Correlation between Serum Osteopontin and miR-181a Levels in Allergic Rhinitis Children

Background. Osteopontin (OPN) has been proved to be associated with allergic airway inflammation. However, the roles of OPN and its regulation in childhood allergic rhinitis (AR) are poorly understood. Objective. This study aims to evaluate the expression of OPN and miR-181a in children with AR and their association with Th1/Th2 immune response. Methods. Children who suffered from AR were included along with control subjects. Serum was collected to examine the level of OPN and Th1/Th2 cytokines by enzyme-linked immunosorbent assay (ELISA) and the level of miR-181a by quantitative polymerase chain reaction (qPCR). Results. Children with AR had significantly higher serum levels of OPN and lower serum levels of miR-181a than healthy controls. Furthermore, serum levels of OPN were positively correlated with Th2 cytokine and negatively correlated with Th1 cytokine. On the contrary, miR-181a level had a negative correlation with IL-4/IL-5 and positive correlation with IFN-γ/IL-12. More importantly, there was also significant negative correlation between OPN and miR-181a. Conclusion. The OPN protein and miR-181a levels may serve as predictors of disease severity in childhood AR and appear to be promising targets for modulating AR

A human embryonic stem cell-based model of trophoblast formation

Ph.DDOCTOR OF PHILOSOPH

A local tool path smoothening scheme for micromachining

Linear and circular representations are widely used to define tool paths, however, the tangency discontinuity between the linear and circular segments leads to large fluctuations in velocity and acceleration, as a result, the machining accuracy and efficiency are degraded. It becomes the key problem in some micromachining situations where the quality of freeform surfaces is critical, such as moulds and knee implants, etc. This research aims to develop a local tool path smoothening scheme to achieve C2 continuity at the transition positions. This scheme applies to sections consisting of high density of short segments. These segments will be approximated by cubic B-splines. The approximation is carried out within the specific error tolerance. High frequency energy to be injected into the servo loop control system is greatly reduced by the C2 continuity. The proposed scheme is feasible to be implemented in real-time microcontrollers due to the computational efficiency and reliability of B-spline algorithms

Hydrophobicity of pyramid structures fabricated by micro milling

Surgical site infection is the most common infection, which occurs after surgery in the part of the body where the surgery took place. Hydrophobic structure is an effective method to improve the anti-infection ability of surgical tools. The hydrophobic surface prepared by the conventional chemical coating method has poor durability. In this study, the micro-milling method was used to process the microstructure efficiently. 6 different sizes of microstructure is designed and manufactured on 7C27Mo2 which is commonly used for surgical tools. The capability of applying micro-milling for these structures is assessed. The optimal microstructure size is obtained. The experimental results show that the smooth surface of 7C27Mo2 is hydrophilic with contact angle of 64.1°. However, after micro-cutting, the hydrophilic surface can be converted into the hydrophobic surface, the contact angle contact angle nearly doubled (from 64.1° to 127.3°). This study lays the foundation for the manufacture of surgical tools with hydrophobicity and antibacterial properties

Design of a new fast tool positioning system and systematic study on its positioning stability

The challenge of maintaining good surface quality under high operational frequencies in freeform machining invokes the need for a deterministic error analysis approach and a quantitative understanding on how structural design affects the positioning errors. This paper proposes a novel stiff-support positioning system with a systematic error analysis approach which reveals the contributions of disturbances on the tool positioning errors. The new design reduces the structural complexity and enables the detailed modelling of the closed loop system. Stochastic disturbances are analysed in the frequency domain while the non-stochastic disturbances are simulated in the time domain. The predicted following error spectrum agrees with the measured spectrum across the frequency range and this approach is justified. The real tool positioning error, which is free from sensor noise, is revealed for the first time. The influences of moving mass under various bandwidth settings have been studied both theoretically and experimentally. It is found that a larger moving mass helps combating disturbances except the sensor noises. The influences of cutting force are modelled and experimentally verified in the micro lens array cutting experiments. The origins of the form errors of the lenslet are discussed based on the error analysis model

