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.     

On the use of a dead-time meter for pile-up corrections

Correction for pile-up losses in the amplifier is possible by the dead-time fraction indicator of the ADC in case of long-lived radionuclides. If the dead-time meter has been calibrated, an accuracy of 1.5% is feasible up to a dead-time fraction of 25%. The precision decreases from 1.5% at 10% dead-time fraction to 3% at a deadtime fraction of 30%.     

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.     

The composition of volatile and particulate hydrocarbons in urban air

Summary The hydrocarbon composition of the particle and gas phases in the urban atmosphere has been studied by filtration and parallel adsorption on active charcoal and polyurethane foam (PUF). Gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS) have been used for the analysis of the organic matter extracts obtained with each system. In the case of the particle and PUF samples these extracts were fractionated into aliphatic and aromatic compounds. This approach has allowed to identify up to 247 hydrocarbon molecules showing that C0–C5 alkylbenzenes are the major compounds in the charcoal extracts whereas C14–C23 n-alkanes, C0–C4 alkylnaphthalenes, C0–C4 alkylbiphenyls and C3–C5 alkylbenzenes are those predominantly found in the PUF materials. The particles essentially contain C17–C38 n-alkanes and parent polycyclic aromatic hydrocarbons (PAH). These qualitative differences are paralleled by a progressive concentration decrease from the more to the less volatile hydrocarbons. Thus, the total charcoal extracts average 80 g/m³, the PUF compounds represent 4 /m³ and the particle hydrocarbons 0.7 g/m³. These latter airborne materials are essentially composed of petrogenic residues 0.6 g/m³ (aliphatic fraction) whereas the pyrolytic PAH only involve 0.08 g/m³.     

Determination of239,240Pu and241Am in environmental samples

An accurate and reliable method has been developed and routinely carried out for the sequential determination of^239,240Pu and²⁴¹Am in environmental samples. After suitable pretreatment.^239,240Pu and²⁴¹Am are separated from other elements by means of the anion exchange resin method. Americium-241 is purified by coprecipitation with calcium oxalate and then ion exchanged in mixed media of the mineral acid-methanol. In the analysis,²⁴²Pu (or²³⁶Pu) and²⁴⁴Cm are used as chemical yield monitors. The recoveries of the yield monitors in the analyses of some kinds of environmental samples were 7080% for plutonium and 7686% for curium. The concentration of^239,240Pu in the coastal sea water were 7.022 Bq/l and that of²⁴¹Am was 1.26.3 Bq/l. The mean concentrations of^239,240Pu in the edible parts of the marine products ranged from 0.22 to 7.4 mBq/kg · fresh and those of²⁴¹Am ranged from 0.11 to 2.6 mBq/kg · fresh.     

Field performance test of PASS,an instrument for the rapid assay of plutonium and other γ-ray emitting radionuclides

A field performance test was conducted at the INEL with the mobile Rapid Transuranic Monitoring Laboratory (RTML) that was developed for the analysis of samples from sites or facilities potentially contaminated with plutonium, other actinides, and -ray emitting activation and fission-product radionuclides. The performance test and results are described for the Photon Analysis Spectrometer System (PASS), one of three RTML assay systems. This system consists of a thin-window, n-type Ge spectrometer, that automatically analyzes soil, smear, and air particulate-filter samples for actinides emitting L x rays, and for activation and fission products that emit rays. The measurements were blind and performed with 11-g soil samples gathered from the Cold Test Pit and with spiked samples containing known mixtures of²³⁹Pu,²⁴¹Am⁶⁰Co, and¹³⁷Cs. In the spiked samples the plutonium activity concentrations ranged from 75 to 500 pCi/g while the other radionuclides ranged from 10 to 130 pCi/g. Lower limits of detection (LLDs) were verified to be 1, 5, 5, and 40 pCi/g for²⁴¹Am,⁶⁰Co,¹³⁷Cs, and²³⁹Pu, respectively. Results from the performance test are presented.     

