Singularities in five-axis machining are a series of deadly positions, which may cause unstable axis movements and deteriorate the performance of machine tools. This paper presents an optimization ...strategy to locally deform the tool path so that singularities of five-axis machine tools can be avoided. To achieve this purpose, a new concept of “forbidden circle”, which is the projection of the three dimensional “singular cone” associated with tool orientations in a two dimensional space named P-plane, is established for the first time to transform the complicated three dimensional problem into a two dimensional problem. Based on this idea, the projected points in P-plane are interpolated as B-spline first, and then, the B-spline control points are locally optimized by taking the “forbidden circle” as the geometrical constraint to keep the B-spline from crossing it. Especially, in the optimization procedure, the constraints are linearized with the changes of B-spline control points to change the whole optimization problem as a typical positive definite quadratic programming problem, which can achieve one and only global optimal solution. By doing so, singularity is avoided, and at the same time, the machining errors caused by tool path deformation can be minimized. Simulation and experimental results verify the effectiveness of the singularity avoidance method.
•Singularities of five-axis machine tools are avoided through introducing geometrical constraints.•A one-to-one projection principle is proposed, which can ensure the unity vector property of tool orientations.•A new concept “forbidden circle” is defined for the first time aiming at singularity avoidance.•Efficiency and effectiveness of the proposed singularity avoidance method is verified by simulations and experiments.
•TiO2 QDs anchored on GNRs was facilely prepared by a simple hydrolysis strategy.•The TiO2 QDs with a size of ~5 nm were preferentially dispersed at edges of GNRs.•The desirable electrochemical ...performance of TiO2@GNRs as anodes are achieved.•The enhanced performance can be ascribed to interfacial confinement of GNRs.
A hybrid-material of titanium-oxide quantum dots (QDs) anchored on graphene nanoribbons (TiO2@GNRs) was prepared by a simple hydrolysis strategy followed by heat-treatment. The GNRs can effectively accelerate the charge transference in the TiO2@GNRs. And the TiO2 QDs of ~5 nm can be thoroughly lithiatied/sodiated in electrically confined space of GNRs. Motivated by its unique structure, the electrochemical charge/discharge behaviors of the TiO2@GNRs serving as anodes for Li/Na-ion batteries (LIBs/SIBs) were evaluated. Reversible charge capacities of 320.8 mAh g−1 for LIBs and 101.6 mAh;g−1 for SIDs were demonstrated over 100 cycles at a rate of 0.5 A g−1, respectively. And Li and Na storage capacities of 209.0 and 42.2 mAh g−1 were retained at 8.0 A g−1, respectively. The desirable charge capacities, stable cyclic ability, and excellent rate performance of TiO2@GNRs can be ascribed to the ultra-small TiO2 size benefiting for full insertion/extraction of alkali ions and shortening their transfer pathway as well as enhanced electronic and ionic conductivity of the overall electrodes and interfacial confinement of GNRs for maintaining the electrode integrity.
Aging causes a decline in skeletal muscle function, resulting in a progressive loss of muscle mass, quality, and strength. A weak regenerative capacity is one of the critical causes of dysfunctional ...skeletal muscle in elderly individuals. The extracellular matrix (ECM) maintains the tissue framework structure in skeletal muscle. As shown by previous reports and our data, the gene expression of ECM components decreases with age, but the accumulation of collagen substantially increases in skeletal muscle. We examined the structural changes in ECM in aged skeletal muscle and found restricted ECM degradation. In aged skeletal muscles, several genes that maintain ECM structure, such as transforming growth factor β (TGF-β), tissue inhibitors of metalloproteinases (TIMPs), matrix metalloproteinases (MMPs), and cathepsins, were downregulated. Muscle injury can induce muscle repair and regeneration in young and adult skeletal muscles. Surprisingly, muscle injury could not only efficiently induce regeneration in aged skeletal muscle, but it could also activate ECM remodeling and the clearance of ECM deposition. These results will help elucidate the mechanisms of muscle fibrosis with age and develop innovative antifibrotic therapies to decrease excessive collagen deposition in aged muscle.
