A common characteristic of all chemical allergens, both respiratory and skin allergens, is the ability to form stable associations with proteins; the resulting hapten-protein complex being sufficient to provoke an immune response. There is evidence to suggest that selective binding of chemicals with proteins or peptides may impact on the quality of immune response that will develop. In the investigations described here, we have taken a reductionist approach to protein reactivity and evaluated the binding characteristics of 20 of the most commonly reported chemical respiratory allergens towards defined peptides with a single reactive amino acid of interest. The hypothesis is that it is possible to identify and characterize different forms of chemical allergens as a function of preferential peptide binding.Utilizing the standardized reaction conditions of a direct peptide reactivity assay (DPRA), the reactivity of respiratory allergens for cysteine and lysine peptides was evaluated. Activity in the DPRA is reported as the percent depletion of peptide following 24 h incubation. An important and intriguing observation was that, when compared with skin sensitizers, chemical respiratory allergens exhibited a preferential reactivity for lysine. This preference was characterized quantitatively as a ratio of the mean depletion of lysine compared with cysteine (Lys:Cys ratio). The Lys:Cys ratio was observed to be robust and reproducible over time.A limitation of many in chemico methods for hazard identification is the lack of a metabolic component that allows for the identification of pro-haptens. In order to address this limitation, reported here is the use of the peroxidase peptide reactivity assay (PPRA), which utilizes a horseradish peroxidase/hydrogen peroxide (HRP/P) enzymatic system as a proxy for oxidative metabolism. Additionally, reactivity in the PPRA is characterized after a 24 h reaction time utilizing a concentration-response model (thus, permitting consideration of dose-response relationships defined as an EC15 value). Unexpectedly, the preferences for lysine observed with chemical respiratory allergens in the DPRA were lost or blunted in PPRA. The EC15 values demonstrated that relative reactivity between chemical respiratory allergens varied by up to 4 orders of magnitude. The identification of quantitative differences in reactivity could prove useful as a guide to evaluate potency in the future, should reliable metrics become available.To characterize the selectivity of binding by chemical respiratory allergens, the DPRA was modified to allow for the evaluation of reactivity to histidine, tyrosine and arginine. Confirming our previous observations, each of the respiratory sensitizers was observed to react to both lysine and cysteine, with in most instances, a preference for the former. Reactive promiscuity was a function of the other peptides with histidine being the most reactive followed by arginine and tyrosine. To model more complex reactive conditions, a novel modification was made to the DPRA to allow competition for lysine and cysteine to be assessed in a single reaction mixture. The results of these competitive reactivity experiments identified a range of binding patterns to lysine and cysteine that in some cases resulted in different binding being expressed.At present, there are no methods available to reliably identify potential chemical respiratory allergens. The work presented here has demonstrated that respiratory allergens can be identified as potential sensitizers based on their ability to react with lysine and cysteine. More importantly, the balance of reactivity to these two peptides can provide a means of discriminating between respiratory and skin sensitizers.

d-Limonene (Lim) was used in various polymer formulations to achieve a more sustainable polymerization. Lim is a renewable and essentially non-toxic compound, derived from citrus fruit peels, that may replace some of the many toxic and fossil-based chemicals used in polymer synthesis. Bulk free-radical polymerizations of n-butyl acrylate (BA) with Lim were performed to investigate Lim co-polymerization kinetics and estimate the monomer reactivity ratios, important parameters in the prediction of copolymer composition. Kinetic modeling of the BA/Lim copolymerization was performed with PREDICI simulation software. The model supports the presence of a significant degradative chain transfer reaction due to Lim. This reaction mechanism is due to the presence of allylic hydrogen in Lim. Nonetheless, relatively high molecular weight polymers were produced. It was concluded that Lim behaves more like a chain transfer agent than a co-monomer. Terpolymerizations of BA, butyl methacrylate (BMA) with Lim were then performed. In order to predict the terpolymer composition, the monomer reactivity ratios for BA/BMA were estimated. By applying the three pairs of co-monomer reactivity ratios to the integrated Mayo-Lewis equation, terpolymer compositions were ably predicted up to high monomer conversion levels. Lim was then used as a chain transfer agent to prepare core-shell latex-based pressure sensitive adhesives (PSA) comprising BA and styrene via seeded semi-batch emulsion polymerization. By varying the concentration of Lim and divinylbenzene crosslinker, the core polymer microstructure was modified to yield different molecular weights and degrees of crosslinking. The core latex was then used as a seed to prepare core-shell latexes. By changing the Lim concentration during the shell-stage polymerization, the molecular weight of shell polymer was also modified. The latexes were characterized for their microstructure and were cast as films for PSA performance evaluation. The PSA performance was shown to be highly related to the polymer microstructure. Tack and peel strength showed a decrease with increasing Lim concentration. Shear strength went through a maximum with a core Lim concentration increase from 0 to 5 phm.

