Dry sliding wear behavior of an extruded Mg–Dy–Zn alloy with long period stacking ordered phase

AbstractThe dry sliding wear behavior of extruded Mg-2Dy-0.5Zn alloy (at.%) was investigated using a pin-on-disk configuration. The friction coefficient and wear rate were measured within a load range 20–760 N at a sliding velocity of 0.785 m/s. Microstructure and wear surface of alloy were examined using scanning electron microscopy. The mechanical properties of alloy were tested at room and elevated temperatures. Five wear mechanisms, namely abrasion, oxidation, delamination, thermal softening and melting dominated the whole wear behavior with increasing applied load. The extruded Mg-2Dy-0.5Zn alloy exhibited the better wear resistance as compared with as-cast Mg97Zn1Y2 alloy under the given conditions through contact surface temperature analysis. The improved wear resistance was mainly related to fine grain size, good thermal stability of long period stacking order (LPSO) phase and excellent higher-temperature mechanical properties

Abnormal hubs in global network as potential neuroimaging marker in generalized anxiety disorder at rest

BackgroundMounting studies have reported altered neuroimaging features in generalized anxiety disorder (GAD). However, little is known about changes in degree centrality (DC) as an effective diagnostic method for GAD. Therefore, we aimed to explore the abnormality of DCs and whether these features can be used in the diagnosis of GAD.MethodsForty-one GAD patients and 45 healthy controls participated in the study. Imaging data were analyzed using DC and receiver operating characteristic (ROC) methods.ResultsCompared with the control group, increased DC values in bilateral cerebellum and left middle temporal gyrus (MTG), and decreased DC values in the left medial frontal orbital gyrus (MFOG), fusiform gyrus (FG), and bilateral posterior cingulate cortex (PCC). The ROC results showed that the DC value of the left MTG could serve as a potential neuroimaging marker with high sensitivity and specificity for distinguishing patients from healthy controls.ConclusionOur findings demonstrate that abnormal DCs in the left MTG can be observed in GAD, highlighting the importance of GAD pathophysiology

Nanoparticles of Poly(Lactide-Co-Glycolide)-d-a-Tocopheryl Polyethylene Glycol 1000 Succinate Random Copolymer for Cancer Treatment

Cancer is the leading cause of death worldwide. Nanomaterials and nanotechnologies could provide potential solutions. In this research, a novel biodegradable poly(lactide-co-glycolide)-d-a-tocopheryl polyethylene glycol 1000 succinate (PLGA-TPGS) random copolymer was synthesized from lactide, glycolide and d-a-tocopheryl polyethylene glycol 1000 succinate (TPGS) by ring-opening polymerization using stannous octoate as catalyst. The obtained random copolymers were characterized by 1H NMR, FTIR, GPC and TGA. The docetaxel-loaded nanoparticles made of PLGA-TPGS copolymer were prepared by a modified solvent extraction/evaporation method. The nanoparticles were then characterized by various state-of-the-art techniques. The results revealed that the size of PLGA-TPGS nanoparticles was around 250 nm. The docetaxel-loaded PLGA-TPGS nanoparticles could achieve much faster drug release in comparison with PLGA nanoparticles. In vitro cellular uptakes of such nanoparticles were investigated by CLSM, demonstrating the fluorescence PLGA-TPGS nanoparticles could be internalized by human cervix carcinoma cells (HeLa). The results also indicated that PLGA-TPGS-based nanoparticles were biocompatible, and the docetaxel-loaded PLGA-TPGS nanoparticles had significant cytotoxicity against Hela cells. The cytotoxicity against HeLa cells for PLGA-TPGS nanoparticles was in time- and concentration-dependent manner. In conclusion, PLGA-TPGS random copolymer could be acted as a novel and promising biocompatible polymeric matrix material applicable to nanoparticle-based drug delivery system for cancer chemotherapy

Evolution of rheocast microstructure of AZ31 alloy in semisolid state

Semisolid rheoforming (SSR) is a promising technology for the production of Mg wrought alloy in foundry settings. In order to realize SSR, it is necessary to characterize the grain structure evolution during slurry preparation. In this paper, slurry of AZ31 alloy was produced by a novel rheocast process known as self-inoculation method (SIM). Interrupted quenching technology was applied to investigate the primary α-Mg evolution during continuous cooling and isothermal holding. Results indicate that the initial microstructure of slurry produced by SIM is a mixture of irregular grains, which becomes ideally globular when the slurry slowly cools to 620 ℃ and isothermally held for at least 30 s. The local solute diffusion leads to dendritic fragmentation and forms separated particles. During prolonged holding, the particle surface gradually becomes smooth because of protuberance melting and groove advancement. Coarsening of α-Mg grains in isothermal holding was analyzed using Lifshitz-Slyozov-Wagner theory. Results suggest that coalescence is most likely the dominant coarsening mechanism in the early stage while Ostwald ripening tends to be the principal one later. The EDS results indicate that a longer holding time leads to Al solute element segregation at the grain boundaries, but Zn distribution within liquid matrix has no obvious change

