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1.
In this paper, the effect of cubic zinc metaborate Zn4O(BO2)6 on the sintering of MnZn-ferrites for medium frequency power applications is investigated. Zinc metaborate is synthesized in the laboratory using zinc oxide and boric acid as metal precursors. As observed, when zinc metaborate is added to the MnZn-ferrites at an optimum amount of 0.02 wt%, it significantly enhances densification and therefore allows, for a given density, reduction of the firing temperature by almost 200 °C. MnZn-ferrites exhibiting power losses of 70 mW/cm3 (measured at a frequency of 400 kHz, magnetic field 50 mT and temperature of 90 °C) are synthesized from conventionally milled powders with average particle diameter 0.6 μm, compacted and fired at 1100 °C. Identical experiments conducted under the same conditions on specimens without zinc metaborate additions revealed power losses greater than 300 mW/cm3, because of insufficient densification. 相似文献
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3.
Single and double wavelength excitation of laser-induced fluorescence of normal and atherosclerotic peripheral vascular tissue 总被引:1,自引:0,他引:1
Filippidis G Zacharakis G Katsamouris A Giannoukas A Papazoglou TG 《Journal of photochemistry and photobiology. B, Biology》2000,56(2-3):163-171
Laser-induced fluorescence spectra were recorded from the exposure of peripheral vascular tissue to both helium-cadmium and argon-ion laser radiation. Spectral analysis was based on simple algebraic expressions constructed using the intensity difference of the various spectral regions. The above methods were developed in order to determine the degree of atherosclerosis according to the laser-induced fluorescence signal. Similar results with single wavelength excitation were observed during in vivo irradiation of peripheral vessels. 相似文献
4.
We continue the comparison of the results of an interlayer model, based on the theory of elastic continua, and a molecular model, derived from a theory of mixtures, previously presented in terms of bulk moduli K. We now derive expressions for the dependence of the thermal expansivity
c
on the volume fraction
f
of the filler, at low and elevated values of
f
. Correspondencies between the characteristic parameters, viz. adhesion and repulsion ratios on the one hand, and interlayer content and thermal properties of matrix, filler, and layer, on the other, are examined. Since in the molecular theory both andK are derived from an equation of state, the identical set of parameters determines both functions and suggests correlations between them. 相似文献
5.
Georgios Papazoglou Jorge Sierra Katharina Homberger Armin Guggisberg Wolf-Dietrich Woggon Manfred Hesse 《Helvetica chimica acta》1991,74(3):565-571
Aphelandrine ( 1 ) is shown to be biosynthesized in the root cells of Aphelandra tetragona (VAHL ) NEES from labelled putrescine ( 4 ), spermidine ( 5 ), and cinnamic acid ( 3 ). Whether spermine ( 6 ) and the (p-hydroxycinnamoyl)spermidine 8 are precursors of 1 is uncertain, since the latter is hydrolysed to a large extent before incorporation, and the former is metabolized to 4 and 5 . Methionine ( 7 ) is the source of the 3-aminopropyl unit of 5 and 6 . 相似文献
6.
CM Thaker S Rayaprol Krushna Mavani DS Rana MS Sahasrabudhe SI Patil DG Kuberkar 《Pramana》2002,58(5-6):1035-1039
The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good
example of these properties is (La1−2x
Pr
x
Ca
x
)MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T
c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using
X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for
understanding the structural, transport and magnetic properties are discussed in detail. 相似文献
7.
Elisabeth Papazoglou Chetana Sunkari Mike Neidrauer John F. Klement Jouni Uitto 《Photochemistry and photobiology》2010,86(1):138-145
Acute exposure to UV radiation (UVR) causes visible skin damage such as erythema and results in local and systemic immunosuppression while chronic exposure can result in photocarcinogenesis. These deleterious effects can be quantified by histology and by bioassays of key biological markers, including matrix metalloproteinases (MMPs), or tryptophan moieties. We now report our results in quantifying UV skin damage with noninvasive optical methods based on reflectance and fluorescence spectroscopy and compare these noninvasive measurements to histopathology and MMP-13 expression. A solar simulator with spectral output nearly identical to that of solar radiation was developed and used in our experiments. SKH1 hairless mice were exposed to solar-simulated UVR at a total dose of 21 MED delivered over 10 weeks. Changes in oxygenated and deoxygenated hemoglobin were measured by diffuse reflectance spectroscopy, and tryptophan changes were monitored via a fluorescence monitor. Our results show that there is an increase in erythema, skin fluorescence, sunburn cells and MMP-13 after a series of suberythemal doses of UV irradiation on a hairless mouse animal model. Increased skin fluorescence is observed with increasing UV exposure. The levels of MMP-13 increase as the cumulative UV dose increases but their increase does not correspond to noninvasively measured changes. 相似文献
8.
Plasma strings from ultraviolet laser filaments drive permanent structural modifications in fused silica 总被引:1,自引:0,他引:1
Long self-trapped femtosecond ultraviolet filaments created in the bulk of pure fused silica are used to induce permanent structural changes in the medium. We monitor the laser pulse propagation as a filamentary structure and the plasma string left at its trail. We investigate and demonstrate the link of the filament-induced plasma to the permanent structural changes left in the medium. Specific electron density thresholds are found for the induced modifications. 相似文献
9.
We have described the transfer of modulated radiation in a random medium in terms of the Bethe-Salpeter equation. Based on the obtained expression for the scattering intensity, we have developed an original technique of modeling the photon density waves in terms of the Monte Carlo method. Expressions for measurable parameters in the frequency domain have been derived, and, based on them, the amplitude and phase of the photon density waves have been calculated. We have studied how the parameters of the photon density waves depend on the scattering anisotropy for model states with the Henyey-Greenstein phase function. The range of applicability of the diffusion approximation for the interpretation of signals of photon density waves has been investigated. 相似文献
10.
We demonstrate the realization of intense Airy-Airy-Airy (Airy(3)) light bullets by combining a spatial Airy beam with an Airy pulse in time. The Airy(3) light bullets belong to a family of linear spatiotemporal wave packets that do not require any specific tuning of the material optical properties for their formation and withstand both diffraction and dispersion during their propagation. We show that the Airy(3) light bullets are robust up to the high intensity regime, since they are capable of healing the nonlinearly induced distortions of their spatiotemporal profile. 相似文献