Genotoxicity analysis of different magnetite-based nanoparticles applied in chemical catalysis processes

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A molecular dynamics simulation of hydrogen atoms collisions on an H-preadsorbed silica surface

The interaction of hydrogen atoms and molecules with a silica surface is relevant for many research and technological areas. Here, the dynamics of hydrogen atoms colliding with an H-preadsorbed -cristobalite (001) surface has been studied using a semiclassical collisional method in conjunction with a recently developed analytical potential energy surface based on Density Functional Theory (DFT) calculations. The atomic recombination probability via an Eley-Rideal (E-R) mechanism as well as the probabilities for other competitive molecular surface processes have been determined in a broad range of collision energies (0.04-3.0) eV eV) for off-normal (v=45°) and normal (v=0°) incidence and for two different surface temperatures (TS = 300 and 1000 K). H2,gas molecules form in roto-vibrational excited levels while the energy transferred to the solid surface is below of 10% for all simulated conditions. Finally, the global atomic recombination coefficient (E-R) and vibrational state resolved recombination coefficients (v) were calculated and compared with the available experimental values. The calculated collisional data are of interest in chemical kinetics studies and fluid dynamics simulations of silica surface processes in H-based low-temperature, low-pressure plasmas

Molecular dynamics study of hydrogen atom recombination over silica, based on a new analytical DFT potential energy surface

A new analytical potential energy surface (PES) based on new density functional theory data is constructed for the interaction of atomic hydrogen with both a clean and an H-preadsorbed -cristobalite (001) surface. For the atomic interaction, six adsorption sites have been considered, the Si site (T1') being the most stable one. The PES was developed as a sum of pairwise atom-atom interactions between the gas-phase hydrogen atoms and the Si and O atoms of the -cristobalite surface. A preliminary molecular dynamics semiclassical study of the different heterogeneous processes (e.g., H2 formation via Eley-Rideal reaction, H adsorption) that occur when H collides with an H-preadsorbed beta-cristobalite (001) surface was carried out. The calculations were performed for collisional energy in the range (0.06 ≤ Ekin ≤ 3.0 eV), normal incidence and a surface temperature Tsurf = 1000 K. The recombination probability reaches its maximum value of approximately 0.1 for collisional energies in the range 0.3 ≤ Ekin ≤ 0.8 eV. The H2 molecules are formed in medium-lying vibrational levels, while the energy exchanged with the surface in the recombination process is very low

Alteraciones anatómicas y funcionales en la muñeca después de la fractura de la extremidad distal del radio

Se revisaron retrospectivamente 75 casos de fracturas de la extremidad distal del radio tratadas ortopédicamente. Los resultados se valoraron desde el punto de vista anatómico y funcional. En el 49% de los casos existió trazo articular y en el 23% se asoció la lesión de la apó- fisis estiloides del cúbito. Asimismo obtuvimos un 60% de excelentes y buenos resultados a pesar de existir en el 37% de los casos complicaciones evolutivas.A series of 75 cases with fracture of the distal radius treated by conservative methods were retrospectively reciewed. Results were evaluated from anatomical and functional standpoints. In 49% of cases there was an articular extension of the fracture, and 23% had an associated fracture of the ulnar styloid process. Satisfactory outcome was achieved in 60% of cases, although there way 37% of cases showing complications during follow-up

Mutational status of K- ras and TP53 genes in primary sarcomas of the heart

We investigated three patients with cardiac angiosarcomas and two with cardiac rhabdomyosarcomas, all for mutations at exons 5, 6, 7 and 8 of the p53 gene and at exon 1 of K- ras. No point mutations were observed in the p53 gene in any of the five cases; however, at exon 1 of K- ras, three patients (60%) presented the same mutation at the first base of codon 13 (G to A transition). Interestingly, this mutation was detected in both rhabdomyosarcoma and angiosarcoma histologic sarcoma types. © 2000 Cancer Research Campaig

Factores pronósticos del resultado de la quimionucleosis

Los resultados exitosos de la quimionucleosis dependen íntimamente de una estricta selección de los pacientes. En el presente trabajo se revisa la influencia de diferentes factores preoperatorios, clínicos y radiológicos, sobre el resultado de la quimionucleosis a los dos años de evolución, a través de un estudio estadístico de los casos. Los autores destacan como factores de mal pronóstico, en su casuística, las lumbalgias aisladas o prolongadas y el régimen laboral autónomo. Ni el tamaño ni la localizatción, central o lateral, de la imagen herniaria influyeron de manera estadística significativa en el resultado de la discolisis. Tampoco el número de discos explorados o inyectados, ni la presencia de signos radiológicos o tomodensitométricos asociados a la hernia discal sintomática.Successful results of chemonucleolysis depend specially on a strict patient selection. In this paper the influence of different preoperative, clinical and radiologic factors on the results two years after chemonucleolysis, is reviewed through the statistical analysis of the cases. The author s hav e observed the isolated or persistent low back pain (rather than sciatica), and being an autonomous worke r as poor prognosis factors in their environment. Size and site, either midline or lateral, of the disc herniation did not influence the results of chemonucleolysis with statistical significance; nor did the number of discs explored or injected, neither the presence of radiologic or tomodensitometric findings associated with symptomatic disc herniation

Atomic and molecular data for spacecraft re-entry plasmas

The modeling of atmospheric gas, interacting with the space vehicles in re-entry conditions in planetary exploration missions, requires a large set of scattering data for all those elementary processes occurring in the system. A fundamental aspect of re-entry problems is represented by the strong non-equilibrium conditions met in the atmospheric plasma close to the surface of the thermal shield, where numerous interconnected relaxation processes determine the evolution of the gaseous system towards equilibrium conditions. A central role is played by the vibrational exchanges of energy, so that collisional processes involving vibrationally excited molecules assume a particular importance. In the present paper, theoretical calculations of complete sets of vibrationally state-resolved cross sections and rate coefficients are reviewed, focusing on the relevant classes of collisional processes: resonant and non-resonant electron-impact excitation of molecules, atom-diatom and molecule-molecule collisions as well as gas-surface interaction. In particular, collisional processes involving atomic and molecular species, relevant to Earth (N2, O2, NO), Mars (CO2, CO, N2) and Jupiter (H2, He) atmospheres are considered

Elemental nitrogen partitioning in dense interstellar clouds

Many chemical models of dense interstellar clouds predict that the majority of gas-phase elemental nitrogen should be present as N2, with an abundance approximately five orders of magnitude less than that of hydrogen. As a homonuclear diatomic molecule, N2 is difficult to detect spectroscopically through infrared or millimetre-wavelength transitions so its abundance is often inferred indirectly through its reaction product N2H+. Two main formation mechanisms each involving two radical-radical reactions are the source of N2 in such environments. Here we report measurements of the low temperature rate constants for one of these processes, the N + CN reaction down to 56 K. The effect of the measured rate constants for this reaction and those recently determined for two other reactions implicated in N2 formation are tested using a gas-grain model employing a critically evaluated chemical network. We show that the amount of interstellar nitrogen present as N2 depends on the competition between its gas-phase formation and the depletion of atomic nitrogen onto grains. As the reactions controlling N2 formation are inefficient, we argue that N2 does not represent the main reservoir species for interstellar nitrogen. Instead, elevated abundances of more labile forms of nitrogen such as NH3 should be present on interstellar ices, promoting the eventual formation of nitrogen-bearing organic molecules.Comment: Accepted for publication in the Proceedings of the National Academy of Sciences of the United States of America - published online since June 11, 201