Experimental study of the bond behavior of 400MPa grade hot-rolled ribbed steel bars in steel fibre reinforced concrete.

Present studies show that steel fibres can improve the bond of steel bar in steel fibre reinforced concrete (SFRC) with a correlation to the fibre factor and the fibre distribution uniformity. As a foundation of high-flowability SFRC working together with 400 MPa grade hot-rolled ribbed (HRB400) steel bar in reinforced structures, the bond between them was evaluated through a series of pull-out testing on 48 specimens with a central arranged steel bar. The bond behaviours of steel bar were estimated with a constant bond length of 5d (d is the diameter of steel bar) embedded in high-flowability SFRC, the main research parameters included the ingot mill steel fibres with a fibre volume fraction varied from 0.8 to 2.0%, the strength grade C40 and C50 of SFRC or referenced conventional concrete, and the diameter of steel bars varied from 14 to 20 mm. Results showed that the high-flowability SFRC compacted with a slight vibration is beneficial to improve the bond failure pattern since steel fibres effectively eliminate the crack appeared on the SFRC blocks during the pulling out of steel bar, leading to all specimens failed with the steel bar pull out of SFRC blocks. The bond strength was dominant by the SFRC strength, and obviously strengthened with the increase of fibre volume fraction, while the peak-slip was slightly influenced by the diameter of steel bar. By conducting analyses of test data, equations for calculating the bond strength and the peak-slip are proposed accounting for the effect of steel fibres. Then the predicting method for the anchorage length is suggested linking with different design codes for concrete structures. Compared with test results of this study, a little shorter anchorage length of steel bar in SFRC is obtained from the specification of Chinese code JGJ/T46, which should be noticed to ensure a rational anchorage of ribbed steel bar in SFRC with ingot mill steel fibres.

A self-adapting woven net trap based on the evolution mechanism of orb-web topology.

The development of structures that can adapt spontaneously to achieve desired functions in complex environments is crucial for new unmanned countermeasures, such as prey capture or net-recovery. Conventional structural optimization methods based on a singular net-like configuration may lead to functional limitations and fail to achieve specific objectives. In this study, we utilized an evolutionary algorithm that incorporated mechanical features and biological corrections to construct spider threads with advanced properties capable of efficient and reliable trapping behavior in arbitrary boundary conditions. We employed distinct thread types in different components, which achieved distinguished stiffness and strength that could not be accomplished by a single kind of thread. By assembling prestress reinforcement threads, we developed an orb-web-like trap that demonstrated effective trapping performance in experiments. The adaptive evolutionary method could be applied to design intelligent intercepting devices suited to particular functions and extreme environments, with wide application prospects in net-recovery system of UAV. STATEMENT OF SIGNIFICANCE: Structures that adapt spontaneously to perform desired functions in difficult environments are crucial for rising unmanned countermeasures. Conventional structural optimization methods based on a singular net-like configuration may lead to functional limitations and fail to achieve specific objectives. We used an evolutionary algorithm that combined mechanical features and biological corrections to create spider threads in arbitrary boundary circumstances in this work. The adaptive evolutionary method could be applied to design intelligent intercepting devices suited to particular functions and extreme environments, with wide application prospects in net-recovery system of UAV.

A Numerical Modelling Framework for Investigating the Ballistic Performance of Bio-Inspired Body Armours.

Biological structures possess excellent damage tolerance, which makes them attractive for ballistic protection applications. This paper develops a finite element modelling framework to investigate the performance of several biological structures that are most relevant for ballistic protection, including nacre, conch, fish scales, and crustacean exoskeleton. Finite element simulations were conducted to determine the geometric parameters of the bio-inspired structures that can survive projectile impact. The performances of the bio-inspired panels were benchmarked against a monolithic panel with the same 4.5 mm overall thickness and projectile impact condition. It was found that the biomimetic panels that were considered possessed better multi-hit resistant capabilities compared to the selected monolithic panel. Certain configurations arrested a fragment simulating projectile with an initial impact velocity of 500 m/s, which was similar to the performance of the monolithic panel.

