A novel class of organosoluble and light-colored fluorinated polyamides derived from 2,2-bis(4-amino-2-trifluoromethylphenoxy)biphenyl or 2,2-bis(4-amino-2-trifluoromethylphenoxy)-1,1-binaphthyl

Two series of novel fluorinated aromatic polyamides were prepared from 2,2^′-bis(4-amino-2-trifluoromethylphenoxy)biphenyl (2) and 2,2^′-bis(4-amino-2-trifluoromethylphenoxy)-1,1^′-binaphthyl (4) with various aromatic dicarboxylic acids using the phosphorylation polycondensation technique. The polyamides had inherent viscosities ranging from 0.43 to 0.62 dl/g and 0.36 to 0.74 dl/g, respectively. All the fluorinated polyamides were soluble in many polar organic solvents such as N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone, and afforded transparent, light-colored, and flexible films upon casting from DMAc solvent. These polyamides showed glass-transition temperatures in the ranges of 190-240 °C (for the 6 series from diamine 2) and 247-255 °C (for the 7 series from diamine 4) by differential scanning calorimetry, softening temperatures in the ranges of 196-230 °C (6 series) and 241-291 °C (7 series) by thermomechanical analysis, and decomposition temperatures for 10% weight loss above 420 °C in both nitrogen and air atmospheres.     

Simultaneous determination of radionuclides separable into natural decay series by use of time-interval analysis

A delayed coincidence method, time-interval analysis (TIA), has been applied to successive – decay events on the millisecond time-scale. Such decay events are part of the ²²⁰Rn²¹⁶Po (T_1/2 145 ms) (Th-series) and ²¹⁹Rn²¹⁵Po (T_1/2 1.78 ms) (Ac-series). By using TIA in addition to measurement of ²²⁶Ra (U-series) from -spectrometry by liquid scintillation counting (LSC), two natural decay series could be identified and separated. The TIA detection efficiency was improved by using the pulse-shape discrimination technique (PSD) to reject -pulses, by solvent extraction of Ra combined with simple chemical separation, and by purging the scintillation solution with dry N₂ gas. The U- and Th-series together with the Ac-series were determined, respectively, from alpha spectra and TIA carried out immediately after Ra-extraction. Using the ²²¹Fr²¹⁷At (T_1/2 32.3 ms) decay process as a tracer, overall yields were estimated from application of TIA to the ²²⁵Ra (Np-decay series) at the time of maximum growth. The present method has proven useful for simultaneous determination of three radioactive decay series in environmental samples.     

On the Fe-CO molecule

Using a perturbational configuration interaction approach, it is found that the Fe-CO molecule has a low-spin ground state (i.e. ^3–), at variance with similar compounds formed by the first transition elements of this series (e.g. Sc and Ti). Binding energies, interatomic distances and vibration frequencies have been calculated for the ^3– state as well as for the ^5– high-spin state.Dedicated to Professor J. Koutecký on the occasion of his 65th birthday     

Isomeric yields of130Sb,132Sb,134I,and136I in the thermal neutron fission of235U

Isomer yield ratios of¹³⁰Sb,¹³²Sb,¹³⁴I and¹³⁶I isomers formed in the thermal neutron fission of²³⁵U have been calculated from our previous experimental studies that led to the identification of these species. In those studies the iodine and antimony fractions formed in fission were rapidly separated and the decay of -rays belonging to each isomer pair were followed using Ge(Li) detectors and a multichannel analyzer. The isomer ratios were calculated from growth and decay considerations of these -rays. The results are compared with the recently published values obtained with an on-line isotope separator, those from LOHENGRIN, and those from model calculations. Angular momenta of fission fragments corresponding to the measured isomer yields have also been calculated.     

Thorium determination in a liver autopsy sample via direct γ-spectrometry and neutron activation analysis

Thorium was determined in a liver autopsy sample from a person treated with Thorotrast ca. 40 y earlier. The decay products²²⁸Ac,²²⁴Ra,²¹²Pb,²¹²Bi, and²⁰⁸Tl from the²³²Th series were identified by direct -spectrometry. Instrumental neutron activation analysis yielded a value of ca 22 g thorium per kg dry liver material. The total radiation dose to the whole liver was estimated in the order of 16 Gy.     

