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The speciation of Tc(VII) in 12 M sulfuric acid was studied by NMR, UV-visible and XAFS spectroscopy, experimental results were supported by DFT calculation and were in agreement with the formation of TcO{sub 3}OH(H{sub 2}O){sub 2}. In summary, the speciation of heptvalent technetium has been investigated in sulfuric acid. In 12 M H{sub 2}SO{sub 4}, a yellow solution is observed, and its {sup 99}Tc NMR spectrum is consistent with a heptavalent complex. The yellow solution was further characterized by EXAFS spectroscopy, and results are consistent with the formation of TcO{sub 3}(OH)(H{sub 2}O){sub 2}. No technetium heptoxide or sulfato- complexes were detected in these conditions. The molecular structure of TcO{sub 3}(OH)(H{sub 2}O){sub 2} has been optimized by DFT techniques, and the structural parameters are well in accordance with those found by XAFS spectroscopy. The experimental electronic spectra exhibit ligand-to-metal charge transfer transitions that have been assigned using TDDFT methods. Calculations demonstrate the theoretical electronic spectrum of TcO{sub 3}(OH)(H{sub 2}O){sub 2} to be in very good agreement with the experimental one. Recent experiments in 12 M H{sub 2}SO{sub 4} show the yellow solution to be very reactive in presence of reducing agents presumably forming low valent Tc species. Current spectroscopic works focus …

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Current leads are utilized to deliver electrical power from a room temperature junction mounted on the vacuum vessel to a superconducting magnet located within the vacuum space of a cryostat. There are many types of current leads used at laboratories throughout the world; however, conduction-cooled current leads are often chosen for their simplicity and reliability. Conduction-cooled leads have the advantage of using common materials, have no superconducting/normal state transition, and have no boil-off vapor to collect. This paper presents a numerical model for conduction-cooled current lead heat loads. This model takes into account varying material and fluid thermal properties, varying thicknesses along the length of the lead, heat transfer in the circumferential and longitudinal directions, electrical power dissipation, and the effect of thermal intercepts. The model is validated by comparing the numerical model results to ideal cases where analytical equations are valid. In addition, the XFEL (X-Ray Free Electron Laser) prototype current leads are modeled and compared to the experimental results from testing at DESY's XFEL Magnet Test Stand (XMTS) and Cryomodule Test Bench (CMTB).

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The Western Renewable Energy Zone (WREZ) initiative brings together a diverse set of voices to develop data, tools, and a unique forum for coordinating transmission expansion in the Western Interconnection. In this paper we use a new tool developed in the WREZ initiative to evaluate possible renewable resource selection and transmission expansion decisions. We evaluate these decisions under a number of alternative future scenarios centered on meeting 33percent of the annual load in the Western Interconnection with new renewable resources located within WREZ-identified resource hubs. Our analysis finds that wind energy is the largest source of renewable energy procured to meet the 33percent RE target across nearly all scenarios analyzed (38-65percent). Solar energy is almost always the second largest source (14-41percent). We find several load zones where wind energy is the least cost resource under a wide range of sensitivity scenarios. Load zones in the Southwest, on the other hand, are found to switch between wind and solar, and therefore to vary transmission expansion decisions, depending on uncertainties and policies that affect the relative economics of each renewable option. Further, we find that even with total transmission expenditures of $17-34 billion these costs still represent just 10-19percent of the total …

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A 14-year study of snag characteristics was established in 41- to 44-year old loblolly pine (Pinus taeda L.) stands in southeastern USA. During the initial 5.5 years, no stand manipulation or unusually high-mortality events occurred. Afterwards, three treatments were applied consisting of trees thinned and removed, trees felled and not removed, and artificial creation of snags produced by girdling and herbicide injection. The thinned treatments were designed to maintain the same live canopy density as the snag-created treatment, disregarding snags that remained standing.We monitored snag height, diameter, density, volume, and bark percentage; the number of cavities was monitored in natural snags only. During the first 5.5 years, recruitment and loss rates were stable, resulting in a stable snag population. Large snags (≥25 cm diameter) were common, but subcanopy small snags (10 to <25 cm diameter) dominated numerically. Large natural snags survived (90% quantile) significantly longer (6.0–9.4 years) than smaller snags (4.4–6.9 years). Large artificial snags persisted the longest (11.8 years). Cavities in natural snags developed within 3 years following tree death. The mean number of cavities per snag was five times greater in large versus small snags and large snags were more likely to have multiple cavities, emphasizing the importance …

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Our previously developed finite-element/ discrete variable representation in prolate spheroidal coordinates is extended to two-electron systems with a study of double ionization of H$_2$ with fixed-nuclei. Particular attention is paid to the development of fast and accurate methods for treating the electron-electron interaction. The use of exterior complex scaling in the implementation offers a simple way of enforcing Coulomb boundary conditions for the electronic double continuum. While the angular distributions calculated in this study are found to be completely consistent with our earlier treatments that employed single-center expansions in spherical coordinates, we find that the magnitude of the integrated cross sections are sensitive to small changes in the initial-state wave function. The present formulation offers significant advantages with respect to convergence and efficiency and opens the way to calculations on more complicated diatomic targets.

