20,089 research outputs found

    History Abroad: How Do Denmark and the U.S. Measure Up?

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    By viewing bias itself as a product of history, educators and scholars can understand it better in their own times. By studying the historical path of the United States and Denmark, scholars can see that the nature of history can have subtle but important impacts on common education. Even when educators are aware of potential bias, history itself warps its dissemination

    Germany and History in Flux: The Generational Changes in Approaching Germany\u27s Past

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    Historical memory, how a people remember the past, is in a state of almost eternal flux. By following the development of historical memory in post-war Germany, historians can better understand the generational and contemporary impact on popular history. German history illustrates the importance of this concept, as German history has a great deal of 20th century historical baggage

    Imperial Electioneering: The Evolution of the Election in the Holy Roman Empire from the Collapse of the Carolingians to the Rise of the Ottonians

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    The Holy Roman Empire had an electoral process for choosing the Holy Roman Emperor. The heritage of this unique medieval institution can be traced through from Charlemagne empire to the Ottonians. The Empire of Charlemagne had several serious problems that led to its collapse. In the wake of this collapse, the lords of Germany asserted their power and chose leaders for themselves. Between the fall of the Carolingians and the rise of the Ottonians, Germany moved toward an elected kingship with a ducal power base. Only when Otto I became emperor was there a marriage between the German electoral system and the title of Holy Roman Emperor, resulting in the Holy Roman Empire of the late medieval period

    SEATO Stumbles: The Failure of the NATO Model in the Third World

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    NATO as an alliance has stood the test of time since the early post-war years. Yet similar alliances such as SEATO passed into history long ago. The problem with the NATO model of alliance was its inability to be applied to the Third World. The particular circumstances of Southeast Asia prevented SEATO from becoming a true successor to the NATO alliance system. In addition, the approach of Eisenhower and his administration to Southeast Asia and anti-communist alliances was undermined by their own political needs and personal experiences. Southeast Asia was fit into the mold of the post-war period and the Cold War

    1 1/2 Years in Death Valley

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    This paper is an exploration into the historian as an independent source of history. Homer T. Rosenberger was an amateur historian in Pennsylvania during the better part of the 20th century. His works on Pennsylvania history, early American history, and contemporary historical events are valuable, if unknown, resources in those fields. However, Rosenberger becomes his own source of history when his battle with cancer is examined in the context of the American 1950\u27s. Rosenberger\u27s reactions to his plight help illustrate the mindset American brought to cancer in the 1950\u27s and the transition in American society since then

    A Pulse-Gated, Predictive Neural Circuit

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    Recent evidence suggests that neural information is encoded in packets and may be flexibly routed from region to region. We have hypothesized that neural circuits are split into sub-circuits where one sub-circuit controls information propagation via pulse gating and a second sub-circuit processes graded information under the control of the first sub-circuit. Using an explicit pulse-gating mechanism, we have been able to show how information may be processed by such pulse-controlled circuits and also how, by allowing the information processing circuit to interact with the gating circuit, decisions can be made. Here, we demonstrate how Hebbian plasticity may be used to supplement our pulse-gated information processing framework by implementing a machine learning algorithm. The resulting neural circuit has a number of structures that are similar to biological neural systems, including a layered structure and information propagation driven by oscillatory gating with a complex frequency spectrum.Comment: This invited paper was presented at the 50th Asilomar Conference on Signals, Systems and Computer

    Graded, Dynamically Routable Information Processing with Synfire-Gated Synfire Chains

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    Coherent neural spiking and local field potentials are believed to be signatures of the binding and transfer of information in the brain. Coherent activity has now been measured experimentally in many regions of mammalian cortex. Synfire chains are one of the main theoretical constructs that have been appealed to to describe coherent spiking phenomena. However, for some time, it has been known that synchronous activity in feedforward networks asymptotically either approaches an attractor with fixed waveform and amplitude, or fails to propagate. This has limited their ability to explain graded neuronal responses. Recently, we have shown that pulse-gated synfire chains are capable of propagating graded information coded in mean population current or firing rate amplitudes. In particular, we showed that it is possible to use one synfire chain to provide gating pulses and a second, pulse-gated synfire chain to propagate graded information. We called these circuits synfire-gated synfire chains (SGSCs). Here, we present SGSCs in which graded information can rapidly cascade through a neural circuit, and show a correspondence between this type of transfer and a mean-field model in which gating pulses overlap in time. We show that SGSCs are robust in the presence of variability in population size, pulse timing and synaptic strength. Finally, we demonstrate the computational capabilities of SGSC-based information coding by implementing a self-contained, spike-based, modular neural circuit that is triggered by, then reads in streaming input, processes the input, then makes a decision based on the processed information and shuts itself down

    The crossover from single file to Fickian diffusion

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    The crossover from single-file diffusion, where the mean-square displacement scales as ~t^(1/2), to normal Fickian diffusion, where ~t,isstudiedasafunctionofchannelwidthforcolloidalparticles.BycomparingBrowniandynamicstoahybridmoleculardynamicsandmesoscopicsimulationtechnique,wecanstudytheeffectofhydrodynamicinteractionsonthesinglefilemobilityandonthecrossovertoFickiandiffusionforwiderchannelwidths.Fordisc−likeparticleswithasteepinterparticlerepulsion,thesinglefilemobilitiesfordifferentparticledensitiesarewelldescribedbytheexactlysolvablehard−rodmodel.Thisholdsbothforsimulationsthatincludehydrodynamics,aswellasforthosethatdon′t.Whenthesinglefileconstraintislifted,thenforparticlesofdiameterσandpipeofwidth, is studied as a function of channel width for colloidal particles. By comparing Brownian dynamics to a hybrid molecular dynamics and mesoscopic simulation technique, we can study the effect of hydrodynamic interactions on the single file mobility and on the crossover to Fickian diffusion for wider channel widths. For disc-like particles with a steep interparticle repulsion, the single file mobilities for different particle densities are well described by the exactly solvable hard-rod model. This holds both for simulations that include hydrodynamics, as well as for those that don't. When the single file constraint is lifted, then for particles of diameter \sigma and pipe of width L$ such that (L- 2 \sigma)/\sigma = \delta_c << 1 the particles can be described as hopping past one-another in an average time t_{hop}. For shorter times t << t_{hop} the particles still exhibit sub-diffusive behaviour, but at longer times t > t_{hop}, normal Fickian diffusion sets in with an effective diffusion constant D_{hop} ~ t_{hop}^(1/2). For the Brownian particles, t_{hop} ~ 1/\delta_c^(2) when \delta << 1, but when hydrodynamic interactions are included, we find a stronger dependence than \delta_c^{-2}. We attribute this difference to short-range lubrication forces that make it more difficult for particles to hop past each other in very narrow channels

    Atlas of wide-field-of-view outgoing longwave radiation derived from Nimbus 6 Earth radiation budget data set, July 1975 to June 1978

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    An atlas of monthly mean outgoing longwave radiation global contour maps and associated spherical harmonic coefficients is presented. The atlas contains 36 months of continuous data from July 1975 to June 1978. The data were derived from the first Earth radiation budget experiment, which was flown on the Nimbus-6 Sun-synchronous satellite in 1975. Only the wide-field-of-view longwave measurements are cataloged in this atlas. The contour maps along with the associated sets of spherical harmonic coefficients form a valuable data set for studying different aspects of our changing climate over monthly, annual, and interannual scales in the time domain, and over regional, zonal, and global scales in the spatial domain
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