分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We show that the time-averaged Poynting vector in parity-time (PT ) symmetric coupled waveguides is always positive and cannot explain the stopped light at exceptional points (EPs). In order to solve this paradox, we must accept the fact that the fields E and H and the Poynting vector in non-Hermitian systems are in general complex. Based on the original definition of the instantaneous Poynting vector, a formula on the group velocity is proposed, which agrees perfectly well with that calculated directly from the dispersion curves. It explains not only the stopped light at EPs, but also the fast-light effect near it. This investigation bridges a gap between the classic electrodynamics and the non-Hermitian physics, and highlights the novelty of non-Hermitian optics.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Understanding the characteristics of the solar magnetic field is essential for interpreting solar activities and dynamo. In this research, we investigated the asymmetric distribution of the solar photospheric magnetic field values, using synoptic charts constructed from space-borne high-resolution magnetograms. It is demonstrated that the Lorentzian function describes the distribution of magnetic field values in the synoptic charts much better than the Gaussian function, and this should reflect the gradual decay process from strong to weak magnetic fields. The asymmetry values are calculated under several circumstances, and the results generally show two periodicities related to the variation of the solar B_0 angle and the solar cycle, respectively. We argue that it is the small-scale magnetic fields, the inclination of the solar axis, the emergence and evolution of magnetic flux, and the polar fields that are responsible for the features of asymmetry values. We further determined the polar field reversal time of solar cycles 23 and 24 with the flip of asymmetry values. Specifically, for cycle 24, we assert that the polar polarities of both hemispheres reversed at the same time - in March 2014; as to cycle 23, the reversal time of the S-hemisphere is March 2001, while the determination of the N-hemisphere is hampered by missing data.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We investigate the implications of the long-rang self-interaction on both the self-capture and the annihilation of the self-interacting dark matter (SIDM) trapped in the Sun. Our discussion is based on a specific SIDM model in which DM particles self-interact via a light scalar mediator, or Yukawa potential, in the context of quantum mechanics. Within this framework, we calculate the self-capture rate across a broad region of parameter space. While the self-capture rate can be obtained separately in the Born regime with perturbative method, and the classical limits with the Rutherford formula, our calculation covers the gap between in a non-perturbative fashion. Besides, the phenomelogy of both the Sommerfeld-enhanced s- and p-wave annihilation of the solar SIDM is also involved in our discussion. Moreover, by combining the analysis of the Super-Kamiokande (SK) data and the observed DM relic density, we constrain the nuclear capture rate of the DM particles in the presence of the dark Yukawa potential. The consequence of the long-range dark force on probing the solar SIDM turns out to be significant if the force-carrier is much lighter than the DM particle, and a quantitative analysis is provided.
分类： 农、林、牧、渔 >> 植物保护学 提交时间： 2025-01-08
摘要： Pepper (Capsicum annuum), a crucial economic crop worldwide(Tang et al. 2020), has been observed in multiple fields depicting susceptibility symptoms across Anhui Province, China, a primary region for pepper cultivation. Data obtained in November 2023, revealed that infected pepper plants exhibited yellowing leaves with wrinkling, curling, and mottling, while fruits displayed more severe symptoms, including browning, blackening, and necrosis. The infection significantly impaired the appearance and internal quality of pepper fruits, adversely affecting local production. Surveys indicated that approximately 25% to 35% of pepper plants showed these symptoms.We hypothesize that a viral disease is causing these symptoms(Wu et al. 2024).To determine the pathogenic virus, we mixed the collected samples and sent them to Lianchuan Co., Ltd. (Hangzhou, China) for small RNA sequencing (Wu et al. 2015). The library preparation was carried out using the TruSeq™ Small RNA Sample Prep Kits (Illumina, San Diego, USA). Subsequently, the constructed library was sequenced on the Illumina Hiseq2000/2500 platform. From the 18059475 raw readings obtained, we removed 3’ adapters and low-quality sequences, resulting in 14020232 clean readings, accounting for 77.63% of the initial raw readings. After removing the host genome, align the sequence with the virus database and analyze the distribution of hot-spots.Additional sequence assembly was conducted using virus detection software to generate longer contigs. Later, the concatenated sequences were annotated with viral sequences from the NT and NR databases. The raw data had been deposited in GenBank (PRJNA1194353). Specific sequence analysis showed that the average number of times each base in the sequence of tomato leaf curl New Delhi virus (ToLCNDV, HM159454.1) was sequenced and covered was 59.92%, and the sequence homology was 100%. ToLCNDV isclassified within the genus Begomovirusof the family Geminiviridaeand are known to be transmitted by the whitefly Bemisia tabaci(Lopezet al.2015).To further validate the presence of ToLCNDVin Pepper. The expected size 771-base pair (bp)RT-PCR productof ToLCNDV coat protein(CP)gene was obtained from all 24 tested