Dynamic Mechanical Properties of TC11 Titanium Alloys Fabricated by Wire Arc Additive Manufacturing.

To study the compressive mechanical properties and failure modes of TC11 titanium alloy fabricated by wire arc additive manufacturing (WAAM) technology in a large strain rate range at room temperature, the quasi-static and dynamic compression tests were carried out. In addition, optical microscopy (OM) and scanning electron microscopy (SEM) were employed to observe the metallographic structure and fracture morphology, respectively. The stress-strain curves in the range of 0.001 s-1-4000 s-1, original and post-deformation microstructures, macroscopic damage patterns, and microscopic fracture morphology were obtained at two different loading directions, including the scanning and deposition directions, respectively. In uniaxial compression experiments, the material showed little difference in mechanical properties between the scanning and deposition directions, exhibiting a strain rate strengthening effect. However, the strain rate sensitivity of the material under quasi-static loading conditions is much less than that under dynamic loading conditions. In addition, combining the stress-strain curve with the fracture morphology analysis, the plasticity in the scanning direction is better than in the deposition direction. Based on the experimental results, a modified Johnson-Cook (JC) constitutive model considering strain rate sensitivity and the effect of strain rate on strain hardening was proposed, and the parameters were determined using a Multiple Population Genetic Algorithm (MPGA). The obtained constitutive model is in good agreement with the experimental data, which can provide a reference for the engineering numerical calculation of TC11 titanium alloy for WAAM. This study also provides a fundamental databank for the application and design of WAAM TC11 alloy in the manufacturing of large and complex structural parts.

Influences of Extrusion and Silver Content on the Degradation of Mg-Ag Alloys In Vitro and In Vivo.

Binary magnesium-silver (Mg-Ag) alloys were designed as antibacterial materials for biomedical implant applications. In the present study, we focused on the effects of extrusion (extrusion ratio (ER): 1, 7.1, and 72.2) and Ag content (Ag = 0, 3, and 6 wt.%) on the degradation of Mg-Ag alloys in vitro and in vivo via microstructure characterization and corrosion/degradation measurements. The results showed that the Ag promoted a galvanic reaction with the Mg matrix to accelerate degradation or formed a protective oxide mesh texture to inhibit degradation, especially in vivo. Ag might also be beneficial for product crystallization, biomineralization, and organic matter deposition. For pure Mg, extrusion produced a more refined grain and decreased the degradation rate. For the Mg-Ag alloys, a low extrusion ratio (7.1) accelerated the degradation caused by the increase in the proportion of the precipitate. This promoted the release of Mg2+ and Ag+, which led to more deposition of organic matter and calcium phosphate, but also more H2 bubbles, which led to disturbance of product deposition in some local positions or even inflammatory reactions. Extrusion at a higher ratio (72.2) dissolved the precipitates. This resulted in moderate degradation rates and less gas production, which promoted osteogenesis without an obvious inflammation reaction.

Patients with chronic insomnia disorder have increased serum levels of neurofilaments, neuron-specific enolase and S100B: does organic brain damage exist?

OBJECTIVES: The aims of this study were to investigate whether serum levels of neurofilaments heavy chain (NfH) and light chain (NfL), neuron-specific enolase (NSE) and S100 calcium binding protein B (S100B): (1) change, (2) alleviate in post-therapy and (3) are associated with sleep quality and cognitive dysfunction, in patients with chronic insomnia disorder (CID). METHODS: Forty CID outpatients constituted free-therapy group (ft-CID), in which twenty-four patients completed follow-up after six-month treatment to form re-visiting group (rv-CID), and twenty healthy good sleepers constituted control group (HC). All subjects completed questionnaires, polysomnography, Chinese-Beijing Version of Montreal Cognitive Assessment (MoCA-C) and Nine Box Maze Test (NBMT) to assess sleep and neuropsychological function. The serum levels of NfH, NfL, NSE and S100B were detected using enzyme-linked immunosorbent assay. RESULTS: The ft-CID had higher levels of NfH, NfL, NSE and S100B than the HC. Of note, the levels of NfH, NfL and NSE were significantly reduced in the rv-CID compared to the ft-CID, but not the level of S100B. Principal components analysis revealed that in these serum biomarkers, NfL and S100B had a substantial correlation with subjective and objective sleep parameters. CONCLUSIONS: The CID patients had elevated serum levels of NfH, NfL, NSE and S100B, indicating existence of damaged brain microstructure, including neurons, astrocytes and neuronal terminals, which were associated with the insomniac severity or/and cognitive dysfunction and could significantly reduce after effective therapy apart from the S100B.

[Study of mental disorder due to brain damage].

OBJECTIVE: To study the incidence rate, pattern and affective factors of mental disorder due to brain damage. METHODS: According to CCMD-2-R, 388 subjects with traumatic brain damage in the Psychiatric Hospital of Huainan city within last 5 years were assessed by three psychiatrists 6 months to 1 year after brain injury. RESULTS: (1) 74.2% of the mental disordered due to brain injury have intellectual impairment, most of them is mild; (2) The intracranial hematoma, brain stem injury, brain injury extent, GCS, complicated mental disorder, and education have great effect on intellectual impairment; (3) There is an intimate relationship between the intellectual impairment and the brain stem injury, intracranial hematoma, GCS, brain injury extent, and unconsciousness time. There is an intimate relationship between the mental symptom and the brain injury extent, contusion and laceration of brain, frontal lobe injury, and intracranial hematoma. There is also an intimate relationship between the personality change and the frontal lobe injury, unfolding brain case treatment, and intracranial hematoma. CONCLUSION: To assess overall mental disorder should rely on the characteristics of craniocerebral injuries.