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Nucleic acids are a special class of negatively charged polymers, and they can complex with cationic small molecules and polymers to form polyelectrolyte complexes of rich morphology. The initial a...

Constant velocity (CV) joints are the primary component of a vehicle that transmits the driving force from an engine/transmission to a wheel at a constant speed. A CV joint comprises numerous mechanical parts. The roller and housing are in contact and, therefore, subjected to contact stresses. Contact stress causes sliding friction because of microslip in the contact area inside the CV joint. This internal friction generates an axial force, dependent on the kinematics. A generated axial force (GAF) is caused by the internal friction in a plunging-type CV joint. This force can have a direct impact on the degradation of the noise, vibration, and harshness characteristics of a vehicle. The typical vibration of a CV joint transmitted to the vehicle is shudder, which degrades the lateral oscillation of the vehicle. Shudder is generated by the GAF and results from the rotation of the CV joint during rapid acceleration, stimulating the lateral movement of the vehicle and causing discomfort to passengers. In this study, the radii of the roller and the housing were selected as the design parameters, and the contact stress was minimized through the sensitivity analysis. The GAF of the existing CV joint and optimized CV joint are compared through a multibody dynamic simulation. An axial force test is performed on the CV joint of a C-segment vehicle to verify the dynamic simulation results. The friction characteristics of the greases used in the CV joint were also confirmed by the schwingung reibung verschleiss (SRV) friction test. The results obtained can be used to reduce the GAF of the CV joint and to build an optimized CV joint model.

This paper examines the characteristics of stick-slip phenomena between the glass plate and Magneto-Rheological Elastomer (MRE) surface. Stick-slip phenomena are the spontaneous jerking motion that occurs while two objects are sliding over each other, usually accompanied by noise. Stick-slip is generated when it involves discontinuous frictional degradation when moving from static friction to dynamic friction. The phenomena can lead to uneven wear patterns, vibration and squeal noise which cause a shorter lifespan for the corresponding mechanical elements. MREs are kind of function materials to consist of a polymeric matrix with embedded ferromagnetic particles. Mechanical properties of the MREs can be controlled by the application of magnetic fields. The magnetic field-based controllability can be applied to the control of stick-slip phenomena. The friction experiment is conducted with the Reciprocating Friction Tester (RFT). The sliding speed of the RFT should be in low-speed conditions in order to make the stick-slips relatively easy to occur. A uniform magnetic field and a weight load are applied to the MRE sample to observe the effect of various experimental parameters on the movement of the stick-slip. In addition, frictional sounds due to the stick-slip phenomenon under different loads and magnetic field strength are measured and analyzed. The results of this experiment show that as the strength of the magnetic field increases, the difference in stiffness between the wipers-glass decreases, mitigating fricatives. The result is expected to be well applied to low-noise automotive wipers based on the controllability of friction behavior and squeal noise.

A B-hypergraph consisting of nodes and directed hyperedges is a generalization of the directed graph. A directed hyperedge in the B-hypergraph represents a relation from a set of source nodes to a single destination node. We suggest one possible definition of betweenness centrality (BC) in B-hypergraphs, called Participation-based BC (PBC). A PBC score of a node is computed based on the number of the shortest paths in which the node participates. This score can be expressed in terms of dependency on the set of its outgoing hyperedges. In this article, we focus on developing efficient computation algorithms for PBC. We first present an algorithm called ePBC for computing exact PBC scores of nodes, which has a cubic-time complexity. This algorithm, however, can be used for only small-sized B-hypergraphs because of its cubic-time complexity, so we propose linearized PBC ( ℓ PBC) that is an approximation method of ePBC. ℓ PBC that comes with a guaranteed upper bound on its error, uses a linearization of dependency on a set of hyperedges. ℓ PBC improves the computing time of ePBC by an order of magnitude (i.e., it requires a quadratic time) while maintaining a high accuracy. ℓ PBC works well on small to medium-sized B-hypergraphs, but is not scalable enough for a very large B-hypergraph with more than a million hyperedges. To cope with such a very large B-hypergraph, we propose a very fast heuristic sampling-based method called sampling-based ℓ PBC (s ℓ PBC). We show through extensive experiments that ℓ PBC and s ℓ PBC can efficiently estimate PBC scores in various real-world B-hypergraphs with a reasonably good precision@ k . The experimental results show that s ℓ PBC works efficiently even for a very large B-hypergraph.

