A Nationwide Nitrogen Deposition Monitoring Network (NNDMN) containing 43 monitoring sites was established in China to measure gaseous NH3, NO2, and HNO3 and particulate NH4+ and NO3− in air and/or ...precipitation from 2010 to 2014. Wet/bulk deposition fluxes of Nr species were collected by precipitation gauge method and measured by continuous-flow analyzer; dry deposition fluxes were estimated using airborne concentration measurements and inferential models. Our observations reveal large spatial variations of atmospheric Nr concentrations and dry and wet/bulk Nr deposition. On a national basis, the annual average concentrations (1.3–47.0 μg N m−3) and dry plus wet/bulk deposition fluxes (2.9–83.3 kg N ha−1 yr−1) of inorganic Nr species are ranked by land use as urban > rural > background sites and by regions as north China > southeast China > southwest China > northeast China > northwest China > Tibetan Plateau, reflecting the impact of anthropogenic Nr emission. Average dry and wet/bulk N deposition fluxes were 20.6 ± 11.2 (mean ± standard deviation) and 19.3 ± 9.2 kg N ha−1 yr−1 across China, with reduced N deposition dominating both dry and wet/bulk deposition. Our results suggest atmospheric dry N deposition is equally important to wet/bulk N deposition at the national scale. Therefore, both deposition forms should be included when considering the impacts of N deposition on environment and ecosystem health.
AbstractClayey/silty sands are widespread as naturally sedimentary soils such as marine deposits in estuaries and offshore locations. They belong to a unique class of gap-graded soils featuring a ...deficiency of certain range of particle sizes and behave differently from those containing pure sand aggregates. The fines improve the stiffness of host sands, which reduces the postconstruction settlement and arching effect of foundations and dams. In this study, a simple yet effective compression model is proposed for clayey/silty sands using the equivalent void-ratio concept. A structure parameter is incorporated into the model to denote the contribution of fines on the effective force chains of gap-graded mixtures. The structure parameter is affected by the particle-size distribution and basic features of sand aggregates. It can be approximated by a constant value, which represents a combination effect of the influence factors. The limit (inactive) void ratio of clayey/silty sands decreases linearly with the increase of fine content and the structure parameter. The proposed model contains only three model parameters, all of which have clear physical meanings and can be readily calibrated based on two conventional compression tests. Simulations using the newly proposed model revealed that it is versatile to capture key features of gap-graded mixtures, including the effect of initial void ratio, interaggregate void ratio, and fine content. The performance of the proposed model is verified with tests data for six clayey sands and five silty sands (or sandy gravel). The differences between the test data and model predictions for both clayey sands and gap-graded granular mixtures are marginally small. The model can be practically useful for predicting the deformation of clayey/silty sands.
AbstractWeathered gap-graded soils are a common geological body in mountainous regions, and they are widely used as construction materials. The shear strength is the controlling parameter for the ...design of civil projects; however, there is still a controversy on the coarse fraction effect on the shear strength of gap-graded soils. To this end, 22 triaxial shear tests are performed on gap-graded soils, and the factors affecting the coarse fraction effect have been analyzed, including the confining stress, the particle shape of aggregates, and the initial density of sand matrix. Partial contacts and sand bridges between aggregates are responsible for the transmission of loading and thus affect the coarse fraction effect. The results of triaxial tests reveal: (1) The overall shear strength of sand-beads mixtures is rather independent of the confining stress and the coarse fraction, and even the volume of aggregates is as high as 44.5%. (2) The effect of the shape of aggregates is effective only at a high coarse volume fraction (44.5%) for loose-sand-gravel mixtures, where the partial contacts between aggregates play an important role in forming the interaggregate structure. (3) The overall shear strength of gap-graded soils with a denser matrix increases continuously with a rising coarse fraction. The formation of a densified sand bridge is correlated with the initial density of sand matrix, contributing to the loading transmission in the interaggregate structure and, in turn, affecting the overall critical state behavior of gap-graded soils. The insights drawn from this study provide a reference for assessing the deformation behavior of weathered residual soils.
Thermoelectric (TE) materials facilitate direct heat-to-electricity conversion. The performance of a TE material is characterised by its figure of merit zT (=S
2
σT/κ) that depends on both electronic ...transport properties, i.e. the Seebeck coefficient S and the electrical conductivity σ, and on thermal transport properties, i.e. the thermal conductivity κ of a material. The intrinsically counter-correlated behaviour between electronic and thermal transport properties makes the enhancement of zT a very challenging task. In the past 10 years, the zTs in bulk TE materials have been significantly enhanced due to intensive exploratory efforts, the discovery of new physical phenomena and effects, and applications of advanced synthesis methods. In this review, we summarise the recent progress in bulk TE materials. After the introduction of fundamental principles of thermoelectricity, the recently achieved enhancements in the TE performance encompassing the use of electronic band structure engineering, lattice phonon engineering and nanostructure tailoring will be emphasised. Next, the highlights of typical TE materials will be presented, focusing especially on the great progress achieved during the past decade. Finally, new techniques and approaches developed to fabricate TE materials will be outlined and their impact on the performance and economic viability of large-scale TE applications will be considered. The progress made during the past dozen or so years provides great opportunities for the use of bulk TE materials in a much broader range of applications and bodes well for a more efficient utilisation of energy.