samples using the pair of specific primer (ToLCNDV5′-ATGGCGAAGCGACCAGCAGATATC-3′/5′-TTAATTTGTGGCCGAATCATAAAAG-3′).Each set of sequences showed 100%identity within their respective groups. The sequence had been deposited in GenBank with accession numbers PQ638334for the CP gene of ToLCNDV. When compared with nucleotide sequences in the NCBI database, the CP gene of ToLCNDV in pepper exhibited 99.87%nucleotide homology with the Tomato leaf curl New Delhi virus isolate Ningbo6 segment DNA-A (OP585370).Field investigations were conducted across various regions of Anhui Province in China, where 46 pepper samples displaying symptoms such as yellowing, mottling, and wrinkling of leaves were collected. These samples were then subjected to RT-PCR and dot enzyme-linked immunosorbent assay (Dot-ELISA) testing, utilizing ToLCNDV-specific primers and viral antibodies for detection. 35 of these symptomatic samples,tested positive forToLCNDV, theinfection rate of up to76%.The above results show that thepepper leaves in Anhui Province exhibit symptoms of wrinkling and mottlingare most likely caused by ToLCNDVinfection. To verify this assumption，healthy Nicotiana benthamianaplants were inoculated with above mentioned crude extract of the samples containing the virus. Wrinkled and mottled leaves, shortplantstature and some other similar symptomswereobserved in 5 out of 10inoculated Pepper plants 22days post inoculation which was later confirmed with RT-PCR and sequencing results.These findings indicate that the symptoms observed in pepper leaves, characterized by wrinkling, mottling, and stunted plant growth, are most probably the result of infection by ToLCNDV. To our knowledge, this is the first report of presence ToLCNDV in pepper plants inChina.
分类： 物理学 >> 核物理学 提交时间： 2024-02-21
摘要： By the Skyrme density functional theory (DFT), potential energy surfaces (PES) of ^{240}Pu with constraints on the axial quadrupole and octupole deformations(q_{20} and q_{30}) are calculated.The volume-like, and the surface-like pairing forces, and the mixing between these two forces are used, within the Hartree-Fock-Bogoliubov (HFB) approximation. The variations of the least-energy fission path, fission barrier, paring energy, total kinetic energy, scission line, and mass distribution of fission fragments by the different forms of paring force are analyzed and discussed. The fission dynamics is studied based on the time-dependent generator coordinate method (TDGCM) plus Gaussian overlap approximation (GOA). The results show a sensitivity of the mass and charge distributions of fission fragments to the form of the pairing force. Based on the investigation of the neutron-induced fission of ^{239}Pu, among the volume, mixed, and surface pairing forces, the mixed-type of pairing force can give a good reproduction of experimental data.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Consensus has been reached that recollision, as the most important post-tunneling process, is responsible for nonsequential double ionization process in intense infrared laser field, however, its effect has been restricted to interaction between the first ionized electron and the residual univalent ion so far. Here we identify the key role of recollision between the second ionized electron and the divalent ion in the below-threshold nonsequential double ionization process by introducing a Coulomb-corrected quantum-trajectories method, which enables us to well reproduce the experimentally observed cross-shaped and anti-correlated patterns in correlated two-electron momentum distributions, and also the transition between these two patterns. Being significantly enhanced relatively by the recapture process, recolliding trajectories of the second electron excited by the first- or third-return recolliding trajectories of the first electron produce the cross-shaped or anti-correlated distributions, respectively. And the transition is induced by the increasing contribution of the third return with increasing pulse duration. Our work provides new insight into atomic ionization dynamics and paves the new way to imaging of ultrafast dynamics of atoms and molecules in intense laser field.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Ultrafast sub-ps THz pulse conveys rich distinctive spectral fingerprints related to the vibrational or rotational modes of biomolecules and can be used to resolve the time-dependent dynamics of the motions. Thus, an efficient platform for enhancing the THz light-matter interaction is strongly demanded. Waveguides, owing to their tightly spatial confinement of the electromagnetic fields and the longer interaction distance, are promising platforms. However, the efficient feeding of the sub-ps THz pulse to the waveguides remains challenging due to the ultra-wide bandwidth property of the ultrafast signal. We propose a sensing chip comprised of a pair of back-to-back Vivaldi antennas and a 90{\deg} bent slotline waveguide to overcome the challenge. The effective operating bandwidth of the sensing chip ranges from 0.2 to 1.15 THz, with the free-space to chip coupling efficiency up to 50%. Over the entire band, the THz signal is 42.44 dB above the noise level with a peak of 73.40 dB. To take advantages of the efficient sensing chip, we have measured the characteristic fingerprint of {\alpha}-lactose monohydrate, and a sharp absorption dip at near 0.53 THz has been successfully observed demonstrating the accuracy of the proposed solution. The proposed sensing chip has the advantages of efficient in-plane coupling, ultra-wide bandwidth, easy integration and fabrication, large-scale manufacturing capability, and cost-effective, and can be a strong candidate for THz light-matter interaction platform.
