The density dependence of nuclear symmetry energy is among the most uncertain parts of the Equation of State (EOS) of dense neutron-rich nuclear matter. It is currently poorly known especially at ...suprasaturation densities partially because of our poor knowledge about isovector nuclear interactions at short distances. Because of its broad impacts on many interesting issues, pinning down the density dependence of nuclear symmetry energy has been a longstanding and shared goal of both astrophysics and nuclear physics. New observational data of neutron stars including their masses, radii, and tidal deformations since GW170817 have helped improve our knowledge about nuclear symmetry energy, especially at high densities. Based on various model analyses of these new data by many people in the nuclear astrophysics community, while our brief review might be incomplete and biased unintentionally, we learned in particular the following: (1) The slope parameter L of nuclear symmetry energy at saturation density ρ0 of nuclear matter from 24 new analyses of neutron star observables was about L≈57.7±19 MeV at a 68% confidence level, consistent with its fiducial value from surveys of over 50 earlier analyses of both terrestrial and astrophysical data within error bars. (2) The curvature Ksym of nuclear symmetry energy at ρ0 from 16 new analyses of neutron star observables was about Ksym≈−107±88 MeV at a 68% confidence level, in very good agreement with the systematics of earlier analyses. (3) The magnitude of nuclear symmetry energy at 2ρ0, i.e., Esym(2ρ0)≈51±13 MeV at a 68% confidence level, was extracted from nine new analyses of neutron star observables, consistent with the results from earlier analyses of heavy-ion reactions and the latest predictions of the state-of-the-art nuclear many-body theories. (4) While the available data from canonical neutron stars did not provide tight constraints on nuclear symmetry energy at densities above about 2ρ0, the lower radius boundary R2.01=12.2 km from NICER’s very recent observation of PSR J0740+6620 of mass 2.08±0.07M⊙ and radius R=12.2–16.3 km at a 68% confidence level set a tight lower limit for nuclear symmetry energy at densities above 2ρ0. (5) Bayesian inferences of nuclear symmetry energy using models encapsulating a first-order hadron–quark phase transition from observables of canonical neutron stars indicated that the phase transition shifted appreciably both L and Ksym to higher values, but with larger uncertainties compared to analyses assuming no such phase transition. (6) The high-density behavior of nuclear symmetry energy significantly affected the minimum frequency necessary to rotationally support GW190814’s secondary component of mass (2.50–2.67) M⊙ as the fastest and most massive pulsar discovered so far. Overall, thanks to the hard work of many people in the astrophysics and nuclear physics community, new data of neutron star observations since the discovery of GW170817 have significantly enriched our knowledge about the symmetry energy of dense neutron-rich nuclear matter.
Abstract
Given an Equation of State (EOS) for neutron star (NS) matter, there is a unique mass–radius sequence characterized by a maximum mass
M
NS
max
at radius
R
max
. We first show analytically ...that the
M
NS
max
and
R
max
scale linearly with two different combinations of the NS central pressure
P
c
and energy density
ε
c
, by dissecting perturbatively the dimensionless Tolman–Oppenheimer–Volkoff (TOV) equations governing NS internal variables. The scaling relations are then verified via 87 widely used and rather diverse phenomenological as well as 17 microscopic NS EOSs with/without considering hadron–quark phase transitions and hyperons, by solving numerically the original TOV equations. The EOS of the densest NS matter allowed before it collapses into a black hole is then obtained. Using the universal
M
NS
max
and
R
max
scalings and Neutron Star Interior Composition Explorer and XMM-Newton mass–radius observational data for PSR J0740+6620, a very narrow constraining band on the NS central EOS is extracted directly from the data for the first time, without using any specific input EOS model.
Direct asymmetric functionalization of the pyridyl C–H bond represents a longstanding challenge in organic chemistry. We herein describe the first enantioselective para-C–H activation of pyridines ...through the use of a Ni–Al bimetallic catalyst system and N-heterocyclic carbene (NHC) ligand for intermolecular hydroarylation of styrenes. The reaction procceds in high to excellent enantioselectivities (up to 98.5:1.5 er) and high site-selectivities for both styrene and pyridine components (up to >98:2). Consequently, a broad range of enantioenriched 1,1-diarylalkanes containing pyridine moieties could be prepared in a single step with 100% atom economy. Computational studies supported a mechanism involving a ligand-to-ligand H-transfer (LLHT) and reductive elimination sequence, with LLHT being the rate- and enantioselectivity-determining step. DFT studies indicate that the π–π stacking interaction between the NHC aryl fragment and trans-styrenes is critical for high reactivity and enantiocontrol.
We examine critically how tightly the density dependence of nuclear symmetry energy EsymeqT is constrained by the universal equation of state of the unitary Fermi gas EUGeqT considering currently ...known uncertainties of higher order parameters describing the density dependence of the equation of state of isospin asymmetric nuclear matter. We found that EUGeqT does provide a useful lower boundary for the EsymeqT . However, it does not tightly constrain the correlation between the magnitude Esymeq0T and slope L unless the curvature Ksym of the symmetry energy at saturation density q0 is more precisely known. The large uncertainty in the skewness parameters affects the Esymeq0T versus L correlation by the same almost as significantly as the uncertainty in Ksym.
