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Structural basis for the modulation of plant cytosolic triosephosphate isomerase activity by mimicry
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Structure and function of LCI1: a plasma membrane CO[subscript 2] channel in the Chlamydomonas CO[subscript 2] concentrating mechanism
Abstract not provided
Determination of background doping type in type-II superlattice using capacitance-voltage measurements with double mesa structure.
Abstract not provided.
Electronic structure of aqueous solutions: Bridging the gap between theory and experiments
Predicting the electronic properties of aqueous liquids has been a long-standing challenge for quantum mechanical methods. However, it is a crucial step in understanding and predicting the key role played by aqueous solutions and electrolytes in a wide variety of emerging energy and environmental technologies, including battery and photoelectrochemical cell design. Here, we propose an efficient and accurate approach to predict the electronic properties of aqueous solutions, on the basis of the combination of first-principles methods and experimental validation using state-of-the-art spectroscopic measurements. We present results of the photoelectron spectra of a broad range of solvated ions, showing that first-principles molecular dynamics simulations and electronic structure calculations using dielectric hybrid functionals provide a quantitative description of the electronic properties of the solvent and solutes, including excitation energies. The proposed computational framework is general and applicable to other liquids, thereby offering great promise in understanding and engineering solutions and liquid electrolytes for a variety of important energy technologies.
Structural and spectroscopic characterization of an Fe(VI) bis(imido) complex
Abstract not provided
Metagenomic and Metatranscriptomic Analyses Reveal the Structure and Dynamics of a Dechlorinating Community Containing Dehalococcoides mccartyi and Corrinoid-Providing Microorganisms under Cobalamin-Limited Conditions
The aim of this paper is to obtain a systems-level understanding of the interactions between Dehalococcoides and corrinoid-supplying microorganisms by analyzing community structures and functional compositions, activities, and dynamics in trichloroethene (TCE)-dechlorinating enrichments. Metagenomes and metatranscriptomes of the dechlorinating enrichments with and without exogenous cobalamin were compared. Seven putative draft genomes were binned from the metagenomes. At an early stage (2 days), more transcripts of genes in the Veillonellaceae bin-genome were detected in the metatranscriptome of the enrichment without exogenous cobalamin than in the one with the addition of cobalamin. Among these genes, sporulation-related genes exhibited the highest differential expression when cobalamin was not added, suggesting a possible release route of corrinoids from corrinoid producers. Other differentially expressed genes include those involved in energy conservation and nutrient transport (including cobalt transport). The most highly expressed corrinoid de novo biosynthesis pathway was also assigned to the Veillonellaceae bin-genome. Targeted quantitative PCR (qPCR) analyses confirmed higher transcript abundances of those corrinoid biosynthesis genes in the enrichment without exogenous cobalamin than in the enrichment with cobalamin. Furthermore, the corrinoid salvaging and modification pathway of Dehalococcoides was upregulated in response to the cobalamin stress. Finally, this study provides important insights into the microbial interactions and roles played by members of dechlorinating communities under cobalamin-limited conditions.
Geology and in situ stress of the MH-2 borehole, Idaho, USA: Insights into western Snake River Plain structure from geothermal exploration drilling
Project HOTSPOT, the Snake River Scientific Drilling Project (International Continental Scientific Drilling Program), tested for deep geothermal resources and examined the petrology of volcanic rocks with three drillholes in the central and western Snake River Plain (western USA). The MH-2 drillhole targeted fractured crystalline and hydrothermally altered basalt in the area of the Mountain Home Air Force Base (Idaho) to a total depth of 1821 m. At 1745 m depth the drillhole encountered flowing artesian hydrothermal fluids of at least 150 °C. We integrate geological analyses of core, image log, and borehole geophysical data, and in situ stress analyses to describe the structural environment that produces permeability for artesian flow. The rocks in the lower 540 m of the drillhole consist of basalt flows as much as 30 m thick, altered basalt, and thin sedimentary horizons. The mechanical stratigraphy is defined by nine mechanical horizons that are in three ranges of rock strength on the basis of experimentally determined strength data, core logging, and geophysical log signatures. Hydrothermal alteration products and mineralization in the core are associated with three highly faulted sections; the lowermost section is associated with the zone of flowing thermal water. Shear slip indicators on faults observed in core indicate slip ranging from pure strike slip to normal failure mechanisms in the stronger horizons. The borehole breakouts indicate that the maximum horizontal stress, SH, is oriented 047° ± 7°, and drilling-induced tensile fractures indicate that SH is oriented at 67° ± 21°. The in situ stress orientations exhibit little variation over the depth of the measured interval, but the SH magnitude varies with depth, and is best explained by an oblique normal fault stress regime. The geomechanical model indicates that if pore pressures at depth are elevated above the normal hydrostatic gradient, as observed here, the system has the potential to deform by mixed normal and strike-slip failure. Our observations and interpretations suggest that the MH-2 borehole was drilled into oblique normal faults that intersect a buried 300°-trending fault block masked by the basaltic volcanic complex. These data indicate that the transition from the central to western Snake River Plain is characterized by complex structures developed in response to a transitional stress state related to Snake River Plain and western Basin and Range stress regimes. Furthermore, the western Basin and Range stress and tectonic regime may extend from northern Nevada into western Idaho and may enhance the potential for geothermal resources by creating interconnected fracture and fault-related permeability at depth.
