Special techniques for deep purification of ZnO and WO3 have been developed in this work. A ZnWO4 single crystal has been grown by the Czochralski method using purified ZnO and WO3 chemicals, along ...with the ZnWO4 crystal-etalon, which has been grown at the same conditions using commercially available 5N ZnO and WO3 chemicals. The actual accidental impurities compositions of both the initial chemicals and the grown crystals have been measured by inductively coupled plasma mass-spectrometry. A complex of comparative spectroscopic studies of the crystals has been performed, including optical absorption spectra, photo-, X-ray-, and cathodoluminescence spectra and decay kinetics, as well as the photoluminescence excitation spectra. The revealed differences in the measured properties of the crystals have been analyzed in terms of influence of the accidental impurities on these properties.
Ultra-low-radioactive titanium is the main perspective material for cryostat fabrication in dark matter search experiments. The pathways of the uranium and thorium contamination of Ti sponges ...produced by the Kroll process were analyzed. The general role of Mg in Ti sponge contamination by U and Th was established. It was found that when transformed to MgCl
in the Kroll process, Mg was purified from U and Th, and further MgCl
reduction and sublimation makes it possible to produce low-radioactive Ti sponges.
A simple method of synthesis of high pure tris(8-hydroxyquinoline)aluminum (Alq
) from commercial available 5N Al
O
and 8-hydroxyquinolinol has been developed. One-step exchange chemical reaction has ...been conducted under controlled 8-hydrixyquinoline vapor at a temperature of 190-240 °C with water removal by phosphorus anhydride. According to analysis of inductively coupled plasma mass-spectrometry, the chemical purity of synthesized Alq
was 99.998 wt%. Photoluminescence of the synthesized Alq
has been measured and slightly differed from those of Alq
obtained by traditional organic synthesis.
Ultra-low-radioactivity titanium alloys are promising materials for the manufacture of low-background detectors which are being developed for experiments in astroparticle physics and neutrino ...astrophysics. Structural titanium is manufactured on an industrial scale from titanium sponge. The ultra-low-background titanium sponge can be produced on an industrial scale with a contamination level of less than 1 mBq/kg of uranium and thorium isotopes. The pathways of contaminants during the industrial production of structural titanium were analyzed. The measurements were carried out using two methods: inductively coupled plasma mass spectroscopy (ICP-MS) and gamma spectroscopy using high-purity germanium detectors (HPGes). It was shown that the level of contamination with radioactive impurities does not increase during the remelting of titanium sponge and mechanical processing. We examined titanium alloy samples obtained at different stages of titanium production, namely an electrode compaction, a vacuum arc remelting with a consumable electrode, and a cold rolling of titanium sheets. We found out that all doped samples that were studied would be a source of uranium and thorium contamination in the final titanium alloys. It has been established that the only product allowed obtaining ultra-low-background titanium was the commercial VT1-00 alloy, which is manufactured without master alloys addition. The master alloys in the titanium production process were found cause U/Th contamination.
Introduction.
An increasing number of studies conducted in various countries in the field of biopharmacy convincingly show the differences in the physiological effects on the human body of ...stereoisomers of pharmaceutical substances. As a rule, one of the enantiomers has the necessary pharmacological effect, the other enantiomer is either inert or has a negative side effect. Currently, it is important to obtain enantiomerically pure pharmacological substances from their racemic mixtures.
Aim.
Obtaining the R-isomer of salbutamol from a racemic mixture of salbutamol and developing a preparative procedure for chiral separation by supercritical fluid chromatography (SFC) with a yield of the target product sufficient for the production process.
Materials and Methods.
Supercritical fluid chromatography (SFC) is widely used for analytical and preparative separations of enantiomers of pharmaceutical substances. The relevance of the use of supercritical fluid chromatography SFC is largely due to the fact that it uses sub- or supercritical carbon dioxide (SC-CO
2
) as the main component of the mobile phase (MP). Studies were carried out on semi-preparative Investigator SFC (Waters Corporation, USA) and preparative Prep 200 qSFC (Waters Corporation, USA) supercritical fluid chromatographs with PDA detectors. Samples were weighed to the nearest 0.0001 g on a XPE206DR balance (Mettler Toledo, USA).
Results and discussion.
The process of chiral separation of salbutamol sulfate by the SFC method on Prep 200 qSFC (Waters Corporation, USA) was studied. It was revealed that in the chromatographic system under supercritical conditions, the salt is separated into acidic and basic residues, which significantly reduces productivity and shortens the duration of continuous operation of the chromatograph. Conditions for the preparative chiral separation of the racemic mixture of salbutamol base into R- and S-isomers with high enantioselectivity and productivity have been developed. The resulting R-isomer of salbutamol base can be converted into the pharmaceutical substance in the form of sulfate or other salt without loss of enantiomeric purity, the S-isomer can be subjected to racemization and subsequent use.
Conclusion.
