Search Results

You are looking at 91 - 100 of 229 items for :

  • "emulsions" x
  • All content x
Clear All

Abstract  

Ammonium dinitramide (ADN) prills were prepared by emulsion crystallization and characterized by optical microscopic, thermogravimetric (TG) and differential scanning calorimetric (DSC) techniques. The isothermal and non-isothermal decomposition kinetics of ADN prills were studied by TG. The differential isoconversional method of Friedman (FR) and integral isoconversional method of Vyazovkin were used to investigate the dependence of activation energy (E a) with conversion (α) and the results were compared with literature data. The dependence of activation energy was also derived from isothermal data. A strong dependence of E a with α is observed for the ADN prills. All the methods showed an initial increase in E a up to α=∼0.2 and later decreases over the rest of conversion. The apparent E a values of FR method are higher than that of Vyazovkin method up to α=∼0.45. The calculated mean E a values by FR, Vyazovkin and standard isoconversional method for α between 0.05 and 0.95 were 211.0, 203.9 and 156.9 kJ mol−1, respectively.

Restricted access

Abstract  

Poly(dimethylbutadiene) (PDMB) was synthesized through the inclusion polymerization technique, by γ-irradiation of a clathrate of 2,3-dimethyl-1,3-butadiene in deoxycholic acid (DOCA) at 75, 150, 320 and 430 kGy. The resulting inclusion complexes PDMB@DOCA were studied by FTIR spectroscopy and by thermal analysis (DTA, TGA and DTG). Pure PDMB was isolated by extracting the complex PDMB@DOCA with ethanol. The best sample in terms of purity was that prepared at 75 kGy, while the other samples prepared at higher doses suffered of DOCA grafting on PDMB chains. Pure PDMB isolated from PDMB@DOCA complex was studied by FT-IR spectroscopy and by thermal analysis in comparison to a reference highly crystalline and ≈=100% trans-1,4-PDMB prepared by inclusion polymerization in thiourea and in comparison to PDMB prepared by emulsion polymerization. A lower degree of regularity and crystallinity has been found on the PDMB sample prepared as inclusion compound in DOCA in comparison to the reference PDMB obtained by inclusion polymerization in thiourea.

Restricted access

A water-in-oil microemulsion has been used for the first time as a mobile phase in thin-layer chromatography of amino acids. A new TLC system comprising silica gel layers impregnated with micellar copper sulfate solution as stationary phase and a water-in-oil microemulsion as mobile phase has been proposed for selective separation of DL -phenylalanine from other amino acids. Experimental conditions have been optimized and TLC conditions for separation of DL -phenylalanine in the presence of foreign impurities were determined. Improved separation of amino acids, but with reduced sensitivity, was realized on silica gel layers impregnated with metal ions such as Li + , Cu 2+ , Ni 2+ , Zn 2+ , Cd 2+ , Hg 2+ , and Th 4+ . Silica gel impregnated with a 1:1 mixture of 2% aqueous CuSO 4 and 3% Brij-35 was found to be the best layer material for rapid separation of amino acids (development time 10 min) using a water-in-oil microemulsion as mobile phase. The water content of the emulsion had little effect on the mobility of the amino acids.

Restricted access

As immune responses to live and inactivated vaccines might differ, temporal responses of broiler chickens to vaccination were examined on the basis of the abundance in the circulating blood of gene transcripts of IFN-α, IFN-γ and IL-2, critical cytokines for immune responses. Blood samples were collected 6, 12 and 24 hours, and 7 and 14 days following vaccination with either live or inactivated Newcastle disease virus, La Sota strain, at 14 days of age, and the abundance of transcripts for each cytokine was assayed by real-time RT-PCR. Physiological saline and vaccine emulsion without viral antigen were administered to control groups for live and inactivated vaccine groups, respectively. The abundance of IFN-γ transcripts was elevated during the early times following vaccination and had reached baseline by the seventh day but the abundance of IFN-α transcripts remained elevated. Transcripts for neither IFN gene were detected in the control birds. The abundance of transcripts for each IFN was not different between the two vaccinated groups at any time. Transcripts for IL-2 were detected only in spleens from chicken embryos that had been inoculated with the live virus. The results show that cells stimulated to produce IFN-α and IFN-γ enter the circulating blood but those stimulated to produce IL-2 do not, or in very low number, and the IFN responses to both vaccines are the same.

