Efficiencies of contamination source for flooring and some materials used in unencapsulated radioactivity handling facilities

The efficiencies of contamination source, defined in ISO Report 7506-1, were experimentally determined for such materials as flooring, polyethylene, smear-tested filter paper and stainless steel plate. 5 nuclides of 147Pm, 60Co, 137Cs, 204Tl and 90Sr-Y were used to study beta-ray energy dependence of the efficiency, and 241Am as alpha-ray emitter. The charge-up effect in the measurement by a window-less 2 pi-proportional counter was evaluated to obtain reliable surface emission rate. The measured efficiencies for non-permeable materials, except for two cases, are more than 0.5 even for 147Pm. The ISO recommendations were shown to be conservative enough on the basis of present results.     

Anodically oxidised aluminium layer as a useful substrate for the fabrication of147Pm sources for beta-ray thickness gauges

An anodically oxidised layer of aluminium was found to be a satisfactory substrate for holding millicurie amounts of carrier-free¹⁴⁷Pm activity, which is used as a source of -radiation in -ray thickness gauges. The sources fabricated by this method showed satisfactory performance regarding leaching and adherence of the radioactivity held up in the oxide layer. Details regarding the anodic oxidation conditions used for making these source substrates are given. Leaching studies conducted on these sources indicated influence of the acid concentration at which¹⁴⁷Pm activity was deposited in the oxide layer. Better performance characteristics of these sources could be achieved whenever¹⁴⁷Pm activity was absorbed in the oxide layer under near neutral conditions of acidity.     

Is a small number of charge neutralizations sufficient to bend nucleosome core DNA onto its superhelical ramp?

X-ray diffraction structures of the nucleosome core particle along with a variety of experiments are consistent with the idea that an important source of the free energy holding DNA to the superhelical ramp on the histone octamer surface is obtained from a relatively small amount of electrostatic neutralization of the DNA phosphate charge by positively charged histone groups, especially arginine residues. Here we present a theoretical analysis of a simple model that emphasizes the competition between the high degree of bending of the stiff DNA molecule required for its tight curvature on the histone octamer and the neutralization of the DNA phosphate charge by basic histone residues. Our calculation accounts for the strong influence of condensed counterions on the electrostatic interactions. We find that the minimum amount of free energy required to bend DNA into axial conformity with the superhelical ramp at physiological salt concentration can be provided by a scant 6% neutralization of the phosphate charge, in close correspondence to the stoichiometric neutralization of phosphate charge by the arginine side chain that intrudes into the inward-facing minor groove of each DNA double helical turn.     

Flocculation mechanism induced by cationic polymers investigated by light scattering

Three cationic polymers with molecular weights and charge densities of 3.0 x 10(5) g/mol and 10%, 1.1 x 10(5) g/mol and 40%, and 1.2 x 10(5) g/mol and 100% were chosen as flocculants to aggregate silica particles (90 nm), under various conditions, including change in polymer dosage, particle concentration, background electrolyte concentration, and shear rate. The size and structure of flocs produced were determined using the static light scattering technique. On the basis of measurements of polymer adsorption and its effect on the zeta potential and floc properties, it has been found that the polymer charge density plays an important role in determining the flocculation mechanism. Polymers with a 10% charge density facilitate bridging, 40% charged polymers bring about either a combination of charge neutralization and bridging or bridging, depending on the polymer dosage, and polymers with the charge density of 100% induce electrostatic patch flocculation mechanism at the optimum polymer dosage and below but bring about bridging mechanism at the polymer dosage approaching the adsorption plateau value. Bridging aggregation can readily be affected by the particle concentration, and an increase in particle concentration results in the formation of larger but looser aggregates, whereas electrostatic patch aggregation is independent of particle concentration. The addition of a background electrolyte aids in bridging aggregation while it is detrimental to electrostatic patch aggregation. It has also been found that the effect of shear rate on the mass fractal dimension depends on polymer charge density.     

