The role of induced secondary radiation in in situ sorption studies using β-, γ-emitting radionuclides

This article is focused on the effect of -induced radiation in in situ sorption measurements of⁶⁰Co (emitting -and -radiation). The results presented show that the intensity of solution background is primarily due to the -induced radiation (possibly caused by photoeffect and Compton-scattering) and does not change during cobalt accumulation. Experiments were carried out with a pure -emitting isotope (⁹⁹Tc) in order to elaborate a method for the separation of the intensities originating from -and -induced radiations. Various methods of evaluation of sorption measurements are discussed. The extension of the method to application of different radioactive nuclides is considered.     

LLX separation of carrier-free,94,95,97,103Ru,93,94,95,96,99mTc and95,96Nb produced in alpha-particle activated molybdenum by TOA

A radiochemical charged particle activation procedure for the simultaneous production of carrier-free radioisotopes of more than one element in a single target and their subsequent separation through LLX has been demonstrated. The carrier free isotopes,^95,96Nb,^{93,94,95,96,99m}Tc and^94,95,97,103Ru formed through Mo(,pxn), Mo(,pxn) and Mo(,xn) nuclear reactions with 40 MeV -particle as detected by nondestructive -ray spectroscopy, have been effectively separated through LLX using TOA as an anionic extractant. Separation of the bulk matrix of molybdenum from the carrier free products has been monitored radiometrically using isotopic^93,99mMo formed through the Mo(,xn) reaction, as radioindicators for the target element. Purity of the separated carrier free radionuclide has been verified by -ray spectrometry.     

Actinide uptake onto zeolite-L and SAPO-34

The characteristics of ion exchange of uranyl and americium, which are -emitting radioactive nuclides, were examined by batch and column methods. SAPO-34 showed good selectivity for uranyl ion at pH 2–3.5, and distribution coefficients of Am³⁺ and UO ₂ ²⁺ increased with equilibrium pH. -irradiation (2 MGy) did not show any significant effect on the uptake of both of actinide ions onto L and SAPO-34. Higher does of -irradiation (up to 10 MGy) created a change of equilibrium pH, and hence uptake, due to radiolysis of water and heat localization generated by -radiation and annealing processes.     

Gamma radiolysis of Methyl Red solution and reaction induced by γ-irradiated NaCl in Methyl Red

The -radiolysis of Methyl Red solution in HCl medium at pH=2 has been studied along with energy transfer reaction brought about byF and hole centers of -irradiated NaCl. The G-values for degradation of the azo dye indicator by radiolysis and -irradiated salt were determined as 9·10^–1 and 4.8·10^–3, respectively. The kinetic rate constants (k) of degradation are evaluated as 2·10^–5 rad^–1 in the case of direct radiolysis, while for the irradiated salt it is 2·10^–7 rad^–1. The extent of degradation by direct -radiolysis is 100–200 times greater as compared to that by the -irradiated salt. The same mechanism is proposed for radiolysis as well as the reaction induced by -irradiated sodium chloride.     

The effects of cyclodextrin inclusion of the ferrocenemonocarboxylate anion on the kinetics of its oxidation by bis(pyridine-2,6-dicarboxylato)cobaltate(III) in aqueous solution

The effects of -, -, dm-(heptakis(2,6-di-O-methyl)--) and -cyclodextrins (CD) on the kinetics of the electron-transfer reaction of the ferrocenemonocarboxylate anion (FCA^–) with bis(pyridine-2,6-dicarboxylato)cobaltate(III) have been investigated in aqueous solution (0.20 M Na₂HPO₄, pH 9.2) at 25.0°C. Substantial decreases in the rate constants for the electron-transfer reactions were observed upon cyclodextrin inclusion of the reductant, due to an increase in the FCA^0/– reduction potential and to the insulation of the reductant from oxidant. The inclusion stability constants for {FCA·CD}^– were evaluated from the¹H NMR and kinetic data, and the order of the stability constants was found to be -CDdm-CD-CD>-CD.     

