact‐angle test liquids. A polylauryllactam–polydimethylsiloxane block copolymer compatible with polyethylene was similarly studied.

An important application for such composites is to provide a dry lubricated surface, therefore the kinetic coefficients of friction of steel against these copolymer‐treated nylon 6 samples were determined demonstrating at best a reduction to one third that of the untreated control.
The laboratory evaluation of polyelectrolyte flocculants
Authors: Packham R. F.
Published: March 2007

The application of polyelectrolyte flocculants as primary coagulants, coagulant aids and sludge conditioners in the treatment of water for public supply is discussed. Laboratory techniques that have been used to evaluate commercial polyelectrolytes for these uses are described and exemplified with results. The difficulty of defining floc characteristics is emphasised.
Flammability of polymers. v. thermal volatilisation analysis of polyester resin compositions
Authors: Learmonth G. S. , Nesbit A.
Published: March 2007

Thermovolatilisation analysis has been used as part of an investigation of the flammability of an insaturated polyester resin. It was clearly possible to distinguish two reaction stages which were attributed to breakdown of the styrene and polyester chains respectively and in neither case did flame retardants affect the reaction very much.
trans‐polypentenamer: A general purpose rubber from a novel reaction
Authors: Amass A. J.
Published: March 2007

The nature of the catalysts for the ring‐opening polymerisation of cycloolefins is reviewed with particular reference to the production of trans‐polypentenamer. The roles of the components of the catalyst systems are discussed and a mechanism for the ring‐opening polymerisation of cycloolefins is proposed.
Synthesis and polymerisation of polycyclic compounds with strained C—C single bonds
Authors: Hall H. K.
Published: March 2007

Ring opening polymerisation of bicyclobutanes possessing electronegative substituents (CN, COOCH3, etc.) at one or both bridgeheads can be accomplished readily with either radical or anionic initiators. The polymer chains consist exclusively of cyclobutane rings linked through the 1,3 positions. Readily obtained in high molecular weight, they possess attractive physical properties for the formation of fibres and films. These new monomers copolymerise readily with vinyl compounds, exhibiting reactivities comparable to the latter, and provide a wide variety of new copolymers. Other bicyclic compounds containing strained C—C bonds whose polymerisation has been demonstrated include bicyclo‐[2.1.0]‐pentane‐1‐carbonitrile, 1‐methyl‐2,3‐benzocyclopropenecarbonitrile, and 1,3‐dehydroadamantane. The ability to polymerise requires a high strain energy, but a high degree of p character in the C—C single bond as well.
Kinetic investigation of the synthesis of a polyethersulphone
Authors: Attwood T. E. , Newton A. B. , Rose J. B.
Published: March 2007

This paper summarises results obtained from a kinetic investigation of the processes occuring during the synthesis of polyethersulphones by reactions such as:

magnified image

The factors determining the variations in functional group reactivities due to ‘bridge’ effects are described with reference to the reactivities of these groups in model systems, and the detailed kinetics shown by the polycondensations are explained. Evidence is presented to show that ether interchange can occur in a manner analogous to ester interchange in a polyesterification, and that in polycondensations where potassium fluoride (as opposed to the chloride or bromide) is eliminated chain extension is reversible and the use of high reactant concentrations is required to obtain polymers of high molecular weight.
A branching model for crystallisation kinetics
Authors: Iguchi M.
Published: March 2007

In order to test whether the branching probability of crystallites plays an important role in determining the structure and the mutual interaction of growing bodies in bulk crystallisation system, mathematical model experiments for dendrite growth on a hexagonal lattice were performed. It was shown that, when the branching frequency is high enough, a definite contour was developed for each growing body from different primary nuclei, giving rise to a sharp boundary. As the branching frequency decreased, however, the boundary became blurred as the result of the interaction of growing units from different origins, suggesting the inadequacy of the Avrami‐type kinetic model, i.e. the expanding‐and‐over‐lapping sphere model. For the latter case, a calculation of kinetic equations was made (with simple assumptions) assuming a growth of one‐dimensional unit which branches in succession. Crystallisation curves similar to those derived from current theories were obtained without restriction in the constant (i.e. without integer constant). A basic question cast by Gordon on the Avrami‐expression of one‐dimensional crystal growth was discussed briefly.
Application of polymer physics to practical problems associated with polyurethane solings
Authors: Whittaker R. E.
Published: March 2007

The cut growth and fatigue properties of a typical cellular polyurethane soling material are considered in terms of the tearing energy theory established for vulcanised solid rubbers. The minimum value of tearing energy (T0) below which no cut growth occurs in the absence of chemical effects is compared with practical results from shoe soles in wear.