Traditional fatigue fracture theory and practice focus principally on structural design. It is thus too conservative and inappropriate when used to predict the high-cycle fatigue life of dies used for metal forming, especially cold forging. We propose a novel mean stress correction model and diagram to predict the high-cycle fatigue lives of cold forging dies, which focuses on the upper part of the equivalent fatigue strength curve. Considering the features of die materials characterized by high yield strength and low ductility, a straight line is assumed for the tensile yield line. To the contrary, a general curve is used to represent the fatigue strength. They are interpolated, based on the distance ratio, when finding an appropriate equivalent fatigue strength curve at the mean stress and stress amplitude between the line and curve. The approach is applied to a well-defined literature example to verify its validity and shed light on the characteristics of die fatigue life. The approach is also applied to practical forging and useful qualitative results are obtained.

The 26S proteasome is an essential protease that selectively eliminates dysfunctional and short-lived regulatory proteins in eukaryotes. To define the composition of this proteolytic machine in plants, we tagged either the core protease (CP) or the regulatory particle (RP) sub-complexes in Arabidopsis to enable rapid affinity purification followed by mass spectrometric analysis. Studies on proteasomes enriched from whole seedlings, with or without ATP needed to maintain the holo-proteasome complex, identified all known proteasome subunits but failed to detect isoform preferences, suggesting that Arabidopsis does not construct distinct proteasome sub-types. We also detected a suite of proteasome-interacting proteins, including likely orthologs of the yeast and mammalian chaperones Pba1, Pba2, Pba3, and Pba4 that assist in CP assembly; Ump1 that helps connect CP half-barrels; Nas2, Nas6, and Hsm3 that assist in RP assembly; and Ecm29 that promotes CP–RP association. Proteasomes from seedlings exposed to the proteasome inhibitor MG132 accumulated assembly intermediates, reflecting partially built proteasome sub-complexes associated with assembly chaperones, and the CP capped with the PA200/Blm10 regulator. Genetic analyses of Arabidopsis UMP1 revealed that, unlike in yeast, this chaperone is essential, with mutants lacking the major UMP1a and UMP1b isoforms displaying a strong gametophytic defect. Single ump1 mutants were hypersensitive to conditions that induce proteotoxic, salt and osmotic stress, and also accumulated several proteasome assembly intermediates, consistent with its importance for CP construction. Insights into the chaperones reported here should enable study of the assembly events that generate the 26S holo-proteasome in Arabidopsis from the collection of 64 or more subunits.

NAM, ATAF1/2 and CUC2 (NAC) domain transcription factors function as master switches in regulating secondary cell wall (SCW) biosynthesis in Arabidopsis (Arabidopsis thaliana) stems. Despite the importance of these NACs in fiber development, the upstream signal is still elusive. Using a large-scale mutant screening, we identified a dominant activation-tagging mutant, fiberless-d (fls-d), showing defective SCW development in stem fibers, similar to that of the nac secondary wall thickening promoting factor1-1 (nst1-1)nst3-3 double mutant. Overexpression of LATERAL ORGAN BOUNDARIES DOMAIN29 (LBD29) is responsible for the fls-d mutant phenotypes. By contrast, loss-of-function of LBD29, either in the dominant repression transgenic lines or in the transfer-DNA (T-DNA) insertion mutant lbd29-1, enhanced SCW development in fibers. Genetic analysis and transgenic studies demonstrated LBD29 depends on master regulators in mediating SCW biosynthesis, specifically NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1), NST2, and NST3. Increasing indole-3-acetic acid (IAA) levels, either in stem tissues above a N-1-naphthylphthalamic acid–treated region or in plants directly sprayed with IAA, inhibits fiber wall thickening. The inhibition effect of naphthylphthalamic acid treatment and exogenous IAA application depends on a known auxin signaling pathway involving AUXIN RESPONSE FACTOR7 (ARF7)/ARF19 and LBD29. These results demonstrate auxin is upstream of LBD29 in repressing NAC master regulators, and therefore shed new light on the regulation of SCW biosynthesis in Arabidopsis.

