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Large bone defects, usually associated to victims of natural disasters, wars and severe accidents, represent a major clinical problem. The search for an effective and efficient treatment is a key area of research. Our group is exploring a novel and fully automatic approach to produce synthetic grafts anatomically designed to fit on the defect site and able to promote tissue regeneration.

There is a significant unmet clinical need to prevent amputations due to large bone loss injuries. We are addressing this problem by developing a novel, cost-effective osseointegrated prosthetic solution based on the use of modular pieces, bone bricks, made with biocompatible and biodegradable materials that fit together in a Lego-like way to form the prosthesis. This paper investigates the anatomical designed bone bricks with different architectures, pore size gradients, and material compositions. Polymer and polymer-composite 3D printed bone bricks are extensively morphological, mechanical, and biological characterized. Composite bone bricks were produced by mixing polycaprolactone (PCL) with different levels of hydroxyapatite (HA) and β-tri-calcium phosphate (TCP). Results allowed to establish a correlation between bone bricksarchitecture and material composition and bone bricks performance. Reinforced bone bricks showed improved mechanical and biological results. Best mechanical properties were obtained with PCL/TCP bone bricks with 38 double zig-zag filaments and 14 spiral-like pattern filaments, while the best biological results were obtained with PCL/HA bone bricks based on 25 double zig-zag filaments and 14 spiral-like pattern filaments.

In this paper a neural network based modeling approach is proposed for localization and estimation of loads acting on aircraft wings from full field depth measurements. These measurements can be provided by a multitude of sensors such as depth cameras. Depth cameras have many advantages over other intensity sensors in that they can work in low light conditions and they are invariant to texture and color changes. First, an autoencoder is proposed to extract maximum informative data from the depth images and encode them at a much smaller dimension. Next, to develop the models for localization and estimation of loads, supervised multinomial classification and logistic regression networks are proposed, where the encoded depth features are utilized as input in both networks. The performance of the proposed method is validated on a composite wing subject to concentrated and distributed loads, during which the proposed methods for localization and estimation of loads achieved high accuracies of 90.6% and 90.5%, respectively.

The capabilities of additive manufacturing for fabrication of complex and thin-walled ceramic-based objects are restricted by the availability of ceramics inks. Formulations of current ink systems strictly depend on using a high content of organic additives (5-30 wt%). The high amounts of additives affect uniformity and dimensional accuracy of the final object. Here, we designed a single additive that enables printing of high aspect ratio and thin-walled structures (height/width = 58) from an ink of alumina nanoparticles that comprises very low organic content (i.e., 1.25 wt % of nanoparticles mass). In addition to the generally exploited electrostatic effect, this additive has purpose-driven tailoring to harness steric hindrance to control the viscoelastic response of ceramic suspensions and realize an optimum ink for extrusion-based 3D printing. We pursued a stepwise approach in developing such an additive through synthesis of series of copolymers with backbone monomers of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid and side chains of poly(ethylene glycol). When the optimized additive is used, the suspension attains ∼80 wt % solid loading−99% of the theoretical limit calculated by the Krieger−Dougherty equation. The shrinkage and deflection of the printed patterns as well as compactness and sinter-ability of dried structures are monitored. The printed structures did not experience any deformation or deflection during printing and reached 68% of theoretical density (TD: 3.98 g/cm3) after drying. This compactness allowed sintering at lower temperatures and improved dimensional control of the final product. Our approach to formulate ceramic inks enables the embodiment of fully aqueous systems with the utmost material content and has the potential to expand the limited portfolio of ceramic inks.