The existence of large holes in a soling material which can contribute to flex cracking failure is considered and a recent theory for their existence in solid rubbers is discussed. The scanning electron microscope has been used to illusstrate poor water absorption properties of low density polyurethane soling materials.
The characterisation of polyolefins using a curie‐point pyrolyser and gas chromatography
Authors: Northmore B. R.
Published: March 2007

The products of controlled thermal degradation of polyolefins have been examined by gas chromatography. The factors determining the formation of decomposition products in the Curie‐point pyrolyser have been studied and a highly reproducible distribution of products has been obtained at a pyrolysis temperature of 595 °C. The probable degradation mechanisms are discussed and a diagnostic scheme has been derived for determining from the degradation products the nature of the branches and thus identifying the comonomer in an ethylene copolymer.
A study of branching in ethylene copolymers by X‐ray diffraction
Authors: Preedy John E.
Published: March 2007

By slow cooling and annealing polyethylene a semiequilibrium crystallisation state is obtained. Under such crystallisation conditions changes in unit cell dimensions and crystallinities, as measured by X‐ray diffraction, may be related to the size and number of branch groups in polyethylene copolymers. Thus methyl and ethyl groups may be accommodated within the crystalline lattice whereas butyl groups are not. The method may be used to determine the type and extent of branching in unknown ethylene copolymers.
A study of sequence distribution in an aromatic copolyamide
Authors: Curnuck Peter A. , Jones Michael E. B.
Published: March 2007

Addition of lithium chloride to solutions of a copolyamide prepared from di(p‐aminophenyl) ether, di(p‐aminophenyl) sulphone and isophthaloyl chloride enables the sequence distribution of the co‐units in the copolymer to be determined by nuclear magnetic resonance spectroscopy. Copolymers of controlled sequence distribution can be prepared by correct selection of polymerisation solvent, acid acceptor and the mixing sequence of the polymer forming reactants.
Mechanism and side reactions of the anionic condensation of styrene with alkyl halides
Authors: Iguchi Masatoshi , Ranson Richard J. , Gordon Manfred
Published: March 2007

The reactions occurring in the system styrene + butyl bromide + lithium in tetrahydrofuran are studied as a model for olefine/dihalide reactions pioneered by Richards and co‐workers for the purpose of synthesising highly regular copolymers. Computer fittings of a kinetic scheme and of gel permeation chromatographs of the products leads to the conclusion that homopolymerisation of styrene tends to be a serious side reaction to the desired condensation between the styrene dianion and two moles of butyl bromide. As expected from previous work, this is found to be much less serious in the analogous system with alpha methyl styrene in place of styrene.
The use of gel permeation chromatography to study the condensation of resorcinol with formaldehyde
Authors: Hope Paul , Anderson Roger , Bloss Alan S.
Published: March 2007

Gel permeation chromatography has been used to study the acid‐catalysed condensation of resorcinol with formaldehyde in concentrated solution. Rate curves for the consumption of resorcinol and the formation of some of the oligomeric products, and changes in molecular weight distribution during the reaction have been compared for condensates prepared using various reaction conditions.
Experience with PV‐diesel hybrid village power systems in Southern Morocco
Authors: Muñoz J. , Narvarte L. , Lorenzo E.
Published: March 2007

In October 2002, under the auspices of Spanish Cooperation, a pilot electrification project put into operation two centralised PV‐diesel hybrid systems in two different Moroccan villages. These systems currently provide a full‐time energy service and supply electricity to more than a hundred of families, six community buildings, street lighting and one running water system. The appearance of the electricity service is very similar to an urban one: one phase AC supply (230 V/50 Hz) distributed up to each dwelling using a low‐voltage mini‐grid, which has been designed to be fully compatible with a future arrival of the utility grid. The management of this electricity service is based on a ‘fee‐for‐service’ scheme agreed between a local NGO, partner of the project, and electricity associations created in each village, which are in charge of, among other tasks, recording the daily energy production of systems and the monthly energy consumption of each house. This register of data allows a systematic evaluation of both the system performance and the energy consumption of users. Now, after 4 years of operation, this paper presents the experience of this pilot electrification project and draws lessons that can be useful for designing, managing and sizing this type of small village PV‐hybrid system. Copyright © 2007 John Wiley & Sons, Ltd.
Multi‐crystalline Si solar cells with very fast deposited (180 nm/min) passivating hot‐wire CVD silicon nitride as antireflection coating
Authors: Verlaan V. , van der Werf C. H. M. , Houweling Z. S. , Romijn I. G. , Weeber A. W. , Dekkers H. F. W. , Goldbach H. D. , Schropp R. E. I.
Published: March 2007

