Calculation of average L shell fluorescence yields for the elements with 25≤Z≤101

Average L shell fluorescence yield , average L shell Auger yields and the total L shell X-ray fluorescence (LXRF) cross sections (σ _L ^x ) at 30 keV have been calculated theoretically for the elements with 25≤Z≤101. These calculated values have been compared with the other experimental and theoretical values.     

Interferences in the determination of trace elements in high-purity tin

Reactor neutron activation analysis of antimony, indium and cadmium in high-purity tin is interfered with by nuclear reactions on the tin matrix. For a number of interfering reactions the cross-sections were determined. The following results were obtained:¹²²Sn(n,γ)^123mSn:σ_th=0.145 barn, I=0.79 barn;¹²²Sn(n,γ)¹¹³Sn:σ_th=0.52, I=25.4 barn;¹¹²Sn(n, 2n)¹¹¹Sn: microbarn;¹¹⁸Sn(n, α)¹¹⁵Cd: microbarn; and¹¹⁴Sn(n, p)^114m1In: microbarn.     

Critical evaluation of the effective resonance energy concept and the epithermal neutron spectrum shape-factorα for reactor NAA purposes

The epithermal reactor neutron spectrum shape-factor, and the associated effective resonance energy for a given nuclide, are examined theoretically in great detail. First the necessity, meaning and importance of the choice of a reference neutron energy in a non-ideal spectrum (0) are explained. Next, the definition and practical calculation of are discussed, showing that the relation between the reasonance integrals in ideal and non-ideal spectra cannot be described adequately by two independent parameters and . The exact meaning of the logarithmic expression defining an independent of is clarified, its limits of validity are established as a function of and, as a result, it follows that relatively large systematic errors on can be introduced by its use. It is shown that is dominated by the first lowest resonance energies for a given nuclide, making its vulnerability to literature updates of resonance parameters almost equal to those of individual resonances. The effect, on the epithermal and total activation of specific nuclides, of large systematic and statistical errors on and, is calculated for a series of nuclides (different I₀/₀ and ) and irradiation facilities (different and _the), and represented graphically.Finally, the effect of important errors on and is calculated for final NAA results in terms of concentrations, botained by a comparator technique based on the¹⁹⁷Au reference nuclide. Conclusions are drawn concerning the impact of the foregoing on the usefulness of comparator type reactor NAA as an alternative to classical NAA using multi-element standards.     

A method for experimental determination of effective resonance energies related to (n, γ) reactions

When making use of some single comparator or absolute standardization methods in reactor neutron and in epicadmium neutron activation analysis, the knowledge of the effective resonance energy ( ) is essential to correct for the effect of the nonideal epithermal flux distribution on the analysis result. can be calculated from neutron resonance data, but when these are incomplete, not accurate or even not known at all, experimental determination should be considered. Such a method, providing both and the resonance integral to 2200 ms^–1 cross-section ratio (Q_O), is described in this paper. Results are given for 11 isotopes.     

Applicability of the 1/E1+α epithermal spectrum representation and the effective resonance energy\bar E_r in NAA

The practical applicability of the 1/E¹⁺ epithermal spectrum representation and of the effective resonance energy in NAA is investigated. Attention is paid to fundamental considerations such as definitions and approximations, error propagation functions, uncertainty statements, reliability of nuclear data and formal dimensioning problems. As to the latter, it is concluded that the applicability of the -concept is not dependent on the choice of a reference energy. The usefulness of the parameters and in NAA is demonstrated by new experimental evidence obtained from and Q₀ determinations in three different reactors: the WWR-M reactor (Budapest, Hungary), the THETIS reactor (Gent, Belgium) and the DR-3 reactor (Risø, Denmark).     

Oscillatory variation in yields of I2 and the reactivity of γ-irradiated TiO2 in KI solution

The reactivity of preheated and -irradiated TiO₂ was observed in KI solution by studying the kinetics of liberation of I₂. The rate of the reaction was found to be low. species proposed on the surface of oxide probably dissociate into . surface sites which oxidize I^– ions to produce free I₂. During irradiation and are produced which are reducing in nature and therefore very low yields of I₂ are observed for low -doses. In further irradiation the reformation of –O–O–, peroxy linkages is proposed hence the observed higher yields. All the processes ultimately lead to an oscillatory variation in yields of I₂ with -doses.     

Analysis of the stages of the equilibrium interaction of 2,4,6-trinitrohalobenzenes with 4-[4-(dimethylamino)styryl]pyridine as a model for activated nucleophilic substitution

A quantitative analysis was carried out on the rate and equilibrium constants of the stages of reversible activated nucleophilic substitution: σ-ionogens σ-ion pair ⇄ free ions L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg St., 340114 Donetsk, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 72–74, March–April, 1997.     

