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  • 1
    Electronic Resource
    Electronic Resource
    On the computation of complex equilibria (1972)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 18 (1972), S. 299-304 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method is described for solving the problem: given fixed pressure, temperature, the amounts of the chemical elements, and the chemical potentials of possible chemical species at the pressure and temperature specified, determine the equilibrium composition. The method requires a minimum of judgment on the part of the user.A modification of Naphtali's method for direct minimization of Gibbs' function provides an estimate of the composition of sufficient accuracy to insure convergence of solution, by the Newton-Raphson method, of the nonlinear equations describing the equilibrium.Problems in treating multiple phaes of unknown stability and chemical species present in small amouts are handled by ignoring unstable phases and small quantitites in the direct minimization until the amounts of the major consitituents have been at least approximately determined. To accomplish this, species temporarily ignored are assigned a ficitious mol fraction so that their re-entry into the calculation can be established. Truncation errors in the direct minimziation can be tolerated because of the two-step method.Examples of some of the problems solved are given.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690180209
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  • 2
    Electronic Resource
    Electronic Resource
    Multicomponent rates of sorption of SO2 and CO2 in sodium mordenite (1973)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 19 (1973), S. 1055-1059 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690190531
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  • 3
    Electronic Resource
    Electronic Resource
    Transient diffusion in solids with a bipore distribution (1976)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 22 (1976), S. 147-152 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient diffusion of n-butane, iso-butane, and 1-butene in synthetic CaX(Na) spherical pellets is studied in a constant volume, well-stirred system. The intracrystalline diffusion coefficients are in the order of 10-14 cm2/s, and the activation energy is about 7.0 Kcal/g-mole. Experimental data agree well with a mathematical model developed to describe transient diffusion.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690220118
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of liquid chromatography with nonuniform crystallite particles (1990)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1569-1576 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical analysis for the pulse responses of a liquid chromatographic column packed with crystal powders having a particle size distribution and a nonlinear adsorption isotherm is presented. The mathematical model is solved numerically by the orthogonal collocation method. Based on the parametric analysis of the model, the effects of a symmetrical and moderately asymmetric PSD on the LC responses are shown to be negligible in comparison with the effects of other parameters, such as isotherm nonlinearity, whose effects are much more profound. The simulated responses are compared with the experimental response data for an LC column packed with silicalite crystals, and a good agreement is found between the theoretical and experimental results. Using the nonlinear LC model, the simultaneous determination of nonlinear adsorption isotherms and intraparticle diffusivities from LC pulse responses is demonstrated for liquids in porous adsorbents.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690361013
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  • 5
    Electronic Resource
    Electronic Resource
    Theory of gas diffusion and permeation in inorganic molecular-sieve membranes (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 58-67 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Theoretical models of gas diffusion and permeation in microporous molecularsieve membranes are presented. The effect of the adsorbed diffusant on the total transmembrane flow is insignificant for permanent gases. For highly adsorbable gases the effect of the adsorbed molecules on the total transmembrane flux may be high at low temperatures. The activation energy of diffusion increases when the kinetic diameter of the diffusant increases. The activation energy of gas diffusion compares well with the values calculated based on the Lennard-Jones potential. Maximum possible permeability coefficients calculated for He in the molecular-sieve membranes do not exceed ˜30,000 Barrer at room temperature. The experimentally observed value for He permeability is ˜1,000 Barrer (T=30°C) because of the high tortuosity (τ≍ 25) and low porosity (θ = 0.22) of the membrane porous structure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410107
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  • 6
    Electronic Resource
    Electronic Resource
