230 research outputs found
Semantic optimisation in datalog programs
Bibliography: leaves 138-142.Datalog is the fusion of Prolog and Database technologies aimed at producing an efficient, logic-based, declarative language for databases. This fusion takes the best of logic programming for the syntax of Datalog, and the best of database systems for the operational part of Datalog. As is the case with all declarative languages, optimisation is necessary to improve the efficiency of programs. Semantic optimisation uses meta-knowledge describing the data in the database to optimise queries and rules, aiming to reduce the resources required to answer queries. In this thesis, I analyse prior work that has been done on semantic optimisation and then propose an optimisation system for Datalog that includes optimisation of recursive programs and a semantic knowledge management module. A language, DatalogiC, which is an extension of Datalog that allows semantic knowledge to be expressed, has also been devised as an implementation vehicle. Finally, empirical results concerning the benefits of semantic optimisation are reported
A Novel Multistage Equalization Algorithm
A novel equalization algorithm utilizing improper nature of the intersymbol interference (ISI) is introduced in this paper. We show that full exploitation of the available information on the second-order statistics of the observed signal entails widely linear processing and that previously known linear minimum mean square error (MMSE) equalizers represent sub-optimum solutions. The proposed scheme is generally applicable for both real and complex signal constellations. The results show that accounting for the improper nature of the ISI leads to significant performance gain compared to conventional equalization schemes
Milli-arcsecond images of the Herbig Ae star HD 163296
The very close environments of young stars are the hosts of fundamental
physical processes, such as planet formation, star-disk interactions, mass
accretion, and ejection. The complex morphological structure of these
environments has been confirmed by the now quite rich data sets obtained for a
few objects by near-infrared long-baseline interferometry. We gathered numerous
interferometric measurements for the young star HD163296 with various
interferometers (VLTI, IOTA, KeckI and CHARA), allowing for the first time an
image independent of any a priori model to be reconstructed. Using the
Multi-aperture image Reconstruction Algorithm (MiRA), we reconstruct images of
HD 163296 in the H and K bands. We compare these images with reconstructed
images obtained from simulated data using a physical model of the environment
of HD 163296. We obtain model-independent and -band images of the
surroundings of HD 163296. The images present several significant features that
we can relate to an inclined asymmetric flared disk around HD 163296 with the
strongest intensity at about 4-5 mas. Because of the incomplete spatial
frequency coverage, we cannot state whether each of them individually is
peculiar in any way. For the first time, milli-arcsecond images of the
environment of a young star are produced. These images confirm that the
morphology of the close environment of young stars is more complex than the
simple models used in the literature so far.Comment: 11 pages, 10 figures, accepted A&A pape
Correction: Carbon dioxide uptake from natural gas by binary ionic liquid–water mixtures
Correction for ‘Carbon dioxide uptake from natural gas by binary ionic liquid–water mixtures’ by Kris Anderson et al., Green Chem., 2015, DOI: 10.1039/c5gc00720h
Carbon dioxide uptake from natural gas by binary ionic liquid water mixtures