Three-dimensional (3D) melt electrospinning writing (MEW) is a promising technique for 3D printing of porous scaffolds with well-defined geometrical features. The diameter of electrospun fibers strongly affect the achievable resolution and consequently several other physical, mechanical, and structural properties of the fabricated scaffold. However, there are a few process parameters which significantly affect the size of electrospun fibers. In this study, response surface methodology (RSM) was used to investigate the critical and optimized process parameters and their interaction effects on the desired fiber diameter. Four process parameters, including collector speed, tip-to-collector distance, applied pressure, and voltage were studied considering their practical ranges. The results showed that all the parameters except the applied voltage had a significant effect on the printed fiber diameters. A generalized model for the interaction effects of the parameters was introduced which can be used as a framework for selecting the process parameters to achieve the desired fiber diameter. The developed model was validated by choosing random process parameters and printing three-dimensional scaffolds. The results confirm that the predicted fiber diameters match closely with the actual fiber diameters measured directly from the printed scaffold. © 2018 Elsevier Ltd 213M687 Türkiye Bilimsel ve Teknolojik AraÅ?tirma Kurumu This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) [grant number 213M687 ]. We thank Adnan Tasdemir for assistance with the SEM work, Navid Khani for suggestions and comments that greatly improved the concept, and Ali Nadernezhad for his comments on the manuscript.

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.

This paper deals with the development of a realtime structural health monitoring system for airframe structures to localize and estimate the magnitude of the loads causing deflections to the critical components, such as wings. To this end, a framework that is based on artificial neural networks is developed where features that are extracted from a depth camera are utilized. The localization of the load is treated as a multinomial logistic classification problem and the load magnitude estimation as a logistic regression problem. The neural networks trained for classification and regression are preceded with an autoencoder, through which maximum informative data at a much smaller scale are extracted from the depth features. The effectiveness of the proposed method is validated by an experimental study performed on a composite unmanned aerial vehicle (UAV) wing subject to concentrated and distributed loads, and the results obtained by the proposed method are superior when compared with a method based on Castigliano&rsquo, s theorem.

In this paper, a novel method of integrated modelling and bio-additive manufacturing of hybrid bioinspired structures is presented. An algorithm is developed to generate optimized and continuous path plan while changing material and internal composition spatially and hierarchically based on the assigned functionality. Biodegradable polymers and hydrogels are used as reinforcing and biological functional bioinks respectively. A new hybrid multi-head 3D bioprinter is developed to manufacture designed three-dimensional constructs depositing bioinks layer-by-layer. Simultaneous incorporation of multiple deposition heads and integrated path planning provide the benefits of using the deposition-on-demand of multi-material bio-inks. The modelled constructs are analyzed and bioprinted. (C) 2017 Published by Elsevier Ltd on behalf of CIRP.

Thousands of people die each year due the cardiovascular health problems. The most common treatments for cardiovascular health diseases are autografts and blood vessel transplantations which has limitations due to lack of donors and the patient's conditions. Although there are several scaffold based studies about vascular tissue engineering, scaffold-based vascular grafts have some side effects including chronic inflammation, thrombosis and rejection after in-vivo implantation. Additionally, there are some problems with cell to cell interaction, the assembly and alignment of ECM components and the host response to scaffolds. Therefore, vascular tissue engineering studies tend towards scaffold-free techniques. In this paper, novel computer aided algorithms and methods are developed for 3D printing of scaffold-free macrovascular structures. An example aorta model is generated using imaging and segmentation software. The developed algorithms are implemented using Rhinoscript. In order to support printed cell aggregates, support structures with 'Cake' and 'Zigzag' patterns are developed and 3D printed. (C) 2013 The Authors. Published by Elsevier Ltd.

Multimaterial additive manufacturing or three-dimensional (3D) printing of hydrogel structures provides the opportunity to engineer geometrically dependent functionalities. However, current fabrication methods are mostly limited to one type of material or only provide one type of functionality. In this paper, we report a novel method of multimaterial deposition of hydrogel structures based on an aspiration-on-demand protocol, in which the constitutive multimaterial segments of extruded filaments were first assembled in liquid state by sequential aspiration of inks into a glass capillary, followed by in situ gel formation. We printed different patterned objects with varying chemical, electrical, mechanical, and biological properties by tuning process and material related parameters, to demonstrate the abilities of this method in producing heterogeneous and multi-functional hydrogel structures. Our results show the potential of proposed method in producing heterogeneous objects with spatially controlled functionalities while preserving structural integrity at the switching interface between different segments. We anticipate that this method would introduce new opportunities in multimaterial additive manufacturing of hydrogels for diverse applications such as biosensors, flexible electronics, tissue engineering and organ printing.

