Reverse Osmosis and Ultrafiltration Membrane Surface Nano-Structuring with Tethered Hydrophilic Polymer Layers for Seawater Desalination

A systematic investigation of membrane surface nano-structuring (SNS) with surface tethered hydrophilic polymer layers was conducted in order to mitigate fouling of reverse osmosis (RO) and ultrafiltration (UF) membranes and tune membrane performance in seawater desalination. Surface tethered hydrophilic polymer (i.e., polyacrylic acid (PAA)) layers were synthesized onto base polysulfone (PSf) UF and polyamide (PA) thin film composite (TFC) RO membranes via membrane surface activation with an atmospheric pressure plasma (APP), followed by graft polymerization (GP) of acrylic acid. Both APP surface activation and GP conditions impacted the structure of the synthesized tethered PAA layers and RO membrane desalination performance. Detailed characterization of tethered PAA chain extension length via atomic force microscopy (AFM) based force spectroscopy (FS) revealed that the number average molecular weight of the synthesized tethered PAA chains was estimated to be in the range of ∼13,000–35,000 with chain-chain separation of 1.5–2.4 nm. Extension of the tethered PAA chains in DI water was significantly greater in DI water than in high salinity aqueous environment. UF fouling stress tests with alginic acid in high salinity water and post-cleaning with non-saline water demonstrated permeability restoration of up to 90–100% for a surface nano-structured (SNS)-PAA-PSf membrane relative to 50–70% for the native PSf membrane. Synthesized SNS-PAA-PA BWRO and SWRO membranes having water and salt permeability coefficient in the range of 2.3 – 3.4 L�m-2�h-1�bar-1 and 0.15 – 0.54 L�m-2�h-1 revealed that membrane surface structuring with a tethered PAA layer enabled tuning membrane performance (in terms of Lp and B) to achieve water/salt selectivity (evaluated as Lp:B ratio) that was significantly higher (by up to 56%) relative to the base PA membranes. It was demonstrated that, depending on APP surface activation and GP conditions, PA TFC membranes could be tuned to have essentially the same salt rejection over a wide permeability range or a given permeability over a range of salt rejection. It was also shown that membrane performance could be achieved that overcomes the permeability-selectivity trade-off. Lastly, the present study developed an approach to scale up the APP surface activation and GP process by performing membrane surface nano-structuring for large PA TFC flat sheet membranes that are suitable for fabricating 2.5” x 21” spiral wound RO elements

Surface characterization data for tethered polyacrylic acid layers synthesized on polysulfone surfaces.

The data presented are supplementary to an article [Kim et al., 2019] on synthesis and surface characterization of tethered polyacrylic acid (PAA) layers on polysulfone (PSf) film/membrane surfaces via atmospheric pressure plasma-induced graft polymerization (APPIGP). Data on surface characterization of the synthesized tethered PAA layers includes: AFM topographic surface images and height distributions of surface features, dry layer thickness, chain rupture length distributions determined via AFM based force spectroscopy (AFM-FS), in addition to measurements of water contact angles. Fouling propensity data for ultrafiltration of alginic acid as a model foulant are also provided for native and PAA grafted PSf ultrafiltration (UF) membranes

Baicalein, a small molecule regulating R-loop formation

Department of Biological SciencesR-loop is a tri-nucleotide structure composed of DNA:RNA hybrid and non-template ssDNA. Tight regulation of R-loop formation is important for maintaining genomic stability. Abnormal R-loop formations are shown in some cancers and neurological disorders. Some of small molecules commonly used as DNA damaging reagents are discovered to regulate R-loop formation. For example, camptothecin (CPT), which induces DNA damage by inhibiting Topoisomerase I, enhances R-loop formation. To find out small molecules regulating R-loop formation, High Content Screening (HCS) to visualize R-loops in high-throughput manner was established. Baicalein was identified as the first small molecule reducing CPT-induced R-loops. Though it is still unclear whether baicalein directly binds to R-loop, R-loop reduction by baicalein depended on XPF. DNA damage marker, 53BP1 recruitment to chromatin was decreased by baicalein treatment in XPF-dependent manner. However, the catalytic activity of XPF was dispensable for reduction of R-loop formation and 53BP1 recruitment to chromatin by baicalein treatment. Collectively, I found a small molecule, baicalein, can regulate R-loop formation and 53BP1 recruitment to the chromatin in XPF dependent manner.clos

Preschoolers’ leadership-followership communication in outdoor pretend play on a child care playground

