Search

Polyurethane is a versatile polymer with a high degree of toughness and ductility used in a wide variety of applications. In this study, two-part thermoset polyurethane was used as a matrix material to prepare hybrid and non-hybrid composites. Hybrid laminates were prepared by combining either glass fiber or basalt fibers with steel fibers. The mechanical properties of prepared composite specimens were characterized and scanning electron microscope (SEM) observation was performed around the fracture region of the tested specimens. The results revealed a significant increment in tensile strength, and flexural strength in BS1-PU (8 layers of basalt-1 layer of steel) hybrid laminate by 357.74 % and 64.59 %, respectively, compared to steel fibers reinforced polyurethane composites. Furthermore, GS4-PU hybrid composite (5 layers of glass-4 layers of steel) achieved an improvement in tensile strain by 12.07 %, flexural strain by 25.32 %, and absorbed energy by 18.21 %, compared to glass fibers reinforced polyurethane composite. Moreover, the SEM observations revealed that the replacement of some basalt and glass layers with steel layers leads to a positive hybridization effect of the overall produced hybrid composites.

In the study for this contribution, production of in situ synthesized TiB2 particles in iron-based composite coatings using four different submerged arc welding powders (fluxes) containing increasing amounts of ferrotitanium and ferroboron with S1 welding wire, were targeted. For this purpose, coating deposition was carried out to improve the hardness and wear properties of the AISI 1020 steel surfaces using hybrid submerged arc welding. In hybrid submerged arc welding, the welding pool is protected by both welding powders and an argon gas atmosphere. To examine the composite coatings, visual, chemical, microstructural analyses and hardness and wear tests were carried out. With the use of increasing amounts of ferrotitanium and ferroboron in the welding powders, it was observed that the microstructure of the coatings changed in terms of TiB2 particle geometries such as rectangular and hexagonal; volume fractions of TiB2 particles in the coating microstructures increased; hardness values of coatings were enhanced from 34 HRC to 41 HRC; the wear resistance of the coatings improved, and worn surface images of the coatings caused by the counter body changed from continuous with deep scratches to discontinuous with fine scratches and crater cavities.

Slag waste generated during the metallurgical process in a ferrochromium plant in Elazig, Turkey, ferro alloys and other required ceramic based powders were mixed to obtain recycled powders produced by submerged arc welding using the agglomeration method. High carbon ferrochromium was also added to the recycled powder mixtures to improve the microstructure, hardness, and wear properties of SAE 1020 steel using a submerged arc welding technique for hardfacing. After the powder production and welding process, there were no crack and porosities on the surface of the hardfacings. As the amount of high carbon ferrochromium in the recycled powders increased, homogeneity and slag removal properties of the hardfacings decreased. Their microstructures changed, macrohardness values increased, and wear losses decreased. The highest macrohardness value 46 HRC and the lowest wear loss 4.8 g were observed in hardfacing obtained using the recycled powder with 16 wt.-% high carbon ferrochromium.

Background: Electrochemical oxidation mechanism and electrochemical determination of meloxicam (M), an anti-artrithtis agent, were investigated by cyclic voltammetry and square wave adsorptive stripping voltammetry, respectively. Objective: In this study, we aimed to investigate the electrochemical redox mechanism and develop a nano-sensor for sensitive, fast and selective analysis of meloxicam. Methods: In this study, the three-electrode system was used for all voltammetric measurements. Firstly, the graphene content of GR/CPE sensor was changed in the range of 1.67% to 6.68%. Then, the surface characterization of modified electrode was carried out by using Electrochemical Empedance Spectroscopy and Surface Electron Microscopy methods. Some analytical parameters, such as pH, accumulation potential and accumulation time were optimized and by using optimum parameters, calibration study was established. Results: The GR/CPE with a graphene content of 3.33 % was found to have the best voltammetric signal with a linear working range of 0.1–10 µM. The sensitivity of the quantitative voltammetric method towards M is fairly good with an LOQ of 0.0088 µmol/L and LOD of 0.0026 µmol/L. Conclusion: The optimum pH, accumulation time and accumulation potential were found to be 2.0, 150s and 0.0 V, respectively. The height of the voltammetric signal obtained with the GR/CPE electrode was stable with a 4.0 % deviation for a period of not shorter than 1 months.

