Three-dimensional modeling and simulation of muscle tissue puncture process

Needle biopsy is an essential part of modern clinical medicine. The puncture accuracy and sampling success rate of puncture surgery can be effectively improved through virtual surgery. There are few three-dimensional puncture (3D) models, which have little significance for surgical guidance under complicated conditions and restrict the development of virtual surgery. In this paper, a 3D simulation of the muscle tissue puncture process is studied. Firstly, the mechanical properties of muscle tissue are measured. The Mooney-Rivlin (M-R) model is selected by considering the fitting accuracy and calculation speed. Subsequently, an accurate 3D dynamic puncture model is established. The failure criterion is used to define the breaking characteristics of the muscle, and the bilinear cohesion model defines the breaking process. Experiments with different puncture speeds are carried out through the built in vitro puncture platform. The experimental results are compared with the simulation results. The experimental and simulated reaction force curves are highly consistent, which verifies the accuracy of the model. Finally, the model under different parameters is studied. The simulation results of varying puncture depths and puncture speeds are analyzed. The 3D puncture model can provide more accurate model support for virtual surgery and help improve the success rate of puncture surgery

Association between long-term exposure to fine particulate matter constituents and progression of cerebral blood flow velocity in Beijing: Modifying effect of greenness

Few studies have explored the effects of fine particulate matter (PM2.5) and its constituents on the progression of cerebral blood flow velocity (BFV) and the potential modifying role of greenness. In this study, we investigated the association of PM2.5 and its constituents, including sulfate (SO42−), nitrate (NO3−), ammonium (NH4+), organic matter (OM), and black carbon (BC), with the progression of BFV in the middle cerebral artery. Participants from the Beijing Health Management Cohort who underwent at least two transcranial Doppler sonography examinations during 2015–2020 were recruited. BFV change and BFV change rate were used to define the progression of cerebral BFV. Linear mixed effects models were employed to analyze the data, and the weighted quantile sum regression assessed the contribution of PM2.5 constituents. Additionally, greenness was examined as a modifier. Among the examined constituents, OM exhibited the strongest association with BFV progression. An interquartile range increase in PM2.5 and OM exposure concentrations was associated with a decrease of −16.519 cm/s (95% CI: −17.837, −15.201) and −15.403 cm/s (95% CI: −16.681, −14.126) in BFV change, and −10.369 cm/s/year (95% CI: −11.387, −9.352) and −9.615 cm/s/year (95% CI: −10.599, −8.632) in BFV change rate, respectively. Furthermore, stronger associations between PM2.5 and BFV progression were observed in individuals working in areas with lower greenness, those aged under 45 years, and females. In conclusion, reducing PM2.5 levels in the air, particularly the OM constituent, and enhancing greenness could potentially contribute to the protection of cerebrovascular health

Periodontal therapy for primary or secondary prevention of cardiovascular disease in people with periodontitis

