Nuclear weak rates in stellar environments are obtained by taking into account recent advances in shell-model studies of spin-dependent excitation modes in nuclei including Gamow–Teller (GT) and ...spin-dipole transitions. They are applied to nuclear weak processes in stars such as cooling and heating of the cores of stars and nucleosynthesis in supernovae. The important roles of accurate weak rates for the study of astrophysical processes are pointed out in the following cases. (1) The electron-capture (e-capture) and β-decay rates in sd-shell are evaluated with the USDB Hamiltonian and used to study the evolution of O-Ne-Mg cores in stars with 8–10 M⊙. The important roles of the A = 23 and 25 pairs of nuclei for the cooling of the cores by nuclear Urca processes are investigated. (2) They are also used to study heating of the O-Ne-Mg core by double e-captures on 20Ne in later stages of the evolution. Especially, the e-capture rates for a second-forbidden transition in 20Ne are evaluated with the multipole expansion method by Walecka as well as the method of Behrens–Bühring. Possible important roles of the transition in heating the O-Ne-Mg cores and implications on the final fate of the cores (core-collapse or thermonuclear explosion) are discussed. (3) The weak rates in pf-shell nuclei are evaluated with a new Hamiltonian, GXPF1J, and applied to nucleosynthesis of iron-group elements in Type Ia supernova explosions. The over-production problem of neutron-rich iron isotopes compared with the solar abundances, which remained for the rates according to Fuller, Fowler and Newman, is much improved, and the over-production is now reduced to be within a factor of two. (4) The weak rates for nuclei with two-major shells are evaluated. For sd-pf shell in the island of inversion, the weak rates for the A = 31 pair of nuclei, which are important for nuclear Urca processes in neutron-star crusts, are evaluated with the effective interaction obtained by the extended Kuo–Krenciglowa (EKK) method. Neutron-rich nuclei with and near neutron number (N) of 50 are important for core-collapse processes in supernova explosions. The transition strengths and e-capture rates in 78Ni are evaluated with a new shell-model Hamiltonian for the pf-sdg shell, and compared with those obtained by the random-phase-approximation (RPA) and an effective rate formula. (5) β-decay rates and half-lives of N=126 isotones, the waiting point nuclei for r-process nucleosynthesis, are evaluated by shell-model calculations with both the GT and first-forbidden transitions. The important roles of the forbidden transitions are pointed out for the isotones with larger proton number (Z). The half-lives are found to be shorter than those obtained by standard models such as the finite-range droplet model (FRDM) by Möller. (6) Neutrino-nucleus reaction cross sections on 13C, 16O and 40Ar are obtained with new shell-model Hamiltonians. Implications on nucleosynthesis, neutrino detection, neutrino oscillations and neutrino mass hierarchy are discussed.
Suzuki and Niida (2015) showed the following results on independent distributions (IDs) on an AND–OR tree, where they took only depth-first algorithms into consideration. (1) Suppose that a positive ...real number r<1 is given, and let I(r) denote the class of all IDs such that the probability of the root having value 0 is r; if, among members of I(r), d is a maximizer of cost of the best algorithm then d is an independent and identical distribution (IID). (2) The same as above holds for the set of all IDs in place of I(r). In the case where non-depth-first algorithms are taken into consideration, the counterparts of (1) and (2) are left open in the above work. Peng et al. (2017) extended (1) and (2) to multi-branching trees, where in (2) they put an additional hypothesis on ID d that the probability of the root having value 0 is neither 0 nor 1. We give positive answers for the two questions of Suzuki–Niida. A key to the proof is that if ID d achieves the equilibrium among IDs then d has an optimal algorithm that is depth-first. In addition, we extend theorem 3 of Peng et al. to the case where non-depth-first algorithms are taken into consideration.
•Investigate non-depth-first algorithms against independent distributions.•An equilibrium point among independent distributions has optimal algorithm that is depth-first.•Give positive answers to the questions in Suzuki–Niida (2015).•Extend theorem 3 of Peng et al. (2017) to the non-depth-first case.