A simple procedure for the fabrication of high activity beta-radiation sources of147Pm for use in beta-ray thickness gauges

A simple procedure is described for the fabrication of mCi level strong sources of¹⁴⁷Pm radioisotope on a noble metal substrate like Palladium as a source for β⁻-ray thickness gauge. The procedure is based on the principle of internal electro-deposition of¹⁴⁷Pm from aqueous solutions containing¹⁴⁷Pm³⁺ ions, using metallic magnesium for the purpose. Investigations conducted towards ascertaining the adherence of the¹⁴⁷Pm radioactivity onto the palladium substrate. Leaching studies conducted on these source indicated that the radioactive film is satisfactorily adherent to the palladium substrate, suggesting that the method can be used for fabricating satisfactorily safe high β⁻-activity sources of¹⁴⁷Pm contained in small active dimensions. Results of leaching studies keeping the sources fully immersed in boiling water for 15 minutes are also presented.     

Charge Neutralization Drives the Shape Reconfiguration of DNA Nanotubes

Reconfiguration of membrane protein channels for gated transport is highly regulated under physiological conditions. However, a mechanistic understanding of such channels remains challenging owing to the difficulty in probing subtle gating‐associated structural changes. Herein, we show that charge neutralization can drive the shape reconfiguration of a biomimetic 6‐helix bundle DNA nanotube (6HB). Specifically, 6HB adopts a compact state when its charge is neutralized by Mg²⁺; whereas Na⁺ switches it to the expanded state, as revealed by MD simulations, small‐angle X‐ray scattering (SAXS), and FRET characterization. Furthermore, partial neutralization of the DNA backbone charges by chemical modification renders 6HB compact and insensitive to ions, suggesting an interplay between electrostatic and hydrophobic forces in the channels. This system provides a platform for understanding the structure–function relationship of biological channels and designing rules for the shape control of DNA nanostructures in biomedical applications.     

Salient Features in the Preparation of Promethium-147 Activated Zinc Sulphide Phosphor Light Sources

Activation of zinc sulphide phosphor with beta radiation of ¹⁴⁷Pm will provide self-sustaining light sources and are widely used as nocturnal illumination devices. Use of ¹⁴⁷Pm as energy source is most promising since it forms non-volatile salts. By virtue of this property, it has been precipitated as hydroxide from its aqueous solution for in situ deposition on zinc sulphide phosphor. In this paper, the details of various reaction parameters such as the rate of deposition of ¹⁴⁷Pm(OH)₃ on ZnS, duration of shaking, specific activity of phosphor and effect of fatty acid (additive) concentration versus luminosity are illustrated with experimental evidence so as to obtain, under optimum conditions, an overall luminosity of 1000 micro lamberts (lm).     

Simultaneous determination of lanthanides by radioisotope x-ray fluorescence spectrometry based on characteristic K-radiation

The use of radiosiotope-induced x-ray fluorescence is examined for the determination of lanthanides via their characteristic K x-ray lines. Various synthetic mixtures of barium and 14 rare-earth elements were prepared and their homogeneity was checked. The intensity from each mixture was measured for 10 min with excitation by the 88-keV γ-ray from a 3.5-mCi cadmium-109 source or by direct β-particles from a 100-μCi promethium-147 source. Typical spectra and their corrected peak intensities are presented. The spectral backgrounds produced by ¹⁴⁷Pm and ¹⁰⁹Cd are considered.     

Sorption of144Ce(III) and147Pm(III) on hydrated iron sesquioxide

The sorption of¹⁴⁴Ce(III) and of¹⁴⁷Pm(III) on hydrated iron sesquioxide suspension and the sorption of¹⁴⁴Ce(III) on hydrated iron sesquioxide in a laboratory column were studied. The dependence of the sorption on pH and time, the sorption isotherm, the temperature-dependence of sorption, and the effects of ionic strength on sorption and desorption were determined under static conditions. The maximum sorptions of¹⁴⁴Ce(III) and¹⁴⁷Pm(III) were reached at pH=7.4 (K_d=8.9·10⁵) and pH=9.1 (K_d=6.2·10⁵), respectively.     