Chemical composition of T-21 silica tubing and implications for neutron activation analysis

T-21 silica, a commonly used encapsulation material in neutron activation analysis of small samples, was analyzed by INAA to determine trace levels of the following impurities: Na, Sc, Cr, Fe, Co, Ni, Zn, Br, Sb, La, Ce, Sm, Tb, Hf and Au. In the unprocessed form supplied by the manufacturer, pieces of T-21 weighing 50 mg contain 6·10^–2 g Na; 9·10^–3 g Fe; 3·10^–7–7·10^–6 g light REE, Sc and Hf and 4·10^–8 g Tb and Au. In a series of glass-blowing steps, in which unfiltered gases were used for fuel, and cleaning steps, in which reagent grade aqua regia was used, irradiation vials were produced which contain higher average levels of Sc, La, Sm, Tb and Hf, by factors ranging from 1.3 for Sm to 11.5 for La, and lower average levels of Co, Na and Fe, by factors of 1.4, 2.0 and 4.0, respectively, than the unprocessed material. These contamination levels lead to blank corrections of 21% for La, 2.6% for Ce and 3.0% for Hf in 40 g samples of refractory inclusions from carbonaceous chondrites, if counted in their irradiation vials.     

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.     

Photometric detection of cyclodextrins in liquid chromatography by using iodine generated electrochemically in-situ

A method has been developed for photometric detection of cyclodextrins (CD) in liquid chromatography using iodine (I₂) generated electrochemically in-situ. Iodide ion in the mobile phase was electrochemically oxidized to I₂ which was subsequently reacted with I^–, in an electrochemical flow cell, forming I₃^–. The absorbance of I₃^– was found to be greatly enhanced when CD were present in the mobile phase. The absorbance enhancement was caused by the change in the mole fraction of I₃^–, because of the inclusion reaction of I₃^– with CD. On the basis of this phenomenon, CD were detected by means of a photodiode-array UV–visible detector positioned downstream of the electrochemical flow cell. The signals were found to be linearly dependent on CD concentration. Because the formation constants of I₃^– with CD decrease in the order -CD>-CD>-CD, -CD was most detectable by the method. Detection limits were 1.0 mol L^–1 for -CD, 65 mol L^–1 for monoG1--CD, 100 mol L^–1 for -CD, and 200 mol L^–1 for -CD.     

Determination of traces of sodium alkylbenzenesulphonate by high-performance liquid chromatography. Application to water

Summary For the trace determination of sodium alkylbenzenesulphonate (ABS) by HPLC the following conditions were employed: Shimadzu ZORBAX SIL Column (5 m, 4.6 mm i.d. x 150 mm) as stationary phase, 0.2% ammoniaethanol (v/v) as mobile phase, UV detector at 225 nm, injection volume 12 l. The chromatograms of ABS were simple and sharp (detection limit of ABS 0.02 g in 12 l of ethanol). The calibration curves of ABS were linear in a concentration range of 0.03 0.3 g in 12 l of ethanol. In the case of linear sodium dodecylbenzenesulphonate positive errors of 1 4% were caused by non-ionic surfactants or laurylsulphate (6 times excess), 10 50% positive errors were caused by 2 6 times excess of household detergents.Standard water samples containing ABS were treated with a weak base anion-exchange resin, the adsorbed ABS were eluted, and then determined either by HPLC or by the methylene blue spectrophotometric method. Recoveries of ABS in water were about 92 107% by HPLC.

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Bestimmung von Spuren Natriumalkylbenzolsulfonat mit Hilfe der HPLC. Anwendung auf Wasser

Zusammenfassung Für die Spurenbestimmung von Natriumalkylbenzolsulfonat (ABS) durch HPLC werden die folgenden Bedingungen empfohlen:Shimadzu ZORBAX SIL (5 m, 4,6 mm x 150 mm) als stationäre Phase, 0,2% Ammoniak/Ethanol als mobile Phase, UV-Detektor bei 225 nm, Injektionsvolumen 12 l. Die erhaltenen Chromatogramme sind einfach und scharf (Nachweisgrenze 0,02 g in 12 ml Ethanol). Die Eichkurven sind im Konzentrationsbereich von 0,03–0,3 g in 12 l Ethanol linear. Im Falle des linearen Natriumdodecylbenzolsulfonats werden bei Anwesenheit von nicht-ionischen oberflächenaktiven Substanzen oder von Laurylsulfat in 6fachem Überschuß positiver Fehler von 1–4% erhalten; bei 2–6fachem Überschuß von Haushaltswaschmitteln ergeben sich positive Fehler von 10–50%.Standard-Wasserproben werden zunächst einer Behandlung mit einem Anionenaustauscher unterzogen, die adsorbierten ABS eluiert und durch HPLC oder nach der Methylenblaumethode analysiert. Wiederfindungsraten liegen bei 92–107%.

