14,998 results on '"Xu K"'
Search Results
202. The Causes of Death and Conditional Survival for Long-Term Survivors of Thymoma
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Xu, K., primary, Jiang, W., additional, Liang, J., additional, and Wang, L., additional
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- 2023
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203. EP02.29: A morphology‐based deep learning for fetal head circumference measurement
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Feng, M., primary, Xu, K., additional, Liu, Y., additional, and Liu, B., additional
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- 2023
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- View/download PDF
204. The evolution of the dust and gas content in galaxies
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Santini, P., Maiolino, R., Magnelli, B., Lutz, D., Lamastra, A., Causi, G. Li, Eales, S., Andreani, P., Berta, S., Buat, V., Cooray, A., Cresci, G., Daddi, E., Farrah, D., Fontana, A., Franceschini, A., Genzel, R., Granato, G., Grazian, A., Floc'h, E. Le, Magdis, G., Magliocchetti, M., Mannucci, F., Menci, N., Nordon, R., Oliver, S., Popesso, P., Pozzi, F., Riguccini, L., Rodighiero, G., Rosario, D. J., Salvato, M., Scott, D., Silva, L., Tacconi, L., Viero, M., Wang, L., Wuyts, S., and Xu, K.
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Astrophysics - Cosmology and Nongalactic Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
We use deep Herschel PACS and SPIRE observations in GOODSS, GOODSN and COSMOS to estimate the average dust mass (Mdust) of galaxies on a redshift-stellar mass (Mstar)-SFR grid. We study the scaling relations between Mdust, Mstar and SFR at z<=2.5. No clear evolution of Mdust is observed at fixed SFR and Mstar. We find a tight correlation between SFR and Mdust, likely a consequence of the Schmidt-Kennicutt (S-K) law. The Mstar-Mdust correlation observed by previous works flattens or sometimes disappears when fixing the SFR. Most of it likely derives from the combination of the Mdust-SFR and Mstar-SFR correlations. We then investigate the gas content as inferred by converting Mdust by assuming that the dust/gas ratio scales linearly with the gas metallicity. All galaxies in the sample follow, within uncertainties, the same SFR-Mgas relation (integrated S-K law), which broadly agrees with CO-based results for the bulk of the population, despite the completely different approaches. The majority of galaxies at z~2 form stars with an efficiency (SFE=SFR/Mgas) ~5 times higher than at z~0. It is not clear what fraction of such variation is an intrinsic redshift evolution and what fraction arises from selection effects. The gas fraction (fgas) decreases with Mstar and increases with SFR, and does not evolve with z at fixed Mstar and SFR. We explain these trends by introducing a universal relation between fgas, Mstar and SFR, non-evolving out to z~2.5. Galaxies move across this relation as their gas content evolves in time. We use the 3D fundamental fgas-Mstar-SFR relation and the redshift evolution of the Main Sequence to estimate the evolution of fgas in the average population of galaxies as a function of z and Mstar, and we find evidence a downsizing scenario., Comment: Accepted for publication in A&A
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- 2013
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205. EMS induced SNP changes led to mutation of Wx protein in common wheat
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Lan, J., Li, Y., Xu, K., Zhang, X., Tang, H., Qi, P., Ma, J., Wang, J., Chen, G., Pu, Z., Li, W., Li, Z., Harwood, W., Lan, X., Deng, M., Wei, Y., Zheng, Y., and Jiang, Q.
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- 2020
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206. An association analysis between psychophysical characteristics and genome-wide gene expression changes in human adaptation to the extreme climate at the Antarctic Dome Argus
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Xu, C, Ju, X, Song, D, Huang, F, Tang, D, Zou, Z, Zhang, C, Joshi, T, Jia, L, Xu, W, Xu, K-F, Wang, Q, Xiong, Y, Guo, Z, Chen, X, Xu, J, Zhong, Y, Zhu, Y, Peng, Y, Wang, L, Zhang, X, Jiang, R, Li, D, Jiang, T, Xu, D, and Jiang, C
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Biomedical and Clinical Sciences ,Biological Psychology ,Clinical and Health Psychology ,Clinical Sciences ,Psychology ,Human Genome ,Genetics ,Mental Health ,Aetiology ,2.1 Biological and endogenous factors ,Adaptation ,Physiological ,Adult ,Antarctic Regions ,Asian People ,Climate ,Databases ,Bibliographic ,Gene Expression ,Gene Expression Profiling ,Genetic Association Studies ,Genome ,Human ,Humans ,Male ,Middle Aged ,Oligonucleotide Array Sequence Analysis ,Phenotype ,Psychophysics ,Statistics as Topic ,Testosterone ,Biological Sciences ,Medical and Health Sciences ,Psychology and Cognitive Sciences ,Psychiatry ,Clinical sciences ,Biological psychology ,Clinical and health psychology - Abstract
Genome-wide gene expression measurements have enabled comprehensive studies that integrate the changes of gene expression and phenotypic information to uncover their novel associations. Here we reported the association analysis between psychophysical phenotypes and genome-wide gene expression changes in human adaptation to one of the most extreme climates on Earth, the Antarctic Dome Argus. Dome A is the highest ice feature in Antarctica, and may be the coldest, driest and windiest location on earth. It is considered unapproachable due to its hostile environment. In 2007, a Chinese team of 17 male explorers made the expedition to Dome A for scientific investigation. Overall, 133 psychophysical phenotypes were recorded, and genome-wide gene expression profiles from the blood samples of the explorers were measured before their departure and upon their arrival at Dome A. We found that mood disturbances, including tension (anxiety), depression, anger and fatigue, had a strong, positive, linear relationship with the level of a male sex hormone, testosterone, using the Pearson correlation coefficient (PCC) analysis. We also demonstrated that significantly lowest-level Gene Ontology groups in changes of gene expression in blood cells with erythrocyte removal were consistent with the adaptation of the psychophysical characteristics. Interestingly, we discovered a list of genes that were strongly related to significant phenotypes using phenotype and gene expression PCC analysis. Importantly, among the 70 genes that were identified, most were significantly related to mood disturbances, where 42 genes have been reported in the literature mining, suggesting that the other 28 genes were likely novel genes involved in the mood disturbance mechanism. Taken together, our association analysis provides a reliable method to uncover novel genes and mechanisms related to phenotypes, although further studies are needed.
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- 2015
207. Shock-Enhanced C+ Emission and the Detection of H2O from Stephan's Quintet's Group-Wide Shock using Herschel
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Appleton, P. N., Guillard, P., Boulanger, F., Cluver, M. E., Ogle, P., Falgarone, E., Forets, G. Pineau Des, O'Sullivan, E., Duc, P. -A., Gallagher, S., Gao, Y., Jarrett, T., Konstantopoulos, I., Lisenfeld, U., Lord, S., Lu, N., Peterson, B. W., Struck, C., Sturm, E., Tuffs, R., Valchanov, I., van der Werf, P., and Xu, K. C.
