Liquid-state mercury(II) ion-selective electrode based on N-(O,O-diisopropylthiophosphoryl)thiobenzamide

A liquid ion-exchange electrode containing a complex of mercury(II) with N-(O,O-diisopropylthiophosphoryl)thiobenzamide in carbon tetrachloride is described. The electrode shows excellent sensitivity and good selectivity. The slope of the calibration graph is 29.0 mV/pHg²⁺ in the pHg²⁺ in the pHg²⁺ range 2–15.2 in mercury(II) ion buffers. The electrode can be used for determination of 5 × 10^?5–10^?2 M Hg(II) in the presence of 10^?2 M Cu(II), Ni(II), Co(II), Zn(II), Pb(II), Cd(II), Mn(II), Fe(III), Cr(III), Bi(III) or Al(III) ions and in the presence of 10^?3 M Ag(I) ions. It can bealso used for end-point detection in titrations with EDTA of 10^?3–10^?4 M mercury(II) at pH 2.     

Multistability of impact, utility and threshold concepts of binary choice models

The decision making problem in the context of binary choice is considered by means of impact function, utility function and threshold model approaches. The properties of generalized impact function and utility function are examined; it is shown that these two approaches are equivalent. Their relation to the threshold model is studied and the correspondence between respective cumulative distribution functions is displayed. The stationary state corresponding to the thermodynamic equilibrium is determined within mean field approximation. Multistability of the stationary state is expressed in terms of the distribution function of the random variable of impact/utility function. The correspondence with statistical physics predictions for Ising model is discussed: logistic distribution leads to the mean-field result, i.e. Curie-Weiss approximation. Variations of the distribution functions and/or other model parameters, of social character, self-support, nonlinearity of social interactions, etc., would break the direct correspondence to statistical physics of Ising model, leading in particular cases to richer structure of the multistability.     

Means and their applications

General considerations about means and expectations are preceded by a short historical overview. The existing approaches to the definition of means are classified into three groups: approximational, functional, and axiomatic. In some particular cases all of them are equivalent. The problem of meaningfulness of means is discussed for ordinal data and for some important cases of metric data. A survey of the main areas of applications: decision theory, group decision, insurance, economical equity and inequality is also provided. This revised version was published online in June 2006 with corrections to the Cover Date.     

Extraction-spectrophotometric determination of lead in heavy metal salts with cryptand (2.2.2) and eosin

A rapid, extraction-spectrophotometric determination of trace amounts of lead in heavy metal salts is proposed. Owing to application of ammonia as masking agent, the extraction system cryptand (2.2.2)-eosin-chlorobenzene exhibits very high selectivity towards transition metal cations. Using standard addition method, lead is determined without matrix separation in nitrates, chlorides, acetates and sulphates of such metals as Ag, Cd, Ni, Cu and Zn. The effect of matrix on lead extraction efficiency and blank value is also discussed. The high sensitivity and selectivity of the proposed method allow to determine of lead at the level 10^–3–10^–4%.     

Thermodynamics of Molecular Chains with a Local Asymmetric Double-Well Potential

The thermodynamics of one dimensional chains with asymmetric double-well on-site potential is investigated. Pseudo-Schrödinger equation resulting from the transfer integral method is solved numerically and in terms of semiclassical approximation. This allows exact calculation and qualitative interpretation of the partition function, free energy and the specific heat function. The specific heat exhibits a characteristic hump similar to the one observed in the structures with a symmetric double-well potential. In some systems, another extremely narrow and extremely high, peak might be developed indicating an entropy driven phase transformation. Comparison between this highly simplified model and more practical approaches to the phenomena of photoinduced phase transformations is discussed underlying the possibility of manifestation of quantum effects in some (spin-crossover) systems.     

Extraction studies of metal complexes with some macrocyclic tetraaza ligands and xanthene dyes : Spectrophotometric determination of Cadmium(II) with Tetramethyltetraazacyclotetradecane and Erythrosin A

The liquid-liquid extraction of ion-pair complexes of zinc(II), copper(II) and cadmium(II) is described. The macrocyclic ligands 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4Me-cyclam-14) and rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (Tet b) are used with xanthene dyes as the counter ions. The apparent extraction constants (D′_c) are reported. The sequences of extraction efficiency of both ligands are related to the structure of the complexes. The apparent molar absorptivity of the Cd(4Me-cyclam-14)—erythrosin A ion-associate is 1.1 × 10⁵ l mol^? cm^?1. The calibration graph is linear over the range 0—10^?5 M, which allows even 0.05 μg ml^?1 cadmium to be determined in a 0.5 M sodium hydroxide medium. No interference was observed from Ni²⁺, Pb²⁺, Zn²⁺, Mg²⁺, Sn⁴⁺, Ga³⁺, Al³⁺ and Fe³⁺. Interferences were Cu²⁺, Hg²⁺, Ag⁺ and large anions.     

A new approach to fuzzy programming

A fuzzy program is defined in the usual way as a sequence of statements (instruction) which are considered as functions (possibly fuzzy functions) and fuzzy predicates defined on the given input domain. The essential difference in the approach presented in this paper is the new interpretation of the execution of fuzzy programs, and a new method of evaluating fuzzy predicates. The result of the fuzzy program execution is an appropriate fuzzy subset in the output domain.     

Two-dimensional LC-MS/MS in detection of peptides in hypothalamus of the rat subjected to hypoxic stress

A capillary 2-D LC method coupled with IT MS has been used for separation and identification of peptides in rat hypothalamus. Animals of two different age groups (8 and 50 wk) were exposed to two different rates of CO(2 )in inhaled air to investigate the influence of different hypoxia/hypercapnia levels and their stress-related factor on the peptide excretion. Peptide compounds were fractionated (strong cation exchange chromatography), trapped, and separated (RP chromatography), and MS/MS mass spectra were used for identification. About 107 peptide compounds were identified and 88 of them were semiquantified. Among the characterized peptides, there were fragments from proteins such as proenkephalin A, proSAAS, prosomatostatin, prooxytocin, vasopressin, etc. Explorative principal component analysis (PCA) combined with hypothesis testing was applied to the obtained data to investigate the impact of age and hypoxic stress factors on the peptide pattern. Twenty-six peptides revealed significant differences in concentrations between the animal groups influenced by age and influx rate.     

Spectrophotometric determination of trace amounts of lead(II) by ion-pair extraction with cryptand (2.2.2) and eosin

The solvent extraction of ion-pair complexes of calcium, strontium and lead (2.2.2) cryptates is described. The extraction equilibrium constants (D_C, K_ex and K_D) at room temperature are reported. The formation of the positively-charged lead cryptate ion and its extraction into chlorobenzene as an ion-pair with eosin are the basis of the proposed spectrophotometric determination of traces of lead. The high molar absorptivity of the ion-pair complex (? = 1.1 × 10⁵ l mol^-1 cm^-1) and the linearity of the calibration graph over the range 0–10^-5 M, allow even 0.1 ppm lead to be determined. The selectivity is high; there is no interference from cations often occurring with lead, such as Bi³⁺, Sn²⁺, Hg²⁺, Zn²⁺, Cd²⁺, Cu²⁺, Ca²⁺, Pd²⁺, Ag⁺ and Tl⁺.