Stars with ∼8-10 M evolve to form a strongly degenerate ONeMg core. When the core mass becomes close to the Chandrasekhar mass, the core undergoes electron captures on 24Mg and 20Ne that induce an ...electron-capture supernova (ECSN). In order to clarify whether the ECSN leads to a collapse or thermonuclear explosion, we calculate the evolution of an 8.4 M star from the main sequence until the oxygen ignition in the ONeMg core. We apply the latest electron-capture rate on 20Ne, including the second forbidden transition, and investigate how the location of the oxygen ignition (center or off-center) and the Ye distribution depend on the input physics and the treatment of the semiconvection and convection. The central density when the oxygen deflagration is initiated, c,def, can be significantly higher than that of the oxygen ignition thanks to the convection, and we estimate . We perform two-dimensional simulations of the flame propagation to examine how the final fate of the ONeMg core depends on the Ye distribution and c,def. We find that the deflagration starting from leads to a collapse (thermonuclear explosion). Since our estimate of c,def exceeds this critical value, the ONeMg core is likely to collapse, although further studies of the convection and semiconvection before the deflagration are important.
In this work, Na isotopes with mass varying from A=20 to 31 have been studied using DJ16A, JISP16 and N3LO microscopic effective interactions in the sd-shell. These effective interactions are derived ...for sd-shell using no-core shell model wavefunctions and a unitary transformation method. We have also performed calculation with IMSRG effective interactions targeted for a particular nucleus. The studies include a detailed analysis of ground state binding energy, low-lying spectra, and electromagnetic properties such as reduced electric quadrupole transition strengths, quadrupole and magnetic dipole moments of the Na chain. The results obtained from these microscopic effective interactions were compared with the experimental data as well as with the results of phenomenological interaction USDB. The charge radii of Na isotopes are evaluated using shell model harmonic oscillator wave functions. In addition to charge radii, matter radii and neutron skin thickness in the Na chain are discussed with a focus on neutron-deficient Na isotopes.
Impact of Anode Microstructure on Solid Oxide Fuel Cells Suzuki, Toshio; Hasan, Zahir; Funahashi, Yoshihiro ...
Science (American Association for the Advancement of Science),
08/2009, Letnik:
325, Številka:
5942
Journal Article
Recenzirano
We report a correlation between the microstructure of the anode electrode of a solid oxide fuel cell (SOFC) and its electrochemical performance for a tubular design. It was shown that the ...electrochemical performance of the cell was extensively improved when the size of constituent particles was reduced so as to yield a highly porous microstructure. The SOFC had a power density of greater than 1 watt per square centimeter at an operating temperature as low as 600°C with a conventional zirconia-based electrolyte, a nickel cermet anode, and a lanthanum ferrite perovskite cathode material. The effect of the hydrogen fuel flow rate (linear velocity) was also examined for the optimization of operating conditions. Higher linear fuel velocity led to better cell performance for the cell with higher anode porosity. A zirconia-based cell could be used for a low-temperature SOFC system under 600°C just by optimizing the microstructure of the anode electrode and operating conditions.
Abstract
Cancer and cardiovascular disease share several risk factors. Clonal heamatopoiesis, a novel risk factor associated with both diseases, has received increasing attention in the fields of ...cardiology, heamatology and oncology. Clonal heamatopoiesis of indeterminate potential refers to the presence of at least one driver mutation in the heamatopoietic cells of peripheral blood without heamatological malignancy. Clonal heamatopoiesis of indeterminate potential is a common age-related condition that affects up to 60% of individuals aged > 80 years. Importantly, clonal heamatopoiesis of indeterminate potential carriers have a 2- to 4-fold higher risk of developing cardiovascular disease than non-carriers. Therefore, we performed an up-to-date review of clonal heamatopoiesis and its association with various forms of cardiovascular disease, including atherosclerotic disease, heart failure, aortic stenosis and pulmonary hypertension. In addition, we reviewed experimental studies that examined the causality and directionality between clonal heamatopoiesis and cardiovascular disease. Lastly, we discussed future research directions that will aid in the design of personalized therapies and preventive strategies for individuals with clonal heamatopoiesis. This review showed that clonal heamatopoiesis of indeterminate potential is a common condition, especially in older patients, and is associated with an increased risk of cardiovascular disease and worse prognosis. However, further research is needed to determine whether anti-inflammatory therapies or therapies that can reduce or eliminate clone size are effective in preventing cardiovascular disease in patients with clonal heamatopoiesis of indeterminate potential.
