Unprecedented transformation of [I(-)·I3(-)] to [I4(2-)] polyiodides in the solid state: structures, phase transitions and characterization of dipyrazolium iodide triiodide.

Dipyrazolium iodide triiodide, [C3N2H5(+)]2[I(-)·I3(-)], has been synthesized and studied by means of X-ray diffraction, differential scanning calorimetry, dielectric measurements, and UV-Vis spectroscopy. Two reversible, solid-solid phase transitions (Imma (I) ↔ (II) ↔Pbam (III)) at 254 K and 182/188 K respectively have been revealed. The anionic network experiences spectacular changes associated with a huge rebuilding of the inorganic network from [I(-)·I3(-)] to [I4(2-)]. The low frequency dielectric relaxation process occurs in phase II with the activation energy of ca. 34 kJ mol(-1). The molecular motion of the pyrazolium cations in [C3N2H5(+)]2[I(-)·I3(-)] has been studied by means of proton magnetic resonance studies ((1)H NMR). The ferroelastic properties of all phases have been confirmed by polarizing microscopy observations. The molecular mechanism of the phase transitions in the compound is proposed.

Thermodynamics of the hydration equilibrium derived from the luminescence spectra of the solid state for the case of the Eu-EDTA system.

The luminescence properties of two compounds, [C(NH2)3][Eu(EDTA)(H2O)3] (I) and [C(NH2)3]2[Yb0.97Eu0.03(EDTA)(H2O)2]ClO4·6H2O (II), were determined. The weighted sum of luminescence spectra of I and II was used to reproduce the spectra of the Eu-EDTA system in aqueous solution in the temperature range 276-363 K. By implementing this method it was possible to determine the thermodynamic functions (ΔH = 18113 ± 506 J mole(-1) and ΔS = 62.5 ± 4.9 J mole(-1) K(-1)) of the reaction [Eu(EDTA)(H2O)3](-)⇆ [Eu(EDTA)(H2O)2](-) + H2O, which is difficult using other methods.

Pairwise comparisons and visual perceptions of equal area polygons.

The number of studies related to visual perception has been plentiful in recent years. Participants rated the areas of five randomly generated shapes of equal area, using a reference unit area that was displayed together with the shapes. Respondents were 179 university students from Canada and Poland. The average error estimated by respondents using the unit square was 25.75%. The error was substantially decreased to 5.51% when the shapes were compared to one another in pairs. This gain of 20.24% for this two-dimensional experiment was substantially better than the 11.78% gain reported in the previous one-dimensional experiments. This is the first statistically sound two-dimensional experiment demonstrating that pairwise comparisons improve accuracy.

Toxicity of uricosuric diuretics in rat hepatocyte culture.

Several aryloxyacetic acid diuretics have shown hepatotoxicity in humans, yet there continues to be interest in developing these compounds because of the uricosuric properties of some of them. This study was designed to test the utility of the hepatocyte monolayer culture as a model for studying these compounds. In addition, an attempt was made to define the structural components that are common to hepatotoxicity. Ticrynafen, indacrinone, ethacrynic acid and A-49816, an investigational compound, were found to be toxic in hepatocyte cultures; thus, with the exception of indacrinone, paralleling the experience in humans. The toxic compounds share a ketodichlorophenoxyacetic acid chemical structure. A-56234, an investigational uricosuric, was also found to be toxic in cultures but has not been demonstrated to be hepatotoxic in humans in limited clinical experience. It does not possess the ketodichlorophenoxyacetic acid structure proper but may be metabolized to a closely related structure. Furosemide, which does not have the ketodichlorophenoxyacetic acid structure, was not toxic in hepatocyte cultures and has not been hepatotoxic in humans. Thus, the structure common to the toxic compounds is ketodichlorophenoxyacetic acid or a closely related compound. The hepatocyte monolayer system appears to be a good model for demonstrating toxicity and, perhaps, for predicting toxicity of new compounds under development.

Comparison of erythromycin ethyl succinate, stearate and estolate treatments of group A streptococcal infections of the upper respiratory tract.

The microbiologic and clinical responses of acute Group A beta-hemolytic streptococcal infections of the upper respiratory tract to oral treatment with erythromycin ethyl succinate, stearate, and estolate were studied in 303 patients. Streptococcal M and T typing was done on all positive cultures. The overall cure rate was 95.4 per cent, with no statistically significant differences in clearing organisms from the pharynx. Of the 285 cured patients who completed the prescribed follow-up period, 11 had recurrences between the 12th and 31st day after initiation of therapy, and five developed new infections. No cases of rheumatic fever or glomerulonephritis were encountered during a follow-up study. Eight gastrointestinal reactions and one transient rash occurred. Results with these forms of erythromycin compare favorably with published results for similar infections treated with oral penicillins.

DDT: disrupted osmoregulatory events in the intestine of the eel Anguilla rostrata adapted to seawater.

The drinking of seawater and absorption of water along with sodium across the intestinal epithelium are well-known osmoregulatory events in marine teleosts. The insecticide DDT impairs fluid absorption in intestinal sacs from eels adapted to seawater. Furthermore, this functional impairment has an enzymatic basis; DDT also inhibits the (Na(+) and K(+)) activated, Mg(2+)-dependent adenosine triphosphatase in homogenates of the intestinal mucosa. Thus, the extreme sensitivity of teleosts to organochlorine pollutants may involve the disruption of osmoregulatory transport mechanisms.