A Novel Friction Compensation Method for Machine Tool Drive Systems in Insufficient Lubrication.

Friction is the dominant factor restricting tracking accuracy and machining surface quality in mechanical systems such as machine tool feed-drive. Hence, friction modeling and compensation is an important method in accurate tracking control of CNC machine tools used for welding, 3D printing, and milling, etc. Many static and dynamic friction models have been proposed to compensate for frictional effects to reduce the tracking error in the desired trajectory and to improve the surface quality. However, most of them focus on the friction characteristics of the pre-sliding zone and low-speed sliding regions. These models do not fully describe friction in the case of insufficient lubrication or high acceleration and deceleration in machine tool systems. This paper presents a new nonlinear friction model that includes the typical Coulomb-Viscous friction, a nonlinear periodic harmonic friction term for describing the lead screw property in insufficient lubrication, and a functional component of acceleration for describing the friction lag caused by the acceleration and deceleration of the system. Experiments were conducted to compare the friction compensation performance between the proposed and the conventional friction models. Experimental results indicate that the root mean square and maximum absolute tracking error can be significantly reduced after applying the proposed friction model.

PGAM5 expression levels in heart failure and protection ROS-induced oxidative stress and ferroptosis by Keap1/Nrf2.

OBJECTIVES: As a common and frequently occurring disease, heart failure has been paid more and more attention, but the mechanism of its occurrence and development is still unclear. This study investigated that PGAM5 expression levels in heart failure and its underlying mechanisms in vivo and in vitro. METHODS: The inhibition of PGAM5 mRNA expression levels in patients with heart failure was compared with the normal group. RESULTS: The serum of PGAM5 mRNA expression was negative correlation with collagen I and collagen III in patients with heart failure. PGAM5 mRNA and protein expression in the heart tissue of mice with heart failure were down-regulated at a time-dependent rate. The inhibition of PGAM5 presented heart failure in the model. PGAM5 reduced inflammation and inhibited ROS-induced oxidative stress in models of heart failure. PGAM5 reduced Ferroptosis in models of heart failure. PGAM5 regulated Keap1/Nrf2 signaling pathway. IP also showed that PGAM5 protein combined with the Keap1 protein. PGAM5 could increase Keap1 protein ubiquitination. Keap1 inhibition affected the effects of PGAM5 in model of heart failure. CONCLUSIONS: We conclude that the protection of PGAM5 reduced ROS-induced oxidative stress and ferroptosis by the Keap1/Nrf2 signaling pathway in heart failure, suggesting that targeting this mechanism of PGAM5 may be a feasible strategy to treat heart failure.

A Droplet-Manipulation Method Based on the Magnetic Particle-Stabilized Emulsion and Its Direct Numerical Simulation.

Droplet manipulation has found broad applications in various engineering fields, such as microfluidic systems. This work reports a droplet-manipulation method based on particle-stabilized emulsions, where the magnetic particles adsorbed to the droplet surface serve as the actuator. The movement and the release of the droplet can be controlled by applying an external magnetic field. A lattice Boltzmann model for a three-phase system containing liquids and solid particles is adopted, which could provide a full coupling between fluids and particles. The effectiveness of the present droplet-manipulation method is validated through experiments and numerical simulations. Furthermore, the numerical simulation can provide insight into the interactions between the magnetic particles and the droplet during the droplet-driven process. To drive the droplet successfully, the magnetic particle needs to adhere to its surface and act as an "engine" to provide the driving force. As it is a surface-tension-dominant problem, the capillary effect can be considered as an "energy transfer station". The magnetic driving force on the particle is transmitted primarily to the droplet through interfacial capillary forces at the three-phase contact line, which assists the droplet in overcoming the viscous resistance and moving forward. A dimensionless number is proposed as a predictor of droplet transport and particle detachment.

Maximum Spreading of Impacting Ferrofluid Droplets under the Effect of Nonuniform Magnetic Field.

