المؤلفون: Cao, Zhen, Aharonian, F., An, Q., Axikegu, Bai, Y. X., Bao, Y. W., Bastieri, D., Bi, X. J., Bi, Y. J., Cai, J. T., Cao, Q., Cao, W. Y., Cao, Zhe, Chang, J., Chang, J. F., Chen, A. M., Chen, E. S., Chen, Liang, Chen, Lin, Chen, Long, Chen, M. J., Chen, M. L., Chen, Q. H., Chen, S. H., Chen, S. Z., Chen, T. L., Chen, Y., Cheng, N., Cheng, Y. D., Cui, M. Y., Cui, S. W., Cui, X. H., Cui, Y. D., Dai, B. Z., Dai, H. L., Dai, Z. G., Danzengluobu, Dong, X. Q., Duan, K. K., Fan, J. H., Fan, Y. Z., Fang, J., Fang, K., Feng, C. F., Feng, L., Feng, S. H., Feng, X. T., Feng, Y. L., Gabici, S., Gao, B., Gao, C. D., Gao, L. Q., Gao, Q., Gao, W., Gao, W. K., Ge, M. M., Geng, L. S., Giacinti, G., Gong, G. H., Gou, Q. B., Gu, M. H., Guo, F. L., Guo, X. L., Guo, Y. Q., Guo, Y. Y., Han, Y. A., He, H. H., He, H. N., He, J. Y., He, X. B., He, Y., Hor, Y. K., Hou, B. W., Hou, C., Hou, X., Hu, H. B., Hu, Q., Hu, S. C., Huang, D. H., Huang, T. Q., Huang, W. J., Huang, X. T., Huang, X. Y., Huang, Y., Huang, Z. C., Ji, X. L., Jia, H. Y., Jia, K., Jiang, K., Jiang, X. W., Jiang, Z. J., Jin, M., Kang, M. M., Ke, T., Kuleshov, D., Kurinov, K., Li, B. B., Li, Cheng, Li, Cong, Li, D., Li, F., Li, H. B., Li, H. C., Li, H. Y., Li, J., Li, Jian, Li, Jie, Li, K., Li, W. L., Li, X. R., Li, Xin, Li, Y. Z., Li, Zhe, Li, Zhuo, Liang, E. W., Liang, Y. F., Lin, J., Liu, B., Liu, C., Liu, D., Liu, H., Liu, H. D., Liu, J., Liu, J. L., Liu, J. Y., Liu, M. Y., Liu, R. Y., Liu, S. M., Liu, W., Liu, Y., Liu, Y. N., Lu, R., Luo, Q., Lv, H. K., Ma, B. Q., Ma, L. L., Ma, X. H., Mao, J. R., Min, Z., Mitthumsiri, W., Mu, H. J., Nan, Y. C., Neronov, A., Ou, Z. W., Pang, B. Y., Pattarakijwanich, P., Pei, Z. Y., Qi, M. Y., Qi, Y. Q., Qiao, B. Q., Qin, J. J., Ruffolo, D., Sáiz, A., Semikoz, D., Shao, C. Y., Shao, L., Shchegolev, O., Sheng, X. D., Shu, F. W., Song, H. C., Stenkin, Yu. V., Stepanov, V., Su, Y., Sun, Q. N., Sun, X. N., Sun, Z. B., Tam, P. H. T., Tang, Q. W., Tang, Z. B., Tian, W. W., Wang, C., Wang, C. B., Wang, G. W., Wang, H. G., Wang, H. H., Wang, J. C., Wang, K., Wang, L. P., Wang, L. Y., Wang, P. H., Wang, R., Wang, W., Wang, X. G., Wang, X. Y., Wang, Y., Wang, Y. D., Wang, Y. J., Wang, Z. H., Wang, Z. X., Wang, Zhen, Wang, Zheng, Wei, D. M., Wei, J. J., Wei, Y. J., Wen, T., Wu, C. Y., Wu, H. R., Wu, S., Wu, X. F., Wu, Y. S., Xi, S. Q., Xia, J., Xia, J. J., Xiang, G. M., Xiao, D. X., Xiao, G., Xin, G. G., Xin, Y. L., Xing, Y., Xiong, Z., Xu, D. L., Xu, R. F., Xu, R. X., Xu, W. L., Xue, L., Yan, D. H., Yan, J. Z., Yan, T., Yang, C. W., Yang, F., Yang, F. F., Yang, H. W., Yang, J. Y., Yang, L. L., Yang, M. J., Yang, R. Z., Yang, S. B., Yao, Y. H., Yao, Z. G., Ye, Y. M., Yin, L. Q., Yin, N., You, X. H., You, Z. Y., Yu, Y. H., Yuan, Q., Yue, H., Zeng, H. D., Zeng, T. X., Zeng, W., Zha, M., Zhang, B. B., Zhang, F., Zhang, H. M., Zhang, H. Y., Zhang, J. L., Zhang, L. X., Zhang, Li, Zhang, P. F., Zhang, P. P., Zhang, R., Zhang, S. B., Zhang, S. R., Zhang, S. S., Zhang, X., Zhang, X. P., Zhang, Y. F., Zhang, Yi, Zhang, Yong, Zhao, B., Zhao, J., Zhao, L., Zhao, L. Z., Zhao, S. P., Zheng, F., Zheng, J. H., Zhou, B., Zhou, H., Zhou, J. N., Zhou, M., Zhou, P., Zhou, R., Zhou, X. X., Zhu, C. G., Zhu, F. R., Zhu, H., Zhu, K. J., Zuo, X.

