Effects of ammonium molybdophosphate (AMP) on strontium, actinides, and RCRA metals in SRS simulated waste

Three radionuclide-spiked salt solutions have been prepared that simulate a range of typical compositions in Savannah River Site waste solutions. The Savannah River National Laboratory performed a series of tests with the three salt solutions designed to determine the propensity of ammonium molybdophosphate (AMP) to bind some of the common analytes such as the actinides (Pu, Am, Np, U), strontium, or the elements (Ag, As, Ba, Cd, Cr, Hg, Pb, Se) regulated by the Resource Conservation Recovery Act (RCRA). The results of the tests indicate that within the protocol conditions, AMP exhibited no appreciable affinity for plutonium, neptunium, uranium and strontium. AMP showed a possible minor affinity for americium; however, the data is not as clear due to continued americium solubility changes during the duration of the experiment. Of the eight RCRA elements studied, AMP exhibited affinity for only silver under our experimental conditions.     

Junctionless nanowire transistor fabricated with high mobility Ge channel

The junctionless nanowire metal–oxide–semiconductor field‐effect transistor (JNT) has recently been proposed as an alternative device for sub‐20‐nm nodes. The JNT architecture eliminates the need for forming PN junctions, resulting in simple processing and competitive electrical characteristics. In order to further boost the drive current, alternative channel materials such as III–V and Ge, have been proposed. In this Letter, JNTs with Ge channels have been fabricated by a CMOS‐compatible top–down process. The transistors exhibit the lowest subthreshold slope to date for JNT with Ge channels. The devices with a gate length of 3 μm exhibit a subthreshold slope (SS) of 216 mV/dec with an I_ON/I_OFF current ratio of 1.2 × 10³ at V_D = –1 V and drain‐induced‐barrier lowering (DIBL) of 87 mV. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Supermode dispersion and waveguide-to-slot mode transition in arrays of silicon-on-insulator waveguides

In this Letter, we report group index measurements of the supermodes of an array of two strongly coupled silicon-on-insulator waveguides. We observe coupling-induced dispersion that is greater than the material and waveguide dispersion of the individual waveguides. We demonstrate that the system transforms from supporting the two supermodes associated with two coupled waveguides to the single mode of a slot waveguide within the investigated spectral range. During the cutoff of the antisymmetric supermode, an anti-crossing between the symmetric TM and antisymmetric TE supermodes has been observed.     

A novel instrument for transient photoelasticity

A new instrument has been developed for the photoelastic analysis of transient events. The instrument is based on the Phase-Stepped Images Obtained Simultaneously (PSIOS) system developed by Patterson and Wang, which enables four phase-stepped photoelastic images to be collected simultaneously. Where the new instrument differs is that the original instrument requires four cameras to collect the four images, whereas the new instrument requires only one camera. This makes the use of phase-stepping viable for events, in which the fringe order varies with time. Three examples are given of the use of the instrument in static and dynamic photoelasticity to generate full field maps of isochromatic fringes. The instrument has been found to work well and significantly increases the potential for the use of photoelasticity to study transient and possibly dynamic events. J.W. Hobbs was a Research Associate, R.J. Greene was a Research Associate     

Thermomorphic polyethylene-supported olefin metathesis catalysts

The preparation of polyethylene-oligomer (PE(olig))-supported N-heterocyclic carbene ligands (NHCs) and their Ru complexes is described. These complexes are structurally analogous to their low molecular weight counterparts and can serve as thermomorphic, recoverable/recyclable ring-closing metathesis (RCM) catalysts. Because of the insolubility of PE(olig)-supported species at 25 °C, such complexes can perform homogeneous RCM reactions at 65 °C and, upon cooling, precipitate as solids. This allows for their quantitative separation from solutions of products.     

Protein micro- and nanopatterning using aminosilanes with protein-resistant photolabile protecting groups

An approach to the integration of nanolithography with synthetic chemical methodology is described, in which near-field optical techniques are used to selectively deprotect films formed by the adsorption of aminosilanes protected by modified 2-nitrophenylethoxycarbonyl (NPEOC) groups. The NPEOC groups are functionalized at the m- or p-position with either a tetraethyleneglycol or a heptaethylene glycol adduct. We describe the synthesis of these bioresistant aminosilanes and the characterization of the resulting photoreactive films. Photodeprotection by exposure to UV light (λ = 325 nm) yielded the amine with high efficiency, at a similar rate for all four adsorbates, and was complete after an exposure of 2.24 J cm(-2). Following photodeprotection, derivatization by trifluoroacetic anhydride was carried out with high efficiency. Micropatterned samples, formed using a mask, were derivatized with aldehyde-functionalized polymer nanoparticles and, following derivatization with biotin, were used to form patterns of avidin-coated polymer particles. Fluorescence microscopy and atomic force microscopy data demonstrated that the intact protecting groups conferred excellent resistance to nonspecific adsorption. Nanometer-scale patterns were created using scanning near-field photolithography and were derivatized with biotin. Subsequent conjugation with avidin-functionalized polymer nanoparticles yielded clear fluorescence images that indicated dense attachment to the nanostructures and excellent protein resistance on the surrounding surface. These simple photocleavable protecting group strategies, combined with the use of near-field exposure, offer excellent prospects for the control of surface reactivity at nanometer resolution in biological systems and offer promise for integrating the top-down and bottom-up molecular fabrication paradigms.     

Testing partonic charge symmetry at a high-energy electron collider

We examine the possibility that one could measure partonic charge symmetry violation (CSV) by comparing neutrino or antineutrino production through charged-current reactions induced by electrons or positrons at a possible electron collider at the LHC. We calculate the magnitude of CSV that might be expected at such a facility. We show that this is likely to be a several percent effect, substantially larger than the typical CSV effects expected for partonic reactions.     

Multicomponent synthesis of chiral sulfinimines

Two oxathiozolidine-S-oxide templates have been developed and used in a four-component coupling protocol for the synthesis of a wide range of chiral sulfinimines in high enantiomeric excesses. The templates can be synthesized from cheap commodity chemicals in three steps in high yields. Furthermore the template is easily recovered in high yields for recycling.