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Astrophysics - Cosmology and Nongalactic Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
We present the first Herschel spectroscopic detections of the [OI]63 and [CII]158 micron fine-structure transitions, and a single para-H2O line from the 35 x 15 kpc^2 shocked intergalactic filament in Stephan's Quintet. The filament is believed to have been formed when a high-speed intruder to the group collided with clumpy intergroup gas. Observations with the PACS spectrometer provide evidence for broad (> 1000 km s^-1) luminous [CII] line profiles, as well as fainter [OI]63micron emission. SPIRE FTS observations reveal water emission from the p-H2O (111-000) transition at several positions in the filament, but no other molecular lines. The H2O line is narrow, and may be associated with denser intermediate-velocity gas experiencing the strongest shock-heating. The [CII]/PAH{tot) and [CII]/FIR ratios are too large to be explained by normal photo-electric heating in PDRs. HII region excitation or X-ray/Cosmic Ray heating can also be ruled out. The observations lead to the conclusion that a large fraction the molecular gas is diffuse and warm. We propose that the [CII], [OI] and warm H2 line emission is powered by a turbulent cascade in which kinetic energy from the galaxy collision with the IGM is dissipated to small scales and low-velocities, via shocks and turbulent eddies. Low-velocity magnetic shocks can help explain both the [CII]/[OI] ratio, and the relatively high [CII]/H2 ratios observed. The discovery that [CII] emission can be enhanced, in large-scale turbulent regions in collisional environments has implications for the interpretation of [CII] emission in high-z galaxies., Comment: 18-pages, 10 figures Accepted for ApJ
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- 2013
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208. Extension of continuum time-dependent Hartree-Fock method to proton states
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Pardi, C. I., Stevenson, P. D., and Xu, K.
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Nuclear Theory - Abstract
This paper deals with the solution of the spherically symmetric time-dependent Hartree-Fock approximation applied to nuclear giant monopole resonances in the small amplitude regime. The problem is spatially unbounded as the resonance state is in the continuum. The practical requirement to perform the calculation in a finite-sized spatial region yields an artificial boundary, which is not present physically. The question of how to ensure the boundary does not interfere with the internal solution, while keeping the overall calculation time low is studied. Here we propose an absorbing boundary condition scheme to handle the conflict. The derivation, via a Laplace transform method, and implementation is described. An inverse Laplace transform required by the absorbing boundaries is calculated using a method of non-linear least squares. The accuracy and efficiency of the scheme is tested and results presented to support the case that they are a effective way of handling the artificial boundary., Comment: 17 pages, 10 figures
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- 2013
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209. Exclusion of $c\bar c$ Interpretation for $X(3940)$
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Sreethawong, W., Xu, K., and Yan, Y.
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High Energy Physics - Phenomenology - Abstract
Partial decay widths of the $X(3940)$ are evaluated in the $^3P_0$ quark model, assuming a charmonium scenario for its structure. In the study all model parameters are predetermined by other reactions. The work reveals that it is difficult to accommodate the $X(3940)$ with any $c\bar c$ meson state in the picture of the potential quark model plus the $^3P_0$ quark dynamics., Comment: 8 pages, 1 figure, title changed, reference added
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- 2013
210. Lipoprotein(a) and Atherosclerotic Cardiovascular Disease: Current Understanding and Future Perspectives
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Wu, M. F., Xu, K. Z., Guo, Y. G., Yu, J., Wu, Y., and Lin, L. M.
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- 2019
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211. Mid-Infrared Properties of Nearby Luminous Infrared Galaxies I: Spitzer IRS Spectra for the GOALS Sample
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Stierwalt, S., Armus, L., Surace, J. A., Inami, H., Petric, A. O., Diaz-Santos, T., Haan, S., Charmandaris, V., Howell, J., Kim, D. C., Marshall, J., Mazzarella, J. M., Spoon, H. W. W., Veilleux, S., Evans, A., Sanders, D. B., Appleton, P., Bothun, G., Bridge, C. R., Chan, B., Frayer, D., Iwasawa, K., Kewley, L. J., Lord, S., Madore, B. F., Melbourne, J. E., Murphy, E. J., Rich, J. A., Schulz, B., Sturm, E., U, V., Vavilkin, T., and Xu, K.
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Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The Great Observatories All-Sky LIRG Survey (GOALS) is a multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here we present low resolution Spitzer spectra covering 5-38um and provide a basic analysis of the mid-IR spectral properties for nearby LIRGs. In a companion paper, we discuss detailed fits to the spectra. The GOALS sample of 244 nuclei in 180 luminous and 22 ultraluminous IR galaxies represents a complete subset of the IRAS RBGS and covers a range of merger stages, morphologies and spectral types. The majority (>60%) of GOALS LIRGs have high 6.2um PAH equivalent widths (EQW > 0.4um) and low levels of silicate absorption (s_9.7um >-1.0). There is a general trend among the U/LIRGs for silicate depth and MIR slope to increase with LIR. U/LIRGs in the late stages of a merger also have on average steeper MIR slopes and higher levels of dust obscuration. Together these trends suggest that as gas & dust is funneled towards the center of a coalescing merger, the nuclei become more compact and obscured. The sources that depart from these correlations have very low PAH EQW (EQW < 0.1um) consistent with their MIR emission being dominated by an AGN. The most heavily dust obscured sources are the most compact in their MIR emission, suggesting that the obscuring (cool) dust is associated with the outer regions of the starburst. As the merger progresses a marked decline is seen for the fraction of high EQW (star formation dominated) sources while the fraction of composite sources increases but the fraction of AGN-dominated sources remains low. When compared to the MIR spectra of submillimeter galaxies (SMGs) at z~2, the average GOALS LIRG is more absorbed at 9.7um and has more PAH emission. However, when the AGN contributions to both the local LIRGs and the high-z SMGs are removed, the average local starbursting LIRG closely resembles the starbursting SMGs., Comment: Accepted for publication in ApJS
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- 2013
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212. Limitation principle for computational fluid dynamics
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Liu, C., Zhou, G., Shyy, W., and Xu, K.
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- 2019
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213. Influence of SiO2 insulation layers thickness distribution on magnetic behaviors of Fe-Si@SiO2 soft magnetic composites
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Liu, L., Yue, Q., Li, G.Q., Xu, K., Wang, J., Wu, Z.Y., and Fan, X.A.
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- 2019
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214. Microstructure and influence of buffer layer on threading dislocations in (0 0 0 1) AlN/sapphire grown by hydride vapor phase epitaxy
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Su, X.J., Huang, J., Zhang, J.P., Wang, J.F., and Xu, K.
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- 2019
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215. Activity of coumarin against Candida albicans biofilms
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Xu, K., Wang, J.L., Chu, M.P., and Jia, C.
