280 research outputs found

    A new model for the double well potential

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    A new model for the double well potential is presented in the paper. In the new potential, the exchanging rate could be easily calculated by the perturbation method in supersymmetric quantum mechanics. It gives good results whether the barrier is high or sallow. The new model have many merits and may be used in the double well problem.Comment: 3pages, 3figure

    Identification of key bioactive anti-migraine constituents of Asari radix et rhizoma using network pharmacology and nitroglycerin-induced migraine rat model

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    Purpose: To elucidate the bioactive constituents of Asari radix et rhizoma (ARR) in treating migraine based on network pharmacology and nitroglycerin-induced migraine rat model. Methods: The potential bioactive constituents of ARR were identified with the aid of literature retrieval and virtual screening, and the migraine-related hub genes were identified using protein-protein interaction and topology analyses. Then, the interaction between the potential bioactive constituents and hub genes was determined with molecular docking and topology, leading to the prediction of the anti-migraine constituents of ARR. Moreover, a rat model of nitroglycerin-induced migraine was used to confirm the prediction by measuring the frequency of head-scratching and head-shaking behavior (FHHB) in the rats. In addition, levels of nitric oxide (NO) and calcitonin gene-related peptide (CGRP) in blood, norepinephrine (NE) and 5-hydroxytryptamine (5-HT) in brain were measured using appropriate commercial kits. Results: Network pharmacology revealed that naringenin-7-O-β-D-glucopyranoside and higenamine might be the key anti-migraine bioactive constituents of ARR. On addition of naringenin-7-O-β-D- glucopyranoside or higenamine to ARR, there was marked enhancement of the mitigating effect of ARR on nitroglycerin-induced abnormalities in levels of NO, CGRP, 5-HT and NE, as well as FHHB in rats (p < 0.05 or 0.01). Conclusion: These findings indicate that naringenin-7-O-β-D-glucopyranoside and higenamine might be the key bioactive and anti-migraine constituents of ARR. However, in addition to naringenin-7-O-β-D- glucopyranoside and higenamine, there were many other anti-migraine constituents in ARR. Therefore, there is need for further investigations on the actual contributions of these two constituents of ARR in treating migraine

    (S)-Ethyl 1,2,3,9-tetra­hydro­pyrrolo[2,1-b]quinazoline-1-carboxyl­ate

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    The title chiral compound, C14H16N2O2, was prepared by esterification of (S)-1,2,3,9-tetra­hydro­pyrrolo[2,1-b]quinazol­in-1-carboxylic acid in the presence of HCl/EtOH. In the mol­ecule, the quinazoline ring is non-planar and exhibits a distorted half-chair conformation, while the five-membered ring shows a typical envelope conformation. Inter­molecular C—H⋯N hydrogen bonding helps to stabilize the crystal structure

    Determination of dissolved nitric oxide in coastal waters of the Yellow Sea off Qingdao

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    We developed a new method for the determination of dissolved nitric oxide (NO) in discrete seawater samples based on the combination of a purge-and-trap setup and a fluorometric detection of NO. 2,3-diaminonaphthalene (DAN) reacts with NO in seawater to form the highly fluorescent 2,3-naphthotriazole (NAT). The fluorescence intensity was linear for NO concentrations in the range from 0.14 to 19 nmol L−1. We determined a detection limit of 0.068 nmol L−1, an average recovery coefficient of 83.8 % (80.2–90.0 %), and a relative standard deviation of ±7.2 %. With our method we determined for the first time the temporal and spatial distributions of NO surface concentrations in coastal waters of the Yellow Sea off Qingdao and in Jiaozhou Bay during a cruise in November 2009. The concentrations of NO varied from below the detection limit to 0.50 nmol L−1 with an average of 0.26 ± 0.14 nmol L−1. NO surface concentrations were generally enhanced significantly during daytime, implying that NO formation processes such as NO2− photolysis are much higher during daytime than chemical NO consumption, which, in turn, lead to a significant decrease in NO concentrations during nighttime. In general, NO surface concentrations and measured NO production rates were higher compared to previously reported measurements. This might be caused by the high NO2− surface concentrations encountered during the cruise. Moreover, additional measurements of NO production rates implied that the occurrence of particles and a temperature increase can enhance NO production rates. With the method introduced here, we have a reliable and comparably easy to use method at hand to measure oceanic NO surface concentrations, which can be used to decipher both its temporal and spatial distributions as well as its biogeochemical pathways in the oceans

    Resolving the Speciation Patterns and Evolutionary History of the Intercontinental Disjunct Genus Corylus (Betulaceae) Using Genome-Wide SNPs

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    Understanding the underlying mechanisms of species origin, divergence, and distribution patterns of the intercontinental disjunct taxa has long fascinated botanists. Based on 4,894 genome-wide single-nucleotide polymorphism dataset, we present a molecular phylogenetic reconstruction of genus Corylus (Betulaceae), which have a disjunct distribution between Eurasia and North America (NA). The aim is to explore the speciation patterns and evolutionary relationships of Corylus species by establishing a general phylogenetic framework with extensive sampling. Both the molecular phylogeny inferred from recombination-free dataset and structure analysis support the division of Corylus into four major clades (A–D). Recombination tests and hybridization detection reveal extensive recombination and hybridization events among different clades, which have potentially influenced the speciation process of Corylus. Divergence time estimation indicates that recent common ancestor (MRCA) of Corylus occurred in late Eocene (∼36.38 Ma) and subsequent rapid diversification began during Miocene. Ancestral area reconstruction shows that Corylus originated from southwest China. The arrival of two clades (Clades B and C) to NA was well supported by the long distance dispersal crossing the Bering land bridge. The Himalayas, European-Mediterranean area, and other distribution regions are primarily the recipients of dispersal taxa. Vicariance after dispersal plays an important role in speciation