A Scheme for Information Erasure in a Double-Well Potential

We design an experimental scheme to realize one-bit information erasure and restoring processes by considering an overdamped colloidal particle in a double-well optical trap, which is added by a controllable laser tweezer. Using the Monte Carlo method, we simulate numerically the Langevin equation to calculate the mean work spent during the entire process and validate the entropy production fluctuation theory. Our result shows that the distribution of entropy production becomes narrow with increasing temperature and becomes stationary, represents the diminishing extent of irreversibility.     

Mechanism for Alternating Electric Fields Induced-Effects on Cytosolic Calcium

In this work, from the point of calcium ions in the cytosol, we extend a V_m-[Ca²⁺]_cyt model to explain the changes of action potential V_m of the plasma membrane and the calcium concentration in the cytosol [Ca²⁺]_cyt under an alternating electric field in cells. An alternating external electric field may exert an oscillating force to each of the free electrolytes, existing on both sides of the plasma membrane. The mechanism for the alternating electric field induced-effects on V_m and [Ca²⁺]_cyt is elucidated. The simulation results show a correlation between the changes of [Ca²⁺]_cyt and the alternating electric field. When the numerical ratio between the intensity E₀(mV/m) and the frequency υ (Hz) of the field was about 1-2, the [Ca²⁺]_cyt signal is changed dramatically. The bioactive changes of [Ca²⁺]_{_cyt} appear at low frequency, in the range of 0-100Hz.     

Computer simulation study of the Levy flight process

The random walk simulation of a Levy flight shows a linear relation between the mean square displacement 〈r²〉 and time. We have analyzed different aspects of this linearity. It is shown that the restriction of jump length to a maximum value (l_m) affects the diffusion coefficient, even though it remains constant for l_m greater than 1464. So, this factor has no effect on the linearity. In addition, it is shown that the number of samples does not affect the results. We have demonstrated that the relation between the mean square displacement and time remains linear in a continuous space, while continuous variables just reduce the diffusion coefficient. The results also imply that the movement of a Levy flight particle is similar to the case in which the particle moves in each time step with an average jump length 〈l〉. Finally, it is shown that the non-linear relation of the Levy flight will be satisfied if we use a time average instead of an ensemble average. The difference between the time average and ensemble average results shows that the Levy distribution may be a non-ergodic distribution.     

Influence of sublayer atoms on Si(100) surface reconstructions

Influence of sublayer atoms on Si(100) surface reconstruction has been examined with density functional theory and molecular dynamic simulation. We found that the displacements of sublayer atoms under the buckled dimer affect the motions of their neighboring atoms and thus play an important role in determining the surface reconstructions. The present results reveal the relationship between the surface dimer reconstruction and the motion of the sublayer atoms and provide an account for experimental observations of Si(100) surface reconstructions at very low temperatures.     

Molecular dynamics simulation about porous thin-film growth in secondary deposition

The thin film growth has been confirmed to be assembled by an enormous number of clusters in experiments of CVD. Sequence of clusters’ depositions proceeds to form the thin film at short time as gas fluids through surface of substrate. In order to grow condensed thin film using series of cluster deposition, the effect of initial velocity, substrate temperature and density of clusters on property of deposited thin film, especially appearance of nanoscale pores inside thin film must be investigated. In this simulation, three different cluster sizes of 203, 653, 1563 atoms with different velocities (0, 10, 100, 1000 and 3000 m/s) were deposited on a Cu(0 0 1) substrate whose temperatures were set between 300 and 1000 K. Four clusters and one cluster were used in primary deposition and secondary deposition, respectively. We have clarified that adhesion between clusters and substrate is greatly influenced by initial velocity. As a result, the exfoliation pattern of deposited thin film is dependent on initial velocity and different between them. One borderline dividing whole region into porous region and nonporous region are obtained to show the effect of growth conditions on appearance of nanoscale pores inside thin film. Moreover, we have also shown that the likelihood of porous thin film is dependent on the point of impact of a cluster relative to previously deposited clusters.     

Imaging and post-processing of laser-induced fluorescence from NO in a diesel engine

Received: 11 July 1996/Revised version: 12 November 1996     

Visualisation of a supersonic free-jet expansion using laser-induced fluorescence spectroscopy: Application to the measurement of rate constants at ultralow temperatures

2 Σ⁺, v^′=0) by air at 26±4 K. A value of 2.56±0.40×10^-10 molecule^-1 cm³ s^-1 was obtained, a factor of more than four higher than at room temperature, and consistent with attractive forces dominating the quenching of OH(A²Σ⁺). A d etailed computational fluid dynamics (CFD) simulation of the supersonic free-jet expansion was performed, providing a two-dimensional visualisation of temperature and density variations throughout the expansion. The CFD calculations reproduced the salient features of the experimental temperature and density profiles along the centreline. Comparison between experiment and computation has allowed validation of CFD codes. Received: 31 January 1997/Revised version: 24 March 1997     

Interaction of electronic structure and nuclear dynamics on the S1 reaction surface for the ring opening of cyclohexadiene

