Fatima Zivic

Effect of vacuum-treatment on deformation properties of PMMA bone cement.

Deformation behavior of polymethyl methacrylate (PMMA) bone cement is explored using microindentation. Two types of PMMA bone cement were prepared. Vacuum treated samples were subjected to the degassing of the material under vacuum of 270 mbar for 35 s, followed by the second degassing under vacuum of 255 mbar for 35 s. Air-cured samples were left in ambient air to cool down and harden. All samples were left to age for 6 months before the test. The samples were then subjected to the indentation fatigue test mode, using sharp Vickers indenter. First, loading segment rise time was varied in order to establish time-dependent behavior of the samples. Experimental data showed that viscous part of the deformation can be neglected under the observed test conditions. The second series of microindentation tests were realized with variation of number of cycles and indentation hardness and modulus were obtained. Approximate hardness was also calculated using analysis of residual impression area. Porosity characteristics were analyzed using CellC software. Scanning electron microscopy (SEM) analysis showed that air-cured bone cement exhibited significant number of large voids made of aggregated PMMA beads accompanied by particles of the radiopaque agent, while vacuum treated samples had homogeneous structure. Air-cured samples exhibited variable hardness and elasticity modulus throughout the material. They also had lower hardness values (approximately 65-100 MPa) than the vacuum treated cement (approximately 170 MPa). Porosity of 5.1% was obtained for vacuum treated cement and 16.8% for air-cured cement. Extensive plastic deformation, microcracks and craze whitening were produced during indentation of air-cured bone cement, whereas vacuum treated cement exhibited no cracks and no plastic deformation.

Custom design of furniture elements by fused filament fabrication

Additive manufacturing technologies enable rapid prototyping of different parts, according to the three-dimensional model software solution. This paper presents some aspects of fused deposition modeling technology and its application in the wood industry. The fused deposition modeling technology was initially developed for three-dimensional printing of plastic parts, whereas acrylonitrile butadiene styrene and polylactic acid plastics filament are commonly applied. Possibilities for application of different composites with fused deposition modeling in the wood industry are reviewed and presented in this paper. Several industrial applications were considered also, from aspects of material durability, mechanical strength, low cost, and customization. Directions of further research have been discussed, considering graphene and carbon nanotubes as composite reinforcement materials and bio-organic composites with wooden particles or fibers mixed into the polymer matrix. Development of new composites for use with the fused deposition modeling technology is promising area taking into account that new low-cost extruders are already commercially available, as a support to fused deposition modeling device. Three-dimensional printing is very convenient for investigation of different custom-made composite materials, as well as custom shapes of final parts, starting from powders, their mixing, drawing of composite material filament, which are further used for three-dimensional printing with solidification and fabrication of custom-made products. New composites for fused deposition modeling, made of wood and plastic combinations were experimentally investigated for use as functional and customized elements of furniture. Obtained results strongly indicated that both new composite materials and fused deposition modeling printing can be efficiently used for broad customization from aspects of material properties and product shapes, thus enabling low-cost fabrication of small series of complex furniture elements, especially fixtures or clamp tools.

Characteristics and Applications of Silver Nanoparticles

This review provides an insight into the level of knowledge about the properties of silver nanoparticles, their already existing applications and possible further developments, as well as their effects on different behaviour and properties of the products wherein they are used. This chapter reviews the application fields of nanosilver, starting from basic silver properties and influential parameters in definition of silver nanoparticles (Ag NPs). Toxicity of Ag NPs is observed from various aspects in relation to cell toxicity and relevant mechanisms of their behaviour within tissue environment. Range of sizes and surface chemistry of Ag NPs and possible effects, as well as known in vivo effects are reviewed, based on the already established research results. Antibacterial properties of Ag NPs and relevant mechanisms of action are presented. Application areas where commercialization of nanosilver has started are presented: medicine (wound dressings, drug delivery, biosensors and medical diagnostics, orthopedics), food and textile industries, and water disinfection systems. Environment related issues have been considered and important conclusions derived from established results are presented. Each application sector comprises descriptions of basic mechanisms related to Ag NPs, gained benefits, but also possible risks and recognised limitations in application of Ag NPs. Future directions as recognised in specific research groups dealing with some of the sectors are listed. Exquisite properties of Ag NPs, especially antibacterial and optical properties, along with availability and lower cost of fabrication, processing and storage, compared to other noble elements makes them very promising for numerous future applications. However, proven cell toxicity must be further studied and methods to overcome these adverse effects on tissue in general are subject of current research. One important application field is drug delivery for targeted cancer cell destruction that is expected to show particular results very soon. Even with all the limitations that need to be imposed on usage of Ag NPs, they are promising nanoagent for novel advancements in different areas.

Review of Existing Biomaterials—Method of Material Selection for Specific Applications in Orthopedics

Biomaterials have emerged as a very important material class for wide application in medicine. Intensive research during the last decade strongly indicates that many health-related problems can be efficiently overcome with these new materials. Quality of life has been significantly increased for patients who need reconstructive surgeries, especially in comparison with old solutions. This paper reviews biomaterials in orthopedics that are used either as a support or substitute for bone tissues, from the aspect of their properties and state-of-the-art results in real clinical cases. Limitations and further directions of research are presented. Metal, ceramic and polymer materials, as well as new composites and new material structures, are reviewed, such as biodegradable porous materials and scaffolds. Nowadays, optimal selection of materials is one of the challenges imposed by the presence of many novel materials that can be used in specific applications. A general method of material selection is presented related to the hip stem and permanent metal biomaterials.

