6,307 research outputs found
Highly stable multi-layered silicon-intercalated graphene anodes for lithium-ion batteries
No full text© 2020 Cambridge University Press. All rights reserved.To avoid degradation of silicon anodes in lithium-ion batteries (LIBs), the authors report a new two-dimensional multi-layered Si-intercalated rGO (rGO/Si) anode prepared by direct growth of Si into a porous multi-layered reduced graphene oxide (rGO) film. Direct Si deposition onto the porous rGO film allows the Si layers to be intercalated into the film via in situ replacement of the oxygen groups of the multi-layered graphene oxide (GO) with Si through thermal reduction of the GO film. The porous rGO acts as a cushion against the expansion of the Si layer during lithiation, preventing the Si from being pulverized and producing highly stable LIBs11Nsciescopu
Efficient and Stable Solar Hydrogen Generation of Hydrophilic Rhenium-Disulfide-Based Photocatalysts via Chemically Controlled Charge Transfer Paths
No full text© 2020 American Chemical Society.Effective charge separation and rapid transport of photogenerated charge carriers without self-oxidation in transition metal dichalcogenide photocatalysts are required for highly efficient and stable hydrogen generation. Here, we report that a molecular junction as an electron transfer path toward two-dimensional rhenium disulfide (2D ReS2) nanosheets from zero-dimensional titanium dioxide (0D TiO2) nanoparticles induces high efficiency and stability of solar hydrogen generation by balanced charge transport of photogenerated charge carriers. The molecular junctions are created through the chemical bonds between the functionalized ReS2 nanosheets (e.g., -COOH groups) and -OH groups of two-phase TiO2 (i.e., ReS2-C6H5C(≠O)-O-TiO2 denoted by ReS2-BzO-TiO2). This enhances the chemical energy at the conduction band minimum of ReS2 in ReS2-BzO-TiO2, leading to efficiently improved hydrogen reduction. Through the molecular junction (a Z-scheme charge transfer path) in ReS2-BzO-TiO2, recombination of photogenerated charges and self-oxidation of the photocatalyst are restrained, resulting in a high photocatalytic activity (9.5 mmol h-1 per gram of ReS2 nanosheets, a 4750-fold enhancement compared to bulk ReS2) toward solar hydrogen generation with high cycling stability of more than 20 h. Our results provide an effective charge transfer path of photocatalytic TMDs by preventing self-oxidation, leading to increases in photocatalytic durability and a transport rate of the photogenerated charge carriers11sciescopu
Highly efficient nanostructured metal-decorated hybrid semiconductors for solar conversion of CO2 with almost complete CO selectivity
No full text© 2019 Elsevier LtdPhotocatalytic reduction of CO2 into solar fuels is regarded as a promising method to address global warming and energy crisis problems. Although heterostructured hybrid metal oxide catalysts have been used for CO2 reduction, selective control for CO production-only remains the subject of debate. In this paper, we report an absolute selectivity for CO production-only with enhanced photocatalytic ability using Ag-decorated reduced titanium oxide/tungsten hybrid nanoparticles (blue TiO2/WO3–Ag HNPs) at 1166.72 μmol g−1 h−1 with an apparent quantum yield of 34.8%. The construction of a Z-scheme between blue TiO2 and WO3 domains with an excellent band alignment provided remarkably improved separation of photoinduced charges. Importantly, the presence of novel Ag not only produces the highest selectivity up to 100% CO production-only, but also increases the photocatalytic electron reaction rate (2333.44 μmol g−1 h−1)11sciescopu
Band restructuring of ordered/disordered blue TiO2for visible light photocatalysis
No full text© The Royal Society of Chemistry 2021.Black TiO2with/without noble metals has been proposed for visible light photocatalysis, but such structures still exhibit poor catalytic efficiency. Alternatively, phase-mixed TiO2such as the anatase and rutile phases has been commonly used for visible light catalysis with the inevitable inclusion of noble metals. Herein, we present a noble metal-free visible light photocatalyst, blue TiO2, with type-II band-aligned ordered anatase/disordered rutile structuresviaphase-selective reduction with alkali metals. The changed band alignment in this heterostructure was identified by absorption and ultraviolet photoemission spectroscopy, which was further confirmed by transient charge separation. The band alignment of the type-I and type-II structures was clearly restructured by converting from the ordered to the disordered phase with a prolonged reduction period. We note that after this, light absorbance enhancement was also observed. After initiating the type-I structure in a pristine sample, the type-II structure was organized based on the disordered rutile phase during 3 days of Li-reduction. The type-II disordered rutile TiO2heterostructure exhibits a remarkable photocatalytic performance that is 55 times higher than that of conventional P25 TiO2in the solar-light driven hydrogen evolution reaction, owing to the efficient electron and hole separation of the type-II heterojunction. Furthermore, this restructured heterojunction type-II TiO2required 10 times less Pt as a co-catalyst for comparable photocatalytic performance, compared to Pt decorated type-I pristine anatase/rutile phase-mixed TiO2.11Nsciescopu
