Design and preparation of an artificial vascular scaffold with internal surface modification.

BACKGROUND: Advances in regeneration methods have brought us improved vascular scaffolds with small diameters (φ < 6 mm) for enhancing biological suitability that solve their propensity for causing intimal hyperplasia post-transplantation. METHODS: The correlation between the rehydration ratio of the hydrogel and its material concentration is obtained by adjusting the material ratio of the hydrogel solution. The vascular model with helical structure has been established and analyzed to verify the effect of helical microvascular structure on thrombosis formation by the fluid simulation methods. Then, the helical structure vascular has been fabricated by self-developed 3D bioprinter, the vascular scaffolds are freeze-dried and rehydrated in polyethylene glycol (PEG) solution. RESULTS: The experimental results showed that the hybrid hydrogel had a qualified rehydration ratio when the content of gelatin, sodium alginate, and glycerol was 5, 6, and 3 wt%. The established flow channel model can effectively reduce thrombus deposition and improve long-term patency ratio. After PEG solution modification, the contact angle of the inner wall of the vascular scaffold was less than 30°, showing better hydrophilic characteristics. CONCLUSION: In study, a small-diameter inner wall vascular scaffold with better long-term patency was successfully designed and prepared by wrinkling and PEG modification of the inner wall of the vascular scaffold. This study not only creates small-diameter vascular scaffolds with helical structure that improves the surface hydrophilicity to reduce the risk of thrombosis but also rekindles confidence in the regeneration of small caliber vascular structures.

Pharmacokinetics, withdrawal period and risk assessment of enrofloxacin in the northern snakehead (Channa argus) following bath administration.

Enrofloxacin (ENR) is widely used in aquaculture practice, but little is known about its pharmacokinetic, withdrawal period and dietary risk in fish via bath administration. The purpose of this study was to provide data support for the use of ENR bath therapy in the northern snakehead (Channa argus). The pilot study was carried out to evaluate the therapy concentrations of ENR in northern snakehead with immersion concentrations ranged from 5 to 40 mg/L for 6 h. Based on results of the pilot study, an ENR immersion concentration of 20 mg/L was used for the formal experiment. At this dose, the peak concentrations of ENR in plasma, muscle plus skin, liver and kidney were 4.85, 4.55, 3.87 and 7.42 µg/mL (or g), respectively. According to the AUC0-∞ values, the distribution of ENR in northern snakehead followed the order of kidney > plasma > liver > muscle + skin. The elimination of ENR in northern snakehead was very slow, the half-lives (T1/2λz ) were up to 90.31, 85.5, 104.56 and 120.9 h in plasma, muscle plus skin, liver and kidney, respectively. Ciprofloxacin (CIP) was not detected in any samples in the pilot study and was only occasionally detected in muscle plus skin and liver samples in formal experiment. Based on the calculated PK/PD index AUC/MIC and Cmax /MIC, the current bath treatment regimen will have a good therapeutic effect on infections caused by bacteria with MIC below 0.6 µg/mL. The dietary risk assessment suggested that there was a dietary risk (Hazard Quotients > 10%) until day 6 after bath treatment. It is mandatory for ENR to maintain a withdrawal period of at least 450°C-day in northern snakehead after bath treatment ceased.

No Difference Unicompartmental Knee Arthroplasty for Medial Knee Osteoarthritis With or Without Anterior Cruciate Ligament Deficiency: A Systematic Review and Meta-analysis.

