1,497 research outputs found
A Study on Pulsed Power Supply based on Separate Excitation
© ASEE 2007Regular power supply cannot be used for some special applications such as discharging plasma generator, air purification system, medical discharging equipment, etc. Instead, a special low-power high-voltage pulsed power supply is required. In this paper, the design and simulation of a separate excited pulse power supply are proposed. The power supply can produce high-voltage small-current pulses adaptive to different loads. The working principle of the power supply is analyzed. A comparison between this power supply and other pulsed power supply based on capacitance energy storage is discussed. The circuit implementation of power supply is proposed. The key component for the power supply, pulse transformer, as well as other components is studied in detail. Based on the analysis, an optimized design of the power supply is proposed. Computer simulation is used to verify the performance of the designed power supply, such as the output characteristics under different load resistances, the pulse frequency and the duty ratio. Simulation results demonstrate the effectiveness of the designed power supply. Some possible performance improvements on the power supply are also suggested. The designed power supply can satisfy the requirements for commercial applications such as plasma generation and air purification system
Non-Abelian Chiral Spin Liquid on the Kagome Lattice
We study spin liquid states on the kagome lattice constructed by
Gutzwiller-projected superconductors. We show that the obtained spin
liquids are either non-Abelian or Abelian topological phases, depending on the
topology of the fermionic mean-field state. By calculating the modular matrices
and , we confirm that projected topological superconductors are
non-Abelian chiral spin liquid (NACSL). The chiral central charge and the spin
Hall conductance we obtained agree very well with the (or,
equivalently, ) field theory predictions. We propose a local
Hamiltonian which may stabilize the NACSL. From a variational study we observe
a topological phase transition from the NACSL to the Abelian spin liquid.Comment: 12 pages, 7 figures, 1 tabl
Effect of ultrasound on physicochemical properties of emulsion stabilized by fish myofibrillar protein and xanthan gum
peer-reviewedTo investigate the effects ultrasound (20âŻkHz, 150â600âŻW) on physicochemical properties of emulsion stabilized by myofibrillar protein (MP) and xanthan gum (XG), the emulsions were characterized by Fourier transform infrared (FT-IR) spectroscopy, ζ-potential, particle size, rheology, surface tension, and confocal laser scanning microscopy (CLSM). FT-IR spectra confirmed the complexation of MP and XG, and ultrasound did not change the functional groups in the complexes. The emulsion treated at 300âŻW showed the best stability, with the lowest particle size, the lowest surface tension (26.7âŻmNmâ1) and the largest ζ-potential absolute value (25.4âŻmV), that were confirmed in the CLSM photos. Ultrasound reduced the apparent viscosity of the MP-XG emulsions, and the changes of particle size were manifested in flow properties. Generally, ultrasound was successfully applied to improve the physical stability of MP-XG emulsion, which could be used as a novel delivery system for functional material
BcBIM: A Blockchain-Based Big Data Model for BIM Modification Audit and Provenance in Mobile Cloud
Building Information Modeling (BIM) is envisioned as an indispensable opportunity in the architecture, engineering, and construction (AEC) industries as a revolutionary technology and process. Smart construction relies on BIM for manipulating information flow, data flow, and management flow. Currently, BIM model has been explored mainly for information construction and utilization, but rare works pay efforts to information security, e.g., critical model audit and sensitive model exposure. Moreover, few BIM systems are proposed to chase after upcoming computing paradigms, such as mobile cloud computing, big data, blockchain, and Internet of Things. In this paper, we make the first attempt to propose a novel BIM system model called bcBIM to tackle information security in mobile cloud architectures. More specifically, bcBIM is proposed to facilitate BIM data audit for historical modifications by blockchain in mobile cloud with big data sharing. The proposed bcBIM model can guide the architecture design for further BIM information management system, especially for integrating BIM cloud as a service for further big data sharing. We propose a method of BIM data organization based on blockchains and discuss it based on private and public blockchain. It guarantees to trace, authenticate, and prevent tampering with BIM historical data. At the same time, it can generate a unified format to support future open sharing, data audit, and data provenance
Magnetic coupling of a rotating black hole with its surrounding accretion disk
Effects of magnetic coupling (MC) of a rotating black hole (BH) with its
surrounding accretion disk are discussed in detail in the following aspects:
(i) The mapping relation between the angular coordinate on the BH horizon and
the radial coordinate on the disk is modified based on a more reasonable
configuration of magnetic field, and a condition for coexistence of the
Blandford-Znajek (BZ) and the MC process is derived. (ii) The transfer
direction of energy and angular momentum in MC process is described
equivalently by the co-rotation radius and by the flow of electromagnetic
