DS-SLAM: A Semantic Visual SLAM towards Dynamic Environments

Simultaneous Localization and Mapping (SLAM) is considered to be a fundamental capability for intelligent mobile robots. Over the past decades, many impressed SLAM systems have been developed and achieved good performance under certain circumstances. However, some problems are still not well solved, for example, how to tackle the moving objects in the dynamic environments, how to make the robots truly understand the surroundings and accomplish advanced tasks. In this paper, a robust semantic visual SLAM towards dynamic environments named DS-SLAM is proposed. Five threads run in parallel in DS-SLAM: tracking, semantic segmentation, local mapping, loop closing, and dense semantic map creation. DS-SLAM combines semantic segmentation network with moving consistency check method to reduce the impact of dynamic objects, and thus the localization accuracy is highly improved in dynamic environments. Meanwhile, a dense semantic octo-tree map is produced, which could be employed for high-level tasks. We conduct experiments both on TUM RGB-D dataset and in the real-world environment. The results demonstrate the absolute trajectory accuracy in DS-SLAM can be improved by one order of magnitude compared with ORB-SLAM2. It is one of the state-of-the-art SLAM systems in high-dynamic environments. Now the code is available at our github: https://github.com/ivipsourcecode/DS-SLAMComment: 7 pages, accepted at the 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2018). Now the code is available at our github: https://github.com/ivipsourcecode/DS-SLA

Hypergraph Transformer for Skeleton-based Action Recognition

Skeleton-based action recognition aims to predict human actions given human joint coordinates with skeletal interconnections. To model such off-grid data points and their co-occurrences, Transformer-based formulations would be a natural choice. However, Transformers still lag behind state-of-the-art methods using graph convolutional networks (GCNs). Transformers assume that the input is permutation-invariant and homogeneous (partially alleviated by positional encoding), which ignores an important characteristic of skeleton data, i.e., bone connectivity. Furthermore, each type of body joint has a clear physical meaning in human motion, i.e., motion retains an intrinsic relationship regardless of the joint coordinates, which is not explored in Transformers. In fact, certain re-occurring groups of body joints are often involved in specific actions, such as the subconscious hand movement for keeping balance. Vanilla attention is incapable of describing such underlying relations that are persistent and beyond pair-wise. In this work, we aim to exploit these unique aspects of skeleton data to close the performance gap between Transformers and GCNs. Specifically, we propose a new self-attention (SA) extension, named Hypergraph Self-Attention (HyperSA), to incorporate inherently higher-order relations into the model. The K-hop relative positional embeddings are also employed to take bone connectivity into account. We name the resulting model Hyperformer, and it achieves comparable or better performance w.r.t. accuracy and efficiency than state-of-the-art GCN architectures on NTU RGB+D, NTU RGB+D 120, and Northwestern-UCLA datasets. On the largest NTU RGB+D 120 dataset, the significantly improved performance reached by our Hyperformer demonstrates the underestimated potential of Transformer models in this field

Preparation of PVA-GO Composite Hydrogel and Effect of Ionic Coordination on Its Properties

This paper adopts a method combining hybrid self-assembly, cyclic freezing-thawing and annealing treatment to prepare polyvinyl alcohol (PVA) and graphene oxide (GO) composite hydrogel. Then, the PVA-GO composite hydrogels are re-swelled in different ionic solutions (NaCl, MgCl2, CaCl2 and AlCl3) to improve mechanical strength, toughness and wear resistance by the ionic coordination bonds. The microstructure and morphology are characterized by Fourier transforms infrared spectroscopy (FTIR), x-ray diffraction (XRD) and Scanning electron microscopy (SEM), finding that the internal structure is porous three-dimensional network. Mechanical experiments indicate that the composite hydrogel with GO content of 0.05 wt% immersed in MgCl2 solution displays the best mechanical properties overall. Its tensile strength can reach 11.10 MPa and the elastic modulus reaches 1.72 MPa, which is 175% and 85% higher than the pure PVA, respectively. Sliding friction experiments illustrate that the composite hydrogel immersed in AlCl3 solution exhibits the lowest friction coefficient, and the higher the valence state of metal cation is, the better the wear reduction effect is. We expect to enrich the development of PVA-GO hydrogels in tissue engineering through synergy of hydrogen bonds and ionic coordination bonds

NLRP6 Serves as a Negative Regulator of Neutrophil Recruitment and Function During Streptococcus pneumoniae Infection

