8,088 research outputs found
Discovery of six high-redshift quasars with the Lijiang 2.4m telescope and the Multiple Mirror Telescope
Quasars with redshifts greater than 4 are rare, and can be used to probe the
structure and evolution of the early universe. Here we report the discovery of
six new quasars with -band magnitudes brighter than 19.5 and redshifts
between 2.4 and 4.6 from the YFOSC spectroscopy of the Lijiang 2.4m telescope
in February, 2012. These quasars are in the list of quasar candidates
selected by using our proposed criterion and the photometric redshift
estimations from the SDSS optical and UKIDSS near-IR photometric data. Nine
candidates were observed by YFOSC, and five among six new quasars were
identified as quasars. One of the other three objects was identified as
a star and the other two were unidentified due to the lower signal-to-noise
ratio of their spectra. This is the first time that quasars have been
discovered using a telescope in China. Thanks to the Chinese Telescope Access
Program (TAP), the redshift of 4.6 for one of these quasars was confirmed by
the Multiple Mirror Telescope (MMT) Red Channel spectroscopy. The continuum and
emission line properties of these six quasars, as well as their central black
hole masses and Eddington ratios, were obtained.Comment: 7 pages, 2 figures, published in Research in Astronomy and
Astrophysics (RAA) as a lette
Liquid Metal-Enabled Filtering Switches and Switchplexers
The via-pad-slot (VPS) structure, as the switchable element, has been used to demonstrate a single-pole-triple-throw (SPTT) filtering switch and a switchplexer. The VPS can be flexibily switched using liquid metal (LM) or high dielectric constant materials to either cover or uncover the slot. Since the LM only moves on the surface of the VPS and the substrate-integrated waveguide (SIW), the implementation and actuation of the LM is simple and does not cause excessive loss on the device. In the switchplexer design, all channels can be switched on and off to form filters or multiplexers of various channel combinations. Additional transmission zeros (TZs) can be generated by the loaded, partially switched-off channel. The generation of the TZs was discussed and analyzed using coupling matrix approach. The demonstrated <italic>X</italic>-band (9.56&#x2013;10.44 GHz) cross-shaped SPTT fifth-order filtering switch exhibits a suppression level of better than 40 dB at 8 and 12 GHz, an insertion loss (IL) of 1.55 dB at 10 GHz, and an isolation level of 58 dB at 10 GHz. The <italic>X</italic>-band switchplexer operates at three frequency bands, e.g., 11.08&#x2013;11.55 GHz, 10.61&#x2013;10.99 GHz, and 9.76&#x2013;10.33 GHz. The LM-enabled VPS-based switchable element can be integrated with other multifunctional circuits and systems for channel control and reconfiguration.</p
Preparation and Properties of Fe3O4 Biomimetic Micro-nano Structure Coatings
Nanoparticles filling is one of the most effective methods to build the micro-nano structure. In this paper, the composite coatings containing Fe3O4 nanoparticles were prepared from fluorinated silicon polymer by in-situ polymerization. FT-IR was used to characterize the structure of the composite material. SEM and AFM were performed to observe the microstructure of the coatings. The contact angle of water and coatings was tested. The results showed that the biomimetic micro-nano structure of the coatings, which formed on the glass plate, was exactly familiar with that of the surface of lotus leaves. Keyword: micro-nano structure; Fe3O4 nanoparticles; in-situ polymerization; biomimeti
4-(Imidazol-1-yl)benzoic acid
In the title molÂecule, C10H8N2O2, the imidazole and benzene rings form a dihedral angle of 14.5 (1)°. In the crystal, interÂmolecular O—H⋯N hydrogen bonds link the molÂecules into chains extending in [01], which are further linked into sheets parallel to (102) through weak C—H⋯O interÂactions
Thiopeptide Antibiotics Exhibit a Dual Mode of Action against Intracellular Pathogens by Affecting Both Host and Microbe
SummaryThiostrepton (TSR) is an archetypal thiopeptide antibiotic possessing a quinaldic acid (QA) moiety in the side ring system. According to the mechanism of TSR previously known to target bacterial ribosome, we recently designed and biosynthesized several TSR derivatives that varied in QA substitution. Utilizing these thiopeptide antibiotics to treat the intracellular pathogen Mycobacterium marinum, we herein report a novel mode of action of TSRs, which induce ER stress-mediated autophagy to enhance host cell defense. This intracellular response, which is sensitive to the modification of the QA group, serves as an indirect but unignorable mechanism for eliminating intracellular pathogens. TSRs are thus the only type of antibiotics, to our knowledge, with the dual action on both the parasitic bacteria and the infected host cells. The newly observed mechanism of TSRs may inspire the future change in the treatment of intracellular pathogens, by taking host response into account
Onset of chaotic gravitational lensing in non-Kerr rotating black holes with quadrupole mass moment
In the electromagnetic channel, chaotic gravitational lensing is a peculiar
phenomenon in strong gravitational lensing. In this work, we analyze the
properties and emergence of chaotic gravitational lensing in the Manko-Novikov
black hole spacetime. Aiming to understand better the underlying physics, we
elaborate on the boundaries of the accessible region in terms of the analyses
of the contours of the effective potentials. The latter is associated with the
two roots of a quadratic equation. In particular, we explore its interplay with
ergoregion, which leads to specific features of the effective potentials, such
as the emergence of cuspy edge and the formation of {\it pocket}, that serves
as a static constraint on the geodesics. Besides, we investigate the properties
of the radial and angular accelerations at the turning points in photons'
trajectories. Moreover, the accelerations are analyzed, which is argued to
provide a kinematic constraint on the geodesics. It is concluded that the onset
of the chaotic lensing is crucially related to both constraints, and as a
result, an arbitrarily slight deviation in the incident photon is significantly
amplified during the course of evolution through an extensive period,
demonstrating the complexity in the highly nonlinear deterministic
gravitational system.Comment: 18 pages, 13 figure
(2 +1)-dimensional Duffin-Kemmer-Petiau oscillator under a magnetic field in the presence of a minimal length in the noncommutative space
Using the momentum space representation, we study the (2 +1)-dimensional
Duffin-Kemmer-Petiau oscillator for spin 0 particle under a magnetic field in
the presence of a minimal length in the noncommutative space. The explicit form
of energy eigenvalues are found, the wave functions and the corresponding
probability density are reported in terms of the Jacobi polynomials.
Additionally, we also discuss the special cases and depict the corresponding
numerical results
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