- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Optical polarisation variability of radio-loud narrow-line Seyfert 1 galaxies
摘要： Context. Narrow-line Seyfert 1 galaxies (NLSy1s) constitute the active galactic nuclei subclass associated with systematically lower black hole masses. A few radio-loud NLSy1s have been detected in MeV–GeV energy bands by Fermi, and evidence that blazar-like jets are operating also in radio-loud NLSy1s, has been accumulated. Aims. We wish to quantify the temporal behaviour of the optical polarisation, fraction, and angle for a selected sample of radio-loud NLSy1s. We also search for rotations of the polarisation plane similar to those commonly observed in blazars. Methods. We have conducted R-band optical linear polarisation monitoring of a sample of ten radio-loud NLSy1 galaxies; five of them have previously been detected by Fermi. The dataset obtained with our pivoting instrument, the RoboPol polarimeter of the Skinakas observatory, has been complemented with observations from the KANATA, Perkins, and Steward observatories. When evidence for long rotations of the polarisation plane was found (at least three consecutive measurements covering at least 90?), we carried out numerical simulations to assess the probability that they are caused by intrinsically evolving electric vector position angles (EVPAs) instead of observational noise. Results. Even our moderately sampled sources show clear indications of variability in both polarisation fraction and angle. For the four best-sampled objects in our sample we find multiple periods of significant polarisation angle variability. Several of these events qualify as long rotations. In the two best-sampled cases, namely J1505+0326 and J0324+3410, we find indications for three long rotations of the polarisation angle. We show that although noise can induce the observed behaviour, it is much more likely that the apparent rotation is indeed caused by intrinsic evolution of the EVPA. To our knowledge, this is the very first detection of such events in this class of sources. In the largest dataset (J0324+3410), we find that the EVPA concentrates around a direction that is at 49.3? to the 15 GHz radio jet, implying a projected magnetic field at an angle of 40.7? to that axis. Conclusions. We assess the probability that pure measurement uncertainties are the reason behind the observed long rotations of the polarisation plane. We conclude that although this is not improbable, it is much more likely that intrinsic rotations are responsible for the observed phenomenology. We conclude, however, that much better sampled and larger datasets of larger source samples are necessary to constrain the physical mechanism(s) that generate long EVPA rotations in NLSy1s.
关键词： galaxies: active,methods: statistical,galaxies: Seyfert,methods: numerical,polarization,techniques: polarimetric
更新于2025-09-23 15:23:52
-
Characterization of M1 and M2 polarization phenotypes in peritoneal macrophages after treatment with graphene oxide nanosheets
摘要： Macrophages play a key role in nanoparticle removal and are primarily responsible for their uptake and trafficking in vivo. Due to their functional plasticity, macrophages display a spectrum of phenotypes between two extremes identified as pro-inflammatory M1 and reparative M2 macrophages, characterized by the expression of specific cell surface markers and the secretion of different cytokines. The influence of graphene oxide (GO) nanosheets functionalized with poly(ethylene glycol-amine) and labelled with fluorescein isothiocyanate (FITC-PEG-GO) on polarization of murine peritoneal macrophages towards M1 and M2 phenotypes was evaluated in basal and stimulated conditions by flow cytometry and confocal microscopy through the expression of different cell markers: CD80 and iNOS as M1 markers, and CD206 and CD163 as M2 markers. Although FITC-PEG-GO did not induce M1 or M2 macrophage polarization after 24 and 48 h in basal conditions, this nanomaterial decreased the percentage of M2 reparative macrophages. We have also compared control macrophages with macrophages that have or have not taken up FITC-PEG-GO after treatment with these nanosheets (GO+ and GO- cells, respectively). The CD80 expression diminished in GO+ macrophages after 48 h of GO treatment but the CD206 expression in GO+ population showed higher values than in both GO- population and control macrophages. In the presence of pro-inflammatory stimuli (LPS and IFN-γ), a significant decrease of CD80+ cells was observed after treatment with GO. This nanomaterial also induced significant decreases of CD206+ and CD163+ cells in the presence of reparative stimulus (IL-4). The CD80, iNOS and CD206 expression was lower in both GO- and GO+ cells than in control macrophages. However, higher CD163 expression was obtained in both GO- and GO+ cells in comparison with control macrophages. All these facts suggest that FITC-PEG-GO uptake did not induce the macrophage polarization towards the M1 pro-inflammatory phenotype, promoting the control of the M1/M2 balance with a slight shift towards M2 reparative phenotype involved in tissue repair, ensuring an appropriate immune response to these nanosheets.