Three dimensional (3D) bioprinting is a rapidly advancing tissue engineering technology that holds great promise for the regeneration of several tissues, including bone. However, to generate a successful 3D bone tissue engineering construct, additional complexities should be taken into account such as nutrient and oxygen delivery, which is often insufficient after implantation in large bone defects. We propose that a well-designed tissue engineering construct, that is, an implant with a specific spatial pattern of cells in a matrix, will improve the healing outcome. By using a computational model of bone regeneration we show that particular cell patterns in tissue engineering constructs are able to enhance bone regeneration compared to uniform ones. We successfully bioprinted one of the most promising cell-gradient patterns by using cell-laden hydrogels with varying cell densities and observed a high cell viability for three days following the bioprinting process. In summary, we present a novel strategy for the biofabrication of bone tissue engineering constructs by designing cell-gradient patterns based on a computational model of bone regeneration, and successfully bioprinting the chosen design. This integrated approach may increase the success rate of implanted tissue engineering constructs for critical size bone defects and also can find a wider application in the biofabrication of other types of tissue engineering constructs.

PurposeThe objective of this paper is to develop geometric algorithms and planning strategies to enable the development of a novel hybrid manufacturing process, which combines rapidly re‐configurable mold tooling and multi‐axis machining.Design/methodology/approachThe presented hybrid process combines advantages of both reconfigurable molding and machining processes. The mold's re‐configurability is based on the concept of using an array of discrete pins. By positioning the pins, the reconfigurable molding process allows forming the mold cavity directly from the object's 3D design model, without any human intervention. After a segment of the part is molded using the reconfigurable molding process, a multi‐axis machining operation is used to create accurate parts with better surface finish. Geometric algorithms are developed to decompose the design model into segments based on the part's moldability and machinability. The decomposed features are used for planning the reconfigurable molding and the multi‐axis machining operations.FindingsComputer implementation and illustrative examples are also presented in this paper. The results showed that the developed algorithms enable the proposed hybrid re‐configurable molding and multi‐axis machining process. The developed decomposition and planning algorithms are used for planning the reconfigurable molding and the multi‐axis machining operations. Owing to the decomposition strategy, more geometrically complex parts can be fabricated using the developed hybrid process.Originality/valueThis paper presents geometric analysis and planning to enable the development of a novel hybrid manufacturing process, which combines rapidly re‐configurable mold tooling and multi‐axis machining. It is expected that the proposed hybrid manufacturing process can produce highly customized parts with better surface finish, and part accuracy, with shorter build times, and reduced setup and tooling costs.

This paper presents a stochastic modeling of tissue engineering scaffolds (porous artifacts) with controlled porosity. The internal architecture of the scaffolds is determined based on a given distribution and porosity level function. The discrete porosity levels are used to determine required expected number of pores for each region of the scaffold. Design variables with random distribution are used to model the spatial location of pores bio-mimetically. Because of the randomness of the distribution of pores, overlapped pores must be determined for calculating the porosity levels accurately. A new computational method based on simulation has been developed to calculate the expected overlapped volumes. Using the calculated overlapping factors, the required numbers of pores are determined to satisfy the required porosity levels at each region. The presented methods are implemented in a computing environment and examples are presented in this paper.

