Sparse Signal Reconstruction Based on Multiparameter Approximation Function with Smoothed l

The smoothed l0 norm algorithm is a reconstruction algorithm in compressive sensing based on approximate smoothed l0 norm. It introduces a sequence of smoothed functions to approximate the l0 norm and approaches the solution using the specific iteration process with the steepest method. In order to choose an appropriate sequence of smoothed function and solve the optimization problem effectively, we employ approximate hyperbolic tangent multiparameter function as the approximation to the big “steep nature” in l0 norm. Simultaneously, we propose an algorithm based on minimizing a reweighted approximate l0 norm in the null space of the measurement matrix. The unconstrained optimization involved is performed by using a modified quasi-Newton algorithm. The numerical simulation results show that the proposed algorithms yield improved signal reconstruction quality and performance

[2,6-Bis(p-tol­ylimino­meth­yl)pyridine-κ3 N,N′,N′′]dichloridocopper(II)

The title compound, [CuCl2(C21H19N3)], lies on a twofold rotation axis that passes through the Npyrid­yl—Cu bond; this symmetry element relates one half of the organic ligand to the other as well as one Cl ligand to the other. The three N atoms span the axial–equatorial–axial sites of the trigonal-bipyramidal coordination polyhedron; the geometry of the CuII atom is 31% distorted from trigonal-bipyramidal (towards square-pyramidal along the Berry pseudorotation pathway)

[2,6-Bis(6-methyl­quinolin-2-yl)pyridine-κ3 N,N′,N′′]dichloridoiron(II)

In the mol­ecule of the title compound, [FeCl2(C25H19N3)], the three N atoms span the axial–equatorial–axial sites of the trigonal-bipyramidal coordination polyhedron; the geometry of the FeII atom is 32% distorted from trigonal-bipyramidal (towards square-pyramidal along the Berry pseudorotation pathway). One of the Cl atoms is disordered over two positions in a 0.938 (11):0.062 (11) ratio. Inter­molecular C—H⋯Cl hydrogen bonding occurs in the crystal structure

[2,6-Bis(6-methyl­quinolin-2-yl)pyridine-κ3 N,N′,N′′]dichloridomanganese(II)

In the mol­ecule of the title compound, [MnCl2(C25H19N3)], the three N atoms span the axial–equatorial–axial sites of the trigonal-bipyramidal coordination polyhedron; the geometry of the MnII atom is 34% distorted from trigonal-bipyramidal (towards square-pyramidal along the Berry pseudorotation pathway). One of the Cl atoms is disordered over two positions in a 0.82 (3):0.18 (3) ratio. Weak inter­molecular C—H⋯Cl hydrogen bonding occurs in the crystal structure

{2,6-Bis[(4-bromo­phen­yl)imino­meth­yl]pyridine-κ3 N,N′,N′′}trichlorido­chromium(III)

In the title compound, [CrCl3(C19H13Br2N3)], the Cr3+ ion is coordinated by the tridentate 2,6-bis­[(4-bromo­phen­yl)imino­meth­yl]pyridine Schiff base ligand in a fac-octa­hedral geometry. The dihedral angles between the pyridine and benzene rings are 23.9 (6) and 70.7 (1)°

Early Triassic oceanic red beds coupled with deep sea oxidation in South Tethys

Carbonate oceanic red beds (ORBs) are unusual in Phanerozoic shelf settings but can be widespread during discrete intervals. Several scenarios have been invoked to explain the origin of these ORBs but there remains uncertainty about the process by which the red pigmentation of ORBs forms. Here, we propose that the occurrence of ORBs at intermediate water depths in shelf regions is controlled by fluctuations in the redox state of deeper waters. We have examined Early Triassic Peri-Gondwana shelf sections in South Tibet which show the development of Spathian (late Early Triassic) ORBs at intermediate water depths. The red color of these ORBs is imparted by randomly dispersed hematite crystals that are microns in size, showing weak alteration by late burial diagenesis. Widespread anoxia, in both shelf seas and the oceanic realm, was well developed in the Early Triassic. Synchronous occurrence of Spathian ORBs in deep shelf regions is closely related to the improved oxidation in deeper settings, from anoxia to dysoxia, based on changes in the redox proxy of pyrite framboid sizes. It is, therefore, inferred that prolonged deep-water anoxia might serve as source of Fe (II) for the formation of ORBs when intensified upwelling develops. The global occurrence of Early Triassic ORBs is coincident with the significant rebound of biodiversity after the Permian-Triassic mass extinction, indicating the occurrence of ORBs marks the terminal stage of an oceanic anoxic event and ORBs can serve as an indicator of the ameliorated marine ecosystem

