9 research outputs found

    Demographic characteristics, reasons for not participating at follow up interview, and how walkers described their attendance at walking groups and walk leaders’ demographic characteristics.

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    <p>Demographic characteristics, reasons for not participating at follow up interview, and how walkers described their attendance at walking groups and walk leaders’ demographic characteristics.</p

    Diastereoselective 1,4-Conjugate Addition of Alkyl Cuprates to Methyl Cyclopent-1-enecarboxylates

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    Starting from readily available homochiral Vince lactam, trisubstituted cyclopentanes were obtained utilizing conjugate addition of alkyl cuprates as an efficient approach to introduce different side chains. Although the 1,4-conjugate addition reactions gave the products as mixtures of diastereomers, an epimerization approach followed by crystallization furnished the stereoisomerically pure cyclopentanes

    Symptoms expected and experienced by participants.

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    <p><i>Note.</i> %, percentage of participants who expected or experienced each symptom.</p

    Diffusion and Tortuosity in Porous Functionalized Calcium Carbonate

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    Calcium carbonate can be “functionalized” by use of etching agents such as phosphoric acid to create inter- and intraparticle porosity with a range of morphologies. Functionalized calcium carbonate has potential for use as a carrier for the delayed release of actives, such as drugs, plant protection chemicals, and food additives such as flavors. The drug or flavor is released slowly by permeation and diffusion. In order to measure the effective rate of diffusion within a range of morphologies, and hence gain insights into the optimum mode of functionalization, the diffusion of vanillin in ethanol is reported. Effective diffusion coefficients <i>D</i>′ were measured in a flow cell connected to a high performance liquid chromatograph (HPLC). Samples were also subjected to mercury intrusion porosimetry. The resulting percolation characteristics were inverse modeled using the PoreXpert package to generate representative void structures with estimated tortuosities. It is shown that the primary particle size of a sample was a better predictor of <i>D</i>′ calculated from the experimental diffusion curves, and also of the porosity-scaled tortuosity values, than the porosity or surface area. There was also a correlation between intraparticle tortuosity, scaled by porosity, and diffusion coefficient. The approach is validated by experimental evidence from this and related studies
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