Extending Goldberg's method to parametrize and control the geometry of Goldberg polyhedra.

Goldberg polyhedra have been widely studied across multiple fields, as their distinctive pattern can lead to many useful applications. Their topology can be determined using Goldberg's method through generating topologically equivalent structures, named cages. However, the geometry of Goldberg polyhedra remains underexplored. This study extends Goldberg's framework to a new method that can systematically determine the topology and effectively control the geometry of Goldberg polyhedra based on the initial shapes of cages. In detail, we first parametrize the cage's geometry under specified topology and polyhedral symmetry; then, we manipulate the predefined independent variables through optimization to achieve the user-defined geometric properties. The benchmark problem of finding equilateral Goldberg polyhedra is solved to demonstrate the effectiveness of the proposed method. Using this method, we have successfully achieved nearly exact spherical Goldberg polyhedra, with all vertices on a sphere and all faces being planar under extremely low numerical errors. Such results serve as strong numerical evidence for the existence of this new type of Goldberg polyhedra. Furthermore, we iteratively perform k-means clustering and optimization to significantly reduce the number of different edge lengths to benefit the cost reduction for architectural and engineering applications.

Blocking stanniocalcin 2 reduces sunitinib resistance in clear cell renal cell carcinoma.

Stanniocalcin 2 (STC2) has been identified as a prognostic marker in renal cell carcinoma. However, the role of STC2 in renal cell carcinoma is still unclear. In this study, we investigated the relationship between high expression of STC2 and sunitinib resistance in cells and the underlying mechanism. Through GEPIA platform analysis based on TCGA database, it showed that the expression of STC2 in kidney renal clear cell carcinoma (KIRC) was significantly higher than that in the normal population. Real-time quantitative PCR and western blotting detected significantly higher expression levels of STC2 in clear cell renal cell carcinoma (ccRCC) cells than that in normal renal cells. Enzyme-linked immunosorbent assay (ELISA) determined whether there is a high secretion of STC2 in ccRCC cells. The sunitinib resistance could be significantly reduced by STC2 neutralizing antibody but aggravated by the addition of recombinant human STC2 in ccRCC cells. Sunitinib suppressed STC2 expression and secretion, destroyed lysosomal acidic pH, and accumulated in the cells. However, STC2 neutralizing antibody can reduce the accumulation of sunitinib in cells to improve the inhibitory efficiency of sunitinib on cell proliferation. This study suggested STC2 could serve as a potential novel target for the treatment of ccRCC, anti-STC2 antibody might be an option of immunotherapy in the future.

Topology of leaf veins: Experimental observation and computational morphogenesis.

The unique, hierarchical patterns of leaf veins have attracted extensive attention in recent years. However, it remains unclear how biological and mechanical factors influence the topology of leaf veins. In this paper, we investigate the optimization mechanisms of leaf veins through a combination of experimental measurements and numerical simulations. The topological details of three types of representative plant leaves are measured. The experimental results show that the vein patterns are insensitive to leaf shapes and curvature. The numbers of secondary veins are independent of the length of the main vein, and the total length of veins increases linearly with the leaf perimeter. By integrating biomechanical mechanisms into the topology optimization process, a transdisciplinary computational method is developed to optimize leaf structures. The numerical results show that improving the efficiency of nutrient transport plays a critical role in the morphogenesis of leaf veins. Contrary to the popular belief in the literature, this study shows that the structural performance is not a key factor in determining the venation patterns. The findings provide a deep understanding of the optimization mechanism of leaf veins, which is useful for the design of high-performance shell structures.

Pleural lump after paragonimiasis treated by thoracoscopy: A case report.

