Understanding the physiological mechanisms of biomass accumulation and partitioning in the grain, and the nitrogen (N) uptake associated with different plant densities and N management strategies, is ...essential for achieving both high yield and N use efficiency (NUE) in maize plants. A field experiment was conducted in 2013 and 2014, using five rates of N application and three plant densities (6·0, 7·5 and 9·0 plants/m2) in Quzhou County on the North China Plain (NCP). The objective was to evaluate whether higher plant density can produce more biomass allocated to the grain to achieve higher grain yield and to determine the optimal N management strategies for different plant densities. The highest grain yield and NUE were achieved in the 7·5 plants/m2 treatment; both the sub-optimal (6·0 plants/m2) and supra-optimal (9·0 plants/m2) plant densities resulted in diminished yield and NUE. Compared to 6·0 plants/m2, the 7·5 plants/m2 treatment displayed higher biomass accumulation during the grain-filling period and also exhibited more biomass allocated to kernels with similar total biomass accumulation compared with the 9·0 plants/m2 treatment, which contributed to its higher grain yield. The N uptake in the 7·5 plants/m2 treatment was similar to that in the 9·0 plants/m2 treatment up to pre-silking. However, the post-silking N uptake of the 7·5 plants/m2 treatment was 66·4 kg/ha, which was 29·1% higher than that of the 9·0 plants/m2 treatment. Furthermore, the highest maize grain yield was achieved in the 0·7 × optimal N rate (ONR × 0·7), ONR and ONR × 1·3 treatments for 6·0, 7·5 and 9·0 plants/m2, respectively, which suggests that different N management strategies are needed for different plant densities. In conclusion, selecting a planting density of 7·5 plants/m2 with an in-season root zone N management is a potentially effective strategy for achieving high grain yield and high NUE for maize production on the NCP.
Abstract
We report the energy-resolved broadband timing analysis of the black hole X-ray transient MAXI J1631-479 during its 2019 outburst from February 11 to April 9, using data from the ...Insight−Hard X-ray Modulation Telescope (Insight-HXMT), which caught the source from its hard-intermediate state to the soft state. Thanks to the large effective area of Insight-HXMT at high energies, we are able to present the energy dependence of fast variability up to ∼100 keV. Type-C quasi-periodic oscillations (QPOs) with a frequency varying between 4.9 and 6.5 Hz are observed in the 1–100 keV energy band. While the QPO fractional rms increases with photon energy from 1 keV to ∼10 keV and remains more or less constant from ∼10 keV to ∼100 keV, the rms of the flat-top noise first increases from 1 keV to ∼8 keV and then drops to less than 0.1% above ∼30 keV. We suggest that the disappearance of the broadband variability above 30 keV could be caused by the nonthermal acceleration in the Comptonizing plasma. At the same time, the QPOs could be produced by the precession of either a small-scale jet or a hot inner flow model.
Grassland soil organic carbon (SOC) is sensitive to anthropogenic activities. Increased anthropogenic disturbance related to overgrazing has led to widespread alpine grassland degradation on the ...Tibetan Plateau. The degraded grasslands are considered to have great potential for carbon sequestration after adoption of improved management practices. Here, we calibrated and employed the Century model to investigate the effects of overgrazing and improved managements on the SOC dynamics in alpine meadows. We calibrated the Century model against plant productivity at the Haibei Research Station. SOC stocks for validation were obtained in 2009–2010 from degraded alpine meadows in two communes. We found that Century model can successfully capture grassland SOC changes. Overall, our simulation suggests that degraded alpine meadow SOC significantly increased with the advent of restoration management from 2011 to 2030. Carbon sequestration rates ranged between 0.04 Mg C ha−1 yr−1 in lightly degraded winter grazing grasslands and 2.0 Mg C ha−1 yr−1 in moderately degraded summer grazing grasslands. Our modelling work also predicts that improve management in degraded Tibetan grasslands will contribute to an annual carbon sink of 0.022–0.059 Pg C yr−1. These results imply that restoration of degraded grasslands in the Tibetan Plateau has great potential for soil carbon sequestration to mitigate greenhouse gases.
