3,234 research outputs found
Calcium channel blockers are overused and thiazides are underused in a hypertension outpatient clinic
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The mechanism and kinetics of methyl isobutyl ketone synthesis from acetone over ion-exchanged hydroxyapatite
The synthesis of methyl isobutyl ketone (MIBK) can be carried out by the condensation of acetone in the presence of hydrogen over a supported metal catalyst. Previous studies have shown that hydroxyapatite is an excellent catalyst for condensation reactions. The present investigation was undertaken in order to elucidate the reaction mechanism and site requirements for acetone coupling to MIBK over a physical mixture of hydroxyapatite and Pd/SiO2. The reaction is found to proceed by consecutive aldol addition to form diacetone alcohol (DAA), dehydration of DAA to mesityl oxide (MO), and hydrogenation of MO to MIBK. The products formed by feeding DAA and MO reveal that aldol addition of acetone is rapid and reversible, and that the subsequent dehydration of DAA is rate-limiting. Pyridine and CO2 titration show that aldol dehydration occurs over basic sites via an E1cB mechanism. A series of cation-substituted hydroxyapatite samples were prepared by ion-exchange to further investigate the role of acid-base strength on catalyst performance. Characterization of these samples by PXRD, BET, ICP-OES, XPS, CO2-TPD, and Raman spectroscopy demonstrated that the exchange procedure used does not affect the bulk properties of hydroxyapatite. DFT calculations reveal that in addition to affecting the Lewis acidity/basicity of the support, the size of the cation plays a significant role in the chemistry: cations that are too large (Ba2+) or too small (Mg2+) adversely affect reaction rates due to excessive stabilization of intermediate species. Strontium-exchanged hydroxyapatite was found to be the most active catalyst because it promoted α-hydrogen abstraction and C–O bond cleavage of DAA efficiently
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Mediating and catalysing innovation: A framework for anticipating the standardisation needs of emerging technologies
The development of technology strategies are often supported by strategic frameworks. Although standards can be critical in fostering technological innovation, particularly by supporting knowledge diffusion, their importance is often neglected by commonly used strategic frameworks. This paper presents a framework which uses the knowledge that needs to transition between key anticipated innovation activities to anticipate potential standardisation needs for emerging technologies. The framework draws attention to strategic considerations and dimensions that might otherwise be overlooked, including different types of standards; standardisation stakeholders; the alignment, coordination, and sequencing of standards; and how these all change over time. A technology roadmapping based framework was used because it explicitly characterises the alignment, coordination, and sequencing of innovation activities (over time) and can be configured to draw out information against the other above strategic considerations and dimensions. The principles and utility of the framework are demonstrated in three contrasting case studies: synthetic biology, additive manufacturing, and smart grid. These show how standards mediate between innovation actors by codifying and diffusing knowledge and can enhance and catalyse innovation. The proposed framework can be used to reveal where standards might be used to support innovation, better characterise the types of standards needed, identify the stakeholders needed to develop them, and highlight any potential alignment, coordination, and sequencing issues related to standardisation activities.Thanks are due to colleagues in BIS, BSI, TSB and Innovate UK for insights, useful conversations and advice on technological domains, and to BIS, BSI and The Gatsby Charitable Foundation, United Kingdom (GA3230) for their financial support. Thanks also due to two anonymous reviewers who helped to refine and more clearly articulate the messages in the article.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.technovation.2015.11.00
Comparison of the utilisation of antihypertensive drugs in a hypertension outpatient clinic in 1996 and 1998
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Plasma bradykinin level is related to angiotensin-converting enzyme inhibition and gene polymorphism in hypertensive patients
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Drug utlisation in a hypertension outpatient clinic 1996-1999
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Zeolite-Catalyzed Isobutene Amination: Mechanism and Kinetics
Amination of isobutene with NH was investigated over Brønsted acidic zeolites at 1 atm and 453-483 K. To compare catalytic activities over different zeolites, the measured reaction rates are normalized by the number of active sites determined by tert-butylamine temperature-programmed desorption (TPD). Small- A nd medium-pore zeolites with one-dimensional channels exhibit low activity because of pore blockage by adsorbed tert-butylammonium ions. However, turnover frequencies and activation energies are not sensitive to framework identity, as long as the active site is accessible to isobutene and tert-butylamine. Kinetic measurements and FTIR spectroscopy reveal that the Brønsted acid sites in MFI are covered predominantly with tert-butylammonium ions under reaction conditions. The desorption of tert-butylamine is assisted by the concurrent adsorption of isobutene. DFT simulations show that at very low tert-butylamine partial pressures, for example, at the inlet to the reactor, tert-butylamine desorption is rate-limiting. However, at sufficiently high tert-butylamine partial pressures (>0.03 kPa), protonation of isobutene to the corresponding carbenium ion limits the rate of amination.
Randomised controlled trial of low salt diet in the treatment of hypertension
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Reducing sodium intake reduces ambulatory blood pressure in hypertensive patients
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