Effects of novel self-inoculation method on microstructure of AM60 alloy

A novel cast processing method, self-inoculation method (SIM), was proposed. The process involves the addition of self-inoculant to melt, then pouring the melt to a mould through a multi-stream mixing cooling channel. In this paper, the process parameters were investigated. Results indicate that the melt treatment temperature, the amount of self-inoculant added, and the slope angle of the cooling channel are the key factors for SIM process. The optimized parameters are that the melt treatment temperature is between 680 and 700°C; the addition of self-inoculant is between 5wt.% and 7wt.%; and the slope angle of the cooling channel is between 30°and 45°. Further analysis reveals that SIM changes the solidification microstructure of slurry by controlling the nucleation and growth of the primary phase in the mel

Effect of cognitive behavioral therapy on pain, knee function, and psychological status in patients after primary total knee arthroplasty: a systematic review and meta-analysis

Abstract Objective The clinical efficacy of cognitive behavioral therapy (CBT) after Total knee arthroplasty (TKA) is still controversial, and the purpose of this meta-analysis was to evaluate the effect of CBT on pain, knee function, and psychological status of patients after TKA. Methods We systematically searched electronic databases such as CNKI, CBM, VIP, PubMed, Cochrane Library, and EMBASE for randomized controlled studies up to February 30, 2023. Screening against inclusion criteria to select valid studies and extract data. The quality of included studies was evaluated by the Cochrane Collaboration risk-of-bias 2 (RoB 2) tool for randomized trials. Statistical analysis of the data from this study was carried out using Stata 15.1 software. Results Finally, our meta-analysis incorporated seven randomized controlled studies of high quality, including 608 patients. The findings of the meta-analysis demonstrated a noteworthy decrease in kinesiophobia levels during the early postoperative phase in the CBT group as compared to the usual care group (WMD = -6.35, 95% CI: -7.98 to -4.72, Z = 7.64, P < 0.001). However, no statistically significant difference between the CBT and usual care groups in terms of postoperative pain as well as knee function. Conclusion CBT may effectively reduce the level of kinesiophobia in the short term after TKA, but did not significantly relieve knee pain or improve knee function

A Multivariate Statistics-Based Approach for Detecting Diesel Engine Faults with Weak Signatures

The problem of timely detecting the engine faults that make engine operating parameters exceed their control limits has been well-solved. However, in practice, a fault of a diesel engine can be present with weak signatures, with the parameters fluctuating within their control limits when the fault occurs. The weak signatures of engine faults bring considerable difficulties to the effective condition monitoring of diesel engines. In this paper, a multivariate statistics-based fault detection approach is proposed to monitor engine faults with weak signatures by taking the correlation of various parameters into consideration. This approach firstly uses principal component analysis (PCA) to project the engine observations into a principal component subspace (PCS) and a residual subspace (RS). Two statistics, i.e., Hotelling&rsquo;s T 2 and Q statistics, are then introduced to detect deviations in the PCS and the RS, respectively. The Hotelling&rsquo;s T 2 and Q statistics are constructed by taking the correlation of various parameters into consideration, so that faults with weak signatures can be effectively detected via these two statistics. In order to reasonably determine the control limits of the statistics, adaptive kernel density estimation (KDE) is utilized to estimate the probability density functions (PDFs) of Hotelling&rsquo;s T 2 and Q statistics. The control limits are accordingly derived from the PDFs by giving a desired confidence level. The proposed approach is demonstrated by using a marine diesel engine. Experimental results show that the proposed approach can effectively detect engine faults with weak signatures

Microstructure, mechanical and corrosion properties of Mg–2Dy–xZn (x=0, 0.1, 0.5 and 1 at.%) alloys

Microstructure, mechanical and corrosion properties of as-cast Mg–2Dy-xZn (x = 0, 0.1, 0.5, and 1) (at.%) alloys were investigated. The microstructures of the as-cast Mg–2Dy and Mg–2Dy–0.1Zn alloys mainly consisted of α-Mg phase and Mg24Dy5 eutectic phase. With 0.5 at.% Zn addition, Mg12ZnDy phase with 18R-type long period stacking ordered (LPSO) structure and Mg2Dy phase precipitated at the grain boundaries. When the content of Zn is 1 at.%, only the Mg3Zn3Dy2 phase formed in the α-Mg matrix. The electrochemical measurements and immersion testing results indicated that the Mg–2Dy–0.1Zn alloy exhibited the best corrosion resistance. It revealed that the morphology, scale, amount and distribution of the second phase have a great effect on the corrosion resistance of alloy. Additionally, the tensile testing results showed that the Mg–2Dy–0.5Zn alloy exhibited the higher tensile strength and good elongation, especially at 200 °C. The improvement of mechanical properties was mainly due to the strengthening of LPSO phase and grain refinement of α-Mg

Vibrations Based Lubricity Condition Monitoring of Journal Bearings

Journal bearings as the important components are widely used in the rotating machinery. Early fault detection and diagnosis of journal bearings have received great more attention to ensure the high efficiency and safety operations. To overcome the shortages of low sensitivity from physical and chemical properties based monitoring, vibro-acoustics monitoring is focused on this study in that it can give real-time indication of tribodynamics of the bearing. In this paper, experimental investigations were carried out to monitor the lubrication regimes of journal bearings under varying loads ranged from 0 bar to 20 bar. Depending on the vibration analysis in the time domain (RMS) and short-time Fourier transform (STFT), the main effect of loads on the lubrication regimes can be found in the low frequency response (100 Hz–1000 Hz). Based on Stribeck curves, experimental results also allows for identifying the critical load under which the lubrication regime changes from full-film to mixed lubrication and even boundary lubrication, therefore, providing critical diagnostic features for online monitoring the lubricity of journal bearings