Ebner, Armin D., Ho, Jason G. S., and Ritter, James A.
Adsorption. Feb 2018, Vol. 24 Issue 2, p221, 12 p.
A graphical unit block was used to formulate new PSA cycle schedules that include an unlimited number of equalization steps, no idle steps, no dead time and a minimum number of just three PSA beds assisted with two or more equalization tanks. The approach to designing these PSA cycle schedules is based on three simple rules: (1) restrict the placement of all the equalization steps within the boxes of the PSA cycle schedule to be in sequence with no other cycle steps in between them (2) place all the equalization steps in the left most boxes of the PSA cycle schedule underneath the Bed 1 feed step with no other cycle steps below them except other equalization steps and (3) add equalization tanks as needed. These new 3-bed PSA cycle schedules may include any of the common PSA cycle steps in such a way that the equalization steps do not interfere with any of the non-equalization steps affording the non-equalization steps additional degrees of freedom. Since a bed-to-tank-to-bed equalization step may not be as effective as a bed-to-bed equalization step, a forced cocurrent depressurization (CoD) step coupled with an intermediary light end pressurization (LEP) step can be added to this 3-bed PSA cycle schedule. These coupled steps take place after the last of the equalization down and up steps with the aid of a compressor or vacuum pump. Since the utilization of several equalization steps and the utilization of forced CoD/LEP steps may limit the duration of the countercurrent depressurization (CnD) and/or light reflux (LR) steps, one or more additional beds can also be added to this 3-bed PSA cycle schedule. These additional beds increase the durations of the CnD and LR steps without affecting the duration of the feed step. Any combination of these PSA cycle schedule improvements can be used to improve the PSA process performance in terms of capital and operating costs, productivity or throughput, and recovery and purity of the species of interest whether it is the heavier, lighter or both species.
Trezza, Christine, Ford, Susan L., Gould, Elizabeth, Lou, Yu, Huang, Chuyun, Ritter, James M., Buchanan, Ann M., Spreen, William, and Patel, Parul
British Journal of Clinical Pharmacology. July 2017, Vol. 83 Issue 7, p1499, 7 p.
Women -- Health aspects, Progesterone, Estradiol, Glycoproteins, Contraceptives, Luteinizing hormone, Contraceptive drugs, and Pituitary hormones
To purchase or authenticate to the full-text of this article, please visit this link: http://onlinelibrary.wiley.com/doi/10.1111/bcp.13236/abstract Byline: Christine Trezza, Susan L. Ford, Elizabeth Gould, Yu Lou, Chuyun Huang, James M. Ritter, Ann M. Buchanan, William Spreen, Parul Patel Keywords: cabotegravir; contraceptive; ethinyl oestradiol; levonorgestrel; pharmacokinetics Aims This study aimed to investigate whether cabotegravir (CAB), an integrase inhibitor in development for treatment and prevention of human immunodeficiency virus-1, influences the pharmacokinetics (PK) of a levonorgestrel (LNG) and ethinyl oestradiol (EO)-containing oral contraceptive (OC) in healthy women. Methods In this open-label, fixed-sequence crossover study, healthy female subjects received LNG 0.15 mg/EO 0.03 mg tablet once daily Days 1-10 alone and with oral CAB 30 mg once daily Days 11-21. At the end of each treatment period, subjects underwent predose sampling for concentrations of follicle-stimulating hormone, luteinizing hormone, and progesterone and serial PK sampling for plasma LNG, EO, and CAB concentrations. Results Twenty women were enrolled, and 19 completed the study. One subject was withdrawn due to an adverse event unrelated to study medications. Geometric least squares mean ratios (90% confidence interval) of LNG + CAB vs. LNG alone for LNG area under the plasma concentration-time curve over the dosing interval of duration I and maximum observed plasma concentration were 1.12 (1.07-1.18) and 1.05 (0.96-1.15), respectively. Geometric least squares mean ratio (90% confidence interval) of EO + CAB vs. EO alone for EO area under the plasma concentration-time curve over the dosing interval of duration I and maximum observed plasma concentration were 1.02 (0.97-1.08) and 0.92 (0.83-1.03), respectively. Steady-state CAB PK parameters were comparable to historical values. There was no apparent difference in mean luteinizing hormone, follicle-stimulating hormone, and progesterone concentrations between periods. No clinically significant trends in laboratory values, vital signs, or electrocardiography values were observed. Conclusions Repeat doses of oral CAB had no significant effect on LNG/EO PK or pharmacodynamics, which supports CAB coadministration with LNG/EO OCs in clinical practice.