Tissue engineering is an emerging multidisciplinary field to regenerate damaged or diseased tissues and organs. Traditional tissue engineering strategies involve seeding cells into porous scaffolds to regenerate tissues or organs. However, there are still some challenges such as difficulty in seeding different type of cells spatially into a scaffold, limited oxygen and nutrient delivery and removal of metabolic waste from scaffold and weak cell-adhesion to scaffold material need to be overcome for clinically successful results. Because of those challenges, novel scaffold-free approaches based on cellular self-assembly or three-dimensional (3D) bioprinting have been recently pursued. Bioprinting is a relatively new technology where living cells with or without biomaterials are printed layer-by-layer in order to create 3D living structures. In 3D bioprinting, cell aggregates and hydrogels are termed as bioink used as building blocks that are placed by the bioprinter into precise architecture according to developed computer models. In this chapter, we focus on the scaffold-free, self-assembly based bioprinting approaches and some of the novel developments in this field. This chapter will also discuss the importance as well as the challenges for 3D bioprinting using stem cells. We aim to highlight the importance of the continuous cell printing in order to fabricate 3D biological structures with predefined shapes as being the building blocks of large and complex tissues.

In this paper, a new feature-based method is proposed to represent and design heterogeneous objects. Material governing features are defined to control material composition inside the objects. Interrelations between the material governing features and material attributes are established in the design process and retained in the object model. Free-form B-spline functions are used to represent complex shapes of geometry and material features. A new material feature blending method is used to determine continuous material variation. To obtain the best material features, an optimization problem is constructed based on the object's functional requirements. Variant models are easily generated by changing the geometric and material features using the constraints between them. Implementation and examples are also presented in this paper.

This paper presents geometric algorithms for developing a re-configurable tooling system for fabrication of freeform objects. The proposed method involves a mold block, with n faces, in which the mold cavity is formed by moving a set of discrete pins on each face of the block. The part surfaces are approximated in the mold cavity using the pins from the suitable mold block faces. The geometric algorithms detailed in this paper analyze the part and determine the face of mold block from which the part model is approximated best. Further, the algorithms detect possible interference between pins from different faces, and suitably alter the approximating face to alleviate interferences. By moving these pins in and out of the mold block, the shape of the mold cavity is reconfigured rapidly to suit the changes in part geometry. Since, the proposed method approximates free-form objects with discrete pins, a surface-error calculation method is also developed to control the accuracy. Computer implementation and examples are also presented in this paper.

In the distributed and horizontally integrated manufacturing environment found in agile manufacturing, there is a great demand for new product development methods that are capable of generating new customized assembly designs based on mature component designs that might be dispersed at geographically distributed partner sites. To cater for this demand, this paper addresses the methodology for complex assembly variant design in agile manufacturing. It consists in fundamental research in two parts: (i) assembly modeling; and (ii) assembly variant design methodology. This paper, the first of a two-part series, presents the assembly variant design system architecture and the assembly modeling methodology. First, a complementary assembly modeling concept is proposed with two kinds of assembly models, the hierarchical assembly model and the relational assembly model. The first explicitly captures the hierarchical and functional relationships between constituent components whereas the second explicitly captures ...

In the first paper of this two-part series, the assembly variant design system architecture and complementary assembly methodology were presented. The general complementary assembly models, hierarchical assembly model and relational assembly model, are established which were further specified as the Assembly Variants Model (AVM) and the Assembly Mating Graphs (AMGs) respectively to cater for the needs for assembly variant design. This paper discusses the assembly variant design methodology which is based on these assembly models. The matching components are searched and retrieved from the AVM and then the constraint groups are identified by manipulating the AMGs. Then the assembly variant design process is formulated as a mixed-integer (linear or non-linear) programming problem which is solved using a standard solver or heuristic. This methodology provides a systematic approach to facilitate the variant design of complex assembly products in the agile manufacturing environment. Finally, a prototype system...

This paper presents a new method of using non-uniform offsetting and biarcs fitting to hollow out solid objects or thick walls to speed up the part building processes on rapid prototyping (RP) systems. Building a hollowed prototype instead of a solid part can significantly reduce the material consumption and the build time. A rapid prototyped part with constant wall thickness is important for many different applications of rapid prototyping. To provide the correct offset wall thickness, we develop a non-uniform offsetting method and an averaged surface normals method to find the correct offset contours of the stereolithography (STL) models. Detailed algorithms are presented to eliminate self-intersections, loops and irregularities of the offsetting contours. Biarcs fitting is used to generate smooth cross-section boundaries and offset contours for RP processes. Implementation results show that the developed techniques can generate smoothed slicing contours with accuracy for rapid prototyping without suffering from handling the huge number of linear segments of the traditional methods.