BACKGROUND: A functional intact anterior cruciate ligament (ACLI) is considered to be a prerequisite for unicompartmental knee arthroplasty (UKA). However, UKA has been shown to have good clinical efficacy in ACL-deficient (ACLD) knees at 3 to 10 years follow-up. Therefore, the role of ACLD in UKA remains controversial, and more evidence is needed to clarify the role of ACLD in UKA. METHODS: PubMed, the Web of Science, EMBASE, and Cochrane Central were queried for articles comparing the results of the ACLD and ACLI groups after UKA. Outcomes of interest included the Tegner Activity Scale, the Oxford Knee Score (OKS), postoperative slope of the implant (PSI), the Knee Injury and Osteoarthritis Outcomes Score (KOOS), the Lysholm score, and revision rate. There were eight studies included. The mean age was 66 years (range 49 to 87 year old) and the mean follow-up time was 6.9 years (range 1.3 to 16.6 years). There was baseline comparability regarding mean age, duration of follow-up, and body mass index (P > .5) between the ACLD and ACLI groups. RESULTS: The ACLD and ACLI groups had improved postoperative functional indicators, and that postoperative revision rate (mean difference [MD], 1.24; 95% confidence interval [CI], 0.75 to 2.04; P = .4), Tegner score (MD, -0.1; 95% CI, -0.26 to 0.05; P = .19), and Lysholm score (95% CI, -2.46 to 7.32; P = .33) were similar between the groups, with no significant differences; however, the ACLD groups had significantly better KOOS Activities of Daily Living scores, with a significant difference (MD, 4.53; 95% CI, 1.75 to 7.3; P = .001). Also, there were no significant differences between two groups in the PSI, OKS, KOOS. CONCLUSION: ACL deficiency is not always a contraindication for UKA. With correct patient selection, UKA could be considered for medial knee osteoarthritis with ACL deficiency without antero-posterior instability, especially these people over 60 years of age.

The toxicokinetics and risk assessment of pyrethroids pesticide in tilapia (Oreochromis mossambicus) upon short-term water exposure.

Pyrethroids pesticides (PPs) are the widely adopted synthetic pesticides for agriculture and fishery. The frequent use of these pesticides leads to the accumulation of residues in the freshwater environments in China, subsequently affecting aquatic organisms and ecosystems. However, there are few reports on the toxicological and risk assessment of aquaculture aquatic products. In this study, the uptake, depuration kinetics and potential risk to human health and ecology of fenpropathrin, cypermethrin, fenvalerate, and deltamethrin were assessed using tilapia. The results indicated that four PPs were readily accumulated by tilapia. The bioconcentration factors (BCF) of the PPs in plasma and muscle were between 71.3 and 2112.1 L/kg and 23.9-295.3 L/kg, respectively. The half-lives (t1/2) of muscle and plasma were 2.90-9.20 d and 2.57-8.15 d. The risks of PPs residues in the muscle of tilapia and exposed water were evaluated by hazard quotient (HQ) and risk quotient (RQ). Although PPs residues in tilapia had a low dietary risk to human health, the residues in the exposed water had a high ecological risk to fish, daphnia, and green algae. Therefore, assessing the PPs content in freshwater aquaculture and monitoring their dosages and frequencies are highly necessitated to avoid their adverse effect on the aquaculture environment.

Effect of Hydrogel Contact Angle on Wall Thickness of Artificial Blood Vessel.

Vascular replacement is one of the most effective tools to solve cardiovascular diseases, but due to the limitations of autologous transplantation, size mismatch, etc., the blood vessels for replacement are often in short supply. The emergence of artificial blood vessels with 3D bioprinting has been expected to solve this problem. Blood vessel prosthesis plays an important role in the field of cardiovascular medical materials. However, a small-diameter blood vessel prosthesis (diameter < 6 mm) is still unable to achieve wide clinical application. In this paper, a response surface analysis was firstly utilized to obtain the relationship between the contact angle and the gelatin/sodium alginate mixed hydrogel solution at different temperatures and mass percentages. Then, the self-developed 3D bioprinter was used to obtain the optimal printing spacing under different conditions through row spacing, printing, and verifying the relationship between the contact angle and the printing thickness. Finally, the relationship between the blood vessel wall thickness and the contact angle was obtained by biofabrication with 3D bioprinting, which can also confirm the controllability of the vascular membrane thickness molding. It lays a foundation for the following study of the small caliber blood vessel printing molding experiment.

Clinical Evaluation a New Treatment for Infection After Ventriculoperitoneal Shunt.

