Search results

RSS feed for this result

11,808 results

Book
1 online resource (Article No. 13945 ): digital, PDF file.
Here, IRMOF-74 analogues are among the most widely studied metal-organic frameworks (MOFs) for adsorption applications because of their one-dimensional channels and high metal density. Most studies involving the IRMOF-74 series assume that the crystal lattice is rigid. This assumption guides the interpretation of experimental data, as changes in the crystal symmetry have so far been ignored as a possibility in the literature. Here, we report a deformation pattern, induced by the adsorption of argon, for IRMOF-74-V. This work has two main implications. First, we use molecular simulations to demonstrate that the IRMOF-74 series undergoes a deformation that is similar to the mechanism behind breathing MOFs, but is unique because the deformation pattern extends beyond a single unit cell of the original structure. Second, we provide an alternative interpretation of experimental small-angle X-ray scattering profiles of these systems, which changes how we view the fundamentals of adsorption in this MOF series.
The present invention provides an adsorbent catalytic nanoparticle including a mesoporous silica nanoparticle having at least one adsorbent functional group bound thereto. The adsorbent catalytic nanoparticle also includes at least one catalytic material. In various embodiments, the present invention provides methods of using and making the adsorbent catalytic nanoparticles. In some examples, the adsorbent catalytic nanoparticles can be used to selectively remove fatty acids from feedstocks for biodiesel, and to hydrotreat the separated fatty acids.
A process includes casting a solution including poly(phenylene oxide), inorganic nanoparticles, a solvent, and a non-solvent on a substrate; and removing the solvent to form a porous film; wherein: the porous film is configured for use as a porous separator for a lithium ion battery.
Book
1 online resource (p. 115-124 ): digital, PDF file.
Here we discuss the oxygen reduction reaction (ORR) is one of the major factors that is limiting the overall performance output of microbial fuel cells (MFC). In this study, Platinum Group Metal-free (PGM-free) ORR catalysts based on Fe, Co, Ni, Mn and the same precursor (Aminoantipyrine, AAPyr) were synthesized using identical sacrificial support method (SSM). The catalysts were investigated for their electrochemical performance, and then integrated into an air-breathing cathode to be tested in “clean” environment and in a working microbial fuel cell (MFC). Their performances were also compared to activated carbon (AC) based cathode under similar conditions. Results showed that the addition of Mn, Fe, Co and Ni to AAPyr increased the performances compared to AC. Fe-AAPyr showed the highest open circuit potential (OCP) that was 0.307 ± 0.001 V (vs. Ag/AgCl) and the highest electrocatalytic activity at pH 7.5. On the contrary, AC had an OCP of 0.203 ± 0.002 V (vs. Ag/AgCl) and had the lowest electrochemical activity. In MFC, Fe-AAPyr also had the highest output of 251 ± 2.3 μWcm<sup>–2</sup>, followed by Co-AAPyr with 196 ± 1.5 μWcm<sup>–2</sup>, Ni-AAPyr with 171 ± 3.6 μWcm<sup>–2</sup>, Mn-AAPyr with 160 ± 2.8 μWcm<sup>–2</sup> and AC 129 ± 4.2 μWcm<sup>–2</sup>. The best performing catalyst (Fe-AAPyr) was then tested in MFC with increasing solution conductivity from 12.4 mScm<sup>–1</sup> to 63.1 mScm<sup>–1</sup>. A maximum power density of 482 ± 5 μWcm<sup>–2</sup> was obtained with increasing solution conductivity, which is one of the highest values reported in the field.
A method of stripping tritium from flowing stream of molten salt includes providing a tritium-separating membrane structure having a porous support, a nanoporous structural metal-ion diffusion barrier layer, and a gas-tight, nonporous palladium-bearing separative layer, directing the flowing stream of molten salt into contact with the palladium-bearing layer so that tritium contained within the molten salt is transported through the tritium-separating membrane structure, and contacting a sweep gas with the porous support for collecting the tritium.
The present invention relates to methods and compositions for increasing production of methyl ketones in a genetically modified host cell that overproduces .beta.-ketoacyl-CoAs through a re-engineered .beta.-oxidation pathway and overexpresses FadM.
Book
1 online resource (p. 762-771 ): digital, PDF file.
Femtosecond two-dimensional Fourier transform spectroscopy is used to determine the static bandgap inhomogeneity of a colloidal quantum dot ensemble. The excited states of quantum dots absorb light, so their absorptive two-dimensional (2D) spectra will typically have positive and negative peaks. It is shown that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodal line slope is independent of excited state parameters not known from the absorption and emission spectra. The absorption bandgap inhomogeneity is compared to a size and shape distribution determined by electron microscopy. The electron microscopy images are analyzed using new 2D histograms that correlate major and minor image projections to reveal elongated nanocrystals, a conclusion supported by grazing incidence small-angle X-ray scattering and high-resolution transmission electron microscopy. Finally, the absorption bandgap inhomogeneity quantitatively agrees with the bandgap variations calculated from the size and shape distribution, placing upper bounds on any surface contributions.
Book
