Magnetic ordering, electronic structure and magnetic anisotropy energy in the high-spin Mn10_{10} single molecule magnet

We report the electronic structure and magnetic ordering of the single molecule magnet [Mn$_{10}$O$_{4}$(2,2'-biphenoxide)$_{4}$Br$_{12}$]$^{4-}$ based on first-principles all-electron density-functional calculations. We find that two of the ten core Mn atoms are coupled antiferromagnetically to the remaining eight, resulting in a ferrimagnetic ground state with total spin S=13. The calculated magnetic anisotropy barrier is found to be 9 K in good agreement with experiment. The presence of the Br anions impact the electronic structure and therefore the magnetic properties of the 10 Mn atoms. However, the electric field due to the negative charges has no significant effect on the magnetic anisotropy.Comment: 4 pages, submitted to PR

Active salt deformation and rapid, transient incision along the Colorado River near Moab, Utah

In certain settings, erosion is driven by and balanced with tectonic uplift, but the evolution of many landscapes is dominated by other factors such as geologic substrate, drainage history, and transient incision. The Colorado Plateau is an example where these controls are debated and where salt deformation is hypothesized to be locally active and driven by differential unloading, although this is unconfirmed and unquantified in most places. We use luminescence-dated Colorado River terraces upstream of Moab, Utah, to quantify rates of salt-driven subsidence and uplift at the local scale. Active deformation in the study area is also supported by patterns of concavity along tributary drainages crossing salt structures. Subsidence in Professor Valley at a time-averaged rate of _500 m/Myr (meters/million years) is superimposed upon rapid bedrock incision rates that increase from _600 to _900 m/Myr upstream through the study area. Such high rates are unexpected given the absence of sources of regional tectonic uplift here. Instead, the incision rate pattern across the greater area is consistent with a transient signal, perhaps still from ancient drainage integration through Grand Canyon far downstream, and then amplified by unloading at both the broad regional scale and at the local canyon scale. ©2015. American Geophysical Union. All Rights Reserved

The Hamiltonian of the V15_{15} Spin System from first-principles Density-Functional Calculations

We report first-principles all-electron density-functional based studies of the electronic structure, magnetic ordering and anisotropy for the V$_{15}$ molecular magnet. From these calculations, we determine a Heisenberg Hamiltonian with four antiferromagnetic and one {\em ferromagnetic} coupling. We perform direct diagonalization to determine the temperature dependence of the susceptibility. This Hamiltonian reproduces the experimentally observed spin $S$=1/2 ground state and low-lying $S$=3/2 excited state. A small anisotropy term is necessary to account for the temperature independent part of the magnetization curve.Comment: 4 pages in RevTeX format + 2 ps-figures, accepted by PRL Feb. 2001 (previous version was an older version of the paper

Predicted Infrared and Raman Spectra for Neutral Ti_8C_12 Isomers

Using a density-functional based algorithm, the full IR and Raman spectra are calculated for the neutral Ti_8C_12 cluster assuming geometries of Th, Td, D2d and C3v symmetry. The Th pentagonal dodecahedron is found to be dynamically unstable. The calculated properties of the relaxed structure having C3v symmetry are found to be in excellent agreement with experimental gas phase infrared results, ionization potential and electron affinity measurements. Consequently, the results presented may be used as a reference for further experimental characterization using vibrational spectroscopy.Comment: 6 pages, 5 figures. Physical Review A, 2002 (in press

Predictors of Remission Maintenance after Etanercept Tapering or Withdrawal in Early Rheumatoid Arthritis: Results from the PRIZE Study

Objective: To explore the influence of early treatment response to etanercept-methotrexate therapy on sustained remission after tapering/withdrawal of etanercept in methotrexate/biologic-naïve patients with early rheumatoid arthritis in the PRIZE study (ClinicalTrials.gov: NCT00913458). Method: In the initial 52-week open-label phase, enrolled patients received once-weekly etanercept 50 mg plus methotrexate. Patients who achieved DAS28 ≤3.2 at week 39 and <2.6 at week 52 were randomized to etanercept 25 mg plus methotrexate, methotrexate monotherapy, or placebo once weekly for 39 weeks in the double-blind phase. The relationships between responses in the open-label phase and sustained remission (DAS28 <2.6 at weeks 76 and 91, without glucocorticoid rescue therapy from weeks 52 to 64) in the double-blind phase were analyzed. Results: In the open-label phase, 70% of patients achieved DAS28 remission at week 52. In the double-blind phase, 63%, 40%, and 23% of patients had sustained DAS28 remission in the reduced-dose combination-therapy, methotrexate-monotherapy, and placebo groups, respectively. In patients receiving reduced-dose combination therapy, sustained remission was more likely in those who achieved DAS28 remission (p = 0.005) or low disease activity (p=0.044) in a shorter time, and who had a lower DAS28 (p = 0.016) or achieved ACR/EULAR Boolean remission (p < 0.05) at the end of the open-label phase. In patients receiving methotrexate monotherapy, sustained remission was associated with a lower acute-phase response (C-reactive protein, p = 0.007; erythrocyte sedimentation rate, p = 0.016) at the end of the open-label phase. Conclusion: Fast response and suppression of inflammation with etanercept-methotrexate therapy may predict successful etanercept tapering/withdrawal in patients with early rheumatoid arthritis