Streptococcus pneumoniae is an invasive pathogen with high morbidity and mortality in the immunocompromised children and elderly. NOD-like receptor family pyrin domain containing 6 (NLRP6) plays an important role in the host innate immune response against pathogen infections. Our previous studies have shown that NLRP6 plays a negative regulatory role in host defense against S. pneumoniae, but the underlying mechanism is still unclear. The further negative regulatory role of NLRP6 in the host was investigated in this study. Our results showed that NLRP6(-/-) mice in the lung had lower bacterial burdens after S. pneumoniae infection and expressed higher level of tight junction (TJ) protein occludin compared to WT mice, indicating the detrimental role of NLRP6 in the host defense against S. pneumoniae infection. Transcriptome analysis showed that genes related to leukocytes migration and recruitment were differentially expressed between wild-type (WT) and NLRP6 knockout (NLRP6(-/-)) mice during S. pneumoniae infection. Also, NLRP6(-/-) mice showed higher expression of chemokines including C-X-C motif chemokine ligand 1 (CXCL1) and 2 (CXCL2) and lower gene expression of complement C3a receptor 1 (C3aR1) and P-selectin glycoprotein ligand-1 (PSGL-1) which are the factors that inhibit the recruitment of neutrophils. Furthermore, NLRP6(-/-) neutrophils showed increased intracellular bactericidal ability and the formation of neutrophil extracellular traps (NETs) during S. pneumoniae infection. Taken together, our study suggests that NLRP6 is a negative regulator of neutrophil recruitment and function during S. pneumoniae infection. Our study provides a new insight to develop novel strategies to treat invasive pneumococcal infection

Current Status of Indocyanine Green Tracer-Guided Lymph Node Dissection in Minimally Invasive Surgery for Gastric Cancer

With the rapid development and popularization of laparoscopic and robotic radical gastrectomy, gastric cancer surgery has gradually entered a new era of precise minimally invasive surgery. The era of precision medicine has put forth new requirements for minimally invasive surgical treatment of patients with gastric cancer at different disease stages. For patients with early gastric cancer, avoiding surgical trauma caused by excessive lymph node dissection improves quality of life while pursuing radical treatment of the tumor. In patients with advanced gastric cancer, systematic lymph node dissection can be achieved without increasing surgical complications. With the successful application of indocyanine green (ICG) fluorescence imaging technology in minimally invasive surgical instrumentation in recent years, researchers have found that ICG fluorescence imaging yields good tissue penetration and can identify lymph nodes in fat tissue better than other dyes. Therefore, whether ICG fluorescence imaging technology can guide surgeons in performing safe and effective lymph node dissection has attracted much attention. The present review discusses the clinical applications and research progress of ICG tracer-guided lymph node dissection in patients with gastric cancer

Ultra-efficient frequency comb generation in AlGaAs-on-insulator microresonators

Recent advances in nonlinear optics have revolutionized integrated photonics, providing on-chip solutions to a wide range of new applications. Currently, state of the art integrated nonlinear photonic devices are mainly based on dielectric material platforms, such as Si₃N₄ and SiO₂. While semiconductor materials feature much higher nonlinear coefficients and convenience in active integration, they have suffered from high waveguide losses that prevent the realization of efficient nonlinear processes on-chip. Here, we challenge this status quo and demonstrate a low loss AlGaAs-on-insulator platform with anomalous dispersion and quality (Q) factors beyond 1.5 × 10⁶. Such a high quality factor, combined with high nonlinear coefficient and small mode volume, enabled us to demonstrate a Kerr frequency comb threshold of only ∼36 µW in a resonator with a 1 THz free spectral range, ∼100 times lower compared to that in previous semiconductor platforms. Moreover, combs with broad spans (>250 nm) have been generated with a pump power of ∼300 µW, which is lower than the threshold power of state-of the-art dielectric micro combs. A soliton-step transition has also been observed for the first time in an AlGaAs resonator

Laparoscopic resection for gastric GISTs: surgical and long-term outcomes of 133 cases