Lignin is a by-product of paper and pulp production resulting from extraction of cellulose, the world's most abundant natural polymer. In this study, we manufactured polypropylene (PP)/PP-grafted maleic anhydride (PP-g-MAH)/glass fiber (GF)/lignin composites via reactive extrusion process for value-addition of lignin, often discarded as wood waste. To enhance adhesion in composites at interphases, diisocyanate was added in-situ during the extrusion process, leading to chemical primary bonding. Structure-property relationship of PP/PP-g-MAH/GF/lignin composites revealed two different reinforcement mechanisms that were supported by FT-IR, TGA, hardness, tensile, flexural, and impact tests, SEM, and density. Up to 7.5 wt% of isocyanate loading, linear urethane bonding was formed; further addition of isocyanate resulted in evolution of chemical crosslinking via allophanate bonding.

Controlling the interactions between cells and viruses is critical for treating infected patients, preventing viral infections, and improving virus-based therapeutics. Chemical methods using small molecules and biological methods using proteins and nucleic acids are employed for achieving this control, albeit with limitations. We found, for the first time, that retroviral DNA integration patterns in the human genome, the result of complicated interactions between cells and viruses, can be engineered by adapting cells to the defined nanotopography of silica bead monolayers. Compared with cells on a flat glass surface, cells on beads with the highest curvature harbored retroviral DNAs at genomic sites near transcriptional start sites and CpG islands during infections at more than 50% higher frequencies. Furthermore, cells on the same type of bead layers contained retroviral DNAs in the genomic regions near cis-regulatory elements at frequencies that were 2.6-fold higher than that of cells on flat glass surfaces. Systems-level genetic network analysis showed that for cells on nanobeads with the highest curvature, the genes that would be affected by cis-regulatory elements near the retroviral integration sites perform biological functions related to chromatin structure and antiviral activities. Our unexpected observations suggest that novel engineering approaches based on materials with specific nanotopography can improve control over viral events.

3D printing provides the advantage of the capability to manufacture a wide range of geometric models without constraint and using various materials. Owing to the recent rapid development of 3D printing technologies, manufacturing accuracy has also been improved. Precisely 3D-printed parts are used in various industries such as medical, robotics, and manufacturing industries. In this study, the friction performance of 3D printed ball bearing is evaluated to verify its feasibility as an engineering part. Multi-jet printing (MJP) method is utilized to prepare the ball bearing specimen as it provides the advantages of straightforward manufacturing process and high surface quality. The test rig is designed and constructed to evaluate the friction performance under various rotating speed and radial load conditions. From the experiments, the friction performance and feasibility of 3D printed ball bearings are evaluated, and effective operating conditions of 3D printed bearings are recommended. The results in this study can be used as a reference to design ball bearings using 3D printing method. Keywords: Multi-jet printing, 3D printed bearing, Ball bearing, Friction performance

This paper describes the optimized design of a knee joint for an active transfemoral prosthesis with a fully active knee joint. The active transfemoral prosthesis which can help amputees to walk naturally with a powered motor has been actively developed around the world with advances in battery technology and others. However, most of them are designed for level walking, especially in South Korea, research about active prosthesis is insufficiently carried out, also depends on foreign technology. Therefore, this study focuses on the development of prosthetic knee joint that can overcome complex walking environment including stair walking. The developed prosthesis has one degree of freedom at the knee joint and can mimic the human walking mechanism. The prosthetic knee joint has a simple high-torque mechanism comprising a flat BLDC motor, harmonic drive, and pulley to generate the torque required for walking on stairs, which requires the largest torque. As one of the most important factors for comfort and fatigue, the total weight of the prosthesis should be minimized. Topology optimization was carried out to reduce the weight, and an advanced knee joint design was developed based on the optimization. The structural safety was validated via finite element analysis and a strain experiment under working conditions.

