Amino acid adsorption effects on nanotube electronics

We discuss effects of the adsorption of glycine, histidine, phenylalanine, and cysteine on the electronic structure of the metallic (3,3) carbon nanotube through calculations within density functional theory. Results show good nanotube electronic structure stability in the presence of the biomolecules. Molecule-nanotube band mixing and band degeneracy lifting are observed, though the limited extents to which these effects are manifested on the system electronics affirm the weak, noncovalent connection at their interface

Quantum states of hydrogen atom motion on the Pd(111) surface and in the subsurface

We investigate the quantum states of hydrogen atom motion on Pd(111) surface and in its subsurface by calculating the wavefunctions and the eigenenergies for hydrogen atom motion within the framework of the variation method on an adiabatic potential energy surface (PES), obtained through first-principles calculations, for the hydrogen atom motion. The calculated results show that the ground-state wavefunction for the hydrogen atom motion localizes on the face-centered cubic (fcc) hollow site of the surface. The higher excited state wavefunctions are distributed between the first and second layers, and subsequently delocalized under the second atom layer. These suggest that an effective diffusion path of the hydrogen atom into the subsurface area passes through the fcc hollow site to the octahedral sites in the subsurface. Moreover, activation energies for diffusion of H and D atoms over the saddle point of the PES between the fcc hollow site and the first (second) octahedral site are estimated as 598 (882)meV and 646 (939)meV, respectively. Furthermore, the activation energies for diffusion of H and D atoms over the saddle point of the PES between the first (second) octahedral site and the fcc hollow site are estimated as 285 (483)meV and 323 (532)meV, respectively. © IOP Publishing Ltd

Polybutylene terephthalate adhesion on metals: A density functional theory investigation

We investigate the adhesion strength of poly(butylene terephthalate) or PBT on aluminum using density functional theory based energy calculations on periodic models. Instead of dealing with a bigger polymer system, we considered, as a first step, a small scale configuration to examine the key point of adhesion between PBT and Al surface. We placed the PBT monomer horizontally and vertically on aluminum surface. We also considered placing aluminum on top of the bulk PBT. By calculating the total energy of the system when PBT monomer approaches aluminum surface and comparing them with their energies when they are isolated, we obtain the binding energy of PBT on aluminum surface. The adhesion is stronger when the PBT monomer is oriented vertically than horizontally. Strong binding is also observed when the aluminum atom is placed on bulk PBT

Potential energy of hydrogen atom motion on Pd(111) surface and in subsurface: A first principles calculation

We calculate the adiabatic potential energy for hydrogen atom motion on a Pd(111) surface and in a subsurface within the framework of the density functional theory in order to understand the diffusion mechanism of a hydrogen atom from the Pd(111) surface to the subsurface. According to the calculated adiabatic potential energy surface for the hydrogen atom motion up to the third atom layer, an effective diffusion path of the hydrogen atom into the Pd bulk starts from the fcc hollow site on the Pd(111) surface. Moreover, the diffusion path passes through the octahedral site between the first and the second Pd atom layers, the tetrahedral site beneath a Pd atom of the first layer or above the Pd atom of the third layer, and the octahedral site between the second and third layer. © 2007 American Institute of Physics

Multi-angle lidar sensing of traffic aerosol in Manila

Multi-angle lidar sensing of traffic aerosols was conducted in a very busy Manila area. The backscatter coefficients for 355 nm and 532 nm were calculated from Fernald\u27s inversion method using calibration results retrieved from the slant-path method. An aerosol extinction-to-backscatter ratio of 30 sr was assumed in the calculation. Several scans were conducted on 31 July 2003 during peak traffic hours to observe the two-dimensional spatial and temporal distribution of traffic aerosols. The presence of a constant aerosol mass near a busy intersection was observed throughout the scanning period. The calculated backscatter coefficient for these aerosol mass ranged from 3.56×10 -6 m-1sr-1 to 5.01×10-6 m -1sr-1 for 532 nm and 1.76×10-5 m -1sr-1 to 2.02×10-5m-1sr -1 for 355 nm