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- 2019
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216. A multicentre observational study on management of general anaesthesia in elderly patients at high-risk of postoperative adverse outcomes
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Bruder, N., Vaisse, C., Bechis, C., Bernard, L., Leone, M., Poirier, M., Vincent, A., Abdelkrim, N., Paugam, C., Lion, F., Montravers, P., Langeron, O., Raux, M., Baussier, M., Xu, K., Bart, F., Dagois, S., Plaud, B., Rabuel, C., Roland, E., Biais, M., Nouette-Gaulain, K., Cabart, A., Hanouz, J.L., Lambert, C., Godet, T., Thibault, S., Bouhemad, B., Chambade, E., Bouzat, P., Garot, M., Lebuffe, G., Lallemant, F., Lemery, C., Tavernier, B., de Jong, A., Jaber, S., Verzilli, D., Delannoy, M., Meistelman, C., Carles, M., Tran, L., Bertran, S., Cuvillon, P., Ripart, J., Simon-Pene, S., Boisson, M., Debaene, B., Beloeil, H., Godet, G., Collange, O., Mertes, P.M., Diemunsch, P., Joganah, D., Oehlkern, L., Baulieu, M., Beauchesne, B., Beraud, A.M., Berthier-Berrada, S., Bien, J.Y., Dupont, G., Gavory, J., Lambert, P., Lanoiselée, J., Zufferey, P., Ferré, F., Martin, C., Minville, V., Planté, B., Baffeleuf, B., Ben Abdelkarim, M., David, J.S., Incagnoli, P., Khaled, M., Laplace, M.C., Lefevre, M., Piriou, V., Aubrun, F., Cero, V., Delsuc, C., Faulcon, C., Meuret, P., Rimmelé, T., Truc, C., Molliex, Serge, Passot, Sylvie, Morel, Jerome, Futier, Emmanuel, Lefrant, Jean Yves, Constantin, Jean Michel, Le Manach, Yannick, and Pereira, Bruno
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- 2019
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217. First results from HerMES on the evolution of the submillimetre luminosity function
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Eales, S., Raymond, G., Roseboom, I. G., Altieri, B., Amblard, A., Arumugam, V., Auld, R., Aussel, H., Babbedge, T., Blain, A., Bock, J., Boselli, A., Brisbin, D., Buat, V., Burgarella, D., Castro-Rodriguez, N., Cava, A., Chanial, P., Clements, D. L., Conley, A., Conversi, L., Cooray, A., Dowell, C. D., Dwek, E., Dye, S., Elbaz, D., Farrah, D., Fox, M., Franceschini, A., Gear, W., Glenn, J., Gonzalez~Solares, E. A., Griffin, M., Harwit, M., Hatziminaoglou, E., Huang, J., Ibar, E., Isaak, K., Ivison, R. J., Lagache, G., Levenson, L., Lonsdale, C. J., Lu, N., Madden, S., Maffei, B., Mainetti, G., Marchetti, L., Morrison, G. E., Mortier, A. M. J., Nguyen, H. T., O'Halloran, B., Oliver, S. J., Omont, A., Owen, F. N., Page, M. J., Pannella, M., Panuzzo, P., Papageorgiou, A., Pearson, C. P., Perez-Fournon, I., Pohlen, M., Rawlings, J. I., Rigopoulou, D., Rizzo, D., Rowan-Robinson, M., Portal, M. Sanchez, Schulz, B., Scott, Douglas, Seymour, N., Shupe, D. L., Smith, A. J., Stevens, J. A., Strazzullo, V., Symeonidis, M., Trichas, M., Tugwell, K. E., Vaccari, M., Valtchanov, I., Vigroux, L., Wang, L., Ward, R., Wright, G., Xu, K., and Zemcov, M.
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Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We have carried out two extremely deep surveys with SPIRE, one of the two cameras on Herschel, at 250 microns, close to the peak of the far-infrared background. We have used the results to investigate the evolution of the rest-frame 250-micron luminosity function out to z=2. We find evidence for strong evolution out to a redshift of around 1 but evidence for at most weak evolution beyond this redshift. Our results suggest that a significant part of the stars and metals in the Universe today were formed at z<1.4 in spiral galaxies., Comment: Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter; 5 pages
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- 2010
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218. The Buried Starburst in the Interacting Galaxy II Zw 096 as Revealed by the Spitzer Space Telescope
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Inami, Hanae, Armus, L., Surace, J. A., Mazzarella, J. M., Evans, A. S., Sanders, D. B., Howell, J. H., Petric, A., Vavilkin, T., Iwasawa, K., Haan, S., Murphy, E. J., Stierwalt, S., Appleton, P. N., Barnes, J. E., Bothun, G., Bridge, C. R., Chan, B., Charmandaris, V., Frayer, D. T., Kewley, L. J., Kim, D. C., Lord, S., Madore, B. F., Marshall, J. A., Matsuhara, H., Melbourne, J. E., Rich, J., Schulz, B., Spoon, H. W. W., Sturm, E., U, V., Veilleux, S., and Xu, K.
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Astrophysics - Cosmology and Nongalactic Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
An analysis of data from the Spitzer Space Telescope, Hubble Space Telescope, Chandra X-ray Observatory, and AKARI Infrared Astronomy Satellite is presented for the z=0.036 merging galaxy system II Zw 096 (CGCG 448-020). Because II Zw 096 has an infrared luminosity of log(L_IR/L_sun) = 11.94, it is classified as a Luminous Infrared Galaxy (LIRG), and was observed as part of the Great Observatories All-sky LIRG Survey (GOALS). The Spitzer data suggest that 80% of the total infrared luminosity comes from an extremely compact, red source not associated with the nuclei of the merging galaxies. The Spitzer mid-infrared spectra indicate no high-ionization lines from a buried active galactic nucleus in this source. The strong detection of the 3.3 micron and 6.2 micron PAH emission features in the AKARI and Spitzer spectra also implies that the energy source of II Zw 096 is a starburst. Based on Spitzer infrared imaging and AKARI near-infrared spectroscopy, the star formation rate is estimated to be 120 M_sun/yr and > 45 M_sun/yr, respectively. Finally, the high-resolution B, I, and H-band images show many star clusters in the interacting system. The colors of these clusters suggest at least two populations - one with an age of 1-5 Myr and one with an age of 20-500 Myr, reddened by 0-2 magnitudes of visual extinction. The masses of these clusters span a range between 10^6-10^8 M_sun. This starburst source is reminiscent of the extra-nuclear starburst seen in NGC 4038/9 (the Antennae Galaxies) and Arp 299 but approximately an order of magnitude more luminous than the Antennae. The source is remarkable in that the off-nuclear infrared luminosity dominates the enitre system., Comment: 46 pages, 10 figures, accepted for publication in AJ
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- 2010
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219. GOALS: The Great Observatories All-Sky LIRG Survey
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Armus, L., Mazzarella, J. M., Evans, A. S., Surace, J. A., Sanders, D. B., Iwasawa, K., Frayer, D. T., Howell, J. H., Chan, B., Petric, A. O., Vavilkin, T., Kim, D. C., Haan, S., Inami, H., Murphy, E. J., Appleton, P. N., Barnes, J. E., Bothun, G., Bridge, C. R., Charmandaris, V., Jensen, J. B., Kewley, L. J., Lord, S., Madore, B. F., Marshall, J. A., Melbourne, J. E., Rich, J., Satyapal, S., Schulz, B., Spoon, H. W. W., Sturm, E., U, V., Veilleux, S., and Xu, K.
- Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
The Great Observatories All-sky LIRG Survey (GOALS) combines data from NASA's Spitzer, Chandra, Hubble and GALEX observatories, together with ground-based data into a comprehensive imaging and spectroscopic survey of over 200 low redshift Luminous Infrared Galaxies (LIRGs). The LIRGs are a complete subset of the IRAS Revised Bright Galaxy Sample (RBGS). The LIRGs targeted in GOALS span the full range of nuclear spectral types defined via traditional optical line-ratio diagrams as well as interaction stages. They provide an unbiased picture of the processes responsible for enhanced infrared emission in galaxies in the local Universe. As an example of the analytic power of the multi-wavelength GOALS dataset, we present data for the interacting system VV 340 (IRAS F14547+2449). Between 80-95% of the total far-infrared emission (or about 5E11 solar luminosities) originates in VV 340 North. While the IRAC colors of VV 340 North and South are consistent with star-forming galaxies, both the Spitzer IRS and Chandra ACIS data indicate the presence of a buried AGN in VV 340 North. The GALEX far and near-UV fluxes imply a extremely large infrared "excess" (IRX) for the system (IR/FUV = 81) which is well above the correlation seen in starburst galaxies. Most of this excess is driven by VV 340 N, which alone has an IR excess of nearly 400. The VV 340 system seems to be comprised of two very different galaxies - an infrared luminous edge-on galaxy (VV 340 North) that dominates the long-wavelength emission from the system and which hosts a buried AGN, and a face-on starburst (VV 340 South) that dominates the short-wavelength emission., Comment: 17 pages, 2 tables, 7 postscript figures. Accepted for publication in PASP. Updated manuscript includes complete source table (Table 1)
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- 2009
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220. The evolution of the dust and gas content in galaxies⋆
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Santini, P, Maiolino, R, Magnelli, B, Lutz, D, Lamastra, A, Causi, G Li, Eales, S, Andreani, P, Berta, S, Buat, V, Cooray, A, Cresci, G, Daddi, E, Farrah, D, Fontana, A, Franceschini, A, Genzel, R, Granato, G, Grazian, A, Le Floc’h, E, Magdis, G, Magliocchetti, M, Mannucci, F, Menci, N, Nordon, R, Oliver, S, Popesso, P, Pozzi, F, Riguccini, L, Rodighiero, G, Rosario, DJ, Salvato, M, Scott, D, Silva, L, Tacconi, L, Viero, M, Wang, L, Wuyts, S, and Xu, K
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galaxies: evolution ,galaxies: fundamental parameters ,galaxies: high-redshift ,galaxies: ISM ,infrared: galaxies ,astro-ph.CO ,astro-ph.GA ,Astronomical and Space Sciences ,Astronomy & Astrophysics - Abstract
We use deep Herschel observations taken with both PACS and SPIRE imaging cameras to estimate the dust mass of a sample of galaxies extracted from the GOODS-S, GOODS-N and the COSMOS fields. We divide the redshift-stellar mass (Mstar)-star formation rate (SFR) parameter space into small bins and investigate average properties over this grid. In the first part of the work we investigate the scaling relations between dust mass, stellar mass and SFR out to z = 2.5. No clear evolution of the dust mass with redshift is observed at a given SFR and stellar mass. We find a tight correlation between the SFR and the dust mass, which, under reasonableassumptions, is likely a consequence of the Schmidt-Kennicutt (S-K) relation. The previously observed correlation between the stellar content and the dust content flattens or sometimes disappears when considering galaxies with the same SFR. Our finding suggests that most of the correlation between dust mass and stellar mass obtained by previous studies is likely a consequence of the correlation between the dust mass and the SFR combined with the main sequence, i.e., the tight relation observed between the stellar mass and the SFR and followed by the majority of star-forming galaxies. We then investigate the gas content as inferred from dust mass measurements. We convert the dust mass into gas mass by assuming that the dust-to-gas ratio scales linearly with the gas metallicity (as supported by many observations). For normal star-forming galaxies (on the main sequence) the inferred relation between the SFR and the gas mass (integrated S-K relation) broadly agrees with the results of previous studies based on CO measurements, despite the completely different approaches. We observe that all galaxies in the sample follow, within uncertainties, the same S-K relation. However, when investigated in redshift intervals, the S-K relation shows a moderate, but significant redshift evolution. The bulk of the galaxy population at z ~ 2 converts gas into stars with an efficiency (star formation efficiency, SFE = SFR/Mgas, equal to the inverse of the depletion time) about 5 times higher than at z ~ 0. However, it is not clear what fraction of such variation of the SFE is due to an intrinsic redshift evolution and what fraction is simply a consequence of high-z galaxies having, on average, higher SFR, combined with the super-linear slope of the S-K relation (while other studies find a linear slope). We confirm that the gas fraction (fgas = Mgas/(Mgas + Mstar)) decreases with stellar mass and increases with the SFR. We observe no evolution with redshift once Mstarand SFR are fixed. We explain these trends by introducing a universal relation between gas fraction, stellar mass and SFR that does not evolve with redshift, at least out to z ~ 2.5. Galaxies move across this relation as their gas content evolves across the cosmic epochs. We use the 3D fundamental fgas-Mstar-SFR relation, along with the evolution of the main sequence with redshift, to estimate the evolution of the gas fraction in the average population of galaxies as a function of redshift and as a function of stellar mass: we find that Mstar ≠1011 M ⊙ galaxies show the strongest evolution at z ≠1.3 and a flatter trend at lower redshift, while fgas decreases more regularly over the entire redshift range probed in M star ≠1011 M ⊙ galaxies, in agreement with a downsizing scenario. © 2014 ESO.
