Phase diagram of superconducting vortex ratchet motion in a superlattice with noncentrosymmetry

Ratchet motion of superconducting vortices, which is a directional flow of vortices in superconductors, is highly useful for exploring quantum phenomena and developing superconducting devices, such as superconducting diode and microwave antenna. However, because of the challenges in the quantitative characterization of the dynamic motion of vortices, a phase diagram of the vortex ratchet motion is still missing, especially in the superconductors with low dimensional structures. Here we establish a quantitative phase diagram of the vortex ratchet motion in a highly anisotropic superlattice superconductor, (SnS)1.17NbS2, using nonreciprocal magnetotransport. The (SnS)1.17NbS2, which possesses a layered atomic structure and noncentrosymmetry, exhibits nonreciprocal magnetotransport in a magnetic field perpendicular and parallel to the plane, which is considered a manifest of ratchet motion of superconducting vortices. We demonstrated that the ratchet motion is responsive to current excitation, magnetic field and thermal perturbation. Furthermore, we extrapolated a giant nonreciprocal coefficient ({\gamma}), which quantitatively describes the magnitude of the vortex ratchet motion, and eventually established phase diagrams of the ratchet motion of the vortices with a quantitative description. Last, we propose that the ratchet motion originates from the coexistence of pancake vortices (PVs) and Josephson vortices (JVs). The phase diagrams are desirable for controlling the vortex motion in superlattice superconductors and developing next-generation energy-efficient superconducting devices

Submarine groundwater discharge in Dongshan Bay, China: A master regulator of nutrients in spring and potential national significance of small bays

Despite over 90% of China’s coastal bays have an area less than 500 km2, the geochemical effects of SGD on those ecosystems are ambiguous. Based on mapping and time-series observations of Ra isotopes and nutrients, a case study of small bays (<500 km2), we revealed that submarine groundwater discharge (SGD) predominately regulated the distribution of nutrients and fueled algal growth in Dongshan Bay, China. On the bay-wide scale, the SGD rate was estimated to be 0.048 ± 0.022 m day−1 and contributed over 95% of the nutrients. At the time-series site where the bay-wide highest Ra activities in the bottom water marked an SGD hotspot with an average rate an order of magnitude greater, the maximum chlorophyll concentration co-occurred, suggesting that SGD may support the algal bloom. The ever-most significant positive correlations between 228Ra and nutrients throughout the water column (P< 0.01, R2 > 0.90 except for soluble reactive phosphorus in the surface) suggested the predominance of SGD in controlling nutrient distribution in the bay. Extrapolated to a national scale, the SGD-carried dissolved inorganic nitrogen flux in small bays was twice as much as those in large bays (>2,000 km2). Thus, the SGD-carried nutrients in small bays merit immediate attention in environmental monitoring and management

One-Pot Visual Detection of African Swine Fever Virus Using CRISPR-Cas12a

African swine fever virus (ASFV) is a leading cause of worldwide agricultural loss. ASFV is a highly contagious and lethal disease for both domestic and wild pigs, which has brought enormous economic losses to a number of countries. Conventional methods, such as general polymerase chain reaction and isothermal amplification, are time-consuming, instrument-dependent, and unsatisfactorily accurate. Therefore, rapid, sensitive, and field-deployable detection of ASFV is important for disease surveillance and control. Herein, we created a one-pot visual detection system for ASFV with CRISPR/Cas12a technology combined with LAMP or RPA. A mineral oil sealing strategy was adopted to mitigate sample cross-contamination between parallel vials during high-throughput testing. Furthermore, the blue fluorescence signal produced by ssDNA reporter could be observed by the naked eye without any dedicated instrument. For CRISPR-RPA system, detection could be completed within 40 min with advantageous sensitivity. While CRISPR-LAMP system could complete it within 60 min with a high sensitivity of 5.8 × 102 copies/μl. Furthermore, we verified such detection platforms display no cross-reactivity with other porcine DNA or RNA viruses. Both CRISPR-RPA and CRISPR-LAMP systems permit highly rapid, sensitive, specific, and low-cost Cas12a-mediated visual diagnostic of ASFV for point-of-care testing (POCT) applications

Prediction of Soil Organic Carbon in a New Target Area by Near-Infrared Spectroscopy: Comparison of the Effects of Spiking in Different Scale Soil Spectral Libraries

Near-infrared (NIR) spectroscopy is widely used to predict soil organic carbon (SOC) because it is rapid and accurate under proper calibration. However, the prediction accuracy of the calibration model may be greatly reduced if the soil characteristics of some new target areas are different from the existing soil spectral library (SSL), which greatly limits the application potential of the technology. We attempted to solve the problem by building a large-scale SSL or using the spiking method. A total of 983 soil samples were collected from Zhejiang Province, and three SSLs were built according to geographic scope, representing the provincial, municipal, and district scales. The partial least squares (PLS) algorithm was applied to establish the calibration models based on the three SSLs, and the models were used to predict the SOC of two target areas in Zhejiang Province. The results show that the prediction accuracy of each model was relatively poor regardless of the scale of the SSL (residual predictive deviation (RPD) < 2.5). Then, the Kennard-Stone (KS) algorithm was applied to select 5 or 10 spiking samples from each target area. According to different SSLs and numbers of spiking samples, different spiked models were established by the PLS. The results show that the predictive ability of each model was improved by the spiking method, and the improvement effect was inversely proportional to the scale of the SSL. The spiked models built by combining the district scale SSL and a few spiking samples achieved good prediction of the SOC of two target areas (RPD = 2.72 and 3.13). Therefore, it is possible to accurately measure the SOC of new target areas by building a small-scale SSL with a few spiking samples

