ABSTRACT
Carbon nanoscrolls (CNSs) formed spontaneously on the basal plane of highly ordered pyrolytic graphite (HOPG) show winding and unwinding movements when potential steps from 0 V to -0.5 V, -0.6 V and -0.9 V are applied on HOPG immersed in an aqueous electrolyte solution (0.1 M H2SO4). Reversible changes in CNS radial dimensions exceeding 10 nm in the axial direction and 50 nm in the lateral direction are ascribed to variations in the surface tension and electric double-layer structure under applied potentials. Radial motion is observed exclusively on scrolled tube-shaped nanostructures, while other parts of the HOPG surface including planar areas, simple bended and lifted step edges, and kinks remain intact. The mechanism explaining the observed phenomenon is proposed and its significance for prospective applications in electrochemically controlled nanomechanical actuators is outlined.
ABSTRACT
The distribution of pollutants in two urban scale models (point emission source and street canyon with extensive transport) was investigated by means of CO(2) laser photoacoustic spectroscopy in the region of the atmospheric window (9-10 mum). The experimental results of physical modeling are in a good agreement with the numerical calculations performed in the frame of computational fluid dynamic (CFD) modeling. Methanol, ethanol, and ozone (examples of light pollutants), as well as sulfur hexafluoride and 1,2 dichlorethane (examples of heavy pollutants), were selected on the basis of their high resolution spectra acquired by Fourier transform and laser diode spectroscopy.
ABSTRACT
The nu3 fundamental band (C-N stretch) and four associated hot bands (01(1)1-01(1)0, 10(0)1-10(0)0, 02(0)1-02(0)0, and 02(2)1-02(2)0) of natural 79/81Br12C14N have been recorded and analyzed in the 4.8-µm region using an FTIR spectrometer. Analyses of the same hot bands, previously recorded using a diode laser spectrometer, are also presented for the 13C and 15N isotopically labeled species. Copyright 1998 Academic Press.
ABSTRACT
The infrared diode laser spectrum of the nu2 + nu5 - nu2 hot band of acetylene has been observed within the discharge plasma of acetylene diluted in He. The concentration of acetylene in the nu2 state was modulated by applying a few kHz of ac current, and the spectrum of the hot band was recorded selectively by the discharge modulation technique. In total, 46 P, R, and Q-branch lines have been assigned to the nu2 + nu5 - nu2 hot band and molecular constants including the band origin 727.59318(27) cm-1 were derived. The lifetime of acetylene in the nu2 state was measured to be about 1 ms, proving that the nu2 state is metastable. The collisional relaxation rate constant of acetylene in the nu2 state by helium was measured to be k = 8.01 ± 0.19 x 10(-14) cm3 molec-1 s-1. Copyright 1998 Academic Press. Copyright 1998Academic Press
ABSTRACT
The formation of triplet states of photosensitizers and singlet oxygen during reactions sensitized by protoporphyrin IX dimethyl ester (PPDME) and the products of its photo-oxidation in solution were studied by time-resolved spectroscopy. Irradiation with long-wavelength light (670 nm), which is absorbed by the products of photo-oxidation of PPDME, provides lower quantum yields of singlet oxygen than in sensitization with PPDME alone, which absorbs light with a wavelength of 630 nm. Spectroscopic measurements also confirmed the lower rate of sensitized photo-oxidation of bilirubin during irradiation with light with a wavelength of 670 nm.
Subject(s)
Oxygen/metabolism , Photosensitizing Agents/pharmacology , Protoporphyrins/pharmacology , Bilirubin/radiation effects , Lasers , Light , Photochemistry , Photochemotherapy , Singlet Oxygen , Spectrophotometry, Ultraviolet , XenonABSTRACT
Owing to the linearity of the photoacoustic signal, the absorption coefficients of Freons were measured on isotopic (13)C(16)O(2) laser lines.