- Published
- 2014
221. The evolution of the dust and gas content in galaxies â†
- Author
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Santini, P, Maiolino, R, Magnelli, B, Lutz, D, Lamastra, A, Li Causi, G, Eales, S, Andreani, P, Berta, S, Buat, V, Cooray, A, Cresci, G, Daddi, E, Farrah, D, Fontana, A, Franceschini, A, Genzel, R, Granato, G, Grazian, A, Le Floc'H, E, Magdis, G, Magliocchetti, M, Mannucci, F, Menci, N, Nordon, R, Oliver, S, Popesso, P, Pozzi, F, Riguccini, L, Rodighiero, G, Rosario, DJ, Salvato, M, Scott, D, Silva, L, Tacconi, L, Viero, M, Wang, L, Wuyts, S, and Xu, K
- Subjects
galaxies: evolution ,galaxies: fundamental parameters ,galaxies: high-redshift ,galaxies: ISM ,infrared: galaxies ,astro-ph.CO ,astro-ph.GA ,Astronomy & Astrophysics ,Astronomical and Space Sciences - Abstract
We use deep Herschel observations taken with both PACS and SPIRE imaging cameras to estimate the dust mass of a sample of galaxies extracted from the GOODS-S, GOODS-N and the COSMOS fields. We divide the redshift-stellar mass (Mstar)-star formation rate (SFR) parameter space into small bins and investigate average properties over this grid. In the first part of the work we investigate the scaling relations between dust mass, stellar mass and SFR out to z = 2.5. No clear evolution of the dust mass with redshift is observed at a given SFR and stellar mass. We find a tight correlation between the SFR and the dust mass, which, under reasonableassumptions, is likely a consequence of the Schmidt-Kennicutt (S-K) relation. The previously observed correlation between the stellar content and the dust content flattens or sometimes disappears when considering galaxies with the same SFR. Our finding suggests that most of the correlation between dust mass and stellar mass obtained by previous studies is likely a consequence of the correlation between the dust mass and the SFR combined with the main sequence, i.e., the tight relation observed between the stellar mass and the SFR and followed by the majority of star-forming galaxies. We then investigate the gas content as inferred from dust mass measurements. We convert the dust mass into gas mass by assuming that the dust-to-gas ratio scales linearly with the gas metallicity (as supported by many observations). For normal star-forming galaxies (on the main sequence) the inferred relation between the SFR and the gas mass (integrated S-K relation) broadly agrees with the results of previous studies based on CO measurements, despite the completely different approaches. We observe that all galaxies in the sample follow, within uncertainties, the same S-K relation. However, when investigated in redshift intervals, the S-K relation shows a moderate, but significant redshift evolution. The bulk of the galaxy population at z ~ 2 converts gas into stars with an efficiency (star formation efficiency, SFE = SFR/Mgas, equal to the inverse of the depletion time) about 5 times higher than at z ~ 0. However, it is not clear what fraction of such variation of the SFE is due to an intrinsic redshift evolution and what fraction is simply a consequence of high-z galaxies having, on average, higher SFR, combined with the super-linear slope of the S-K relation (while other studies find a linear slope). We confirm that the gas fraction (fgas = Mgas/(Mgas + Mstar)) decreases with stellar mass and increases with the SFR. We observe no evolution with redshift once Mstarand SFR are fixed. We explain these trends by introducing a universal relation between gas fraction, stellar mass and SFR that does not evolve with redshift, at least out to z ~ 2.5. Galaxies move across this relation as their gas content evolves across the cosmic epochs. We use the 3D fundamental fgas-Mstar-SFR relation, along with the evolution of the main sequence with redshift, to estimate the evolution of the gas fraction in the average population of galaxies as a function of redshift and as a function of stellar mass: we find that Mstar ≠1011 M ⊙ galaxies show the strongest evolution at z ≠1.3 and a flatter trend at lower redshift, while fgas decreases more regularly over the entire redshift range probed in M star ≠1011 M ⊙ galaxies, in agreement with a downsizing scenario. © 2014 ESO.
- Published
- 2014
222. A possible origin of the lunar spinel-bearing lithologies as told by the meteorite NWA 13191.
- Author
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Xie, Lan F., Chen, Hong Y., Miao, Bing K., Song, Wen L., Xia, Zhi P., Zhang, Chuan T., Chen, Guo Z., Zhang, Jin Y., Zhao, Si Z., and Gao, Xu K.
- Subjects
METEORITES ,LUNAR surface ,OLIVINE ,CHEMICAL properties ,MELT crystallization ,PLAGIOCLASE - Abstract
Pink spinel anorthosite (PSA) and pink spinel troctolite (PST) are two lunar lithologies known to contain Mg-rich spinel. PSA rich in spinel and lacking mafic minerals, was detected by the visible and near-infrared reflectance spectroscopy. PST clasts were found in returned lunar samples and meteorites. NWA 13191 is a recently approved lunar meteorite that contains a large amount of spinel-bearing clasts and provides an opportunity to discuss its origin. Sixty-four spinel-bearing clasts were studied in this research. These clasts are dominated by anorthitic feldspars (20.8–80.9 vol%, An
90.9–96.8 ), mafic-rich and aluminum-rich glass (14.7–72.1 vol%) quenched from a melt, and spinels (0.19–5.18 vol%). Forty-nine of these clasts appear to have unusually low modal abundances of mafic silicates (avg. olivine ± pyroxene, 1.87 vol%), which distinguishes them from known spinel-bearing lunar samples (e.g., PST). The spinel compositions (avg. Mg# = 90.6, Al# = 97.4) and mafic minerals contents are basically consistent with those of PSA. The absorption characteristics of glass in the reflection spectrum are not obvious, so it is not clear if the PSA contains melt. The simulated crystallization experiment clearly shows that it contains a large amount of melt at the spinel crystallization stage. These phenomena provide experimental and sample evidence for the existence of glass in the lunar spinel-bearing lithologies. NWA 13191 records the highest known bulk Mg# (avg. 89.8), and the spinel records the highest Al# (98.8) and Mg# (93.1) of lunar samples to date. The chemical properties of spinel-bearing clasts in NWA 13191 are consistent with the slightly REE-enriched and alkali-poor Mg-suite rocks, such as PST, magnesian anorthosites (MANs), and olivine-enriched Mg-suite rocks. These phenomena and previous simulated crystallization experiments indicate that a Mg-Al-rich melt may be produced by impact melting of Mg-rich anorthosite precursors. The spinel is a metastable crystallization product along with plagioclase and vitric melt near the Moon's surface. This realization provides observational evidence for previous simulated crystallization experiments and theoretical speculations. [ABSTRACT FROM AUTHOR]- Published
- 2024
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223. Interfacial Tensions, Solubilities, and Transport Properties of the H2/H2O/NaCl System: A Molecular Simulation Study.
- Author
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van Rooijen, W. A., Habibi, P., Xu, K., Dey, P., Vlugt, T. J. H., Hajibeygi, H., and Moultos, O. A.