A new approach to determine Pm in irradiated fuel solutions

Developments carried out in the Laboratory of Isotopic, Nuclear and Elementary Analyses in order to quantify ¹⁴⁷Pm in spent nuclear fuels analyzed at the CEA within the framework of the Burn Up Credit research program for neutronic code validation are presented here. This determination is essential for safety-criticality studies.The quantity and the nature of the radionuclides in irradiated fuel solutions force us to separate the elements of interest before measuring their isotopic content by mass spectrometry. The main objective of this study is to modify the separation protocol used in our laboratory in order to recover and to measure the ¹⁴⁷Pm at the same time as the other lanthanides and actinides determined by mass spectrometry.A very complete study on synthetic solution (containing or not ¹⁴⁷Pm) was undertaken in order to determine the yield of the various stages of separation carried out before obtaining the isolated Pm fraction from the whole of the elements present in the spent fuel solutions. With the lack of natural tracer to carry out the measurement with the isotope dilution technique, the great number of isotopes in fuel, the originality of this work rests on the use of another present lanthanide in fuel to define the output of separation. The yields were measured at the conclusion of each stage of separation with two others lanthanides in order to show that one of them could be used as a tracer to correct the measurement of the ¹⁴⁷Pm with the separation yield. The total yield (at the conclusion of the two stages of separation) was measured at the same time by ICP-MS and liquid scintillation. This last determination made it possible to validate the use of the ¹⁴⁷Sm (natural) to measure the ¹⁴⁷Pm in ICP-MS since the outputs determined in liquid scintillation and ICP-MS (starting from the radioactive decrease of the source having been used to make the synthetic solution) were equivalent. It is the first time that such measurement is performed in ICP-MS.The measurement of the ¹⁴⁷Pm was finally taken on fuels UOx and MOx by using the ¹⁵³Eu like a tracer of the separation yield. The results obtained are in very good agreement with those obtained from neutronic calculation code.     

Chemical study on the separation and purification of promethium-147

A chemical process for the separation of¹⁴⁷Nd/¹⁴⁷Pm from fission products of synthetic radioactive waste solution has been developed. The process includes: (1) denitration, (2) removal of high concentration of uranium by 30% TBP/kerosene extraction, (3) removal of⁹⁵Nb,¹⁰³Ru,¹³⁷Cs and part of⁹⁰Sr by 50% TBP/dodecane extraction, (4) separation of¹⁴⁷Nd/¹⁴⁷Pm from part of⁹⁰Sr and⁹⁵Zr by oxalic acid precipitation, and (5) removal of¹⁴⁴Ce by mixture of 0.4M D2EHPA and 0.2M TBP extraction. Experimental results indicate that the recovery of¹⁴⁷Nd/¹⁴⁷Pm in the final separated solution is about 90%. The purification of¹⁴⁷Nd and¹⁴⁷Pm from some other rare earth elements, viz.¹⁵³Sm,¹⁵⁴Eu and¹⁴⁴Ce was further investigated by using a Dowex 50W×8 ion-exchanger. Parameters of flow rate, eluent concentration and pH were examined. The results show that the recovery and radionuclide purity of¹⁴⁷Nd plus¹⁴⁷Pm under the present separation conditions are 77.8% and 98.6% for diethylenetriaminepentaacetic acid (DTPA) and 87.3% and 99.5% for nitrilotriacetic acid (NTA), respectively.     

Formation of piezoelectric single-crystal nanorings and nanobows

Bending of polar-surface-dominated (PSD) nanobelts of ZnO can be explained by one of two processes: electrostatic neutralization of the dipole moment via deformation (called an electrostatic polar charge model) or imbalances between surface tensions via surface-termination induced stresses. This article presents experimental data on the structural features of nanorings and nanobows formed by bending single-crystal, PSD ZnO nanobelts. Our data exclusively support the electrostatic polar charge model as the dominant mechanism for bending.     

