Collision dynamics of cytosine under proton irradiation

In the framework of the time-dependent density-functional theory, applied to valence electrons, coupled non-adiabatically to molecular dynamics of ions, the collision dynamics of cytosine impacted by proton is studied. We especially focus on the effect of the collision orientations on the damage of cytosine by choosing two collision orientations taking the oxygen atom on the double bond CO as the collision site with the incident energy of proton ranging from 150 eV to 1000 eV. First, two collision dynamical processes are explored by analyzing the molecular ionization, the ionic position and the kinetic energy, the energy loss of proton and the electronic density evolution. The results show that the damage process of cytosine induced by proton impact is mainly the capture of electrons by proton, the departments of ions and groups as well as the opening of ring. It is found that the orientation has little effect on the loss of the kinetic energy of proton, which is about 21.5[Formula: see text] of the incident energy of proton. Although the scattering angle [Formula: see text] has a polynomial relationship with [Formula: see text] in both cases, it is greatly affected by the orientation. When [Formula: see text] eV, the scattering angle of proton colliding with O along the x-axis is greater than that of proton colliding with O along the y-axis. The orientation also has a great effect on the mass distribution of the fragments and the fragmentation route. When proton moves along the x-axis, the fragmentation route is that O leaves the cytosine and the rest keeps on vibration, while products are not only related to the incident kinetic energy, but also show diversity when proton moves along the y-axis.

Characteristics of the projectile and target fragments produced in 84Kr36 — emulsion interaction at 1GeV per nucleon

In the present analysis, we have focused on the emission characteristics of the projectile and target fragments produced from the interaction of [Formula: see text]Kr with nuclear emulsion at 1 A GeV. We have studied the variation of the fragmentation parameter for singly charged [Formula: see text], doubly charged [Formula: see text], lower multiple-charged [Formula: see text]–[Formula: see text], medium multiple-charged [Formula: see text]–[Formula: see text] and higher multiple-charged [Formula: see text], projectile fragments with respect to mass of the projectile and found that they are showing the different behaviors for different projectile fragments. We have also studied the emission behavior of shower particles, with respect to the black and gray particles. The present studies show that the production of shower particles strongly depends on the incident kinetic energy of the projectile and also depending on the interaction of the different types of target nuclei of nuclear emulsion.

Experimental Dynamical Characterization of Beach Tennis Rackets by Modal Analysis

The term sweet spot is used for tennis racket in describing that point or region where the ball should be hit for optimal results. From a vibration standpoint, the sweet spot is determined by the location of the nodal lines across the racket head. In this paper, several methodologies based on modal analysis techniques are explored in order to estimate such a sweet spot for a beach tennis racket. Particular attention was addressed in the detection of the optimal boundary conditions to which the beach tennis racket should be constrained. It is the first time this item is dynamically characterized by experimental techniques. Test results are presented and the sweet spot related to minimal vibration perception is identified for a beach tennis racket. A further experimental study is also carried out in order to identify the Maximum Coefficient of Restitution in beach tennis rackets; this coefficient is related to racket efficiency and characterized by a minimum absorption of the ball incident kinetic energy by the racket. This study could be useful for design, development and practical use of beach tennis rackets.

Deposition of Gan Films Using Seeded Supersonic Jets

GaN films were deposited on sapphire (0001) from triethylgallium (TEG) and NH3 seeded in separate He free jets. as the dissociative chemisorption of NH3 is expected to be rate-limiting in GaN growth, the NH3/He nozzle temperature was varied to control the incident kinetic energy of the NH3 molecules. Using an NH3/TEG flow ratio of 205 and an NH3/He nozzle temperature of 400°C, stoichiometric films were deposited at substrate temperatures ≥530°C. Scanning electron microscopy revealed that films deposited at 580°C are polycrystalline α-GaN with randomly oriented 0.5-μm grains. Films with a closely similar morphology are deposited by using an NH3/He nozzle temperature of 90°C. IN contrast, films deposited at 580°C using an NH3/He nozzle temperature of 510°C consist of whiskers (aspect ratio = c A. 4) which exhibit a-GaN (0001)/sapphire (0001) heteroepitaxy, as evidenced by X-ray diffraction and reflection high-energy electron diffraction.

Dissociative Chemisorption at Hyperthermal Energies: Benchmark Studies in Group IV Systems

We present a review of our recent work concerning supersonic molecular beam scattering of thin film precursors from the Si(100) and Si(111) surfaces. Both SiH4 and Si2H6 exhibit translationally activated dissociation channels at sufficiently high incident kinetic energies, (E┴) 0.5 eV. the dominant variables under our reaction conditions are the incident kinetic energy and the angle of incidence, whereas mean internal energy and substrate temperature play relatively minor roles. the former two variables couple to produce a universal relationship between the reaction probability and a scaled kinetic energy given by (E┴) = Eі[(l-Δ)cos2θі + 3Δsin2θі], where θі is the angle of incidence, a is a corrugation parameter, and 0 ≤ Δ ≤ 1. IN addition to the reaction probability, the reaction mechanism for Si2H6 is also dependent upon incident kinetic energy and surface structure, where a SiH4(g) production channel is observed on the Si(111)-(7x7) surface at low to moderate incident kinetic energies. the reactions of SiH3CH3 and PH3 provide convenient comparative examples. Methylsilane, reacting on a β-SiC surface, exhibits a translationally activated dissociation channel, similar to what is observed for SiH4 and Si2H6. Phosphine, on the other hand, exhibits the characteristics of trapping, precursor-mediated dissociative chemisorption. these results act to underscore the important role played by the frontier orbital topology, even at hyperthermal incident kinetic energies.

The Effect of Incident Kinetic Energy on Stress in Sputter-Deposited Refractory-Metal Thin Films

ABSTRACTIn magnetron sputter deposition the intrinsic stress in refractory-metal films changes from compressive to tensile on increasing the working-gas pressure. This pressure dependence is linked to the particle transport process from target to substrate during deposition. In this work we apply a Monte Carlo (MC) technique to simulate the transport of sputtered atoms and reflected neutrals in a background gas. Specific examples of Cr, Mo and W thin film growth in Ar and Ne gas ambients are presented. Trends in thermalization of the depositing atoms coincided with the observed trends in the compressive-to-tensile stress curves, for the different target and working-gas combinations studied. Furthermore, a quantitative correlation between the stress transition pressures and the incident kinetic energy of both sputtered atoms and reflected neutrals during film growth was found. In this case the contribution of the latter species was weighted with a relatively low factor.