Density functional calculations for H2 adsorption on Fe(OH) 3 by considering molecular orientation

H2 adsorption on Fe(OH)3 is investigated by using the density functional theory (DFT) for the H2 molecular orientation θ= 10° with respect to the surface normal and that for the H 2 molecular orientation θ = 70°. From the PES results of H2-Fe(OH)3 system, we find that for the H2 molecular orientation θ= 10°, a potential well is at Z = 4.2 Å with a depth of around 4.4 meV while for the H2 molecular orientation θ = 70°, a potential well is at Z = 3.0 Å with a depth of around 17.7 meV. The small binding energy and the positions of potential well with respect to the surface of these adsorption states are typical for physisorption

Examining poly(phenylene sulfide) adhesion using cluster models

Density functional theory-based calculations on representative cluster models have been performed to investigate the adhesion strength of poly(phenylene sulfide) (PPS) onto magnesium, silicon and titanium, in addition to previously studied aluminum, copper, silver, and gold. Energy relations of substrate atom interactions with the sulfur end of a PPS monomer showed strongest binding with titanium and aluminum, while the larger transition metals showed the weakest results. A further investigation on the interaction of aluminum with the sulfur atom of a diphenyl sulfide model suggests a strong orientation dependence of the adhesion process, as shown in the greater preference for the in-plane case

Multi-instrument particulate matter characterization during the 2004 New Year celebration in Manila (14°33.978\u27 N; 120°59.523\u27 E)

Particulate matter from firecracker emission during the 2004 New Year Celebration in Manila (14°33.978\u27 N; 120°9.523\u27 E) were characterized using a horizontal LIDAR, low-volume air sampler, scanning electron microscopy (SEM) and x-ray microanalysis (EDX). Extinction coefficient measurements at 532 and 355nm were made using the LIDAR at an altitude 20m above sea level. 532nm depolarization ratio was also determined. SEM and EDX analysis of air samples collected, simultaneous to the LIDAR experiments, using a low volume impactor/sampler was done. SEM provides morphology and sizes of the particles. EDX analysis on New Year\u27s particles revealed elements used in manufacturing firecrackers such as A, C, Ca, Cl, Cul K, Na, O, Ba, Mg, S, Zn, and Fe

Multi-instrument particulate matter characterization during the 2004 new year celebration in Manila (14°33.978' N; 120°59.523' E)

Particulate matter from firecracker emission during the 2004 New Year Celebration in Manila (14°33.978' N; 120°9.523' E) were characterized using a horizontal LIDAR, low-volume air sampler, scanning electron microscopy (SEM) and x-ray microanalysis (EDX). Extinction coefficient measurements at 532 and 355nm were made using the LIDAR at an altitude 20m above sea level. 532nm depolarization ratio was also determined. SEM and EDX analysis of air samples collected, simultaneous to the LIDAR experiments, using a low volume impactor/sampler was done. SEM provides morphology and sizes of the particles. EDX analysis on New Year's particles revealed elements used in manufacturing firecrackers such as A, C, Ca, Cl, Cul K, Na, O, Ba, Mg, S, Zn, and Fe

Characterization of airborne fine particulate matter by air sampling and electron microscopy during the 2004 New Year fireworks celebration in Manila

Airborne fine participate matter, during the 2004 New Year fireworks festivities, were collected by a low-volume impactor on the third floor of the science and technology research center building (14033.971\u27N,120059.524 \u27E) approximately 30m above sea level located at the LIDAR station in De La Salle University, Malate, Manila in order to investigate the characteristics of fine particle aerosols during the new year festivities. Morphologies and elemental composition of individual particles were analyzed using scanning electron microscope and an energy dispersive x-ray spectrometer. Elemental analysis on the fine particles revealed various elements used for fireworks such as Al, Ba, C, Ca, Cl, Cu, Fe, K, Mg, Na, O, S, and Zn