Biodegradable Metals as Biomaterials for Clinical Practice: Iron-Based Materials

This review presents the state-of-the-art in the development of iron-based degradable medical implants. Basic properties demanded by the new concept of degradable implants are elaborated, along with the work devoted to understand the underlying mechanism and to improve the properties towards best fitted to the natural tissue. Three application areas are considered: vascular stents, orthopedic implants and tissue engineering scaffolds. Each of these has its own specific demands imposed upon the artificial substitution materials. Biocompatibility is an essential feature that each medical implant must have, but different aspects can be considered depending on the end application. Furthermore, adequate mechanical properties and various characteristics related to the fabrication and in vitro and in vivo testing are presented for pure iron, alloys and composites, as well as joint structures. Corrosion control is a foundation in the development of these materials development and different aspects are also given. Iron-based materials need increased degradation rate because they are still more similar to the permanent implants, due to the slow corrosion process and various methods to overcome this issue have been tried. Porosity and its relation to material structures, mechanical properties, degradation behaviour, magnetic properties, and fabrication technologies, as well as methods of numerical simulations as a supporting tool have been elaborated. Porous structures represent one way to enhance corrosion, while maintaining intact other necessary properties of the biomaterial. Economic impact of the biomaterials sector in general is significant and justifies large investments in research. Iron-based materials for degradable implants are not in clinical practice yet, but the research results achieved so far promise the future applications.

Differences Between Adopters and Non-adopters of Innovation: Case Study of New Technologies|Adoption by Small and Medium Enterprises in Serbia

This article explores the factors that govern the process of innovation adoption by companies. We have studied the factors that promote the willingness or resistance of companies to adopt new research results or novelty, in general. As one case study, we will elaborate factors that influence a website adoption by smaller companies that mainly do not have their own ICT departments. The study investigated the attitudes of managers towards Internet-mediated business development and promotion, comprising a case study of small and medium-sized enterprises (SMEs) in Serbia. Special focus was placed on low income micro-SMEs. The results showed that, in the case of larger organisations, the models proposed by Flanagin (Hum Commun Res 26(4):618–646, 2000) and Davis (MIS Q 13(3):319–339, 1989) can be effectively used as guidance for website adoption. However, in the case of very small companies, with limited budgets and locally oriented markets, a few of those factors are more prominent, while some have very little influence on the adoption process. Education background of the owners essentially determines decision making and the adoption process, and competitive pressures have no significant influence. The annual income of the company has a certain influence, but, even with the available budget, micro-SMEs will not consider introduction of a website if they cannot perceive any benefits, often due to a lack of awareness of innovations in ICT and marketing. If the owners can perceive website benefits, the cost of introduction and maintenance has little influence. Specific cultural aspects of the region should be considered as the significant factor influencing innovation introduction.

Introduction—The Current Status and Momentum in Nanotechnology Commercialisation

Everybody is talking about nanoscience and nanotechnology. Nowadays ‘nano’ is very popular in science and technology, as well as in everyday news in journals, magazines and newspapers. If you ask non-scientific people “What is nano?”, the majority would probably respond “something small and new”… We can use some of the definitions, starting from Feynman’s famous sentence, “There’s Plenty of Room at the Bottom” or some officially adopted such as “Nanotechnology is science, engineering, and technology conducted at the nanoscale, which is about 1 to 100 nm.”, USA National Nanotechnology Initiative. Today, the term nano has become more than this simple definition. It is probably also becoming a kind of philosophy, as once in ancient Greece, philosophy was the science comprising mathematics, biology and other fields of natural science.

Development of New Composites Made of Waste Materials for Wood Pallet Element

The recycling of waste products and its further use for new products is of the utmost importance nowadays. The quantities of waste product originating from industries involving plastics, paper, wood, textile and metal foils, such as the related automotive, paper, wood and food industries, represent extremely large numbers, strongly indicating the need for efficient waste management. On the other side of things, companies are always looking for ways to lower material costs. The combination of different waste materials can be used for production of new composite materials. This paper will present a brief overview of existing possibilities in the development of new composites completely made of waste materials, as well as further research directions. A preliminary study of material combinations that can provide a composite aimed at load bearing applications is given, for the purpose of replacing elements such as wood blocks in transport pallets. Several combinations of waste material from different industries were studied in a composite structure: paper, cardboard boxes, tetra-pak containers, expanded polystyrene (styrofoam), polyurethane (PU) foam, artificial leather, textile, wood chips and dust. Preliminary compressive tests were performed. The results indicated unsuitable combinations, but also some that provided a stable compact composite which endured high compressive loads. An important result is that such a composite can be made without adding any adhesives. Waste materials from different industries can be efficiently used for new composites, and further study of this is clearly needed.

Advances in Applications of Industrial Biomaterials

Environmentally responsible behaviour should be promoted in all spheres of life. This issue applies to the automotive industry as much as it does elsewhere. This is one of the most important reasons for the expansion of the use of biomaterials in car manufacturing. They have numerous advantages in terms of eco-friendly production technologies, reduction in the exploitation of fossil resources and waste minimization due to their features of biodegradability and recyclability. The paper shows an overview of the basic definitions of and methods for obtaining certain biomaterials. Here, the emphasis is placed on bio-based plastics, rubber and composites, because of their overwhelming presence in newly oriented industries. Due to the various applications and characteristics of bio-plastics, an overview of the tensile strength of each variation is given, with an emphasis that similar tests were conducted for all of them. Furthermore, knowing that the mechanical, chemical, thermal and other characteristics of biomaterials are all considered to be satisfactory, there has been a reasonable attempt to use them instead of conventional materials whenever possible. Consequently, the work contains an overview of the application of biomaterials in making different parts in the automotive industry and descriptions of their incorporation into branded vehicles, as a tool for increasing human consciousness of the fact that making a profit and preserving nature can result from the same activity. The paper also involves analysis of the conditions that biomaterials have to satisfy in order to expand their usage in the production of parts for the automotive industry.