About 3196 EA-type binaries (EAs) were observed by LAMOST by 2017 June 16 and their spectral types were derived. Meanwhile, the stellar atmospheric parameters of 2020 EAs were determined. In this ...paper, those EAs are cataloged and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EW-type binaries (EWs), indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-period EWs ( days) are the same as those of EAs with the same periods, while their values of Log (g) are usually smaller than those of EAs. These support the evolutionary process that EAs evolve into long-period EWs through the combination of angular momentum loss (AML) via magnetic braking and case A mass transfer. For short-period EWs, their metallicities are lower than those of EAs, while their gravitational accelerations are higher. These reveal that they may be formed from cool short-period EAs through AML via magnetic braking with little mass transfer. For some EWs with high metallicities, they may be contaminated by material from the evolution of unseen neutron stars and black holes or they have third bodies that may help them to form rapidly through a short timescale of pre-contact evolution. The present investigation suggests that the modern EW populations may have formed through a combination of these mechanisms.
BACKGROUND AND PURPOSE—Microglia are among the first cells to respond to intracerebral hemorrhage (ICH), but the mechanisms that underlie their activity following ICH remain unclear. IL ...(interleukin)-15 is a proinflammatory cytokine that orchestrates homeostasis and the intensity of the immune response following central nervous system inflammatory events. The goal of this study was to investigate the role of IL-15 in ICH injury.
METHODS—Using brain slices of patients with ICH, we determined the presence and cellular source of IL-15. A transgenic mouse line with targeted expression of IL-15 in astrocytes was generated to determine the role of astrocytic IL-15 in ICH. The expression of IL-15 was controlled by a glial fibrillary acidic protein promoter (GFAP-IL-15). ICH was induced by intraparenchymal injection of collagenase or autologous blood.
RESULTS—In patients with ICH and wild-type mice subjected to experimental ICH, we found a significant upregulation of IL-15 in astrocytes. In GFAP-IL-15 mice, we found that astrocyte-targeted expression of IL-15 exacerbated brain edema and neurological deficits following ICH. This aggravated ICH injury in GFAP-IL-15 mice is accompanied by increased microglial accumulation in close proximity to astrocytes in perihematomal tissues. Additionally, microglial expression of CD86, IL-1β, and TNF-α is markedly increased in GFAP-IL-15 mice following ICH. Furthermore, depletion of microglia using a colony stimulating factor 1 receptor inhibitor diminishes the exacerbation of ICH injury in GFAP-IL-15 mice.
CONCLUSIONS—Our findings identify IL-15 as a mediator of the crosstalk between astrocytes and microglia that exacerbates brain injury following ICH.
Abstract
Noting the weakest modulation and relatively high metal abundance of the ab-type RR Lyrae star V838 Cyg, we collected the photometric data of this star from several sky surveys to carry out ...an in-depth analysis. The
O
−
C
diagram shows that the pulsation period of V838 Cyg increases linearly over a long timescale. In a reanalysis of the high-precision Kepler data, we confirmed the modulation with a period of 59.45 ± 0.07 days found by Benkő et al., and also found an additional weak modulation with a longer period (840 ± 21 days). After a series of analyses, we incline to the view that the mechanisms causing the two modulations are different: the former is more similar to the typical Blazhko effect, while the mechanism leading to the latter may be an extrinsic factor. We also collected and compared the modulation and physical parameters of other Blazhko RR Lyrae stars from several works in the literature, and find that there is a potential negative correlation between the modulation amplitude (or upper limit of amplitude) and the metal abundance. We infer that the relatively high metal abundance will promote convection in the outer stellar atmosphere, and then inhibit those factors (turbulence, shock wave, etc.) that may cause Blazhko modulation. Future observations and research work can be carried out with reference to this viewpoint. We also introduce the moiré effects that appear in the Kepler long-cadence light curves and their possible interference in the previous analyses.
The origin of enhanced superconductivity over 50 K in the recently discovered FeSe monolayer films grown on SrTiO
(STO), as compared to 8 K in bulk FeSe, is intensely debated. As with the ...ferrochalcogenides A
Fe
Se
and potassium-doped FeSe, which also have a relatively high-superconducting critical temperature (T
), the Fermi surface (FS) of the FeSe/STO monolayer films is free of hole-like FS, suggesting that a Lifshitz transition by which these hole FSs vanish may help increasing T
. However, the fundamental reasons explaining this increase of T
remain unclear. Here we report a 15 K jump of T
accompanying a second Lifshitz transition characterized by the emergence of an electron pocket at the Brillouin zone centre, which is triggered by high-electron doping following in situ deposition of potassium on FeSe/STO monolayer films. Our results suggest that the pairing interactions are orbital dependent in generating enhanced superconductivity in FeSe.
Naturally formed soils (e.g., residual soils and deposit clays) usually show an absent range of particle size. Frequently used by geotechnical communities worldwide, such gap-graded soils can be ...simplified as binary mixtures composed of fine soil matrix and coarse rock aggregates. In this study, an elastoplastic model is proposed for gap-graded soils based on a volume average scheme and homogenization theory. The proposed model incorporates a structural variable to account for the evolution of the inter-granular skeleton of rock aggregates. The model is then implemented in a numerical code by the linearized integration technique proposed by Bardet and Choucair (1991). It is shown that the model can predict a wide range of variations of the overall shear responses with the increase in volume fraction of rock aggregates. An isotropic loading induces a nonuniform stress distribution in gap-graded soils, where the stress in the soil matrix is lower than that of the rock aggregates. The stress path of the matrix is approximately parallel with that of the rock aggregates during triaxial shear loading. The proposed model contains only one additional structure parameter compared with the generalized modified Cam clay model, which can be easily calibrated from the data of a conventional triaxial compression tests. Comparison between our model predictions and the experimental data from literature indicates that the propose model can well reproduce the mechanical responses of gap-graded soils within a wide range fraction of rock aggregates.