Long range dipole-dipole interaction in low-density atomic vapors probed by double-quantum two-dimensional coherent spectroscopy

Optical double-quantum two-dimensional coherent spectroscopy (2DCS) was implemented to probe interatomic dipole-dipole interactions in both potassium and rubidium atomic vapors. The dipole-dipole interaction was detected at densities of $4.81 \times 10^8$ cm$^{-3}$ and $8.40 \times 10^9$ cm$^{-3}$ for potassium and rubidium, respectively, corresponding to a mean interatomic separation of 15.8 $\mu$m or $3.0\times 10^5a_0$ for potassium and 6.1 $\mu$m or $1.2\times 10^5a_0$ for rubidium, where $a_0$ is the Bohr radius. We report the lowest atomic density at which dipole-dipole interactions are detected. The experimental results confirm the long range nature of the dipole-dipole interaction which is critical for understanding many-body physics in atoms/molecules. The long range interaction also has implications in atom-based applications involving many-body interactions. Additionally, we demonstrated that double-quantum 2DCS is sufficiently sensitive to probe dipole-dipole interaction at densities that can be achieved with cold atom in a magneto-optical trap, paving the way for double-quantum 2DCS studies of cold atoms and molecules. The method can also open a new avenue to study long-range interactions in solid states systems such as quantum dots and color centers in diamonds.Comment: 5 pages, 4 figure

Genomic imprinting defect in Zfp57 mutant iPS cell lines

AbstractZFP57 maintains genomic imprinting in mouse embryos and ES cells. To test its roles during iPS reprogramming, we derived iPS clones by utilizing retroviral infection to express reprogramming factors in mouse MEF cells. After analyzing four imprinted regions, we found that parentally derived DNA methylation imprint was largely maintained in the iPS clones with Zfp57 but missing in those without maternal or zygotic Zfp57. Intriguingly, DNA methylation imprint was lost at the Peg1 and Peg3 but retained at the Snrpn and Dlk1-Dio3 imprinted regions in the iPS clones without zygotic Zfp57. This finding will be pursued in future studies

Unsupervised Learning of Hybrid Latent Dynamics: A Learn-to-Identify Framework

Modern applications increasingly require unsupervised learning of latent dynamics from high-dimensional time-series. This presents a significant challenge of identifiability: many abstract latent representations may reconstruct observations, yet do they guarantee an adequate identification of the governing dynamics? This paper investigates this challenge from two angles: the use of physics inductive bias specific to the data being modeled, and a learn-to-identify strategy that separates forecasting objectives from the data used for the identification. We combine these two strategies in a novel framework for unsupervised meta-learning of hybrid latent dynamics (Meta-HyLaD) with: 1) a latent dynamic function that hybridize known mathematical expressions of prior physics with neural functions describing its unknown errors, and 2) a meta-learning formulation to learn to separately identify both components of the hybrid dynamics. Through extensive experiments on five physics and one biomedical systems, we provide strong evidence for the benefits of Meta-HyLaD to integrate rich prior knowledge while identifying their gap to observed data.Comment: Under Revie

Zfp57 mutant ES cell lines directly derived from blastocysts

Zfp57 is a master regulator of genomic imprinting in mouse embryos. To further test its functions, we have derived multiple Zfp57 mutant ES clones directly from mouse blastocysts. Indeed, we found DNA methylation imprint was lost at most examined imprinting control regions in these Zfp57 mutant ES clones, similar to what was observed in Zfp57 mutant embryos in the previous studies. This result indicates that these blastocyst-derived Zfp57 mutant ES clones can be employed for functional analyses of Zfp57 in genomic imprinting

Adsorption of magnetic manganese ferrites to simulated monomeric mercury in flue gases.

Magnetic MnFe2O4 nanoparticles were successfully prepared by the rapid combustion method at 500 °C for 2 h with 30 mL absolute ethanol, and were characterized by SEM, TEM, XRD, VSM, and XPS techniques, their average particle size and the saturation magnetization were about 25.3 nm and 79.53 A·m2/kg, respectively. The magnetic MnFe2O4 nanoparticles were employed in a fixed bed experimental system to investigate the adsorption capacity of Hg0 from air. The MnFe2O4 nanoparticles exhibited the large adsorption performance on Hg0 with the adsorption capacity of 16.27 μg/g at the adsorption temperature of 50 °C with the space velocity of 4.8×104 h-1. The VSM and EDS results illustrated that the prepared MnFe2O4 nanoparticles were stable before and after adsorption and successfully adsorbed Hg0. The TG curves demonstrated that the mercury compound formed after adsorption was HgO, and both physical and chemical adsorption processes were observed. Magnetic MnFe2O4 nanoparticles revealed excellent adsorbance of Hg0 in air, which suggested that MnFe2O4 nanoparticles be promising for the removal of Hg0

Working Mechanism and Progress of Electromagnetic Metamaterial Perfect Absorber

Electromagnetic metamaterials are artificial subwavelength composites with periodic structures, which can interact strongly with the incident light to achieve effective control of the light field. Metamaterial absorbers can achieve nearly 100% perfect absorption of incident light at a specific frequency, so they are widely used in sensors, optical switches, communication, and other fields. Based on the development history of metamaterials, this paper discusses the research background and significance of metamaterial perfect absorbers. Some perfect absorption mechanisms, such as impedance matching and coherent perfect absorption, are discussed. According to the functional division, the narrowband, dual frequency, multi-frequency, broadband, and tunable metamaterial perfect absorbers are briefly described

Dynamic Interactions of a Cable-Laying Vessel with a Submarine Cable during Its Landing Process

The rapid development of offshore electricity grid construction has led to a great demand for submarine cable deployment. In this study, a numerical model is established based on the commercial software ANSYS-AQWA to investigate the dynamic interactions between a cable-laying vessel and a submarine cable during its landing process, which has not yet been reported and is critical to the safety of the cable. The numerical model was validated by an experimental test on the mooring stability of a vessel conducted in a wave tank. The effects of the cable length, the current velocity, the incident wave, and the wind direction on vessel stability and the tensions in the mooring lines and cable were investigated. When the cable length is short, the submarine cable acts as a mooring cable that can stabilize the hull, but it is not safe to apply force to the submarine cable. At the same time, an increase in the current speed also increases the tensile force of the submarine cable. The influence of different incident wave directions and wind directions on the stability and tension of ships in mooring lines and cables was studied, and the most unfavorable environmental conditions for submarine cable laying were determined under different environmental conditions

Derivation of hybrid ES cell lines from two different strains of mice

Parental origin-dependent expression of the imprinted genes is essential for mammalian development. Zfp57 maintains genomic imprinting in mouse embryos and ES cells. To examine the allelic expression patterns of the imprinted genes in ES cells, we obtained multiple hybrid ES clones that were directly derived from the blastocysts generated from the cross between mice on two different genetic backgrounds. The blastocyst-derived ES clones displayed largely intact DNA methylation imprint at the tested imprinted regions. These hybrid ES clones will be useful for future studies to examine the allelic expression of the imprinted genes in ES cells and their differentiated progeny