Low pressure materials pre-treatment process has been developed as an alternative to the existing high-temperature sludge drying, limestone calcination, and limonite dehydroxylation. Using the thermodynamic equilibrium relationship between temperature and pressure represented by the Clausius-Clapeyron equation, the operational temperature of these reactions could be lowered at reduced pressure for increased energy efficiency. For industrial sludge drying, the evaporation rate was controlled by interfacial kinetics showing a constant rate with time and significant acceleration in the reaction could be observed with reduced pressure. At this modified reaction rate under low pressure, the rate was also partially controlled by mass transfer. Temperature of limestone calcination was lowered, but the reaction was limited at the calculated equilibrium temperature of the Clausius-Clapeyron equation and slightly higher temperatures were required. The energy consumption during limestone calcination and limonite dehydroxylation were evaluated, where lower processing pressures could enhance the energy efficiency for limestone calcination, but limonite dehydroxylation could not achieve energy-savings due to the greater power consumption of the vacuum pump under lower pressure and reduced temperatures.

Direct fabrication of titanium (Ti) and niobium (Nb) alloys by direct magnesiothermic reduction from the respective initial metal oxides and complex oxides has been studied. TiO2, Nb2O5, and complex TiNb2O7 oxides were used as raw materials with Mg used as a reductant. To ensure a high chemical potential of the reactants to drive the spontaneous magnesiothermic reduction of the oxide mixtures, excess Mg five times higher than the required stoichiometric molar ratio was added. Samples were heated in a glove box under recycled and purified Ar atmosphere at 1073 K (800 °C) for 10 h. After the reduction of TiO2, intermediate oxide phases of Ti6O could still be observed, but reduction of Nb2O5 and TiNb2O7 showed metallic Nb and Ti-Nb to be present with negligible oxides according to the scanning electron microscope-energy dispersive spectroscopy and x ray diffraction analysis. This indicated that direct fabrication of Ti-Nb alloys through a complex TiNb2O7 oxide is possible and can be more efficient than alloying pure metallic elements of Ti and Nb.

Surface texture patterns have great potential for improving tribological performance in terms of reducing friction and wear. The most common methods for surface texturing are laser and injection molding. The 3D printing method is also used to build parts, patterns, and molds that feature fine details for a wide range of applications because texture manufacturing by 3D printing is faster, more flexible, and less expensive than traditional techniques. To date, there has been no research on textured surfaces produced by 3D printing. Therefore, a new fabrication method using 3D printing to improve friction and wear properties is a topic worth exploring. In this study, a reciprocating friction tester was used to evaluate the friction and wear properties of different surface textures produced by 3D printing. The surface of specimens was examined by electron microscope and scanning electron microscope before and after the test. The results show that surface texturing can be applied to 3D printed parts to improve their friction and wear performance.

This paper describes the complete design process of a passive prosthetic foot manufactured of Polylactic acid (PLA). It focuses on the reduction in the weight of prosthetic feet. Most of the prosthetic feet are designed with more weight and material than required. The structure of this passive prosthetic foot is designed and optimized as light as possible by using topology optimization. The topology-optimized model is printed from a Three-dimensional (3D) printer directly rather than interpreting the model using a Computer-aided design (CAD) software. The finite element analysis and the experiments are conducted to validate the structure. The test equipment is designed and installed for simulating the boundary conditions of the Heel strike (HS) and Toe off (TO). Since the weight of the prosthetic directly affects the mobility of patients, the weight of the proposed model is reduced 62 % when compared initial model to the final model.

Magnetically active helical soft robots were synthesized to achieve tether-less manipulation of the magnetomotility in order to avoid the on-board weight penalty and the distance restrictions originating from connection lines. Magnetic iron particles were dispersed in elastomeric polymer matrices and pre-cured in a two-dimensional film geometry, followed by post-curing in a three-dimensional (3D) helical geometry. To manipulate movements of the 3D helical soft robots, an external magnetic field was applied by placing a neodymium permanent magnet on a motorized linear translation stage. The 3D helical geometry of the soft robots enabled efficient maneuvering with local deformations and a low magnetic threshold for actuation by the introduction of the rolling resistance unlike the absence of the local deformations observed for rigid 3D coils. As rolling is induced by the action and reaction with the substrate, the helix angle causes divergence of the soft robots from linear translational motility. In order to regulate the directionality of rolling and to minimize temporal and spatial deviation of the soft robots, the magnitude of the magnetic flux density and the velocity of the permanent magnet on the linear stage were investigated.

