220 research outputs found
Dynamical generation of dark solitons in spin-orbit-coupled Bose-Einstein condensates
We numerically investigate the ground state, the Raman-driving dynamics and
the nonlinear excitations of a realized spin-orbit-coupled Bose-Einstein
condensate in a one-dimensional harmonic trap. Depending on the Raman coupling
and the interatomic interactions, three ground-state phases are identified:
stripe, plane wave and zero-momentum phases. A narrow parameter regime with
coexistence of stripe and zero-momentum or plane wave phases in real space is
found. Several sweep progresses across different phases by driving the Raman
coupling linearly in time is simulated and the non-equilibrium dynamics of the
system in these sweeps are studied. We find kinds of nonlinear excitations,
with the particular dark solitons excited in the sweep from the stripe phase to
the plane wave or zero-momentum phase within the trap. Moreover, the number and
the stability of the dark solitons can be controlled in the driving, which
provide a direct and easy way to generate dark solitons and study their
dynamics and interaction properties.Comment: 10 pages, 9 figur
Quantum plasmonic hot-electron injection in lateral WSe2/MoSe2 heterostructures
Lateral two-dimensional (2D) transitional metal dichalcogenide (TMD)
heterostructures have recently attracted a wide attention as promising
materials for optoelectronic nanodevices. Due to the nanoscale width of lateral
heterojunctions, the study of their optical properties is challenging and
requires using subwavelength optical characterization techniques. We
investigated the photoresponse of a lateral 2D WSe2/MoSe2 heterostructure using
tip-enhanced photoluminescence (TEPL) with nanoscale spatial resolution and
with picoscale tip-sample distance dependence. We demonstrate the observation
of quantum plasmonic effects in 2D heterostructures on a non-metallic
substrate, and we report the nano-optical measurements of the lateral 2D TMD
heterojunction width of ~ 150 nm and the charge tunneling distance of ~ 20 pm.
Controlling the plasmonic tip location allows for both nano-optical imaging and
plasmon-induced hot electron injection into the heterostructure. By adjusting
the tip-sample distance, we demonstrated the controllability of the
hot-electron injection via the competition of two quantum plasmonic
photoluminescence (PL) enhancement and quenching mechanisms. The directional
charge transport in the depletion region leads to the increased hot electron
injection, enhancing the MoSe2 PL signal. The properties of the directional
hot-electron injection in the quantum plasmonic regime make the lateral 2D
MoSe2/WSe2 heterostructures promising for quantum nanodevices with tunable
photoresponse
Janus Monolayer Transition Metal Dichalcogenides
A novel crystal configuration of sandwiched S-Mo-Se structure (Janus SMoSe)
at the monolayer limit has been synthesized and carefully characterized in this
work. By controlled sulfurization of monolayer MoSe2 the top layer of selenium
atoms are substituted by sulfur atoms while the bottom selenium layer remains
intact. The peculiar structure of this new material is systematically
investigated by Raman, photoluminescence and X-ray photoelectron spectroscopy
and confirmed by transmission-electron microscopy and time-of-flight secondary
ion mass spectrometry. Density-functional theory calculations are performed to
better understand the Raman vibration modes and electronic structures of the
Janus SMoSe monolayer, which are found to correlate well with corresponding
experimental results. Finally, high basal plane hydrogen evolution reaction
(HER) activity is discovered for the Janus monolayer and DFT calculation
implies that the activity originates from the synergistic effect of the
intrinsic defects and structural strain inherent in the Janus structure.Comment: 22 pages, 12 figure
Visualizing the elongated vortices in -Ga nanostrips
We study the magnetic response of superconducting -Ga via low
temperature scanning tunneling microscopy and spectroscopy. The magnetic vortex
cores rely substantially on the Ga geometry, and exhibit an unexpectedly-large
axial elongation with aspect ratio up to 40 in rectangular Ga nano-strips
(width 100 nm). This is in stark contrast with the isotropic circular
vortex core in a larger round-shaped Ga island. We suggest that the unusual
elongated vortices in Ga nanostrips originate from geometric confinement effect
probably via the strong repulsive interaction between the vortices and Meissner
screening currents at the sample edge. Our finding provides novel conceptual
insights into the geometrical confinement effect on magnetic vortices and forms
the basis for the technological applications of superconductors.Comment: published in Phys. Rev. B as a Rapid Communicatio
Synergy between Toxoplasma gondii type I Δ GRA17 immunotherapy and PD-L1 checkpoint inhibition triggers the regression of targeted and distal tumors
