Nano-black carbon (biochar) released from pyrogenic carbonaceous matter as a super suspending agent in water/soil environments

Nano-black carbon (BC) is one of the most active fractions in the pyrogenic carbonaceous matter continuum. The majority of recent studies mainly focus on the role of nano-BC in the global carbon cycle. However, based on literature and our recent studies, we suggest that nano-BC may also serve as a super suspending agent, carrier, and redox mediator for sorbates during its migration from terrestrial to water bodies due to its unique properties such as high colloidal stability, strong sorption capacity, and high surface reactivity. The full implications of nano-BC in water/soil environments are far more than we expected. Thus, we call for more detailed investigations on the activity and reactivity of nano-BC in water/soil environments

Carrier-envelope phase measurement from half-cycle high harmonics

We present a method to distinguish the high harmonics generated in individual half-cycle of the driving laser pulse by mixing a weak ultraviolet pulse, enabling one to observe the cutoff of each half-cycle harmonic. We show that the detail information of the driving laser pulse, including the laser intensity, pulse duration and carrier-envelope phase, can be {\it in situ} retrieved from the harmonic spectrogram. In addition, our results show that this method also distinguishes the half-cycle high harmonics for a pulse longer than 10 fs, suggesting a potential to extend the CEP measurement to the multi-cycle regime.Comment: 6 figures, 3 movie

Suppression of Grain Boundaries in Graphene Growth on Superstructured Mn-Cu(111) Surface

As undesirable defects, grain boundaries (GBs) are widespread in epitaxial graphene using existing growth methods on metal substrates. Employing density functional theory calculations, we first identify that the misorientations of carbon islands nucleated on a Cu(111) surface lead to the formation of GBs as the islands coalesce. We then propose a two-step kinetic pathway to effectively suppress the formation of GBs. In the first step, large aromatic hydrocarbon molecules are deposited onto a $\sqrt{3}\times\sqrt{3}$ superstructured Cu-Mn alloyed surface to seed the initial carbon clusters of a single orientation; in the second step, the seeded islands are enlarged through normal chemical vapor deposition of methane to form a complete graphene sheet. The present approach promises to overcome a standing obstacle in large scale single-crystal graphene fabrication

Investigation of the Factors Influencing Volume Fracturing of Tight Reservoir by Using Numerical Simulation

Based on finite element method, a complex fracture model of volume fracturing has been established for tight oil in this paper, which achieves the actual description of complex fractures. For water injection conditions, the volume of fractures network after fractured which considered the influence of fracture segment was analyzed by using numerical simulation. By comparing and analyzing the simulation results, the most optimal fracture segment is 10. The research results provide a theoretical basis for the optimized design of volume fracturing in tight oil.Key words: Tight oil; Volume fracturing; Numerical simulation; Finite element metho

Wind power ramp detection algorithms based on slope point correction

Wind power ramp event refers to the large fluctuation of wind power in a short time interval, which will seriously affect the safe and stable operation of power grid system. In order to maintain the stable operation of power grid system, wind power ramp detection is extremely necessary. Therefore, how to improve the accuracy of wind power ramp detection is a problem worthy of study. In the existing wind power ramp detection algorithms, the accuracy of the ramp endpoint is not considered. Aiming at the problem of end-point accuracy in climbing section, this work proposes a wind power climbing detection algorithm RPCRD (ramp point correct climbing detection) based on ramp point correction, which considers the detection accuracy of wind power climbing point for the first time. In this algorithm, a merging method of climbing sections is proposed to solve the fracture problem, and a scoring mechanism for selecting climbing points is proposed to find the two extreme points that most conform to the climbing characteristics, and the climbing points at both ends of the climbing section of wind power are modified