分类： 天文学 >> 天文学 提交时间： 2024-08-28 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope, we conducted observations of the neutral hydrogen (H i) in the circumgalactic medium of Andromeda's (M31) satellite galaxies, specifically Andromeda II, NGC 205, and NGC 185. Initially, three drift scans were executed for these satellites, with a detection limit of 4 × 1018 cm−2 (approximately 1.88 × 103M⊙ of H i mass), followed by a more in-depth scan of a specific region. We discovered a C-shaped H i arc structure sharing a position and line-of-sight velocity similar to a stellar ring structure around Andromeda II, hinting at a potential connection with Andromeda II. In the context of NGC 205, we identified two mass concentrations in the northeast direction, which could be indicative of tidal streams resulting from the interaction between this galaxy and M31. These new lumps discovered could be very helpful in solving the missing interstellar medium problem for NGC 205. Observations regarding NGC 185 are consistent with previous studies, and we did not detect any additional H i material around this galaxy. These observational results enhance our understanding of the evolution of these satellite galaxies and provide insight into their historical interactions with the galaxy M31.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper, we report on 606 S-type stars identified from Data Release 9 of the LAMOST medium-resolution spectroscopic (MRS) survey, and 539 of them are reported for the first time. The discovery of these stars is a three-step process, i.e., selecting with the ZrO band indices greater than 0.25, excluding non-S-type stars with the iterative Support Vector Machine method, and finally retaining stars with absolute bolometric magnitude larger than -7.1. The 606 stars are consistent with the distribution of known S-type stars in the color-magnitude diagram. We estimated the C/Os using the [C/Fe] and [O/Fe] provided by APOGEE and the MARCS model for S-type stars, respectively, and the results of the two methods show that C/Os of all stars are larger than 0.5. Both the locations on the color-magnitude diagram and C/Os further verify the nature of our S-type sample. Investigating the effect of TiO and atmospheric parameters on ZrO with the sample, we found that log g has a more significant impact on ZrO than Teff and [Fe/H], and both TiO and log g may negatively correlate with ZrO. According to the criterion of Tian et al. (2020), a total of 238 binary candidates were found by the zero-point-calibrated radial velocities from the officially released catalog of LAMOST MRS and the catalog of Zhang et al. (2021). A catalog of these 606 S-type stars is available from the following link https://doi.org/10.12149/101097.
分类： 天文学 >> 天文学 提交时间： 2025-03-11 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： BFOSC and YFOSC are the most frequently used instruments in the Xinglong 2.16 m telescope and Lijiang 2.4 m telescope, respectively. We developed a software package named "BYSpec" (BFOSC and YFOSC Spectra Reduction Package) dedicated to automatically reducing the long-slit and echelle spectra obtained by these two instruments. The package supports bias and flat-fielding correction, order location, background subtraction, automatic wavelength calibration, and absolute flux calibration. The optimal extraction method maximizes the signal-to-noise ratio and removes most of the cosmic rays imprinted in the spectra. A comparison with the 1D spectra reduced with IRAF verifies the reliability of the results. This open-source software is publicly available to the community.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Lue Wu
Weiqiang Xie
Chao Xiang
Lin Chang
Yan Yu
Hao-Jing Chen
Yoshihisa Yamamoto
John E. Bowers
Kerry J. Vahala
Myoung-Gyun Suh
摘要： Chip-integrated optical frequency combs are attractive optical sources in comb applications requiring high-repetition-rate, low power consumption, or compact size. Spontaneous soliton formation via Kerr parametric oscillation is a promising generation principle in these frequency combs, and has been demonstrated in several material platforms over the past decade. Of these materials, AlGaAs has one of the largest Kerr nonlinearity coefficients allowing low pump threshold comb generation. However, bright soliton generation using this material has only been possible at cryogenic temperature because of the large thermo-optic effect at room temperature, which hinders stable access to the soliton regime. Here, we report self-stabilized single soliton generation in AlGaAs microresonators at room temperature by utilizing a rising soliton step in large free-spectral-range resonators. With sub-milliWatt optical pump power, 1 THz repetition-rate soliton generation is demonstrated. Perfect soliton crystal formation and soliton breather states are also observed. Besides the advantages of large optical nonlinearity, the devices are natural candidates for integration with III-V pump lasers.
点击量
待评议
点击量
下载量
评论
通过