Restricted access

1998 47 1033 1042 Guardia, M., Vidal, M. T. (1984): The use of emulsions in the preparation of samples and standards for

Restricted access

Célkitűzés: Vizsgálatunkban felmértük az intenzív osztályos nővérek ismeretét a CVC (centrális vénás kanül) okozta fertőzések megelőzésének evidencia alapú ajánlásairól. Módszer: A vizsgálatban részt vevő intenzív osztályok nővérei önkéntes részvétellel validált, többszörös választásos kérdőívet töltöttek ki 2006. október és december között. A kérdőív válaszai mellett demográfiai adatokat is gyűjtöttünk: a válaszadó neme, intenzív osztályos (ITO) gyakorlati évek száma, ágyszám, intenzíves szakápolói, illetve főiskolai diploma megléte. Eredmények: 11 intenzív osztályról 178 kérdőívet elemeztünk. A 10 kérdésre adott helyes válaszok átlaga 36,6% volt. A válaszadók közül csak kevesen (18%) tudták, hogy a CVC-k rutinszerű cseréje nem ajánlott, a többség (61,2%) viszont helyesen választotta, hogy a kanülcsere vezetődróton áthúzva nem megfelelő. A nyomásmérő szerelék cseréjét 47,8% végezné minden 4. napon, az antibiotikummal impregnált kanül használatának előnyét pedig 66,3% ismerte. A CVC fedőkötését csak 15,2% végezné el hetente, és csak 34,8% tudta, hogy mind a poliuretán, mind a géz alapú fedőkötés használható. A bőrfertőtlenítésre a 2%-os klór-hexidin ajánlott, ezt 19,8% jelölte meg helyesen; az antibiotikumos kenőcs rezisztenciaokozó hatását 13,6% tudta. Zsíroldatok adásakor 24 óránként cserélné a szereléket a válaszadók 86,4%-a, de csak 4,5% cserélné a tiszta infúziós szereléket 96 óránként. Az intenzív osztályos gyakorlati évek és az ITO-ágyszám nem mutatott korrelációt az eredményekkel. Megbeszélés: Vizsgálatunk alapján az intenzív osztályos nővérek ismerete a CVC okozta fertőzések megelőzéséről nem megfelelő. A nemzetközi ajánlások ismertetése a nővérek graduális és posztgraduális képzésében szükséges volna.

Restricted access

Abstract  

In this article, synthesis, characterization, and thermal properties of diacrylic/divinylbenzene copolymers based on the new aromatic tetrafunctional acrylate monomers are presented. The new monomers were generated by treatment of epoxides derived from various aromatic diols: naphthalene-2,3-diol (NAF), biphenyl-4,4′-diol (BIF), bis(4-hydroxyphenyl)methanone (BEP) or 4,4′-thiodiphenol (BES), and epichlorohydrin with acrylic acid. The addition reaction was carried out by a ratio of 0.5 mol of suitable epoxy derivative and 1 mol of acrylic acid in the presence of 0.7 wt% of triethylbenzylammonia chloride (TEBAC) as a catalyst and 0.045 wt% of hydroquinone as a polymerization inhibitor. The chemical structure of the prepared acrylate monomers was confirmed by 13C NMR and GC MS spectra. The emulsion–suspension polymerization of acrylate monomers with divinylbenzene (DVB) in the presence of pore-forming diluents (toluene + decan-1-ol) allowed obtaining microspheres containing pendant functional groups (hydroxyl groups). This process was carried out at constant mol ratio of acrylate monomers: DVB (1:1), and constant volume ratio of pore-forming diluents to monomers (1:1). The different concentrations of toluene in the mixture with decan-1-ol were used for qualifying the effect of the diluents on the microsphere characteristics. The influence of synthesis’s parameters on the properties of copolymer beads, e.g., pore size and surface area by BET method, the surface texture by AFM, swelling behavior in polar and non-polar solvents as well as thermal stability by differential scanning calorimetry (DSC), and thermogravimetric analysis (TG) was studied and discussed.

