Processing of Bioceramic Implants Via Fused Deposition Process

Porous ceramic structures have long been a subject of investigation as bone sl..bstitute. Most of these porous structures are typically made by techniques that result .randomly arranged pores with a wide variety of pore sizes. In recent years, SFF methods are being used for the fabrication of porous bioceramic implants. Porous ceramic structures have been fabricated using indirect route where a .polymeric mold is fitst created via fused deposition process. The mold was then infiltrated with ceramic slurry, dried. and ·then subjected to a binder bum out and sintering cycle. In this paper, processing of 3D honeycomb porous alumina ceramic structures and some.initial mechanical properties for bone implants will be discussed.Mechanical Engineerin

Novel Ceramics and Metal-Ceramic Composites via Fused Deposition Process

Indirect fused·· deposition process is utilized.·.. to ·fabricate controlled porosity ceramic structures using alumina, mullite, zirconia, LSCF-perovskite, tricalcium phosphate and hydroxyapatite, where pore size, pore shape and pore connectivity are varied from one end to the other end of the parts. Some of these porous ceramics are then infiltrated with metals via pressureless reactive metal infiltration to form novel metal-ceramic composites. Thispaper will describe processing, structures of various porous and metal-infiltrated composites and their physical and mechanical properties.Mechanical Engineerin

Fused Deposition of Ceramics (FDC) and Composites

Fabrication of functional ceramics and composites has been attempted using fused deposition of ceramics process. In this work, first a polypropylene (PP) binder system has been developed for the FDM. The PP binder system was mixed with ceramic powders and then extruded in the form of filament for the FDC. Controlled porosity ceramic parts were directly fabricated using a FDM 1650 machine with mullite, fused silica and titania powder loaded green filaments. The parts were then binder removed and sintered. Some of the porous parts were then infiltrated in Al metal to form the metal-ceramic composites. This article discusses feedstock development, part fabrication and methods to improve the quality of parts during processing.Mechanical Engineerin

Ameliorating effect of quercetin against UV radiation-induced damage in Drosophila melanogaster

Quercetin is a plant flavonoid found in various fruits, leaves such as tea, vegetables and has been extensively studied due to its antioxidative, anticancer, anti-inflammatory and anti-neurodegenarative effects. UV radiation is harmful for human being as it may cause several complications such as skin cancer. Fruit fly (Drosophila sp.) has long been used as an arthropod model for genetics related studies. In the present study, the protective effect of quercetin is evaluated against UV-C radiation induced damage using Drosophila melanogaster. Pre-treatment with quercetin (10 µM) recovered the shortened lifespan caused by UV radiation and has also increased eclosion rate and the dose of quercetin is lower than the previously reported doses of other flavonoids. Flies subjected to moderate dose of UV radiation showed distinct abnormal characters such as incomplete abdominal pigmentation, curly wings or outstretched wings, whereas quercetin pretreatment showed no such abnormal characters or mutant phenotypes.  There is a considerable amount of change in the eclosed adult fly size, pupal size and pupal migration distance as well. Gel electrophoresis study of salivary gland DNA of D. melanogaster demonstrates the efficacy of quercetin in conferring protection to DNA against UV radiation-induced damage. Therefore, it can be concluded that quercetin may act as an effective protective agent against UV radiation-induced damage. DOI: http://dx.doi.org/10.5281/zenodo.358854

High Thermal Conductivity Coatings via LENS™ for Thermal Management Applications

Surface modification has been used to improve wear resistance, corrosion resistance and thermal barrier properties of metals. However, no significant attempts have been made to improve thermal conductivity by surface modification. In this work, we have examined the feasibility of enhancing thermal conductivity (TC) of stainless steel by depositing brass using Laser Engineered Net Shaping (LENS). The coating increased the TC of the substrate by 65% at 100 C°. Significantly low thermal contact resistance was observed between the coating and the substrate due to minimal dilution and defect free sound interface. Our results indicate that laser processing can be used on low coefficient of thermal expansion metal matrix composites to create feature based coatings to enhance their heat transfer capability.Mechanical Engineerin

