Papers by Robert A Bellantone
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Physical Review A, 1993
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Laser drilling of metals and the consequent gas dynamics is investigated. A transient mathematica... more Laser drilling of metals and the consequent gas dynamics is investigated. A transient mathematical model is presented for the drilling process which includes: (1) heat conduction and convection; (2) effects of phase change, including vaporization, melting and solidification; and (3) viscous, incompressible flow of melt with a free surface at the melt/vapor interface. The model is evaluated for some two dimensional axisymmetric cases and the results are presented. A transient model for the gas dynamics resulting from the laser induced vaporization in the presence of ambient air is formulated in one dimension. A Knudsen layer analysis is used to model the melt/vapor transition, and flow boundary conditions at the vapor/air interface and at the shock front (when applicable) are included. It was found that the gas dynamics could be modeled by requiring the material derivative of the entropy density to vanish.
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International Journal of Pharmaceutics, 2015
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Physical Review A, 1989
Dielectronic recombination (DR) cross sections and rate coefficients for the H-like and He-like C... more Dielectronic recombination (DR) cross sections and rate coefficients for the H-like and He-like C and O ions are calculated in the zero-field, zero-density limit. The peak rates are approximately (1.2--1.6){times}10{sup {minus}12} cm{sup 3}/sec for all four ions. For the H-like ions, the contribution to total rates from high Rydberg states ({ital n}{ge}6) is found large, accounting for nearly one-half of the total rates. Agreements with earlier estimates are at a {plus minus}5% level. For the He-like ions, the high-Rydberg-state contribution is strongly suppressed because of the extra Auger channel which opens up at {ital n}=5--7. Agreement with previous calculations is again at a 5% level. The DR cross sections for the initial metastable states of the He-like ions are also estimated for a few low-lying resonance states near the DR threshold. The cross section for the 2{ital s} {sup 1}S{r arrow}1s2p {sup 1}P+nl excitation capture is found to be very large.
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Physical Review A, 1991
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Physica Scripta, 1993
Cross sections for resonant transfer excitation followed by X-ray emission (RTEX) are calculated ... more Cross sections for resonant transfer excitation followed by X-ray emission (RTEX) are calculated for K-shell excitation in Caz+ + H2 and He collision systems, with Z = 17, 18 and 19 by folding the DR cross sections over the momentum distribution (Compton profile) of H2 and He target gases. These calculations are in agreement with recent experimental data where available. However, the location of the resonance peaks seems to be shifted by as much as 9 ~ 12 MeV in all cases, and the contribution of the uncorrelated transfer excitation (UTE) at the high energy tail of the RTE cross section is clearly evident. The effect of intermediate coupling is found to be significant for Z = 17, but negligible for the Z = 18 and 19 cases.
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Physica Scripta, 1990
ABSTRACT Dielectronic recombination rates and cross sections for the metastable C V and O VII ion... more ABSTRACT Dielectronic recombination rates and cross sections for the metastable C V and O VII ions are calculated and found to be extremely large, with cross sections of the order of 10−15 cm2 and rates of the order of 10−9 cm3 s−1 for individual resonances. Electric field enhancement and composition of the metastable 1s2s ion beams in terms of (1S) and (3S) are used to reproduce the recent experimental data of Andersen et al. [Phys. Rev. Lett. 62, 2656 (1989)] for O VII and unpublished data for C V. The overall features are well explained in the case of carbon, while the features for oxygen are well explained except for the broad prominent peaks at 2.5 and 6.8 eV, which are only partially explained.
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Physica Scripta, 1991
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Journal of Computational Physics, 1996
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Journal of Applied Physics, 1994
A mathematical model for the transient gas dynamics in one dimension resulting from laser vaporiz... more A mathematical model for the transient gas dynamics in one dimension resulting from laser vaporization of metals in the presence of an ambient atmosphere (air) is presented. The gas dynamics is analyzed by considering four regions: a transition zone between the melt surface and the bulk vaporized metal (known as the Knudsen layer), the bulk vaporized metal, the disturbed, and the undisturbed air. The ratios of the temperature and density across the Knudsen layer are modeled by constructing a velocity distribution which is a sum of two variably weighted Maxwellian distributions. The formation of a shock front is considered, and where appropriate the shock front location and velocity are included in the boundary conditions. Profiles in space and time for the velocity, temperature, pressure, and density are determined in a mathematically consistent way by appropriate matching across the Knudsen layer, the vapor/air interface, and the interface between the disturbed and undisturbed air ...
