The discovery of singular organic radical ligands is a formidable challenge due to high reactivity arising from the unpaired electron. Matching radical ligands with metal ions to engender magnetic coupling is crucial for eliciting preeminent physical properties such as conductivity and magnetism that are crucial for future technologies. The metal-radical approach is especially important for the lanthanide ions exhibiting deeply buried 4f-orbitals. The radicals must possess a high spin density on the donor atoms to promote strong coupling. Combining diamagnetic 89Y (I = 1/2) with organic radicals allows for invaluable insight into the electronic structure and spin-density distribution. This approach is hitherto underutilized, possibly owing to the challenging synthesis and purification of such molecules. Herein, evidence of an unprecedented bisbenzimidazole radical anion (Bbim3−˙) along with its metalation in the form of an yttrium complex, [K(crypt-222)][(Cp*2Y)2(μ-Bbim˙)] is provided. Access of Bbim3−˙ was feasible through double-coordination to the Lewis acidic metal ion and subsequent one-electron reduction, which is remarkable as Bbim2− was explicitly stated to be redox-inactive in closed-shell complexes. Two molecules containing Bbim2− (1) and Bbim3−˙ (2), respectively, were thoroughly investigated by X-ray crystallography, NMR and UV/Vis spectroscopy. Electrochemical studies unfolded a quasi-reversible feature and emphasize the role of the metal centre for the Bbim redox-activity as neither the free ligand nor the Bbim2− complex led to analogous CV results. Excitingly, a strong delocalization of the electron density through the Bbim3−˙ ligand was revealed via temperature-dependent EPR spectroscopy and confirmed through DFT calculations and magnetometry, rendering Bbim3−˙ an ideal candidate for single-molecule magnet design.

SN - 2041-6520 UR - http://dx.doi.org/10.1039/D1SC07245E JO - Chem. Sci. ER - TY - JOUR T1 - Information-theoretic characterization of the complete genotype-phenotype map of a complex pre-biotic world: Comment on “From genotypes to organisms: State-of-the-art and perspectives of a cornerstone in evolutionary dynamics” by Susanna Manrubia et al. JF - Physics of Life Reviews Y1 - 2021 A1 - Nitash C G A1 - Christoph Adami AB -How information is encoded in bio-molecular sequences is difficult to quantify since such an analysis usually requires sampling an exponentially large genetic space. Here we show how information theory reveals both robust and compressed encodings in the largest complete genotype-phenotype map (over 5 trillion sequences) obtained to date.

VL - 38 UR - https://www.sciencedirect.com/science/article/pii/S1571064521000403 ER - TY - JOUR T1 - Ice cover, winter circulation, and exchange in Saginaw Bay and Lake Huron JF - Limnology and Oceanography Y1 - 2017 A1 - Tuan D. Nguyen A1 - Nathan Hawley A1 - Mantha S. Phanikumar AB -Winter circulation exerts a strong control on the release and timing of nutrients and contaminants from bays into the adjoining lakes. To estimate winter residence times of solutes in the presence of ice cover, we used an ice model coupled to hydrodynamic, thermal and solute transport models of Saginaw Bay and Lake Huron for two low (2010 and 2013) and two high (2009 and 2014) ice years. The models were tested using temperature data from thermistor chains and current data from ADCP moorings deployed during the winter- time. Simulated water temperatures compared favorably to lake-wide average surface temperatures derived from NOAA’s AVHRR satellite imagery. Simulated results of ice cover are in agreement with observed data from the Great Lakes Ice Atlas. Our results indicate that ice cover significantly dampens water movement producing almost stagnant conditions around February. Estimates of residence times for Saginaw Bay (defined as the e-folding flushing time based on vertically integrated dye concentrations) show that the mean resi- dence times in a low ice year (2013) are 2.2 months for the inner bay, and 3.5 months for the entire bay. The corresponding numbers for a high ice year (2014) are 4.9 and 5.3 months, respectively. Considering the entire bay, solutes stored in the bay can be expected to be released into the lake between March (low ice year) and April (high ice year). These results are expected to aid in understanding the behavior of contami- nants in the Great Lakes during the winter months and in early spring.

