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Halogen-free flame retardant additives based on phosphorus function by developing a protective char. A variety of additives are available, ranging from the element itself, in the form of amorphous red phosphorus, to specialty organophosphorus compounds, and examples of their use in a range of thermoplastics are given. Intumescent formulations based on phosphates are especially designed for polyolefins. The behavior of a typical intumescent system is described with respect to flame retardant performance, thermal stability, water sensitivity, and filler compatibility. 相似文献
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Dickie R. Cahill R. Gamble H.S. Fusco V.F. Huggard P.G. Moyna B.P. Oldfield M.L. Grant N. de Maagt P. 《Electronics letters》2007,43(19):1013-1015
The spectral transmittance of a frequency selective surface (FSS), which consists of two free-standing arrays of short-circuited nested annular slots, is presented. The FSS was designed to provide a minimum of 20 dB isolation between the frequency bands 316.5-325.5 and 349.5-358.5 GHz when the filter operates in the TE and TM planes at 45deg incidence. Experimental results, which are in close agreement with the computed transmission coefficients, show that the maximum insertion loss is 0.9 dB, and the minimum cross-polar discrimination is at least 21 dB in the passbands. The FSS yields virtually identical spectral responses in the two polarisation planes over the frequency range 315-359 GHz. 相似文献
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DJ Torpy RD Gordon JP Lin PR Huggard SE Taymans M Stowasser GP Chrousos CA Stratakis 《Canadian Metallurgical Quarterly》1998,83(9):3214-3218
Familial hyperaldosteronism type II (FH-II) is characterized by autosomal dominant inheritance and hypersecretion of aldosterone due to adrenocortical hyperplasia or an aldosterone-producing adenoma; unlike FH type I (FH-I), hyperaldosteronism in FH-II is not suppressible by dexamethasone. Of a total of 17 FH-II families with 44 affected members, we studied a large kindred with 7 affected members that was informative for linkage analysis. Family members were screened with the aldosterone/PRA ratio test; patients with aldosterone/PRA ratio greater than 25 underwent fludrocortisone/salt suppression testing for confirmation of autonomous aldosterone secretion. Postural testing, adrenal gland imaging, and adrenal venous sampling were also performed. Individuals affected by FH-II demonstrated lack of suppression of plasma A levels after 4 days of dexamethasone treatment (0.5 mg every 6 h). All patients had negative genetic testing for the defect associated with FH-I, the CYP11B1/CYP11B2 hybrid gene. Genetic linkage was then examined between FH-II and aldosterone synthase (the CYP11B2 gene) on chromosome 8q. A polyadenylase repeat within the 5'-region of the CYP11B2 gene and 9 other markers covering an approximately 80-centimorgan area on chromosome 8q21-8qtel were genotyped and analyzed for linkage. Two-point logarithm of odds scores were negative and ranged from -12.6 for the CYP11B2 polymorphic marker to -0.98 for the D8S527 marker at a recombination distance (theta) of 0. Multipoint logarithm of odds score analysis confirmed the exclusion of the chromosome 8q21-8qtel area as a region harboring the candidate gene for FH-II in this family. We conclude that FH-II shares autosomal dominant inheritance and hyperaldosteronism with FH-I, but, as demonstrated by the large kindred investigated in this report, it is clinically and genetically distinct. Linkage analysis demonstrated that the CYP11B2 gene is not responsible for FH-II in this family; furthermore, chromosome 8q21-8qtel most likely does not harbor the genetic defect in this kindred. 相似文献
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W. M. Huber T. Veit P. G. Huggard W. Prettl 《Journal of Infrared, Millimeter and Terahertz Waves》1995,16(10):1757-1768
YBa2Cu3O7-δ thin films may be epitaxially grown, on suitably prepared substrates, with a non-zero tilt angle between the film's c-axis and its surface normal. These films are fast, room-temperature, thermoelectric detectors with a response extending from UV to FIR wavelengths. We have found that tilted c-axis films, when cooled below Tc, also exhibit a fast and sensitive Josphson photoresponse to 250 µm and 496 µm radiation, in contrast to the nil response of c-axis normal films. It is believed that the non-zero component of the radiation electric field along the c-axis of tilted films modulates relatively weak Josephson critical currents in this direction, generating a photoresponse from current biased samples. 相似文献
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Huggard P.G. Ellison B.N. Shen P. Gomes N.J. Davies P.A. Shillue W. Vaccari A. Payne J.M. 《Electronics letters》2002,38(7):327-328