This paper presents a new method for 5-axis rough cutting of ruled surface pockets. An inclined zig-zag method is proposed for rough cutting the core material region, and an ellipse-offset method is developed for semi-roughing the residual material regions of ruled surface pockets. The ellipse-offset method is developed to calculate the non-constant offset curves for 5-axis tool path planning of rough cutting. Different from the traditional 21/2D machining method, the developed ellipse-offset method allows the cutter to change its tool orientation and to get as close to the part surface as possible in roughing. The proposed method allows the manufacturing engineers to use 5-axis machining to rough cut the parts to near-finish shape for finishing. Computer implementation and illustrative examples are presented in this paper.

Porous scaffolds with interconnected and continuous pores have recently been developed to stimulate tissue regeneration. Even though few researches have focused on the internal architecture of porous scaffolds but concluded that properly interconnected and continuous pores with spatial distribution might perform diverse mechanical, biological and chemical functions of a scaffold. Thus the need for reproducible and fabricatable scaffold design with controllable gradient porosity is obvious but is hardly achieved because of design and fabrication limitations. In this paper, a novel functionally gradient variational porosity architecture has been proposed with continuous material deposition planning scheme. The medial axis transformation for the scaffold has been calculated to generate an internal feature of the geometric domain. The medial axis is then used as a base to develop the medial boundary to define the medial regions. Then the complex internal architecture of scaffolds is divided into sub-regions using the ruling lines that are generated between the slice’s contour and the medial boundary. The desired controlled variational porosity along the scaffold architecture has been achieved with the combination of two geometrically oriented consecutive layers while meeting the tissue scaffold design constraints. This ensures truly porous structures in every direction as well as controllable porosity with interconnected pores along the scaffold architecture. The proposed methodology has been implemented and illustrative examples are also provided. A sample designed structure has been fabricated with a NC motion controlled micro-nozzle deposition system.

This paper presents a novel computer-aided modeling of 3D hollowed tissue scaffolds with a controlled internal architecture. Functionally gradient variational porosity architecture is proposed with continuous material deposition planning scheme. The complex internal architecture of scaffolds is discritized into sub-regions accumulated from ruling lines that are generated from outer to inner features. The desired pore size and hence the porosity have been achieved by geometrically partitioning those sub-regions based on the area while meeting the tissue scaffold design constraint. Thus the desired controlled variational porosity along the scaffold architecture has been achieved with the combination of two geometrically oriented consecutive layers. A continuous, interconnected and optimized tool-path has been generated for both layers aiming at the standard solid free form fabrication process. A zigzag pattern tool-path has been proposed for accumulated sub-region layer. And a concentric spiral like optimal tool-path pattern has been derived for the successive layer to ensure fabricatable continuity along the structure. A micro-nozzle biomaterial deposition system driven by NC motion control has been used to fabricate sample designed structure with desired pore size and porosity level. Besides proper characterization of the fabrication sample has been performed to validate the proposed methodology. Moreover a comparative study between proposed design and conventional cartesian coordinate scaffolds has been performed. The results demonstrate significant reduction in design error with the proposed method.Copyright © 2011 by ASME

