Nelson S.M.,Washington University
Brain structure & function | Year: 2010
In humans, the anterior insula (aI) has been the topic of considerable research and ascribed a vast number of functional properties by way of neuroimaging and lesion studies. Here, we argue that the aI, at least in part, plays a role in domain-general attentional control and highlight studies (Dosenbach et al. 2006; Dosenbach et al. 2007) supporting this view. Additionally, we discuss a study (Ploran et al. 2007) that implicates aI in processes related to the capture of focal attention. Task-level control and focal attention may or may not reflect information processing supported by a single functional area (within the aI). Therefore, we apply a novel technique (Cohen et al. 2008) that utilizes resting state functional connectivity MRI (rs-fcMRI) to determine whether separable regions exist within the aI. rs-fcMRI mapping suggests that the ventral portion of the aI is distinguishable from more dorsal/anterior regions, which are themselves distinct from more posterior parts of the aI. When these regions are applied to functional MRI (fMRI) data, the ventral and dorsal/anterior regions support processes potentially related to both task-level control and focal attention, whereas the more posterior aI regions did not. These findings suggest that there exists some functional heterogeneity within aI that may subserve related but distinct types of higher-order cognitive processing.
Luke D.A.,George Washington University |
Stamatakis K.A.,Washington University
Annual Review of Public Health | Year: 2012
Complex systems abound in public health. Complex systems are made up of heterogeneous elements that interact with one another, have emergent properties that are not explained by understanding the individual elements of the system, persist over time, and adapt to changing circumstances. Public health is starting to use results from systems science studies to shape practice and policy, for example in preparing for global pandemics. However, systems science study designs and analytic methods remain underutilized and are not widely featured in public health curricula or training. In this review we present an argument for the utility of systems science methods in public health, introduce three important systems science methods (system dynamics, network analysis, and agent-based modeling), and provide three case studies in which these methods have been used to answer important public health science questions in the areas of infectious disease, tobacco control, and obesity. © 2012 by Annual Reviews. All rights reserved.
Kelton K.F.,Washington University |
Kelton K.F.,Oak Ridge National Laboratory
Nature Materials | Year: 2013
Discrepancies in the glass-forming ability of metallic glasses have been explained in terms of the presence of local structural features in the liquid. Findings from molecular dynamics simulations now show that the structure of the crystal/liquid interface may play a bigger role than previously thought. More recently, metallic liquids that form glasses at the modest cooling rates typically required for silicate glasses have been discovered. These allow for the preparation of glasses with thicker cross-sections and have led to the development of new methods for metallic glass processing. Certainly, the demonstration that ordering in the liquid can have a strong influence on the crystal growth rate provides a useful conceptual addition to the arsenal of tools used to identify glass-forming liquids. The results of Tang and Harrowell make it clear that liquid ordering must also be considered when deepening the understanding of crystal growth.
Wang F.,Washington University |
Buhro W.E.,Washington University
Journal of the American Chemical Society | Year: 2012
Di-n-octylphosphine oxide (DOPO) and di-n-octylphosphinic acid (DOPA), as two of impurities found in commercial tri-n-octylphosphine oxide (TOPO), generate significant differences in the outcomes of CdSe-nanocrystal (NC) syntheses. Using n-tetradecylphosphonic acid (TDPA) as the primary acid additive, quantum dots (QDs) are grown with DOPO added, whereas quantum rods (QRs) are grown in the presence of DOPA. While using oleic acid (OA) as the primary acid additive, QDs are generated and the QDs produced with DOPA exhibit larger sizes and size distributions than those produced with DOPO. 31P NMR analyses of the reaction mixtures reveal that the majority of the DOPO has been converted into DOPA and di-n-octylphosphine (DOP) with DOP being removed via evacuation over the course of Cd-precursor preparation. The origin of the puzzling differences in the shape control of CdSe NCs in the presence of DOPO and DOPA is elucidated to be the small quantity of DOPO present, which liberates DOP during NC synthesis. In the presence of DOP, regardless of DOPA, the precursor-conversion kinetics and thus the nucleation kinetics are dramatically accelerated, generating a large number of nuclei by consuming a significant amount of CdSe nutrients, favoring QD growth. Similarly, QD growth is favored by the fast nucleation kinetics in the presence of OA, and the broader size distributions of QDs with DOPA are due to a second nucleation event initiated by the more stable Cd-di-n-octylphosphinate component. In contrast, a slow nucleation event results in the growth of QRs in the case of using DOPA and TDPA, where no DOPO or DOP is present. The results, thus, demonstrate the important role of precursor-conversion kinetics in the control of NC morphologies. © 2012 American Chemical Society.