The predictive accuracy for estimating infinite dilution activity coefficients by γ∞-based UNIFAC

The predictive accuracy for estimating infinite dilution activity coefficients by a modification of the UNIFAC method wherein the group interaction parameters were based on only data (referred to as -based UNIFAC) has been studied. Estimates and measured values were compared for six prototypical solutes in a series of homologous n-alkanes, l-alcohols and alkanenitrile solvents. Despite the fact that the interaction parameters were derived using only data, this approach still gave serious errors due to several inherent problems in the original UNIFAC model. Its performance is sometimes even poorer than that of the original UNIFAC method. For example for nitromethane in alcohols and p-dioxane in nitriles values predicted by the -based UNIFAC are essentially zero. The large errors for these systems are most likely due to inaccurate interaction parameters in the -based UNIFAC method.     

Condensation of 2-(1-ethoxyvinyl)oxiranes with sodiomalonic ester and decarboxylation of the reaction products obtained

-(1-Ethoxyvinyl)- and -(1-ethoxyvinyl)--ethoxycarbonyl--butyrolactones were obtained by the reaction of 2-(1-ethoxyvinyl)oxiranes with sodiomalonic ester. Decarboxylation of the -(1-ethoxyvinyl)--ethoxycarbonyl-butyrolactones in DMSO leads to -(1-ethoxyvinyl)--butyrolactones, the hydrolysis of which gives -acetyl-butyrolactones. Ethyl trans-3-acetyl-3-pentenoate was obtained by decarboxylation of -methyl--(1-ethoxyvinyl)--ethoxycarbonyl--butyrolactone in DMSO.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 22–25, January, 1992.     

Transfer activity coefficient of the proton in water-pyridine mixtures. A comparison of some extrathermodynamic assumptions

Various water-pyridine mixtures have been selected in order to compare several of the most popular extrathermodynamic assumptions involved in the determination of the transfer activity coefficient of the proton, _t(H⁺). Two techniques have been utilized for this purpose: voltammetry [study of the ferrocene, ferricyanide, or thallium(1) systems] and potentiometry at equilibrium (emf measurements of various galvanic cells, including liquid junctions and hydrogen electrode or silver electrode as a test electrode). The assumptions have been classified into various groups [e.g., _t(Z^p+)=_t(Z^q+) or _t(X^–)=_t(Y⁺)], and the values of _t(H⁺) have been experimentally determined in each case. The results vary depending upon the basic assumption (several pH units); less important differences (e.g., 0.5 pH unit) occur within a given group, and this may be assigned to the nature of the reference species chosen. A simple model of solvation has been also examined; the application of the law of mass action to the corresponding equilibrium provides results close to the _t(X^–) =_t(Y⁺)type of assumptions which ultimately leads to most self-consistent results.     

Activation analysis of129I

Different methods (-, - and X-ray spectrometry, activation analysis, mass spectrometry) are reviewed for¹²⁹I determination in environmental samples. The sensitivities and the¹²⁹I/¹²⁷I ratios of the different methods are given. The influence of the¹²⁷I(n, )¹²⁸I(n, )¹²⁹I(n, )¹³⁰I reactions on¹²⁹I determination by activation analysis has been studied. A chart of optimal sample irradiation conditions is given.     

Mechanical properties of poly(vinyl methyl ether) hydrogels below and above their volume phase transition

The mechanical properties of radiation cross-linked poly(vinyl methyl ether) hydrogels below and above the volume phase transition (VPT) under isobar conditions were studied. The viscoelastic properties as a function of radiation dose, radiation source and polymer concentration at the state of irradiation were examined. Increased radiation doses led to higher cross-linking densities and higher moduli. Hydrogels irradiated with -rays were much harder than those obtained with electron beam irradiation at the same radiation dose. It was found that the modulus strongly increased by up to 1 order of magnitude at a temperature of the VPT of about 37 °C. In the collapsed state at temperatures well above the VPT a frequency dependence of the E() moduli in the range 0.1–22 Hz was detected, indicating viscoelastic behavior. To study the influence of solvent quality on the modulus of the hydrogels, rheological measurements were performed in water, 2-propanol and cyclohexane. A scaling exponent for the modulus according to de Gennes (G^2.25) was not found. Possible reasons for deviations (G^3.54) on poly(vinyl methyl ether) hydrogels were discussed in the context of deviations from ideal networks.     

