Within the parameter space of the equation of state (EOS) of dense neutron-rich matter limited by existing constraints mainly from terrestrial nuclear experiments, we investigate how the neutron star ...maximum mass Mmax > 2.01 0.04 M , radius 10.62 km < R1.4 < 12.83 km and tidal deformability Λ1.4 ≤ 800 of canonical neutron stars together constrain the EOS of dense neutron-rich nucleonic matter. While the 3D parameter space of Ksym (curvature of nuclear symmetry energy), Jsym, and J0 (skewness of the symmetry energy and EOS of symmetric nuclear matter, respectively) is narrowed down significantly by the observational constraints, more data are needed to pin down the individual values of Ksym, Jsym, and J0. The J0 largely controls the maximum mass of neutron stars. While the EOS with J0 = 0 is sufficiently stiff to support neutron stars as massive as 2.37 M , supporting the hypothetical ones as massive as 2.74 M (composite mass of GW170817) requires J0 to be larger than its currently known maximum value of about 400 MeV and beyond the causality limit. The upper limit on the tidal deformability of Λ1.4 = 800 from the recent observation of GW170817 is found to provide upper limits on some EOS parameters consistent with but far less restrictive than the existing constraints of other observables studied.
The radius R1.4 of neutron stars (NSs) with a mass of 1.4 M has been extracted consistently in many recent studies in the literature. Using representative R1.4 data, we infer high-density nuclear ...symmetry energy Esym( ) and the associated nucleon specific energy E0( ) in symmetric nuclear matter (SNM) within a Bayesian statistical approach using an explicitly isospin-dependent parametric equation of state (EOS) for nucleonic matter. We found the following. (1) The available astrophysical data can already significantly improve our current knowledge about the EOS in the density range of 0 − 2.5 0. In particular, the symmetry energy at twice the saturation density 0 of nuclear matter is determined to be Esym(2 0)= MeV at a 68% confidence level. (2) A precise measurement of R1.4 alone with a 4% 1 statistical error but no systematic error will not greatly improve the constraints on the EOS of dense neutron-rich nucleonic matter compared to what we extracted from using the available radius data. (3) The R1.4 radius data and other general conditions, such as the observed NS maximum mass and causality condition, introduce strong correlations for the high-order EOS parameters. Consequently, the high-density behavior of Esym( ) inferred depends strongly on how the high-density SNM EOS E0( ) is parameterized, and vice versa. (4) The value of the observed maximum NS mass and whether it is used as a sharp cutoff for the minimum maximum mass or through a Gaussian distribution significantly affects the lower boundaries of both E0( ) and Esym( ) only at densities higher than about 2.5 0.
Verticillium dahliae isolates are most virulent on the host from which they were originally isolated. Mechanisms underlying these dominant host adaptations are currently unknown. We sequenced the ...genome of V. dahliae Vd991, which is highly virulent on its original host, cotton, and performed comparisons with the reference genomes of JR2 (from tomato) and VdLs.17 (from lettuce).
Pathogenicity-related factor prediction, orthology and multigene family classification, transcriptome analyses, phylogenetic analyses, and pathogenicity experiments were performed.
The Vd991 genome harbored several exclusive, lineage-specific (LS) genes within LS regions (LSRs). Deletion mutants of the seven genes within one LSR (G-LSR2) in Vd991 were less virulent only on cotton. Integration of G-LSR2 genes individually into JR2 and VdLs.17 resulted in significantly enhanced virulence on cotton but did not affect virulence on tomato or lettuce. Transcription levels of the seven LS genes in Vd991 were higher during the early stages of cotton infection, as compared with other hosts. Phylogenetic analyses suggested that G-LSR2 was acquired from Fusarium oxysporum f. sp. vasinfectum through horizontal gene transfer.
Our results provide evidence that horizontal gene transfer from Fusarium to Vd991 contributed significantly to its adaptation to cotton and may represent a significant mechanism in the evolution of an asexual plant pathogen.
According to the Hugenholtz–Van Hove theorem, nuclear symmetry energy Esym(ρ) and its slope L(ρ) at an arbitrary density ρ are determined by the nucleon isovector (symmetry) potential Usym(ρ,k) and ...its momentum dependence ∂Usym∂k. The latter determines uniquely the neutron–proton effective k-mass splitting mn−p⁎(ρ,δ)≡(mn⁎−mp⁎)/m in neutron-rich nucleonic matter of isospin asymmetry δ. Using currently available constraints on the Esym(ρ0) and L(ρ0) at normal density ρ0 of nuclear matter from 28 recent analyses of various terrestrial nuclear laboratory experiments and astrophysical observations, we try to infer the corresponding neutron–proton effective k-mass splitting mn−p⁎(ρ0,δ). While the mean values of the mn−p⁎(ρ0,δ) obtained from most of the studies are remarkably consistent with each other and scatter very closely around an empirical value of mn−p⁎(ρ0,δ)=0.27⋅δ, it is currently not possible to scientifically state surely that the mn−p⁎(ρ0,δ) is positive within the present knowledge of the uncertainties. Quantifying, better understanding and then further reducing the uncertainties using modern statistical and computational techniques in extracting the Esym(ρ0) and L(ρ0) from analyzing the experimental data are much needed.