BACKGROUND: Paragonimiasis is a parasitic disease that has multiple symptoms, with pulmonary types being common. According to our clinical practices, the pleural effusion of our patients is full of fibrous contents. Drainage, praziquantel, and triclabendazole are recommended for the treatment, but when fibrous contents are contained in pleural effusion, surgical interventions are necessary. However, no related reports have been noted. Herein, we present a case of pulmonary paragonimiasis treated by thoracoscopy. CASE SUMMARY: A 12-year-old girl presented to our outpatient clinic complaining of shortness of breath after exercise for several days. Enzyme-linked immunosorbent assay revealed positivity for antibodies against Paragonimus westermani, serological test showed eosinophilia, and moderate left pleural effusion and calcification were detected on computed tomography (CT). She was diagnosed with paragonimiasis, and praziquantel was prescribed. However, radiography showed an egg-sized nodule in the left pleural cavity during follow-up. She was then admitted to our hospital again. The serological results were normal except slight eosinophilia. CT scan displayed a cystic-like node in the lower left pleural cavity. The patient underwent a thoracoscopic mass resection. A mass with a size of 6 cm × 4 cm × 3 cm adhered to the pleura was resected. The pathological examination showed that the mass was composed of non-structured necrotic tissue, indicating a granuloma. The patient remainded asymptomatic and follow-up X-ray showed complete removal of the mass. CONCLUSION: This case highlights that thoracoscopic intervention is necessary when fibrous contents are present on CT scan or chest roentgenogram to avoid later fibrous lump formation in patients with pulmonary paragonimiasis.

Mechanical Properties of Additively Manufactured Thermoplastic Polyurethane (TPU) Material Affected by Various Processing Parameters.

Thermoplastic polyurethane (TPU) is a polymer material that has high ductility, good biocompatibility and excellent abrasion resistance. These properties open a pathway to manufacturing functional TPU parts for applications in various fields such as aerospace engineering, medical devices and sports equipment. This study aims to investigate the mechanical properties of additively manufactured TPU material affected by three different processing parameters, including build orientation, mix ratio of the new and reused powders and post-processing. A series of material tests are conducted on TPU dumb-bell specimens. It is found that the mix ratio of the new powder is the most critical factor in improving the mechanical properties of the printed TPU parts. Compared to reused powder, new powder has better particle quality and thermal properties. Besides, build orientation is also a very important factor. TPU parts printed in flat and on-edge orientations show better tensile strength and deformability than those printed in upright orientation. In addition, post-processing is found to significantly enhance the deformability of TPU parts.

A computational investigation into the impact resistance of a precise finite element model derived from micro-CT data of a woodpecker's head.

Numerical investigation into the impact-resistance of complex biological organs remains challenging because of the difficulties in obtaining accurate models and precise material properties. In this work, the elegance of a woodpecker's head, including a slender hyoid connected by a spherical hinge and two revolute hinges, a long upper beak, a short lower beak, and an encephalocoele filled with viscoelastic brain substances, was obtained via a reaction-diffusion based imaging process on the micro-CT data. The material heterogeneity was fully considered in subsequent finite element analysis in LS-Dyna via categorizing the intensity into 53 groups and interpolating their properties from available data of rhamphotheca, hyoid, skull, and beak. Compared to a non-hyoid model, we found the hyoid helps to significantly alleviate the strain in the brain and restrain opposite velocity for maintaining structural stability, especially after impact. Numerical investigation also indicates that a longer upper beak is favorable in flatting the curve of impact force and improve structural crashworthiness.

Additive manufacturing of specific ankle-foot orthoses for persons after stroke: A preliminary study based on gait analysis data.

