Thermodynamic properties of alloys In—Tb system

The method of isoportic calorimetry investigated the thermochemical properties of the melt In—Tb system in the range of compositions 0 < xIn < 0,4 at 1625 ± 1 K. The obtained data were extrapolated on a non-investigated concentration interval, given that when xTb = 1 integral and partial to Tb enthalpia mixing is zero. It was established that the first partial for Terbium and the minimum enthalpy of mixing is –145 ± 7 and –40,1 ± 0,2 kJ/mol respectively. Comparison of ΔHmin, the melt of five previously investigated In—Ln systems from the serial number Ln (zLn), together with the data obtained in this papper, showed that they are described by one trend line. For ΔHmin In—Eu (Yb) melts (Yb) are very slight deviations from the trend line. But for dimensional factor, these deviations from the trend line are more significant. Enthalpia of the formation of some In—Ln intermetallides are known, with most of them relate to the LnIn3 compound. But there is no full reconciliation between these data. The results of the most modern work exhibit less dependence on the serial number of lanthanides and are more exothermic for heavy lanthanides, compared with other data. Comparing thermochemical properties of double Sn (Sb) —REM melt systems. It has been established that the energy of the interaction between the data p-elements and REM increases in such a sequence: In-REM → Sn—REM → Sb—REM. This is due to the fact that the stibium is the best acceptor of electrons. Keywords: thermochemical properties, melts, compounds, In, Tb.

PHYSICO-CHEMICAL INTERACTION OF THE COPPER AND ANTIMONY IODIDES

The character of the mutual interaction of the components in the CuI-SbI3 system was studied by differential thermal analysis and X-ray phase analysis methods and its phase diagram was constructed. It was found that the system is quasi-binary and forms a monotectic phase diagram. The immiscibility region covers ~15-93 mol% SbI3 concentration interval at the monotectic equilibrium temperature (~ 4930С). The temperatures of polymorphic transformations of the CuI compound in the system drop slightly and these phase transitions take place by metatectic reactions

Mesoporous Silicon / Polypyrrole Based Structures for Paranitrophenol Sensing

Elaboration of new structures based on semi-conductors and conducting polymers can procure a new alternative to the development of various electrochemical sensors with good sensibility.The key idea of this paper is to develop a facile technique for the detection of the para-nitrophenol which is considered as an important toxic pollutant. In this context, different structures based on mesoporous silicon modified with Polypyrrole (PPy) were elaborated.The hybrid structures have been characterized by several techniques such as FTIR, SEM and Contact angle measurements.In addition, the behavior of these new structures for para-nitrophenol detection by cyclic voltammetry was studied. The results show a high sensitivity of the sensor in a large concentration interval.

Impedance Spectroscopy of Nickel-Containing Solid Solutions of CaCu3Ti4O12

Samples of CaCu3Ti4-4хNi4хO12-δ. were obtained by solid phase synthesis method. X-ray diagrams of all preparations show trace amounts of the impurity phase of copper oxide(II), at x ≥ 0.04 the impurity CaTiO3 reflexes are shown. Admixtures of nickel-containing phases in samples in all investigated concentration interval by X-ray analysis and electronic scanning microscopy are not fixed. It is established that the polarization processes in the samples are carried out at different speeds by two mechanisms. As a result of modeling using two equivalent schemes, it was found that the homogeneity of samples with growth x decreases, in the sample CaCu3Ti4-4хNi4хO12-δ (х = 0.03) polarization proceeds three times faster than in x = 0.06. The sample CaCu3Ti3.88Ni0.12O12-δ conducts direct electric current better and polarizes faster in a variable electric field than x = 0.06. The activation energy of the samples is practically the same: 0.491 (x = 0.03) and 0.499 eV (x = 0.06). After 350 °C the homogeneity of the material deteriorates, which indicates a possible disorder of the structure or a break in the chemical bonds

