993 resultados para St. Catharines and Welland Canal Gas Light Company
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Mode of access: Internet.
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Mode of access: Internet.
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Although well known for delivering various pharmaceutical agents, liposomes can be prepared to entrap gas rather than aqueous media and have the potential to be used as pressure probes in magnetic resonance imaging (MRI). Using these gas-filled liposomes (GFL) as tracers, MRI imaging of pressure regions of a fluid flowing through a porous medium could be established. This knowledge can be exploited to enhance recovery of oil from the porous rock regions within oil fields. In the preliminary studies, we have optimized the lipid composition of GFL prepared using a simple homogenization technique and investigated key physico-chemical characteristics (size and the physical stability) and their efficacy as pressure probes. In contrast to the liposomes possessing an aqueous core which are prepared at temperatures above their phase transition temperature (Tc), homogenization of the phospholipids such as 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC) or 1,2-distearoyl-sn-glycero-3-phosphocoline (DSPC) in aqueous medium below their Tc was found to be crucial in formation of stable GFL. DSPC based preparations yielded a GFL volume of more than five times compared to their DPPC counter part. Although the initial vesicle sizes of both DSPC and DPPC based GFL were about 10 μm, after 7 days storage at 25°C, the vesicle sizes of both formulations significantly (p < 0.05) increased to 28.3 ± 0.3 μm and 12.3 ± 1.0 μm, respectively. When the DPPC preparation was supplemented with cholesterol at a 1:0.5 or 1:1 molar ratio, significantly (p < 0.05) larger vesicles were formed (12-13 μm), however, compared to DPPC only vesicles, both cholesterol supplemented formulations displayed enhanced stability on storage indicating a stabilizing effect of cholesterol on these gas-filled vesicles. In order to induce surface charge on the GFL, DPPC and cholesterol (1: 0.5 molar ratio) liposomes were supplemented with a cationic surfactant, stearylamine, at a molar ratio of 0.25 or 0.125. Interestingly, the ζ potential values remained around neutrality at both stearylamine ratios suggesting the cationic surfactant was not incorporated within the bilayers of the GFL. Microscopic analysis of GFL confirmed the presence of spherical structures with a size distribution between 1-8 μm. This study has identified that DSPC based GFL in aqueous medium dispersed in 2% w/v methyl cellulose although yielded higher vesicle sizes over time were most stable under high pressures exerted in MRI. Copyright © Informa Healthcare USA, Inc.
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The effect of friction and interparticle cohesion forces on the gas-solid flow hydrodynamics was discussed. A proposed interparticle cohesion and frictional force terms have been tested in a continuum fully developed flow model to investigate their effect on the general hydrodynamic features of vertical duct flow. It was observed that both terms have direct effect on lowering the material carryover, which implies a reduced bed expansion in freely bubbling column. The parametric analysis shows that cohesion and frictional forces are high when compared to kinetic stress and hence it can play a major role in describing the hydrodynamics features of the flow.
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The high gains in performance predicted for optical immersion are difficult to achieve in practice due to total internal reflection at the lens/detector interface. By reducing the air gap at this interface optical tunneling becomes possible and the predicted gains can be realized in practical devices. Using this technique we have demonstrated large performance gains by optically immersing mid-infrared heterostructure InA1Sb LEDs and photodiodes using hypershperical germanium lenses. The development of an effective method of optical immersion that gives excellent optical coupling has produced a photodiode with a peak room temperature detectivity (D*) of 5.3 x 109 cmHz½W-1 at λpeak=5.4μm and a 40° field of view. A hyperspherically immersed LED showed a f-fold improvement in the external efficiency, and a 3-fold improvement in the directionality compared with a conventional planar LED for f/2 optical systems. The incorporation of these uncooled devices in a White cell produced a NO2 gas sensing system with 2 part-per-million sensitivity, with an LED drive current of <5mA. These results represent a significant advance in the use of solid state devices for portable gas sensing systems.
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Record small and low loss slow light optical signal processing devices are proposed and demonstrated using the recently invented Surface Nanoscale Axial Photonics (SNAP) technology.
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Tin oxide is considered to be one of the most promising semiconductor oxide materials for use as a gas sensor. However, a simple route for the controllable build-up of nanostructured, sufficiently pure and hierarchical SnO2 structures for gas sensor applications is still a challenge. In the current work, an aqueous SnO2 nanoparticulate precursor sol, which is free of organic contaminants and sorbed ions and is fully stable over time, was prepared in a highly reproducible manner from an alkoxide Sn(OR)4 just by mixing it with a large excess of pure neutral water. The precursor is formed as a separate liquid phase. The structure and purity of the precursor is revealed using XRD, SAXS, EXAFS, HRTEM imaging, FTIR, and XRF analysis. An unconventional approach for the estimation of the particle size based on the quantification of the Sn-Sn contacts in the structure was developed using EXAFS spectroscopy and verified using HRTEM. To construct sensors with a hierarchical 3D structure, we employed an unusual emulsification technique not involving any additives or surfactants, using simply the extraction of the liquid phase, water, with the help of dry butanol under ambient conditions. The originally generated crystalline but yet highly reactive nanoparticles form relatively uniform spheres through self-assembly and solidify instantly. The spheres floating in butanol were left to deposit on the surface of quartz plates bearing sputtered gold electrodes, producing ready-for-use gas sensors in the form of ca. 50 μm thick sphere-based-films. The films were dried for 24 h and calcined at 300°C in air before use. The gas sensitivity of the structures was tested in the temperature range of 150-400°C. The materials showed a very quickly emerging and reversible (20-30 times) increase in electrical conductivity as a response to exposure to air containing 100 ppm of H2 or CO and short (10 s) recovery times when the gas flow was stopped.
