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Journal articles on the topic 'MMMC'
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Madichetty, Sreedhar, Abhijit Dasgupta, and Sambeet Mishra. "Voltage Balancing Scheme in MMC – A New Approach." International Journal of Emerging Electric Power Systems 15, no. 4 (August 1, 2014): 389–99. http://dx.doi.org/10.1515/ijeeps-2014-0096.
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Abstract This article proposes an online voltage balancing scheme using a new comparative reference wave modulation technique applied to modified modular multilevel converter (MMMC). Recent applications of modular multilevel converter (MMC) in high-voltage DC systems experience many problems with unbalancing of upper and lower arms, due to which circulating currents are rotating in the legs of MMC. These circulating currents pass through the arm inductors and create power loss across the inductor which consequently affects the efficiency of system. In order to overcome the unbalancing and to reduce the power losses, it proposes a new topology for existing MMC called as MMMC. Its main idea is to the balance the system voltage according to the difference between upper and lower arm currents. The upper and lower arm capacitors voltages can be well balanced by proposed technique. Compared to conventional PWM methods, this method can be realized easily. Particularly, this method has not used any kind of sorting technique, which makes it suitable for MMC with a large number of sub-modules. With experiments, the proposed method has been verified successfully.
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Li, Chen, and Hu. "An Optically Transparent Metasurface-Based Resonant Cavity Fed by Patch Antenna for Improved Gain." Materials 12, no. 23 (November 20, 2019): 3805. http://dx.doi.org/10.3390/ma12233805.
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An optically transparent metasurface (MS) is proposed to design a resonant cavity fed by a patch antenna operating at 5.6 GHz. In the proposed MS, a transparent micro metal mesh conductive (MMMC) film is used as the transparent conducting film (TCF), and it has a high optical transmittance of more than 75% and a low sheet resistance of 0.7 Ω/sq. The MS is composed of a layer of glass substrate and a layer of MMMC film. The unit cell of MS consists of a square patch using MMMC film patterned on a square glass substrate. The transparent MS, patch antenna, ground plane, and air-filled half-wavelength cavity form a resonant cavity antenna, to achieve an improved gain. The MS is designed, optimized and analyzed using the EM simulation software CST. Results show that the MS can improve the simulated boresight gain from 4.7 to 13.2 dBi by 8.5 dB, without affecting the impedance bandwidth (IMBW) much. The losses of MS with different values of sheet resistance are also studied, showing the MS using MMMC with sheet resistance of 0.7 Ω/sq has very small losses.
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Browne, W. J., H. Goldstein, and J. Rasbash. "Multiple membership multiple classification (MMMC) models." Statistical Modelling 1, no. 2 (February 1, 2001): 103–24. http://dx.doi.org/10.1191/147108201128113.
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Browne, William J., Harvey Goldstein, and Jon Rasbash. "Multiple membership multiple classification (MMMC) models." Statistical Modelling: An International Journal 1, no. 2 (July 2001): 103–24. http://dx.doi.org/10.1177/1471082x0100100202.
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Zhang, Qi Rong, and Zhong Shi He. "Two-Dimensional Locality Discriminant Preserving Projections for Face Recognition." Advanced Materials Research 121-122 (June 2010): 391–98. http://dx.doi.org/10.4028/www.scientific.net/amr.121-122.391.
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In this paper, we propose a new face recognition approach for image feature extraction named two-dimensional locality discriminant preserving projections (2DLDPP). Two-dimensional locality preserving projections (2DLPP) can direct on 2D image matrixes. So, it can make better recognition rate than locality preserving projection. We investigate its more. The 2DLDPP is to use modified maximizing margin criterion (MMMC) in 2DLPP and set the parameter optimized to maximize the between-class distance while minimize the within-class distance. Extensive experiments are performed on ORL face database and FERET face database. The 2DLDPP method achieves better face recognition performance than PCA, 2DPCA, LPP and 2DLPP.
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Kumar, Dinesh, and Lalit Thakur. "Recent Studies on the Fabrication of Magnesium Based Metal Matrix Nano-Composites by Using Ultrasonic Stir Casting Technique - A Review." Materials Science Forum 969 (August 2019): 889–94. http://dx.doi.org/10.4028/www.scientific.net/msf.969.889.
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This paper presents the recent studies on the fabrication of magnesium based metal matrix nanocomposites (MMMC) by using ultrasonic assisted stir casting technique. The pure metal and alloys, due to their limited mechanical properties are not suitable for various engineering applications. It has been observed that the addition of suitable reinforcements into metallic matrix improves the specific strength, ultimate tensile strength, porosity and wear properties as compared to the conventional and monolithic engineering materials for aerospace and automotive applications. The effects of ultrasonic vibrations and the resulting uniform dispersion of reinforcements on the mechanical and tribological properties of magnesium based MMCs are specifically highlighted in this paper.
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Hern, Khoo, Muhammad Yusof, Fatin Zaifulbahri, Nurfarah Azahar, Grace Sugumaran, and Navin Sarkunam. "An Interventional Study Comparing the Memory Retention of Verbal & Pictorial Materials among MMMC Students." British Journal of Medicine and Medical Research 21, no. 10 (January 10, 2017): 1–10. http://dx.doi.org/10.9734/bjmmr/2017/33618.
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Salway, Ruth, Lydia Emm-Collison, Simon J. Sebire, Janice L. Thompson, Deborah A. Lawlor, and Russell Jago. "A Multilevel Analysis of Neighbourhood, School, Friend and Individual-Level Variation in Primary School Children’s Physical Activity." International Journal of Environmental Research and Public Health 16, no. 24 (December 4, 2019): 4889. http://dx.doi.org/10.3390/ijerph16244889.
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Physical activity is influenced by individual, inter-personal and environmental factors. In this paper, we explore the variability in children’s moderate-to-vigorous physical activity (MVPA) at different individual, parent, friend, school and neighbourhood levels. Valid accelerometer data were collected for 1077 children aged 9, and 1129 at age 11, and the average minutes of MVPA were derived for weekdays and weekends. We used a multiple-membership, multiple-classification model (MMMC) multilevel model to compare the variation in physical activity outcomes at each of the different levels. There were differences in the proportion of variance attributable to the different levels between genders, for weekdays and weekends, at ages 9 and 11. The largest proportion of variability in MVPA was attributable to individual variation, accounting for half of the total residual variability for boys, and two thirds of the variability for girls. MVPA clustered within friendship groups, with friends influencing peer MVPA. Including covariates at the different levels explained only small amounts (3%–13%) of variability. There is a need to enhance our understanding of individual level influences on children’s physical activity.
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Shetty, Smitha Sammith, Abigail Renee Johnli, Nur Fatihah Binti Mohd, Siti Nabila Adilah Binti Md Nor, Amirah Binti Haron, Lavinia A/p Gunasegaram, Muhammad Nur Taufiq Bin Mustafa, and Nor Hafizah Ain Binti Mohd Zakaria. "Dermatoglyphics: A prediction tool for dental caries." International Journal of Dental Research 4, no. 2 (July 31, 2016): 30. http://dx.doi.org/10.14419/ijdr.v4i2.6394.
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Background: Dermatoglyphics has been used as a powerful tool in diagnosis of physiological, medical or genetic conditions. Hence its role in predicting the dental caries which is a multifactorial disease with genetic influence has to be investigated.Objective: The present study was conducted to investigate the role of dermatoglyphics in predicting the susceptibility of individuals to develop dental caries.Material and methods: The study included 200 students of MMMC Manipal. Dental caries pattern was recorded using the DMFT index. The impression of thumb ridge pattern was recorded using duplicating inkpads.Results: The male subjects showed maximum of loop pattern with 53.6% and 71% in right and left thumb respectively. The female subjects also showed the maximum of loop pattern with 54.2% both in right and left thumb. Subjects who had arch type of pattern on right thumb (66.7%) and left thumb (57.1%) were found to be caries free compared to loop and whorl pattern. Subjects with whorl pattern on the left thumb (34.2%) and right (34.9%) had DMFT > 3 compared to loop and arch.Conclusion: Dermatoglyphics serve to strengthen the diagnostic impression of the disease from an early age and hence preventive oral health measures can be considered.
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Dimmer, Kai Stefan, Stefan Jakobs, Frank Vogel, Katrin Altmann, and Benedikt Westermann. "Mdm31 and Mdm32 are inner membrane proteins required for maintenance of mitochondrial shape and stability of mitochondrial DNA nucleoids in yeast." Journal of Cell Biology 168, no. 1 (January 3, 2005): 103–15. http://dx.doi.org/10.1083/jcb.200410030.