The objective of this study is to develop a damper that can reduce the amplitude of vibration in various frequency ranges. Previous H/Shaft vibration reduction methods work in a passive way. A dynamic damper reduces the amplitude of vibration at its first mode, but vibration still appears at the second mode. A mass damper or hollow shaft can shift the natural frequency to a lower or higher region. The fixed operating frequency prevents vibration from being reduced outside the operating frequency range. The proposed damper uses electromagnets as either masses or actuators to change the damper mode between dynamic damper mode and mass damper mode. The electromagnetic damper (EMD) can change its mode to respond to the vibration excitation at both low and high frequencies. The vibration reduction performance was evaluated by FRF tests in laboratory and vehicle conditions. The results were compared with those of a dynamic damper and indicate that the amplitude of vibration is reduced by 95.6 % when the EMD is implemented on an H/Shaft, whereas only 61.9 % vibration reduction is achieved by the dynamic damper.

In this study, the friction characteristics of a magneto-rheological fluid are examined with different surface process technologies such as polytetrafluoroethylene coatings and diamond-like carbon coatings by using a reciprocating friction tester. The friction characteristics of the magneto-rheological fluid are also examined with diamond-like carbon coatings at various temperatures. The substrate material (plate) used for coating with diamond-like carbon and polytetrafluoroethylene is aluminum (Al6061), which is widely used in engineering applications. The descending sequence of the coefficients of friction is Al6061 > diamond-like carbon > polytetrafluoroethylene. The surfaces are observed by scanning electron microscopy before and after the experiment. In addition, the chemical compositions of the worn surfaces were analyzed using energy-dispersive X-ray spectroscopy. By comparing the results, the friction characteristics of the magneto-rheological fluid are analyzed based on the different coating methods.

A magnetorheological fluid (MRF) performs differently under different magnetic field strength. This study examined the fretting friction and wear characteristics of MRFs under a range of magnetic field strengths and oscillation frequencies. The fretting friction and wear behaviors of MRF are investigated using a fretting friction and wear tester. The surfaces of specimen are examined by optical microscopy and 3D surface profilometer before and after the tests and wear surface profiles, the wear volume loss and wear coefficient for each magnetic field strength are evaluated. The results show that the friction and wear properties of MRF change according to the magnetic field strength and oscillation frequency.

In this study, the friction and wear properties of magnetorheological elastomer (MRE) were examined under various vibration conditions. The variation of the friction coefficient and wear of the MRE was investigated experimentally with an applied magnetic field and different frequencies and amplitudes of normal vibration. To accomplish this, a reciprocating friction tester and test samples were designed and fabricated. The results show that the friction coefficient decreased with the magnetic field in all test conditions. The friction coefficient increased when vibration was applied and the frequencies were increased. The friction coefficient decreased as the amplitudes increased. The wear also significantly changes under different vibration frequencies and amplitudes with and without a magnetic field.

Proteotoxic stress, which is generated by the accumulation of unfolded or aberrant proteins due to environmental or cellular perturbations, can be mitigated by several mechanisms, including activation of the unfolded protein response and coordinated increases in protein chaperones and activities that direct proteolysis, such as the 26S proteasome. Using RNA-seq analyses combined with chemical inhibitors or mutants that induce proteotoxic stress by impairing 26S proteasome capacity, we defined the transcriptional network that responds to this stress in Arabidopsis thaliana This network includes genes encoding core and assembly factors needed to build the complete 26S particle, alternative proteasome capping factors, enzymes involved in protein ubiquitylation/deubiquitylation and cellular detoxification, protein chaperones, autophagy components, and various transcriptional regulators. Many loci in this proteasome-stress regulon contain a consensus cis-element upstream of the transcription start site, which was previously identified as a binding site for the NAM/ATAF1/CUC2 78 (NAC78) transcription factor. Double mutants disrupting NAC78 and its closest relative NAC53 are compromised in the activation of this regulon and notably are strongly hypersensitive to the proteasome inhibitors MG132 and bortezomib. Given that NAC53 and NAC78 homo- and heterodimerize, we propose that they work as a pair in activating the expression of numerous factors that help plants survive proteotoxic stress and thus play a central regulatory role in maintaining protein homeostasis.

