14,109 research outputs found

    Defying the dragon : stories of three generations of Japanese American struggle against racism on the Monterey Peninsula

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    Three short stories explore the lives of three generations of Japanese Americans during difficult times. The first story takes place at the turn of the 20th century, the second on December 7th, 1941, and the third on September 11th, 2001

    Shock Formation in a Multidimensional Viscoelastic Diffusive System

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    We examine a model for non-Fickian "sorption overshoot" behavior in diffusive polymer-penetrant systems. The equations of motion proposed by Cohen and White [SIAM J. Appl. Math., 51 (1991), pp. 472–483] are solved for two-dimensional problems using matched asymptotic expansions. The phenomenon of shock formation predicted by the model is examined and contrasted with similar behavior in classical reaction-diffusion systems. Mass uptake curves produced by the model are examined and shown to compare favorably with experimental observations

    CI emission in Ultra Luminous Infrared Galaxies as a molecular gas mass tracer

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    We present new sensitive wide-band measurements of the fine structure line 3^P_1 -> 3^P_0 (J=1-0, 492GHz) of neutral atomic carbon (CI) in the two typical Ultra Luminous Infrared Galaxies NGC6240 and Arp220. We then use them along with several other CI measurements in similar objects found in the literature to estimate their global molecular gas content under the assumption of a full CI-H_2 concomitance. We find excellent agreement between the H_2 gas mass estimated with this method and the standard methods using 12^CO. This may provide a new way to measure H_2 gas mass in galaxies, and one which may be very valuable in ULIRGs since in such systems the bright 12^CO emission is known to systematically overestimate the gas mass while their 13^CO emission is usually very weak. At redshifts z>=1 the CI J=1-0 line shifts to much more favorable atmospheric windows and can become a viable alternative tracer of the H_2 gas fueling starburst events in the distant Universe.Comment: 11 pages, 2 figures. Accepted for publication in ApJ Letter

    Plasmon-enhanced internal photoemission for photovoltaics: Theoretical efficiency limits

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    Plasmon-enhanced internal photoemission in metal-semiconductor Schottky junctions has recently been proposed as an alternative photocurrent mechanism for solar cells. Here, we identify and discuss the requirements for efficient operation of such cells and analyze their performance limits under standard solar illumination. We show that the maximum efficiency limit is 20%.We acknowledge the Australian Research Council and the Australian Solar Institute for financial support

    Evolution of X-ray cluster scaling relations in simulations with radiative cooling and non-gravitational heating

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    We investigate the redshift dependence of X-ray cluster scaling relations drawn from three hydrodynamic simulations of the LCDM cosmology: a Radiative model that incorporates radiative cooling of the gas, a Preheating model that additionally heats the gas uniformly at high redshift, and a Feedback model that self-consistently heats cold gas in proportion to its local star-formation rate. While all three models are capable of reproducing the observed local Lx-Tx relation, they predict substantially different results at high redshift (to z=1.5), with the Radiative, Preheating and Feedback models predicting strongly positive, mildly positive and mildly negative evolution, respectively. The physical explanation for these differences lies in the structure of the intracluster medium. All three models predict significant temperature fluctuations at any given radius due to the presence of cool subclumps and, in the case of the Feedback simulation, reheated gas. The mean gas temperature lies above the dynamical temperature of the halo for all models at z=0, but differs between models at higher redshift with the Radiative model having the lowest mean gas temperature at z=1.5. We have not attempted to model the scaling relations in a manner that mimics the observational selection effects, nor has a consistent observational picture yet emerged. Nevertheless, evolution of the scaling relations promises to be a powerful probe of the physics of entropy generation in clusters. First indications are that early, widespread heating is favored over an extended period of heating that is associated with galaxy formation.Comment: Accepted for publication in ApJ. Minor changes following referee's comment

    Photonic crystal nanocavities fabricated from chalcogenide glass fully embedded in an index-matched cladding with a high Q-factor (>750,000)

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    We have designed and fabricated a 2-D photonic crystal hetero-structure cavity in the chalcogenide glass Ge11.5As24Se64.5 that is fully embedded in a cladding with refractive index of 1.44. The low index contrast of this structure (≈1.21) means that high-Q resonances cannot be obtained using standard hetero-structure cavity designs based on W1 waveguides. We show that reducing the waveguide width can substantially improve light confinement, leading to high-Q resonances in a hetero-structure cavity. Numerical simulations indicate intrinsic Qv > 107 are possible with this approach. Experimentally, an optical cavity with a high intrinsic Qv>7.6 x 105 was achieved in a structure with a theoretical Qv = 1.7 x 106.The research was conducted by the Australian Research Council Centre for Excellence for Ultrahigh bandwidth Devices for Optical Systems (project number CE110001018). The device fabrication was partially supported by the facilities of the Australian National Fabrication Facility (ANFF). The calculation was supported by the National Computational Infrastructure (NCI) National Facility