The aim of present study is to investigate the feasibility of patient-specific ankle-foot orthoses fabricated using additive manufacturing (AM) techniques. Then, clinical performance of the AFOs manufactured using material PA12 was evaluated in stroke survivors based on gait analysis data. The ankle and foot were scanned by EinScan-Pro 3D scanner. The software Geomagic Studio was used for modifying the AFO model. After processing the original AFO model into the final required model, material PA12 were used to fabricate the AFOs by Multi Jet Fusion (MJF) technique. Finally, gait analysis of 12 stroke patients was conducted to compare the effects with and without AFO. It took 2 hours from processing the initial AFO model to the completion of final model, and the printing time was 8 hours. The printing thickness of the AFO was 1.2 mm. With respect to the temporal-spatial parameters, the velocity and stride length in the gait with AFO increased significantly as compared to the gait without AFO (P=0.001, P=0.002). The cadence increased, double limb support phase decreased, and the step length difference decreased in the gait with AFO; however, the difference was not statistically significant (P=0.117, P=0.075, P=0.051).This study confirmed the feasibility of patient-specific AFO fabricated by AM techniques, and demonstrated the process of modifying AFO models successfully. The specific ankle-foot orthoses fabricated by material PA12 have a significant effect on the improvement of velocity and stride length in people with stroke.

Preparation of nanocellulose and lignin-carbohydrate complex composite biological carriers and culture of heart coronary artery endothelial cells.

Lignin-carbohydrate complexes, i.e. LCC-48 and LCC-72 were isolated with vibrational ball milling for 48 h and 72 h, respectively. Composite tubular carriers were prepared by casting film formation and crimping with the LCCs and cellulose nanofibrils (CNFs) as raw materials. The structures and chemical properties of different milling time LCCs were analyzed. The carriers were used to culture human coronary artery endothelial cells (HCAEC), and the activities of these cells were examined in vitro. The FT-IR and chemical composition results showed that the biocarriers were composed of lignin moieties and polysaccharides. The SEM and inverted microscope studies revealed that a large number of cells adhered to the porous carriers. HCAEC grown on the LCC-72/CNF carriers outperformed the LCC-48/CNF and control groups in every observed category, including cell proliferation rate and metabolic activity. In summary, tubular carriers prepared from LCC/CNF composite had high biocompatibility and have potential applications in heart tissue engineering.

Comparison of Mechanical Properties and Energy Absorption of Sheet-Based and Strut-Based Gyroid Cellular Structures with Graded Densities.

Bio-inspired functionally graded cellular materials (FGCM) have improved performance in energy absorption compared with a uniform cellular material (UCM). In this work, sheet-based and strut-based gyroid cellular structures with graded densities are designed and manufactured by stereo-lithography (SLA). For comparison, uniform structures are also designed and manufactured, and the graded structures are generated with different gradients. The mechanical behaviors of these structures under compressive loads are investigated. Furthermore, the anisotropy and effective elastic modulus of sheet-based and strut-based unit gyroid cellular structures are estimated by a numerical homogenization method. On the one hand, it is found from the numerical results that the sheet-based gyroid tends to be isotropic, and the elastic modulus of sheet-based gyroid is larger than the strut-based gyroid at the same volume fraction. On the other hand, the graded cellular structure has novel deformation and mechanical behavior. The uniform structure exhibits overall deformation and collapse behavior, whereas the graded cellular structure shows layer-by-layer deformation and collapse behavior. Furthermore, the uniform sheet-based gyroid is not only stiffer but also better in energy absorption capacity than the uniform strut-based gyroid structure. Moreover, the graded cellular structures have better energy absorption capacity than the uniform structures. These significant findings indicate that sheet-based gyroid cellular structure with graded densities have potential applications in various industrial applications, such as in crashworthiness.

Thermal shrinkage and stability of diamondene nanotubes.

By curving a rectangular diamondene, an sp 2/sp 3 composite carbon film, a diamondene nanotube (DNT) can be formed when the two straight edges are sewn together. In this study, thermal stabilities of DNTs are investigated using molecular dynamics simulation approaches. An interesting thermal shrinkage of damaged DNTs is discovered. Results indicate that DNTs have critical temperatures between 320 K and 350 K. At temperatures higher than the critical value, the interlayer bonds, i.e., the sp 3-sp 3 bonds, may break. The broken ratio of the interlayer bonds mainly depends on the temperature. For the DNT with a high broken ratio of interlayer bonds, it has thermal shrinkage in both the cross section and tube axis. The sp 2-sp 3 bonds in either the inner or the outer surface are much more stable. Even at 900 K, only a few sp 2-sp 3 bonds break. These properties can be used in the design of metamaterials.

