1,722,192 research outputs found
Ab initio study of boron hydroxy species: B(OH), B(OH)4 and B(OH)3O-
Get PDF553-557Ab initio SCF studies at STO-3G and 4-31G levels have been performed on B(OH) as well as
on the recently reported radicals B(OH)4 and B(OH)3O-. The RHF calculations for B(OH) lead
to Td structure, which is in agreement with the experimental results. The B(OH) radical is found to
prefer a C2v geometry rather than Td or D2d structures according to UHF calculations. The Td and
D2d structures are 23.7 and 12.6 kcal/mol higher respectively in energy than the C2v structure at the
STO-3G level. STO 4-31G calculations show that the corresponding values are 16.3 and 11.5 kcal/
mol respectively for the Td and D2d structures. The UHF calculations using both the basis sets indicate
that the two geometries considered for the B(OH)3O- radical anion, Td and C3v, are very close
energetically
Generation and characterization of ionic and neutral dihydroxy boron B(OH)(2)(+/0) in the gas phase
No full textThe dicoordinated borinium ion, dihydroxyborinium, B(OH)(2)(+) is generated from methyl boronic acid CH3B(OH)(2) by dissociative electron ionization and its connectivity confirmed by collisional activation. Neutralization-reionization (NR) experiments on this ion indicate that the neutral B(OH)(2) radical is a viable species in the gas phase. Both vertical neutralization of B(OH)(2)(+) and reionization of B(OH)(2) in the NR experiment are, however, associated with particularly unfavorable Franck-Condon factors. The differences in adiabatic and vertical electron transfer behavior can be traced back to a particular pi stabilization of the cationic species compared to the sp(2)-type neutral radical. Thermochemical data on several neutral and cationic boron compounds are presented based on calculations performed at the G2 level of theory
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
Synthesis, Crystal Structure, and Characterization of a New Metal Borophosphate: PbII4{Co2[B(OH)2P2O8](PO4)2}Cl
No full textA new metal borophosphate Pb-4(II){Co-2[B(OH)(2)P2O8](PO4)(2)}Cl (1), containing both Pb2+ cations and Cl- anions, was hydrothemially synthesized and characterized by powder X-ray diffraction, ICP, TG/DTA, and FTIR spectroscopic analyses. The crystal structure determination from single-crystal X-ray diffraction reveals that compound 1 crystallizes in the trigonal space group R (3) over barc (No. 167), a = 9.7513(7) angstrom, c = 91.060(13) angstrom, V = 7498.7(13) angstrom(3) and Z = 18. Its structure features a new cobalt borophosphate layer {Co-2[B(OH)(2)P2O8](PO4)(2)}(7-) built up from CoO5 square pyramids, [B(OH)(2)P2O8](5-) borophosphate timers and PO4 tetrahedra. Extraframework Pb2+ and Cl- ions are located at the vacancy of layers to achieve the charge neutrality of the framework. Magnetic measurements indicate that antiferromagnetic interactions exist between Co2+ ions with a negative Weiss constant of -20.3 K
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
INFRARED SPECTRA OF MATRIX ISOLATED . HOBO AND .
No full textAuthor Institution: Research Department Physics Division, Naval Ordnance Station, Indian Head, Maryland, 20640Infrared spectra of and have been obtained in neon, argon and nitrogen matrices near over the region . The various isotopically enriched molecules containing and have also been studied. The metaboric acid monomer molecules were generated by the reaction (g) at temperatures near . The fundamental vibrations have been assigned assuming symmetry (linear heavy atom array). Force constants and thermodynamic functions have been calculated and will be discussed. The orthoboric acid monomer molecules were generated by the reaction: at . The infrared active modes of all the isotopic species have been carefully measured. Values for the infrared inactive modes were obtained by studying the mixed and molecules and applying an isotopic correction factor. Force constants and thermodynamic functions have been calculated. The hydrogen frequency differences between isolated and crystalline boric acid, ca. for the stretching and ca. for the bending modes, suggest moderately strong hydrogen bonds in the crystal. Trimeric metaboric acid was produced via vaporization of the crystalline material: near . A qualitative assignment of the infrared data has been made and interpretation of the results will be discussed
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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