A method for measuring tissue-equivalent dose using a pin diode and activation foil in epithermal neutron beams with EN < 100 keV

Silicon (Si) pin diodes can be used for neutron dosimetry by observing the change in forward bias voltage caused by neutron induced displacement damage in the diode junction. Pin diode energy response depends on Si displacement damage KERMA (K(Si)). It is hypothesised that tissue-equivalent (TE) neutron dose could be expressed as a linear combination of K(Si) and foil activation terms. Monte Carlo simulations (MCNP) of parallel monoenergetic neutron beams incident on a cylindrical TE phantom were used to calculate TE dose, K(Si) and Au, Cu and Mn foil activations along the central axis of the phantom. For spectra with neutron energies <100 keV, it is possible to estimate the TE kerma based on silicon damage kerma and Cu or Mn foil measurements. More accurate estimates are possible for spectra where the maximum neutron energy does not exceed 30 keV.     

Biosorbents based on pine sawdust and malt sprouts for preconcentration and ICP-OES determination of nonferrous,heavy, and precious metals in the environmental samples

Pine sawdust and malt sprouts modified with orthophosphoric acid and carbamide have been proposed for solid-phase extraction (SPE) of nonferrous, heavy, and precious metals and their subsequent determination in the environmental samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Modified adsorbents were characterized by SEM, TGA, and FT-IR and compared with native matrixes. SPE of some nonferrous and precious metal ions by biosorbents was studied. Depending on the SPE conditions, it was possible to separate nonferrous and heavy metals from alkali and alkaline earth metals. The proposed adsorbents are effective for preconcentration of nonferrous and heavy metals from natural waters and precious metals from solutions after digestion of geological samples.     

Development and Application of a Label-Free Fluorescence Method for Determining the Composition of Gold Nanoparticle–Protein Conjugates

A method was developed for determining the composition of the conjugates between gold nanoparticles and proteins based on the intrinsic fluorescence of unbound protein molecules. The fluorescence was evaluated after separation of the conjugates from the reaction mixture by centrifugation. Gold nanoparticles obtained using the citrate technique (average diameter 24 nm) were conjugated at pH 5.4 with the following four proteins: human immunoglobulin G (IgG), bovine serum albumin (BSA), recombinant streptococcal protein G (protein G), and Kunitz-type soybean trypsin inhibitor (STI). The compositions of these conjugates were determined using the developed method. The conjugate compositions were dependent on the concentration of the added protein, and in all cases reached saturation. The equilibrium dissociation constants of the gold nanoparticle conjugates with IgG, BSA, protein G, STI in the initial section of the concentration dependence curve were 4, 6, 10, and 15 nM, respectively. Close to saturation, the corresponding values were 25, 76, 175, and 100 nM, respectively. The maximal binding capacities of a single gold nanoparticle for IgG, BSA, Protein G, and STI were 52, 90, 500, and 550, respectively, which agrees well with the hypothesis of monolayer immobilization.     

Application of the contact potential difference technique for on-line rubbing surface monitoring (review)

The Kelvin technique for measuring contact potential differences has been adapted for continuous non-destructive monitoring of changes in the electron work function of a rubbing surface. The method can be used to investigate tribological materials for a wide range of conditions, including changes in load, sliding speed, and environment, with or without lubrication. It relies on the sensitivity of the work function to the various events which accompany friction, e.g., plastic deformation, creation of new surface material, adsorption, oxidation, phase changes and redistribution of alloy components. At present, this is the only method which is sensitive to both surface and near-surface defects and permits study of one of the two interacting surfaces during sliding. Current work emphasizes two aspects of sliding behavior: (1) critical points with respect to changes in normal load, with relevance to materials selection and optimization, and (2) the kinetics of friction processes, including periodic changes which may be related to those in fatigue. This revised version was published online in June 2006 with corrections to the Cover Date.     

Molecular plasmonics with tunable exciton-plasmon coupling strength in J-aggregate hybridized Au nanorod assemblies

Controlling coherent electromagnetic interactions in molecular systems is a problem of both fundamental interest and important applicative potential in the development of photonic and opto-electronic devices. The strength of these interactions determines both the absorption and emission properties of molecules coupled to nanostructures, effectively governing the optical properties of such a composite metamaterial. Here we report on the observation of strong coupling between a plasmon supported by an assembly of oriented gold nanorods (ANR) and a molecular exciton. We show that the coupling is easily engineered and is deterministic as both spatial and spectral overlap between the plasmonic structure and molecular aggregates are controlled. We think that these results in conjunction with the flexible geometry of the ANR are of potential significance to the development of plasmonic molecular devices.     

Polyphenols Fingerprinting in Olive Oils Through Maximum-Quantum NMR Spectroscopy

An NMR protocol based on multiple-quantum spectroscopy is presented for an analytical screening of polyphenols in olive oils. Three Italian olive oils with different total polyphenols content were used as study case. A total of 24 compounds were identified as follows: 1 polyphenol in the 5Q–1Q, 15 more in the 4Q–1Q, and 8 components in the 3Q–1Q spectra, consisting of organic phenols, secoiridoids, lignans, and flavonols. In the three Italian olive oils investigated here, the polyphenols profile turned out to be significantly different, with specific characteristics going beyond simple considerations based on the total polyphenol content. The approach presented here can be easily extended for rapid qualitative and semi-quantitative screening of the polyphenol composition in many food products.     

Surface plasmon polariton amplification upon electrical injection in highly integrated plasmonic circuits

We propose a very efficient approach for amplification of surface plasmon polaritons (SPPs) in a nanoscale waveguiding geometry with strong (～λ/10) mode confinement. The implemented scheme of electric pumping is based on a single-heterostructure Schottky-barrier diode and has been numerically shown to ensure full compensation of the SPP propagation losses at wavelengths around 3 μm and, moreover, to provide net SPP gain. The presented concept creates the backbone for the implementation of highly integrated large-scale hybrid electronic-plasmonic circuits operating at extremely high speeds and opens the prospects for the realization of integrated coherent SPP sources.     

Synthesis and characterization of a mesoporous hydrous zirconium oxide used for arsenic removal from drinking water

Powder (20-50 μm) mesoporous hydrous zirconium oxide was prepared from a zirconium salt granular precursor. The effect of some process parameters on product morphology, porous structure and adsorption performance has been studied. The use of hydrous zirconium oxide for selective arsenic removal from drinking water is discussed.     

Effect of competitive ions on the arsenic removal by mesoporous hydrous zirconium oxide from drinking water

Adsorption properties of 302-type commercially available hydrous zirconium oxide (302-HZO) towards arsenic and some competitive anions and cations have been studied under batch and column conditions. Due to amphoteric properties, anion exchange performance of hydrous zirconium oxide is pH dependent. Media exhibits high affinity towards arsenic in a broad pH range, with high adsorption capacity at pH < 8. It was shown that silicate and phosphate ions are arsenic's main competitors affecting media adsorption capacity. Presence of transition metal cations in <1 ppm does not affect 302-HZO capacity on arsenic, whereas alkaline-earth cations improve arsenic removal. The possibility for significant increase of 302-HZO adsorption capacity on arsenic at pH > 8 by using “solid acidifier” technique is discussed. Results of 302-HZO field trials are presented.