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The MDM31 and MDM32 genes are required for normal distribution and morphology of mitochondria in the yeast Saccharomyces cerevisiae. They encode two related proteins located in distinct protein complexes in the mitochondrial inner membrane. Cells lacking Mdm31 and Mdm32 harbor giant spherical mitochondria with highly aberrant internal structure. Mitochondrial DNA (mtDNA) is instable in the mutants, mtDNA nucleoids are disorganized, and their association with Mmm1-containing complexes in the outer membrane is abolished. Mutant mitochondria are largely immotile, resulting in a mitochondrial inheritance defect. Deletion of either one of the MDM31 and MDM32 genes is synthetically lethal with deletion of either one of the MMM1, MMM2, MDM10, and MDM12 genes, which encode outer membrane proteins involved in mitochondrial morphogenesis and mtDNA inheritance. We propose that Mdm31 and Mdm32 cooperate with Mmm1, Mmm2, Mdm10, and Mdm12 in maintenance of mitochondrial morphology and mtDNA.
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Siddique, Tawsif, Naba K. Dutta, and Namita Roy Choudhury. "Mixed-Matrix Membrane Fabrication for Water Treatment." Membranes 11, no. 8 (July 23, 2021): 557. http://dx.doi.org/10.3390/membranes11080557.
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In recent years, technology for the fabrication of mixed-matrix membranes has received significant research interest due to the widespread use of mixed-matrix membranes (MMMs) for various separation processes, as well as biomedical applications. MMMs possess a wide range of properties, including selectivity, good permeability of desired liquid or gas, antifouling behavior, and desired mechanical strength, which makes them preferable for research nowadays. However, these properties of MMMs are due to their tailored and designed structure, which is possible due to a fabrication process with controlled fabrication parameters and a choice of appropriate materials, such as a polymer matrix with dispersed nanoparticulates based on a typical application. Therefore, several conventional fabrication methods such as a phase-inversion process, interfacial polymerization, co-casting, coating, electrospinning, etc., have been implemented for MMM preparation, and there is a drive for continuous modification of advanced, easy, and economic MMM fabrication technology for industrial-, small-, and bulk-scale production. This review focuses on different MMM fabrication processes and the importance of various parameter controls and membrane efficiency, as well as tackling membrane fouling with the use of nanomaterials in MMMs. Finally, future challenges and outlooks are highlighted.
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Ikbaal, Muhammad Yassin, and Nurhazirah 'Aqilah Salim Musa. "Prevalence of Impostor Phenomenon among Medical Students in a Malaysian Private Medical School." International Journal of Medical Students 6, no. 2 (July 21, 2018): 66–70. http://dx.doi.org/10.5195/ijms.2018.10.
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Background: Impostor phenomenon is described as an "internal experience of intellectual fraudulence" among high achievers, which include medical students who often doubt their ability to become good doctors in the future. This study sought to determine the prevalence of impostor phenomenon among medical students and how impostorism is correlated with other psychological distresses namely anxiety, depression and low self-esteem.
Methods: To conduct this cross-sectional study, various scales were distributed to all 4th-year medical students in Melaka-Manipal Medical College (MMMC), Muar campus to measure impostorism, depression, anxiety and self-esteem. Clance Impostor Phenomenon Scale (CIPS) was used to measure impostorism and a score of 62 was set as the cut off value to classify a participant as an "imposter".
Results: Out of 300, 256 (85.3%) students completed the questionnaires. 48% and 44% of male and female students respectively scored as ‘impostors’ with no significant difference between the two genders. Positive correlations were noted between impostor phenomenon with low self-esteem (rho=0.56), depression (rho=0.42) and anxiety (rho=0.41). Impostors significantly have stronger intentions of quitting medical school (p < 0.001) and felt that they were not ready to cope with challenges during housemanship (p < 0.05).
Conclusion: Impostors suffer greatly from psychological distress. They are not confident to face the future challenges of housemanship and have stronger intentions of quitting the course. It is necessary for medical colleges to acknowledge this feeling and help the students to cope with it to ensure a smooth transition from medical school to housemanship period.
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Kim, Eun, Hyun Kim, Donghwi Kim, Jinsoo Kim, and Pyung Lee. "Preparation of Mixed Matrix Membranes Containing ZIF-8 and UiO-66 for Multicomponent Light Gas Separation." Crystals 9, no. 1 (December 26, 2018): 15. http://dx.doi.org/10.3390/cryst9010015.
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Mixed matrix membranes (MMMs) containing zeolitic imidazolite framework-8 (ZIF-8) and UiO-66 as microporous fillers were prepared and evaluated their potential for the separation of a gas mixture produced by a methane reforming process. Hydrothermal synthesis was performed to prepare both the ZIF-8 and UiO-66 crystals, with crystal sizes ranging from 50 to 70 nm for ZIF-8 and from 200 to 300 nm for UiO-66. MMMs were prepared with 15% filler loading for both MMM (ZIF-8) and MMM (UiO-66). MMM (UiO-66) exhibited H2 permeability of 64.4 barrer and H2/CH4 selectivity of 153.3 for single gas permeation, which are more than twice the values that were exhibited by a neat polymer membrane. MMM (ZIF-8) also showed better separation properties than that of a neat polymer membrane with H2 permeability of 27.1 barrer and H2/CH4 selectivity of 123.2. When a gas mixture consisting of 78% Ar/18% H2/4% CH4 flowed into the membranes at 5 bar, the H2 purity increased to as high as 93%. However, no improvement in the mixture gas separation performance was achieved by the MMMs as compared to that of a neat polymer membrane.
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Monsalve-Bravo, Gloria, and Suresh Bhatia. "Modeling Permeation through Mixed-Matrix Membranes: A Review." Processes 6, no. 9 (September 18, 2018): 172. http://dx.doi.org/10.3390/pr6090172.
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Over the past three decades, mixed-matrix membranes (MMMs), comprising an inorganic filler phase embedded in a polymer matrix, have emerged as a promising alternative to overcome limitations of conventional polymer and inorganic membranes. However, while much effort has been devoted to MMMs in practice, their modeling is largely based on early theories for transport in composites. These theories consider uniform transport properties and driving force, and thus models for the permeability in MMMs often perform unsatisfactorily when compared to experimental permeation data. In this work, we review existing theories for permeation in MMMs and discuss their fundamental assumptions and limitations with the aim of providing future directions permitting new models to consider realistic MMM operating conditions. Furthermore, we compare predictions of popular permeation models against available experimental and simulation-based permeation data, and discuss the suitability of these models for predicting MMM permeability under typical operating conditions.
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Dilawari, Asma Ali, Leatt Gilboa, Renee Kakareka, and Emily Ratner. "Integrative therapies for symptom management in cancer survivors: Assessment of an on-site integrative medicine (IM) program." Journal of Clinical Oncology 36, no. 7_suppl (March 1, 2018): 142. http://dx.doi.org/10.1200/jco.2018.36.7_suppl.142.
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142 Background: Up to 89% of oncology patients utilize integrative therapies with reported improvements in quality of life. However, less than half of patients report IM use to providers, potentially impeding optimal care. In September 2016, MedStar Montgomery Medical Center (MMMC), part of the MedStar Georgetown Cancer Network, opened the Center for Integrative Medicine (CIM) with support from MedStar’s Institute for Innovation (MI2). This clinical program offers IM consultation, acupuncture, mindfulness, psychology services, nutrition, and reiki. The purpose of this analysis is to examine oncology patient utilization of the CIM. Methods: Medical records of 174 patients seen September 2016 - October 2017 were reviewed, and 39 patients with a cancer diagnosis identified. Data regarding chief complaints, treatments, number of visits, and outcomes were analyzed. Results: 39 (22%) of 174 patients had a cancer diagnosis. After initial consultation, 29 of these patients received IM treatment; 14 returned for ≥5 treatments. Most common chief complaints were pain, stress/anxiety, fatigue, insomnia, and arthralgias (Table 1). The majority of CIM’s oncology patients was female and referred from in-network clinicians. The CIM referred 7 patients to other medical providers for unexpected medical issues and 2 required same-day appointments arranged by the CIM. Conclusions: These data illustrate oncology patients’ utilization and benefit of IM services within a hospital network. Communication between IM and referring providers may address unexpected clinical situations, potentially avoiding care delays and facilitating transparency with the use of IM services. Unpleasant symptom treatment may improve therapy adherence and quality of life. This review illustrates feasibility for an on-site CIM and the benefit to cancer survivors when IM services are offered collaboratively.[Table: see text]
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Weldearegay, Yenehiwot, Sandy Müller, Jana Hänske, Anja Schulze, Aline Kostka, Nancy Rüger, Marion Hewicker-Trautwein, et al. "Host-Pathogen Interactions of Mycoplasma mycoides in Caprine and Bovine Precision-Cut Lung Slices (PCLS) Models." Pathogens 8, no. 2 (June 20, 2019): 82. http://dx.doi.org/10.3390/pathogens8020082.