The Influence of Hydrogenation on the Structure, Magnetic and Magnetocaloric Properties of Tb–Dy–Co Alloys with a Laves Phase Structure
A complex study of structure, phase composition, surface topology, magnetic, and magnetocaloric properties was performed for TbCo{sub 2} and Tb{sub 0.3}Dy{sub 0.7}Co{sub 2} compounds and for a Tb{sub 0.3}Dy{sub 0.7}Co{sub 2}H{sub 0.5} hydride with a low hydrogen content. The hydrogenation was established to impact the structural features at the micro- and nanolevels, as well as the fundamental and functional properties. Introducing even a small amount of hydrogen in the crystal lattice of Tb{sub 0.3}Dy{sub 0.7}Co{sub 2} compound is found to cause an increase in both the Curie temperature and the magnetic moment at the cobalt atoms. The magnetic phase transition from the paramagnetic to the magnetically ordered state changes from the first (in Tb{sub 0.3}Dy{sub 0.7}Co{sub 2}) to the second (in TbCo{sub 2} and Tb{sub 0.3}Dy{sub 0.7}Co{sub 2}H{sub 0.5}) order, leading to a noticeable decrease in the magnetocaloric effect.
Dual Effect of Structure and Hydration on Magnesium-Ion Insertion into Electrodeposited V 2 O 5 Thin Films
Not provided.
Idealized Simulations of a Squall Line from the MC3E Field Campaign Applying Three Bin Microphysics Schemes: Dynamic and Thermodynamic Structure
The squall line event on May 20, 2011, during the Midlatitude Continental Convective Clouds (MC3E) field campaign has been simulated by three bin (spectral) microphysics schemes coupled into the Weather Research and Forecasting (WRF) model. Semi-idealized three-dimensional simulations driven by temperature and moisture profiles acquired by a radiosonde released in the pre-convection environment at 1200 UTC in Morris, Oklahoma show that each scheme produced a squall line with features broadly consistent with the observed storm characteristics. However, substantial differences in the details of the simulated dynamic and thermodynamic structure are evident. These differences are attributed to different algorithms and numerical representations of microphysical processes, assumptions of the hydrometeor processes and properties, especially ice particle mass, density, and terminal velocity relationships with size, and the resulting interactions between the microphysics, cold pool, and dynamics. This study shows that different bin microphysics schemes, designed to be conceptually more realistic and thus arguably more accurate than bulk microphysics schemes, still simulate a wide spread of microphysical, thermodynamic, and dynamic characteristics of a squall line, qualitatively similar to the spread of squall line characteristics using various bulk schemes. Future work may focus on improving the representation of ice particle properties in bin schemes to reduce this uncertainty and using the similar assumptions for all schemes to isolate the impact of physics from numerics.
Assessment of impinged flame structure in high-pressure direct diesel injection
Spray impingement often occurs during cold-start in direct-injection diesel engines, affecting the subsequent combustion process by altering the local flow condition. This work has investigated the impinged flame structure by examining local expansion distance and planar curvature of the boundary in details. The experiments were carried out in a constant volume combustion chamber. The injection pressure and ambient density were varied from 120 to 180 MPa and 14.8 to 30.0 kg/m 3 under non-vaporizing conditions, respectively. For reacting conditions, the injection pressure and ambient density were fixed at 150 MPa and 22.8 kg/m 3 but with different ambient temperatures from 800 to 1000 K. Unlike orthogonal spray impingement, the profile of expansion distance along the radial direction at the 60° impinging angle is non-uniform but the profile is comparable between the non-vaporizing and reacting conditions under the same injection pressure and ambient density. With the help of Intensity-aXial-Time method, the most intensive soot luminosity region and Mie scattering intensity region are identified and the region has been found to be along the impinged spray axial direction. Outmost boundary of an impinged flame is found to have wrinkles attributed to air entrainment. The temporal level of flame wrinkles is higher in reacting conditions than in non-vaporizing conditions. The scatter distribution of the boundary curvature and near-field soot formation illustrates an inverted “S” shape correlation with time. High flame luminosity is found to be formed in concave regions while less soot is formed in convex regions. This inverted S-shape is a new finding of the state relationship at the solid–liquid–gas impinged flame propagation. Finally, heat flux measurement through the plate is examined.