[EN] Carbon dioxide solubility in a set of carboxylate ionic liquids formulated with stoicheiometric amounts of water is found to be significantly higher than for other ionic liquids previously reported. This is due to synergistic chemical and physical absorption. The formulated ionic liquid/water mixtures show greatly enhanced carbon dioxide solubility relative to both anhydrous ionic liquids and aqueous ionic liquid solutions, and are competitive with commercial chemical absorbers, such as activated N-methyldiethanolamine or monoethanolamine.The authors would like to acknowledge PETRONAS for financial support of this research, and Cytec (especially Dr Al Robertson) for supplying some of the phosphonium ionic liquids used.Anderson, K.; Atkins, MP.; Estager, J.; Kuah, Y.; Ng, S.; Oliferenko, AA.; Plechkova, NV.... (2015). Carbon dioxide uptake from natural gas by binary ionic liquid water mixtures. Green Chemistry. 17(8):4340-4354. https://doi.org/10.1039/c5gc00720hS43404354178Cenovus, http://www.cenovus.com/operations/technology/co2-enhanced-oil-recovery.htmlV. Alvarado and E.Manrique, Enhanced Oil Recovery: Field Planning and Development Strategies, Gulf Professional Publishing, Amsterdam, 2010British Petroleum , In Salah Gas, http://www.insalahco2.com/index.php?option=com_content&view=frontpage&Itemid=1&lang=enN. Stern , The Economics of Climate Change: The Stern Review, Cambridge University Press, Cambridge, 2007Alvarado, V., & Manrique, E. (2010). Enhanced Oil Recovery: An Update Review. Energies, 3(9), 1529-1575. doi:10.3390/en3091529S. Rackley , Carbon Capture and Storage, Elsevier Science, Oxford, 2009H. 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G.Compton and C.Hardacre, Chloride Determination in Ionic Liquids, in Ionic Liquids IIIB: Fundamentals, Progress, Challenges, and Opportunities - Transformations and Processes, ed. R. D. Rogers and K. R. Seddon, ACS Symp. Ser., Vol. 902, American Chemical Society, Washington D.C., 2005, vol. 902, pp. 244–258J. L. Anthony , E. J.Maginn and J. F.Brennecke, Gas Solubilities in 1-n-Butyl-3-methylimidazolium Hexafluorophosphate, in Ionic Liquids: Industrial Applications to Green Chemistry, ed. R. D. Rogers and K. R. Seddon, ACS Symp. Ser, Vol. 818, American Chemical Society, Washington D.C., 2002, vol. 818, pp. 260–269J. H. Davis Jr. , Working Salts: Syntheses and Uses of Ionic Liquids Containing Functionalized Ions, in Ionic Liquids: Industrial Applications to Green Chemistry, ed. R. D. Rogers and K. R. Seddon, ACS Symp. Ser, Vol. 818, American Chemical Society, Washington D.C., 2002, vol. 818, pp. 247–259Bates, E. D., Mayton, R. D., Ntai, I., & Davis, J. H. (2002). CO2Capture by a Task-Specific Ionic Liquid. Journal of the American Chemical Society, 124(6), 926-927. doi:10.1021/ja017593dWang, C., Luo, X., Zhu, X., Cui, G., Jiang, D., Deng, D., … Dai, S. (2013). The strategies for improving carbon dioxide chemisorption by functionalized ionic liquids. RSC Advances, 3(36), 15518. doi:10.1039/c3ra42366bRamdin, M., de Loos, T. W., & Vlugt, T. J. H. (2012). State-of-the-Art of CO2Capture with Ionic Liquids. Industrial & Engineering Chemistry Research, 51(24), 8149-8177. doi:10.1021/ie3003705Zhang, X., Zhang, X., Dong, H., Zhao, Z., Zhang, S., & Huang, Y. (2012). Carbon capture with ionic liquids: overview and progress. Energy & Environmental Science, 5(5), 6668. doi:10.1039/c2ee21152aYokozeki, A., & Shiflett, M. B. (2009). Separation of Carbon Dioxide and Sulfur Dioxide Gases Using Room-Temperature Ionic Liquid [hmim][Tf2N]. Energy & Fuels, 23(9), 4701-4708. doi:10.1021/ef900649cCabaço, M. I., Besnard, M., Danten, Y., & Coutinho, J. A. P. (2012). Carbon Dioxide in 1-Butyl-3-methylimidazolium Acetate. I. Unusual Solubility Investigated by