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Respiratory infections caused by mycoplasma species in ruminants lead to considerable economic losses. Two important ruminant pathogens are Mycoplasma mycoides subsp. Mycoides (Mmm), the aetiological agent of contagious bovine pleuropneumonia and Mycoplasma mycoides subsp. capri (Mmc), which causes pneumonia, mastitis, arthritis, keratitis, and septicemia in goats. We established precision cut lung slices (PCLS) infection model for Mmm and Mmc to study host-pathogen interactions. We monitored infection over time using immunohistological analysis and electron microscopy. Moreover, infection burden was monitored by plating and quantitative real-time PCR. Results were compared with lungs from experimentally infected goats and cattle. Lungs from healthy goats and cattle were also included as controls. PCLS remained viable for up to two weeks. Both subspecies adhered to ciliated cells. However, the titer of Mmm in caprine PCLS decreased over time, indicating species specificity of Mmm. Mmc showed higher tropism to sub-bronchiolar tissue in caprine PCLS, which increased in a time-dependent manner. Moreover, Mmc was abundantly observed on pulmonary endothelial cells, indicating partially, how it causes systemic disease. Tissue destruction upon prolonged infection of slices was comparable to the in vivo samples. Therefore, PCLS represents a novel ex vivo model to study host-pathogen interaction in livestock mycoplasma.
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Pacheco, Marquidia J., Luis J. Vences, Hilda Moreno, Joel O. Pacheco, Ricardo Valdivia, and Celso Hernández. "Review: Mixed-Matrix Membranes with CNT for CO2 Separation Processes." Membranes 11, no. 6 (June 21, 2021): 457. http://dx.doi.org/10.3390/membranes11060457.
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The membranes’ role is of supreme importance in the separation of compounds under different phases of matter. The topic addressed here is based on the use of membranes on the gases separation, specifically the advantages of mixed-matrix membranes (MMMs) when using carbon nanotubes as fillers to separate carbon dioxide (CO2) from other carrier gas. MMMs consist of a polymer support with additive fillers to improve their efficiency by increasing both selectivity and permeability. The most promising fillers in the MMM development are nanostructured molecules. Due to the good prospects of carbon nanotubes (CNTs) as MMM fillers, this article aims to concentrate the advances and developments of CNT–MMM to separate gases, such as CO2. The influence of functionalized CNT or mixtures of CNT with additional materials such as zeolites, hydrogel and, graphene sheets on membranes performance is highlighted in the present work.
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Abraham, RR, V. Pallath, C. AM, K. Ramnarayan, and A. Kamath. "Avenues for Professional Development: Faculty Perspectives from an Indian Medical School." Kathmandu University Medical Journal 10, no. 4 (September 3, 2014): 60–65. http://dx.doi.org/10.3126/kumj.v10i4.10997.
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Background Medical school faculty in India are challenged to balance teaching and professional development. Melaka Manipal Medical College (MMMC), Manipal Campus, Manipal University, India offers the Bachelor of Medicine and Bachelor of Surgery (MBBS) program. The institution incorporates certain effective practices based on adult learning principles which are aimed at fostering the professional development of faculty members. Objectives The present study was undertaken to explore the perceptions of faculty members regarding the scope for professional development at Melaka Manipal Medical College, Manipal Campus. Methods In September 2009, a questionnaire comprising items (23) focusing on five adult learning principles (active participation, relevant learning, constructive feedback, safe, non-threatening environment and previous experiences) was designed and faculty members (n=23) were asked to respond to it on a 5-point Likert scale. Additionally, a force field analysis was conducted by asking the faculty to identify three factors which facilitated them to consciously get involved in professional development activities. They were also asked to identify three unfavorable factors that hindered their professional development. Results Among the five characteristics, relevant learning was found to have a high mean score. Frequency analysis of responses revealed that at Melaka Manipal Medical College, there was ample scope for relevant self-learning that fosters professional development (91.3%). Force field response analysis revealed Melaka Manipal Medical College offered considerable flexibility and opportunities for continuing professional development along with faculty members’ prevailing role as teachers. Nevertheless, the need for more research facilities and funds was highlighted. Conclusions Adherence to adult learning principles may provide avenues for professional development in medical schools. An organized attempt to make the medical school faculty aware of the scope of these practices appears to be necessary to nurture professional development in settings where there are resource constraints. DOI: http://dx.doi.org/10.3126/kumj.v10i4.10997 Kathmandu Univ Med J 2012;10(4):60-65
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Yap, Yun Kee, and Pei Ching Oh. "Effects of an Alternating Magnetic Field towards Dispersion of α-Fe2O3/TiO2 Magnetic Filler in PPOdm Polymer for CO2/CH4 Gas Separation." Membranes 11, no. 8 (August 20, 2021): 641. http://dx.doi.org/10.3390/membranes11080641.
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Magnetic-field-induced dispersion of magnetic fillers has been proven to improve the gas separation performance of mixed matrix membranes (MMMs). However, the magnetic field induced is usually in a horizontal or vertical direction. Limited study has been conducted on the effects of alternating magnetic field (AMF) direction towards the dispersion of particles. Thus, this work focuses on the incorporation and dispersion of ferromagnetic iron oxide–titanium (IV) dioxide (αFe2O3/TiO2) particles in a poly (2,6-dimethyl-1,4-phenylene) oxide (PPOdm) membrane via an AMF to investigate its effect on the magnetic filler dispersion and correlation towards gas separation performance. The fillers were incorporated into PPOdm polymer via a spin-coating method at a 1, 3, and 5 wt% filler loading. The MMM with the 3 wt% loading showed the best performance in terms of particle dispersion and gas separation performance. The three MMMs were refabricated in an alternating magnetic field, and the MMM with the 3 wt% loading presented the best performance. The results display an increment in selectivity by 100% and a decrement in CO2 permeability by 97% to an unmagnetized MMM for the 3 wt% loading. The degree of filler dispersion was quantified and measured using Area Disorder of Delaunay Triangulation mapped onto the filler on binarized MMM images. The results indicate that the magnetized MMM presents a greater degree of dispersion than the unmagnetized MMM.
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Bizzi, Jorge Wladimir Junqueira, Carlos Eduardo Da Silva, José Ricardo Vanzin, and Luis Carlos Teixeira. "Meningomielocele cervical." JBNC - JORNAL BRASILEIRO DE NEUROCIRURGIA 12, no. 3 (April 3, 2018): 154–57. http://dx.doi.org/10.22290/jbnc.v12i3.1495.
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A meningomielocele cervical (MMCC) é uma afecção com características embriológicas e anatômicas que a diferencia das meningomieloceles (MMC) que ocorrem nos outros segmentos medulares. O comprometimento neurológico, a abordagem cirúrgica, assim como o prognóstico desse tipo de malformação, são igualmente distintos daqueles observados nos casos de MMC torácica ou lombar. Este relato de caso tem por objetivo salientar os aspectos peculiares dessa afecção e o seu manejo terapêutico.
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Wu, Haoyu, Maryam Zamanian, Boguslaw Kruczek, and Jules Thibault. "Gas Permeation Model of Mixed-Matrix Membranes with Embedded Impermeable Cuboid Nanoparticles." Membranes 10, no. 12 (December 15, 2020): 422. http://dx.doi.org/10.3390/membranes10120422.
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In the packaging industry, the barrier property of packaging materials is of paramount importance. The enhancement of barrier properties of materials can be achieved by adding impermeable nanoparticles into thin polymeric films, known as mixed-matrix membranes (MMMs). Three-dimensional numerical simulations were performed to study the barrier property of these MMMs and to estimate the effective membrane gas permeability. Results show that horizontally-aligned thin cuboid nanoparticles offer far superior barrier properties than spherical nanoparticles for an identical solid volume fraction. Maxwell’s model predicts very well the relative permeability of spherical and cubic nanoparticles over a wide range of the solid volume fraction. However, Maxwell’s model shows an increasingly poor prediction of the relative permeability of MMM as the aspect ratio of cuboid nanoparticles tends to zero or infinity. An artificial neural network (ANN) model was developed successfully to predict the relative permeability of MMMs as a function of the relative thickness and the relative projected area of the embedded nanoparticles. However, since an ANN model does not provide an explicit form of the relation of the relative permeability with the physical characteristics of the MMM, a new model based on multivariable regression analysis is introduced to represent the relative permeability in a MMM with impermeable cuboid nanoparticles. The new model possesses a simple explicit form and can predict, very well, the relative permeability over an extensive range of the solid volume fraction and aspect ratio, compared with many existing models.