Coupling effect of van der Waals, centrifugal, and frictional forces on a GHz rotation-translation nano-convertor.

A nano rotation-translation convertor with a deformable rotor is presented, and the dynamic responses of the system are investigated considering the coupling among the van der Waals (vdW), centrifugal and frictional forces. When an input rotational frequency (ω) is applied at one end of the rotor, the other end exhibits a translational motion, which is an output of the system and depends on both the geometry of the system and the forces applied on the deformable part (DP) of the rotor. When centrifugal force is stronger than vdW force, the DP deforms by accompanying the translation of the rotor. It is found that the translational displacement is stable and controllable on the condition that ω is in an interval. If ω exceeds an allowable value, the rotor exhibits unstable eccentric rotation. The system may collapse with the rotor escaping from the stators due to the strong centrifugal force in eccentric rotation. In a practical design, the interval of ω can be found for a system with controllable output translation.

Softening to hardening of stretched diamondene nanotubes.

Diamondene, a carbon nanomaterial containing both sp2 and sp3 carbon atoms, is obtained by compressing two or more layers of graphene. By curving rectangular diamondene and matching the unsaturated C-C bonds on the two unbent edges, a nanotube is built. We build two diamondene nanotubes (DNTs) with different radii and test their strengths under uniaxial tension. From the stress-strain curves, we discover that DNTs exhibit softening followed by hardening. The mechanism is as follows: the bond lengths and bond angles impart different stiffnesses to the tube at different axial strains. Molecular dynamics simulations demonstrate that the feature of the softening-hardening process is independent of either the tube radii or the system temperature. The critical strain for the tensile strength of a DNT becomes lower at a higher temperature. This is caused by thermal vibration of the atoms in the tubes. At the same temperature, for a DNT with a larger radius, the value of critical strain is higher. These properties will be beneficial for the potential applications of DNTs in nanodevices.

Shell buckling: from morphogenesis of soft matter to prospective applications.

Being one of the commonest deformation modes for soft matter, shell buckling is the primary reason for the growth and nastic movement of many plants, as well as the formation of complex natural morphology. On-demand regulation of buckling-induced deformation associated with wrinkling, ruffling, folding, creasing and delaminating has profound implications for diverse scopes, which can be seen in its broad applications in microfabrication, 4D printing, actuator and drug delivery. This paper reviews the recent remarkable developments in the shell buckling of soft matter to explain the most representative natural morphogenesis from the perspectives of theoretical analysis in continuum mechanics, finite element analysis, and experimental validations. Imitation of buckling-induced shape transformation and its applications are also discussed for the innovations of sophisticated materials and devices in future.

Examination of needle surface corrosion in electroacupuncture.

BACKGROUND: Electroacupuncture (EA) is a modern form of acupuncture therapy where stainless steel acupuncture needles are used as percutaneous electrodes to apply electrical stimulation. The concern about electrolytic corrosion of needles during EA has not been conclusively addressed. AIM: To examine whether corrosion of stainless steel acupuncture needles occurs after EA to establish the safety profile of this therapy. METHODS: The study comprised four EA sessions on healthy participants mimicking a common clinical practice, with needle surface examinations conducted immediately after each session. Used acupuncture needles that did not undergo electrical stimulation and unused needles taken from the original package were also examined as control comparisons. Two commonly used types of single-use, silicone-coated, stainless steel needles were selected for the experiment. The ES-160 digital acupunctoscope (a charge-balanced electric stimulator) was used to deliver electrical stimulation, and an oscilloscope was used to record the waveforms and electric currents. All needles were sterilised before examination by a scanning electron microscope (SEM), where images of needle tips and shafts were taken for further analysis. RESULTS AND CONCLUSIONS: 32 needles were examined under the SEM. As the main findings, the SEM images showed the surface finish, burr attachments and surface characteristics of needle samples. No evidence of electrolytic corrosion was detected on any needle that underwent electrical stimulation for 30 min delivered by a charge-balanced acupunctoscope in healthy participants. The choice of a charge-balanced acupunctoscope is recommended to avoid any potential corrosion of needles in EA clinical practice.