Background There may be an association between periodontitis and cardiovascular disease (CVD); however, the evidence so far has been uncertain about whether periodontal therapy can help prevent CVD in people diagnosed with chronic periodontitis. This is the second update of a review originally published in 2014, and first updated in 2017. Although there is a new multidimensional staging and grading system for periodontitis, we have retained the label 'chronic periodontitis' in this version of the review since available studies are based on the previous classification system. Objectives To investigate the effects of periodontal therapy for primary or secondary prevention of CVD in people with chronic periodontitis. Search methods Cochrane Oral Health's Information Specialist searched the Cochrane Oral Health's Trials Register, CENTRAL, MEDLINE, Embase, and CINAHL, two trials registries, and the grey literature to September 2019. We placed no restrictions on the language or date of publication. We also searched the Chinese BioMedical Literature Database, the China National Knowledge Infrastructure, the VIP database, and Sciencepaper Online to August 2019. Selection criteria We included randomised controlled trials (RCTs) that compared active periodontal therapy to no periodontal treatment or a different periodontal treatment. We included studies of participants with a diagnosis of chronic periodontitis, either with CVD (secondary prevention studies) or without CVD (primary prevention studies). Data collection and analysis Two review authors carried out the study identification, data extraction, and 'Risk of bias' assessment independently and in duplicate. They resolved any discrepancies by discussion, or with a third review author. We adopted a formal pilot‐tested data extraction form, and used the Cochrane tool to assess the risk of bias in the studies. We used GRADE criteria to assess the certainty of the evidence. Main results We included two RCTs in the review. One study focused on the primary prevention of CVD, and the other addressed secondary prevention. We evaluated both as being at high risk of bias. Our primary outcomes of interest were death (all‐cause and CVD‐related) and all cardiovascular events, measured at one‐year follow‐up or longer. For primary prevention of CVD in participants with periodontitis and metabolic syndrome, one study (165 participants) provided very low‐certainty evidence. There was only one death in the study; we were unable to determine whether scaling and root planning plus amoxicillin and metronidazole could reduce incidence of all‐cause death (Peto odds ratio (OR) 7.48, 95% confidence interval (CI) 0.15 to 376.98), or all CVD‐related death (Peto OR 7.48, 95% CI 0.15 to 376.98). We could not exclude the possibility that scaling and root planning plus amoxicillin and metronidazole could increase cardiovascular events (Peto OR 7.77, 95% CI 1.07 to 56.1) compared with supragingival scaling measured at 12‐month follow‐up. For secondary prevention of CVD, one pilot study randomised 303 participants to receive scaling and root planning plus oral hygiene instruction (periodontal treatment) or oral hygiene instruction plus a copy of radiographs and recommendation to follow‐up with a dentist (community care). As cardiovascular events had been measured for different time periods of between 6 and 25 months, and only 37 participants were available with at least one‐year follow‐up, we did not consider the data to be sufficiently robust for inclusion in this review. The study did not evaluate all‐cause death and all CVD‐related death. We are unable to draw any conclusions about the effects of periodontal therapy on secondary prevention of CVD. Authors' conclusions For primary prevention of cardiovascular disease (CVD) in people diagnosed with periodontitis and metabolic syndrome, very low‐certainty evidence was inconclusive about the effects of scaling and root planning plus antibiotics compared to supragingival scaling. There is no reliable evidence available regarding secondary prevention of CVD in people diagnosed with chronic periodontitis and CVD. Further trials are needed to reach conclusions about whether treatment for periodontal disease can help prevent occurrence or recurrence of CVD

Episodes of single-crystal material removal mode and machinability in the micro-cutting process of superalloy Inconel-718

The development tendency of miniaturization gives birth to the demand for Inconel-718 miniature parts, and micro-cutting is a promising technique to produce crystalline material miniature parts. Unfortunately, due to the non-negligible edge radius and property anisotropy, the material deformation behaviour and removal mode vary with cutting conditions, resulting in volatile machinability and inferior quality, which hinders the widespread application of Inconel-718 miniature parts. Therefore, it is urgent to clarify the evolution of material removal mode and machinability of Inconel-718 micro-cutting. Existing researches fail to consider the property anisotropy, strain-rate sensitivity and strain-rate inhomogeneity. This paper establishes strain rate-considered single-crystal micro-cutting models and performs simulations under varying cutting conditions, aiming to depict the episodes of material removal mode and machinability of Inconel-718 micro-cutting. Results show that, uncut chip thickness and cutter rake angle influence the material removal mode, and in turn influence machinability. For Inconel-718 single-crystal with [0° 0° 0°] orientation, the transition from the scratching mode to the ploughing mode is in the uncut chip thickness range of 0.2Re∼0.4Re, and the transition from the ploughing mode to the cutting mode is in the uncut chip thickness range of 0.6Re∼0.8Re or the rake angle range of −30°∼-15°. In comparison, cutting speed and clearance angle have little effect on material removal mode. Cutting speed influences the strain rate of the cutting-affected zone, and in turn influences machinability. The maximum strain rate of the cutting-affected zone is respectively around 0.45 s−1 and 10,960 s−1 under the cutting speeds of 2Re/s and 20000Re/s