Since last decade, sugar based biopolymers are recognized in nanomedicine as promising materials for cancer imaging and therapy. Their durable, biocompatible and adhesive properties enable the fine tuning of their molecular weights (MW) and their miscellaneous nature makes the molecules acquire various conformations. These in turn provide effective endocytosis by cancer cell membranes that have already been programmed for internalization of different kinds of sugars. Therefore, biocompatible sugar based nanoparticles (SBNPs) are suitable for both cell-selective delivery of drugs and imaging through the human body. Recently, well known sugar-based markers have displayed superior performance to overcome tumor metastasis. Thereby, targeting strategies for cancer cells have been broadened to sugar-based markers as noticed in various clinic phases. In these studies, biopolymers such as chitosan, hyaluronic acid, mannan, dextran, levan, pectin, cyclodextrin, chondroitin sulphate, alginates, amylose and heparin are chemically functionalized and structurally designed as new biocompatible nanoparticles (NPs). The future cancer treatment strategies will mainly comprise of these multifunctional sugar based nanoparticles which combine the therapeutic agents with imaging technologies with the aim of rapid monitoring response to therapies. While each individual imaging and treatment step requires a long time period in effective treatment of diseases, these multifunctional sugar based nanoparticles will have the advantage of rapid detection, right drug efficiency evaluation and immediate interfere opportunity to some important diseases, especially rapidly progressing cancers. In this article, we evaluated synthesis, characterization and applications of main sugar based biopolymers and discussed their great promise in nano-formulations for cancer imaging and therapy. However much should be done and optimized prior to clinical applications of these nano-formulations for an efficient drug treatment without overall toxicity for getting most effective clinical results.

Background: Screw fixation of syndesmotic injuries facilitates ligament healing and restoration of ankle stability, but failure of the screw might threaten the success of the treatment. Screw design parameters, such as outer diameter, inner diameter, thread pitch, leading edge radius, trailing edge radius, leading edge angle, and trailing edge angle, might have effects on the stresses that occur in the screws. This is the first study, to our knowledge, to investigate which geometric screw parameters play key roles in stresses that occur in screws used for syndesmotic fixation.Methods: A three-dimensional finite element model of an ankle was reconstructed. Four different types of titanium screws—4.5-mm malleolar, 4-mm cancellous, 4-mm machine, and 3.5-mm cortical—were placed on this model. Physiologic load was applied to evaluate the stress in the screw. Then the contribution of each design factor to stress in the screws was analyzed systematically by Taguchi's robust design method.Results: The maximum equivalent ductile failure (von Mises equivalent stress) value was found in the 4-mm cancellous screw (402 MPa). Taguchi's analysis showed that the descending order of contribution of the design factors to stress emerging on the screw is inner diameter, leading edge angle, thread pitch, outer diameter, and trailing edge angle.Conclusions: Stress that occurs in syndesmotic screws is closely related to their geometry and dimensions. According to the results, a 3.5-mm cortical screw with the ideal screw design regarding optimal parameters to resist against stresses in the syndesmosis seems more reasonable to choose in syndesmotic fixation.

Stress fracture of the femoral neck in skeletally immature individuals is a rare condition and generally seen as compressive type. Because the condition may lead to disastrous complications, femoral neck stress fracture must also be kept in mind in the differential diagnosis of pediatric hip pain. We present a case of compressive-type stress fracture of the femoral neck in a 10-year-old girl with left hip pain that was sustained for 4 weeks and emphasize the difficulty of early diagnosis with only a radiographic evaluation and put forward an algorithm for diagnosis and treatment.

In the present study, the effect of talc content on the mechanical, thermal, and microstructural properties of the isotactic polypropylene (i‐PP) and elastomeric ethylene/propylene/diene terpolymer (EPDM) blends were investigated. In the experimental study, five different talc concentrations, 3, 6, 9, 12, and 15 wt %, were added to i‐PP/EPDM (88/12) blends to produce ternary composites. The mechanical properties such as yield and tensile strengths, elongation at break, elasticity modulus, izod impact strength for notch tip radius of 1 mm, and hardness with and without heat treatments and thermal properties, such as melt flow index (MFI), of the ternary composites have been investigated. The annealing heat treatment was carried out at 100°C for holding time of 75 h. From the tensile test results, an increased trend for the yield and tensile strengths and elasticity modulus was seen for lower talc contents, while elongation at break showed a sharp decrease with the addition of talc. In the case of MFI, talc addition decreased the MFI of i‐PP/EPDM blends. It was concluded that, taking into consideration, mechanical properties and annealing heat treatment, heat treatment has much more effect on higher yield and tensile strengths, elongation at break, elasticity modulus, impact strength, and hardness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3033–3039, 2006

Ride characteristics of a vehicle moving on a rough ground with changing travel velocity are analyzed in this paper. The solution is difficult due to the non-stationary characteristics of the problem. Hence a new technique has been proposed to overcome this difficulty. This new technique is employed in the analysis of ride characteristics of a vehicle with changing velocity in the time/frequency domain. It is found that the proposed technique gives successful results in modelling non-stationary responses in terms of a series of stationary responses.

Ride characteristics of a vehicle moving on a rough ground with changing travel velocity are analyzed in this paper. The solution is difficult due to the non-stationary characteristics of the problem. Hence a new technique has been proposed to overcome this difficulty. This new technique is employed in the analysis of ride characteristics of a vehicle with changing velocity in the time/frequency domain. It is found that the proposed technique gives successful results in modelling non-stationary responses in terms of a series of stationary responses.

