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1. chinaXiv:202009.00012 [pdf]

Shadows of rotating Hayward-de Sitter black holes with astrometric observables

Peng-Zhang He; Qi-Qi Fan; Hao-Ran Zhang; Jian-Bo Deng
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics

Motivated by recent work on rotating black hole shadow [Phys. Rev. D101, 084029 (2020)], we investigate the shadow behaviors of rotating Hayward-de Sitter black hole for static observers at a finite distance in terms of astronomical observables. This paper uses the newly introduced distortion parameter in [arXiv:2006.00685] to describe the shadow's shape quantitatively. We show that the spin parameter would distort shadows and the magnetic monopole charge would increase the degree of deformation. At the same time, the distortion could be relieved because of the cosmological constant and the distortion would increase with the distance from the black hole. Besides, the spin parameter, magnetic monopole charge and cosmological constant increase will cause the shadow to shrink.

submitted time 2020-09-09 Hits4005Downloads284 Comment 0

2. chinaXiv:202009.00011 [pdf]

The cosmological constant from space-time discreteness

Qi-Qi Fan; Cong Li; Hao-Ran Zhang; Peng-Zhang He,; Jian-Bo Deng
Subjects: Physics >> The Physics of Elementary Particles and Fields

We regard the background of space-time as a physical system composed of discrete volume elements at the Planck scale and get the internal energy of space-time by Debye model. A temperature-dependent minimum energy limit of the particles is proposed from the thermal motion part of the internal energy. As decreases of the temperature caused by the expansion of the universe, more and more particles would be "released" because of the change of the energy limit, we regard these new particles as a source of dark energy. The minimum energy limit also leads to a corrected number of particles in universe and a modified conservation equation. According to the modified conservation equation, an effective cosmological constant consistent with its observed value is obtained.

submitted time 2020-09-06 Hits2808Downloads228 Comment 0

3. chinaXiv:202002.00062 [pdf]

Furin, a potential therapeutic target for COVID-19

Hua Li; Canrong Wu; Yueying Yang; Yang Liu; Peng Zhang; Yali Wang; Qiqi Wang; Yang Xu; Mingxue Li; Mengzhu Zheng; Lixia Chen
Subjects: Medicine, Pharmacy >> Pharmacology

A novel coronavirus (SARS-CoV-2) infectious disease has broken out in Wuhan, Hubei Province since December 2019, and spread rapidly from Wuhan to other areas, which has been listed as an international concerning public health emergency. We compared the Spike proteins from four sources, SARS-CoV-2, SARS-CoV, MERS-CoV and Bat-CoVRaTG13, and found that the SARS-CoV-2 virus sequence had redundant PRRA sequences. Through a series of analyses, we propose the reason why SARS-CoV-2is more infectious than other coronaviruses. And through structure based virtual ligand screening, we foundpotentialfurin inhibitors, which might be used in the treatment of new coronary pneumonia.

submitted time 2020-02-23 Hits135287Downloads18814 Comment 0

4. chinaXiv:201703.00587 [pdf]

Modification of source contribution in PALS by simulation using Geant4 code

Xia Ning; Xingzhong Cao; Chong Li; Demin Li; Peng Zhang; Yihao Gong; Rui Xia; Baoyi Wang; Long Wei
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The contribution of positron source for the results of a positron annihilation lifetime spectrum (PALS) is simulated using Geant4 code. The geometrical structure of PALS measurement system is a sandwich structure: the 22Na radiation source is encapsulated by Kapton films, and the specimens are attached on the outside of the films. The probabilities of a positron being annihilated in the films, annihilated in the targets, and the effect of positrons reflected back from the specimen surface, are simulated. The probability of a positron annihilated in the film is related to the species of targets and the source film thickness. The simulation result is in reasonable agreement with the available experimental data. Thus, modification of the source contribution calculated by Geant4 is viable, and it beneficial for the analysis of the results of PALS.

submitted time 2017-03-26 Hits1554Downloads880 Comment 0

5. chinaXiv:201703.00586 [pdf]

Estimation of dislocation concentration in plastically deformed FeCrNi alloy by positron annihilation lifetime

Eryang Lu; Xingzhong Cao; Shuoxue Jin; Yihao Gong; Peng Zhang; Runsheng Yu; Baoyi Wang
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Dislocations would be induced after plastic deformation, which might change the mechanical properties of solids. FeCrNi austenitic model alloy and its Mo-diluted alloy were cold rolled with different degree of thickness reduction. Positrons are sensitive to point defects, which are easily trapped and annihilated around the trapping sites. The mean positron lifetimes have been used to estimate the average dislocation concentration in solids. Meanwhile, the trapping efficiency μ was calculated from the lifetime results. The trapping efficiency value is estimated about 3.31×10-7 cm3s-1 for FeCrNi alloy and 3.31×10-7 cm3s-1 for Mo-diluted alloy, respectively. The increment of the hardness value during plastic deformation is related to the increase of the dislocation density and dislocation pile up in solids.

submitted time 2017-03-26 Hits1573Downloads891 Comment 0

6. chinaXiv:201703.00585 [pdf]

Irradiation induced defects by Fe-ion in 316L stainless steel studied by Positron Annihilation Spectroscopy

Xingzhong Cao; Eryang Lu; Shuoxue Jin; Yihao Gong; Yuanchao Hu; Te Zhu; Peng Zhang; Long Wei; Baoyi Wang
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Solution annealed type 316L austenitic stainless steels were irradiated using 2 MeV Fe ions at room temperature. The implanted fluences were 2012 ions/cm2 and 1013 ions/cm2, respectively. Variable mono-energetic positron beam was performed to characterize the evolution of microstructure and irradiation induced defects. Results show that large amount of vacancy defects formed after heavy ion irradiation. In which, some of mono-vacancies might migrate to form small-sized clusters at room temperature. After irradiation, implanted Fe atoms mainly be interstitials atoms, but some Fe atoms might recombine with vacancies due to their high mobility, which could decrease the defect concentration, effectively.

submitted time 2017-03-26 Hits1549Downloads862 Comment 0

7. chinaXiv:201703.00584 [pdf]

Study of tunable monoenergy positron annihilation spectroscopy of polyethylene glycol thin-films?