- Published
- 2024
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224. Broadly neutralizing antibody VRC34-combo.1 in complex with HIV fusion peptide (residue 512-519)
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Xu, K., primary and Kwong, P.D., additional
- Published
- 2023
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225. Controllable Lorentz Force via Mutual Inductance in Split Ring Resonators
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Xu, K., primary, Stevens, C.J., additional, Solymar, L., additional, and Shamonina, E., additional
- Published
- 2023
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226. The Dependence of the Location and Pressure Variations of the Martian Magnetic Pileup Boundary on the Interplanetary Magnetic Field: An MHD Simulation Study
- Author
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Wang, M., primary, Xu, K., additional, Lu, J. Y., additional, Yin, M. X., additional, Sui, H. Y., additional, Guan, Z. J., additional, and Zhang, J. Q., additional
- Published
- 2023
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- View/download PDF
227. Spatiotemporal measurements of striations in a glow discharge’s positive column using laser-collisional induced fluorescence
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White, Z. K., primary, Gott, R. P., additional, Bentz, B. Z., additional, and Xu, K. G., additional
- Published
- 2023
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- View/download PDF
228. Zeno Quantum Gates in Semiconductor Quantum Dots
- Author
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Xu, K. J., Huang, Y. P., Moore, M. G., and Piermarocchi, C.
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Condensed Matter - Other Condensed Matter ,Quantum Physics - Abstract
We propose a scheme for a two-qubit conditional phase gate by quantum Zeno effect with semiconductor quantum dots. The system consists of two charged dots and one ancillary dot that can perform Rabi oscillations under a resonant laser pulse. The quantum Zeno effect is induced by phonon-assisted exciton relaxation between the ancillary dot and the charged dots, which is equivalent to a continuous measurement. We solve analytically the master equation and simulate the dynamics of the system using a realistic set of parameters. In contrast to standard schemes, larger phonon relaxation rates increase the fidelity of the operations.
- Published
- 2008
229. A three-dimensional multidimensional gas-kinetic scheme for the Navier-Stokes equations under gravitational fields
- Author
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Tian, C. L., Xu, K., Chan, K. L., and Deng, L. C.
- Subjects
Physics - Computational Physics ,Physics - Fluid Dynamics - Abstract
This paper extends the gas-kinetic scheme for one-dimensional inviscid shallow water equations (J. Comput. Phys. 178 (2002), pp. 533-562) to multidimensional gas dynamic equations under gravitational fields. Four important issues in the construction of a well-balanced scheme for gas dynamic equations are addressed. First, the inclusion of the gravitational source term into the flux function is necessary. Second, to achieve second-order accuracy of a well-balanced scheme, the Chapman-Enskog expansion of the Boltzmann equation with the inclusion of the external force term is used. Third, to avoid artificial heating in an isolated system under a gravitational field, the source term treatment inside each cell has to be evaluated consistently with the flux evaluation at the cell interface. Fourth, the multidimensional approach with the inclusion of tangential gradients in two-dimensional and three-dimensional cases becomes important in order to maintain the accuracy of the scheme. Many numerical examples are used to validate the above issues, which include the comparison between the solutions from the current scheme and the Strang splitting method. The methodology developed in this paper can also be applied to other systems, such as semi-conductor device simulations under electric fields., Comment: The name of first author was misspelled as C.T.Tian in the published paper. 35 pages,9 figures
- Published
- 2007
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230. Evidence for Superfluidity of Ultracold Fermions in an Optical Lattice
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Chin, J. K., Miller, D. E., Liu, Y., Stan, C., Setiawan, W., Sanner, C., Xu, K., and Ketterle, W.
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Condensed Matter - Other Condensed Matter - Abstract
The study of superfluid fermion pairs in a periodic potential has important ramifications for understanding superconductivity in crystalline materials. Using cold atomic gases, various condensed matter models can be studied in a highly controllable environment. Weakly repulsive fermions in an optical lattice could undergo d-wave pairing at low temperatures, a possible mechanism for high temperature superconductivity in the cuprates. The lattice potential could also strongly increase the critical temperature for s-wave superfluidity. Recent experimental advances in the bulk include the observation of fermion pair condensates and high-temperature superfluidity. Experiments with fermions and bosonic bound pairs in optical lattices have been reported, but have not yet addressed superfluid behavior. Here we show that when a condensate of fermionic atom pairs was released from an optical lattice, distinct interference peaks appear, implying long range order, a property of a superfluid. Conceptually, this implies that strong s-wave pairing and superfluidity have now been established in a lattice potential, where the transport of atoms occurs by quantum mechanical tunneling and not by simple propagation. These observations were made for unitarity limited interactions on both sides of a Feshbach resonance. For larger lattice depths, the coherence was lost in a reversible manner, possibly due to a superfluid to insulator transition. Such strongly interacting fermions in an optical lattice can be used to study a new class of Hamiltonians with interband and atom-molecule couplings., Comment: accepted for publication in Nature
- Published
- 2006
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231. Powerful High Velocity-Dispersion Molecular Hydrogen Associated with an Intergalactic Shock Wave in Stephan's Quintet
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Appleton, P. N., Xu, K. C., Reach, W., Dopita, M. A., Gao, Y., Lu, N., Popescu, C. C., Sulentic, J. W., Tuffs, R. J., and Yun, M. S.
- Subjects
Astrophysics - Abstract
We present the discovery of strong mid-infrared emission lines of molecular hydrogen of apparently high velocity dispersion (~870 km/s) originating from a group-wide shock wave in Stephan's Quintet. These Spitzer Space Telescope observations reveal emission lines of molecular hydrogen and little else. this is the first time an almost pure H_2 line spectrum has been seen in an extragalactic object. Along with the absence of PAH features and very low excitation ionized gas tracers, the spectra resemble shocked gas seen in Galactic supernova remnants, but on a vast scale. The molecular emission extends over 24 kpc along the X-ray emitting shock-front, but has ten times the surface luminosity as the soft X-rays, and about one-third the surface luminosity of the IR continuum. We suggest that the powerful H_2 emission is generated by the shock wave caused when a high-velocity intruder galaxy collides with filaments of gas in the galaxy group. Our observations suggest a close connection between galaxy-scale shock-waves and strong broad H_2 emission lines, like those seen in the spectra of Ultraluminous Infrared Galaxies where high-speed collisions between galaxy disks are common., Comment: 4 pages, 4 figures and 1 table
- Published
- 2006
- Full Text
- View/download PDF
232. Star formation in the nearby universe: the ultraviolet and infrared points of view
- Author
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Iglesias-Paramo, J., Buat, V., Takeuchi, T. T., Xu, K., Boissier, S., Boselli, A., Burgarella, D., Madore, B. F., de Paz, A. Gil, Bianchi, L., Barlow, T. A., Byun, Y. -I., Donas, J., Forster, K., Friedman, P. G., Heckman, T. M., Jelinski, P. N., Lee, Y. -W., Malina, R. F., Martin, D. C., Milliard, B., Morrissey, P. F., Neff, S. G., Rich, R. M., Schiminovich, D., Seibert, M., Siegmund, O. H. W., Small, T., Szalay, A. S., and Welsh, B. Y.
