http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Kim, Sangwon,Li, Wei,Fredrickson, Glenn H.,Hawker, Craig J.,Kramer, Edward J. The Royal Society of Chemistry 2016 SOFT MATTER Vol.12 No.27
<P>We present experimental and theoretical investigations of the order-disorder transition (ODT) in thin films of cylinder-forming diblock copolymers with asymmetric wetting conditions. Grazing incidence small-angle X-ray scattering (GISAXS) was implemented to determine the ODT temperatures (T-ODT) for poly(styrene-b-2-vinyl pyridine) (PS-P2VP) block copolymer thin films on a P2VP-preferential silicon substrate. Specifically, films consisting of multilayers of horizontally-oriented cylindrical structures (from 1- to 9-layers) were tested. We find that films with more than 2 cylindrical layers have a T-ODT comparable to the bulk case. However, T-ODT decreases as the film becomes thinner and the monolayer system has an ODT 30 degrees C below the bulk. Using self-consistent field theory (SCFT), we studied the ordering in corresponding thin films with asymmetric (top and bottom surface) wetting conditions. Surprisingly, SCFT is found to predict an opposite trend in T-ODT with film thickness than observed experimentally. Field-theoretic simulations with complex Langevin sampling were employed to resolve this discrepancy and demonstrate that thermal fluctuations in the PS-P2VP thin-film system dominate its ordering behavior in monolayer and bilayer films.</P>
( Anamika Khanal ),( Hor-gil Hur ),( James K. Fredrickson ),( Ji-hoon Lee ) 한국미생물 · 생명공학회 2021 Journal of microbiology and biotechnology Vol.31 No.11
Hexavalent chromium (Cr(VI)) is recognized to be carcinogenic and toxic and registered as a contaminant in many drinking water regulations. It occurs naturally and is also produced by industrial processes. The reduction of Cr(VI) to Cr(III) has been a central topic for chromium remediation since Cr(III) is less toxic and less mobile. In this study, fermentative Fe(III)-reducing bacterial strains (Cellu-2a, Cellu-5a, and Cellu-5b) were isolated from a groundwater sample and were phylogenetically related to species of Cellulomonas by 16S rRNA gene analysis. One selected strain, Cellu-2a showed its capacity of reduction of both soluble iron (ferric citrate) and solid iron (hydrous ferric oxide, HFO), as well as aqueous Cr(VI). The strain Cellu-2a was able to reduce 15 μM Cr(VI) directly with glucose or sucrose as a sole carbon source under the anaerobic condition and indirectly with one of the substrates and HFO in the same incubations. The heterogeneous reduction of Cr(VI) by the surface-associated reduced iron from HFO by Cellu-2a likely assisted the Cr(VI) reduction. Fermentative features such as large-scale cell growth may impose advantages on the application of bacterial Cr(VI) reduction over anaerobic respiratory reduction.