This article investigates the maximum spreading of ferrofluid droplets impacting on a hydrophobic surface under nonuniform magnetic fields. A generalized model for scaling the maximum spreading is developed. It is observed that, if the magnetic field strength is zero, a ferrofluid droplet not only demonstrates similar spreading dynamics as the water droplet but also obeys the same scaling law for the maximum spreading factor. Therefore, this article emphasizes the effects of magnetic field strength. In this regard, a dimensionless parameter (Nm) is introduced as the ratio between inertial force and Kelvin force, with an assumption that the kinetic energy mainly transforms to thermal energy. This parameter allows us to rescale all experimental data on a single curve with the Padé approximant, which is applicable to a wide range of impact velocities and magnetic field strengths.

Nocturnal dexmedetomidine alleviates post-intensive care syndrome following cardiac surgery: a prospective randomized controlled clinical trial.

BACKGROUND: Dexmedetomidine is a sedative agent that may have the potential to reduce the risk of post-intensive care syndrome (PICS). This study aimed to establish whether prophylactic nocturnal dexmedetomidine safely reduces postoperative PICS incidence and to develop an easy-to-use model for predicting the risk of PICS following cardiac surgery. METHODS: This was a single-center, double-blind, randomized, prospective, placebo-controlled trial. Patients undergoing cardiac surgery were randomly assigned (1:1) to dexmedetomidine or placebo (normal saline) groups between January 2019 and July 2020. Dexmedetomidine or a similar volume of saline was administered, with an infusion rate up to 1.2 µg/kg/h until the RASS remained between - 1 and 0. The primary study endpoint was PICS incidence at 6 months follow-up, as defined by cognitive, physical, or psychological impairments. RESULTS: We assessed 703 individuals for eligibility, of whom 508 were enrolled. Of these, there were 251 in the dexmedetomidine group and 257 in the placebo group that received the trial agent, forming a modified intention-to-treat population. PICS incidence at 6-month follow-up was significantly decreased in the dexmedetomidine group (54/251, 21.5%) relative to the placebo group (80/257, 31.1%) (odds ratio [OR] 0.793, 95% CI 0.665-0.945; p = 0.014). Psychological impairment was significantly reduced in the dexmedetomidine group relative to the placebo group (18.7% vs. 26.8%, OR 0.806, CI 0.672-0.967, p = 0.029). However, dexmedetomidine treatment was associated with a higher rate of hypotension. A nomogram revealed that age, education, a medical history of diabetes and smoking, dexmedetomidine treatment, postoperative atrial fibrillation, and sequential organ failure assessment scores at 8 h post-surgery were independent predictors of PICS. CONCLUSIONS: Prophylactic nocturnal dexmedetomidine administration significantly reduced PICS incidence by a marked reduction in psychological impairment within a 6-month follow-up period. TRIAL REGISTRATION: ChiCTR, ChiCTR1800014314 . Registered 5 January 2018, http://www.chictr.org.cn/index.aspx.

Tuning the magneto-rheological properties of magnetic fluid using hydrophilic fumed silica nanoparticles.

In this work, we study the effect of hydrophilic fumed silica nanoparticles with different mass fractions on the magneto-rheological properties of magnetic fluid, and reveal the mechanism by the coarse-grained molecular dynamics simulation. The magneto-rheological experimental results show that the viscosity of the magnetic fluid with silica nanoparticles will first decrease and then increase (larger than that of the pure magnetic fluid) as the mass fraction of silica nanoparticles increases. We use the molecular dynamics calculations to further explain the influence mechanism of the silica nanoparticles on the magneto-rheological properties of the magnetic fluid. We find that non-magnetic particles will hinder the formation of chains of magnetic particles and shorten the length of the chains under magnetic fields. Our research shows that the magneto-rheological properties of magnetic fluid can be optimized with appropriate hydrophilic fumed silica nanoparticles, which is of great significance in the fields of dynamic seals and microfluidics.

Early and Intermediate-Term Results for the Combined Superior Approach Correction of Supracardiac Total Anomalous Pulmonary Venous Connection in Neonatal Patients.

