China
Africa
Explore chapters and articles related to this topic
Chemical Permeation through Disposable Gloves
Published in Robert N. Phalen, Howard I. Maibach, Protective Gloves for Occupational Use, 2023
Solvent permeation studies have been published since the early 2000s, likely due to improvements in the sensitivity of analytical chemistry laboratory methods for solvent analysis. For example, nitrile disposable gloves (0.63 ± 0.03 mm) were tested against several pure organic solvents using the ASTM F 739 method.86 Chao et al.86 used the solvent's SSPR to calculate an effective diffusion coefficient. Solvents through nitrile gloves had effective diffusion coefficients that were inversely correlated to the molecular weight of the compounds, in the following order: benzene > toluene > ethyl benzene > xylene > styrene. While benzene and toluene first permeated (i.e., BT) at approximately 30 min, the other solvents permeated through nitrile gloves after about an hour, which meant that the physicochemical properties of the solvent were a good predictor of permeation rates. In a follow-up study, nitrile gloves (0.63 ± 0.03 mm) were compared with neoprene/NR gloves (0.72 ± 0.05 mm) and determined to be better at protecting against benzene, toluene, and styrene, with the greatest difference regarding benzene—specifically, nitrile gloves had a breakthrough of approximately 10 min, while neoprene/NR gloves had a breakthrough of approximately 5 min.87
Techniques for Assessing the Health Risks of Dermal Contact with Chemicals in the Environment
Published in Rhoda G. M. Wang, James B. Knaak, Howard I. Maibach, Health Risk Assessment, 2017
Dennis J. Paustenbach, Hon-Wing Leung
The effective diffusion coefficient through the stratum corneum is on the order of 10−13 to 10−14 m2/sec for (low) molecular weight compounds and 10−15 to 10−17 m2/sec for higher molecular weight compounds.
The Adsorptivity of Charged and Uncharged Cellulose Ethers
Published in E. Desmond Goddard, James V. Gruber, Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
E. Desmond Goddard, James V. Gruber
Further evidence favoring a diffusion mechanism for polymer sorption is obtained from a consideration of the sorption isotherm on hair and rayon in Figure 6. The data do not conform to the Langmuir adsorption equation. Langmuirian behavior would imply that the adsorbing sites along the polymer act independently of one another, a situation that would be approached in the case of extensive looping of the polymer at the interface. The observed data are found, rather, to fit the Freundlich isotherm. Crank (9) has shown that diffusion accompanied by nonlinear adsorption is governed by the concentration of free diffusant, which is, in turn, governed by the total initial concentration of diffusant. In the case of the Freundlich isotherm , when , the effective diffusion coefficient, , is given by
Dyes adsorption properties of KOH-activated resorcinol-formaldehyde carbon gels -kinetic, isotherm and dynamic studies
Published in Toxin Reviews, 2022
Azrul Nurfaiz Mohd Faizal, Muhammad Abbas Ahmad Zaini
The Boyd’s model further elicits accurate understanding on the rate-limiting step and removal mechanisms by particle diffusion or film diffusion (Karthikeyan et al.2010). The time constant, B was used to determine the effective diffusion coefficient, Di (cm2/s). The film diffusion coefficient, Df holds a value between 10−6 to 10−8 cm2/s for film diffusion to be the actual slow step. Particle diffusion is the rate-limiting step for Dp in the range of 10−11 to 10−13 cm2/s (Michelson et al.1975, Karthikeyan et al.2010). The deviation from origin implies that the rate-limiting step is film diffusion with effective diffusion coefficient, Di = Df in the range of 8.67 × 10−9 to 1.01 × 10−8 cm2/s.
Application of HIPEC simulations for optimizing treatment delivery strategies
Published in International Journal of Hyperthermia, 2023
Daan R. Löke, H. Petra Kok, Roxan F. C. P. A Helderman, Bella Bokan, Nicolaas A. P. Franken, Arlene L. Oei, Jurriaan B. Tuynman, Pieter J. Tanis, Johannes Crezee
Several assumptions had to be made regarding governing equations and boundary conditions to reduce the computation time. These assumptions were discussed above and are listed below. The consequences and future strategies regarding these assumptions are considered in the ‘Discussion’ section. Summarizing, in this study we made the following assumptions:Tissues were modeled as a solid medium. Veins and capillaries were assumed isotropic and heterogeneous throughout tissues. Only large structures were modeled explicitly. This can affect sink terms in Equations (5) and (6). In this study, we made the following assumptions:Only intraperitoneal organs were modeled explicitly.Vascular concentration during a HIPEC treatment was considered negligible.No convective particle transport was modeled. An effective diffusion coefficient was used, based on experimental data.Heat loss through the closed abdomen was modeled using a heat resistance factor. No explicit diffusion between the fluid and surroundings was modeled.Cellular uptake was modeled using a first-order elimination constant. Back flow was not taken into account.A single geometry was modeled, excluding possible anatomical variations between patients.
Mathematical analysis of oxygen and carbon dioxide exchange in the human capillary and tissue system
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Ahsan Ul Haq Lone, M. A. Khanday
The expression in parenthesis can be considered an effective diffusion coefficient, Deff. Using Henry”s Law, we conclude that the diffusion of oxygen is enhanced by a factor