The dissolution of organic solvents from Amerlock 400 epoxy paint

2003 ◽  
Vol 81 (7) ◽  
pp. 850-860 ◽  
Author(s):  
J M Ball ◽  
J C Wren ◽  
J R Mitchell
Keyword(s):  
Organic Solvents ◽  
Release Rate ◽  
Radiolysis Product ◽  
Fickian Diffusion ◽  
Ethyl Benzene ◽  
Water Radiolysis ◽  
Reactor Accident ◽  
Release Process ◽  
Paint Thickness ◽  
Epoxy Paint

The dissolution of organic solvents from containment coatings into the sump water is expected to be a key rate-controlling process, influencing the pH, the steady-state water radiolysis product concentration, and the formation of organic iodides in containment following a postulated reactor accident. The dissolution process is therefore an important component in modelling iodine behaviour in post-accident containment. The rate of release of ethyl benzene and m- and o-xylene from Amerlock 400 epoxy paint in contact with water has been measured. The release rate was found to be comparable to the release rate of methyl isobutyl ketone from various polyurethane, vinyl, and epoxy paints. The pseudo-first-order rate constant for dissolution of the solvents from these containment coatings is dependent only upon paint thickness and temperature, whereas the total amount of solvent released depends upon paint thickness. The solvent-release process is governed by the rate of uptake of water by the coupons, a Fickian diffusion-controlled process.Key words: dissolution, kinetics, organic solvents, paint.

The reduction of I2 by H2O2 in aqueous solution

2001 ◽  
Vol 79 (3) ◽  
pp. 304-311 ◽  
Author(s):  
J M Ball ◽  
J B Hnatiw
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Nuclear Reactor ◽  
Ph Dependence ◽  
Radiolysis Product ◽  
Molecular Iodine ◽  
Water Radiolysis ◽  
Reactor Accident ◽  
Rate Law ◽  
Accident Conditions

The reduction of I2 by hydrogen peroxide, a primary water radiolysis product, has been identified as a key reaction that would influence iodine volatility in nuclear reactor accident conditions (1–3). Although there have been a number of studies of the reduction of I2, there exists a great degree of controversy regarding the intermediates involved, the effect of buffers, and the general rate law (1–9). Because the rates and the mechanism of this reaction are important in predicting the pH dependence of iodine behaviour in reactor containment building after a postulated reactor accident, we have undertaken a kinetic study of I2 reduction by H2O2 in aqueous solution over a pH range of 6–9. The experiments were performed using stopped-flow instrumentation and monitoring the decay of I–3 spectrophotometrically. The effects of buffer catalysis have been examined by comparison of kinetic data obtained in sodium barbital (5,5-diethylbarbituric acid), disodium citrate, and disodium hydrogen phosphate buffers. The effect of buffers, combined with the complex acid dependence of the rate law, explains many of the discrepancies reported in earlier literature.Key words: hydrogen peroxide, molecular iodine, kinetics, iodine volatility.

STUDY OF THE DIFFERENT RELEASE CHARACTERISTICS OF ANTIBIOTICS FROM PATIENTS: A DYNAMIC ELUTING SYSTEM TO INVESTIGATE DRUG RELEASE FROM ANTIBIOTIC-IMPREGNATED CALCIUM SULFATE DELIVERY

2015 ◽  
Vol 15 (01) ◽  
pp. 1550012
Author(s):  
YANG ZHANG ◽  
RENJIE WU ◽  
YING HU ◽  
YU DONG ◽  
LIFENG SHEN ◽  
...  
Keyword(s):  
Drug Release ◽  
Delivery System ◽  
Release Rate ◽  
Calcium Sulfate ◽  
Fickian Diffusion ◽  
Release Behavior ◽  
Cumulative Release ◽  
In Vivo Release

