27 research outputs found

    The hydrolysis of geminal ethers: A kinetic appraisal of orthoesters and ketals

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    © 2016 Repetto et al. A novel approach to protecting jet fuel against the effects of water contamination is predicated upon the coupling of the rapid hydrolysis reactions of lipophilic cyclic geminal ethers, with the concomitant production of a hydrophilic acyclic hydroxyester with de-icing properties (Fuel Dehydrating Icing Inhibitors - FDII). To this end, a kinetic appraisal of the hydrolysis reactions of representative geminal ethers was undertaken using a convenient surrogate for the fuel-water interface (D2 O/CD3 CN 1:4). We present here a library of acyclic and five/six-membered cyclic geminal ethers arranged according to their hydroxonium catalytic coefficients for hydrolysis, providing for the first time a framework for the development of FDII. A combination of 1H NMR, labelling and computational studies was used to assess the effects that may govern the observed relative rates of hydrolyses

    Characterization of the Muscles within the Beef Forequarter

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    Thirty - four muscles/muscle groups, each greater than .1 kg, were dissected from 16 forequarters to establish a data base of individual muscle yields, palatability profiles and chemical composition. Carcass data from the 16 steers revealed the following averages: carcass weight - 288.4 kg, yield grade - 3.2, and quality grade – low choice. Individual muscle yields, tenderness profiles and chemical analyses indicated that the muscles within the forequarter are extremely variable. However, several of the larger muscles within the forequarter possess tenderness profiles comparable to the longissimus dorsi, the major muscle within rib steaks. This study suggests that maximum utilization of the beef forequarter may best be achieved when individual muscles are fabricated and marketed according to their size and tenderness potential

    The Experiment Data Depot: A Web-Based Software Tool for Biological Experimental Data Storage, Sharing, and Visualization

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    Although recent advances in synthetic biology allow us to produce biological designs more efficiently than ever, our ability to predict the end result of these designs is still nascent. Predictive models require large amounts of high-quality data to be parametrized and tested, which are not generally available. Here, we present the Experiment Data Depot (EDD), an online tool designed as a repository of experimental data and metadata. EDD provides a convenient way to upload a variety of data types, visualize these data, and export them in a standardized fashion for use with predictive algorithms. In this paper, we describe EDD and showcase its utility for three different use cases: storage of characterized synthetic biology parts, leveraging proteomics data to improve biofuel yield, and the use of extracellular metabolite concentrations to predict intracellular metabolic fluxes

    Isolation of chromosome clusters from metaphase-arrested HeLa cells

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    We have developed a simplified approach for the isolation of metaphase chromosomes from HeLa cells. In this method, all the chromosomes from a cell remain together in a bundle which we call a “metaphase chromosome cluster”. Cells are arrested to 90–95% in metaphase, collected by centrifugation, extracted with non-ionic detergent in a low ionic strength buffer at neutral pH, and homogenised to strip away the cytoskeleton. The chromosome clusters which are released can then be isolated in a crude state by pelleting or they can be purified away from nearly all the interphase nuclei and cytoplasmic debris by banding in a Percoll TM density gradient. — This procedure has the advantages that it is quick and easy, metaphase chromatin is recovered in high yield, and Ca ++ is not needed to stabilise the chromosomes. Although the method does not yield individual chromosomes, it is nevertheless very useful for both structural and biochemical studies of mitotic chromatin. The chromosome clusters also make possible biochemical and structural studies of what holds the different chromosomes together. Such information could be useful in improving chromosome isolation procedures and for understanding suprachromosomal organisation of the nucleus.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47359/1/412_2004_Article_BF00327351.pd

    The Development of Novel Fuel Dehydrating Icing Inhibitors

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    Dissolved water is a normal component of jet fuel which is vapourised during combustion; however, free water is a contaminant that can starve engines, freeze to form ice crystals capable of blocking fuel feeds, support microbial growth, and contribute towards corrosion. Jet fuel may be protected from the potentially hazardous effects of free-water using biocides and icing/corrosion inhibitors. This investigation seeks to identify novel chemical approaches to the dual management of both water contamination and ice formation in jet fuel. The strategy of using organic molecules as dehydrating agents remains a relatively neglected approach perhaps because of the complexity of the physical organic chemistry involved in developing and refining these systems. However, organic molecules with well characterised dehydrating properties - such as ortho esters, acetals, hemiacetals, ketals, and hemiketals - present themselves as an excellent starting-point for the development and optimisation of novel Fuel Dehydrating Icing Inhibitors (FDII). This paper describes our systematic approach towards the development of jet fuel additives which are kinetically fast, selective, lipophilic water scavengers that produce, upon hydrolysis, a hydrophilic ice inhibitor. A brief human and environmental toxicological screening of candidates is described. We anticipate that this class of FDII represents a novel approach towards protecting jet fuel against the effects of water contamination. Copyright © 2013 SAE International

    Analysis and effect of large synchronous motors on power systems

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    Thesis (M. Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2005.Large synchronous machines are frequently utilised in industry and have several advantages and disadvantages. Although a synchronous motor is more efficient than an induction motor, it is also far more complex and sensitive in terms of starting and voltage dips respectively. It is therefore important to understand the impact and sensitivities of a synchronous motor. The impact that a large synchronous motor has on a power system network can be significant. The impact of the quality of supply of the power system on a large synchronous motor can also impact negatively on the operational availability of the motor and should be well understood. A synchronous motor will be installed in a production facility and as such, this investigation is in the form of a case study. This document entails the detailed study, modelling and simulation of the impact of a large low-speed synchronous motor on a power system network, as well as the impact of the power system network on the motor (in terms of voltage dips). Detailed machine and system parameters were gathered from the motor supplier and utility. The effect that the motor has on the network and the effect of the network on the motor were analysed with detailed actual system and motor data. These analyses included load flows, short circuits, motor starting and a transient stability. A comparison of the supplier-suggested stability limits was made with the outcome of an undervoltage stability study. The study revealed that the supplier was over-pessimistic about the voltage dip ride-through capability. Graph 3.28: Voltage dip scatter plot indicating different tripping areas indicates a significant improvement from what was initially offered by the supplier. The dip ride-through capability was increased almost threefold after the interaction of the motor with the power system was studied in detail. This increased dip ride-through capability will have a significant impact on the plant performance. This however must be achieved without any damage to the motor or the associated equipment of this machine. Proper control with a thorough understanding of the synchronous motor's behaviour will lead to an increase in the machine's operational availability (on-line time for a continuous process)Master
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