Oligomeric proanthocyanidin glycosides ofClementsia semenovii

Five new proanthocyanidins have been isolated from the roots ofClementsia semenovii A. Bor. The structures of two of these compounds have been established by various chemical and physical methods: 7-0-[6-0-galloyl-β-D-Glcp 0-β-D-Glcp 0-βD-Glcp 0-β-D-Glcp ]-(+)-gallocatechin-(4a-8)-(+)-gallo-catechin-(4a-8)-(-)-epigallocatechin-(4β-8)-(-)-epigallocatechin-(4β-8)-(-) -epigalloactechin-(4β-8)-(+)-catechin - CS-1 and 3-0-galloyl-7-0-(β-D-Glcp 0-B-D-Glcp)-(-)-epigallocatechin-(4β-8)-[3-0-galloyl-(-)-epigallocatechin]-(4β-8)-[3-0-galloyl-5-0-(6-0-galloyl-0-β-D-Glcp)]-(-)-epicatechin - CS-2. 1) Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 120 64 75; 2) Osh State University, Osh, fax (33 222) 2 23 73. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 756–763, November–December, 1998.     

Mass transfer in shell-core inorganic TIP1 ion exchanger

The ion exchange processes of (OAc^–) and (OAc^–) proceeding in shell-core inorganic ion exchanger Ti (HPO₄)₂·1/2H₂O has been studied and the diffusion equation whose boundary conditions are satisfied by a shell-core model was solved. Based on the equation solved and experimental data, the diffusion coefficients corresponding to the exchange process (OAc^–) and Li⁺–H⁺ (OAc^–) at 17°C are found to be 7.7×10^–9 and 6.2×10^–8 cm² s^–1 and the activation energies 3.4×10⁴ and 5.0×10³ J mol^–1, respectively. Compared to the gel type of styrene-divinylbenzene strong acid exchanger with 20% cross linking, it can be concluded that the rate of or exchange is 3.5 times faster than that in the organic exchanger.TIP was obtained from the Salt Lake Institute of the Academy of Science of China.     

The standard transported entropy of chloride ion in H2O and D2O

Transported entropies of the chloride ion, , in H₂O and in D₂O at 25°C and at concentrations ranging from 0.001 to 0.04m have been determined from the measurements of the steady-state (final) thermoelectric powers of the silver-silver chloride thermocell. Experimental data was extrapolated to infinite dilution to obtain the standard transported entropy . The concentration dependence of is examined and the solvent-isotope effect on the transported entropy is investigated. Thermodynamic data on the entropy of transfer of chloride ion from H₂O to D₂O is used to estimate the difference of the standard ionic entropy of transport in H₂O and D₂O for chloride ion.     

Studies on ion exchange equilibria and kinetics

¹⁶⁰Tb was used as radiotracer and the equilibria and kinetics of cation exchange with zeolite-Y were studied. The ion exchange isothems and the Kielland plots at 298 and 303 K were obtained. It was found that the ion exchange rate is controlled by particle diffusion. The integral interdiffusion coefficients for the direct and reverse exchanges at 298 K and 303 K were calculated. In addition, the isotopic ion exchange was studied too.     

Some conjectures on S n -derived nuclear permutational(or NMR) spin encodings

On existence of limiting ‐module decompositional sets for weak ‐branching at high n; on Voronoi polyhedral dual as geometric analogues to Cayley’s SU2 embedding theorem; and on SU dual group with retention of self‐associacy over subduced irrep set, as being the sufficient further condition to ensure the determinacy of SU embeddings. In the context of structures arising from nuclear permutation (NP) or NMR dual‐group spin algebras, the first conjecture sets out the high‐index n, and thus weak‐branching limit (WBL), aspects of module decompositions as giving rise to a set of numerical values for the associated Kostka coefficients which are invariant to further incrementation in the index; the existence of such combinatorial limit properties, implicit in sst tableaux enumerations, has not been addressed in the mathematics literature to date. Conjectures 2 and 3 are concerned with the questions of geometric and sufficient algebraic realisations of the determinacy of natural finite group embeddings in specific SU permutation groups. In conjecture 2, the Voronoi dual‐structures to the regular polyhedra for NP/NMR automorphic SU2 embedded spin symmetries hold the key to physical insight. Specifically, they provide a novel combinatorial geometric view of Cayley’s theorem; the mid‐face intersecting ‐axes of the initial NMR automorphic solids become (vertex) body‐diagonal axes of the specific‐dual Voronoi polyhedra, where a distinctness condition from the spin‐sites gives raise to a geometric statement of Cayley’s theorem. Conjecture 3 is concerned with SU embeddings for which the simple Cayley criterion alone is an insufficient condition to guarantee determinacy. The self‐associacy property and its retention over the subduced irrep‐subset(s) (i.e., comparable to studies of system‐invariants via Yamanouchi–Gel’fand subduction chains) is now seen as indicative of retention of determinacy for such SU group embeddings through the above sufficiency condition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Non-destructive determination of nuclear fuel burn-up by measuring the gamma radiation of fission products in irradiated uranium oxide

The burn-up of²³⁵U was determined in two uranium oxide samples (0.713 and 89.9%²³⁵U in mixture) irradiated simultaneously with a cobalt monitor, from the amounts of⁹⁵Zr,¹⁰³Ru,¹³⁷Cs,¹⁴⁰Ba and¹⁴⁴Ce obtained by measuring the intensities of the corresponding gamma radiations. The samples were irradiated for 23 days, and the fission products were measured after cooling for 100 days, nondestructively, by means of a Ge(Li) spectrometer. The integrated neutron flux was determined by measuring the produced⁶⁰Co in the cobalt monitor. The burn-up in both samples was determined by measuring the intensity of eight gamma energies (0.5–1.6 MeV). The determined values are in good agreement. The standard deviation of the mean value ( ) is 5%. The atom per cent fission of²³⁵U in both samples, calculated according to , differs by 1%. The measured σ _f for²³⁵U is in good agreement with the data reported in the literature.     