- Subjects
Astrophysics - Abstract
This work presents the main ultraviolet (UV) and far-infrared (FIR) properties of two samples of nearby galaxies selected from the GALEX ($\lambda = 2315$\AA, hereafter NUV) and IRAS ($\lambda = 60\mu$m) surveys respectively. They are built in order to get detection at both wavelengths for most of the galaxies. Star formation rate (SFR) estimators based on the UV and FIR emissions are compared. Systematic differences are found between the SFR estimators for individual galaxies based on the NUV fluxes corrected for dust attenuation and on the total IR luminosity. A combined estimator based on NUV and IR luminosities seems to be the best proxy over the whole range of values of SFR. Although both samples present similar average values of the birthrate parameter b, their star-formation-related properties are substantially different: NUV-selected galaxies tend to show larger values of $b$ for lower masses, SFRs and dust attenuations, supporting previous scenarios for the star formation history (SFH). Conversely, about 20% of the FIR-selected galaxies show high values of $b$, SFR and NUV attenuation. These galaxies, most of them being LIRGs and ULIRGs, break down the downsizing picture for the SFH, however their relative contribution per unit volume is small in the local Universe. Finally, the cosmic SFR density of the local Universe is estimated in a consistent way from the NUV and IR luminosities., Comment: 43 pages, 13 figures, accepted for publication in Astrophysical Journal Supplement Series
- Published
- 2006
- Full Text
- View/download PDF
233. Observation of Strong Quantum Depletion in a Gaseous Bose-Einstein Condensate
- Author
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Xu, K., Liu, Y., Miller, D. E., Chin, J. K., Setiawan, W., and Ketterle, W.
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
We studied quantum depletion in a gaseous Bose-Einstein condensate. An optical lattice enhanced the atomic interactions and modified the dispersion relation resulting in strong quantum depletion. The depleted fraction was directly observed as a diffuse background in the time-of-flight images. Bogoliubov theory provided a semi-quantitative description for our observations of depleted fractions in excess of 50%., Comment: Replaced with accepted version in PRL
- Published
- 2006
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- View/download PDF
234. Remarkable Disk and Off-nuclear Starburst Activity in the 'Tadpole Galaxy' as revealed by the Spitzer Space Telescope
- Author
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Jarrett, T. H., Polletta, M., Fournon, I. P., Stacey, G., Xu, K., Siana, B., Farrah, D., Berta, S., Hatziminaoglou, E., Rodighiero, G., Surace, J., Domingue, D., Shupe, D., Fang, F., Lonsdale, C., Oliver, S., Rowan-Robinson, M., Smith, G., Babbedge, T., Gonzalez-Solares, E., Masci, F., Franceschini, A., and Padgett, D.
- Subjects
Astrophysics - Abstract
We present ground-based optical and Spitzer infrared imaging observations of the interacting galaxy UGC 10214, the "Tadpole Galaxy" (z = 0.0310), focusing on the star formation activity in the nuclear, disk, spiral arms and tidal tail regions. The major findings of this study are that the Tadpole is actively forming stars in the main disk outside of the nucleus and in the tidal plume, with an estimated mean star formation rate of ~2 to 4 M_sun/yr. The most prominent sites of mid-infrared emission define a "ring" morphology that, combined with the overall morphology of the system, suggest the interaction may belong to the rare class of off-center collisional ring systems that form both shock-induced rings of star formation and tidal plumes. The nuclear emission is solely powered by older stars, with little evidence for ongoing star formation at the center of the Tadpole. Extra-nuclear star formation accounts for >50% of the total star formation in the disk and spiral arms, featuring infrared-bright 'hot spots' that exhibit strong PAH emission, whose band strength is comparable to that of late-type star-forming disk galaxies. The tidal tail, which extends 2 arcmin (~75 kpc) into the intergalactic medium, is populated by super massive star clusters likely triggered by the galaxy-galaxy interaction that has distorted UGC 10214 into its current "tadpole" shape., Comment: to appear in the January 2006 (vol 131) issue of the Astronomical Journal; high quality graphics are located here: http://spider.ipac.caltech.edu/staff/jarrett/tadpole.html
- Published
- 2005
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- View/download PDF
235. Sodium Bose-Einstein Condensates in an Optical Lattice
- Author
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Xu, K., Liu, Y., Abo-Shaeer, J. R., Mukaiyama, T., Chin, J. K., Miller, D. E., Ketterle, W., Jones, Kevin M., and Tiesinga, Eite
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
The phase transition from a superfluid to a Mott insulator has been observed in a $^{23}$Na Bose-Einstein condensate. A dye laser detuned $\approx 5$nm red of the Na $3^2$S$ \to 3^2$P$_{1/2}$ transition was used to form the three dimensional optical lattice. The heating effects of the small detuning as well as the three-body decay processes constrained the timescale of the experiment. Certain lattice detunings were found to induce a large loss of atoms. These loss features were shown to be due to photoassociation of atoms to vibrational levels in the Na$_2$ $(1) ^3\Sigma_g^+$ state., Comment: Figures somewhat compromised due to size reduction
- Published
- 2005
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236. Preliminary assessment on safety performance of updated HCCB blanket module for CFETR
- Author
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Lei, M.Z., Xu, S.L., Wang, J., Song, Y.T., Liu, S.M., Lu, K., Xu, K., and Pei, K.
- Published
- 2018
- Full Text
- View/download PDF
237. A Feasibility Study of a New Unibody Branched Stent Graft Applied to Reconstruct the Canine Aortic Arch
- Author
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Li, W., Zhai, S., Xu, K., Li, Q., Zhong, H., Li, T., and Zhang, Z.
- Published
- 2018
- Full Text
- View/download PDF
238. Facile synthesis of Fe-6.5wt%Si/SiO2 soft magnetic composites as an efficient soft magnetic composite material at medium and high frequencies
- Author
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Wu, Z.Y., Jiang, Z., Fan, X.A., Zhou, L.J., Wang, W.L., and Xu, K.
- Published
- 2018
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239. High-Contrast Interference in a Thermal Cloud of Atoms
- Author
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Miller, D. E., Anglin, J. R., Abo-Shaeer, J. R., Xu, K., Chin, J. K., and Ketterle, W.
- Subjects
Condensed Matter - Statistical Mechanics - Abstract
The coherence properties of a gas of bosonic atoms above the BEC transition temperature were studied. Bragg diffraction was used to create two spatially separated wave packets, which interfere during expansion. Given sufficient expansion time, high fringe contrast could be observed in a cloud of arbitrary temperature. Fringe visibility greater than 90% was observed, which decreased with increasing temperature, in agreement with a simple model. When the sample was "filtered" in momentum space using long, velocity-selective Bragg pulses, the contrast was significantly enhanced in contrast to predictions.
