The realization of long-range ferromagnetic order in two-dimensional van der Waals crystals, combined with their rich electronic and optical properties, could lead to new magnetic, magnetoelectric ...and magneto-optic applications. In two-dimensional systems, the long-range magnetic order is strongly suppressed by thermal fluctuations, according to the Mermin-Wagner theorem; however, these thermal fluctuations can be counteracted by magnetic anisotropy. Previous efforts, based on defect and composition engineering, or the proximity effect, introduced magnetic responses only locally or extrinsically. Here we report intrinsic long-range ferromagnetic order in pristine Cr
Ge
Te
atomic layers, as revealed by scanning magneto-optic Kerr microscopy. In this magnetically soft, two-dimensional van der Waals ferromagnet, we achieve unprecedented control of the transition temperature (between ferromagnetic and paramagnetic states) using very small fields (smaller than 0.3 tesla). This result is in contrast to the insensitivity of the transition temperature to magnetic fields in the three-dimensional regime. We found that the small applied field leads to an effective anisotropy that is much greater than the near-zero magnetocrystalline anisotropy, opening up a large spin-wave excitation gap. We explain the observed phenomenon using renormalized spin-wave theory and conclude that the unusual field dependence of the transition temperature is a hallmark of soft, two-dimensional ferromagnetic van der Waals crystals. Cr
Ge
Te
is a nearly ideal two-dimensional Heisenberg ferromagnet and so will be useful for studying fundamental spin behaviours, opening the door to exploring new applications such as ultra-compact spintronics.
To identify the influence of microstructural variation on the X-ray diffraction intensities, X-ray diffraction patterns of hexagonal graphite (h-graphite) and turbostratic carbon (t-carbon) were ...simulated by using the general Debye equation. The numeric density of interatomic distance (NDID) is sensitive to the size and microstructure of a crystallite, so that it is used to characterize the structures of h-graphite and t-carbon. The dependence of the diffraction angles and full width at half maximums (FWHMs) of diffraction lines on the crystallite size and distortion factors is examined by computer simulation. The distortion factors for t-carbon, including rotation, translation, curvature, local positive fluctuation of interlayer spacing of graphene layers and fluctuation of atomic positions, have different influence on the NDIDs, hence on the X-ray diffraction patterns. The simulation results indicate that the diffraction angles and FWHMs of diffraction lines cannot be simply used to characterize the lattice parameters and crystallite sizes of t-carbon.
Background and Aims
Mast cell activation interferes with the effects of allergen‐specific immunotherapy (SIT). Galectin‐1 (Gal‐1) is capable of regulating immune cells’ functions. This study tests ...the hypothesis that administration of Gal‐1 promotes and prolongs the efficacy of SIT via suppressing mast cell activation.
Methods
An intestinal allergy mouse model was developed. The coadministration of SIT and Gal‐1 on suppression of the allergic responses, prevention of mast cell activation, and generation of antigen‐specific regulatory T cells (Treg) in the intestine was observed in sensitized mice.
Results
The coadministration of Gal‐1 and SIT markedly suppressed the allergic responses in the mouse intestine vs the use of either SIT alone or Gal‐1 alone. The Gal‐1 binds to the IgE/FcɛRI complexes on the surface of mast cells to prevent mast cell activation during SIT. Gal‐1 promoted the SIT‐generated allergen‐specific Tregs in the intestine of sensitized mice. Coadministration of Gal‐1 and SIT significantly enhanced the efficacy of immunotherapy in suppressing allergic responses in the intestine, which lasted for at least for 12 months.
Conclusions
Long‐term effects of specific immunotherapy on intestinal allergy can be achieved with Gal‐1/SIT therapy by inhibiting mast cell activation and facilitating Treg development.
High-energy cosmic-ray electrons and positrons (CREs), which lose energy quickly during their propagation, provide a probe of Galactic high-energy processes and may enable the observation of ...phenomena such as dark-matter particle annihilation or decay. The CRE spectrum has been measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments, and indirectly up to approximately 5 teraelectronvolts using ground-based Cherenkov γ-ray telescope arrays. Evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements, although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the Dark Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The largest part of the spectrum can be well fitted by a 'smoothly broken power-law' model rather than a single power-law model. The direct detection of a spectral break at about 0.9 teraelectronvolts confirms the evidence found by previous indirect measurements, clarifies the behaviour of the CRE spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt CREs.
An analytical model has been developed for analyzing the radial vibration force in fractional-slot permanent-magnet machines. It is compared extensively by finite-element analyses and used to ...investigate the influence of the following: 1) stator slotting; 2) tangential field component; 3) radius in the air gap for computation; 4) load condition, etc. The major findings include the following: 1) even on an open circuit, the low harmonic component (e.g., the second for a 10-pole/12-slot machine) of the radial force exists due to the slotting effect, although the amplitude is relatively low, while the slotless analytical model cannot predict this phenomenon; 2) on a load, the slotless analytical model is accurate enough for the radial force analysis since the low-order harmonic component of the radial force is mainly due to the interaction between the magnet field and the armature-reaction field and is largely determined by the combination of the pole and slot numbers; 3) it is much more reliable to calculate the radial force in the middle of the air gap rather than close to the stator bore; and 4) the simple formula accounting only for the radial field component in the middle of the air gap is accurate enough for the radial force calculation.
