Discharge domains regulation and dynamic processes of direct-current triboelectric nanogenerator.

Direct-current triboelectric nanogenerators arising from electrostatic breakdown can eliminate the bottleneck problem of air breakdown in conventional triboelectric nanogenerators, offering critical benefits of constant-current output, resistance to electromagnetic interference, and high output power density. Previous understanding is that its output characteristics are described by a capacitor-breakdown model or dictated by one or two discharge domains in direct-current triboelectric nanogenerators. Here, we demonstrate that the former holds only for ideal conditions and the latter cannot fully explain the dynamic process and output performance. We systematically image, define, and regulate three discharge domains in direct-current triboelectric nanogenerators, then a "cask model" is developed to bridge the cascaded-capacitor-breakdown dynamic model in ideal conditions and real outputs. Under its guidance, the output power is increased by an order of magnitude within a wide range of resistive loads. These unexplored discharge domains and optimization methods revolutionize the output performance and potential applications of direct-current triboelectric nanogenerators.

Localization on a-priori information of plane extraction.

Localization constitutes a critical challenge for autonomous mobile robots, with flattened walls serving as a fundamental reference for indoor localization. In numerous scenarios, prior knowledge of a wall's surface plane is available, such as planes in building information modeling (BIM) systems. This article presents a localization technique based on a-priori plane point cloud extraction. The position and pose of the mobile robot are estimated through real-time multi-plane constraints. An extended image coordinate system is proposed to represent any planes in space and establish correspondences between visible planes and those in the world coordinate system. Potentially visible points representing the constrained plane in the real-time point cloud are filtered using the filter region of interest (ROI), derived from the theoretical visible plane region within the extended image coordinate system. The number of points representing the plane influences the calculation weight in the multi-plane localization approach. Experimental validation of the proposed localization method demonstrates its allowance for redundancy in initial position and pose error.

Precision-Driven Multi-Target Path Planning and Fine Position Error Estimation on a Dual-Movement-Mode Mobile Robot Using a Three-Parameter Error Model.

The multi-target path planning problem is a universal problem to mobile robots and mobile manipulators. The two movement modes of forward movement and rotation are universally implemented in integrated, commercially accessible mobile platforms used in logistics robots, construction robots, etc. Localization error in multi-target path tracking is one of the crucial measures in mobile robot applications. In this article, a precision-driven multi-target path planning is first proposed. According to the path's odometry error evaluation function, the precision-optimized path can be discovered. Then, a three-parameter odometry error model is proposed based on the dual movement mode. The error model describes localization errors in terms of the theoretical motion command values issued to the mobile robot, the forward moving distances, and the rotation angles. It appears that the three error parameters follow the normal distribution. The error model is finally validated using a mobile robot prototype. The error parameters can be identified by analyzing the actual moving trajectory of arbitrary movements. The experimental localization error is compared to the simulated localization error in order to validate the proposed error model and the precision-driven path planning method. The OptiTrack motion capture device was used to capture the prototype mobile robot's pose and position data.

Bioinspired morphing wings: mechanical design and wind tunnel experiments.

Bioinspired morphing wings are part of a novel research direction offering greatly increased adaptability for use in unmanned aerial vehicles. Recent models published in the literature often rely on simplifications of the bird wing apparatus and fail to preserve many of the macroscopic morphological features. Therefore, a more holistic design approach could uncover further benefits of truly bioinspired bird wing models. With this issue in mind, a prototype inspired by crow wings (Corvusgenus) is developed, which is capable of planform wing morphing. The prototype imitates the feather structure of real birds and replicates the folding motion with a carbon fiber reinforced polymer skeleton with one controllable degree of freedom. The mechanism supplies a smooth airfoil lifting surface through a continuous morphing motion between a fully extended and a folded state. When extended, it has an elliptic planform and emarginated slots between primary remiges. In the folded state, the wingspan is reduced by 50% with a 40% reduction in surface area and the aspect ratio decreases from 2.9 to 1.2. Experimental data from a subsonic wind tunnel investigation is presented for flow velocities ranging from 5 to 20 m s-1, corresponding to Reynolds numbers between 0.7 × 105-2.8 × 105. The wing is analyzed in the three static states (folded, intermediate, and extended) through aerodynamic coefficients and flow visualizations along the surface. The bioinspired design enables the wing to capture several phenomena found on real bird wings. Through its morphing capabilities and intrinsic softness, the wing can sustain large angles of attack with greatly delayed stall and maintain optimal performance at different velocities.

Reconstruction of Flight Parameters of a Bat for Flapping Robots.