angular momentum and redshifted energy, where the latter is based on an
assumption that the theory of BH magnetosphere is applicable to both the BZ and
MC processes. (iii) The profile of the current on the BH horizon and that of
the current density flowing from the magnetosphere onto the horizon are given
in terms of the angular coordinate of the horizon. It is shown that the current
on the BH horizon varies with the latitude of the horizon and is not continuous
at the angular boundary between the open and closed magnetic field lines. (iv)
The MC effects on disk radiation are discussed, and a very steep emissivity is
produced by MC process, which is consistent with the recent XMM-Newton
observation of the nearby bright Seyfert 1 galaxy MCG-6-30-15 by a variety of
parameters of the BH-disk system.Comment: 24 pages, 19 figures. Accepted by Ap
C. elegans fatty acid two-hydroxylase regulates intestinal homeostasis by affecting heptadecenoic acid production
Background/Aims: The hydroxylation of fatty acids at the C-2 position is the first step of fatty acid α-oxidation and generates sphingolipids containing 2-hydroxy fatty acyl moieties. Fatty acid 2-hydroxylation is catalyzed by Fatty acid 2-hydroxylase (FA2H) enzyme. However, the precise roles of FA2H and fatty acid 2-hydroxylation in whole cell homeostasis still remain unclear. Methods: Here we utilize Caenorhabditis elegans as the model and systemically investigate the physiological functions of FATH-1/C25A1.5, the highly conserved worm homolog for mammalian FA2H enzyme. Immunostaining, dye-staining and translational fusion reporters were used to visualize FATH-1 protein and a variety of subcellular structures. The âclick chemistryâ method was employed to label 2-OH fatty acid in vivo. Global and tissue-specific RNAi knockdown experiments were performed to inactivate FATH-1 function. Lipid analysis of the fath-1 deficient mutants was achieved by mass spectrometry. Results: C. elegans FATH-1 is expressed at most developmental stages and in most tissues. Loss of fath-1 expression results in severe growth retardation and shortened lifespan. FATH-1 function is crucially required in the intestine but not the epidermis with stereospecificity. The âclick chemistryâ labeling technique showed that the FATH-1 metabolites are mainly enriched in membrane structures preferable to the apical side of the intestinal cells. At the subcellular level, we found that loss of fath-1 expression inhibits lipid droplets formation, as well as selectively disrupts peroxisomes and apical endosomes. Lipid analysis of the fath-1 deficient animals revealed a significant reduction in the content of heptadecenoic acid, while other major FAs remain unaffected. Feeding of exogenous heptadecenoic acid (C17: 1), but not oleic acid (C18: 1), rescues the global and subcellular defects of fath-1 knockdown worms. Conclusion: Our study revealed that FATH-1 and its catalytic products are highly specific in the context of chirality, C-chain length, spatial distribution, as well as the types of cellular organelles they affect. Such an unexpected degree of specificity for the synthesis and functions of hydroxylated FAs helps to regulate protein transport and fat metabolism, therefore maintaining the cellular homeostasis of the intestinal cells. These findings may help our understanding of FA2H functions across species, and offer potential therapeutical targets for treating FA2H-related diseases
Screw instability of the magnetic field connecting a rotating black hole with its surrounding disk
Screw instability of the magnetic field connecting a rotating black hole (BH)
with its surrounding disk is discussed based on the model of the coexistence of
the Blandford-Znajek (BZ) process and the magnetic coupling (MC) process
(CEBZMC). A criterion for the screw instability with the state of CEBZMC is
derived based on the calculations of the poloidal and toroidal components of
the magnetic field on the disk. It is shown by the criterion that the screw
instability will occur, if the BH spin and the power-law index for the
variation of the magnetic field on the disk are greater than some critical
values. It turns out that the instability occurs outside some critical radii on
the disk. It is argued that the state of CEBZMC always accompanies the screw
instability. In addtition, we show that the screw instability contributes only
a small fraction of magnetic extraction of energy from a rotating BH.Comment: 18 pages, 13 figures; Accepted by Ap
miR-202 suppresses cell proliferation in human hepatocellular carcinoma by downregulating LRP6 post-transcriptionally
AbstractMicroRNAs have emerged as important regulators of carcinogenesis. In the current study, we observed that microRNA-202 (miR-202) is downregulated in hepatocellular carcinoma (HCC) cells and tissues, indicating a significant correlation between miR-202 expression and HCC progression. Overexpression of miR-202 in HCC cells suppressed cell proliferation and tumorigenicity, while downregulation of miR-202 enhanced the cellsâ proliferative capacity. Furthermore, we identified low-density lipoprotein receptor-related protein 6 (LRP6) as a direct target of miR-202. miR-202 suppresses the expression of LRP6 by binding to the 3âČ-untranslated region (UTR) of its mRNA. Finally, we found that silencing the expression of LRP6 is the essential biological function of miR-202 during HCC cell proliferation. Collectively, our findings reveal that miR-202 is a potential tumor suppressive miRNA that participates in carcinogenesis of human HCC by suppressing LRP6 expression
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