Bis(μ-3-nitro­phthalato-κ2 O 1:O 2)bis­[(thio­urea-κS)zinc] dihydrate

In the title complex, [Zn2(C8H3NO6)2(CH4N2S)4]·2H2O, the carboxyl­ate groups of the 3-nitro­phthalate ligands coordinate in a bis-monodentate mode to the ZnII cations. This results in the formation of a centrosymmetric dimer containing two ZnII cations with distorted tetra­hedral geometries provided by the O atoms of two different 3-nitro­phthalate dianions and the S atoms of two non-equivalent coordinated thio­urea mol­ecules. The crystal structure exhibits N—H⋯O and O—H⋯O hydrogen bonds which link the dimers into a three-dimensional network

Comparing hierarchical black hole mergers in star clusters and active galactic nuclei

Star clusters (SCs) and active galactic nuclei (AGNs) are promising sites for the occurrence of hierarchical black hole (BH) mergers. We use simple models to compare hierarchical BH mergers in two of the dynamical formation channels. We find that the primary mass distribution of hierarchical mergers in AGNs is higher than that in SCs, with the peaks of $\sim$$50\,M_{\odot}$ and $\sim$$13\,M_{\odot}$, respectively. The effective spin ($\chi_{\rm eff}$) distribution of hierarchical mergers in SCs is symmetrical around zero as expected and $\sim$$50\%$ of the mergers have $|\chi_{\rm eff}|>0.2$. The distribution of $\chi_{\rm eff}$ in AGNs is narrow and prefers positive values with the peak of $\chi_{\rm eff}\ge0.3$ due to the assistance of AGN disks. BH hierarchical growth efficiency in AGNs, with at least $\sim$$30\%$ of mergers being hierarchies, is much higher than the efficiency in SCs. Furthermore, there are obvious differences in the mass ratios and effective precession parameters of hierarchical mergers in SCs and AGNs. We argue that the majority of the hierarchical merger candidates detected by LIGO-Virgo may originate from the AGN channel as long as AGNs get half of the hierarchical merger rate.Comment: 12 pages, 5 figures, 2 tables, accepted for publication in PHYS. REV. D; v2. add Figs. 4 and 5, showing mass-ratios and effective precession parameters, respectively; v3. delete an additional free parameter (maximum generation, $N_{\rm max}^{\rm G}$), replot Fig. 3 using the mergers detected by LIGO-Virgo, and add Yong Yuan as the third author of this manuscript; v4. add more details for SN

Do invasive quagga mussels alter CO2 dynamics in the Laurentian Great Lakes?

The Laurentian Great Lakes have experienced unprecedented ecological and environmental changes, especially after the introduction of invasive quagga mussel (Dreissena rostriformis bugensis). While impacts on ecological functions have been widely recognized, the response of carbon dynamics to invasive species remains largely unknown. We report new CO(2) data showing significant increases in pCO(2) (up to 800 μatm in Lake Michigan) and CO(2) emission fluxes in most of the Great Lakes compared to those prior to or during the early stage of the colonization of invasive quagga mussels. The increased CO(2) supersaturation is most prominent in Lakes Huron and Michigan, followed by Lakes Ontario and Erie, but no evident change was observed in Lake Superior. This trend mirrors the infestation extent of invasive quagga mussels in the Great Lakes and is consistent with the decline in primary production and increase in water clarity observed pre- and post-Dreissena introduction, revealing a close linkage between invasive species and carbon dynamics. The Great Lakes have become a significant CO(2) source to the atmosphere, emitting >7.7 ± 1.0 Tg-C annually, which is higher than the organic carbon burial rate in global inland-seas and attesting to the significant role of the Laurentian Great Lakes in regional/global CO(2) budget and cycling

Ruthenium atomically dispersed in carbon outperforms platinum toward hydrogen evolution in alkaline media.

Hydrogen evolution reaction is an important process in electrochemical energy technologies. Herein, ruthenium and nitrogen codoped carbon nanowires are prepared as effective hydrogen evolution catalysts. The catalytic performance is markedly better than that of commercial platinum catalyst, with an overpotential of only -12 mV to reach the current density of 10 mV cm-2 in 1 M KOH and -47 mV in 0.1 M KOH. Comparisons with control experiments suggest that the remarkable activity is mainly ascribed to individual ruthenium atoms embedded within the carbon matrix, with minimal contributions from ruthenium nanoparticles. Consistent results are obtained in first-principles calculations, where RuCxNy moieties are found to show a much lower hydrogen binding energy than ruthenium nanoparticles, and a lower kinetic barrier for water dissociation than platinum. Among these, RuC2N2 stands out as the most active catalytic center, where both ruthenium and adjacent carbon atoms are the possible active sites

Joint parameter identification, vibration and noise analysis of gearbox

A certain type of gearbox is investigated for the problem that the stiffness and damping of bearings are difficult to be accurately determined and then affect the analysis of vibration and noise of gearbox. Firstly, a coupled dynamic lumped parameter model of three-stage helical gear system with consideration of bearing stiffness, bearing damping, and transmission error is established. The modal parameters of gear system are obtained by using the experimental modal analysis method with single-input and multiple-output. The equation for joint parameter identification of gearbox is established which is based on the experimental modal analysis theory and the dynamic lumped parameter model, and subsequently the parameters of the joint are obtained by the least square method. Then, a gear-shaft-bearing- housing coupled dynamic finite element model is developed on the basis of the identified parameters, and after that the dynamic response results of gearbox are solved by using the modal superposition method and compared with the vibration test results. Finally, an acoustic boundary element model of gearbox is established by taking the dynamic response results as the acoustic boundary condition, and the surface sound pressure and radiation noise of gearbox are solved by the boundary element method (BEM), and then the results are compared with the noise test. The results show that the simulation laws and test laws are in good agreement, and thus the method of joint parameter identification, vibration and noise analysis of gearbox is feasible

Constraints on Axion-like Particles from Observations of Mrk 421 using the CLs{\rm CL_s} Method

Axion-like particles (ALPs) could mix with photons in the presence of astrophysical magnetic fields, and result in oscillations in the high energy $\gamma$-ray spectra observed by experiments. In this work, we investigate the ALP-photon oscillation effect through the blazar Mrk 421 spectra of 15 periods observed by Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) and Fermi Large Area Telescope (Fermi-LAT). Compared with previous studies, we generate the mock data under the ALP hypothesis and apply the ${\rm CL_s}$ method to set constraints on the ALP parameters. This method is widely employed in high energy experiments and could avoid the possibility of excluding some parameter regions due to the fluctuation. We find that the ALP-photon coupling $g_{a\gamma}$ is constrained to be smaller than $\sim 2\times10^{-11}$ GeV$^{-1}$ for ALP mass ranging from $10^{-9}$ eV to $10^{-7}$ eV at a 95\% confidence level. The constraints obtained with the method based on the TS distribution under the null hypothesis, which is adopted in many previous astrophysical ALP studies, are also shown. Our results demonstrate that the joint constraints of all the periods from both methods are consistent. However, the latter method fails to provide constraints for some observation periods, whereas the ${\rm CL_s}$ method remains effective in such cases.Comment: 10 pages, 26 figure