Measurement of <Superscript>3</Superscript>H,gross <Emphasis Type="Italic">α/β</Emphasis> and <Superscript>222</Superscript>Rn in drinking water using the new Quantulus GCT 6220

Since the introduction of the European Council Directive 2013/51 Euratom in October 2013, the analysis of drinking water has increasingly become the focus of many laboratories in Europe. The activity of tritium, radon and the gross α/β-activity is determined routinely. In order to cope with the increased sample numbers and to reach the necessary detection limits, sensitive measuring devices are required. This work was done with the new Quantulus GCT 6220 to test the sensitivity of this system for drinking water analysis. The results indicate that this instrument is very well suited for this type of analysis and counting times are typically below the required counting times of established systems.     

Structural requirement of C11b chirality of tetrabenazine analogs as VMAT2 imaging ligands: synthesis and in vivo evaluation

We studied on the structural requirement of C11b chirality of tetrabenazine (TBZ) analogs as vesicular monoamine transporter 2 (VMAT2) ligands. TBZ analogs (2, 6a, 6b) and ¹⁸F-radiolabeled [¹⁸F]6a and [¹⁸F]6b with eliminated C11b chirality were synthesized and characterized. Competition studies demonstrated that 2, 6a and 6b displayed much lower in vivo VMAT2 bindings than TBZ. MicroPET imaging studies of [¹⁸F]6a and [¹⁸F]6b showed negligible accumulation in VMAT2-enriched regions as compared with the known VMAT2 ligand ¹⁸F-FP-(+)-DTBZ. These results suggest that C11b chirality of TBZ analogs is essential for in vivo VMAT2 binding bioactivity.     

Radiolysis products and degradation mechanism studies on di-1-methyl heptyl methyl phosphonate

Di-1-methyl heptyl methyl phosphonate (DMHMP) is a promising alternative extractant for Th-U fuel reprocessing, in which the irradiation stability of extractant should be systematically studied. In this paper, the radiolysis products of DMHMP were analyzed qualitatively and quantitatively with gas and ion chromatograph, the possible radiolysis mechanism of DMHMP was also concluded. Moreover, the effect of structure on the radiolysis products and irradiation stability of neutral organophosphorus compound extractant was also discussed.

     

Chemical treatments on the cuticle layer enhancing the uranium(VI) uptake from aqueous solution by amidoximated wool fibers

Urea, sodium hydroxide and sodium sulfide were used to treat the cuticle layer of wool before graft copolymerization and amidoximation to enhance the uranium uptaking capacity of amidoximated wool fiber based adsorbent (Wool-g-AOs). The wool-g-AOs were used for recovery of U(VI) from aqueous solutions. The simulated nuclear industry effluent was used for investigating the selectivity and industrial applicability of Wool-g-AOs. The adsorption of uranium(VI) on Wool-g-AOs was pH dependent. The Langmuir model fitted well with the equilibrium data. Kinetic data were fitted well to pseudo second order model.

     

Detection efficiency calculations using Geant4 for a broad-energy germanium gamma spectrometer

In assistance of radionuclide measurements at Canada’s Comprehensive Nuclear-Test-Ban Treaty (CTBT) laboratory, a Geant4 Monte Carlo application has been developed in simulating a broad-energy germanium detector and calculating detection efficiencies. The detector model was optimized in a reliable and non-biased manner through simultaneous tuning on gap distance and detector dimension, and was validated over various realistic measurement scenarios. All work is based on a series of experiments which covers the typical energy range of gamma radiation in environmental analysis, and considers the variety of the CTBT sample type, dimension and distance-to-detector. In all cases, the predicted efficiencies are consistent with the empirical ones within 5%, with a typical deviation of 3% in majority.     

