19 research outputs found
Exploring Reionization-Era Quasars IV: Discovery of Six New Quasars with DES, VHS and unWISE Photometry
This is the fourth paper in a series of publications aiming at discovering
quasars at the epoch of reionization. In this paper, we expand our search for
quasars to the footprint of the Dark Energy Survey (DES) Data Release
One (DR1), covering deg of new area. We select quasar
candidates using deep optical, near-infrared (near-IR) and mid-IR photometric
data from the DES DR1, the VISTA Hemisphere Survey (VHS), the VISTA Kilo-degree
Infrared Galaxy (VIKING) survey, the UKIRT InfraRed Deep Sky Surveys -- Large
Area Survey (ULAS) and the unblurred coadds from the Wide-field Infrared Survey
Explore () images (unWISE). The inclusion of DES and unWISE photometry
allows the search to reach 1 magnitude fainter, comparing to our quasar survey in the northern sky (Wang et al. 2018). We report
the initial discovery and spectroscopic confirmation of six new luminous
quasars at , including an object at , the fourth quasar yet
known at , from a small fraction of candidates observed thus far. Based on
the recent measurement of quasar luminosity function using the
quasar sample from our survey in the northern sky, we estimate that there will
be 55 quasars at at in the full DES
footprint.Comment: 8 pages, 3 figures, submitted to A
The Discovery of a Gravitationally Lensed Quasar at z = 6.51
Strong gravitational lensing provides a powerful probe of the physical
properties of quasars and their host galaxies. A high fraction of the most
luminous high-redshift quasars was predicted to be lensed due to magnification
bias. However, no multiple imaged quasar was found at z>5 in previous surveys.
We report the discovery of J043947.08+163415.7, a strongly lensed quasar at
z=6.51, the first such object detected at the epoch of reionization, and the
brightest quasar yet known at z>5. High-resolution HST imaging reveals a
multiple imaged system with a maximum image separation theta ~ 0.2", best
explained by a model of three quasar images lensed by a low luminosity galaxy
at z~0.7, with a magnification factor of ~50. The existence of this source
suggests that a significant population of strongly lensed, high redshift
quasars could have been missed by previous surveys, as standard color selection
techniques would fail when the quasar color is contaminated by the lensing
galaxy.Comment: 8 pages, 4 figures, submitted to ApJ
Development characteristics and main controlling factors of Carboniferous volcanic reservoirs in the Shixi area, Junggar Basin
The Carboniferous volcanic reservoirs in the Shixi area of the Junggar Basin are complex and diverse. Identifying the characteristics and main factors controlling high-quality volcanic reservoirs is the key to increasing oil and gas reserves and production in this area. Through core observations, thin section identification, physical property and pore structure analyses, combined with production data, the main controlling factors and development modes of high-quality reservoirs were analysed. The results show that the Carboniferous strata in the Shixi area mainly contain andesite and dacite of overflow facies, followed by volcanic breccia and tuff of explosive facies. Volcanic reservoirs in the study area are high-porosity–low-permeability and medium-porosity–low-permeability reservoirs. Volcanic breccia of explosive facies has the best physical properties, showing the characteristics of high porosity and medium permeability. The reservoir space is mainly composed of gas cavities, corrosion pores and fractures, among which the corrosion pores are the most important reservoir spaces of the Carboniferous volcanic rocks. Lithology and lithofacies, weathering and corrosion, and fractures are the main factors controlling the development of high-quality volcanic reservoirs. Volcanic rocks that had experienced weathering and denudation for a long time developed a large number of secondary corrosion pores due to the corrosion of soluble minerals or volcanic ash. Fractures further improved the physical properties, causing volcanic rocks to eventually develop into weathering crust reservoirs. The physical properties of the volcanic rocks far away from the weathering crust were improved through primary gas cavities and structural fractures, and these volcanic rocks eventually developed into the inner reservoir
Bulk and Surface Chemical Composition of Wheat Flour Particles of Different Sizes
