ABSTRACT
Water balance is crucial for the growth and flowering of plants. However, the mechanisms by which flowers maintain water balance are poorly understood across different angiosperm branches.
...Here, we investigated 29 floral hydraulic and economic traits in 24 species from ANA grade, magnoliids, monocots, and eudicots. Our main objective was to compare differences in flower water use strategies between basal angiosperms (ANA grade and magnoliids) and derived group (monocots and eudicots).
We found that basal angiosperms had richer petal stomatal density, higher pedicel hydraulic diameter, and flower mass per area, but lower pedicel vessel wall reinforcement and epidermal cell thickness compared to monocots and eudicots. We also observed significant trade‐offs and coordination among different floral traits. Floral traits associated with reproduction, such as floral longevity and size, were strongly linked with physiological and anatomical traits.
Our results systematically reveal the variation in flower economic and hydraulic traits from different angiosperm branches, deepening understanding of flower water use strategies among these plant taxa. We conclude that basal angiosperms maintain water balance with high water supply, whereas monocots and eudicots maintain a more conservative water balance.
The flowers of monocots and eudicots tend to use water more conservatively than basal angiosperms, and their physiological and anatomical properties are strongly linked to traits associated with reproduction.
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.
Topological semimetals are characterized by symmetry-protected band crossings, which can be preserved in different dimensions in momentum space, forming zero-dimensional nodal points, one-dimensional ...nodal lines, or even two-dimensional nodal surfaces. Materials harboring nodal points and nodal lines have been experimentally verified, whereas experimental evidence of nodal surfaces is still lacking. Here, using angle-resolved photoemission spectroscopy (ARPES), we reveal the coexistence of Dirac nodal surfaces and nodal lines in the bulk electronic structures of ZrSiS. As compared with previous ARPES studies on ZrSiS, we obtained pure bulk states, which enable us to extract unambiguously intrinsic information of the bulk nodal surfaces and nodal lines. Our results show that the nodal lines are the only feature near the Fermi level and constitute the whole Fermi surfaces. We not only prove that the low-energy quasiparticles in ZrSiS are contributed entirely by Dirac fermions but also experimentally realize the nodal surface in topological semimetals.
ABSTRACT
Based on Insight-HXMT data, we report on the pulse fraction evolution during the 2017–2018 outburst of the newly discovered first Galactic ultraluminous X-ray (ULX) source Swift ...J0243.6+6124. The pulse fractions of 19 observation pairs selected in the rising and fading phases with similar luminosity are investigated. The results show a general trend of the pulse fraction increasing with luminosity and energy at supercritical luminosity. However, the relative strength of the pulsation between each pair evolves strongly with luminosity. The pulse fraction in the rising phase is larger at luminosity below 7.71 × 1038 erg s−1, but smaller at above. A transition luminosity is found to be energy independent. Such a phenomenon is first confirmed by Insight-HXMT observations and we speculate that it may have relation with the radiation-pressure-dominated accretion disc.
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.
Topological Dirac and Weyl semimetals not only host quasiparticles analogous to the elementary fermionic particles in high-energy physics, but also have a non-trivial band topology manifested by ...gapless surface states, which induce exotic surface Fermi arcs1,2. Recent advances suggest new types of topological semimetal, in which spatial symmetries protect gapless electronic excitations without high-energy analogues3–11. Here, using angle-resolved photoemission spectroscopy, we observe triply degenerate nodal points near the Fermi level of tungsten carbide with space group \P\bar{6}m2\ (no. 187), in which the low-energy quasiparticles are described as three-component fermions distinct from Dirac and Weyl fermions. We further observe topological surface states, whose constant-energy contours constitute pairs of ‘Fermi arcs’ connecting to the surface projections of the triply degenerate nodal points, proving the non-trivial topology of the newly identified semimetal state.
Abstract
We present a study of timing properties of the accreting pulsar 2S 1417-624 observed during its 2018 outburst, based on Swift/BAT, Fermi/GBM, Insight-HXMT and NICER observations. We report a ...dramatic change of the pulse profiles with luminosity. The morphology of the profile in the range 0.2-10.0 keV switches from double to triple peaks at ∼2.5 $\rm \times 10^{37}{\it D}_{10}^2\ erg\ s^{-1}$ and from triple to quadruple peaks at ∼7 $\rm \times 10^{37}{\it D}_{10}^2\ erg\ s^{-1}$. The profile at high energies (25-100 keV) shows significant evolutions as well. We explain this phenomenon according to existing theoretical models. We argue that the first change is related to the transition from the sub to the super-critical accretion regime, while the second to the transition of the accretion disc from the gas-dominated to the radiation pressure-dominated state. Considering the spin-up as well due to the accretion torque, this interpretation allows to estimate the magnetic field self-consistently at ∼7 × 1012 G.
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