A 70 GHz bandwidth commercial photodiode has been used to create a photomixer source of radiation at frequencies from 70 GHz to above 600 GHz. The waveguide source is driven by two 1.55 μm lasers and delivers a peak, nonsaturated, power of -7.5 dBm at 110 GHz with a power conversion efficiency above 1%. Detected power decreases approximately as 1/(frequency)4 above 150 GHz 相似文献
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Martinez B. Ederra I. Gonzalo R. Alderman B. Azcona L. Huggard P.G. Bas de Hon Hussain A. Andrews S.R. Marchand L. de Maagt P. 《Microwave Theory and Techniques》2007,55(4):672-681
The sensitivity of the characteristic band edge frequencies of three different 500-GHz electromagnetic-bandgap crystals to systematic variations in unit cell dimensions has been analyzed. The structures studied were square bar woodpiles made with dielectric having epsiv rap12 and epsivr=37.5 and two wide bandgap epsivr=37.5 crystals designs proposed by Fan and Johnson and Joannopoulos. These epsivr values correspond to high-resistivity silicon and a zirconium-tin-titanate ceramic, respectively. For the woodpiles, the fractional frequency bandgap varied very little for dimensional deviations of up to plusmn5% from the optimum. The bandgaps of the Fan and Johnson and Joannopoulos structures were affected to a greater extent by dimensional variations, particular sensitivity being exhibited to the air-hole radius. For all crystals, the effect of increasing the amount of dielectric in the unit cell was to shift the bandgap edges to lower frequencies. Both silicon and ceramic woodpiles, along with a ceramic Fan structure, were fabricated and dimensionally characterized. Mechanical processing with a semiconductor dicing saw was used to form the woodpiles, while the Fan structure required both dicing and UV laser drilling of circular thru-holes. Good agreement with predicted normal incidence transmissions were found on the low-frequency side of the bandgap in all cases, but transmission values above the upper band edge were lower than expected in the ceramic structures 相似文献
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Pengbo Shen Gomes N.J. Davies P.A. Huggard P.G. Ellison B.N. 《Lightwave Technology, Journal of》2007,25(11):3257-3264
Fiber-ring-based optical frequency comb generators are analyzed to understand their behavior and limitations. A numerical frequency-domain model is described for studying dispersion and other phase mismatch causing effects in the fiber ring cavity, as well as for predicting the spectral and temporal evolutions of the comb in time. The results from this analysis are verified with experimental measurements. A flat optical comb, with a terahertz span within a 6-dB power envelope and containing 100 comb lines, with a suppressed central comb line, is demonstrated. The comb shows an excellent coherence dependent on the phase noise from the radio frequency synthesizer that drives the comb generator. Improvement in the error correction loop also enables the comb spacing to be set at precise 12.5-MHz intervals without having to adjust the system. Fast frequency switching of the comb line spacing is demonstrated for the first time. The comb line spacing can be switched to any operation frequency with a resolution of 12.5 MHz between 6 and 12.5 GHz, as limited only by the microwave circuit used. The switching time is less than 1 s, and the spectral profile of the comb is maintained. 相似文献
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Huggard P.G. Ellison B.N. Shen P. Gomes N.J. Davies P.A. Shillue W.P. Vaccari A. Payne J.M. 《Photonics Technology Letters, IEEE》2002,14(2):197-199
A 70-GHz bandwidth commercial photodiode has been coupled to W-band waveguide and used as a photomixing source from 75 to 170 GHz. Maximum power conversion efficiency of 1.8% was obtained at 75 GHz, where an optical input of +10 dBm yielded a nonsaturated millimeter-wave (mm-wave) power of -7.5 dBm. Optimizing the photomixer backshort tuning at individual frequencies showed that the mm-wave power decreased with frequency to a level of -30 dBm at 170 GHz. Fixed tuning allowed the generation of power across the full waveguide band from 75 to 110 GHz, with a variation within 5 dB across the majority of the band 相似文献
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W. Prettl H. Lengfellner J. P. Kaminski Gi. Schneider P. G. Huggard T. O'Brien W. Blau 《Journal of Infrared, Millimeter and Terahertz Waves》1992,13(10):1659-1666
The far infrared response of granular thin-film Bi2Sr2CaCu2O8 superconductor has been investigated using long (≈5 μs) but sharply truncated free electron laser pulses in the frequency range between 50 cm?1 and 125 cm?1. Under constant current bias, a fast response and a slow bolometric signal component could be identified in this energy range, which is below the BCS energy gap (≈ 200 cm?1). Measurements of the power dependences of the signal voltages showed that both the fast and the thermal responses are consistent with the predictions of the resistively shunted Josephson junction model. 相似文献
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