The essential materials paradigms for regenerative medicine

Medical technology is changing rapidly. Several disease states can now be treated very effectively by implantable devices that restore mechanical and physical functionality, such as replacement of hip joints or restoration of heart rhythms by pacemakers. These techniques, however, are rather limited, and no biological functionality can be restored through the use of inert materials and devices. This paper explores the role of new types of biomaterials within the emerging area of regenerative medicine, where they are able to play a powerful role in persuading the human body to regenerate itself.     

Zirconium-based composites for orthopedic applications

A relatively new composite material consisting of a ZrC matrix reinforced by ZrB₂ platelets and containing residual zirconium exhibits a combination of high strength, fracture toughness, and specific stiffness. In preliminary tests, this material compared favorably to the commonly used implant alloys Ti-6Al-4V and Co-Cr-Mo. In addition, the results of wear tests on this material against ultrahigh-molecular-weight polyethylene indicate promising results for use in orthopedic devices.     

双蓄热式加热炉炉压控制方法研究

针对蓄热式加热炉炉压控制精度不高的问题,提出一种炉压控制方法,包括带燃气流量修正计算、炉门位置前馈控制的炉压控制器,并对脉冲换向策略及烧嘴切断阀操作进行优化,实现了炉压的高精度调节。     

Calcium phosphate scaffolds for bone repair

Calcium phosphates, with their chemical similarity to bone mineral, show biocompatibility with hard and soft tissues and offer massive potential for bone repair, both as scaffolds to be implanted directly into the defect and as structures for cell transplantation or to guide new bone growth in tissue engineering. This paper reviews the requirements and motivation for synthetic bone graft alternatives and the production routes for, particularly, hydroxyapatite porous scaffolds. It also considers the important role of substitution of ions such as silicate into calcium phosphates so as to more closely mirror the chemistry of bone mineral and to elicit specific biological responses.     

Bioactive Ca-P scaffolds used for bone reconstruction

1　INTRODUCTIONSkeletalreconstructionorregenerationisre quiredincasesinvolvinglargedefectscreatedbytu morresection ,trauma ,andskeletalabnormalities .Graftsandflapsofautogenoustissuearetwoofthemostsuccessfulmeansofreconstructionbecausetheyallowthetransplantationofbonecontainingbioactivemolecules,livecells ,andfrequently ,avascularsup plythatallowthetransplanttosurviveandremodeleveninhostileradiatedenvironments .However ,onlyaminimalamountoftissuecanbeharvestedforauto grafts,anditisverydiff…     

Three-dimensional chitosan-nanohydroxyapatite composite scaffolds for bone tissue engineering

We describe the structure of biodegradable chitosan-nanohydroxyapatite (nHA) composites scaffolds and their interaction with pre-osteoblasts for bone tissue engineering. The scaffolds were fabricated via freezing and lyophilization. The nanocomposite scaffolds were characterized by a highly porous structure and pore size of ∼50–125 μm, irrespective of nHA content. The observed significant enhancement in the biological response of pre-osteoblast on nanocomposite scaffolds expressed in terms of cell attachment, proliferation, and widespread morphology in relation to pure chitosan points toward their potential use as scaffold material for bone regeneration.     

Novel nanostructured hydroxyapatite coating for dental and orthopedic implants

A novel hybrid coating process, combining NanoSpray® (built on electrostatic spray coating) technology with microwave sintering process, was developed for synthesizing hydroxyapatite- (HA-) based nanostructured coating with favorable properties for dental and orthopedic implants. Specifically, HA nanoparticles were deposited on commercially pure titanium substrates using NanoSpray technique to produce the HA coating, which was then sintered in a microwave furnace under controlled conditions. The study showed that the use of NanoSpray followed by microwave sintering results in nanoscale HA coating for dental/orthopedic application.     