(1-x)SrTiO3-x(Na0.5Bi0.5)TiO3 ((1-x)ST-xNBT) ceramics have been prepared by solid-state route and their structure, electric and energy storage properties have been investigated. Dielectric anomalies ...at Tm and T′m show strong frequency dispersion as the typical relaxor ferroelectrics behavior over a broad temperature range. The Tm of (1-x)ST-xNBT ceramics dramatically shifted to a higher temperature (from −118 °C to 106 °C at 1 kHz) with increasing x. All samples showed the broad relaxor behavior due to the increase in the degree of lattice disorder and the thermal evolution of PNRs, and exhibited a discharge energy density of more than 1.18 J/cm3. The x = 0.4 sample exhibited a maximum discharge energy density of 1.70 J/cm3, consistent with the high value of Eb (∼21 kV/mm) and Pm (∼25 μC/cm2). The results indicate that (1-x)ST-xNBT ceramics might be a promising environmental friendly material for energy storage application.
•(1-x)SrTiO3-x(Na0.5Bi0.5)TiO3 ceramics were synthesized via solid state route.•The structure, electric and energy storage properties of the ceramics were investigated.•The maximum discharge energy density of x = 0.4 sample reaches up to 1.70 J/cm3.
Colorectal polyp is an important early manifestation of colorectal cancer, which is significant for the prevention of colorectal cancer. Despite timely detection and manual intervention of colorectal ...polyps can reduce their chances of becoming cancerous, most existing methods ignore the uncertainties and location problems of polyps, causing a degradation in detection performance. To address these problems, in this paper, we propose a novel colorectal image analysis method for polyp diagnosis via PAM-Net. Specifically, a parallel attention module is designed to enhance the analysis of colorectal polyp images for improving the certainties of polyps. In addition, our method introduces the GWD loss to enhance the accuracy of polyp diagnosis from the perspective of polyp location. Extensive experimental results demonstrate the effectiveness of the proposed method compared with the SOTA baselines. This study enhances the performance of polyp detection accuracy and contributes to polyp detection in clinical medicine.
Cembrane-type diterpenoids are among the most frequently encountered natural products from the soft corals of the genus Lobophytum. In the course of our investigation to identify anti-inflammatory ...constituents from a wild-type soft coral Lobophytum crassum, two new cembranoids, lobophyolide A (1) and B (2), along with five known compounds (3–7), were isolated. The structures of these natural products were identified using NMR and MS spectroscopic analyses. Compound 1 was found to possess the first identified α-epoxylactone group among all cembrane-type diterpenoids. The in vitro anti-inflammatory effect of compounds 1–5 was evaluated. The results showed that compounds 1–5 not only reduced IL-12 release, but also attenuated NO production in LPS-activated dendritic cells. Our data indicated that the isolated series of cembrane-type diterpenoids demonstrated interesting structural features and anti-inflammatory activity which could be further developed into therapeutic entities.
Nitrogen-doped carbon wrapped Si nanoparticles (NPs) hybridized with 3D graphene conductive network (N-C/Si@G) is developed as a novel nanocomposite for lithium-ion battery (LIB) anodes. The ...nanocomposite is synthesized via a facile technique that involves self-assembly of Si NPs (~50 nm) with graphene oxide (Si@GO) and formation of mixture of Si@GO and polyacrylonitrile (PAN) in the presence of dimethyl sulfoxide (DMSO), followed by a carbonization treatment under a temperature of 750 °C. Si NPs encapsulated in nitrogen-doped amorphous carbon shell are completely filled in a 3D graphene network. When employed as a LIB anode, N-C/Si@G was able to achieve a high specific capacity of 1750 mAh g−1 at a current density of 0.1 A g−1. In addition, the N-C/Si@G nanocomposite showed the excellent cyclic performance with a specific capacity of ~701 mAh g−1 at 5 A g−1 over 800 cycles. Based on the collective results, the enhanced electrochemical performance of N-C/Si@G nanocomposite might be largely ascribed to the synergistic effect arised from N-doped carbon shell and large void space of the 3D graphene network. Individually, N-doped carbon shell can help to enhance the overall electronic conductivity of the material, while the large void in 3D graphene network can provide enough space to accommodate the severe volume change of Si NPs.
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•Nitrogen-doped carbon wrapped Si NPs hybridized with 3D graphene (N-C/Si@G) is developed as a novel anode.•Si NPs of ~50 nm enveloped with nitrogen-doped carbon were fully encapsulated in a 3D graphene network.•Self-standing N-C/Si@G nanocomposite exhibited superior Li-storage performance.•Enhanced performance is mainly due to the synergistic effects of N-doped carbon coating and 3D graphene buffering.
