Coated Ellipsoid

Hematite ellipsoids coated with an Sn(OH)2 shell were prepared by heating an aqueous dispersion of hematite (0.3 g L ) with 4.10 M Sn(S04)2, 1.85 M urea and 0.31 M HCl at 80 °C for up to one hr both continuous stirring during precipitation and careful control of the ratio of reactants/solid were essential to ensure that coated particles rather than a mixture of coated hematite and precipitated (Sn(OH)2, were obtained (ul Haq and Matijevic, 1998). 

The shift of the amide I mode (FTIR spectra) from 1657 to 1646 cm-1 was attributed to a change in the a-helix native structure to fl-sheets, secondary structure conformations. Atomic Force Microscopy (AFM) images display the coating of the manganese oxide surface as well as the unfolding in a ellipsoidal chain of the protein molecules after adsorption and immobilization on the surface. 

In a number of studies, ellipsoidal hematite (a-Fe203) (71) was the core material of preference, because the coating materials appeared, as a rule, as spheres when precipitated alone. This morphological difference made it possible to clearly... 

Figure 1.1.20 shows the differential thermal analysis (DTA) data for the cores, of chromium hydrous oxides particles prepared in the absence of hematite, and of coated particles. It is obvious that the latter behave as the coating material, when alone. This example clearly indicates the possibility of having the surface site characteristics of chromium hydrous oxide induced onto ellipsoidal iron oxide particles. The latter morphology cannot be achieved by diiecl precipitation of the same chromium compound. 

Fig. 1.1.19 (A) TEM of ellipsoidal hematite (a-Fci03) particles and (B) of the same particles coated by chromium hydrous oxide obtained by aging at 85°C for 6 h 40 cm3 of a dispersion containing 30 mg dm-3 of the cores in the presence of 5.0 X 10-4 mol dm-3 chrome alum. (From Ref. 144.)...

Although the necessary labor is increased, no new concepts are required to extend the results above for a homogeneous ellipsoid to a coated ellipsoid. We denote by el the permittivity of the inner or core ellipsoid with semiaxes flj, c, e2 is the permittivity of the outer ellipsoid with semiaxes a2,b2,c2. This coated ellipsoidal particle is in a medium with permittivity em. As in the preceding section, we introduce ellipsoidal coordinates , tj, f ... 

Further experimental evidence of shape effects in absorption spectra of SiC particles is found in the data of Pultz and Herd (1966), who investigated infrared absorption by SiC fibers with and without Si02 coatings. Although these measurements were not mass-normalized, they show a strong absorption band at 795 cm-1 and a weaker band at 941 cm-1. If the fibers are approximated as ellipsoids with L2 = L3 = and Lx = 0 (i.e., a cylinder), then the ellipsoid equation (12.27) predicts absorption peaks for particles in air at frequencies where c = -1 and c = — oo. This corresponds to absorption bands at 797 and 945 cm-1 for the dielectric function of isotropic SiC, in excellent agreement with the experimental peak positions for the fibers. 

Gilra (1972ab) has very thoroughly discussed absorption by small ellipsoidal particles, including those with coatings, in the surface mode region. 

The observed darkening of the indium slides results from a shift of the absorption peak because of the coating on the particles. Because of the cumbersomeness of the expressions for coated ellipsoids (Section 5.4) this shift can be understood most easily by appealing to (12.15), the condition for surface mode excitation in a coated sphere. For a small metallic sphere with dielectric function given by the Drude formula (9.26) and coated with a nonabsorbing material with dielectric function c2, the wavelength of maximum absorption is approximately... 

Ambjomsson, T., Mukhopadhyay, Gautam,. Apell, P., Kail, M. (2006). Resonant coupling between localized plasmons and anisotropic molecular coatings in ellipsoidal metal nanoparticles. Phys. Rev. B 73 085412. 

Pinchuk, A. Optical bistability in nonlinear composites with coated ellipsoidal nanoparlicles. J. Phys. D Appl. Phys. 36. 460-464 (2003)... 

A) The protein coat of horse spleen apoferritin deduced from x-ray diffraction of crystals of the protein.The outer surface of the protein coat shows the arrangement of the 24 ellipsoidal polypeptide subunits. N refers to the N-terminus of each polypeptide and E to the E-helix (see B). Note the channels that form at the four-fold axes where the E-helices interact, and at the threefold axes near the N-termini of the subunits. (B) A ribbon model of a subunit showing the packing of the four main alpha-helices (A, B, C, and D), the connecting L-loop and the E-helix. 

Participating research teams Naval Research Laboratory At the NSLS a large number of participating research teams (PRTs) have established beam lines on the NSLS and a number of instruments use diffractometers as well as oscillation cameras. One of these, for instance, is the Naval Research Laboratory (NRL) and National Bureau of Standards PRT as part of this effort, NRL is constructing a materials analysis X-ray beam line. The beam optics design consists of a platinum coated copper pre-mirror dynamically bent to approximate a parabolic cylinder, followed by a fixed-exit double crystal monochromator and a platinum coated fused silica cylinder bent to approximate an ellipsoid. The hutch contains a six-circle diffractometer (Kirkland, Nagel and Cowan 1983). 

Abbreviations EPR - electron paramagnetic resonance HE -high-energy IPS-isopentane solution LB-Langmuir-Blodgett LE - low-energy MCD - microcrystals dispersed in a KBr disk ORTEP - Oak Ridge thermal ellipsoid plot ROC - randomly oriented crystals SC-spin-coated SCE-spin-coated film... 

In some samples, a few of the prills were only partially coated. This enabled observation of the contact angle between the sulfur and the conditioned urea surface. The sulfur-surface interfaces in Figure 14 show that the contact angles are positive and less than 90°, indicating that the sulfur is wetting the conditioned urea surface. The sulfur is present as flattened hemi-ellipsoids. 

We have shown that ion-assisted deposited on rubber and silicon thin metal films include not only metal atoms but also carbon, oxygen, hydrogen and silicon (from Si substrate), and sulphure, calcium, and zinc (from rubber). The coatings on rubber are characterized by semi-ellipsoids surface topography and increased roughness. The coatings on silicon are uniform with smooth surface. 

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