A new perspective and analysis for regenerative machine tool chatter

The paper contains a practical perspective on regenerative machine tool chatter. Chatter is a well known phenomenon, occurrence of which is undesired in manufacturing. Aggressive machining conditions, in the sense of removing more metal rapidly, usually cause chatter. In most cases, these conditions can be determined a priori to the operation. A chatter stability study and its reasoning based on root locus plot analysis of time delayed systems is presented as a new and practical perspective in the field. At the junction of root locus and chatter concepts an area of particular interest to the authors arises: a new method for active vibration suppression, the Delayed Resonator. It is an active vibration absorber tuning of which is achieved utilizing a simple time delayed feedback. The cross linking between the Delayed Resonator study and the subject matter, machine tool chatter, is exciting to share. This is the primary motivation in pursuing this study. One of the highlights of the work appears at the phenomenon called Dual Frequency Delayed Resonator. This feature has been conjectured in the literature using the well known “stability lobes”, but never discussed with detail.     

蓄热式铝熔炼炉熔炼过程的数值模拟

为了更好地研究和优化铝熔炼炉的性能,针对现有的蓄热式圆形铝熔炼炉,在建立合理的铝熔炼炉基本模型的基础上,通过耦合用户自定义熔化模型和氧化烧损模型,运用计算流体力学软件FLUENT实现燃烧空间和熔池的耦合物理场的数值模拟。着重研究不同固液区和不同孔隙率对铝及铝合金熔炼过程的影响。结果表明,该模型较好地反映铝熔炼炉的熔炼现象,可运用该模型进行铝熔炼炉熔炼过程工艺参数的优化研究。同时获得了固液区和孔隙率对熔炼参数影响规律:铝液温度在固液区上升缓慢,而离开固液相线时,铝液温度上升速度加快,炉膛温度和氧化层质量随着熔炼时间分别呈周期性增加和呈抛物线增加;随着氧化层厚度的增加,铝液温度随着孔隙率的增加而增加变得缓慢。     

Optimisation of variable helix tool geometry for regenerative chatter mitigation

It is well known that regenerative chatter can result in excessive tool wear, poor surface finish, and hence limited productivity during metal machining. Various mitigation methods can be applied to suppress chatter; however, the current paper focuses on applying optimal variable helix tool geometry. A semi-discretisation method is combined with Differential Evolution to optimise variable helix end milling tools so as to avoid chatter by modifying the variable helix and variable pitch tool geometry. The semi-discretisation method is first validated experimentally. The numerical optimisation procedure is then used to optimise tool geometry for a machining problem involving a flexible workpiece. The analysis predicted total mitigation of chatter using the optimised variable helix milling tool at a low radial immersion. However, in practice a five fold increase in chatter stability was obtained, compared to the traditional milling tool.     

高温蓄热式锻造加热炉喷口参数的设计

基于传热学及燃烧学,利用有限元分析软件Fluent对某高温蓄热式锻造加热炉内的流场进行了稳态数值模拟研究.通过对烧嘴喷口间距离及喷口角度对炉温及出口烟气浓度的影响分析,获得了加热炉中温度场及污染物的排放情况.结果表明,烧嘴喷口间距离及喷口角度对炉温及污染物的排放量影响均较大;对于本文所研究的某高温蓄热式双室锻造加热炉而言,其最佳喷口间距离为900 mm、最佳喷口角度为0°.     

蓄热式加热炉的维护

以唐山钢铁股份有限公司中型厂蓄热式加热炉为例，对影响加热炉使用的蓄热体板结、蓄热室漏火漏气，以及换向阀不到位的问题进行了分析，并介绍了解决其问题的有效措施。     

Biomanufacturing of customized modular scaffolds for critical bone defects

There is a significant unmet clinical need for modular and customized porous biodegradable constructs (scaffolds) for non-union large bone loss injuries. This paper proposes modelling and biomanufacturing of modular and customizable porous constructs for patient-specific critical bone defects. A computational geometry-based algorithm was developed to model modular porous constructs using a parametric femur model based on the frequency of common injuries. The generated modular constructs are used to generate biomimetic path planning for three-dimensional (3D) printing of modular scaffold pieces. The developed method can be used for regenerating bone tissue for treating non-union large bone defects.     

