188 research outputs found
Studies on Bis(imido) molybdenum complexes containing unsaturated hydrocarbon ligands
No full textThis thesis describes the synthesis and characterisation of molybdenum bis(imido) complexes containing unsaturated hydrocarbon ligands. A principal objective of the work was to examine the effect of various imido substituents on the coordination number of the complex and the orientations adopted by olefin and acetylene ligands. Chapter One highlights areas of transition metal chemistry relevant to the thesis, with particular emphasis on the psuedo-isolobal analogy between cyclopentadienyl and imido ligands, A convenient one-pot synthesis of molybdenum bis(imido) complexes of the type Mo(NR)(NR')Cl(_2).DME (R=R'=l-adamantyl, 2-t- BUC(_6)H(_4); R=2,6-i-Pr(_2)C(_6)H(_3), R'=t-Bu) is described in Chapter Two. Mo(N-l- adamantyl)(O)Cl(_2).DME has been synthesised, and its structure determined by single crystal X-ray diffraction.- The preparation of olefin complexes Mo(NR)(NR')(C(_2)H(_4))(PMe(_3))n (R=R'=l-adamantyl, n=l; R=R'=2-t-BuC(_6)H(_4), n=2; R=2,6-i-Pr(_2)C(_6)H(_3), R'=t- Bu, n=l) is outlined in Chapter Three. Structural information derived from NMR data has allowed comparison with metallocene-like olefin adducts. Chapter Four describes the synthesis of complexes containing σ-bound phenyl ligands (Mo(NR)(NR')(σ-C(_6)H(_5))(PMe(_3)) (R=R'=l-adamantyl, 2-t-BuC(_6)H(_4); R=2,6-i-Pr(_2)C(_6)H(_3), R'=t-Bu)) as potential precursors to benzyne complexes. Chapter Five describes the preparation of diphenylacetylene complexes Mo(NR)(NR')(PhC=CPh)(PMe(_3)), structural information derived from NMR data allows comparison with previously known metallocene-like acetylene complexes. Full experimental details for Chapters Two to Five are given in Chapter Six
Investigation of Production of Dimethyl Ether (DME) from Renewable Resources and its Integration into the Oil Production System
No full textExergy investment in producing hydrocarbons is a relatively small fraction of the energy of the oil produced; yet it can reduce energy consumption in the order of percentages. In areas of high insolation or high wind speed, it can be considered that part of the exergy required for these purposes can be retrieved from sustainable energy sources. This idea is expected to be more important when applying enhanced oil recovery. As an example we use solvent (Dimethyl Ether - DME) enhanced water drive recovery. DME is a chemical solvent that has proven to be an efficient oil recovery agent. The recovered DME and oil are both considered products. The main invested exergy considered are the circulation costs of the fluids, separation/retrieval costs and the manufacturing costs of DME – it is assumed that DME is manufactured from natural gas using the single step direct method. To improve the insight in the production process we develop a simple model of DME enriched brine injection in a 1-D reservoir. The model shows that about 92% of the oil in place is recovered using DME, which includes about 30% incremental production after water flooding. Moreover, 100% of the DME injected is recovered.For the production /retrieval costs, we use a data set from the literature. The data set gives us the amount of DME /water injected and the amount of DME /oil/water produced. Moreover it gives the pressure drop, which allows us to calculate the power required for circulation of the fluids. Using these data, the exergy recovery factor (ExRF), which is defined as the exergy of the resources minus the exergy invested divided by the exergy of the resources produced (oil and DME) is calculated. It is observed that the ExRF initially increases with time before it declines and becomes negative. The time at which the ExRF becomes zero is called the exergy zero time. The result shows a negative exergy at the beginning of the DME enhanced water flood (DEW) process. As the incremental oil produced increases due to the presence of DME, and as more DME is back produced, which leads to less manufacturing of DME, the ExRF becomes positive. For DME enhanced recovery the initial area below exergy zero time plus the area above the exergy zero time is positive. Cumulatively, the result shows that at the end of the project, about 71% of the exergy is recovered. The exergy analysis helps us to identify the various components that contribute the most to the exergy loss (~29%). DME manufacturing is found to be the most important contributor to the exergy loss, contributing ~80% (cumulative) to the total invested exergy. It shows that reducing the exergy of manufacturing DME increases the ExRF. The amount of DME lost in the reservoir is shown to also have an effect on the ExRF (not as much as the exergy of manufacturing DME), as it affects the utilization factor of DME. The utilization factor is the ratio of the oil produced (bbls) and the mass of DME injected. If DME is lost more DME must be injected without any increase in oil recovery and thus, DME loss reduces the ExRF.CO2 hydrogenation is chosen as one of the innovative ways of producing DME from renewable sources. The method utilizes CO2 captured from burning the oil produced from the field in power plants and uses solar PV (photovoltaic) as the source of energy to produce H2 from water electrolysisThe results show that the CO2 captured from the power plant can be used to produce more DME than what is needed in the field. The excess DME can be reinjected or used for other purposes such as electricity generation, methanol production or for other uses e.g. as transportation fuel. It is also found that using CO2 hydrogenation has the potential to reduce greenhouse gas emissions by about 82% compared to using natural gas for DME production, which means the method is cleaner and more sustainable.Applied Earth Science
ANALISIS PENURUNAN JANGKAUAN PANCARAN T-DME (TERMINAL-DISTANCE MEASURING EQUIPMENT) MERK NEC NNG-1796A DI BANDARA INTERNASIONAL MINANGKABAU