High‐energy‐density polymer nanocomposites with high‐dielectric‐constant ceramic nanoparticles as the reinforcement exhibit great potential for energy storage applications in modern electronic and ...electrical systems. However, the decline of breakdown strength by high loading of ceramic nanoparticles hinders this composite approach from sustainable promotion of energy density. In this work, an approach is proposed and demonstrated by constructing gradient distribution of the spherical ceramic nanoparticles in the polymer matrix. These gradient‐structured nanocomposites possess remarkably improved mechanical and electrical behaviors, which give rise to ultrahigh breakdown strength and much‐promoted energy density. Moreover, this enhancement effect can be further enlarged via increasing the grades number of gradient structures. This work provides an effective strategy for developing flexible high‐energy‐density polymer/ceramic nanocomposites for dielectric and energy storage applications.
Gradient distribution of ceramic nanoparticles in polymer films is constructed through a layer‐by‐layer process, which greatly improves the electrical and mechanical properties of polymer nanocomposites, resulting in ultrahigh breakdown strength and energy density. This work provides an effective strategy for developing flexible high‐energy‐density polymer/ceramic nanocomposites for dielectric and energy storage applications.
Academic geographical mobility is considered to be critical to academic excellence, but it is a gendered terrain. This study seeks to examine the career progression of Chinese women academics, as ...shaped by gender norms, regarding academic geographical (im)mobility throughout their doctoral education, in retrospect.
To address this issue, driven by the Butlerian theoretical concept of "a stylized repetition of acts," the present study analyzed the qualitative data from semi-structured interviews with seven Chinese women academics to investigate their academic geographical mobility decisions throughout their doctoral education based on contested discourses of traditional Chinese culture and the advantages of academic geographical mobility for their career advancement.
This study determined that, shaped by gender norms, stylized geographical academic (im)mobility for these Chinese female doctoral students operate in the condition of gender- norms maintenance to make them recognizable and understandable in social and institutional culture. However, it may have a negative impact on their future academic career progression.
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By numerically inverting the Tolman-Oppenheimer-Volkov (TOV) equation using an explicitly isospin-dependent parametric Equation of State (EOS) of dense neutron-rich nucleonic matter, a restricted ...EOS parameter space is established using observational constraints on the radius, maximum mass, tidal deformability and causality condition of neutron stars (NSs). The constraining band obtained for the pressure as a function of energy (baryon) density is in good agreement with that extracted recently by the LIGO+Virgo Collaborations from their improved analyses of the NS tidal deformability in GW170817. Rather robust upper and lower boundaries on nuclear symmetry energies are extracted from the observational constraints up to about twice the saturation density
ρ
0
of nuclear matter. More quantitatively, the symmetry energy at
2
ρ
0
is constrained to
E
sym
(
2
ρ
0
)
=
46
.
9
±
10
.
1
MeV excluding many existing theoretical predictions scattered between
E
sym
(
2
ρ
0
)
=
15
and 100 MeV. Moreover, by studying variations of the causality surface where the speed of sound equals that of light at central densities of the most massive neutron stars within the restricted EOS parameter space, the absolutely maximum mass of neutron stars is found to be 2.40
M
⊙
approximately independent of the EOSs used. This limiting mass is consistent with findings of several recent analyses and numerical general relativity simulations about the maximum mass of the possible super-massive remanent produced in the immediate aftermath of GW170817. deformability
Using as references the posterior probability distribution functions of the equation of state (EOS) parameters inferred from the radii of canonical neutron stars (NSs) reported by the LIGO/VIRGO and ...NICER Collaborations based on their observations of GW170817 and PSR J0030+0451, we investigate how future radius measurements of more massive NSs will improve our current knowledge about the EOS of superdense neutron-rich nuclear matter, especially its symmetry energy term. Within the Bayesian statistical approach using an explicitly isospin-dependent parametric EOS for the core of NSs, we infer the EOS parameters of superdense neutron-rich nuclear matter from three sets of imagined mass-radius correlation data representing typical predictions by various nuclear many-body theories, that is, the radius stays the same, decreases, or increases with increasing NS mass within 15% between 1.4 and 2.0 M . The corresponding NS average density increases quickly or slowly or slightly decreases as the NS mass increases from 1.4 to 2.0 M . While the EOSs of symmetric nuclear matter (SNM) inferred from the three data sets are approximately the same, the corresponding symmetry energies above about twice the saturation density of nuclear matter are very different, indicating that the radii of massive NSs carry important information about the high-density behavior of nuclear symmetry energy with little influence from the remaining uncertainties of the SNM EOS at suprasaturation densities.
Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has ...been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.
Background: The nuclear symmetry energy Esym(ρ) encodes information about the energy necessary to make nuclear systems more neutron-rich. While its slope parameter L at the saturation density ρ0 of ...nuclear matter has been relatively well constrained by recent astrophysical observations and terrestrial nuclear experiments, its curvature Ksym characterizing the Esym(ρ) around 2ρ0 remains largely unconstrained. Over 520 calculations for Esym(ρ) using various nuclear theories and interactions in the literature have predicted several significantly different Ksym–L correlations. Purpose: If a unique Ksym–L correlation of Esym(ρ) can be firmly established, it will enable us to progressively better constrain the high-density behavior of Esym(ρ) using the available constraints on its slope parameter L. Here, we investigate if and by how much the different Ksym–L correlations may affect neutron star observables. Method: A meta-model of nuclear Equation of States (EOSs) with three representative Ksym–L correlation functions is used to generate multiple EOSs for neutron stars. We then examine effects of the Ksym–L correlation on the crust-core transition density and pressure as well as the radius and tidal deformation of canonical neutron stars. Results: The Ksym–L correlation affects significantly both the crust-core transition density and pressure. It also has strong imprints on the radius and tidal deformability of canonical neutron stars especially at small L values. The available data from LIGO/VIRGO and NICER set some useful limits for the slope L but can not distinguish the three representative Ksym–L correlations considered.
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