General Kinetostatic Modeling and Deformation Analysis of a Two-Module Rod-Driven Continuum Robot with Friction Considered

Continuum robots actuated by flexible rods have large potential applications,such as detection and operation tasks in confined environments,since the push and pull actuation of flexible rods withstand tension and compressive force,and increase the structure's rigidity.In this paper,a generalized kinetostatics model for multi-module and multi-segment continuum robots considering the effect of friction based on the Cosserat rod theory is established.Then,the model is applied to a two-module rod-driven continuum robot with winding ropes to analyze its deformation and load characteristics.Four different in-plane configurations under the external load term as S1,S2,C1,and C2 are defined.Taking a bending plane as an example,the tip deformation along thex-axis of these shapes is simulated and compared,which shows that the load capacity of C1 and C2 is generally larger than that of S1 and S2.Furthermore,the deformation experiments and simulations show that the maximum error ratio without external loads relative to the total length is no more than 3%,and it is no more than 4.7%under the external load.The established kinetostatics model is proven sufficient to accurately analyze the rod-driven continuum robot with the consideration of internal friction.

Selection of optimal window length using STFT for quantitative SNR analysis of LFM signal

An adaptive approach to select analysis window param- eters for linear frequency modulated （LFM） signals is proposed to obtain the optimal 3 dB signal-to-noise ratio （SNR） in the short- time Fourier transform （STFT） domain. After analyzing the instan- taneous frequency and instantaneous bandwidth to deduce the relation between the window length and deviation of the Gaus- sian window, high-order statistics is used to select the appropriate window length for STFT and get the optimal SNR with the right time-frequency resolution according to the signal characteristic under a fixed sampling rate. Computer simulations have verified the effectiveness of the new method.

Design of a Passive Gait‑based Ankle‑foot Exoskeleton with Self‑adaptive Capability

Propulsion during push-off is the key to realizing human locomotion.Humans have evolved a way of walking with high energy utilization,but it can be further improved.Drawing inspiration from the muscle-tendon unit,a passive spring-actuated ankle-foot exoskeleton is designed to assist with human walking and to lengthen walking duration by mechanically enhancing walking efficiency.Detection of the gait events is realized using a smart clutch,which is designed to detect the contact states between the shoe sole and the ground,and automatically switch its working state.The engagement of a suspended spring behind the human calf muscles is hence controlled and is in synchrony with gait.The device is completely passive and contains no external power source.Energy is stored and returned passively using the clutch.In our walking trials,the soleus electromyography activity is reduced by as much as 72.2%when the proposed ankle-foot exoskeleton is worn on the human body.The influence of the exoskeleton on walking habits is also studied.The results show the potential use of the exoskeleton in humans’daily life.

Dynamic Analysis and Performance Verification of a Novel Hip Prosthetic Mechanism

To assist an amputee in regaining his or her daily quality of life,based on analysis of the motion characteristics of the human hip,a 2-UPR/URR parallel mechanism with a passive limb was designed.The inverse kinematics of this mechanism was analyzed based on a closed-loop vector method.The constrained Jacobian matrix and kinematic Jacobian matrix of each limb were then analyzed,and a 6×6 fully Jacobian matrix was constructed.Based on this,kinematic performances were analyzed and summarized.Finally,the dynamic model of the mechanism was constructed based on the virtual work principle,and its theoretical solution was compared with the numerical results,which were obtained in a simulation environment.Results showed that the prosthetic mechanism had a larger rotating workspace and better mechanical performance,which accorded a range of motion and bearing capacity similar to that of the human hip in multiple gait modes.Moreover,the validity of the dynamic model and inverse kinematics were verified by comparing the theoretical and simulation results.Furthermore,with flexion and extension,the torque change in the hip prosthetic mechanism was similar to that of the human hip,which demonstrated the feasibility of the hip prosthetic mechanism and its good dynamic performance.

Versatile subtypes of pericytes and their roles in spinal cord injury repair,bone development and repair

Vascular regeneration is a challenging topic in tissue repair. As one of the important components of the neurovascular unit(NVU),pericytes play an essential role in the maintenance of the vascular network of the spinal cord. To date, subtypes of pericytes have been identified by various markers, namely the PDGFR-β, Desmin, CD146, and NG2, each of which is involved with spinal cord injury(SCI) repair. In addition, pericytes may act as a stem cell source that is important for bone development and regeneration, whilst specific subtypes of pericyte could facilitate bone fracture and defect repair. One of the major challenges of pericyte biology is to determine the specific markers that would clearly distinguish the different subtypes of pericytes, and to develop efficient approaches to isolate and propagate pericytes. In this review, we discuss the biology and roles of pericytes, their markers for identification, and cell differentiation capacity with a focus on the potential application in the treatment of SCI and bone diseases in orthopedics.