关键词： Graphene oxide nanosheets,Macrophage polarization,Peritoneal macrophages,Cytokine profiling
更新于2025-09-23 15:23:52
-
Implementation of quantum permutation algorithm with classical light
摘要： We report the experimental implementation of quantum permutation algorithm using polarization and orbital angular momentum of the classical optical beam. The easy-handling optical setup to realize all eight cyclic permutation transformations for an four-dimensional system has been constructed. The two-to-one speed-up ratio to determine the parity of each permutation has been demonstrated. Moreover, we have theoretically discussed the extension to the case with eight elements, and the limitations on the generalization of our proposal to higher-dimensional cases. Our scheme exhibits outstanding stability and demonstrates that optical quantum computation is possible using classical states of light.
关键词： classical light,quantum permutation algorithm,polarization,orbital angular momentum
更新于2025-09-23 15:23:52
-
Control of the creation of bottle-hollow beam by polarization shaping
摘要： We propose a method for generating bottle-hollow (BH) beams by tailoring the polarization state of the incident field in a tightly focused system. An optical BH field can be generated in the vicinity of the focus by tailoring azimuthal and radial polarization indices of the incident field. Calculations show that the length and diameter are mainly affected by the radial polarization index. While for the azimuthal index, it affects the width of the hollow greatly. As a result, an all-optical controlled tunable BH beam is achieved. The generated BH beam may find application in optical tweezers.
关键词： Diffractive optics,Singular optics.,Polarization,Propagation
更新于2025-09-23 15:23:52
-
Ferroelectric enhanced photoelectrochemical water splitting in BiFeO3/TiO2 composite photoanode
摘要： A facile sol-gel methodology was used to synthesize single-phase BiFeO3 (BFO) film on TiO2 photoanode to improve photoelectrochemical (PEC) water-splitting efficiency. The BFO films with controllable thickness induced a considerable ferroelectric polarization under bias voltage, which effectively tuned the electric band bending of BFO/TiO2. The photocurrent density of the as-prepared BFO-5/TiO2 could reach up to 11.25 mA/cm2, which is over 20 times higher than that of bare TiO2. Moreover, the positively poled BFO-5/TiO2 photoanode yielded a photocurrent density of 28.75 mA/cm2 at 1.5 V vs.SCE under AM 1.5G illumination. This work suggests that BFO/TiO2 with combined ferroelectric and semiconducting features could be a promising solution to improve PEC performance by concurrently promoting the light absorption and charge-separation and transportation properties.
关键词： BiFeO3,Ferroelectric polarization,Photoanode,Water-splitting
更新于2025-09-23 15:23:52
-
A feasibility study of the time reversal violation test based on polarization of annihilation photons from the decay of ortho-Positronium with the J-PET detector
摘要： The Jagiellonian Positron Emission Tomograph (J-PET) is a novel device being developed at Jagiellonian University in Krakow, Poland based on organic scintillators. J-PET is an axially symmetric and high acceptance scanner that can be used as a multi-purpose detector system. It is well suited to pursue tests of discrete symmetries in decays of positronium in addition to medical imaging. J-PET enables the measurement of both momenta and the polarization vectors of annihilation photons. The latter is a unique feature of the J-PET detector which allows the study of time reversal symmetry violation operator which can be constructed solely from the annihilation photons momenta before and after the scattering in the detector.
关键词： Time reversal symmetry,Momenta,Polarization,Annihilation photons,J-PET detector,Discrete symmetries,Ortho-positronium
更新于2025-09-23 15:23:52
-
GroundBIRD: Observation of CMB Polarization with a Rapid Scanning and MKIDs
摘要： Cosmic microwave background (CMB) radiation is an afterglow from the Big Bang. CMB contains rich information about the early stage of the universe. In particular, odd-parity patterns (B-mode) in the CMB polarization on a large angular scale would provide an evidence of the cosmic in?ation. The aim of the GroundBIRD experiment is to observe the B-mode on large angular scales from the ground. One of the most novel characteristics of the telescope used for this experiment is its rapid rotational scanning technique. In addition, the telescope uses cold optics and microwave kinetic inductance detectors. We have developed a telescope mount with a three-axis rotation mechanism (azimuth, elevation, and boresight) and measured the vibration at the focal plane stage at 20 RPM scan rotation rate. We also performed focal plane detector tests on this mount. The tests con?rmed the expected response from the geomagnetism associated with the mount rotation. We have also developed a design for the magnetic shields and a detector array on a 3-in wafer. The preparations to begin the observations at the Teide Observatory in the Canary Islands in 2018 are proceeding smoothly.