Background It aims to evaluate the surgical efficacy and long-term survival of different laparoscopic surgeries for gastric GISTs. Methods From a prospectively collected database, 133 patients with primary gastric GISTs undergoing laparoscopic surgery were selected from January 2008 to December 2014. They were divided into three groups according to the different operations that were performed, including laparoscopic gastric wedge resection (LWR Group, n=103), laparoscopic subtotal gastrectomy (LSG Group, n=18) and laparoscopic total gastrectomy (LTG group, n=12). Clinicopathological features and short- and long-term outcomes were analyzed retrospectively. Results All patients had received R0 resection. There were no differences among the three groups in age, BMI or NIH risk classification. Compared with the LSG group and LTG group, the LWR group had a shorter operative time, less blood loss, fewer operative complications and shorter time to ground activities, semi-liquid diet and hospital stay (P<0.05). There was no statistically significant difference in time to first flatus and liquid diet or in the rate of postoperative complications (P<0.05). In the patients with a large tumor (size≥5 cm), LWR was significantly associated with shorter operative time, less blood loss and shorter hospital stay compared with the laparoscopic gastric non-wedge resection (N-LWR) (P<0.05). The median follow-up was 30 months, with 4 cases of recurrence and 3 deaths. The 5-year cumulative survival rate was similar among the three groups (P>0.05). Conclusions Compared with LSG and LTG, more favorable minimally invasive results can be achieved from LWR for gastric GISTs, which may be the optimal surgical procedure

Long-term proton pump inhibitor use and the incidence of gastric cancer: A systematic review and meta-analysis

Background: There are controverted whether the long-term use of proton pump inhibitors (PPI) will increase the risk of gastric cancer. We performed a meta-analysis to assess the risk of gastric cancer in PPI users compared with non-PPI users. Methods: The main inclusion criteria were original studies reporting the incidence of gastric cancer in PPI users compared with non-PPI users. Key outcomes were the risk ratios (RR) for gastric cancer in association with PPI users or non-PPI users. Results: We analyzed data from 8 studies, comprising more than 927,684 patients. The risk of gastric cancer in PPI users was significantly higher than in non-PPI users [RR= 2.10, 95% CI (1.17-3.97)]. The risk of gastric cancer was similar between the 2 groups when the duration was ≤1 year [RR= 2.18, 95% CI (0.66-7.11)]. While the risk of gastric cancer for PPI users was higher than in non-PPI users when the duration was between 1-3 years, ≥1 year, ≥3 years and ≥5 years. The risk of non-cardiac gastric cancer for PPI users was higher than for non-PPI users [RR= 2.66, 95% CI (1.66 -4.27)], and the risk of non-cardiac gastric cancer for PPI users was higher than for non-PPI users when the duration ≥1 year [RR= 1.99, 95% CI (1.03-3.83)], but the risk for cardiac gastric cancer was similar between the 2 groups [RR= 1.86, 95% CI (0.71-4.89)]. Conclusions: We found the long-term use of PPI (duration ≥1 year) was significantly associated with a higher risk of non-cardiac gastric cancer

Laparoscopic-assisted total gastrectomy with D2 lymph node dissection: a case of 12-year-old child with advanced gastric cancer

The video shows the operation of laparoscopic-assisted total gastrectomy with D2 lymph node dissection for a 12-year-old child with advanced gastric cancer

Landau Quantization of Massless Dirac Fermions in Topological Insulator

The recent theoretical prediction and experimental realization of topological insulators (TI) has generated intense interest in this new state of quantum matter. The surface states of a three-dimensional (3D) TI such as Bi_2Te_3, Bi_2Se_3 and Sb_2Te_3 consist of a single massless Dirac cones. Crossing of the two surface state branches with opposite spins in the materials is fully protected by the time reversal (TR) symmetry at the Dirac points, which cannot be destroyed by any TR invariant perturbation. Recent advances in thin-film growth have permitted this unique two-dimensional electron system (2DES) to be probed by scanning tunneling microscopy (STM) and spectroscopy (STS). The intriguing TR symmetry protected topological states were revealed in STM experiments where the backscattering induced by non-magnetic impurities was forbidden. Here we report the Landau quantization of the topological surface states in Bi_2Se_3 in magnetic field by using STM/STS. The direct observation of the discrete Landau levels (LLs) strongly supports the 2D nature of the topological states and gives direct proof of the nondegenerate structure of LLs in TI. We demonstrate the linear dispersion of the massless Dirac fermions by the square-root dependence of LLs on magnetic field. The formation of LLs implies the high mobility of the 2DES, which has been predicted to lead to topological magneto-electric effect of the TI.Comment: 15 pages, 4 figure