Both alterations to the intestinal microflora and chronic systemic inflammation predispose towards type 2 diabetes (T2D). Changes in the composition of the intestinal microflora are associated with ...glucose metabolism changes in rats with T2D. Here, we demonstrate that a berberine fumarate (BF) has a hypoglycemic effect by regulating the intestinal microflora and metabolism of diabetic rats. The T2D rats had disorders of glucose and lipid metabolism, an abnormal intestinal microflora, fewer butyrate-producing and probiotic-type bacteria, larger numbers of potentially pathogenic and sulfate-reducing bacteria, and tissue inflammation. Administration of berberine fumarate significantly ameliorated the metabolic disorder; increased the populations of Bacteroidetes, Clostridia, Lactobacillales, Prevotellaceae, and Alloprevotella; and reduced those of Bacteroidales, Lachnospiraceae, Rikenellaceae, and Desulfovibrio. In addition, it reduced inflammation, inhibiting the overexpression of TLR4 and p-JNK and increasing the expression of PI3K, GLUT2, and other proteins, which are closely related to oxidative stress, thereby promoting the metabolism of glucose.
Paris polyphylla var. yunnanensis, named Chong Lou, is considered an antitumor substance. In this study, we investigated the effect of
PP‐22, a monomer purified from
P. polyphylla var. yunnanensis, ...on the nasopharyngeal carcinoma cell line CNE‐2 in vitro. The results showed that
PP‐22 could inhibit the proliferation of CNE‐2 cells via the induction of apoptosis, with evidence of the characteristic morphological changes in the apoptosis in the nucleus and an increase in Annexin V‐positive cells. In addition, we found that
PP‐22 could activate the p38 mitogen‐activated protein kinase (MAPK) pathway and that this activation was reversed by SB203580, a specific inhibitor of the p38 MAPK pathway. In contrast,
PP‐22 promoted apoptosis via an intrinsic pathway, including the endoplasmic reticulum stress pathway, in a caspase‐dependent manner. A further study showed that
PP‐22 also induced apoptosis by downregulating the signal transducers and activators of transcription 3 (STAT3) pathway, and the inhibitory effect was also confirmed by STAT3 small interfering RNA. In addition,
PP‐22 could promote autophagy by inhibiting the extracellular regulated protein kinases (ERK) pathway. And autophagy plays a protective role against apoptosis. Together, these data show that
PP‐22 promotes autophagy and apoptosis in the nasopharyngeal carcinoma CNE‐2 cell line.
PP‐22 activates p‐p38 and endoplasmic reticulum (ER) stress and inhibits the signal transducers and activators of transcription 3 (STAT3) pathway to activate the caspase‐9/3 signaling pathway to trigger apoptosis. In addition, PP‐22 inhibits the mitogen‐activated protein kinase (MAPK)/ERK pathway to induce autophagy in CNE‐2 cells. Furthermore, autophagy is a protective mechanism for CNE‐2 cells in the context of PP‐22‐induced apoptotic cell death.
Defects at the interfaces of perovskite (PVK) thin films are the main factors responsible for instability and low photoelectric conversion efficiency (PCE) of PVK solar cells (PSCs). Here, a ...SnO2‐MXene composite electron transport layer (ETL) is used in PSCs to improve interfacial contact and passivate defects at the SnO2/perovskite interface. The introduced MXene regulates SnO2 dispersion and induces a vertical growth of PVK. The lattice matching of MXene and perovskite suppresses the concentration of interfacial stress, thereby obtaining a perovskite film with low defects. Compared with SnO2‐based device, the PCE of SnO2‐MXene‐based device is improved by 15 % and its short‐circuit current is up to 25.07 mA cm−2. Furthermore, unencapsulated device maintained about 90 % of its initial efficiency even after 500 h of storage at 30–40 % relative humidity in ambient air. The composite ETL strategy provides a route to engineer interfacial passivation between metal halide perovskites and ETLs.
MXene nanosheets introduced to SnO2‐based perovskite solar cells maximize the interface matching between SnO2 and perovskite and induce vertically aligned crystal growth. As a result, the photoelectric conversion efficiency (PCE) is improved by 15 %, reaching 23.07 %, and the short‐circuit current is up to 25.07 mA cm−2. In addition, an unencapsulated device maintains 90 % of its initial PCE after 500 h of storage in ambient air.
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