1 online resource (p. 762-771 ): digital, PDF file.
Femtosecond two-dimensional Fourier transform spectroscopy is used to determine the static bandgap inhomogeneity of a colloidal PbSe quantum dot ensemble. It is shown that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodal line slope is independent of excited state parameters not known from the absorption and emission spectra. The absorption bandgap inhomogeneity is compared to a size and shape distribution determined by electron microscopy. The electron microscopy images are analyzed using new 2D histograms that correlate major and minor image projections to reveal elongated nanocrystals, a conclusion supported by grazing incidence small angle X-ray scattering and high resolution transmission electron microscopy. Lastly, the absorption bandgap inhomogeneity quantitatively agrees with the bandgap variations calculated from the size and shape distribution, placing upper bounds on any surface contributions.
A catalytic composition from earth-abundant transition metal salts and biomass is disclosed. A calcined catalytic composition formed from soybean powder and ammonium molybdate is specifically exemplified herein. Methods for making the catalytic composition are disclosed as are electrodes for hydrogen evolution reactions comprising the catalytic composition.
Book
1 online resource (19 p.) : digital, PDF file.
No abstract provided.
A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a microstructure exhibiting substantially uniform pore size distribution as a result of using PMMA pore forming materials or a bi-modal particle size distribution of the porous support layer materials. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.
Catalysts that include at least one catalytically active element and one helper catalyst can be used to increase the rate or lower the overpotential of chemical reactions. The helper catalyst can simultaneously act as a director molecule, suppressing undesired reactions and thus increasing selectivity toward the desired reaction. These catalysts can be useful for a variety of chemical reactions including, in particular, the electrochemical conversion of CO.sub.2 or formic acid. The catalysts can also suppress H.sub.2 evolution, permitting electrochemical cell operation at potentials below RHE. Chemical processes and devices using the catalysts are also disclosed, including processes to produce CO, OH.sup.-, HCO.sup.-, H.sub.2CO, (HCO.sub.2).sup.-, H.sub.2CO.sub.2, CH.sub.3OH, CH.sub.4, C.sub.2H.sub.4, CH.sub.3CH.sub.2OH, CH.sub.3COO.sup.-, CH.sub.3COOH, C.sub.2H.sub.6, O.sub.2, H.sub.2, (COOH).sub.2, or (COO.sup.-).sub.2, and a specific device, namely, a CO.sub.2 sensor.
The present invention, among other things, provides highly syndiotactic poly(dicyclopentadiene) and/or hydrogenated poly(dicyclopentadiene), compositions thereof, and compounds and methods for preparing the same. In some embodiments, a provided compound is a compound of formula I, II or III. In some embodiments, a provided method comprises providing a compound of formula I, II or III.
The present invention provides a catalyst including a mesoporous silica nanoparticle and a catalytic material comprising iron. In various embodiments, the present invention provides methods of using and making the catalyst. In some examples, the catalyst can be used to hydrotreat fatty acids or to selectively remove fatty acids from feedstocks.
Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.
Book
1 online resource (Article No. 41121 ): digital, PDF file.
N-Acylethanolamines (NAEs) are a group of fatty acid amides that play signaling roles in diverse physiological processes in eukaryotes. We used fatty acid amide hydrolase (FAAH) degrades NAE into ethanolamine and free fatty acid to terminate its signaling function. In animals, chemical inhibitors of FAAH for therapeutic treatment of pain and as tools to probe deeper into biochemical properties of FAAH. In a chemical genetic screen for small molecules that dampened the inhibitory effect of N-lauroylethanolamine (NAE 12:0) on Arabidopsis thaliana seedling growth, we identified 6-(2-methoxyphenyl)-1,3-dimethyl-5-phenyl-1H-pyrrolo[3,4-d]pyrim idine-2,4(3 H, 6 H)-dione (or MDPD). MDPD alleviated the growth inhibitory effects of NAE 12:0, in part by enhancing the enzymatic activity of Arabidopsis FAAH (AtFAAH). In vitro, biochemical assays showed that MDPD enhanced the apparent Vmax of AtFAAH but did not alter the affinity of AtFAAH for its NAE substrates. Furthermore, structural analogs of MDPD did not affect AtFAAH activity or dampen the inhibitory effect of NAE 12:0 on seedling growth indicating that MDPD is a specific synthetic chemical activator of AtFAAH. Our study demonstrates the feasibility of using an unbiased chemical genetic approach to identify new pharmacological tools for manipulating FAAH- and NAE-mediated physiological processes in plants.
A chemical looping system that contains an oxidizer and a reducer is in fluid communication with a gas purification unit. The gas purification unit has at least one compressor, at least one dryer; and at least one distillation purification system; where the gas purification unit is operative to separate carbon dioxide from other contaminants present in the flue gas stream; and where the gas purification unit is operative to recycle the contaminants to the chemical looping system in the form of a vent gas that provides lift for reactants in the reducer.
Book
1 online resource (xviii, 649 pages) : illustrations (some color)