For the ultrafast photoinduced ring opening of cyclohexadiene the S₁ state plays a central role, providing the possibility to rapidly decay to the ground state. In this paper we follow the path of a wavepacket propagating in the reactive coordinate space of the S₁ surface. We present a detailed analysis of the corresponding electronic and nuclear motions. With the help of a projection method and a normal-mode analysis, the vibrational modes driving the reaction might be detected experimentally. Received: 10 November 1999 / Published online: 13 July 2000     

Quantitative evaluation about property of thin-film formation

Chemical vapor deposition (CVD) is gradually emphasized as one promising method for nanomaterial formation. Such growth mechanism has been mainly investigated on basis of experiment. Due to large cost of the equipment of experiment and low level of current measurement, the comprehension about authentic effect of formation condition on properties of nanomaterial is limited in qualitative manner. Three quantitative items: flatness of primary deposition, adhesion between cluster and substrate, and degree of epitaxial growth were proposed to evaluate the property of thin film. In this simulation, three different cluster sizes of 203, 653, 1563 atoms with different velocities (0, 10, 100, 1000, 3000 m/s) were deposited on a Cu(0 0 1) substrate whose temperatures were set between 300 and 1000 K. Within one velocity range, not only the speed of epitaxial growth and adhesion between thin film and substrate were enhanced, but also the degree of epitaxy increased and the shape of thin film became more flat with velocity increasing. Moreover, the epitaxial growth became well as the temperature of substrate was raised within a certain range, and the degree of epitaxy of small cluster was larger than larger cluster. The results indicated that the property of thin film could be controlled if the effect of situations of process was made clear.     

Study ofA+A→0 with probability of reaction and diffusion in one dimension and in fractal substrata

We present Monte Carlo simulations of annihilation reactionA+A0 in one dimensional lattice and in three different fractal substrata. In the model, the particles diffuse independently and when two of them attempt to occupy the same substratum site, they react with a probabilityp. For different kinds of initial distributions and in the short an intermediate time regimes, the results for 0<p1 show that the density ofA particles approximately behaves as (t)=(t=0)f(t/t ₀), with the scaling functionf(x)1 forx1,f(x)x ^–y forx1. The crossover timet ₀, behaves ast _{0 0eff} ^–1y where theeffective initial density _0eff depends on (t=0) and on the kind of initial distribution. For a given substratum of spreading dimensiond _s, the exponenty(d _s/2<y<1) depends only onp and its value increases asp decreases (y1 whenp0). In the very long time regime it is expected thatp(t)t ^–ds/2 independently ofp.     

Computer study of boron and phosphorus at the Si(100)̶2 ╳ 1 surface

The AM1 semiempirical numerical method combined with the geometry optimization procedure was used to study the energetics of active impurities (B, P) in substitutional positions at the Si(100)- surface. It has been found that phosphorus prefers to be in the first layer (in dimers). Boron has the lowest energy in the second layer. Energy profits, counting from the fourth bulk-like layer, for B and P are 1.33 eV and 0.56 eV, respectively. Comparing of the P-Si and P-P dimers energetics has shown that P-Si dimers are more preferable energetically. Received: 26 March 1998 / Accepted: 9 June 1998     

N-acetyl-L-aspartic acid-N'-methylamide with side-chain orientation capable of external hydrogen bonding

In this study, we generated and analyzed the side-chain conformational potential energy hypersurfaces for each of the nine possible backbone conformers for N-acetyl-L-aspartic acid-N' methylamide. We found a total of 27 out of the 81 possible conformers optimized at the B3LYP/6-31G(d) level of theory. The relative energies, as well as the stabilization energies exerted by the side-chain on the backbone, have been calculated for each of the 27 optimized conformers at this level of theory. Various backbone-backbone (N-H ^{. . .} O=C) and backbone-side-chain (N-H ^{. . .} O=C; N-H ^{. . .} OH) hydrogen bonds were analyzed. The appearance of the notoriously absent backbone conformer may be attributed to such side-chain-backbone (SC/BB) and backbone-backbone (BB/BB) hydrogen bonds. Received 10 February 2002 Published online 13 September 2002     

Evaluation of the collisionless contribution to the measured infrared multiphoton decomposition

Some of the problems associated with modelling infrared multiphoton decomposition of gaseous molecules are presented. As an example, the cumulative log normal distribution function model is presented in an experimental context where the effects of laser beam geometry and molecular collisions have been taken into account. It is argued that any laser radial profile other than Gaussian, including tophat, can unnecessarily complicate the testing of a model and should be used with caution.     

