160 research outputs found
Constraints on the Spacetime Variation of the Fine-structure Constant Using DESI Emission-line Galaxies
No full textLinhua Jiang et al.The DESI CollaborationWe present strong constraints on the spacetime variation of the fine-structure constant α using the Dark Energy Spectroscopic Instrument (DESI). In this pilot work, we utilize ∼110,000 galaxies with strong and narrow [O iii] λ λ4959, 5007 emission lines to measure the relative variation Δα/α in space and time. The [O iii] doublet is arguably the best choice for this purpose owing to its wide wavelength separation between the two lines and its strong emission in many galaxies. Our galaxy sample spans a redshift range of 0 < z < 0.95, covering half of all cosmic time. We divide the sample into subsamples in 10 redshift bins (Δz = 0.1), and calculate Δα/α for the individual subsamples. The uncertainties of the measured Δα/α are roughly between 2 × 10−6 and 2 × 10−5. We find an apparent α variation with redshift at a level of Δα/α = (2-3) × 10−5. This is highly likely to be caused by systematics associated with wavelength calibration, since such small systematics can be caused by a wavelength distortion of 0.002-0.003 Å, which is beyond the accuracy that the current DESI data can achieve. We refine the wavelength calibration using sky lines for a small fraction of the galaxies, but this does not change our main results. We further probe the spatial variation of α in small redshift ranges, and do not find obvious, large-scale structures in the spatial distribution of Δα/α. As DESI is ongoing, we will include more galaxies, and by improving the wavelength calibration, we expect to obtain a better constraint that is comparable to the strongest current constraint.We acknowledge support from the National Science Foundation of China (12225301) and the National Key R&D Program of China (2022YFF0503401).
This research used data obtained with the Dark Energy Spectroscopic Instrument (DESI). DESI construction and operations is managed by the Lawrence Berkeley National Laboratory. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High-Energy Physics, under Contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract. Additional support for DESI was provided by the U.S. National Science Foundation (NSF), Division of Astronomical Sciences under Contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technology Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: www.desi.lbl.gov/collaborating-institutions. The DESI collaboration is honored to be permitted to conduct scientific research on Iolkam Du'ag (Kitt Peak), a mountain with particular significance to the Tohono O'odham Nation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. National Science Foundation, the U.S. Department of Energy, or any of the listed funding agencies.Peer reviewe
The sloan digital sky survey reverberation mapping project : ensemble spectroscopic variability of quasar broad emission lines
No full textM.Y.S. acknowledges support from the China Scholarship Council (No. [2013]3009). J.R.T. and Y.S. acknowledge support from NASA through Hubble Fellowship grants #51330 and #51314, respectively, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS 5-26555. W.N.B. acknowledges support from NSF grant AST-1108604 and the V. M. Willaman Endowment. KDD is supported by an NSF AAPF fellowship awarded under NSF grant AST-1302093.We explore the variability of quasars in the Mg ii and Hβ broad emission lines and ultraviolet/optical continuum emission using the Sloan Digital Sky Survey Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic study of quasar variability to date: our study includes 29 spectroscopic epochs from SDSS-RM over 6 months, containing 357 quasars with Mg ii and 41 quasars with Hβ . On longer timescales, the study is also supplemented with two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional 2854 quasars with Mg ii and 572 quasars with Hβ . The Mg ii emission line is significantly variable (Δƒ/ƒ ~ 10% on ~100-day timescales), a necessary prerequisite for its use for reverberation mapping studies. The data also confirm that continuum variability increases with timescale and decreases with luminosity, and the continuum light curves are consistent with a damped random-walk model on rest-frame timescales of ≳5 days. We compare the emission-line and continuum variability to investigate the structure of the broad-line region. Broad-line variability shows a shallower increase with timescale compared to the continuum emission, demonstrating that the broad-line transfer function is not a δ-function. Hβ is more variable than Mg ii (roughly by a factor of ~1.5), suggesting different excitation mechanisms, optical depths and/or geometrical configuration for each emission line. The ensemble spectroscopic variability measurements enabled by the SDSS-RM project have important consequences for future studies of reverberation mapping and black hole mass estimation of 1<픃<2 quasars.Peer reviewe
Super resolution reconstruction based on adaptive sparse domain and total variation regularization of wavelet transform
No full textThe Sloan digital sky survey reverberation mapping project : technical overview