Biogenic Formation of As-S Nanotubes by Diverse Shewanella Strains
Jiang, Shenghua,Lee, Ji-Hoon,Kim, Min-Gyu,Myung, Nosang V.,Fredrickson, James K.,Sadowsky, Michael J.,Hur, Hor-Gil American Society for Microbiology 2009 Applied and environmental microbiology Vol.75 No.21
<B>ABSTRACT</B><P><I>Shewanella</I> sp. strain HN-41 was previously shown to produce novel, photoactive, As-S nanotubes via the reduction of As(V) and S2O3<SUP>2−</SUP> under anaerobic conditions. To determine if this ability was unique to this bacterium, 10 different <I>Shewanella</I> strains, including <I>Shewanella</I> sp. strain HN-41, <I>Shewanella</I> sp. strain PV-4, <I>Shewanella alga</I> BrY, <I>Shewanella amazonensis</I> SB2B, <I>Shewanella denitrificans</I> OS217, <I>Shewanella oneidensis</I> MR-1, <I>Shewanella putrefaciens</I> CN-32, <I>S. putrefaciens</I> IR-1, <I>S. putrefaciens</I> SP200, and <I>S. putrefaciens</I> W3-6-1, were examined for production of As-S nanotubes under standardized conditions. Of the 10 strains examined, three formed As-S nanotubes like those of strain HN-41. While <I>Shewanella</I> sp. strain HN-41 and <I>S. putrefaciens</I> CN-32 rapidly formed As-S precipitates in 7 days, strains <I>S. alga</I> BrY and <I>S. oneidensis</I> MR-1 reduced As(V) at a much lower rate and formed yellow As-S after 30 days. Electron microscopy, energy-dispersive X-ray spectroscopy, and extended X-ray absorption fine-structure spectroscopy analyses showed that the morphological and chemical properties of As-S formed by strains <I>S. putrefaciens</I> CN-32, <I>S. alga</I> BrY, and <I>S. oneidensis</I> MR-1 were similar to those previously determined for <I>Shewanella</I> sp. strain HN-41 As-S nanotubes. These studies indicated that the formation of As-S nanotubes is widespread among <I>Shewanella</I> strains and is closely related to bacterial growth and the reduction rate of As(V) and thiosulfate.</P>
Self-consistent field theory for diblock copolymers grafted to a sphere
Vorselaars, Bart,Kim, Jaeup U.,Chantawansri, Tanya L.,Fredrickson, Glenn H.,Matsen, Mark W. Royal Society of Chemistry 2011 SOFT MATTER Vol.7 No.11
<P>An efficient numerical self-consistent field theory (SCFT) algorithm is developed for treating structured polymers on spherical surfaces. The method solves the diffusion equations of SCFT with a pseudo-spectral approach that combines a spherical-harmonics expansion for the angular coordinates with a modified real-space Crank–Nicolson method for the radial direction. The self-consistent field equations are solved with Anderson-mixing iterations using dynamical parameters and an alignment procedure to prevent angular drift of the solution. A demonstration of the algorithm is provided for thin films of diblock copolymer grafted to the surface of a spherical core, in which the sequence of equilibrium morphologies is predicted as a function of diblock composition. The study reveals an array of interesting behaviors as the block copolymer pattern is forced to adapt to the finite surface area of the sphere.</P> <P>Graphic Abstract</P><P>An efficient SCFT algorithm is developed and used to predict the morphologies of diblock copolymers grafted to a spherical nanoparticle. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sm01242d'> </P>
Water Sorption/Desorption Characteristics of Eutectic LiCl-KCl Salt-Occluded Zeolites
Allison Harward,Levi Gardner,Claire M. Decker Oldham,Krista Carlson,유 태식,Guy Fredrickson,Michael Patterson,Michael F. Simpson 한국방사성폐기물학회 2022 방사성폐기물학회지 Vol.20 No.3
Molten salt consisting primarily of eutectic LiCl-KCl is currently being used in electrorefiners in the Fuel Conditioning Facility at Idaho National Laboratory. Options are currently being evaluated for storing this salt outside of the argon atmosphere hot cell. The hygroscopic nature of eutectic LiCl-KCl makes is susceptible to deliquescence in air followed by extreme corrosion of metallic cannisters. In this study, the effect of occluding the salt into a zeolite on water sorption/desorption was tested. Two zeolites were investigated: Na-Y and zeolite 4A. Na-Y was ineffective at occluding a high percentage of the salt at either 10 or 20wt% loading. Zeolite-4A was effective at occluding the salt with high efficiency at both loading levels. Weight gain in salt occluded zeolite-4A (SOZ) from water sorption at 20% relative humidity and 40℃ was 17wt% for 10% SOZ and 10wt% for 20% SOZ. In both cases, neither deliquescence nor corrosion occurred over a period of 31 days. After hydration, most of the water could be driven off by heating the hydrated salt occluded zeolite to 530℃. However, some HCl forms during dehydration due to salt hydrolysis. Over a wide range of temperatures (320–700℃) and ramp rates (5, 10, and 20℃ min−1), HCl formation was no more than 0.6% of the Cl− in the original salt.