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Ching, Oh Pei, and Mason Wong Bak Lung. "Effects of Montmorillonite (MMT) Inorganic Fillers on Polyvinylidene (PVDF) Mixed Matrix Membrane." Applied Mechanics and Materials 625 (September 2014): 696–700. http://dx.doi.org/10.4028/www.scientific.net/amm.625.696.
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Asymmetric nanoclay-polyvinylidene (PVDF) mixed matrix membranes (MMMs) were prepared by the reaction of various amount of montmorillonite (MMT) nanoclay mineral with PVDF. The MMMs were fabricated via dry-wet phase inversion method withN,N-dimethyl-acetamide (DMAc) as the solvent and ethanol as the coagulant. The fabricated MMMs were characterized by means of fourier-transform infrared (FTIR) and scanning electron microscopy (SEM). The separation performances of the prepared membranes were evaluated by pure gases (CO2and CH4). From the FTIR spectrum, MMMs exhibited new peaks compared to pristine PVDF membrane, indicating assimilation of MMT into the PVDF membrane. The morphology of the membranes depends on the clay mineral loading as confirmed by SEM. PVDF/3wt% MMT MMM showed the highest CO2permeance and CO2/CH4selectivity relative to neat PVDF membrane.
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Klymentiy, Nastasia, Svitlana Pukas, Bohdan Kuzhel, and Roman E. Gladyshevskii. "The Ternary Systems {Sc, Ti}-Cu-Al at 800°C." Solid State Phenomena 289 (April 2019): 28–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.289.28.
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The isothermal section at 800°C of the phase diagram of the ternary system Sc–Cu–Al was constructed in the whole concentration range using X-ray powder diffraction data. The existence of eight ternary compounds was confirmed: ScCu4.9‑6.0Al7.1‑6.0 (structure type ThMn12, Pearson symbol tI26, space group I4/mmm), Sc6Cu24.1Al11.9 (own structure type, cI176, Im-3), Sc2Cu6.25Al4.75 (own structure type, oS108, Cmmm), Sc3Cu7.5Al7.5 (Sc3Ni11Ge4, hP38, P63/mmc), ScCu2Al (MnCu2Al, cF16, Fm-3m), ScCu0.8Al0.2 (CsCl, cP2, Pm-3m), ScCu0.6Al1.4 (MgNi2, hP24, P63/mmc), and ScCuAl (MgZn2, hP12, P63/mmc), and the existence of a continuous solid solution ScCu1-xAlx (x = 0-1), based on the binary compounds ScCu and ScAl with CsCl-type structure (cP2, Pm-3m), was established. The investigation of the Ti–Cu–Al system at 800°C confirmed the existence of four ternary compounds: TiCu0.25Al2.75 (ZrAl3, tI16, I4/mmm), TiCu0.3-0.6Al2.7-2.4 (Cu3Au, cP4, Pm-3m), TiCu2-2.7Al1-0.3 (MnCu2Al, cF16, Fm-3m), and TiCu0.54-1.16All.46-0.84 (MgZn2, hP12, P63/mmc). Electrical resistivity measurements were performed for three compounds in the Sc–Cu–Al system and confirmed metal behavior in the temperature range 5-290 K.
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Safak Boroglu, Mehtap, Ismail Boz, and Busra Kaya. "Effect of new metal–organic framework (zeolitic imidazolate framework [ZIF-12]) in mixed matrix membranes on structure, morphology, and gas separation properties." Journal of Polymer Engineering 41, no. 4 (March 15, 2021): 259–70. http://dx.doi.org/10.1515/polyeng-2020-0288.
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AbstractIn our study, the synthesis of zeolitic imidazolate framework (ZIF-12) crystals and the preparation of mixed matrix membranes (MMMs) with various ZIF-12 loadings were targeted. The characterization of ZIF-12 and MMMs were carried out by Fourier transform infrared spectroscopy analysis, thermogravimetric analysis, scanning electron microscopy (SEM), and thermomechanical analysis. The performance of MMMs was measured by the ability of binary gas separation. Commercial polyetherimide (PEI-Ultem®1000) polymer was used as the polymer matrix. The solution casting method was utilized to obtain dense MMMs. In the SEM images of ZIF-12 particles, the particles with a rhombic dodecahedron structure were identified. From SEM images, it was observed that the distribution of ZIF-12 particles in the MMMs was homogeneous and no agglomeration was present. Gas permeability experiments of MMMs were measured for H2, CO2, and CH4gases at steady state, at 4 bar and 35 °C by constant volume-variable pressure method. PEI/ZIF-12-30 wt% MMM exhibited high permeability and ideal selectivity values for H2/CH4and CO2/CH4werePH2/CH4=331.41${P}_{{\text{H}}_{2}/{\text{CH}}_{4}}=331.41$andPCO2/CH4=53.75${P}_{{\text{CO}}_{2}/{\text{CH}}_{4}}=53.75$gas pair.
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Jain, Anand, Mohd Zamidi Ahmad, Audrey Linkès, Violeta Martin-Gil, Roberto Castro-Muñoz, Pavel Izak, Zdeněk Sofer, Werner Hintz, and Vlastimil Fila. "6FDA-DAM:DABA Co-Polyimide Mixed Matrix Membranes with GO and ZIF-8 Mixtures for Effective CO2/CH4 Separation." Nanomaterials 11, no. 3 (March 8, 2021): 668. http://dx.doi.org/10.3390/nano11030668.
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This work presents the gas separation evaluation of 6FDA-DAM:DABA (3:1) co-polyimide and its enhanced mixed matrix membranes (MMMs) with graphene oxide (GO) and ZIF-8 (particle size of <40 nm). The 6FDA-copolyimide was obtained through two-stage poly-condensation polymerization, while the ZIF-8 nanoparticles were synthesized using the dry and wet method. The MMMs were preliminarily prepared with 1–4 wt.% GO and 5–15 wt.% ZIF-8 filler loading independently. Based on the best performing GO MMM, the study proceeded with making MMMs based on the mixtures of GO and ZIF-8 with a fixed 1 wt.% GO content (related to the polymer matrix) and varied ZIF-8 loadings. All the materials were characterized thoroughly using TGA, FTIR, XRD, and FESEM. The gas separation was measured with 50:50 vol.% CO2:CH4 binary mixture at 2 bar feed pressure and 25 °C. The pristine 6FDA-copolyimide showed CO2 permeability (PCO2) of 147 Barrer and CO2/CH4 selectivity (αCO2/CH4) of 47.5. At the optimum GO loading (1 wt.%), the PCO2 and αCO2/CH4 were improved by 22% and 7%, respectively. A combination of GO (1 wt.%)/ZIF-8 fillers tremendously improves its PCO2; by 990% for GO/ZIF-8 (5 wt.%) and 1.124% for GO/ZIF-8 (10 wt.%). Regrettably, the MMMs lost their selectivity by 16–55% due to the non-selective filler-polymer interfacial voids. However, the hybrid MMM performances still resided close to the 2019 upper bound and showed good performance stability when tested at different feed pressure conditions.
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Guo, Fei, Bingzhang Li, Rui Ding, Dongsheng Li, Xiaobin Jiang, Gaohong He, and Wu Xiao. "A Novel Composite Material UiO-66@HNT/Pebax Mixed Matrix Membranes for Enhanced CO2/N2 Separation." Membranes 11, no. 9 (September 7, 2021): 693. http://dx.doi.org/10.3390/membranes11090693.
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Mixing a polymer matrix and nanofiller to prepare a mixed matrix membrane (MMM) is an effective method for enhancing gas separation performance. In this work, a unique UiO-66-decorated halloysite nanotubes composite material (UiO-66@HNT) was successfully synthesized via a solvothermal method and dispersed into the Pebax-1657 matrix to prepare MMMs for CO2/N2 separation. A remarkable characteristic of this MMM was that the HNT lumen provided the highway for CO2 diffusion due to the unique affinity of UiO-66 for CO2. Simultaneously, the close connection of the UiO-66 layer on the external surface of HNTs created relatively continuous pathways for gas permeation. A suite of microscopy, diffraction, and thermal techniques was used to characterize the morphology and structure of UiO-66@HNT and the membranes. As expected, the embedding UiO-66@HNT composite materials significantly improved the separation performances of the membranes. Impressively, the as-obtained membrane acquired a high CO2 permeability of 119.08 Barrer and CO2/N2 selectivity of 76.26. Additionally, the presence of UiO-66@HNT conferred good long-term stability and excellent interfacial compatibility on the MMMs. The results demonstrated that the composite filler with fast transport pathways designed in this study was an effective strategy to enhance gas separation performance of MMMs, verifying its application potential in the gas purification industry.