Summary: Poly(-3-hydroxy alkanoate) containing unsaturated side chains, PHA-soybean, were produced by feeding Pseudomonas oleovorans with soybean oily acids obtained from soybean oil. Unsaturation of PHA-soybean were found to be 10 mol-% of unsaturated side chains. Main saturated part of the biopolymer was Poly(3-hydroxy octanoate) with minor hexanoate and decanoate units. PHA films were crosslinked via free radical mechanism by means of thermally or under UV irradiation in the presence of benzoyl peroxide, benzophenon, and /or ethylene glycol dimethacrylate (EGDM). Crosslinking yield of the PHA films were found to be from 81 to 93 wt.-% from the sol-gel analysis. Swelling properties of the crosslinked PHA films in chloroform and toluene were also studied. Mc values of crosslinked PHAs were also calculated using Flory-Rehner equation. The crosslinked biopolyester obtained by thermally at 60 °C with benzoyl peroxide indicated the highest crosslinking density. Glass transition temperatures (Tg) of crosslinked biopolyester samples were changed from −33 to −45 °C while that of PHA-soybean was −60 °C.

Change in the surface free energy of poly(glycidyl azide) (PGA) networks prepared with different reactive systems was investigated using the van Oss‐Good contact‐angle evaluation methodology in order to estimate their wettability properties. The apolar Lifshitz–van der Waals (LW) component of the surface free energy of these energetic PGA networks was found to differ only in a minor amount and an average γLWS= 32.2 mJ m−2was calculated. The network surface was found to be monopolar and basic (electron donor) in varying degrees in accordance with change of the network bulk structure, mainly due to the presence of oxygen atoms in the PGA chain. The set of the network containing only PGA and Desmodur N‐100 components showed the highest γ−Svalues compared to the other two sets. The main γ−Scontribution was found to come from the PGA polymer. A slight decrease of the γ−Scomponent was seen when the Desmodur N‐100 component was substituted with hexamethylene diisocyanate (HMDI); however a large decrease was seen when Desmodur N‐100 was substituted with the isophorone diisocyanate (IPDI) component. This large reduction in the surface basicity of the network was due to increase of the apolar IPDI groups at the surface having low surface tension and also due to decrease of the oxygen atoms belonging to the main chain of PGA at the surface, which resulted in the minimization of the network's basic surface free‐energy component. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2848–2855, 1999

Poly(glycidyl azide), PGA, was grafted onto Hydroxyl Terminated Poly(butadiene), HTPB, via free radical mechanism. PGA-macro azoinitator and HTPB polymer mixture was casted from solution and the polymer film was kept at 90°C for 4 hours. The grafted polymer was isolated from the product by fractional precipitation and characterized by NMR and FT-IR spectroscopy. Graft copolymer structure was also confirmed that volume ratio of nonsolvent to the solution of the graft copolymer was between those of corresponding homopolymers. TGA traces of the block polymers were containing two different maxima at 253°C (for PGA units) and 469°C (for HTPB units). Because of the incompatibility of the blocks, DSC curve showed two Tg's which belong to the related segments.

Designing the 3D bioprinted scaffolds has been a promising tool which assists cells to adhere and supports the self-repair mechanism of native tissues. In order to practice this hypothesis, we used 3D bioprinting methods and fabricated Polylactic acid (PLA) and β-tricalcium phosphate (β-TCP) scaffolds and incorporated them with four different hydrogels (Collagen (Col), Sodium Alginate (SAlg), Halamomas Levan (HLh), Chitosan (Ch). Furthermore, PLA/β-TCP Scaffolds incorporated with chitosan were further enhanced with Amoxicillin (AMX). These scaffolds were further characterized for their chemical, morphological, antibacterial and cellular biocompatibility. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, compressive strength test, agar diffusion test and in vitro cellular behaviour tests were performed to reveal structural, mechanical and biological characteristics of scaffolds. Among others, chitosan including samples demonstrated significantly superior and beneficial features such as the highest biocompatibility and structural integrity regarding morphology, compared to the other samples. Therefore, chitosan including samples were loaded with amoxicillin (AMX) to increase antimicrobial activity of the scaffolds. All together, these data show that PLA/β-TCP 3D printed scaffolds incorporated with different hydrogels has the ability to assist the tissue to repair and regeneration.

A 16-year-old boy presented with a patellar mass and anterior knee pain without any trauma. On physical and radiologic assessment, a mass at the superolateral edge of the patella and a hyperintense lesion on T2 sequences of magnetic resonance imaging was detected. Excisional biopsy revealed a chondroma of patella. Primary bone tumors of the patella are extremely rare and occurence of chondroma in this localization is very uncommon. Although anterior knee pain is a very frequent and usually harmless, it is essential to consider the more severe disorders such as bone tumors.