Visibility impairment has become an important environmental issue receiving great attention from both the scientific community and the public. Long-term meteorological data from Baoji, China, were ...collected to investigate the trend in visibility change from 1980 to 2012. The 33-year average visual range is 12.0km. The best 20% of the visibility observations in a calendar year shows a general decreasing trend from 1994 onwards, while the worst 20% exhibits a slight increasing trend from 1997 onwards. These results suggest the progressive degradation of air quality in Baoji in recent years. Intensive PM2.5 measurements were conducted from March 2012 to February 2013 to determine the causes of visibility impairment. An analysis based on IMPROVE equation reveals that PM2.5 organic matter (OM) contributes to 34.2% of the light extinction coefficient (bext) on an annual basis, followed by (NH4)2SO4 (30.0%), NH4NO3 (20.1%), elemental carbon (9.2%) and soil dust (6.5%). The largest contributor to bext for the Worst 20% group is (NH4)2SO4, and the contribution of NH4NO3 for the Worst 20% group increases by a factor of ~3 compared with the Best 20% group. Source apportionment using a positive matrix factorization receptor model indicates that secondary sulfate is the main source of PM2.5 (23.0%), followed by fugitive dust (20.5%), coal combustion (19.9%), secondary nitrate (15.5%), biomass burning (14.3%) and motor vehicle emissions (6.8%). These quantitative results could be useful for policy makers to take effective measures to control the haze pollution in Baoji. Further, the results also are likely to be relevant for other mid-sized cities in China.
•The 33-year average visual range is 12.0km.•(NH4)2SO4 is the largest contributor to bext for the worst 20% group.•Secondary sulfate, fugitive dust and coal combustion are the main sources of PM2.5.
Summary
Steatosis could affect liver stiffness measurement in patients with nonalcoholic fatty liver disease and chronic hepatitis C. In this study, we aimed to investigate the impact of steatosis on ...liver stiffness in hepatitis B virus (HBV)‐infected patients and develop a diagnostic algorithm for prediction of liver fibrosis by liver stiffness based on the controlled attenuation parameter. A total of 488 HBV‐infected patients who underwent clinical examination, Fibroscan and liver biopsy were prospectively enrolled. The best liver stiffness measurement (kPa) cut‐offs for significant fibrosis (S≥3) and advanced fibrosis (S≥4) were 8.1 and 10.9, respectively. The best controlled attenuation parameter cut‐off for severe steatosis (≥30%) was 287 dB/m. Among patients with low‐grade fibrosis (S0‐S2/S0‐S3), mean liver stiffness values were significantly higher in subjects with severe steatosis or controlled attenuation parameter ≥287 dB/m compared with those without. Moreover, in subjects with low‐grade fibrosis, a higher rate of false‐positive rate was observed in patients with severe steatosis than those in patients without (F0‐F2: 28.2% vs 9.7%; F0‐F3: 17.0% vs 5.3%), and in patients with CAP≥287 dB/m compared with their counterpart (F0‐F2: 23.7% vs 9.2%; F0‐F3: 14.1% vs 4.8%). Low‐grade fibrosis was accurately identified by γ‐glutamyl transpeptidase‐to‐platelet ratio (GPR) with a cut‐off value of 0.17. In patients with GPR<0.17, similar results were observed. The presence of steatosis may lead to overestimation of fibrosis assessed by liver stiffness measurement in patient with chronic hepatitis B. A diagnostic algorithm for assessing fibrosis using liver stiffness was developed by combining both controlled attenuation parameter and GPR values.
ABSTRACT
Recent studies show that a universal relation between black hole (BH) growth and stellar mass (M⋆) or star formation rate (SFR) is an oversimplification of BH–galaxy coevolution, and that ...morphological and structural properties of host galaxies must also be considered. Particularly, a possible connection between BH growth and host-galaxy compactness was identified among star-forming (SF) galaxies. Utilizing ≈6300 massive galaxies with I814W < 24 at z < 1.2 in the Cosmic Evolution Survey (COSMOS) field, we perform systematic partial correlation analyses to investigate how sample-averaged BH accretion rate ($\rm \overline{BHAR}$) depends on host-galaxy compactness among SF galaxies, when controlling for morphology and M⋆ (or SFR). The projected central surface mass density within 1 kpc, Σ1, is utilized to represent host-galaxy compactness in our study. We find that the $\rm \overline{BHAR}$–Σ1 relation is stronger than either the $\rm \overline{BHAR}$–M⋆ or $\rm \overline{BHAR}$–SFR relation among SF galaxies, and this $\rm \overline{BHAR}$–Σ1 relation applies to both bulge-dominated galaxies and galaxies that are not dominated by bulges. This $\rm \overline{BHAR}$–Σ1 relation among SF galaxies suggests a link between BH growth and the central gas density of host galaxies on the kpc scale, which may further imply a common origin of the gas in the vicinity of the BH and in the central ∼kpc of the galaxy. This $\rm \overline{BHAR}$–Σ1 relation can also be interpreted as the relation between BH growth and the central velocity dispersion of host galaxies at a given gas content (i.e. gas mass fraction), indicating the role of the host-galaxy potential well in regulating accretion on to the BH.
•Mesoporous titania spheres were prepared using CS/PVA hydrogel beads as a template.•The titania spheres prepared was mesoporous structure.•The photocatalytic activity of the mesoporous titania ...spheres calcined at 500°C was highest.
