Descripción: A recently reported symmetry breaking of density profiles of fluid argon confined by two parallel solid walls of carbon dioxide is studied. The calculations are performed in the framework of a nonlocal density functional theory. It is shown that the existence of such asymmetrical solutions is restricted to a special choice for the adsorption potential, where the attraction of the solid-fluid interaction is reduced by the introduction of a hard-wall repulsion. The behavior as a function of the slit's width is also discussed. All the results are placed in the context of the current knowledge on this matter. © 2008 American Institute of Physics.

Descripción: A comparison of the compressibility factors of argon and xenon reduced in terms of the Kihara intermolecular core model potential is presented. It is found that corresponding-states behavior is better obeyed by using the Kihara rather than the Lennard-Jones potential. The results of this paper indicate that the assumption of the pairwise additivity of the potential seems to be valid within the range covered by the presently available experimental data.

Descripción: A stationary, one-dimensional fluid model is presented to describe the interelectrode region of a nonfiltered vacuum arc operated with a background gas. The model includes the electron energy equation and the main elastic and inelastic atomic processes among metallic ions, electrons, and gas particles. To validate the model predictions an experimental study of the plasma-neutral gas structure, using a titanium (Ti) cathode and argon (Ar) as the background gas, is presented. The measured electron temperature and the experimental dependence on the pressure of neutral Ti and Ar spectroscopic emission lines are well reproduced, using a simple atomic model to interpret the plasma radiation emission. © 2006 American Institute of Physics.

Descripción: A simple model that employs a periodic, planar array of parallel cylinders representing the nanotubes is presented. Using this method, the existence of several phase transitions in the film is demonstrated. These include both two-dimensional (2D) transitions and quasi-1D transitions.

Descripción: High resolution spectra in polarized light of oriented crystalline films of chloroform at 77°K were obtained. The ratio of intensities of Davydov components for different angles of polarization were also determined. Comparison with the oriented gas model approximation allowed the assignment of components to the proper representations of the D 2h factor group : all bands were assigned to the infrared active factor group symmetry species B 1u, B 2u, and B 3u corresponding to vibrations along a, b, and c crystallographic axes. Comparison with results of measurements in solid solutions in argon made by King allowed the distinction between crystallographic effect and isotopic shifts.

Descripción: We present the design of phase shift interferometer for the extreme ultraviolet (EUV) that will be used with the illumination provided by a table top Ne-like Ar laser emitting at 46.9 nm. We develop a model that computes the beam propagation trough the instrument, taking into account the influence of the fluctuations from shot-to-shot of the pulsed EUV laser on the retrieved wavefront.

Descripción: Using high energy, pulsed X-rays, generated by a 4.7 kJ Plasma Focus operated with deuterium - argon admixtures, images of fast rotating metallic pieces were obtained. This illustrates the potential application of Plasma Focus devices for non invasive scanning of moving metallic objects. The samples for radiographic imaging were located outside the plasma focus chamber. High-sensitivity, fast-response commercial radiographic film was used as X-ray detector. The use of small doses of argon helps to enhance both the neutron production and the hard X-ray emission. By analyzing the mean attenuation of the studied radiation in different metals, an X-ray effective energy of about 100 keV was obtained.

Descripción: Cerro Falkner is composed of granitic rocks underlying volcanic rocks of the Ventana Formation of Paleogene age. Those intrusives are graniodioritic in composition, metaluminous to peraluminous, subalkaline, with characteristics of volcanic arc granites that are concordant with other granitoids of the Cordillera Patagónica Septentrional's northern segment. The age obtained by the K-Ar method on tschemakitic amphiboles (125 ± 20 Ma) points out a minimun age from the lower Cretaceous for the Cerro Falkner's granodiorite. Therefore the use of the term Los Machis Formation (Upper Cretaceous) would be incorrect for these rocks. This age, allows us to relate the granitic rocks on the study area to the lower Cretaceous, coeval with the volcanism of the Divisadero Group.

Descripción: The characteristic geometry of a pulsed capillary discharge (PCD), a narrow open end tube with a large aspect ratio, establishes natural conditions for the generation of plasma jets, that propagate in the neutral background gas surrounding the capillary. We have investigated the plasma jet emission in a PCD, with electron beam assisted on-axis initiation. A local storage capacitor, coaxial with the capillary assembly, is pulse charged up to a maximum of -11 kV, which results in an initial ∼ 10 ns, ∼ 2 kA current pulse. The discharge is operated in Argon and Nitrogen, in a continuous pulsing mode, at frequencies between 5 to 20 Hz, and in a pressure range between 300 to 1100 Torr. A fast Langmuir probe, placed at the anode side, close to the capillary exit, is used to measure the characteristic electron temperature (Te) and electron density (Ne) of the plasma jets. Results obtained in Nitrogen at 10 Hz indicate that Te is in the 10 to 60 eV range with Ne of the order of 1014 (cm-3). Significant changes in the probe floating potential are observed for a fixed operating pressure when the pulsing frequency is varied, which can be ascribed to the presence of metastables in the gas fed into the capillary, which result from the interaction of the plasma jet with the plenum gas, at the cathode side. The presence of metastables reduces the energy cost involved in the capillary plasma production, which results in a pulsing frequency dependence of the plasma parameters. © 2006 American Institute of Physics.