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961.
Fundus reflection densitometry or retinal densitometry is a non-invasive technique to examine the visual photopigment kinetics in living eyes. The technique is based on the comparison of the reflected light from the fundus in a fully light adapted eye (when all visual photopigment has been bleached) with the reflected light following complete dark adaptation (when the retina contains its maximum amount of visual photopigment). The technique provides a measure of the density of visual photopigment, its time constant of regeneration, its distribution and spectral characteristics if measured at a series of wavelengths. Fundus reflection densitometry in the human eye was introduced 40 years ago. Presently, it is the only available technique from which direct and objective insight can be obtained into visual photopigment. This knowledge is particularly relevant in eyes where abnormalities of photoreceptor function are suspected. This paper summarizes the current knowledge of fundus reflection densitometry in the diseased and in the aging human retina, gathered over the last 30 years. Considerable improvements of the instrument for clinical purposes have been obtained, and are also discussed. 相似文献
962.
963.
A two-stage balanced Ku-band coplanar waveguide amplifier design is presented which has been miniaturised by using impedance transforming couplers which considerably reduce the required matching networks to the MESFETs. The amplifier, measuring only 2*1.7 mm/sup 2/, exhibits a gain of 13.7 dB with less than +or-0.2 dB of ripple over the range 14-16 GHz.<> 相似文献
964.
Rectangular waveguides with two L-shaped septa attached to the broad walls in antipodal configuration have been shown theoretically by the authors (see ibid. vol.40, no.4, p.777-781, 1992) to be an improved variant of the double T-septa guide having larger cut-off wavelength and broader bandwidth of the dominant TE mode. Numerical data on the attenuation, impedance, and power handling capability of this new type of broadband guide are presented as additional design information 相似文献
965.
Gamebirds provide a considerable incentive to plant and manage new woodlands. The supplementary income thus generated can improve their overall value. Other studies suggest that Short Rotation Coppice (SRC) crops may provide an attractive habitat for some gamebird species and could increase the value of the crop. To investigate this, the use by pheasants and partridge of different types of SRC at one site was assessed.
A method using sand quadrats to record gamebird footprints and hence relative use was developed. Pheasant footprints were recorded more frequently in the quadrats alongside the willow coppice, whereas partridge footprints occurred more frequently alongside the poplar coppice. Footprint analysis offers a reliable method of investigating how gamebirds use different types of SRC within small areas. The results are considered in terms of the placement of short rotation coppice plantations in the landscape to improve their ecological design. 相似文献
966.
Films of electroactive polymers, such as polyaniline (PAN) in its emeraldine base form, and poly(3-alkylthiophene), poly(3-hexylthiophene) (P6TH), poly(3-octylthiophene) (P8TH), and poly(3-dodecylthiophene) (P12TH) can be readily functionalized via thermal or near ultraviolet-light-induced surface graft copolymerization with monomers of polyelectrolyte, polyampholyte and polymeric acids. The monomers used in the present work include dimethyl sulphate quaternized dimethylamino-ethylmethacrylate (DMAEM·C2H6SO4), 3-dimethyl(methacryloyloxyethyl)ammonium propane sulphonate (DMAPS), acrylic acid (AAc) and a sodium salt of styrene sulphonic acid (NaSS). The surface structures and compositions of the electroactive polymer films after functionalization via graft copolymerization were characterized by angle-resolved X-ray photoelectron spectroscopy. Graft copolymerization of poly(3-alkylthiophene) films, but not PAN films, with the hydrophilic monomers readily results in a stratified surface microstructure arising from the migration of the hydrophilic graft chains beneath a thin surface layer which is much richer in the substrate chains. On the other hand, graft copolymerization of PAN films with AAc and NaSS readily gives rise to a self-protonated (and thus conductive) surface structure. 相似文献
967.
S. Scalat D. Banu D. Hawes J. Parish F. Haghighata D. Feldman 《Solar Energy Materials & Solar Cells》1996,44(1):49
Full scale thermal storage tests were conducted in a room lined with PCM wallboard having latent heat storage capacity. The results were compared with those obtained from tests conducted in a similar room lined with ordinary wallboard. The research showed that PCM wallboard can function efficiently as a thermal storage medium which can be applied to peak load shifting, improved use of waste and solar heat as well as more efficient operation of heating and cooling equipment. 相似文献
968.
This work pertains to output voltage stability of soft adjacent layer biased magnetoresistive heads with abutted permanent magnetic films for domain stabilization. A micromagnetic model has been developed to study the effect of the permanent magnet film microstructure and the micromagnetic properties of the abutted junction interface on head stability. The impact on head stability is analyzed with respect to interfacial ferromagnetic coupling across the junction interface and intergranular exchange coupling in the permanent magnet films among other film properties 相似文献
969.
Minimal inhibition concentrations (MIC) of gentamycin (Ge), neomycin (Neo), rifampicin (Rif), ampicillin (Amp), lincomycin (Lin), erythromycin (Ery), and streptomycin (STM) were determined by the agar dilution technique using 46, 130, 131, 125, 140, 139 and 142 strains of Staphylococcus aureus, respectively. The strains, selected from the collection of the authors' laboratory, were isolated from mammary gland secretions of cows affected with clinical or subclinical mastitis. The following ranges of MIC (micrograms/ml) were assessed for the antibiotics under study: Ge 0.125-0.50, Neo 0.06-0.50, Rif 0.0039-0.030, Amp 0.015-1.00, Lin 0.25-1.00, Ery 0.06-0.25, STM 0.50-64.0. Modal MIC (micrograms/ml) were as follows; Ery 0.125 (86%), Lin 0.5 (71.4%), Rif 0.007 (68.7%), Ge 0.25 (56.5%), STM 1.00 (54.2%), Neo 0.25 (53.8%), Amp 0.06 (41.6%). The order of efficiency expressed in MIC 90 (micrograms/ml) was as follows: Rif (0.015), Ery (0.125), Ge (0.25), Neo (0.25), Amp (0.5), STM (4.0). 相似文献
970.
Flexion-extension moments acting at the L5/S1 level and hip joints were calculated using three different techniques; a pure static analysis, a static analysis including the inertial force of the load, and a dynamic analysis. Ten subjects participated in the study and were asked to lift a box weighing either 50 N or 150 N, using a freestyle technique. The lifts were performed at normal and fast speed. The intra-subject lifting techniques were consistent when lifting the same loads. The moments predicted by the dynamic analysis and the static analysis were the same when holding weights in static postures. When performing the lifts, differences in the peak moments occurred between static and dynamic analyses. These differences were influenced by external load and by lifting speed. Taking the effect of the inertia of load into account in the static analysis resulted in an increase in the moment magnitude, but the predicted moment was still much less than in the dynamic analysis which yielded the largest moment magnitudes. The difference between dynamic and static analysis was greatest when lifting 50 N at fast speed; an 87% increase in L5/S1 moment and a 95% increase in hip moment was observed when replacing the pure static with a dynamic analysis. 相似文献