Few-photon single ionization of cold rubidium in the over-the-barrier regime

Photoionization of the rubidium (Rb) atoms cooled in a magneto-optical trap, characterized by the coexistence of the ground 5$S_{1/2}$ and the excited 5$P_{3/2}$ states, is investigated experimentally and theoretically with the 400 nm femtosecond laser pulses at intensities of $I=3\times10^9$ W/cm$^2$ - $4.5\times10^{12}$ W/cm$^2$. Recoil-ion momentum distribution (RIMD) of Rb$^+$ exhibits rich ring-like structures and their energies correspond to one-photon ionization of the 5$P_{3/2}$ state, two-photon and three-photon ionizations of the 5$S_{1/2}$ state, respectively. With the increasing of $I$, we find that experimental signals near zero-momentum (NZM) in RIMDs resulted from the 5$P_{3/2}$ state enhance dramatically and its peaked Rb$^+$ momenta dwindle obviously while that from the 5$S_{1/2}$ state is maintained. Meanwhile, the ion-yield ratio of the 5$S_{1/2}$ over the 5$P_{3/2}$ states varies from $I$ to $I^{1.5}$ as $I$ increases. These features indicate a transition from perturbative ionization to strong-perturbative ionization for the 5$P_{3/2}$ state. Numerical simulations by solving the time-dependent Schr\"odinger equation (TDSE) can qualitatively explain the measurements of RIMD, photoion angular distributions, as well as ion-yield ratio. However, some discrepancies still exist, especially for the NZM dip, which could stem from the electron-electron correlation that is neglected in the present TDSE simulations since we have adopted the single-active-electron approximation

Study on Soil Microbial Diversity of Cymbidium goeringii and Cymbidium faberi in Qinling Mountains after Introduction and Domestication

Rhizosphere microbial communities have abundant species and a large number, and affect the physiology and growth of plants. When studying rhizosphere microbes, the rhizosphere ecosystem function and protection of wild orchids will be facilitated. By using high-throughput sequencing technology, the rhizosphere and non-rhizosphere bacteria and fungi of wild Cymbidium goeringii and Cymbidium faberi in the Qinling Mountains were analyzed at phylum, class, order, family, and genus levels to explore the rhizosphere bacterial and fungal community structure and diversity of orchid plants (C. goeringii and C. faberi) under natural conditions. The results showed that at the phylum level Proteobacteria was dominant in rhizosphere and non-rhizosphere soil of C. goeringii and C. faberi, but the proportion was different. The abundance of Proteobacteria in rhizosphere soil of C. faberi was the highest (35.5%), which was about 1.3 times of that in non-rhizosphere soil. Bacteroidetes accounted for 17.2% in rhizosphere soil of C. goeringii, much higher than that of non-rhizosphere soil (7.92%). The dominant groups of fungi in rhizosphere soil of C. goeringii and C. faberi were both Ascomycota. At the genus level, PCoA analysis showed that the community structure of bacteria and fungi in different samples was not only common but also specific, which was manifested in the similar dominant species but different subdominant species. This difference is reflected in the composition and relative abundance of microbial communities between different samples, and will gradually become obvious with the refinement of genera

Template-based category-agnostic instance detection for robotic manipulation

An intelligent robotic system is one of the key pillars of a smart factory that requires flexibility to handle a variety of tasks. Perception is a key enabling technology for robots. Most existing object detection studies have mainly focused on category-specific objects and have achieved impressive performance. However, robotic systems, particularly in industrial scenarios, typically interact with many category-agnostic objects, which the robot must detect instantly without pre-training. Therefore, in this study, we proposed a template-based detection and segmentation approach, which incorporated a multi-level correlation model and a similarity-refine module, for handling the category-agnostic instance. The proposed approach was then validated and demonstrated in an interactive and adaptive robotic application scenario designed for the typical pick-and-place task. Among them, the picking scan path and location were instructed through human guidance with hand tracking. The neural rendering technology was also introduced to render novel views of the template. The proposed approach was evaluated using a benchmark and verified through a real demonstration.Submitted/Accepted versionThis work was supported in part by the RIE2020 Industry Alignment Fund – Industry Collaboration Projects (IAF-ICP) Funding Initiative, and in part by Cash and In-kind Contribution from the Industry Partner(s)

Priming Watermelon Resistance by Activating Physiological Response and Defense Gene Expression to Alleviate Fusarium Wilt in Wheat-Watermelon Intercropping

