1,555 research outputs found
Atrial fibrillation: Prevention and termination with pacing
published_or_final_versio
Outstanding Issues in Solar Dynamo Theory
The magnetic activity of the Sun, as manifested in the sunspot cycle,
originates deep within its convection zone through a dynamo mechanism which
involves non-trivial interactions between the plasma and magnetic field in the
solar interior. Recent advances in magnetohydrodynamic dynamo theory have led
us closer towards a better understanding of the physics of the solar magnetic
cycle. In conjunction, helioseismic observations of large-scale flows in the
solar interior has now made it possible to constrain some of the parameters
used in models of the solar cycle. In the first part of this review, I briefly
describe this current state of understanding of the solar cycle. In the second
part, I highlight some of the outstanding issues in solar dynamo theory related
to the the nature of the dynamo -effect, magnetic buoyancy and the
origin of Maunder-like minima in activity. I also discuss how poor constraints
on key physical processes such as turbulent diffusion, meridional circulation
and turbulent flux pumping confuse the relative roles of these vis-a-vis
magnetic flux transport. I argue that unless some of these issues are
addressed, no model of the solar cycle can claim to be ``the standard model'',
nor can any predictions from such models be trusted; in other words, we are
still not there yet.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
Psychometric precision in phenotype definition is a useful step in molecular genetic investigation of psychiatric disorders
Affective disorders are highly heritable, but few genetic risk variants have been consistently replicated in molecular genetic association studies. The common method of defining psychiatric phenotypes in molecular genetic research is either a summation of symptom scores or binary threshold score representing the risk of diagnosis. Psychometric latent variable methods can improve the precision of psychiatric phenotypes, especially when the data structure is not straightforward. Using data from the British 1946 birth cohort, we compared summary scores with psychometric modeling based on the General Health Questionnaire (GHQ-28) scale for affective symptoms in an association analysis of 27 candidate genes (249 single-nucleotide polymorphisms (SNPs)). The psychometric method utilized a bi-factor model that partitioned the phenotype variances into five orthogonal latent variable factors, in accordance with the multidimensional data structure of the GHQ-28 involving somatic, social, anxiety and depression domains. Results showed that, compared with the summation approach, the affective symptoms defined by the bi-factor psychometric model had a higher number of associated SNPs of larger effect sizes. These results suggest that psychometrically defined mental health phenotypes can reflect the dimensions of complex phenotypes better than summation scores, and therefore offer a useful approach in genetic association investigations
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Novel and simple patterning process of quantum dots via transfer printing for active matrix qd-led
© 2020 SID. The next generation of a self-emitting display requires precise and stable patterning techniques to shape Red, Green, and Blue pixels using quantum dots. In this study, we propose the novel and simple transfer printing process for the active matrix QD-LEDs
TGF-beta 1 induces human alveolar epithelial to mesenchymal cell transition (EMT)
Background: Fibroblastic foci are characteristic features in lung parenchyma of patients with idiopathic pulmonary fibrosis (IPF). They comprise aggregates of mesenchymal cells which underlie sites of unresolved epithelial injury and are associated with progression of fibrosis. However, the cellular origins of these mesenchymal phenotypes remain unclear. We examined whether the potent fibrogenic cytokine TGF-β1 could induce epithelial mesenchymal transition (EMT) in the human alveolar epithelial cell line, A549, and investigated the signaling pathway of TGF-β1-mediated EMT.
Methods: A549 cells were examined for evidence of EMT after treatment with TGF-β1. EMT was assessed by: morphology under phase-contrast microscopy; Western analysis of cell lysates for expression of mesenchymal phenotypic markers including fibronectin EDA (Fn-EDA), and expression of epithelial phenotypic markers including E-cadherin (E-cad). Markers of fibrogenesis, including collagens and connective tissue growth factor (CTGF) were also evaluated by measuring mRNA level using RT-PCR, and protein by immunofluorescence or Western blotting. Signaling pathways for EMT were characterized by Western analysis of cell lysates using monoclonal antibodies to detect phosphorylated Erk1/2 and Smad2 after TGF-β1 treatment in the presence or absence of MEK inhibitors. The role of Smad2 in TGF-β1-mediated EMT was investigated using siRNA.