مصطلحات موضوعية: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena

الوصف: KM2A is one of the main sub-arrays of LHAASO, working on gamma ray astronomy and cosmic ray physics at energies above 10 TeV. Detector simulation is the important foundation for estimating detector performance and data analysis. It is a big challenge to simulate the KM2A detector in the framework of Geant4 due to the need to track numerous photons from a large number of detector units (>6000) with large altitude difference (30 m) and huge coverage (1.3 km^2). In this paper, the design of the KM2A simulation code G4KM2A based on Geant4 is introduced. The process of G4KM2A is optimized mainly in memory consumption to avoid memory overffow. Some simpliffcations are used to signiffcantly speed up the execution of G4KM2A. The running time is reduced by at least 30 times compared to full detector simulation. The particle distributions and the core/angle resolution comparison between simulation and experimental data of the full KM2A array are also presented, which show good agreement.

الوصول الحر: http://arxiv.org/abs/2404.04801Test

المؤلفون: Cao, Zhen, Aharonian, F., An, Q., Axikegu, A., Bai, Y. X., Bao, Y. W., Bastieri, D., Bi, X. J., Bi, Y. J., Cai, J. T., Cao, Q., Cao, W. Y., Cao, Zhe, Chang, J., Chang, J. F., Chen, A. M., Chen, E. S., Chen, Liang, Chen, Lin, Chen, Long, Chen, M. J., Chen, M. L., Chen, Q. H., Chen, S. H., Chen, S. Z., Chen, T. L., Chen, Y., Cheng, N., Cheng, Y. D., Cui, M. Y., Cui, S. W., Cui, X. H., Cui, Y. D., Dai, B. Z., Dai, H. L., Dai, Z. G., Danzengluobu, della Volpe, D., Dong, X. Q., Duan, K. K., Fan, J. H., Fan, Y. Z., Fang, J., Fang, K., Feng, C. F., Feng, L., Feng, S. H., Feng, X. T., Feng, Y. L., Gabici, S., Gao, B., Gao, C. D., Gao, L. Q., Gao, Q., Gao, W., Gao, W. K., Ge, M. M., Geng, L. S., Giacinti, G., Gong, G. H., Gou, Q. B., Gu, M. H., Guo, F. L., Guo, X. L., Guo, Y. Q., Guo, Y. Y., Han, Y. A., He, H. H., He, H. N., He, J. Y., He, X. B., He, Y., Heller, M., Hor, Y. K., Hou, B. W., Hou, C., Hou, X., Hu, H. B., Hu, Q., Hu, S. C., Huang, D. H., Huang, T. Q., Huang, W. J., Huang, X. T., Huang, X. Y., Huang, Y., Huang, Z. C., Ji, X. L., Jia, H. Y., Jia, K., Jiang, K., Jiang, X. W., Jiang, Z. J., Jin, M., Kang, M. M., Ke, T., Kuleshov, D., Kurinov, K., Li, B. B., Li, Cheng, Li, Cong, Li, D., Li, F., Li, H. B., Li, H. C., Li, H. Y., Li, J., Li, Jian, Li, Jie, Li, K., Li, W. L., Li, X. R., Li, Xin, Li, Y. Z., Li, Zhe, Li, Zhuo, Liang, E. W., Liang, Y. F., Lin, S. J., Liu, B., Liu, C., Liu, D., Liu, H., Liu, H. D., Liu, J., Liu, J. L., Liu, J. Y., Liu, M. Y., Liu, R. Y., Liu, S. M., Liu, W., Liu, Y., Liu, Y. N., Lu, R., Luo, Q., Lv, H. K., Ma, B. Q., Ma, L. L., Ma, X. H., Mao, J. R., Min, Z., Mitthumsiri, W., Mu, H. J., Nan, Y. C., Neronov, A., Ou, Z. W., Pang, B. Y., Pattarakijwanich, P., Pei, Z. Y., Qi, M. Y., Qi, Y. Q., Qiao, B. Q., Qin, J. J., Ruffolo, D., Sáiz, A., Semikoz, D., Shao, C. Y., Shao, L., Shchegolev, O., Sheng, X. D., Shu, F. W., Song, H. C., Stenkin, Yu. V., Stepanov, V., Su, Y., Sun, Q. N., Sun, X. N., Sun, Z. B., Tam, P. H. T., Tang, Q. W., Tang, Z. B., Tian, W. W., Wang, C., Wang, C. B., Wang, G. W., Wang, H. G., Wang, H. H., Wang, J. C., Wang, K., Wang, L. P., Wang, L. Y., Wang, P. H., Wang, R., Wang, W., Wang, X. G., Wang, X. Y., Wang, Y., Wang, Y. D., Wang, Y. J., Wang, Z. H., Wang, Z. X., Wang, Zhen, Wang, Zheng, Wei, D. M., Wei, J. J., Wei, Y. J., Wen, T., Wu, C. Y., Wu, H. R., Wu, S., Wu, X. F., Wu, Y. S., Xi, S. Q., Xia, J., Xia, J. J., Xiang, G. M., Xiao, D. X., Xiao, G., Xin, G. G., Xin, Y. L., Xing, Y., Xiong, Z., Xu, D. L., Xu, R. F., Xu, R. X., Xu, W. L., Xue, L., Yan, D. H., Yan, J. Z., Yan, T., Yang, C. W., Yang, F., Yang, F. F., Yang, H. W., Yang, J. Y., Yang, L. L., Yang, M. J., Yang, R. Z., Yang, S. B., Yao, Y. H., Yao, Z. G., Ye, Y. M., Yin, L. Q., Yin, N., You, X. H., You, Z. Y., Yu, Y. H., Yuan, Q., Yue, H., Zeng, H. D., Zeng, T. X., Zeng, W., Zha, M., Zhang, B. B., Zhang, F., Zhang, H. M., Zhang, H. Y., Zhang, J. L., Zhang, L. X., Zhang, Li, Zhang, P. F., Zhang, P. P., Zhang, R., Zhang, S. B., Zhang, S. R., Zhang, S. S., Zhang, X., Zhang, X. P., Zhang, Y. F., Zhang, Yi, Zhang, Yong, Zhao, B., Zhao, J., Zhao, L., Zhao, L. Z., Zhao, S. P., Zheng, F., Zhou, B., Zhou, H., Zhou, J. N., Zhou, M., Zhou, P., Zhou, R., Zhou, X. X., Zhu, C. G., Zhu, F. R., Zhu, H., Zhu, K. J., Zuo, X.