Background: In this study, we hypothesize that the ability of the protozoan Toxoplasma gondii to modulate immune response within the tumor might improve the therapeutic effect of immune checkpoint blockade. We examined the synergetic therapeutic activity of attenuated T. gondii RH ΔGRA17 strain and programmed death ligand-1 (PD-L1) treatment on both targeted and distal tumors in mice. Methods: The effects of administration of T. gondii RH ΔGRA17 strain on the tumor volume and survival rate of mice bearing flank B16-F10, MC38, or LLC tumors were studied. We characterized the effects of ΔGRA17 on tumor biomarkers’ expression, PD-L1 expression, immune cells infiltrating the tumors, and expression of immune-related genes by using immunohistochemistry, immunofluorescence, flow cytometry, NanoString platform, and real time quantitative PCR, respectively. The role of immune cells in the efficacy of ΔGRA17 plus PD-L1 blockade therapy was determined via depletion of immune cell subtypes.Results: Treatment with T. gondii ΔGRA17 tachyzoites and anti-PD-L1 therapy significantly extended the survival of mice and suppressed tumor growth in preclinical mouse models of melanoma, Lewis lung carcinoma, and colon adenocarcinoma. Attenuation of the tumor growth was detected in the injected and distant tumors, which was associated with upregulation of innate and adaptive immune pathways. Complete regression of tumors was underpinned by late interferon-gamma-producing CD8+ cytotoxic T cells.Conclusion: The results from these models indicate that intratumoral injection of ΔGRA17 induced a systemic effect, improved mouse immune response, and sensitized immunologically ‘cold’ tumors and rendered them sensitive to immune checkpoint blockade therapy
Synthesis of Bessel Beam Using Time-Reversal Method Incorporating Metasurface
In this paper, a synthesis and implementation method for generating Bessel beams based on time-reversal theory incorporating electromagnetic (EM) meta-lens is proposed. As is known, time-reversal EM waves has the unique characteristic of adaptive backtracking. Therefore, with this characteristic, the EM characteristics of the radiation aperture can be obtained and further utilized to generate Bessel waves with any departure angle. Based on this concept, two meta-lenses for generating Bessel beams tilted in different directions were designed. Both meta-lenses were designed at the center frequency of 15 GHz, and the simulation results were consistent with the target expectation. A representative meta-lens was fabricated and measured. The final size of the meta-lens was 350 mm mm, and a Bessel beam with a 30° emergence angle was generated by this structure. The experimental results were in good agreement with the simulation results and the theoretical derivation. This synthetic method of Bessel beam generation using the time-reversal operation may be of great use for the application of Bessel beams in microwave communications, and it can broaden the application scope of non-diffracting beams
The LAMOST Survey of Background Quasars in the Vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the Commissioning Observations and the Pilot Surveys
We present new quasars discovered in the vicinity of the Andromeda and
Triangulum galaxies with the LAMOST during the 2010 and 2011 observational
seasons. Quasar candidates are selected based on the available SDSS, KPNO 4 m
telescope, XSTPS optical, and WISE near infrared photometric data. We present
509 new quasars discovered in a stripe of ~135 sq. deg from M31 to M33 along
the Giant Stellar Stream in the 2011 pilot survey datasets, and also 17 new
quasars discovered in an area of ~100 sq. deg that covers the central region
and the southeastern halo of M31 in the 2010 commissioning datasets. These 526
new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to
3.2. They represent a significant increase of the number of identified quasars
in the vicinity of M31 and M33. There are now 26, 62 and 139 known quasars in
this region of the sky with i magnitudes brighter than 17.0, 17.5 and 18.0
respectively, of which 5, 20 and 75 are newly-discovered. These bright quasars
provide an invaluable collection with which to probe the kinematics and
chemistry of the ISM/IGM in the Local Group of galaxies. A total of 93 quasars
are now known with locations within 2.5 deg of M31, of which 73 are newly
discovered. Tens of quasars are now known to be located behind the Giant
Stellar Stream, and hundreds behind the extended halo and its associated
substructures of M31. The much enlarged sample of known quasars in the vicinity
of M31 and M33 can potentially be utilized to construct a perfect astrometric
reference frame to measure the minute PMs of M31 and M33, along with the PMs of
substructures associated with the Local Group of galaxies. Those PMs are some
of the most fundamental properties of the Local Group.Comment: 26 pages, 6 figures, AJ accepte
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