Role of inflammatory gene variants in Helicobacter pylori-related gastric cancer

Helicobacter pylori-related gastric cancer results from a chronic inflammatory process that arises from atrophic gastritis, and develops into intestinal metaplasia, hyperplasia, and eventually gastric adenocarcinoma. Although approximately half of the world＇s population is infected with Helicobacter pylori （H. pylori）, less than 3% of these infected individuals develop gastric cancer. H. pylori infection can cause both acute and chronic inflammation, and may be present for decades within its host. Inflammatory gene variants are particularly important factors that may influence a host＇s susceptibility to H. pylori-related gastric cancer. The inflammatory gene variants uncovered thus far include interleukin gene clusters, tumor necrosis fac- tor-e, Toll-like receptors （TLRs）, and inflammatory gene polymorphisms found in genome-wide association studies （GWAS）. The association between these gene variants and the risk of H. pylori-related gastric cancer will aid in our understanding of the pathogenesis of gastric cancer in order to prevent and defeat this malignancy.

Engineered high-strength biohydrogel as a multifunctional platform to deliver nucleic acid for ameliorating intervertebral disc degeneration

Intervertebral disc degeneration(IVDD)is a leading cause of low back pain.The strategy of using functional materials to deliver nucleic acids provides a powerful tool for ameliorating IVDD.However,the immunogenicity of nucleic acid vectors and the poor mechanical properties of functional materials greatly limit their effects.Herein,antagomir-204-3p(AM)shows low immunogenicity and effectively inhibits the apoptosis of nucleus pulposus cells.Moreover,a high-strength biohydrogel based on zinc-oxidized sodium alginate-gelatin(ZOG)is designed as a multifunctional nucleic acid delivery platform.ZOG loaded with AM(ZOGA)exhibits great hygroscopicity,antibacterial activity,biocompatibility,and biodegradability.Moreover,ZOGA can be cross-linked with nucleus pulposus tissue to form a high-strength collagen network that improves the mechanical properties of the intervertebral disc(IVD).In addition,ZOGA provides an advantageous microenvironment for genetic expression in which AM can play an efficient role in maintaining the metabolic balance of the extracellular matrix.The results of the radiological and histological analyses demonstrate that ZOGA restores the height of the IVD,retains moisture in the IVD,and maintains the tissue structure.The ZOGA platform shows the sustained release of nucleic acids and has the potential for application to ameliorate IVDD,opening a path for future studies related to IVD.

Solid-state yet flexible supercapacitors made by inkjet-printing hybrid ink of carbon quantum dots/graphene oxide platelets on paper

Paper-based flexible supercapacitors(SCs) show advantages due to the improved adhesion between paper and active materials, the simplified printing process and the lower cost, compared to other substrates such as plastics. Here we report the fabrication of solid-state yet flexible SCs by inkjetprinting a hybrid ink consisting of carbon quantum dots(CQDs) and graphene oxide(GO) platelets, followed by casting of polyvinyl alcohol(PVA)/sulfuric acid(H2SO4) gel electrolyte. The SC obtained from 100-time-printing of the hybrid ink shows a specific capacitance of ~1.0 mF cm-2 at a scan rate of 100 mV s-1, which is enhanced by nearly 150%;the whole device including paper substrate, gel electrolyte and active material demonstrates an energy density of 0.078 mW h cm-3 at a power density of 0.28 mW cm-3. In addition, the excellent mechanical strength of GO platelets ensures the good flexibility and mechanical robustness of the printed SCs, which show a retention of 98% in capacitance after being bended for 1,000 cycles at a bending radius of 7.6 mm. This study demonstrates a promising strategy for the large-scale preparation of low-cost, lightweight, and flexible/wearable energy storage devices based on carbon-based ink and paper substrate.