Reconfigurable software architecture for a hybrid micro machine tool

Hybrid micro machine tools are increasingly in demand for manufacturing microproducts made of hard-to-machine materials, such as ceramic air bearing, bio-implants and power electronics substrates etc. These machines can realize hybrid machining processes which combine one or two non-conventional machining techniques such as EDM, ECM, laser machining, etc. and conventional machining techniques such as turning, grinding, milling on one machine bed. Hybrid machine tool developers tend to mix and match components from multiple vendors for the best value and performance. The system integrity is usually at the second priority at the initial design phase, which generally leads to very complex and inflexible system. This paper proposes a reconfigurable control software, architecture for a hybrid micro machine tool, which combines laser-assisted machining and 5-axis micro-milling as well as incorporating a material handling system and advanced on-machine sensors. The architecture uses finite state machine (FSM) for hardware control and data flow. FSM simplifies the system integration and allows a flexible architecture that can be easily ported to similar applications. Furthermore, component-based technology is employed to encapsulate changes for different modules to realize “plug-and-play”. The benefits of using the software architecture include reduced lead time and lower cost of development

Design of compliant parallel grippers using the position space concept for manipulating submillimeter objects

The structure or configuration of compliant mechanisms can be reconfigured through changing the positions of each compliant module thereof within their position spaces. A number of 1-DOF 2-PRRP compliant parallel grippers (CPGs) can be obtained using the structure re-configurability for manipulating sub-millimeter objects. Even with the geometrical parameters for the system’s pseudorigid-body model (PRBM) and each compliant module kept at the same values, the position of each compliant joint can be anywhere within its position space. The performance of the resulting CPG varies with the position of the compliant joint. In this paper two typical CPG designs are presented and analyzed. Comparisons between FEA simulaiton resutls and analytical models show that the input-output kinematic relationship of the non-compact design agrees better with that of the PRBM due to its better load transmissibility. One can design different structures based on specific design requirements

A real-time interpolator for parametric curves

Driven by the ever increasing need for the high-speed high-accuracy machining of freeform surfaces, the interpolators for parametric curves become highly desirable, as they can eliminate the feedrate and acceleration fluctuation due to the discontinuity in the first derivatives along the linear tool path. The interpolation for parametric curves is essentially an optimization problem, and it is extremely difficult to get the time-optimal solution. This paper presents a novel real-time interpolator for parametric curves (RTIPC), which provides a near time-optimal solution. It limits the machine dynamics (axial velocities, axial accelerations and jerk) and contour error through feedrate lookahead and acceleration lookahead operations, meanwhile, the feedrate is maintained as high as possible with minimum fluctuation. The lookahead length is dynamically adjusted to minimize the computation load. And the numerical integration error is considered during the lookahead calculation. Two typical parametric curves are selected for both numerical simulation and experimental validation, a cubic phase plate freeform surface is also machined. The numerical simulation is performed using the software (open access information is in the Acknowledgment section) that implements the proposed RTIPC, the results demonstrate the effectiveness of the RTIPC. The real-time performance of the RTIPC is tested on the in-house developed controller, which shows satisfactory efficiency. Finally, machining trials are carried out in comparison with the industrial standard linear interpolator and the state-of-the-art Position-Velocity-Time (PVT) interpolator, the results show the significant advantages of the RTIPC in coding, productivity and motion smoothness

Development of a compact ultra-precision six-axis hybrid micro-machine

High precision miniature and micro products which possess 3D complex structures or free-form surfaces are now widely used in industries. These micro products are usually fabricated by several machining processes in order to apply for various materials such as hard-to-machine steel and ceramic etc. The integration of these machining processes onto one machine becomes necessary since this will help reduce realignment errors and also increase the machining efficiency. In this research, an ultra-precision hybrid micro-machine which is capable of micro milling, micro grinding, micro turning, laser machining and laser assisted micro-machining has been designed and commissioned. Control software for on-machine metrology system (contact probe and dispersed reference interferometry (DRI)) and several plug-in modules including camera and handle system are integrated through a customised human-machine interface (HMI)

A generic control architecture for hybrid micro-machines

Hybrid micro-machining, which integrates several micro-manufacturing processes on one platform, has emerged as a solution to utilize the so-called "1 + 1 = 3" effect to tackle the manufacturing challenges for high value-added 3D micro-products. Hybrid micro-machines tend to integrate multiple functional modules from different vendors for the best value and performance. However, the lack of plug-and-play solutions leads to tremendous difficulty in system integration. This paper proposes a novel three-layer control architecture for the first time for the system integration of hybrid micro-machines. The interaction of hardware is encapsulated into software components, while the data flow among different components is standardized. The proposed control architecture enhances the flexibility of the computer numerical control (CNC) system to accommodate a broad range of functional modules. The component design also improves the scalability and maintainability of the whole system. The effectiveness of the proposed control architecture has been successfully verified through the integration of a six-axis hybrid micro-machine. Thus, it provides invaluable guidelines for the development of next-generation CNC systems for hybrid micro-machines