Ex Perimental Study on Water Absorption of Coal Under Different Pressure Source Conditions

AbstractIn order to study the effect of pressure on the water absorption capability of coal, the water injection experiments of two coal samples were done under different pressure source conditions and room temperature by using self-designed pressurized water device. The experimental results show that pressure has a positive effect on water absorbability; water absorbability gets large as the pressure increases; the earlier water absorbability of coal is rapid, and the water absorbability of coal displays a similar Langmuir-isothermal adsorption curve with the changes of time, and it has saturated water absorbability. The water injection pressure is higher, which not only strengthened the ability of expanding seepage space, but also developed the transporting water and storage water space. The later water absorption curve of coal becomes weaker, and water adsorption process is mainly influenced by capillary force. The pressure water only supplies provisions and time is the main influential factor

Experimental realization of chiral Landau levels in two-dimensional Dirac cone systems with inhomogeneous effective mass

Chiral zeroth Landau levels are topologically protected bulk states that give rise to chiral anomaly. Previous discussions on such chiral Landau levels are based on three-dimensional Weyl degeneracies. Their realizations using two-dimensional Dirac point systems, being more promising for future applications, were never reported before. Here we propose a theoretical and experimental scheme for realizing chiral Landau levels in a photonic system. By introducing an inhomogeneous effective mass through breaking local parity inversion symmetries, the zeroth-order chiral Landau levels with one-way propagation characteristics are experimentally observed. In addition, the robust transport of the chiral zeroth mode against defects in the system is experimentally tested. Our system provides a new pathway for the realization of chiral Landau levels in two-dimensional Dirac systems, and may potentially be applied in device designs utilizing the transport robustness

Effect of Carbon Particles on Aerodynamic Performance of a Radial Inflow Turbine in Closed Brayton Cycle

For the closed Brayton cycle using carbon heaters, working fluid contains some solid particles generally. These impurities will enter turbine along with gas, influence aerodynamic performance, and even make turbine work under off-design condition. Therefore, it is necessary to study the influence of particles on turbine. In this paper, a turbine using argon with carbon particles as working fluid is investigated. Particles are assumed to have no volume and are evenly divided into ten different sizes. Based on the discrete phase model (DPM), CFD method is adopted to simulate turbine flow field, and influences of carbon particle mass fraction, particle diameter and incident velocity on aerodynamic performance are analyzed. The results indicate that as particle mass fraction increases, total pressure, static pressure and Mach number decrease significantly, isentropic efficiency decreases slightly, while temperature increases. Collision and rebound of particles in flow field are more intense with a larger particle diameter, but flow field is less influenced under the same mass fraction due to decrease of particle number. Incident velocity has little effect on aerodynamic performance; however, with increase of incident velocity, diameter of particles on blade surface is larger and collision of particles is more intense especially in nozzle. These results will help understand the influence of solid particles on turbines

Multicolor CRISPR labeling of chromosomal loci in human cells

The intranuclear location of genomic loci and the dynamics of these loci are important parameters for understanding the spatial and temporal regulation of gene expression. Recently it has proven possible to visualize endogenous genomic loci in live cells by the use of transcription activator-like effectors (TALEs), as well as modified versions of the bacterial immunity clustered regularly interspersed short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) system. Here we report the design of multicolor versions of CRISPR using catalytically inactive Cas9 endonuclease (dCas9) from three bacterial orthologs. Each pair of dCas9-fluorescent proteins and cognate single-guide RNAs (sgRNAs) efficiently labeled several target loci in live human cells. Using pairs of differently colored dCas9-sgRNAs, it was possible to determine the intranuclear distance between loci on different chromosomes. In addition, the fluorescence spatial resolution between two loci on the same chromosome could be determined and related to the linear distance between them on the chromosome\u27s physical map, thereby permitting assessment of the DNA compaction of such regions in a live cell

CRISPR-Cas9 nuclear dynamics and target recognition in living cells

The bacterial CRISPR-Cas9 system has been repurposed for genome engineering, transcription modulation, and chromosome imaging in eukaryotic cells. However, the nuclear dynamics of clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) guide RNAs and target interrogation are not well defined in living cells. Here, we deployed a dual-color CRISPR system to directly measure the stability of both Cas9 and guide RNA. We found that Cas9 is essential for guide RNA stability and that the nuclear Cas9-guide RNA complex levels limit the targeting efficiency. Fluorescence recovery after photobleaching measurements revealed that single mismatches in the guide RNA seed sequence reduce the target residence time from \u3e3 h to as low as time

