204 research outputs found
Small-Size Resonant Photoacoustic Cell of Inclined Geometry for Gas Detection
A photoacoustic cell intended for laser detection of trace gases is
represented. The cell is adapted so as to enhance the gas-detection performance
and, simultaneously, to reduce the cell size. The cell design provides an
efficient cancellation of the window background (a parasite response due to
absorption of laser beam in the cell windows) and acoustic isolation from the
environment for an acoustic resonance of the cell. The useful photoacoustic
response from a detected gas, window background and noise are analyzed in
demonstration experiments as functions of the modulation frequency for a
prototype cell with the internal volume ~ 0.5 cm^3. The minimal detectable
absorption for the prototype is estimated to be ~ 1.2 10^{-8} cm^{-1} W
Hz^{-1/2}.Comment: 11 pages, 5 figure
Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell during initial stage of shell expansion
Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell, created under laser heating of nanoparticle in water, were theoretically investigated. Vapor shell expansion leads to decreasing up to one to two orders of magnitude in comparison with initial values of scattering and extinction of the radiation with wavelengths 532 and 633 nm by system while shell radius is increased up to value of about two radii of nanoparticle. Subsequent increasing of shell radius more than two radii of nanoparticle leads to rise of scattering and extinction properties of system over initial values. The significant decrease of radiation scattering and extinction by system of nanoparticle-vapor shell can be used for experimental detection of the energy threshold of vapor shell formation and investigation of the first stages of its expansion
In situ measurement of bovine serum albumin interaction with gold nanospheres
Here we present in situ observations of adsorption of bovine serum albumin (BSA) on citratestabilized
gold nanospheres. We implemented scattering correlation spectroscopy as a tool to
quantify changes in the nanoparticle Brownian motion resulting from BSA adsorption onto the
nanoparticle surface. Protein binding was observed as an increase in the nanoparticle
hydrodynamic radius. Our results indicate the formation of a protein monolayer at similar albumin
concentrations as those found in human blood. Additionally, by monitoring the frequency and
intensity of individual scattering events caused by single gold nanoparticles passing the
observation volume, we found that BSA did not induce colloidal aggregation, a relevant result
from the toxicological viewpoint. Moreover, to elucidate the thermodynamics of the gold
nanoparticle-BSA association, we measured an adsorption isotherm which was best described by
an anti-cooperative binding model. The number of binding sites based on this model was
consistent with a BSA monolayer in its native state. In contrast, experiments using poly-ethylene
glycol capped gold nanoparticles revealed no evidence for adsorption of BSA
Influence of shear stress and size on viability of endothelial cells exposed to gold nanoparticles
Ensuring road safety on the basis of engineering-psychological evaluation of drivers labour
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