Choomphon-Anomakhun, Natthaphon, Ebner, Armin D., Natenapit, Mayuree, and Ritter, James A.
Journal of Magnetism and Magnetic Materials. April 15, 2017, Vol. 428, p493, 13 p.
Magnetization -- Analysis, Ferromagnetism -- Analysis, and Magnetic fields -- Analysis
A new approach for modeling high gradient magnetic separation (HGMS)-type systems during the time-dependent capture and accumulation of magnetic particles by a ferromagnetic wire was developed. This new approach assumes the fluid (slurry) viscosity, comprised of water and magnetic particles, is a function of the magnetic particle concentration in the fluid, with imposed maxima on both the particle concentration and fluid viscosity to avoid unrealistic limits. In 2-D, the unsteady-state Navier-Stokes equations for compressible fluid flow and the unsteady-state continuity equations applied separately to the water and magnetic particle phases in the slurry were solved simultaneously, along with the Laplace equations for the magnetic potential applied separately to the slurry and wire, to evaluate the velocities and concentrations around the wire in a narrow channel using COMSOL Multiphysics. The results from this model revealed very realistic magnetically attractive and repulsive zones forming in time around the wire. These collection zones formed their own impermeable viscous phase during accumulation that was also magnetic with its area and magnetism impacting locally both the fluid flow and magnetic fields around the wire. These collection zones increased with an increase in the applied magnetic field. For a given set of conditions, the capture ability peaked and then decreased to zero at infinite time during magnetic particle accumulation in the collection zones. Predictions of the collection efficiency from a steady-state, clean collector, trajectory model could not show this behavior; it also agreed only qualitatively with the dynamic model and then only at the early stages of collection and more so at a higher applied magnetic field. Also, the collection zones decreased in size when the accumulation regions included magnetic particle magnetization (realistic) compared to when they excluded it (unrealistic). Overall, this might be the first time a mathematical model was shown to be capable of realistically predicting the dynamic nature of magnetic particle capture and accumulation around a wire in HGMS-type systems.
Ritter, James, Knox, James, Jan, Darrell, Belancik, Grace, Huang, Roger, Cmarik, Gregory E, Richardson, Tra-My Justine, and Ebner, Armin
International Conference on Environmental Systems; 16-20 Jul. 2017; Charleston, SC; United States
Man/System Technology and Life Support and Chemistry and Materials (General)
In support of air revitalization system sorbent selection for future space missions, Ames Research Center (ARC) has performed CO2 capacity tests on various solid sorbents to complement structural strength tests conducted at Marshall Space Flight Center (MSFC). The materials of interest are: Grace Davison Grade 544 13X, Honeywell UOP APG III, LiLSX VSA-10, BASF 13X, and Grace Davison Grade 522 5A. CO2 capacity was for all sorbent materials using a Micromeritics ASAP 2020 Physisorption Volumetric Analysis machine to produce 0 C, 10 C, 25 C, 50 C, and 75 C isotherms. These data are to be used for modeling data and to provide a basis for continued sorbent research. The volumetric analysis method proved to be effective in generating consistent and repeatable data for the 13X sorbents, but the method needs to be refined to tailor to different sorbents.