المصدر: Science Advances, 9, eadj2778 (2023) 15 November 2023

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The highest energy gamma-rays from gamma-ray bursts (GRBs) have important implications for their radiation mechanism. Here we report for the first time the detection of gamma-rays up to 13 TeV from the brightest GRB 221009A by the Large High Altitude Air-shower Observatory (LHAASO). The LHAASO-KM2A detector registered more than 140 gamma-rays with energies above 3 TeV during 230$-$900s after the trigger. The intrinsic energy spectrum of gamma-rays can be described by a power-law after correcting for extragalactic background light (EBL) absorption. Such a hard spectrum challenges the synchrotron self-Compton (SSC) scenario of relativistic electrons for the afterglow emission above several TeV. Observations of gamma-rays up to 13 TeV from a source with a measured redshift of z=0.151 hints more transparency in intergalactic space than previously expected. Alternatively, one may invoke new physics such as Lorentz Invariance Violation (LIV) or an axion origin of very high energy (VHE) signals.
Comment: 49pages, 11figures

الوصول الحر: http://arxiv.org/abs/2310.08845Test

المؤلفون: MA, C. Y., SHI, J.-J., WU, X.-F., GUO, M., LI, C.-C.

المصدر: Applied Ecology & Environmental Research; 2023, Vol. 21 Issue 6, p5009-5037, 29p

مصطلحات موضوعية: PRINCIPAL components analysis, CHLOROPHYLL, WHEAT, SUPPORT vector machines, REMOTE sensing, NUTRITIONAL status

مستخلص: Chlorophyll content is an important index to measure the nutritional status of wheat. Rapid and accurate estimation of chlorophyll content is crucial to monitor the photosynthetic capacity and growth status of wheat and optimize its quality. To solve the problem of low precision in the hyperspectral estimation of crop chlorophyll content, this paper selects vegetation indices, spectral characteristic parameters, fractional differential spectrum, and wavelet energy coefficient as index parameters. Meanwhile, principal component analysis (PCA) is exploited to reduce and fuse these index parameters to eliminate the multicollinearity among the index parameters. Then, based on multiple linear regression and support vector machine algorithms, the estimation model of wheat chlorophyll content in different growth stages is constructed. The results show that the PCA reduces the dimension of hyperspectral data while retaining the original information, which improves the operation efficiency of the model, and ensures the effect of chlorophyll content estimation. The experimental results indicate that the multiple linear regression method achieves a better estimation effect of chlorophyll content at the booting stage, and the R2, RMSE, and nRMSE of the estimation model are 0.79, 2.21, and 5.50% respectively. This study provides a new technical method for estimating crop chlorophyll content using hyperspectral remote sensing data and comprehensive index parameters. [ABSTRACT FROM AUTHOR]

: Copyright of Applied Ecology & Environmental Research is the property of ALOKI Applied Ecological Research & Forensic Institute Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Dai, Z. G., Wang, X. Y., Wu, X. F., Zhang, B.

المصدر: Science 311 (2006) 1127-1129

مصطلحات موضوعية: Astrophysics

الوصف: Recent observations support the suggestion that short-duration gamma-ray bursts are produced by compact star mergers. The X-ray flares discovered in two short gamma-ray bursts last much longer than the previously proposed postmerger energy release time scales. Here we show that they can be produced by differentially rotating, millisecond pulsars after the mergers of binary neutron stars. The differential rotation leads to windup of interior poloidal magnetic fields and the resulting toroidal fields are strong enough to float up and break through the stellar surface. Magnetic reconnection--driven explosive events then occur, leading to multiple X-ray flares minutes after the original gamma-ray burst.
Comment: 10 pages, published in Science

الوصول الحر: http://arxiv.org/abs/astro-ph/0602525Test

المؤلفون: Wu, X. F., Li, X., Kang, W. Y., Zhang, X. C., Chen, L., Zhong, Z. B., Zhou, Y., Åkerman, Johan, 1970, Wu, Y. P., Zhang, R., Kang, J. Y.