In our previous study, X-31ca-based H5N1 LAIVs, in particular, became more virulent in mice than the X-31ca MDV, possibly by the introduction of the surface antigens of highly pathogenic H5N1 influenza virus, implying that additional attenuation is needed in this cases to increase the safety level of the vaccine. In this report we suggest an approach to further increase the safety of LAIV through additional cold-adapted mutations in the hemagglutinin. The cold-adaptation of X-31 virus resulted in four amino acid mutations in the HA. We generated a panel of 7:1 reassortant viruses each carrying the hemagglutinins with individual single amino acid mutations. We examined their phenotypes and found a major attenuating mutation, N81K. This attenuation marker conferred additional temperature-sensitive and attenuation phenotype to the LAIV. Our data indicate that the cold-adapted mutation in the HA confers additional attenuation to the LAIV strain, without compromising its productivity and immune response.

Cold-adapted live attenuated influenza vaccines (CAIVs) have been considered as a safe prophylactic measure to prevent influenza virus infections. The safety of a CAIV depends largely on genetic markers that confer specific attenuation phenotypes. Previous studies with other CAIVs reported that polymerase genes were primarily responsible for the attenuation. Here, we analyzed the genetic mutations and their phenotypic contribution in the X-31 ca strain, a recently developed alternative CAIV donor strain. During the cold-adaptation of its parental X-31 virus, various numbers of sequence changes were accumulated in all six internal genes. Phenotypic analysis with single-gene and multiple-gene reassortant viruses suggests that NP gene makes the largest contribution to the cold-adapted (ca) and temperature-sensitive (ts) characters, while the remaining other internal genes also impart attenuation characters with varying degrees. A balanced contribution of all internal genes to the attenuation suggests that X-31 ca could serve as an ideal master donor strain for CAIVs preventing influenza epidemics and pandemics.

Improper clamping of wiper arms can cause problems in the operation of the wiper. An excessive clamping force can cause damage to the wiper arm head. On the other hand, an insufficient clamping force can cause self-loosening of the nut. Given the lack of direct research on the clamping force of the fastener in wiper assembly, this study verifies the existing clamping performance of the fastener in windshield wiper assembly by theoretical and experimental methods. The theoretical calculation results show that all the clamping performance are satisfied under the general snow load condition. However, under the critical load condition, maximum assembly preload and safety margin against slipping are in disagreement with the standard values. This problem is solved by increasing the strength grade of the bolt. The experimental results show a reducing tendency of the clamping force during the snow durability test. However, this reducing clamping force during the 60,000 test cycles is acceptable. In the case of nut reusing more than two times possibly cause a problem of its loosening because of insufficient clamping force. Therefore, it is recommended that the nut should not be reused more than two times.

PURPOSE TP53, the most frequently mutated gene in breast cancer, is more frequently altered in HER2-enriched and basal-like breast cancer. However, no studies have clarified the role of TP53 status as a prognostic and predictive marker of triple-negative breast cancer (TNBC). MATERIALS AND METHODS We performed p53 immunohistochemistry (IHC), nCounter mRNA expression assay, and DNA sequencing to determine the relationship between TP53 alteration and clinical outcomes of TNBC patients. RESULTS Seventy-seven of 174 TNBC patients were found to harbor a TP53 mutation. Patients with missense mutations showed high protein expression in contrast to patients with deletion mutations (positivity of IHC: wild type vs. missense vs. deletion mutation, 53.6% vs. 89.8% vs. 25.0%, respectively; p < 0.001). TP53 mRNA expression was influenced by mutation status (mRNA expression [median]: wild type vs. missense vs. deletion mutation, 207.36± 132.73 vs. 339.61±143.21 vs. 99.53±99.57, respectively; p < 0.001). According to survival analysis, neither class of mutation nor protein or mRNA expression status had any impact on patient prognosis. In subgroup analysis, low mRNA expression was associated with poor prognosis in patients with a TP53 missense mutation (5-year distant recurrence-free survival [5Y DRFS]: low vs. high, 50.0% vs. 87.8%; p=0.009), while high mRNA expression with a TP53 deletion mutation indicated poor prognosis (5Y DRFS: low vs. high, 91.7% vs. 75.0%; p=0.316). CONCLUSION Association between TP53 mutation and expression indicates a potential prognostic marker of TNBC; hence both DNA sequencing and mRNA expression analysis may be required to predict the prognosis of TNBC patients.