Ritter, James, Knox, James, Belancik, Grace, Jan, Darrell, Cmarik, Gregory, Ebner, Armin D, and Huang, Roger
International Conference for Environmental Systems (ICES); 16-20 JUl. 2016; Charleston, SC; United States
Life Sciences (General)
In support of air revitalization system sorbent selection for future space missions, Ames Research Center (ARC) has performed CO2 capacity tests on various sorbents to complement structural strength tests from Marshall Space Flight Center (MSFC). The materials of interest are: Grace Davison Grade 544 13x, Honeywell UOP APG III, VSA-10, BASF 13x, and Grace Davison Grade 522 5A. Each sorbents CO2 capacity was measured using a Micromeritics ASAP 2020 Physisorption Volumetric Analysis machine to produce 0C, 10C, 25C, 50C, and 75C isotherms. These datasets were then extrapolated using Langmuir 3-Site and Toth isotherm models to compare with previously measured capacity data from MSFC using a thermogravimetric analysis approach. The modeling and extrapolation from ARC data correlated well with data measured at MSFC.
Hossain, Mohammad I., Ebner, Armin D., and Ritter, James A.
Adsorption. Oct 2016, Vol. 22 Issue 7, p939, 12 p.
A simple, semi-empirical, generalized expression was developed for the LDF mass transfer coefficient k as a function of the half cycle time I[cedilla] .sub.c that encompasses and transitions between the well-known regions governed by the long cycle time constant Glueckauf k and the short cycle time dependent k. This new expression can be used to estimate k = f(I[cedilla] .sub.c) for any system, irrespective of the loading and irrespective of I[cedilla] .sub.c, no matter if k is in the cycle time dependent region or not. A three times wider transition region between the Glueckauf k and the cycle time dependent k was also established, with the Glueckauf LDF limit now valid for I[cedilla] .sub.c > 0.3 and the short cycle time limit now valid for I[cedilla] .sub.c < 0.01. When evaluating this region for several adsorbate-adsorbent systems, the minimum Glueckauf I[cedilla] .sub.c spanned three orders of magnitude from thousands of seconds to just a few seconds, indicating a cycle time dependent k is not necessarily limited to what is normally considered a short cycle time. For virtually any I[cedilla] .sub.c less than this minimum Glueckauf I[cedilla] .sub.c, this new first-of-its-kind expression can be used to readily provide an accurate value of k = f(I[cedilla] .sub.c). Since the widely accepted half cycle time concept does not apply to the actual simulation of a multi-step, unequal step time, pressure swing adsorption process, the value of k = f(I[cedilla] .sub.c) from this new expression can be based on either the shortest cycle step in the cycle or a different value of k = f(I[cedilla] .sub.c) for each cycle step time in the cycle, with validity confirmed either by experiment or by process simulation using the exact solution to the pore diffusion equation.
This work examined in detail the a priori prediction of the axial dispersion coefficient from available correlations versus obtaining it and also mass transfer information from experimental breakthrough data and the consequences that may arise when doing so based on using a 1-D axially dispersed plug flow model and its associated Danckwerts outlet boundary condition. These consequences mainly included determining the potential for erroneous extraction of the axial dispersion coefficient and/or the LDF mass transfer coefficient from experimental data, especially when non-plug flow conditions prevailed in the bed. Two adsorbent/adsorbate cases were considered, i.e., carbon dioxide and water vapor in zeolite 5A, because they both experimentally exhibited significant non-plug flow behavior, and the water-zeolite 5A system exhibited unusual concentration front sharpening that destroyed the expected constant pattern behavior (CPB) when modeled with the 1-D axially dispersed plug flow model. Overall, this work showed that it was possible to extract accurate mass transfer and dispersion information from experimental breakthrough curves using a 1-D axial dispersed plug flow model when they were measured both inside and outside the bed. To ensure the extracted information was accurate, the inside the bed breakthrough curves and their derivatives from the model were plotted to confirm whether or not the adsorbate/adsorbent system was exhibiting CPB or any concentration front sharpening near the bed exit. Even when concentration front sharpening was occurring with the water-zeolite 5A system, it was still possible to use the experimental inside and outside the bed breakthrough curves to extract fundamental mass transfer and dispersion information from the 1-D axial dispersed plug flow model based on the systematic methodology developed in this work.