Background: Antibiotic-impregnated calcium sulfate delivery systems (ACDS) are commonly used to treat chronic osteomyelitis. Our research is to investigate drug release in vitro over a longer period, as a cautious predictor of in vivo release. Methods: The local release behavior of antibiotic in vitro was simulated. The consecutive dynamic eluting experiment was performed based on the pro-operative characteristic of osteomyelitis patients and the determined results of drug concentration in the human drainage tissue fluid (DTF). The concentration of each drug in the receiving solution was detected by ultra-performance liquid chromatography-tandem quadrupole detector mass spectrometry. The ACDS was reviewed by scanning electronic microscopy (SEM) after 48 h, and prepared to be eluted for another examination after 33 days. The mechanism of antibiotic release was analyzed by using the Ritger–Peppas and Weibull equations. Results: The cumulative release rate of vancomycin in a vancomycin-calcium sulfate delivery system (VCDS) was 77.50 % (3.0 mm diameter) and 72.43 % (4.8 mm diameter), while that of the tobramycin in a tobramycin-calcium sulfate delivery system (TCDS) was 88.0 % (3.0 mm diameter) and 84.55 % (4.8 mm diameter). At the 15th day, approximately 27.92% of vancomycin was and 29.35% of tobramycin was released from the local implant in vivo. Using SEM, numerous vancomycin and tobramycin particles were found to be attached to the columnar calcium sulfate crystals at the start of the experiment. The release behavior of the two antibiotics followed a combination of Fickian diffusion and Case II transport mechanisms within the first 48 h, and a Fickian diffusion mechanism during the subsequent time period. The correlation coefficient of tobramycin and vancomycin in vivo and in vitro was 0.9704–0.9949 and 0.9549–0.9782, respectively. Conclusion: A good correlation of the in vivo and in vitro cumulative release rates was observed by comparing the cumulative release rate of drugs in vitro by means of the dynamic eluting model, and in the DTF. Therefore, our study has proved that it is possible to use the dynamic eluting model as a cautious predictor of in vivo release.

Synthesis and Evaluation of Starch – Urea – Borate as Rate Controlling Matrix for Controlled Release

1970 ◽  
Vol 1 (2) ◽  
pp. 167-170
Author(s):  
Chowdary KPR ◽  
Murali Krishna MN
Keyword(s):  
Controlled Release ◽  
Release Rate ◽  
Guar Gum ◽  
Matrix Tablets ◽  
Fickian Diffusion ◽  
Release Mechanism ◽  
Drug Release Mechanism ◽  
Zero Order Kinetics ◽  
Diffusion Controlled ◽  
Controlled Release Tablets

The objective of the present investigation is to synthesize starch – urea – borate, a new starch based polymer and to evaluate its application in the design of controlled release matrix tablets of diclofenac and gliclazide. The release rate controlling efficiency of starch – urea – borate was also compared with that of known polymers. Starch – urea – borate (SUB) polymer was synthesized by gelatinization of starch in the presence of urea and borax. Matrix tablets of diclofenac (100 mg) and gliclazide (60 mg) were formulated employing starch – urea – borate polymer in different proportions of drug and polymer and the tablets were evaluated. With both diclofenac and gliclazide, release from the formulated matrix tablets was slow and spread over 24 h and depended on percent polymer in the tablet. Release was diffusion controlled and followed zero order kinetics. Non – fickian diffusion was the drug release mechanism from the formulated tablets. Diclofenac release from matrix tablets formulated employing 33 % SUB (DF3) and Gliclazide release from matrix tablets formulated employing 50 % SUB (GF4) was similar to that from the corresponding commercial SR tablets. Starch – urea – borate polymer was found suitable for the design of oral controlled release tablets of diclofenac and gliclazide. The order of increasing release rate controlling efficiency with various polymers was ethyl cellulose = guar gum > SUB > sodium CMC > HPMC. Starch – urea – borate is a better release rate controlling polymer than HPMC and sodium CMC for obtaining controlled release over    24 hours.