BACKGROUND: There are different surgical approaches used for repairing a supracardiac total anomalous pulmonary venous connection (TAPVC), with different results. This retrospective study evaluated the outcomes of surgical repair for supracardiac TAPVC through the combined superior approach in neonatal patients. METHODS: Medical records were retrospectively reviewed and 21 neonates who underwent supracardiac TAPVC repair with the combined superior approach between July 2014 and January 2020 were identified. There were 13 males and eight females. RESULTS: The patients' median age was 20.6±8.9 days (range, 3-27). The median weight was 3.1±0.39 kg (range, 2.5-3.7) The median aortic cross-clamp and cardiopulmonary bypass times were 49.3±19.5 minutes (range, 27-86) and 91.1±23.7 minutes (range, 57-146). They were two deaths during the intensive care unit stay. One (1) patient died 2 months after discharge, the other remaining patients had no pulmonary venous obstruction (PVO) at the 6-month and intermediate-term follow-ups. CONCLUSIONS: The combined superior approach is a useful method for repair of neonatal critical supracardiac TAPVC. This technique may be more helpful in preventing early postoperative anastomotic stenosis and contribute to an improved patient outcome.

Study on the yielding behaviors of ferrofluids: a very shear thinning phenomenon.

The yielding behaviors of the ferrofluids are vital for many applications. However, previous studies have mainly focused on the magnetoviscous effect under relatively high shear rates and rarely involved the yielding process of ferrofluids under very low shear rates. In this study, ferrofluid samples of different particle volume concentrations were prepared and their shear thinning behaviors within a wide shear stress range were systematically studied under various magnetic field strengths and temperatures. The very shear thinning phenomenon of ferrofluids was first observed and its microscopic mechanism was analyzed. A precipitous fall-off stage as the mark of yielding appeared between the low shear and high shear plateaus in the viscosity curves of ferrofluids. The precipitous fall-off stage in the viscosity curves became steeper with the increase of the magnetic field strength or decrease in the temperature. For ferrofluids with relatively low particle volume concentrations, the high viscosity limit under the low shear region disappeared when temperature exceeded a certain value and was interpreted as the disappearance of the equilibrium columnar structures under high Brownian thermal interaction level. A composite Ellis model was proved to be suitable for the fitting of different types of yield stresses and a structural number, Sn was proposed for the dimensionless analysis of the shear thinning behaviors of ferrofluids. The findings in this study contribute to a better understanding of the microscopic mechanism of yielding behaviors of ferrofluids and also provide guidance for many practical applications.

High-performance plasmonic refractive index sensors via synergy between annealed nanoparticles and thin films.

Plasmonic nanostructure-based refractive index (RI) sensors are the core component of biosensor systems and play an increasingly important role in the diagnosis of human disease. However, the costs of traditional plasmonic RI sensors are not acceptable to everyone due to their expensive fabrication process. Here, a novel low-cost and high-performance visible-light RI sensor with a particle-on-film configuration was experimentally demonstrated. The sensor was fabricated by transferring annealed Au nanoparticles (NPs) onto a thin gold film with polymethyl methacrylate (PMMA) as a support. RI sensitivities of approximately 209 nm/RIU and 369 nm/RIU were achieved by reflection and transmission spectrum measurements, respectively. The high sensitivity is due to the strong plasmon-mediated energy confinement within the interface between the particles and the film. The possibility of wafer-scale production and high working stability achieved by the transfer process, together with the high sensitivity to the environmental RI, provides an extensive impact on the realization of universal biosensors for biological applications.

Spatial self-phase modulation of a Gaussian beam transmitted through a ferrofluid.

We report on the experimental observation of the diffraction pattern formed in the far-field region when a high-power continuous-wave laser convergent or divergent Gaussian beam passes through a cuvette with ferrofluid. Two different types of diffraction rings with opposite light-intensity distribution are shown in the far field. The difference between the diffractive patterns is attributed to the interaction of the strong spatial self-phase modulation caused by the refractive index change of the medium with wavefront curvature of the input Gaussian beam. The observed behavior of the diffraction pattern dynamics is interpreted theoretically based on the Fresnel-Kirchhoff integral. The negative polarity of nonlinear refraction can be identified by the central interference profiles and the diffraction pattern. At the same time, the self-defocusing phenomena of the ferrofluid can be determined by the type of pattern. The nonlinear refraction coefficients of the ferrofluid were estimated to be ∼-2.89×10-5cm2/W (convergent Gaussian beam) and ∼-3.53×10-5cm2/W (divergent Gaussian beam). In addition, the corresponding third-order nonlinear optical susceptibility of the sample was also estimated as ∼1.43×10-5esu and ∼1.75×10-5esu, respectively. The experimental results imply a novel potential application of ferrofluid in nonlinear phase modulation devices.