Systematic review of acupuncture placebo devices with a focus on the credibility of blinding of healthy participants and/or acupuncturists.

BACKGROUND: An ideal placebo design in clinical research should resemble the intervention under investigation to facilitate blinding, yet remain clinically inert. With regard to physical interventions such as acupuncture, a true placebo device has not been developed and validated. Since 1998, researchers have designed several placebo acupuncture devices (PADs). The three most widely used PADs are the Streitberger, the Park and the Takakura device. AIM: This review focuses on evaluating studies of these devices, in the context of credibility of blinding (COB), assessment of penetrating pain or sensation, and de qi sensation. METHODS: Electronic database searches were conducted in four English and two Chinese databases from their inception until November 2016. All studies included in the review were conducted on healthy participants and compared verum manual acupuncture with any of the aforementioned PADs with respect to one or more of the above three outcomes related to blinding effect. RESULTS: The synthesised analyses of the 15 included studies showed that the Streitberger and Park placebo devices may not blind participants successfully when tested at a sensitive acupuncture point (LI4). In terms of penetrating sensation, there were significant differences between these two placebo devices and verum acupuncture when applied at this point. The Takakura device was the only PAD that had the potential to blind the acupuncturist. However, the blinding analyses of all outcome measures were inconsistent. CONCLUSION: Overall, there were insufficient data to confirm the blinding effects of these skin-contact PADs as each device was associated with limitations that warrant further design improvements.

A nano continuous variable transmission system from nanotubes.

A nano continuous variable transmission (nano-CVT) system is proposed by means of carbon nanotubes (CNTs). The dynamic behavior of the CNT-based nanosystem is assessed using molecular dynamics simulations. The system contains a rotary CNT-motor and a CNT-bearing. The tube axes of the nanomotor and the rotor in the bearing are laid in parallel, and the distance between them is known as the eccentricity of the rotor with a diameter of d. By changing the eccentricity (e) of the rotor from 0 to d, some interesting rotation transmission phenomena are discovered, whose procedures can be used to design various nanodevices. This might include the failure of rotation transmission-i.e. the rotor has no rotation-when e ≥ d at an extremely low temperature, or when the edges of the two tubes are orthogonal at their intersections in any condition. This hints that the state of the nanosystem can be used as an on/off switch or breaker. For a system with e = d and a high temperature, the rotor rotates in the reverse direction of the motor. This means that the output signal (rotation) is the reverse of the input signal. When changing the eccentricity from 0 to d continuously, the output signal gradually decreases from a positive value to a negative value; as a result a nano-CVT system is obtained.

High-speed spinning disks on flexible threads.

A common spinning toy, called "buzzer", consists of a perforated disk and flexible threads. Despite of its simple construction, a buzzer can effectively transfer translational motions into high-speed rotations. In the present work, we find that the disk can be spun by hand at an extremely high rotational speed, e.g., 200,000 rpm, which is much faster than the previously reported speed of any manually operated device. We explore, both experimentally and theoretically, the detailed mechanics and potential applications of such a thread-disk system. The theoretical prediction, validated by experimental measurements, can help design and optimize the system for, e.g., easier operation and faster rotation. Furthermore, we investigate the synchronized motion of multiple disks spinning on a string. Distinctly different twist waves can be realized by the multi-disk system, which could be exploited in the control of mechanical waves. Finally, we develop two types of manually-powered electric generators based on the thread-disk system. The high-speed rotation of the rotors enables a pulsed high current, which holds great promise for potential applications in, for instance, generating electricity and harvesting energy from ocean waves and other rhythmic translational motions.