656 research outputs found

    Momentum dynamics of one dimensional quantum walks

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    We derive the momentum space dynamic equations and state functions for one dimensional quantum walks by using linear systems and Lie group theory. The momentum space provides an analytic capability similar to that contributed by the z transform in discrete systems theory. The state functions at each time step are expressed as a simple sum of three Chebyshev polynomials. The functions provide an analytic expression for the development of the walks with time.Ian Fuss, Langord B. White, Peter J. Sherman, Sanjeev Naguleswara

    Charge Photoinjection in Intercalated and Covalently Bound [Re(CO)_(3)(dppz)(py)]^(+)–DNA Constructs Monitored by Time-Resolved Visible and Infrared Spectroscopy

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    The complex [Re(CO)_(3)(dppz)(pyâ€Č-OR)]+ (dppz = dipyrido[3,2-a:2â€Č,3â€Č-c]phenazine; pyâ€Č-OR = 4-functionalized pyridine) offers IR sensitivity and can oxidize DNA directly from the excited state, making it a promising probe for the study of DNA-mediated charge transport (CT). The behavior of several covalent and noncovalent Re–DNA constructs was monitored by time-resolved IR (TRIR) and UV/visible spectroscopies, as well as biochemical methods, confirming the long-range oxidation of DNA by the excited complex. Optical excitation of the complex leads to population of MLCT and at least two distinct intraligand states. Experimental observations that are consistent with charge injection from these excited states include similarity between long-time TRIR spectra and the reduced state spectrum observed by spectroelectrochemistry, the appearance of a guanine radical signal in TRIR spectra, and the eventual formation of permanent guanine oxidation products. The majority of reactivity occurs on the ultrafast time scale, although processes dependent on slower conformational motions of DNA, such as the accumulation of oxidative damage at guanine, are also observed. The ability to measure events on such disparate time scales, its superior selectivity in comparison to other spectroscopic techniques, and the ability to simultaneously monitor carbonyl ligand and DNA IR absorption bands make TRIR a valuable tool for the study of CT in DNA

    Evaluation of a Multi-Sensor Platform in a Large-Scale Geophysical Survey at BrĂș na BĂłinne World Heritage Site, Ireland

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    This poster presents comparative results from the first use of the Geophysical Exploration Equipment Platform (GEEP) in Ireland in carrying out a multi-sensor survey in the vicinity of a possible Neolithic passage tomb known as Site E in the BrĂș na BĂłinne World Heritage Site. BrĂș na BĂłinne, a UNESCO World Heritage Site, has been an important ritual, social and economic centre for thousands of years. Much research has been undertaken in the area, including large-scale excavations at the Neolithic passage tombs of Newgrange and Knowth. However we still lack an in-depth understanding of the site’s broad range of archaeological monuments, and the landscape and communities that shaped them. To date there has been no systematic large-scale use of ground geophysical techniques although a number of successful spatially discrete geophysical surveys have been carried out. The landscape has many large, open fields under pasture or tillage suitable for systematic large-scale ground geophysical survey. Such a survey, integrated with the interpretation of other available remote sensing data is an obvious next step in the investigation of this internationally important landscape. The evaluation was successful and the results from the GEEP dataset will be presented with a comparative study of data collected by traditional hand-carried magnetic gradiometry, earth resistance and magnetic susceptibility surveys

    Triggered Star Formation in Galaxy Pairs at z=0.08-0.38

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    We measure the strength, frequency, and timescale of tidally triggered star formation at redshift z=0.08-0.38 in a spectroscopically complete sample of galaxy pairs drawn from the magnitude-limited redshift survey of 9,825 Smithsonian Hectospec Lensing Survey (SHELS) galaxies with R<20.3. To examine the evidence for tidal triggering, we identify a volume-limited sample of major (|\Delta M_R|1/5) pair galaxies with $M_R < -20.8 in the redshift range z=0.08-0.31. The size and completeness of the spectroscopic survey allows us to focus on regions of low local density. The spectrophotometric calibration enables the use of the 4000 Ang break (D_n4000), the H\alpha specific star formation rate (SSFR_{H\alpha}), and population models to characterize the galaxies. We show that D_n4000 is a useful population classification tool; it closely tracks the identification of emission line galaxies. The sample of major pair galaxies in regions of low local density with low D_n4000 demonstrates the expected anti-correlation between pair-wise projected separation and a set of star formation indicators explored in previous studies. We measure the frequency of triggered star formation by comparing the SSFR_{H\alpha} in the volume-limited sample in regions of low local density: 32 +/-7% of the major pair galaxies have SSFR_{H\alpha} at least double the median rate of the unpaired field galaxies. Comparison of stellar population models for pair and for unpaired field galaxies implies a timescale for triggered star formation of ~300-400 Myr.Comment: 25 pages, 15 figures. Accepted to A
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