A preparative method has been developed for the chiral separation of a racemic mixture of salbutamol by supercritical fluid chromatography (SFC) with a yield of the target product (R-isomer) of 5.5 g per shift (8 hours).
In this study, a novel vapor–liquid equilibrium equation has been presented based on a simple theory for pure substances. This equation shows a relation between the non-ideal behaviors of the ...saturated liquid and vapor phases of pure substances, which are in equilibrium with each other. The special shape of this relation lets us to calculate the equilibrium values of the temperature, pressure or molar volume of each one of these phases. Although the idea of this theory-based equation has been raised from investigation of equilibrium PVT values of water, the empirical values of 14 substances have been used for validating the accuracy of the predictions of this equation. This comparison confirms this accuracy with RMSE
mean–
= 0.0254.
► An inverse method is used to analyze experimental thermogram in order to correctly identify the thermodynamical parameters of phase change materials. ► Thanks to a rigorous approach, based on ...thermodynamical principles, enthalpy of pure substances or binary solutions may be accurately represented. ► Sensitivity analysis and numerous results are provided.
Thermal energy storage is now a key parameter to overcome the delay between energy supply and demand in many applications. To address this issue, the use of phase change materials (PCM) tends to be more and more common. Given the attempted objectives of such applications, performances of the PCM are a cornerstone of the whole system. Therefore, a correct determination of their intrinsic properties is crucial. To perform this step, one may use a calorimetry experiment. Unfortunately, the interpretation of the thermogram is not straightforward and consequently, when not feasible at all, estimations may be wrong. As an example, pure substance as sometimes said to melt at a non-uniform temperature (their enthalpy being smeared over several degrees), and binary solutions are associated with liquidus temperature and latent heat that do not match the correct form of their enthalpy. The present work proposes a new method to avoid such issues. To summarize the novelty of our approach, the main idea is to use an inverse method to identify the thermodynamical parameters of the sample through a matching step between the experimental curves and theoretical ones. It means that contrary to many others methods, we do not directly extrapolate the thermodynamical properties (e.g. the enthalpy) from the thermogram. Instead, we suppose an a priori formulation of the enthalpy, based on thermodynamical principles. Thus the thermodynamical parameters are inputs of which only values are computed from the experiments. Capabilities of the method are shown on pure substances and binary solutions examples.
The present study aimed to develop, introduce, and conduct an activity for the integration of augmented reality to the jigsaw IV technique in a planned and systematic manner. The activity developed ...for secondary school students is related to the "Pure Substances" subject which it is included in the "Particulate structure of matter" topic. The activity was arranged as; an attractive introduction, expert group studies, home team studies and assessment stages. Whereas augmented reality was used during the "home team study" stage for the jigsaw IV technique. Students are given the opportunity to examine a lot of resources during the "expert group study" and "home team study" stages to encourage them to be educated as science literate individuals. Whereas the students are subject to individual examinations during the assessment stage. This activity is an example for increasing the usage area of augmented reality in the education environment. Moreover, it is also considered that the activity will provide benefits in ensuring meaningful learning by embodying abstract concepts and helping students in improving 21st-century skills (e.g., cooperative study skills, learning to learn, communication, entrepreneurship, adaptation, leadership, social skills, and responsibility, etc.).
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
An equation of state to describe the complete phase diagram of a pure substance is developed. The equation of state is constructed by using a generic cubic equation plus the term −fT/(v−e)10. This ...term (where f>0 and e are adjustable parameters) is the attractive contribution of the solid phase. It has a volume short-range contribution, and extends the traditional use of a cubic equation, incorporating the thermodynamics description of the solid phase, which allows to represent the experimental triple point, the solid–liquid, and the solid–vapor phase transitions, together with the traditional description of the liquid–vapor transition. For the solid–liquid phase coexistence at any temperature, molar volume predictions of the solid phase define a curve which never connects to its corresponding liquid phase curve. This feature is in agreement with experimental evidences that seem to not accept the existence of a solid–liquid critical point. Finally, calculations for the complete phase diagram for carbon dioxide and argon were carried out in order to show the capabilities and features of the equation of state, and these results were also compared with other predictions from the literature.
An equation of state (EOS) for square-well chain molecules with variable range developed on the basis of statistical mechanics for chemical association in our previous work is employed for the ...calculations of
pVT properties and vapor–liquid equilibria (VLE) of pure non-associating fluids. The molecular parameters for 73 normal substances and 46 polymers are obtained from saturated vapor pressure and liquid molar volume data for normal fluids or
pVT data for polymers. Linear relations are found for the molecular parameters of normal fluids with their molecular weight of homologous compounds. This indicates that the model parameters of homologous series, subsequently
pVT and VLE, can be predicted when experimental data are not available. The predicted saturated vapor pressures and/or liquid volumes are satisfactory through the generalized model parameters. The calculated VLE and
pVT for normal fluids and polymers by this EOS are compared with those from other engineering models, respectively.
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