Raman Spectroscopy and DFT Calculations. The Journal of Physical Chemistry A, 116(6), 1605-1620. doi:10.1021/jp211211nCarvalho, P. J., Álvarez, V. H., Schröder, B., Gil, A. M., Marrucho, I. M., Aznar, M., … Coutinho, J. A. P. (2009). Specific Solvation Interactions of CO2on Acetate and Trifluoroacetate Imidazolium Based Ionic Liquids at High Pressures. The Journal of Physical Chemistry B, 113(19), 6803-6812. doi:10.1021/jp901275bGoodrich, B. F., de la Fuente, J. C., Gurkan, B. E., Zadigian, D. J., Price, E. A., Huang, Y., & Brennecke, J. F. (2011). Experimental Measurements of Amine-Functionalized Anion-Tethered Ionic Liquids with Carbon Dioxide. Industrial & Engineering Chemistry Research, 50(1), 111-118. doi:10.1021/ie101688aGoodrich, B. F., de la Fuente, J. C., Gurkan, B. E., Lopez, Z. K., Price, E. A., Huang, Y., & Brennecke, J. F. (2011). Effect of Water and Temperature on Absorption of CO2by Amine-Functionalized Anion-Tethered Ionic Liquids. The Journal of Physical Chemistry B, 115(29), 9140-9150. doi:10.1021/jp2015534Ferguson, J. L., Holbrey, J. D., Ng, S., Plechkova, N. V., Seddon, K. R., Tomaszowska, A. A., & Wassell, D. F. (2011). A greener, halide-free approach to ionic liquid synthesis. Pure and Applied Chemistry, 84(3), 723-744. doi:10.1351/pac-con-11-07-21Shiflett, M. B., Kasprzak, D. J., Junk, C. P., & Yokozeki, A. (2008). Phase behavior of {carbon dioxide+[bmim][Ac]} mixtures. The Journal of Chemical Thermodynamics, 40(1), 25-31. doi:10.1016/j.jct.2007.06.003Shiflett, M. B., & Yokozeki, A. (2009). Phase Behavior of Carbon Dioxide in Ionic Liquids: [emim][Acetate], [emim][Trifluoroacetate], and [emim][Acetate] + [emim][Trifluoroacetate] Mixtures. Journal of Chemical & Engineering Data, 54(1), 108-114. doi:10.1021/je800701jShiflett, M. B., Drew, D. W., Cantini, R. A., & Yokozeki, A. (2010). Carbon Dioxide Capture Using Ionic Liquid 1-Butyl-3-methylimidazolium Acetate. Energy & Fuels, 24(10), 5781-5789. doi:10.1021/ef100868aCabaço, M. I., Besnard, M., Danten, Y., & Coutinho, J. A. P. (2011). Solubility of CO2in 1-Butyl-3-methyl-imidazolium-trifluoro Acetate Ionic Liquid Studied by Raman Spectroscopy and DFT Investigations. The Journal of Physical Chemistry B, 115(13), 3538-3550. doi:10.1021/jp111453aGurau, G., Rodríguez, H., Kelley, S. P., Janiczek, P., Kalb, R. S., & Rogers, R. D. (2011). Demonstration of Chemisorption of Carbon Dioxide in 1,3-Dialkylimidazolium Acetate Ionic Liquids. Angewandte Chemie International Edition, 50(50), 12024-12026. doi:10.1002/anie.201105198Besnard, M., Cabaço, M. I., Vaca Chávez, F., Pinaud, N., Sebastião, P. J., Coutinho, J. A. P., … Danten, Y. (2012). CO2 in 1-Butyl-3-methylimidazolium Acetate. 2. NMR Investigation of Chemical Reactions. The Journal of Physical Chemistry A, 116(20), 4890-4901. doi:10.1021/jp211689zJaniczek, P., Kalb, R. S., Thonhauser, G., & Gamse, T. (2012). Carbon dioxide absorption in a technical-scale-plant utilizing an imidazolium based ionic liquid. Separation and Purification Technology, 97, 20-25. doi:10.1016/j.seppur.2012.03.003Ober, C. A., & Gupta, R. B. (2012). pH Control of Ionic Liquids with Carbon Dioxide and Water: 1-Ethyl-3-methylimidazolium Acetate. Industrial & Engineering Chemistry Research, 51(6), 2524-2530. doi:10.1021/ie201529dStevanovic, S., Podgoršek, A., Pádua, A. A. H., & Costa Gomes, M. F. (2012). Effect of Water on the Carbon Dioxide Absorption by 1-Alkyl-3-methylimidazolium Acetate Ionic Liquids. The Journal of Physical Chemistry B, 116(49), 14416-14425. doi:10.1021/jp3100377Stevanovic, S., Podgorsek, A., Moura, L., Santini, C. C., Padua, A. A. H., & Costa Gomes, M. F. (2013). Absorption of carbon dioxide by ionic liquids with carboxylate anions. 