Study of the structure development during the melt spinning of nylon 6 fiber by on‐line wide‐angle synchrotron X‐ray scattering techniques

The melt spinning of nylon 6 has been studied with on‐line wide‐angle synchrotron X‐ray scattering techniques. The apparatus consisted of a single screw extruder and a metering pump mounted on a horizontal platform that could be translated in the vertical direction allowing a range of distances to be sampled with the X‐ray beam. The structure development, equatorial crystallinity index, and crystalline orientation were studied as a function of take‐up speed and position along the spinline. For low‐speed (50 mpm) situations, the nylon chains crystallize into independent hydrogen bonded sheets that start to interact with each other as their concentration starts to increase. For higher speed situations, the nylon chains crystallize directly into the interacting hydrogen‐bonded sheet structure. Upon conditioning at room temperature for 24 h, this interacting hydrogen‐bonded sheet structure transforms into the well‐known three‐dimensional alpha and gamma phases of nylon 6, probably existing in a shish‐kabob structure. The equatorial crystallinity index increases as distance from the spinneret increases and as take‐up speed decreases. The crystalline orientation function is constant along the spinline for a constant take‐up speed, and increases as take‐up speed is increased. Conditioning further increases both the crystallinity and crystalline orientation of the fibers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1277–1287, 1999     

Triboelectric spray ionization

Triboelectric spray ionization (TESI) is a variation of electrospray ionization (ESI) using common instrumental components, including gas flow, solvent flow rate and heat, the only difference being the use of a high‐voltage power supply for ESI or a static charge for TESI. The ionization of solvent or analyte is due to the electrostatic potential difference formed between the spray electrode and counter electrode. The ion source contains a pneumatic spray operated over a range of flow rates (0.15–1.5 µl/min) and gas pressures (0–100). This new design contains a standalone spray assembly and an optional metal mesh in front of the spray. There are several parameters that affect the performance during ionization of molecules including the flow rate of solvent, gas pressure, temperature, solvent acidity, distance and potential difference between emitter and counter electrode. A variable electrostatic potential can be applied for higher ionization efficiency. The new ionization method was successfully applied to solutions of various proteins under different conditions. The same charge‐state distributions compared to other ESI techniques are observed for all the protein samples. The unique feature of TESI is very efficient spraying by using a natural electrostatic potential even at the potential that a human body can produce. This provides very gentle ionization efficiency of peptides and proteins in different solvents. Copyright © 2013 John Wiley & Sons, Ltd.     

Performance of Orbitrap Mass Analyzer at Various Space Charge and Non-Ideal Field Conditions: Simulation Approach

The orbital trap mass analyzer provides a number of unique analytical features along with inevitable limitations as an electrostatic instrument operating in high space charge regimes resulting in systematic measured frequency errors as an effect of stored ion clouds on the trap field and each other effect of non-ideal machining the trap electrodes, effect of injection slot, effect of real versus theoretical trap dimensions, etc. This paper deals with determining the influence of the space charge effect and imperfection of the electrostatic field on the motion of ion ensembles in the orbital trap. We examine effects of theoretically modeled non-harmonicity of the electrostatic potential and the number of confined ions on stability of coherent ion motion in the trap that determines the frequency shifts of axial ion oscillation. Three different Orbitrap geometries were considered: geometry close to preproduction Orbitrap, close to standard Orbitrap, close to high field Orbitrap. Frequency shifts for m/z = 500 and for charge state +23 of cytochrome c isotopic cluster particles with 10⁴ {10^4} -6*10⁶ {10^6} elemental charges in the trap were considered. Refined spectra were calculated using the filter diagonalization method proposed by Mandelshtam et al. and applied to mass spectrometry by O’Connor and Aizikov.     

Electrostatic patterning of a silica surface: a new model for charge build-up on a dielectric solid

The polarization of interdigitated gold electrodes mounted over a silica thin film formed by oxidation of a Si wafer produces reproducible electrostatic patterns with overall excess negative charge, as observed by scanning electric potential microscopy. Domain charge concentrations as high as 76 charge units per square micrometer are obtained when a 5 V difference is applied to the electrodes thus producing fields in the 10(6) V m(-1) range. These patterns vanish when the electrodes are short-circuited and grounded. Characteristic times for pattern formation and relaxation are in the order of 10 min. The results are consistent with a model based on the discharge of H(+) ions at the negative electrodes, leaving behind immobile surface-bound SiO(-) groups and thus showing that chemisorption phenomena are decisive for electrostatic charging of insulators.     

