Multiwalled Carbon Nanotubes for Heterogeneous Nanocatalytic Ozonation

Multiwalled carbon nanotubes functionalized by plasma oxygen (CNTs) have been used as heterogeneous catalysts for the ozonation of methyl orange (MO) dye (CI 13025) in aqueous solutions. It was found that the addition of CNTs significantly enhanced the dye decolorization as compared to ozone alone or when activated carbon was used at the same dose as CNTs. Both the initial ozone concentration and catalyst dosage enhanced the removal of MO. However, ozone gas concentrations higher than 6 g/m3 NTP did not further improve the decolorization rates. The removal efficiency of MO increased with pH in the range 2 to 3, while a reverse trend was observed when the pH increased from 3 to 9. The addition of a radical scavenger resulted in only a limited change in the decolorization rates suggesting that molecular ozone was the main pathway by which MO decolorization occurred in solution. However, under favorable conditions for MO attraction to CNT surface (pH = 3), the decolorization rate has significantly increased. At higher pH than the pKa value of MO (3.47) and the point of zero charge of CNT (3.87), a condition that favors the electrostatic repulsion of MO from CNT, the rates were reduced in the presence of CNT as compared to ozone alone possibly due to loss of part of the supplied ozone in un-useful parallel reactions

SAF-BRET-FMEF: a developmental LMR fuel cycle facility

The SAF-BRET-FMEF complex represents a versatile fuel cycle facility for processing LMR fuel. While originally conceived for processing FFTF and CRBRP fuel, it represents a facility where LMR fuel from the first generation of innovative LMRs could be processed. The cost of transporting fuel from the LMR to the Hanford site would have to be assessed when the LMR site is identified. The throughput of BRET was set at 15 MTHM/yr during conceptual design of the facility, a rate which was adequate to process all of the fuel from FFTF and fuel and blanket material from CRBRP. The design is currently being reevaluated to see if BRET could be expanded to approx.35 MTHM/yr to process fuel and blanket material from approx.1300 MWe generating capacity of the innovative LMRs. This expanded throughput is possible by designing the equipment for an instantaneous throughput of 0.2 MTHM/d, and by selected additional modifications to the facility (e.g., expansion of shipping and receiving area, and addition of a second entry tunnel transporter), and by the fact that the LMR fuel assemblies contain more fuel than the FFTF assemblies (therefore, fewer assemblies must be handled for the same throughput). The estimated cost of such an expansion is also being assessed. As stated previously, the throughput of SAF and Fuel Assembly could be made to support typical LMRs at little additional cost. The throughput could be increased to support the fuel fabrication requirements for 1300 MWe generating capacity of the innovative LMRs. This added capacity may be achieved by increasing the number of operating shifts, and is affected by variables such as fuel design, fuel enrichment, and plutonium isotopic composition

Biochar Reduced Nitrous Oxide and Carbon Dioxide Emissions from Soil with Different Water and Temperature Cycles

Interactions among biochar, respiration, nitrification, and soils can result in biochar increasing, decreasing, or not impacting greenhouse gas (GHG) emissions. This experiment determined the impact of water-filled porosity (WFP) and corn (Zea mays L.) stover biochar on CO2 and N2O emissions in May (spring) and August (summer). The May experiment contained two N rates [0 and 224 kg Ca(NO3)2–N ha–1], whereas the August had three N rates [0, 224 kg Ca(NO3)2–N ha–1, and 224 kg (NH4)2SO4–N ha–1]. The average temperatures in the May and Augusts 2014 experiments were 14 and 24°C, respectively. Biochar reduced CO2–C emissions in the high WFP Ca(NO3)2 treatment in the May and August experiments 15.4 and 16.3 kg ha–1, respectively. Associated with the CO2–C decrease was a 15.7% reduction in the soil solution dissolved organic C. In addition, N2O–N and CO2–C emissions were not correlated in the May Ca(NO3)2 ha–1 treatment, whereas in the August experiment, N2O–N and CO2–C emissions were correlated (r2 = 0.98, P \u3c 0.01). In August, biochar increased the apparent nitrification from 16 to 25 kg NH4–N (ha × d)–1 in the low WFP (NH4)2SO4treatment, and it did not influence the nitrification rate in the high WFP (NH4)2SO4 treatment. In general, N2O–N emissions increased with WFP and N rate and were reduced 21.7% by biochar. The findings suggest that multiple mechanisms contributed to N2O emissions and seasonal differences in soil temperature could result in biochar having a mixed impact on GHG emissions

Josephson current in s-wave superconductor / Sr_2RuO_4 junctions

The Josephson current between an s-wave and a spin-triplet superconductor Sr$_2$RuO$_4$ (SRO) is studied theoretically. In spin-singlet / spin-triplet superconductor junctions, there is no Josephson current proportional to $\sin \phi$ in the absence of the spin-flip scattering near junction interfaces, where $\phi$ is a phase-difference across junctions. Thus a dominant term of the Josephson current is proportional to $\sin 2\phi$ . The spin-orbit scattering at the interfaces gives rise to the Josephson current proportional to $\cos\phi$, which is a direct consequence of the chiral paring symmetry in SRO

Competing Orders in Coupled Luttinger Liquids

We consider the problem of two coupled Luttinger liquids both at half filling and at low doping levels, to investigate the problem of competing orders in quasi-one-dimensional strongly correlated systems. We use bosonization and renormalization group equations to investigate the phase diagrams, to determine the allowed phases and to establish approximate boundaries among them. Because of the chiral translation and reflection symmetry in the charge mode away from half filling, orders of charge density wave (CDW) and spin-Peierls (SP) diagonal current (DC) and $d$-density wave (DDW) form two doublets and thus can be at most quasi-long range ordered. At half-filling, umklapp terms break this symmetry down to a discrete group and thus Ising-type ordered phases appear as a result of spontaneous breaking of the residual symmetries. Quantum disordered Haldane phases are also found, with finite amplitudes of pairing orders and triplet counterparts of CDW, SP, DC and DDW. Relations with recent numerical results and implications to similar problems in two dimensions are discussed.Comment: 16 pages, 5 figures, 4 tables. Revised manuscript; a misprint in Eq. B3 has been corrected. The paper is already in print in PR

Pairing and Density Correlations of Stripe Electrons in a Two-Dimensional Antiferromagnet

We study a one-dimensional electron liquid embedded in a 2D antiferromagnetic insulator, and coupled to it via a weak antiferromagnetic spin exchange interaction. We argue that this model may qualitatively capture the physics of a single charge stripe in the cuprates on length- and time scales shorter than those set by its fluctuation dynamics. Using a local mean-field approach we identify the low-energy effective theory that describes the electronic spin sector of the stripe as that of a sine-Gordon model. We determine its phases via a perturbative renormalization group analysis. For realistic values of the model parameters we obtain a phase characterized by enhanced spin density and composite charge density wave correlations, coexisting with subleading triplet and composite singlet pairing correlations. This result is shown to be independent of the spatial orientation of the stripe on the square lattice. Slow transverse fluctuations of the stripes tend to suppress the density correlations, thus promoting the pairing instabilities. The largest amplitudes for the composite instabilities appear when the stripe forms an antiphase domain wall in the antiferromagnet. For twisted spin alignments the amplitudes decrease and leave room for a new type of composite pairing correlation, breaking parity but preserving time reversal symmetry.Comment: Revtex, 28 pages incl. 5 figure