From the practicable viewpoint for environmental radioactivity measurement and monitoring, the liquid scintillation radioassay has been applied to low-level pure-beta and -emitter mixtures by using the most probable value theory. In low activity measurement, it is required to select a suitable emulsion scintillator and to deal with the calculated data statistically. Detection limit for a solution sample has been roughly estimated to be 10–2 Bq ml–1.
Authors:B. Benicewicz, G. Jarvinen, D. Kathios, and B. Jorgensen
Open-celled polymeric foam monoliths prepared by high internal phase emulsion polymerization (HIPE) are being investigated
as improved materials for separation of heavy metals. In column flow studies, the foam monoliths have high flow rates and
are durable up to at least 40 psi. A 4-vinylpyridine functionality has been incorporated into vinylbenzylchloride/styrene
copolymer foams by graft-polymerization of vinylpyridine. The open structure of the foam and the flexible graft-polymerized
ion-exchange chains result in improved kinetics in metal uptake. Iron uptake kinetics were greatly increased in the grafted
foams over resin beads of similar structure. Plutonium uptake kinetics were moderately increased in the foams.
The determination of uranium by a fluorimetric method using a conventional spectrophotometer has been elaborated. The quenching effect of the matrix was reduced by separation with liquid-liquid extraction and emulsion liquid membrane extraction methods using D2EHPA as a selective extraction reagent. The method was employed for uranium determination in radioactive waste solutions and proved to be very fast and easy to perform. It was found that it is possible to determinate as low as 0.2 ppm of uranium in a 10 ml sample.
Poly(AN—co—St) (PAS) and poly(AN—St—MMA)(PASM) were synthetized by emulsion polymerisation. The glass transition temperatures (Tg) of the copolymers and the relationship between Tg and the components of the copolymers were investigated by differential scanning calorimetry. The results show that Tg for the AN—St bipolymers has apeak value in the range 115–118°C at a content of 50 mass% St. When methyl methacrylate was added, the Tg of the terpolymer was decreased by about 2–6°C.The thermostability and the activation energy E of degradation were determined by thermogravimetric analysis.
Authors:M. Szafran, P. Wiśniewski, G. Rokicki, and L. Łukasik
The studies on the application of the emulsions of poly(vinyl acetate-co-allyl ether)s containing nonionic hydrophilic poly(oxyethylene)
fragments as binders in the die pressing of alumina is presented. It was found that introduction of hydrophilic fragments
into molecules of a typical water dispersible polymer led to better polymer affinity to the ceramic powders. It was also shown
that low molecular mass of such copolymers should be relatively low ca 1500 g mol–1 to increase the density and thickening uniformity of the samples before and after sintering. The resultant sinters indicated
exceptionally high mechanical strength (bending strength ca 500 MPa).
Technetium(VII) extraction has been investigated to obtain useful information concerming the back-extraction of Tc(VII). Radioactive technetium-95m was used to determine the distribution ratio (DTc) of95mTcO
for Tc(VII) extraction using Primene JMT (RNH2) in heptane solution. An emulsion formation did not occur in the ammonium carbonate system but occurred in the sodium hydroxide solutions. The extraction mechanism has also determined by using the slope analysis method to study the relationships between logDTc and log [RNH2], and between logDTc and pH.
An experimental method was conducted to evaluate the minimum bubble nucleation energy of freon-12 for application in the superheated-liquid-droplet
(SLD) technique. The minimum energy needed for an incident particle to cause the bubble nucleation is based on the theoretical
calculation ofWmin/ηkrc value. The calculated value may mislead the result of measured intensity due to its under/overestimation ofWmin/ηkrc values at various temperatures. Nevertheless, the experimental evaluation ofWmin/ηkrc of freon-12 for causing the bubble nucleation is barely touched because the proper methodology has not developed fully. The
minimum energy needed to produce the bubble nucleation, can be evaluated by mixing the alpha-emitting nuclides with the SLD.
By direct hitting the SLD with alpha-particle, the energy deposited inside the SLD may cause the bubble nucleation if the
deposited energy is larger than theWmin/ηkrc of freon-12 droplet at that specific temperature. The experimental evaluated values in this study agree with the theoretical
estimation in 78% for SLD emulsion temperature within 22–34°C. Tests suggest that to apply the SLD in measuring the alpha-emitting
nuclides, the emulsion temperature should be maintained below 30°C to get a maximum efficiency and to avoid interference from
beta or gamma event.
Authors:İ. Gülçin, Ş. Beydemir, ?.G. Şat, and Ö.İ. Küfrevioğlu
In present study, water extract of cornelian cherry (Cornus mas L.) (WECM) was studied for antioxidant properties. The antioxidant properties of WECM were evaluated using different antioxidant tests, including reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities. These properties may be the major reason for the inhibition of lipid peroxidation. The concentration of 20, 40 and 60 µg ml-1 of WECM showed 75.8, 93.4 and 97.5% inhibition on peroxidation of linoleic acid emulsion, respectively. On the other hand, 60 µg ml-1 of standard antioxidants such as BHA, BHT and a-tocopherol exhibited 96.5, 99.2 and 61.1% inhibition on peroxidation of linoleic acid emulsion, respectively. In addition, the WECM had effective reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities at the same concentrations (20, 40, and 60 µg ml-1). Those various antioxidant activities were compared to reference antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and a -tocopherol. In addition, total phenolic compounds in the WECM were determinedas gallic acid equivalent.
Authors:Eszter Csizmazia, Mária Budai-Szűcs, István Erős, Zsolt Makai, Piroska Szabó-Révész, Gábor Varju, and Erzsébet Csányi
Our aim was to develop potential dermal drug delivery systems (DDSs) with a good and lasting moisturizing effect. Lyotropic
liquid crystals (LLCs), gel-emulsions and hydrogels were investigated by means of thermogravimetry, which can give information
about the structure of these preparations, and we could study the water binding mechanisms indirectly in them. We found that
the preparations with a complex structure and strong water bonds hydrate the skin well and lastingly by in vivo tests. Since
the thermoanalytical results correlate with the in vivo test results, this method could be suited for predicting the moisturizing
effect of the vehicles and provide the possibility to select the potential semisolid DDSs for in vivo tests cost and time
A new way to perform reactions in core—shell double emulsions is reported herein. The phase boundaries of the threephase droplet flow were used to pressurize the reactants in the shell liquid, enhancing the reaction rate of a cycloaddition greatly in comparison to known methods. As key parameters, solvophobic effects and precise control over the droplet sizes were used to exploit a reaction with a negative volume of activation. The internal pressure of the reaction solution was regulated purely by the thickness of the shell liquid without adding additional reagents. Additionally, the reaction performed better when the core droplet was used to stir the shell droplet, considerably improving the mass transfer inside the otherwise diffusion-limited process.