Structures of neurexophilin–neurexin complexes reveal a regulatory mechanism of alternative splicing
Neurexins are presynaptic, cell-adhesion molecules that specify the functional properties of synapses via interactions with trans-synaptic ligands. Neurexins are extensively alternatively spliced at six canonical sites that regulate multifarious ligand interactions, but the structural mechanisms underlying alternative splicing-dependent neurexin regulation are largely unknown. Here, we determined high-resolution structures of the complex of neurexophilin-1 and the second laminin/neurexin/sex-hormone-binding globulin domain (LNS2) of neurexin-1 and examined how alternative splicing at splice site #2 (SS2) regulates the complex. Our data reveal a unique, extensive, neurexophilin–neurexin binding interface that extends the jelly-roll β-sandwich of LNS2 of neurexin-1 into neurexophilin-1. The SS2A insert of LNS2 augments this interface, increasing the binding affinity of LNS2 for neurexophilin-1. Taken together, our data reveal an unexpected architecture of neurexophilin–neurexin complexes that accounts for the modulation of binding by alternative splicing, which in turn regulates the competition of neurexophilin for neurexin binding with other ligands.
Electronic Structure and Spin Correlations in Novel Magnetic Structures
The research has advanced understanding of the interrelation between the crystal structure and magnetism in several materials which are or can be of interest for the development of improved, specialized or more cost-effective permanent magnets, as well as in selected materials for biomedical and catalytic applications. Fundamental aspects of ferromagnetism were investigated for Mn-Ge, Co-V and Co-Ge nanoclusters and for melt-spun Co-Sn alloys. New solution-chemistry synthesis methods were designed and tested for Fe-Pt, Fe3C and Fe3O4 nanoparticles. Off-stoichiometric Laves phases in the Fe-Si-Zr, Fe-Nb and Fe-Ta systems, as well as Fe5(Si,Ge)B2 compounds were assessed as new rare-earth-free permanent magnet materials; all except the Fe-Si-Zr Laves phases were found to be promising enough to merit a further exploration. A new method for manufacturing rare-earth-free magnets based on the MnBi compound was developed; by purposely avoiding oxidation-sensitive fine single-crystalline powders, the new method yields magnets with a 50% larger energy storage capacity. Studies of rare-earth-lean permanent-magnet materials (lean compared to the currently predominant Nd-Fe-B materials) were focused on the tetragonal compound of the ThMn12 structure type and included both discovery and characterization of new formulations and exploration of new fabrication/processing techniques. Among the most significant achievements were successful preparation of a vanadium-lean SmFe11V compound, the first observation of thermomechanically induced texture in nanocrystalline Sm(Fe,V)12 alloys, and a breakthrough reduction-diffusion synthesis of Sm1-xZrx(Fe0.8Co0.2)11.2Ti0.8 single-crystal particles with a coercivity as high as 12.6 kOe. Several experiments aimed at improvement of the Nd-Fe-B magnet have also been undertaken including a five-fold increase of the coercivity through a grain-boundary diffusion treatment of a Nd10Fe84B6 nanocrystalline alloy.
A Structural engineering Graduate Degree Program with specialization in structural health monitoring & non-destructive evaluation [Slides]
The promotional presentation discusses the graduate degree program at the University of California, San Diego, Jacobs School of Engineering, related to structural engineering. Structural Health Monitoring (SHM) encompasses the integration of a broad range of technologies from sensing/actuating, data interrogation, and statistical modeling to enable system-level or component-level health assessment and predictive modeling. The course is available via distance learning to Los Alamos National Laboratory engineers.
Structures via Reasoning - Applying AI to Cryo Electron Microscopy to Reveal Structural Variability
There have been breakthroughs of latest cryo electron microscopy (cryo-EM) data analysis algorithms to classify cryo-EM image data. However, most of these cryo-EM reconstruction methods have focused on classifying distinctly different biomolecule structures. Here, we present our approaches of deep learning to differentiate homologous structures that are distinguishable only with inner morphological differences. We succeeded supervised classification of these subtly different homologues. However, we could not differentiate them with unsupervised methods. Here we discuss what further approaches are likely needed for successful unsupervised classification.