Semidiscrete optical vortex droplets in quasi-phase-matched photonic crystals

A new scheme for producing semidiscrete self-trapped vortices (\textquotedblleft swirling photon droplets\textquotedblright ) in photonic crystals with competing quadratic ($\chi ^{(2)}$) and self-defocusing cubic ($\chi ^{(3)}$) nonlinearities is proposed. The photonic crystal is designed with a striped structure, in the form of spatially periodic modulation of the $\chi ^{(2)}$ susceptibility, which is imposed by the quasi-phase-matching technique. Unlike previous realizations of semidiscrete optical modes in composite media, built as combinations of continuous and arrayed discrete waveguides, the semidiscrete vortex droplets are produced here in the fully continuous medium. This work reveals that the system supports two types of semidiscrete vortex droplets, \textit{viz}., onsite- and intersite-centered ones, which feature, respectively, odd and even numbers of stripes, $\mathcal{N}$. Stability areas for the states with different values of $\mathcal{N}$ are identified in the system's parameter space. Some stability areas overlap with each others, giving rise to multistability of states with different $\mathcal{N}$. The coexisting states are mutually degenerate, featuring equal values of the Hamiltonian and propagation constant. An experimental scheme to realize the droplets is outlined, suggesting new possibilities for the long-distance transmission of structured light carrying orbital angular momentum in nonlinear media.Comment: 9 pages, 7 figures, and 82 reference

Larmor precession: observation and utilization for boosting the signal intensity of radio frequency glow discharge mass spectrometry

A novel magnet array system was constructed to use Larmor precession for boosting the signal intensity of rf-GD-MS. The enhancement mechanism with four magnet array devices of single block magnet and 2×2, 3×2, and 3×4 magnet arrays was simulated and studied by COMSOL Multiphysics Software 5.4.0 (COMSOL) to determine if the electrons in the discharge plasma could perform Larmor precession along the direction perpendicular to the magnetic field. Induced by Larmor precession, inelastic collisions between the primary electrons and sample produced numerous secondary electrons and further improved the ionization efficiency. Moreover, the fuzzy synthetic evaluation result predicted that the device with 3×2 magnet array would display the greatest enhancement effect among the four devices. Based on these theoretical studies, a magnet array system with four magnet array devices was fabricated and utilized for studies of two scintillation crystals BGO and PWO. The observations indicated that the signal intensities obtained for 209Bi and 208Pb with the magnet array system were 630-3600 times of that obtained without magnet, and were enhanced by a factor of 1.5-2.8 compared with a previously reported stacked magnetic device. Two NIST samples were used to validate the method, and the results suggested that relative errors were less than 10% and the lowest detection limit for the 3×2 magnet array could reach 0.0032μg•g−1. Furthermore, the magnet array enhancement system with Larmor precession offers an efficient and sensitive approach for the direct analysis of non-conducting materials

Synthesis of the System Modeling and Signal Detecting Circuit of a Novel Vacuum Microelectronic Accelerometer

A novel high-precision vacuum microelectronic accelerometer has been successfully fabricated and tested in our laboratory. This accelerometer has unique advantages of high sensitivity, fast response, and anti-radiation stability. It is a prototype intended for navigation applications and is required to feature micro-g resolution. This paper briefly describes the structure and working principle of our vacuum microelectronic accelerometer, and the mathematical model is also established. The performances of the accelerometer system are discussed after Matlab modeling. The results show that, the dynamic response of the accelerometer system is significantly improved by choosing appropriate parameters of signal detecting circuit, and the signal detecting circuit is designed. In order to attain good linearity and performance, the closed-loop control mode is adopted. Weak current detection technology is studied, and integral T-style feedback network is used in I/V conversion, which will eliminate high-frequency noise at the front of the circuit. According to the modeling parameters, the low-pass filter is designed. This circuit is simple, reliable, and has high precision. Experiments are done and the results show that the vacuum microelectronic accelerometer exhibits good linearity over -1 g to +1 g, an output sensitivity of 543 mV/g, and a nonlinearity of 0.94 %

Oil and gas prediction basing on seismic inversion of elastic properties in Chaoshan depression, south China sea

