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71.
Spectroscopic ellipsometry study of liquid crystal and polymeric thin films in visible and near infrared 总被引:1,自引:0,他引:1
Tkachenko V Marino A Vita F D'Amore F De Stefano L Malinconico M Rippa M Abbate G 《The European physical journal. E, Soft matter》2004,14(2):185-192
In this work, we propose spectroscopic ellipsometry as a suitable method for measuring optical properties in soft materials, polymers and liquid crystals, specially selected for use in photonics applications. We show the results of our measurements on some multilayered samples, in the range from visible to the near-IR region, of interest for telecom applications. We point out potentialities and limits of the technique and compare the obtained results with another experimental method, the m-lines spectroscopy, and/or with existing data in the literature. The results about the optical parameters for the analysed materials (the nematic liquid crystal 5CB, one commercial and one lab made optical polymer, and an Indium Tin Oxide film) are useful and interesting by themselves. In fact, as a paradigmatic example, we briefly discuss how an incomplete knowledge of this kind of data can lead to a wrong design of a Bragg grating device. However, more than in the provided data, we put the interest of the present analysis in the warnings about spectroscopic ellipsometry utilization and eventually the necessity of getting complementary information.Received: 13 May 2004, Published online: 29 June 2004PACS:
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity) - 78.66.Qn Polymers; organic compounds - 07.60.Fs Polarimeters and ellipsometers 相似文献
72.
Liang JF Shapira D Gross CJ Beene JR Bierman JD Galindo-Uribarri A Gomez del Campo J Hausladen PA Larochelle Y Loveland W Mueller PE Peterson D Radford DC Stracener DW Varner RL 《Physical review letters》2003,91(15):152701
Evaporation residue cross sections have been measured with neutron-rich radioactive 132Sn beams on 64Ni in the vicinity of the Coulomb barrier. The average beam intensity was 2 x 10(4) particles per second and the smallest cross section measured was less than 5 mb. Large sub-barrier fusion enhancement was observed. Coupled-channel calculations taking into account inelastic excitation significantly underpredict the measured cross sections below the barrier. The presence of several neutron transfer channels with large positive Q values suggests that multinucleon transfer may play an important role in enhancing the fusion of 132Sn and 64Ni. 相似文献
73.
With the application of RDCs in high-resolution NMR studies of macromolecules, there has been an interest in the development of accurate, sensitive methods for measuring 15N-1H and 13C-1H one-bond coupling constants. Most methods for determining these couplings are based on the measurement of the displacement between cross-peak components in J-coupled spectra. However, for large macromolecules and macromolecular complexes, these methods are often unreliable since differential relaxation can significantly broaden one of the multiplet components (i.e., the anti-TROSY component) and thereby make accurate determination of its position difficult. To overcome this problem, a J-evolved transverse relaxation optimized (JE-TROSY) method is presented for the determination of one-bond couplings that involves J-evolution of the sharpest cross-peak multiplet component selected in a TROSY experiment. Couplings are measured from the displacement of the TROSY component in the additional J-evolution dimension relative to a zero frequency origin. The JE-TROSY method is demonstrated on uniformly labeled 15N, 13C-labeled RNA and peptide samples, as well as with an RNA-protein complex, in which the protein is uniformly 15N, 13C-labeled. In all cases, resolved, sensitive spectra are obtained from which heteronuclear one-bond J-couplings could be accurately and easily measured. 相似文献
74.
Giuseppe Marino 《Journal of Mathematical Analysis and Applications》2003,284(2):775-778
Let X be a real Banach space. Let be a family of closed, convex subsets of X. We show that either the intersection ?γ∈Γ(Gγ)? of the ?-neighborhood of the sets Gγ is bounded for each ?>0, or it is unbounded for each ?>0. From this we derive a fixed point theorem for suitable maps that move some points along a bounded direction in Hilbert spaces. 相似文献
75.
Platinum is added to thermal barrier coatings (TBCs) as it is observed empirically to extend their lifetime, but the mechanism by which Pt acts is unknown. Since Pt has been proposed to alter diffusivities in NiAl, a key component of TBCs, we use first‐principles quantum mechanics calculations to investigate atomic level diffusion mechanisms. Here, we examine the effect of Pt on five previously proposed mechanisms for Ni diffusion in NiAl: next‐nearest‐neighbor jumps, the triple defect mechanism, and three variants of the six jump cycle. We predict that Pt increases the rate of Ni diffusion by stabilizing point defects and defect clusters that are diffusion intermediates. Previously, we predicted the triple defect mechanism to be a dominant Ni diffusion mechanism; it simultaneously results in long‐range Al diffusion in the opposite direction. Since Pt increases the rate of Ni diffusion, it also increases Al diffusion in NiAl, which may be key to extending the coating lifetime. 相似文献
76.
77.
78.
Most methods of measuring the interfacial tension between two immiscible polymers are based on the analysis of the shape
that a drop of one polymer immersed in the other one exhibits under the action of flow or gravity. In such a situation, the
small, yet nonzero mutual solubility between the two polymers acts toward mass transfer between the drop and the surrounding
fluid. In this work, diffusion effects on the interfacial tension of the pair polyisobutylene/polydimethylsiloxane have been
investigated by drop deformation under shear flow. When the drop was made of polyisobutylene, drop size decreased with time
due to diffusion. Drop shrinkage was associated with a significant increase in interfacial tension, until an apparent plateau
value was reached. The effect was attributed to a selective migration of molecular weights, which would act to enrich the
drop with higher molar mass material. To support such an interpretation, drop viscosity was evaluated by drop shape analysis
and it was actually found to increase with time. In some cases, the ratio between drop and continuous phase viscosity became
higher than the critical value for drop breakup in shear flow. Upon inverting the phases (i.e., when the drop was made of
polydimethylsiloxane), no significant transient effects were observed. In the light of these results, the problem of what
are the correct values of interfacial tension and viscosity ratio for a polymer blend of a certain composition will also be
discussed.
Received: 25 January 1999 Accepted: 24 May 1999 相似文献
79.
K. Fabich und A. del Campo Cerdan 《Fresenius' Journal of Analytical Chemistry》1930,82(10):382-383
Ohne Zusammenfassung 相似文献
80.