Studies in dipyridyl chemistry. VII. Sulfur trioxide sulfonation of γ,γ′-dipyridyl

Reaction of ,-dipyridyl with sulfur trioxide at room temperature gives ,-dipyridyld'isulfotrioxide, which latter on heating at 200° gives ,-dipyridyl-sulfonic acid. Salts of ,-dipyridyl-3-sulfonic acid are prepared, among them the potassium, sodium, barium, and 3-cyano-,-dipyridyl salts.For Part VI see [1].     

Surface free energies of styrene-acrylic acid copolymer plates prepared in various frames

Styrene (St)-acrylic acid (AA) copolymer plates were synthesized in the frames made of glass, aluminum (Al) and poly(difluoroethylene) (PDFE). Surface properties of the prepared copolymer plates were characterized with regard to critical surface tension ( _C ), chemical components by IR analysis and surface energies (total energy, _S ; dispersion force components, _S ^d ; polar component, _S ^p ; hydrogen bonding component, _S ^h ) and the following results were obtained.The _C values of the copolymer plates increased with AA content and also depended on the sort of the used frame. The increasing order of the _C values of the copolymer plates corresponded to those of the used frames, namely, PDFE frame < Al frame < Glass frame.The prepared copolymer plates with low AA contents (ca. 10 mol%) were enriched in the AA moiety in the surface layer regardless of the kind of the used frame.The total and the individual components of the surface free energies of the copolymer plates were largely affected by the property of the used frame. The glass frame gave the plate with higher _S ^h values suggesting preferential orientation of the polar site of AA component.     

Effect of aminoacids on the surface free energy of nitrofurantoin

Changes in nitrofurantoin surface free energy components, Lifshitz-van der Waals, _s ^LW , electron donor, _s ^– , and electron acceptor, _s ⁺ , due to adsorption of the aminoacids: lysine, alanine and glutamic acid, were determined by means of the thin-layer wicking technique. It was found that the aminoacids slightly increase the _s ^– component already at 10^–4 M concentration. They reduce the _s ⁺ component practically to zero, and a very sharp increase of _s ^– was observed when the nitrofurantoin surface was precovered from the solutions at concentrations larger tan 10^–4 M. It is concluded that the adsorption of the aminoacids takes place via hydrogen bonding and electrostatic interactions between nitrofurantoin surface and aminoacid molecules. The increase in the _s ^– parameter is probably caused by the presence of carboxyl groups in the aminoacid molecules.     

Determination of dispersive and nondispersive components of the surface free energy of glass fibers

The dispersive component _s ^d of the surface free energy of glass fibers and its interaction energy with alkanes, benzene, 1-nitropropane, ethyleneglycol, glycerol, formamide, and water were quantitatively determined by the tensiometric method within two liquids. The values of nondispersive interaction energy I _SL ^p were found to be a linear function of the square root of the nondispersive component of the surface free energy of liquids. This suggests that the nondispersive interaction energy may be represented by the geometric mean of the nondispersive component of the surface free energy of a solid and a liquid. The slope gave the nondispersive component _s ^p of the surface free energy. The _s ^p values are 33 and 14 mJ/m² for the untreated and aminosilane-treated fibers, respectively, suggesting that organophilic character has developed on the surface after aminosilane treatment. The _s ^p value was almost similar after the treatment, probably because of the polar characteristics of amino groups.     

The determination of tin in explosive materials by thermal neutron activation analysis

A method, based on the measurement of the -photopeak at 332 keV arising from a¹²⁴Sn(n, )^125mSn reaction, has been developed for the rapid measurement of Sn at concentrations of 20 g g^–1, present as the cross-linking agent, in explosive charges. The method is comparative, and has a limit of detection of 0.6 g g^–1 and a precision of 5% RSD. The method requires no sample preparation and is economical in effort.     