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Hsieh, Ching-Wen, Bo-Xian Li, and Shing-Yi Suen. "Alicyclic Polyimide/SiO2 Mixed Matrix Membranes for Water/n-Butanol Pervaporation." Membranes 11, no. 8 (July 27, 2021): 564. http://dx.doi.org/10.3390/membranes11080564.
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Alicyclic polyimides (PIs) have excellent properties in solubility, mechanical strength, thermal property, etc. This study developed two types of alicyclic PI-based mixed matrix membranes (MMMs) for water/n-butanol pervaporation application, which have never been investigated previously. The fillers were hydrophilic SiO2 nanoparticles. The synthesized PI was mixed with SiO2 nanoparticles in DMAc to make the casting solution, and a liquid film was formed over PET substrate using doctor blade. A dense MMM was fabricated at 80 °C and further treated via multi-stage curing (100–170 °C). The prepared membranes were characterized by FTIR, TGA, FE-SEM, water contact angle, and solvent swelling. The trends of pure solvent swelling effects agree well with the water contact angle results. Moreover, the pervaporation efficiencies of alicyclic PI/SiO2 MMMs for 85 wt% n-butanol aqueous solution at 40 °C were investigated. The results showed that BCDA-3,4′-ODA/SiO2 MMMs had a larger permeation flux and higher separation factor than BCDA-1,3,3-APB/SiO2 MMMs. For both types of MMMs, the separation factor increased first and then decreased, with increasing SiO2 loading. Based on the PSI performance, the optimal SiO2 content was 0.5 wt% for BCDA-3,4′-ODA/SiO2 MMMs and 5 wt% for BCDA-1,3,3-APB/SiO2 MMMs. The overall separation efficiency of BCDA-3,4′-ODA-based membranes was 10–30-fold higher.
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Keskin and Alsoy Altinkaya. "A Review on Computational Modeling Tools for MOF-Based Mixed Matrix Membranes." Computation 7, no. 3 (July 18, 2019): 36. http://dx.doi.org/10.3390/computation7030036.
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Computational modeling of membrane materials is a rapidly growing field to investigate the properties of membrane materials beyond the limits of experimental techniques and to complement the experimental membrane studies by providing insights at the atomic-level. In this study, we first reviewed the fundamental approaches employed to describe the gas permeability/selectivity trade-off of polymer membranes and then addressed the great promise of mixed matrix membranes (MMMs) to overcome this trade-off. We then reviewed the current approaches for predicting the gas permeation through MMMs and specifically focused on MMMs composed of metal organic frameworks (MOFs). Computational tools such as atomically-detailed molecular simulations that can predict the gas separation performances of MOF-based MMMs prior to experimental investigation have been reviewed and the new computational methods that can provide information about the compatibility between the MOF and the polymer of the MMM have been discussed. We finally addressed the opportunities and challenges of using computational studies to analyze the barriers that must be overcome to advance the application of MOF-based membranes.
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Zhang, Jurong, Ermiao Sun, Xiaolei Feng, Hanyu Liu, Simon A. T. Redfern, V. Kanchana, Guangtao Liu, and Hongbo Wang. "Phase transition and superconductivity in ReS2, ReSe2 and ReTe2." Physical Chemistry Chemical Physics 20, no. 46 (2018): 29472–79. http://dx.doi.org/10.1039/c8cp05333b.
Full textAbstract:
Five energetically stable phases of P1̄′, P63/mmc, I41/amd, I4/mmm and I4/mmm′ were predicted in the ReX2 family of compounds at high pressures. The coordination environment of a Re atom changes from a ReX6 octahedron or a trigonal prism to a ReX8 cuboid coordination with increasing pressure. The high-pressure metallic phases of ReX2 exhibit superconductivity.
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Ismail, N. M., A. F. Ismail, A. Mustafa, A. K. Zulhairun, and N. A. H. M. Nordin. "Enhanced carbon dioxide separation by polyethersulfone (PES) mixed matrix membranes deposited with clay." Journal of Polymer Engineering 36, no. 1 (January 1, 2016): 65–78. http://dx.doi.org/10.1515/polyeng-2015-0048.
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Abstract Asymmetric mixed matrix membranes (MMMs) incorporating Cloisite15A (C15A) clay particles were prepared using solvent evaporation and phase inversion with polyethersulfone (PES) as the membrane matrix. C15A loadings varied at 1 wt% and 5 wt%. Membrane morphological and thermal properties were evaluated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Addition of the C15A favorably altered the microscopic structure of membranes from finger-like to homogeneous sponge-like structure as the loading increased. While the amorphous nature of MMMs was retained, the thermal stability was also found to be improved with a slight decrease in glass transition temperature (Tg). PES/C15A1 MMM showed the best gas transport properties, with 37% and 65% improvement in CO2 permeance and CO2/CH4 selectivity, respectively. Unlike 1 wt%, the loss in selectivity shown by 5 wt% clay loadings suggested that the interphase voids and extent of silicate layers dispersion play a significant role in the overall performance of MMMs.
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Mahenthiran, Ashvin Viknesh, and Zeinab Abbas Jawad. "A Prospective Concept on the Fabrication of Blend PES/PEG/DMF/NMP Mixed Matrix Membranes with Functionalised Carbon Nanotubes for CO2/N2 Separation." Membranes 11, no. 7 (July 10, 2021): 519. http://dx.doi.org/10.3390/membranes11070519.
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With an ever-increasing global population, the combustion of fossil fuels has risen immensely to meet the demand for electricity, resulting in significant increase in carbon dioxide (CO2) emissions. In recent years, CO2 separation technology, such as membrane technology, has become highly desirable. Fabricated mixed matrix membranes (MMMs) have the most desirable gas separation performances, as these membranes have the ability to overcome the trade-off limitations. In this paper, blended MMMs are reviewed along with two polymers, namely polyether sulfone (PES) and polyethylene glycol (PEG). Both polymers can efficiently separate CO2 because of their chemical properties. In addition, blended N-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF) solvents were also reviewed to understand the impact of blended MMMs’ morphology on separation of CO2. However, the fabricated MMMs had challenges, such as filler agglomeration and void formation. To combat this, functionalised multi-walled carbon nanotube (MWCNTs-F) fillers were utilised to aid gas separation performance and polymer compatibility issues. Additionally, a summary of the different fabrication techniques was identified to further optimise the fabrication methodology. Thus, a blended MMM fabricated using PES, PEG, NMP, DMF and MWCNTs-F is believed to improve CO2/nitrogen separation.
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Abbasi, Kololi, Qomsheh Tabatabaei, Maziar Noei, and Masoud Saberi. "Enhanced gas permeation performance of mixed matrix membranes containing polysulfone and modified mesoporous MCM-41." Journal of the Serbian Chemical Society 86, no. 9 (2021): 871–87. http://dx.doi.org/10.2298/jsc210219034a.
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The aim of this study was the development of mixed matrix membranes (MMMs) based on silica MCM-41 dispersed in polysulfone (PSf) for the separation of carbon dioxide from methane. For this purpose, MCM-41 was synthesized by a hydrothermal method and was modified with 3-aminopropyltrietoxysilane (APTES). SEM, FTIR, BET and XRD analyses were used for characterization of the modified and unmodified particles. Then, various MMMs containing PSf at different weight percents (5, 10, 15 and 20) of modified and unmodified particles were prepared and the morphology and structure of the prepared membranes were studied using SEM and XRD analyses. Regardless of the particle type, the addition of MCM-41 to PSf caused an increase in gas permeability compared to a neat PSf membrane. Adding unmodified particles to PSf matrix resulted in undesirable effects, including particle agglomeration and/or the formation of interfacial voids. The MMMs with modified MCM-41 showed relatively better separation performance compared to MMMs with unmodified MCM-41. As a result, the MMM of PSf with 20 wt. % modified MCM-41 showed a significant increase in selectivity of carbon dioxide/methane and the value of selectivity reached 25.24.
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Nordin, Nik Abdul Hadi Md, Ahmad Fauzi Ismail, Surya Murali Racha, Ng Be Cheer, Muhammad Roil Bilad, Zulfan Adi Putra, and Mohd Dzul Hakim Wirzal. "Limitation in Fabricating PSf/ZIF-8 Hollow Fiber Membrane for CO2/CH4 Separation." Indonesian Journal of Science and Technology 3, no. 2 (August 30, 2018): 138. http://dx.doi.org/10.17509/ijost.v3i2.12757.
