| 1. |
- Abedi, Parisa, 1968, et al.
(författare)
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Inherent safety evaluation in process plants— a comparison of methodologies
- 2005
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Ingår i: Central European Journal of Chemistry. - 1895-1066. ; 3:4, s. 756-779
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Tidskriftsartikel (refereegranskat)abstract
- Abstract A global population increase and an improved standard of living are generally expected. To meet these demands, an increased production of chemicals will be necessary while protecting human health and the environment. However, most current methods of chemical production are unsustainable. New designs must result in plants that assure process and operator safety, the sustained health of workers and the community, and the protection of the environment. Traditional safety precautions and process controls minimize risk but cannot guarantee the prevention of accidents followed by serious consequences. Therefore, the general approach to environmental and safety problems must be changed from reactive to proactive. One way is to further develop the concept of inherent safety. In this paper some methods for inherent safety evaluations are reviewed. The aim of the study is to analyze the different tools available for inherent safety evaluation and identify the most important criteria in determining the inherent safety of a process plant. A model is proposed to show the interactions of different factors on the inherent safety level of a process and the model is illustrated by a case study.
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| 2. |
- Balau, Luminita, et al.
(författare)
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Physico-chemical properties of Chitosan films
- 2004
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Ingår i: Central European Journal of Chemistry. - 1895-1066 .- 1644-3624. ; 2:4, s. 638-647
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Tidskriftsartikel (refereegranskat)abstract
- Chitosan films obtained by dry phase inversion were prepared from an aqueous solution of chitosan in acetic acid. The films, of thickness less than 20 μm, were transparent, very flexible and had smooth surfaces. Increasing the film thickness induced an increase of the internal tensions and the consequent formation of a rough surface. Structural investigations by X-ray diffraction and Fourier transform IR analysis, showed that the chitosan films, as prepared, are amorphous. Further annealing to evaporate acetic acid and water traces, changed the amorphous phase into a more ordered phase, characterized by diffraction peaks at 2θ values of 9, 17, 20 and 23 degrees. Thermal investigations by TG, DTG, and DTA revealed that the decomposition of the chitosan films as prepared proceeds in two stages, starting from 180°C and 540°C.
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| 3. |
- Baranowska, Irena, et al.
(författare)
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Use of multivariate statistical techniques to optimize the separation of isoflavones by liquid chromatography
- 2011
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Ingår i: Central European Journal of Chemistry. - : Springer Verlag (Germany). - 1895-1066 .- 1644-3624. ; 9:6, s. 972-981
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to optimize and validate a high performance liquid chromatography (HPLC) method for separation and quantification of five isoflavones. A statistical central composite design was used to separate all peaks. These multivariate procedures were efficient in determining the optimal separation condition using resolution, capacity factor, asymmetry and number of theoretical plates. less thanbrgreater than less thanbrgreater thanThe effective separation of the examined compounds was applied on a Develosil RP Aqueous AR 5 RP-30 column with a gradient mobile phase system and a DAD detector. less thanbrgreater than less thanbrgreater thanThe isolation and preconcentration of the isoflavones from urine and plasma samples were conducted by means of the solid-phase extraction (SPE). For optimize SPE conditions various sorbents were tested. Furthermore, high recoveries and good relative standard deviations were obtained when the samples were passed through the Oasis HLB column. The developed method was validated and successfully applied for determination of isoflavones in urine and plasma.
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| 4. |
- Baykal, Abdulhadi, et al.
(författare)
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Sonochemical synthesis and chracterization of Mn3O4 nanoparticles
- 2010
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066. ; 8:3, s. 633-638
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis of Mn3O4 nanoparticles (NPs) using a novel sonochemical method without requiring any pH adjustment. Synthesized material was identified as tetragonal hausmannite crystal structure model of Mn3O4 from XRD analysis. Crystallite size was estimated from x-ray line profile fitting to be 17 +/- 5 nm. FTIR analysis revealed stretching vibrations of metal ions in tetrahedral and octahedral coordination confirming the crystal structure. TEM analysis revealed a dominantly cubic morphology of NPs with an average size of similar to 20 nm. Magnetic evaluation revealed a blocking temperature, T-B of 40 K above which the material behaves paramagnetic. Asymmetric coercive field is attributed to the interaction between ferromagnetic Mn3O4 and antiferromagnetic Mn oxide at the surface of nanoparticles.
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| 5. |
- Kosa, Ladislav, et al.
(författare)
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Phase transitions of K2TaF7 within 680-800 degrees C
- 2008
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066. ; 6:1, s. 27-32
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Tidskriftsartikel (refereegranskat)abstract
- Three thermal effects on heating/cooling of K2TaF7 in the temperature interval of 680-800 degrees C were investigated by the DSC method. The values determined for the enthalpy change of the individual processes are: Delta H-transII(m)(K2TaF7; 703 degrees C) = 1.7(2) kJ mol(-1), Delta H-transI(m)(K2TaF7; 746 degrees C) = 19(1) kJ mol(-1) and Delta H-transIII(m)(K2TaF7; 771 degrees C) = 13(1) kJ mol(-1). The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K2TaF7 and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654-794 degrees C.
