6,553 research outputs found
A feedback-driven bubble G24.136+00.436: a possible site of triggered star formation
We present a multi-wavelength study of the IR bubble G24.136+00.436. The
J=1-0 observations of CO, CO and CO were carried out with
the Purple Mountain Observatory 13.7 m telescope. Molecular gas with a velocity
of 94.8 km s is found prominently in the southeast of the bubble,
shaping as a shell with a total mass of . It is
likely assembled during the expansion of the bubble. The expanding shell
consists of six dense cores. Their dense (a few of cm) and
massive (a few of ) characteristics coupled with the broad
linewidths ( 2.5 km s) suggest they are promising sites of forming
high-mass stars or clusters. This could be further consolidated by the
detection of compact HII regions in Cores A and E. We tentatively identified
and classified 63 candidate YSOs based on the \emph{Spitzer} and UKIDSS data.
They are found to be dominantly distributed in regions with strong emission of
molecular gas, indicative of active star formation especially in the shell. The
HII region inside the bubble is mainly ionized by a O8V star(s), of the
dynamical age 1.6 Myr. The enhanced number of candidate YSOs and
secondary star formation in the shell as well as time scales involved, indicate
a possible scenario of triggering star formation, signified by the "collect and
collapse" process.Comment: 13 pages, 10 figures, 4 tables, accepted by Ap
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Visualizing Morphogenesis through Instability Formation in 4-D Printing.
Heterogeneous growth in a myriad of biological systems can lead to the formation of distinct morphologies during the maturation processes of different species. We demonstrate that the distinct circumferential buckling observed in pumpkins can be reproduced by a core-shell barrel structure using four-dimensional (4D) printing, taking advantage of digital light processing (DLP)-based three-dimensional (3D) printing and stimulus-responsive hydrogels. The mechanical mismatch between the stiff core and compliant shell results in buckling instability on the surface. The initiation and development of the buckling are governed by the ratio of core/shell radius, the ratio of core/shell swelling ratios, and the mismatch between the core and shell in stiffness. Furthermore, the rigid core not only acts as a source of circumferential confinement but also sets a boundary at the poles of the entire structure. The heterogeneous structures with controllable buckling geometrically and structurally behave much like plants' fruits. This replicates the biological morphologic change and elucidates the general mechanism and dynamics of the complex instability formation of heterogeneous 3D objects
Nonlinear Decoupling Sliding Mode Control of Permanent Magnet Linear Synchronous Motor Based on α-th Order Inverse System Method
AbstractIn this paper, a nonlinear dynamic decoupling controller is proposed for the permanent magnet linear synchronous motor (PMLSM) servo system to improve dynamic operating performance. Firstly, the reversibility of the PMLSM mathematical model is analyzed, and it is proved that the system is reversible. Then an inverse system method is applied to the PMLSM servo system, and it is decoupled into a linear velocity subsystem and a linear current subsystem based on the α-th order inverse system method. Considering the both ideal linear subsystems are sensitive to parameter disturbances and various disturbances, a variable rate reaching law approach based subsystem sliding mode controller for higher system stability and robustness is proposed. Finally, simulation results are provided to demonstrate the effectiveness of the proposed control method
Productive infection of human immunodeficiency virus type 1 in dendritic cells requires fusion-mediated viral entry
AbstractHuman immunodeficiency virus type 1 (HIV-1) enters dendritic cells (DCs) through endocytosis and viral receptor-mediated fusion. Although endocytosis-mediated HIV-1 entry can generate productive infection in certain cell types, including human monocyte-derived macrophages, productive HIV-1 infection in DCs appears to be dependent on fusion-mediated viral entry. It remains to be defined whether endocytosed HIV-1 in DCs can initiate productive infection. Using HIV-1 infection and cellular fractionation assays to measure productive viral infection and entry, here we show that HIV-1 enters monocyte-derived DCs predominately through endocytosis; however, endocytosed HIV-1 cannot initiate productive HIV-1 infection in DCs. In contrast, productive HIV-1 infection in DCs requires fusion-mediated viral entry. Together, these results provide functional evidence in understanding HIV-1 cis-infection of DCs, suggesting that different pathways of HIV-1 entry into DCs determine the outcome of viral infection
(2-Amino-5-chloroÂbenzeneÂsulfonato)bisÂ(triphenylÂphosphine)silver(I)
The asymmetric unit of the title mononuclear compound, [Ag(C6H5ClNO3S)(C18H15P)2], contains four independent molÂecules. In each of the molÂecules, the AgI cation is three-coordinated by two triphenylÂphosphine ligands, and one N atom from a 2-amino-5-chloroÂbenzeneÂsulfonate anion. The molÂecules are linked into a one-dimensional supraÂmolecular structure by N—H⋯O hydrogen bonds
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