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In this paper, the limit cycles and local bifurcation of critical periods for a class of switching Z 2 equivariant quartic system with two symmetric singularities are investigated. First, through the computation of Lyapunov constants, the conditions of the two singularities to become the centers are determined. Then, we prove that there are at most 18 limit cycles with a distribution pattern of 9-9 around the two symmetric singular points of the system. Numerical simulation is conducted to validate the obtained results. Furthermore, by calculating the period constants, we determine the conditions for the critical point to be a weak center of finite order. Finally, the number of local critical periods that bifurcate from the equilibrium point under the center conditions is discussed. This study presents the first example of a quartic switching smooth system with 18 limit cycles and 4 local critical periods bifurcating from two symmetric singular points. [ABSTRACT FROM AUTHOR]

Sulfate radicals-based Fenton-like technology has placed more emphasis on effectively dealing with the threat of dye wastewater. In this work, the Zn-doped CuFe2O4@biochar composite (Cu0.9Zn0.1Fe2O4@BC) was prepared through the convenient sol–gel pyrolysis process and applied as heterogeneous persulfate (PS) activator for crystal violet (CV) degradation. The crystal morphology and physicochemical properties of Cu0.9Zn0.1Fe2O4@BC were investigated by scanning electron microscope (SEM), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), Brunauer–Emmett–Teller method (BET), and X-ray photoelectron spectroscopy (XPS). The morphology of the catalyst changed before and after Zn doping. The crystallite size, lattice constant, saturation magnetization, and oxygen vacancy content increased after doping Zn. Compared with CuFe2O4@BC, the CV degradation efficiency of Cu0.9Zn0.1Fe2O4@BC activating PS increased from 87.7 to 96.9%, and the corresponding reaction rate constant increased by about 3.69 times. The effect of experimental conditions was systematically studied on the degradation progress. The degradation efficiency of CV was 91% after five times cycle experiments. Multiple experiments indicated that SO4•–, •OH and O2•– predominated for CV degradation. The degradation mechanism of CV in the Cu0.9Zn0.1Fe2O4@BC/PS system involved both free radical (SO4•–, •OH and O2•–) and non-free radical pathways (electron transfer). The possible degradation pathways were investigated according to the ultra-performance liquid chromatography mass spectrometry (UPLC-MS) analysis of degradation intermediates. The result showed that Cu0.9Zn0.1Fe2O4@BC have an excellent catalyst performance, which provides a new strategy for improving catalytic activity. [ABSTRACT FROM AUTHOR]

In this paper, Hopf bifurcation and center problem are investigated for a class of more generalized Lorenz systems, which are Z 2 symmetric and quadratic three-dimensional systems. Firstly, the singular point quantities of one equilibrium are calculated carefully, and the two symmetric fourth-order weak foci are found. Secondly, the corresponding invariant algebraic surfaces are figured out, and the center conditions on a center manifold are determined. In this way it is proved that there exist at most eight small limit cycles from the two symmetric equilibria via a Hopf bifurcation, which is a new result for general Lorenz models. At the same time, when the center conditions are satisfied, the complete classification of Darboux invariants is established for this system. [ABSTRACT FROM AUTHOR]

Hypoxia-inducible factors (HIFs) are α/β heterodimeric transcription factors modulating cellular responses to the low oxygen condition. Among three HIF-α isoforms, HIF-3α is the least studied to date. Here we show that oleoylethanolamide (OEA), a physiological lipid known to regulate food intake and metabolism, binds selectively to HIF-3α. Through crystallographic analysis of HIF-3 α/β heterodimer in both apo and OEA-bound forms, hydrogen-deuterium exchange mass spectrometry (HDX-MS), molecular dynamics (MD) simulations, and biochemical and cell-based assays, we unveil the molecular mechanism of OEA entry and binding to the PAS-B pocket of HIF-3α, and show that it leads to enhanced heterodimer stability and functional modulation of HIF-3. The identification of HIF-3α as a selective lipid sensor is consistent with recent human genetic findings linking HIF-3α with obesity, and demonstrates that endogenous metabolites can directly interact with HIF-α proteins to modulate their activities, potentially as a regulatory mechanism supplementary to the well-known oxygen-dependent HIF-α hydroxylation. Whether hypoxia-inducible factors (HIFs) can be directly regulated by endogenous small molecules is a long-standing question. Here authors identified the metabolite oleoylethanolamide as a HIF-3α ligand and further revealed its mechanism of action. [ABSTRACT FROM AUTHOR]

Falls impose substantial health and economic burdens on older adults. Over half of falls in older adults occur at home, with many involving bathroom areas. Limited information is available on the presence of bathroom modifications for those who experience them. Therefore, we examined factors associated with bathroom modifications among older adults with at least one fall in the United States. We analysed the nationally representative 2016 Medicare Current Beneficiary Survey Public Use File of Medicare beneficiaries aged ≥65 years with ≥1 fall (n = 2,404). A survey‐weighted logistic model was used to examine associations between bathroom modifications and factors including socio‐demographic characteristics, health‐related conditions, and fear of falling. Among Medicare beneficiaries with ≥1 fall, 55.5% had bathroom modifications and 50.1% had repeated falls (≥2 falls). Approximately 40.2% of those with repeated falls had no bathroom modifications. In the adjusted model, non‐Hispanic Blacks (odds ratio [OR] = 0.38; p < 0.001) and Hispanics (OR = 0.64; p = 0.039) had lower odds of having bathroom modifications than non‐Hispanic Whites. Fear of falling and activities of daily living limitations had incremental impacts on having bathroom modifications. This study highlights the need to improve disparities in bathroom modifications for non‐Hispanic Black and Hispanic Medicare beneficiaries, including those with repeated falls. With the aging population and growing number of older minorities in the United States, reducing these disparities is vital for fall prevention efforts and aging‐in‐place. [ABSTRACT FROM AUTHOR]

