Surface-enhanced infrared (SEIR) and surface-enhanced Raman scattering (SERS) spectroscopies are applied to the study of the adsorption on Au films of the dimethyldithiocarbamate derivative fungicides thiram and ziram. The specificity and sensitivity of both techniques in relation to the detection and surface stability of the above compounds is analyzed comparatively. We have found that both fungicides undergo a breakdown when adsorbed on Au films, although this breakdown takes place to a different extent; thiram seems to be less stable than ziram. The sensitivity of infrared techniques is higher, although a lower enhancement in relation to SERS is observed. Whereas the SEIR technique allows the detection of all the adsorbed fungicide forms, SERS displays a high sensitivity toward only certain adsorbed molecules, those that undergo a strong adsorption induced by the fungicide breakdown.

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Human platelet plasma membrane glycoproteins IIb (GPIIb) and IIIa (GPIIIa) form a Ca(2+)-dependent heterodimer, the integrin GPIIb/IIIa, which serves as the receptor for fibrinogen and other adhesive proteins at the surface of activated platelets. Below the critical micellar concentration of Triton X100 (TtX), the three glycoproteins do not bind appreciably to TtX and form association products of large size. The size-exclusion chromatographic patterns of GPIIb, GPIIIa and GPIIb/IIIa have been obtained at 0.2% TtX, and the molecular properties of the association products and monomer fractions have been determined by analysis of the detergent bound to the glycoproteins, laser-light scattering, sedimentation velocity, and electron microscopy (TEM). The monomer of the GPIIb-TtX complex was identified by the molecular mass (M) of the glycoprotein moiety (125 +/- 15 kDa), the molecular size (9.5 +/- 1.5 nm x 11 +/- 1.5 nm) and globular shape observed by TEM. It has a molecular mass (M*) of 197 +/- 20 kDa, a sedimentation coefficient s degrees 20* of 5.8 +/- 0.1 S, a Stokes radius R s* of 6.8 +/- 0.4 nm, and a frictional ratio f*/fmin* of 1.7 +/- 0.14. The (GPIIb)n-TtX complexes are disulphide-bonded size-heterogeneous association products of GPIIb, tetramers being the smallest species found. GPIIIa has a greater propensity to self-associate than GPIIb, this tendency being lower below 1 mg GPIIIa/ml, 0.1 mM Ca2+, pH 9.0. The (GPIIIa)n-TtX complexes are noncovalent size-heterogeneous association products of GPIIIa, tetramers being the smallest form observed. The monomer of the GPIIIa-TtX complex was identified by the 103 +/- 15 kDa M determined for the glycoprotein moiety, and the 9 +/- 1.5 nm x 10 +/- 1.5 nm size and globular shape observed by TEM. It has a M* of 136 +/- 15 kDa, a s degrees 20* of 3.9 +/- 0.3 S, a Rs* of 6.4 +/- 0.5 nm, a f*/fmin* of 1.9 +/- 0.3, and, when stored at pH 7.4, has a certain tendency to form filamentous association products (20-70 nm x 2-5 nm), as observed by TEM. The GPIIb/IIIa-TtX complex in 0.2% TtX/0.1 mM Ca2+ elutes as a single monomeric fraction, as deduced from the 210 +/- 15 kDa M determined for its glycoprotein moiety and the 12 +/- 1.5 nm x 14 +/- 1.5 nm size of the globular forms observed by TEM.(ABSTRACT TRUNCATED AT 400 WORDS)

The optical constants of ion-beam-sputtered SiC films have been measured by ellipsometry in the 190 to 950 nm range. The set of data has been extended both toward shorter and longer wavelengths with data in the literature, along with inter- and extrapolations, in order to obtain a self-consistent set of data by means of Kramers-Krönig analysis. All data correspond to films that were deposited by sputtering on nonheated substrates, and hence they are expected to be amorphous. A bandgap of 1.9 eV for the films was fitted from the obtained optical constants. A good global accuracy of the data was estimated through the use of various sum rules. The consistent dataset includes the visible to the extreme ultraviolet (EUV); this large spectrum of characterization will enable the design of multilayer coatings that combine a high reflectance in parts of the EUV with desired performance at a secondary range, such as the visible. To our knowledge, this paper provides the first compilation of the optical constants of amorphous SiC films.

The optical constants of electron-beam evaporated boron from 6.8 to 900 eV were calculated through transmittance measurements of boron thin films deposited onto carbon-coated microgrids or LiF substrates in ultrahigh-vacuum conditions. In the low-energy part of the spectrum the measurements were performed in situ on freshly deposited samples, whereas in the high-energy range the samples were exposed to the atmosphere before the measurements. The extinction coefficient was calculated directly from the transmittance data, and a Kramers-Kronig analysis that combined the current data with data from the literature was performed to determine the dispersive part of the index of refraction. Finally, two different sum-rule tests were performed that indicated the good consistency of the data.