关键词： Cosmic microwave background,Polarization,Microwave kinetic inductance detector
更新于2025-09-23 15:23:52
-
Dispersion flattened extremely high-birefringent kagome lattice elliptic core photonic crystal fiber in THz regime
摘要： A highly birefringent elliptic porous-core photonic crystal fiber with kagome lattice cladding has been presented for terahertz (THz) wave transmission. The slotted airholes inside the elliptic core effectively disrupt the symmetry of the porous-core which offers extremely high modal birefringence whereas the kagome cladding structure results in significantly low effective material loss (EML). The birefringence of the proposed structure is 9.73 × 10?2 for y-polarized mode at an operating frequency of 1 THz. The suggested structure also provides very flat dispersion over a bandwidth of 300 GHz. It is highly expected that this elliptic core waveguide would be remarkably useful in numerous polarization maintaining THz applications.
关键词： Photonic crystal fibers,Microstructured fibers,Fibres, polarization-maintaining,Optical communications,Fiber design and fabrication
更新于2025-09-23 15:23:52
-
Broadband generation of the first-order OAM modes in two-mode fiber by offset splicing and fiber rotating technology
摘要： We demonstrate a simple, compact, and cost-effective all-fiber structure to generate the first-order orbital angular momentum (OAM) modes over a broad wavelength range. The offset splicing between a polarization-maintaining single mode fiber (PM-SMF) and a two-mode fiber (TMF) is adopted to excite LP11 mode in the TMF from LP01 mode in SMF. Then the OAM ± 1,1 modes are generated by rotating a customized fiber rotator, which can modulate the phase difference of the two degenerate LP11 modes (OAM ± 1,1 = LP11a ± i × LP11b). The interference phenomenon formed between OAM and Gaussian beams, which displays a fork-shape or spiral interference pattern, is used to confirm the generation of OAM modes. It should be noted that a PM fiber coupler and PM-SMFs are utilized in the experiment, which can avoid coupling of modes with orthogonal polarizations and then improves the OAM mode stability. Besides, the complexity of the OAM generation system is also reduced because the devices like polarization controller and half-wave plate are omitted by employing PM fibers. Based on this simple offset splicing and fiber rotating technology, the broadband generation of OAM ± 1,1 modes are experimentally demonstrated in wavelength range of 1530–1566 nm.
关键词： Fiber rotating,Polarization-maintaining single mode fiber,Two mode fiber,Offset-splicing,Orbital angular momentum mode
更新于2025-09-23 15:23:52
-
A label-free aptamer-based nanogap capacitive biosensor with greatly diminished electrode polarization effects
摘要： A significant impediment to the use of impedance spectroscopy in bio-sensing is the electrode polarization effect that arises from the movement of free ions to the electrode–solution interface, forming an electrical double layer (EDL). The EDL screens the dielectric response of the bulk and its large capacitance dominates the signal response at low frequency, masking information particularly relevant for biological samples, such as molecular conformation changes and DNA hybridization. The fabrication of nanogap capacitors with electrode separation less than the EDL thickness can significantly reduce electrode polarization effects and provide enormous improvement in sensitivity due to better matching of the sensing volume with the size of the target entities. We report on the fabrication of a horizontal thin-film nanogap capacitive sensor with electrode separation of 40 nm that shows almost no electrode polarization effects when measured with water and ionic buffer solutions, thereby allowing direct quantification of their relative permittivity at low frequencies. Surface modification of the electrodes with thiol-functionalized single strand DNA aptamers transforms the device into a label-free biosensor with high sensitivity and selectivity towards the detection of a specific protein. Using this approach, we have developed a biosensor for the detection of human alpha thrombin. In addition, we also examine frequency dependent permittivity measurements on high ionic strength solutions contained within the nanogap and discuss how these support recent experimental observations of large Debye lengths. A large shift in the Debye relaxation frequency to lower frequency is also found, which is consistent with water molecules being in a rigid-like state, possibly indicating the formation of an ordered ‘‘ice-like’’ phase. Altogether, this work highlights the need for better understanding of fluids in confined, nanoscale geometries, from which important new applications in sensing may arise.
关键词： electrode polarization,aptamer,nanogap,capacitive biosensor,dielectric spectroscopy,thrombin
更新于2025-09-23 15:23:52