Co‐based metal–organic frameworks (MOFs) as electrocatalysts for two‐electron oxygen reduction reaction (2e− ORR) are highly promising for H2O2 production, but suffer from the intrinsic ...activity‐selectivity trade‐off. Herein, we report a ZnCo bimetal‐triazole framework (ZnCo‐MTF) as high‐efficiency 2e− ORR electrocatalysts. The experimental and theoretical results demonstrate that the coordination between 1,2,3‐triazole and Co increases the antibonding‐orbital occupancy on the Co−N bond, promoting the activation of Co center. Besides, the adjacent Zn−Co sites on 1,2,3‐triazole enable an asymmetric “side‐on” adsorption mode of O2, favoring the reduction of O2 molecules and desorption of OOH* intermediate. By virtue of the unique ligand effect, the ZnCo‐MTF exhibits a 2e− ORR selectivity of ≈100 %, onset potential of 0.614 V and H2O2 production rate of 5.55 mol gcat−1 h−1, superior to the state‐of‐the‐art zeolite imidazole frameworks. Our work paves the way for the design of 2e− ORR electrocatalysts with desirable coordination and electronic structure.
A ZnCo bimetal‐triazole framework has been developed as high‐efficiency 2e− ORR electrocatalysts. The unique ligand effect of 1,2,3‐triazole optimizes the electronic structure of Co sites and enables an asymmetric “side‐on” adsorption mode of O2 molecule, resulting in an excellent 2e− ORR performance with a selectivity of ≈100 % and an H2O2 production rate of 5.55 mol gcat−1 h−1.
•We estimate China's energy consumption in the building sector from 2001 to 2013.•China's building energy consumption has increased about 7% annually since 2001.•Buildings’ life-cycle energy ...accounted for over 40% of China's total energy use.•Buildings’ operation energy occupied a predominant place in total life-cycle energy.•More focus should be drawn on the manufacturing stage and rural buildings of China.
Currently, there is no clear and unified understanding about the status quo of China's energy consumption in the building sector. In addition, a considerable underestimation of energy associated with buildings has impeded the effective implementation of measures to improve building energy efficiency of China. Thus, in this paper, we seek to identify the building sector's energy consumption of China by establishing an estimation model of building energy consumption from a life cycle perspective. On the basis of macro-level statistical data and relevant literature, we analyze the activities in each phase and calculate associated energy consumptions throughout buildings’ whole life cycle in China from 2001 to 2013. The results show that China's energy consumption associated with buildings has reached 1.66 billion tons coal equivalent in 2013, with a stable growth rate of 7% annually since 2001. Buildings’ life-cycle energy has approximately accounted for 43% of China's total energy consumption for recent three years (2011–2013). What's more, energy consumption in buildings’ operation phase has been salient, accounting for over 20% of China's total energy consumption. More focus should be drawn on energy efficiency in building material production phase and energy consumed in China's rural residential buildings as both have been significantly neglected.
The central speed of sound (SS) measures the stiffness of the equation of state (EOS) of superdense neutron star (NS) matter. Its variations with density and radial coordinate in NSs in conventional ...analyses often suffer from uncertainties of the specific nuclear EOS used. Using the central SS and NS mass/radius scaling obtained from solving perturbatively the scaled Tolman-Oppenheimer-Volkoff (TOV) equations, we study the variations of SS, trace anomaly and several closely related properties of NSs in an EOSmodel- independent manner. We find that the SS increases with the reduced central pressure Pˆc ≡ Pc=εc (scaled by the central energy density εc), and the conformal bound for SS tends to break down for NSs with masses higher than about 1.9M⊙. The ratio P=ε is upper bounded as P=ε ≲ 0.374 around the centers of stable NSs. We demonstrate that it is an intrinsic property of strong field gravity and is more relevant than the perturbative QCD bound on it. While a sharp phase transition at high densities characterized by a sudden vanishing of SS in cores of massive NSs are basically excluded, the probability for a continuous crossover signaled by a peaked radial profile of SS is found to be enhanced as Pˆc decreases, implying it likely happens near the centers of massive NSs. Moreover, a new and more stringent causality boundary as Rmax=km ≳ 4.73$M$$^{max}_{NS}$ =M⊙ þ 1.14 for the NS mass-radius curve is found to be excellently consistent with observational data on NS masses and radii. Here, new constraints on the ultimate energy density and pressure allowed in NSs before collapsing into black holes are obtained and compared with earlier predictions in the literature
Negative regulation of type I IFN signaling Arimoto, Kei‐Ichiro; Miyauchi, Sayuri; Stoner, Samuel A. ...
Journal of leukocyte biology,
June 2018, Letnik:
103, Številka:
6
Journal Article
Recenzirano
Type I IFNs (α, β, and others) are a family of cytokines that are produced in physiological conditions as well as in response to the activation of pattern recognition receptors. They are critically ...important in controlling the host innate and adaptive immune response to viral and some bacterial infections, cancer, and other inflammatory stimuli. However, dysregulation of type I IFN production or response can contribute to immune pathologies termed “interferonopathies”, pointing to the importance of balanced activating signals with tightly regulated mechanisms of tuning this signaling. Here, we summarize the recent advances of how type I IFN production and response are controlled at multiple levels of the type I IFN signaling cascade.
Review on the fine‐tuning of IFN signaling by negative regulators of the IFN production and response.
Optical methods to manipulate and detect nanoscale objects are highly desired in both nanomaterials and molecular biology fields. Optical tweezers have been used to manipulate objects that range in ...size from a few hundred nanometres to several micrometres. The emergence of near-field methods that overcome the diffraction limit has enabled the manipulation of objects below 100 nm. A highly free manipulation with signal-enhanced real-time detection, however, remains a challenge for single sub-100-nm nanoparticles or biomolecules. Here we show an approach that uses a photonic nanojet to perform the manipulation and detection of single sub-100-nm objects. With the photonic nanojet generated by a dielectric microlens bound to an optical fibre probe, three-dimensional manipulations were achieved for a single 85-nm fluorescent polystyrene nanoparticle as well as for a plasmid DNA molecule. Backscattering and fluorescent signals were detected with the enhancement factors up to ∼10
and ∼30, respectively. The demonstrated approach provides a potentially powerful tool for nanostructure assembly, biosensing and single-biomolecule studies.
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