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Hollow fiber membrane configuration is way forward in membrane development since it possesses higher packing density and effective surface area per unit module compared to other configuration. Since majority of mixed matrix membrane (MMM) for gas separation reported focuses on flat sheet membrane development, this report aims to address the challenges faced in fabricating hollow fiber MMM. In this study, hollow fiber formulation is fabricated and their MMM using different types of fillers (virgin and modified ZIF-8) are prepared and used as a dispersed phase. The neat hollow fiber membrane shows good results with CO2 permeance of 104.39 GPU and CO2/CH4 selectivity of 29.28, in comparison with reported literature. Upon filler incorporation, the resulted MMMs appear to be diminished in both CO2 permeance and CO2/CH4 selectivity. While using modified ZIF-8, lesser deterioration was shown compared to pure ZIF-8, this phenomenon is likely to occur due to the changes in solution stability which causes notable changes in membrane morphology and performances.
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Dzhyvak, V. H., O. I. Khlibovska, and I. M. Klishch. "ROLE OF ENDOGENIC INTOXICATION IN MUSCLE INJURY IN EXPERIMENT." International Journal of Medicine and Medical Research 5, no. 2 (February 18, 2020): 122–27. http://dx.doi.org/10.11603/ijmmr.2413-6077.2019.2.10310.
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Background. Endogenous intoxication is a multicomponent complex process due to the endogenous biological products or dysfunction of systemic natural detoxification.
Objective. The aim of the research was to study the dynamics of indices of endogenous intoxication in rats with traumatic muscle damage in the experiment.
Methods. The experiment was performed on 45 non-linear white rats, which were modeled with traumatic muscle damage. The level of endogenous intoxication was assessed by the content of medium plasma molecules (MMM), leukocyte and erythrocytic index of intoxication (LII and EII). The research was conducted on the 1st, 3rd, 7th, 14th days after the injury.
Results. It was found that traumatic muscle damage causes endotoxemia. Manifestations of endogenous intoxication are: the increase of MMM1 in 2.3 times, MMM2 in 2.8 times compare to the intact animals. The level of this indicator slightly decreased in 7 days. Simultaneously with an increase in the MCT level in the post-traumatic period, the total toxic effect on the erythrocyte membrane also increased, which was manifested by a significant increase in EII in all terms of observation.
Conclusions. Traumatic damage of the muscles is accompanied by the growth of molecules of average mass in upto 7 days of observation, which significantly differ from the indicators of the intact group. The results of our research prove that traumatic muscle damage causes endotoxicosis development evidenced by accumulation of endotoxins in the animals’ body that is proved by significant changes in endogenous intoxication indices: i.e. erythrocytic and leukocytic indexes of intoxication and content of medium mass molecules.
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Liu, Yongsheng, Kyosuke Takata, Yu Mukai, Hidetoshi Kita, and Kazuhiro Tanaka. "Nano-porous Zeolite and MOF Filled Mixed Matrix Membranes for Gas Separation." MATEC Web of Conferences 333 (2021): 04008. http://dx.doi.org/10.1051/matecconf/202133304008.
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The commercial SAPO-34 zeolite with 0.38 nm pore size and ZIF-8 particles with 0.34 nm aperture size were separately dispersed into different polymer matrix, to prepare the mixed matrix membranes (MMMs) for gas separation. The dispersed situation of the SAPO-34 and ZIF-8 particles in matrix and the influence of the fillers on the separation performance of the membrane had been investigated in this study. The as-synthesized MMMs showed a better trade-off between permeability and selectivity than the pure polymer membrane and the performance could exceed or close to the upper bound line of polymer membrane for CO2 and CH4 separation. The CO2 permeability and CO2/CH4 ideal selectivity of the 6FDA-mDAT MMM containing 40 wt% SAPO-34 zeolite was 190 barrer and ca. 60, respectively. The 6FDA-TrMPD based MMMs containing 20 wt% ZIF-8 provided a permeability of C3H6 and an ideal selectivity of C3H6/C3H8 at 24 barrer and ca. 17, respectively. These separation performances were in a suitable agreement of the theoretical value from Maxwell model.
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Liu, Yongsheng, Kyosuke Takata, Yu Mukai, Hidetoshi Kita, and Kazuhiro Tanaka. "Nano-porous Zeolite and MOF Filled Mixed Matrix Membranes for Gas Separation." MATEC Web of Conferences 333 (2021): 04008. http://dx.doi.org/10.1051/matecconf/202133304008.
Full textAbstract:
The commercial SAPO-34 zeolite with 0.38 nm pore size and ZIF-8 particles with 0.34 nm aperture size were separately dispersed into different polymer matrix, to prepare the mixed matrix membranes (MMMs) for gas separation. The dispersed situation of the SAPO-34 and ZIF-8 particles in matrix and the influence of the fillers on the separation performance of the membrane had been investigated in this study. The as-synthesized MMMs showed a better trade-off between permeability and selectivity than the pure polymer membrane and the performance could exceed or close to the upper bound line of polymer membrane for CO2 and CH4 separation. The CO2 permeability and CO2/CH4 ideal selectivity of the 6FDA-mDAT MMM containing 40 wt% SAPO-34 zeolite was 190 barrer and ca. 60, respectively. The 6FDA-TrMPD based MMMs containing 20 wt% ZIF-8 provided a permeability of C3H6 and an ideal selectivity of C3H6/C3H8 at 24 barrer and ca. 17, respectively. These separation performances were in a suitable agreement of the theoretical value from Maxwell model.
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Fazil, Nabilah, Hilmi Mukhtar, Dzeti Farhah Mohshim, and Rizwan Nasir. "Gas Permeation Properties of Multiwalled Carbon Nanotubes on Polyether Block Amide (Pebax-1657)/Polyethersulfone(PES) Blend Mixed Matrix Membrane for CO2/CH4 Separation." Solid State Phenomena 307 (July 2020): 258–63. http://dx.doi.org/10.4028/www.scientific.net/ssp.307.258.
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Mixed matrix membrane (MMM), a developing research area, is a membrane formed by incorporating fillers in the polymeric membrane to enhance gas separation performance. In this study, MMMs comprised of blend rubbery block copolymers of polyether block amide (Pebax-1657) with a glassy polyethersulfone (PES) polymer and multi-walled carbon nanotubes (MWCNTs) were synthesized by dry phase inversion method and explored further by gas permeability test. Pebax-1657/PES/MWCNTs membrane resulted in an increased permeability as well as CO2/CH4 selectivity. The Pebax-1657/PES polymer blend MMM with 10wt% of MWCNTs has shown the most superior performance of CO2 permeability, CH4 permeability and CO2/CH4 selectivity in comparison with the pure Pebax-1657 resulted in 66.3% and 11.6% difference respectively.
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Baele, Guy, Mandev S. Gill, Paul Bastide, Philippe Lemey, and Marc A. Suchard. "Markov-Modulated Continuous-Time Markov Chains to Identify Site- and Branch-Specific Evolutionary Variation in BEAST." Systematic Biology 70, no. 1 (May 16, 2020): 181–89. http://dx.doi.org/10.1093/sysbio/syaa037.
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Abstract Markov models of character substitution on phylogenies form the foundation of phylogenetic inference frameworks. Early models made the simplifying assumption that the substitution process is homogeneous over time and across sites in the molecular sequence alignment. While standard practice adopts extensions that accommodate heterogeneity of substitution rates across sites, heterogeneity in the process over time in a site-specific manner remains frequently overlooked. This is problematic, as evolutionary processes that act at the molecular level are highly variable, subjecting different sites to different selective constraints over time, impacting their substitution behavior. We propose incorporating time variability through Markov-modulated models (MMMs), which extend covarion-like models and allow the substitution process (including relative character exchange rates as well as the overall substitution rate) at individual sites to vary across lineages. We implement a general MMM framework in BEAST, a popular Bayesian phylogenetic inference software package, allowing researchers to compose a wide range of MMMs through flexible XML specification. Using examples from bacterial, viral, and plastid genome evolution, we show that MMMs impact phylogenetic tree estimation and can substantially improve model fit compared to standard substitution models. Through simulations, we show that marginal likelihood estimation accurately identifies the generative model and does not systematically prefer the more parameter-rich MMMs. To mitigate the increased computational demands associated with MMMs, our implementation exploits recent developments in BEAGLE, a high-performance computational library for phylogenetic inference. [Bayesian inference; BEAGLE; BEAST; covarion, heterotachy; Markov-modulated models; phylogenetics.]
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Li, Maijun, Zhibo Zheng, Zhiguang Zhang, Nanwen Li, Siwei Liu, Zhenguo Chi, Jiarui Xu, and Yi Zhang. "“All Polyimide” Mixed Matrix Membranes for High Performance Gas Separation." Polymers 13, no. 8 (April 19, 2021): 1329. http://dx.doi.org/10.3390/polym13081329.
