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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

A study of the pyrolysis of normal butane with steam ...

Witham, William Clifford, January 1934 (has links)
Thesis (Ph. D.)--Columbia University, 1934. / Vita. Description based on print version record. Bibliography: p. 31-32.
52

The heats of dissociation of hydrogen, oxygen and nitrogen

Troxel, Shirley Monroe, January 1930 (has links)
Abstract of Thesis (Ph. D.)--University of Illinois, 1930. / Vita. Bibliography: p. [6].
53

A study of the activation energy and mechanisms of some elementary reactions

Bryan, Mary Leo, January 1953 (has links)
Thesis--Catholic University of America.
54

Conductivity, temperature coefficient of conductivity and percentage dissociation of some rather unusual salts in aqueous solutions ...

Watkins, Charles, January 1900 (has links)
Thesis (Ph. D.)--Johns Hopkins University, 1915. / Biography.
55

The thermal decomposition of trifluoromethyl iodide

Downs, Gordon Wylie January 1959 (has links)
The pyrolysis of trifluoromethyl lodide has been investigated under two entirely different sets of conditions (i) in a low pressure flow system (ii) in sealed tubes at higher pressure in the flow system, nickel and pyrox reaction vessels were used. The nickel vessel was used when no material was added to react with OF5 radicals which it was feared would attack pyrex glass. During the course of the Investigations, it was deoided to add toluene, hydrogen iodine as additional reagents. The conditions in the flow system were varied within the following Limits:- Temperature 698°K to 797°K Contact Time. 526 to 2.52 secs. CF3I Pressure 0.016 mms to 0.58 mms. Toluene Pressure 0 to 3.76 mms. Hydrogen Iodide Pressure 0 to 4.08 mms. N2 carrier gas Pressure 1.50 to 14.5 mms. A carrier gas Pressure 1.59 to 12.4 mms. C6H5OF5 Pressure 0 to 2.65 mms. Pressure of added iodine (as atoms) 0 to. 0176 mms. Surface to Volume Retio 1.95 to 6.15 cms−1 only pyrex reaction vessels were used in the sealed tube reactions. OF5 I was never heated alone but always in the presence of HI. In these reactions, conditions were varied within the Limits:- Temperature 440°K to 522°K Reaction Time 10,800 secs. To 259,200 secs. CF5I Pressure 4.0 mms to 57 mms. Hydrogen Iodide Pressure 5.7 mms to 565 mms. Pressure of added iodine (as molecules) 0 to 5.0 mms. An attempt was made to find the stoichiometry of the reaction under all conditions. In order to do this, titration, Low temperature distillation, U.V. and I.R. absorption spectrophotometry and mass spectrometry were used. A reaction scheme has been proposed which agrees with the major experimental findings.
56

The thermal decomposition of dibenzyl

Pittilo, Robert Neilson January 1959 (has links)
The opening pages of this section are devoted to a review of the evidence revealed by the various experiment al techniques which have been applied to the problem. The relationships between the several products and their variations with temperature and pressure have been illustrated graphically and the significance of thane change discussed. The lack of stoichiometric balance is also considered and some possible explanations proposed. This is followed by an outline of the various mechanisms which are available for the production of the resultants in the observed quantities, and the relative merits of these are discussed. On the basis of this discussion a value is proposed for the dissociation energy of the central c-c bond. The final section is concerned with the conclusions which can be drawn from this value regarding the energies involved in other steps of the reaction and their significance in the general scheme of bond energies.
57