Induction of Autophagy by Cystatin C: A Mechanism That Protects Murine Primary Cortical Neurons and Neuronal Cell Lines

Cystatin C (CysC) expression in the brain is elevated in human patients with epilepsy, in animal models of neurodegenerative conditions, and in response to injury, but whether up-regulated CysC expression is a manifestation of neurodegeneration or a cellular repair response is not understood. This study demonstrates that human CysC is neuroprotective in cultures exposed to cytotoxic challenges, including nutritional-deprivation, colchicine, staurosporine, and oxidative stress. While CysC is a cysteine protease inhibitor, cathepsin B inhibition was not required for the neuroprotective action of CysC. Cells responded to CysC by inducing fully functional autophagy via the mTOR pathway, leading to enhanced proteolytic clearance of autophagy substrates by lysosomes. Neuroprotective effects of CysC were prevented by inhibiting autophagy with beclin 1 siRNA or 3-methyladenine. Our findings show that CysC plays a protective role under conditions of neuronal challenge by inducing autophagy via mTOR inhibition and are consistent with CysC being neuroprotective in neurodegenerative diseases. Thus, modulation of CysC expression has therapeutic implications for stroke, Alzheimer's disease, and other neurodegenerative disorders

A Two-Stage Bi-Objective Data Envelopment Analysis Problem

This paper proposes a novel two-stage bi-objective Data Envelopment Analysis (DEA) model. The objectives considered are maximization of overall efficiency and maximization of labor efficiency. The existing literature has not yet proposed any multi-objective DEA model till date. However, such model is in demand because most of the real life problems consist of multiple stages. The proposed model has also considered dissimilar intermediate weights. The proposed model has been applied to a multi-stage insurance problem with two input variables, two intermediate variables and two output variables in order to establish the effectiveness of the proposed model. The proposed model is an algorithmically complex problem and therefore a hybrid Multi-Objective Genetic Algorithm has been applied in order to solve the proposed model

Interaction of CeO2 and ZnO nanoparticles towards the symbiotic association of alfalfa (Medicago sativa) and Sinorhizobium meliloti in soil

