Quantum key distribution (QKD)
allows two distant parties to share encryption keys with security based on physical laws. Experimentally, QKD has been implemented via optical means, achieving key ...rates of 1.26 megabits per second over 50 kilometres of standard optical fibre
and of 1.16 bits per hour over 404 kilometres of ultralow-loss fibre in a measurement-device-independent configuration
. Increasing the bit rate and range of QKD is a formidable, but important, challenge. A related target, which is currently considered to be unfeasible without quantum repeaters
, is overcoming the fundamental rate-distance limit of QKD
. This limit defines the maximum possible secret key rate that two parties can distil at a given distance using QKD and is quantified by the secret-key capacity of the quantum channel
that connects the parties. Here we introduce an alternative scheme for QKD whereby pairs of phase-randomized optical fields are first generated at two distant locations and then combined at a central measuring station. Fields imparted with the same random phase are 'twins' and can be used to distil a quantum key. The key rate of this twin-field QKD exhibits the same dependence on distance as does a quantum repeater, scaling with the square-root of the channel transmittance, irrespective of who (malicious or otherwise) is in control of the measuring station. However, unlike schemes that involve quantum repeaters, ours is feasible with current technology and presents manageable levels of noise even on 550 kilometres of standard optical fibre. This scheme is a promising step towards overcoming the rate-distance limit of QKD and greatly extending the range of secure quantum communications.
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KISLJ, NUK, SBMB, UL, UM, UPUK
Plants in infertile habitats are thought to have a high rate of nutrient resorption to enable them reuse nutrients more efficiently than those in fertile habitats. However, there is still much debate ...on how plant nutrient resorption responds to nutrient availability. Here we used a meta-analysis from a global data set of 9703 observations at 306 sites from 508 published articles to examine the effects of nitrogen (N) and phosphorus (P) fertilization on plant foliar N and P concentrations and resorption efficiency. We found that N fertilization enhanced N concentration in green leaves by 27% and P fertilization enhanced green-leaf P by 73% on average. The N and P concentrations in senesced leaves also increased with respective nutrient fertilization. Resorption efficiencies (percentage of nutrient recovered from senescing leaves) of both N and P declined in response to respective nutrient fertilization. Combined N and P fertilization also had negative effects on both N and P resorption efficiencies. Whether nutrient resorption efficiency differs among plant growth types and among ecosystems, however, remains uncertain due to the limited sample sizes when analyzed by plant growth types or ecosystem types. Our analysis indicates that fertilization decreases plant nutrient resorption and the view that nutrient resorption is a critical nutrient conservation strategy for plants in nutrient-poor environments cannot be abandoned. The response values to fertilization presented in our analysis can help improve biogeochemical models.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
The smooth muscle cell directly drives the contraction of the vascular wall and hence regulates the size of the blood vessel lumen. We review here the current understanding of the molecular ...mechanisms by which agonists, therapeutics, and diseases regulate contractility of the vascular smooth muscle cell and we place this within the context of whole body function. We also discuss the implications for personalized medicine and highlight specific potential target molecules that may provide opportunities for the future development of new therapeutics to regulate vascular function.
ABSTRACT
The dynamical state of galaxy clusters describes if clusters are relaxed dynamically or in a merging process of subclusters. Using archival images from the Chandra X-ray Observatory, we ...derive a set of parameters to describe the dynamical state for 964 galaxy clusters. Three widely used indicators for dynamical state, the concentration index c, the centroid shift ω, and the power ratio P3/P0 are calculated in the circular central region with a radius of 500 kpc. We also derive two adaptive parameters, the profile parameter κ and the asymmetry factor α, in the best fitted elliptical region. The morphology index δ is then defined by combining these two adaptive parameters, which indicates the dynamical state of galaxy clusters and has good correlations to the concentration index c, the centroid shift ω, the power ratio P3/P0, and the optical relaxation factor Γ. For a large sample of clusters, the dynamical parameters are continuously distributed from the disturbed to relaxed states with a peak in the between, rather than the bimodal distribution for the two states. We find that the newly derived morphology index δ works for the similar fundamental plane between the radio power, cluster mass, and the dynamical state for clusters with diffuse radio giant-haloes and mini-haloes. The offset between masses estimated from the Sunyaev–Zeld́ovich effect and X-ray images depends on dynamical parameters. All dynamical parameters for galaxy clusters derived from the Chandra archival images are available on http://zmtt.bao.ac.cn/galaxy_clusters/dyXimages/.
Abstract
High-precision light curves were extracted from TESScut images. Together with APOGEE and LAMOST medium-resolution spectra, a joint study was made for six early K-type contact binary ...candidates selected unbiasedly with orbital periods around 0.268 day. It is found that all of them (RV CVn, EK Com, V384 Ser, V1038 Her, EH CVn, and CSS_J125403.7+503945) are W-subtype shallow contact systems, though with different mass ratios (1/
q
= 0.27–0.62). The effective temperature differences between the binary components are around a few hundred kelvins. The original definitions of the A and W subtypes were compared with the customarily used methods, which rely on the shape or photometric solutions of the light curves. The latter two methods are not always reliable; therefore, the radial velocity analysis is strongly recommended. Through a collection of all available K-type contact binaries with both photometric and spectroscopic measurements, it is found that almost all of them are W-subtype systems, except for a few objects that have nearly identical temperatures for binary components. This W-subtype phenomenon for K-type contact binaries should be further checked with more samples in the future. Finally, the physical parameters of the targets were determined with joint data analysis, and the multiplicity is discussed for these targets. Objects V384 Ser and RV CVn are confirmed to very likely be triple systems from comprehensive analysis, while V1038 Her is a candidate of a triple system based on photometric and spectroscopic solutions.