Synthesis and some properties of compounds Cu2PrSb3S7 and Cu2ErSb3S7

The phase equilibrium in systems of CuSbS2 – PrSbS3 and CuSbS2 – ErSbS3 has been studied by physicochemical methods (Differential thermal analysis – DTA, X-ray diffraction phase analysis, Scanning Electron Microscopy – SEM analysis and microhardness testing) and their T-x diagrams were drawn. It was determined that both systems are quazibinary and characterized by formation of Cu2LnSb3S7 -type (Ln = Pr, Er) compounds. Cu2PrSb3S7 melts congruently at 1050 K and is the phase with unstable content. Its dissolution zone changes within concentration interval of 32-37 mole% of PrSbS3. Cu2PrSb3S7 divides the system into two sub-systems: CuSbS2-Cu2PrSb3S7 and Cu2PrSb3S7-PrSbS3. Both of sub-systems are eutectic. The coordinates of the eutectic point are like following: 15 mole % PrSbS3, T = 740 K and 50 mole % PrSbS3, T = 790 K. Cu2ErSb3S7 melts at 920 K by decomposition. At 725K between Cu2ErSb3S7 and CuSbS2 compounds in content of 15 mole % of ErSbS3 is formed eutectic balance. 4 mole % of solid solution is formed on base of CuSbS2. Both compounds are crystallized by naffildite-type structure in the form of rhombic syngonia (Cu2PrSb3S7 – a = 1.444; b = 2.146; c = 0.3995 nm; z = 4; Cu2ErSb3S7 – a = 1.430; b = 2.128; c = 0.380 nm; z = 4; stereogroup Pbnm or Pbn21).

Morphophysiological responses of Billbergia zebrina Lindl. (Bromeliaceae) in function of types and concentrations of carbohydrates during conventional in vitro culture

When propagated in vitro, explants receive all the nutrients needed for their growth, including carbohydrates, from the culture medium. However, it is not well understood how the type and concentration of carbohydrates can affect the functioning of the photosynthetic apparatus (particularly photosystem II) of these plants. The aim was to assess the morphophysiological responses of Billbergia zebrina plants in function of sources and concentrations of carbohydrates during in vitro culture. Side shoots of plants previously established in vitro were individualized and transferred to a culture medium containing fructose, glucose or sucrose in four concentrations (0, 15, 30 or 45 g L−1). After growth for 55 days, the chlorophyll a fluorescence transient, leaf anatomy and growth were analyzed. The concentration and type of carbohydrate employed during in vitro culture did not decrease the photosynthetic apparatus performance. However, concentrations above 30 g L−1 led to anatomical modifications, revealing some degree of stress suffered by the plants. When grown in concentrations of 15 and 30 g L−1, irrespective of the carbohydrate used, the plants presented greater stomatal density. The supplementation of the culture medium with monosaccharides caused alterations in the development of the xylem vessels, such as increased number and diameter, allowing adjustment to the microenvironmental conditions. The in vitro conditions influenced the photosynthetic and anatomical responses of plants. The concentration interval from 15 to 30 g L−1 sucrose had a better effect by not causing large changes in the performance of the photosynthetic apparatus and anatomy of plants.

Calculation of the Macromolecular Size of Bovine Serum Albumin from the Viscosity of Its Aqueous Solutions

On the basis of experimental data for the shear viscosity of aqueous bovine serum albumin (BSA) solutions and in the framework of the Malomuzh–Orlov cellular approach, the surface of effective radii of BSA macromolecules has been plotted for the constant pH = 5.2 in the concentration interval of 2.0–27.2 wt% and the temperature interval 278–318 K. A rapid nonlinear increase in the effective radii of BSA macromolecules is shown to take place up to BSA concentrations of about 5 wt% in the whole examined temperature interval. The maxima of the effective radii of BSA macromolecules are observed at a BSA concentration of 5 wt%, and their position is temperature-independent. In the concentration interval 5.0–27.2 wt%, the effective radii of BSA macromolecules decrease, and this reduction is linear at BSA concentrations higher than 10 wt%. A comparison of the calculation results with literature data on the self-diffusion coefficient of macromolecules in solutions testifies to the efficiency of the Malomuzh–Orlov formula for calculating the macromolecular radii of globular proteins on the basis of shear viscosity data for their aqueous solutions.

