The low emission mode in PSR B0329+54 Tu, Z Y; Yuen, R; Wen, Z G ...
Monthly notices of the Royal Astronomical Society,
03/2022, Letnik:
512, Številka:
2
Journal Article
Recenzirano
ABSTRACT
We investigate properties of the low emission mode in PSR B0329+54 based on four single-pulse observations at frequency centred at 1.54 GHz using Nanshan radio telescope in Urumqi. The low ...emission mode is characterized by an intensity drop in the central component below that of the other two components. Referred here as the low mode, it has an average duration of 3P0 and is observed in both abnormal and normal emission modes of the pulsar occupying 3.6 per cent of the observed pulses. We demonstrate that the properties of low modes are related to the two modes. We find that the integrated profile of low modes is unique to the two modes, and that low modes occur more frequently when the pulsar is in the normal mode. Analysis of the energy distribution for normal low modes suggests that the cause for the intensity drop in the central component is separated from the emission of the other two components. We demonstrate that the pulse emission characteristics in the normal emission mode shortly after a low-mode bears some similarities with the abnormal mode and gradually recovering to the original normal emission in about three pulsar periods. In addition, the occurrence rate for low modes in different normal modes is mostly consistent, which implies that the duration of low modes is related to a normal mode for this pulsar. Our results imply profile modes each corresponds to specific magnetospheric plama density in particular geometric configuration, and profile mode changing signifies distinct changes of both at different parts of the profile.
Abstract
We have carried out a detailed study of single-pulse emission from the pulsar J2048−1616 (B2045−16), observed at 732, 1369, and 3100 MHz frequencies using the Parkes 64 m radio telescope. ...The pulsar possesses three well-resolved emission components, with the central component resembling core emission. The single pulses show the presence of two distinct periodic modulations using fluctuation spectral analysis. About 12% nulls are found to create alternating bunches of nulls and bursts in a quasiperiodic manner with longer periodicities of 83, 28, and 14 rotational periods for simultaneous observations at 732 and 3100 MHz. At 1369 MHz, the quasiperiodic nulling is detected, as well, to modulate across the entire profile both in the core and conal components simultaneously with a fluctuation rate of about 50 rotational periods, and the nulling fraction is estimated to be around 10%. Additionally, the quasiperiodic modulations are significantly dependent on time. In addition to nulling, the pulsar also presents subpulse drifting in the single-pulse sequences with shorter periodicity. The subpulse drifting is presented in the conal components and is absent in the central core emission. The leading component is modulated in longitude with a period of three pulses. The trailing component remains phase stationary within the pulse window but periodically modulates in amplitude with a period of three pulses. Finally, possible physical mechanisms are discussed.
ABSTRACT
Microalgae (Nannochloropsis sp., NS), with high contents of eicosapentaenoic acid (EPA) and crude protein, may be one of the important n-3 polyunsaturated fatty acid (PUFA) sources and ...potential protein feed ingredient. The purposes of this study were to enrich yolk with n-3 PUFA by dietary EPA-rich NS supplementation and to evaluate whether it is feasible to partly substitute for soybean meal in laying hens diet. A total of 360 37-wk-old healthy Lohmann Brown laying hens, with similar laying rate and body weight, were randomly allotted to 5 groups (6 replicates, 12 birds/replicate) and fed 5 experimental diets (0, 1, 2, 4, and 8% NS) for 4 wk. The hen performance and egg quality (except yolk color) were not affected (P > 0.05) by the NS supplemental diets. Yolk color score was increased as NS supplementation in diets (P < 0.001), and peaked on about the seventh day in all NS supplemental groups. The concentration of total n-3 PUFA was increased (P < 0.001), while total n-6 PUFA and n-6/n-3 ratio were decreased (P < 0.001) in yolk with increasing NS levels in diets. The 8% NS group had highest docosahexaenoic acid (DHA) and total n-3 PUFA levels, reaching 111.6 mg DHA and 148.6 mg total n-3 PUFA per egg. Maximum DHA, total n-3 PUFA, very long-chain (LC-) n-3 PUFA, and LC-PUFA levels were all observed at day 13 of NS supplementation. In conclusion, dietary NS supplementation enriched yolk with n-3 PUFA (especially DHA) and enhanced yolk color score without adverse effects on performance and egg quality, and indicated the practical feasibility of partial replacement for soybean meal in laying hens diet.
