Sudden, large-scale and diffuse human migration can amplify localized outbreaks of disease into widespread epidemics
. Rapid and accurate tracking of aggregate population flows may therefore be ...epidemiologically informative. Here we use 11,478,484 counts of mobile phone data from individuals leaving or transiting through the prefecture of Wuhan between 1 January and 24 January 2020 as they moved to 296 prefectures throughout mainland China. First, we document the efficacy of quarantine in ceasing movement. Second, we show that the distribution of population outflow from Wuhan accurately predicts the relative frequency and geographical distribution of infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) until 19 February 2020, across mainland China. Third, we develop a spatio-temporal 'risk source' model that leverages population flow data (which operationalize the risk that emanates from epidemic epicentres) not only to forecast the distribution of confirmed cases, but also to identify regions that have a high risk of transmission at an early stage. Fourth, we use this risk source model to statistically derive the geographical spread of COVID-19 and the growth pattern based on the population outflow from Wuhan; the model yields a benchmark trend and an index for assessing the risk of community transmission of COVID-19 over time for different locations. This approach can be used by policy-makers in any nation with available data to make rapid and accurate risk assessments and to plan the allocation of limited resources ahead of ongoing outbreaks.
Copper/diamond composites have drawn lots of attention in the last few decades, due to its potential high thermal conductivity and promising applications in high-power electronic devices. However, ...the bottlenecks for their practical application are high manufacturing/machining cost and uncontrollable thermal performance affected by the interface characteristics, and the interface thermal conductance mechanisms are still unclear. In this paper, we reviewed the recent research works carried out on this topic, and this primarily includes (1) evaluating the commonly acknowledged principles for acquiring high thermal conductivity of copper/diamond composites that are produced by different processing methods; (2) addressing the factors that influence the thermal conductivity of copper/diamond composites; and (3) elaborating the interface thermal conductance problem to increase the understanding of thermal transferring mechanisms in the boundary area and provide necessary guidance for future designing the composite interface structure. The links between the composite’s interface thermal conductance and thermal conductivity, which are built quantitatively via the developed models, were also reviewed in the last part.
Two-dimensional (2D) materials are not expected to be metals at low temperature owing to electron localization1. Consistent with this, pioneering studies on thin lms reported only superconducting and ...insulating ground states, with a direct transition between the two as a function of disorder or magnetic eld26. However, more recent works have revealed the presence of an intermediate quantum metallic state occupying a substantial region of the phase diagram710, whose nature is intensely debated1117. Here, we observe such a state in the disorder-free limit of a crystalline 2D superconductor, produced by mechanical co-lamination of NbSe2 in an inert atmosphere. Under a small perpendicular magnetic eld, we induce a transition from superconductor to the quantum metal. We nd a unique power-law scaling with eld in this phase, which is consistent with the Bose-metal model where metallic behaviour arises from strong phase uctuations caused by the magnetic field1114.
Biocomposites consisting of hydroxyapatite (HAp) and natural polymers such as collagen, chitosan, chitin, and gelatin have been extensively investigated. However, studies on the combination of HAp ...with bacterial cellulose (BC) have not been conducted yet. In this work, our latest results concerning the biomimetic synthesis and characterization of HAp-BC nanocomposites with a 3-dimensional (3-D) network are reported. The present research focuses on characterizing the structure of this novel class of nanocomposites. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier-transformed infrared spectroscopy (FTIR) were employed to characterize the HAp-BC nanocomposites. It is found that HAp crystals are formed when the phosphorylated and CaCl
2-treated BC fibers are soaked in a 1.5 simulated body fluid (SBF). XRD reveals that the crystallite sizes of the HAp crystals are nano-sized and their crystallinities are low. The FTIR results show that the HAp crystals are partially substituted with carbonate, resembling natural bones. The nanocomposites containing HAp with structural features close to those of biological apatites are attractive for applications as artificial bones and scaffolds for tissue engineering.
Magnetic topological phases of quantum matter are an emerging frontier in physics and material science. Along these lines, several kagome magnets have appeared as the most promising platforms. Here, ...we explore magnetic correlations in the kagome magnet Co
Sn
S
. Using muon spin-rotation, we present evidence for competing magnetic orders in the kagome lattice of this compound. Our results show that while the sample exhibits an out-of-plane ferromagnetic ground state, an in-plane antiferromagnetic state appears at temperatures above 90 K, eventually attaining a volume fraction of 80% around 170 K, before reaching a non-magnetic state. Strikingly, the reduction of the anomalous Hall conductivity (AHC) above 90 K linearly follows the disappearance of the volume fraction of the ferromagnetic state. We further show that the competition of these magnetic phases is tunable through applying either an external magnetic field or hydrostatic pressure. Our results taken together suggest the thermal and quantum tuning of Berry curvature induced AHC via external tuning of magnetic order.
