56 resultados para STATIONARY PHASES


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Characterization of a new family of salts, based on a number of 1-alkyl-2-methyl pyrrolinium cations and the bis(trifluoromethane sulfonyl) amide anion (TFSA), is presented. From the thermal analysis, conductivity and X-ray diffraction (XRD) measurements, at least one of the compounds of the family, 1-ethyl-2-methyl pyrrolinium TFSA, was found to exhibit plastic crystal phases before melting and to exhibit high conductivity in the solid state (1×10−4 S cm−1 at 25 °C). This plastic crystal behaviour is discussed in comparison with other members of this pyrrolinium salt family.

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There is a large literature that tests the univariate time series properties of the real output series following the seminal work of Nelson and Plosser (1982). Whether or not real output is characterized by a unit root process has important implications. A unit root in real output, for instance, is inconsistent with the notion that business cycles are stationary fluctuations around a deterministic trend. In this paper, we investigate the univariate time series properties of real output for 79 developing countries using the conventional augmented Dickey and Fuller (1979) unit root test, the Zivot and Andrews’ (1992) one structural break unit root test, and the Lumsdaine and Papell (1997) two structural breaks unit root test. Our main finding is that, for 40 countries, real output is stationary around a trend. This indicates that business cycles are stationary fluctuations around a deterministic trend for only 51% of the developing countries in our sample.

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The daily metabolizable energy intake of an animal is potentially limited by either the available feeding time or by its capacity to process energy. Animals are generally considered not to be time-limited but rather to be energy-processing-limited. This is concluded from the common observation that an animal's feeding time per day increases with a decrease in food density. We argue that such changes in feeding time are in theory also expected when no constraints are operating. Thus, a study of the constraints on energy intakes of free-living animals should be performed during demanding phases of the year. As an example, we collected data on time and energy budgets of Bewick's swan (Cygnus columbianus bewickii) refuelling during migration on fennel pondweed (Potamogeton pectinatus) tubers in two years differing two-fold in tuber biomass density. As predicted by time limitation, the feeding time (defined as the time with the head submerged) did not change in response to a change in food biomass density, both within and between years (averaging 12.2 h d−1). Contrary to energy-processing limitation, and again in line with time limitation, the daily metabolizable energy intake varied, being greater in the year with high than in the year with low food densities. We conclude that more studies are needed of animals operating under demanding conditions before it can be assessed whether free-living animals are generally energy-processing- or time-limited.

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The chromatographic capacity factors (log k‘) for 32 structurally diverse drugs were determined by high performance liquid chromatography (HPLC) on a stationary phase composed of phospholipids, the so-called immobilized artificial membrane (IAM). In addition, quantitative structure-retention relationships (QSRR) were developed in order to explain the dependence of retention on the chemical structure of the neutral, acidic, and basic drugs considered in this study. The obtained retention data were modeled by means of multiple regression analysis (MLR) and partial least squares (PLS) techniques. The structures of the compounds under study were characterized by means of calculated physicochemical properties and several nonempirical descriptors. For the carboxylic compounds included in the analysis, the obtained results suggest that the IAM-retention is governed by hydrophobicity factors followed by electronic effects due to polarizability in second place. Further, from the analysis of the results obtained of two developed quantitative structure-permeability studies for 20 miscellaneous carboxylic compounds, it may be concluded that the balance between polarizability and hydrophobic effects is not the same toward IAM phases and biological membranes. These results suggest that the IAM phases could not be a suitable model in assessing the acid-membrane interactions. However, it is not possible to generalize this observation, and further work in this area needs to be done to obtain a full understanding of the partitioning of carboxylic compounds in biological membranes. For the non-carboxylic compounds included in the analysis, this work shows that the hydrophobic factors are of prime importance for the IAM-retention of these compounds, while the specific polar interactions, such as electron pair donor−acceptor interactions and electrostatic interactions, are also involved, but they are not dominant.

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Implementation of certain types of protocols on wireless sensor networks (WSNs) can be difficult due to the architecture of the motes. Identification of these issues and recommendations for workarounds can be very useful for the WSN research community testing hardware. In recent work, the authors developed and implemented clustering, reprogramming and authentication protocols involved in recovering WSNs with low resources. In attempting to integrate these protocols, several issues arose in the implementation phase connected to pre-set configurations of the motes used. In this paper, we describe the issues arising in integrating our protocols using Zigbee with IEEE 802.15.4 and the reprogramming module Deluge, and compare our challenges and solutions with those faced by other researchers in this area. Finally, we provide recommendations for consideration by researchers who may in future consider integrating several protocols on these platforms.

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Anecdotal evidence indicated that some kindergartens in the Geelong region were suffering from significant absenteeism or children arriving late or leaving early. Some educators felt that this was linked to the status of Health Care Card Holders. The research project analysed kindergarten attendance records to determine if there was evidence to support the educators’ beliefs. Data did support some of the conjecture. Researchers then undertook interviews with Educators and parents to investigate possible reasons for irregular attendance.

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The Pacific Islands Project (PIP), funded by AusAid and managed by the Royal Australasian College of Surgeons (RACS), has progressed through three phases from 1995 to 2010. During this time, it has sent over 520 teams to 11 Pacific Island Countries, providing over 60 000 consultations and some 16 000 procedures. In addition to this delivery of specialist medical and surgical services that were not previously available in-country, the project has contributed as a partner in capacity building with the Fiji School of Medicine and Ministries of Health of the individual nations. By 2011, Fiji School of Medicine, which began postgraduate specialist training in 1998, had awarded 51 doctors a diploma in surgery (1 year), 20 of whom had completed their Masters in Medicine (4 years). PIP was independently evaluated on completion of every phase, including the bridging Phase III (2006–2010). The project delivered on its design, to deliver services, and also helped build capacity. The relationship established with the RACS throughout the project allowed Pacific Island graduates to access the Rowan Nicks scholarship, and the majority of MMed graduates received International Travel Grants to attend the Annual Scientific Meeting. PIP has been a highly successful partnership in delivering and building specialist medical services. Although AusAid contributed some $20 million over 16 years, the value added from pro bono contributions by Specialist Teams, Specialty Coordinators and the Project Directors amounted to an equivalent amount. With the emergence of Pacific Island-trained specialists, PIP is ready to move into a new phase where the agendas are set, monitored and managed within the Pacific, and RACS fulfils the role of a service provider. A critical mass of Pacific Island surgeons has been trained, so that sub-specialization will be an option for the general surgeons of the larger island nations.

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The addition of up to 4 mol% of the strong acids, trifluoromethane sulfonic acid (TfOH) and bis-trifluoromethanesulfonyl imide [HN(Tf) 2], to the organic ionic plastic crystal (OIPC) [Choline][DHP] has been shown to dramatically increase the ionic conductivity by up to three orders of magnitude whilst still retaining the crystalline structure of the OIPC matrix. This enhanced proton diffusivity led to a significant proton reduction reaction in the electrochemical measurements. Powder XRD and DSC thermal analyses strongly suggest that these mixtures are single phase, crystalline materials. The work here also confirms that an increase in TfOH acid concentration (8 mol% and 12 mol%) results in a higher content of the amorphous phase as previously observed for the H 3PO 4/[Choline][DHP] system. © 2012 The Royal Society of Chemistry.