Mergers of neutron stars are known to be associated with short γ-ray bursts
. If the neutron-star equation of state is sufficiently stiff (that is, the pressure increases sharply as the density ...increases), at least some such mergers will leave behind a supramassive or even a stable neutron star that spins rapidly with a strong magnetic field
(that is, a magnetar). Such a magnetar signature may have been observed in the form of the X-ray plateau that follows up to half of observed short γ-ray bursts
. However, it has been expected that some X-ray transients powered by binary neutron-star mergers may not be associated with a short γ-ray burst
. A fast X-ray transient (CDF-S XT1) was recently found to be associated with a faint host galaxy, the redshift of which is unknown
. Its X-ray and host-galaxy properties allow several possible explanations including a short γ-ray burst seen off-axis, a low-luminosity γ-ray burst at high redshift, or a tidal disruption event involving an intermediate-mass black hole and a white dwarf
. Here we report a second X-ray transient, CDF-S XT2, that is associated with a galaxy at redshift z = 0.738 (ref.
). The measured light curve is fully consistent with the X-ray transient being powered by a millisecond magnetar. More intriguingly, CDF-S XT2 lies in the outskirts of its star-forming host galaxy with a moderate offset from the galaxy centre, as short γ-ray bursts often do
. The estimated event-rate density of similar X-ray transients, when corrected to the local value, is consistent with the event-rate density of binary neutron-star mergers that is robustly inferred from the detection of the gravitational-wave event GW170817.
•The oblique fin maintains boundary layer to be re-developed periodically.•The injection of secondary flow accelerates the heat propagation into fluid core.•The temperatures on the oblique fin are ...lower than those on the straight channel.•The T uniformity on oblique fin is much uniform than that on straight channel.•The oblique LCP achieves higher heat transfer coefficient.
The development of electric vehicles (EVs) demands for complementary technologies in battery thermal management. To achieve fast charging/discharging capacity, liquid cooling is an effective means of maintaining temperature of a battery in operation within a narrow optimal range. In conventional straight channels, convective heat transfer deteriorates along the axial direction with the development of the hydrodynamic boundary layer, resulting in elevated maximum temperature and significant temperature gradient in the fully developed region. This is a serious problem as temperature uniformity is of utmost importance to the performance and lifespan of a Li–ion battery. In this research, a simple configuration of oblique cuts across the straight fins of a conventional straight channel design was developed, to enhance the performance of the conventional channel with minimal pressure penalty. These oblique cuts across the straight fins form an oblique fin array. The designed liquid cold plate (LCP) contains these simple oblique fins with optimized angle and width. This segmentation of the continuous fin into oblique sections leads to the re-initialization of boundary layers, providing a solution to the elevated temperatures caused by a thick boundary layer in the fully developed region. Experimental results show that heat transfer coefficients of oblique minichannel are higher than those of conventional straight minichannel. The oblique LCP is able to maintain the battery surface average temperature below 50°C for a heat load of 1240W at a flow rate lower than 0.9l/min. This implies that a proper designed minichannel cold plate could be a promising solution for EV battery thermal management.
This study discusses the approach of adaptatively regulating the surface charge and electric field distributions by nonlinear conductivity materials. Three groups of surface nonlinear conductivity ...(SNC) spacers, namely, SNC30, SNC60, and SNC90, were prepared by coating the epoxy (EP)/Al 2 O 3 spacers with EP/SiC composites of 30-, 60-, and 90-phr doping contents. Based on a downsized direct current gas-insulated transmission line (dc-GIL) model, the regulation effects of the SNC spacers are verified by changing the voltage waveforms and temperature gradients in both simulation and experimental studies. Results show impressive abilities of the SNC spacers on relaxing the electric field distortion by adaptively regulating the surface charge accumulation through nonlinear surface conduction. Under dc stress, the SNC spacers can significantly increase the discharge inception and the flashover voltages at room temperature. As the temperature gradient increases, the discharge suppression effects of the SNC spacers weaken first and then increase. Surface charges on the SNC60 and SNC90 spacers can make a rapid adjustment along with the polarity reversal voltage; the corresponding flashover voltages are improved by 18% and 29% compared with that of the original spacer.
