UPLC Rapid Quantification of Ascorbic Acid in Several Fruits and Vegetables Extracted Using Different Solvents

Ascorbic acid or vitamin C is mostly found in natural products such as fruits and vegetables. Ultra performance liquid chromatography (UPLC) method has been developed to compare the ascorbic acid content in some fresh fruits (apple, orange) and vegetables (carrot, beet, cherry tomato) extracts with two different extraction solvents; i) 9% metaphosphoric acid, ii) 3% citric acid. The compound has been detected and quantified by the use of UPLC equipped with Photodiode Array (PDA) detector. The amount of ascorbic acid detected in fruits and vegetables extracts prepared with the two solvents mentioned was different. For the orange extracted using citric acid 3% recorded the highest concentration of ascorbic acid (38.2mg/100g FW) higher than with 9% metaphosphoric acid (33.3mg/100g FW), respectively the extractions of both varieties of apples, carrot, beet and cherry tomato with metaphosphoric extraction solvent recorded the highest values of ascorbic acid: 4.1mg/100g FW in case of ‘Golden’, 9.92mg/100g FW for carrot and 13.56mg/100g FW for beet. The results showed that ascorbic acid content was higher by extraction with 9% metaphosphoric acid as compared, by extraction with 3% citric acid

Radio Frequency Magnetron Sputter Deposition as a Tool for Surface Modification of Medical Implants

The resent advances in radio frequency (RF)‐magnetron sputtering of hydroxyapatite films are reviewed and challenges posed. The principles underlying RF‐magnetron sputtering used to prepare calcium phosphate‐based, mainly hydroxyapatite coatings, are discussed in this chapter. The fundamental characteristic of the RF‐magnetron sputtering is an energy input into the growing film. In order to tailor the film properties, one has to adjust the energy input into the substrate depending on the desired film properties. The effect of different deposition control parameters, such as deposition time, substrate temperature, and substrate biasing on the hydroxyapatite (HA) film properties is discussed

Biodegradable ceramics consisting of hydroxyapatite for orthopaedic implants

This study aims to analyze hydroxyapatite (HAP) coatings enriched with Mg and Ti prepared by a magnetron sputtering technique on Ti6Al4V substrate. For preparation of the coatings, three magnetron targets (HAP, MgO and TiO2) were simultaneously co-worked. The concentration of Mg added was varied by modifying the power applied to the MgO target. In all coatings, the Ti concentration was maintained constant by keeping the same cathode power fed during the whole deposition. The influence of different Mg dopant contents on the formation of phase, microstructure and morphology of the obtained Ti-doped HAP coatings were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Moreover, the effects of Mg addition upon corrosion, mechanical and biological properties were also investigated. Mg- and Ti-doped HAP coating obtained at low radio-frequency (RF) power fed to the MgO target provided material with high corrosion resistance compared to other coatings and bare alloy. A slight decrease in hardness of the coatings was found after the Mg addition, from 8.8 to 5.7 GPa. Also, the values of elastic modulus were decreased from 87 to 53 GPa, this being an advantage for biomedical applications. The coatings with low Mg concentration proved to have good deformation to yielding and higher plastic properties. Biological test results showed that the novel surfaces exhibited excellent properties for the adhesion and growth of bone cells. Moreover, early adherent vital cell numbers were significantly higher on both coatings compared to Ti6Al4V, suggesting that Mg ions may accelerate initial osteoblast adhesion and proliferation

Phase Evolution and Microstructure Analysis of CoCrFeNiMo High-Entropy Alloy for Electro-Spark-Deposited Coatings for Geothermal Environment

Publisher's version (útgefin grein)In this work, a CoCrFeNiMo high-entropy alloy (HEA) material was prepared by the vacuum arc melting (VAM) method and used for electro-spark deposition (ESD). The purpose of this study was to investigate the phase evolution and microstructure of the CoCrFeNiMo HEA as as-cast and electro-spark-deposited (ESD) coating to assess its suitability for corrosvie environments encountered in geothermal energy production. The composition, morphology, and structure of the bulk material and the coating were analyzed using scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The hardness of the bulk material was measured to access the mechanical properties when preselecting the composition to be pursued for the ESD coating technique. For the same purpose, electrochemical corrosion tests were performed in a 3.5 wt.% NaCl solution on the bulk material. The results showed the VAM CoCrFeNiMo HEA material had high hardness (593 HV) and low corrosion rates (0.0072 mm/year), which is promising for the high wear and corrosion resistance needed in the harsh geothermal environment. The results from the phase evolution, chemical composition, and microstructural analysis showed an adherent and dense coating with the ESD technique, but with some variance in the distribution of elements in the coating. The crystal structure of the as-cast electrode CoCrFeNiMo material was identified as face centered cubic with XRD, but additional BCC and potentially σ phase was formed for the CoCrFeNiMo coating.This work is part of the H2020 EU project Geo-Coat: Development of novel and cost-effective corrosion resistant coatings for high temperature geothermal applications. Call H2020-LCE-2017-RES-RIA-TwoStage (Project No. 764086).Peer Reviewe

