Cooling and Crack Suppression of Bone Material Drilling Based on Microtextured Bit Modeled on Dung Beetle

In recent years, the number of patients with orthopedic diseases such as cervical spondylosis has increased, resulting in an increase in the demand for orthopedic surgery. However, thermal necrosis and bone cracks caused by surgery severely restrict the development and progression of orthopedic surgery. For the material of cutting tool processing bone in bone surgery of drilling high temperature lead to cell death, easy to produce the problem such as crack cause secondary damage effects to restore, in this paper, a bionic drill was designed based on the micro-structure of the dung beetle’s head and back. The microstructure configuration parameters were optimized by numerical analysis, and making use of the optical fiber laser marking machine preparation of bionic bit; through drilling test, the mathematical model of drilling temperature and crack generation based on micro-structure characteristic parameters was established by infrared thermal imaging technology and acoustic emission signal technology, and the cooling mechanism and crack suppression strategy were studied. The experimental results show that when the speed is 60 m/min, the cooling effects of the bionic bit T1 and T2 are 15.31% and 19.78%, respectively, and both kinds of bits show obvious crack suppression effect. The research in this paper provides a new idea for precision and efficient machining of bone materials, and the research results will help to improve the design and manufacturing technology and theoretical research level in the field of bone drilling tools

Calcium-magnesium-alumino-silicate induced degradation of La2(Zr0.7Ce0.3)2O7/YSZ double-ceramic–layer thermal barrier coatings prepared by electron beam-physical vapor deposition

During last decades, much effort has been made to develop new alternative thermal barrier coating (TBC) to traditional YSZ for applications above 1250oC. La2(Zr0.7Ce0.3)2O7(LZ7C3) is deemed as a very promising TBC candidate for advanced gas turbine because of its extremely low thermal conductivity, high sintering resistance and phase stability from room temperature to 1600oC. Thermal cycling with a gas burner showed that the LZ7C3/YSZ double-ceramic-layer (DCL) coatings prepared by electron beam-physical vapor deposition (EB-PVD) or atmospheric plasma spraying had a much longer lifetime than that of YSZ coating at 1250± 50oC.The use of the new TBC can allow higher gas temperatures, resulting in further improved thermal efficiency and engine performance. However, at these high operating temperatures, TBCs become susceptible to attack by calcium-magnesium-alumino-silicate (CMAS, relative to the main chemical components Ca, Mg, Al and Si) deposits resulting from the ingestion of siliceous minerals (dust, sand, volcanic ash, runway debris) with the intake air. CMAS becomes molten at temperatures above 1200oC and then rapidly penetrates the TBCs by capillary force, resulting in the loss of strain tolerance and premature failure of the coatings. In this paper, CMAS induced degradation of LZ7C3/YSZ DCL coatings prepared by EB-PVD method were investigated. Hot corrosion tests were performed at 1250oC at durations varying from 0.5 h to 24 h. It is observed that the infiltration of CMAS in the intercolumnar gaps was largely suppressed in the case of EB-PVD LZ7C3 coating. The penetration depth rarely exceeded 40 μm below the original surface even after 24 h exposure at 1250oC. This was ascribed to rapid dissolution of the LZ7C3 and essentially concurrent formation of a sealing layer made of crystalline apatite and fluorite phases, which is consistent with the observation on Gd2Zr2O7. However, large vertical cracks would form in the EB-PVD LZ7C3 coating during thermal cycling as a result of re-crystallization, sintering and thermal expansion mismatch between ceramic coating and substrate. These vertical cracks can also act as channels to CMAS melt infiltration. Since the kinetics of the dissolve-reprecipitation reaction was slower than the infiltration rate of CMAS in the vertical crack, the majority of vertical cracks were not sealed. As a result, CMAS flowed down to the LZ7C3/YSZ interface along the vertical cracks, and then easily penetrated the YSZ buffer layer by capillary force. Chemical interaction also occurred in the YSZ buffer layer. What\u27s more, the YSZ layer in the DCL coating even underwent a severer CMAS attack than the single YSZ coating. After 4 h CMAS exposure, the YSZ layer of the LZ7C3/YSZ bilayer coating was totally dissolved by molten CMAS followed by precipitation of a large number of globular ZrO2 particles, while the single YSZ coating just suffered a slight degradation in the same experimental conditions and still kept its columnar structure. The probable reason was that the CMAS melt in the YSZ layer of the DCL coating had a higher CaO/SiO2 ration than the original CMAS composition due to the formation of apatite phase when CMAS reacted with the upper LZ7C3 layer. The initial Si: Ca ratio (Si: Ca≈1.4) in CMAS melt is less than the corresponding apatite (Si: Ca≈3), leading to progressive CaO enrichment during apatite crystallization. For this reason, it is suggested that the effectiveness of the CMAS mitigation strategy for YSZ TBCs by adopting a so-called CMAS-resistant top layer needs to be assessed in the context of more realistic conditions. If the formation of large vertical cracks in TBCs was not avoided, this CMAS mitigation approach may not as effective as expected

