The Deresination of Guayule: A Physical Model. Part II: A Two-Component Analog for Deresination

1984 ◽  
Vol 57 (2) ◽  
pp. 370-378
Author(s):  
S. Budiman ◽  
D. McIntyre
Keyword(s):  
Diffusion Coefficients ◽  
Abietic Acid ◽  
Additive Model ◽  
Molecular Size ◽  
Design Parameters ◽  
Model Compounds ◽  
Diffusion Behavior ◽  
Diffusion Studies ◽  
Two Component ◽  
Physical Geometry

Abstract Based on GPC, the worm resin can be separated into two distinct groups, large and small. To obtain the overall diffusion coefficients for the two groups that could be useful as commercial design parameters, the worms were converted into wet worm crepe. Diffusion studies with model compounds, abietic acid, and trilinolein, reveal that: (a) their diffusion coefficients for desorption into acetone are inversely proportional to their respective molecular size, (b) the diffusion behavior of the two model compounds in a mixture can be fitted to a simple additive model, and (c) their diffusion coefficients are quite similar to those of the two groups of resin constituents (large and small). It is, therefore, possible to model and optimize a commercial deresination process for guayule worms on the basis of the diffusion behavior of two model compounds linolein and abietic acid and the physical geometry.

Determination of Hydrocarbons Using Sapphire Fibers Coated with Poly(Dimethylsiloxane)

2003 ◽  
Vol 57 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Rhona Howley ◽  
B. D. MacCraith ◽  
Kieran O'Dwyer ◽  
Hugh Masterson ◽  
P. Kirwan ◽  
...  
Keyword(s):  
Film Thickness ◽  
Diffusion Model ◽  
Diffusion Coefficients ◽  
Molecular Size ◽  
Infrared Region ◽  
Sensor Response ◽  
Fickian Diffusion ◽  
Prototype System ◽  
Pdms Film ◽  
Diffusion Behavior

A poly(dimethylsiloxane) (PDMS) coated sapphire fiber has been investigated as a sensor for hydrocarbons (HCs) in the mid-infrared region around 3000 cm−1. In order to optimize and predict sensor response, the diffusion behavior of the analytes into the PDMS preconcentration medium has been examined. A diffusion model based on Fickian diffusion was used to quantify diffusion. The model incorporated such factors as film thickness, refractive index of the polymer and the fiber core, and principal wavelength at which the analyte absorbs. A range of hydrocarbons, from hexane to pentadecane, was analyzed at 2930 cm−1 using both fiber-coupled Fourier transform infrared spectroscopy and a modular prototype system. Diffusion coefficients were determined for these compounds and diffusion behavior examined and related to factors such as analyte polarity and molecular size. The diffusion coefficients were found to range from 6.41 × 10−11 ± 5 × 10−12 to 5.25 × 10−11 ± 9 × 10−13 cm2 s−1 for hexane and pentadecane into a 2.9 μm PDMS film, respectively. The diffusion model was also used to examine the effect of changing system parameters such as film thickness in order to characterize sensor response.

Diffusion Studies. I. Diffusion Coefficients in Liquids by a Radiometric Porous-Frit Method1

1965 ◽  
Vol 69 (1) ◽  
pp. 303-309 ◽  
Author(s):  
Arthur E. Marcinkowsky ◽  
Frederick Nelson ◽  
Kurt A. Kraus
Keyword(s):  
Diffusion Coefficients ◽  
Diffusion Studies

Non-Stoichiometry and Cation Tracer Diffusion Studies in the Magnetite-UlvÖSpinel Solution, (Fe,Ti)3-δO4

1994 ◽  
Vol 369 ◽  
Author(s):  
Sanjeev Aggarwal ◽  
Rudiger Dieckmann
Keyword(s):  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Oxygen Activity ◽  
Spinel Solid Solution ◽  
Low Oxygen ◽  
Cation Diffusion ◽  
Deviation From Stoichiometry ◽  
Diffusion Studies ◽  
Tracer Diffusion Coefficients ◽  
Point Defect Structure