The rate of thermal dissociation of direnzyl

Davidson, Iain Munro Thomson January 1958 (has links)
1) The most recent work on the pyrolysis of dibenzyl suggested that a thermal equilibrium:- PhCH2CH2Ph == 2 PhCH2- was set up as a preliminary to decomposition. The aim of this research was to test this idea by heating mixtures of PhCH2CH2Ph (M.W. 182) and PhCD2CD2Ph (M.W. 186) and following mass spectrometrically the growth of PhCH2CH2Ph (M.W. 184) formed by radical recombination. 2) A four stage synthesis of deuterated dibenzyl was developed and used to prepare dibenzyl of 95% isotopic purity with the composition:- PhCD2CD2Ph, 81%; PhCD2CDHPh, 18 %; PhCDHCDHPh, 1%. PhCH2CD2Ph was synthesized by the same sequence of reactions. 3) In order to provide the necessary experimental equipment, the following items have been developed and constructed and descriptions of them are given in this Thesis:- a) a 2 litre reaction vessel with an electronically controlled furnace was arranged with a gas circulating system feeding the inlet of a mass spectrometer; b) an existing mass spectrometer was extensively modified in order to give resolution of 1 in 200:- i) the spectrometer tube was stiffened and accurately re-aligned; ii) the ion collector unit was made detachable and its construction improved; iii) a new ion source was designed and built to the required high accuracy; iv) a new scanning unit was built for variation of the magnetic field. 4) The rate of formation of PhCH2CD2Ph was followed in mixtures of PhCH2CD2Ph and PhCD2CD2Ph at pressures of 0.08 to 0.66 mm. in the reaction vessel, and at pressure up to 142 mm. in sealed tubes, using temperatures between 400° and 500°C. Data were also obtained on the rate of decomposition of PhCH2CH2Ph alone in similar systems. 5) The rate of radical exchange was found to be first order, independent of surface and of pressure of added A, N2, D2, and O2. The decomposition reaction was shown to be 1.5 order at low pressures, and tended to first order at high pressures. At lower pressures it was much slower than the radical exchange. 6) A rate equation for radical exchange in terms of the rate of dissociation of dibenzyl, making due allowance for the simultaneous decomposition of dibenzyl has been developed and applied in the lower pressure region where exchange was of major importance. It gives:- kf sec−1 = 10 14.03 exp -6000/RT 7) The energy of activation in 6) has been identified with D(PhCH2-CD2Ph) in dibenzyl. This value has been discussed in relation to current data on the heat of formation of the benzyl radical and bond dissociation energies in benzyl compounds, notably D(PhCH2-H) in toluene. 8) The energy of activation for the decomposition was found to be 47 kcal and the nature and proportions of the reaction products were established and compared with previous work. The proportions of side-chain deuterated toluenes formed were consistent with a deuterium isotope effect of 2 or less, and with toluene being made by the abstraction of hydrogen from the central carbon atoms of dibenzyl by benzyl radicals. Benzyl radicals were also shown to react with deuterium to form toluene.
58

Phase studies of inorganic sulphates at high temperatures

Campbell, David Alexander January 1985 (has links)
The theme of this thesis is the high-temperature phase studies of inorganic metal sulphates and the aspects specifically dealt with are phase diagrams and drop calorimetry. Chapters 1,2, and 3 are concerned with the first of these. Chapter 1 briefly describes the features encountered in one and two-component systems and provides the thermodynamic background which allows such systems to be calculated. Chapter 2 describes a selection of experimental techniques used to determine phase diagrams. Apparatus to perform Differential Thermal Analysis (DTA) was constructed as part of the work of this thesis and so this technique is fully described, including details of the apparatus, and a section on interpretation of DTA results relating to phase studies. Pointers are included as to further applications of this technique and improvements or modifications that might be made to the present apparatus. Chapter 3 presents the phase diagram of the previously undetermined system Ag2SO4-LA2(SO4)3 and also includes some observations on the kinetics of some phase changes and a description of the optical furnace which was built to study them. Also presented is a re-investigation of the system Ag2SO4-CdSO4, which contains many features not evident in an earlier study. Chapter 4 is concerned with the thermodynamics of substances at high-temperatures and describes in detail the design, construction and experimental procedure for a drop calorimeter. This apparatus allows the equilibrium temperature of high-temperature polymorphic phase transitions and their enthalpies of transition to be determined. A preliminary study on CdSO4 was performed, which ties in with the study in Chapter 3, and an attempt was made to resolve the long standing controversy on the temperatures of the CdSO4 phase transitions. Drop Calorimetry can provide some of the data necessary for the calculation of phase diagrams as described in Chapter 1, and so a brief introduction to the thermodynamics of non-reacting systems and the treatment of results is presented.
59

