971 resultados para Efficient dominating set


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One of the most challenging tasks for a synthetic organic chemist today, is the development of chemo, regio, and stereoselective methodologies toward the total synthesis of macromolecules. r . The objective of my thesis was to develop methodologies towards this end. The first part of my project was to develop highly functionalized chirons from D-glucose, a cheap, chiral starting material, to be utilized in this capacity. The second part of the project dealt with modifying the carbon-carbon bond forming Suzuki reaction, which is utilized quite often as a means of combining molecular sub units in total synthesis applications. As previously stated the first area of the project was to develop high value chirons from D-glucose, but the mechanism of their formation was also investigated. The free radical initiated oxidative fragmentation of benzylidene acetals was investigated through the use of several test-case substrates in order to unravel the possible mechanistic pathways. This was performed by reacting the different acetals with N-bromosuccinimide and benzoyl peroxide in chlorobenzene at 70^C in all cases. Of the three mechanistic pathways discussed in the literature, it was determined, from the various reaction products obtained, that the fragmentation of the initial benzylic radical does not occur spontaneously but rather, oxidation proceeds to give the benzyl bromide, which then fragments via a polar pathway. It was also discovered that the regioselectivity of the fragmentation step could be altered through incorporation of an allylic system into the benzylidene acetal. This allows for the acquisition of a new set of densely functionalized. chiral, valuable synthetic intermediates in only a few steps and in high yields from a-Dglucose. The second part of the project was the utilization of the phosphonium salt room temperature ionic liquid tetradecyltrihexylphosphonium chloride (THPC) as an efficient reusable medium for the palladium catalyzed Suzuki cross-coupling reaction of aryl halides, including aryl chlorides, under mild conditions. The cross-coupling reactions were found to proceed in THPC containing small amounts of water and toluene using potassium phosphate and 1% Pd2(dba)3. Variously substituted iodobenzenes, including electron rich derivatives, reacted efficiently in THPC with a variety of arylboronic acids and afforded complete conversion within 1 hour at 50 ^C. The corresponding aryl bromides also reacted under these conditions with the addition of a catalytic amount of triphenylphosphine that allowed for complete conversion and high isolated yields. The reactions involving aryl chlorides were considerably slower, although the addition of triphenylphosphine and heating at 70 ^C allowed high conversion of electron deficient derivatives. Addition of water and hexane to the reaction products results in a triphasic system in which the top hexane phase contained the biaryl products, the palladium catalyst remained fully dissolved in the central THPC layer, while the inorganic salts were extracted into the lower aqueous phase. The catalyst was then recycled by removing the top and bottom layers and adding the reagents to the ionic liquid which was heated again at 50 ^C; resulting in complete turnover of iodobenzene. Repetition of this procedure gave the biphenyl product in 82-97% yield (repeated five times) for both the initial and recycled reaction sequences.