- Published
- 2004
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- View/download PDF
240. Coherent Molecular Optics using Sodium Dimers
- Author
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Abo-Shaeer, J. R., Miller, D. E., Chin, J. K., Xu, K., Mukaiyama, T., and Ketterle, W.
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
Coherent molecular optics is performed using two-photon Bragg scattering. Molecules were produced by sweeping an atomic Bose-Einstein condensate through a Feshbach resonance. The spectral width of the molecular Bragg resonance corresponded to an instantaneous temperature of 20 nK, indicating that atomic coherence was transferred directly to the molecules. An autocorrelating interference technique was used to observe the quadratic spatial dependence of the phase of an expanding molecular cloud. Finally, atoms initially prepared in two momentum states were observed to cross-pair with one another, forming molecules in a third momentum state. This process is analogous to sum-frequency generation in optics.
- Published
- 2004
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241. Dissociation and Decay of Ultra-cold Sodium Molecules
- Author
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Mukaiyama, T., Abo-Shaeer, J. R., Xu, K., Chin, J. K., and Ketterle, W.
- Subjects
Condensed Matter - Soft Condensed Matter - Abstract
The dissociation of ultracold molecules is studied by ramping an external magnetic field through a Feshbach resonance. The observed dissociation energy shows non-linear dependence on the ramp speed and directly yields the strength of the atom-molecule coupling. In addition, inelastic molecule-molecule and molecule-atom collisions are characterized.
- Published
- 2003
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- View/download PDF
242. Formation of Quantum-Degenerate Sodium Molecules
- Author
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Xu, K., Mukaiyama, T., Abo-Shaeer, J. R., Chin, J. K., Miller, D. E., and Ketterle, W.
- Subjects
Condensed Matter - Statistical Mechanics - Abstract
Ultra-cold sodium molecules were produced from an atomic Bose-Einstein condensate by ramping an applied magnetic field across a Feshbach resonance. More than $10^5$ molecules were generated with a conversion efficiency of $\sim$4%. Using laser light resonant with an atomic transition, the remaining atoms could be selectively removed, preventing fast collisional relaxation of the molecules. Time-of-flight analysis of the pure molecular sample yielded an instantaneous phase-space density greater than 20., Comment: 5 pages, 4 figures (final published version)
- Published
- 2003
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- View/download PDF
243. The influence of surface stress and surface-induced internal residual stresses on the size-dependent behaviors of Kirchhoff microplate
- Author
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Yue, Y. M., Xu, K. Y., Tan, Z. Q., Wang, W. J., and Wang, D.
- Published
- 2019
- Full Text
- View/download PDF
244. Maximizing the hard magnetic properties of melt-spun Ce–La–Fe–B alloys
- Author
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Liao, X. F., Zhang, J. S., Yu, H. Y., Zhong, X. C., Zhao, L. Z., Xu, K., Peng, D. R., and Liu, Z. W.
- Published
- 2019
- Full Text
- View/download PDF
245. Generation of macroscopic pair-correlated atomic beams by four-wave mixing in Bose-Einstein condensates
- Author
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Vogels, J. M., Xu, K., and Ketterle, W.
- Subjects
Condensed Matter - Soft Condensed Matter ,Condensed Matter - Statistical Mechanics - Abstract
By colliding two Bose-Einstein condensates we have observed strong bosonic stimulation of the elastic scattering process. When a weak input beam was applied as a seed, it was amplified by a factor of 20. This large gain atomic four-wave mixing resulted in the generation of two macroscopically occupied pair-correlated atomic beams., Comment: Please take eps files for best details in figures
- Published
- 2002
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- View/download PDF
246. Experimental observation of the Bogoliubov transformation for a Bose-Einstein condensed gas
- Author
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Vogels, J. M., Xu, K., Raman, C., Abo-Shaeer, J. R., and Ketterle, W.
- Subjects
Condensed Matter - Soft Condensed Matter ,General Relativity and Quantum Cosmology - Abstract
Phonons with wavevector $q/\hbar$ were optically imprinted into a Bose-Einstein condensate. Their momentum distribution was analyzed using Bragg spectroscopy with a high momentum transfer. The wavefunction of the phonons was shown to be a superposition of +q and -q free particle momentum states, in agreement with the Bogoliubov quasiparticle picture., Comment: 4 pages, 3 figures, please take postscript version for the best version of Fig 1
- Published
- 2001
- Full Text
- View/download PDF
247. Vortex Nucleation in a Stirred Bose-Einstein Condensate
- Author
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Raman, C., Abo-Shaeer, J. R., Vogels, J. M., Xu, K., and Ketterle, W.
- Subjects
Condensed Matter - Soft Condensed Matter - Abstract
We studied the nucleation of vortices in a Bose-Einstein condensate stirred by a laser beam. We observed the vortex cores using time-of-flight absorption imaging. By varying the size of the stirrer, we observed either discrete resonances or a broad response as a function of the frequency of the stirrer's motion. Stirring beams small compared to the condensate size generated vortices below the critical rotation frequency for the nucleation of surface modes, suggesting a local mechanism of generation. In addition, we observed the centrifugal distortion of the condensate due to the rotating vortex lattice and found evidence for bent vortices.
- Published
- 2001
- Full Text
- View/download PDF
248. Investigation of energy transfer mechanism in Er3+ and Tm3+ doped AlN crystalline films
- Author
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Wang, X.D., Yang, M.M., Zeng, X.H., Mo, Y.J., Zhang, J.C., Wang, J.F., and Xu, K.
- Published
- 2017
- Full Text
- View/download PDF
249. A MULTI-STEP DE-NOISING METHOD FOR INTERFEROGRAM IN PS-INSAR
- Author
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Wang, R. J., Xu, K., and Liu, X. L.
- Abstract
In order to reduce the influences of the noises in Synthetic Aperture Radar (SAR) image on accurate extraction of permanent scattered (PS) points in PS-InSAR technology, a multi-step de-noising approach considering the characteristics of the noises is proposed in this study. The method can deal with the noises from one-dimensional signals perspective. First, the two-dimensional interferogram is transformed into one-dimensional phase signals by extracting the phase values of each row in S-shaped. Next, the phase signals are decomposed by the extreme-point symmetric mode decomposition (ESMD) method. Then, for the purpose of reserving more useful phase information, the Lee filtering method is applied to the high-frequency noisy part identified based on the Spearman's correlation coefficients in ESMD decomposition. Finally, the de-noised interferogram is recovered from the phase signals by ways in S-shaped in reverse. The experimental results show that the proposed method is effective in dealing with the noises and can achieve a higher accuracy of interferogram for PS-InSAR.
- Published
- 2022
250. Ethnic Differences in Parents' Perception of Participatory Decision-Making Style of Their Children's Physicians
- Author
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Xu, K. Tom and Arif, Ahmed A.
- Published
- 2004
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