AbstractCation diffusion in the spinel solid solution (Fe1-xTix)3-δO4 (0≤ x ≤ 0.3) was investigated at 1200 ºC as a function of oxygen activity, aO2 and cationic composition, x. At different cationic compositions, cation tracer diffusion coefficients, D*Me of Me = Fe and Ti were measured as a function of oxygen activity. Plots of log DMe vs. loga0 show V-shaped curves, indicating that different types of point defects prevail at high anc low oxygen activities. Thermogravimetric experiments were conducted, using a high resolution microbalance, to determine the deviation from stoichiometry in (Fe1-xTix)3-δO4 at 1200 °C. δversus log aO2 curves are S-shaped. An analysis of the oxygen activity dependences of thecation diffusion coefficients and the deviation from stoichiometry with regardto the point defect structure suggests that at high oxygen activities cation vacancies are the predominant defects governing the deviation from stoichiometry and the diffusion ofcations. At low oxygen activities, and at small values of x, cation interstitials determine the deviation from stoichiometry, while they dominate for 0 ≤ x ≤ 0.3 inthe cation diffusion.

scholarly journals Effects of Design Factors on Drag Forces and Deformations on Marine Aquaculture Cages: A Parametric Study Based on Numerical Simulations

2020 ◽  
Vol 8 (2) ◽  
pp. 125 ◽  
Author(s):  
Shuchuang Dong ◽  
Xinxing You ◽  
Fuxiang Hu
Keyword(s):  
Additive Model ◽  
Design Parameters ◽  
Marine Aquaculture ◽  
Drag Forces ◽  
Solidity Ratio ◽  
Parametric Studies ◽  
Net Cage ◽  
Fast Prediction ◽  
Bp Neural Network Model ◽  
Design Factors

In Japan, the marine aquaculture net cage has an important role in farming pacific bluefin tuna farming in oceans, and the design of the net cage needs to ensure robustness against hostile oceanic conditions. Accordingly, this study focuses on the drag forces and the cage volume of the net cage, and on their variations induced by different design parameters (netting solidity ratio, netting height, and bottom weight). A series of parametric studies on drag force and deformation of the net cage was conducted using a numerical simulation model. Accordingly, the contribution of each parameter to the drag and volume was analyzed using a generalized additive model. The results indicate that the bottom weight had the highest contribution to the holding ratio of the cage volume, whereas the netting height had the highest contribution to the drag coefficient of the net cage. Finally, a fast prediction model was created by a backpropagation (BP) neural network model and was examined for the accurate prediction of the objective variables.

Observation of Diffusion Behavior in Al-Implanted ZnO Single Crystal

2009 ◽  
Vol 421-422 ◽  
pp. 197-200 ◽  
Author(s):  
Tsubasa Nakagawa ◽  
Isao Sakaguchi ◽  
Kenji Matsumoto ◽  
Masashi Uematsu ◽  
Hajime Haneda ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Oxygen Diffusion ◽  
Depth Profiling ◽  
Implantation Technique ◽  
Constant Concentration ◽  
Concentration Region ◽  
Diffusion Behavior ◽  
Oxygen Interstitial ◽  
Zno Single Crystal ◽  
Diffusion Behaviors

Diffusion behaviors of aluminum (Al) in zinc-oxide (ZnO) single crystals were measured by means of ion implantation technique and SIMS depth profiling. It was found that Al concentration profile had a peculiar shape with a constant-concentration region and a steep tail, which was also found in profiles of other donors such as Ga and In. Detailed analysis of the profiles revealed that the diffusivity of Al was proportional to the square of Al concentration and its intrinsic diffusivity was much smaller than previously reported values. Oxygen diffusion experiments were also performed and the implantation of Al ions enhanced the oxygen diffusion coefficients by about 20 times. This result indicates that oxygen interstitial diffusion occurs in n-type ZnO.