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The present study examined individual differences in Absorption and fantasy, as well as in Achiievement and achievement striving as possible moderators of the perceptual closure effect found by Snodgrass and Feenan (1990). The study also examined whether different instructions (experiential versus instrumental) interact with the personality variables to moderate the relationship between priming and subsequent performance on a picture completion task. 1 28 participants completed two sessions, one to fill out the MPQ and NEO personality inventories and the other to complete the experimental task. The experimental task consisted of a priming phase and a test phase, with pictures presented on a computer screen for both phases. Participants were shown 30 pictures in the priming phase, and then shovm the 30 primed pictures along with 30 new pictures for the test phase. Participants were randomly assigned to receive one of the two different instruction sets for the task. Two measures of performance were calculated, most fragmented measure and threshold. Results of the present study confirm that a five-second exposure time is long enough to produce the perceptual closure effect. The analysis of the two-way interaction effects indicated a significant quadratic interaction of Absorption with priming level on threshold performance. The results were in the opposite direction of predictions. Possible explanations for the Absorption results include lack of optimal conditions, lack of intrinsic motivation and measurement problems. Primary analyses also revealed two significant between-subject effects of fantasy and achievement striving on performance collapsed across priming levels. These results suggest that fantasy has a beneficial effect on performance at test for pictures primed at all levels, whereas achievement striving seems to have an adverse effect on performance at test for pictures primed at all levels. Results of the secondary analyses with a revised threshold performance measure indicated a significant quadratic interaction of Absorption, condition and priming level. In the experiential condition, test performance, based on Absorption scores for pictures primed at level 4, showed a positive slope and performance for pictures primed at levels 1 and 7 based on Absorption showed a negative slope. The reverse effect was found in the instrumental condition. The results suggest that Absorption, in combination with experiential involvement, may affect implicit memory. A second significant result of the secondary analyses was a linear three-way interaction of Achievement, condition and priming level on performance. Results suggest that as Achievement scores increased, test performance improved for less fragmented primed pictures in the instrumental condition and test performance improved for more highly fragmented primes in the experiential condition. Results from the secondary analyses suggest that the revised threshold measure may be more sensitive to individual differences. Results of the exploratory analyses with Openness to Experience, Conscientiousness and agentic positive emotionality (PEM-A) measures indicated no significant effects of any of these personality variables. Results suggest that facets of the scales may be more useful with regard to perceptual research, and that future research should examine narrowly focused personality traits as opposed to broader constructs.

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Part I: Ultra-trace determination of vanadium in lake sediments: a performance comparison using O2, N20, and NH3 as reaction gases in ICP-DRC-MS Thermal ion-molecule reactions, targeting removal of specific spectroscopic interference problems, have become a powerful tool for method development in quadrupole based inductively coupled plasma mass spectrometry (ICP-MS) applications. A study was conducted to develop an accurate method for the determination of vanadium in lake sediment samples by ICP-MS, coupled with a dynamic reaction cell (DRC), using two differenvchemical resolution strategies: a) direct removal of interfering C10+ and b) vanadium oxidation to VO+. The performance of three reaction gases that are suitable for handling vanadium interference in the dynamic reaction cell was systematically studied and evaluated: ammonia for C10+ removal and oxygen and nitrous oxide for oxidation. Although it was able to produce comparable results for vanadium to those using oxygen and nitrous oxide, NH3 did not completely eliminate a matrix effect, caused by the presence of chloride, and required large scale dilutions (and a concomitant increase in variance) when the sample and/or the digestion medium contained large amounts of chloride. Among the three candidate reaction gases at their optimized Eonditions, creation of VO+ with oxygen gas delivered the best analyte sensitivity and the lowest detection limit (2.7 ng L-1). Vanadium results obtained from fourteen lake sediment samples and a certified reference material (CRM031-040-1), using two different analytelinterference separation strategies, suggested that the vanadium mono-oxidation offers advantageous performance over the conventional method using NH3 for ultra-trace vanadium determination by ICP-DRC-MS and can be readily employed in relevant environmental chemistry applications that deal with ultra-trace contaminants.Part II: Validation of a modified oxidation approach for the quantification of total arsenic and selenium in complex environmental matrices Spectroscopic interference problems of arsenic and selenium in ICP-MS practices were investigated in detail. Preliminary literature review suggested that oxygen could serve as an effective candidate reaction gas for analysis of the two elements in dynamic reaction cell coupled ICP-MS. An accurate method was developed for the determination of As and Se in complex environmental samples, based on a series of modifications on an oxidation approach for As and Se previously reported. Rhodium was used as internal standard in this study to help minimize non-spectral interferences such as instrumental drift. Using an oxygen gas flow slightly higher than 0.5 mL min-I, arsenic is converted to 75 AS160+ ion in an efficient manner whereas a potentially interfering ion, 91Zr+, is completely removed. Instead of using the most abundant Se isotope, 80Se, selenium was determined by a second most abundant isotope, 78Se, in the form of 78Se160. Upon careful selection of oxygen gas flow rate and optimization ofRPq value, previous isobaric threats caused by Zr and Mo were reduced to background levels whereas another potential atomic isobar, 96Ru+, became completely harmless to the new selenium analyte. The new method underwent a strict validation procedure where the recovery of a suitable certified reference material was examined and the obtained sample data were compared with those produced by a credible external laboratory who analyzed the same set of samples using a standardized HG-ICP-AES method. The validation results were satisfactory. The resultant limits of detection for arsenic and selenium were 5 ng L-1 and 60 ng L-1, respectively.