Wheat intercropping in watermelon could provide relief from the occurrence of Fusarium wilting of watermelon, a severe soil-borne disease caused by the fungus Fusarium oxysporum f. sp. niveum (FON). The current study aims to investigate the effect of root exudates from three wheat cultivars and one watermelon cultivar on the growth of FON and the responses of Fusarium wilt in watermelon to intercropping with wheat. The results revealed the contrasting effects of root exudates on the mycelial growth of FON; the wheat root exudates inhibited the mycelial growth of FON, and watermelon root exudates promoted the mycelial growth of FON. Watermelon plants suffered less Fusarium wilt in the intercropping system than in the monocropping system. Wheat intercropping reduced the incidence of Fusarium wilt in watermelon, and this effect was associated with the role of wheat root exudates that inhibited the growth of FON. Malondialdehyde (MDA) contents decreased in the intercropping system compared with the monocropping system after FON inoculation. The catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO) activities, and total phenolics and flavonoid contents in the roots of watermelon in the intercropping system were significantly higher than those in the monocropping system. Real-time PCR analysis showed that ClCAT, ClSOD, ClAPX, and ClPPO defensive enzymes and ClPDF2.1 and ClPDF2.4 defensin-like gene expression were significantly induced during the early stage after FON inoculation in the intercropping system compared to the monocropping system, while peroxidases did not show a significant response to FON infection. It is suggested that intercropping with wheat alleviates Fusarium wilt of watermelon by reducing the population of FON in rhizospheric soil and activating physiological responses and defense gene expression to protect watermelon from FON infection and improve the resistance of watermelon to FON in the intercropping system

Study on the Soil Microbial Diversity of <i>Cymbidium goeringii</i> and <i>Cymbidium faberi</i> in the Qinling Mountains after Introduction and Domestication

Rhizosphere microbial communities have abundant species and a large number, and affect the physiology and growth of plants. When studying rhizosphere microbes, the rhizosphere ecosystem function and protection of wild orchids will be facilitated. By using high-throughput sequencing technology, the rhizosphere and non-rhizosphere bacteria and fungi of wild Cymbidium goeringii and Cymbidium faberi in the Qinling Mountains were analyzed at phylum, class, order, family, and genus levels to explore the rhizosphere bacterial and fungal community structure and diversity of orchid plants (C. goeringii and C. faberi) under natural conditions. The results showed that at the phylum level Proteobacteria was dominant in rhizosphere and non-rhizosphere soil of C. goeringii and C. faberi, but the proportion was different. The abundance of Proteobacteria in rhizosphere soil of C. faberi was the highest (35.5%), which was about 1.3 times of that in non-rhizosphere soil. Bacteroidetes accounted for 17.2% in rhizosphere soil of C. goeringii, much higher than that of non-rhizosphere soil (7.92%). The dominant groups of fungi in rhizosphere soil of C. goeringii and C. faberi were both Ascomycota. At the genus level, PCoA analysis showed that the community structure of bacteria and fungi in different samples was not only common but also specific, which was manifested in the similar dominant species but different subdominant species. This difference is reflected in the composition and relative abundance of microbial communities between different samples, and will gradually become obvious with the refinement of genera

Fluid Inclusions and Stable Isotope Geochemistry of Gold Mineralization Associated with Fine-Grained Granite: A Case Study of the Xiawolong Gold Deposit, Jiaodong Peninsula, China

