In this study, based on the variational principle and Faddeev method, we present a general framework for finding the propagating solutions of multiple interacting particles on a torus. Two different ...versions of multiparticle secular equations are presented. Version one shows how the propagating solutions on a torus and the infinite volume dynamics are connected. The second version may be more suitable and robust for the task of lattice quantum chromodynamics data analysis. The proposed formalism may also be useful for studying the effects of few-body interactions on the electronic band structure in condensed matter physics.
The discovery of non-magnetic extreme magnetoresistance (XMR) materials has induced great interest because the XMR phenomenon challenges our understanding of how a magnetic field can alter electron ...transport in semimetals. Among XMR materials, the LaSb shows XMR and field-induced exotic behaviors but it seems to lack the essentials for these properties. Here, we study the magnetotransport properties and electronic structure of LaBi, isostructural to LaSb. LaBi exhibits large MR as in LaSb, which can be ascribed to the nearly compensated electron and hole with rather high mobilities. More importantly, our analysis suggests that the XMR as well as field-induced resistivity upturn and plateau observed in LaSb and LaBi can be well explained by the two-band model with the compensation situation. We present the critical conditions leading to these field-induced properties. It will contribute to the understanding of the XMR phenomenon and explore novel XMR materials.
In this work, we propose an approach to the solution of finite volume three-body problem by considering asymptotic forms and periodicity property of wave function in configuration space. The ...asymptotic forms of wave function define on-shell physical transition amplitudes that are related to distinct dynamics, therefore, secular equations of finite volume problem in this approach require only physical transition amplitudes. For diffractive spherical part of wave function, it is convenient to map a three-body problem into a higher dimensional two-body problem, thus, spherical part of solutions in finite volume resembles higher spatial dimensional two-body Lüscher's formula. The idea is demonstrated by an example of two light spinless particles and one heavy particle scattering in one spatial dimension.
The oxygen reduction reaction (ORR) is essential in many life processes and energy conversion systems. It is desirable to design transition metal molecular catalysts inspired by enzymatic oxygen ...activation/reduction processes as an alternative to noble‐metal‐Pt‐based ORR electrocatalysts, especially in view point of fuel cell commercialization. We have fabricated bio‐inspired molecular catalysts electrografted onto multiwalled carbon nanotubes (MWCNTs) in which 5,10,15,20‐tetra(pentafluorophenyl) iron porphyrin (iron porphyrin FeF20TPP) is coordinated with covalently electrografted axial ligands varying from thiophene to imidazole on the MWCNTs’ surface. The catalysts’ electrocatalytic activity varied with the axial coordination environment (i. e., S‐thiophene, N‐imidazole, and O‐carboxylate); the imidazole‐coordinated catalyst MWCNTs‐Im‐FeF20TPP exhibited the highest ORR activity among the prepared catalysts. When MWCNT‐Im‐FeF20TPP was loaded onto the cathode of a zinc−air battery, an open‐cell voltage (OCV) of 1.35 V and a maximum power density (Pmax) of 110 mW cm−2 were achieved; this was higher than those of MWCNTs‐Thi‐FeF20TPP (OCV=1.30 V, Pmax=100 mW cm−2) and MWCNTs‐Ox‐FeF20TPP (OCV=1.28 V, Pmax=86 mW cm−2) and comparable with a commercial Pt/C catalyst (OCV=1.45 V, Pmax=120 mW cm−2) under similar experimental conditions. This study provides a time‐saving method to prepare covalently immobilized molecular electrocatalysts on carbon‐based materials with structure–performance correlation that is also applicable to the design of other electrografted catalysts for energy conversion.
A time‐saving electrografting method (within a couple of minutes) for the covalent functionalization of carbon nanotube surfaces with an imidazole or thiophene ligand that is axially coordinated with iron porphyrin as electrocatalyst for the oxygen reduction reaction (ORR) has been demonstrated. The N‐imidazole‐coordinated catalyst, MWCNT‐Im‐FeF20TPP, exhibited the highest ORR activity followed by the S‐thiophene and O‐carboxylate axially coordinated catalysts.
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High-power direct laser deposition (HP DLD) was utilized to fast generate AISI 316L stainless steel parts with large size and excellent mechanical properties. In order to efficiently ...manufacture the stainless steel parts with high surface quality and dimensional accuracy, a dry milling finish was applied. During the DLD process, heat retaining powder was employed to prevent buckling deformation. The effect of building direction on the microstructure, mechanical properties and machinability of the stainless steel was investigated. It was found that the microstructure was homogeneous, at the building direction of 0°, while a number of larger dendritic grains were present in the microstructure, at the building direction of 90°. The tensile properties and hardness values at the building direction of 0° were higher than those at the building direction of 90°. For both building directions, the decrement in surface roughness and the increment in cutting force and tool wear, were observed with the increase in cutting speed. The cutting force, tool wear and surface roughness of the additive manufactured stainless steel at the building direction of 0° were relatively higher, which implies that the anisotropy in the machinability could be utilized to increase efficiency and reduce production cost.