    Diffusion in synthetic faujasite powder and pellets (1974)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 20 (1974), S. 279-284 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient sorption rates of allene and methylacetylene in synthetic faujasite (Linde 13X) powder and self-bonded pellets are studied in a constant-volume, constant-pressure system at three temperatures. The intracrystalline diffusion coefficients are found to be in the order of 10-11 cm2/s and the activation energy for diffusion is 4.0 kcal/g-mole.A simple bipore distribution model for transient diffusion in macropores and micropores is presented. It agrees well with the experimental data and quantitatively predicts the macropore diffusion coefficients. The flow in the macropores is found to be in the Knudsen flow regime.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690200211
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  • 7
    Electronic Resource
    Electronic Resource
    Xylene isomerization using zeolites in a gradientless reactor system (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1233-1240 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A gradientless reactor was used to study the xylene isomerization reaction over a series of cation-exchanged (H+, Li+, Na+, and K+) ultrastable faujasite and on ZSM5 and silicalite to observe the effects of site modification on the reaction. Adsorption, diffusion, and kinetic parameters were determined in the presence of the reaction; the results generally agreed with the available literature data. The gradientless reactor and associated modeling techniques are shown to be effective tools in investigating catalyst behavior. Precise analytical techniques are required to directly measure the diffusion coefficient in the presence of reaction.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690330802
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  • 8
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    Greater Bone Formation Induction Occurred in Aged than Young Cancellous Bone Sites (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We have determined the differences in the effects of continual prostaglandin E(sub 2) (PGE(sub 2) treatment in aged (non-growing) and young (growing) cancellous bone sites in 7-month-old Sprague-Dawley rats. The sites involved are the aged distal tibial metaphysis (DTM) with a closed epiphysis and the young proximal tibial metaphysis (PTM) with a slow growing, open epiphysis. The study involved rats treated with 0, 1, 3 or 6 mg PGE(sub 2)/kg/d for 60, 120 and 180 days. Static and dynamic histomorphometry of percent trabecular area, and tissue-referent bone formation rate (BFR/TV) were determined in both DTM and PTM. In pretreatment controls, the secondary spongiosa of the two metaphyses contain the same amount of cancellous bone (11% in DTM vs. 13% in PTM), but markedly less bone formation in DTM (0.6%/y in DTM vs. 41.5%/y in PTM). After 60 days of 6 mg PGE(sub 2)/kg/d treatment, %Tb.Ar was increased 607% in DTM and 199% in PTM, BFR/TV was increased to nearly 14 fold in DTM and only 5 fold in PTM. These results indicated the aged metaphysis of the DTM was much more responsive to PGE(sub 2) treatment than young, growing metaphysis of the PTM. The results of 120 and 180 days treatment did not significantly differ from 60 days treatment in both sites, indicating that the effect of continuous daily PGE2 treatment were in equilibrium after 60 days. We concluded that aged metaphysis was much more responsive to PGE(sub 2) treatment than young growing metaphysis.
    Keywords: Life Sciences (General)
    Type: NASA-CR-204211 , NAS 1.26:204211 , Bone (ISSN 8756-3282); 14; 481-485
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  • 9
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    Prostaglandin E2 Restores Cancellous Bone to Immobilized Limb and Adds Bone to Overloaded Limb in Right Hindlimb Immobilization Rats (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The purpose of this study was to determine whether prostaglandin E2 (PGE2) can restore cancellous bone mass and architecture to osteopenic, continuously immobilized (IM), proximal tibial metaphysis (PTM) in female rats. The right hindlimb of three and one-half-month-old Sprague-Dawley female rats were immobilized by right hindlimb immobilization (RHLI) in which the right hindlimb was underloaded and the contralateral left limb was overloaded during ambulation. After 4 or 12 weeks of RHLI, the rats were treated with 3 or 6 mg PGE2/kg/day and RHLI for 8 or 16 weeks. Bone histomorphometry was performed on microradiographs of PTM. Immobilization (IM) induced a transient cancellous bone loss and decreased trabecular thickness, number and node density, and increased free end density that established a new steady state after 4 weeks of IM. Three or 6 mg PGE2/kg/d for 8 weeks beginning at 4 or 12 weeks of IM completely restored cancellous bone mass (+127 to +188 percent) and structure to the age-related control levels in spite of continuous IM. Another 8 weeks of treatment maintained bone mass and architecture at these levels. No differences in cancellous bone mass and architecture were found between the overloaded PTM or RHLI rats and the age-related controls. However, 3 and 6 mg/kg/d of PGE2 treatment started at 4 or 12 weeks for 8 weeks significantly increased cancellous bone mass in the overloaded PTM (+45 to +74% of untreated controls), and another 8 weeks of treatment maintained bone mass at these levels. Our findings indicate that daily 3 or 6 mg PGE2/kg/d treatment restores and maintains PTM cancellous bone mass in continuously immobilized (right) tibiae, and adds and maintains extra bone to slightly overloaded PTM cancellous bone in female rats.
