Influence of different position modal parameters on milling chatter stability of orthopedic surgery robots

Abstract This research is dedicated to exploring the dynamics of milling chatter stability in orthopedic surgery robots, focusing on the impact of position modal parameters on chatter stability. Initially, we develop a dynamic milling force model for the robotic milling process that integrates both modal coupling and regenerative effects. We then employ the zero-order frequency domain method to derive a chatter stability domain model, visually represented through stability lobe diagrams (SLDs). Through conducting hammer test experiments, we ascertain the robot's modal parameters at varying positions, enabling the precise generation of SLDs. This study also includes experimental validation of the chatter SLD analysis method, laying the groundwork for further examination of chatter stability across different positional modal parameters. Finally, our analysis of the variations in modal parameters on the stability of robot milling chatter yields a theoretical framework for optimizing cutting parameters and developing control strategies within the context of orthopedic surgery robots

Influence of drilling parameters on bone drilling force and temperature by FE simulation and parameters optimization based Taguchi method

During bone drilling surgery, the bone drill can generate drilling force and frictional heat, which may lead to mechanical and thermal damage to the bone tissue. This paper presents a finite element (FE) simulation of bone drilling for cortical and cancellous bone, analyzing the influence of drilling parameters on bone drilling force and temperature. The simulation results reveal the change laws of axial force and temperature during different density bone drilling for various parameters. To optimize the bone drilling parameters, the Taguchi method is applied to conduct bone drilling simulation experiments based on the FE simulation model. The optimal values of axial force and temperature are predicted and calculated under the condition of optimal drilling parameters. Furthermore, a robot bone drilling experiment platform is used to verify the bone drilling FE simulation model and the optimal parameters. The research demonstrates that the FE simulation model effectively explores the influence of drilling parameters on bone drilling force and temperature, while the Taguchi method optimizes the drill parameters to minimize the mechanical and thermal damage to the bone tissue

Surface strengthening and fatigue life improvement of single crystal Ni-based superalloys via laser shock peening without coating

Improving fatigue properties of engineering alloys using conventional laser shock peening (LSP) with protective coating frequently causes surface grain subdivision, which is undesirable for single crystal (SX) superalloys. Herein, an alternative approach, i.e., LSP without coating (LSPwC), is proven to be feasible in the surface strengthening of SX superalloys with preserving its original SX nature. The thermal effect of LSPwC generates a layered heterogeneous near-surface microstructure, comprising a recast layer (∼0.8 μm thick) and a severely deformed layer. Upon rapid remelting process, the recast layer converts to a γ solid solution with its outer layer (∼0.4 μm thick) decorated by densely dispersed Al-rich oxide nanoparticles. Such a particulate-reinforced composite possesses a nanohardness 55% higher than the base metal. The severely deformed layer with denser dislocations in the γ matrix than in the γ′ interior forms a 400 μm-deep work-hardened layer. Under cyclic loads, the near-surface structure still preserves the SX structure with increased stacking faults density in the γ matrix. Despite increased surface roughness, the synergistic action of compressive residual stress, work hardening, and heterogeneous near-surface microstructure prolongs the fatigue life of SX superalloys by ∼36.5%. This work sheds light on the development of novel surface-strengthening techniques for engineering applications

The effect of PACAP administration on LPS-induced cytokine expression in the Atlantic salmon SHK-1 cell line.

Recent work has identified pituitary adenylate cyclase activating polypeptide (PACAP) as a potential antimicrobial and immune stimulating agent which may be suitable for use in aquaculture. However, its effects on teleost immunity are not well studied and may be significantly different than what has been observed in mammals. In this study we examined the effects of PACAP on the Atlantic salmon macrophage cell line SHK-1. PACAP was able to increase the expression of LPS-induced il-1β in at concentrations of 1 uM when administered 24h prior to LPS stimulation. Furthermore, concentrations as low as 40nM had an effect when administered both 24h prior and in tandem with LPS. PACAP was also capable of increasing the expression of il-1β and tnf-α in SHK-1 cells challenged with a low dose of heat-killed Flavobacterium columnare. We attempted to get a better understanding of the mechanism underlying this enhancement of il-1β expression by manipulating downstream signaling of PACAP with inhibitors of phosphodiesterase and phospholipase C activity. We found that inducing cAMP accumulation with phosphodiesterase inhibitors failed to recapitulate the effect of PACAP administration on LPS-mediated il-1β expression by PACAP, while use of a phospholipase C inhibitor caused a PACAP-like enhancement in LPS-mediated il-1β expression. Interestingly, the VPAC1 receptor inhibitor PG97-269, but not the PAC1 inhibitor max.d.4, also was capable of causing a PACAP-like enhancement in LPS-mediated il-1β expression. This suggests that fish do not utilize the PACAP receptors in the same manner as mammals, but that it still exerts an immunostimulatory effect that make it a good immunostimulant for use in aquaculture

Effect of the Mixing on the Dielectric Constant of Poly(vinylidene fluoride)/Isotactic Polypropylene Blends

