Minimizing the Instant and Accumulative Effects of Salt Permeability to Sustain Ultrahigh Osmotic Power Density

We have investigated the instant and accumulative effects of salt permeability on the sustainability of high power density in the pressure-retarded osmosis (PRO) process experimentally and theoretically. Thin-film composite (TFC) hollow-fiber membranes were prepared. A critical wall thickness was observed to ensure sufficient mechanical stability and hence a low salt permeability, <i>B</i>. The experimental results revealed that a lower <i>B</i> was essential to enhance the maximum power density from 15.3 W/m² to as high as 24.3 W/m² when 1 M NaCl and deionized water were feeds. Modeling work showed that a large <i>B</i> not only causes an instant drop in the initial water flux but also accelerates the flux decline at high hydraulic pressures, leading to reduced optimal operating pressure and maximal power density. However, the optimal operating pressure to harvest energy can be greater than one-half of the osmotic pressure gradient across the membrane if one can carefully design a PRO membrane with a large water permeability, small <i>B</i> value, and reasonably small structural parameter. It was also found that a high <i>B</i> accumulates salts in the feed, leads to the oversalinization of the feed, and largely lowers both the water flux and power density along the membrane module. Therefore, a low salt permeability is highly desirable to sustain high power density not only locally but also throughout the whole module

Facile Preparation of Antifouling Hollow Fiber Membranes for Sustainable Osmotic Power Generation

Organic fouling in the membrane support is one of the major causes for the flux decline and low efficiency in the pressure retarded osmosis (PRO) process for osmotic power generation, especially when the fouling is complicated by inorganic salt ions. A facile method to fabricate antifouling hollow fiber membranes was demonstrated in this study, which employed the readily available poly­(vinyl alcohol) (PVA) as the modification agent. The poly­(ether sulfone) (PES) support for the thin film composite (TFC) membranes was first coated by polydopamine (PDA) and then coated with PVA with the aid of glutaraldehyde (GA). PDA was found to detach from the support in the first 2 h and gradually stabilized at pH 2, verifying its applicability for PRO processes. In addition, the existence of a PVA layer was confirmed by X-ray photoelectron spectroscopy. It is important to note that by controlling the reaction conditions, the water flux and salt reverse flux in the PRO process were not sacrificed, proving that the modification can well maintain the porous structure of the support. The modified membranes showed significantly improved fouling resistance to not only alginate but also complex alginate–calcium solutions. The water flux remained ∼80% instead of ∼64% in the latter case. Moreover, much of the fouling was converted from irreversible to reversible, which helped enhance the efficiency of physical cleaning to ∼90%, and hence improved the sustainability of the PRO process

The GLS is required for <i>gurken</i> RNA localization and gene function.

<p>(A–B) Wild-type expression patterns of endogenous <i>gurken</i> RNA (A) and protein (B) as revealed by whole mount <i>in situ</i> hybridization and immunofluorescence, respectively. Anterodorsal localization of transcripts and protein is only apparent in the rightmost egg chambers, which are stage 8 and 9, respectively. (C–E) The <i>gurken</i> RNA and protein distribution patterns of <i>gurken</i> null mutants (<i>grk^ΔFRT</i>) carrying the wild-type <i>gurken</i> transgene, <i>grk^wt</i> (C–D) or no transgene (E). (F–H) <i>grk^ΔFRT</i> eggs and egg chambers (from <i>gurken</i> null mothers) carrying the <i>grkGLS^mut</i> transgene. (F) Left panel: representative <i>grk^ΔFRT</i>; <i>grkGLS^mut</i> egg exhibiting a completely ventralized phenotype, i.e., complete loss of dorsal appendage material. Right panel; anterior end of a <i>grk^ΔFRT</i>; <i>grkGLS^mut</i> egg exhibiting a strong, but not complete, ventralized phenotype. Note, for example the short, fused dorsal appendage. (G) <i>grk^ΔFRT</i>; <i>grkGLS^mut</i> ovariole following <i>in situ</i> hybridization with <i>gurken</i> probe. Transcripts are dispersed throughout the germ-line cysts with only slight enrichment in the oocyte and no subcellular localization. (H) <i>grk^ΔFRT</i>; <i>grkGLS^mut</i> ovariole following immunofluorescence using an anti-Grk antibody. The protein is generally dispersed throughout the germ-line cysts, although slight enrichment around the oocyte nucleus is seen in rare stage 10 and 11 egg chambers.</p

Structure of GLS variants.

<p>The wild-type GLS is shown at the left for comparison. The GLS mutant (referred to as <i>grkGLS^mut</i> in Text) contains 12 point mutations (shown in red), which are predicted to disrupt the predicted base pairing pattern of the GLS at five sites (circled). None of the 12 mutations affect the protein coding sequence as shown at the bottom portion of the figure.</p

Conservation and predicted secondary structure of the GLS.