ABSTRACT: To explore a new surgical treatment for infection and obstruction of ventriculoperitoneal shunt in hydrocephalus. Two cases of post-operative infection of ventriculoperitoneal shunt were analyzed retrospectively. One case was cryptococcal infection, the other case was Acinetobacter lwoffii. The number of cerebrospinal fluid cells was high, the infection of ventriculoperitoneal shunt was generally complicated with abdominal obstruction, and the hydrocephalus was aggravated again, The authors try to pull out the drainage tube at the end of abdominal cavity for external drainage, combined with intravenous antibiotics, completely control of infection, and then use the original shunt device for intraventricular jugular shunt. The authors explore that this method is simple, safe and effective, and it is an effective and feasible method for the treatment of infection after ventriculoperitoneal shunt.

Pharmacokinetics and tissue residues of enrofloxacin in the largemouth bass (Micropterus salmoides) after oral administration.

The study was carried out to evaluate the pharmacokinetic disposition of enrofloxacin (ENF) with a single dose of 20 mg/kg after oral administration in largemouth bass (Micropterus salmoides) at 28°C. The concentrations of ENF and of its metabolite ciprofloxacin (CIP) in plasma, liver, and muscle plus skin in natural proportions were determined using HPLC. The concentration-time data for ENF in plasma were best described by a two-compartment open model. After oral administration, the maximum ENF concentration (Cmax ) of 10.99 µg/ml was obtained at 0.60 hr. The absorption half-life (T1/2Ka ) of ENF was calculated to be 0.07 hr whereas the elimination half-life (T1/2ß ) of the drug was 90.79 hr. The estimates of area under the plasma concentration-time curve (AUC) and apparent volume of distribution (Vd/F) were 1,185.73 µg hr/ml and 2.21 L/kg, respectively. ENF residues were slowly depleted from the liver and muscle plus skin of largemouth bass with the T1/2ß of 124.73 and 115.14 hr, respectively. Very low levels of ciprofloxacin were detected in the plasma and tissues. A withdrawal time of 24 days was necessary to ensure that the residues of ENF + CIP in muscle plus skin were less than the maximal residue limit (MRL) of 100 µg/kg established by the European Union.

Pharmacokinetic/pharmacodynamic relationship of enrofloxacin against Aeromonas hydrophila in crucian carp (Carassius auratus gibelio).

The pharmacokinetic (PK) properties of enrofloxacin (ENR) and its metabolite ciprofloxacin (CIP) were investigated in crucian carp following oral administration at different dose levels (5, 10, 20, 40 mg/kg body weight). The disposition kinetics of ENR was found to be linear over the dose range studied. Serum half-lives ranged from 64.56 to 72.68 hr. The in vitro and ex vivo activities of ENR in serum against a pathogenic strain of Aeromonas hydrophila were determined. In vitro and ex vivo bactericidal activity of ENR was concentration dependent. Dosing of 10 mg/kg resulted in an AUC/minimum inhibitory concentration (MIC) ratio of 368.92 hr and a Cmax /MIC ratio of 7.23, respectively, against A. hydrophila 147 (MIC = 0.48 µg/ml), indicating a likely high level of effectiveness in clinical infections caused by A. hydrophila with MIC value ≤ 0.48 µg/ml. Modeling of ex vivo growth inhibition data to the sigmoid Emax equation provided the values of AUC24 hr /MIC required to produce bacteriostasis, bactericidal activity, and elimination of bacteria, these values were 21.70, 53.01, and 125.21 hr, respectively. These findings in conjunction with MIC90 data suggested that ENR at the dose of 7.81 mg/kg predicted a positive clinical outcome and minimize the risk of emergence of resistance.

Investigation of the interaction between the fate of antibiotics in aquafarms and their level in the environment.

