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Precise Manufacturing and Performance Validation of Paper-Based Passive Microfluidic Micromixers
Mahdee Samae,Pawarit Ritmetee,Somyot Chirasatitsin,Sanja Kojić,Tijana Kojić,Jovana Jevremov,Goran Stojanović,Hani Al Salami 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.3
Micromixers are one of the most frequently used components in microfluidics. Passive micromixers are an emerging type with unique features in terms of reliability, robustness and efficiency. Hence, this study aimed to design, fabricate and test new multilayered passive micromixers consisting of three ad hoc layers, by means of a precise and cost-effective xurography manufacturing technique. The first and third layers are PVC foils, whereas the second layer is paper, incorporating microchannels of straight line or zig-zag configuration. Three different types of papers were analyzed as materials for the middle layer. Results demonstrated that immersing the papers into paraffin wax resulted in significantly improved physical characteristics, including solidification and intactness that reduced leakage of fluids into inside channels, thereby enhancing internal efficacy and delivery mechanisms. Subsequent assessments were carried out on mixing performance at various flow rates, pattern-related flow rates at various pressures and paper types, and results showed the impact of a zig-zag versus straight line configuration, demonstrating the importance of flow patterns on features of micromixers and their applications in microfluidic devices. Furthermore, image analysis was conducted to determine mixing efficiency of the proposed microfluidic micromixers.
Temperature Sensors Manufactured from Edible Materials Intended for Oral Cavity Operation
Goran M. Stojanović,Milan Radovanović,Sanja Kojić,Lazar Milić,Mitar Simić,Naturality Company,Raphael Georges Duval,Jelena Vukmirović,Bojan Petrović 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.1
Following the circular economy concept, all areas of science, including electronics, require individual approach. The green electronics approach implies processing natural based materials for development of electronic components even for single use, so that waste does not exist. This paper describes the production of thermistors from 3 different types of edible materials, their testing in laboratory conditions, as well as the application for measuring the temperature in the human oral cavity. To make the thermistor, three types of natural materials were used (carrageenan, polyvinyl alcohol and apple pomace-based). After fabrication, materials were poured into molds. Aluminium foil contacts were placed so that the electrical characterization of the materials could be performed. Several parameters were measured: resistance (R), impedance (Z) and the phase angle (θ) as a function of frequency. In order to determine whether the thermistors have a positive or negative temperature coefficient and to determine their sensitivity, measurements were conducted at three different temperatures: 25 ℃ (room temperature), 37 ℃ (human body temperature), and 50 ℃. The thermistors demonstrated negative temperature coefficient behaviour. Additionally, it was demonstrated that the apple pomace-based thermistor can successfully measure healthy volunteer's temperature.
Liver graft from donation after circulatory death donor: Real practice to improve graft viability
Koji Hashimoto 대한간학회 2020 Clinical and Molecular Hepatology(대한간학회지) Vol.26 No.4
Donation after circulatory death (DCD) is an increasing source of liver grafts for transplantation, yet outcomes have been inferior compared to donation after brain death liver transplantation. These worse outcomes are mainly due to the severe graft injury resulting from mandatory warm ischemia during DCD organ recovery. New evidence, however, indicates that improved donor selection and surgical techniques can decrease the risk of graft failure and ischemic cholangiopathy (IC). Under current best practices, DCD organs are retrieved with the super-rapid technique, optimizing timing and protecting the liver graft from detrimental warm ischemia. Graft viability is influenced by both the quantity and quality of warm ischemia, which is unique to each donor and causes various degrees of pathophysiologic consequences. Evidence also shows that the choice of preservation solution and premortem heparin administration influences graft viability. Additionally, although the precise mechanism of IC remains unknown, stasis of blood during donor warm ischemia may cause the formation of microthrombi in the peribiliary vascular plexus and ischemia of the bile duct. Importantly, thrombolytic protocols show a possible preventive modality for IC. Finally, while ex vivo machine perfusion technology has gained an interest in DCD liver transplantation, further studies are necessary to evaluate the effectiveness of this evolving field to improve graft quality and transplant outcomes.
General Analysis of Horizontal Merger
Koji Okuguchi,Takeshi Yamazaki 서울대학교 경제연구소 1994 Seoul journal of economics Vol.7 No.3
A new method of proof is presented for the existence of a unique Cournot equilibrium in oligopoly with a merged entity and independent firms. The method is then applied to derive price-enhancing effect of an increase in the number of merged firms. On the basis of the existence proof and stability condition, a sufficient condition is derived for an increase in the number of merged firms to be profitable. This condition is illustrated for a simple case of linear demand and identical quadratic cost functions. Finally, a numerical example is given.