Thermodynamic and Transport Properties of H<sub>2</sub>/H<sub>2</sub>O/NaB(OH)<sub>4</sub> Mixtures Using the Delft Force Field (DFF/B(OH)<sub>4</sub><sup>-</sup>)
No full textSodium borohydride (NaBH4) has a high hydrogen (H2 ) gravimetric capacity of 10.7 wt %. NaBH4 releases H2 through a hydrolysis reaction in which aqueous NaB(OH)4 is formed as a byproduct. NaB(OH)4 strongly influences the thermophysical properties of aqueous solutions (i.e., densities, viscosities, and electrical conductivities) and the hydrolysis reaction kinetics and conversion of NaBH4. Here, molecular dynamics (MD) simulations are performed to compute viscosities, electrical conductivities, and self-diffusivities of H2 , Na+, and B(OH)4- for a temperature and concentration range of 298-353 K and 0-5 mol NaB(OH)4/kg water, respectively. Continuous fractional component Monte Carlo (CFCMC) simulations are used to compute the solubilities of H2 and activities of water in aqueous NaB(OH)4 solutions for the same temperature and concentration range. A new force field is developed (Delft force field of B(OH)4-: DFF/B(OH)4-) in which B(OH)4- is modeled as a tetrahedral structure with a scaled charge of −0.85. The OH group in B(OH)4- is modeled as a single interaction site. This force field is based on TIP4P/2005 water and the Madrid-2019 Na+ force field. The MD simulations can accurately capture the densities and viscosities within 2.5% deviation from available experimental data at 298 K up to a concentration of 5 mol NaB(OH)4/kg water. The computed electrical conductivities deviate by ca. 10% from experimental data at 298 K for the same concentration range. Based on the molecular simulations results, engineering equations are developed for shear viscosities, self-diffusivities of H2, Na+, and B(OH)4-, and solubilities of H2, which can be used to design and model NaBH4 hydrolysis reactors.Engineering ThermodynamicsComplex Fluid ProcessingTeam Poulumi De
Oh Holly, The Fish is Dead
No full textFrom Kurt Vonnegut to Stephen King, many novelists use metanarrative techniques to insert fictional versions of themselves in the stories they tell. The function of deploying such techniques is often to draw attention to the liminal space between the fictional constructs inherent in the novel as a form, and the real world from which the constructs draw inspiration, and indeed, are read by an audience. For emerging writers working in short form narratives, however, the structural demands of the short story or flash fiction make the use of similar techniques problematic in the level of depth to which they can be deployed.\ud
\ud
‘Oh Holly, the fish is dead’ is the fourth in a series of short stories that work to overcome the structural limitations of a succinct form by developing a fractured fictional version of the author over a number of pieces and published across a range of sites. The accumulative affect is a richer metanarrative textual arrangement that also allows for the individual short stories to function independently
Phase-Selective Disordered Anatase/Ordered Rutile Interface System for Visible-Light-Driven, Metal-Free CO2 Reduction
No full textVisible-light-driven photocatalytic CO2 reduction using TiO2 that can absorb light of all wavelengths has been sought for over half a century. Herein, we report a phase-selective disordered anatase/ordered rutile interface system for visible-light-driven, metal-free CO2 reduction using a narrow band structure, whose conduction band position matches well with the reduction potential of CO2 to CH4 and CO. A mixed disordered anatase/ordered rutile (Ad/Ro) TiO2 was prepared from anatase and rutile phase-mixed P25 TiO2 at room temperature and under an ambient atmosphere in sodium alkyl amine solutions. The Ad/Ro TiO2 showed a narrow band structure due to multi-internal energy band gaps of Ti3+ defect sites in the disordered anatase phase, leading to high visible light absorption and simultaneously providing fast charge separation through the crystalline rutile phase, which was faster than that of pristine P25 TiO2. The band gap of Ad/Ro TiO2 is 2.62 eV with a conduction band of -0.27 eV, which matches well with the reduction potential of -0.24 VNHE of CO2/CH4, leading to effective electron transfer to CO2. As a result, the Ad/Ro TiO2 provided the highest CH4 production (3.983 μmol/(g h)), which is higher than that of even metal (W, Ru, Ag, and Pt)-doped P25, for CO2 reduction under visible light11sciescopu
Continuous Hamiltonian dynamics and area-preserving homeomorphism group of D2