The Xiawolong gold deposit, located in the Muping–Rushan gold metallogenic belt (eastern Jiaodong Peninsula), is a newly discovered deposit that developed in the late Early Cretaceous as fine-grained granite. Gold mineralization, which mainly occurs in the middle of fresh fine-grained granite dikes, consists of stockwork-style and disseminated ores. They are characterized by middle-high-temperature mineral assemblages, such as molybdenite and magnetite, associated with gold-bearing pyrite. Four types of primary fluid inclusions, contained within the quartz grains from the gold-bearing disseminated and stockwork-style fine-grained granitic ores, were identified based on microthermometry and Raman spectroscopy. The types identified were type 1 aqueous inclusions with middle-high temperature (201 to 480 °C) and middle-low salinity of 0.18 to 17.00 wt.% NaCl equiv.; type 2 H2O–CO2 inclusions, which show middle-high temperatures (218 to 385 °C), middle-low salinities (1.23 to 13.26 wt.% equiv. NaCl), and variable XCO2 (0.031 to 0.044); type 3 daughter mineral-bearing inclusions with high temperature (416 to 446 °C) and relatively constant and high salinity (28.59 to 32.87 wt.% NaCl equiv.); and type 4 CO2 fluid inclusions, which possess a bulk density of 0.405 to 0.758 g/cm3 and a constant XCO2 (0.952 to 0.990) (according to the decreasing abundance of fluid inclusions). The δ18Owater range is between 3.4 and 5.9‰, and the range of the δD is from −97.1 to −77.4‰, which indicates that the ore-forming process is of a magmatic water origin. The δ34S values possess a narrow range between 4.5 and 9.3‰, indicating the source of the Mesozoic Kunyushan granitoids. The Pb isotopic compositions of pyrite show that the Mesozoic Kunyushan granitoids are the main lead source for pyrites. Types 1, 2, and 3 fluid inclusions coexist in the same view field of the quartz grain, which are suggested to occur as the result of fluid immiscibility because of the boiling of a single homogeneous NaCl-CaCl2-KCl-CO2-H2O system. The fluid immiscibility, rather the fluid mixing and wall-rock sulfidation, is the mechanism of gold precipitation in the Xiawolong deposit. Compared with both the “Linglong-type” and “Jiaojia-type” gold deposits in the Jiaodong Peninsula in terms of geological–petrographic evidence and all of the available geochemical data, it can be concluded the Xiawolong gold deposit is of magmatic hydrothermal origin, having a genetic relation to the fine-grained granite

Mesozoic Magmatic and Geodynamic Evolution in the Jiaodong Peninsula, China: Implications for the Gold and Polymetallic Mineralization

The intrusive age ranges of Linglong, Guojialing, Weideshan, and Laoshan granites in the Jiaodong Peninsula are 155–154 Ma, 131–130 Ma, 118–111 Ma, and 116 Ma, respectively. Together with the Shidao granite (227–200 Ma), five phases of magmatism can be classified by the time, all of which have different degrees of gold and polymetallic mineralization. The type of granites evolved from A–, S–type to I–, A–type from the Late Triassic to the Early Cretaceous, thus reflects the evolution of geodynamics in the Mesozoic, indicating the switch from North China Craton (NCC)–Yangtze Craton (YC) collision to subduction of the Paleo–Pacific Plate (PPP), with crustal thickening switching to lithospheric thinning and a compressional tectonic setting changing to an extensional setting. It directly leads to a series of extensional structures evolving in the Jiaodong Peninsula and demonstrates affinity for the extensive mineralization in the Early Cretaceous. The key markers of Jiaodong gold and polymetallic mineralization are magmatism, fluid activity and extensional structure. Extensive magmatic uplift and extensional structures in the Early Cretaceous formed the extensional tectonic system. During the formation process, a large proportion of crust and mantle materials exchanged and mixed, and the fluid interaction was highly active, resulting in a magmatic fluid metallogenic system, which provided favorable metallogenic conditions for gold and nonferrous metal hydrothermal deposits. Thus, a large-scale explosive mineralization occurred in Jiaodong in the middle and late Early Cretaceous

Label-Free Fluorescence Sensing Strategy Based on Functional Nucleic Acids via Energy Transfer between DNA-Templated Silver Nanoclusters and Gold Nanorods

A simple and low-cost fluorescence signal-on sensing strategy has been developed based on functional nucleic acids (FNAs) via energy transfer between DNA-templated silver nanoclusters (DNA-AgNCs) and gold nanorods (GNRs). FNAs were used as highly selective recognition probes, in which an aptamer was used to detect small molecules represented by tetracycline, and DNAzyme was used to detect heavy metal ions represented by Pb2+. The fluorescent DNA-AgNCs were synthesized by the designed oligonucleotide sequences, which consisted of three parts: AgNCs synthesis template C6G5C6, spacer T5, and complementary sequences of the aptamer or enzyme strand. The difference in electrostatic interactions between ss/dsDNA and positively charged GNRs leads to energy transfer with different efficiencies. The analytes represented by tetracycline and Pb2+ can destroy the dsDNA structure and reduce the energy-transfer efficiency between DNA-AgNCs and GNRs, thus achieving fluorescence recovery and a signal-on analytical strategy. This strategy has excellent specificity and sensitivity with limit of detections of 4.411 nM for tetracycline and 1.416 nM for Pb2+ and has been successfully applied to detect tetracycline in milk and Pb2+ in river water. Using DNA-AgNCs formed in situ as signal probes, this strategy does not require labels or modifications and can be completed without complex analytical instruments. Moreover, this strategy can be extended to detect other targets by replacing FNA sequences. Therefore, it has promising prospects in the sensitive, simple, and rapid detection of contaminants in food and environment samples