The role of surface thermodynamics and kinetics in the removal of PFOA from aqueous solutions

Perfluorooctanoic acid (PFOA) has been extensively used as surfactant in industrial applications. Human exposure to PFOA through contaminated water has been linked to serious adverse health effects. In this work, the removal of PFOA from water in all-silica zeolites, which are hydrophobic materials with diverse pore geometries and exceptional hydrothermal stability, is studied. Molecular scale structure, dynamics, kinetics, and free energy landscapes associated with PFOA adsorption are characterized. Interfacial adsorption constitutes the rate limiting step and the adsorption of PFOA is orientation competitive. The PFOA orientation where the hydrophobic perfluorinated methyl group is adsorbed first on the zeolite surface is thermodynamically favored; whereas the adsorption kinetics is faster when the hydrophilic carboxyl group is adsorbed first. Furthermore, the adsorption of PFOA in deprotonated state in hydrophobic pores is thermodynamically prohibitive. Based on computed permeabilities in the pores and kinetic rates associated with the adsorption of PFOA from water, three zeolites, MTW, VET and GON, are estimated to exhibit several orders of magnitude better PFOA removal performance compared to the benchmark material, zeolite Beta (BEA)

A cobalt arylphosphonate MOF – superior stability, sorption and magnetism

We report a novel metal-organic framework (MOF) based on a cobalt arylphosphonate, namely, [Co2(H4-MTPPA)]·3NMP·H2O (1·3NMP·H2O), which was prepared solvothermically from the tetrahedral linker tetraphenylmethane tetrakis-4-phosphonic acid (H8-MTPPA) and CoSO4·7H2O in N-methyl-2-pyrrolidone (NMP). Compound 1 has the highest porosity (BET surface area of 1034 m2 g−1) ever reported for a MOF based on an aryl phosphonic acid linker. The indigo blue crystals of 1·3NMP·H2O are composed of edge-shared eight-membered Co2P2O4 rings, and are thermally very stable up to 500 °C.TU Berlin, Open-Access-Mittel - 201

Selective Water Transport in an Alanine-Functionalized Metal–Organic Framework: A Computational Study

Applications of metal–organic frameworks (MOFs) functionalized with biomolecules have primarily focused on the use of these frameworks for bioimaging, catalysis, chiral separation, nanomotors, and drug delivery. However, their use in the design of artificial water channels (AWCs) has yet to be explored. In this work, we computationally explore the performance of a zwitterionic alanine-functionalized Ni-CPO-27 MOF as an AWC. Using density functional theory (DFT) calculations and equilibrium/nonequilibrium molecular dynamics (MD) simulations, the stability, water permeability, and ion selectivity of the proposed AWC are studied. The DFT calculations predict that zwitterionic alanine binds to the coordinatively unsaturated Ni sites almost twofold stronger compared to water. Using the quantum theory of atoms in molecules, it is also found that the zwitterionic alanine molecules are further stabilized through hydrogen bonding between their carboxylate (COO–) and amino (NH3+) groups. Nonequilibrium MD simulations show that the proposed AWC possesses a high osmotic water permeability of 2.2 ± 0.3 × 10–15 cm3/s/channel, which lies between that observed in aquaporin-0 and aquaporin-1 proteins, while completely excluding Na+ and Cl– ions from the channel. The free energies associated with the water and ion transport show that fast water transport may be attributed to the relatively low free energy barriers for water in the channel, whereas the ion exclusion is due to large free energy barriers that the ions cannot overcome even under 100 MPa of applied pressure. By using a crystalline material, the proposed design of an amino acid-functionalized MOF-based AWC represents a departure from previously developed AWCs, which rely on the self-assembly of curated molecules in lipid bilayers or polymer matrices and are susceptible to long-term stability issues

Semiconductive microporous hydrogen-bonded organophosphonic acid frameworks

Herein, we report a semiconductive, proton-conductive, microporous hydrogen-bonded organic framework (HOF) derived from phenylphosphonic acid and 5,10,15,20‐tetrakis[p‐phenylphosphonic acid] porphyrin (GTUB5). The structure of GTUB5 was characterized using single crystal X-ray diffraction. A narrow band gap of 1.56 eV was extracted from a UV-Vis spectrum of pure GTUB5 crystals, in excellent agreement with the 1.65 eV band gap obtained from DFT calculations. The same band gap was also measured for GTUB5 in DMSO. The proton conductivity of GTUB5 was measured to be 3.00 × 10−6 S cm−1 at 75 °C and 75% relative humidity. The surface area was estimated to be 422 m2 g−1 from grand canonical Monte Carlo simulations. XRD showed that GTUB5 is thermally stable under relative humidities of up to 90% at 90 °C. These findings pave the way for a new family of organic, microporous, and semiconducting materials with high surface areas and high thermal stabilities.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Co-existence of Two Rare Conditions: Oculo-Palato-Cerebral Syndrome and Congenital Chylothorax

Background: Oculo-palato-cerebral syndrome is an extremely rare condition characterized by various features, including low-birth weight, microcephaly, cerebral atrophy, mild-to-severe developmental delay, cleft palate, persistent hyperplastic primary vitreous, microphthalmia, small hands and feet, joint laxity, and large ears with thick helices. Diagnosis of this syndrome is based on the clinical manifestations, particularly the presence of persistent hyperplastic primary vitreous in association with other malformations. Congenital chylothorax is also a rare condition in the neonatal period, which is caused by the abnormal accumulation of the lymphatic fluid within the pleural space. This condition may be detected prenatally or during the neonatal period.  Case report: We presented the case of a patient with oculo-palato-cerebral syndrome and congenital chylothorax based on a literature review. Conclusion: Oculo-palato-cerebral syndrome and congenital chylothorax are both rare conditions. To the best of our knowledge, this was the first case report on congenital chylothorax in association with oculo-palato-cerebral syndrome in the available literature. Since there have only been five case reports on these patients, further evidence is required to confirm the possible association between these rare conditions