Peng Kuang; Xiao-Long Han; Xing-Zhong Cao; Rui Xia; Peng Zhang; Bao-Yi Wang
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Doppler broadening and Coincidence Doppler broadening of annihilation radiation experiments have been performed in three kinds of polyethylene glycol (PEG) membrane formed with different average molecular weight using the tunable monoenergy slow positron probe as a function of implantion energy. The obtained positron annihilation parameters are interpreted from two aspects: surface effect and differences in micro-structure or chemical environment of positron annihilation. The experimental results show that the regulation of densification of PEG molecular packing and distribution uniformity from the near surface layer to bulk region in film forming process can be well realized by changing its molecular weight. Combining a variable monoenergetic slow positron beam and these two positron annihilation spectroscopy methods are powerful tool to study positron annihilation characteristics and for polymeric thin-film fine structure analysis.

submitted time 2017-03-26 Hits1236Downloads715 Comment 0

8. chinaXiv:201703.00583 [pdf]

Detection of helium in irradiated Fe9Cr alloys by coincidence Doppler broadening of slow positron annihilation

Xingzhong Cao; Te Zhu; Shuoxue Jin; Peng Kuang; Peng Zhang; Eryang Lu; Yihao Gong; Liping Guo; Baoyi Wang
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

An element analysis method, coincidence Doppler broadening spectroscopy of slow positron annihilation, was employed to detect helium in ion irradiated Fe9Cr alloys. Spectra with higher peak to background ratio were recorded using a two-HPGe-detector coincidence measuring system. It means that information in the high-momentum area of the spectra can be used to identify helium in metals. This identification is not entirely dependent on the helium concentration in the specimens, but is related to the structure and microscopic arrangement of atoms surrounding the positron annihilation site. The results of Doppler broadening spectroscopy and transmission electron microscopy show that vacancies and dislocations were formed in ion irradiated specimens. Thermal helium desorption spectrometry was performed to obtain the types of He traps.

submitted time 2017-03-26 Hits1385Downloads797 Comment 0

9. chinaXiv:201703.00581 [pdf]

Probing sub-nano level molecular packing and correlated positron annihilation characteristics in ionic cross-linked Chitosan membrane using Positron Annihilation Spectroscopy

Rui Xi; Xingzhong Cao; Meizhen Gao; Peng Zhang; Minfeng Zeng; Baoyi Wang; Long Wei
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Chitosan, CS, cross-linked with bivalent palladium has shown enhanced mechanical and thermal properties depending on the transformation of the structure at a microscopic scale. In the present study, CS directly cross-linked by palladium cation membranes (CS-cr-PM) were prepared through solution-casting method. The motion of chitosan chains was great suppressed after crosslinking, making a great reduce of swelling ratio by a water-swelling degree measurement, which led to molecular chain rigidity to be improvement. In order to investigate the chain packing at the molecular level in the ionic cross-linked CS system, the structure of chemically-crosslinked CS is investigated by means of the combined use of wide angle X-ray diffraction (WAXD), Infrared measurements, and a combination of positron annihilation lifetime spectroscopy (PALS) and simultaneous coincidence Doppler broadening (CDB) spectroscopy offers coherent information on both the free-volume related sub-nano level molecular packing and the chemical surrounding of free volume nanoholes in CS-cr-PM as a function of palladium salt loading. The variations in free volume size and size distribution have been determined through the ortho-positroium (o-Ps) lifetime and its lifetime distribution. The studies showed that strong interaction between CS molecules and palladium cations results in the change of crystallinity in formed CS-cr-PM leading to variational chain packing density. Meanwhile, significant inhibition effects on positronium formation due to doping are observed, which could be interpreted in terms of the existence of chlorid ion. Applications of positron annihilation spectroscopy to study the microstructure and correlated positron annihilation characteristics in ionic cross-linked CS system are systematic discussed.

submitted time 2017-03-26 Hits1418Downloads816 Comment 0

10. chinaXiv:201703.00575 [pdf]

Effect of annealing on Cu precipitates in H ion irradiated Fe–0.6%Cu studied by positron annihilation

Shuoxue Jin; Peng Zhang; Eryang Lu; Baoyi Wang; Daqing Yuan; Long Wei; Xingzhong Cao
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Fe–0.6%Cu alloy was irradiated with H ions to 0.1 dpa, and then annealed for 30 min from 150 oC to 500 oC. We focused the evolution of Cu precipitates in irradiated Fe–0.6%Cu alloy after the isochronal annealing from the perspective of positron annihilation. The ΔW parameters after thermal annealing (400 oC and 500 oC) were much larger than that induced by 0.1 dpa H irradiation. Annealing could promote the aggregation of the Cu-vacancy complexes, and form the Cu cluster–vacancies complexes. When the vacancy-like defects recovered around 500 oC, it meant the formation and growing of the defect-free Cu precipitates.

submitted time 2017-03-26 Hits1491Downloads781 Comment 0

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