Effect of charge on the standard partial molar volumes and heat capacities of organic electrolytes in methanol and water

Previously developed additivity schemes for nonelectrolytes have been used to estimate and for tetraalkyl and tetraphenyl methanes in methanol and water. Corrections have been applied to the thermodynamic values of these model compounds to account for a variation in size of the central atom, and these were used to ascertain the effect of charge on and of alkyl and phenyl quaternary ions having N, P and B as central atoms. Investigations of R₄NBr, (R=methyl to heptyl) salts show that the charge effect on and of R₄N⁺ ions is large and relatively independent of ion size suggesting that the solvent molecules penetrate the ions. The ability to estimate and of the quaternary ions in the bromide salt solutions has made it possible to make ionic assignments with some confidence; (Br^–) has been evaluated as 19.7±2 and 30.2±7 cm³-mol^–1 and (Br^–) as –83±7 and –68±30 J-K^–1-mol^–1 in methanol and water, respectively. The use of organic ions for making ionic assignments of and is critically examined and comparisons with other assignments are made. The scaled particle theory is employed to divide the heat capacities of electrolytes into cavity and interaction contributions.     

Extent of exchange of bromine-82 with bromamine-T in strong acid medium

The extent of exchange of bromine-82 with bromamine-T in strong acid medium is low due to the formation of at lower acid concentrations and bromine at higher acidities. formation occurs over a narrow acid concentration range and is less stable than .     

Laser-induced fluorescence study on the interaction of Eu(III) with polycarboxylates

Laser-induced fluorescence spectroscopy was applied to obtaining hydration structure of Eu(III) complexes with synthetic polycarboxylates of poly(acrylic acid), poly(maleic acid), poly(methacrylic acid), and poly(a-hydroxyacrylic acid). Dependence of (the number of water molecules in the first coordination sphere of Eu(III) ion) on pH and supporting electrolyte concentration was obtained for these complexes. The spectroscopic results show that Eu(III) is surrounded by the “cage” of polycarboxylate ligands. The pH-induced transition in conformation of poly(methacrylic acid) ligand was clearly observed in the plot vs. pH.     

Die Aluminiumoxidfluoreszenz von 3-Keto-Δ4-steroiden

Zusammenfassung Die blauen Fluoreszenzchromogene, die beim Erhitzen von auf einer Aluminiumoxid-Dünnschichtplatte gebildet werden [1], wurden als Oberfl?chen-verbindungen von . Das Aluminiumoxid reagiert hier als ein Oxydationskatalysator für eine aktivierte Methylengruppe. Bei einer Heizdauer von 20 Minuten bleibt die Empfindlichkeit im Bereich von 150–180°C konstant. Die Selektivit?t der Reaktion nimmt mit abnehmender Temperatur zu. Die intramolekulare Wasserstoffbrückenbindung der freien Chromogene führt auf Silicagel gegenüber den Ausgangssubstanzen zu einer Erh?hung der R _f -Werte.

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Fluorescence of 3-Keto-Δ⁴-steroids on alumina

Summary The blue-fluorescence chromogens which are formed on heating on a thin layer plate of alumina [1] were identified as surface compounds of . The alumina is acting here as an oxidation catalyst for an activated methylene group. With a heating time of 20 minutes the sensitivity remains constant in the range 150 to 180°C. The selectivity of the reaction increases with decreasing temperature. Owing to the intramolecular hydrogen bonding in the free chromogens an increased R _f -value on silica gel compared to the original substances is found.

     

Reactions of alkoxy and hydroxy radicals generated photochemically from hydroperoxide molecules

In the present work as well as HRO^. radicals were generated in the photochemical interaction of 1,2-benzanthracene with -ethyl phenyl hydroperoxide /HROOH/ in C₆H₆ and CCl₄ at 304 K. radicals were trapped by C₆H₆. The main reaction of HRO^. radicals is hydrogen abstraction from the hydroperoxide group of HROOH. Although OH radicals are less selective, the hydrogen abstraction is the main process during their interaction with aromatics in contrast to reactions in aqueous solutions, where addition to the benzene ring is the rate-determining process in CCl₄:

Potentiometric investigation of NaSO 4 − ion pair formation in NaClO4 medium

The ion pair formation of NaSO ₄ ⁻ has been investigated potentiometrically in 1M NaClO ₄ medium at 25°C using two different sodium-selective indicator electrodes and a perchlorate reference electrode. The stability constant of NaSO ₄ ⁻ obtained in this study was . Although is small, it lowers the free sulfate concentration drastically in 1M NaClO ₄ medium and is a factor which should be considered in the use of NaClO ₄ as inert supporting electrolyte.