Gauge Field Induced Chiral Zero Mode in Five-dimensional Yang Monopole Metamaterials

Owing to the chirality of Weyl nodes characterized by the first Chern number, a Weyl system supports one-way chiral zero modes under a magnetic field, which underlies the celebrated chiral anomaly. As a generalization of Weyl nodes from three-dimensional to five-dimensional physical systems, Yang monopoles are topological singularities carrying nonzero second-order Chern numbers c2 = +1 or -1. Here, we couple a Yang monopole with an external gauge field using an inhomogeneous Yang monopole metamaterial, and experimentally demonstrate the existence of a gapless chiral zero mode, where the judiciously designed metallic helical structures and the corresponding effective antisymmetric bianisotropic terms provide the means for controlling gauge fields in a synthetic five-dimensional space. This zeroth mode is found to originate from the coupling between the second Chern singularity and a generalized 4-form gauge field - the wedge product of the magnetic field with itself. This generalization reveals intrinsic connections between physical systems of different dimensions, while a higher dimensional system exhibits much richer supersymmetric structures in Landau level degeneracy due to the internal degrees of freedom. Our study offers the possibility of controlling electromagnetic waves by leveraging the concept of higher-order and higher-dimensional topological phenomena.Comment: 64 pages including supplementary material, to appear in Physical Review Letter

Topologically protected edge state in two-dimensional Su–Schrieffer–Heeger circuit

Topological circuits, an exciting field just emerged over the last two years, have become a very accessible platform for realizing and exploring topological physics, with many of their physical phenomena and potential applications as yet to be discovered. In this work, we design and experimentally demonstrate a topologically nontrivial band structure and the associated topologically protected edge states in an RF circuit, which is composed of a collection of grounded capacitors connected by alternating inductors in the x and y directions, in analogy to the Su–Schrieffer–Heeger model. We take full control of the topological invariant (i.e., Zak phase) as well as the gap width of the band structure by simply tuning the circuit parameters. Excellent agreement is found between the experimental and simulation results, both showing obvious nontrivial edge state that is tightly bound to the circuit boundaries with extreme robustness against various types of defects. The demonstration of topological properties in circuits provides a convenient and flexible platform for studying topological materials and the possibility for developing flexible circuits with highly robust circuit performance

CRISPR-Based DNA Imaging in Living Cells Reveals Cell Cycle-Dependent Chromosome Dynamics [preprint]

In contrast to the well-studied condensation and folding of chromosomes during mitosis, their dynamics in interphase are less understood. We developed a sensitive, multicolor system, CRISPR-Sirius, allowing the real-time tracking of the dynamics of chromosomal loci. We tracked loci kilobases to megabases apart and found significant variation in the inter-locus distances of each pair, indicating differing degrees of DNA contortion. We resolved two distinct modes of dynamics of loci: saltatory local movements as well as translational movements of the domain. The magnitude of both of these modes of movements increased from early to late G1, whereas the translational movements were reduced in early S. The local fluctuations decreased slightly in early S and more markedly in mid-late S. These newly observed movements and their cell cycle-dependence are indicative of a hitherto unrecognized compaction-relaxation dynamic of the chromosomal fiber operating concurrently with changes in the extent of observed genomic domain movements

Overcoming losses in superlenses with synthetic waves of complex frequency

Superlenses made of plasmonic materials and metamaterials have been exploited to image features of sub-diffractional scale. However, their intrinsic losses impose a serious restriction on the imaging resolution, which is a long-standing problem that has hindered wide-spread applications of superlenses. Optical waves of complex frequency exhibiting a temporally attenuating behavior have been proposed to offset the intrinsic losses in superlenses via virtual gain, but the experimental realization has been missing due to the challenge involved in preparing the illumination with temporal decay. Here, by employing multi-frequency measurement, we successfully implement a synthetic optical wave of complex frequency to experimentally observe deep-subwavelength superimaging patterns enabled by the virtual gain. Our work represents a practical approach to overcoming the intrinsic losses of plasmonic systems for imaging and sensing applications.Comment: 17 pages, 3 figure