32 research outputs found

    Direct observation of Anderson localization of matter-waves in a controlled disorder

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    We report the observation of exponential localization of a Bose-Einstein condensate (BEC) released into a one-dimensional waveguide in the presence of a controlled disorder created by laser speckle . We operate in a regime allowing AL: i) weak disorder such that localization results from many quantum reflections of small amplitude; ii) atomic density small enough that interactions are negligible. We image directly the atomic density profiles vs time, and find that weak disorder can lead to the stopping of the expansion and to the formation of a stationary exponentially localized wave function, a direct signature of AL. Fitting the exponential wings, we extract the localization length, and compare it to theoretical calculations. Moreover we show that, in our one-dimensional speckle potentials whose noise spectrum has a high spatial frequency cut-off, exponential localization occurs only when the de Broglie wavelengths of the atoms in the expanding BEC are larger than an effective mobility edge corresponding to that cut-off. In the opposite case, we find that the density profiles decay algebraically, as predicted in [Phys. Rev. Lett. 98, 210401 (2007)]. The method presented here can be extended to localization of atomic quantum gases in higher dimensions, and with controlled interactions

    Molecular Mechanics of the α-Actinin Rod Domain: Bending, Torsional, and Extensional Behavior

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    α-Actinin is an actin crosslinking molecule that can serve as a scaffold and maintain dynamic actin filament networks. As a crosslinker in the stressed cytoskeleton, α-actinin can retain conformation, function, and strength. α-Actinin has an actin binding domain and a calmodulin homology domain separated by a long rod domain. Using molecular dynamics and normal mode analysis, we suggest that the α-actinin rod domain has flexible terminal regions which can twist and extend under mechanical stress, yet has a highly rigid interior region stabilized by aromatic packing within each spectrin repeat, by electrostatic interactions between the spectrin repeats, and by strong salt bridges between its two anti-parallel monomers. By exploring the natural vibrations of the α-actinin rod domain and by conducting bending molecular dynamics simulations we also predict that bending of the rod domain is possible with minimal force. We introduce computational methods for analyzing the torsional strain of molecules using rotating constraints. Molecular dynamics extension of the α-actinin rod is also performed, demonstrating transduction of the unfolding forces across salt bridges to the associated monomer of the α-actinin rod domain

    Language in international business: a review and agenda for future research

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    A fast growing number of studies demonstrates that language diversity influences almost all management decisions in modern multinational corporations. Whereas no doubt remains about the practical importance of language, the empirical investigation and theoretical conceptualization of its complex and multifaceted effects still presents a substantial challenge. To summarize and evaluate the current state of the literature in a coherent picture informing future research, we systematically review 264 articles on language in international business. We scrutinize the geographic distributions of data, evaluate the field’s achievements to date in terms of theories and methodologies, and summarize core findings by individual, group, firm, and country levels of analysis. For each of these dimensions, we then put forward a future research agenda. We encourage scholars to transcend disciplinary boundaries and to draw on, integrate, and test a variety of theories from disciplines such as psychology, linguistics, and neuroscience to gain a more profound understanding of language in international business. We advocate more multi-level studies and cross-national research collaborations and suggest greater attention to potential new data sources and means of analysis

    Persistent Place-Making in Prehistory: the Creation, Maintenance, and Transformation of an Epipalaeolithic Landscape

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    Most archaeological projects today integrate, at least to some degree, how past people engaged with their surroundings, including both how they strategized resource use, organized technological production, or scheduled movements within a physical environment, as well as how they constructed cosmologies around or created symbolic connections to places in the landscape. However, there are a multitude of ways in which archaeologists approach the creation, maintenance, and transformation of human-landscape interrelationships. This paper explores some of these approaches for reconstructing the Epipalaeolithic (ca. 23,000–11,500 years BP) landscape of Southwest Asia, using macro- and microscale geoarchaeological approaches to examine how everyday practices leave traces of human-landscape interactions in northern and eastern Jordan. The case studies presented here demonstrate that these Epipalaeolithic groups engaged in complex and far-reaching social landscapes. Examination of the Early and Middle Epipalaeolithic (EP) highlights that the notion of “Neolithization” is somewhat misleading as many of the features we use to define this transition were already well-established patterns of behavior by the Neolithic. Instead, these features and practices were enacted within a hunter-gatherer world and worldview

    Urban and Transport Scaling: Northern Mesopotamia in the Late Chalcolithic and Bronze Age

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    Scaling methods have been applied to study modern urban areas and how they create accelerated, feedback growth in some systems while efficient use in others. For ancient cities, results have shown that cities act as social reactors that lead to positive feedback growth in socioeconomic measures. In this paper, we assess the relationship between settlement area expressed through mound area from Late Chalcolithic and Bronze Age sites and mean hollow way widths, which are remains of roadways, from the Khabur Triangle in northern Mesopotamia. The intent is to demonstrate the type of scaling and relationship present between sites and hollow ways, where both feature types are relatively well preserved. For modern roadway systems, efficiency in growth relative to population growth suggests roads should show sublinear scaling in relation to site size. In fact, similar to modern systems, such sublinear scaling results are demonstrated for the Khabur Triangle using available data, suggesting ancient efficiency in intensive transport growth relative to population levels. Comparable results are also achieved in other ancient Near East regions. Furthermore, results suggest that there could be a general pattern relevant for some small sites (0–2 ha) and those that have fewer hollow ways, where β, a measure of scaling, is on average low (≈ < 0.2). On the other hand, a second type of result for sites with many hollow ways (11 or more) and that are often larger suggests that β is greater (0.23–0.72), but still sublinear. This result could reflect the scale in which larger settlements acted as greater social attractors or had more intensive economic activity relative to smaller sites. The provided models also allow estimations of past roadway widths in regions where hollow ways are missing
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