Marfan syndrome (MFS) is associated with TGF (transforming growth factor) β-stimulated ERK (extracellular signal-regulated kinase) activity in vascular smooth muscle cells (VSMCs), which adopt a ...mixed synthetic/contractile phenotype. In VSMCs, TGFβ induces IL (interleukin) 11) that stimulates ERK-dependent secretion of collagens and MMPs (matrix metalloproteinases). Here, we examined the role of IL11 in the MFS aorta.
We used echocardiography, histology, immunostaining, and biochemical methods to study aortic anatomy, physiology, and molecular endophenotypes in
mice, an established murine model of MFS (mMFS). mMFS mice were crossed to an IL11-tagged EGFP (enhanced green fluorescent protein;
) reporter strain or to a strain deleted for the IL11 receptor (
). In therapeutic studies, mMFS were administered an X209 (neutralizing antibody against IL11RA IL11 receptor subunit alpha) or IgG for 20 weeks and imaged longitudinally.
IL11 mRNA and protein were elevated in the aortas of mMFS mice, as compared to controls. mMFS mice crossed to
mice had increased IL11 expression in VSMCs, notably in the aortic root and ascending aorta. As compared to the mMFS parental strain, double mutant mMFS:
mice had reduced aortic dilatation and exhibited lesser fibrosis, inflammation, elastin breaks, and VSMC loss, which was associated with reduced aortic COL1A1 (collagen type I alpha 1 chain), IL11, MMP2/9, and phospho-ERK expression. To explore therapeutic targeting of IL11 signaling in MFS, we administered either a neutralizing antibody against IL11RA (X209) or an IgG control. After 20 weeks of antibody administration, as compared to IgG, mMFS mice receiving X209 had reduced thoracic and abdominal aortic dilation as well as lesser fibrosis, inflammation, elastin breaks, and VSMC loss. By immunoblotting, X209 was shown to reduce aortic COL1A1, IL11, MMP2/9, and phospho-ERK expression.
In MFS, IL11 is upregulated in aortic VSMCs to cause ERK-related thoracic aortic dilatation, inflammation, and fibrosis. Therapeutic inhibition of IL11, imminent in clinical trials, might be considered as a new approach in MFS.
A gas-filled recoil separator, SHANS2 (Spectrometer for Heavy Atoms and Nuclear Structure-2), with five magnets arranged in a Qv-D-Qh-Qv-D configuration is constructed at the China Accelerator ...Facility for Superheavy Elements (CAFE2) of the Institute of Modern Physics (IMP) in Lanzhou. It is dedicated to the study of the heavy nuclei produced in heavy-ion-induced fusion evaporation reactions, especially to the experiments on the superheavy elements with cross-sections lower than 1 pb. The maximum magnetic rigidity of the main dipole magnet is designed to be 2.5 T m. The detailed design of the SHANS2 and the results of several test experiments are presented.
Scalable video coding is an ongoing standard, and the current working draft (WD) is an extension of H.264/AVC. In the WD, an exhaustive search technique is employed to select the best coding mode for ...each macroblock. This technique achieves the highest possible coding efficiency, but it results in extremely large encoding time which obstructs it from practical use. This paper proposes a fast mode decision algorithm for inter-frame coding for spatial, coarse grain signal-to-noise ratio, and temporal scalability. It makes use of the mode-distribution correlation between the base layer and enhancement layers. Specifically, after the exhaustive search technique is performed at the base layer, the candidate modes for enhancement layers can be reduced to a small number based on the correlation. Experimental results show that the fast mode decision scheme reduces the computational complexity significantly with negligible coding loss and bit-rate increases
ABSTRACT
The follow-up timing observations were carried out for 24 pulsars discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in Commensal Radio Astronomy FAST Survey. ...We report their phase-connected timing ephemeris, polarization pulse profiles, and Faraday rotation measurements. With their spin periods spanning from 2.995 ms to 4.34 s, their period derivatives were determined to spread between 7.996(8) × 10−21 and 9.83(3) × 10−15 s s−1, which imply that they have characteristic ages from 1.97 × 106 to 5.93 × 109 yr. It is inferred that PSRs J0211+4235 and J0518+2431 are beyond the ‘traditional death line’. PSR J0211+4235 is beyond the ‘death valley’. The death line model of Zhang et al. also cannot explain the radio presence of PSR J0211+4235. This suggests that radiation theory needs to be improved. Besides, ten of the 22 canonical pulsars show nulling phenomena. Moreover, PSR J1617+1123 exhibits variation of emission and J0540+4542 shows subpulse drifting. The DM of five pulsars is larger than the estimated by the YMW16 electron density model, which could suggest that electron density models need updates for higher Galactic latitude regions. PSRs J0447+2447 and J1928−0548 are isolated millisecond pulsars. With their flux densities spanning from 5(1)–553(106) μJy, some of these new pulsars found by FAST are distant, dim, and low-$\dot{E}$ ones and are suitable for testing pulsar emission theories.
