Nature, 202 1, Vol.592, No.7856.

Nature 202 1 April 29th, 2002, Vol.592, No.7856.

Astronomy astronomy

Quasi-periodic bursts of x-rays from two previously stationary galaxies

Quasi-periodic bursts of x-rays in two previously stationary galaxies

Authors: R. Arcodia, A. Merloni, K. Nandra, J. Buchner, M. Salvato, etc.

Link:

/articles/s 4 1586-02 1-03394-6

abstract

Quasi-periodic bursts (QPEs) are bursts of high-amplitude X-ray radiation that occur every few hours, and usually originate near the supermassive black hole at the core of the Milky Way. Here, we report QPEs observations of two other galaxies, which were obtained through systematic blind search of half of the X-ray sky.

The spectra of these galaxies do not show the characteristics of black hole activity, which indicates that the pre-existing accretion flow of a typical active galactic nucleus does not need to trigger these events. In fact, the period, amplitude and profile of QPEs reported here are inconsistent with the current model, which leads to the instability of radiation pressure driving in accretion disks.

On the contrary, qpe may be driven by dense objects in orbit. In addition, their observation properties require that the mass of secondary celestial bodies is much smaller than that of the main body, and future X-ray observation may limit the periodic changes caused by orbital evolution.

abstract

Quasi-periodic bursts (QPEs) are very high-amplitude bursts of X-ray radiation, which occur every few hours and originate near the central supermassive black hole at the core of the Milky Way. Here, we report the observations of qpe in two other galaxies, which were obtained by blind system search for half of the X-ray sky. The spectra of these galaxies show no signs of black hole activity, which indicates that a typical accretion flow of pre-existing active galactic nuclei is not needed to trigger these events. In fact, the period, amplitude and profile of QPEs reported here are inconsistent with the current model, which believes that the instability driven by radiation pressure exists in the reaction plate. On the contrary, qpe may be driven by a dense celestial body in orbit. In addition, their observed characteristics require that the mass of secondary objects is much smaller than that of the main body, and future X-ray observation may limit the possible changes of their periods due to orbital evolution.

Chemical chemistry

The transition of Bose-Einstein condensed state from atom to molecule

The transition of Bose-Einstein condensate from atom to molecule

Author:,; Chen; Yao Kaixuan &; Zheng Jin

Link:

/articles/s 4 1586-02 1-03443-0

abstract

Molecular quantum gas (ultra-cold high-density molecular gas) has many potential applications, including quantum control of chemical reactions, accurate measurement, quantum simulation and quantum information processing. Here, we report the preparation of two-dimensional Bose-Einstein condensates (BECs) of rotating molecules by the induced pair interaction in atomic condensates near G-wave Fischbach vibration.

The geometry of traps and the low temperature of molecules help to reduce inelastic losses and ensure thermal balance. From the measurement of the equation of state, we determine that the molecular scattering length is +220( 30) Bohr radius (95% confidence interval). We also study the dynamics of the solution pair under the condition of strong coupling, and find that the time scale of dynamics near Feshbach * * * vibration conforms to the unified limit.

abstract

Molecular quantum gas (ultracold dense molecular gas) has many potential applications, including quantum control of chemical reactions, precise measurement, quantum simulation and quantum information processing. Here, we report the preparation of two-dimensional Bose-Einstein condensates (BECs) of spin molecules by inducing pairing interactions in atomic condensates near the G-wave Feshbach resonance. The geometry of the trap and the low temperature of the molecule are helpful to reduce the inelastic loss and ensure the thermal balance. According to the measurement of the equation of state, we determine that the molecular scattering length is+220( 30) Bohr radius (95% confidence interval). We also study the unpaired dynamics in the strong coupling region, and find that the dynamic time scale is consistent with the unitary limit near Feshbach resonance.

Direct observation of chemical short-range order in medium entropy alloys

Direct observation of chemical short-range sequences in medium entropy alloys

Authors:,, Cheng Zhiying,, Zhu,,, etc.

Link:

/articles/s 4 1586-02 1-03428-z

abstract

Here, we find that CSRO in the concentrated solution of face-centered cubic VCoNi can be clearly found by using transmission electron microscope, appropriate regional axis, micro/nano-beam diffraction, atomic resolution imaging and chemical mapping.

Our supplementary tool kit provides specific information about the degree of CSRO, the configuration of atomic filling and the preferential occupation of adjacent lattice planes/positions by chemicals. The modeling of the order parameters and correlation of CSRO on the nearest atomic shell shows that CSRO originates from the nearest neighbor preference, faces different (V-Co and V-Ni) pairs and avoids V-V pairs.

Our findings provide a method to identify CSRO in concentrated solution alloys. We also use atomic strain diagram to show the dislocation interaction enhanced by CSRO, and clarify the influence of these CSRO on plastic mechanism and mechanical properties during deformation.

abstract

Here, we find that CSRO in concentrated solution of face-centered cubic VCoNi can be clearly revealed by using appropriate band axis, micro/nano beam diffraction, atomic resolution imaging and chemical drawing through transmission electron microscope. Our supplementary tool kit provides specific information about the degree/range of CSRO, the atomic stacking structure and the preferential occupation of adjacent lattice planes/positions by chemical species. The order parameters of CSRO on the nearest atomic shell and the model of pair correlation show that CSRO originated from the nearest neighbor preference for different (V Co and V Ni) pairs and the avoidance of V V pairs. Our findings provide a method to identify CSRO in concentrated solution alloys. We also use the atomic strain diagram to demonstrate the dislocation interaction enhanced by csro, and clarify the influence of these csro on plastic mechanism and mechanical properties during deformation.