Mesoporous titania spheres were prepared by modified sol–gel method using chitosan/poly(vinyl alcohol) hydrogel beads as a template. Effects of calcination temperature on physical parameters were investigated by X-ray diffraction (XRD), N2 adsorption–desorption, Fourier transform infrared (FT-IR) spectra, thermogravimetry and differential thermal analyses (TG-DTA), high-resolution transmission electron microscope (HRTEM) and scanning electron microscopy (SEM). The photocatalytic activity of mesoporous titania spheres prepared was also evaluated by photocatalytic degradation of phenol as a model molecule under UV irradiation. With increasing calcination temperature, average crystallite size and pore size increased. In contrast, Brunauer–Emmett–Teller (BET) specific surface areas, porosity and pore volumes steadily decreased. Results of characterization proved that prepared titania spheres with highly organized pores were mesoporous structure. The photocatalytic activity of mesoporous titania spheres calcined at 500°C was more effective than those calcined at other temperatures, which were attributed to the porous structure, large BET surface area, crystalline, and smaller crystallite size. This work may provide new insights into the preparation of novel mesoporous titania spheres and further practical applications in the treatment of wastewater.
AIMS: To assess strains of lactobacilli for their capacity to produce functional fatty acid‐conjugated linoleic acid. To assess the linoleate isomerase for CLA production in the most efficient CLA ...producer. METHODS AND RESULTS: In this study, strains of food‐derived lactobacilli were cultured in media with linoleic acid and CLA production was assessed. Most of the selected strains produced CLA at different levels, with Lactobacillus plantarum ZS2058 being the most efficient CLA producer converting over 50% of linoleic acid to c9, t11‐CLA and t9, t11‐CLA. Some intermediates 10‐hydroxy‐cis‐12‐octadecenoic acid, 10‐oxo‐cis‐12‐octadecenoic acid and 10‐oxo‐trans‐11‐octadecenoic acid were determined via GC‐MS. The genes coding the multicomponent linoleate isomerase containing myosin‐cross‐reactive antigen, short‐chain dehydrogenase/oxidoreductase and acetoacetate decarboxylase for CLA production in Lact. plantarum ZS2058 were cloned and expressed in Escherichia coli. With the mixture of recombinant E. coli, c9, t11‐CLA and three kinds of intermediates were produced from linoleic acid, which were in line with those in the lactobacilli. CONCLUSIONS: The ability for CLA production by lactobacilli exhibited variation. Lactobacillus plantarum and Lact. bulgaricus were the most efficient producers in the selected strains. Lact. plantarum ZS2058 converted linoleic acid to CLAs with 10‐hydroxy‐cis‐12‐octadecenoic acid, 10‐oxo‐cis‐12‐octadecenoic acid and 10‐oxo‐trans‐11‐octadecenoic acid as intermediates. The multiple‐step reactions for CLA production catalysed by multicomponent linoleate isomerase in Lact. plantarum ZS2058 were confirmed successfully. SIGNIFICANCE AND IMPACT OF THE STUDY: Multicomponent linoleate isomerase provides important results for the illustration of the mechanism for CLA production in lactic acid bacteria. Food‐derived lactobacilli with CLA production ability offers novel opportunities for functional foods development.
Intense near-infrared (NIR) emission around 1534 nm has been obtained from ZnO-SiO2:Er3+ composites upon broadband ultraviolet light excitation. Remarkably, enhancement of the NIR emission as much as ...20 times was achieved by optimal codoping with Li+ ions. To elucidate the relevant mechanisms, comprehensive spectroscopic measurements have been performed on ZnO-SiO2 composites with and without Er3+ ions doping. Photoluminescence spectroscopy and fluorescence decay dynamics clearly verify the efficient energy transfer from ZnO quantum dots (QDs) to Er3+ ions. Our results have not only demonstrated an efficient approach of color down-conversion but also indicated that ZnO-SiO2:Er3+ composites could be a promising material for optical amplifier using broadband UV pumping.
We present a bistable electromagnetically induced-transparency-like meta-molecule configuration consisting of a microstrip line side-coupled with an open-ended comb line and a varactor-embedded split ...ring resonator. We find that such a configuration can generate an extremely high transmission contrast up to 15 dB between two bistable states in its transmission with a low bistability threshold of − 1.7 dBm. We also show that the sample length is shorter than one-twelfth of wavelength in the transmission line. These features may be useful in the applications based on nonlinear devices.
We investigate the dependence of black hole accretion rate (BHAR) on host-galaxy star formation rate (SFR) and stellar mass (M*) in the CANDELS/GOODS-South field in the redshift range of . Our sample ...consists of galaxies, allowing us to probe galaxies with and/or . We use sample-mean BHAR to approximate long-term average BHAR. Our sample-mean BHARs are derived from the Chandra Deep Field-South 7 Ms observations, while the SFRs and M* have been estimated by the CANDELS team through spectral energy distribution fitting. The average BHAR is correlated positively with both SFR and M*, and the BHAR-SFR and BHAR-M* relations can both be described acceptably by linear models with a slope of unity. However, BHAR appears to be correlated more strongly with M* than SFR. This result indicates that M* is the primary host-galaxy property related to supermassive black hole (SMBH) growth, and the apparent BHAR-SFR relation is largely a secondary effect due to the star-forming main sequence. Among our sources, massive galaxies ( ) have significantly higher BHAR/SFR ratios than less massive galaxies, indicating that the former have higher SMBH fueling efficiency and/or higher SMBH occupation fraction than the latter. Our results can naturally explain the observed proportionality between and M* for local giant ellipticals and suggest that their is higher than that of local star-forming galaxies. Among local star-forming galaxies, massive systems might have higher compared to dwarfs.
PDF