WOS: 000282816900010 PubMed: 21040380 Objective To investigate the analgesic and side effects of epidural morphine or a fentanyl patch after ovariohysterectomy in dogs. Study design Prospective, randomized clinical study. Animals Twenty female mongrel dogs undergoing ovariohysterectomy. Methods The dogs were allocated to one of two groups: epidural morphine or transdermal fentanyl patch. Anaesthesia was induced with propofol and maintained with isoflurane. Morphine (0.1 mg kg-1) was administered epidurally in the epidural morphine group and a transdermal fentanyl patch was applied 24 hours before the operation in the fentanyl patch group. The heart rate, respiratory rate, body temperature, plasma cortisol concentration, and sedation and analgesia scores were recorded during the 24 hour post-operative period. Adverse effects such as vomiting, anorexia, skin reactions, urinary retention, and time to start licking the surgical site were also recorded. p < 0.05 was considered significant. Statistical analyses utilized anova for repeated measures, Friedman tests, Mann-Whitney U-tests and independent sample t-tests as relevant. Results Pain scores were lower in the epidural group than in the fentanyl group at all post-operative times. The dogs in the epidural morphine group were calm and relaxed, whereas discomfort and vocalization were recorded in the fentanyl patch group. The sedation scores were higher in the fentanyl patch group throughout the 12 hour period. Salivation and anorexia lasted longer in the fentanyl patch group than in the epidural morphine group. Plasma cortisol concentrations were high in the early post-operative period in both groups. The fentanyl patch group had higher cortisol concentrations than the epidural morphine group. Slight erythema was recorded in two dogs when the patches were removed. Conclusion and clinical relevance Epidurally administered morphine provided better analgesia and caused fewer adverse effects than the fentanyl patch after ovariohysterectomy in dogs.

Assembly variant design in agile manufacturing involves modifying components or mixing and matching existing components from valid assemblies to proliferate new variant products. Wanget al. (2001, “Assembly Modeling for Complex Assembly Variant Design,” Tenth Industrial Engineering Research Conference, Dallas TX; 2005, “Complex Assembly Variant Design in Agile Manufacturing. Part I: System Architecture and Assembly Modeling Methodology,” IIE Transactions on Design and Manufacturing, 37(1), pp. 1–15; 2005, “Complex Assembly Variant Design in Agile Manufacturing. Part II: Assembly Variant Design Methodology,” IIE Transactions on Design and Manufacturing, 37(1), pp. 17–33) developed an assembly variant design methodology based on a component relationship model that captures assembly mating relationships at the feature level referred as assembly mating graph. This paper is devoted to formulation of assembly mating graphs from legacy computer-aided design models. Mating relationships are classified as direct, indirect, and interference relationships. Direct mating relationships are identified using geometric methods while a ray-firing algorithm is used to identify indirect and interference type mating relationships. The effectiveness of the developed methodology is demonstrated using illustrative examples.

In this paper, a new feature-based material blending method is proposed to represent and design heterogeneous objects. Geometric features dictating the material variation are defined as material governing features to control material composition inside the objects. Interrelations between the material governing features and material attributes are established by constraining the geometric and material features and retained in the object model. Using these relationships, variant heterogeneous objects are developed easily by changing the geometric and material features of the heterogeneous object. Geometric methods are developed to blend not only the geometric features but also the property requirements at each of the feature. To obtain the best material variation inside the object, an optimization-based solution method based on the object's functional requirements are developed. Implementation and illustrative examples are also presented in this paper.

A new curve matching method is proposed to generate non-self-intersecting and non-twisted ruled layers for application in diverse fields such as layered manufacturing, offsetting and multi-axis CNC machining. The method establishes point-to-point correspondence represented by a set of ruling lines between two directrices of the ruled surface. The directrices are given as non-self-intersecting, closed, at least C1 continuous, planar, B-spline curves. To match the points on the directrices, a heuristic optimization method developed with the objective is to maximize the sum of the inner products of the unit normals at the end points of the ruling lines and minimize the sum of the lengths of connecting ruling lines. The generated ruling lines can be used as cutter location data for multi-axis NC machining of ruled surfaces. Moreover, by subdividing the ruling lines into equal number of segments, one can construct a series of intermediate piecewise linear curves that represent the metamorphosis between the directrices. Implementation and examples are also presented.