Quantum communications promise to revolutionize the way information is exchanged and protected. Unlike their classical counterpart, they are based on dim optical pulses that cannot be amplified by ...conventional optical repeaters. Consequently, they are heavily impaired by propagation channel losses, confining their transmission rate and range below a theoretical limit known as repeaterless secret key capacity. Overcoming this limit with today’s technology was believed to be impossible until the recent proposal of a scheme that uses phase-coherent optical signals and an auxiliary measuring station to distribute quantum information. Here, we experimentally demonstrate such a scheme for the first time and over significant channel losses, in excess of 90 dB. In the high loss regime, the resulting secure key rate exceeds the repeaterless secret key capacity, a result never achieved before. This represents a major step in promoting quantum communications as a dependable resource in today’s world.A proof-of-principle experiment on twin-field quantum key distribution is demonstrated. The key rate overcomes the repeaterless secret key capacity bound limit at channel losses of 85 dB, corresponding to 530 km of ultralow-loss optical fibre.
Hyperactive ribosomal biogenesis is widely observed in cancer, which has been partly attributed to the increased rDNA transcription by Pol I in cancer. However, whether small nucleolar RNAs ...(snoRNAs), a class of non-coding RNAs crucial in ribosomal RNA (rRNA) maturation and functionality, are involved in cancer remains elusive. We report that snoRNAs and fibrillarin (FBL, an enzymatic small nucleolar ribonucleoprotein, snoRNP) are frequently overexpressed in both murine and human breast cancer as well as in prostate cancers, and significantly, that this overexpression is essential for tumorigenicity in vitro and in vivo. We demonstrate that when the elevated snoRNA pathway is suppressed, the tumor suppressor p53 can act as a sentinel of snoRNP perturbation, the activation of which mediates the growth inhibitory effect. On the other hand, high level of FBL interferes with the activation of p53 by stress. We further show that p53 activation by FBL knockdown is not only regulated by the ribosomal protein-MDM2-mediated protein stabilization pathway, but also by enhanced PTB-dependent, cap-independent translation. Together, our data uncover an essential role of deregulated snoRNA biogenesis in tumors and a new mechanism of nucleolar modulation of p53.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Fine roots <2 mm in diameter play a key role in regulating the biogeochemical cycles of ecosystems and are important to our understanding of ecosystem responses to global climate changes. Given the ...sensitivity of fine roots, especially in boreal region, to climate changes, it is important to assess whether and to what extent fine roots in this region change with climates. Here, in this synthesis, a data set of 218 root studies were complied to examine fine root patterns in the boreal forest in relation to site and climatic factors. The mean fine root biomass in the boreal forest was 5.28 Mg ha
−1
, and the production of fine roots was 2.82 Mg ha
−1
yr
−1
, accounting for 32% of annual net primary production of the boreal forest. Fine roots in the boreal forest on average turned over 1.07 times per year. Fine roots contained 50.9 kg ha
−1
of nitrogen (N) and 3.63 kg ha
−1
of phosphorous (P). In total, fine roots in the boreal forest ecosystems contain 6.1 × 10
7
Mg N and 4.4×10
6
Mg P pools, respectively, about 10% of the global nutrients of fine roots. Fine root biomass, production, and turnover rate generally increased with increasing mean annual temperature and precipitation. Fine root biomass in the boreal forest decreased significantly with soil N and P availability. With increasing stand age, fine root biomass increased until about 100 years old for forest stands and then leveled off or decreased thereafter. These results of meta analysis suggest that environmental factors strongly influence fine root biomass, production, and turnover in boreal forest, and future studies should place a particular emphasis on the root-environment relationships.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
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.
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IJS, NUK, SBMB, UL, UM, UPUK
ABSTRACT
The alignment between the brightest cluster galaxies (BCGs) and host clusters can reveal the mystery of the formation and evolution of galaxy clusters. We measure cluster orientations in ...optical based on the projected distribution of member galaxies and in X-ray by fitting the morphology of intracluster medium (ICM). Cluster orientations determined in the two wavelengths are generally consistent. The orientation alignment between BCGs and host clusters is confirmed and more significant than in previous works. We find that BCGs are more aligned with cluster orientations measured in X-ray than those from optical data. Clusters with a brighter BCG generally show a stronger alignment. We argue that the detected redshift evolution of the alignment is probably caused by observational bias rather than intrinsic evolution. The alignment is not related to the ellipticity of BCGs, and the richness, ellipticity, and dynamical state of host clusters. The strong alignment between BCGs and the morphology of ICMs may be the consequence of the co-evolution between the central massive galaxy and host clusters.
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