Restricted access

A simple, rapid, cost-effective, and eco-friendly method is proposed for the simultaneous determination of some common over-the-counter drugs (aspirin, paracetamol, and caffeine [APC]) in saliva and pharmaceutical formulations based on the coupling of ultrasound-assisted emulsification microextraction (USEME) with thin-layer chromatography (TLC)‒image-processing analysis. The process involves the rapid injection of 65 μL of chloroform in diluted saliva samples (2 mL) followed by ultrasonication, which results in the formation of an emulsion. This solution is centrifuged, and 20 μL was spotted on TLC plate which was allowed to develop in mobile phase of ethyl acetate and acetic acid (95:5, v/v). The developed TLC plate was photographed, and the spots of APC were quantified by using the freely available ImageJ software (National Institute of Health [NIH], Bethesda, MD, USA). Factors which can influence the yield of USEME were screened using 27‒4 Placket–Burman design (PBD), and significant factors were optimized using central composite design (CCD). The recoveries and detection limits for all the analytes were found to be in the range of 89.2–94.1% and 0.007–0.012 mg spot−1, respectively. The assay was found to be linear in the range of 0.04–0.2 mg spot−1 with correlation of coefficient of 0.990–0.994. Intra- and inter-day precision for the assay were found to be in the range of 3.12–4.93% and 5.66–8.61%, respectively. The developed method does not require any special instrument and handling skill for the quantitative analysis of APC in saliva and pharmaceutical formulations.

Restricted access

Abstract  

The first works in this field were realized approximately 25 years ago, when BLOCK et al. reported1,2 their studies about carrier-mediated transport (also called pertraction or membrane extraction) of uranium through plasticized membranes with neutral esters derived from phosphoric acid. At this time, the methodical principles of selective pertraction of ionic compounds through so-called bulk liquid membranes containing carriers were known.3 However, these membranes, similarly as plasticized membranes, have not achieved a broader use. This is probably because bulk liquid membranes are from a technical point of view fairly distant from the idea of a typical membrane system, and plasticized membranes (sometimes also called gel membranes) present great resistance. By the end of the 1960's and at the beginning of the 1970's, LI4–7 and CUSSLER8 worked out the principles for two widely used pertraction techniques, called pertraction through emulsion liquid and supported liquid membranes (ELM and SLM). These two techniques not only have greatest significance in laboratory practice, but they also are interesting for technological aims because of the attainable large phase boundaries, e. g. 103–104 m2/m3. Many ways to arrange membrane systems are described in papers.9,10 Recently, the significance of carrier-mediated transport through liquid membranes has grown to have (since 1980) separate section at the International Solvent Extraction Conference.This paper does not deal with mathematical models and the mechanism of pertraction in general, but it gives an overview of results obtained in publications referring to pertraction of two related element groups — actinoids and rare earth elements — using various membrane types.

Restricted access

Abstract  

The Volta clam Galatea paradoxa is a highly priced shellfish providing nutrition, jobs and poverty alleviation for the inhabitants of the lower Volta estuary. Clams are filter feeders straining particulate materials in the surrounding water, thus concentrating microorganisms and other metal elements in the gut and mantle which present possible health hazards. The elemental composition of the water, clam mantle, gut, shell, and bottom sediments were determined using Neutron Activation Analysis for the presence of Ca, Cl, Cu, Mg, Mn, V, Fe, Co, Br, Na and K. Proximate analysis of the mantle for the levels of protein, fat, carbohydrate, ash, wood fiber, phosphorus, free fatty acids and energy were carried out using the method of the Association of Official Analytical Chemists. The riverine water was laden with heavy metals V, Co, Cu, Mn, and Fe, as well as Al. These same metallic elements were detected in higher concentrations in the bottom sediments. Bioaccumulation factor (BAF) which is the measure of the distribution of heavy metals between water and biota (Clam mantle and gut), ranged from 2 to 145 times, depending on the type of contaminant. The clam meat contained high protein (15.3 ± 0.2%), no crude fiber, low fat content (1.80 ± 0.11%), fatty acids as oleic (25.2 ± 0.1%), energy (85.5 ± 0.21 kcal/100 g), carbohydrates (22.10 ± 0.03%), P (485 ± 1 mg/100 g), Ca (793 ± 75 mg/kg), Mg (860.3 ± 90.0 mg/kg). The high concentration of Ca (21,402.7 ± 797.0 mg/kg), Fe (18,071.2 ± 94.0 mg/kg), K (96 ± 14 mg/kg), Mg (540.8 ± 81.1 mg/kg), Na (4,570.0 ± 0.2 mg/kg) gives credence to the use of the shell for poultry feed mineral supplements, and in the emulsion paint manufacturing industry.

Restricted access