Chemical composition and particle size are the critical factors influencing the quality and application of flour. The present study investigated the microstructure and distribution of bulk and surface chemical composition in wheat flour particles of different size. Eight samples of wheat flour of different particle size were obtained from the same native wheat flour by sieving (sieve aperture from 25 to 112 μm). Results from scanning electron microscopy and bulk chemical composition analyze showed that flour particles of different sizes differed in microstructure, protein, and starch composition. Further analysis of protein fractions with varying solubility implied that the relative smaller flour particles (diameter <48 μm) had higher gluten protein (gliadin and glutenin) ratio (60.88–64.06%). Furthermore, amino acid analysis showed that glutamic acid was rich in the medium particles. The results of XPS showed that the surface chemical composition of wheat flour of different sizes had no correlation with the bulk chemical composition, indicating that they would have an independent effect on the quality of flour
The adsorption and simulated separation of light hydrocarbons in isoreticular metal-organic frameworks based on dendritic ligands with different aliphatic side chains
Three isoreticular metal–organic frameworks, JUC-100, JUC-103 and JUC-106, were synthesized by connecting six-node dendritic ligands to a [Zn<sub>4</sub>O(CO<sub>2</sub>)<sub>6</sub>] cluster. JUC-103 and JUC-106 have additional methyl and ethyl groups, respectively, in the pores with respect to JUC-100. The uptake measurements of the three MOFs for CH<sub>4</sub>, C<sub>2</sub>H<sub>4</sub>, C<sub>2</sub>H<sub>6</sub> and C<sub>3</sub>H<sub>8</sub> were carried out. At 298 K, 1 atm, JUC-103 has relatively high CH<sub>4</sub> uptake, but JUC-100 is the best at 273 K, 1 atm. JUC-100 and JUC-103 have similar C<sub>2</sub>H<sub>4</sub> absorption ability. In addition, JUC-100 has the best absorption capacity for C<sub>2</sub>H<sub>6</sub> and C<sub>3</sub>H<sub>8</sub>. These results suggest that high surface area and appropriate pore size are important factors for gas uptake. Furthermore, Ideal Adsorbed Solution Theory (IAST) analyses show that all three MOFs have good C<sub>3</sub>H<sub>8</sub>/CH<sub>4</sub> and C<sub>2</sub>H<sub>6</sub>/CH<sub>4</sub> selectivities for an equimolar quaternary CH<sub>4</sub>/C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub>/C<sub>3</sub>H<sub>8</sub> gas mixture maintained at isothermal conditions at 298 K and JUC-106 has the best C<sub>2</sub>H<sub>6</sub>/CH<sub>4</sub> selectivity. The breakthrough simulations indicate that all three MOFs have good capability for separating C2 hydrocarbons from C3 hydrocarbons. The pulse chromatographic simulations also indicate that all three MOFs are able to separate CH<sub>4</sub>/C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub>/C<sub>3</sub>H<sub>8</sub> mixture into three different fractions of C1, C2 and C3 hydrocarbons
Unveiling the Role of Defects on Oxygen Activation and Photodegradation of Organic Pollutants
10.1021/acs.est.8b03558ENVIRONMENTAL SCIENCE & TECHNOLOGY522313879-1388
Hyaluronic acid reduction-sensitive polymeric micelles achieving co-delivery of tumor-targeting paclitaxel/apatinib effectively reverse cancer multidrug resistance
Multidrug resistance (MDR) of cancer cells is a significant challenge in chemotherapy, highlighting the urgent medical need for simple and reproducible strategies to reverse this process. Here, we report the development of an active tumor-targeting and redox-responsive nanoplatform (PA-ss-NP) using hyaluronic acid-g-cystamine dihydrochloride-poly-ε-(benzyloxycarbonyl)-L-lysine (HA-ss-PLLZ) to co-deliver paclitaxel (PTX) and apatinib (APA) for effective reversal of MDR. This smart nanoplatform specifically bound to CD44 receptors, leading to selective accumulation at the tumor site and uptake by MCF-7/ADR cells. Under high concentrations of cellular glutathione (GSH), the nanocarrier was degraded rapidly with complete release of its encapsulated drugs. Released APA effectively inhibited the function of the P-glycoprotein (P-gp) drug pump and improved the sensitivity of MDR cells to chemotherapeutic agents, leading to the recovery of PTX chemosensitivity in MDR cells. As expected, this newly developed intelligent drug delivery system could effectively control MDR, both in vitro and in vivo