المصدر: Nature Electronics. 6(7)

مصطلحات موضوعية: Physical Sciences, Fysik

الوصف: Millimetre-scale meron lattices that are stable at room temperature and under zero magnetic field can be used as spin injectors in light-emitting diodes, providing 22.5% circularly polarized electroluminescence. Merons are a class of topologically protected particle-like structures created in in-plane magnetized magnetic films. The structures can act as information carriers and could be used for magnetic storage. However, the development of such applications is hampered by limitations in the size, thermal stability and magnetic-field requirements of the systems. Here we report the construction of millimetre-scale meron lattices that are stable at room temperature and under zero magnetic field. Our system is based on a trilayer structure composed of a thin iron film sandwiched between films of palladium and magnesium oxide (Pd/Fe/MgO) on a gallium nitride wafer. It is fabricated using a molecular-beam epitaxy approach that is assisted by a high magnetic field, which leads to a strong Dzyaloshinskii-Moriya interaction. The lattices can be used for chirality transfer from merons to electrons and then to photons, and we show that the meron lattices can be used as spin injectors in nitride-based light-emitting diodes. The topology-induced spin light-emitting diode can provide 22.5% circularly polarized electroluminescence at room temperature and under zero magnetic field.

الوصول الحر: https://gup.ub.gu.se/publication/329159Test

المؤلفون: Yang, X, Zhang, S-B, Wang, J-S, Wu, X-F

المصدر: Monthly Notices of the Royal Astronomical Society; Jul2023, Vol. 522 Issue 3, p4342-4351, 10p

مصطلحات موضوعية: DIMENSIONAL reduction algorithms, DIMENSION reduction (Statistics), SPECTROGRAMS

مستخلص: Fast radio bursts (FRBs) are mysterious astronomical phenomena, and it is still uncertain whether they consist of multiple types. In this study, we use two nonlinear dimensionality reduction algorithms – Uniform Manifold Approximation and Projection (UMAP) and t-distributed stochastic neighbour embedding (t-SNE) – to differentiate repeaters from apparently non-repeaters in FRBs. Based on the first Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB catalogue, these two methods are applied to standardized parameter data and image data from a sample of 594 sub-bursts and 535 FRBs, respectively. Both methods are able to differentiate repeaters from apparently non-repeaters. The UMAP algorithm using image data produces more accurate results and is a more model-independent method. Our result shows that in general repeater clusters tend to be narrowband, which implies a difference in burst morphology between repeaters and apparently non-repeaters. We also compared our UMAP predictions with the CHIME/FRB discovery of six new repeaters, the performance was generally good except for one outlier. Finally, we highlight the need for a larger and more complete sample of FRBs. [ABSTRACT FROM AUTHOR]

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المؤلفون: SHEN, X. H., JIANG, C., XU, Y. Q., WU, X. F., WANG, S. H., XIE, S.

المصدر: Applied Ecology & Environmental Research; 2023, Vol. 21 Issue 3, p2493-2505, 13p

مصطلحات موضوعية: SORGHUM, SOWING, MATERIALS testing, GRAIN yields, REGRESSION analysis, MULTIVARIATE analysis

مصطلحات جغرافية: JIANGXI Sheng (China), CHINA

مستخلص: Sorghum varieties J67 and Jiniang 2nd (JN2) were used as test materials in this experiment. Regression analysis and multivariate comparison were used to explore the relationship between sorghum yield, quality and climate factors in different sowing dates, which provided a theoretical basis for the study of sorghum adaptability in Jiangxi region, China. The results showed that the inter annual, sowing date and sorghum yield reached significant (P < 0.05) and extremely significant level (P < 0.01), respectively. The yield of J67 and JN2 was the highest on the 25th April, and 5th May, respectively, and the average yield was 34.67% and 11.85% higher than that of other sowing dates. The content of protein, fat and starch increased first and then decreased with the delay of sowing date. The relationship between effective precipitation and yield is linear function, while the relationship between effective temperature, daily average temperature, sunshine hours and yield is quadratic function. In addition, the climate factor that has the greatest impact on the quality is the daily average temperature, while the hours of sunshine have the least impact. The results showed that suitable sowing date was the key to the formation of sorghum yield and grain quality. [ABSTRACT FROM AUTHOR]