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Acta Crystallographica, 15(1), 77-81. doi:10.1107/s0365110x62000158Adamová, G., Gardas, R. L., Nieuwenhuyzen, M., Puga, A. V., Rebelo, L. P. N., Robertson, A. J., & Seddon, K. R. (2012). Alkyltributylphosphonium chloride ionic liquids: synthesis, physicochemical properties and crystal structure. Dalton Transactions, 41(27), 8316. doi:10.1039/c1dt10466gGottlieb, H. E., Kotlyar, V., & Nudelman, A. (1997). NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities. The Journal of Organic Chemistry, 62(21), 7512-7515. doi:10.1021/jo971176vSheldrick, G. M. (2007). A short history ofSHELX. Acta Crystallographica Section A Foundations of Crystallography, 64(1), 112-122. doi:10.1107/s0108767307043930Allen, F. H., & Motherwell, W. D. S. (2002). Applications of the Cambridge Structural Database in organic chemistry and crystal chemistry. Acta Crystallographica Section B Structural Science, 58(3), 407-422. doi:10.1107/s0108768102004895Ramnial, T., Taylor, S. A., Bender, M. 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Alkyltributylphosphonium chloride ionic liquids: synthesis, physicochemical properties and crystal structure. Dalton Transactions, 41(27), 8316. doi:10.1039/c1dt10466gM. B. Shiflett and A.Yokozeki, Phase Behaviour of Gases in Ionic Liquids, in Ionic Liquids UnCOILed: Critical Expert Overviews, ed. N. V. Plechkova and K. R. Seddon, Wiley, Hoboken, New Jersey, 2013, pp. 349–398Ibrahim, A. Y., Ashour, F. H., Ghallab, A. O., & Ali, M. (2014). Effects of piperazine on carbon dioxide removal from natural gas using aqueous methyl diethanol amine. Journal of Natural Gas Science and Engineering, 21, 894-899. doi:10.1016/j.jngse.2014.10.011Anonymous , Piperazine – Why It's Used And How It Works, The Contractor (Optimized Gas Treating, Inc.), Houston, 2008, 2 [4], http://www.ogtrt.com/files/contactors/vol_2_issue_4.pd
Exploring patterns of recurrent melanoma in Northeast Scotland to inform the introduction a digital self-examination intervention
Peer reviewedPublisher PD
High-resolution polarimetry of Parsamian 21: revealing the structure of an edge-on FU Ori disc
We present the first high spatial resolution near-infrared direct and
polarimetric observations of Parsamian 21, obtained with the VLT/NACO
instrument. We complemented these measurements with archival infrared
observations, such as HST/WFPC2 imaging, HST/NICMOS polarimetry, Spitzer IRAC
and MIPS photometry, Spitzer IRS spectroscopy as well as ISO photometry. Our
main conclusions are the following: (1) we argue that Parsamian 21 is probably
an FU Orionis-type object; (2) Parsamian 21 is not associated with any rich
cluster of young stars; (3) our measurements reveal a circumstellar envelope, a
polar cavity and an edge-on disc; the disc seems to be geometrically flat and
extends from approximately 48 to 360 AU from the star; (4) the SED can be
reproduced with a simple model of a circumstellar disc and an envelope; (5)
within the framework of an evolutionary sequence of FUors proposed by Green et
al. (2006) and Quanz et al. (2007), Parsamian 21 can be classified as an
intermediate-aged object.Comment: Accepted for publication in the MNRAS. 16 pages, 18 figures and 5
table
A Fabry-Perot Imaging Search for Lyman-alpha Emission in Quasar Absorbers at z ~ 2.4
We have carried out a deep narrow-band imaging survey of six fields with
heavy-element quasar absorption lines, using the Goddard Fabry-Perot (FP)
system at the Apache Point Observatory (APO) 3.5-meter telescope. The aim of
these observations was to search for redshifted Ly- emission from the
galaxies underlying the absorbers at and their companion
galaxies. The 3 sensitivity levels ranged between
and erg s cm in