Distributed Equivalent Substitution Training for Large-Scale Recommender Systems

We present Distributed Equivalent Substitution (DES) training, a novel distributed training framework for large-scale recommender systems with dynamic sparse features. DES introduces fully synchronous training to large-scale recommendation system for the first time by reducing communication, thus making the training of commercial recommender systems converge faster and reach better CTR. DES requires much less communication by substituting the weights-rich operators with the computationally equivalent sub-operators and aggregating partial results instead of transmitting the huge sparse weights directly through the network. Due to the use of synchronous training on large-scale Deep Learning Recommendation Models (DLRMs), DES achieves higher AUC(Area Under ROC). We successfully apply DES training on multiple popular DLRMs of industrial scenarios. Experiments show that our implementation outperforms the state-of-the-art PS-based training framework, achieving up to 68.7% communication savings and higher throughput compared to other PS-based recommender systems.Comment: Accepted by SIGIR '2020. Proceedings of the 43rd International ACM SIGIR Conference on Research and Development in Information Retrieval. 202

Tailoring Plasmonic Enhanced Upconversion in Single NaYF4:Yb3+/Er3+ Nanocrystals

By using silver nanoplatelets with a widely tunable localized surface plasmon resonance (LSPR) and their corresponding local field enhancement, here we show large manipulation of plasmonic enhanced upconversion in NaYF4:Yb3+/Er3+ nanocrystals at the single particle level. In particular, we show that when the plasmonic resonance of silver nanolplatelets is tuned to 656 nm, matching the emission wavelength, an upconversion enhancement factor ~5 is obtained. However, when the plasmonic resonance is tuned to 980 nm, matching the nanocrystal absorption wavelength, we achieve an enhancement factor of ~22 folds. The precise geometric arrangement between fluorescent nanoparticles and silver nanoplatelets allows us to make, for the first time, a comparative analysis between experimental results and numerical simulations, yielding a quantitative agreement at the single particle level. Such a comparison lays the foundations for a rational design of hybrid metal-fluorescent nanocrystals to harness the upconversion enhancement for biosensing and light harvesting applications

Realization of a two-dimensional checkerboard lattice in monolayer Cu2_2N

Two-dimensional checkerboard lattice, the simplest line-graph lattice, has been intensively studied as a toy model, while material design and synthesis remain elusive. Here, we report theoretical prediction and experimental realization of the checkerboard lattice in monolayer Cu$_2$N. Experimentally, monolayer Cu$_2$N can be realized in the well-known N/Cu(100) and N/Cu(111) systems that were previously mistakenly believed to be insulators. Combined angle-resolved photoemission spectroscopy measurements, first-principles calculations, and tight-binding analysis show that both systems host checkerboard-derived hole pockets near the Fermi level. In addition, monolayer Cu$_2$N has outstanding stability in air and organic solvents, which is crucial for further device applications.Comment: Nano Letters, in pres

High-Throughput Screen Reveals sRNAs Regulating crRNA Biogenesis by Targeting CRISPR Leader to Repress Rho Termination

Discovery of CRISPR-Cas systems is one of paramount importance in the field of microbiology. Currently, how CRISPR-Cas systems are finely regulated remains to be defined. Here we use small regulatory RNA (sRNA) library to screen sRNAs targeting type I-F CRISPR-Cas system through proximity ligation by T4 RNA ligase and find 34 sRNAs linking to CRISPR loci. Among 34 sRNAs for potential regulators of CRISPR, sRNA pant463 and PhrS enhance CRISPR loci transcription, while pant391 represses their transcription. We identify PhrS as a regulator of CRISPR-Cas by binding CRISPR leaders to suppress Rho-dependent transcription termination. PhrS-mediated anti-termination facilitates CRISPR locus transcription to generate CRISPR RNA (crRNA) and subsequently promotes CRISPR-Cas adaptive immunity against bacteriophage invasion. Furthermore, this also exists in type I-C/-E CRISPR-Cas, suggesting general regulatory mechanisms in bacteria kingdom. Our findings identify sRNAs as important regulators of CRISPR-Cas, extending roles of sRNAs in controlling bacterial physiology by promoting CRISPR-Cas adaptation priming