Social media mining under the COVID-19 context: Progress, challenges, and opportunities

Social media platforms allow users worldwide to create and share information, forging vast sensing networks that allow information on certain topics to be collected, stored, mined, and analyzed in a rapid manner. During the COVID-19 pandemic, extensive social media mining efforts have been undertaken to tackle COVID-19 challenges from various perspectives. This review summarizes the progress of social media data mining studies in the COVID-19 contexts and categorizes them into six major domains, including early warning and detection, human mobility monitoring, communication and information conveying, public attitudes and emotions, infodemic and misinformation, and hatred and violence. We further document essential features of publicly available COVID-19 related social media data archives that will benefit research communities in conducting replicable and repro�ducible studies. In addition, we discuss seven challenges in social media analytics associated with their potential impacts on derived COVID-19 findings, followed by our visions for the possible paths forward in regard to social media-based COVID-19 investigations. This review serves as a valuable reference that recaps social media mining efforts in COVID-19 related studies and provides future directions along which the information harnessed from social media can be used to address public health emergencies

Effect of Lycii fructus polysaccharides on ovulation failure in rats

Purpose: To investigate the effect of Lycii Fructus polysaccharides (LFPS) on ovulation failure.Methods: A rat model of ovulation failure was established by intragastric administration of hydroxyurea (300 mg/kg). Rats with ovulation failure then received LFPS via oral administration at doses of 100, 200, or 400 mg/kg. The body, uterus and ovary of each rat were weighed using electronic scales. The hypothalamic-pituitary-ovarian (HPO) axis hormones, including estradiol (E2) level, follicle-stimulating hormone (FSH) activity, and luteinizing hormone (LH) activity in the serum of each rat were determined by enzyme-linked immunosorbent assay (ELISA). The levels of pro-apoptotic proteins (Fas, FasL, FADD, c-caspase-8, c-caspase-10, c-caspase-3, c-caspase-6, and c-caspase-7) in the ovarian tissue of each rat were detected by western blot.Results: Hydroxyurea reduced significantly (p < 0.01) uterus and ovary indices (uterus or ovary weight/body weight) (0.119 and 0.026 %), E2 level (3.42 pmol/L), and FSH and LH activities (2.28 and 2.76 U/L), compared with those in the normal group (0.169 and 0.039 %; 6.72 pmol/L; 2.76 and 3.75 U/L). Hydroxyurea increased significantly (p < 0.01) the levels of the above-mentioned pro-apoptotic proteins relative to those in the normal group. LFPS (100, 200, or 400 mg/kg) reversed significantly (p < 0.05 or 0.01) the effect of hydroxyurea on all of the above indices.Conclusion: LFPS exhibits a protective effect on hydroxyurea-induced ovulation failure by regulating the HPO axis hormones and death receptor-mediated apoptotic pathway.Keywords: Lycii Fructus polysaccharides, Ovulation failure, Hypothalamic-pituitary-ovarian axis, Death receptor-mediated apoptotic pathwa

Re-appearance of precipitated aragonite crystal fans as evidence for expansion of oceanic dissolved inorganic carbon reservoir in the aftermath of the Lomagundi-Jatuli Event

The initial accumulation of atmospheric oxygen is marked by the unprecedented positive δ13Ccarb excursions of the Lomagundi-Jatuli Event (LJE) and records an interval of abnormal O2 production through elevated rates of organic carbon burial. Emerging evidence suggests that the post-LJE atmosphere-ocean system might have suffered a significant deoxygenation. These dynamic perturbations in the oceanic redox state and biogeochemical cycles would have led to fundamental changes in carbonate precipitation dynamics. Here, we report the discovery of centimeter-sized crystal fans in the post-LJE Huaiyincun Formation, Hutuo Supergroup in the North China Craton. The hexagonal cross-sections and square terminations suggest that these fan-like dolomitic structures were originally aragonite crystal fans (ACF). Variations of stromatolite morphology and frequent occurrences of storm-related deposits in the Huaiyincun Formation point to repeated cycles of sea level changes. The bedding-parallel distribution of the ACF and the homogeneous δ13C values of the ACF-bearing dolostones are consistent with a primary depositional origin for the ACF. An updated compilation of published records of ACF throughout geological history highlights a clear absence of ACF from the initiation of the Paleoproterozoic Great Oxidation Event until the end of the LJE, and a global reappearance of ACF in the post-LJE late Paleoproterozoic. We propose that the reappearance of ACF is in agreement with the expansion of the oceanic dissolved inorganic carbon reservoir. At the same time, consumption of dissolved oxygen during the oxidation of organic matter might have been stimulated by ferruginous deep seawater, facilitating the formation of Huiayincun ACF