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To improve the interfacial compatibility of mixed matrix membranes (MMMs) for gas separation, microporous polyimide particle (AP) was designed, synthesized, and introduced into intrinsic microporous polyimide matrix (6FDA-Durene) to form “all polyimide” MMMs. The AP fillers showed the feature of thermal stability, similar density with polyimide matrix, high porosity, high fractional free volume, large microporous dimension, and interpenetrating network architecture. As expected, the excellent interfacial compatibility between 6FDA-Durene and AP without obvious agglomeration even at a high AP loading of 10 wt.% was observed. As a result, the CO2 permeability coefficient of MMM with AP loading as low as 5 wt.% reaches up to 1291.13 Barrer, which is 2.58 times that of the pristine 6FDA-Durene membrane without the significant sacrificing of ideal selectivity of CO2/CH4. The improvement of permeability properties is much better than that of the previously reported MMMs, where high filler content is required to achieve a high permeability increase but usually leads to significant agglomeration or phase separation of fillers. It is believed that the excellent interfacial compatibility between the PI fillers and the PI matrix induce the effective utilization of porosity and free volume of AP fillers during gas transport. Thus, a higher diffusion coefficient of MMMs has been observed than that of the pristine PI membrane. Furthermore, the rigid polyimide fillers also result in the excellent anti-plasticization ability for CO2. The MMMs with a 10 wt.% AP loading shows a CO2 plasticization pressure of 300 psi.
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Li, Sipei, Yang Liu, Dana A. Wong, and John Yang. "Recent Advances in Polymer-Inorganic Mixed Matrix Membranes for CO2 Separation." Polymers 13, no. 15 (July 31, 2021): 2539. http://dx.doi.org/10.3390/polym13152539.
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Since the second industrial revolution, the use of fossil fuels has been powering the advance of human society. However, the surge in carbon dioxide (CO2) emissions has raised unsettling concerns about global warming and its consequences. Membrane separation technologies have emerged as one of the major carbon reduction approaches because they are less energy-intensive and more environmentally friendly compared to other separation techniques. Compared to pure polymeric membranes, mixed matrix membranes (MMMs) that encompass both a polymeric matrix and molecular sieving fillers have received tremendous attention, as they have the potential to combine the advantages of both polymers and molecular sieves, while cancelling out each other’s drawbacks. In this review, we will discuss recent advances in the development of MMMs for CO2 separation. We will discuss general mechanisms of CO2 separation in an MMM, and then compare the performances of MMMs that are based on zeolite, MOF, metal oxide nanoparticles and nanocarbons, with an emphasis on the materials’ preparation methods and their chemistries. As the field is advancing fast, we will particularly focus on examples from the last 5 years, in order to provide the most up-to-date overview in this area.
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Youngman, Matthew J., Alyson E. Aiken Hobbs, Shawn M. Burgess, Maithreyan Srinivasan, and Robert E. Jensen. "Mmm2p, a mitochondrial outer membrane protein required for yeast mitochondrial shape and maintenance of mtDNA nucleoids." Journal of Cell Biology 164, no. 5 (February 23, 2004): 677–88. http://dx.doi.org/10.1083/jcb.200308012.
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The mitochondrial outer membrane protein, Mmm1p, is required for normal mitochondrial shape in yeast. To identify new morphology proteins, we isolated mutations incompatible with the mmm1-1 mutant. One of these mutants, mmm2-1, is defective in a novel outer membrane protein. Lack of Mmm2p causes a defect in mitochondrial shape and loss of mitochondrial DNA (mtDNA) nucleoids. Like the Mmm1 protein (Aiken Hobbs, A.E., M. Srinivasan, J.M. McCaffery, and R.E. Jensen. 2001. J. Cell Biol. 152:401–410.), Mmm2p is located in dot-like particles on the mitochondrial surface, many of which are adjacent to mtDNA nucleoids. While some of the Mmm2p-containing spots colocalize with those containing Mmm1p, at least some of Mmm2p is separate from Mmm1p. Moreover, while Mmm2p and Mmm1p both appear to be part of large complexes, we find that Mmm2p and Mmm1p do not stably interact and appear to be members of two different structures. We speculate that Mmm2p and Mmm1p are components of independent machinery, whose dynamic interactions are required to maintain mitochondrial shape and mtDNA structure.
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Escorihuela, Sara, Lucía Valero, Alberto Tena, Sergey Shishatskiy, Sonia Escolástico, Torsten Brinkmann, and Jose Serra. "Study of the Effect of Inorganic Particles on the Gas Transport Properties of Glassy Polyimides for Selective CO2 and H2O Separation." Membranes 8, no. 4 (December 9, 2018): 128. http://dx.doi.org/10.3390/membranes8040128.
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Three polyimides and six inorganic fillers in a form of nanometer-sized particles were studied as thick film solution cast mixed matrix membranes (MMMs) for the transport of CO2, CH4, and H2O. Gas transport properties and electron microscopy images indicate good polymer-filler compatibility for all membranes. The only filler type thatdemonstrated good distribution throughout the membrane thickness at 10 wt. % loading was BaCe0.2Zr0.7Y0.1O3 (BCZY). The influence of this filler on MMM gas transport properties was studied in detail for 6FDA-6FpDA in a filler content range from one to 20 wt. % and for Matrimid® and P84® at 10 wt. % loading. The most promising result was obtained for Matrimid®—10wt. % BCZY MMM, which showed improvement in CO2 and H2O permeabilities accompanied by increased CO2/CH4 selectivity and high water selective membrane at elevated temperatures without H2O/permanent gas selectivity loss.
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Chuah, Chong Yang, Junghyun Lee, Juha Song, and Tae-Hyun Bae. "CO2/N2 Separation Properties of Polyimide-Based Mixed-Matrix Membranes Comprising UiO-66 with Various Functionalities." Membranes 10, no. 7 (July 17, 2020): 154. http://dx.doi.org/10.3390/membranes10070154.
Full textAbstract:
Nanocrystalline UiO-66 and its derivatives (containing -NH2, -Br, -(OH)2) were developed via pre-synthetic functionalization and incorporated into a polyimide membrane to develop a mixed-matrix membrane (MMM) for CO2/N2 separation. Incorporation of the non-functionalized UiO-66 nanocrystals into the polyimide membrane successfully improved CO2 permeability, with a slight decrease in CO2/N2 selectivity, owing to its large accessible surface area. The addition of other functional groups further improved the CO2/N2 selectivity of the polymeric membrane, with UiO-66-NH2, UiO-66-Br, and UiO-66-(OH)2 demonstrating improvements of 12%, 4%, and 17%, respectively. Further evaluation by solubility–diffusivity analysis revealed that the functionalized UiO-66 in MMMs can effectively increase CO2 diffusivity while suppressing N2 sorption, thus, resulting in improved CO2/N2 selectivity. Such results imply that the structural tuning of UiO-66 by the incorporation of various functional groups is an effective strategy to improve the CO2 separation performance of MMMs.
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Castro-Muñoz, Roberto, Francesco Galiano, Vlastimil Fíla, Enrico Drioli, and Alberto Figoli. "Mixed matrix membranes (MMMs) for ethanol purification through pervaporation: current state of the art." Reviews in Chemical Engineering 35, no. 5 (July 26, 2019): 565–90. http://dx.doi.org/10.1515/revce-2017-0115.
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Abstract Over the last few decades, different polymers have been employed as materials in membrane preparation for pervaporation (PV) application, which are currently used in the preparation of mixed matrix membranes (MMMs) for ethanol recovery and ethanol dehydration. The ethanol-water and water-ethanol mixtures are, in fact, the most studied PV systems since the bioethanol production is strongly increasing its demand. The present review focuses on the current state of the art and future trends on ethanol purification by using MMMs in PV. A particular emphasis will, therefore, be placed on the enhancement of specific components transport and selectivity through the incorporation of inorganic materials into polymeric membranes, mentioning key principles on suitable filler selection for a synergistic effect toward such separations. In addition, the following topics will be discussed: (i) the generalities of PV, including the theoretical aspects and its role in separation; (ii) a general overview of the methodologies for the preparation of MMMs; and (iii) the most recent findings based on MMMs for both ethanol recovery and ethanol dehydration for better evolution in the field. From the last decade of literature inputs, the poly(vinyl alcohol) has been the most used polymeric matrix targeting ethanol dehydration, while the zeolites have been the most used embedded materials. Today, the latest developments on MMM preparation declare that the future efforts will be directed to the chemical modification of polymeric materials as well as the incorporation of novel fillers or enhancing the existing ones through chemical modification.
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Liu, Jiyang, Miaoqing Liu, and Jianjun Lu. "Fabrication of polyimide and covalent organic frameworks mixed matrix membranes by in situ polymerization for preliminary exploration of CO2/CH4 separation." High Performance Polymers 31, no. 6 (June 25, 2018): 671–78. http://dx.doi.org/10.1177/0954008318783045.