The marine Mesozoic is widely distributed in the northeastern waters of the South China Sea and is an important field for oil-gas exploration in the South China Sea. The Chaoshan Depression is the largest residual depression in this sea. At a previous well, LF35-1-1, no oil and gas have been discovered with then pre-drilling prediction techniques. Post-drill analysis shows that the physical properties of the Mesozoic reservoir are not favorable there. So, in accurate prediction of the oil-gas reservoirs is necessary. Since the drilling at the LF35-1-1, extensive surveys and studies have been carried out which shows a number of favorable trapping structures. In the middle low bulge of the Chaoshan Depression, the DS-A structures found with potential reservoirs, complete trap structures, and dual source hydrocarbon supply on both sides, making it the most favorable zone for oil-gas accumulation. We apply the state of art prediction techniques for it using pre-stack seismic raw gather. The sensitivity analysis results of reservoir physical properties indicate that the difference in P- wave velocity between sand and mudstone is 500 m/s, the difference in density is 0.02 g/cm3, and the Poisson’s ratio ranges between 0.11 and 0.33. The Mesozoic sandstone reservoirs in the Chaoshan Depression have characteristics of high velocity and low Poisson’s ratio, and the P-wave velocity, density, and Poisson’s ratio are the main sensitive parameters for predicting reservoir and its oil-gas bearing properties. The density inversion, P-wave impedance inversion, and S-wave impedance inversion jointly characterize the “wedge-shaped” sand body in the DS-A structural area, with a maximum thickness of over 400 m and an area of ∼130 km2. The overlap of the sand body contour map and Poisson’s ratio inversion results indicates that the “wedge-shaped” sand body is an oil-gas bearing sand body. It can be concluded that pre-stack elastic parameter inversion is an effective method for reservoir prediction in deep-sea no-well exploration areas. It has the characteristics of high signal-to-noise ratio, strong stability and reliability, and high accuracy, which is conducive to reduce the non-uniqueness and uncertainty of seismic inversion. The inversion results predict that the DS-A structure is an oil-gas bearing structure

Protection effect of gut microbiota composition and acetate absorption against hypertension-induced damages on the longevity population in Guangxi, China

IntroductionRecent evidence supports a role for the gut microbe-metabolites in longevity. However, the phenomenon of hypertension is more common in the longevity area and whether hypertension is associated with longevity remains unclear. Here, we hypothesize that the levels of gut microbiota, SCFAs, and urine metabolites were different between hypertension elderly and hypertension longevity.MethodsWe recruited 46 elderly volunteers from Donglan County, Guangxi, and 32 were selected and included in the experiment. The subjects with hypertension were divided into two groups according to age, Hypertension Elderly (HTE, aged 70.5 ± 8.59, n = 19) and Hypertension Longevity (HTL, aged 100 ± 5.72, n = 13). The gut microbiota, SCFAs, and urine metabolites were determined by three-generation 16S rRNA full-length sequencing, GC-MS, and 1H-NMR, respectively.ResultsCompared with the HTL group, the HTE group had higher levels of hypertension-related genera Klebsiella and Streptococcus, while having lower levels of the SCFA-producing genera Bacteroides, Faecalibacterium, and Alistipes. Based on LEFse analysis, Klebsiella pneumoniae, Lactobacillus gasseri, Streptococcus salivarius, Ruminococcus, Actinomyces, Rikenellaceae, f_Saccharimonadaceae, Clostridium perfringens, and Bacteroids, Faecalibacterium prausnitzii, Parabacteroides, Alistipes were biomarkers that showed significant differences between the groups. In addition, the microbial pathways associated with K. pneumoniae and E. coli may promote hypertension, while A. muciniphila may play a role in reversing the development of hypertension in long-lived elderly. Metabolomics revealed that HTL contained a lower concentration of fecal acetate and propionate than HTE, while it contained a higher concentration of serum acetate and urine acetate. Furthermore, their immune cells exhibited no significant changes in SCFAs receptors.ConclusionAlthough long-lived elderly have extremely high systolic blood pressure, their unique gut microbiota composition and efficient acetate absorption in the colon may offset the damages caused by hypertension and maintain healthy homeostasis

Development and application of a porous cage carrier method for detecting trace elements in soils by direct current glow discharge mass spectrometry

The accurate and reliable determination of trace elements in soil still remains a big challenge for glow discharge mass spectrometry due to the poor conductive nature of soils. In the present work, a porous cage carrier was developed and used in the analysis of soils. The investigation results suggested that the carrier with a circular cross-sectional area in the range from 20 to 38 mm2, length from 15 to 17 mm and diameter of hole size from 1.5 mm to 2.0 mm could obtain good signals. Then the porous cage carrier method was systematically evaluated by analysing three types of soil reference materials. The discharge process was kept stable for more than 100 minutes, which was much longer than the boric acid method and indium sheet method. The investigations suggested that the internal precision was obtained within 16%, the external precision was better than 20% and the relative error was in the range from 0.7% to 17%. The detection limit of Tb could reach 0.014 μg g−1, which indicated that the new method qualified for the analysis of trace elements in soils. Compared to traditional tablet-pressed methods, the porous cage carrier method was not only convenient for sample preparation, but also showed good stability, reproducibility and better detection limits for trace elements. Furthermore, this method was proved to promote the potential application of GD-MS in the environmental field