Quantitative Analysis of Terpenic Compounds in Microsamples of Resins by Capillary Liquid Chromatography

A method has been developed for the separation and quantification of terpenic compounds typically used as markers in the chemical characterization of resins based on capillary liquid chromatography coupled to UV detection. The sample treatment, separation and detection conditions have been optimized in order to analyze compounds of different polarities and volatilities in a single chromatographic run. The monoterpene limonene and the triterpenes lupeol, lupenone, β-amyrin, and α-amyrin have been selected as model compounds. The proposed method provides linear responses and precision (expressed as relative standard deviations) of 0.6% to 17%, within the 0.5–10.0 µg mL−1 concentration interval; the limits of detection (LODs) and quantification (LOQs) were 0.1–0.25 µg mL−1 and 0.4–0.8 µg mL−1, respectively. The method has been applied to the quantification of the target compounds in microsamples. The reliability of the proposed conditions has been tested by analyzing three resins, white copal, copal in tears, and ocote tree resin. Percentages of the triterpenes in the range 0.010% to 0.16% were measured using sample amounts of 10–15 mg, whereas the most abundant compound limonene (≥0.93%) could be determined using 1 mg portions of the resins. The proposed method can be considered complementary to existing protocols aimed at establishing the chemical fingerprint of these kinds of samples.

EXTRACTION OF Pd(II), Ni(II), Co(II), Cu(II), Fe(III) AND Zn(II) IONS WITH 1,2,3-BENZOTRIAZOLE IN SYSTEMS BASED ON ANIONIC SURFACTANTS

The phase state and extraction capacities of aqueous systems based on sulfonol, sodium dodecylsulfate or alkylbenzenesulfonic acid as anionic surfactants and hydrochloric (or sulfuric) acid against the influence of 1,2,3-benzotriazole as an organic complexing reagent were studied. Introduc-tion of 1,2,3-benzotriazole into the systems resulted in its exfoliation in two liquid phases. Optimal concentration parameters of the extraction process in the systems under investigation were found: the total volume of the system (10 ml) contained sulfonol or sodium dodecyl sulfate (0.6 g), alkylbenzenesulphonic acid (0.5 g), and 1,2,3-benzotriazole (0.35 g). The aliquation state was maintained in the following concentration interval of HCl (H2SO4), mol L-1, for the systems with: (a) sodium dodecylsulfate: 0.5-6 (0.5-4), (b) sulfonol: 0.1-4 (0.05-3), (c) alkylbenzenesulfonic acid: 0-4 (0-3). Distribution of 0.01 mol L-1 of Pd(II), Ni(II), Cu(II), Co(II), Zn(II) and Fe(III) ions in the above systems was studied at the optimal components ratios. In the systems containing sodium dodecylsulfate, no quantitative extraction of metal ions was observed. In the systems with sulfonol and alkylbenzenesulfonic acid, practically complete (99.9%) extraction of palladium appeared to be possible in the entire range of acid concentrations; with minimal acid content, over 95% of copper and nickel were extracted. The extraction of palladium ions in the presence of interfering ions was studied. Quantitative recovery of palladium ions was found to not be obstructed by 500-fold molar excess of copper, 300-fold excess of cobalt and 70-fold excess of nickel.

Casein-Conjugated Gold Nanoparticles for Amperometric Detection of Leishmania infantum

Sensitive and reliable approaches targeting the detection of Leishmania are critical for effective early diagnosis and treatment of leishmaniasis. In this frame, this paper describes a rapid quantification assay to detect Leishmania parasites based on the combination of the electrocatalytic ability of gold nanoparticles (AuNPs) to act as a catalyst for the hydrogen formation reaction along with the specificity of the interaction between casein and the major surface protease of the Leishmania parasite, GP63. First, pure and casein-modified AuNPs were prepared and characterized by scanning electron microscopy and ultraviolet–visible spectroscopy. Then, casein-conjugated AuNPs were incubated with Leishsmania parasites in solution; the formed complex was collected by centrifugation, treated by acidic solution, and the pelleted AuNPs were placed on screen-printed carbon electrodes (SPCEs) and chronoamperometric measurements were carried out. Our results suggest that it is possible to detect Leishmania parasites, with a limit less than 1 parasite/mL. A linear response over a wide concentration interval, ranging from 2 × 10−2 to 2 × 105 parasites/mL, was achieved. Additionally, a pretreatment of Leishmania parasites with Amphotericin B, diminished their interaction with casein. This findings and methodology are very useful for drug efficacy assessment.