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A tunable bottle microresonator can trap an optical pulse of the given spectral width, hold it as long as the material losses permit, and release without distortion.
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The financial crisis of 2007-2009 has shaken both money and capital markets. Its consequences have not even left European markets untouched and divided spirits in the financial world. In some countries efforts by the monetary policy to protect the national currency throughout the crisis seemed to be ineffective. In the present paper we are investigating the effect of the most important macroeconomic and economic policy factors on the exchange rate of the forint and zloty in the last decade. For an analysis of exchange rates we are relying on some preceding research results based on equilibrium exchange rate theories.
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A paradigma kifejezést Thomas Kuhn honosította meg a tudományfilozófiában: így nevezte el azt a sajátos szemléletmódot, ahogyan egy kutatási irányzat rátekint vizsgálata tárgyára. Azonos paradigmát használó kutatók hasonló kérdésekre keresik a választ, hasonló módszereket és fogalmakat alkalmaznak. A szerző 1999-ben publikált cikkében vezette be a "rendszerparadigma" kifejezést, amely a társadalomban működő rendszereket helyezi a vizsgálat középpontjába. A tanulmány a posztszocialista átalakulás során szerzett tapasztalatok alapján fejleszti tovább a korábbi cikkben kifejtett elméleti gondolatokat. Az első rész a szocialista és a kapitalista rendszert hasonlítja össze; leírja fő jellemzőiket, majd megállapítja, hogy Észak-Korea és Kuba kivételével az egykori szocialista országokban meghonosodott a kapitalista rendszer. A második rész a politikai-kormányzati formák szerint tipologizálja a kapitalizmus változatait. Három markáns típust különböztet meg: a demokráciát, az autokráciát és a diktatúrát. Huntington a demokratizálás harmadik hullámáról írt. A tanulmány arra a következtetésre jut, hogy ez a hullám elapadt, a 47 posztszocialista ország lakosságának mindössze egytizede él demokráciában, a többiben autokrácia vagy diktatúra uralkodik. A harmadik rész Magyarországra alkalmazza a kialakított fogalmi és elemzési apparátust: itt kapitalizmus van, a politikai-kormányzati forma autokrácia - lényeges közös jellemzők mutathatók ki más kapitalista országokkal, illetve más autokráciákkal. Ez összefér azzal a felismeréssel, hogy egyes - nem alapvető jelentőségű - vonások egyediek, "hungarikumok", különböznek minden más ország tulajdonságaitól. _____ The expression paradigm, introduced into the philosophy of science by Thomas Kuhn for the way a research trend views the subject examined, denotes a case where researchers pursue similar questions by similar methods with similar concepts. The author introduced the expression system paradigm" in a 1999 article centred on the systems operating in society. This paper takes those theoretical ideas further, based on experience in the post-socialist transformation. The first part compares the socialist and capitalist systems and their main features, establishing that all former socialist countries but North Korea and Cuba have embraced the capitalist system. The second adds a typology of the varieties of capitalism by politico-governmental form, marking three types: democracy, autocracy and dictatorship. Huntington writes of a third wave of democratization, which this study concludes has ceased. Democracy reigns in only 10 per cent of the 47 post-socialist countries, autocracy or dictatorship in the others. The third part applies this conceptual and analytical framework to Hungary, where capitalism prevails, with autocracy as its politico-governmental form. It shows strongly similar features to other capitalist countries and other autocracies. This is compatible with recognizing that some features of less than fundamental importance are specific to Hungary and differ from those elsewhere.
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The effects of ocean acidification on the life-cycle stages of the coccolithophore Emiliania huxleyi and their by light were examined. Calcifying diploid and noncalcifying haploid cells (Roscoff culture collection 1216 and 1217) were acclimated to present-day and elevated CO2 partial pressures (PCO2; 38.5 vs. 101.3 Pa, ., 380 vs. 1000 matm) under low and high light (50 vs. 300 mmol photons m-2 s-1). Growth rates as well as quotas and production rates of C and N were measured. Sources of inorganic C for biomass buildup were using a 14C disequilibrium assay. Photosynthetic O2 evolution was measured as a function of dissolved inorganic C and light by means of membrane-inlet mass spectrometry. The diploid stage responded to elevated PCO2 by shunting resources from the production of particulate inorganic C toward organic C yet keeping the production of total particulate C constant. As the effect of ocean acidification was stronger under low light, the diploid stage might be less affected by increased acidity when energy availability is high. The haploid stage maintained elemental composition and production rates under elevated PCO2. Although both life-cycle stages involve different ways of dealing with elevated PCO2, the responses were generally modulated by energy availability, being typically most pronounced under low light. Additionally, PCO2 responses resembled those induced by high irradiances, indicating that ocean acidification affects the interplay between energy-generating processes (photosynthetic light reactions) and processes competing for energy (biomass buildup and calcification). A conceptual model is put forward explaining why the magnitude of single responses is determined by energy availability.