The flight of bats is comparatively less documented and understood than birds and insects and may provide novel inspiration for the design of flapping flight robots. This study captured the natural flight of short-nosed fruit bats (Cynopterus sphinx) by an optical motion capture system, "OptiTrack", with pasted markers on the wings and body to reconstruct the flight parameters. Due to the self-occlusion at some moments, points on the membrane wings cannot be captured by any cameras. To draw a smooth trajectory, it is desired to reconstruct all missing data. Therefore, an algorithm is proposed by using numerical techniques, accompanied by modern mathematical and computational tools, to envisage the missing data from the captured flight. The least-square fitted polynomial engendered the parameter equations for x-, y-, and z-coordinates of marked points which were used to reconstruct the trajectory of the flight. The parameter equations of position coordinates were also used to compute the morphological and aerodynamic characteristics of the flight. The most outstanding contribution of the work is that not only the trajectory, velocity, and velocity field but also the morphing areas of the membrane wings were recreated using the reconstructed data. These data and reconstructed curves of trajectory and velocity field will be used for the further aerodynamic analysis and mechanism design of the flapping robot. This method can also be generalized to reconstruct the performance parameters of any other animals for bionic design.

Direct Measurements of the Wing Kinematics of a Bat in Straight Flight.

Bat is the only mammal in the nature that can fly. Compared with birds and insects, bats are quite special in that their wings are formed by an elastic membrane, which renders that the airfoil deforms greatly during downstroke and upstroke. Due to the compliant skin of a bat, the movements of its wings are three-dimensionally complex during diverse flight behaviors. To understand the maneuverability and flight performance, three-dimensional reconstruction of the flight kinematics is essential. This study focuses on the reconstruction of the wing kinematics of the bat and identifies the primary relationship of parameters of aerodynamics in straight flight. With markers pasted on the wings and body of a bat, the motions of these points are recorded by a computerized optical motion capture system. The kinematic analysis shows that the motion of wings is very intricate. The digits of the wing display the sign of coupled motion. A novel approach was developed to measure the angle of attack and flapping angle of the wing. The angle of attack of leading edge differs with the overall angle of attack of the wing. The kinematics of the bat's wing is helpful to interpret the secret of the bat's flight.

Data of feather recovering performance of birds and micro structure of pigeons' feathers.

Data is presented to explain why birds can recover their ruffled feather vanes by shaking wings and preening feathers with the beak [1]. Presented data includes the SEM microscopic images of rachis, barbs and barbules of pigeon's feather and the images recording the experiments of observing and mimicking the recovering performance of pigeons. Besides, based on the measurement and observation of the micro structure of feathers, the mechanical models of barbules were developed to better understand the wings performance. These high-quality images and models could be used for future research on feathers. Data helps to better understand the micro structure of feathers and the reason birds can fly. Data also support bioinspired mechanical structure development, especially for flapping robot development.

Identification of avian flapping motion from non-volant winged dinosaurs based on modal effective mass analysis.

The origin of avian flight is one of the most controversial debates in Paleontology. This paper investigates the wing performance of Caudipteryx, the most basal non-volant dinosaur with pennaceous feathered forelimbs by using modal effective mass theory. From a mechanical standpoint, the forced vibrations excited by hindlimb locomotion stimulate the movement of wings, creating a flapping-like motion in response. This shows that the origin of the avian flight stroke should lie in a completely natural process of active locomotion on the ground. In this regard, flapping in the history of evolution of avian flight should have already occurred when the dinosaurs were equipped with pennaceous remiges and rectrices. The forced vibrations provided the initial training for flapping the feathered wings of theropods similar to Caudipteryx.

Winged forelimbs of the small theropod dinosaur Caudipteryx could have generated small aerodynamic forces during rapid terrestrial locomotion.

Pennaceous feathers capable of forming aerodynamic surfaces are characteristic of Pennaraptora, the group comprising birds and their closest relatives among non-avian dinosaurs. However, members of the basal pennaraptoran lineage Oviraptorosauria were clearly flightless, and the function of pennaceous feathers on the forelimb in oviraptorosaurs is still uncertain. In the basal oviraptorosaur Caudipteryx both the skeleton and the plumage, which includes pennaceous feathers forming wing-like arrangements on the forelimbs, are well known. We used mathematical analyses, computer simulations and experiments on a robot Caudipteryx with realistic wing proportions to test whether the wings of Caudipteryx could have generated aerodynamic forces useful in rapid terrestrial locomotion. These various approaches show that, if both wings were held in a fixed and laterally extended position, they would have produced only small amounts of lift and drag. A partial simulation of flapping while running showed similarly limited aerodynamic force production. These results are consistent with the possibility that pennaceous feathers first evolved for a non-locomotor function such as display, but the effects of flapping and the possible contribution of the wings during manoeuvres such as braking and turning remain to be more fully investigated.

Roscovitine attenuates intimal hyperplasia via inhibiting NF-κB and STAT3 activation induced by TNF-α in vascular smooth muscle cells.

Roscovitine is a selective CDK inhibitor originally designed as anti-cancer agent, which has also been shown to inhibit proliferation in vascular smooth muscle cells (VSMCs). However, its effect on vascular remodeling and its mechanism of action remain unknown. In our study, we created a new intimal hyperplasia model in male Sprague-Dawley rats by trypsin digestion method, which cause to vascular injury as well as the model of rat carotid balloon angioplasty. Roscovitine administration led to a significant reduction in neointimal formation and VSMCs proliferation after injury in rats. Western blot analysis revealed that, in response to vascular injury, TNF-α stimulation induced p65 and STAT3 phosphorylation and promoted translocation of these molecules into the nucleus. p65 can physically associate with STAT3 and bind to TNF-α-regulated target promoters, such as MCP-1 and ICAM-1, to initiate gene transcription. Roscovitine can interrupt activation of NF-κB and reduce expression of TNF-α-induced proinflammatory gene, thus inhibiting intimal hyperplasia. These findings provide a novel mechanism to explain the roscovitine-mediated inhibition of intimal hyperplasia induced by proinflammatory pathways.