Ultrathin yet transferrable Pt- or PtRu-decorated graphene films as efficient electrocatalyst for methanol oxidation reaction

Direct methanol fuel cell (DMFC)has been regarded as one of promising electric generators in portable electronic equipment and electric vehicles because of the high energy conversion efficiency and low pollutant emissions [1,2].Electro-oxidation of methanol has been studied extensively in terms of its application in DMFC and related theoretical analysis promising anode catalyst [3-5].To date,the most for methanol oxidation is platinum (Pt).However,the development of commercial Pt-based fuel cells has been limited by the toxicity of carbon monoxide,the high cost of Pt and the aggregation of catalyst particles [6-9].Using binary or alloy catalysts is an effective strategy for the removal of CO from the catalyst surface [10-13].Extensive research reveals that ruthenium (Ru)-modified Pt nanoparticles (Pt NPs)are efficient binary electro-catalysts for methanol oxidation reaction (MOR)[14].The addition of Ru to Pt-based catalysts significantly lowers the overpotential in MOR and enhances the CO-tolerance through the ‘bifunctional mechanism'[11,12,14-18].

Light rays and waves on geodesic lenses

Starting from well-known absolute instruments that provide perfect imaging, we analyze a class of rotationally symmetric compact closed manifolds, namely, geodesic lenses. We demonstrate with a numerical method that light rays confined on geodesic lenses form closed trajectories, and that for optical waves, the spectrum of a geodesic lens is(at least approximately) degenerate and equidistant. Moreover, we fabricate two geodesic lenses in micrometer and millimeter scales and observe curved light rays along the geodesics. Our experimental setup may offer a new platform to investigate light propagation on curved surfaces.

Design method and verification of a hybrid prosthetic mechanism with energy-damper clutchable device for transfemoral amputees

Transfemoral amputees(TAs)have difficulty in mobility during walking,such as restricted movement of lower extremity and body instability,yet few transfemoral prostheses have explored human-like multiple motion characteristics by simple structures to fit the kinesiology,biomechanics,and stability of human lower extremity.In this work,the configurations of transfemoral prosthetic mechanism are synthesized in terms of human lower-extremity kinesiology.A hybrid transfemoral prosthetic(HTP)mechanism with multigait functions is proposed to recover the gait functions of TAs.The kinematic and mechanical performances of the designed parallel mechanism are analyzed to verify their feasibility in transfemoral prosthetic mechanism.Inspired by motion-energy coupling relationship of the knee,a wearable energy-damper clutched device that can provide energy in knee stance flexion to facilitate the leg off from the ground and can impede the leg’s swing velocity for the next stance phase is proposed.Its co-operation with the springs in the prismatic pairs enables the prosthetic mechanism to have the energy recycling ability under the gait rhythm of the knee joint.Results demonstrate that the designed HTP mechanism can replace the motion functions of the knee and ankle to realize its multimode gait and effectively decrease the peak power of actuators from 94.74 to 137.05 W while maintaining a good mechanical adaptive stability.

In vitro assessment of the effect of microencapsulation techniques on the stability,bioaccessibility and bioavailability of mulberry leaf bioactive compounds

Mulberry(Morus alba L.)leaf extract is well-known for its health-promoting features.However,food processing conditions affect its bioactive profile,which could be limited by encapsulation.Nevertheless,assessing the impact of encapsulating techniques on the digestibility of embedded biocompounds requires further knowledge.Hence,the aimed of this study was to assess the effects of carrier materials and drying techniques on(i)bioaccessibility and bioavailability indexes,(ii)stability of nutraceuticals,and(iii)changes in antioxidant activities of mulberry leaf extract powder by using an in vitro oral-gastrointestinal digestion.Digestion was performed out at 37°C in darkness by shaking encapsulated extract with human saliva during 2 min,followed by 2 h of incubation with a pepsin-HCl mixture,then mixed for 2 h with bile salts and pancreatin.After digestion the samples were acidified and HPLC assayed.A significant(p<0.05)decrease in nutraceuticals content was noted during the intestinal phase with more reduction in gamma-aminobutyric acid(34.91–51.14%)compared to that of flavonols(16.58–28.90%),1-deoxynojirimycin(17.56–20.42%)and phenolic acids(0.53–0.67%)in the gastric digesta.Although encapsulation was observed to enhance the bioaccessibility,negative effects were found in terms of the bioefficiency and bioavailability.Furthermore,encapsulation techniques mostly affected the ion reducing capacity than the radical scavenging capacity.The outcomes suggested that carriers had a major effect on the digestibility and antioxidative activity,whilst the drying techniques mostly affect the bioaccessibility and bioavailability of the flavonols.