Effects of aqueous complexation on reductive precipitation of uranium by Shewanella putrefaciens

We have examined the effects of aqueous complexation on rates of dissimilatory reductive precipitation of uranium by Shewanella putrefaciens. Uranium(VI) was supplied as sole terminal electron acceptor to Shewanella putrefaciens (strain 200R) in defined laboratory media under strictly anaerobic conditions. Media were amended with different multidentate organic acids, and experiments were performed at different U(VI) and ligand concentrations. Organic acids used as complexing agents were oxalic, malonic, succinic, glutaric, adipic, pimelic, maleic, citric, and nitrilotriacetic acids, tiron, EDTA, and Aldrich humic acid. Reductive precipitation of U(VI), resulting in removal of insoluble amorphous UO(2 )from solution, was measured as a function of time by determination of total dissolved U. Reductive precipitation was measured, rather than net U(VI) reduction to U(IV), to assess overall U removal rates from solution, which may be used to gauge the influence of chelation on microbial U mineralization. Initial linear rates of U reductive precipitation were found to correlate with stability constants of 1:1 aqueous U(VI):ligand and U(IV):ligand complexes. In the presence of strongly complexing ligands (e.g., NTA, Tiron, EDTA), UO(2 )precipitation did not occur. Our results are consistent with ligand-retarded precipitation of UO(2), which is analogous to ligand-assisted solid phase dissolution but in reverse: ligand exchange with the U(4+ )aquo cation acts as a rate-limiting reaction moderating coordination of water molecules with U(4+), which is a necessary step in UO(2 )precipitation. Ligand exchange kinetics governing dissociation rates of ligands from U(VI)-organic complexes may also influence overall UO(2 )production rates, although the magnitude of this effect is unclear relative to the effects of U(IV)-organic complexation. Our results indicate that natural microbial-aqueous systems containing abundant organic matter can inhibit the formation of biogenic amorphous UO(2)

The Ursinus Weekly, March 13, 1944

Girls grab gobs for gala gathering as leap-year Lorelei looms at last • Y will entertain at spring reception • Students sell $13,744.70 in war bond drive as Eileen Smith wins second individual prize • Dr. W. Fuller explains CED work after war • Rex Gregor is awarded silver star for bravery • Chaplain tells students progress is inevitable • Senators to direct Red Cross drive here • Curtain Club to give three one-act plays • Marian Martin becomes IRC secretary-treasurer • Freshmen to receive colors in ceremony on Thursday • World Student Service Fund helps Chinese students solve problems • Delegates to be chosen for Penn State conference • Coeds to hear Mrs. Mooney • Carpenters, painters give new face to rec center • Dr. Oppenheimer speaks to pre-medical society • Lt. Norris A. Johnson \u2736, Navy radioman, writes from southwest Pacific about Air Corps duties • Frosh end sorority blues • Loyal Irish to praise St. Patrick on Friday • Improved girls\u27 team upsets Beaver after deadlocking for three periods • J.V.\u27s take Jenkintown six; Mid Halbruegge sets pace • Baseball team practices indoors under Heffernan • One-act play will be given at Women\u27s Club session • Betty Tyson reviews poetryhttps://digitalcommons.ursinus.edu/weekly/1726/thumbnail.jp

Assimilation of solids during ascent of magmas from the Bartoy Field of the Baikal Region, Siberia

Most investigators ascribe mare basalt magma genesis to partial melting at depths of approximately 130 to greater than 400 km within the cumulate pile deposited from a lunar magma ocean. Mare basalts share with mid-ocean ridge basalts the characteristic of relative depletion in LREE and other incompatible trace elements that arises from melting within 'used' mantle, from which crust-forming elements have already been separated. Some mare basalt types do not show the classical, La-Nd depleted mare basalt REE distributions; however, some types are isotopically heterogeneous. These differences have been ascribed to assimilation, mainly AFC-style, of KREEPy highland material overlying the source region. Might such assimilation occur during magma ascent through the KREEPy material? To gain information from a terrestrial setting on possible assimilation during ascent, we have studied a suite of Quaternary nepheline-hawalites and nepheline-mugearites from the Bartoy cinder cone complex of the Baikal Rift, Siberia. The Bartoy magmas originated from greater than 80 km deep, and erupted through thick Archean crust. We find evidence for assimilation of approximately 31 wt. percent xenocrysts of garnet, aluminous clinopyroxene, kaersutite, and olivine, all presumably from the basalt source region, but no appreciable assimilation of overlying crust, consistent with isotopic constraints. Magmatic superheat made available by rapid ascent and decomposition accounts adequately for the energy of assimilation; no accompanying fractional crystallization is required or evident

A novel topographic parameterization scheme indicates that martian gullies display the signature of liquid water

Martian gullies resemble gullies carved by water on Earth, yet are thought to have formed in an extremely cold (2-driven processes. That this argument persists demonstrates the limitations of morphological interpretations made from 2D images, especially when similar-looking landforms can form by very different processes. To overcome this we have devised a parameterization scheme, based on statistical discriminant analysis and hydrological terrain analysis of meter-scale digital topography data, which can distinguish between dry and wet surface processes acting on a landscape. Applying this approach to new meter-scale topographic datasets of Earth, the Moon and Mars, we demonstrate that martian gullied slopes are dissimilar to dry, gullied slopes on Earth and the Moon, but are similar to both terrestrial debris flows and fluvial gullies. We conclude that liquid water was integral to the process by which martian gullies formed. Finally, our work shows that quantitative 3D analyses of landscape have great potential as a tool in planetary science, enabling remote assessment of processes acting on planetary surfaces