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Employing critical pedagogy and transformative theory as a theoretical framework, I examined a learning process associated with building capacity in community-based organizations (CBOs) through an investigation of the Institutional Capacity Building Program (ICBP) initiated by a Foundation. The study sought to: (a) examine the importance of institutional capacity building for individual and community development; (b) investigate elements of a process associated with a program and characteristics of a learning process for building capacity in CBOs; and (c) analyze the Foundation’s approach to synthesizing, systematizing, and sharing learning. The study used a narrative research design that included 3 one-on-one, hour-long interviews with 2 women having unique vantage points in ICBP: one is a program facilitator working at the Foundation and the other runs a CBO supported by the Foundation. The interviews’ semistructured questions allowed interviewees to share stories regarding their experience with the learning process of ICB and enabled themes to emerge from their day-to-day experience. Through the analysis of this learning process for institutional capacity building, a few lessons can be drawn from the experience of the Foundation.

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Although the link between macroeconomic news announcements and exchange rates is well documented in recent literature, this connection may be unstable. By using a broad set of macroeconomic news announcements and high frequency forex data for the Euro/Dollar, Pound/Dollar and Yen/Dollar from Nov 1, 2004 to Mar 31, 2014, we obtain two major findings with regards to this instability. First, many macroeconomic news announcements exhibit unstable effects with certain patterns in foreign exchange rates. These news effects may change in magnitude and even in their sign over time, over business cycles and crises within distinctive contexts. This finding is robust because the results are obtained by applying a Two-Regime Smooth Transition Regression Model, a Breakpoints Regression Model, and an Efficient Test of Parameter Instability which are all consistent with each other. Second, when we explore the source of this instability, we find that global risks and the reaction by central bank monetary policy to these risks to be possible factors causing this instability.

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Feature selection plays an important role in knowledge discovery and data mining nowadays. In traditional rough set theory, feature selection using reduct - the minimal discerning set of attributes - is an important area. Nevertheless, the original definition of a reduct is restrictive, so in one of the previous research it was proposed to take into account not only the horizontal reduction of information by feature selection, but also a vertical reduction considering suitable subsets of the original set of objects. Following the work mentioned above, a new approach to generate bireducts using a multi--objective genetic algorithm was proposed. Although the genetic algorithms were used to calculate reduct in some previous works, we did not find any work where genetic algorithms were adopted to calculate bireducts. Compared to the works done before in this area, the proposed method has less randomness in generating bireducts. The genetic algorithm system estimated a quality of each bireduct by values of two objective functions as evolution progresses, so consequently a set of bireducts with optimized values of these objectives was obtained. Different fitness evaluation methods and genetic operators, such as crossover and mutation, were applied and the prediction accuracies were compared. Five datasets were used to test the proposed method and two datasets were used to perform a comparison study. Statistical analysis using the one-way ANOVA test was performed to determine the significant difference between the results. The experiment showed that the proposed method was able to reduce the number of bireducts necessary in order to receive a good prediction accuracy. Also, the influence of different genetic operators and fitness evaluation strategies on the prediction accuracy was analyzed. It was shown that the prediction accuracies of the proposed method are comparable with the best results in machine learning literature, and some of them outperformed it.

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List (11 pages, handwritten) of remarks upon the titles as set forth in the abstracts, n.d.