The 2010 Conference on the Cell and Molecular Biology of Chlamydomonas was held June 6-10 near Boston, MA, and attracted a record 273 participants, 146 from US labs, 10 from Canada, and the remainder from 18 other countries. The single-celled algal protist Chlamydomonas is a key research organism for many investigators, including those who study photosynthesis, cell motility, adaptation to environmental stresses, the evolution of multicellularity, and the production of biofuels. Chlamydomonas researchers gather every two years at a research conference to exchange methods, develop collaborative efforts, disseminate recent findings, and plan large-scale studies to improve the usefulness of this unique research organism. This conference provides the only opportunity for Chlamydomonas scientists who work on different research problems to meet face to face, and greatly speeds progress in their respective fields. An important function of these Chlamydomonas conferences is to promote and showcase the work of younger scientists, and to attract new investigators into the Chlamydomonas community. DOE award SC0004085 was used to offset the travel and registration costs for 18 young investigators, 9 of whom were women, including one African American. Most of these scientists would not have been able to attend the conference without DOE support. A total …

Most searches for ultra-high energy (UHE) astrophysical neutrinos look for radio emission from the electromagnetic and hadronic showers produced in their interactions. The radio frequency spectrum and angular distribution depend on the shower development, so are sensitive to the interaction cross sections. At energies above about 1016 eV (in ice), the Landau-Pomeranchuk-Migdal (LPM) effect significantly reduces the cross sections for the two dominant electromagnetic interactions: bremsstrahlung and pair production. At higher energies, above about 1020 eV, the photonuclear cross section becomes larger than that for pair production, and direct pair production and electronuclear interactions become dominant over bremsstrahlung. The electron interaction length reaches a maximum around 1021 eV, and then decreases slowly as the electron energy increases further. In this regime, the growth in the photon cross section and electron energy loss moderates the rise in nu e shower length, which rises from ~;;5 m at 1016 eV to ~;;40 m at 1019 eV and ~;;100 m at 1020 eV, but only to ~;;300 m at 1024 eV. In contrast, without photonuclear and electronuclear interactions, the shower length would be over 10 km at 1024 eV.

The SLAC National Accelerator Laboratory is developing a second generation Marx-type modulator for the ILC, the P2-Marx. The modulator is expected to operate reliably in excess of 10{sup 5} hours with minimum downtime. A prognostic system is being implemented with the development of the P2-Marx to monitor and track the health of key high voltage components. This paper discusses the way in which the prognostic system will be implemented and used to monitor the health of the P2-Marx modulator.

Results from single photon vacuum ultraviolet photoionization of astrophysically relevant CnN clusters, n = 4 - 12, in the photon energy range of 8.0 eV to 12.8 eV are presented. The experimental photoionization efficiency curves, combined with electronic structure calculations, provide improved ionization energies of the CnN species. A search through numerous nitrogen-terminated CnN isomers for n=4-9 indicates that the linear isomer has the lowest energy, and therefore should be the most abundant isomer in the molecular beam. Comparison with calculated results also shed light on the energetics of the linear CnN clusters, particularly in the trends of the even-carbon and the odd-carbon series. These results can help guide the search of potential astronomical observations of these neutral molecules together with their cations in highly ionized regions or regions with a high UV/VUV photon flux (ranging from the visible to VUV with flux maxima in the Lyman- region) in the interstellar medium.

The primary subject of working group 7 at the 2012 Advanced Accelerator Concepts Workshop was muon accelerators for a muon collider or neutrino factory. Additionally, this working group included topics that did not fit well into other working groups. Two subjects were discussed by more than one speaker: lattices to create a perfectly integrable nonlinear lattice, and a Penning trap to create antihydrogen.

The effect of geometrical frustration on the development of the heavy-fermion state and quantum criticality is studied in UAuCu{sub 4}, UAuPt{sub 4}, UAu{sub 3}Ni{sub 2} samples through measurements of their magnetic susceptibility, heat capacity, and electrical resistivity. In addition, since lattice disorder can play a large role in defining magnetic properties in frustrated systems, extended X-ray absorption fine structure (EXAFS) data have also been obtained. The local structure results show a strong correlation with the magnetic properties in these samples.

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The 2011 Gordon Research Conference on Superconductivity will commemorate the 100th anniversary of the discovery of superconductivity by providing a forum for discussion of the latest experimental and theoretical advances in this field. The conference will bring together experts to address the current challenges in understanding correlated superconductors - from cuprates and pnictides to heavy fermion superconductors. The fundamental mechanisms of superconducting pairing, the underlying explanations for thermodynamic phase diagrams including potential importance of competing phases, the correspondence between these phenomena, and the transport and spectroscopic properties of these materials will be among the themes of the conference. We will also discuss the feasibility of using lessons learned from the study of known superconductors as a guide to the future discovery of novel and higher temperature superconductors. Speakers will be strongly encouraged to present new, unpublished work, which will ensure that discussions evoke and explore new research directions. The participation of young scientists at the graduate student or post-doctoral level will be encouraged by the offering of selected presentations, focused discussions with invited speakers, and poster sessions. In addition, the organizers have earmarked funds to facilitate attendance of members of groups underrepresented in science and engineering.

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Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters. A numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger was developed and the effect of various design parameters on overall heat exchanger size was investigated. It was found that highly …