China is the largest freshwater aquaculture producer and antibiotics consumer in the world, and rivers in China are generally polluted by antibiotics. However, there is little information available regarding the linkage of antibiotics in aquaculture and the aquatic environment. Therefore, this study investigated the fate of antibiotics in several open water culture-based freshwater aquafarms, including integrated livestock/fish systems and non-integrated fish ponds, and explored the contamination profiles of antibiotics in the Beijiang River. Then the study tried to clarify the two-way interaction of antibiotics in aquaculture and the environment. The results showed that, when compared with the effluent from livestock farms and wastewater treatment plants, the contribution of antibiotics from non-integrated fish pond water without livestock sewage input was limited, while that of effluent from the integrated livestock/fish system was quite high. The total concentrations of antibiotics detected in the aquafarm source water were similar to those in the upper river water and generally higher than those in the corresponding fish pond water, implying that the occurrence of antibiotics in intensive aquafarms can mainly be attributed to the antibiotic residues in nearby river water. Overall, the results underscore the need to develop a sewage infrastructure for the treatment of effluent from integrated livestock/fish aquafarms, and suggest that open water culture-based fish farms should be located far from seriously contaminated sections of rivers.

Evolution of sediment plumes in the Chesapeake bay and implications of climate variability.

Fluvial sediment transport impacts fisheries, marine ecosystems, and human health. In the upper Chesapeake Bay, river-induced sediment plumes are generally known as either a monotonic spatial shape or a turbidity maximum. Little is known about plume evolution in response to variation in streamflow and extreme discharge of sediment. Here we propose a typology of sediment plumes in the upper Chesapeake Bay using a 17 year time series of satellite-derived suspended sediment concentration. On the basis of estimated fluvial and wind contributions, we define an intermittent/wind-dominated type and a continuous type, the latter of which is further divided into four subtypes based on spatial features of plumes, which we refer to as Injection, Transport, Temporary Turbidity-Maximum, and Persistent Turbidity-Maximum. The four continuous types exhibit a consistent sequence of evolution within 1 week to 1 month following flood events. We also identify a "shift" in typology with increased frequency of Turbidity-Maximum types before and after Hurricane Ivan (2004), which implies that extreme events have longer-lasting effects upon estuarine suspended sediment than previously considered. These results can serve as a diagnostic tool to better predict distribution and impacts of estuarine suspended sediment in response to changes in climate and land use.

Correction of pathlength amplification in the filter-pad technique for measurements of particulate absorption coefficient in the visible spectral region.

Spectrophotometric measurement of particulate matter retained on filters is the most common and practical method for routine determination of the spectral light absorption coefficient of aquatic particles, ap(λ), at high spectral resolution over a broad spectral range. The use of differing geometrical measurement configurations and large variations in the reported correction for pathlength amplification induced by the particle/filter matrix have hindered adoption of an established measurement protocol. We describe results of dedicated laboratory experiments with a diversity of particulate sample types to examine variation in the pathlength amplification factor for three filter measurement geometries; the filter in the transmittance configuration (T), the filter in the transmittance-reflectance configuration (T-R), and the filter placed inside an integrating sphere (IS). Relationships between optical density measured on suspensions (ODs) and filters (ODf) within the visible portion of the spectrum were evaluated for the formulation of pathlength amplification correction, with power functions providing the best functional representation of the relationship for all three geometries. Whereas the largest uncertainties occur in the T method, the IS method provided the least sample-to-sample variability and the smallest uncertainties in the relationship between ODs and ODf. For six different samples measured with 1 nm resolution within the light wavelength range from 400 to 700 nm, a median error of 7.1% is observed for predicted values of ODs using the IS method. The relationships established for the three filter-pad methods are applicable to historical and ongoing measurements; for future work, the use of the IS method is recommended whenever feasible.

Fusing remote sensing data with spatiotemporal in situ samples for red tide (Karenia brevis) detection.