Abstract
We present a spectral study of the black hole candidate MAXI J1348−630 during its 2019 outburst, based on monitoring observations with Insight-HXMT and Swift. Throughout the outburst, the ...spectra are well fitted with power-law plus disk-blackbody components. In the soft-intermediate and soft states, we observed the canonical relation
L
∝
T
in
4
between disk luminosity
L
and peak color temperature
T
in
, with a constant inner radius
R
in
(traditionally identified with the innermost stable circular orbit). At other stages of the outburst cycle, the behavior is more unusual, inconsistent with the canonical outburst evolution of black hole transients. In particular, during the hard rise, the apparent inner radius is smaller than in the soft state (and increasing), and the peak color temperature is higher (and decreasing). This anomalous behavior is found even when we model the spectra with self-consistent Comptonization models, which take into account the upscattering of photons from the disk component into the power-law component. To explain both anomalous trends at the same time, we suggest that the hardening factor for the inner-disk emission was larger than the canonical value of ≈1.7 at the beginning of the outburst. A more physical trend of radii and temperature evolution requires a hardening factor evolving from ≈3.5 at the beginning of the hard state to ≈1.7 in the hard-intermediate state. This could be evidence that the inner disk was in the process of condensing from the hot, optically thin medium and had not yet reached a sufficiently high optical depth for its emission spectrum to be described by the standard optically thick disk solution.
To explore the value of radiomics for predicting the expression of programmed death ligand 1 (PD-L1) in non-small-cell lung cancer (NSCLC) based on multiparameter spectral computed tomography (CT) ...images.
A total of 220 patients with NSCLC were enrolled retrospectively and divided into the training (n=176) and testing (n=44) cohorts. The radiomics features were extracted from the conventional CT images, mono-energy 40 keV images, iodine density (ID) maps, Z-effective maps, and electron density maps. The logistic regression (LR) and support vector machine (SVM) algorithms were employed to build models based on radiomics signatures. The prediction abilities were qualified by the area under the curve (AUC) obtained from the receiver operating characteristic (ROC) curve. Internal validation was performed on the independent testing dataset.
The combined model for PD-L1 ≥1%, which consisted of the radiomics score (rad-score; p<0.0001), white blood cell (WBC; p=0.027) counts, and air bronchogram (p=0.003), reached the highest performance with the AUCs of 0.873 and 0.917 in the training and testing dataset, respectively, which was better than the radiomics model with the AUCs of 0.842 and 0.886. The combined model for PD-L1 ≥50%, which consisted of rad-score (p<0.0001) and WBC counts (p=0.027), achieved the highest performance in the training and testing dataset with AUCs of 0.932 and 0.903, respectively, which was better than the radiomics model with AUCs of 0.920 and 0.892, respectively.
The radiomics model based on the multiparameter images of spectral CT can predict the expression level of PD-L1 in NSCLC. The combined model can obtain higher prediction efficiency and serves as a promising method for immunotherapy selection.
•Immune checkpoint inhibitors (e.g. PD-L1 inhibitors) are used to treat NSCLC.•Radiomics is a novel and non-invasive radiological analysis technique.•We used radiomics to build a PD-L1 expression prediction model for NSCLC.•The model combined demographic, visual CT, and DLCT parameters.•The model had good prediction efficiency (AUCs >0.8).
Tensile properties of a single-crystal Co–Al–W–Ni–Cr–Ta alloy with low tungsten content have been studied within the temperatures ranging from 20 to 1000°C at a constant strain rate of 1.0×10−4s−1. ...The alloy exhibits comparable yield strength with that of Co–Al–W-base alloys containing more tungsten. From 600°C to 800°C, a yield strength anomaly is observed, probably due to the cross-slip of superdislocations from the octahedral plane to the cube plane. TEM analysis demonstrates that stacking faults (SFs) appear both in γ channels and γ′ precipitates in a wide temperature range. These SFs are responsible for the obvious strain hardening observed in stress–strain curves. From room temperature to 900°C, the deformation is dominated by dislocations shearing γ′ particles. At 1000°C, the main deformation mechanism is dislocations bypassing γ′ particles.
We study the evolution of the temporal properties of MAXI J1820+070 during the 2018 outburst in its hard state from MJD 58,190 to 58,289 with Insight-HXMT in a broad energy band 1-150 keV. We find ...different behaviors of the hardness ratio, the fractional rms and time lag before and after MJD 58,257, suggesting a transition occurred around this point. The observed time lags between the soft photons in the 1-5 keV band and the hard photons in higher energy bands, up to 150 keV, are frequency-dependent: the time lags in the low-frequency range, 2-10 mHz, are both soft and hard lags with a timescale of dozens of seconds but without a clear trend along the outburst; the time lags in the high-frequency range, 1-10 Hz, are only hard lags with a timescale of tens of milliseconds; they first increase until around MJD 58,257 and decrease after this date. The high-frequency time lags are significantly correlated to the photon index derived from the fit to the quasi-simultaneous NICER spectrum in the 1-10 keV band. This result is qualitatively consistent with a model in which the high-frequency time lags are produced by Comptonization in a jet.