Passively Q-switched Nd:YVO4 laser operating at 1.3 µm with a graphene oxide and ferroferric-oxide nanoparticle hybrid as a saturable absorber.

A self-made saturable absorber (SA) based on hybridized graphene oxide (GO) and ${{\rm Fe}_{3}}{{\rm O}_{4}}$Fe3O4 nanoparticles (FONP) was inserted into a linear cavity to generate a passively $ Q $Q-switched solid-state ${\rm Nd}\text:{{\rm YVO}_4}$Nd:YVO4 laser operating at the 1.3 µm waveband. The laser had a minimum pulse width of 163 ns and a maximum repetition rate of 314 kHz. This experiment, to the best of our knowledge, is the first to demonstrate that hybridized GO and FONP (GO-FONP) can be used as an SA in passively $ Q $Q-switched pulse lasers. Results show that GO-FONP has the potential to be used for passively $ Q $Q-switched laser generation.

Anxiety Administrated by Dexmedetomidine to Prevent New-Onset of Postoperative Atrial Fibrillation in Patients Undergoing Off-Pump Coronary Artery Bypass Graft.

This study aims to evaluate the effect of dexmedetomidine (DEX) sedation for relieving anxiety and the incidence of atrial fibrillation (AF) after off-pump coronary artery bypass graft (OPCABG).This randomized, double-blind, controlled trial was conducted on 196 patients who underwent OPCABG in Shandong Provincial Hospital from July 2017 to June 2018. The patients were randomly assigned to two groups, intervention of DEX group and Propofol (PROP) group. Episodes of postoperative AF (POAF) were identified within 5 days after OPCABG. Perioperative anxiety status was assessed using Zung's Self-Rating Anxiety Scale (SAS). The baseline demographic and surgical characteristics of the population and other outcome variables were evaluated.We analyzed 62 patients in the DEX group and 61 patients in the PROP group. There was no significant difference in SAS anxiety scores between two groups before surgery (P = 0.104), while SAS had significantly after surgery (P = 0.018). The incidence of POAF in the DEX group was lower than that of the PROP group (16.1% versus 32.8%, P = 0.037), and a total of 30 patients (30/123, 24.4%) manifested POAF after OPCABG. Some univariable predictors of POAF were detected. The conceptual model of mediator analyses showed DEX was not only directly related to POAF but was also indirectly related through the independent effect of anxiety level.The findings indicated that patients receiving DEX were more likely to have less incidence of POAF, also uniquely showed DEX administration and POAF processes as a function of anxiety status.

Influence of the Carrier Fluid Viscosity on the Rotational and Oscillatory Rheological Properties of Ferrofluids.

This work mainly presents a comprehensive experimental study on the magnetorheological behavior of ferrofluids with carrier fluids of different viscosities. Three lubrication oil based ferrofluids of different viscosities and similar saturation magnetization values were prepared and characterized. Static and dynamic rheological tests of the three ferrofluids were performed using an advanced rotational rheometer with a magnetic field generating module. According to the experimental results, the magneto viscous effect, yield stress and storage modulus increase with the viscosity of carrier fluid, indicating that the structures of ferrrofluids tend to be larger and more stable in a carrier fluid with larger viscosity. The emergence and growth of "crossover" region with the increase in carrier fluid viscosity was observed using the strain-rate frequency superposition method, which were explained according to the microscopic mechanism of magnetorheology. These findings contribute to a better understanding of the microscopic mechanism of magnetorheology and provide guidance for practical applications.

Infected Anastomotic Pseudoaneurysm after Aortic Valve Replacement with Annular Enlargement.

Anastomotic pseudoaneurysm remains one of the main life-threatening complications of cardiac and thoracic aorta surgery. We report a rare case of infected pseudoaneurysm at the anastomotic line found during follow-up. Blood culture results suggested Enterococcus faecium infection. Transthoracic echocardiography and computed tomography scans revealed the presence of a pseudoaneurysm of the ascending aorta. The pseudoaneurysm was resected and the ascending aorta was reconstructed with an artificial vascular patch without complications. Reducing the anastomotic tension, with complete hemostasis at the anastomotic incision, is the most important means of preventing the formation of pseudoaneurysm.