This paper describes geometric algorithms for manufacturing freeform objects using a re-configurable mold system. The proposed process involves a mold block, with n faces, in which the mold cavity is formed. Each face of the mold block holds a uniform grid of pins, which are used to approximate the part surfaces. The geometric algorithms presented in this paper analyze the part and determine the face of mold block from which the part model is approximated best using the pins from that face. By moving these pins in and out of the mold block, the shape of the mold cavity can be configured dynamically to suit the changes in the part geometry. Since the proposed process approximates free-form objects with discrete pins, a surface-error calculation method is also developed to control the accuracy. Computer implementation and examples are also provided in this paper.Copyright © 2003 by ASME

This paper presents a new method of generating adaptive ruled layers for rapid prototyping of 3D complex parts. To increase the accuracy and reduce the build time, an adaptive ruled layer approximation of the Stereolithography (STL) models for rapid prototyping processes is presented. Surface errors are analyzed to find the maximum errors at different layers of RP parts. By finding the RP surface errors, adaptive ruled layers are generated from the STL models. Using the constructed ruled layers of the STL models, multi-axis material removal process is integrated with the traditional rapid prototyping process to achieve better surface accuracy and to reduce the total build time.

This paper presents a novel continuous tool-path planning methodology for hollowed scaffold fabrication in tissue engineering. A new functionally gradient porous architecture is proposed with a continuous material deposition planning scheme. A controllable variational pore size and hence the porosity have been achieved with a combination of two geometrically oriented consecutive layers. The desired porosity has been achieved with consecutive layers by geometrically partitioning each layer into sub-regions based on the area and the tissue scaffold design constraints. A continuous, interconnected and optimized tool-path for layers has been generated for a three-dimensional biomaterial deposition/printing process. A zigzag pattern tool-path has been proposed for an accumulated sub-region layer, and a concentric spiral-like optimal tool-path pattern has been generated for the successive layer to ensure continuity along the structure. Three-dimensional layers, formed by the proposed tool-path plan, vary the pore size and the porosity based on the biological and mechanical requirements. Several examples demonstrate the proposed methodology along with illustrative results. Also a comparative study between the proposed design and conventional Cartesian coordinate scaffolds has been performed. The results demonstrate a significant reduction in design error with the proposed method. Moreover, sample examples have been fabricated using a micro-nozzle biomaterial deposition system, and characterized for validation.

In this research, geometric algorithms for representation and fabrication of three-dimensional (3D) freeform multi-material objects using a rapidly reconfigurable moulding process have been presented. The rapidly reconfigurable moulding system consists of many discrete arrays of pins each forming the mould-face of a mould block. A new material representation scheme is proposed for freeform multi-material objects. The geometric algorithms detailed in this paper analyse the given multi-material object and decompose it based on the material regions and manufacturability of the regions using silhouette-edge based method. The processing sequence is then determined to fabricate the decomposed multi-material object using the reconfigurable moulding process. Computer implementation and illustrative examples are also presented.

Factors including heritability, climate features, co-morbid diseases and methodological differences between studies may underlie variation in the prevalence of restless legs syndrome (RLS). The purpose of this study was to assess the prevalence of RLS in Trabzon and to evaluate associated factors by including biochemical investigations.This community-based study was conducted among a random sample of 3789 adults. The criteria suggested by the International RLS Study Group were used in the assessment of RLS. Individuals responding affirmatively to at least one question were interviewed and examined by neurologists for definitive diagnosis of RLS. Age- and gender-matched RLS-negative individuals were enrolled in the control group. Blood samples from RLS patients and control subjects were collected after 12-hour fasting to evaluate fasting blood glucose, ferritin, vitamin B12, folic acid and creatinine.The prevalence of RLS was 4.5%. Age, female gender and educational level were identified as independent risk factors for RLS. Peak prevalence rates were observed in the fourth decade in women and in the sixth decade in man. A familial history of RLS, low ferritin and vitamin B12 levels and multiparity were more common in women with RLS. Fasting blood glucose, folic acid and creatinine levels were not significantly different between the patients and controls.The prevalence of RLS is relatively consistent in different regions of Turkey. Women with RLS may have different risk factors from men with RLS that may lead to increased prevalence at earlier ages. Low socioeconomic status may also affect the prevalence of RLS.