No full textTerminal Distance Measuring Equipment (T-DME) is a type of aviation navigation equipment that helps pilots provide distance information to landing location points. This T-DME is usually installed side by side with the Landing System Instrument equipment, namely Glide-Path, in this case the T-DME has the function of providing distance information, especially to the Glide Path ground station when carrying out aircraft landing procedures. To ensure that the T-DME equipment is in normal operating condition, calibration activities need to be carried out so that the T-DME equipment remains in accordance with the provisions and parameters. In this research, a problem was found with the T-DME where the beam range was reduced during the calibration process. The method that will be used in this research is a qualitative method to support the data needed in cases of problems that occur. The author analyzes the problems in this research with stages that can help resolve related problems with the aim of ensuring that the T-DME equipment can operate normally and restore the beam range of this T-DME equipment for use in the aircraft flight process safely and appropriately.Terminal Distance Measuring Equipment (T-DME) is a type of aviation navigation equipment that helps pilots provide distance information to landing location points. This T-DME is usually installed side by side with the Landing System Instrument equipment, namely Glide-Path, in this case the T-DME has the function of providing distance information, especially to the Glide Path ground station when carrying out aircraft landing procedures. To ensure that the T-DME equipment is in normal operating condition, calibration activities need to be carried out so that the T-DME equipment remains in accordance with the provisions and parameters. In this research, a problem was found with the T-DME where the beam range was reduced during the calibration process. The method that will be used in this research is a qualitative method to support the data needed in cases of problems that occur. The author analyzes the problems in this research with stages that can help resolve related problems with the aim of ensuring that the T-DME equipment can operate normally and restore the beam range of this T-DME equipment for use in the aircraft flight process safely and appropriately
Experimental study on fuel line pressure fluctuation of biodiesel-DME blends in a common-rail injection system
No full textThe fuel line pressure fluctuations at the injector outlet of biodiesel-DME blends in a common-rail injection system are investigated using the wavelet packet transform. The effects of injection condition and dimethyl ether (DME) blending ratio on the pressure fluctuation characteristics are determined. The results show that the pressure fluctuation intensity determines wavelet packet energy distribution in the three sub-signals. The overall pressure fluctuation is reflected by sub-signal Sig1, which is composed of sub-signal Sig2 and Sig3. Sig2 exhibits medium frequency pressure fluctuations, and mainly occurs in the pressure rise stage and the pressure drop stage. Sig3 exhibits high frequency pressure fluctuations, mainly locates in the pressure stabilization stage. The pressure fluctuations at high injection pressure are more significant compared to those at low injection pressure. Biodiesel-DME blends display similar effects of injection pressure. With the increase of injection pressure, the mean energy and the standard deviation of Sig1, Sig 2 and Sig3 increase, especially those of Sig1 and Sig3. When DME is blended in the biodiesel, the pressure fluctuations for biodiesel-DME blends are more significant compared to biodiesel. With the increase of DME blended ratio, the mean energy and the standard deviation of Sig1 and Sig3 gradually increases.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
PHOTOISOMERIZATION DYNAMICS OF dMe-OMe-NAIP, A MODEL FOR THE RETINAL CHROMOPHORE
No full textAuthor Institution: Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706; Universit di Siena, Siena, I-53100, Italy; Universit di Siena, Siena, I-53100, Italy and Bowling Green State University, Bowling Green, OH 43403; Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706The N-alkylated indanylidene pyrroline Schiff bases (NAIP) mimic the speed and efficiency of photoisomerization of retinal, whose photoisomerization is a key step in the molecular mechanism of vision. We present here a study of the ultrafast isomerization and subsequent relaxation of dMe-OMe-NAIP, a newly synthesized compound in the NAIP class with less steric congestion near the reactive double bond. We show that the excited-state dynamics of dMe-OMe-NAIP are slower than in previously studied NAIP compounds. This simpler compound also lacks the pronounced coherent vibrational motion observed in retinal and other NAIP compounds. We attribute these differences to pre-twisting about the double bond in the ground state of the previously studied compounds that is absent in dMe-OMe-NAIP. The speed of the isomerization and structure of the electronically excited potential energy surface in NAIP compounds make them attractive targets for studies of vibrationally mediated photochemistry. Previous studies from our group have shown that vibrational excitation before promotion to reactive electronic states can influence the course of reactions in isolated molecules. We seek to extend these experiments to molecules in more complicated environments, specifically the solution phase. To that end, we also present preliminary results of experiments probing the timescale of vibrational energy transfer in dMe-OMe-NAIP and other photoreactive Schiff bases
Improving and sustaining quality of child health care through IMCI training and supervision: experience from rural Bangladesh
No full textCAUL read and publish agreementFALS
An assessment of the quantum for financial provision of mine closures: a Monte Carlo approach.