Selective determination of extremely low-levels of the thorium series in environmental samples by a new delayed coincidence method

An attempt was made to apply a delayed coincidence method for the absolute determination of trace quantities of the thorium series. This method is based on selective counting of the relatively short lived nuclide²¹⁶Po (half-life 145 ms) in the thorium series members. For this purpose, a list mode time analyzing system combined with a liquid scintillation counter was assembled by means of a conventional microcomputer. A multiple time analysis was employed in the processing and data compilation of delayed coincidences to distinguish them from the true coincidences due to random events.From a time spectrum, the decay component of²¹⁶Po (145 ms) can be selectively measured. Absolute activities of its progenitors,²²⁴Ra and²²⁸Th as well as²²⁰Rn, can be determined even in the presence of the background radiations of the almost equivalent activity-strength of concomitant uranium series.     

The decay of153Gd

The sum peak method has been applied to calculate electron capture probability changes to 97 keV and 103 keV levels in the decay of¹⁵³Gd in different environments, e.g., HClO₄ and HNO₃. The relative and absolute intensities of KX-rays and -rays have been measured using a HPGe detector. In addition to these, electron capture intensities and electron capture decay energies (Q _Ec) have also been calculated.     

Decay of 1.643-hr 95Ru to 95Tc

The decay of ⁹⁵Ru has been investigated by means of -ray spectroscopy. The ⁹⁵Ru nuclei were produced by the reaction ⁹²Mo(,n)⁹⁵Ru at the beam energy of 17 MeV. High-purity Ge detectors have been used singly and in coincidence to study -rays in the decay of ⁹⁵Ru to ⁹⁵Tc. 132 -rays are reported, among them, energies and intensities for 127 transitions have been determined. A decay scheme of ⁹⁵Ru with 31 levels is proposed which accommodates 127 of these transitions. Spins and parities for three new levels are proposed from calculated logft values, measured -ray branching ratios, and in-beam experiment results of the daughter nucleus ⁹⁵Tc.     

Acid–Base Zeta-Metric Titration of Quartz Dispersions in Ethanol Solutions of Electrolytes

The conductivity of dilute quartz suspensions and electrophoretic mobility of quartz particles in solutions with the concentration C = 10^–5–10^–2 M XBr (X = H, Cs, Na, and Li) and NaOH, as well as in mixed solutions of 10^–4 M XBr (X = Cs, Na, and Li) + 10^–4–10^–2 M HBr and 10^–4 M XBr + 10^–4–10^–2 M XOH (X = Cs, Na, and Li) in ethanol containing 6 vol % of water were measured using conductometry and microelectrophoresis. The values of surface conductivity of quartz were calculated by the Wagner formula and used to calculate zeta potential by the Henry–Booth formula. The resultant dependences (logC) suggest that the value and sign of zeta potential are determined not only by the adsorption of potential-determining ions ⁺ and ^–, but also by the competitive specific adsorption of all ions of the aforementioned electrolytes, the adsorption values increasing in a cation series Li⁺ < Na⁺ < Cs⁺ < H⁺ and an anion series Br^– < OH^–. In particular, it is found that the titration of the above suspensions with XOH bases results in the reversal of zeta potential sign from negative to positive at a concentration depending on the adsorption capacity of alkali cation.     

Determination of some trace elements in high-purity aluminium, zinc and commercial steel by AAS after preconcentration on amberlite XAD-1180 resin

The determination of trace metals, e.g. Bi, Cd, Pb, in high-purity aluminium, zinc and commercial steel by flame or graphite furnace atomic absorption spectrometry following their preconcentrations as iodo complexes on XAD-1180 resin by means of a short column system is described. The recoveries are quantitative (95%). The relative standard deviations varies between 6% and 10%. The relative errors are less than 8% in a concentration range of 1 × 10^–3 –4 × 10^–5%. Detection limits for flame AAS and GFAAS were in the ranges of 0.002–0.110 g/ml and 0.0003–0.004 g/ml or in the ranges of 0.08–4.40 g/g and 0.012–0.16 g/g with respect to the solid samples, respectively.     