  • Overview: Sustaining Water, the World's Most Crucial Resource / S. Ahuja
  • Progress and Lessons Learned from Water-Quality Monitoring Networks / D.N. Myers, A.S. Ludtke
  • Impact of Climate Change on Water with Reference to the Ganges--Brahmaputra--Meghna River Basin / M.A. Islam, S.L. Islam, A. Hassan
  • Forested Watersheds, Water Resources, and Ecosystem Services, with Examples from the United States, Panama, and Puerto Rico / M.C. Larsen
  • Water Quality and Sustainability in India: Challenges and Opportunities / R.K. Sharma, M. Yadav, R. Gupta
  • Challenges and Solutions to Water Problems in the Middle East / Y. Shevah
  • Challenges and Solutions to Water Problems in Africa / S.O. Wandiga, S. Ngigi Mbugua, J.W. Macharia, M.A. Otieno
  • Comparative Analysis of Existing Water Resources Data in the Western Balkan States of Bosnia and Herzegovina, Macedonia, Montenegro, and Serbia / J. Markovski, K.D. Hristovski, L.W. Olson
  • Ion Chromatography Instrumentation for Water Analysis / K. Srinivasan
  • Use of Ion Chromatography for Monitoring Ionic Contaminants in Water / C. Pohl
  • Can Incongruent Studies Effectively Characterize Long-Term Water Quality? / J.R. Peller, R.L. Whitman, J.K. Schoer
  • Historical Perspectives on Water Purification / L. Smith
  • Evaluation of Animal Manure Composition for Protection of Sensitive Water Supplies Through Nutrient Recovery Processes / U. Shashvatt, H. Aris, L. Blaney
  • Effect of Upflow Velocity on Nutrient Recovery from Swine Wastewater by Fluidized Bed Struvite Crystallization / R.R.M Abarca, R.S. Pusta, Jr., R.B. Labad, J.L.A. Andit, C.M. Rejas, M.D.G. de Luna, M.-C. Lu
  • Drought-Inspired Economic Use of Water in Wine Production / J.N. Seiber, K.A. Gibson, V. Tiangco, J. Real
  • Developing a Global Hydrohub: Singapore's Leadership in Water Innovation / A.M. Dhalla
  • Water Quality and Public Health: Role of Wastewater / S. Tongesayi, T. Tongesayi
  • Challenges to Achieving the Sustainable Development Goals: Water Treatment / J. Luh, J. Bartram.
After air, water is the most crucial resource for human survival. To achieve water sustainability, we will have to deal with its scarcity and quality, and find ways to reclaim it from various sources. Chemistry and Water: The Science Behind Sustaining the World's Most Crucial Resource applies contemporary and sophisticated separation science and chromatographic methods to address the pressing worldwide concerns of potable water for drinking and safe water for irrigation to raise food for communities around the world. Edited and authored by world-leading analytical chemists, the book presents the latest research and solutions on topics including water quality and pollution, water treatment technologies and practices, watershed management, water quality and food production, challenges to achieving sustainable water supplies, water reclamation techniques, and wastewater reuse.
(source: Nielsen Book Data)9780128093306 20170117
Book
1 online resource (p. 1389-1401 ): digital, PDF file.
Ion specificity, a widely observed macroscopic phenomenon in condensed phases and at interfaces, is essentially a fundamental chemical physical issue. We have been investigating such effects using cluster models in an “atom-by-atom” and “molecule-by-molecule” fashion not possible with condensed-phase methods. We use electrospray ionization (ESI) to generate molecular and ionic clusters to simulate key molecular entities involved in local binding regions, and characterize them employing negative ion photoelectron spectroscopy (NIPES). Inter- and intramolecular interactions and binding configurations are directly obtained as functions of cluster size and composition, providing insightful molecular-level description and characterization over the local active sites that play crucial roles in determining solution chemistry and condensed phase phenomena. Finally, the topics covered in this article are relevant to a wide scope of research fields ranging from ion specific effects in electrolyte solutions, ion selectivity/recognition in normal functioning of life, to molecular specificity in aerosol particle formation, as well as in rational material design and synthesis.
Book
1 online resource (p. 3496-3504 ): digital, PDF file.
The interesting and tunable properties of layered metal dichalcogenides heavily depend on their phase and layer stacking. Here, we show and explain how the layer stacking and physical properties of WSe<sub>2</sub> are influenced by screw dislocations. A one-to-one correlation of atomic force microscopy and high- and low-frequency Raman spectroscopy of many dislocated WSe<sub>2</sub> nanoplates reveals variations in the number and shapes of dislocation spirals and different layer stackings that are determined by the number, rotation, and location of the dislocations. Plates with triangular dislocation spirals form noncentrosymmetric stacking that gives rise to strong second-harmonic generation and enhanced photoluminescence, plates with hexagonal dislocation spirals form the bulk 2H layer stacking commonly observed, and plates containing mixed dislocation shapes have intermediate noncentrosymmetric stackings with mixed properties. Multiple dislocation cores and other complexities can lead to more complex stackings and properties. Finally, these previously unobserved properties and layer stackings in WSe<sub>2</sub> will be interesting for spintronics and valleytronics.

Looking for different results?

Modify your search: Remove limit(s) Search all fields

Search elsewhere: Search WorldCat Search library website