In this study, a downsized direct current (dc)-gas-insulated transmission line (GIL) model is applied to investigate the surface charging and discharging characteristics of the basin-type spacer in ...0.1-MPa SF 6 and air. Under a low electric field, the surface charge accumulation is dominated by the bulk conduction of the spacer. As the charging voltage increases, gas ionization occurs in the localized strong electric field, taking over the dominant position. In 0.1-MPa SF 6 gas, flashovers typically develop along the convex surface of the spacer under both positive and negative voltages because the homo-charge accumulation induced by brush discharges on the concave surface aggravates the electric field distortion at the convex side. In air, the dc flashovers have the polarity effect. Under the negative voltage, the flashover development is similar to that in SF 6 gas. But for positive polarity, the space charge region of positive polarity intensifies the electric field ahead of the corona region, thus promoting the air-gap breakdown at the concave side of the spacer.
► Complete accounting of net GWP and GHGI including soil carbon change of a rice cropping system under 5 different management practices. ► Three integrated soil crop system management strategies ...(ISSMs) were examined for mitigating GHGs, increasing yield and NUE in rice agriculture. ► Two ISSMs are advocated for rice agriculture due to less net GWPs and GHGIs, while another ISSM need more work with increased net GWPs.
The impact of management practices on the net global warming potential (GWP) and greenhouse gas intensity (GHGI) of rice cropping systems is not well documented. A field experiment was established in 2009 to gain insight into the net ecosystem carbon budget and the net GWP and GHGI on the crop seasonal scale over two cycles of rice–wheat rotations. With the local farmer's practices (FP) as the control, three integrated soil–crop system management (ISSM) practices at different nitrogen (N) application rates were established – ISSM-N1, ISSM-N2 and ISSM-N3 – for improvement of rice yield and agronomic nitrogen use efficiency (NUE). Compared with the FP, the rice yields significantly increased by 8.2%, 18% and 31%, while the agronomic NUE increased by 68%, 74% and 99% for ISSM-N1, ISSM-N2 and ISSM-N3, respectively. Within the three ISSM practices averaged over the two cycles, the soil organic carbon sequestration potentials, CH4 and N2O emissions were estimated to be 0.089–0.67tCha−1yr−1, 166–288kgCH4Cha−1yr−1 and 4.27–5.47kgN2ONha−1yr−1, respectively. Compared to the net GWPs (8.36tCO2eqha−1yr−1) and GHGI (0.58kgCO2eqkg−1 grain) from the FP, the ISSM-N1 and ISSM-N2 reduced both the net GWPs and GHGIs to some extent, indicating that GHG mitigation can be simultaneously achieved with improved food production and NUE. Although it produced similar GHGIs, the ISSM-N3 increased the net GWPs by 16% compared to the FP, indicating that more research is required on ISSMs for mitigating GHGs to further increase the grain yield and NUE in rice agriculture.
Interface charges are easy to accumulate between two different dielectrics with various characteristics, which may cause accelerated degradation of insulation systems. Ethylene-propylene-diene ...terpolymer (EPDM) is used mainly for HVDC cable joint, which is the most vulnerable part of the cable system because of the interface. Particles with nonlinear conductivity can be doped into the polymer matrix to modify the interface charge behaviors through altering the conductivity under combined stresses. In this paper, silicon carbide (SiC) particles were dispersed into EPDM with 0, 10, 30 and 50 wt% respectively. The space charge behaviors at the interface between LDPE and EPDM filled with SiC particles was measured under 15 and 30 kV/mm. Besides, dielectric constant, dc conduction and trap distribution were introduced to elaborate the suppression mechanism with SiC doping. The SEM results show that the particles are well distributed in the EPDM. The permittivity increases with the fillgrade and the dc conductivity shows an obvious nonlinear trend under various electrical fields. SiC doping can effectively suppress the interface charge accumulation under different stresses. The suppression mechanism is attributed to the nonlinear conductivity and more shallow traps of EPDM/SiC composite. As a consequence, the approximate SiC doped EPDM can availably suppress the interface charge accumulation and offers a possible method for the improvement of cable accessory performance.
Field tracer experiments were conducted to examine tracer transport properties in a fracture‐dominated crystalline rock mass at the Grimsel Test Site, Switzerland. In the experiments reported here, ...both the DNA nanotracers and solute dye tracers were simultaneously injected. We compare the transport of DNA nanotracers to solute dye tracers by performing temporal moment analysis on the recorded tracer breakthrough curves and estimate the swept volumes and flow geometries. The DNA nanotracers, approximately 166 nm in diameter, are observed to travel at a higher average velocity than the solutes but with lower mass recoveries, lower swept volumes, and less dispersion. Moreover, size exclusion and potentially, particle density effects are observed during the transport of the DNA nanotracers. Compared to solute tracers, the greatest strength of DNA nanotracers is the demonstrated zero signal interference of background noise during repeat or multitracer tests. This work provides encouraging results in advancing the use of DNA nanotracers in hydrogeological applications, for example, during contaminant transport investigations or geothermal reservoir characterization.