Hot‐wire chemical vapor deposition (HWCVD) is a promising technique for very fast deposition of high quality thin films. We developed processing conditions for device‐ quality silicon nitride (a‐SiNx:H) anti‐reflection coating (ARC) at high deposition rates of 3 nm/s. The HWCVD SiNx layers were deposited on multicrystalline silicon (mc‐Si) solar cells provided by IMEC and ECN Solar Energy. Reference cells were provided with optimized parallel plate PECVD SiNx and microwave PECVD SiNx respectively. The application of HWCVD SiNx on IMEC mc‐Si solar cells led to effective passivation, evidenced by a Voc of 606 mV and consistent IQE curves. For further optimization, series were made with HW SiNx (with different x) on mc‐Si solar cells from ECN Solar Energy. The best cell efficiencies were obtained for samples with a N/Si ratio of 1·2 and a high mass density of >2·9 g/cm3. The best solar cells reached an efficiency of 15·7%, which is similar to the best reference cell, made from neighboring wafers, with microwave PECVD SiNx. The IQE measurements and high Voc values for these cells with HW SiNx demonstrate good bulk passivation. PC1D simulations confirm the excellent bulk‐ and surface‐passivation for HW SiNx coatings. Interesting is the significantly higher blue response for the cells with HWCVD SiNx when compared to the PECVD SiNx reference cells. This difference in blue response is caused by lower light absorption of the HWCVD layers (compared to microwave CVD; ECN) and better surface passivation (compared to parallel plate PECVD; IMEC). The application of HW SiNx as a passivating antireflection layer on mc‐Si solar cells leads to efficiencies comparable to those with optimized PECVD SiNx coatings, although HWCVD is performed at a much higher deposition rate. Copyright © 2007 John Wiley & Sons, Ltd.
Identification of carbonylated proteins from enriched rat skeletal muscle mitochondria using affinity chromatography‐stable isotope labeling and tandem mass spectrometry
Authors: Meany Danni L. , Xie Hongwei , Thompson LaDora V. , Arriaga Edgar A. , Griffin Timothy J.
Published: March 2007

We describe a strategy for the identification of carbonylated proteins from complex protein mixtures that combines biotin hydrazide labeling of protein carbonyl groups, avidin affinity chromatography, multiplexed iTRAQ reagent stable isotope labeling, and analysis using pulsed Q dissociation (PQD) operation on an LTQ linear ion trap mass spectrometer. This strategy provided the ability to distinguish biotin hydrazide labeled, avidin purified, carbonylated proteins from non‐carbonylated background proteins with affinity for the avidin column, derived from a control sample. Applying this strategy to the identification of crudely enriched rat skeletal muscle mitochondrial protein isolates, we generated a catalogue of over 200 carbonylated proteins by virtue of their quantitative enrichment compared to the control sample. The catalogue contains many mitochondrial localized proteins shown to be susceptible to carbonyl modification for the first time, including numerous transmembrane proteins involved in oxidative phosphorylation. Other oxidative modifications (e.g. nitrosylation, hydroxylation) were also identified on many of the carbonylated proteins, providing further evidence of the susceptibility of these proteins to oxidative damage. The results also demonstrate the utility of PQD operation on the LTQ instrument for quantitative analysis of iTRAQ reagent‐labeled peptide mixtures, as well as the quantitative reproducibility of the avidin‐affinity enrichment method.
Exploring proteasome complexes by proteomic approaches
Authors: Drews Oliver , Zong Chenggong , Ping Peipei
Published: March 2007