No full textThe Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project is a dedicated multi-object RM experiment that has spectroscopically monitored a sample of 849 broad-line quasars in a single 7 deg2 field with the SDSS-III Baryon Oscillation Spectroscopic Survey spectrograph. The RM quasar sample is flux-limited to i psf = 21.7 mag, and covers a redshift range of 0.1 0.3, and will investigate the prospects of RM with all major broad lines covered in optical spectroscopy. SDSS-RM will provide guidance on future multi-object RM campaigns on larger scales, and is aiming to deliver more than tens of BLR lag detections for a homogeneous sample of quasars. We describe the motivation, design, and implementation of this program, and outline the science impact expected from the resulting data for RM and general quasar science.Peer reviewe
Collagen-mediated survival signaling is modulated by CD45 in Jurkat T cells
No full textT cell activation is a critical step in the development of a proper immune response to infection and inflammation. This dynamic process requires efficient T cell receptor signaling, which in turn is modulated by integrin receptor activation and the actin cytoskeleton. CD45 is a key player in T cell receptor mediated signal transduction. However, its exact role in integrin mediated signaling in T cells remains to be elucidated. The present study addresses the relationship between CD45 and beta1-integrin mediated survival signaling in the human T leukemic cell line Jurkat, in which collagen receptors alpha1 beta1 and alpha2 beta1 integrins are localized. Wild type (WT)-Jurkat T cells treated with collagen demonstrated increased cell proliferation and survival. Monitoring the intracellular signaling pathways activated by collagen in WT-Jurkat cells revealed increased focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK) activation. Moreover, examination of the actin cytoskeleton of WT-Jurkat T cells treated with collagen demonstrated the presence of an organized cortical actin structure, reminiscent of the survival phenotype. This is in contrast to CD45-deficient J45.01 T cells, where collagen treatment failed to enhance cell proliferation/survival and was unable to stimulate FAK and ERK activity. In addition, the actin cytoskeleton of collagen treated J45.01 T cells was disorganized with cortical actin aggregates present throughout. The importance of an organized actin cytoskeleton to proper cell signaling and survival was further demonstrated by the inability of collagen treated WT-Jurkat cells to activate the FAK and ERK survival pathway in the presence of cytochalasin D, a cytoskeleton-disrupting drug. Consistently, addition of the CD45 specific inhibitor abolished collagen-stimulated FAK and ERK activation in WT-Jurkat cells, further depicting CD45 as the key mediator. Furthermore, collagen-mediated T cell signaling alone was able to activate IL-2 gene transcription devoid of concomitant T cell receptor activation. Taken together, these results are the first to demonstrate that CD45 is important in promoting cell survival by modulating integrin-mediated FAK/ERK signaling in Jurkat T cells and is involved in a distinct signal transduction pathway, separate from T cell receptor signaling, influencing T cell immune responses. Hence, this study will help further our knowledge about beta1-integrin mediated signaling in T cells, which may prove to be essential for the regulation of various T cell mediated immune responsesNRC publication: Ye
Trust to test translation practices: A case study of Shanghai, China
No full textTrust is important in public health communication to culturally and linguistically diverse (CALD) communities during pandemics. This empirical research, using quantitative data from 107 foreign nationals at a university in Shanghai, probes into how trust varied in official translation services (OTS) and non-official translation services (NOTS) during COVID-19. Statistical analysis was carried out by IBM SPSS Statistics 26 and it was found that (1) NOTS which are more frequently used are more trusted compared with OTS; (2) NOTS are uncorrelated with demographics while OTS are correlated with demographics, among which education and trust in OTS suggest a linear positive relationship (Sig. = 0.003, β = 0.467), whereas age and trust in OTS suggest a linear negative relationship (Sig. = 0.027, β = −0.348); (3) there is a positive relationship between the frequency of using services and trust, i.e., higher frequency implies higher trust. The findings of this case study can have implications for policy makers and the representatives of CALD communities.Quantum Circuit Architectures and Technolog
An Applied Research on the Compound Air Conditioning System of Ground Source Direct Cooling System and Water Storage Tank System
No full textAbstractEnergy is an important material basis for China's economic and social development. The green building with the rule of energy saving and environmental protection and the reasonable and efficient air-conditioning systems arises at the historic moment. A Compound Air Conditioning System (CACS) of Ground Source Direct Cooling (GSDC) system and Water Storage Tank System (WSTS) is applied in an clod area and in details presented. The monitored data shows that the average operating cost of the air conditioning each year is lower than 10 Chinese yuan/m2. Therefore, this CACS system has a great potentiality in the demand of building energy saving in the cold areas
Numerical Evaluation of the Indoor Environment in a Room with Capillary Radiation Air Conditioning System
No full textAbstractNumerical simulation has been conducted in a conference room with capillary radiation air conditioning system in Jinan. The influence of the different supply air speed on the indoor temperature field, velocity field, air age, PMV and PPD have been studied. It is found that the indoor thermal comfort level is the highest when supply air velocity is in the range of 1.75 to 2 m/s
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