Theory for transport through a single magnetic molecule: Endohedral N@C60

We consider transport through a single N@C60 molecule, weakly coupled to metallic leads. Employing a density-matrix formalism we derive rate equations for the occupation probabilities of many-particle states of the molecule. We calculate the current-voltage characteristics and the differential conductance for N@C60 in a break junction. Our results reveal Coulomb-blockade behavior as well as a fine structure of the Coulomb-blockade peaks due to the exchange coupling of the C60 spin to the spin of the encapsulated nitrogen atom.Comment: 5 pages, 4 figures, v2: version as publishe

Fertilizer and Swine Manure Management Systems: Impacts on Crop Production and Nitrate-Nitrogen Leaching with Subsurface Drainage

Nutrient losses from row-crop land can cause nonpoint source water quality problems and “impaired waters.” Nitrogen (N) losses due to nitrate (NO3) leaching cause drinking water problems and possibly increase hypoxia (low oxygen) problems in the Gulf of Mexico. Phosphorus (P) losses can cause eutrophication problems in surface waters (lakes, streams, and reservoirs) in Iowa where algal blooms decrease oxygen, kill fish, and result in murky and bad tasting water. The U.S. EPA and the Iowa Department of Natural Resources are developing nutrient criteria/standards and implementation plans to address TMDL’s (Total Maximum Daily Load) and to improve the quality of impaired waters. These plans need to be based on sound information. To address the need for information about water quality impacts from the use of swine manure as a source of nutrients (N and P), a field study was funded by the Leopold Center for Sustainable Agriculture in 1999. Properly managed, swine manure can supply N and P needed by corn and soybeans. This study is being conducted at the Northeast Research Farm on 36 one-acre plots that are instrumented to monitor subsurface drainage for continuous water quality assessment

Non-Compositional Term Dependence for Information Retrieval

Modelling term dependence in IR aims to identify co-occurring terms that are too heavily dependent on each other to be treated as a bag of words, and to adapt the indexing and ranking accordingly. Dependent terms are predominantly identified using lexical frequency statistics, assuming that (a) if terms co-occur often enough in some corpus, they are semantically dependent; (b) the more often they co-occur, the more semantically dependent they are. This assumption is not always correct: the frequency of co-occurring terms can be separate from the strength of their semantic dependence. E.g. "red tape" might be overall less frequent than "tape measure" in some corpus, but this does not mean that "red"+"tape" are less dependent than "tape"+"measure". This is especially the case for non-compositional phrases, i.e. phrases whose meaning cannot be composed from the individual meanings of their terms (such as the phrase "red tape" meaning bureaucracy). Motivated by this lack of distinction between the frequency and strength of term dependence in IR, we present a principled approach for handling term dependence in queries, using both lexical frequency and semantic evidence. We focus on non-compositional phrases, extending a recent unsupervised model for their detection [21] to IR. Our approach, integrated into ranking using Markov Random Fields [31], yields effectiveness gains over competitive TREC baselines, showing that there is still room for improvement in the very well-studied area of term dependence in IR

Report on the 2013 Rapid Assessment Survey of Marine Species at New England Bays and Harbors

Introduced species (i.e., non-native species that have become established in a new location) have increasingly been recognized as a concern as they have become more prevalent in marine and terrestrial environments (Mooney and Cleland 2001; Simberloff et al. 2005). The ability of introduced species to alter population, community, and ecosystem structure and function, as well as cause significant economic damage is well documented (Carlton 1989, 1996b, 2000; Cohen and Carlton 1995; Cohen et al. 1995; Elton 1958; Meinesz et al. 1993; Occhipinti-Ambrogi and Sheppard 2007; Pimentel et al. 2005; Thresher 2000). The annual economic costs incurred from managing the approximately 50,000 introduced species in the United States alone are estimated to be over $120 billion (Pimentel et al. 2005). Having a monitoring network in place to track new introductions and distributional changes of introduced species is critical for effective management, as these efforts may be more successful when species are detected before they have the chance to become established. A rapid assessment survey is one such method for early detection of introduced species. With rapid assessment surveys, a team of taxonomic experts record and monitor marine species–providing a baseline inventory of native, introduced, and cryptogenic (i.e., unknown origin) species (as defined by Carlton 1996a)–and document range expansions of previously identified species. Since 2000, five rapid assessment surveys have been conducted in New England. These surveys focus on recording species at marinas, which often are in close proximity to transportation vectors (i.e., recreational boats). Species are collected from floating docks and piers because these structures are accessible regardless of the tidal cycle. Another reason for sampling floating docks and other floating structures is that marine introduced species are often found to be more prevalent on artificial surfaces than natural surfaces (Glasby and Connell 2001; Paulay et al. 2002). The primary objectives of these surveys are to: (1) identify native, introduced, and cryptogenic marine species, (2) expand on data collected in past surveys, (3) assess the introduction status and range extensions of documented introduced species, and (4) detect new introductions. This report presents the introduced, cryptogenic, and native species recorded during the 2013 survey