Key Points
DNA‐labeled nanotracer transport is evaluated on a first field demonstration in crystalline rock
Heterogeneity of flow field and size exclusion strongly influences DNA nanotracer response curves
DNA nanotracer is highly suitable for tracer tomography and tracing particulate‐bound contaminant transport
Abstract The pathogenesis of Parkinson's disease is characterized by progressive degeneration of dopaminergic neurons in substantia nigra (SNpc). FLZ, a novel synthetic squamosamide derivative from a ...Chinese herb, has been shown to have neuroprotective effects in experimental Parkinson's disease (PD) models. However, it is still unclear whether FLZ protects against PD through regulating the function of dopaminergic system. In this study, we carried out a set of in vitro and in vivo experiments to address these questions. Oral administration of FLZ significantly improved motor dysfunction of mice challenged by MPTP. The beneficial effects of FLZ on motor behavior attributed to the elevation of dopamine level in striatum, tyrosine hydroxylase (TH)-positive cells, and TH activity in the middle brain of mouse. Mechanism study showed that treatment of FLZ increased the phosphorylation of activating protein kinase B (Akt) and mammalian target of rapamycin (mTOR). Using LY294002 to block phosphoinositide 3-kinases (PI3K)/Akt signaling pathway prevented the phosphorylation of mTOR and attenuated the neuroprotection of FLZ in MN9D cells challenged by MPP+ . In addition, FLZ reduced the expression of RTP801, an important protein in PD, in mice and cells intoxicated by MPTP/MPP+ . Taken together, these results revealed a novel role that FLZ elevated TH expression and activity in dopaminergic neuron through activation of Akt/mTOR survival pathway and inhibition of RTP801 in MPTP/MPP+ -induced PD models. The data also provided evidence that FLZ had potent neuroprotecive effects and might become a new promising anti-PD drug.
Although the pullout capacity of plate anchors in clay has been studied extensively, the results considering the coupling effects of anchor inclination, clay non-homogeneity and self-weight are ...relatively rare. In the present paper, finite-element analyses are carried out to investigate the coupling effects of these factors on the pullout capacity of strip plate anchors in clay. The numerical solutions are presented in the familiar form of pullout capacity factors based on various anchor embedment depth, clay strength profile and clay self weight, and are also compared with existing numerical and empirical solutions. A design procedure based on the data-fitting equations of the present finite-element solutions is also presented for the convenience of design engineers.
With the presence of highly permeable pathways, such as faults and fractures zones, coal seam gases, particularly CO2, could potentially migrate upwardly from the coal deposits into the shallow ...subsurface and then to the atmosphere. This letter reports soil gas mapping and gamma ray survey in coal basin of Hunter River Valley, Australia. The survey facilitated the delineation of fault structures across the sampling regions, where the identified faults were confirmed by an independent drilling investigation later. Furthermore, to evaluate the gas emission fluxes from coalbeds through fault zones, the measured CO2 concentrations, coupled with an inverse modeling, enable the estimation of the width of the fault zone and associated CO2 emission flux in the range of 2 × 10−5–6 × 10−5 mol/m2/s at the study site. Our new approach provides a way to determine emissions of gases from deep formations, which may contribute considerably to the greenhouse gases cycles.
Plain Language Summary
Australia is one of the world's biggest coal exporters. Total fugitive emissions in Australia have increased in line with the expanding coal and gas production sector. CO2 emissions may occur during the operation and following the closure of coal mines and coal seam gas fields. Leakage of gases to the atmosphere may be induced through fractured gas‐bearing strata and open vents. Hence, the emissions of CO2 from coal basins should be counted toward the overall emissions budget. The new approach proposed by the current study can be applied to estimate emissions of CO2 from fracture and fault zones, which have not been well quantified and yet can be potentially an important source of greenhouse gases contributing to the overall budget at a global scale. So this work could provide a better track progress on international emission commitments.
Key Points
Field assessments on gas emission fluxes from coal basin at fault zones in the Hunter River Valley, Australia
Soil gas mapping and gamma ray survey delineated several fault structures across the sampling transects, which were later confirmed by an independent borehole drilling investigation
An inverse modeling is applied to determine the width of the fault zone and its CO2 emission flux at the study site
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