The production of engineered nanoparticles (ENPs) has rapidly increased due to their wide range of applications in the field of electronics, medicine, chemistry and biology. Consequently, concerns have risen about the environmental release and potential negative impact of NPs. A few reports have described the effects of TiO2 NPs and quantum dots upon nitrogen fixing bacteria. However, the understanding of the interaction of NPs in plant-microbe interface (symbiotic association), like alfalfa (Medicago sativa L.)-Sinorhizobium meliloti, is still in its infancy. Alfalfa is the world\u27s most important forage crop. It grows in association with S. meliloti, which is very important in terms of nitrogen fixation and, hence, global nitrogen cycling. This research project was aimed at understanding the effect of two ENPs (CeO2 and ZnO) on S. meliloti and alfalfa, separately, and on their symbiosis. This investigation was completed in three phases. Initially, the associated bacterium was treated, separately, with CeO2 and ZnO NPs. Ten nm CeO2 and ZnO NPs were exposed towards S. meliloti at 10, 31, 62.5,125, and 250 mg/l in liquid Yeast Mannitol Broth (YMB). Toxicological parameters evaluated included UV/Vis measurement of minimum inhibitory concentration, disk diffusion tests, and dynamic growth. Advanced scanning transmission electron microscope (STEM) and infrared spectroscopy (FTIR) were utilized to determine the spatial distribution of NPs and macromolecule changes in bacterial cells, respectively. Results indicate that ZnO NPs were more toxic than CeO2 NPs in terms of inhibition of dynamic growth and viable cells counts. STEM images revealed that CeO2 and ZnO NPs were found on bacterial cell surfaces and ZnO NPs were internalized into the periplasmic space of the cells. FTIR spectra showed changes in protein and polysaccharide structures of extra cellular polymeric substances present in bacterial cell walls treated with both NPs. The growth data showed a bacteriostatic effect of CeO2 NPs, whereas ZnO NPs was bactericidal to S. meliloti. Overall, ZnO NPs were found to be more toxic than CeO2 NPs to S. meliloti . In phase II, the alfalfa plant in association with S. meliloti , were cultivated for 30 d in soil treated with ZnO NPs, ionic (ZnCl 2) and bulk ZnO, concentrations ranging from 0 (control)-750 mg kg -1. Plant growth, Zn bioaccumulation, dry biomass, leaf area, total protein, and catalase (CAT) activity were measured. Results showed 50% germination reduction by bulk ZnO at 500 and 750 mg/kg and all ZnCl2 concentrations. ZnO NPs and ionic Zn reduced root and shoot biomass by 80% and 25%, respectively. Conversely, bulk ZnO at 750 mg/kg increased shoot and root biomass by 225% and 10%, respectively, compared to control. At 500 and 750 mg/kg, ZnCl 2 reduced CAT activity in stems and leaves. Total leaf protein significantly decreased as external ZnCl2 concentrations increased. STEM analysis revealed the presence of ZnO particles in tissues, suggesting the uptake of NPs. However, ZnO NPs showed less toxicity compared to ZnCl2 on measured traits. Phase III was performed in soil treated with either ZnO or CeO2 NPs at 0, 250, 500, and 750mg/kg for 30 days to study the toxicity effect of ZnO and CeO2 towards alfalfa\u27s secondary metabolites and antioxidative properties. The toxicity was evaluated for leaf using chlorophyll (a & b), carotenoids, phenolic, and flavonoid contents. Results showed that, compared to control, leaf chlorophyll a content reduced to 60% and 40% at 750 mg/kg of CeO2 and ZnO NP treatments, respectively. Chlorophyll b reduced by 64%, 48%, and 60% at 250, 500 and 750 mg/kg CeO2 NP treatments, while chlorophyll b remained the same except 40% reduction at 750 mg/kg bulk ZnO treatment. CeO2 NPs enhanced the root flavonoids content by 34% at 750 mg/kg treatment and 86% in shoot at 500 mg/kg treatment, compared to control. Total root flavonoids decreased by 49% in plants treated with 750 mg/kg of ZnO NP treatment, whereas total flavonoids in shoots remained similar to control in all treatments, except 250 mg/kg ZnO NP treatment, where the flavonoid content decreased to 77%. This is the first complete study in a symbiotic system in terms of nano, bulk and ionic Zn species comparison in soil matrix. In addition, to the best of the authors\u27 knowledge, this is the first report on the effects ZnO and CeO2 on alfalfa\u27s secondary metabolites and chlorophyll content. Our results will help to reveal the toxicity of CeO2 and ZnO NPs on alfalfa and S. meliloti species, as well as to understand the eco-toxicity of NPs in plant-microbe symbiosis

Influence of Pentavalent Dopant Addition to Polarization and Bioactivity of Hydroxyapatite

Influence of pentavalent tantalum doping in bulk hydroxyapatite (HAp) ceramics has been investigated for polarizability and bioactivity. Phase analysis from X-ray diffraction measurement indicates that increasing dopant concentration decreased the amount of HAp phase and increased β-TCP and/or α-TCP phases during sintering at 1250 °C in a muffle furnace. Results from thermally stimulated depolarization current (TSDC) measurements showed that doping hindered charge storage ability in HAp ceramics, and doped samples stored fewer charge compared to pure HAp. However, doping enhanced wettability of HAp samples, which was improved further due to polarization. In vitro human osteoblast cell-materials interactions study revealed an increase in bioactivity due to dopant addition and polarization compared to pure HAp. This increase in bioactivity was attributed to the increase in wettability due to surface charge and dopant addition