    Keywords: Life Sciences (General)
    Type: NASA-CR-202477 , NAS 1.26:202477 , Bone (ISSN 8756-3282); 14; 283-288
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  • 10
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    Effects of Prostaglandin E2 and Risedronate Administration on Cancellous Bone in Older Female Rats (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The effects of Prostaglandin E2 (PGE2) and Risedronate (Ris) both separately and in combination (PGE2 + Ris) were studied on the intact aged female rat skeleton to determine whether the combination of PGE2 with an antiresorptive agent is more effective anabolically than PGE2 alone. Nine month-old Sprague-Dawley rats were injected subcutaneously either with vehicle, 6 mg PGE2/kg per day, 1 or 5 microgram Ris/kg twice a week, or 6 mg PGE2/kg per day plus 1 or 5 microgram Ris/kg twice a week (PGE2 + 1 Ris or PGE2 + 5 Ris) for 60 days. After the treatment, we determined the longitudinal bone growth rate, the qualitative appearance of the primary spongiosa (PS), and the static and dynamic bone histomorphometry of the secondary spongiosa (SS) of the proximal tibial metaphysis (PTM) by examining undecalcified longitudinal sections after double fluorescent labeling. The relative effects of these treatments on longitudinal bone growth were ranked as follows: PGE2 + 5 Ris greater than PGE2 + 1 Ris = basal greater than PGE2 greater than 1 microgram Ris = 5 microgram Ris = aging. The density of the PS was ranked as follows: PGE2 + 5 Ris greater than PGE2 + 1 Ris = PGE2 = 5 microgram Ris = 1 microgram Ris greater than basal = aging. The increase in density of the PS was the result of stimulated longitudinal growth and the action of bisphosphonate. Bone mass in the SS was ranked as follows: PGE2 + 5 Ris = PGE2 + 1 Ris = PGE2 greater than 5 microgram Ris = 1 microgram Ris = aging = basal. However, PGE2 alone and its cotreatment with Ris accumulated bone by different tissue mechanisms. PGE2 alone created new bone by increasing activation frequency 8.3-fold and the formation to resorption ratio 1.3-fold from the controls. The combination of PGE2 and Ris depressed activation frequency (-54% to -74%), and bone formation rate (tissue-based -31%, and bone-based -42%) and eroded surface (-79% to -81%), so as to increase the formation to resorption ratio (three- to four-fold) over PGE2 alone. The increased ratio was due primarily to a greater decrease in eroded perimeter than in labeled perimeter. The major finding of this study is that the combination of PGE2 and a bisphosphonate (Ris) is more anabolic than PGE2 or Ris alone when endochondral ossification is active, but PGE2 + Ris is no more anabolic than PGE2 alone in old bone without endochondral ossification. However, the tissue mechanisms by which PGE2 alone and PGE2 + Ris treatments accumulated bone differed in that the latter allowed the same bone mass to accumulate with lower levels of cell recruitment and activity.
    Keywords: Life Sciences (General)
    Type: NASA-CR-202671 , NAS 1.26:202671 , Bone (ISSN 8756-3282); 15; 5; 489-496
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