Most of the binary black hole (BBH) mergers detected by LIGO and Virgo could be explained by first-generation mergers formed from the collapse of stars, while others might come from second (or ...higher) generation mergers, namely hierarchical mergers, with at least one of the black holes (BHs) being the remnant of a previous merger. A primary condition for the occurrence of hierarchical mergers is that the remnant BHs can be retained by the host star cluster. We present a simple formula to estimate the hierarchical merger rate in star clusters. We find this latter to be proportional to the retention probability. Further, we show that ∼2% of BBH mergers in nuclear star clusters (NSCs) may instead be of hierarchical mergers, while the percentage in globular clusters (GCs) is only a few tenths of a percent. However, the rates of hierarchical merger in GCs and NSCs are about the same, namely of ∼ (10
−2
) Gpc
−3
yr
−1
, because the total BBH merger rate in GCs is larger than that in NSCs. This suggests that if a gravitational-wave event detected by LIGO-Virgo is identified as a hierarchical merger, then it is equally likely that this merger originated from a GC or an NSC.
The El Niño-Southern Oscillation (ENSO) can significantly affect the rapid intensification of tropical cyclones over the western North Pacific (WNP). However, ENSO events have various durations, ...which can lead to different atmospheric and oceanic conditions. Here we show that during short duration El Niño events, the WNP tropical cyclone rapid-intensification mean occurrence position migrates westward by ~8.0° longitude, which is caused by reduced vertical wind shear, increased mid-tropospheric humidity, and enhanced tropical cyclone heat potential over the westernmost WNP. The changes in these factors are caused by westward advected upper ocean heat during the decaying phase of a short duration El Niño. As super El Niño events tend to have short durations and their frequency is projected to increase under global warming, our findings have important implications for future projections of WNP tropical cyclone activity.
Participating in social practice can help guide young people to better realize the unity of knowledge and action, learning to use, in order to be able to “gain what it can’t”, so this paper on how to ...better realize the social practice of college students to explore. First of all, this paper comprehends the structure and mechanism of college students’ social practice and researches the function of social practice through the operation mechanism of college students’ social practice. Then, based on the goal of solving the problems existing in social practice, the problem of multi-objective optimization is proposed, and the NSGA-II algorithm is optimized by adding the NDX operator and adaptive adjustment of the variation operator so as to solve the multi-objective optimization problem. The proposal for achieving social practice is made from three aspects: curriculum, theme, and research. Finally, the performance of the algorithm, the effect of social practice, and the optimization effect of social practice are analyzed through empirical evidence and algorithmic experiments. The results show that the range of the offspring using the NDX operator is between −1.75 and 3, the maximum number of occurrences of the offspring individuals are all around 2500, and the best comprehensive performance of HV and IGD are 0.93 and 0.11, respectively. The gains of ideological and moral literacy, personal ability enhancement as well and the practice object before optimization are all within 4.5, and the enhancement of the three conditions after optimization is around 0.7.
Aim
Species ranges in mountain areas may shift both horizontally and altitudinally, resulting from climate change and anthropogenic impact. Two hypotheses (the abundant centre hypothesis and the ...contagion hypothesis) have been proposed to account for patterns of horizontal range contraction. However, undulating topograph causes a mosaic of unsuitable habitats, which may complicate the spatial pattern of range contraction. We develop a framework incorporating horizontal and altitudinal range contraction patterns of a species living in mountain areas, to better understand the underlying mechanisms of species range contraction.
Location
China, Northern Laos and Northern Vietnam
Taxon
Western black crested gibbon, Nomascus concolor
Methods
We collected occurrence data of the gibbons from various sources and modelled their potential distribution range in the 1950s, 1980s and 2010s, using ecological niche modelling. We compared distances from the centre point of the potential range in the 1950s to centre points of the largest 100 patches in the 1950s and the 2010s to understand the patterns of horizontal range contraction. We also calculated potential distributions within different altitudinal ranges for six populations in each period to understand the patterns of altitudinal range contraction.
Results
Potential horizontal distribution of the gibbons decreased by 69% from the 1950s to the 2010s. The centre point of the 100 largest patches in the 2010s was further apart than in the 1950s, supporting the contagion hypothesis. No populations extended their range to higher altitude, suggesting climate change did not have a profound effect on altitudinal shifts in gibbon range. All populations lost a substantial proportion of their ranges at lower altitudes (500–1,500 m) but to different degrees, suggesting that populations experienced different anthropogenic pressures.
Main conclusions
Anthropogenic threats including human population increase, agricultural expansion and hunting, were more likely than climate change to have caused range contraction in western black‐crested gibbons. This study highlights the importance of studying horizontal and altitudinal range contraction simultaneously.
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