The iridium(III) methyl diarylphosphide complexes, Ir(CH₃PR₂-[N(SiMe₂CH₂PPh₂)₂] (2a: R = phenyl, 2b: R = meta-tolyl) had been prepared previous to this work. The iridium(III) dimethylphosphide complex, Ir(CH₃)PMe₂-[N(SiMe₂CH₂PPh₂)₂], 2c, is readily prepared in situ by transmetallation of the Ir(CH₃)I[N(SiMe₂CH₂PPh₂)₂] with KPMe₂ at -30°C. The synthesis of the phenylphosphide complex Ir(CH₃)PHPh[N(SiMe₂CH₂PPh₂)₂], 2d, involves deprotonation of the six-coordinate iridium(III) phenylphosphine complex, Ir(CH₃)I-(PH₂Ph)[N(SiMe₂CH₂PPh₂)₂], with KO¹Bu. Thermolysis of 2a and 2b yields the six-coordinate iridium(III) cyclometallated hydride complexes fac-Ir(ɳ²-CH₂PR₂)H[N(SiMe₂CH₂PPh₂)₂], 3a and 3b. The dimethylphosphide complex 2c undergoes the same rearrangement to afford 3c but more rapidly. Thermolysis of 3a-3c yields the square planar iridium(I) phosphine complexes of the formula, Ir(PCH₃R₂)[N(SiMe₂CH₂PPh₂)₂], 4a-4c. Some of the intermediates proposed in the thermolysis of 2a are synthesised independently by the reaction of iridium methylidene complex, Ir=CH₂[N(SiMe₂CH₂PPh₂)₂]. 10, with PHPh₂. The complex fac-Ir(ɳ²-CHPhPMe₂)H[N(SiMe₂CH₂PPh₂)₂] is generated from the reaction of Ir(CH₂Ph)Br[N(SiMe₂CH₂PPh₂)₂] with KPMe₂ without intermediacy of the corresponding phosphide complex. The photolysis of 2a-2c also yields species 4a-4c; however, no intermediacy of the cyclometallated hydride complexes 3a-3c is observed during this transformation. Upon thermolysis of the phenylphosphide complex 2d, only the corresponding iridium(I) phosphine complex, Ir(PHCH3Ph)[N(SiMe2CH2PPh2)2], 4d, is obtained, which is also the photolysis product of 2d. Ir(CH₃)PPh₂[N(SiMe₂CH₂PPh₂)₂], 2a, reacts at -78°C with dimethyl-acetylenedicarboxylate to yield an octahedral iridium(III) complex in which the alkyne has bridged between the phosphide ligand and the phosphine group of the chelating ligand. In addition, one of the phenyl groups from the chelating phosphine has migrated to the metal. On the other hand, Ir(CH₃)PMe₂[N(SiMe₂CH₂PPh₂)₂], 2c, reacts with the same alkyne to yield a product in which the alkyne has bridged between the phosphide group and the iridium centre. The reaction of 2a with diphenylacetylene affords Ir(PhC≡CPh)[N(SiMe₂CH₂PPh₂)₂] and free methyl-diphenylphosphine. Complex 2a reacts with terminal alkynes (RC≡CH; R = H, Ph, ¹Bu) to yield acetylide complexes of formula Ir(CH₃)PHPh₂(C≡CR)[N(SiMe₂CH₂PPh₂)₂]- The methylidene complex, lr=CH₂[N(SiMe₂CH₂PPh₂)₂], 10, prepared by the reaction of Ir(CH₃)I[N(SiMe₂CH₂PPh₂)₂] with KO¹Bu, reacts with phosphines PHR₂ (R = Ph, ¹Bu) to afford the cyclometallated hydride complexes, fac-Ir(ɳ²-CH₂PR₂)H[N(SiMe₂CH₂PPh₂)₂], via a five-coordinate methylidene phosphine intermediate. The reaction of 10 with PH₂Ph yields similar cyclometallated hydride product, but in this case the five-coordinate intermediate is not observed. The methylidene complex 10 reacts with the electrophiles MeI and AlMe₃ to yield Ir(ɳ²-C₂H₄)H(I)[N(SiMe₂CH₂PPh₂)₂] and Ir((µ-AlMe₂)H[N(SiMe₂CH₂PPh₂)₂], respectively. Reaction of 10 with HC≡CH affords an ɳ³˗allyl acetylide complex Ir(ɳ³-C₃H₅)(C≡CH)[N(SiMe₂CH₂PPh₂)₂]. A trimethylenemethane complex, fac-Ir{ɳ⁴-C(CH⁴₂)₃}[N(SiMe₂CH₂PPh₂)₂], is obtained readily upon exposing 10 to 1,2-propadiene. The reaction of 10 with 1,3-butadiene affords a pentenyl product, Ir(σ-ɳ³-C₅H₈)[N(SiMe₂CH₂PPh₂)₂]. In previous studies, the iridium(I) ɳ²-cyclooctene species, Ir(ɳ²-C₈H₁₄)-[N(SiMe₂CH₂PPh₂)₂], 25, has served as a useful starting material in the