Concepts for direct frequency-comb spectroscopy of 229m^{229\text{m}}Th and an internal-conversion-based solid-state nuclear clock

A new concept for narrow-band direct nuclear laser spectroscopy of $^{229\text{m}}$Th is proposed, using a single comb mode of a vacuum ultraviolet frequency comb generated from the 7th harmonic of an Yb-doped fiber laser system. In this concept more than $10^{14}$ $^{229}$Th atoms on a surface are irradiated in parallel and a successful nuclear excitation is probed via the internal-conversion (IC) decay channel. A net scanning time of 15 minutes for the most recent 1~$\sigma$ energy uncertainty interval of 0.34 eV appears to be achievable when searching for the nuclear transition. In case of successful observation, the isomer's energy value would be constrained to an uncertainty of about 100~MHz, which is a factor of $10^6$ of improvement compared to today's knowledge. Further, the comb mode could be stabilized to the nuclear transition using the same detection method, allowing for the development of an IC-based solid-state nuclear clock, which is shown to achieve the same performance as a crystal-lattice nuclear clock, however, with the advantage of a drastically simpler detection scheme. Finally, it is shown that the same laser system could be used to narrow down the isomer's transition energy by further six orders of magnitude during laser excitation of $^{229}$Th$^{3+}$ ions in a Paul trap and to drive nuclear Rabi oscillations, as required for the development of a nuclear clock based on a single $^{229}$Th$^{3+}$ ion

Analysis of Pollution in Dianchi Lake and Consideration of Its Application in Crop Planting

AbstractAfter investigating the distribution and composition of N-cycle-related bacteria of different sites and different depth of Dianchi sediment, we analyzed the longitudinal distribution, lateral distribution of N, its transportation and transformation in Dianchi sediment, as well as the involvement of these bacteria in nitrogen cycle. Conclusion was drawn as follows, (1) Azotobateria could be effectively used as indicative strains to track the changes of Dianchi pollution because the distribution of Azotobateria can not only indicate N contamination but also P enrichment, (2) ammoniate and nitrite is mainly existed in top sediment of Dianchi Lake while other forms of nitrogen mainly in deeper sediment, (3) due to the fact that Dianchi is rich in P, together with the mutual promotion between N pollution and P pollution, the pollution of south part will worsen rapidly, (4) if the south part is also polluted badly, the pollution distribution will appear as peaking at both ends (north and south), and the pollution will definitely extend toward the middle, and finally Dianchi Lake will totally be seriously polluted. Combining with the fact that 40% of Dianchi pollution was caused by abusive use of chemical fertilizer, we put forward the idea of “changing pollutants into things of value”, which could be specified as “using the sediment as agricultural fertilizer”. Such method can solve the problem of internal pollution, and what's more, it can develop agriculture, while cut down the use of chemical fertilizer and thus reduce relative pollution source

Noncollinear enhancement cavity for record-high out-coupling efficiency of an extreme-UV frequency comb

We demonstrate a femtosecond enhancement cavity with a crossed-beam geometry for efficient generation and extraction of extreme-ultraviolet (XUV) frequency combs at a 154 MHz repetition rate. We achieve a record-high out-coupled power of 600 {\mu}W, directly usable for spectroscopy, at a wavelength of 97 nm. This corresponds to a >60% out-coupling efficiency. The XUV power scaling and generation efficiency are similar to that achieved with a single Gaussian-mode fundamental beam inside a collinear enhancement cavity. The noncollinear geometry also opens the door for the generation of isolated attosecond pulses at >100 MHz repetition rate.Comment: 13 pages, 5 figure

Gate-controlled reversible rectifying behaviour in tunnel contacted atomically-thin MoS2_{2} transistor

Atomically-thin 2D semiconducting materials integrated into van der Waals heterostructures have enabled architectures that hold great promise for next generation nanoelectronics. However, challenges still remain to enable their full acceptance as compliant materials for integration in logic devices. Two key-components to master are the barriers at metal/semiconductor interfaces and the mobility of the semiconducting channel, which endow the building-blocks of ${pn}$ diode and field effect transistor. Here, we have devised a reverted stacking technique to intercalate a wrinkle-free h-BN tunnel layer between MoS$_{2}$ channel and contacting electrodes. Vertical tunnelling of electrons therefore makes it possible to suppress the Schottky barriers and Fermi level pinning, leading to homogeneous gate-control of the channel chemical potential across the bandgap edges. The observed unprecedented features of ambipolar ${pn}$ to ${np}$ diode, which can be reversibly gate tuned, paves the way for future logic applications and high performance switches based on atomically thin semiconducting channel.Comment: 23 pages, 5 main figures + 9 SI figure

Loiss: A Byte-Oriented Stream Cipher

This paper presents a byte-oriented stream cipher -- Loiss, which takes a 128-bit initial key and a 128-bit initial vector as inputs, and outputs a key stream of bytes. The algorithm is based on a linear feedback shift register, and uses a structure called BOMM in the filter generator, which has good property on resisting against algebraic attacks, linear distinguishing attacks and fast correlation attacks. In order for BOMM to be balanced, the S-boxes in BOMM must be orthomorphic permutations. To further improve the capability in resisting against those attacks, the S-boxes in BOMM must also possess some good cryptographic properties, for example, high algebraic immunity, high nonlinearity, and so on. However current researches on orthomorphic permutations pay little attention on their cryptographic properties, and we believe that Loiss not only enriches applications of orthomorphic permutations in cryptography, but also motivates the research on a variety of cryptographic properties of orthomorphic permutations

First Principles Study on the Effect of Pressure on the Structure, Elasticity, and Magnetic Properties of Cubic GaFe(CN)₆ Prussian Blue Analogue

The structure, elasticity, and magnetic properties of Prussian blue analogue GaFe(CN)6 under external pressure ranges from 0 to 40 GPa were studied by first principles calculations. In the range of pressure from 0 to 35 GPa, GaFe(CN)6 not only has the half-metallic characteristics of 100% spin polarization, but also has stable mechanical properties. The external pressure has no obvious effect on the crystal structure and anisotropy of GaFe(CN)6, but when the pressure exceeds 35 GPa, the half-metallicity of GaFe(CN)6 disappears, the mechanical properties are no longer stable, and total magnetic moments per formula unit are no longer integer values

Editorial: Deep Eutectic Solvents/Complex Salts-Based Electrolyte for Next Generation Rechargeable Batteries

Recent years have seen an expansion of renewable energy technologies driven by global demands for energy alongside social and environmental concerns. One of the most significant solutions, rechargeable batteries have promising features which include high capacity, energy density, rate capability, long lifetime, and cost-effectiveness. As the key component in energy storage devices, the electrolyte has had a major impact on the chemistry/electrochemistry of rechargeable batteries/cells for a number of reasons. These include its potential window, which limits the redox potential of an electrochemical reaction. Its electrochemical activity and conductivity also influence the electrochemical reaction and consequently the battery performance. The composition, as well as the stability, of rechargeable batteries, shapes the electrolyte-electrode interface. Furthermore, its corrosivity cannot be neglected. For these reasons, researchers are highly motivated toward breakthroughs in battery performance, exploring the fundamental properties of electrolytes based on novel formulation/synthesis. Hence, this special issue of Deep Eutectic Solvents/Complex Salts Based Electrolyte for Next Generation Rechargeable Batteries focuses on the effects of electrolytes on the electrochemistry/chemistry of rechargeable batteries and cells.Published versio