scholarly journals Determination of the pKa of glucuronic acid and the carboxy groups of heparin by 13C-nuclear-magnetic-resonance spectroscopy

1991 ◽  
Vol 278 (3) ◽  
pp. 689-695 ◽  
Author(s):  
H M Wang ◽  
D Loganathan ◽  
R J Linhardt
Keyword(s):  
Uronic Acid ◽  
Model Compound ◽  
Molecular Size ◽  
Resonance Spectroscopy ◽  
Model Compounds ◽  
Pka Values ◽  
Carboxylate Groups ◽  
13C Nuclear Magnetic Resonance ◽  
Unambiguous Assignment

As part of our continuing studies on heparin, the present paper uses 13C-n.m.r. spectroscopy to examine the acidity of heparin's uronic acid carboxylate groups. Heparin contains three different uronic acids. In porcine mucosal heparin these account for approx. 91, 7 and 2 mol% of the total uronic acid residues. These are alpha-L-idopyranosyluronic acid 2-sulphate, beta-D-glucopyranosyluronic acid and alpha-L-idopyranosyluronic acid. The pKa values of their carboxylate groups were determined as 3.13 (using heparin), 2.79 (using heparin) and 3.0 (predicted by using model compounds) respectively. 18C-n.m.r. spectroscopy, performed at various pH values, provided a convenient method of simultaneously determining the pKa of multiple carboxylate groups, of similar acidity, within heparin D-Glucopyranosyluronic acid and heparin-derived di-, tetra- and hexa-saccharides were used as model compounds to determine pKa values of the different carboxy groups. The results suggested that molecular size had an effect on pKa. Unambiguous assignment of carboxy carbon resonances were accomplished through the use of two-dimensional n.m.r. spectroscopy. Finally, application of this method to the simplest model compound, D-glucopyranosyluronic acid, permitted the determination of the pKa of both its alpha- and beta-anomers.

Oxygen diffusion studies. I. A preliminary ion microprobe investigation of oxygen diffusion in some rock-forming minerals

1982 ◽  
Vol 45 (337) ◽  
pp. 179-192 ◽  
Author(s):  
R. Freer ◽  
P. F. Dennis
Keyword(s):  
Diffusion Coefficients ◽  
Oxygen Diffusion ◽  
Isotope Exchange ◽  
Water Pressure ◽  
Ion Microprobe ◽  
Oxygen Isotope Exchange ◽  
Self Diffusion ◽  
Diffusion Studies ◽  
Diffusion Rates ◽  
Grossular Garnet

AbstractThe self diffusion of oxygen has been studied in prepared natural crystals of albite, grossular garnet, quartz, and ruffle by isotope exchange with hydrothermal water enriched in 18O, and subsequent analysis by ion microprobe. Measured oxygen diffusion coefficients (D) in quartz (‖c) may be described by D = 1.08 × 10−11 exp(−31.5 kcal/RT) cm2s−1 at 600−750°C and 1 kbar water pressure. For grossular, D = 2.5 × 10−16 cm2s−1 at 1050°C and 8 kbar, and D = 4.8 × 10−17 cm2s−1 at 850 °C and 2 kbar. All ruffle crystals exhibited variable amounts of corrosion, and an approximate diffusion coefficient of D(‖c) = 3.16 × 10−15 cm2s−1 cm2s−1 was obtained at 1050 °C and 1 kbar. Oxygen diffusion coefficients in albite, perpendicular to (001) faces, have been determined as a function of pressure at 600 °C Between 0.5 and 8.0 kbar pressure no systematic variation in the results was observed and most of the data may be described by D = 4.1 (±0.5) × 10−15 cm2s−1. Slow oxygen diffusion rates in quartz and garnet suggest that these minerals should have high ‘closure temperatures’ for oxygen exchange, and may provide reliable oxygen isotope exchange geothermometers.

Sign in / Sign up

Export Citation Format

Share Document