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- The first part of the document traces Mr. Haile’s lineage. His father, James Haile was a farmer. His grandfather, Amos Haile was a sailor for the early part of his life. He was placed on a British man-of- war in about 1758. He escaped and settled in Putney. (p.1) - His father’s mother’s maiden name was Parker. His mother’s maiden name was Campbell. Her father was a captain in the Revolutionary Army. (p.2) - His earliest memories revolve around the death of his aunt and the funeral of General Washington (although he did not witness this). At the time, his father was a Lieutenant in a regiment militia of Light Dragoons who wore red coats. (p.3) - In 1804, an addition was added to the Haile house which necessitated that William was to stay home to help with the building. He continued to study and read on his own. He was particularly interested in Napoleon Bonaparte’s victories. In that same year he was sent to Fairfield Academy where Reverend Caleb Alexander was the principal. (p.4) - On June 1, 1812, William was appointed as an Ensign in the Infantry of the Army of the United States. He was put into the recruiting service at Nassau (20 miles east of Albany) where he remained until September. (p.4) - He was assigned to the 11th Regiment of the W.S. Infantry and directed to proceed to Plattsburgh to report to Colonel Isaac Clark. (p.7) - He was assigned to the company commanded by Captain Samuel H. Halley who was not in the best of health and often absent. For a good part of the time William was in charge of the company. (p.8) - The 11th Regiment was encamped beside the 15th Regiment commanded by Col. Zebulon Montgomery Pike [Pike’s Peak was named after him]. Col. Pike generously drilled and disciplined the 11th Regiment since their officers didn’t seem capable of doing so. (p.8) - The first brigade to which William’s regiment was attached to was commanded by Brigadier General Bloomfield of New Jersey. Brigadier Chandler of Maine commanded the second brigade. (p.9) - At the beginning of November, Major General Dearborn took command of the army. He had been a good officer in his time, but William refers to him as “old and inefficient” earning him the nickname “Granny Dearborn” (p.9) - On November 17th, 1812, General Dearborn moved north with his army. The troops ended up in Champlain. There was no fighting, only a skirmish between a party of men under Colonel Pike and a few British troops who he succeeded in capturing. (p.10) - The troops were moved to barracks for the winter. Colonel Pike’s troops were put into suitable barracks and kept healthy but another part of the army (including the 11th Regiment) were sent to a barracks of green lumber north of Burlington. Disease soon broke out in the damp barracks and the hundreds of deaths soon followed. One morning, William counted 22 bodies who had died the previous night. He puts a lot of this down to an inexperienced commanding officer, General Chandler. (p.11) - At the beginning of 1813, William was stationed as a recruiter on the shore of Shoreham across from Fort Ticonderoga. In February, he returned to Burlington with his recruits. In March he received an order from General Chandler to proceed to Whitehall and take charge of the stores and provisions. In April and May it was decided that his half of the regiment (the First Battalion) should march to Sackett’s Harbour, Lake Ontario. They arrived at Sackett’s Harbour about the 10th of June, a few days after the Battle of Sackett’s Harbour. (p.12) - He was camped near the site of Fort Oswego and got word to head back to Sackett’s Harbour. A storm overtook the schooner that he was on. (p.14) - William was involved in the Battle of Williamsburg (or Chrysler’s Farm) which he calls a “stupid and bungling affair on the part of our generals”.(p. 18) - General Covington was wounded and died a few days after the battle. (p.19) - William speaks of being ill. The troops were ordered to march to Buffalo, but he is able to go to his father’s house in Fairfield where his mother nursed him back to health (p.23) - Upon arrival at Buffalo, the “old fogy Generals” were replaced with younger, more efficient men. (p.25) - On page 27 he sums up a few facts: In 1812, the army was assembled on Lake Champlain with the intention of capturing Montreal, and then Quebec. That year, under General Dearborn the army marched as far as Champlain, then turned back and went into winter quarters. In 1813, the army was assembled at Sackett’s Harbour and that year the campaign ended at French Mills which was 70 or 80 miles from Montreal. In 1814, the army at Buffalo were some 400 miles from Montreal with still the same object in view. - He says that these facts make “a riddle – difficult to explain”. (p.27) - On the evening of July 2nd they embarked on the boats with the objective of capturing Fort Erie. The enemy were all made prisoners of war (p.27) - On July 4th they went to Street’s Creek, 2 miles above the Chippewa [Chippawa] River (p.28) - Page 29 is titled The Battle of Chippewa [Chippawa] - He speaks of 2 drummers who were fighting over the possession of a drum when a cannonball came along and took of both of their heads (p.29) - He proclaims that this was one of the “most brilliant battles of the war”. The battle was fought and won in less than an hour after they left their tents. He credits General Scott with this success and states that was due to his rapid orders and movements. (p.30) - The dead of the battle remained on the field during the night. He describes this as quite gloomy seeing friend and foe lying side by side. At daybreak they set to work digging trenches to bury the dead. (p.31) - Colonel Campbell was wounded and advised to have his leg amputated. He refused, and subsequently died. (p.32) - It is said that the British threw several of their dead into the river and they went over the Falls. (p.32) - His troops repaired the bridge over Chippawa which the enemy had partially destroyed and then pursued the British as far as Queenston Heights. (p.32) - On pages 33 and 34 he speaks about meeting an old friend of his, Philip Harter. - The account ends at Queenston Heights