In this review, we summarized the close association between clonal heamatopoiesis and cardiovascular diseases and explored the mechanisms by which clonal heamatopoiesis exacerbates heart disease.
Melting and nucleation of iron nanoparticles were investigated by MD simulation. Melting point and nucleation temperature decreased with particle radius.
The melting and nucleation of the iron ...nanoparticles were investigated by molecular dynamics simulation. The nanoparticle of the bcc single-crystal was uniformly melted from the surface at a melting point during heating, whereas a nucleus was generated near one side of an undercooled liquid droplet and the solidification spread toward another side at a lower temperature during cooling. The melting point and nucleation temperature decreased with particle radius. Moreover, the solid–liquid interfacial energy was estimated to be 0.101
J/m
2 using a Gibbs–Thomson equation, which is of the same order as the experimental value based on Turnbull–Fisher’s classical nucleation theory.
Pulmonary fibrosis is a late manifestation of acute respiratory distress syndrome (ARDS). Sepsis is a major cause of ARDS, and its pathogenesis includes endotoxin-induced vascular injury. Recently, ...endothelial-to-mesenchymal transition (EndMT) was shown to play an important role in pulmonary fibrosis. On the other hand, dipeptidyl peptidase (DPP)-4 was reported to improve vascular dysfunction in an experimental sepsis model, although whether DPP-4 affects EndMT and fibrosis initiation during lipopolysaccharide (LPS)-induced lung injury is unclear. The aim of this study was to investigate the anti-EndMT effects of the DPP-4 inhibitor vildagliptin in pulmonary fibrosis after systemic endotoxemic injury.
A septic lung injury model was established by intraperitoneal injection of lipopolysaccharide (LPS) in eight-week-old male mice (5 mg/kg for five consecutive days). The mice were then treated with vehicle or vildagliptin (intraperitoneally, 10 mg/kg, once daily for 14 consecutive days from 1 day before the first administration of LPS.). Flow cytometry, immunohistochemical staining, and quantitative polymerase chain reaction (qPCR) analysis was used to assess cell dynamics and EndMT function in lung samples from the mice.
Lung tissue samples from treated mice revealed obvious inflammatory reactions and typical interstitial fibrosis 2 days and 28 days after LPS challenge. Quantitative flow cytometric analysis showed that the number of pulmonary vascular endothelial cells (PVECs) expressing alpha-smooth muscle actin (α-SMA) or S100 calcium-binding protein A4 (S100A4) increased 28 days after LPS challenge. Similar increases in expression were also confirmed by qPCR of mRNA from isolated PVECs. EndMT cells had higher proliferative activity and migration activity than mesenchymal cells. All of these changes were alleviated by intraperitoneal injection of vildagliptin. Interestingly, vildagliptin and linagliptin significantly attenuated EndMT in the absence of immune cells or GLP-1.
Inhibiting DPP-4 signaling by vildagliptin could ameliorate pulmonary fibrosis by downregulating EndMT in systemic LPS-induced lung injury.
Abstract The relativistic expression for the $n$th-order moment of the nuclear charge density is presented. For the mean square radius (msr) of the nuclear charge density, the non-relativistic ...expression, which is equivalent to the relativistic one, is also derived consistently up to $1/M^2$ with use of the Foldy–Wouthuysen transformation. The difference between the relativistic and non-relativistic expressions for the msr of the point proton density is also discussed. The $n(\ge 4)$th-order moment of the nuclear charge density depends on the point neutron density. The fourth-order moment yields useful information on the msr of the point neutron density, and is expected to play an important role in electron scattering off neutron-rich nuclei.
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