An optical vortex having an isolated point singularity is associated with the spatial structure of light waves.A polarization vortex(vector beam) with a polarization singularity has spatially variant ...polarizations. A phase vortex with phase singularity or screw dislocation has a spiral phase front. The optical vortex has recently gained increasing interest in optical trapping, optical tweezers, laser machining, microscopy, quantum information processing, and optical communications. In this paper, we review recent advances in optical communications using optical vortices. First, basic concepts of polarization/phase vortex modulation and multiplexing in communications and key techniques of polarization/phase vortex generation and(de)multiplexing are introduced. Second, free-space and fiber optical communications using optical vortex modulation and optical vortex multiplexing are presented. Finally, key challenges and perspectives of optical communications using optical vortices are discussed. It is expected that optical vortices exploiting the space physical dimension of light waves might find more interesting applications in optical communications and interconnects.
Quantum key distribution (QKD) uses individual light quanta in quantum superposition states to guarantee unconditional communication security between distant parties. However, the distance over which ...QKD is achievable has been limited to a few hundred kilometres, owing to the channel loss that occurs when using optical fibres or terrestrial free space that exponentially reduces the photon transmission rate. Satellite-based QKD has the potential to help to establish a global-scale quantum network, owing to the negligible photon loss and decoherence experienced in empty space. Here we report the development and launch of a low-Earth-orbit satellite for implementing decoy-state QKD-a form of QKD that uses weak coherent pulses at high channel loss and is secure because photon-number-splitting eavesdropping can be detected. We achieve a kilohertz key rate from the satellite to the ground over a distance of up to 1,200 kilometres. This key rate is around 20 orders of magnitudes greater than that expected using an optical fibre of the same length. The establishment of a reliable and efficient space-to-ground link for quantum-state transmission paves the way to global-scale quantum networks.
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IJS, KISLJ, NUK, SBMB, UL, UM, UPUK
•This paper studies dynamic egocentric networks as the venue of knowledge creation.•An inverted U-shaped relation between network average tie strength and impact.•A skewed tie strength distribution ...contributes to higher citation impact.•Tie strength skewness moderates the effect of network average tie strength.
This paper studies the relationship between egocentric collaboration networks and knowledge creation at the individual level. For egocentric networks we focus on the characteristics of tie strength and tie configuration, and knowledge creation is assessed by the number of citations. Using a panel of 1042 American scientists in five disciplines and fixed effects models, we found an inverted U-shaped relationship between network average tie strength and citation impact, because an increase in tie strength on the one hand facilitates the collaborative knowledge creation process and on the other hand decreases cognitive diversity. In addition, when the network average tie strength is high, a more skewed network performs better because it still has a “healthy” mixture of weak and strong ties and a balance between exploration and exploitation. Furthermore, the tie strength skewness moderates the effect of network average tie strength: both the initial positive effect and the later negative effect of an increase in tie strength are smaller in a more skewed network than in a less skewed one.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This paper aims to inform choice of citation time window for research evaluation, by answering three questions: (1) How accurate is it to use citation counts in short time windows to approximate ...total citations? (2) How does citation ageing vary by research fields, document types, publication months, and total citations? (3) Can field normalization improve the accuracy of using short citation time windows? We investigate the 31-year life time non-self-citation processes of all Thomson Reuters Web of Science journal papers published in 1980. The correlation between non-self-citation counts in each time window and total non-self-citations in all 31 years is calculated, and it is lower for more highly cited papers than less highly cited ones. There are significant differences in citation ageing between different research fields, document types, total citation counts, and publication months. However, the within group differences are more striking; many papers in the slowest ageing field may still age faster than many papers in the fastest ageing field. Furthermore, field normalization cannot improve the accuracy of using short citation time windows. Implications and recommendations for choosing adequate citation time windows are discussed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Angular momentum, a fundamental physical quantity, can be divided into spin angular momentum (SAM) and orbital angular momentum (OAM) in electromagnetic waves. Helically-phased or twisted light beams ...carrying OAM that exploit the spatial structure physical dimension of electromagnetic waves have benefited wide applications ranging from optical manipulation to quantum information processing. Using the two distinct properties of OAM, i.e., inherent orthogonality and unbounded states in principle, one can develop OAM modulation and OAM multiplexing techniques for twisted optical communications. OAM multiplexing is an alternative space-division multiplexing approach employing an orthogonal mode basis related to the spatial phase structure. In this paper, we review the recent progress in twisted optical communications using OAM in free space and fiber. The basic concept of momentum, angular momentum, SAM, OAM and OAM-carrying twisted optical communications, key techniques and devices of OAM generation/(de)multiplexing/detection, high-capacity spectrally-efficient free-space OAM links, fiber-based OAM links, and OAM processing functions are presented. Ultra-high spectral efficiency and petabit-scale freespace data links are achieved benefiting from OAM multiplexing. The key techniques and challenges of twisted optical communications are also discussed. Twisted optical communications using OAM are compatible with other existing physical dimensions such as frequency/wavelength, amplitude, phase, polarization and time, opening a possible way to facilitate continuous increase of the aggregate transmission capacity and spectral efficiency through
N
-dimensional multiplexing.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Support recovery of sparse signals from compressed linear measurements is a fundamental problem in compressed sensing (CS). In this article, we study the orthogonal matching pursuit (OMP) algorithm ...for the recovery of support under noise. We consider two signal-to-noise ratio (SNR) settings: 1) the SNR depends on the sparsity level K of input signals, and 2) the SNR is an absolute constant independent of K. For the first setting, we establish necessary and sufficient conditions for the exact support recovery with OMP, expressed as lower bounds on the SNR. Our results indicate that in order to ensure the exact support recovery of all K-sparse signals with the OMP algorithm, the SNR must at least scale linearly with the sparsity level K. In the second setting, since the necessary condition on the SNR is not fulfilled, the exact support recovery with OMP is impossible. However, our analysis shows that recovery with an arbitrarily small but constant fraction of errors is possible with the OMP algorithm. This result may be useful for some practical applications where obtaining some large fraction of support positions is adequate.