Doctor of PhilosophySchool of Family Studies and Human ServicesDeborah NorrisLeadership begins to develop during early childhood, positively impacting children’s leadership trajectory. Social pretend play provides enriched environments for multiple cognitive and social purposes. The quality and sustainability of children’s social pretend play depends on the process including children’s back and forth proposals and responses about the play frames. Proposing and responding to play ideas with metacommunication use, leadership-followership interactions during pretend play engagement are required in which the leaders and followers are interdependent to effectively move play frames forward. The purpose of this study was to examine the use of metacommunication strategies and leadership/followership processes expressed in social pretend play. A conceptual framework was built on the works by Murphy and Johnson (2011) and Liu et al. (2020) on leadership development and Vygotsky’s work of pretend play during early years, describing the dynamic nature of leadership process within social pretend play. Results indicated that children’s use of metacommunication in social pretend play varies by what contents and to whom they are communicating. Results also showed how much the factors of interest – children’s use of metacommunication, group characteristics for gender, and the role of followership - may impact children’s successful pretend play

Superconductor Pb10−x_{10-x}Cux_x(PO4_4)6O_{6O} showing levitation at room temperature and atmospheric pressure and mechanism

A material called LK-99, a modified-lead apatite crystal structure with the composition Pb$_{10-x}$Cu$_x$(PO$_4$)$_{6O}$ ($0.9<x<1.1$), has been synthesized using the solid-state method. The material exhibits the Ohmic metal characteristic of Pb(6s1) above its superconducting critical temperature, $T_c$, and the levitation phenomenon as Meissner effect of a superconductor at room temperature and atmospheric pressure below $T_c$. A LK-99 sample shows $T_c$ above 126.85$^\circ$C (400 K). We analyze that the possibility of room-temperature superconductivity in this material is attributed to two factors: the first being the volume contraction resulting from an insulator-metal transition achieved by substituting Pb with Cu, and the second being on-site repulsive Coulomb interaction enhanced by the structural deformation in the one-dimensional(D) chain (Pb2-O$_{1/2}$-Pb2 along the c-axis) structure owing to superconducting condensation at $T_c$. The mechanism of the room-temperature $T_c$ is discussed by 1-D BR-BCS theory.Comment: 18 pages, 7 figure

Real-Time Temporal Dynamics of Bicistronic Expression Mediated by Internal Ribosome Entry Site and 2A Cleaving Sequence

Multicistronic elements, such as the internal ribosome entry site (IRES) and 2A-like cleavage sequence, serve crucial roles in the eukaryotic ectopic expression of exogenous genes. For utilization of multicistronic elements, the cleavage efficiency and order of elements in multicistronic vectors have been investigated; however, the dynamics of multicistronic element-mediated expression remains unclear. Here, we investigated the dynamics of encephalomyocarditis virus (EMCV) IRES- and porcine teschovirus-1 2A (p2A)-mediated expression. By utilizing real-time fluorescent imaging at a minute-level resolution, we monitored the expression of fluorescent reporters bridged by either EMCV IRES or p2A in two independent cultured cell lines, HEK293 and Neuro2a. We observed significant correlations for the two fluorescent reporters in both multicistronic elements, with a higher correlation coefficient for p2A in HEK293 but similar coefficients for IRES-mediated expression and p2A-mediated expression in Neuro2a. We further analyzed the causal relationship of multicistronic elements by convergent cross mapping (CCM). CCM revealed that in all four conditions examined, the expression of the preceding gene causally affected the dynamics of the subsequent gene. As with the cross correlation, the predictive skill of p2A was higher than that of IRES in HEK293, while the predictive skills of the two multicistronic elements were indistinguishable in Neuro2a. To summarize, we report a significant temporal correlation in both EMCV IRES- and p2A-mediated expression based on the simple bicistronic vector and real-time fluorescent monitoring. The current system also provides a valuable platform to examine the dynamic aspects of expression mediated by diverse multicistronic elements under various physiological conditions.National Research Foundation of Korea (NRF) of the Ministry of Science and ICT [NRF-2017R1C1B2008775, NRF-2017R1A4A1015534, NRF-2018M3C7A1022310]; KBRI basic research program through Korea Brain Research Institute - Ministry of Science and ICT [17-BR-04]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Stability for the Mixed Type of Quartic and Quadratic Functional Equations

We establish the general solutions of the following mixed type of quartic and quadratic functional equation: f(2x+y)+f(2x-y)=4f(x+y)+4f(x-y)+2f(2x)-8f(x)-6f(y). Moreover we prove the Hyers-Ulam-Rassias stability of this equation under the approximately quartic and the approximately quadratic conditions