This paper describes a study concerning the interaction of nitric oxide with the clean Si(100)2X 1 surface at room temperature. Differential reflectometry in the photon energy range of 2.4 -4.4 eV, Auger electron spectroscopy (KL& 3L2 3 and L» VV), and low-energy electron diffraction have been used to investigate experimentally the chemisorption process of NO on the freshly cleaned Si(100)2X1 surface. Theoretically, the chemisorption process has been modeled by means of the use of quantum-chemical calculation methods [modified (intermediate) neglect of diatomic overlap, MNDO and MINDO/3]. Within this framework we have calculated the binding energy of several possible adsorption sites and the partial local density of states. The latter has been utilized to simulate the loss-corrected Si -L2 3 VV Auger line shape, in the derivative mode, which proved to be a powerful tool for the interpretation of the newly revealed fine structure. The low nitrogen and oxygen coverages (15% of a monolayer) at saturation could be explained by lateral electrostatic repulsion. Also, evidence for molecular adsorption of NO on the Si(100)2X 1 surface at 300 K has been found. Furthermore, the possibility that a missing-dimer defect could play a role in the adsorption process has been considered.
We present an analysis of particle migration in a natural convection flow between parallel plates and within the annulus of concentric tubes. The flow channel is vertically oriented with one surface maintained a t a higher temperature than the other. Particle migration is dominated by advection in the vertical direction and thermophoresis in the horizontal direction. From scale analysis it is demonstrated that particles are completely removed from air flowing through the channel if its length exceeds LC = ( b 4 g / 2 4~v Z ) , where b is the width of the channel, g is the acceleration of gravity, K is a thermophoretic coefficient of order 0.5, and v is the kinematic viscosity of air. Precise predictions of particle removal efficiency as a function of system parameters are obtained by numerical solution of the governing equations. Based on the model results, it appears feasible to develop a practical filter for removing smoke particles from a smoldering cigarette in an ashtray by using natural convection in comhination with thermophoresis.
Inhalation exposure to environmental tobacco smoke (ETS) particles may increase health risks, but only to the extent that the particles deposit in the respiratory tract. We describe a technique to predict regional lung deposition of environmental tobacco smoke particles. Interpretation of particle size distribution measurements after cigarette combustion by a smoking machine in a test room yields an effective emissions profile. An aerosol dynamics model is used to predict indoor particle concentrations resulting from a specified combination of smoking frequency and building factors. By utilizing a lung deposition model, the rate of ETS mass accumulation in human lungs is then determined as a function of particle size and lung airway generation. Considering emissions of sidestream smoke only, residential exposures of nonsmokers to ETS are predicted to cause rates of total respiratory tract particle deposition in the range of 0.4-0.7 pg/day per kg of body weight for light smoking in a well-ventilated residence and 8-13 pg/day per kg for moderately heavy smoking in a poorly ventilated residence. Emissions of sidestream plus mainstream smoke lead to predicted deposition rates about a factor of 4 higher. This technique should be useful for evaluating health risks and control techniques associated with exposure to ETS particles.
This paper describes a study concerning the interaction of nitric oxide (NO) with the clean Si(100)2 x 1 surface in ultra-high vacuum at room temperature. Differential reflectometry (DR) in the photon energy range of 2.4-4.4 eV. Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) have been used to investigate the chemisorption of NO on Si(100)2 x 1. With this combination of techniques it is possible to make an analysis of the geometric and electronic structure and chemical composition of the surface layer. The aim of the present study was to explain the experimental results of the adsorption of NO on the clean Si(100)2 x 1 at 300 K. Analysing the electronic and geometric structure of a simplified stepped 2 x 1 reconstructed Si(100) surface and of the NO molecule in combination with the use of Woodward-Hoffmann rules (WHR) we were able to model a surface defect specific adsorption mechanism. Surface defects such as missing dimer defects seem to play an important role in the adsorption mechanism of NO on the silicon surface. The experimental results are consistent w:,th this developed model. We also suggest a relation between the missing dimer defects and the number of steps on the silicon surface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.