: Copyright of Applied Ecology & Environmental Research is the property of ALOKI Applied Ecological Research & Forensic Institute Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Ackermann, M., Asano, K., Atwood, W. B., Axelsson, Magnus, Baldini, L., Ballet, J., Barbiellini, G., Baring, M. G., Bastieri, D., Bechtol, K., Bellazzini, R., Berenji, B., Bhat, P. N., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonamente, E., Borgland, A. W., Bouvier, A., Bregeon, J., Brez, A., Briggs, M. S., Brigida, M., Bruel, P., Buson, S., Caliandro, G. A., Cameron, R. A., Caraveo, P. A., Carrigan, S., Casandjian, J. M., Cecchi, C., Celik, Oe., Charles, E., Chiang, J., Ciprini, S., Claus, R., Cohen-Tanugi, J., Connaughton, V., Conrad, J., Dermer, C. D., de Palma, F., Dingus, B. L., do Couto e Silva, E., Drell, P. S., Dubois, R., Dumora, D., Farnier, C., Favuzzi, C., Fegan, S. J., Finke, J., Focke, W. B., Frailis, M., Fukazawa, Y., Fusco, P., Gargano, F., Gasparrini, D., Gehrels, N., Germani, S., Giglietto, N., Giordano, F., Glanzman, T., Godfrey, G., Granot, J., Grenier, I. A., Grondin, M. -H, Grove, J. E., Guiriec, S., Hadasch, D., Harding, A. K., Hays, E., Horan, D., Hughes, R. E., Johannesson, G., Johnson, W. N., Kamae, T., Katagiri, H., Kataoka, J., Kawai, N., Kippen, R. M., Knoedlseder, J., Kocevski, D., Kouveliotou, C., Kuss, M., Lande, J., Latronico, L., Lemoine-Goumard, M., Garde, M. Llena, Longo, F., Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Makeev, A., Mazziotta, M. N., McEnery, J. E., McGlynn, Sinéad, Meegan, C., Meszaros, P., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Moiseev, A. A., Monte, C., Monzani, M. E., Moretti, Elena, 1982, Morselli, A., Moskalenko, I. V., Murgia, S., Nakajima, H., Nakamori, T., Nolan, P. L., Norris, J. P., Nuss, E., Ohno, M., Ohsugi, T., Omodei, N., Orlando, E., Ormes, J. F., Ozaki, M., Paciesas, W. S., Paneque, D., Panetta, J. H., Parent, D., Pelassa, V., Pepe, M., Pesce-Rollins, M., Piron, F., Preece, R., Raino, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Ritz, S., Rodriguez, A. Y., Roth, M., Ryde, Felix, Sadrozinski, H. F. -W, Sander, A., Scargle, J. D., Schalk, T. L., Sgro, C., Siskind, E. J., Smith, P. D., Spandre, G., Spinelli, P., Stamatikos, M., Stecker, F. W., Strickman, M. S., Suson, D. J., Tajima, H., Takahashi, H., Takahashi, T., Tanaka, T., Thayer, J. B., Thayer, J. G., Thompson, D. J., Tibaldo, L., Toma, K., Torres, D. F., Tosti, G., Tramacere, A., Uchiyama, Y., Uehara, T., Usher, T. L., van der Horst, A. J., Vasileiou, V., Vilchez, N., Vitale, V., von Kienlin, A., Waite, A. P., Wang, P., Wilson-Hodge, C., Winer, B. L., Wu, X. F., Yamazaki, R., Yang, Z., Ylinen, Tomi, Ziegler, M.