The common notion suggests that metallic glasses (MGs) are a homogeneous solid at the macroscopic scale; however, recent experiments and simulations indicate that MGs contain nano-scale elastic ...heterogeneities. Despite the fundamental importance of these findings, a quantitative understanding is still lacking for the local elastic heterogeneities intrinsic to MGs. On the basis of Eshelby's theory, here we develop a micromechanical model that correlates the properties of the local elastic heterogeneities, being very difficult to measure experimentally, to the measurable overall elastic properties of MGs, such as shear/bulk modulus and Poisson's ratio. Our theoretical modeling is verified by the experimental data obtained from various MGs annealed to different degrees. Particularly, we revealed that upon annealing, the Poisson's ratio decreases if shear softening dominates the behavior of local soft regions or increase if pressure softening becomes dominant in MGs. Our results provide quantitative insights into the structural mechanism of the Poisson's ratio criterion on the ductility long established for MGs. Finally, The correlation between the Poisson's ratio of a glass and the fragility of its corresponding liquid is also discussed.
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We search for ongoing major dry mergers in a well-selected sample of local brightest cluster galaxies (BCGs) from the C4 cluster catalogue. 18 out of 515 early-type BCGs with redshift between 0.03 ...and 0.12 are found to be in major dry mergers, which are selected as pairs (or triples) with r-band magnitude difference δmr < 1.5 and projected separation rp < 30 kpc, and showing signatures of interaction in the form of significant asymmetry in residual images. We find that the fraction of BCGs in major dry mergers increases with the richness of the clusters, consistent with the fact that richer clusters usually have more massive (or luminous) BCGs. We estimate that present-day early-type BCGs may have experienced on average ∼0.6 (tmerge/0.3 Gyr)−1 major dry mergers and through this process increases their luminosity (mass) by 15 per cent (tmerge/0.3 Gyr)−1 (fmass/0.5) on average since z= 0.7, where tmerge is the merging time-scale and fmass is the mean mass fraction of companion galaxies added to the central ones. We also find that major dry mergers do not seem to elevate radio activities in BCGs. Our study shows that major dry mergers involving BCGs in clusters of galaxies are not rare in the local Universe, and they are an important channel for the formation and evolution of BCGs.
Interstellar Scintillation of PSR J2048−1616 Chen, J. L.; Wen, Z. G.; Yuan, J. P. ...
Astrophysical journal/The Astrophysical journal,
03/2022, Letnik:
927, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
We report on the interstellar scintillation from pulsar J2048−1616 for the first time at 732, 1369, and 3100 MHz observed with the Parkes 64 m radio telescope. Dynamic spectra are obtained ...and diffractive parameters are derived from two-dimensional autocorrelation analyses. The frequency dependencies of the observed diffractive scintillation timescale and decorrelation bandwidth indicate that the electron density fluctuations in the interstellar medium (ISM) do not follow the Kolmogorov spectrum. The secondary spectra are calculated by forming the Fourier power spectra of the corresponding dynamic spectra. Prominent parabolic arcs are revealed in the secondary spectra at three frequencies, which indicate that they originated from scattering by a thin screen. The scattering screen is approximately located centrally between the pulsar and Earth assuming that the ISM is stationary.
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