Results: The data showed that TGF-β1, but not TNF-α or IL-1β, induced A549 cells with an alveolar epithelial type II cell phenotype to undergo EMT in a time-and concentration-dependent manner. The process of EMT was accompanied by morphological alteration and expression of the fibroblast phenotypic markers Fn-EDA and vimentin, concomitant with a downregulation of the epithelial phenotype marker E-cad. Furthermore, cells that had undergone EMT showed enhanced expression of markers of fibrogenesis including collagens type I and III and CTGF. MMP-2 expression was also evidenced. TGF-β1-induced EMT occurred through phosphorylation of Smad2 and was inhibited by Smad2 gene silencing; MEK inhibitors failed to attenuate either EMT-associated Smad2 phosphorylation or the observed phenotypic changes.
Conclusion: Our study shows that TGF-β1 induces A549 alveolar epithelial cells to undergo EMT via Smad2 activation. Our data support the concept of EMT in lung epithelial cells, and suggest the need for further studies to investigate the phenomenon
Solar-type dynamo behaviour in fully convective stars without a tachocline
In solar-type stars (with radiative cores and convective envelopes), the
magnetic field powers star spots, flares and other solar phenomena, as well as
chromospheric and coronal emission at ultraviolet to X-ray wavelengths. The
dynamo responsible for generating the field depends on the shearing of internal
magnetic fields by differential rotation. The shearing has long been thought to
take place in a boundary layer known as the tachocline between the radiative
core and the convective envelope. Fully convective stars do not have a
tachocline and their dynamo mechanism is expected to be very different,
although its exact form and physical dependencies are not known. Here we report
observations of four fully convective stars whose X-ray emission correlates
with their rotation periods in the same way as in Sun-like stars. As the X-ray
activity - rotation relationship is a well-established proxy for the behaviour
of the magnetic dynamo, these results imply that fully convective stars also
operate a solar-type dynamo. The lack of a tachocline in fully convective stars
therefore suggests that this is not a critical ingredient in the solar dynamo
and supports models in which the dynamo originates throughout the convection
zone.Comment: 6 pages, 1 figure. Accepted for publication in Nature (28 July 2016).
Author's version, including Method
Waterproof Flexible InP@ZnSeS Quantum Dot Light-Emitting Diode
The development of flexible displays for wearable electronics applications has created
demand for high-performance quantum dot (QD) light-emitting diodes (QLEDs) based on QD
core@shell structures. Emerging indium phosphide (InP)-based core@shell QDs show
promise as lighting material in the field of optoelectronics because they are environmentally
friendly material, can be produced in a cost-effective manner, and are capable of tunable
emission. While efforts have been made to enhance the performance of InP-based QLED, the
stabilities of InP@ZnSeS QDs film and InP@ZnSeS-based QLED in water/air are not yet
fully understood, limiting their practical applications. Herein, a highly durable, flexible
InP@ZnSeS QLED encapsulated in an ultrathin film of CYTOP, a solution-based amorphous
fluoropolymer, is demonstrated. The CYTOP-encapsulated green flexible QLED shows an
external quantum efficiency (EQE) of 0.904% and a high luminescence of 1593 cd/m2
as
well as outstanding waterproof performance. The flexible device emits strong luminescence
after being immersed in water for ~20 minutes. Even when subjected to continuous tensile
stress with a 5 mm bending radius, the high luminescence is preserved. This waterproof
architecture can be a promising strategy for wearable electronics applications
Allelopathic interactions of linoleic acid and nitric oxide increase the competitive ability of Microcystis aeruginosa
The frequency and intensity of cyanobacterial blooms are increasing worldwide with major societal and economic costs. Interactions between toxic cyanobacteria and eukaryotic algal competitors can affect toxic bloom formation, but the exact mechanisms of interspecies interactions remain unknown. Using metabolomic and proteomic profiling of co-cultures of the toxic cyanobacterium Microcystis aeruginosa with a green alga as well as of microorganisms collected in a Microcystis spp. bloom in Lake Taihu (China), we disentangle novel interspecies allelopathic interactions. We describe an interspecies molecular network in which M. aeruginosa inhibits growth of Chlorella vulgaris, a model green algal competitor, via the release of linoleic acid. In addition, we demonstrate how M. aeruginosa takes advantage of the cell signaling compound nitric oxide produced by C. vulgaris, which stimulates a positive feedback mechanism of linoleic acid release by M. aeruginosa and its toxicity. Our high-throughput system-biology approach highlights the importance of previously unrecognized allelopathic interactions between a broadly distributed toxic cyanobacterial bloom former and one of its algal competitors
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