Unprecedentedly Low CO2 Transport through Vertically Aligned, Conical Silicon Nanotube Membranes.

Nanotube membranes could show significantly enhanced permeance and selectivity for gas separations. Up until now, studies have primarily focused on applying carbon nanotubes to membranes to achieve ultrafast mass transport. Here, we report the first preparation of silicon nanotube (SiNT) membranes via a template-assisted method and investigate the gas transport behavior through these SiNT membranes using single- and mixed-gas permeation experiments. The SiNT membranes consist of conical cylinder-shaped nanotubes vertically aligned on a porous silicon wafer substrate. The diameter of the SiNT pore mouths are 10 and 30 nm, and the average inner diameter of the tube body is 80 nm. Interestingly, among the gases tested, we found an unprecedentedly low CO2 permeance through the SiNT membranes in single-gas permeation experiments, exceeding the theoretical Knudsen selectivity toward small gases/CO2 separation. This behavior was caused by the reduction of CO2 permeability through the blocking effect of CO2 adsorbed in the narrow pore channels of the SiNT cone regions, indicating that CO2 molecules have a high affinity to the native silicon oxide layer (∼2 nm) that is formed on the inner walls of SiNTs. SiNT membranes also exhibited enhanced gas permeance and water flux as compared to classic theoretical models and, as such, may prove useful as a new type of nanotube material for use in membrane applications.

The Role of Orthography in Lexical Processing of the Phonological Variants in Second Language.

There is evidence that orthographic knowledge can influence on-line spoken-word recognition. Interestingly, when graphic and phonetic codes are not congruent due to the application of phonological alternation processes, people report hearing sounds that are matched to graphic (underlying), not phonetic codes (Hallé et al. in J Mem Lang 43:618-639, 2000). It is, however, not known whether the same effect arises in the processing of a non-native language (L2). In the present study, advanced Mandarin learners of Korean as well as native Korean listeners performed a phoneme monitoring task using words undergoing obstruent nasalization in Korean. The results showed that orthographic information dominated the phonetic judgments of the native Korean listeners, while the Mandarin learners' judgments relied more on the phonetic input. These results suggest that even the lexical access of highly experienced L2 learners differs from that of native speakers and that advanced learners still have difficulty employing orthographic information to access the L2 lexicon.

Perception and production of English stops by tonal and non-tonal Korean dialect speakers.

This study examines whether relative weightings of voice onset time and onset F0 in Korean tonal vs non-tonal dialects affect the production and perception of English voiced and voiceless stops. Following Shultz et al. [(2012). J. Acoust. Soc. Am. 132, EL95-EL101], discriminant function analysis and logistic regression were conducted to calculate each speaker's relative weightings of these two cues in the production of target words and the labeling of the synthesized tokens according to these cues, respectively. The results demonstrated that the acquisition of second language (L2) contrasts is influenced by native language dialects, and production and perception are not developed in parallel in L2 acquisition.

Detailed Characterization of an Annealed Reduced Graphene Oxide Catalyst for Selective Peroxide Formation Activity.

Recently, electrochemical hydrogen peroxide (H2O2) generation from oxygen molecules has been extensively studied. Thus far, the best peroxide activity under alkaline conditions has been reported at the surface of a mild reduced graphene oxide annealed at 600 °C (mrGO-600). However, the detailed material information, such as chemical functionality and structural morphology, is unknown, which results in ambiguous debates on its catalytic active sites. To solve this problem, we intensively characterize the structure of mrGO-600 to clarify the origin of its catalytic activity. Various characterizations, including X-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, near-edge X-ray absorption fine spectroscopy, and high-resolution transmittance electron microscopy coupled with in situ infrared spectroelecrochemistry, reveal that the annealing process generates not only various hole edge defects that are related to the ring ether group but also numerous point defects that result in a small-sized disconnected graphitic carbon region. These defects are believed to form a unique atomic level configuration in mrGO-600, which enables it to facilitate high peroxide-generated activity from oxygen molecules in an alkaline electrolyte.

Origin of CO2-philic Sorption by Graphene Oxide Layered Nanosheets and Their Derivatives.

