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.

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.

Fractal Characteristics of Chip Morphology and Tool Wear in High-Speed Turning of Iron-Based Super Alloy.

Considering that iron-based super alloy is a kind of difficult-to-cut material, it is easy to produce work hardening and serious tool wear during machining. Therefore, this work aims to explore the chip change characteristics and tool wear mechanism during the processing of iron-based super alloy, calculate the fractal dimensions of chip morphology and tool wear morphology, and use fractals to analyze their change trend. Meanwhile, a new cutting tool with a super ZX coating is used for a high-speed dry turning experiment. The results indicate that the morphology of the chip is saw-tooth, and its color changes gradually, due to the oxidation reaction. The main wear mechanisms of the tool involve abrasive wear, adhesive wear, oxidation wear, coating spalling, microcracking and chipping. The fractal dimension of the tool wear surface and chip is increased with the improvement of cutting speed. This work investigates the fractal characteristics of chip morphology and tool wear morphology. The fractal dimension changes regularly with the change of tool wear, which plays an important role in predicting this tool wear. It is also provides some guidance for the efficient processing of an iron-based super alloy.

Cutting Performance Evaluation of the Coated Tools in High-Speed Milling of AISI 4340 Steel.

The cutting performance of cutting tools in high-speed machining (HSM) is an important factor restricting the machined surface integrity of the workpiece. The HSM of AISI 4340 is carried out by using coated tools with TiN/TiCN/TiAlN multi-coating, TiAlN + TiN coating, TiCN + NbC coating, and AlTiN coating, respectively. The cutting performance evaluation of the coated tools is revealed by the chip morphology, cutting force, cutting temperature, and tool wear. The results show that the serration and shear slip of the chips become more clear with the cutting speed. The lower cutting force and cutting temperature are achieved by the TiN/TiCN/TiAlN multi-coated tool. The flank wear was the dominant wear form in the milling process of AISI 4340. The dominant wear mechanisms of the coated tools include the crater wear, coating chipping, adhesion, abrasion, and diffusion. In general, a TiN/TiCN/TiAlN multi-coated tool is the most suitable tool for high-speed milling of AISI 4340, due to the lower cutting force, the lower cutting temperature, and the high resistance of the element diffusion.

Analysis of azole fungicides in fish muscle tissues: Multi-factor optimization and application to environmental samples.

Azole fungicides have been reported to be accumulated in fish tissue. In this study, a sensitive and robust method using high-performance liquid chromatography-tandem mass spectrometry combined with ultrasonic extraction, solid-liquid clean-up, liquid-liquid extraction and solid-phase extraction (SPE) for enrichment and purification have been proposed for determination of azole fungicides in fish muscle samples. According to the results of non-statistical analysis and statistical analysis, ethyl acetate, primary secondary amine (PSA) and mixed-mode cation exchange cartridge (MCX) were confirmed as the best extraction solvent, clean-up sorbent and SPE cartridge, respectively. The satisfied recoveries (81.7-104%) and matrix effects (-6.34-7.16%), both corrected by internal standards, were performed in various species of fish muscle matrices. Method quantification limits of all azoles were in the range of 0.07-2.83ng/g. This optimized method was successfully applied for determination of the target analytes in muscle samples of field fish from Beijiang River and its tributaries. Three azole fungicides including climbazole, clotrimazole and carbendazim were detected at ppb levels in fish muscle tissues. Therefore, this analytical method is practical and suitable for further clarifying the contamination profiles of azole fungicides in wild fish species.

[Residues and health risk assessment of HCHs, DDTs and heavy metals in water and Tilapias from fish ponds of Guangdong].

Concentrations of copper, lead, cadmium, arsenic, hexachlorcyclohexane (HCHs) and dichlorodiphenyltrichloroethane (DDTs) in the water and the fish samples collected separately from fish pond, markets and supermarkets in four cities of Guangdong Province were measured by using GC-ECD, flame atomic absorption spectrometry and atomic fluorescence spectrometry. Health risk assessments associated with Cu, Pd, Cd, As, HCHs and DDTs were conducted based on the model of health risk assessment recommended by the US EPA. The results showed that the concentration ranges of Cu, Pd, Cd, As, HCHs and DDTs in water samples were nd-0.101 mg x L(-1), nd-0.097 mg x L(-1), nd-0.003 27 mg x L(-1), 0.0121-0.08127 mg x L(-1), 2.63-37.18 ng x L(-1) and 2.05-12.21 ng x L(-1), respectively. The health risk assessment indicates that the carcinogenic and non-carcinogenic risks of Cu, Pd, Cd, HCHs and DDTs in Tilapias both lower than the highest acceptable level of risk set by ICRP, but As cancer risk value slightly exceeded the upper limit of the acceptable risk levels in city population.