    Feedback Corrections for Ground Motion Effects at ATF2

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    accelconf.web.cern.ch/accelconf/e08/papers/tupc122.pdfInternational audienceGoals of ATF2 will be to provide beams with a few tens of nanometers and stability at the nanometer level. To achieve this, several corrections have to be applied as tra- jectory corrections and optics correction. Once the most critical effects are found, they must be canceled by trajec- tory correction and rematching of the optics quickly and efïŹciently. A method using SVD-determined knobs and how it can be implemented in ATF2 are here described

    Distinct neural mechanisms and temporal constraints govern a cascade of audiotactile interactions

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    Synchrony is a crucial cue indicating whether sensory signals are caused by single or independent sources. In order to be integrated and produce multisensory behavioural benefits, signals must co-occur within a temporal integration window (TIW). Yet, the underlying neural determinants and mechanisms of integration across asynchronies remain unclear. This psychophysics and electroencephalography study investigated the temporal constraints of behavioural response facilitation and neural interactions for evoked response potentials (ERP), inter-trial coherence (ITC), and time-frequency (TF) power. Participants were presented with noise bursts, ‘taps to the face’, and their audiotactile (AT) combinations at seven asynchronies: 0, ±20, ±70, and ±500 ms. Behaviourally we observed an inverted U-shape function for AT response facilitation, which was maximal for synchronous AT stimulation and declined within a ≀70 ms TIW. For ERPs, we observed AT interactions at 110 ms for near-synchronous stimuli within a ≀20 ms TIW and at 400 ms within a ≀70 ms TIW consistent with behavioural response facilitation. By contrast, AT interactions for theta ITC and ERPs at 200 ms post-stimulus were selective for ±70 ms asynchrony, potentially mediated via phase resetting. Finally, interactions for induced theta power and alpha/beta power rebound emerged at 800-1100 ms across several asynchronies including even 500 ms auditory leading asynchrony. In sum, we observed neural interactions that were confined to or extending beyond the behavioural TIW or specific for ±70 ms asynchrony. This diversity of temporal profiles and constraints demonstrates that multisensory integration unfolds in a cascade of interactions that are governed by distinct neural mechanisms

    Programmatic advertising: An exegesis of consumer concerns

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    Programmatic advertising is a nascent and rapidly growing information technology phenomenon that reacts to, and impacts upon, consumers and their behavior. Despite its popularity and widespread use, research in the area remains scant and our current knowledge is based upon a preponderance of practitioner-generated literature. This study contributes to our understanding of this technology by unpacking the means by which it functions and interacts with consumers. The study draws upon paradox theory to deconstruct programmatic advertising's inherent tensions as dilemmas and dialectics. Adopting organisations are faced with the dilemma of pursuing the acquisition of increasingly detailed information in order to provide more personalized offerings, yet doing so increases the likelihood of creating a sense of fear and distrust among consumers. The automation of personalized advertising appears attractive yet presents the dilemma that adverts may be inappropriately placed. Finally, the true cost/benefit of programmatic advertising is unclear, and adopters, platform providers and developers need to engage in dialectic in order to fully understand and communicate its financial implications. Through identifying these fundamental constraints, the study affords pathways for programmatic system actors to ameliorate their, and their customers' concerns

    Time-Dependence of the Mass Accretion Rate in Cluster Cooling Flows

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    We analyze two time-dependent cluster cooling flow models in spherical symmetry. The first assumes that the intracluster gas resides in a static external potential, and includes the effects of optically thin radiative cooling and mass deposition. This corresponds to previous steady-state cooling flow models calculated by White & Sarazin (1987). Detailed agreement is found between steady-state models and time-dependent models at fixed times in the simulations. The mass accretion rate is found either to increase or remain nearly constant once flows reach a steady state. The time rate of change of the accretion rate is strongly sensitive to the value of the mass deposition parameter q, but only mildly sensitive to the ratio beta of gravitational binding energy to gas temperature. We show that previous scaling arguments presented by Bertschinger (1988) and White (1988) are valid only for mature cooling flows with weak mass deposition (q ~< 1). The second set of models includes the effects of a secularly deepening cluster potential and secondary infall of gas from the Hubble flow. We find that such heating effects do not prevent the flows from reaching a steady state within an initial central cooling time.Comment: 22 pages (AASTeX) with 16 EPS figures; accepted for publication in The Astrophysical Journa
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