Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: M. Rękas x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

Both temperatures, T C, (T C —Curie temperature) and heat of the phase transition: ferroelectric-paraelectric, ΔH, in the BaxSr1−xTiO3 materials have been studied by means of the microcalorimetric method. The determined parameters were verified by either temperature dependence of the dielectric permittivity (Curie-Weiss law) or thermodynamic method. The effect of strontium content on T C has been discussed. It was found that microcalorimetry is useful tool studying phase transition phenomena in ferroelectric perovskites.

Restricted access

Abstract  

Calorimetric method for the determination of radiation power of the solar-simulated light sources has been proposed. The application of the differential scanning calorimetry guarantees very high sensitivity (1 mW) of the measuring property, independent of the wavelength (within 300-1200 nm). The applied method yields reliable calibration curves of the radiation power vs. wavelength with good accuracy.

Restricted access

Abstract  

The binary system Li2CO3–BaCO3 was studied by means of differential thermal analysis (DTA), thermogravimetry (TG) and X-ray phase analysis. The composition of carbonate and CO2 partial pressure influence on the thermal behavior of carbonate were examined. It was shown that lithium carbonate does not form the substitutional solid solution with barium carbonate, however the possible formation of diluted interstitial solid solutions is discussed. Above the melting temperature the mass loss is observed on TG curves. This loss is the result of both decomposition of lithium carbonate and evaporation of lithium in Li2CO3–BaCO3 system. Increase of CO2 concentration in surrounding gas atmosphere leads to slower decomposition of lithium carbonate and to increase the melting point.

Restricted access

Abstract  

The mutual reactivity in mixtures containing Nasicon (Na3Zr2Si2PO12) or YSZ (ZrO2:Y2O3) solid electrolytes with Li2CO3 or Li2CO3:BaCO3 sensing electrode materials was investigated using simultaneous DTA and TG and ex situ XRD techniques. The uncontrolled chemical reaction is suspected to be responsible for the instability of electrochemical gas sensors constructed from these materials. DTA and TG results obtained for Nasicon-carbonate mixtures indicate the possibility of reaction in the temperature range from about 470 to 650C, which overlaps the sensor operating temperature range (300–525C). The results obtained for YSZ-carbonate mixtures indicate that reaction between carbonate and the ZrO2 takes place at higher temperatures and cannot explain the instability drift of investigated sensors. The mechanism of observed reactions in systems studied is also discussed.

Restricted access
Acta Biologica Hungarica
Authors: J. Saju, Sz. Németh, Réka Szűcs, Rashmi Sukumaran, Z. Lim, L. Wong, L. Orbán, and M. Bercsényi

The identification of three scorpionfish species, the black scorpionfish (Scorpaena porcus Linnaeus, 1758), the large-scaled scorpionfish (S. scrofa Linnaeus, 1758) and the small red scorpionfish (S. notata Rafinesque, 1810) is possible in adults by morphometry, but often problematic in juveniles due to their similar phenotypes. To develop a molecular species identification tool, first, we have analyzed the genetic similarity of the three species by a PCR-based ‘blind method’ that amplified bands from various locations of the genome. We found high levels of nucleotide similarity between S. porcus and S. scrofa, whereas S. notata showed a higher level of divergence from the other two species. Then, we have searched these patterns for differences between the genomes of Adriatic specimen of these three species and identified several species-specific products in two of them. For the third one a species-specific primer pair amplifying from the 16S ribosomal DNA was designed. One marker for each species was cloned, sequenced and converted into Sequence Characterized Amplified Region (SCAR) markers amplified by specific primer pairs. The SCAR markers amplified robust bands of limited variability from the target species, while no or only occasional weak products were obtained from the other two, proving that they can be used for molecular identification of these three species. These markers can help the conservation and future analysis of these three species as well as their possible selection programs for aquaculture purposes.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: A. Saiki, H. Funakubo, N. Mizutani, K. Shinozaki, T. Bak, J. Nowotny, M. Rekas, and C. Sorrel

Abstract  

The extent of the surface charge, that develops during oxidation of zirconia, is determined using work function measurements for both bulk specimen and thin films. The bulk specimen of yttria-doped zirconia (10 mol%) exhibits maxima of the surface electrical effect at 373 and 973 K (130 and 280 mV, respectively) that can be considered in terms of oxygen chemisorption and oxygen non-stoichiometry. Thin film of undoped zirconia exhibits a maximum at 473 K (260 eV). Addition of yttria (10 mol%) to the thin film results in a substantial reduction of the maximum, to about 140 eV, that is shifted up to 600 K.

Restricted access

Abstract  

The purpose of this work was to investigate the influence of titanium and yttrium dopants on chemical stability of selected Ba(Ce1−xTix)1−yYyO3 compounds. The presented results are the part of wider research concerning the crystallographic structure, microstructure, electrical and transport properties of these groups of materials. Samples of Ba(Ce1−xTix)1−yYyO3 with x=0.05, 0.07, 0.10, 0.15, 0.20, 0.30 and y=0.05, 0.10, 0.20 (for x=0.05) were prepared by solid-state reaction method. Initially, differential thermal analysis (DTA) and thermogravimetry (TG) were used for optimization of preparation conditions. Subsequently, DTA-TG-MS (mass spectrometry) techniques were applied for evaluation of the stability of prepared materials in the presence of CO2. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results were used to determine the phase composition, structure and microstructure of materials and to assist the interpretation of DTA-TG-MS results. The strong influence of Ti and Y dopants contents (x and y) on the properties was found. The introduction of Ti dopant led to the improvement of chemical stability against CO2. The lower Ti concentration the better resistance against CO2 corrosion was observed. Doping by Y had the opposite effect; the decrease of chemical stability was determined. In this case the higher Y dopant concentration the better resistance was observed. The attempt to correlate the influence of dopant on structure and chemical stability was also presented.

Restricted access

Abstract  

The effect of phalloidin on filaments polymerized from ADP-actin monomers of the heart muscle was investigated with differential scanning calorimetry. Heart muscle contains α-skeletal and α-cardiac actin isoforms. In the absence of phalloidin the melting temperature was 55°C for the α-cardiac actin isoform and 58°C for the α-skeletal one when the filaments were generated from ADP-actin monomers. After the binding of phalloidin the melting temperature was isoform independent (85.5°C). We concluded that phalloidin stabilized the actin filaments of α-skeletal and α-cardiac actin isoforms to the same extent when they were polymerized from ADP-actin monomers.

Restricted access