•A high-performance boom control system was designed base on DSP microprocessor.•The developed control software includes three control modes.•A signal processing method was proposed to improve the ...reliability of active suspension.•The effectiveness of the control system is verified by the bench test and field test.
When sprayer is in field operation, the entire boom needs to maintain an ideal height with the ground or crop canopy, which can maximize the quality of pesticide application and minimize the negative effect of application on the environment. This paper introduces a design of high-performance boom control system for pendulum active suspension. The system consists of a human machine interface (HMI) and a real-time controller based on DSP microprocessor. Three different control modes, roll control mode, wing height control mode and hybrid control mode, have been developed to meet the needs of different operators. Considering the irregularity of field ground and the inconsistency of crop canopy height, a signal processing and data fusion algorithm was designed. The DSP-based control system is assembled on a 28 m boom with the pendulum suspension, and the step response and sinusoidal tracking tests of the active boom control system are carried out by using a six-degree-of-freedom motion platform. Firstly, the influence of different control parameters on the control performance was tested, and then three different control modes of the control system are tested and compared, for a given 0.1 Hz sine/cosine test signal, the accuracy of boom roll control mode was 90.27%, the accuracy of wing height control mode was 93.0%. The step response test of hybrid control system was carried out, the height difference between the left wing and the right wing decreases to less than 10% of the initial disturbance within 2.35 s, while the roll control system needs 5.71 s, the response time was shortened by 58.84%. Field test results show that under the roll control system, the maximum roll angle of the boom was only 0.841°, and the maximum roll angle of the chassis was 4.041°. The results show that the DSP-based control system can effectively control the movement of the boom and meet the requirements of field use, also the effectiveness of signal processing algorithm and control method has also been verified.
Corona cooling was detected previously from stacking a series of short type I bursts that occurred during the low/hard state of an atoll outburst. Type I bursts are hence regarded as sharp probes ...used to better our understanding of the basic properties of the corona. The first Chinese X-ray satellite, Insight-HXMT, has a large detection area at hard X-rays that provides a unique opportunity to move further in this research field. We report the first detection of corona cooling by Insight-HXMT from a single short type I burst appearing during the flare of 4U 1636-536. This type I X-ray burst has a duration of ∼13 s and hard X-ray shortage is detected with a significance of 6.2 in 40-70 keV. A cross-correlation analysis between the light curves of the soft and hard X-ray band shows that the corona shortage lags the burst emission by 1.6 1.2 s. These results are consistent with those derived previously from stacking a large amount of bursts detected by RXTE/PCA within a series of flares of 4U 1636-536. Moreover, the broad bandwidth of Insight-HXMT also allows, for the first time, one to infer the burst influence upon the continuum spectrum via performing the spectral fitting of the burst, which points to the finding that hard X-ray shortage appears at around 40 keV in the continuum spectrum. These results suggest that the evolution of the corona, along with the outburst/flare of NS XRB, may be traced via analyzing a series of embedded type I bursts using Insight-HXMT.
ABSTRACT
We studied the 2018 outburst of the black hole transient H 1743 − 322 with a series of Insight-HXMT, NICER, and NuSTAR observations, covering the 1–120 keV band. With our broad-band X-ray ...spectral modelling, we confirm that the source remained in the low/hard state throughout the month-long outburst, although it became marginally softer at peak flux. We detected Type-C quasi-periodic oscillations (QPOs) and followed the evolution of their properties. The QPO frequency increased from ∼0.1 to ∼0.4 Hz during the rising phase of the outburst and decreased again in the decline. Continuum X-ray flux, power-law photon index, QPO frequency, and QPO root-mean-square amplitude were positively correlated. The QPO amplitude was slightly higher in the soft X-ray band (typical values of 12–16 per cent, compared with 8–10 per cent in the hard band). Our spectral-timing results shed light on the initial rising phase in the low/hard state, which has rarely been monitored with such high cadence, time resolution, and broad-band coverage. Combining spectral and timing properties, we find that ‘failed’ (hard state only) and ‘successful’ outbursts follow the same initial evolutionary track, although the former class of outburst never reaches the threshold for a transition to softer (thermally dominated) accretion regimes.
PDF
