2,572 research outputs found

    Snakes of the United States and Canada: Natural History and Care in Captivity

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    Manufacturing process and the integration process needed to create a streamline work cell for instruction at the university level course

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    Internet kao najrašireniji medij današnjice mijenja način komunikacije i poslovanja između proizvođača i potrošača. Marketing u suradnji s internetom dovodi do internetskog marketinga koji koristi informacijsku tehnologiju za ostvarivanje marketinških ciljeva. Nova tehnologija povećava uspješnost širenja informacija i mijenja suštinu marketinga

    Whose streets? Roadway protests and weaponised automobility

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    The article examines the role of automobility in US-based anti-racism demonstrations and counter-demonstrations. We contrast the spatial strategies of highway occupations by racial justice activists, with so-called “weaponised car” attacks by the American far right. Analysing online memes and anti-protest legislation, the article explores under-acknowledged links between “automobile supremacy”—the structure of motorists' privilege as embedded in law, the built environment and the popular imaginary—and the patterns of racial stratification often termed “white supremacy”. We document three ways in which automobility has been enlisted as means of violence against protestors and against wider Black communities in the US: through the use of vehicles, right-of-way conventions, and roadways as weapons. The article demonstrates how the imperative to make way for the motorist has long provided cover for racial injustice.Publisher PDFPeer reviewe

    Patterned probes for high precision 4D-STEM bragg measurements.

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    Nanoscale strain mapping by four-dimensional scanning transmission electron microscopy (4D-STEM) relies on determining the precise locations of Bragg-scattered electrons in a sequence of diffraction patterns, a task which is complicated by dynamical scattering, inelastic scattering, and shot noise. These features hinder accurate automated computational detection and position measurement of the diffracted disks, limiting the precision of measurements of local deformation. Here, we investigate the use of patterned probes to improve the precision of strain mapping. We imprint a "bullseye" pattern onto the probe, by using a binary mask in the probe-forming aperture, to improve the robustness of the peak finding algorithm to intensity modulations inside the diffracted disks. We show that this imprinting leads to substantially improved strain-mapping precision at the expense of a slight decrease in spatial resolution. In experiments on an unstrained silicon reference sample, we observe an improvement in strain measurement precision from 2.7% of the reciprocal lattice vectors with standard probes to 0.3% using bullseye probes for a thin sample, and an improvement from 4.7% to 0.8% for a thick sample. We also use multislice simulations to explore how sample thickness and electron dose limit the attainable accuracy and precision for 4D-STEM strain measurements

    Anomalous relaxation kinetics of biological lattice-ligand binding models

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    We discuss theoretical models for the cooperative binding dynamics of ligands to substrates, such as dimeric motor proteins to microtubules or more extended macromolecules like tropomyosin to actin filaments. We study the effects of steric constraints, size of ligands, binding rates and interaction between neighboring proteins on the binding dynamics and binding stoichiometry. Starting from an empty lattice the binding dynamics goes, quite generally, through several stages. The first stage represents fast initial binding closely resembling the physics of random sequential adsorption processes. Typically this initial process leaves the system in a metastable locked state with many small gaps between blocks of bound molecules. In a second stage the gaps annihilate slowly as the ligands detach and reattach. This results in an algebraic decay of the gap concentration and interesting scaling behavior. Upon identifying the gaps with particles we show that the dynamics in this regime can be explained by mapping it onto various reaction-diffusion models. The final approach to equilibrium shows some interesting dynamic scaling properties. We also discuss the effect of cooperativity on the equilibrium stoichiometry, and their consequences for the interpretation of biochemical and image reconstruction results.Comment: REVTeX, 20 pages, 17 figures; review, to appear in Chemical Physics; v2: minor correction

    Commensurate Stripes and Phase Coherence in Manganites Revealed with Cryogenic Scanning Transmission Electron Microscopy

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    Incommensurate charge order in hole-doped oxides is intertwined with exotic phenomena such as colossal magnetoresistance, high-temperature superconductivity, and electronic nematicity. Here, we map at atomic resolution the nature of incommensurate order in a manganite using scanning transmission electron microscopy at room temperature and cryogenic temperature (\sim 93K). In diffraction, the ordering wavevector changes upon cooling, a behavior typically associated with incommensurate order. However, using real space measurements, we discover that the underlying ordered state is lattice-commensurate at both temperatures. The cations undergo picometer-scale (\sim 6-11 pm) transverse displacements, which suggests that charge-lattice coupling is strong and hence favors lattice-locked modulations. We further unearth phase inhomogeneity in the periodic lattice displacements at room temperature, and emergent phase coherence at 93K. Such local phase variations not only govern the long range correlations of the charge-ordered state, but also results in apparent shifts in the ordering wavevector. These atomically-resolved observations underscore the importance of lattice coupling and provide a microscopic explanation for putative "incommensurate" order in hole-doped oxides

    Bending and Breaking of Stripes in a Charge-Ordered Manganite

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    In complex electronic materials, coupling between electrons and the atomic lattice gives rise to remarkable phenomena, including colossal magnetoresistance and metal-insulator transitions. Charge-ordered phases are a prototypical manifestation of charge-lattice coupling, in which the atomic lattice undergoes periodic lattice displacements (PLDs). Here we directly map the picometer scale PLDs at individual atomic columns in the room temperature charge-ordered manganite Bi0.35_{0.35}Sr0.18_{0.18}Ca0.47_{0.47}MnO3_3 using aberration corrected scanning transmission electron microscopy (STEM). We measure transverse, displacive lattice modulations of the cations, distinct from existing manganite charge-order models. We reveal locally unidirectional striped PLD domains as small as \sim5 nm, despite apparent bidirectionality over larger length scales. Further, we observe a direct link between disorder in one lattice modulation, in the form of dislocations and shear deformations, and nascent order in the perpendicular modulation. By examining the defects and symmetries of PLDs near the charge-ordering phase transition, we directly visualize the local competition underpinning spatial heterogeneity in a complex oxide.Comment: Main text: 20 pages, 4 figures. Supplemental Information: 27 pages, 14 figure

    Icy futures:carving the northern sea route

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    The research examines intersections between globalisation and climate change in the (re)emergence of a 'Northern Sea Route' through the Russian Arctic, which some speculate could soon rival or replace the Suez Canal as major global trade artery. The research explores shifts in the contemporary shipping system, a relatively underexplored area of mobilities research, examining the affordances and risks posed to shipping and resource extraction activities by melting Arctic sea-ice, as sections of the maritime Arctic become increasingly integrated into global circuits. The research examines actual and potential developments surrounding the Northern Sea Route (NSR) in the Russian Arctic, examining the ways geopolitics, geoeconomics and geophysical processes collide in the ‘Anthropocene Arctic’
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