Hyperspectral Imaging Analysis for the Classification of Soil Types and the Determination of Soil Total Nitrogen

Soil is an important environment for crop growth. Quick and accurately access to soil nutrient content information is a prerequisite for scientific fertilization. In this work, hyperspectral imaging (HSI) technology was applied for the classification of soil types and the measurement of soil total nitrogen (TN) content. A total of 183 soil samples collected from Shangyu City (People’s Republic of China), were scanned by a near-infrared hyperspectral imaging system with a wavelength range of 874–1734 nm. The soil samples belonged to three major soil types typical of this area, including paddy soil, red soil and seashore saline soil. The successive projections algorithm (SPA) method was utilized to select effective wavelengths from the full spectrum. Pattern texture features (energy, contrast, homogeneity and entropy) were extracted from the gray-scale images at the effective wavelengths. The support vector machines (SVM) and partial least squares regression (PLSR) methods were used to establish classification and prediction models, respectively. The results showed that by using the combined data sets of effective wavelengths and texture features for modelling an optimal correct classification rate of 91.8%. could be achieved. The soil samples were first classified, then the local models were established for soil TN according to soil types, which achieved better prediction results than the general models. The overall results indicated that hyperspectral imaging technology could be used for soil type classification and soil TN determination, and data fusion combining spectral and image texture information showed advantages for the classification of soil types

Analysis of Nanobridge Tests

This paper analyzes nanobridge tests with consideration of adhesive contact deformation, which occurs between a probe tip and a tested nanobeam, and deformation of a substrate or template that supports the tested nanobeam. Analytical displacement-load relation, including adhesive contact deformation and substrate deformation, is presented here for small deformation of bending. The analytic results are confirmed by finite element analysis. If adhesive contact deformation and substrate deformation are not considered in the analysis of nanobridge test data, they might lead to lower values of Young's modulus of tested nanobeams

Combined Rutile–zircon Thermometry and U-Pb Geochronology: New Constraints on Early Paleozoic HP/UHT Granulite in the South Altyn Tagh, North Tibet, China

HP granulite and garnet peridotite constitute a HP metamorphic unit in the south Altyn Tagh, northern Tibet. Previous data suggest that HP granulites experienced high pressure, ultrahigh-temperature metamorphism (870–1050 °C, 19–25 kbar), followed by a medium pressure granulite facies overprint (780–820 °C, 9.5–12 kbar). Previous zircon U–Pb geochronology of HP granulites gave an age of ca. 500 Ma, but it is unclear if this age reflects the metamorphic peak, or the post-peak overprint. In this contribution, new SHRIMP analyses indicate that the zircons associated with the peak metamorphic assemblage in HP felsic granulite are characterized by flat heavy REE patterns and 30–62 ppm Ti, yielding a temperature of 892–1002 °C by Ti-in-zircon thermometry, suggesting that the growth of the zircons occurred under or close to peak ultrahigh-temperature conditions rather than under post-peak conditions. These zircons gave a SHRIMP U–Pb age of 495 ± 4 Ma, representing the age of peak metamorphism. In contrast, oscillatory zoned zircon cores yield magmatic REE patterns, Ti-in-zircon temperatures of 720-820 °C, and Neoproterozoic U–Pb ages (936 ± 22 Ma). This indicates that the protoliths of the felsic granulites were formed in the early Neoproterozoic and were taken to extreme temperatures and pressures during the early Paleozoic orogenic event. In situ LA-ICPMS and EMP analyses indicate that rutiles are characterized by broad scatter and bimodal distribution in both Zr concentration and U–Pb age, which are interpreted as a result of recrystallization or growth rather than volume diffusion. The first rutile U–Pb age cluster is at ca. 485 Ma with a Zr concentration of ca. 3000 ppm, yielding ca. 950 °C at 20 kbar, implying that they grew at or near the peak metamorphic conditions. The second rutile U–Pb age cluster is at ca. 450 Ma with a Zr concentration of ca. 1000 ppm, corresponding to a temperature around 780 °C at 10 kbar, which is related to post-peak reheating under medium pressure/medium temperature granulite facies conditions. These results demonstrate that HP granulites in the south Altyn Tagh experienced a peak ultrahigh temperature and high pressure metamorphism at ca. 495 Ma, followed by medium pressure/medium temperature granulite facies overprint before ca. 450 Ma

Experimental and Numerical Study of Stagnant Zones in Pebble Bed

The experimental method (side area method) and DEM simulation have been carried out to analyse the stagnant zone in the quasi-two-dimensional silos. The side area method is a phenomenological method by means of investigating the interface features of different areas composed of different coloured pebbles. Two methods have been discussed to define the stagnant zone. In particular, the area of the stagnant zone has been calculated with the mean-streamline method, and the tracking time of different marking pebbles has been investigated with the stagnant time method to explore the kinematics characteristics of the pebbles. The stagnant zone is crucial for the safety of the pebble-bed reactor, and the practical reactor core must avoid the existence of the stagnant zone. Furthermore, this paper also analyses the effects of bed configuration (the bed height, the base angle, and the friction coefficient) on stagnant zone with the two methods mentioned above. In detail, the bed height shows little impact on the stagnant zones when the bed height exceeds a certain limit, while the base angle has negative prominent correlation with the stagnant zone. The friction coefficient effect seems complicated and presents the great nonlinearity, which deserves to be deeply investigated