6,354 research outputs found
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
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‘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
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
Volume 10, Number 27
No full textThis is an 8-page weekly magazine for children in Catholic religious education. Pages 6-7 are given to "Gospel Activity." Six cartoon panels are filled with black-and-white line drawings. Pupils are urged to draw in the last two empty panels. The story is presented as "The Porcupine and the Moles" telling one of Aesop's fables. Porcupine asks the moles if he could share their cave for the winter, and the welcome him. After a week, the moles are suffering from the porcupine's needles. They decide to talk with the porcupine and ask him to leave. "Oh, no! This place suits me well." Pupils are asked to talk through with each other how the porcupine and moles can solve their problem. Five questions help. They are to write or draw their group's solution into the two empty panels. I would say that this is a good challenge. Mom wrote on a post-it note "I wish you could have heard the solutions my students gave to this problem."No Autho
Water Oxidation by the [Co4O4(OAc)4(py)4]+ Cubium is Initiated by OH– Addition
No full textThe cobalt cubium Co4O4(OAc)4(py)4(ClO4) (1A+) containing the mixed valence [Co4O4]5+ core is shown by multiple spectroscopic methods to react with hydroxide (OH-) but not with water molecules to produce O2. The yield of reaction products is stoichiometric (>99.5%): 4 1A+ + 4 OH- → O2 + 2 H2O + 4 1A. By contrast, the structurally homologous cubium Co4O4(trans-OAc)2(bpy)4(ClO4)3, 1B(ClO4)3 produces no O2. EPR/NMR spectroscopies show clean conversion to cubane 1A during O2 evolution with no Co2+ or Co3O4 side products. Mass spectrometry of the reaction between isotopically labeled µ-16O(bridging-oxo) 1A+ and 18O-bicarbonate/water shows: 1) no exchange of 18O into the bridging oxos of 1A+, and 2) 36O2 is the major product, thus requiring two OH- in the reactive intermediate. DFT calculations of solvated intermediates suggest that addition of two OH- to 1A+ via OH- insertion into Co-OAc bonds is energetically favored, followed by outer-sphere oxidation to intermediate [1A(OH)2]0. The absence of O2 production by cubium 1B3+ indicates the reactive intermediate derived from 1A+ requires gem-1,1-dihydoxo stereochemistry to perform O-O bond formation. Outer-sphere oxidation of this intermediate by 2 eq. 1A+ accounts for the final stoichiometry. Collectively, these results, and recent literature (Faraday Disc., doi:10.1039/C5FD00076A and J.Am.Chem.Soc 2015, 12865-12872) validate the [Co4O4]4+/5+ cubane core as an intrinsic catalyst for oxidation of hydroxide by an inner-sphere mechanism.This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://dx.doi.org/10.1021/jacs.5b09152Peer reviewe
Chronic High Fructose Intake Reduces Serum 1,25(OH)<sub>2</sub>D<sub>3</sub>Levels in Calcium-Sufficient Rodents
No full textExcessive fructose consumption inhibits adaptive increases in intestinal Ca2+transport in lactating and weanling rats with increased Ca2+requirements by preventing the increase in serum levels of 1,25(OH)2D3. Here we tested the hypothesis that chronic fructose intake decreases 1,25(OH)2D3 levels independent of increases in Ca2+ requirements. Adult mice fed for five wk a high glucose-low Ca2+ diet displayed expected compensatory increases in intestinal and renal Ca2+ transporter expression and activity, in renal CYP27B1 (coding for 1α-hydroxylase) expression as well as in serum 1,25(OH)2D3 levels, compared with mice fed isocaloric glucose- or fructose-normal Ca2+ diets. Replacing glucose with fructose prevented these increases in Ca2+ transporter, CYP27B1, and 1,25(OH)2D3 levels induced by a low Ca2+ diet. In adult mice fed for three mo a normal Ca2+ diet, renal expression of CYP27B1 and of CYP24A1 (24-hydroxylase) decreased and increased, respectively, when the carbohydrate source was fructose instead of glucose or starch. Intestinal and renal Ca2+ transporter activity and expression did not vary with dietary carbohydrate. To determine the time course of fructose effects, a high fructose or glucose diet with normal Ca2+ levels was fed to adult rats for three mo. Serum levels of 1,25(OH)2 D3 decreased and of FGF23 increased significantly over time. Renal expression of CYP27B1 and serum levels of 1,25(OH)2D3 still decreased in fructose- compared to those in glucose-fed rats after three mo. Serum parathyroid hormone, Ca2+ and phosphate levels were normal and independent of dietary sugar as well as time of feeding. Thus, chronically high fructose intakes can decrease serum levels of 1,25(OH)2D3 in adult rodents experiencing no Ca2+ stress and fed sufficient levels of dietary Ca2+. This finding is highly significant because fructose constitutes a substantial portion of the average diet of Americans already deficient in vitamin D.Peer reviewe
OH reactivity at a rural site (Wangdu) in the North China Plain: contributions from OH reactants and experimental OH budget
No full textIn 2014, a large, comprehensive field campaign was conducted in the densely populated North China Plain. The measurement site was located in a botanic garden close to the small town Wangdu, without major industry but influenced by regional transportation of air pollution. The loss rate coefficient of atmospheric hydroxyl radicals (OH) was quantified by direct measurements of the OH reactivity. Values ranged between 10 and 20 s−1 for most of the daytime. Highest values were reached in the late night with maximum values of around 40 s−1. OH reactants mainly originated from anthropogenic activities as indicated (1) by a good correlation between measured OH reactivity and carbon monoxide (linear correlation coefficient R2 = 0.33) and (2) by a high contribution of nitrogen oxide species to the OH reactivity (up to 30 % in the morning). Total OH reactivity was measured by a laser flash photolysis–laser-induced fluorescence instrument (LP-LIF). Measured values can be explained well by measured trace gas concentrations including organic compounds, oxygenated organic compounds, CO and nitrogen oxides. Significant, unexplained OH reactivity was only observed during nights, when biomass burning of agricultural waste occurred on surrounding fields. OH reactivity measurements also allow investigating the chemical OH budget. During this campaign, the OH destruction rate calculated from measured OH reactivity and measured OH concentration was balanced by the sum of OH production from ozone and nitrous acid photolysis and OH regeneration from hydroperoxy radicals within the uncertainty of measurements. However, a tendency for higher OH destruction compared to OH production at lower concentrations of nitric oxide is also observed, consistent with previous findings in field campaigns in China
DETERMINATION OF THE CHANGING DIPOLE MOMENT OF IN CRYSTALS OF Li(OH). AND
No full textAuthor Institution: U. S. Naval Ordnance LaboratoryLithium hydroxide crystallizes tetragonally and belongs to the space group . Calcium hydroxide and magnesium hydroxide are isomorphic and belong to the space group . These crystals contain two hydroxyl ions per unit cell with their dipoles oriented parallel to the crystalline c-axis and are related to each other through a center of inversion. Consequently from the crystal symmetry two hydroxyl internal vibrations, belonging respectively to the species and are predicted Experiments indicate these hydroxyl vibrations to be split by and respectively in LiOH, and . This frequency separation between the infrared and Raman hydroxyl internal modes is indicative of a small intermolecular coupling between the hydroxyl ions. By assuming an oscillating dipole-dipole interaction it is possible to calculate the magnitude of the hydroxyl changing dipole moment. The value for corresponding to the internal vibration in Li(OH), and is determined to be 1.35, 1.54 and 1.81 Debye/{\AA}
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