The ubiquitin proteasome system (UPS) represents a major pathway for intracellular protein degradation. Proteasome dependent protein quality control participates in cell cycle, immune response and apoptosis. Therefore, the UPS is in focus of therapeutic investigations and the development of pharmaceutical agents. Detailed analyses on proteasome structure and function are the foundation for drug development and clinical studies. Proteomic approaches contributed significantly to our current knowledge in proteasome research. In particular, 2‐DE has been essential in facilitating the development of current models on molecular composition and assembly of proteasome complexes. Furthermore, developments in MS enabled identification of UPS proteins and their PTMs at high accuracy and high‐throughput. First results on global characterization of the UPS are also available. Although the UPS has been intensively investigated within the last two decades, its functional significance and contribution to the regulation of cell and tissue phenotypes remain to be explored. This review recapitulates a variety of applied proteomic approaches in proteasome exploration, and presents an overview of current technologies and their potential in driving further investigations.
Analysis of mouse skin reveals proteins that are altered in a diet‐induced diabetic state: A new method for detection of type 2 diabetes
Authors: List Edward O. , Berryman Darlene E. , Palmer Amanda J. , Qiu Linghua , Sankaran Sudha , Kohn Doug T. , Kelder Bruce , Okada Shigeru , Kopchick John J.
Published: March 2007

In this study, proteomic analysis was performed on the skin of C57BL/6J mice with type 2 diabetes and compared to nondiabetic controls. To induce obesity and subsequent diabetes, mice were placed on a high‐fat diet for 16 wk. After 16 wk, both diabetic and nondiabetic control mice were sacrificed and their skin removed for analysis. Following 2‐DE, proteomic profiles from the skin samples were quantified using PDQuest software. Out of more than 1000 distinct protein spots, 28 were shown to be significantly altered with 6 being decreased and 22 increased in the diabetic state compared to controls. The 28 protein spots were removed from the gels and analyzed by MALDI‐TOF and MS/MS analyses. Protein identifications revealed that 17 of the 28 proteins were involved in energy metabolism (60.7% of changes observed). Collectively, none of the significantly altered proteins had been shown previously to be altered in diabetic skin. This study not only helps to identify proteins found in skin samples of obese mice with type 2 diabetes, but also shows that skin biopsies coupled with proteomic analysis may be useful as a noninvasive method for the diagnosis of hyperinsulinemia and diabetes.
Proteome analysis of Rickettsia felis highlights the expression profile of intracellular bacteria
Authors: Ogawa Motohiko , Renesto Patricia , Azza Saïd , Moinier Danielle , Fourquet Patrick , Gorvel Jean‐Pierre , Raoult Didier
Published: March 2007

The proteome of Rickettsia felis, an obligate intracellular bacterium responsible for spotted fever, was analyzed using two complementary proteomic approaches: 2‐DE coupled with MALDI‐TOF, and SDS‐PAGE with nanoLC‐MS/MS. This strategy allowed identification of 165 proteins and helped to answer some questions raised by the genome sequence of this bacterium. We successfully identified potential virulence factors including two putative adhesins, four proteins of the type IV secretion system, four Sca autotransporters, four components of ABC transporters, some R. felis‐specific proteins, and one antitoxin of the toxin‐antitoxin system. Notably, the antitoxin was the first to be identified in intracellular bacteria. Only one protein containing rickettsia palindromic repeats was found, whereas none of the split genes, transposases, or tetratricopeptide/ankyrin repeats were detectably expressed. Comparison of the protein expression profiles of R. felis and 23 other bacterial species according to functional categories showed that intracellular bacteria express more proteins related to translation, especially ribosomal proteins. However, the remaining bacteria express more proteins related to energy production and carbohydrate/amino acid metabolism. In conclusion, this study reveals R. felis virulence factor expression and highlights the unique protein expression profile of intracellular bacteria.
Addition, elimination, exchange, and epimerization in nitro sulfones
Authors: Kingsbury Charles A. , Weinhold Jon , Winter Jeremy
Published: March 2007

Three reactions were studied in the diastereomers of 1‐(benzenesulfonyl)‐2‐nitro‐1‐phenylpropane (1A and 1B) and briefly in related compounds: elimination of the benzenesulfonyl group, epimerization of one diastereomer to the other, and deuterium/hydrogen exchange at the methine group next to nitro in starting material. The two diastereomers showed quite different reactivity. The high melting diasteromer showed rapid elimination and some exchange. The low melting diastereomer (at approximately a half‐life) showed extensive epimerization, and elimination to the alkene, but little exchange. There is little effect of aromatic substituents on reaction course. The situation is complicated by re‐addition of benzenesulfinate to the alkene. The addition reaction was similar to elimination in agreement with the Principle of Microscopic Reversibility expectations. An electron transfer mechanism for addition is calculated to be comparatively favorable. Copyright © 2007 John Wiley & Sons, Ltd.