preparation of a number of iridium(I) and iridium(III) amide complexes. This complex is thermally stable, but upon photolysis, it yields Ir(H)₂[N(SiMe₂CH₂PPh₂)₂] and a mixture (2:1) of free 1,3-and 1,5-cyclooctadiene. This dehydrogenation process proceeds through ɳ³-allyl hydride intermediate, Ir(ɳ³-C₈H₁₃)H[N(SiMe₂CH₂PPh₂)₂]- The cyclo-octene ligand in 25 can be replaced by 1,3-butadiene and. 1,2-propadiene. The products obtained from these reactions are Ir(ɳ⁴-C₄H₆)[N(SiMe₂CH₂PPh₂)₂] and Ir(ɳ²-C₃H₄)[N(SiMe₂CH₂PPh₂)₂]. respectively. The reaction of 25 with AlMe₃ affords Ir(µ-AlMe₂)Me[N(SiMe₂CH₂PPh₂)₂]. / Science, Faculty of / Chemistry, Department of / Graduate

Mining is an important industry that plays a significant role in the development of human civilization and economies. However, the underground mining process produces a large volume of mine wastes (e.g., tailings) as well as creates large voids that require filling, typically with an engineering backfill material. Filling the voids with mine waste materials provides an environmental-friendly way of disposing mining waste. It is also an effective way of increasing ore recovery and improving the safety of miners. One of the best techniques of mine backfill is called cemented paste backfill (CPB), which is typically a mixture of tailings, binder and water. The most common binder used in the preparation of CPB is Portland cement (PC). PC is not only a costly binder, but its production is highly energy-intensive and also generates a large amount of CO2. The cement consumption can represent up to 75% of the cost of CPB. These above-mentioned factors have compelled mining companies to seek for cement alternatives that enhance the engineering properties of the CPB, decrease the cement content and reduce the carbon footprint of the mining industry. Sodium silicate is the most recent chemical additive that is proposed to reduce the binder content in CPB. Sodium silicate is an alkaline solution that is used to activate a pozzolanic material, such as cement, slag and Fly ash. However, the effect of sodium silicate on the strength and key environmental properties (permeability or saturated hydraulic conductivity, reactivity) of CPB is not well understood. The objective of this thesis is to investigate the possibility of using sodium silicate as an activator in cemented paste backfill and obtain an improvement in the aforementioned engineering properties of CPB. In order to determine the effect of the sodium silicate on backfill properties, some CPB testing methods were developed to fulfill the objectives of this research. Thus, the evolution of hydraulic, mechanical and microstructural properties of CPB samples containing sodium silicate (SS-CPB) have been tested or monitored at different curing ages (1, 3, 7, 28 and 90 days) and different CPB mixtures as well. The results of these studies show that activating CPB with sodium silicate develop CPB strength faster than CPB samples without sodium silicate. In addition, hydraulic conductivity and reactivity results show a positive change in samples containing sodium silicate compared to free sodium silicate CPB samples. Indeed, this activation leads to decreasing permeability and reactivity due to the formation of cement hydration products and acceleration of the binder hydration process. Moreover, binder type and content in the presence of sodium silicate as an alkali activator in the CPB play a significant role in lowering hydraulic conductivity and reactivity of CPB.