We present a novel method for detecting red tide (Karenia brevis) blooms off the west coast of Florida, driven by a neural network classifier that combines remote sensing data with spatiotemporally distributed in situ sample data. The network detects blooms over a 1-km grid, using seven ocean color features from the MODIS-Aqua satellite platform (2002-2021) and in situ sample data collected by the Florida Fish and Wildlife Conservation Commission and its partners. Model performance was demonstrably enhanced by two key innovations: depth normalization of satellite features and encoding of an in situ feature. The satellite features were normalized to adjust for depth-dependent bottom reflection effects in shallow coastal waters. The in situ data were used to engineer a feature that contextualizes recent nearby ground truth of K. brevis concentrations through a K-nearest neighbor spatiotemporal proximity weighting scheme. A rigorous experimental comparison revealed that our model outperforms existing remote detection methods presented in the literature and applied in practice. This classifier has strong potential to be operationalized to support more efficient monitoring and mitigation of future blooms, more accurate communication about their spatial extent and distribution, and a deeper scientific understanding of bloom dynamics, transport, drivers, and impacts in the region. This approach also has the potential to be adapted for the detection of other algal blooms in coastal waters. Integr Environ Assess Manag 2024;00:1-15. © 2024 SETAC.

Novel Synergistic Process of Impurities Extraction and Phophogypsum Crystallization Control in Wet-Process Phosphoric Acid.

Phosphogypsum, as a byproduct of wet-process phosphoric acid reaction, has caused many environmental pollution problems. To improve the property and purity of phosphogypsum in the wet-process phosphoric acid process, a liquid-solid-liquid three-phase acid hydrolysis synergistic extraction reaction system was established by adding a certain amount of extractant in the actual production process. In order to study the extraction effect and residue of impurities in the reaction system, the phase, morphology, and impurity occurrences of phosphogypsum were systematically analyzed. The results showed that when the reaction time was 7 h, the reaction temperature was 80 °C, the reaction speed was 200 r/min, the volume ratio of the extractant to diluent (dilution ratio) was 1:4 and the volume ratio of the oil phase/aqueous phase (O/A ratio) was 1:1, P2O5 conversion was the highest in phosphate rock, and the residual P2O5 content in phosphogypsum was as low as 0.36%. The morphology of the phosphogypsum crystal was uniform and coarse long strip. The main forms of residual impurities were silicate, aluminum fluoride with crystal water, aluminate, phosphate, and fluoride. Meanwhile, the residual amount of main impurities in phosphogypsum was significantly reduced. Through this novel method, the property of phosphogypsum can be improved through the generation process and is greatly beneficial for its utilization and the recycling development of the wet-process phosphoric acid industry.

Satellite observations estimating the effects of river discharge and wind-driven upwelling on phytoplankton dynamics in the Chesapeake Bay.

Phytoplankton growth in estuaries is regulated by a complex combination of physical factors with freshwater discharge usually playing a dominating role controlling nutrient and light availability. The role of other factors, including upwelling-generating winds, is still unclear because most estuaries are too small for upwelling to emerge. In this study, we used remotely sensed proxies of phytoplankton biomass and concentration of suspended mineral particles to compare the effect of river discharge with the effect of upwelling events associated with persistent along-channel southerly winds in the Chesapeake Bay, a large estuary where upwelling and its effects on biogeochemical dynamics have been previously reported. The surface chlorophyll-a concentrations (Chl-a) were estimated from Visible Infrared Imaging Radiometer Suite (VIIRS) satellite data using the Generalized Stacked-Constraints Model (GSCM) corrected for seasonal effects by comparing remotely sensed and field-measured data. Light limitation of phytoplankton growth was assessed from the concentration of suspended mineral particles estimated from the remotely sensed backscattering at blue (443 nm) wavelength bbp (443). The nine-year time series (2012-2020) of Chl-a and bbp (443) confirmed that a primary factor regulating phytoplankton growth in this nearshore eutrophic area is discharge from the Susquehanna River, and presumably the nutrients it delivers, with a time lag up to four months. Persistent southerly wind events (2-3 days with wind speed >4 m/s) affected the water column stratification in the central part of the bay but did not result in significant increases in remotely sensed Chl-a. Analysis of model simulations of selected upwelling-favorable wind events revealed that strong southerly winds resulted in well-defined lateral (East-West) responses but were insufficient to deliver high-nutrient water to the surface layer to support phytoplankton bloom. We conclude that, in the Chesapeake Bay, which is a large, eutrophic estuary, wind-driven upwelling of deep water plays a limited role in driving phytoplankton growth under most conditions compared with river discharge. Integr Environ Assess Manag 2022;18:921-938. © 2022 SETAC.

