Nonholonomic Motion Planning Strategy for Underactuated Manipulator

This paper develops nonholonomic motion planning strategy for three-joint underactuated manipulator, which uses only two actuators and can be converted into chained form. Since the manipulator was designed focusing on the control simplicity, there are several issues for motion planning, mainly including transformation singularity, path estimation, and trajectory robustness in the presence of initial errors, which need to be considered. Although many existing motion planning control laws for chained form system can be directly applied to the manipulator and steer it to desired configuration, coordinate transformation singularities often happen. We propose two mathematical techniques to avoid the transformation singularities. Then, two evaluation indicators are defined and used to estimate control precision and linear approximation capability. In the end, the initial error sensitivity matrix is introduced to describe the interference sensitivity, which is called robustness. The simulation and experimental results show that an efficient and robust resultant path of three-joint underactuated manipulator can be successfully obtained by use of the motion planning strategy we presented

Three-dimensional polarization ray-tracing Mueller algorithm for an optical system with arbitrary surface type

In order to investigate the relationship between the interface parameters of an optical interface/system and its polarization characteristics, a three-dimensional (3D) polarization ray-tracing Mueller algorithm is proposed in this paper. Firstly, using the optical design simulation software CODE V or ZEMAX, the vector modeling of the optical system and the pupil sampling or field of view sampling of the incident light are carried out. Secondly, according to the surface type of each optical interface in the optical system and whether the optical coating is plated, the 3D polarization ray-tracing of each optical interface is carried out, and the 3D Mueller matrix Ml (9×9 order) of each optical interface under the respective local coordinate system is calculated. Then, a 3×3 order rotation transformation matrix R is introduced by using the rotation transformation of the global coordinate system, and the 3D Mueller matrix Mg (9×9 order) of each optical interface under the global coordinate system is obtained. Based on the 3D polarization algorithm proposed in our published paper, the 3D Mueller matrix M of each sampled ray through whole optical system is calculated. Finally, if the polarization state of the incident light of the optical system is known, the polarization state of the emitted light can be accurately calculated. Especially, the 3D polarization ray-tracing Mueller algorithm is not only suitable for handle the totally, partial and unpolarized light through the optical system, but also suitable for quantitative calculation of the polarization properties of an arbitrary surface, including spherical/aspherical/free-form surface

Tumor budding as a predictor for prognosis and therapeutic response in gastric cancer: A mini review

In recent years, the role of tumor budding in gastric cancer has received increased attention across a number of disciplines. Several studies have found associations between tumor budding and the prediction of lymph node metastasis in early gastric cancer, prognosis of advanced gastric cancer, predictors of therapeutic response to immune checkpoint inhibitors, such as microsatellite instability (MSI), and therapeutic targets of molecular targeted therapy, such as human epidermal growth factor receptor 2 (HER-2). Therefore, tumor budding is a major element in the formulation of risk stratification and precision medicine strategies for patients with gastric cancer

Revealing unusual bandgap shifts with temperature and bandgap renormalization effect in phase-stabilized metal halide perovskites

Hybrid organic-inorganic metal halide perovskites are emerging materials in photovoltaics, whose bandgap is one of the most crucial parameters governing their light harvesting performance. Here we present temperature and photocarrier density dependence of the bandgap in two phase-stabilized perovskite thin films (MA0.3FA0.7PbI3 and MA0.3FA0.7Pb0.5Sn0.5I3) using photoluminescence and absorption spectroscopy. Contrasting bandgap shifts with temperature are observed between the two perovskites. By utilizing X-ray diffraction and in situ high pressure photoluminescence spectroscopy, we show that the thermal expansion plays only a minor role on the large bandgap blueshift due to the enhanced structural stability in our samples. Our first-principles calculations further demonstrate the significant impact of thermally induced lattice distortions on the bandgap widening and reveal that the anomalous trends are caused by the competition between the static and dynamic distortions. Additionally, both the bandgap renormalization and band filling effects are directly observed for the first time in fluence-dependent photoluminescence measurements and are employed to estimate the exciton effective mass. Our results provide new insights into the basic understanding of thermal and charge-accumulation effects on the band structure of hybrid perovskites

Ultrasound-Stimulated Microbubbles Enhance Radiosensitization of Nasopharyngeal Carcinoma