Highly localized vibronic wavepackets in large reactive molecules

The ultrafast dynamics of the internal conversion of S₁ azulene and the excited-state intramolecular proton transfer in 2-(2^′-hydroxyphenyl)benzothiazole (HBT) were investigated by pump–probe spectroscopy with tunable pulses as short as 20 fs. In both cases we find very pronounced oscillatory contributions to the transients, which are due to vibrational wavepacket motion in the excited state. The damping times are on the order of 1 ps even for these large reactive molecules in solution at room temperature. For azulene only 2 out of 48 vibrational modes participate and in HBT only 4 out of 69. This high degree of localization of the wavepacket seems to be a general feature, and supports hopes that even for systems of chemical interest coherent control might be possible. Received: 24 January 2000 / Published online: 24 July 2000     

Pulsed CO2 laser induced multiphoton decomposition of cyclobutanone: A comparison of predictions for three models of decomposition probability vs. fluence

The multiphoton decomposition (MPD) probability (f) for photolysis of cyclobutanone (pressure: 0.333 kPa) with a pulsed (pulse width: 40 ns) CO₂ laser tuned to the 9P(20) line, was studied,in a collimated beam geometry, as a function of fluence (=0.75 to 11.7 J/cm²). The values off () were fitted to three suggested 1- or 2-parameter models. Models with two parameters correlated the experimental values equally well, whereas a 1-parameter model was less accurate for low fluences. The MPD yield for two focussed beam geometries was measured and compared to predicted yields obtained by integrating the three models forf () over the focussed beam geometries. All three models predicted yields which agreed well with the measured values.Issued as AECL Contribution Number 8943AECL National Program Summer (1983)     

Theoretical study of the adsorption of CO2 on tungsten carbide nanotubes

The adsorption of CO₂ on the single-walled tungsten carbide nanotubes has been investigated employing density functional theory method. The center of a hexagon of tungsten and carbon atoms in sites on tungsten carbide nanotube surfaces is the most stable adsorption site for CO₂ molecule, with a binding energy of −1.68 eV (−38.72 kcal/mol) and a WO binding distance of 1.95 Å. Furthermore, the adsorption of CO₂ on the single-walled carbon nanotubes has been investigated. Our first-principles calculations predict that the CO₂ adsorptive capacity of tungsten carbide nanotubes is about quadruple that of carbon nanotubes. This might have potential for greenhouse gas detection and bioremediation.     

A polarized CARS investigation of the fine structure population inversion of Cl atoms from laser photolysis of ICl and the quenching of Cl(2 P 1/2) by O2

The time resolved polarized CARS technique has been used to detect Cl atoms produced by photolysis of ICl in the presence and absence of O₂. A population inversion was observed between the ground state electronic levels Cl(² P _1/2) and Cl(² P _3/2). The rate constant for Cl(² P _1/2) decay (quenching + reaction) in ICl was determined to be (3.2±0.2)×10^–13 cm³/molecule×s; the rate constant for Cl(² P _3/2) reaction with ICl was determined to be (7.8±0.5)×10^–12 cm³/molecule×s; and the rate constant for Cl(² P _1/2) quenching by O₂ was determined to be (1.9±0.2)×10^–13 cm³/molecule×s.     

Numerically stable solution of coupled channel equations: The wave function

In two earlier papers a numerically stable solution of the stationary Schrödinger equation for coupled channels was presented. The Schrödinger function and its first derivative were expressed in terms of two matrices: A so-calledlocal reflection matrix (LORE) and aninverse local transmission matrix (INTRA). These matrices obey very simple boundary conditions: They approach asymptotically zero (one) on one side of the reaction path and the reflection (transmission) matrix on the other side. Hence by propagating both matrices along the reaction path one can determine directly the observable scattering matrix elements without ever having to calculate wave functions. On the other hand it is often useful to know the wave functions, for instance in order to interpret scattering data in terms of flow patterns etc. Although the relation between theINTRA-LORE and the wave function is simple, a straight forward calculation is not possible. It would involve an inversion of theINTRA which is numerically ill behaved. In this paper we describe a numerically stable method of computing the wave function and illustrate by two examples of surface reactions.Dedicated to Herbert Wagner on the occasion of his 60th birthday. One of the authors (W.B.) also recalls with great pleasure the stimulating discussions he had with his first graduate student     

Mechanical property of carbon nanotubes with intramolecular junctions: Molecular dynamics simulations

Intramolecular junctions (IMJs) of carbon nanotubes hold a promise of potential applications in nano-electromechanical systems. However, their structure-property relation is still unclear. Using the revised second-generation Tersoff-Brenner potential, molecular dynamics simulations were performed to study the mechanical properties of single-walled to four-walled carbon nanotubes with IMJs under uniaxial tension. The dependence of deformation and failure behaviors of IMJs on the geometric parameters was examined. It was found that the rupture strength of a junction is close to that of its thinner carbon nanotube segment, and the rupture strain and Young's modulus show a significant dependence on its geometry. The simulations also revealed that the damage and rupture of multi-walled carbon nanotube junctions take place first in the innermost layer and then propagate consecutively to the outer layers. This study is helpful for optimal design and safety evaluation of IMJ-based nanoelectronics.     

IR multiple-photon dissociation by a focused uniform beam

An improved analytical method is presented in which the reaction yield in the IR multiple-photon dissociation by a focused uniform beam is expressed in a generalized form as a function of fluence. The analytical solution is derived for a real focusing geometry by assuming the cumulative log-normal distribution (CLND) for the functional form of the dissociation probability vs. fluence. Also presented is a shortcut analytical method with simple and convenient algebraic expressions which approximate the exact analytical solution, thereby speeding up the analysis of experimental data.