The corrosion of 90:10 Cu:Ni and 70:30 Cu:Ni alloys in sulfide polluted flowing sea water has been studied as a function of sulfide concentration. The experimental techniques used include small amplitude cyclic voltammetry, AC impedance measurements, large amplitude cyclic voltammetry, and extensive surface examination by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, X-ray diffraction, and Auger electron spectrometry (AES). It is shown that the presence of sulfide induces a loss in passivity of the alloy surface due to the formation of cuprous sulfide as the principal corrosion product. Furthermore, accelerated corrosion of these materials in sulfide polluted sea water appears to arise from a shift in the corrosion potential to sufficiently active values that hydrogen evolution becomes a viable cathodic process.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Introduction and Objective: T2D evolves through progressive loss of β-cell secretory capacity and insulin reserve. Non-invasive detection of insulin depletion in β-cells has not been possible. We tested a flux-based method for identifying reduced β-cell insulin stores non-invasively. The time for newly synthesized Ins and C-P to appear and become fully labeled in plasma reveals residence time (RT) in β-cells. We hypothesized that depleted insulin reserves results in new Ins and C-P passing through β-cells and appearing in plasma more rapidly (shorter RT). Methods: Female ZDF rats (n=24/group) were fed chow or high fat diet, the latter to induce T2D. 2H2 O was given for 1-48 hr, with high-resolution mass spectrometry of plasma Ins and C-P deuterium labeling patterns over time of 2H2 O exposure Results: Fractional synthesis rate (FSR) of Ins was significantly faster and RT (1.0/FSR) was shorter (A, RT 2.3 vs. 5.4 hr, p<0.0001) in T2D. RT of C-P also was shorter (B, 2.5 vs. 5.9 hr, p<0.0001) in T2D and correlated closely with Ins RT. plasma Ins or C-P RT measured at 3 or 6 hr differentiated all T2D from non-T2D rats (p<0.001). Other markers were consistent with β-cell failure. Conclusion: RT of Ins or C-P measured in plasma is a non-invasive window into depletion of β-cell insulin. This non-invasive assay of β-cell loss of secretory reserve is translatable into humans. Disclosure M.K. Hellerstein: Research Support; Lilly USA LLC. Consultant; Lilly USA LLC. E.J. Zanley: None. J. Willency: Employee; Eli Lilly and Company. V. Pirro: Employee; Eli Lilly and Company. O. Cabrera: Employee; Eli Lilly and Company. Funding Lilly LRAP
No abstract is provided for this article.
This work presents the effects of ≡Ti–OH site distortion in Ti/SiO2 on the kinetics and mechanism of gas-phase cyclohexene (C6H10) epoxidation to form cyclohexene oxide (C6H10O). We utilize an experimentally validated computational method to calculate enthalpies of adsorption and transition states along a well-established mechanism for the catalytic cycle. We discover that adsorption enthalpies correlate with the facet area of the tetrahedral O–Ti–O facets of the ≡Ti–OH group through which the adsorbate binds to Ti. In contrast, enthalpies of H2O2 activation and O atom transfer are relatively insensitive. We then develop a steady-state microkinetic model (MKM) to investigate the effects of distortion on predicted kinetic observables (apparent activation energy (Ea) and reaction orders in the partial pressures of C6H10 and H2O2) and to establish whether the mechanism is consistent with observed kinetics. Product inhibition increases with increasing facet area, significantly impacting the predicted activity. Building on our recent findings that ≡Ti–OH sites in the absence of reaction exhibit facet areas equal to, or greater than, that derived from X-ray absorption spectroscopy (XAS) measurements (≥3.76 Å2), we discover that the predicted kinetics for such sites are inconsistent with experiments. Much smaller facets are required for good agreement (<3.54 Å2) since C6H10O does not inhibit these facets. We show that the adsorption of C6H10O to one facet significantly reduces the facet area of the vacant facets on the opposite side of the same ≡Ti–OH site. C6H10O adsorption also considerably narrows the area distribution of these vacant facets for the set of ≡Ti–OH sites that have more than one fluid-accessible facet. We show that these reduced-area facets can catalyze the epoxidation of cyclohexene, while C6H10O remains co-adsorbed to the other facet (known as Pathway B in this paper). Using our MKM with an expanded mechanism for epoxidation that includes Pathway B, we find that Pathway B dominates the net rate of production of C6H10O at nearly all partial pressures of product expected along the length of a packed bed reactor. We also find that the predicted activity remains essentially constant with the level of ≡Ti–OH site distortion. This mechanism shows quantitative agreement between experiments and our predictions for the Ea, reaction orders in the partial pressures of reactants, and the Gibbs free energy barrier. It also illustrates the key role of adsorbates in influencing the degree of distortion of ≡Ti–OH sites, in addition to the amorphous support itself.
Abstract Review: 120 refs.
The design and synthesis of substituted desyl (2-oxo-1,2-diphenylethyl) groups has been investigated to create new photolabile protecting groups. The photoreactivity of these chromophores stems from the diverse photochemistry of the desyl group. Several chromophore designs have been explored in which the substitution pattern of the parent desyl chromophore was varied systematically. The required benzoin chromophores are prepared by a variety of synthetic routes, depending on the structure of the benzoin chromophore desired. Symmetrical benzoins are readily available via the benzoin condensation. Unsymmetrical benzoins including 2,2-disubstituted α-hydroxy ketones are generally prepared via trimethylsilyl (TMS) masked cyanohydrins. On reaction with a Grignard reagent, the TMS masked cyanohydrin functions as an α-hydroxycarbonyl equivalent to form α-hydroxy ketones. Alternatively, lithiation of a TMS masked cyanohydrin generates a benzoyl anion equivalent which reacts with aldehydes and ketones to generate substituted benzoins. These desyl chromophores have significant potential as new photolabile protecting moieties for a variety of functional groups and are used to mask primary and secondary amines as photosensitive α-keto carbamates. The substituted benzoin carbamates are readily prepared from the appropriate benzoin by reaction with isocyanates or by activation as a mixed carbonate followed by reaction with the free amine. These α-keto carbamates are interesting for two main reasons. First, the facile synthesis of these materials indicates the ease of introduction of the desyl based photolabile group. Second, these α-keto carbamates may be used for rapid evaluation of novel photoactive desyl based chromophores.
(1995). Introduction to Surface Chemistry and Catalysis. Drying Technology: Vol. 13, No. 1-2, pp. 507-508.
Constituency parsing with rich grammars remains a computational challenge. Graphics Processing Units (GPUs) have previously been used to accelerate CKY chart evaluation, but gains over CPU parsers were modest. In this paper, we describe a collection of new techniques that enable chart evaluation at close to the GPU’s practical maximum speed (a Teraflop), or around a half-trillion rule evaluations per second. Net parser performance on a 4-GPU system is over 1 thousand length30 sentences/second (1 trillion rules/sec), and 400 general sentences/second for the Berkeley Parser Grammar. The techniques we introduce include grammar compilation, recursive symbol blocking, and cache-sharing.
The disclosure provides for covalent organic frameworks (COFs) that constructed from weaving a plurality of long organic threads together. In particular, the disclosure provides for the construction of woven COFS, where long organic strands are connected together in a woven pattern using organic ligands/complexes that when orientated in certain geometries are capable of reversibly binding metal ions.