Pickard W.F.,Washington University
Energy Policy | Year: 2012
The Intermittency Challenge and the approaching need for massive storage of rapidly dispatchable energy has led the concept of the National Battery, a unified facility that holds the aggregated outputs from an array of intrinsically episodic renewable sources, releasing energy as demand requires. In this contribution, the original demonstration of Murphy that lead-acid batteries are inappropriate is first reviewed and then extended to show that no commercially available battery technology is at present appropriate. However, prospectively, underground pumped hydro storage could suffice, and at a lesser cost than suitable batteries. © 2012 Elsevier Ltd.
Baloh R.H.,Washington University
FEBS Journal | Year: 2011
Accumulations of aggregated proteins are a key feature of the pathology of all of the major neurodegenerative diseases. Amyotrophic lateral sclerosis (ALS) was brought into this fold quite recently with the discovery of TDP-43 (TAR DNA binding protein, 43 kDa) inclusions in nearly all ALS cases. In part this discovery was fueled by the recognition of the clinical overlap between ALS and frontotemporal lobar degeneration, where ubiquitinated TDP-43 inclusions were first identified. Later the identification of TDP-43 mutations in rare familial forms of ALS confirmed that altered TDP-43 function can be a primary cause of the disease. However, the simple concept that TDP-43 is an aggregation-prone protein that forms toxic inclusions capable of promoting neurodegeneration has not been upheld by initial investigations. This review discusses observations from human pathology, cell culture and animal model systems, to highlight our somewhat murky understanding of the relationship between TDP-43 aggregation and neurodegeneration. Aggregated proteins are a key pathologic feature of the major neurodegenerative diseases. TDP-43 aggregates are present in amyotrophic lateral sclerosis (ALS), and mutations in TDP-43 cause rare familial forms of ALS. This review discusses observations from human pathology, cell culture, and animal model systems, to explore our understanding of the relationship between TDP-43 aggregation and neurodegeneration. © 2011 FEBS.
Catalano J.G.,Washington University
Geochimica et Cosmochimica Acta | Year: 2011
Ordering of interfacial water at the hematite and corundum (0. 0. 1)-water interfaces has been characterized using in situ high resolution specular X-ray reflectivity measurements. The hematite (0. 0. 1) surface was prepared through an annealing process to produce a surface isostructural with corundum (0. 0. 1), facilitating direct comparison. Interfacial water was found to display a similar structure on this pair of isostructural surfaces. A single layer of adsorbed water having a large vibrational amplitude was present on each surface and additional ordering of water extended at least 1. nm into the bulk fluid, with the degree of ordering decreasing with increasing distance from the surfaces. Consistent with prior studies of the (0. 1. 2) and (1. 1. 0) surfaces of hematite and corundum, the configuration of water above the (0. 0. 1) surfaces is primarily controlled by the surface structure, specifically the arrangement of surface functional groups. However, interfacial water at the (0. 0. 1) surfaces displayed significantly larger vibrational amplitudes throughout the interfacial region than at other isostructural sets of hematite and corundum surfaces, indicating weaker ordering. Comparison of the vibrational amplitudes of adsorbed water on a series of oxide, silicate, and phosphate mineral surfaces suggests that the presence or absence of a substantial interfacial electrostatic field is the primary control on water ordering and not the surface structure itself. On surfaces for which charge originates dominantly through protonation-deprotonation reactions the controlling factor appears to be whether conditions exist where most functional groups are uncharged as opposed to the net surface charge. The doubly coordinated functional groups on hematite and corundum (0. 0. 1) surfaces are largely uncharged under slightly acidic to circumneutral pH conditions, leading to weak ordering, whereas singly coordinated groups on (0. 1. 2) and (1. 1. 0) surfaces of these phases are always charged, even when the net surface charge is zero, and induce strong water ordering. Surfaces lacking structural charge can thus be divided into two distinct classes that induce either strong or weak ordering of interfacial water. Surface functional group coordination is the ultimate control on this division as it determines the charge state of such groups under different protonation configurations. Ion adsorption and electron transfer processes may differ between these classes of surfaces because of the effect of water ordering strength on interfacial capacitances and hydrogen bonding. © 2011 Elsevier Ltd.