المصدر: Astrophysical Journal. 716(2):1178-1190

مصطلحات موضوعية: gamma-ray burst: individual (GRB 090510), radiation mechanisms: non-thermal, NATURAL SCIENCES, Physics, Astronomy and astrophysics, NATURVETENSKAP, Fysik, Astronomi och astrofysik

الوصف: We present detailed observations of the bright short-hard gamma-ray burst GRB 090510 made with the Gammaray Burst Monitor (GBM) and Large Area Telescope (LAT) on board the Fermi observatory. GRB 090510 is the first burst detected by the LAT that shows strong evidence for a deviation from a Band spectral fitting function during the prompt emission phase. The time-integrated spectrum is fit by the sum of a Band function with E-peak = 3.9 +/- 0.3 MeV, which is the highest yet measured, and a hard power-law component with photon index -1.62 +/- 0.03 that dominates the emission below approximate to 20 keV and above approximate to 100 MeV. The onset of the high-energy spectral component appears to be delayed by similar to 0.1 s with respect to the onset of a component well fit with a single Band function. A faint GBM pulse and a LAT photon are detected 0.5 s before the main pulse. During the prompt phase, the LAT detected a photon with energy 30.5(-2.6)(+5.8) GeV, the highest ever measured from a short GRB. Observation of this photon sets a minimum bulk outflow Lorentz factor, Gamma greater than or similar to 1200, using simple.. opacity arguments for this GRB at redshift z = 0.903 and a variability timescale on the order of tens of ms for the approximate to 100 keV-few MeV flux. Stricter high confidence estimates imply Gamma greater than or similar to 1000 and still require that the outflows powering short GRBs are at least as highly relativistic as those of long-duration GRBs. Implications of the temporal behavior and power-law shape of the additional component on synchrotron/synchrotron self-Compton, external-shock synchrotron, and hadronic models are considered.

وصف الملف: print

الوصول الحر: https://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-27555Test
https://doi.org/10.1088/0004-637X/716/2/1178Test

المؤلفون: Sun, N., Ruan, J. F., Wu, X. F., Du, Y. S., Fu, G., Ma, L., Li, L., Cheng, G., Wang, J., Zhao, J. T., Rao, G. H.

المصدر: Journal of Materials Science: Materials in Electronics; Mar2023, Vol. 34 Issue 8, p1-10, 10p

مصطلحات موضوعية: MAGNETIC transitions, MAGNETOCALORIC effects, MAGNETIC entropy, INTERMETALLIC compounds, MAGNETIC cooling, CURIE temperature

مستخلص: The structure, magnetic transitions, and magnetocaloric effect of Pr substitution for Nd were studied in Nd7Pd3 intermetallic compounds. All samples are single-phased and crystallized in the tetragonal Th7Fe3-type structure with the space group P63mc. The substitution of Pr for Nd can change the ferromagnetic coupling into an antiferromagnetic coupling, which is unstable and can be induced into a ferromagnetic state under an external magnetic field. The effective magnetic moments, the paramagnetic Curie temperature (θP), and the isothermal magnetic entropy changes in Nd7−xPrxPd3 (x = 0, 1.4, 2.8, 4.2) were determined. The considerable magnetocaloric effect indicates that a series of compounds can be used as candidates for low-temperature magnetic refrigeration materials. [ABSTRACT FROM AUTHOR]

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المؤلفون: Wen, D., Shen, Z., Qi, X., Wu, X.‐F.

المصدر: European Journal of Organic Chemistry; 11/11/2022, Vol. 2022 Issue 42, p1-4, 4p

مصطلحات موضوعية: OXINDOLES, FORMIC acid, ETHANES, CARBONATES, BIOCHEMICAL substrates, SOLVENTS

مستخلص: Dimethyl carbonate (DMC), a non‐toxic liquid, which shows diverse and tunable reactivity in organic synthesis. Herein, we report a nice study on using DMC as both solvent and reactant in palladium‐catalyzed intramolecular Heck/Carbonylation for the synthesis of functionalized isoquinoline‐1,3‐diones and oxindoles. To avoid the usage of toxic CO gas, formic acid is employed as the CO source, and a variety of functionalized isoquinoline‐1,3‐diones and oxindoles were obtained in very good yields. [ABSTRACT FROM AUTHOR]

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