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A contingent contract in a transferable utility game under uncertainty specifies an outcome for each possible state. It is assumed that coalitions evaluate these contracts by considering the minimal possible excesses. A main question of the paper concerns the existence and characterization of efficient contracts. It is shown that they exist if and only if the set of possible coalitions contains a balanced subset. Moreover, a characterization of values that result in efficient contracts in the case of minimally balanced collections is provided.

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We extend the class of M-tests for a unit root analyzed by Perron and Ng (1996) and Ng and Perron (1997) to the case where a change in the trend function is allowed to occur at an unknown time. These tests M(GLS) adopt the GLS detrending approach of Dufour and King (1991) and Elliott, Rothenberg and Stock (1996) (ERS). Following Perron (1989), we consider two models : one allowing for a change in slope and the other for both a change in intercept and slope. We derive the asymptotic distribution of the tests as well as that of the feasible point optimal tests PT(GLS) suggested by ERS. The asymptotic critical values of the tests are tabulated. Also, we compute the non-centrality parameter used for the local GLS detrending that permits the tests to have 50% asymptotic power at that value. We show that the M(GLS) and PT(GLS) tests have an asymptotic power function close to the power envelope. An extensive simulation study analyzes the size and power in finite samples under various methods to select the truncation lag for the autoregressive spectral density estimator. An empirical application is also provided.

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This paper proposes a definition of relative uncertainty aversion for decision models under complete uncertainty. It is shown that, for a large class of decision rules characterized by a set of plausible axioms, the new criterion yields a complete ranking of those rules with respect to the relative degree of uncertainty aversion they represent. In addition, we address a combinatorial question that arises in this context, and we examine conditions for the additive representability of our rules.

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Pérez-Castrillo and Wettstein (2002) propose a multi-bidding mechanism to determine a winner from a set of possible projects. The winning project is implemented and its surplus is shared among the agents. In the multi-bidding mechanism each agent announces a vector of bids, one for each possible project, that are constrained to sum up to zero. In addition, each agent chooses a favorite a object which is used as a tie-breaker if several projects receive the same highest aggregate bid. Since more desirable projects receive larger bids, it is natural to consider the multi-bidding mechanism without the announcement of favorite projects. We show that the merits of the multi-bidding mechanism appear not to be robust to this natural simplification. Specifically, a Nash equilibrium exists if and only if there are at least two individually optimal projects and all individually optimal projects are efficient.

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Affiliation: Zhujun Ao, Éric Cohen & Xiaojian Yao : Département de microbiologie et immunologie, Faculté de Médecine, Université de Montréal