catena-Poly[[[triaqua­cadmium(II)]-μ-2,2′-[oxalylbis(azanediyl)]diacetato-κ2 O,O′] dihydrate]

The structure of the polymeric title complex, {[Cd(C6H6N2O6)(H2O)3]·2H2O}n, consists of chains running parallel to [01] in which the oxamidato ligand, deprotonated only at the carboxyl­ate groups, acts as a bridging bis-monodentate ligand. The Cd atom and the O atom of a coordinated water mol­ecule are located on a twofold axis. The coordination geometry around the Cd atom is distorted trigonal-pyramidal. In the crystal structure, neighbouring chains are linked into a three-dimensional network by inter­chain O—H⋯O and N—H⋯O hydrogen bonds

[N′-(3-Meth­oxy-2-oxidobenzyl­idene)nicotinohydrazidato]diphenyl­tin(IV)

The asymmetric unit of the title compound, [Sn(C6H5)2(C14H11N3O3)], contains two crystallographically independent mol­ecules that differ predominantly in the torsion of the phenyl rings. In both mol­ecules, the SnIV ion is in a distored trigonal-bipyramidal geometry. The Sn—O distances are in the range 2.055 (2)–2.143 (2) Å

Deep Imaging of the HCG 95 Field.I.Ultra-diffuse Galaxies

We present a detection of 89 candidates of ultra-diffuse galaxies (UDGs) in a 4.9 degree$^2$ field centered on the Hickson Compact Group 95 (HCG 95) using deep $g$- and $r$-band images taken with the Chinese Near Object Survey Telescope. This field contains one rich galaxy cluster (Abell 2588 at $z$=0.199) and two poor clusters (Pegasus I at $z$=0.013 and Pegasus II at $z$=0.040). The 89 candidates are likely associated with the two poor clusters, giving about 50 $-$ 60 true UDGs with a half-light radius $r_{\rm e} > 1.5$ kpc and a central surface brightness $\mu(g,0) > 24.0$ mag arcsec$^{-2}$. Deep $z$'-band images are available for 84 of the 89 galaxies from the Dark Energy Camera Legacy Survey (DECaLS), confirming that these galaxies have an extremely low central surface brightness. Moreover, our UDG candidates are spread over a wide range in $g-r$ color, and $\sim$26% are as blue as normal star-forming galaxies, which is suggestive of young UDGs that are still in formation. Interestingly, we find that one UDG linked with HCG 95 is a gas-rich galaxy with H I mass $1.1 \times 10^{9} M_{\odot}$ detected by the Very Large Array, and has a stellar mass of $M_\star \sim 1.8 \times 10^{8}$ $M_{\odot}$. This indicates that UDGs at least partially overlap with the population of nearly dark galaxies found in deep H I surveys. Our results show that the high abundance of blue UDGs in the HCG 95 field is favored by the environment of poor galaxy clusters residing in H I-rich large-scale structures.Comment: Published in Ap

Wavelet-M-Estimation for Time-Varying Coefficient Time Series Models

This paper proposes wavelet-M-estimation for time-varying coefficient time series models by using a robust-type wavelet technique, which can adapt to local features of the time-varying coefficients and does not require the smoothness of the unknown time-varying coefficient. The wavelet-M-estimation has the desired asymptotic properties and can be used to estimate conditional quantile and to robustify the usual mean regression. Under mild assumptions, the Bahadur representation and the asymptotic normality of wavelet-M-estimation are established

New challenges in mitigating climate change: Digital teaching for the sustainable development and innovation

The phenomenon of climate change has become a global challenge that affects human activities in many ways. Exploring the sustainability and innovativeness of digital education is an important reference for the further implementation of science and education strategies and positive effects on climate change mitigation. This study designed two questionnaires for basic and tertiary education to address variability in education and collected 523 samples for basic education and 412 samples for tertiary education respectively. Using digital teaching practices and digital teaching quality as mediators, structural equation modelling (SEM) was used to examine the impact of digital education on sustainability and innovation in education. Research shows that digital teaching and learning in basic and higher education can significantly contribute to the two-way development of educational sustainability and innovation, through digital teaching and learning practices. Digital teaching practice and digital teaching quality in higher education play a complete mediating role, while basic education only plays a partial mediating role. Higher education emphasizes digital teaching and learning practice processes and teaching quality, and most students hope that online teaching and learning can be further integrated with offline education to form a new model of education. This study will help government departments understand the pedagogical reality of digital education at a deeper level and provide ideas for the subsequent sustainable development and educational innovation of digital teaching. It can also provide new ideas for climate change mitigation and sustainable development