Bile acids are abundant in the mammalian gut, where they undergo bacteria-mediated transformation to generate a large pool of bioactive molecules. Although bile acids are known to affect host metabolism, cancer progression and innate immunity, it is unknown whether they affect adaptive immune cells such as T helper cells that express IL-17a (TH17 cells) or regulatory T cells (Treg cells). Here we screen a library of bile acid metabolites and identify two distinct derivatives of lithocholic acid (LCA), 3-oxoLCA and isoalloLCA, as T cell regulators in mice. 3-OxoLCA inhibited the differentiation of TH17 cells by directly binding to the key transcription factor retinoid-related orphan receptor-γt (RORγt) and isoalloLCA increased the differentiation of Treg cells through the production of mitochondrial reactive oxygen species (mitoROS), which led to increased expression of FOXP3. The isoalloLCA-mediated enhancement of Treg cell differentiation required an intronic Foxp3 enhancer, the conserved noncoding sequence (CNS) 3; this represents a mode of action distinct from that of previously identified metabolites that increase Treg cell differentiation, which require CNS1. The administration of 3-oxoLCA and isoalloLCA to mice reduced TH17 cell differentiation and increased Treg cell differentiation, respectively, in the intestinal lamina propria. Our data suggest mechanisms through which bile acid metabolites control host immune responses, by directly modulating the balance of TH17 and Treg cells. Screening of a library of bile acid metabolites revealed two derivatives of lithocholic acid that act as regulators of T helper cells that express IL-17a and regulatory T cells, thus influencing host immune responses. [ABSTRACT FROM AUTHOR]

The hypoxia-inducible factors (HIFs) coordinate cellular adaptations to low oxygen stress by regulating transcriptional programs in erythropoiesis, angiogenesis and metabolism. These programs promote the growth and progression of many tumours, making HIFs attractive anticancer targets. Transcriptionally active HIFs consist of HIF-α and ARNT (also called HIF-1β) subunits. Here we describe crystal structures for each of mouse HIF-2α-ARNT and HIF-1α-ARNT heterodimers in states that include bound small molecules and their hypoxia response element. A highly integrated quaternary architecture is shared by HIF-2α-ARNT and HIF-1α-ARNT, wherein ARNT spirals around the outside of each HIF-α subunit. Five distinct pockets are observed that permit small-molecule binding, including PAS domain encapsulated sites and an interfacial cavity formed through subunit heterodimerization. The DNA-reading head rotates, extends and cooperates with a distal PAS domain to bind hypoxia response elements. HIF-α mutations linked to human cancers map to sensitive sites that establish DNA binding and the stability of PAS domains and pockets. [ABSTRACT FROM AUTHOR]

The presence of Alternaria toxins (ATs) in fruit purees may cause potential harm to the life and health of consumers. As time passes, ATs have become the key detection objects in this kind of food. Based on this, a novel and rapid method was established in this paper for the simultaneous detection of seven ATS (tenuazonic acid, alternariol, alternariol monomethyl ether, altenuene, tentoxin, altenusin, and altertoxin I) in mixed fruit purees using ultra-high performance liquid chromatography-tandem mass spectrometry. The sample was prepared using the modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method to complete the extraction and clean-up steps in one procedure. In this QuEChERS method, sample was extracted with water and acetonitrile (1.5% formic acid), then salted out with NaCl, separated on an ACQUITY UPLC BEH C18 with gradient elution by using acetonitrile and 0.1% formic acid aqueous as eluent, and detected by UPLC-MS/MS under positive (ESI+) and negative (ESI−) electrospray ionization and MRM models. Results showed that the seven ATs exhibited a good linearity in the concentration range of 0.5–200 ng/mL with R2 > 0.9925, and the limits of detection (LODs) of the instrument were in the range of 0.18–0.53 μg/kg. The average recoveries ranged from 79.5% to 106.7%, with the relative standard deviations (RSDs) no more than 9.78% at spiked levels of 5, 10, and 20 μg/kg for seven ATs. The established method was applied to the determination and analysis of the seven ATs in 80 mixed fruit puree samples. The results showed that ATs were detected in 31 of the 80 samples, and the content of ATs ranged from 1.32 μg/kg to 54.89 μg/kg. Moreover, the content of TeA was the highest in the detected samples (23.32–54.89 μg/kg), while the detection rate of Ten (24/31 samples) was higher than the other ATs. Furthermore, the other five ATs had similar and lower levels of contamination. The method established in this paper is accurate, rapid, simple, sensitive, repeatable, and stable, and can be used for the practical determination of seven ATs in fruit puree or other similar samples. Moreover, this method could provide theory foundation for the establishment of limit standard of ATs and provide a reference for the development of similar detection standard methods in the future. [ABSTRACT FROM AUTHOR]

An Amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]