Ion-beam irradiation into biodegradable nanofibers for tissue engineering scaffolds

Tissue engineering scaffolds require cell affinity, biodegradability, and desirable mechanical properties. Poly-_L-lactic acid (PLLA) has been investigated for tissue engineering scaffolds owing to its biodegradability and mechanical strength. Electrospun fibers have large surface area and the fibrous structure provides necessary properties for cell attachment, proliferation, differentiation, and sufficient stiffness. PLLA fibers were irradiated with Kr⁺ at an energy of 50 keV with fluences of 1 × 10¹³, 1 × 10¹⁴, and 1 × 10¹⁵ ions/cm² to improve cell affinity. Morphological change was observed by scanning electron microscopy (SEM). Surface properties were measured by FT-IR-ATR and Raman spectroscopy. L929 cell attachment to Kr⁺-irradiated fibers was evaluated. After the irradiation, the average fiber diameter decreased with high fluence. From the results of the surface analyses, the original chemical bonds were broken and new carbon structures were induced. L929 cell attachment was dramatically improved compared with non-irradiated fibers. Thus, ion-beam irradiated fibers are suitable for tissue engineering scaffolds. This technique is expected to be useful in repairing defects, such as those in nerve, vascular, and liver, in regenerative medicine.     

湿化学法制备磷酸钙/胶原复合材料

人体自然骨的缺损,如断裂、畸变等,形成了对骨替代材料的巨大需求.磷酸三钙/胶原复合材料兼顾了磷酸三钙的生物降解性和胶原的韧性、同时具有良好的生物相容性,正逐渐成为骨替代材料研究的焦点.采用新的合成方法合成出粒径较小的β-TCP颗粒,在pH=2的条件下制备出β-TCP颗粒均匀分布在胶原上的复合材料,并对复合材料的结构进行了研究.     

Understanding biomanufacturing of soy-based scaffolds for cell-cultured meat by vat polymerization

Emerging cell-cultured meat uses advances in stem cell biology and tissue engineering to manufacture animal-derived food from culturing. To achieve complex textures in cell-cultured meat, bioprinted soy-based polymers are proposed as a photosensitive edible scaffold material. Understanding the properties of these scaffolds across critical product development stages (i.e., cooking and consumption) is important in design for manufacturing. The results demonstrated that the thermomechanical and -chemical properties were not affected by high-temperature exposure associated with cooking. This research provides a foundation for high-temperature edible mechanics in photolithographic manufacturing of cell-cultured meat and establishes a new design space for tunable food properties.     

Fabrication of porous scaffolds for bone tissue engineering via low-temperature deposition

A new process of low-temperature deposition manufacturing (LDM) based on the layer-by-layer manufacturing method of solid freeform fabrication is proposed to fabricate poly(l-lactic acid)/(tricalcium phosphate) composite scaffolds for bone tissue engineering. The LDM system and the manufacturing process are analyzed. The manufactured scaffolds are evaluated as bone regeneration scaffolds.     

Modeling regenerative workpiece vibrations in five-axis milling

During milling—especially of thin-walled components—the dynamic behavior of the workpiece-tool-machine-system influences the milling process and particularly the quality of the resulting workpiece surface. This article focuses on the presentation of a simulation concept for predicting regenerative workpiece vibrations, which combines a finite element model for analyzing the dynamic behavior of the workpiece with a time domain simulation for the five-axis milling process. Both concepts, their linking, and the experimental setup for verifying the simulation will be described. A comparison of the simulation results with the data measured in experiments with regard to the vibration frequencies as well as the surface quality will be given.     

Porous ceramic scaffolds with complex architectures

This work compares two novel techniques for the fabrication of ceramic scaffolds for bone tissue engineering with complex porosity: robocasting and freeze casting. Both techniques are based on the preparation of concentrated ceramic suspensions with suitable properties for the process. In robocasting, the computer-guided deposition of the suspensions is used to build porous materials with designed three dimensional geometries and microstructures. Freeze casting uses ice crystals as a template to form porous lamellar ceramic materials. Preliminary results on the compressive strengths of the materials are also reported.