Background/Aims: Recent studies indicate that therapies targeting the vasculature can significantly sensitize tumors to radiation. Ultrasound-stimulated microbubbles (USMBs) are regarded as a promising radiosensitizer. In this study, we investigated the effect of USMBs on the sensitivity of nasopharyngeal carcinoma (NPC) to radiation. Methods: Human NPC (CNE-2) cells and human umbilical vein endothelial cells (HUVECs) were exposed to radiation (0, 2, and 8 Gy) alone or in combination with USMBs. Cell viability and apoptosis were measured with the MTT assay and flow cytometry, respectively. The angiogenic activity of HUVECs was detected using matrigel tubule formation. The in vitro effects induced by these treatments were confirmed in vivo with xenograft models of CNE-2 cells in nude mice by examining vascular integrity using color Doppler flow imaging and cell survival using immunohistochemistry. Additionally, the in vivo and in vitro expressions of angiotensin II (ANG II) and its receptor (AT1R) were detected by immunohistochemistry and western blotting, respectively. With CNE-2 cells and HUVECs transfected with control, ANG II, or AT1R, perindopril (an inhibitor of angiotensin-converting enzyme) and candesartan (an inhibitor of AT1R) were used to verify the role of ANG II and AT1R in the radiosensitivity of tumor and endothelial cells by USMBs, by determining cell viability and apoptosis and angiogenic activity. Results: In the NPC xenografts, USMBs slightly reduced blood flow and CD34 expression, increased tumor cell death and ANG II and AT1R expression, and significantly enhanced the effects of radiation. With CNE-2 cells and HUVECs, the USMBs further enhanced the inhibition of tumor cell viability and endothelial tubule formation and further enhanced the increase in ANG II and AT1R due to radiation. Furthermore, perindopril and candesartan significantly enhanced the inhibitory effect of radiation and USMBs on tumor cell growth and angiogenesis in vitro. Conclusions: We have demonstrated for the first time that USMB exposure can significantly enhance the destructive effect on NPC of radiation, and this effect might be further increased by ANG II and AT1R inhibition. Our findings suggest that USMBs can be used as a promising sensitizer of radiotherapy to treat NPC, and the clinical effect might be increased by ANG II and AT1R inhibition

Polysulfide-mediated solvation shell reorganization for fast Li+ transfer probed by in-situ sum frequency generation spectroscopy

Understanding of interfacial Li$^+$ solvation shell structures and dynamic evolution at the electrode/electrolyte interface is requisite for developing high-energy-density Li batteries. Herein, the reorganization of Li$^+$ solvation shell at the sulfur/electrolyte interface along with the presence of a trace amount of lithium polysulfides is verified by in-situ sum frequency generation (SFG) spectroscopy together with density functional theory (DFT) calculations. Both the spectroelectrochemical and DFT calculation results reveal a strongly competitive anion adsorption of the polysulfide anion additive against the pristine electrolyte anion on the sulfur cathode surface, reorganizing the interfacial local solvation shell structure facilitating rapid Li ion transfer and conduction. Meanwhile, the evolution of the SFG signals along with the discharging/charging cycle exhibits improved reversibility, indicating the transformation of the inner Helmholtz plane layer into a stable molecular-layer polysulfide interphase rather than a dynamic diffusion layer. Consequently, applications in practical Li-S batteries reveal the capacity and cycling stability of the corresponding cells are significantly enhanced. Our work provides a methodology using in-situ SFG for probing solvation reorganization of charge carriers at electrochemical interfaces

A Long-Life, High-Rate Lithium/Sulfur Cell: A Multifaceted Approach to Enhancing Cell Performance

Lithium/sulfur (Li/S) cells are receiving significant attention as an alternative power source for zero-emission vehicles and advanced electronic devices due to the very high theoretical specific capacity (1675 mA·h/g) of the sulfur cathode. However, the poor cycle life and rate capability have remained a grand challenge, preventing the practical application of this attractive technology. Here, we report that a Li/S cell employing a cetyltrimethyl ammonium bromide (CTAB)-modified sulfur-graphene oxide (S-GO) nanocomposite cathode can be discharged at rates as high as 6C (1C = 1.675 A/g of sulfur) and charged at rates as high as 3C while still maintaining high specific capacity (~ 800 mA·h/g of sulfur at 6C), with a long cycle life exceeding 1500 cycles and an extremely low decay rate (0.039% per cycle), perhaps the best performance demonstrated so far for a Li/S cell. The initial estimated cell-level specific energy of our cell was ~ 500 W·h/kg, which is much higher than that of current Li-ion cells (~ 200 W·h/kg). Even after 1500 cycles, we demonstrate a very high specific capacity (~ 740 mA·h/g of sulfur), which corresponds to ~ 414 mA·h/g of electrode: still higher than state-of-the-art Li-ion cells. Moreover, these Li/S cells with lithium metal electrodes can be cycled with an excellent Coulombic efficiency of 96.3% after 1500 cycles, which was enabled by our new formulation of the ionic liquid-based electrolyte. The performance we demonstrate herein suggests that Li/S cells may already be suitable for high-power applications such as power tools. Li/S cells may now provide a substantial opportunity for the development of zero-emission vehicles with a driving range similar to that of gasoline vehicles