VL - 62 UR - http://www.egr.msu.edu/~phani/lno10431.pdf IS - 1 ER - TY - CONF T1 - The Institute for Cyber-Enabled Research: Regional Organization to Promote Computation in Science T2 - In proceedings of 2013 XSEDE Conference Y1 - 2013 A1 - Dirk Colbry A1 - Punch, William A1 - Bauer, Wolfgang AB -The Institute for Cyber-Enabled Research (iCER) at Michigan State University (MSU) was established in 2009 to coordinate and support multidisciplinary resources for computation and computational sciences. iCER is the home of MSU's centralized High Performance Computing resources, which include a heterogeneous compute cluster with various hardware designed to meet the needs of different scientists. The goal of iCER is not to maximize Flops, but instead to maximize the amount of quality science being accomplished. This paper outlines many of the initiatives that iCER has taken to support researchers at MSU and throughout Michigan; describes the structure and evolution of iCER and its relationship with XSEDE and offers insights for other institutions interested in putting together a similar computational organization.

JF - In proceedings of 2013 XSEDE Conference CY - San Diego, California ER - TY - JOUR T1 - Intra-aggregate pore structures are related to total C distribution within soil macro-aggregates JF - Soil Biology and Biochemistry Y1 - 2013 A1 - K. Ananyeva A1 - W. Wang A1 - A.J.M. Smucker A1 - M.L. Rivers A1 - A.N. Kravchenko VL - 57 ER - TY - JOUR T1 - Interfacial friction between semiflexible polymers and crystalline surfaces JF - J. Chem. Phys. Y1 - 2012 A1 - Nikolai V. Priezjev VL - 136 ER - TY - JOUR T1 - Intra-aggregate pore characteristics: X-ray computed microtomography analysis JF - Soil Sci. Soc Am J. Y1 - 2012 A1 - W. Wang A1 - A.N. Kravchenko A1 - A.J.M. Smucker A1 - M.L. Rivers VL - 76 ER - TY - JOUR T1 - Implicit Parallel Time Integrators JF - Journal of Scientific Computing Y1 - 2011 A1 - Andrew Christlieb A1 - Benjamin Ong VL - 49 IS - 2 ER - TY - JOUR T1 - Information Content of Colored Motifs in Complex Networks JF - Artificial Life Y1 - 2011 A1 - Adami, Christoph A1 - Qian, Jifeng A1 - Rupp, Matthew A1 - Hintze, Arend AB -We study complex networks in which the nodes are tagged with different colors depending on their function (colored graphs), using information theory applied to the distribution of motifs in such networks. We find that colored motifs can be viewed as the building blocks of the networks (much more than the uncolored structural motifs can be) and that the relative frequency with which these motifs appear in the network can be used to define its information content. This information is defined in such a way that a network with random coloration (but keeping the relative number of nodes with different colors the same) has zero color information content. Thus, colored motif information captures the exceptionality of coloring in the motifs that is maintained via selection. We study the motif information content of the C. elegans brain as well as the evolution of colored motif information in networks that reflect the interaction between instructions in genomes of digital life organisms. While we find that colored motif information appears to capture essential functionality in the C. elegans brain (where the color assignment of nodes is straightforward), it is not obvious whether the colored motif information content always increases during evolution, as would be expected from a measure that captures network complexity. For a single choice of color assignment of instructions in the digital life form Avida, we find rather that colored motif information content increases or decreases during evolution, depending on how the genomes are organized, and therefore could be an interesting tool to dissect genomic rearrangements.