Korotev R.L.,Washington University
Meteoritics and Planetary Science | Year: 2012
Sixty named lunar meteorite stones representing about 24 falls have been found in Oman. In an area of 10.7×10 3km 2 in southern Oman, lunar meteorite areal densities average 1gkm -2. All lunar meteorites from Oman are breccias, although two are dominated by large igneous clasts (a mare basalt and a crystalline impact-melt breccia). Among the meteorites, the range of compositions is large: 9-32% Al 2O 3, 2.5-21.1% FeO, 0.3-38μgg -1 Sm, and <1 to 22.5ngg -1 Ir. The proportion of nonmare lunar meteorites is higher among those from Oman than those from Antarctica or Africa. Omani lunar meteorites extend the compositional range of lunar rocks as known from the Apollo collection and from lunar meteorites from other continents. Some of the feldspathic meteorites are highly magnesian (high MgO/[MgO+FeO]) compared with most similarly feldspathic Apollo rocks. Two have greater concentrations of incompatible trace elements than all but a few Apollo samples. A few have moderately high abundances of siderophile elements from impacts of iron meteorites on the Moon. All lunar meteorites from Oman are contaminated, to various degrees, with terrestrial Na, K, P, Zn, As, Se, Br, Sr, Sb, Ba, U, carbonates, or sulfates. The contamination is not so great, however, that it seriously compromises the scientific usefulness of the meteorites as samples from randomly distributed locations on the Moon. © The Meteoritical Society, 2012.
Galletto R.,Washington University |
Tomko E.J.,Washington University
Nucleic Acids Research | Year: 2013
In Saccharomyces cerevisiae Pif1 participates in a wide variety of DNA metabolic pathways both in the nucleus and in mitochondria. The ability of Pif1 to hydrolyse ATP and catalyse unwinding of duplex nucleic acid is proposed to be at the core of its functions. We recently showed that upon binding to DNA Pif1 dimerizes and we proposed that a dimer of Pif1 might be the species poised to catalysed DNA unwinding. In this work we show that monomers of Pif1 are able to translocate on single-stranded DNA with 5′ to 3′ directionality. We provide evidence that the translocation activity of Pif1 could be used in activities other than unwinding, possibly to displace proteins from ssDNA. Moreover, we show that monomers of Pif1 retain some unwinding activity although a dimer is clearly a better helicase, suggesting that regulation of the oligomeric state of Pif1 could play a role in its functioning as a helicase or a translocase. Finally, although we show that Pif1 can translocate on ssDNA, the translocation profiles suggest the presence on ssDNA of two populations of Pif1, both able to translocate with 5′ to 3′ directionality. © 2013 The Author(s).
Schuette W.M.,Washington University |
Buhro W.E.,Washington University
ACS Nano | Year: 2013
Various additives are employed in the polyol synthesis of silver nanowires (Ag NWs), which are typically halide salts such as NaCl. A variety of mechanistic roles have been suggested for these additives. We now show that the early addition of NaCl in the polyol synthesis of Ag NWs from AgNO3 in ethylene glycol results in the rapid formation of AgCl nanocubes, which induce the heterogeneous nucleation of metallic Ag upon their surfaces. Ag NWs subsequently grow from these nucleation sites. The conclusions are supported by studies using ex situ generated AgCl nanocubes. © 2013 American Chemical Society.