     

Instrumental neutron activation analysis of carbon containing micro-spheres from Jungfrau-Joch glacier ice

From about 700 kg old, high altitude glacier ice (age 400 y) more than 170 glassy spherical objects with a mean diameter of 100 m were isolated. Neutron activation analysis of individual transparent objects (each 10^–6 g) showed the presence of K, Sc, Cr, Fe, La, Eu, Au, etc., in varying concentrations. A detection limit of 10^–14 g/g was achieved by means of an anticompton circuit. A systematic study by mass spectrometry of positive and negative ions using a LASER microprobe disclosed that the main constituents of some of these smooth glacier spheres consisted of elemental carbon. The chemical composition of some spherules admits the possibility of extraterrestrial origin, e.g. ablation material from meteorites with high carbon contents, which entered the earth's atmosphere.     

Critical evaluation and experimental determination of the nuclear activation and decay parameters for the reactions:6 4Zn(n, γ)6 5Zn,1 1 2Sn(n, γ)1 1 3 (m)Sn (E. C.)1 1 3mIn,1 7 4Yb(n, γ)1 7 5(m)Yb

A best choice from literature was made of the isotopic abundance values for⁶⁴zn,¹¹²Sn and¹⁷⁴Yb, and of the absolute gamma-intensities for⁶⁵Zn,^113mIn and¹⁷⁵Yb. From these data and from activation method experiments, the following 2200 m·s^–1 cross sections were determined:⁶⁵Zn(n, )⁶⁵Zn; ₀=(0.726±0.0007) barn [cf. literature 0.76–0.78 barn];¹¹²Sn(n,)¹¹³(m)Sn; ₀(0.91 m⁺g)=(0.539±0.011) barn [cf. literature 1 barn];¹⁷⁴Yb(n,)¹⁷⁵(m)Yb; ₀(m⁺g)=(130+4) barn [cf. literature 65 barn].     

Preparation and Characterization of Germanium Sulfide Based Sol-Gel Planar Waveguides

Germanium sulfide based glass films have been deposited by spin-coating onto single crystal silicon wafers and silica glass disks, using the reaction between GeCl₄, either pure or doped with of 5 mol% of SbCl₃, dissolved in toluene, with H₂S. The films, heat-treated under different conditions, were characterized by X-ray diffraction, infrared spectroscopy, X-ray photoemission spectroscopy, mechanical profilometry and ellipsometry. Oxide contamination was found in these films, but this was reduced or even eliminated by a heat-treatment in H₂S gas, at 270°C. A maximum film thickness of 1.3 m was achieved and the refractive indices of the films were in the range of 1.9–2.8 at 633 nm. Propagated light was observed by butt-coupling, for waveguides deposited on silica glass disks, at = 633 nm. Optical losses in the range of 1.1–1.9 dB/cm were measured at this wavelength, for different regions of different planar waveguides. The present method has achieved reasonably low loss and low levels of oxide contamination, which are promising for active applications.     

Human prostate specific antigen (hPSA) purification and establishment of hPSA radioimmunoassay

Human prostate specific antigen (hPSA) RIA was developed with hPSA and anti-PSA prepared in our laboratory. Its standard curve was linear with a sensitivity of 0.5 g/L. Serum PSA levels of 130 normal males ranged from 0 to 3.5 g/L (1.15±0.93 g/L), which are consistent with the results of other conventional RIA. The recovery, intra- and inter-assay coefficients of variation conform to the demands of RIA, and the results of 41 samples obtained by both the PSA RIA and PSA RIA of DPC were well correlated (=0.990). PSA level of 23 patients with prostatic carcinoma was 10400 g/L.     