A Study on the Accurate Calculation Method of Heat-Release Rate in Swirl Chamber Indirect Injection Diesel Engine

1989 ◽  
Vol 203 (4) ◽  
pp. 267-275 ◽  
Author(s):  
J P Liu ◽  
X K Ge ◽  
L X Peng
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Flow Coefficient ◽  
Practical Calculation ◽  
Release Process ◽  
Flow Equations ◽  
Swirl Chamber ◽  
Energy Exchanges

Taking the two chambers of swirl chamber indirect injection diesel engine (SC engine) as two relative but independent thermodynamic systems, this paper builds up thermodynamic equations respectively in the two chambers, together with the mass and enthalpy flow equations describing the mass and energy exchanges between them. This model, based on the synchronous pressure diagrams measured in the two chambers, is used to calculate the thermodynamic state of medium and heat-release process in both of the chambers. Furthermore, with the help of the thermodynamic equivalent system, the calculation of the variable flow coefficient of the connecting passage has been successfully achieved. A Model 6105Q SC engine is taken as a practical calculation example to reveal the combustion pattern of this type of engine. In the last part of this paper, several methods currently used for the heat-release rate calculation have been analysed to show their application field and accuracy.

scholarly journals pH-Sensitive Starch-Based Hydrogels: Synthesis and Effect of Molecular Components on Drug Release Behavior

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1974
Author(s):  
Juan Carlos Quintanilla de Stéfano ◽  
Vanessa Abundis-Correa ◽  
Sergio Daniel Herrera-Flores ◽  
Alejandro J. Alvarez
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Release Rate ◽  
Crosslinking Agent ◽  
Ph Sensitive ◽  
Fickian Diffusion ◽  
Butyl Methacrylate ◽  
Release Behavior ◽  
Drug Release Behavior ◽  
Swelling Capacity

The drug release behavior of pH-sensitive starch-based hydrogels was systematically studied. Hydrogels were synthesized by copolymerization of acrylic acid (AA) and other acrylate comonomers onto the starch backbone. The hydrophilic agents 2-hydroxy ethyl methacrylate (HEMA), and acrylamide (AAm), as well as the hydrophobic butyl-methacrylate (BMA), were utilized as comonomers. Methylene-bisacrylamide (MBA) was employed as a crosslinking agent. The synthesized hydrogels were loaded with caffeine as a model drug. The effects of the hydrophobic/hydrophilic character of the comonomers and chemical crosslinking on the swelling capacity and the release rate of caffeine were investigated. The use of the crosslinking agent and hydrophobic monomers decreased the swelling capacity of the hydrogels. The release rate of caffeine increased with the presence of a hydrophobic monomer. The fastest release was obtained with the AA/BMA/AAm formulation, and the slowest release was observed with the AA/HEMA/AAm formulation. The transport mechanism was controlled by Fickian diffusion in formulations containing AAm, and controlled by the polymer-relaxation mechanism in formulations containing MBA. Overall, our results showed that the swelling and drug delivery behavior can be tuned by varying the chemical composition of the copolymer formulations. These starch-based hydrogels can be useful as drug delivery devices in many biomedical applications.

scholarly journals Numerical Simulation Study on Salt Release Across the Sediment–Water Interface at Low-Permeability Area

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2503
Author(s):  
Weijian Li ◽  
Jinguo Wang ◽  
Zhou Chen ◽  
Yun Yang ◽  
Ruitong Liu ◽  
...  
Keyword(s):  
Surface Water ◽  
Release Rate ◽  
Water Exchange ◽  
Molecular Diffusion ◽  
Low Permeability ◽  
Water Interface ◽  
Hydrodynamic Conditions ◽  
Release Process ◽  
Water And Sediment ◽  
Lake Stage