Sex-Based Differences in Age-Related Changes of the Vertebral Column from a Bronze Age Urban Population in Ancient China

The health disparities between males and females in bioarchaeological settings are important indicators of gender-based differences in socioeconomic roles. In this study, sex-based differences of the vertebral column in spine pathology were investigated in human skeletons excavated from a Bronze Age cemetery of the Western Zhou Dynasty at the Dahekou site in Shanxi, China. Results demonstrated that females had a higher prevalence of vertebral compressive fractures, with the majority found in those between twenty-five and thirty years old, suggesting that the fractures were a consequence of osteoporosis and its early onset in females. In contrast, males expressed overall more severe ageing in all vertebral divisions compared to females. Males also had a higher prevalence of vertebral facet joint osteoarthritis in cervical and thoracic divisions than females. Likewise, the incidence of facet joint osteoarthritis was more asymmetric between the left and right joints in males than in females. These findings reflect disparities of vertebral health between the two sexes in an urban setting, in which ageing and injuries of the vertebral column might be driven by different mechanisms. Age-related changes in female vertebral columns may have been more influenced by conditions of hormone deficiency such as menopause, while male vertebral columns might have been more prone to age-related changes due to heavy labor-induced physical stressors. Further studies on the differentiation of ageing mechanisms between the two sexes based on physiology, socioeconomic roles, and living conditions are warranted. The studies are necessary in understanding how multiple sociocultural and physiological factors contribute to health disparities in historic and contemporary environments

Tailoring the plasticity of topologically close-packed phases via the crystals' fundamental building blocks

Brittle topologically close-packed precipitates form in many advanced alloys. Due to their complex structures little is known about their plasticity. Here, we present a strategy to understand and tailor the deformability of these complex phases by considering the Nb-Co {\mu}-phase as an archetypal material. The plasticity of the Nb-Co {\mu}-phase is controlled by the Laves phase building block that forms parts of its unit cell. We find that between the bulk C15-NbCo$_2$ Laves and Nb-Co {\mu}-phase, the interplanar spacing and local elastic modulus of the Laves phase building block change, leading to a strong reduction in hardness and elastic modulus, as well as a transition from synchroshear to crystallographic slip. Furthermore, as the composition changes from Nb$_6$Co$_7$ to Nb$_7$Co$_6$, the Co atoms in the triple layer are substituted such that the triple layer of the Laves phase building block becomes a slab of pure Nb, resulting in inhomogeneous changes in elasticity and a transition from crystallographic slip to a glide-and-shuffle mechanism. These findings open opportunities to purposefully tailor the plasticity of these topologically close-packed phases in bulk, but at the atomic scale of interplanar spacing and local shear modulus of the fundamental crystal building blocks in their large unit cells

Phenotypic Plasticity of Staphylococcus aureus in Liquid Medium Containing Vancomycin