Study of the burr height at hole exit in bone drilling by twist drills.

The burr at the hole exit is one of the key factors affecting bone drilling performances. In order to reduce burr height at hole exit during cortical bone drilling, the four key parameters in twist drilling of bones are analyzed based on the response surface method (RSM). The prediction model of the burr height is obtained via the analysis of variance. The influence trend and size of each factor on the height of the burr are further analyzed based on the RSM. Experimental results show that smaller point angle and diameter of the twist drill, smaller feed speed, and higher rotational speed can effectively reduce the burr height at hole exit. Then, the geometric variables of the twist drill and process parameters are optimized. When the point angle of the twist drill 2Φ = 95°, the diameter D = 2.5 mm, the rotational speed n = 1500 rpm, and the feed speed vf = 10 mm/min, the height of the burr at hole exit reaches the smallest. At the same time, the burr at the exit of the hole with different diameters of twist drills is studied. It is found to be beneficial to select a twist drill with a smaller diameter for drilling when the requirements of drilling are fulfilled.

Experimental study of bone drilling by Kirschner wire.

Mechanical and thermal damage to the bone tissue during drilling process is inevitable and directly affects the postoperative recovery. According to clinical practices and present academic investigations, this study tries to reduce bone damage by experimental investigation of bone drilling by Kirschner wire considering the drilling force and temperature factors. Finite element method has been applied to modelling of the drilling process. Then, grouped experiments have been carried out using bovine femoral bone and analyzed based on the orthogonal experimental method. The influence of key parameters such as Kirschner wire bevel angle, feed speed and rotational speed on the microscopic bone chip size, drilling force, drilling temperature and hole inlet burr was analyzed to conduct comprehensive analysis and optimizations. It is certain that the chips size is closely related to drilling force and drilling temperature. The low drilling temperature does not mean that the damage area is small. The drilling process should be completed quickly at high feed rates. The lower rotational speed, Kirschner wire bevel angle, and higher feed rate help reduce the thermal damage area of the bone drill, effectively reduce the drilling force and hole entrance burrs.

Pharmacokinetics and Tissue Residue Profiles of Enrofloxacin in Crucian Carp (Carassius auratus gibelio) Following Single and Multiple Oral Administration.

The pharmacokinetics, tissue distribution, and elimination of enrofloxacin (ENR) and its metabolite ciprofloxacin (CIP) were investigated to the crucian carp (Carassius auratus gibelio) after single (20 mg/kg b. w.) and multiple oral administration (20 mg/kg b.w. one time daily for 5 days) at 28°C. The concentrations of ENR and CIP in the plasma and tested tissues (muscle/skin, liver, and kidney) were detected simultaneously by high-performance liquid chromatography (HPLC), and the pharmacokinetic data were analyzed with a non-compartmental model using WinNonLin 6.1 PK software (Pharsight Corporation, Mountain View, CA, USA). The pharmacokinetic characteristics of ENR in crucian carp exhibited slow absorption, wide tissue distribution, and long elimination half-life. In the single-dose group, the peak concentrations (Cmax) of ENR in the plasma, muscle/skin, liver, and kidney were 8.93 µg/mL, 13.9 µg/g, 31.2 µg/g, and 27.3 µg/g, respectively, observed at 3 h, 6 h, 1 h, and 3 h after dosing. The elimination half-lives (T1/2λz ) of ENR in plasma, muscle/skin, liver, and kidney were calculated to be 67.4, 82.8, 94.4, and 114 h, respectively. In the multiple-dose group, the Cmax of ENR in the plasma, muscle/skin, liver, and kidney were 18.4 µg/mL, 26.8 µg/g, 82.8 µg/g, and 74.5 µg/g, respectively, achieved at 3 h, 6 h, 1 h, and 1 h after the last dose. The T1/2λz of ENR in the plasma, muscle/skin, liver, and kidney were calculated to be 76.4 h, 91.5 h, 114 h, and 148 h, respectively. During the multiple-dose administration, significant accumulations of ENR and CIP were observed in the plasma and tissues of crucian carp, possibly due to their long elimination half-lives. In both dose groups, the AUC0-∞ for both ENR and CIP followed the order of liver > kidney > muscle/skin > plasma. The finding suggested that the liver may play an important role in the metabolism of ENR. According to the calculated PK/PD indices of Cmax/minimum inhibitory concentrations (MIC) and AUC24h/MIC, the multiple-dose regimen would be highly effective against pathogenic bacteria with a MIC value of ≤ 1.84 µg/ml. Depletion studies indicated that a withdrawal period of at least 29 or 32 days was necessary to guarantee food security after single or multiple oral gavage administration at 28°C.