Trauma, Trust, and Betrayal Awareness

Gobin, Robyn, Gobin, Robyn January 2012 (has links)
Women and men who experience early interpersonal violence are at increased risk for subsequent victimization. Little is known about the mechanisms by which early trauma increases vulnerability for revictimization. According to Betrayal Trauma Theory, harm perpetrated by close others early in life may impair the ability to accurately decipher trust and identify betrayal, thus increasing risk for future violation. Dissociation, a state of cognitive, emotional, and experiential disconnectedness, is theorized to facilitate impaired betrayal awareness, and peritraumatic dissociation (i.e., dissociation at the time of a traumatic event) has been linked to revictimization. The present study extended this existing knowledge and tested predictions made by Betrayal Trauma Theory through the examination of the impact of high betrayal trauma on self-report and behavioral trust tendencies and betrayal awareness in a college sample of 216 individuals with and without histories of trauma high in betrayal. The impact of peritraumatic dissociation on betrayal awareness was examined. Participants completed self-report measures of peritraumatic dissociation and relational and general trust. The Trust Game, an experimental economics task, was used to investigate behavioral trust. A picture drawn to depict sexual abuse of a child was used as a betrayal stimulus to examine betrayal awareness in the sample. Results replicated prior work indicating an increased risk for revictimization among individuals who reported high betrayal trauma during childhood and/or adolescence. As predicted, high betrayal trauma exposure was associated with lower levels of self-reported general and relational trust. Self-reported general trust was positively correlated with behavior during the Trust Game. Participants with histories of high betrayal trauma reported higher levels of peritraumatic dissociation when confronted with the betrayal stimulus, and rates of peritraumatic dissociation contributed significantly to betrayal awareness. The findings of this study suggest betrayal trauma early in life disrupts developing socio-emotional functions, namely the ability to judge trustworthiness. The results provide evidence for the role of peritraumatic dissociation in awareness for betrayal. Despite the preliminary nature of this work, the results represent an important step toward better understanding the long-term consequences of high betrayal trauma, suggesting ways interventions may be tailored to subvert the effects of trauma.
60

Oxidation of omega-3 oils and preservation by natural phenolic antioxidants / Oxydation des huiles oméga-3 et préservation par des antioxydants phénoliques naturels

Guitard, Romain 28 October 2016 (has links)
Les oméga-3 sont reconnus comme étant des acides gras essentiels pour la santé. Ils sont particulièrement sensibles à l’oxygène et sont donc sujets à une dégradation oxydante conduisant à la détérioration de leurs propriétés organoleptique et nutraceutique. Il est donc crucial de protéger les huiles oméga-3 contre l’oxydation par l’ajout d’antioxydants, mais sans danger pour les consommateurs. Afin de retarder l’oxydation, des antioxydants phénoliques synthétiques tels que le BHA et le BHT sont largement utilisés mais suscitent la méfiance des consommateurs. La tendance actuelle est donc de les remplacer par des composés naturels (seuls ou en mélange) conduisant à des effets synergiques, souvent observés mais rarement compris, permettant une meilleure inhibition de l’oxydation. En ajoutant à ceci des mécanismes complexes se produisant lors de la dégradation des acides gras polyinsaturés, ce travail de thèse a été réalisé avec un triple objectif : la détection et l’identification des traces de produits oxydés dans les huiles, la mise en évidence des conditions relatives à la structure chimique des phénols performants et la clarification des mécanismes de fonctionnement des mélanges d’antioxydants. La spectrométrie de masse couplée à une ionisation par électronébulisation (ESI-MS) apparaît être la technique la plus appropriée pour l’ionisation sélective et sensible d’hydroperoxydes intacts identifiés comme les produits d’oxydation primaires. De plus, l’huile de lin, étant l’huile végétale la plus riche en oméga-3, a été notre substrat d’étude. Plus de 70 phénols inhibant l’oxydation radicalaire en chaîne par transfert d’hydrogène aux radicaux péroxyles ont été testés. / Omega-3 has been known as essential fatty acids to health. They are particularly sensitive to oxygen leading to a deterioration of their organoleptic and nutraceutical properties. Protecting omega-3 oils against oxidation is then crucial and requires the addition of highly effective antioxidants but safe for consumers. In order to prevent oxidative degradation, synthetic phenolic antioxidants such as BHT and BHA are widely used but they provoke safety concern from the consumer side. Therefore, the current tendency is to replace them by natural compounds used alone or in mixture, which leads to synergistic effects, often observed but rarely understood. Adding this to the complex mechanism occurring in the degradation of polyunsaturated fatty acids, this thesis was composed by 3 objectives: the detection and identification of traces of oxidation products in oils, the highlight of the requirements of the chemical structures of efficient phenols and the clarification of the mechanisms of action between antioxidants. The electrospray mass spectrometry (ESI-MS) appears as the most suitable technique for the selective and sensitive ionization of intact hydroperoxides which are the primary oxidation products. In addition, the linseed oil, known as the richest vegetable oil in omega-3, was our substrate of study. Over than 70 phenols which inhibit the radical chain oxidation by hydrogen transfer to peroxyl radicals were tested.

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