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AAPS PharmSciTech, 2016
Irinotecan (CPT-11) is used to treat advanced colorectal cancer as an intravenous therapy. Depend... more Irinotecan (CPT-11) is used to treat advanced colorectal cancer as an intravenous therapy. Depending on pH, CPT-11 exists in either a lactone (active) or carboxylate (inactive) form, or both. In this investigation, the feasibility for systemic delivery of CPT-11 through the buccal route was evaluated. Permeation of CPT-11 across porcine buccal mucosa was studied in vitro using side-by-side flow through diffusion cells at 37°C. Experiments were performed over a pH range from 4 to 9, and the permeability of both the lactone and carboxylate forms of CPT-11 was measured. CPT-11 steady state flux was determined over a range of donor concentrations at pH 4 (0.5, 1, 5, 10, 15, 20 mg/ml) and pH 6.8 (0.5, 5, 10 mg/ml). Steady state flux increased linearly with increasing donor concentration of CPT-11 at pH 4 (r (2) = 0.9935) and at pH 6.8 (r (2) = 0.9886). CPT-11 permeability was independent of pH, although the distribution coefficient increased with increasing pH. Estimates of permeability for the lactone and carboxylate forms were 4.16 × 10(-5) cm/s and 2.6 × 10(-5) cm/s, respectively. These calculated permeability values were in agreement with the in vitro experimental data. Overall, CPT-11 was found to permeate through porcine buccal mucosa via passive diffusion. CPT-11 permeability was independent of pH, suggesting that the compound was transported mainly via a paracellular route. Overall, the results of this research suggest that the buccal route is a potential extravascular mode of delivery for CPT-11.
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International Journal of Cosmetic Science, 2005
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International journal of pharmaceutics, Jan 31, 2011
When liquid donors/receivers are used for in vitro skin permeation studies, excess hydration can ... more When liquid donors/receivers are used for in vitro skin permeation studies, excess hydration can change skin properties compared to in vivo conditions. A novel in vitro method of determining the permeability of drugs through skin was developed that avoids exposing the membrane to dilute donor/receiver solutions. The drug is dissolved in an unstirred donor gel, and diffuses through a membrane into an unstirred gel receiver that can potentially be adjusted to mimic physiological conditions. Pulsatile microdialysis (PMD) was used to sample local concentrations in the receiver medium, and a model was developed to allow the determination of permeability. For Doxepin HCl, permeabilities through artificial membranes and human cadaver skin were determined using the new and previously reported methods. For artificial membranes that minimally hydrate, the new method gave consistent but slightly lower permeability values. For human cadaver skin, the permeability determined using the new method...
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PDA journal of pharmaceutical science and technology / PDA
A new controlled-release technology that is based on electrorheological fluids (ERF) is described... more A new controlled-release technology that is based on electrorheological fluids (ERF) is described, and a model system is investigated. Humidified starch (duration of humidification is 30-35 minutes) was used as a filler material (approximately 20% w/w) in olive oil to make the ER system, and benzocaine (BZN) was used as the model drug. The average particle size of starch in the olive oil was approximately 200 nm. 1N HCl was used as the receiver medium and BZN was assayed by UV spectroscopy at 226 nm. A series of studies was done at five temperatures (25 degrees, 30 degrees, 35 degrees, 40 degrees, and 45 degrees C) and two external electric fields (E-fields) that were generated by applying potential drops across the diffusion apparatus of 0 V and 290 V. Control studies of BZN release from olive oil without filler showed little or no increase in release rates resulting from application of E-fields. In addition, while reversing the polarity for BZN in olive oil caused differences in r...
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International Journal of Pharmaceutics, 2005
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International Journal of Pharmaceutics, 2002
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Papers by Robert A Bellantone