No full textThe main purpose of this paper is to propose a scheme of a proof of the nonsimpleness of the group {\rm Homeo}^\Omega(D^2,\del D^2) of area preserving homeomorphisms of the 2-disc . We first establish the existence of Alexander isotopy in the category of Hamiltonian homeomorphisms. This reduces the question of extendability of the well-known Calabi homomorphism \Cal: {\rm Diff}^\Omega(D^1,\del D^2) \to \R to a homomorphism \overline \Cal: {\rm Hameo(}D^2,\del D^2) \to \R to that of the vanishing of the basic phase function , a Floer theoretic graph selector constructed in \cite{oh:jdg}, that is associated to the graph of the topological Hamiltonian loop and its normalized Hamiltonian on that is obtained via the natural embedding . Here {\rm Hameo(}D^2,\del D^2) is the group of Hamiltonian homeomorphisms introduced by M\"uller and the author \cite{oh:hameo1}. We then provide an evidence of this vanishing conjecture by proving the conjecture for the special class of \emph{weakly graphical} topological Hamiltonian loops on via a study of the associated Hamiton-Jacobi equation.1111Ysciescopuskc
Asarum chungbuensis B. U. Oh. Since 2005
No full textAsarum chungbuensis (C.S. Yook & J.G. Kim) B.U. Oh (2005: 24) Basionym: Asiasarum sieboldii Miq. f. chungbuensis C.S. Yook & J.G. Kim (1996: 343) Type (neotype, designated here):— KOREA. Gyeonggi-do: Pocheon-si, Mt. Gwangdeoksan, 294 m, 38°04′51″N, 127°25′18″E, 27 April 2020, H. D.Jang & G. H. Nam 506 (KB! barcode NIBRVP774931)(Fig. 1). Notes: —Regarding the scientific name of this taxon, Yamaki (Feb. 1996) published the name of Asiasarum sieboldii (Miq.) F. Maek. var. versicolor (1996: 1), and Yook & Kim (Nov. 1996) published the name of Asiasarum sieboldii (Miq.) F. Maek. f. chungbuensis in the same year. Later, Lee & Lee (2000) republished it with a new combination name Asarum versicolor (Yamaki) Y.N. Lee (2000: 19). Oh et al. (2005) made a new combination name Asarum chungbuensis (C.S. Yook & J.G. Kim) B.U. Oh. Since then, A. versicolor (Yamaki) Y.N. Lee has been accepted as the legitimate name, having priority (Yamaji et al. 2007, So & Kim 2008, Oh 2008, National Institute of Biological Resources 2011). In contrast, A. chungbuensis (C.S. Yook & J.G. Kim) B.U. Oh has been treated as a superfluous name of A. versicolor. However, we detected problems regarding the scientific name A. versicolor (Yamaki) Y.N. Lee. Lee (2000) referred to the basionym as “ Asiasarum sieboldii Miq. var. versicolor Yamaki, J. Jap. Bot. 71: 1–10, 1995”; thus, the name has not been validly published because whole pages of the protologue have been cited. According to Article 41.5 of the ICN (Turland et al. 2018), a new combination name is not validly published unless its basionym is clearly indicated, and a full and direct reference is given to its author and place of valid publication, with page or plate reference and date on or after January 1, 1953. In addition, according to Article 11.2 of the ICN, although Asiasarum sieboldii var. versicolor Yamaki was published before A. sieboldii f. chungbuensis C.S. Yook & J.G. Kim, neither of these names have any priority outside the rank at which they were published. Consequently, A. versicolor (Yamaki) Y.N. Lee is unacceptable, and A. chungbuensis (C.S. Yook & J.G. Kim) B.U. Oh is accepted as the legitimate name of this taxon.Published as part of Jang, Hyun-Do, Nam, Gi-Heum, Oh, Hyun-Kyung & Leem, Hyosun, 2021, Typification of the names Asarum chungbuensis and A. maculatum (Aristolochiaceae), pp. 295-299 in Phytotaxa 508 (3) on page 298, DOI: 10.11646/phytotaxa.508.3.5, http://zenodo.org/record/542599
Serum 25-hydroxyvitamin D and cognitive decline in the very old: The Newcastle 85+ study
No full textBackground and purpose:
Studies investigating the association between 25-hydroxyvitamin D [25(OH)D] and cognition in the very old (85+) are lacking.
Methods:
Cross-sectional (baseline) and prospective data (up to 3 years follow-up) from 775 participants in the Newcastle 85+ Study were analysed for global (measured by the Standardized Mini-Mental State Examination) and attention-specific (measured by the attention battery of the Cognitive Drug Research test) cognitive performance in relation to season-specific 25(OH)D quartiles.
Results:
Those in the lowest and highest season-specific 25(OH)D quartiles had an increased risk of impaired prevalent (1.66, 95% confidence interval 1.06–2.60, P = 0.03; 1.62, 95% confidence interval 1.02–2.59, P = 0.04, respectively) but not incident global cognitive functioning or decline in functioning compared with those in the middle quartiles adjusted for sociodemographic, health and lifestyle confounders. Random effects models showed that participants belonging to the lowest and highest 25(OH)D quartiles, compared with those in the middle quartiles, had overall slower (log-transformed) attention reaction times for Choice Reaction Time (lowest, b = 0.023, P = 0.01; highest, b = 0.021, P = 0.02), Digit Vigilance Task (lowest, b = 0.009, P = 0.05; highest,b = 0.01, P = 0.02) and Power of Attention (lowest, b = 0.017, P = 0.02;highest, b = 0.022, P = 0.002) and greater Reaction Time Variability (lowest,b = 0.021, P = 0.02; highest, b = 0.02, P = 0.03). The increased risk of worse global cognition and attention amongst those in the highest quartile was not observed in non-users of vitamin D supplements/medication.
Conclusion:
Low and high season-specific 25(OH)D quartiles were associated with prevalent cognitive impairment and poorer overall performance in attention-specific tasks over 3 years in the very old, but not with global cognitive decline or incident impairment
- …