observed-frame Ly- flux. No significant Ly- emitters were
detected at level. The absence of significant Ly- emission
implies limits on the star formation rate (SFR) of 0.9-2.7
yr per 2-pixel x 2-pixel region, if no dust attenuation is assumed. We
compare our results with those from other emission-line studies of absorber
fields and with predictions for global average SFR based on the models of
cosmic chemical evolution. Our limits are among the tightest existing
constraints on Ly- emission from galaxies in absorber fields, but are
consistent with many other studies. In the absence of dust attenuation, these
studies suggest that SFRs in a large fraction of objects in the absorber fields
may lie below the global mean SFR. However, it is possible that dust
attenuation is responsible for the low emission line fluxes in some objects. It
is also possible that the star-forming regions are compact and at smaller
angular separations from the quasar than the width of our point spread function
and, get lost in the quasar emission. We outline future observations that could
help to distinguish between the various possibilities.Comment: Accepted for Publication in the Astrophysical Journal, 32 pages, 8
figures. NOTE: 25 of the 29 subpanels in the figures are included here at
lower resolution to keep the astroph submission size within allowed limits.
Please see http://boson.physics.sc.edu/~kulkarni/fpimaging.html for a pdf
file of the complete paper including all subpanels of all figures in the
original higher resolutio
The origin of hydrogen line emission for five Herbig Ae/Be stars spatially resolved by VLTI/AMBER spectro-interferometry
To trace the accretion and outflow processes around YSOs, diagnostic spectral
lines such as the BrG 2.166 micron line are widely used, although due to a lack
of spatial resolution, the origin of the line emission is still unclear.
Employing the AU-scale spatial resolution which can be achieved with infrared
long-baseline interferometry, we aim to distinguish between theoretical models
which associate the BrG line emission with mass infall or mass outflow
processes. Using the VLTI/AMBER instrument, we spatially and spectrally
(R=1500) resolved the inner environment of five Herbig Ae/Be stars (HD163296,
HD104237, HD98922, MWC297, V921Sco) in the BrG emission line as well as in the
adjacent continuum. All objects (except MWC297) show an increase of visibility
within the BrG emission line, indicating that the BrG-emitting region in these
objects is more compact than the dust sublimation radius. For HD98922, our
quantitative analysis reveals that the line-emitting region is compact enough
to be consistent with the magnetospheric accretion scenario. For HD163296,
HD104237, MWC297, and V921Sco we identify a stellar wind or a disk wind as the
most likely line-emitting mechanism. We search for general trends and find that
the size of the BrG-emitting region does not seem to depend on the basic
stellar parameters, but correlates with the H-alpha line profile shape. We find
evidence for at least two distinct BrG line-formation mechanisms. Stars with a
P-Cygni H-alpha line profile and a high mass-accretion rate seem to show
particularly compact BrG-emitting regions (R_BrG/R_cont<0.2), while stars with
a double-peaked or single-peaked H-alpha-line profile show a significantly more
extended BrG-emitting region (0.6<R_BrG/R_cont<1.4), possibly tracing a stellar
wind or a disk wind.Comment: 20 pages; 11 figures; Accepted by A&A; a high quality version of the
paper can be obtained at
http://www.skraus.eu/papers/kraus.HAeBe-BrGsurvey.pd
Ubiquitin-protein conjugates accumulate in the lysosomal system of fibroblasts treated with cysteine proteinase inhibitors
- …