Sensitivity of femtosecond quantum dynamics and control with respect to non-adiabatic couplings: Model simulations for the cis–trans isomerization of the dideuterated methaniminium cation

We investigate the non-radiative decay in the photo-isomerization of the dideuterated methaniminium cation HDN⁺CDH by means of quantum dynamical simulations of the laser driven torsion. For the present model, the torsional dynamics is nearly adiabatic, but this is shown to be extremely sensitive to the large non-adiabatic coupling elements close to the conical intersection as well as to the apparently small values in the other domains. Neglecting those small couplings artificially changes the nearly adiabatic dynamics into diabatic dynamics. The non-adiabatic coupling terms are calculated ab initio with a test of accuracy which is based on the strict adiabaticity of pure rotational motions. Moreover, we present a novel mechanism for the enhancement of the laser-induced isomerization which may be interpreted as coherent control of competing pump–dump and two interfering non-radiative decay processes.     

The Role of Surfactants in the Formation of Highly Dispersed Iron–Zirconium Oxide Composites with Uniform Pores

The effects of the nature and concentration of surfactants and the preparation conditions on the genesis of iron–zirconium composites with a [Fe³⁺]/[Zr⁴⁺] ratio of 0.123 were studied. The effect of surfactants on the physicochemical properties of precipitates is determined by the conditions of synthesis. The amount of surfactants retained by the precipitate at pH 3 is about an order of magnitude greater than at pH 9. The thermolysis of samples synthesized at acidic pH is accompanied by the dehydration and dehydroxylation of iron–zirconium composites as well as by the decomposition and destruction of surfactants. In the latter processes, compounds or their fragments capable of reducing some phases are removed in a stepped-up manner. The specific surface area of oxide systems formed in this way is at most 100–150 m²/g. In the pH range corresponding to the complete precipitation of the components, highly dispersed single-phase and uniformly porous composites are formed. The choice of a surfactant, its fraction, and preparation conditions enables the preparation of oxides with specific surface areas of 100–400 m²/g. The average pore diameter of the samples ranges from 3.0 to 27.0 nm, and the total pore volume ranges from 0.20 to 0.38 cm³/g.     

Tetrazoles. 9. Acid-base properties of 5-substituted tetrazoles

The basicities of series of 5-R-tetrazoles in aqueous solutions of sulfuric acid were studied by UV and PMR spectroscopy. The pK_BH ⁺ values of these compound correlate with the _p substituent constants. The transmission factor of the p-phenylene ring (' = 0.23) was calculated from the ratio of the reaction constants for protonation of substituted 5-phenyltetrazoles and 5-R-tetrazoles. A linear dependence between the pK_a values and the pK_BH ⁺ values of 5-substituted tetrazoles was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 559–562, April, 1981.     

Activation thermodynamic parameters of binary mixtures of propionic acid ando-substituted anilines

Variations of densities and viscosities with temperature and composition are reported for binary liquid mixtures containing propionic acid+aniline (I),+o-toluidine (II),+o-anisidine (III), and+o-chloroaniline (IV). Entropies S _m and enthalpies H _m of activation as functions of the composition of the mixtures, as well as free energies of activation G _m at 10, 20, 30, 40, and 50°C and different compositions were calculated by means of Eyring's equation. The formation of activated complexes between the components of these binary mixtures is postulated and claimed to result from acid-base and hydrogen bonding exchange interactions.     

Two charge-transfer complex spectrophotometric methods for the determination of sulpiride in pharmaceutical formulations

Two simple, rapid, accurate and sensitive spectrophotometric methods are described for the determination of sulpiride. They are based on charge transfer complexation between the drug as n-electron donor and p-chloranilic acid as π acceptor or iodine as σ-acceptor. These give highly coloured complexes with absorption maxima at 518 and 363, 294 nm, respectively. Beer’s law linear ranges were 13.7–341.4 and 1.7–20.5 µg mL^?1 for the p-chloranilic acid and iodine methods. The methods were successfully applied to the determination of the drug in Dogmatil® Fort tablets and the results compared with the official method. The complex association constants and standard free energy changes were calculated using Benesi-Hildebrand plots.      

