683 research outputs found

    Sensitive Observations of Radio Recombination Lines in Orion and W51: The Data and Detection of Systematic Recombination Line Blueshifts Proportional to Impact Broadening

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    Sensitive spectral observations made in two frequency bands near 6.0 and 17.6 GHz are described for Orion and W51. Using frequency switching we were able to achieve a dynamic range in excess of 10,000 without fitting sinusoidal or polynomial baselines. This enabled us to detect lines as weak as TA 1mKinthesestrongcontinuumsources.Hydrogenrecombinationlineswith_{A} ~1mK in these strong continuum sources. Hydrogen recombination lines with \Delta n$ as high as 25 have been detected in Orion. In the Orion data, where the lines are stronger, we have also detected a systematic shift in the line center frequencies proportional to linewidth that cannot be explained by normal optical depth effects.Comment: 22 pages, 13 figures. Accepted for publication in Astrophysics and Space Scienc

    Entanglement detection via condition of quantum correlation

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    We develop a novel necessary condition of quantum correlation. It is utilized to construct dd-level bipartite Bell-type inequality which is strongly resistant to noise and requires only analyses of O(d)O(d) measurement outcomes compared to the previous result O(d2)O(d^{2}). Remarkably, a connection between the arbitrary high-dimensional bipartite Bell-type inequality and entanglement witnesses is found. Through the necessary condition of quantum correlation, we propose that the witness operators to detect truly multipartite entanglement for a generalized Greenberger-Horne-Zeilinger (GHZ) state with two local measurement settings and a four-qubit singlet state with three settings. Moreover, we also propose the first robust entanglement witness to detect four-level tripartite GHZ state with only two local measurement settings

    Sensors and Systems for in situ Observations of Marine Carbon Dioxide System Variables

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    Autonomous chemical sensors are required to document the marine carbon dioxide system's evolving response to anthropogenic CO2 inputs, as well as impacts on short- and long-term carbon cycling. Observations will be required over a wide range of spatial and temporal scales, and measurements will likely need to be maintained for decades. Measurable CO2 system variables currently include total dissolved inorganic carbon (DIC), total alkalinity (AT), CO2 fugacity (fCO2), and pH, with comprehensive characterization requiring measurement of at least two variables. These four parameters are amenable to in situ analysis, but sustained deployment remains a challenge. Available methods encompass a broad range of analytical techniques, including potentiometry, spectrophotometry, conductimetry, and mass spectrometry. Instrument capabilities (precision, accuracy, endurance, reliability, etc.) are diverse and will evolve substantially over the time that the marine CO2 system undergoes dramatic changes. Different suites of measurements/parameters will be appropriate for different sampling platforms and measurement objectives

    Learner and Teacher Roles in the Treatment of Oral Error in Group Work

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69127/2/10.1177_003368828001100204.pd

    The Swinburne Intermediate Latitude Pulsar Survey

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    We have conducted a survey of intermediate Galactic latitudes using the 13-beam 21-cm multibeam receiver of the Parkes 64-m radio telescope. The survey covered the region enclosed by 5 deg < |b| < 15 deg and -100 deg < l < 50 deg with 4,702 processed pointings of 265 s each, for a total of 14.5 days of integration time. Thirteen 2x96-channel filterbanks provided 288 MHz of bandwidth at a centre frequency of 1374 MHz, one-bit sampled every 125 microsec and incurring ~DM/13.4 cm^-3 pc samples of dispersion smearing. The system was sensitive to slow and most millisecond pulsars in the region with flux densities greater than approximately 0.3--1.1 mJy. Offline analysis on the 64-node Swinburne workstation cluster resulted in the detection of 170 pulsars of which 69 were new discoveries. Eight of the new pulsars, by virtue of their small spin periods and period derivatives, may be recycled and have been reported elsewhere. The slow pulsars discovered are typical of those already known in the volume searched, being of intermediate to old age. Several pulsars experience pulse nulling and two display very regular drifting sub-pulses. We discuss the new discoveries and provide timing parameters for the 48 slow pulsars for which we have a phase-connnected solution.Comment: 19 pages, 11 figures, accepted to MNRA

    Gauged motion in general relativity and in Kaluza-Klein theories

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    In a recent paper [1] a new generalization of the Killing motion, the {\it gauged motion}, has been introduced for stationary spacetimes where it was shown that the physical symmetries of such spacetimes are well described through this new symmetry. In this article after a more detailed study in the stationary case we present the definition of gauged motion for general spacetimes. The definition is based on the gauged Lie derivative induced by a threading family of observers and the relevant reparametrization invariance. We also extend the gauged motion to the case of Kaluza-Klein theories.Comment: 42 pages, revised version, typos correction along with some minor changes, Revtex forma

    The Effect of Chemical Information on the Spatial Distribution of Fruit Flies: I Model Results

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    Animal aggregation is a general phenomenon in ecological systems. Aggregations are generally considered as an evolutionary advantageous state in which members derive the benefits of protection and mate choice, balanced by the costs of limiting resources and competition. In insects, chemical information conveyance plays an important role in finding conspecifics and forming aggregations. In this study, we describe a spatio-temporal simulation model designed to explore and quantify the effects of these infochemicals, i.e., food odors and an aggregation pheromone, on the spatial distribution of a fruit fly (Drosophila melanogaster) population, where the lower and upper limit of local population size are controlled by an Allee effect and competition. We found that during the spatial expansion and strong growth of the population, the use of infochemicals had a positive effect on population size. The positive effects of reduced mortality at low population numbers outweighed the negative effects of increased mortality due to competition. At low resource densities, attraction toward infochemicals also had a positive effect on population size during recolonization of an area after a local population crash, by decreasing the mortality due to the Allee effect. However, when the whole area was colonized and the population was large, the negative effects of competition on population size were larger than the positive effects of the reduction in mortality due to the Allee effect. The use of infochemicals thus has mainly positive effects on population size and population persistence when the population is small and during the colonization of an area

    Quantum entanglement with acousto-optic modulators: 2-photon beatings and Bell experiments with moving beamsplitters

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    We present an experiment testing quantum correlations with frequency shifted photons. We test Bell inequality with 2-photon interferometry where we replace the beamsplitters by acousto-optic modulators, which are equivalent to moving beamsplitters. We measure the 2-photon beatings induced by the frequency shifts, and we propose a cryptographic scheme in relation. Finally, setting the experiment in a relativistic configuration, we demonstrate that the quantum correlations are not only independent of the distance but also of the time ordering between the two single-photon measurements.Comment: 14 pages, 16 figure
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