Roscovitine Protects From Arterial Injury by Regulating the Expressions of c-Jun and p27 and Inhibiting Vascular Smooth Muscle Cell Proliferation.

PURPOSE: Roscovitine (Rosc) is a selective inhibitor of cyclin-dependent kinases (CDKs) and a promising therapy for various cancers. However, limited information is available on the biological significance of Rosc in vascular smooth muscle cells (VSMCs), the cell type critical for the development of proliferative vascular diseases. In this study, we address the effects of Rosc in regulating VSMC proliferation, both in vitro and in vivo, exploring the underlying molecular mechanisms. METHODS: The proliferations and cell-cycle distributions of in vitro cultured VSMCs, as well as several other cancer cell lines, were examined by cell-counting assay and flow cytometry, respectively. Molecular changes in various CDKs, cyclins, and other regulatory molecules were examined by reverse transcription polymerase chain reaction, Western blot, or immunocytochemistry. The in vivo effects of Rosc were examined on a carotid arterial balloon-injury model. RESULTS: Rosc significantly inhibited VSMC proliferation in response to serum or angiotensin II and arrested these cells at the G0/G1 phase. These changes were associated with a specific and robust decrease in CDK4, cyclin E, c-Jun, and a dramatic increase in p27kip1 in VSMCs, which was also translated in vivo and correlated with the protection of Rosc on injury-induced neointimal hyperplasia. CONCLUSIONS: Acting on distinct molecular targets in VSMCs versus cancer cells, Rosc inhibits VSMC proliferation and protects from proliferative vascular diseases.

Endometrial breakdown with sustained progesterone release involves NF-κB-mediated functional progesterone withdrawal in a mouse implant model.

Irregular uterine bleeding is a major side effect of long-acting progestogen-only contraceptives in women, and is the primary reason women discontinue their use. In this study, a mouse model of endometrial breakdown was established using a subcutaneous progesterone implant to understand how irregular bleeding begins. Although progestogens sustained decidualization, endometrial breakdown was still observed in this model. We, therefore, hypothesized that endometrial breakdown might involve functional progesterone withdrawal. Using co-immunoprecipitation assays, we observed the constitutive activation of nuclear factor kappa-b (NF-κB) p65 and its interaction with the progesterone receptor (PGR); moreover, transcriptional activity of the PGR was also repressed by NF-κB activity in primary mouse and human decidual stromal cells that mimic progesterone maintenance. Yet the ratio of PGR-B to PGR-A was not increased in the mouse model. In vivo comparison of endometrial breakdown induced by progesterone withdrawal to that seen during sustained progesterone exposure, in the presence of NF-κB inhibitors, revealed that NF-κB-mediated functional progesterone withdrawal is involved in endometrial breakdown in this implant model. These data prompt further studies to determine the homology of this functional progesterone withdrawal mechanism in human endometrium. Mol. Reprod. Dev. 83: 780-791, 2016 © 2016 Wiley Periodicals, Inc.

Reduced endoplasmic reticulum stress might alter the course of heart failure via caspase-12 and JNK pathways.

BACKGROUND: Endoplasmic reticulum (ER) stress plays an important role in mediating ischemic heart cell death. The aim of this study was to investigate whether manipulation of a key factor of the ER stress pathway, eukaryotic translation initiation factor 2 subunit α (eIF2α), can change the natural history of heart failure (HF). METHODS: HF was induced using coronary artery ligation in adult rats and a selective eIF2α dephosphorylation inhibitor, salubrinal (Sal), was used. Thirty minutes after ligation, rats were randomly assigned to 3 groups: myocardial infarction (MI) plus placebo injections (dimethyl sulfoxide; n = 12), MI plus Sal injection (Sal; n = 12), and MI (HF; n = 12). Hemodynamic parameters were examined. Hearts were harvested for apoptosis assessment after 8 weeks of Sal treatment by terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labelling and flow cytometric analysis. Hearts were harvested to determine ER chaperones by Western analysis, real-time polymerase chain reaction and immunohistochemical analysis. RESULTS: Cardiac function was significantly improved in Sal-treated rats. Apoptosis was reduced by Sal treatment. Glucose-regulated protein-78 and -94 were increased in HF but normalized by Sal treatment. HF caused a significant increase in eIF2α phosphorylation, which was further increased by Sal treatment, and caspase-12 and phospho-c-JUN NH2-terminal kinase were markedly increased in rats with HF alone but significantly reduced by Sal treatment. CONCLUSIONS: Our results suggest that reduction of ER stress and myocardial apoptosis through inhibition of eIF2α dephosphorylation might alter the natural history of HF, which might provide a new approach for its treatment.