The new μ-(l,n)-alkanediyl compounds [(ƞ⁵-C₅R₄Me)Fe(CO)₂ ]₂{μ-(CH₂)n}, (R = H, n = 3 -10 and R =Me, n =3 - 6), [Mn(CO)₅]₂{μ-(CH₂)n} (M = Mn, n = 4-6 and M = Re, n= 3 and 4) have been prepared using essentially two synthetic routes. Thus the iron compounds were synthesized by the reaction of Na[(ƞ⁵-C₅R₄Me)Fe(CO)₂ ] with the appropriate dibromoalkane. The manganese and rhenium compounds on the other hand, were prepared by the decarbonylation of the corresponding diacyl compounds of the type, [M(CO)₅]₂{μ-CO(CH₂)nCO} (M = Mn or Re). These diacyl species in turn were synthesized by the reaction of Na[M(CO)s] with diacyl chlorides. All the new compounds have been fully characterized by microanalysis, infrared, ¹H and ¹³C nmr spectroscopy. The mass spectra of the compounds have been investigated and the fragmentation patterns are discussed and compared with other known polymethylene compounds. An extensive investigation into the reactivity of the new alkanediyl compounds has been carried out. Thus for example the reactivity of the compounds [CpFe(CO)₂]₂{μ-(CH₂)n} with nucleophiles such as tertiary phosphines and isocyanides, yield diacyl compounds of the type [CpFe(CO)L]₂{μ-CO(CH₂)nCO} (Cp = C₅H₄Me or C₅Me₅) and (L = tertiary phosphine or isocyanide). Similar ligand induced CO insertion reactions were observed for the manganese and rhenium alkanediyl compounds. The products from these reactions were characterized using the analytical techniques mentioned earlier. The reactions are discussed and compared with those of mononuclear alkyl compounds of manganese, rhenium and iron. The reactions of some polymethylene bridged compounds with synthesis gas have also been investigated. This reaction is of importance in view of the fact that polymethylene bridged compounds have been implicated in a number of catalytic processes e.g the Fischer- Tropsch reaction. The reaction with synthesis gas was found to yield bifunctional alcohols of the type HO(CH₂)nOH. In a separate study, the binuclear μ-phthaloyl compounds of manganese, rhenium,iron,molybdenum,cobalt and rhodium were prepared and characterized. The phthaloyl compounds of manganese, rhenium and iron were decarbonylated to form the corresponding μ-phenylene compounds. The reactions of some of these compounds with nucleophiles and electrophiles have been studied and the results compared with that of the corresponding mononuclear benzoyl and phenyl compounds.