Graphene oxide (GO) is a promising 2D material for adsorbents and membranes, in particular, for the CO2 separation process. However, CO2 diffusion and sorption in GO and its layered structures are still not well understood because of its heterogeneous structure. Here we report CO2 sorption in GO and its derivatives (e.g., reduced GO (rGO)) in powders and films. These CO2 sorption behaviors reveal that GO is highly CO2-philic via complex CO2-functional-group-surface interactions, as compared with graphite and rGOs. Even in highly interlocked, lamellar GO films, CO2 molecules above a certain threshold pressure can diffuse into GO interlayers, causing GO films to swell and leading to dramatic increases in CO2 sorption. Intercalated water in GO interlayers can be removed by preferential CO2 sorption without any changes in the GO chemical structure. This finding helps to explain the origin of CO2 affinity with GO and has implications for preparing anhydrous GO assemblies for various applications.

Understanding Gas Transport Behavior through Few-Layer Graphene Oxide Membranes Controlled by Tortuosity and Interlayer Spacing.

Here, we elucidate the gas transport behavior through few-layer graphene oxide membranes (FGOMs) that have a systematically controlled diffusion pathway, including tortuosity and channel width. The obtained unusual gas permeation order (especially, CH4 > O2 > N2) of the FGOM provides strong evidence that gas molecules can indeed penetrate through the empty voids created by horizontally assembled GO, which allows selective gas transport features. These unique transport features of the FGOM originate from its continuously connected channel structure, which is an analogue of an ultrapermeable glassy polymer with extremely large free volumes in dense films. Furthermore, variation of the channel width in the range of 0.50-0.55 nm leads to notable changes in the gas permeance orders related to CH4, indicating that there is a transition region for switching the gas transport mechanism between a molecular sieving character and the solution-diffusion model.

Granulosicoccaceae fam. nov., to include Granulosicoccus antarcticus gen. nov., sp. nov., a non-phototrophic, obligately aerobic chemoheterotroph in the order Chromatiales, isolated from Antarctic seawater.

A Gram-negative, motile by tuft flagella, obligately aerobic chemoorganoheterotrophic, sphere-form bacterium, designated IMCC3135(T), was isolated from the Antarctic surface seawater of King George Island, West Antarctica. The strain was mesophilic, neutrophilic, and requiring NaCl for growth, but neither halophilic nor halotolerant. The 16S rRNA gene sequence analysis indicated that the strain was most closely related to genera of the order Chromatiales in the class Gammaproteobacteria. The most closely related genera showed less than 90% 16S rRNA gene sequence similarity and included Thioalkalispira (89.9%), Thioalkalivibrio (88.0%-89.5%), Ectothiorhodospira (87.9%-89.3%), Chromatium (88.3%-88.9%), and Lamprocystis (87.7%-88.9%), which represent three different families of the order Chromatiales. Phylogenetic analyses showed that this Antarctic strain represented a distinct phylogenetic lineage in the order Chromatiales and could not be assigned to any of the defined families in the order. Phenotypic characteristics, including primarily non-phototrophic, non-alkaliphilic, non-halophilic, and obligately aerobic chemoheterotrophic properties, differentiated the strain from other related genera. The very low sequence similarities (<90%) and distant relationships between the strain and members of the order suggested that the strain merited classification as a novel genus within a novel family in the order Chromatiales. On the basis of these taxonomic traits, a novel genus and species is proposed, Granulosicoccus antarcticus gen. nov., sp. nov., in a new family Granulosicoccaceae fam. nov. Strain IMCC3135(T) (=KCCM 42676(T)=NBRC 102684(T)) is the type strain of Granulosicoccus antarcticus.

Oxygen concentration control of dopamine-induced high uniformity surface coating chemistry.

Material surface engineering has attracted great interest in important applications, including electronics, biomedicine, and membranes. More recently, dopamine has been widely exploited in solution-based chemistry to direct facile surface modification. However, unsolved questions remain about the chemical identity of the final products, their deposition kinetics and their binding mechanism. In particular, the dopamine oxidation reaction kinetics is a key to improving surface modification efficiency. Here, we demonstrate that high O(2) concentrations in the dopamine solution lead to highly homogeneous, thin layer deposition on any material surfaces via accelerated reaction kinetics, elucidated by Le Chatelier's principle toward dopamine oxidation steps in a Michael-addition reaction. As a result, highly uniform, ultra-smooth modified surfaces are achieved in much shorter deposition times. This finding provides new insights into the effect of reaction kinetics and molecular geometry on the uniformity of modifications for surface engineering techniques.