Über einige Komplexboride von Übergangsmetallen

Zusammenfassung Dreistofflegierungen in dem Kombinationen {Mo, W}-{Fe, Co, Ni}-B; {V, Nb, Ta, Mo, W}-B-Al werden vornehmlich auf die Existenz von Komplexboriden hin untersucht. Die isotypen Phasen Mo₂CoB₂, Mo₂NiB₂, W₂FeB₂, W₂CoB₂ und W₂NiB₂ sind strukturell mit Mo₂FeB₂ verwandt, aber doch von dieser Phase verschieden. Gefunden werden außerdem die isotypen Phasen MoCoB und WCoB. Das Problem der -Phase wird diskutiert. In manchen Fällen tritt ein Zwischenzustand auf, der vermutlich durch Stapelfehler einer Unterzelle (c/3 in hexagonaler Aufstellung) hervorgerufen wird. Neben dem Auftreten ternärer Phasen bei Nb-B-Al und Ta-B-Al wird eine ausgeprägte Mischphasenbildung: (Nb, Al)B₂ und (Ta, Al)B₂ beobachtet. Der Dreistoff: Mo-B-Al ist durch die ternäre Phase MoBAl gekennzeichmet, ferner tritt der durch Al stabilisierte CrB-Typ auf (Mo_0,45B_0,50Al_0,05). Die Gleichgewichtsverhältnisse in denT-B-Al-Dreistoffen werden abgeschätzt.

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Alloys of the combinations {Mo, W}-{Fe, Co, Ni}-B, {V, Nb, Ta, Mo, W}-B-Al have been examined with respect to the existence of complex borides. The phases of the approximate formula Mo₂CoB₂, Mo₂NiB₂, W₂FeB₂, W₂CoB₂ and W₂NiB₂ have been found to be isotypic. They do however not correspond to Mo₂FeB₂ having U₃Si₂ structure. Two other complex borides of formula MoCoB and WCoB have been detected having the same crystal structure. The problem of the -phases which partially contain boron will be discussed considering the supposedly occurring stacking faults of a subcell unit (c=c/3 for hexagonal symmetry). Besides formation of ternary compounds for: Nb-B-Al and Ta-B-Al an extended solid solution (Nb, Al)B₂ and (Ta, Al)B₂ has been observed. The Mo-B-Al-system is characterized by the ternary phase of formula MoBAl. Mo-monoboride having CrB-type has been found to be stabilized by a small amount of Al, thus Mo_0,45B_0,50Al_0,05 being formed. The phase equilibria within the ternary systems have been established for the major part.

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Mit 4 Abbildungen     

The role of intra- and intermolecular hydrogen bonds in the formation of β-cyclodextrin head-to-head and head-to-tail dimers. The results of ab initio and semiempirical quantum-chemical calculations

The conformation of a free -cyclodextrin molecule optimized by the MNDO/PM3 quantum-chemical calculations has C₇ symmetry. The right orientation of the interglucose hydrogen bonds in -cyclodextrin, in which the 2-OH groups act as the proton donors and the O atoms of the nearby 3"-OH groups function as the proton acceptors, is advantageous for thermodynamic reasons. The ring of seven H bonds thus formed stabilizes the symmetrical form of -cyclodextrin. The -cyclodextrin head-to-head dimer has D ₇ symmetry and consists of molecules whose 2-OH groups partcipate as proton donors in the formation of fourteen complementary intermolecular hydrogen bonds. The energy of H bonds in the -cyclodextrin monomer and dimer was estimated to be 1.0--1.4 kcal mol^–1. Of the two possible -cyclodextrin dimers, the head-to-tail dimer is more thermodynamically stable. The thermodynamic preference of the right orientation of the inter-glucose H bonds in -cyclodextrin was confirmed by the MP2/6-31G(d,p)//6-31G(d,p) ab initio calculations for maltose (-glucodioside). The maltose molecule with inter-glucose H bonds of the type 2-OHO(3")-H is more stable than the structure with the H-(2)OH-O(3") orientation of H bonds with a difference of 2.7 kcal mol^–1. According to the MNDO/PM3 method, the maltose structure with the right H bond orientation is more stable by 3.1 kcal mol^–1.     