On the geometric–arithmetic index by decompositions-CMMSE

The concept of geometric–arithmetic index was introduced in the chemical graph theory recently, but it has shown to be useful. There are many papers studying different kinds of indices (as Wiener, hyper–Wiener, detour, hyper–detour, Szeged, edge–Szeged, PI, vertex–PI and eccentric connectivity indices) under particular cases of decompositions. The main aim of this paper is to show that the computation of the geometric-arithmetic index of a graph G is essentially reduced to the computation of the geometric-arithmetic indices of the so-called primary subgraphs obtained by a general decomposition of G. Furthermore, using these results, we obtain formulas for the geometric-arithmetic indices of bridge graphs and other classes of graphs, like bouquet of graphs and circle graphs. These results are applied to the computation of the geometric-arithmetic index of Spiro chain of hexagons, polyphenylenes and polyethene.     

Performance of a rigid rod statistical mechanical treatment to predict monolayer ordering: a study of chain interactions and comparison with molecular dynamics simulation

A statistical mechanical model that treats hydrocarbon self-assembled monolayer (SAM) chains as rigid rods is examined to interrogate the mechanisms involved in monolayer ordering. The statistical mechanical predictions are compared to fully atomistic molecular dynamics simulations of SAMs with different packing densities. The monolayer chain order is examined as a function of surface coverage, chain-surface interactions, and chain–chain interactions. Reasonable interaction potentials are deduced from ab initio electronic structure calculations of small model systems. It is found that the chain-surface interaction is the most important parameter in formation of flat-lying monolayer phases, while formation of standing phase monolayers is driven most importantly by increased density of molecules at the surface. A brief discussion of the utility and validity of the rigid rod treatment is given in light of the molecular dynamics results.     

New two stages high order symmetric six-step method with vanished phase–lag and its first,second and third derivatives for the numerical solution of the Schrödinger equation

In the present paper, we obtain and analyze, for the first time in the literature, a new two-stages high order symmetric six-step method. The specific characteristics of the new proposed method are the highest possible algebraic order, the elimination of the phase–lag and its first, second and third derivatives. Additionally, for the new method we give the analysis of the method (both error and stability and interval of periodicity analysis) and the comparison of the effectiveness of the new developed method with the effectiveness of well known methods and very recently produced methods in the literature. The comparison is based on the numerical solution of the Schrödinger equation. The theoretical achievements and the numerical results show the effectiveness of the new developed method in comparison with other well known or recently developed numerical methods.     

POSS-modified PEG adhesives for wound closure

PEG-related adhesives are limited in clinical use because they are easy to swell and cannot support the cell growth.In this study,we produced a series of POSS-modified PEG adhesives with high adhesive strength.Introduction of inorganic hydrophobic POSS units decreased the swelling of the adhesives and enhanced cell adhesion and growth.The in vitro cytotoxicity and in vivo inflammatory response experiments clearly demonstrated that the adhesives were nontoxic and possessed excellent biocompatibility.Compared with the sutured wounds,the adhesive-treated wounds showed an accelerated healing process in wounded skin model of the Bama miniature pig,demonstrating that the POSS-modified PEG adhesive is a promising candidate for wound closure.     

Fiber-reinforced three-dimensional graphene aerogels for electrically conductive epoxy composites with enhanced mechanical properties

To enhance the mechanical properties of three-dimensional graphene aerogels with aramid fibers,graphene/organic fiber aerogels are prepared by chemical reduction of graphene oxide in the presence of organic fibers of poly(p-phenylene terephthalamide)(PPTA) and followed by freeze-drying. Thermal annealing of the composite aerogels at 1300 ° C is adopted not only to restore the conductivity of the reduced graphene oxide component but also to convert the insulating PPTA organic fibers to conductive carbon fibers by the carbonization. The resultant graphene/carbon fiber aerogels(GCFAs) exhibit high electrical conductivities and enhanced compressive properties, which are highly efficient in improving both mechanical and electrical performances of epoxy composites. Compared to those of neat epoxy, the compressive modulus, compressive strength and energy absorption of the electrically conductive GCFA/epoxy composite are significantly increased by 60%, 59% and 131%, respectively.