PERFORMANCE ENHANCEMENT OF MEMS-BASED MICROBIAL FUEL CELLS (mu MFC) FOR MICROSCALE POWER GENERATION

This paper reports the design, fabrication, and testing of a microliter scale Microbial Fuel Cell (mu mu MFC) based on silicon MEMS fabrication technology. mu MFC systems are operated under different loads or open circuit to compare the effect of different acclimatization conditions on start-up time. Shewanella oneidensis MR-1 is preferred to be the biocatalyst. The internal resistance is calculated as 20 k Omega under these conditions. Acclimatization of mu MFC under a finite load resulted in shorter start-up time (30 hours) when compared to the open load case. Power and current densities normalized to anode area are 2 mu W/cm(2) and 12 mu A/cm(2) respectively. When the load resistance value is closer to the internal resistance of the mu MFC, higher power and current densities are achieved as expected, and it resulted in a shorter start-up time. Further studies focusing on the different acclimatization techniques for mu MFC could pave the way to use mu MFCs as fast and efficient portable power sources

The mid-term results of treatment for tibial pilon fractures

BACKGROUN

Transcriptome analysis of Rhodobacter capsulatus grown on different nitrogen sources

This study investigated the effect of different nitrogen sources, namely, ammonium chloride and glutamate, on photoheterotrophic metabolism of Rhodobacter capsulatus grown on acetate as the carbon source. Genes that were significantly differentially expressed according to Affymetrix microarray data were categorized into Clusters of Orthologous Groups functional categories and those in acetate assimilation, hydrogen production, and photosynthetic electron transport pathways were analyzed in detail. Genes related to hydrogen production metabolism were significantly downregulated in cultures grown on ammonium chloride when compared to those grown on glutamate. In contrast, photosynthetic electron transport and acetate assimilation pathway genes were upregulated. In detail, aceA encoding isocitrate lyase, a unique enzyme of the glyoxylate cycle and ccrA encoding the rate limiting crotonyl-CoA carboxylase/reductase enzyme of ethylmalonyl-coA pathway were significantly upregulated. Our findings indicate for the first time that R. capsulatus can operate both glyoxylate and ethylmalonyl-coA cycles for acetate assimilation

Enhancement of the Start-Up Time for Microliter-Scale Microbial Fuel Cells (mu MFCs) via the Surface Modification of Gold Electrodes

Microbial Fuel Cells (MFCs) are biological fuel cells based on the oxidation of fuels by electrogenic bacteria to generate an electric current in electrochemical cells. There are several methods that can be employed to improve their performance. In this study, the effects of gold surface modification with different thiol molecules were investigated for their implementation as anode electrodes in micro-scale MFCs (mu MFCs). Several double-chamber mu MFCs with 10.4 mu L anode and cathode chambers were fabricated using silicon-microelectromechanical systems (MEMS) fabrication technology. mu MFC systems assembled with modified gold anodes were operated under anaerobic conditions with the continuous feeding of anolyte and catholyte to compare the effect of different thiol molecules on the biofilm formation ofShewanella oneidensisMR-1. Performances were evaluated using polarization curves, Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron Microcopy (SEM). The results showed that mu MFCs modified with thiol self-assembled monolayers (SAMs) (cysteamine and 11-MUA) resulted in more than a 50% reduction in start-up times due to better bacterial attachment on the anode surface. Both 11-MUA and cysteamine modifications resulted in dense biofilms, as observed in SEM images. The power output was found to be similar in cysteamine-modified and bare gold mu MFCs. The power and current densities obtained in this study were comparable to those reported in similar studies in the literature

Transcriptional Profiling of Hydrogen Production Metabolism of Rhodobacter capsulatus under Temperature Stress by Microarray Analysis

Biohydrogen is a clean and renewable form of hydrogen, which can be produced by photosynthetic bacteria in outdoor large-scale photobioreactors using sunlight. In this study, the transcriptional response of Rhodobacter capsulatus to cold (4 degrees C) and heat (42 degrees C) stress was studied using microarrays. Bacteria were grown in 30/2 acetate/glutamate medium at 30 degrees C for 48 h under continuous illumination. Then, cold and heat stresses were applied for two and six hours. Growth and hydrogen production were impaired under both stress conditions. Microarray chips for R. capsulatus were custom designed by Affymetrix (GeneChip((R)). TR_RCH2a520699F). The numbers of significantly changed genes were 328 and 293 out of 3685 genes under cold and heat stress, respectively. Our results indicate that temperature stress greatly affects the hydrogen production metabolisms of R. capsulatus. Specifically, the expression of genes that participate in nitrogen metabolism, photosynthesis and the electron transport system were induced by cold stress, while decreased by heat stress. Heat stress also resulted in down regulation of genes related to cell envelope, transporter and binding proteins. Transcriptome analysis and physiological results were consistent with each other. The results presented here may aid clarification of the genetic mechanisms for hydrogen production in purple non-sulfur (PNS) bacteria under temperature stress