Pectin coatings on titanium alloy scaffolds produced by additive manufacturing:Promotion of human bone marrow stromal cell proliferation

Ti6Al4V is a popular biomaterial for load-bearing implants for bone contact, which can be fabricated by additive manufacturing technologies. Their long-term success depends on their stable anchoring in surrounding bone, which in turn depends on formation of new bone tissue on the implant surface, for which adhesion and proliferation of bone-forming cells is a pre-requisite. Hence, surface coatings which promote cell adhesion and proliferation are desirable. Here, Ti6Al4V discs prepared by additive manufacturing (EBM) were coated with layers of pectins, calcium-binding polysaccharides derived from citrus (C) and apple (A), which also contained alkaline phosphatase (ALP), the enzyme responsible for mineralization of bone tissue. Adhesion and proliferation of human bone marrow stromal cells (hBMSC) were assessed. Proliferation after 7 days was increased by A-ALP coatings and, in particular, by C-ALP coatings. Cell morphology was similar on coated and uncoated samples. In conclusion, ALP-loaded pectin coatings promote hBMSC adhesion and proliferation

Device Evaluation and Design of GaN Power Converters

The rapid development of high-performance semiconductors such as CPUs and GPUs has risen the demand for point-of-load converters to become smaller and more power dense as to not be the limiting factor when designing a motherboard. Consequently, there has been a drive for designing and manufacturing more efficient point-of-load converters based on new transistor technologies and packing methods. The first goal of this project is to evaluate the performance of state-of-the-art semiconductor devices and to provide key metrics relevant for selecting a device for a certain design, in particular integrated co-packed discrete trench MOSFETs (DrMOS) and Gallium Nitrade (GaN) transistors. The second part of the project will present the design of a high-frequency point-of-load converter based on the series capacitor buck topology for low voltage applications which incorporates an interleaved four phase design with coupled magnetics. The design also allows for two options for the control circuit corresponding to high and very high frequencies (up to 20MHz)

Mechanical, In Vitro Corrosion Resistance and Biological Compatibility of Cast and Annealed Ti25Nb10Zr Alloy

Compared to other alloys, Ti6Al4V is the most used in medicine. In recent years, concerns regarding the toxicity of Al and V elements found in the composition of Ti6Al4V have drawn the attention of the scientific community, due to the release of Al or V ions after long term exposure to human body fluids which can lead to a negative response of the human host. Based on this, the aim of the paper was to manufacture a Ti25Nb10Zr alloy consisting of biocompatible elements which can replace Ti6Al4V usage in medical applications. In order to prove that this alloy possessed improved properties, the mechanical, wear and corrosion resistance, wettability, and cell viability were performed in comparison with those of the Ti6Al4V alloy. The corrosion behavior of this new alloy in simulated body fluid (SBF) and Hank solutions is superior to that of Ti6Al4V. The cast Ti25Nb10Zr alloy has a good tribological performance in SBF, while annealed Ti25Nb10Zr alloy is better in Hank solution. Cell viability and proliferation assay after five days indicated that Ti25Nb10Zr presented a good viability and proliferation with values of approximately 7% and 10% higher, respectively, than the ones registered for pure Ti. When compared with Ti6Al4V, the obtained results for Ti25Nb10Zr indicated smaller values with 20% in the case of both tests. Overall, it can be concluded that cell proliferation and viability tests indicated that the biocompatibility of the Ti25Nb10Zr alloy is as good as pure Ti and Ti6Al4V alloy

Characterizing the Role of Gds1p in the Saccharomyces cerevisiae Environmental Stress Response

The transcription factors Msn2p and Msn4p are major components of the Saccharomyces cerevisiae environmental stress response. Their transient activation/deactivation is dependent on a regulatory network centering on nucleocytoplasmic shuttling but also includes a range of other mechanisms. The acetyltransferase complex, NuA4 has been implicated in repression of Msn2p yet the mechanism is largely unknown. Gds1p is an uncharacterized yeast protein identified in a recent study as a physical interactor and acetylation target of NuA4. Gds1 protein level is dependant both on NuA4 and environmental stress and our analysis shows it to be involved in the nuclear exclusion of Msn2p in the absence of stress. Unstressed cells lacking GDS1 exhibit increased nuclear accumulation Msn2p and an increase in transcription of the stress reporter gene, HSP12. My work supports a model in which Gds1 and NuA4 can work independently to inhibit the Msn2/4 dependant yeast stress response in the absence of stress