International audienceIn this work, the effect of a mixing process on the dielectric constant (epsilon) of a typical immiscible blend, poly(vinylidene fluoride) (PVDF)/isotactic polypropylene (iPP), is investigated. An iPP with a relatively low epsilon (ca. 3.4) is added to a PVDF matrix with a relatively high epsilon (ca. 9.5) to reduce the 8 of the system. The blend has a narrow window of cocontinuity (volume fraction of iPP (v(iPP)) of ca. 50-80 vol%). All of the measured epsilon values for the blends lie within the two limits defined by the parallel alignment and series alignment models, which are the upper and lower limits, respectively. It is found that for blends with v(iPP) of ca. 39.7 vol%, for which PVDF is the continuous matrix and iPP is the dispersed phase, prolonging mixing time and adding compatibilizer cause a monotonic decrease of epsilon for the system, which can be attributed to the increasing dispersion of the low-epsilon iPP filler in the high-epsilon PVDF matrix. Based on these results, a strategy to tune the epsilon of polymer blends and composites is discussed. It is suggested that architecture similar to a series alignment will favor the decrease of epsilon, while architecture similar to a parallel alignment will favor the increase of epsilon

Ultrasound-induced structural changes of different milk fat globule membrane protein-phospholipids complexes and their effects on physicochemical and functional properties of emulsions

Ultrasonic technology is a non-isothermal processing technology that can be used to modify the physicochemical properties of food ingredients. This study investigated the effects of ultrasonic time (5 min, 10 min, 15 min) and power (150 W,300 W,500 W) on the structural properties of three types of phospholipids composed of different fatty acids (milk fat globule membrane phospholipid (MPL), egg yolk lecithin (EYL), soybean lecithin (SL)) and milk fat globule membrane protein (MFGMP). We found that the ultrasound treatment changed the conformation of the protein, and the emulsions prepared by the pretreatment showed better emulsification and stability, the lipid droplets were also more evenly distributed. Meanwhile, the flocculation phenomenon of the lipid droplets was significantly improved compared with the non-ultrasonic emulsions. Compared with the three complexes, it was found that ultrasound had the most significant effect on the properties of MPL-MFGMP, and its emulsion state was the most stable. When the ultrasonic condition was 300 W, the particle size of the emulsion decreased significantly (from 441.50 ± 4.79 nm to 321.77 ± 9.91 nm) at 15 min, and the physical stability constants KE decreased from 14.49 ± 0.702 % to 9.4 ± 0.261 %. It can be seen that proper ultrasonic pretreatment can effectively improve the stability of the system. At the same time, the emulsification performance of the emulsion had also been significantly improved. While the accumulation phenomenon occurred when the ultrasonic power was 150 W and 500 W. These results showed that ultrasonic pretreatment had great potential to improve the properties of emulsions, and this study would provide a theoretical basis for the application of emulsifier in the emulsions

Lipidomic Profiling Reveals Distinct Differences in Sphingolipids Metabolic Pathway between Healthy Apis cerana cerana larvae and Chinese Sacbrood Disease

Chinese sacbrood disease (CSD), which is caused by Chinese sacbrood virus (CSBV), is a major viral disease in Apis cerana cerana larvae. Analysis of lipid composition is critical to the study of CSBV replication. The host lipidome profiling during CSBV infection has not been conducted. This paper identified the lipidome of the CSBV–larvae interaction through high-resolution mass spectrometry. A total of 2164 lipids were detected and divided into 20 categories. Comparison of lipidome between healthy and CSBV infected-larvae showed that 266 lipid species were altered by CSBV infection. Furthermore, qRT-PCR showed that various sphingolipid enzymes and the contents of sphingolipids in the larvae were increased, indicating that sphingolipids may be important for CSBV infection. Importantly, Cer (d14:1 + hO/21:0 + O), DG (41:0e), PE (18:0e/18:3), SM (d20:0/19:1), SM (d37:1), TG (16:0/18:1/18:3), TG (18:1/20:4/21:0) and TG (43:7) were significantly altered in both CSBV_24 h vs. CK_24 h and CSBV_48 h vs. CK_48 h. Moreover, TG (39:6), which was increased by more than 10-fold, could be used as a biomarker for the early detection of CSD. This study provides evidence that global lipidome homeostasis in A. c. cerana larvae is remodeled after CSBV infection. Detailed studies in the future may improve the understanding of the relationship between the sphingolipid pathway and CSBV replication

Case report: A novel PTCH1 frameshift mutation leading to nevoid basal cell carcinoma syndrome

A patient presenting with several basal cell carcinomas, pigmented nevi, and developmental defects was diagnosed with nevoid basal cell carcinoma syndrome. Gene panel sequencing and Sanger sequencing were used to identify a novel heterozygous frameshift mutation, c.1312dupA:p.Ser438Lysfs, in exon 9 of PTCH1. I-Tasser and PyMol analyses indicated that the mutated protein patched homolog 1 (PTCH1) lacked 12 transmembrane domains and the intracellular and extracellular rings of ECD2 compared with the wild-type protein, resulting in a remarkably different structure from that of the wild-type protein. This case extends our knowledge of the mutation spectrum of NBCCS