Mechanism underlying the heart rate dependency of wave reflection in the aorta: a numerical simulation.

Arterial wave reflection has been shown to have a significant dependence on heart rate (HR). However, the underlying mechanisms inherent in the HR dependency of wave reflection have not been well established. This study aimed to investigate the potential mechanisms and role of arterial viscoelasticity using a 55-segment transmission line model of the human arterial tree combined with a fractional viscoelastic model. At varying degrees of viscoelasticity modeled as fractional order parameter α, reflection magnitude (RM), reflection index (RI), augmentation index (AIx), and a proposed novel normalized reflection coefficient (Γnorm) were estimated at different HRs from 60 to 100 beats/min with a constant mean flow of 70 ml/s. RM, RI, AIx, and Γnorm at the ascending aorta decreased linearly with increasing HR at all degrees of viscoelasticity. The means ± SD of the HR dependencies of RM, RI, AIx, and Γnorm were -0.042 ± 0.004, -0.018 ± 0.001, -1.93 ± 0.55%, and -0.037 ± 0.002 per 10 beats/min, respectively. There was a significant and nonlinear reduction in RM, RI, and Γnorm with increasing α at all HRs. In addition, HR and α have a more pronounced effect on wave reflection at the aorta than at peripheral arteries. The potential mechanism of the HR dependency of wave reflection was explained by the inverse dependency of the reflection coefficient on frequency, with the harmonics of the pulse waveform moving toward higher frequencies with increasing HR. This HR dependency can be modulated by arterial viscoelasticity. NEW & NOTEWORTHY This in silico study addressed the underlying mechanisms of how heart rate influences arterial wave reflection based on a transmission line model and elucidated the role of arterial viscoelasticity in the dependency of arterial wave reflection on heart rate. This study provides insights into wave reflection as a frequency-dependent phenomenon and demonstrates the validity of using reflection magnitude and reflection index as wave reflection indexes.

Study of the thixotropic behaviors of ferrofluids.

The thixotropic behaviors of ferrofluid samples of different particle concentration were studied using different measurement methods, including the three interval thixotropic test and the hysteresis loop test. The experimental results demonstrated that ferrofluids exhibit significant thixotropic behaviors and the microstructural evolution in ferrofluids behind the macroscopic rheological mechanics is discussed. The influence of magnetic field strength, particle concentration and temperature on the thixotropy of ferrofluids was also analyzed. Microscopic ferrofluid theory was adopted to study the thixotropic behaviors of ferrofluids under different shearing conditions, indicating that different thixotropic behaviors of ferrofluids can be induced by the presence and evolution of different kinds of microstructures, such as linear chain-like and dense drop-like structures. Furthermore, a phenomenal thixotropic model was employed to analyze the experimental results, indicating that a more specific model for ferrofluids is needed. These findings contribute to a better understanding of the microscopic mechanism of the complex rheological behaviors of ferrofluids.

Arterial viscoelasticity: role in the dependency of pulse wave velocity on heart rate in conduit arteries.

Experimental investigations have established that the stiffness of large arteries has a dependency on acute heart rate (HR) changes. However, the possible underlying mechanisms inherent in this HR dependency have not been well established. This study aimed to explore a plausible viscoelastic mechanism by which HR exerts an influence on arterial stiffness. A multisegment transmission line model of the human arterial tree incorporating fractional viscoelastic components in each segment was used to investigate the effect of varying fractional order parameter (α) of viscoelasticity on the dependence of aortic arch to femoral artery pulse wave velocity (afPWV) on HR. HR was varied from 60 to 100 beats/min at a fixed mean flow of 100 ml/s. PWV was calculated by intersecting tangent method (afPWVTan) and by phase velocity from the transfer function (afPWVTF) in the time and frequency domain, respectively. PWV was significantly and positively associated with HR for α ≥ 0.6; for α = 0.6, 0.8, and 1, HR-dependent changes in afPWVTan were 0.01 ± 0.02, 0.07 ± 0.04, and 0.22 ± 0.09 m/s per 5 beats/min; HR-dependent changes in afPWVTF were 0.02 ± 0.01, 0.12 ± 0.00, and 0.34 ± 0.01 m/s per 5 beats/min, respectively. This crosses the range of previous physiological studies where the dependence of PWV on HR was found to be between 0.08 and 0.10 m/s per 5 beats/min. Therefore, viscoelasticity of the arterial wall could contribute to mechanisms through which large artery stiffness changes with changing HR. Physiological studies are required to confirm this mechanism.NEW & NOTEWORTHY This study used a transmission line model to elucidate the role of arterial viscoelasticity in the dependency of pulse wave velocity on heart rate. The model uses fractional viscoelasticity concepts, which provided novel insights into arterial hemodynamics. This study also provides a means of assessing the clinical manifestation of the association of pulse wave velocity and heart rate.