No full textIncludes abstract.Includes bibliographical references.Poor mine closure policy threatens both society and the environment. Some of the more prominent threats that have manifested are acid mine drainage, slimes dams and toxic dust from dumps. Current legislation requires that new mines set aside funds to cover their rehabilitation costs at closure
Challenges in the Greener Production of Formates/Formic Acid, Methanol, and DME by Heterogeneously Catalyzed CO2 Hydrogenation Processes
No full textThe recent advances in the development of heterogeneous catalysts and processes for the direct hydrogenation of CO2 to formate/formic acid, methanol, and dimethyl ether are thoroughly reviewed, with special emphasis on thermodynamics and catalyst design considerations. After introducing the main motivation for the development of such processes, we first summarize the most important aspects of CO2 capture and green routes to produce H2. Once the scene in terms of feedstocks is introduced, we carefully summarize the state of the art in the development of heterogeneous catalysts for these important hydrogenation reactions. Finally, in an attempt to give an order of magnitude regarding CO2 valorization, we critically assess economical aspects of the production of methanol and DME and outline future research and development directions
Negative catalytic effect of water on the reactivity of hydrogen abstraction from the C-H bond of dimethyl ether by deuterium atoms through tunneling at low temperatures
No full textWe report an experimental study on the catalytic effect of solid water on the reactivity of hydrogen abstraction (H-abstraction) from dimethyl ether (DME) in the low-temperature solid DME-H2O complex. When DME reacted with deuterium atoms on a surface at 15-25 K, it was efficiently deuterated via successive tunneling H-abstraction and deuterium (D)-addition reactions. The 'effective rate constant for DME-H2O + D was found to be about 20 times smaller than that of pure DME + D. This provides the first evidence that the presence of solid water has a negative catalytic effect on tunneling H-abstraction reactions. (C) 2016 Elsevier B.V. All rights reserved
Family caregiver emotional distress in advanced cancer : the DME- C scale psychometric properties
No full textPublisher Copyright: © Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Family caregivers of patients with advanced illness at end of life often report high levels of emotional distress. To address this emotional distress is necessary to have adequate and reliable screening tools. Aim: This study analyses the psychometric properties and clinical utility of the Family Caregiver Emotional Detection Scale for caregivers of patients with end-stage cancer (DME-C, Spanish acronym) who are receiving palliative care (PC). Design: Multicentre, cross-sectional study. Settings/participants: Family caregivers of patients with advanced cancer at end of life receiving palliative treatment were interviewed to explore their emotional distress through the DME-C scale and other instruments measuring anxiety and depression (Hospital Anxiety and Depression Scale (HADS)), distress thermometer (DT) and overload (B), as well as a clinical psychological assessment (CPA). Results: 138 family caregivers, 85 (61.6%) female and 53 (38.4%) male, with an average age of 59.69±13.3 participated in the study. The reliability of the scale, as measured by Cronbach's alpha, was 0.76, and its stability over time was 0.734. Positive, significant correlations were found between the DME-C and the scores for anxiety and depression registered on the HADS scale, as well as with the total result of this latter scale and the results for B, the DT and the CPA. A statistical analysis of the receiver-operating characteristic curves showed that the scale has a sensitivity and specificity of 75%, and that the cut-off point for the detection of emotional distress was a score ≥11. Fifty-four per cent of the caregivers displayed emotional distress according to this scale. Conclusions: The DME-C displays good psychometric properties. It is simple, short, reliable and easy to administer. We believe that the instrument is useful for the detection of emotional distress in the family caregivers of hospitalised patients suffering from end-stage illnesses and receiving PC
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