Quantitative extraction of uranium(VI) in aqueous solutions with n-alkylamine intercalates of γ-titanium phosphate

The intercalation compounds Ti(C₃H₇NH₂)(HPO₄)₂·H₂O (18.4 Å) (-TiP/n-Pr) and Ti(C₄H₉NH₂)(HPO₄)₂·H₂O (20.5 Å) (-TiP/n-Bu) have been prepared using -titanium phosphate, Ti(HPO₄)₂·2H₂O (11.6 Å), as precursor. The retention of UO ₂ ²⁺ , in aqueous solutions by -TiP is very low being only a superficial adsorption phenomenon. When the intercalated materials are used, the retention is quantitative until 95% of the cation exchange capacity in the -TiP/n-Pr case (c.e.c.=6.30 mequiv./g), and over 80% for the -TiP/n-Bu compound (c.e.c.=6.04 mequiv./g).     

Solubilization of lanthanide ions by cyclodextrins in basic aqueous solutions

Cyclodextrins form complexes with lanthanide ions in basic aqueous solutions. This complex formation in basic solution dramatically enhances the solubility of lanthanide ions, which are otherwise insoluble due to the formation of hydroxide gels. Solutions of the -cyclodextrin-Ce³⁺ complex effectively hydrolyze 2-deoxyadenosine-5-monophosphate to 2-deoxyadenosine.     

Cohesion of crystals and the temperature coefficient of their equilibrium surface pressure

Summary Surface tension _e of mercury in equilibrium with crystals (floating on its surface) of octacosane, 1-hexadecanol, 1-octadecanol, ethyl palmitate, benzophenone and azoxybenzene at 7° is almost equal to that at 23° (measured earlier); also the difference between the surface tension ( ₀) of uncontaminated mercury and _e (i. e., equilibrium surface pressure) is independent of temperature within the limits of the experimental error. This shows that the hypothesis making ₀- _e an analog of the vapor pressure of the solid is incorrect. The relation _e= (=cohesion of the crystal,=thickness of the surface layer of mercury) is in agreement with the negligible temperature coefficient of _e . The calculated is approximately 9 angstroems.

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Zusammenfassung Die Oberflächenspannung _e von Quecksilber im Gleichgewicht mit Kristallen (schwimmend auf der Oberfläche) von Octosane, 1-hexadecanol, 1-octodecanol, Äthylpalmitat, Benzophenon und Azoxylbenzol bei 7 °C ist nahezu gleich der bei23 °C gemessenen. Auch die Differenz der Oberflächenspannung von reinstem Quecksilber ( ₀) und ( _e), d. h. dem Gleichgewichtsobderflächendruck ist unabhängig von der Temperatur innerhalb der experimentellen Fehlergrenze. Dies zeigt, daß die Hypothese, nach der man ₀- _e in Analogie zum Dampfdruck des Festen betrachtet, unkorrekt ist. Die Beziehung _e= (=Kohäsion des Kristalls,=Dicke des Oberflächenfilms auf Quecksilber) ist in Übereinstimmung mit dem vernachlässigbaren Temperaturkoefifzienten von _e. Das berechnete beträgt ungefähr 9 Å.

     

Preparation and Characterization of Thin Optically Transparent Alumina and Ce-doped Alumina

Transparent and porous boehmite, -Al₂O₃ (500°C) and -Al₂O₃ (900° and 1000°C) thin sheets (50–100 m) have been prepared from boehmite sols. -Al₂O₃ shows about 48% porosity and 292 m²/g surface area. On transformation from -Al₂O₃ (500°C) to -Al₂O₃ (900°C), the porosity still remains high, i.e. 45%; however, the surface area becomes 138 m²/g. The porosity and surface area of -Al₂O₃ become about 41% and 97 m²/g respectively on further heating to 1000°C. A gradual increase of average pore radius during this thermal treatment suggests that coarsening of the pore occurred during the densification process. Both -Al₂O₃ and -Al₂O₃ show high degree of transmission from UV to NIR wavelength region. Cerium exists in +4 oxidation state in the boehmite as well as in the - and -Al₂O₃. The ultraviolet absorption edge of the alumina was tailored by varying the concentration of cerium.