Synthesis of Photocrosslinkable and Amine Containing Multifunctional Nanoparticles via Polymerization-Induced Self-Assembly.

Photo-crosslinkable and amine-containing block copolymer nanoparticles are synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly of a multifunctional core-forming monomer, 2-((3-(4-(diethylamino)phenyl)acryloyl)oxy)ethyl methacrylate (DEMA), using poly(2-hydroxypropyl methacrylate) macromolecular chain transfer agent as a steric stabilizer in methanol at 65 °C. By tuning the chain length of PDEMA, a range of nanoparticle morphologies (sphere, worm, and vesicle) can be obtained. Since cinnamate groups can easily undergo a [2 + 2] cycloaddition of the carbon-carbon double bonds upon UV irradiation, the as-prepared block copolymer nanoparticles are readily stabilized by photo-crosslinking to produce anisotropic nanoparticles. The crosslinked block copolymer nanoparticles can be used as templates for in situ formation polymer/gold hybrid nanoparticles.

The extrinsic hysteresis behavior of dilute binary ferrofluids.

We report on the magnetization behavior of dilute binary ferrofluids based on γ-Fe(2)O(3)/Ni(2)O(3) composite nanoparticles (A particles), with diameter about 11 nm, and ferrihydrite (Fe(5)O(7)(OH) ・4H2O) nanoparticles (B particles), with diameter about 6 nm. The results show that for the binary ferrofluids with A-particle volume fraction φ(A) = 0.2% and B-particle volume fractions φ(B) = 0.1% and φ(B) = 0.6%, the magnetization curves exhibit quasi-magnetic hysteresis behavior. The demagnetizing curves coincide with the magnetizing curves at high fields. However, for single γ-Fe(2)O(3)/Ni(2)O(3) ferrofluids with φ(A) = 0.2% and binary ferrofluids with φ(A) = 0.2% and φ(B) = 1.0%, the magnetization curves do not behave in this way. Additionally, at high field (750 kA/m), the binary ferrofluid with φ(B) = 1.0% has the smallest magnetization. From the model-of-chain theory, the extrinsic hysteresis behavior of these samples is attributed to the field-induced effects of pre-existing A particle chains, which involve both Brownian rotation of the chains'moments and a Néel rotation of the particles' moments in the chains. The loss of magnetization for the ferrofluids with φ(B) = 1.0% is attributed to pre-existing ring-like A-particle aggregates. These magnetization behaviors of the dilute binary ferrofluids not only depend on features of the strongly magnetic A-particle system, but also modifications of the weaker magnetic B-particle system.

Theoretical and Experimental Study on the Preparation of High-Viscosity Magnetic Nanofluid by Combined Surfactants.

In this study, the mechanism by which combined surfactants affect the dispersion stability of magnetic nanofluids (MNFs) was improved. Two stable lubricating oil-based magnetic nanofluids with high viscosity and one with low viscosity were prepared by chemical coprecipitation. Erucic acid and octanoic acid were used as the combined surfactants to modify the Fe3O4 nanoparticles (MNPs). The size and morphology of the particles were observed using TEM. The rheological properties were tested with a rotational rheometer. The magnetization of the lubricating oil-based magnetic nanofluids was characterized by VSM. The results indicated that the prepared magnetic nanofluids had high viscosity, high magnetism, and good stability. This study provided ideas for the preparation of a high-viscosity magnetic nanofluid. By using combined surfactants, sufficient steric repulsion energy can be provided to counteract the attraction energy of sterically protected nanoparticles, thus achieving a balance of the dispersion stability of MNF.