<p>(A) Sequence alignment of the <i>gurken</i> transcription unit displayed using the Vista Browser at <a href="http://pipeline.lbl.gov/cgi-bin/gateway2" target="_blank">http://pipeline.lbl.gov/cgi-bin/gateway2</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0015448#pone.0015448-Nielsen1" target="_blank">[49]</a>. The estimated years in millions (MYA) of evolution between <i>D</i>. <i>melanogaster</i> and each of the other five species is from Heger and Ponting <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0015448#pone.0015448-Heger1" target="_blank">[24]</a>. The most highly conserved region is circled and includes the first 39 nt of the GLS. The last 25 nt of the GLS map to the 3′ side of the abutting intron. The arrow indicates the direction of transcription. The red shaded region corresponds to a putative transposable element. The numbers at the bottom of the graph indicate nucleotide position along the chromosome. (B) The 5′ end of the <i>gurken</i> mRNA, where the green dot denotes the translation start site, the red arrows the boundaries of the GLS, and the asterisk the position of the intron. The nucleotides beneath the aligned sequence blocks highlight differences between the <i>D. Willistoni</i> and <i>D. melanogaster</i> sequences. (C) Predicted secondary structure of the GLS, with non-conserved residues shown in red.</p

A Scalable Route to Nanoporous Large-Area Atomically Thin Graphene Membranes by Roll-to-Roll Chemical Vapor Deposition and Polymer Support Casting

Scalable, cost-effective synthesis and integration of graphene is imperative to realize large-area applications such as nanoporous atomically thin membranes (NATMs). Here, we report a scalable route to the production of NATMs via high-speed, continuous synthesis of large-area graphene by roll-to-roll chemical vapor deposition (CVD), combined with casting of a hierarchically porous polymer support. To begin, we designed and built a two zone roll-to-roll graphene CVD reactor, which sequentially exposes the moving foil substrate to annealing and growth atmospheres, with a sharp, isothermal transition between the zones. The configurational flexibility of the reactor design allows for a detailed evaluation of key parameters affecting graphene quality and trade-offs to be considered for high-rate roll-to-roll graphene manufacturing. With this system, we achieve synthesis of uniform high-quality monolayer graphene (<i>I</i>_D/<i>I</i>_G < 0.065) at speeds ≥5 cm/min. NATMs fabricated from the optimized graphene, via polymer casting and postprocessing, show size-selective molecular transport with performance comparable to that of membranes made from conventionally synthesized graphene. Therefore, this work establishes the feasibility of a scalable manufacturing process of NATMs, for applications including protein desalting and small-molecule separations

Baseline characteristics by artificially sweetened beverage intake (n = 1,018, median follow-up = 7.3 years).

<p>Baseline characteristics by artificially sweetened beverage intake (n = 1,018, median follow-up = 7.3 years).</p

Associations between artificially sweetened beverage intake and colon cancer recurrence and mortality.

<p>Associations between artificially sweetened beverage intake and colon cancer recurrence and mortality.</p

Results of isovolumetric substitution analysis, calculating change in relative risk of patient outcomes with substitution of 1 serving/day of artificially sweetened beverage for sugar-sweetened beverage.

<p>Change in relative risk is displayed for each outcome as a percentage both graphically and in text, with 95% confidence intervals depicted graphically as error bars. Adjusted for age (continuous variable in years), sex (male or female), depth of invasion through bowel wall (binary variable, pT1-2 or pT3-4), number of positive lymph nodes (binary variable, 1–3 nodes or ≥4 nodes), baseline performance status (binary variable, 0 or 1–2), chemotherapy treatment group (binary variable, 5-fluorouracil and leucovorin or irinotecan, 5-fluorouracil, and leucovorin), consistent aspirin use (yes on both questionnaire 1 and 2), and time-varying total calorie intake (continuous variable, in kilocalories per day), physical activity (continuous variable in metabolic equivalent task hours per week), and body mass index (continuous variable in kilogram per meter-squared). <i>P</i> values are two-sided. Abbreviations: CI, confidence interval.</p

Derivation of the study cohort.

<p>Abbreviations: ASB, artificially sweetened beverages; CAGLB, Cancer and Leukemia Group B; Q1, questionnaire 1 (midway through adjuvant therapy); Q2, questionnaire 2 (6 months after completion of adjuvant therapy). *Caloric intake exclusion = Less than 600 calories or greater than 4,200 calories per day for men and less than 500 calories or greater than 3,500 calories per day for women. † 6 patients in the final sample are missing physical activity in questionnaire 1 and 3 are missing physical activity in questionnaire 2. 1 patient is missing body mass index in questionnaire 1 and 1 is missing body mass index in questionnaire 2.</p