A novel Risley prism (RP) integrated with phase-correcting dielectric lens (PCDLs) is designed and demonstrated at V-band (50-75 GHz) for 2-D beam-steering performance with consistent high-gain ...attributes. The proposed design consists of a pair of dielectric wedges built using high permittivity material integrated with a parabolic PCDL built using a low permittivity material. The proposed RP integrated with PCDL exhibits wideband steering of the incident beam into a 3-D conical space via concurrent axial rotation of the RP elements. The proposed beam-steering structure is capable of providing a consistent gain of ~24 dBi at the V-band based on the aperture size of the RP and the PCDL. The wideband performance of the proposed RP design is experimentally demonstrated using a commercial 20 dBi pyramidal standard gain horn operating at V-band (50-75 GHz). The simulated and measured gain of the proposed arrangement with the pyramidal horn along the broadside are found to be 24.6 and 23.1 dBi, respectively at 62.5 GHz. The proposed work exhibits consistent gain with deviation less than 1.3 dB and scan losses below 2 dB for scan angles of ±40° throughout the V-band (50-75 GHz). The measurement results validate the wideband steering performance of the proposed mechanism. The effect of rotation errors on the steering performance of the proposed design is also investigated.
The recently discovered three-dimensional or bulk topological insulators are expected to exhibit exotic quantum phenomena. It is believed that a trivial insulator can be twisted into a topological ...state by modulating the spin-orbit interaction or the crystal lattice, driving the system through a topological quantum phase transition. By directly measuring the topological quantum numbers and invariants, we report the observation of a phase transition in a tunable spin-orbit system, BiTl(S₁— δ Se δ )₂, in which the topological state formation is visualized. In the topological state, vortex-like polarization states are observed to exhibit three-dimensional vectorial textures, which collectively feature a chirality transition as the spin momentum—locked electrons on the surface go through the zero carrier density point. Such phase transition and texture inversion can be the physical basis for observing fractional charge (±e/2) and other fractional topological phenomena.
Aim
Exchange of plant lineages between Australia and Southeast Asia has had a substantial impact on the evolution of Australia's northern, tropical flora, with important ramifications for its ...conservation and biosecurity. Despite this, floristic exchange tracks between northern Australia and Southeast Asia remain poorly understood. To address this, we conducted a molecular phylogeographic case study to identify exchange tracks between Australia and Southeast Asia.
Location
India, Southeast Asia, Australia and Pacific islands.
Taxon
The widespread tropical monsoonal tree species Aglaia elaeagnoidea (Meliaceae).
Methods
We conducted a DArTseq phylogeographic study of 141 herbarium and silica‐dried samples sourced from across the range of A. elaeagnoidea. We analysed 176,331 single nucleotide polymorphisms (SNPs) across 90,456 loci using multivariate, admixture, genetic differentiation and coalescent methods to characterise phylogeographic and phylogenetic patterns. These analyses were considered in the context of an environmental niche model for the last glacial maximum.
Results
Two exchange tracks were identified: one from New Guinea to Cape York Peninsula in north‐east Australia, and a second from Timor‐Leste to the Kimberley Plateau of north‐west Australia. The Cape York Peninsula track is contemporary, characterised by ongoing genetic exchange, whereas the Kimberley Plateau track is historic, facilitated by multiple past exposures of the Arafura Shelf during the Pleistocene. Overall, we suggest that phylogeographic patterns of A. elaeagnoidea have resulted from a combination of repeated range expansion and contraction cycles concurrent with Quaternary climate fluctuations and stochastic dispersal events.
Main conclusions
This study provides the first molecular phylogeographic evidence for two floristic exchange tracks between northern Australia and Southeast Asia. It also highlights the influence of Quaternary climate fluctuations on the complex biogeography of the region, and supports the idea that the Kimberley Plateau and Cape York Peninsula in northern Australia have separate biogeographic histories.
Searching for space-time variations of the constants of Nature is a promising way to search for new physics beyond general relativity and the standard model motivated by unification theories and ...models of dark matter and dark energy. We propose a new way to search for a variation of the fine-structure constant using measurements of late-type evolved giant stars from the S star cluster orbiting the supermassive black hole in our Galactic Center. A measurement of the difference between distinct absorption lines (with different sensitivity to the fine structure constant) from a star leads to a direct estimate of a variation of the fine structure constant between the star's location and Earth. Using spectroscopic measurements of five stars, we obtain a constraint on the relative variation of the fine structure constant below 10^{-5}. This is the first time a varying constant of nature is searched for around a black hole and in a high gravitational potential. This analysis shows new ways the monitoring of stars in the Galactic Center can be used to probe fundamental physics.
Abstract
Kinship networks are a fundamental social unit in human societies, and like social networks in general, provide social support in times of need. Here, we investigate the impact of sudden ...environmental shock, the M
s
7.0 2013 Ya’an earthquake, on the mobile communications patterns of local families, which we operationalize using anonymized individual-level mobile telecommunications metadata from family plan subscribers of a major carrier (
N
= 35,565 people). We demonstrate that families’ communications dynamics after the earthquake depended on their triadic embeddedness structure, a structural metric we propose that reflects the number of dyads in a family triad that share social ties. We find that individuals in more embedded family structures were more likely to first call other family plan members and slower in calling non-family ties immediately after the earthquake; these tendencies were stronger at higher earthquake intensity. In the weeks after the event, individuals in more embedded family structures had more reciprocal communications and contacted more social ties in their broader social network. Overall, families that are structurally more embedded displayed higher levels of intra-family coordination and mobilization of non-family social connections.
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