Potassium oxalurate monohydrate

The title salt, poly[aqua-μ3-oxalurato-potassium(I)], [K(C3H3N2O4)(H2O)]n, which was obtained from a water solution of oxaluric acid and KOH at room temperature, crystallizes as potassium and oxalurate ions along with a water mol­ecule. The K+ cation lies on a crystallographic twofold rotation axis (site symmetry 2, Wyckoff position f), and the water and oxalurate mol­ecules are located within different mirror planes (site symmetry m, Wyckoff position g). The K+ cation is eight-coordinated by six O atoms of six oxalurate ligands and two O atoms from two water mol­ecules in a distorted square-anti­prismatic geometry. All of the eight coordinated O atoms are in a monodentate bridging mode, with alternate bridged K⋯K distances of 3.5575 (12) and 3.3738 (12) Å. The oxalurate ligand shows a μ3-bridging coordination mode, which links the K+ cation into a three-dimensional network. The oxalurate ligands and the water mol­ecules are involved in inter- and intra­molecular N—H⋯O, and O—H⋯O hydrogen bonds, which stabilize the network

Lower bounds of the Laplacian spectrum of graphs based on diameter

AbstractLet G be a connected graph of order n. The diameter of G is the maximum distance between any two vertices of G. In the paper, we will give some lower bounds for the algebraic connectivity and the Laplacian spectral radius of G in terms of the diameter of G

A Luminous X-ray Flare From The Nucleus of The Dormant Bulgeless Spiral Galaxy NGC 247

NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity up to 2*10^39 erg/s in the 0.3-10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3-4 keV, no pulsations on timescales longer than 150 ms, and a flat power spectrum consistent with Poisson noise from 1 mHz to nearly 10 Hz. Follow-up observations with Swift detected a second flux peak followed by a luminosity drop by factor of almost 20. The spectral and temporal behaviors of the nuclear source are well consistent with the scenario that the flare was due to an outburst of a low-mass X-ray binary that contains a stellar-mass black hole emitting near its Eddington limit at the peak. However, it cannot be ruled out that the sudden brightening in the nucleus was due to accretion onto a possible low-mass nuclear black hole, fed by a tidally disrupted star or a gas cloud; the MAXI observations limit the peak luminosity of the flare to less than ~10^43 erg/s, suggesting that it is either a low mass black hole or an inefficient tidal disruption event (TDE).Comment: accepted for publication in Ap

Tetra­aqua­bis­(2-methyl-1H-benzimidazolium-1,3-diacetato-κO)cobalt(II) tetra­hydrate

In the title compound, [Co(C12H11N2O4)2(H2O)4]·4H2O, the CoII atom lies on an inversion center and is octa­hedrally coordinated by six O atoms from four water mol­ecules and two monodentate zwitterionic 2-methyl­benzimidazolium-1,3-diacetate ligands. An intra­molecular O—H⋯O hydrogen bond occurs. In the crystal, inter­molecular O—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network. π–π inter­actions between the imidazole and benzene rings [centroid–centroid distance = 3.9031 (17) Å] consolidate the crystal packing

Entropy-Based Model for Interpreting Life Systems in Traditional Chinese Medicine

Traditional Chinese medicine (TCM) treats qi as the core of the human life systems. Starting with a hypothetical correlation between TCM qi and the entropy theory, we address in this article a holistic model for evaluating and unveiling the rule of TCM life systems. Several new concepts such as acquired life entropy (ALE), acquired life entropy flow (ALEF) and acquired life entropy production (ALEP) are propounded to interpret TCM life systems. Using the entropy theory, mathematical models are established for ALE, ALEF and ALEP, which reflect the evolution of life systems. Some criteria are given on physiological activities and pathological changes of the body in different stages of life. Moreover, a real data-based simulation shows life entropies of the human body with different ages, Cold and Hot constitutions and in different seasons in North China are coincided with the manifestations of qi as well as the life evolution in TCM descriptions. Especially, based on the comparative and quantitative analysis, the entropy-based model can nicely describe the evolution of life entropies in Cold and Hot individuals thereby fitting the Yin–Yang theory in TCM. Thus, this work establishes a novel approach to interpret the fundamental principles in TCM, and provides an alternative understanding for the complex life systems

4,4′-(1,1,1,3,3,3-Hexafluoro­propane-2,2-diyl)dibenzoic acid

In the title compound, C17H10F6O4, the two benzene rings are twisted with respect to each other, making a dihedral angle of 67.43 (12)°. In the crystal, adjacent mol­ecules are linked by O—H⋯O and C—H⋯F hydrogen bonding, forming a wave-like layered supra­molecular structure