VL - 17 UR - http://dx.doi.org/10.1162/artl_a_00045 ER - TY - JOUR T1 - Implicit Parallel Time Integrators JF - Journal of Scientific Computing Y1 - 2010 A1 - Andrew Christlieb A1 - Benjamin Ong AB -In this work, we discuss a family of parallel implicit time integrators for multicore and potentially multi-node or multi-gpgpu systems. The method is an extension of Revisionist Integral Deferred Correction (RIDC) by Christlieb, Macdonald and Ong (SISC- 2010) which constructed parallel explicit time integrators. The key idea is to re-write the defect correction framework so that, after initial startup costs, each correction loop can be lagged behind the previous correction loop in a manner that facilitates running the predictor and correctors in parallel. In this paper, we show that RIDC provides a framework to use p cores to generate a pth-order implicit solution to an initial value problem (IVP) in approximately the same wall clock time as a single core, backward Euler implementation (p ≤ 12). The construction, convergence and stability of the schemes are presented, along with supporting numerical evidence.

VL - 46 IS - 1 ER - TY - CONF T1 - Investigating whether HyperNEAT produces modular neural networks T2 - Proceedings of the Genetic and Evolutionary Computation Conference Y1 - 2010 A1 - Clune, J. A1 - Beckmann, B.E. A1 - McKinley, P.K. A1 - Ofria, C. JF - Proceedings of the Genetic and Evolutionary Computation Conference PB - ACM ER - TY - JOUR T1 - The influence of cluster emission and the symmetry energy on neutron-proton spectral double ratios JF - Physics Letters B Y1 - 2008 A1 - Yingxun Zhang A1 - P. Danielewicz A1 - M. Famiano A1 - Li, Z. A1 - W. G. Lynch A1 - M. B. Tsang AB -The emissions of neutrons, protons and bound clusters from central {124Sn} + {124Sn} and {112Sn} + {112Sn} collisions are simulated using the Improved Quantum Molecular Dynamics model for two different density-dependent symmetry-energy functions. The calculated neutron-proton spectral double ratios for these two systems are sensitive to the density dependence of the symmetry energy, consistent with previous work. Cluster emission increases the double ratios in the low energy region relative to values calculated in a coalescence-invariant approach. To circumvent uncertainties in cluster production and secondary decays, it is important to have more accurate measurements of the neutron-proton ratios at higher energies in the center of mass system, where the influence of such effects is reduced.

VL - 664 ER - TY - JOUR T1 - Intriguing Accuracies of the Exponential Wave Function Expansions Exploiting Finite Two-Body Correlation Operators in Calculations for Many-Electron Systems JF - Journal of Molecular Structure: THEOCHEM Y1 - 2006 A1 - P.-D. Fan A1 - P. Piecuch KW - xact many-electron wave functions; Generalized coupled-cluster methods; Two-body correlation operators; Nooijen's conjecture; Variational calculations; Multi-determinantal reference states; Excited states AB -Following the ideas laid down by Nooijen and Nakatsuji, several authors have considered an intriguing possibility of representing the exact many-electron wave functions by the exponential cluster expansions involving two-body correlation operators. In particular, inspired by the symmetric form of the Horn–Weinstein exact energy formula, and exploiting the variational principle and numerical analysis, we have demonstrated that one can obtain nearly exact ground-state wave functions for a few many-electron systems using the exponential cluster expansion involving a finite two-body operator acting on the Hartree–Fock determinant [P. Piecuch et al., Phys. Rev. Lett. 90 (2003) 113001]. After summarizing these earlier findings and making some additional comments on the nature of the exponential cluster expansions involving two-body correlation operators, we examine the following issues: (i) the improvements in the accuracy and convergence toward the full configuration interaction (CI) limit offered by cluster operators containing two-body as well as one-body components, (ii) the improvements in the accuracy resulting from the use of multi-determinantal reference states, and (iii) the potential accuracy of the exponential wave function expansions involving finite one- and two-body cluster operators in excited-state calculations. All calculations are performed for an eight electron model system, which is simple enough to allow for the exact, full CI, and other electronic structure calculations, which has fewer independent parameters in the Hamiltonian than the dimension of the corresponding full CI problem, and which enables one to examine ground and excited states with a varying degree of configurational quasi-degeneracy by simple changes in the corresponding nuclear geometry.

VL - 768 IS - 1-3 ER -