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| 6. |
- Nikoleli, Georgia-Paraskevi, et al.
(författare)
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Potentiometric cholesterol biosensing application of graphene electrode with stabilized polymeric lipid membrane
- 2013
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Ingår i: Central European Journal of Chemistry. - : Springer Verlag (Germany). - 1895-1066 .- 1644-3624. ; 11:9, s. 1554-1561
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Tidskriftsartikel (refereegranskat)abstract
- A novel potentiometric cholesterol biosensor has been fabricated through the immobilization of the stabilized polymeric lipid membrane onto graphene electrode. The stabilized polymeric lipid membrane is composed of cholesterol oxidase enzyme and polymerization mixture; which holds paramount influence on the properties of the cholesterol biosensor. The presented biosensor reveals an appreciable reproducibility, good selectivity and high sensing capability with a linear slope curve of similar to 64 mV per decade. The strong biocompatibility among stabilized polymeric lipid membranes and human biofluids provides the possibility to use for real blood samples and other biological applications.
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| 7. |
- Pucetaite, Milda, et al.
(författare)
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Microspectroscopic infrared specular reflection chemical imaging of multi-component urinary stones: MIR vs. FIR
- 2014
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066. ; 12:1, s. 44-52
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Tidskriftsartikel (refereegranskat)abstract
- Specular reflection infrared microspectroscopy was used for chemical imaging of cross-sectioned urinary stones to determine their chemical composition and morphology simultaneously. Absorption spectral bands were recovered from reflection spectra by Kramers-Kronig transform. FUse of far-infrared radiation provides high-contrast images and allows more precise constituent distribution determinations than mid-infrared because band asymmetry after the transform caused by diffuse reflection is less in the far-infrared.
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| 8. |
- Roth, Olivia, et al.
(författare)
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Oxidation of UO2(s) in aqueous solution
- 2008
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066. ; 6:1, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- In this review the kinetics and mechanism of oxidative dissolution of UO2(s), mainly under conditions of relevance for the safety assessment of a deep geological repository for spent nuclear fuel, are discussed. Rate constants for the elementary processes involved (oxidation of UO2 and dissolution of oxidized UO2) are used to calculate the rates of oxidative UO2(s) dissolution under various conditions (type of oxidant, oxidant concentration and HCO3-/CO32- concentration) for which experimental data are also available. The calculated rates are compared to the corresponding experimental values under the assumption that the experimental numbers reflect the steady-state conditions of the system. The agreement between the calculated rates and the corresponding experimental ones is very good, in particular for the higher rates. In general, the calculated rates are somewhat higher than the experimental numbers. This can be due partly to the use of initial concentrations rather than steady-state concentrations in the calculations. The kinetic data are also used to quantitatively discuss the dynamics of spent nuclear fuel dissolution under deep geological repository conditions.
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| 9. |
- Shahid, Robina, et al.
(författare)
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Low temperature synthesis of cubic phase zinc sulfide quantum dots
- 2012
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066 .- 1644-3624. ; 10:1, s. 54-58
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report on a new method for the synthesis of ZnS quantum dots (QDs). The synthesis was carried out at low temperature by a chemical reaction between zinc ions and freshly reduced sulfide ions in ethanol as reaction medium. Zinc chloride and elemental sulfur were used as zinc and sulfur sources, respectively and hydrazine hydrate was used as a strong reducing agent to convert elemental sulfur (S(8)) into highly reactive sulfide ions (S(2-)) which react spontaneously with zinc ions. This facile, less toxic, inexpensive route has a high yield for the synthesis of high quality metal sulfide QDs. Transmission electron microscopy (TEM) image analysis and selected area electron diffraction (SAED) reveal that ZnS QDs are less than 3 nm in diameter and are of cubic crystalline phase. The UV-Vis absorption spectrum shows an absorption peak at 253 nm corresponding to a band gap of 4.9 eV, which is high when compared to the bulk value of 3.68 eV revealing strong quantum confinement. PL emission transitions are observed at 314 nm and 439 nm and related to point defects in ZnS QDs.
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| 10. |
- Sladkovicova, Mariana, et al.
(författare)
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DFT and neutron diffraction study of 1,6-anhydro-beta-D-glucopyranose (levoglucosan)
- 2007
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066. ; 5:1, s. 55-70
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Tidskriftsartikel (refereegranskat)abstract
- Geometries of 27 generated conformers of levoglucosan were optimized in vacuo at DFT level of theory combining several functionals with high quality basis sets. For the sake of comparison a reference molecular and crystal geometry obtained from 30 K single crystal neutron diffraction data was used. Analysis of the conformers' geometries revealed that in all stable conformers intramolecular two- or three centre hydrogen bonds were formed. Relative energy of the conformer, which approximated the molecule in the crystal structure the most, was only similar to 3 kcal/mol higher, than the energy of the most stable conformer in vacuo. The largest discrepancies between the geometries calculated in vacuo and experimental geometry concentrated in the vicinity of anomeric C1. These differences were reduced by involving O1 to intermolecular hydrogen bond using a simple model of the respective hydrogen bond in the crystal.
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