SYNTHESIS OF AMPHIPATHIC PORPHYRINS AND THEIR PHOTOINDUCED ELECTRON TRANSFER REACTIONS AT THE LIPID BILAYER-WATER INTERFACE

A one flask synthesis of cis -substituted amphipathic porphyrins is reported. These porphyrins were used to study electrostatic effects on photoinduced electron transfer across the lipid bilayer-water interface. A neutral porphyrin undergoes only dynamic interfacial electron transfer reactions irrespective of charge of the acceptor, although ionic strength effects indicate a negative charge on the porphyrin donor species. A dianionic porphyrin forms an interfacial static complex with a dicationic electron acceptor, methyl viologen, at low ionic strength. The electron transfer rate within the complex is slow, 10⁵∼ 10⁶ s^-1, which is attributed to a near orthogonal orientation between the donor and the acceptor ∼ orbitals.     

Intraprotein electrostatics derived from first principles: divide-and-conquer approaches for QM/MM calculations

Two divide-and-conquer (DAQ) approaches for building multipole-based molecular electrostatic potentials of proteins are presented and evaluated for use in QM/MM calculations. One approach is a further development of the neutralization method of Bellido and Rullmann (J Comput Chem 1989, 10, 479-487) while the other is based on removing part of the electron density before performing the multipole expansion. Both methods create systems with integer charges without using charge renormalization. To determine their performance in terms of location of cuts and distance to QM region, the new DAQ approaches are tested in calculations of the proton affinity of N(zeta) of Lys55 in the inhibitor turkey ovomucoid third domain. Finally, the two methods are used to build a variety of MM regions, applied to calculations of the pK(a) of Lys55, and compared to other computational methodologies in which force field charges are employed.     

阳离子聚电解质对油污泥的絮凝作用机理

用高密度电荷阳离子聚电解质处理油污泥［１,２］,依靠其与粘土颗粒间的静电作用压缩污泥中固相颗粒的表面双电层,中和ζ电位,使其颗粒间斥力减小,引力增大,油污泥化学脱稳,致使粘土颗粒聚集絮凝成团块,油颗粒聚集,实现油、水、泥渣的三相分离．１　实验部分１．１　样品制备　现场采集的油污泥中油品含量１９％,固含量８％,体系漏斗粘度３７ｓ,密度１．０９ｇ／ｃｍ３．阳离子聚电解质（ＣＦ）、聚丙烯酰胺－丙烯酸β－羟基丙酯基三甲基氯化铵按文献［２,３］方法制备,平均分子量２．６０×１０６,阳离子电荷度４５％．阴离…     

Dissolution and swelling behaviors of random and cross-linked methacrylic acid-ethyl acrylate copolymers

The neutralization behaviors of random and cross-linked methacrylic acid-ethyl acrylate (MAA-EA) copolymers were examined as a function of degree of neutralization (alpha) using potentiometric titration and laser light scattering techniques. The random MAA-EA copolymers exhibit a conformational transition from a compact latex particle to a swollen randomly coiled aggregate upon neutralization over a certain range of alpha. With further addition of NaOH, the swollen aggregates dissociate into several smaller clusters. This conformational change is controlled by the balance between electrostatic repulsion within ionized MAA groups and hydrophobic attraction of EA. The cross-linked MAA-EA copolymers do not undergo a drastic conformational change during neutralization. The polymer latex particles swell slightly upon neutralization, and the extent of chain expansion is proportional to MAA molar composition and inversely proportional to cross-linked density. The electrostatic Gibbs energy (DeltaG(el)) obtained from the potentiometric titration data indicates that a higher MAA portion is favorable for the deprotonization of both the random and cross-linked MAA-EA copolymers, suggesting that the dissociation is mainly dominated by polymer structure instead of the electrostatic attraction between H(+) and -COO(-). Moreover, static and dynamic light scattering results confirmed that the cross-linked latex particle exists as monodispersed hard sphere in the collapsed state, whereas in its swollen state the latex particle possesses a core-shell structure.