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More and more polyimide (PI) mixed matrix membranes (MMMs) have been reported for gas separation. In this study, a novel PI MMM, named as PI/SNW-1 and composed of PI and Schiff base network (SNW) type covalent organic frameworks (COFs) SNW-1, was used for gas permeation measurements of carbon dioxide (CO2) and methane (CH4). The prepared PI/SNW-1 was investigated by the Fourier transform infrared spectroscopy, the field emission scanning electron microscopy, and the thermal gravimetric analysis. The results indicated that PI/SNW-1 had maintained a high thermal stability and uniform distribution of filler. Compared with the pure PI membrane, MMMs showed an increment of 48.7% in ideal selectivity of CO2/CH4 and an enhancement of 106.4% in CO2 permeability at 5 wt% SNW-1. The enhancement of permeability and selectivity was mainly attributed to the high porosity of SNW-1, the specific sorption affinity for CO2, and the close interface interaction with the PI matrix. It can be seen that PI/SNW-1 has a great potential for actual gas separation.
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Shafie, Siti Nur Alwani, Nik Abdul Hadi Md Nordin, Muhammad Roil Bilad, Nurasyikin Misdan, Norazlianie Sazali, Zulfan Adi Putra, Mohd Dzul Hakim Wirzal, Alamin Idris, Juhana Jaafar, and Zakaria Man. "[EMIM][Tf2N]-Modified Silica as Filler in Mixed Matrix Membrane for Carbon Dioxide Separation." Membranes 11, no. 5 (May 19, 2021): 371. http://dx.doi.org/10.3390/membranes11050371.
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This study focuses on the effect of modified silica fillers by [EMIN][Tf2N] via physical adsorption on the CO2 separation performance of a mixed matrix membrane (MMM). The IL-modified silica was successfully synthesized as the presence of fluorine element was observed in both Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectrometer (XPS) analyses. The prepared MMMs with different loadings of the IL-modified silica were then compared with an unmodified silica counterpart and neat membrane. The morphology of IL-modified MMMs was observed to have insignificant changes, while polymer chains of were found to be slightly more flexible compared to their counterpart. At 2 bar of operating pressure, a significant increase in performance was observed with the incorporation of 3 wt% Sil-IL fillers compared to that of pure polycarbonate (PC). The permeability increased from 353 to 1151 Barrer while the CO2/CH4 selectivity increased from 20 to 76. The aforementioned increment also exceeded the Robeson upper bound. This indicates that the incorporation of fillers surface-modified with ionic liquid in an organic membrane is worth exploring for CO2 separation.
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Nandakumar, A., and D. Dinakaran. "Effect of Nanoparticles in Reinforced Metal Matrix Composite on the Machinability Characteristics - A Review." Applied Mechanics and Materials 813-814 (November 2015): 625–28. http://dx.doi.org/10.4028/www.scientific.net/amm.813-814.625.
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Metal Matrix nanoComposites (MMNC) refer to materials consisting of a ductile metal or alloy matrix in which some nanosized reinforcement materials is implanted. These materials combine metal and ceramic features, i.e., ductility and toughness with high strength. Thus, metal matrix nanocomposites are suitable for production of materials with high strength in shear/compression processes and high service temperature capabilities. Both Metal Matrix Composite (MMC) and Ceramic Matrix Composites (CMC) with Carbon nanoTubes (CNT) nanocomposites hold promise, but also pose challenges for real success. In the present paper deals an inclusive review of literature in effect of nanoparticles in reinforced metal matrix composites on the machinability characteristics of the composite materials.
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Jamil, Asif, Momina Zulfiqar, Usama Arshad, Subhan Mahmood, Tanveer Iqbal, Sikander Rafiq, and Muhammad Z. Iqbal. "Development and Performance Evaluation of Cellulose Acetate-Bentonite Mixed Matrix Membranes for CO2 Separation." Advances in Polymer Technology 2020 (December 13, 2020): 1–12. http://dx.doi.org/10.1155/2020/8855577.
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Membrane science is a state-of-the-art environmentally green technology that ascertains superior advantages over traditional counterparts for CO2 capture and separation. In this research, mixed matrix membranes (MMMs) comprising cellulose acetate (CA) with various loadings of bentonite (Bt) clay were fabricated by adopting the phase-inversion technique for CO2/CH4 and CO2/N2 separation. The developed pristine and MMMs were characterized for morphological, thermal, structural, and mechanical analyses. Several techniques such as scanning electron microscopy, thermogravimetric analysis, Fourier transformed infrared spectroscopy, and nano-indentation investigations revealed the promising effect of Bt clay in MMMs as compared to pristine CA membrane. Nano-indentation test identified that elastic modulus and hardness of the MMM with 1 wt. loading was increased by 64% and 200%, respectively, compared to the pristine membrane. The permeability decreased with the incorporation of Bt clay due to uniform dispersion of filler attributed to enhanced tortuosity for the gas molecules. Nevertheless, an increase in gas separation performance was observed with Bt addition up to 1 wt. loading. The opposite trend prevailed with increasing Bt concentration on the separation performance owing to filler agglomeration and voids creation. The maximum value of ideal selectivity (CO2/CH4) was achieved at 2 bar pressure with 1 wt. % Bt loading, which is 79% higher than the pristine CA membrane. For CO2/N2, the ideal selectivity was 123% higher compared to the pristine membrane with 1 wt. % Bt loading at 4 bar pressure.
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Ivanchev, Lilian, Sigqibo Templeton Camagu, and Gonasagren Govender. "Semi-Solid High Pressure Die Casting of Metal Matrix Composites Produced by Liquid State Processing." Solid State Phenomena 192-193 (October 2012): 61–65. http://dx.doi.org/10.4028/www.scientific.net/ssp.192-193.61.
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There are two main technologies for manufacturing of particulate reinforced metal matrix composites (MMC), solid state and liquid state processing. The great challenge of producing cast metal matrix composites is to prevent agglomeration of particulates. This tendency is more pronounced with decreasing the particulate size to fine micro- and nano size. A method for producing MMC was successfully implemented for mixing hybrid, nano and low micron sized, reinforcing particles in an aluminium alloy matrix. The hybrid SiC particles were produced by milling 3µm to 5µm SiC particles to a particle size range between 2.5µm and 150 nm. The hybrid particles were mixed with A356 aluminium alloy under combined magneto-hydrodynamic (MHD) and mechanical stirring. The composite was then transferred to a High Pressure Die Casting (HPDC) machine in the semi-solid state. The micron size particles were found to be predominantly in the intergranular eutectic while the nano-particles were predominantly in the primary α-Al grains. Increased ultimate tensile strength, yield strength and hardness were achieved for the new cast metal matrix hybrid component (MMHC) alloy.
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Pardo, Fernando, Sergio V. Gutiérrez-Hernández, Carolina Hermida-Merino, João M. M. Araújo, Manuel M. Piñeiro, Ana B. Pereiro, Gabriel Zarca, and Ane Urtiaga. "Integration of Stable Ionic Liquid-Based Nanofluids into Polymer Membranes. Part II: Gas Separation Properties toward Fluorinated Greenhouse Gases." Nanomaterials 11, no. 3 (February 26, 2021): 582. http://dx.doi.org/10.3390/nano11030582.
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Membrane technology can play a very influential role in the separation of the constituents of HFC refrigerant gas mixtures, which usually exhibit azeotropic or near-azeotropic behavior, with the goal of promoting the reuse of value-added compounds in the manufacture of new low-global warming potential (GWP) refrigerant mixtures that abide by the current F-gases regulations. In this context, the selective recovery of difluorometane (R32, GWP = 677) from the commercial blend R410A (GWP = 1924), an equimass mixture of R32 and pentafluoroethane (R125, GWP = 3170), is sought. To that end, this work explores for the first time the separation performance of novel mixed-matrix membranes (MMMs) functionalized with ioNanofluids (IoNFs) consisting in a stable suspension of exfoliated graphene nanoplatelets (xGnP) into a fluorinated ionic liquid (FIL), 1-ethyl-3-methylpyridinium perfluorobutanesulfonate ([C2C1py][C4F9SO3]). The results show that the presence of IoNF in the MMMs significantly enhances gas permeation, yet at the expense of slightly decreasing the selectivity of the base polymer. The best results were obtained with the MMM containing 40 wt% IoNF, which led to an improved permeability of the gas of interest (PR32 = 496 barrer) with respect to that of the neat polymer (PR32 = 279 barrer) with a mixed-gas separation factor of 3.0 at the highest feed R410A pressure tested. Overall, the newly fabricated IoNF-MMMs allowed the separation of the near-azeotropic R410A mixture to recover the low-GWP R32 gas, which is of great interest for the circular economy of the refrigeration sector.