Phenotypic plasticity enables individuals to develop different phenotypes in a changing environment and promotes adaptive evolution. Genome-wide association study (GWAS) facilitates the study of the genetic basis of bacterial phenotypes, and provides a new opportunity for bacterial phenotypic plasticity research. To investigate the relationship between growth plasticity and genotype in bacteria, 41 Staphylococcus aureus strains, including 29 vancomycin-intermediate S. aureus (VISA) strains, were inoculated in the absence or presence of vancomycin for 48 h. Growth curves and maximum growth rates revealed that strains with the same minimum inhibitory concentration (MIC) showed different levels of plasticity in response to vancomycin. A bivariate GWAS was performed to map single-nucleotide polymorphisms (SNPs) associated with growth plasticity. In total, 227 SNPs were identified from 14 time points, while 15 high-frequency SNPs were mapped to different annotated genes. The P-values and growth variations between the two cultures suggest that non-coding region (SNP 738836), ebh (SNP 1394043), drug transporter (SNP 264897), and pepV (SNP 1775112) play important roles in the growth plasticity of S. aureus. Our study provides an alternative strategy for dissecting the adaptive growth of S. aureus in vancomycin and highlights the feasibility of bivariate GWAS in bacterial phenotypic plasticity research

NEDD9 Facilitates Hypoxia-Induced Gastric Cancer Cell Migration via MICAL1 Related Rac1 Activation

Aims and Hypothesis: NEDD9 is highly expressed in gastric cancer and has a significant involvement in its pathogenesis. However, the mechanism behind hypoxia-promoted cancer cell migration and its regulation because of NEDD9 is still unknown. The aim of this study is to investigate the involvement of NEDD9 in gastric cancer cell migration under hypoxia and explore the underlying potential molecular mechanisms.MethodsCell motility was measured by wound healing and transwell assay. NEDD9 and MICAL1 expressions were examined by western blot analysis. Interaction between NEDD9 and MICAL1 was assessed by immunohistochemistry and co-immunoprecipitation assay, respectively. Cells were transfected with plasmids or siRNA to upregulate or downregulate the expression of NEDD9 and MICAL1. Rac1, Cdc42, and RhoA activation was assessed by pulldown assay.ResultsThe mRNA and protein level of NEDD9 increased as a result of hypoxia in gastric cancer cell lines BGC-823 and SGC-7901 while decreased levels of NEDD9 caused reduced cell migratory potential in response to hypoxia. Hypoxia also caused the enhancement of MICAL1 expression. Furthermore, it was revealed that there is a positive correlation between NEDD9 and MICAL1 protein while hypoxia played role in increasing their interaction. Under hypoxic conditions, silencing of NEDD9 caused reduction in the stability of MICAL1 protein, while depletion of MICAL1 also inhibited the migration of NEDD9-overexpressing gastric cancer cells. In addition, silencing of NEDD9 or MICAL1 expression reversed the increased GTP forms of Rac1 and Cdc42 in hypoxic cells. However, only the upregulation of Rac1-GTP level was observed in gastric cancer cells that were already overexpressed by MICAL1.ConclusionIn all, it is concluded that MICAL1 is regulated by NEDD9 that facilitates hypoxia-induced gastric cancer cell migration via Rac1-dependent manner

OmniForce: On Human-Centered, Large Model Empowered and Cloud-Edge Collaborative AutoML System

Automated machine learning (AutoML) seeks to build ML models with minimal human effort. While considerable research has been conducted in the area of AutoML in general, aiming to take humans out of the loop when building artificial intelligence (AI) applications, scant literature has focused on how AutoML works well in open-environment scenarios such as the process of training and updating large models, industrial supply chains or the industrial metaverse, where people often face open-loop problems during the search process: they must continuously collect data, update data and models, satisfy the requirements of the development and deployment environment, support massive devices, modify evaluation metrics, etc. Addressing the open-environment issue with pure data-driven approaches requires considerable data, computing resources, and effort from dedicated data engineers, making current AutoML systems and platforms inefficient and computationally intractable. Human-computer interaction is a practical and feasible way to tackle the problem of open-environment AI. In this paper, we introduce OmniForce, a human-centered AutoML (HAML) system that yields both human-assisted ML and ML-assisted human techniques, to put an AutoML system into practice and build adaptive AI in open-environment scenarios. Specifically, we present OmniForce in terms of ML version management; pipeline-driven development and deployment collaborations; a flexible search strategy framework; and widely provisioned and crowdsourced application algorithms, including large models. Furthermore, the (large) models constructed by OmniForce can be automatically turned into remote services in a few minutes; this process is dubbed model as a service (MaaS). Experimental results obtained in multiple search spaces and real-world use cases demonstrate the efficacy and efficiency of OmniForce