Ulvibacter antarcticus sp. nov., isolated from Antarctic coastal seawater.

A seawater bacterium, designated IMCC3101(T), was isolated from Antarctic coastal seawater. The strain was Gram-negative, chemoheterotrophic, obligately aerobic, pigmented dark yellow (flexirubin-type pigments) and devoid of gliding and flagellar motility. On the basis of 16S rRNA gene sequence comparisons, the most closely related species was Ulvibacter litoralis (96.6 %). Phylogenetic trees generated by using 16S rRNA gene sequences confirmed that the strain belonged to the genus Ulvibacter in the family Flavobacteriaceae. The DNA G+C content was 37.0 mol% and the major respiratory quinone was MK-6. Several phenotypic characteristics, including cell and colony morphology, the absence of gliding motility and the temperature range for growth, serve to differentiate the strain from the only species in the genus Ulvibacter with a validly published name (U. litoralis). Therefore, strain IMCC3101(T) represents a novel species of the genus Ulvibacter, for which the name Ulvibacter antarcticus sp. nov. is proposed. The type strain is IMCC3101(T) (=KCCM 42686(T)=NBRC 102682(T)).

Sejongia marina sp. nov., isolated from Antarctic seawater.

A Gram-negative, psychrotolerant, chemoheterotrophic, aerobic, non-gliding, non-motile, yellow-pigmented bacterium, designated IMCC3228(T), was isolated from coastal seawater of the Antarctic. On the basis of 16S rRNA gene sequence comparisons, the strain was most closely related to the genera Sejongia (95.3-96.1 %) and Chryseobacterium (94.2-95.9 %) in the family Flavobacteriaceae. Phylogenetic trees generated using several treeing algorithms based on 16S rRNA gene sequences showed that this Antarctic marine isolate formed a distinct phyletic line within the genus Sejongia. The DNA G+C content of the strain was 35.0 mol% and the major respiratory quinone was MK-6. Several phenotypic and chemotaxonomic characteristics, including temperature and NaCl optima for growth, oxidase activity and the proportions of major cellular fatty acids, served to differentiate the strain from the recognized species of the genus Sejongia. Therefore strain IMCC3228(T) represents a novel species of the genus Sejongia, for which the name Sejongia marina sp. nov. is proposed. The type strain is IMCC3228(T) (=KCCM 42689(T)=NBRC 103143(T)).

Robiginitomaculum antarcticum gen. nov., sp. nov., a member of the family Hyphomonadaceae, from Antarctic seawater.

A seawater bacterium, designated IMCC3195T, was isolated from the Antarctic coast. Cells of the novel strain were Gram-negative, rusty-coloured, strictly aerobic, chemoheterotrophic, non-budding and non-motile rods or vibrioids that possessed a thin prostheca. Based on 16S rRNA gene sequence comparisons, the novel strain was most closely related to the genera Hyphomonas (89.4-90.9%), Maricaulis (90.1-90.4%), Hirschia (89.0%) and Oceanicaulis (87.9%) of the family Hyphomonadaceae. Phylogenetic analyses also showed the Antarctic isolate to be only distantly related to the genera of stalked bacteria of marine origin in the family Hyphomonadaceae. The DNA G+C content of the novel strain was 60.3 mol% and the predominant cellular fatty acids were C18:1omega7c (41.9%), C17:1omega8c (21.4%) and C17:0 (14.3%). The major quinone was Q-10. Several phenotypic and chemotaxonomic characteristics, including optimum temperature and salinity range for growth, cell morphology, pigmentation and fatty acid content, differentiated the novel strain from other related genera in the family Hyphomonadaceae. From the taxonomic evidence collected in this study, it is suggested that strain IMCC3195T (=KCCM 42687T=NBRC 103098T) represents a new genus and novel species in the family Hyphomonadaceae, for which the name Robiginitomaculum antarcticum gen. nov., sp. nov. is proposed.