On-Line Compensation for Micromilling of High-Aspect-Ratio Straight Thin Walls.

In order to improve the machining quality and reduce the dimensional errors of micro high-aspect-ratio straight thin walls, the on-line cutting parameter compensation device has been introduced and corresponding micromilling processes have been investigated. Layered milling strategies for the micromilling of thin walls have been modeled and simulated for thin walls with different thicknesses based on the finite element method. The radial cutting parameters compensation method is adopted to compensate the thin wall deformation by raising the radial cutting parameters since the thin wall deformation make the actual radial cutting parameters smaller than nominal ones. The experimental results show that the dimensional errors of the thin wall have been significantly reduced after the radial cutting parameter compensation. The average relative dimensional error is reduced from 6.9% to 2.0%. Moreover, the fabricated thin walls keep good shape formation. The reduction of the thin wall dimensional error shows that the simulation results are reliable, which has important guiding significance for the improvement of thin wall machining quality, especially the improvement of dimensional accuracy. The experimental results show that the developed device and the machining strategy can effectively improve the micromilling quality of thin walls.

Parametric study of bone drilling by the Kirschner wire.

In order to improve the quality and reduce mechanical damage during bone drilling in surgeries, the three key parameters in drilling by the Kirschner wire are experimentally studied based on the response surface method (RSM). And through response surface analysis, a predictive model of each factor and response value is established. The experimental results found that when the beveled plane angle Φ = 10°, the rotational speed n = 1200 rpm, and the feed speed vf = 20 mm/min. Not only the drilling force is minimized, the delamination coefficient and the height of the hole exit burr are also the minimum. Therefore, the smaller bevel angle, the feed speed and the higher rotation speed can effectively reduce the drilling force, the delamination factor and the height of the hole exit burr, and significantly improve the drilling quality.

Theoretical and Experimental Research on Multi-Layer Vessel-like Structure Printing Based on 3D Bio-Printing Technology.

Cardiovascular disease is the leading cause of death worldwide. Traditional autologous transplantation has become a severe issue due to insufficient donors. Artificial blood vessel is an effective method for the treatment of major vascular diseases, such as heart and peripheral blood vessel diseases. However, the traditional single-material printing technology has been unable to meet the users' demand for product functional complexity, which is not only reflected in the field of industrial manufacturing, but also in the field of functional vessel-like structure regeneration. In order to achieve the printing and forming of multi-layer vessel-like structures, this paper carries out theoretical and experimental research on the printing and forming of a multi-layer vessel-like structure based on multi-material 3D bioprinting technology. Firstly, theoretical analysis has been explored to research the relationship among the different parameters in the process of vessel forming, and further confirm the synchronous relationship among the extrusion rate of material, the tangential speed of the rotating rod, and the movement speed of the platform. Secondly, sodium alginate and gelatin have been used as the experimental materials to manufacture the vessel-like structure, and the corrected parameter of the theoretical analysis is further verified. Finally, the cell-loaded materials have been printed and analyzed, and cell viability is more than 90%, which provides support for the research of multi-layer vessel-like structure printing.