Batteries powering next‐generation flexible and wearable electronic devices require superior mechanical bendability and foldability. Herein, a self‐standing hybrid nanoarchitecture constructed by ...ultralong MnO2 nanowires and graphene nanosheets as an advanced and lightweight cathodes for flexible and foldable zinc‐ion batteries (ZIBs) is designed and fabricated. The new‐designed batteries exhibit not only a high energy density of 436 Wh kg−1 based on the total cathode mass but also good 2000‐cycling durability. More importantly, the shape‐deformable ZIBs can be operated without any capacity loss under both bent and folded circumstances. The foldable ZIBs with high energy density and long lifetime hold great promise for smart and wearable electronics.
A freestanding MnO2/graphene hybrid membrane is fabricated to construct highly flexible and foldable zinc‐ion batteries that delivers an unprecedented high energy density of 436 Wh kg−1 based on the total cathode mass and long lifetime over 2000 cycles.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
RATIONALE:Necrosis is one of the main forms of cardiomyocyte death in heart disease. Recent studies have demonstrated that certain types of necrosis are regulated and programmed dependent on the ...activation of receptor-interacting serine/threonine-protein kinase (RIPK) 1 and 3 which may be negatively regulated by Fas-associated protein with death domain (FADD). In addition, microRNAs and long noncoding RNAs have been shown to play important roles in various biological processes recently.
OBJECTIVE:The purpose of this study was to test the hypothesis that microRNA-103/107 and H19 can participate in the regulation of RIPK1- and RIPK3-dependent necrosis in fetal cardiomyocyte-derived H9c2 cells and myocardial infarction through targeting FADD.
METHODS AND RESULTS:Our results show that FADD participates in H2O2-induced necrosis by influencing the formation of RIPK1 and RIPK3 complexes in H9c2 cells. We further demonstrate that miR-103/107 target FADD directly. Knockdown of miR-103/107 antagonizes necrosis in the cellular model and also myocardial infarction in a mouse ischemia/reperfusion model. The miR-103/107-FADD pathway does not participate in tumor necrosis factor-α–induced necrosis. In exploring the molecular mechanism by which miR-103/107 are regulated, we show that long noncoding RNA H19 directly binds to miR-103/107 and regulates FADD expression and necrosis.
CONCLUSIONS:Our results reveal a novel myocardial necrosis regulation model, which is composed of H19, miR-103/107, and FADD. Modulation of their levels may provide a new approach for preventing myocardial necrosis.
The intrinsic zinc dendrite growth aggravated by the uneven electric field at the Zn anode surface and the water‐induced parasitic reactions have largely impeded rechargeable aqueous zinc‐ion ...batteries for the practical applications in large‐scale energy storage. Here, an effective strategy is proposed to manipulate Zn deposition and simultaneously prevent the generation of insulating by‐products (Zn4SO4(OH)6·xH2O) for improved plating/stripping on Zn anodes by the addition of a nontoxic electrolyte additive, β‐cyclodextrin (β‐CD). The simulation results indicate that β‐CD molecules prefer to adsorb horizontally on Zn (002) plane, regulating the diffusion pathways and deposition sites of Zn2+ for the preferred Zn deposition along (002) plane without dendrite formation and inhibiting the H2 generation and the formation of Zn4SO4(OH)6·xH2O by facilitating desolvation of Zn(H2O)62+. Consequently, an ultra‐long stable cycling up to 1700 h at a high current density of 4 mA cm−2 can be achieved by the addition of β‐CD, 17 times that of the pure ZnSO4 electrolyte and the remarkable stability is also maintained under harsh test condition (40 mA cm−2, 20 mAh cm−2). This study highlights the important role of β‐CD in engineering the interfacial stability during Zn plating/stripping for high‐performing aqueous batteries.
β‐Cyclodextrin (β‐CD) additive with a special cavity structure is developed to regulate the deposition orientation of zinc ions and inhibit the parasitic reaction at the same time, resulting in highly reversible and stable Zn anode. Herein, the Zn//Zn cells with β‐CD display remarkable stability at different current densities ranging from 4 to 40 mA cm−2, much better than that in pure ZnSO4 electrolyte. This study demonstrates the remarkable effect of β‐CD on stabilizing the Zn anodes and provides insight into the design of versatile electrolytes for aqueous ion batteries.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Rechargeable zinc-ion batteries based on Zn/MnO2 in neutral aqueous electrolytes are promising for grid-scale energy storage applications owing to their favorable merits of high safety, low cost and ...environmental benignity. However, MnO2 cathodes are subjected to the challenging issues of poor cyclability and low rate capability. Herein, we report a facile chemical method for the preparation of mesoporous MnO2 flower-like nanospheres with the layered framework stabilized by hydrated Zn2+ pillars. The MnO2 cathode could deliver a reversible specific capacity of 358 mA h g−1 at 0.3 A g−1 after 100 cycles, a high rate capacity of 124 mA h g−1 at 3.0 A g−1, and excellent operating stability over 2000 cycles. Structural and morphological investigations demonstrate an energy storage mechanism of co-insertion/extraction of H+ and Zn2+ accompanied by deposition/dissolution of zinc sulfate hydroxide hydrate flakes on the electrode surface. The superior electrochemical performance makes the zinc ion stabilized MnO2 promising for high capacity and long lifespan zinc-ion batteries.
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