Optical Nanocomposite Planar Waveguides Doped with Rare-Earth and Noble Metal Elements

The present paper is focused on multilayer Er³⁺-doped silica-titania planar waveguides, co-doped with silver, which were prepared by spin-coating on silica glass, or buffered single crystal silicon substrates. The single layer thickness (0.4 m) and refractive index (1.60–1.63) were measured by spectroscopic ellipsometry at 715 nm. The thickness of the waveguides (measured by mechanical profilometry) was 1 m and their optical propagation losses were measured at different laser wavelengths (488 nm, 514 nm and 633 nm), exhibiting an approximately Rayleigh-like behavior. The thermal precipitation of silver nanocrystallites was achieved, both in air and under a controlled atmosphere (dry nitrogen) and these were characterized by visible absorption spectroscopy, which clearly showed the development of a plasmon absorption band near 415 nm, by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The Er³⁺ metastable level lifetimes for the emission at ca. 1.54 m were found to be ca. 4–6 ms, for Er³⁺ concentrations varying between 0.2–2.0 mol% (or (0.4–4.4) × 10²⁰ ions/cm³), but no significant variation was observed with the Ag concentration added (up to 2.5 mol%).     

Study of the absorption spectra of the 4f electron transition of the Nd and Er complexes with 2-isobutylformyl-1,3-dione-indane in the presence of TX-100 and its analytical application

The absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 2-isobutylformyl-1,3-dione-indane and TX-100 have been studied by normal and derivative spectrophotometry. Their molar absorptivities at the maximum absorption bands are about 7.2 (at 571 nm) times greater for neodymium and 13.1 (at 519 nm) times greater for erbium than those in the absence of the complexing agents. Use of second derivative spectra both eliminates the interference from other rare earths and increases the sensitivity from neodymium and erbium. Beers law is obeyed from 020 g/ml for neodymium and 025 g/ml for erbium. The relative standard deviations are 1.2% and 1.6% for 5.0 g/ml of neodymium and 8.0 g/ml of erbium, respectively. The detection limits (signal-to-noise ratio=2) are 0.14 g/ml and 0.20 g/ml. A method for the direct determination of neodymium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.     

Non-Aqueous Capillary Electrophoresis with Indirect Photometric Detection for Direct Analysis of Pb2+, Zn2+ and Cd2+ Ions

A new approach, based on non-aqueous capillary electrophoresis separation and indirect photometric detection, was established for the determination of the transition metal ions Pb²⁺, Zn²⁺ and Cd²⁺. Under optimized conditions, the method produced baseline separation of these three metal ions. The linear range and detection limits were 1050µM, 1.9µM for Cd²⁺; 1050µM, 2.1µM for Zn²⁺; and 20100µM, 3.8µM for Pb²⁺, respectively.     

Insertion of 3d- and 4f-Elements into Silver Iodide

The interaction of manganese and some 4f-metals (M) with silver iodide is studied. The samples are obtained by sputtering M onto the surface of polycrystalline AgI films (0.2 m, 300 K) in a vacuum. Optical absorption in the samples is interpreted as the insertion of M ions into AgI with the formation of dopants AgI:M. A new phase with an optical bandgap of 3.7 eV emerges in the samples with elevated concentrations of La, Ce, Pr, Nd, Sm, or Dy (n _M/n _Ag 0.1). X-ray diffraction patterns for such samples with Sm correspond to structures with large interfacial distances, for example, 0.99, 0.87, 0.76, and 0.67 nm. In air, AgI forms in the samples with a new phase; this process is hindered by the sputtered protective coatings. According to optical absorption data, X-ray diffraction, and local microanalysis the Mn insertion into AgI is followed by the formation of a new phase (2Ag:Mn:4I), which may belong with solid electrolytes Ag₂MI₄, where nonmagnetic M are known (Zn, Cd, Sn, Hg, Pb).