Salt release from dredger filling sediment is a significant threat to freshwater resources in coastal regions around the world. This study focuses on the estimation of the field-scale salt-release process from the low-permeability sediment–water interface under different hydrological and hydrodynamic conditions. In situ sampling tests and physical experiments were implemented to calculate hydrogeological parameters and monitor sediment and water salinity. Numerical modeling was used to calibrate the molecular diffusion coefficient, of which the correlation coefficient was over 0.9, and explore the salt-release process across the sediment–water interface in Yuehu Lake, China. Furthermore, we discuss the influence of hydrologic conditions in terms of the lake stage and hydrodynamic conditions with water-exchange on the process of salt exchange between the sediment and water based on numerical simulations. Our findings showed that water-exchange accelerated the process of salt release from the sediment and maintained a relatively low salinity in the surface water. The salt-release rate decreased gradually as the concentration gradient between the water and sediment decreased. A frequency of water-exchange of 90 d maintained a rapid salt-release rate with fewer water-exchange steps. The influence of the lake stage was weak on the salt-release process at low-permeability area and salt release was not impeded before the salt capacity of water reached the maximum value. When the water–sediment salinity reached equilibrium, the salt-release process between the water and sediment equilibrated as the supply from the lower layers equaled the release to the water at the interface. These results are important in regard to controlling surface water salinization in coastal reclamation areas.

Preparation and the Release Rate Studies of a New Gel Type Slow-Release Solid Chlorine Dioxide

2014 ◽  
Vol 709 ◽  
pp. 441-444
Author(s):  
Qun Li ◽  
Yu Han ◽  
Xiao Wen Li ◽  
Li Ping Wang ◽  
Jian Ping Wang ◽  
...  
Keyword(s):  
Tartaric Acid ◽  
Chlorine Dioxide ◽  
Release Rate ◽  
Solid Acid ◽  
Slow Release ◽  
Sodium Chlorite ◽  
Release Process ◽  
Super Absorbent Polymer ◽  
Absorbent Polymer ◽  
Optimal Formula

A new gel type slow-release solid chlorine dioxide was prepared by mixing two gels together, which were Super Absorbent Polymer (SAP) absorbing sodium chlorite solution and solid acid solution, respectively. The optimal formula was determined by single factor experiment, and the effect of the temperature on chlorine dioxide release rate was investigated. Using tartaric acid as the solid acid, the release rate peak value of chlorine dioxide is 1.61 mg/h, and the release rate become slower of 1.09 mg/h at 72 h and 0.6 mg/h at 144 h, which shows a smooth and sustaining release process. When the volume of water is 25 mL, the optimal formula is SAP:3.5g, sodium chlorine:1.5g, anhydrous sodium sulfate:1.5g, tartaric acid:2g. The release process became more intense when the temperature became higher. The results indicated that this gel type slow-release solid chlorine dioxide should be suitable for eliminating formaldehyde and stink in the environment.

scholarly journals Tris (2-aminoethyl) Amine Functionalized Nanoporous Silica SBA-15 as a Potential Drug Carrier for Citalopram

2019 ◽  
Vol 4 (4) ◽  
pp. 155-162
Author(s):  
Fatemeh Dalayi ◽  
Leila Hajiaghababaei ◽  
Alireza Badiei ◽  
Elham Boorboor Azimi ◽  
Mohammad Reza Ganjali ◽  
...  
Keyword(s):  
Drug Release ◽  
Release Rate ◽  
Ph Value ◽  
Drug Carrier ◽  
Drug Loading ◽  
Controlled Drug Release ◽  
Nanoporous Silica ◽  
Release Process ◽  
Functionalized Mesoporous Silica ◽  
Amine Functionalized