Direct evaluation of acidity of hydroxyl groups on a single surface

Direct evaluation of the acidity of a single surface hydroxyl group

Authors: Margaret Wagner, Bernd Meyer, Martin Setwin, Michael schmid &; Ullrich Diebold

Link:

/articles/s 4 1586-02 1-03432-3

abstract

The acidity of mineral surface is estimated by semi-empirical concepts, such as bond valence sum, and is more and more simulated by first-principles molecular dynamics. At present, this prediction can not be verified by experimental measurements, such as the zero point of charge on the whole surface or in some cases the single crystal facet.

Here we evaluated the acidity of a single hydroxyl group on In2O3 (1 1 1). In2O3 (11) is a model oxide with four different surface oxygen atoms. We tested their hydrogen bond strength with the tip of a non-contact atomic force microscope, and found that it was consistent with the quantitative calculation of density functional theory.

By correlating the results with the proton affinities of gas-phase molecules, we have determined the proton affinities of different surface positions of In2O3 with atomic accuracy.

abstract

For mineral surfaces, acidity is estimated by semi-empirical concepts, such as bond valence sum, and is increasingly modeled by first-principles molecular dynamics simulation. At present, such predictions cannot be verified-experimental measurements, such as zero point of charge, are integrated on the whole surface, or in some cases, on a single crystal plane. Here we evaluate the acidity of a single hydroxyl group on In2O3 (11), which is a model oxide with four different types of surface oxygen atoms. We used non-contact atom probe of ce microscope to detect their hydrogen bond strength, and found that it was consistent with the calculation of density functional theory in quantity. By correlating the results with the known proton affinities of gas-phase molecules, we have determined the proton affinities of different surface positions of In2O3 with atomic accuracy.

earth sciences

2 1 At the beginning of the century, the global glacier quality decreased rapidly.

2 1 The global glaciers disappeared at the beginning of the century.

Authors: Romain Hugonnet, Robert McNabb, Etienne Berthier, et al.

Link:

/article/s 41586-021-03436-z

abstract

Here, we reveal the pattern of accelerated loss of glacier mass in the early 2 1 century. Our research shows that from 2000 to 20 19, glaciers lost 26716 billion tons every year, which is equivalent to 2 1 3% of the observed sea level rise.

We find that the acceleration of mass loss is 4,865,438+06 billion tons every 65,438+00 years, which explains that the observed acceleration of sea level rise has increased from 6% to 65,438+09%. In particular, the rate of thinning of glaciers around the ice sheet has doubled in the past 20 years. At present, compared with Greenland or Antarctic ice sheet, the mass loss of glaciers is greater, and the speed is similar or faster.

By revealing the quality change patterns in many areas, we find that the relative fluctuation of glaciers is consistent with the interdecadal changes of precipitation and temperature. Including the abnormal mass reduction in the North Atlantic, the unusually strong reduction of glaciers in the northwestern United States, and the obvious end of the abnormal increase in the Karakorum Mountains.

abstract

Here, we reveal the acceleration model of glacier mass loss at the beginning of 2 1 century, although this model is opposite. We found that during the period of 2000-20 19, glaciers lost 2671600 million tons every year, which was equivalent to 2 13% of the observed sea level rise. We determine that the acceleration of mass loss is 48 16 gigatons per year every ten years, which explains 6% to 19% of the observed acceleration of sea level rise. In particular, in the past two decades, the rate of thinning of glaciers outside the edge of the ice sheet has doubled. Compared with Greenland or Antarctic ice sheet, glaciers are losing more mass at similar or greater acceleration. By revealing the quality change patterns in many areas, we found the contrast glacier fluctuations consistent with the ten-year changes of precipitation and temperature. These include the deceleration mass loss of the North Atlantic anomaly, the intense acceleration loss of glaciers in the northwestern United States, and the obvious end of the Karakorum anomaly.

Mantle recrystallization of continental lithosphere driven by mantle plume

Regeneration of lithospheric mantle craton driven by mantle plume

Authors: Liu, D Graham Pearson, Lawrence Wang Hongliang, et al.

Link:

/articles/s 4 1586-02 1-03395-5

abstract

The mantle roots of the craton are considered to be the long-term stability of the earth's continent, but there is also evidence that they split in the recent and more distant past. Here, we have studied mantle xenoliths and seismology carried by mantle peridotite in Canadian Arctic Craton, including the area affected by Mackenzie mantle plume event127 billion years ago.

We have demonstrated that the upwelling of mantle plume plays an important role in the destruction and resurrection of the lithospheric mantle about 200 kilometers thick in the northern slave craton. Through numerical simulation, we show how the new molten mantle residue produced by Mackenzie mantle plume event was captured in the lithospheric thinning region between two thick cratons.

Our results confirm that the craton can heal and return to its original thickness after the root of the mountain is destroyed.

abstract

As we all know, the mantle roots of craton are the characteristics of longevity and stability of the earth continent, but there is also evidence that they were destroyed in the recent and more distant past. Here, we have studied the seismology of kimberlite mantle xenoliths and the lithospheric cross section across the Canadian Arctic Craton, including an area affected by the Mackenzie mantle plume event10.27 billion years ago. We have proved the important role of plume upwelling in the destruction and re-cratonization of the lithospheric mantle of the slave craton about 200 kilometers thick in the north. Using numerical simulation, we show how the new and buoyant molten residue produced by Mackenzie mantle plume event was captured in the thin lithosphere between two thick cratons. Our results determine a process in which cratons heal and return to their original lithospheric thickness after their roots are severely damaged.