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 $i$-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 $z>3.6$ quasar candidates selected by using our proposed $J-K/i-Y$ 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 $z>3.6$ 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 $z>4$ 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 &lt;italic&gt;X&lt;/italic&gt;-band (9.56&amp;#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 &lt;italic&gt;X&lt;/italic&gt;-band switchplexer operates at three frequency bands, e.g., 11.08&amp;#x2013;11.55 GHz, 10.61&amp;#x2013;10.99 GHz, and 9.76&amp;#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 mol­ecule, C10H8N2O2, the imidazole and benzene rings form a dihedral angle of 14.5 (1)°. In the crystal, inter­molecular O—H⋯N hydrogen bonds link the mol­ecules into chains extending in [01], which are further linked into sheets parallel to (102) through weak C—H⋯O inter­actions

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

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

(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