Chromatographic Determination of Silicon and Phosphorus as Molybdic Heteropoly Acids with Preconcentration

The chromatographic behavior of molybdic heteropoly acids of silicon and phosphorus as ion pairs with tetrabutylammonium bromide was studied by ion-pair high-performance liquid chromatography on the C₁₈reversed phase (UV detection at 310 nm). Heteropoly acids were preconcentrated as ion pairs with tetrabutylammonium bromide to increase the sensitivity of the determination. Optimal conditions were selected for the chromatographic determination of silicon and phosphorus in water in the presence of each other. Detection limits for silicon and phosphorus are (1.1 × 0.3) × 10^–3and (6.7 × 1.2) × 10^–3g/mL, respectively. Calibration plots are linear in the concentration ranges 0.01–0.1 g/mL (silicon) and 0.02–0.15 g/mL (phosphorus). The procedure was used for the analysis of distilled water.     

Determination of technetium in99Mo/99m Tc-generators

The Tc budget in several ROTOP-generators was determined by neutron activation analysis (NAA) and UV-spectroscopy. The complete procedure included the preparation of the generator, elution cycle in 24 to 72 h intervals and evaporation of the eluates to dryness. The samples were aliquoted, irradiated in the reactor and analyzed via⁹⁹Tc(n, n')^99mTc⁹⁹Tc reaction as well as by UV-absorption due to pertechnetate. The most reliable method proved to be NAA including chemical separation from²⁴Na by ion exchange after the complete decay of³⁸Cl. The detection limit was 50 ppb (3 ng Tc), compared with the total amount of several 10^–5 g down to 10^–7 g Tc in the system and its fractions. The mass balance and the elution profiles obtained correspond very well to the theoretical values. The results permit further quantitative considerations on both elution kinetics and the generator system.     

The determination of lead in environmental and geological materials by proton activation analysis

Lead is determined in environmental samples and in rocks using the^206,207,208Pb(p,xn)²⁰⁶Bi reaction. Bismuth is separated by anion exchange or by extraction with antimony diethyldithiocarbamate. Sources of errors such as volatilization of the matrix due to heating during the irradiation, variations of the abundance of the lead isotopes and the standardization were studied in detail. For concentrations between 11 mg/g and 3.7 g/g the relative standard deviation ranges from 2.6 to 5.4%. The detection limit is 10 ng/g.     

Ultraviolet Spectrophotometric Determination of Primary Amine-Containing Drugs via Their Charge-Transfer Complexes with Tetracyanoethylene

A spectrophotometric method is described for the quantitative determination of some drugs containing a primary amino-group, i.e. amantadine hydrochloride, tranylcypromine sulfate and tranexamic acid in their pure forms as well as in some pharmaceutical dosage forms. The procedure is based on the formation of a charge-transfer complex between tetracyanoethylene (TCNE) as -acceptor and the studied drugs as n-donors in the presence of acetonitrile as solvent. The spectra of the complexes show maxima at 330nm with high apparent molar absorptivities (from 2.1 × 10³ to 2.2 × 10⁴ L·mol^–1 cm^–1). Beers law is obeyed in the concentration ranges of 25–75 µg mL^–1, 2–30µgmL^–1 and 5–25µg mL^–1, and the mean percent recoveries are 99.68±0.92, 100.3±0.75 and 99.8±0.76 for amantadine hydrochloride, tranylcypromine sulfate and tranexamic acid, respectively. The proposed method is simple and can be applied to determine these drugs in their pharmaceutical dosage forms. The results compare favorably with those of reported methods.     

Activation Enthalpy and Entropy for the Decay of 9-Cyanophenanthrene Exciplexes

Activation parameters were studied for the decay of 9-cyanophenanthrene exciplexes with some weak electron donors (the Gibbs energy of electron transfer G ^* _et ranging from –0.02 to –0.09 eV), which displayed fairly high emission in both nonpolar and polar aprotic solvents. It was shown that the activation enthalpy of decay for the exciplexes is low, while the activation entropy reaches –(100–150) J mol^–1 K^–1, which is consistent with the two possible decay mechanisms: by dissociation into free radical ions or by intersystem crossing into the triplet state.