Introduction: Ordered nanoporous silica such as SBA-15 has a great potential for application in controlled drug release systems. Chemical modification of the silanol groups of SBA-15 allows better control over drug loading and release. Therefore, tris(2-aminoethyl) amine-functionalized mesoporous silica SBA-15 was evaluated as a potential carrier for the delivery of citalopram. Methods: Tris (2-aminoethyl) amine-functionalized SBA-15 was synthesized and characterized by various methods. Citalopram was loaded on the functionalized SBA-15 and drug release into simulated body fluid (SBF) solution and phosphate buffers was investigated. Results: The optimal condition for loading of the citalopram was obtained at pH = 9 after stirring for 5 minutes. The release profile of citalopram was monitored in phosphate buffers with three different pH values of 5, 7, and 8. A faster release rate at lower pH value was observed, suggesting a weaker interaction because of the protonation of the amino group of the functionalized SBA15. The average release rate of citalopram from each gram of functionalized SBA-15 was 12 µg h-1 in the SBF. Conclusion: The results showed that loading amount and release rate of citalopram depended on pH value and the release process showed a very slow release pattern. Therefore, tris (2-aminoethyl) amine-functionalized SBA-15 is a suitable carrier for controlled release of citalopram and has a great potential for disease therapy.

scholarly journals Internal combustion engine diagnostics using statistically processed Wiebe function

2021 ◽  
Vol 23 (3) ◽  
pp. 505-511
Author(s):  
Jan Famfulik ◽  
Michal Richtar ◽  
Jakub Smiraus ◽  
Petra Muckova ◽  
Branislav Sarkan ◽  
...  
Keyword(s):  
Internal Combustion Engine ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Combustion Engine ◽  
Combustion Process ◽  
Internal Combustion ◽  
Accurate Estimation ◽  
Release Process ◽  
Wiebe Function

The aim of the article is to present the concept of an indirect diagnostic method using the assessment of the variability of the amount of released heat (mass fraction burn) and the heat release rate. The Wiebe function for the assessment of variability has been used. The Wiebe function parameters from the course of the high-pressure indication in the cylinder of internal combustion engine using linear regression have been calculated. From a sufficiently large number of measured samples, the upper and lower limits of the Wiebe function parameters have been statistically determined. Lower and upper limits characterize variability of the heat release process not only in terms of quantity but also in terms of heat release rate. The assessment of variability is thus more complicated than using one integral indicator, typically the mean value of amount of the released heat. The procedure enabling a more accurate estimation of heat generation beginning has been shown. For the combustion process variability assessment of the engine, statistical test of relative frequencies has been used.

Controlled Release of Salidroside Microspheres Prepared Using a Chitosan and Methylcellulose Interpenetrating Polymer Network

2017 ◽  
Vol 13 (10) ◽  
Author(s):  
Zhenlin Chen ◽  
Fangjian Ning ◽  
Xingcun He ◽  
Hailong Peng ◽  
Hua Xiong
Keyword(s):  
Controlled Release ◽  
Polymer Network ◽  
Interpenetrating Polymer Network ◽  
Fickian Diffusion ◽  
Release Mechanism ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Release Process ◽  
Ft Ir ◽  
Schiff Base Formation

AbstractIn this work, salidroside, a functional food agent, was incorporated into novel interpenetrating polymer network microspheres (IPN-Ms) prepared by chitosan (CS) and methylcellulose (MC) for controlled release and stabilization. IPN-Ms were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry and X-ray diffraction. The result indicated that salidroside-loaded IPN-Ms (S-IPN-Ms) are hollow and highly spherical, with a coarse pleated surface and a particle size ranging from 5 to 30 µm. Schiff base formation and the hemiacetal reaction are the primary mechanisms underlying the interpenetrating network cross-linking of IPN-Ms. In S-IPN-Ms, the CS and MC were homogeneously blended, and the salidroside was molecularly and amorphously dispersed. The encapsulation efficiency of the salidroside within the S-IPN-Ms was up to 75.64 %. In the S-IPN-M complex, the release of salidroside by S-IPN-Ms was governed by burst and sustained release, and Fickian diffusion was the primary release mechanism for the entire release process. Thus, controlled release and stabilization of salidroside were achieved through incorporation of salidroside into IPN-Ms prepared by chitosan (CS) and methylcellulose.

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