Abstract
We searched for the γ-ray signal from M33, one of the largest galaxies in the Local Group, using the Pass8 data from the Fermi Large Area Telescope (LAT). No statistically significant γ-ray ...emission has been detected in the direction of M33, and we report a new upper limit of the high-energy ( > 100 MeV) photon flux of 2.3 × 10− 9 ph cm− 2 s− 1, which is stricter than previous constraints and implies a cosmic ray density for M33 that is lower than that suggested previously. The current limit is still, however, in agreement with the correlation of star formation rate and γ-ray luminosity inferred from the Local group galaxies and a few nearby starburst galaxies.
The paper presents an accurate analytical subdomain model for computation of the open-circuit magnetic field in surface-mounted permanent-magnet machines with any pole and slot combinations, ...including fractional slot machines, accounting for stator slotting effect. It is derived by solving the field governing equations in each simple and regular subdomain, i.e., magnet, air-gap and stator slots, and applying the boundary conditions to the interfaces between these subdomains. The model accurately accounts for the influence of interaction between slots, radial/parallel magnetization, internal/external rotor topologies, relative recoil permeability of magnets, and odd/even periodic boundary conditions. The back-electromotive force, electromagnetic torque, cogging torque, and unbalanced magnetic force are obtained based on the field model. The relationship between this accurate subdomain model and the conventional subdomain model, which is based on the simplified one slot per pole machine model, is also discussed. The investigation shows that the proposed accurate subdomain model has better accuracy than the subdomain model based on one slot/pole machine model. The finite element and experimental results validate the analytical prediction.
FLASH LiDAR SINGLE PHOTON IMAGING OVER 50 KM Xia, Z. Q.
International archives of the photogrammetry, remote sensing and spatial information sciences.,
01/2023, Letnik:
XLVIII-1/W2-2023
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
In order to demonstrate the feasibility of single-photon imaging of flash lidar in the permanent shadow area of the moon, a set of space-based single-photon imaging system is designed, including the ...lidar based on VCSEL array, the optical emitting system based on the uniform beam shaping meta-lens using propagation phase and geometric phase joint control method, the two-axis three-mirror optical receiving system, and the single-photon detector array based on photon counting mode. According to the heavy-tailed pulse laser function, Poisson statistical filtering theory and Monte Carlo simulation method, the echo photon number, the photon counting process, the ranging accuracy and the intensity image are simulated in the condition of 50 km detection distance by setting different of the object reflectivity, the repetition times and the gating interval time. The results show that according to the parameter settings in this paper, the number of echo photons is as low as about 10-4 orders. However, the photon counting waveform can better restore the transmission waveform. The setting of the repetition number and the gating interval time should not only consider the missing detection phenomenon, but also consider the noise accumulation. When the repetition number is 2000 and the gate number is 200, the ranging accuracy can reach 0.075m, and the imaging in the crater without light is realized.
We investigated how developmental stage affects seed traits, including the relative level of desiccation tolerance of Quercus serrata. We tested the hypothesis that the relative level of desiccation ...tolerance is a quantitative trait associated with seed development and that a maximum relative level of desiccation tolerance is reached during development.
Seed growth and physiological traits of Q. serrata from a subtropical forest were examined in detail during the developmental process.
During seed development, the relative level of desiccation tolerance and other seed traits of Q. serrata varied. Dry matter accumulation in seed components increased rapidly beginning in mid‐August, and moisture content declined. At the peak period of seed dispersal in late September, seeds were fully mature, with 100% germination. Relative level of desiccation tolerance increased up to the point of peak dispersal; however, at this time seeds were still recalcitrant. Post‐mature development was accompanied by further increases in seed dry matter and decreases in moisture content, which led to a decrease in seed germination and relative level of desiccation tolerance.
Our results suggest that in species with recalcitrant seeds, the relative level of desiccation tolerance and other seed traits are quantitative at the intraspecific level. The relative level of desiccation tolerance for recalcitrant seeds does not increase infinitely during phase II of development. There is a maximum relative level of desiccation tolerance in recalcitrant seeds within a species.
Relative level of desiccation tolerance of Quercus serrata increased up to the point of peak dispersal but post‐mature development led to a decrease in seed germination and relative level of desiccation tolerance.
During the ionization of atoms irradiated by linearly polarized intense laser fields, we find for the first time that the transverse momentum distribution of photoelectrons can be well fitted by a ...squared zeroth-order Bessel function because of the quantum interference effect of glory rescattering. The characteristic of the Bessel function is determined by the common angular momentum of a number of semiclassical paths termed as glory trajectories, which are launched with different nonzero initial transverse momenta distributed on a specific circle in the momentum plane and finally deflected to the same asymptotic momentum, which is along the polarization direction, through post-tunneling rescattering. Glory rescattering theory based on the semiclassical path-integral formalism is developed to address this effect quantitatively. Our theory can resolve the long-standing discrepancies between existing theories and experiments on the fringe location, predict the sudden transition of the fringe structure in holographic patterns, and shed light on the quantum interference aspects of low-energy structures in strong-field atomic ionization.
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