Debris disks around Sun-like stars

We have observed nearly 200 FGK stars at 24 and 70 microns with the Spitzer Space Telescope. We identify excess infrared emission, including a number of cases where the observed flux is more than 10 times brighter than the predicted photospheric flux, and interpret these signatures as evidence of debris disks in those systems. We combine this sample of FGK stars with similar published results to produce a sample of more than 350 main sequence AFGKM stars. The incidence of debris disks is 4.2% (+2.0/-1.1) at 24 microns for a sample of 213 Sun-like (FG) stars and 16.4% (+2.8/-2.9) at 70 microns for 225 Sun-like (FG) stars. We find that the excess rates for A, F, G, and K stars are statistically indistinguishable, but with a suggestion of decreasing excess rate toward the later spectral types; this may be an age effect. The lack of strong trend among FGK stars of comparable ages is surprising, given the factor of 50 change in stellar luminosity across this spectral range. We also find that the incidence of debris disks declines very slowly beyond ages of 1 billion years.Comment: ApJ, in pres

A survey of performance enhancement of transmission control protocol (TCP) in wireless ad hoc networks

This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Springer OpenTransmission control protocol (TCP), which provides reliable end-to-end data delivery, performs well in traditional wired network environments, while in wireless ad hoc networks, it does not perform well. Compared to wired networks, wireless ad hoc networks have some specific characteristics such as node mobility and a shared medium. Owing to these specific characteristics of wireless ad hoc networks, TCP faces particular problems with, for example, route failure, channel contention and high bit error rates. These factors are responsible for the performance degradation of TCP in wireless ad hoc networks. The research community has produced a wide range of proposals to improve the performance of TCP in wireless ad hoc networks. This article presents a survey of these proposals (approaches). A classification of TCP improvement proposals for wireless ad hoc networks is presented, which makes it easy to compare the proposals falling under the same category. Tables which summarize the approaches for quick overview are provided. Possible directions for further improvements in this area are suggested in the conclusions. The aim of the article is to enable the reader to quickly acquire an overview of the state of TCP in wireless ad hoc networks.This study is partly funded by Kohat University of Science & Technology (KUST), Pakistan, and the Higher Education Commission, Pakistan

The Lantern Vol. 12, No. 3, June 1944

• A Peek Through a Byberry Window • Fragment • My Grudge Against the Fiction Detective • Haunting Refrain • The World and I • They Said • The Brook • By Their Fruits Ye Shall Know Them : 1944 Fogel Prize Essay • Why • Green Leaf • Night Drama • In That Same Hour • The Greeks Had a Word For It • The Call of War • The Promise of a Pearl • The Apiaryhttps://digitalcommons.ursinus.edu/lantern/1033/thumbnail.jp

SOPHIE velocimetry of Kepler transit candidates III. KOI-423b: an 18 Mjup transiting companion around an F7IV star

We report the strategy and results of our radial velocity follow-up campaign with the SOPHIE spectrograph (1.93-m OHP) of four transiting planetary candidates discovered by the Kepler space mission. We discuss the selection of the candidates KOI-428, KOI-410, KOI-552, and KOI-423. KOI-428 was established as a hot Jupiter transiting the largest and the most evolved star discovered so far and is described by Santerne et al. (2011a). KOI-410 does not present radial velocity change greater than 120 m/s, which allows us to exclude at 3 sigma a transiting companion heavier than 3.4 Mjup. KOI-552b appears to be a transiting low-mass star with a mass ratio of 0.15. KOI-423b is a new transiting companion in the overlapping region between massive planets and brown dwarfs. With a radius of 1.22 +- 0.11 Rjup and a mass of 18.0 +- 0.92 Mjup, KOI-423b is orbiting an F7IV star with a period of 21.0874 +- 0.0002 days and an eccentricity of 0.12 +- 0.02. From the four selected Kepler candidates, at least three of them have a Jupiter-size transiting companion, but two of them are not in the mass domain of Jupiter-like planets. KOI-423b and KOI-522b are members of a growing population of known massive companions orbiting close to an F-type star. This population currently appears to be absent around G-type stars, possibly due to their rapid braking and the engulfment of their companions by tidal decay.Comment: 9 pages, 12 figures, accepted in A&

A Conditional Yeast E1 Mutant Blocks the Ubiquitin–Proteasome Pathway and Reveals a Role for Ubiquitin Conjugates in Targeting Rad23 to the Proteasome

E1 ubiquitin activating enzyme catalyzes the initial step in all ubiquitin-dependent processes. We report the isolation of uba1-204, a temperature-sensitive allele of the essential Saccharomyces cerevisiae E1 gene, UBA1. Uba1-204 cells exhibit dramatic inhibition of the ubiquitin–proteasome system, resulting in rapid depletion of cellular ubiquitin conjugates and stabilization of multiple substrates. We have employed the tight phenotype of this mutant to investigate the role ubiquitin conjugates play in the dynamic interaction of the UbL/UBA adaptor proteins Rad23 and Dsk2 with the proteasome. Although proteasomes purified from mutant cells are intact and proteolytically active, they are depleted of ubiquitin conjugates, Rad23, and Dsk2. Binding of Rad23 to these proteasomes in vitro is enhanced by addition of either free or substrate-linked ubiquitin chains. Moreover, association of Rad23 with proteasomes in mutant and wild-type cells is improved upon stabilizing ubiquitin conjugates with proteasome inhibitor. We propose that recognition of polyubiquitin chains by Rad23 promotes its shuttling to the proteasome in vivo