Older adults may be better able to modulate their emotional experiences than younger adults, and thus may recover more quickly from negative stressors. Additionally, older adults may be more likely to experience co-occurrence of negative and positive emotions in the setting of negative stressors, which may facilitate emotion recovery. To date, few studies have investigated the nature of age group differences in spontaneous emotional responses to a standardized stressor. The current study utilizes a laboratory mood manipulation to determine age group differences in emotion recovery in negative and positive affects, as well as age group differences in the co-occurrence of negative and positive affect. Older adults reported greater reactivity in one and greater recovery in two negative affect scales than younger adults; however, these differences did not remain significant when controlling for overall arousal ratings of the mood induction. There were no age group differences in reactivity or recovery of positive affects. Both younger and older adults returned to baseline in negative affects by the end of the recovery period despite age group differences in affect responses and arousal ratings. Older adults reported greater co-occurrence of negative and positive emotions in response to the mood induction as compared to younger adults. Overall, these results provide support for age group similarities in reactivity and recovery in discrete affects, and age group differences in mixed emotion states. Greater co-occurrence appears to reflect greater baseline endorsement of positive affect in older as compared to younger adults. Thus, higher baseline positive affect may create greater opportunities for older adults to experience mixed emotion states, which may in turn serve as an adaptive resource for older adults.

No description available.

The purpose of this thesis was to determine the kinetics and stoichiometry for the aquation of the pentaaquomonobromonmethylchromium(III) complex. The complex was prepared by the reduction of dibromomethane by chromium(II). The products of aquation, in the absence of oxygen, were found to be hexaaquachromium(III), methanol, and bromide. The balanced net ionic reaction can be written: 2H2O + (H2O)5CrCH2Br2+ → (H2O)6Cr3+ + CH3OH + Br-

This investigation provides a comprehensive experimental dataset and kinetic model for biomass gasification, over a wide temperature range (1150-1350 °Ï¹) in CO2, H2O and the combination of these two reactant gases over the mole fraction ranges of 0 to 0.5 for H2O and 0 to 0.9 for CO2. The data come from a unique experimental facility that tracks continuous mass loss rates for poplar wood, corn stover and switchgrass over the size range of 6-12.5 mm. In addition, the data include char size, shape, surface and internal temperature and discrete measurements of porosity, total surface area, pore size distribution and composition. This investigation also includes several first-ever observations regarding char gasification that probably extend to char reactivity of all types and that are quantified in the model. These include: the effect of ash accumulation on the char surface slowing the apparent reaction rate, changes in particle size, porosity and density as functions of burnout, and reaction kinetics that account for all of these changes. Nonlinear least-squares regression produces optimized power-law model parameters that describe gasification with respect to both CO2 and H2O separately and in combination. A single set of parameters reasonably describes rates for all three chars. Model simulations agree with measured data at all stages of char conversion. This investigation details how ash affects biomass char reactivity, specifically the late-stage burnout. The ash contents ratios in the raw fuels in these experiments are as high as 40:1, providing a clear indication of the ash effect on the char reactivity. The experimental results definitively indicate a decrease in char reaction rate with increasing initial fuel ash content and with increasing char burnout -- most pronounced at high burnout. This investigation postulates that an increase in the fraction of the surface covered by refractory material associated with either higher initial ash contents or increased burnout decreases the surface area available for reaction and thus the observed reaction rate. A quantitative model that includes this effect predicts the observed data at any one condition within the data uncertainty and over a broad range of fuel types, particle sizes, temperatures, and reactant concentrations slightly less accurately than the experimental uncertainty. Surface area, porosity, diameter, and density predictions from standard models do not adequately describe the experimental trends. Total surface area increases slightly with conversion, with most of the increase in the largest pores or channels/vascules not measurable by standard surface area techniques but most of the surface area is in the small pores. Porosity also increases with char conversion except for abrupt changes associated with char and ash collapse at the end of char conversion. Char particle diameters decrease during these kinetically controlled reactions, in part because the reaction is endothermic and therefore proceeds more rapidly at the comparatively warmer char surface. SEM images qualitatively confirm the quantitative measurements and imply that the biomass microstructure does not appreciably change during conversion except for the large pore diameters. Extant char porosity, diameter, surface area, and related models do not predict these trends. This investigation suggests alternative models based on these measurements.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 1982 / Includes bibliographical references. / by Lynda Gail Sturgeoff. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Chemistry