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  • 1
    Electronic Resource
    Electronic Resource
    Evidence of chemical reactions in the hydroxyapatite laser ablation plume with a water atmosphere (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3289-3293 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The expansion dynamics of the ablation plume generated by KrF laser irradiation of hydroxyapatite targets in a 0.1 mbar water atmosphere has been studied by fast intensified charge coupled device imaging with the aid of optical bandpass filters. The aim of the filters is to isolate the emission of a single species, which allows separate analysis of its expansion. Images obtained without a filter revealed two emissive components in the plume, which expand at different velocities for delay times of up to 1.1 μs. The dynamics of the first component is similar to that of a spherical shock wave, whereas the second component, smaller than the first, expands at constant velocity. Images obtained through a 520 nm filter show that the luminous intensity distribution and evolution of emissive atomic calcium is almost identical to those of the first component of the total emission and that there is no contribution from this species to the emission from the second component of the plume. The analysis through a 780 nm filter reveals that atomic oxygen partially diffuses into the water atmosphere and that there is a contribution from this species to the emission from the second component. The last species studied here, calcium oxide, was analyzed by means of a 600 nm filter. The images revealed an intensity pattern more complex than those from the atomic species. Calcium oxide also contributes to the emission from the second component. Finally, all the experiments were repeated in a Ne atmosphere. Comparison of the images revealed chemical reactions between the first component of the plume and the water atmosphere. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369673
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  • 2
    Electronic Resource
    Electronic Resource
    Surface treatment of titanium by Nd:YAG laser irradiation in the presence of nitrogen (1999)
    Springer
    Applied physics 69 (1999), S. S699 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 62.20 Qp; 68.55.Jk; 81.65.Lp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. This work presents the surface treatment of commercial titanium alloy by means of a Nd:YAG (1.064 μm) laser in the presence of nitrogen. The treated surface was characterised by using scanning electron microscopy, atomic force microscopy, X-ray diffraction, secondary ion mass spectrometry, UV-visible spectrophotometry and microindentation. Experimental results show the formation of a nitrogen-rich layer, 500 nm thick, with a surface morphology characterised by the presence of polygonal structures which suggest that melting occurred under the action of the laser. The δ phase of titanium nitride was identified, in addition to a nitrogen in α-titanium solid solution. The reflectance spectrum of the yellow-golden sample is similar to that of deposited titanium nitride thin films. The hardness of the treated surface was measured by microindentation and found to be 14 GPa, a value three times higher than that of the titanium alloy. In scratch tests the nitrided layer detached at a load of 0.9 N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390051509
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of hydroxyapatite laser ablation plumes in a water atmosphere (1998)
    Springer
    Applied physics 67 (1998), S. 289-294 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 42.62.Be; 78.47.+p; 81.15.Fg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: 4  m/s, shows the development of a shock wave in its front, resulting from the interaction between the species released from the target and the background gas. The water vapor slows down this component up to values of about 3×103 m/s following a behavior that can be well described by the dynamics of a spherical shock wave. The low intensity of emission of the second component has not allowed us to analyze its dynamics. The third and slowest component expands at a constant velocity of 5×102 m/s and is constituted by hot particulates leaving the target. Spectra recorded in the shock front have shown the presence of emission lines arising from Ca I, Ca II, P I and some impurities, and two strong emission bands that can be assigned to some sort of calcium oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050773
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  • 4
    Electronic Resource
    Electronic Resource
    Study of the plume generated by Nd:YAG laser ablation of a hydroxyapatite target (1999)
    Springer
    Applied physics 69 (1999), S. S183 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 42.62.Be; 78.47.+p; 81.15.Fg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The plume generated by Nd:YAG laser ablation of a hydroxyapatite target has been investigated in vacuum and at 0.1 and 0.2 mbar of water vapor. The investigation has been carried out by means of fast intensified CCD imaging with the aid of bandpass interferential filters that allow the following single species to be isolated: neutral calcium, calcium oxide radicals and neutral oxygen. Results obtained in vacuum reveal that expansion takes place at a constant velocity of about 2×104 m/s for the atomic species and about 3×103 m/s for the molecular ones and that emission is completely dominated by emissive neutral calcium. When ablation is carried out in a water atmosphere, the background gas confines the species in the leading edge of the plume, which results in the formation of a planar shock wave at 0.1 mbar and a spherical shock wave at 0.2 mbar. Comparison of the images with those obtained at 0.1 mbar of Ne has revealed the existence of chemical reactions between the plume and the water atmosphere, leading to the formation of calcium oxide radicals. In that case, plume emission is dominated by these molecular species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390051380
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  • 5
    Electronic Resource
    Electronic Resource
    A novel nonsense mutation at Glu-631 in a Spanish family with complement component 7 deficiency (1999)
    Springer
    Journal of human genetics 44 (1999), S. 215-218 
    Details
    ISSN: 1435-232X
    Keywords: Key words Nonsense mutation ; Complement component 7 ; Deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Deficiency of the seventh component of complement (C7D) is frequently associated with recurrent neisserial infections. We report in the present study the genetic basis for C7D in a Spanish family. We used exon-specific polymerase chain reaction (PCR)/single-strand conformation polymorphism (SSCP) analysis as a screening step for mutations, followed by direct sequencing of the target exon. The mutation in the proband was a homozygous G-to-T transversion at nucleotide 1957, the first nucleotide of the codon GAG for Glu-631, leading to a stop codon TAG (E631X). Our result provides further evidence that the molecular pathogenesis of C7D is heterogeneous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100380050146
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  • 6
    Electronic Resource
    Electronic Resource
    A study of the molecular orbital localization into an extended Hartree - Fock approach: Application to the BeH2 ground state (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 493-504 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article, we present a study of the localization and properties of the molecular orbitals (MOs) of polyatomic systems by using a comprehensive version of the G1 model. In this version, the wave function is written as a DODS product of univocally determined spin orbitals (MOs), “projected” on the singlet ground state. A procedure for determining the MOs is given and applied to the BeH2 ground state. Equivalent split shell and localized MOs are found. The Be orbitals are seen to exhibit sp hybridization and the localized valence MOs are found to produce - 13.7 kcal/mol localization energy. Multistructural calculations are carried out and show that the present approach is able to describe localized and well-oriented bonds whenever the molecule under study presents only a single well-defined nonresonant chemical structure. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Ground-state and some excited states of Li2 by the half-projected Hartree-Fock method (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 54 (1995), S. 305-311 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The half-projected Hartree-Fock wave function (HPHF) is one of simplest models for introducing some electronic correlation effects. In this model, the wave function is built up with only two Slater determinants. This simple form suggests its application for the direct determination of singlet excited states. On the other hand, because the HPHF model does not mix singlet and triplet states with Ms = 0, it can be used for determining independently singlet and triplet states without any mutual contamination. In the present work, we applied this model to determine nine electronic states of the lithium molecule; one of them exhibits even the same symmetry of the fundamental one. For this purpose, the 6-311G(d) basis was used. Potential energy curves were determined and some spectroscopic constants derived. The numerical results were compared with the available experimental data, as well as with other theoretical values. © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560540506
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