This study is an investigation into the relationship between numeric cognition and aging. Specifically, older and younger adults engaged in an experimental protocol that allowed observation of number comparison accuracy and response time latencies associated with the SNARC effect, the distance effect, and number format. The experimental protocol featured a computerized magnitude comparison task wherein the participants were prompted to identify the larger of two numbers. Half of the trials featured whole numbers and half featured fractions. The number stimuli were consistently mapped such that half of all trials were at near distance (i.e., difference of 2) or far distance (i.e., difference of 4) and half of all trials had the larger numerosity on the left side of space and the other half with the larger numerosity on the right side of space. Older adults were significantly slower and less accurate than young adults. Both age groups were significantly slower and less accurate when comparing fractions as opposed to comparing whole numbers. The SNARC effect impaired accuracy in both age groups but did not significantly impact response times. The distance effect impacted both age cohorts in accuracy but differentially impacted older adult response times more than young adult response times. The results of this study support the model of numeric cognition as an automatic process when comparing whole numbers at a far distance and this process is not disrupted by the SNARC effect but is when comparing whole numbers at near distance. The results also indicate that fraction comparison is a controlled process even when the fraction stimuli are consistently mapped. Further investigation is necessary to understand the amount of cognitive resources necessitated by fraction processing and if training can improve fraction comparison.

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There is emerging concern about the potential for elevated lead in water after water utilities conduct EPA mandated (or voluntary) partial replacements of existing lead service lines. Connections between dissimilar metals results in the accelerated corrosion of the less noble metal via galvanic attack, increasing metal concentrations in water and posing potential public health risks. Many practical problems associated with stopping galvanic attack between copper:galvanized iron and copper:lead via use of dielectrics have also been raised. Galvanic corrosion can be effectively stopped by isolating the dissimilar metals; however, completely eliminating electrical continuity may not always be practical or allowed by code. Instead, increasing separation distance between the two metals was hypothesized to considerably reduce galvanic corrosion. Galvanic corrosion and lead leaching were evaluated for lead:copper connections with varying separation distances while maintaining electrical continuity. Increased distance between lead and copper pipe dramatically reduced the galvanic current and the magnitude of lead release. Galvanized iron and copper connections were also investigated using various commercial fittings, and results verified that a controlling factor was separation distance between the two dissimilar metals. When considering the long-term behavior of partially replaced lead service lines, detrimental effects from galvanic corrosion worsened with time. Even when water was sampled consistently at moderate flow rate, the condition representing traditional partial service line replacement was 40% worse than a full lead service line. At elevated flowrates, lead concentrations and variability increased for partly replaced lead pipe versus full lead pipe due to reservoirs of lead rust formed via galvanic corrosion. At low flowrates, these negative impacts were not observed. Finally, crevices formed by the use of commercial couplings increased lead release. Overall, the results enhance practical understanding of galvanic corrosion impacts and use of dielectrics in water service lines and premise plumbing. / Master of Science

Numbers convey different meanings when used in different contexts (Wiese, 2003). In a cardinal context, a number will tell us how many entities are in a set and convey quantity meaning. In an ordinal context, a number will refer to the relative position (or rank) of one element within a sequence; non-numerical ordered series (e.g. the letters of the alphabet) can also be used to provide meaningful order information. Because quantity and order are linked up with each other in the cognitive number domain (the larger the quantity a number refers to, the later it is located in the conventional number sequence), the question of whether they rely on some common or distinct underlying mechanism(s) is theoretically relevant and was addressed in the present thesis. Experimental studies showed evidence of both similarities (similar distance and SNARC effects, recruitment of parietal and frontal regions, and conjoint impairment or preservation after brain damage) and dissociations (different developmental course, dissociation after cerebral lesion, and specific behavioural markers) between quantity and order neuro-functional processes. The aim of the present thesis was to clarify the relationship between numerical quantity and order processing and to test the hypothesis that they rely on (at least partially) dissociated mechanisms. We tested this hypothesis in a single case study, an electrophysiological study and in two behavioural experiments. In the neuropsychological study, we reported the case of patient CO, who showed Gerstmann syndrome after bilateral parietal damage and became unable to process sequence order relations (e.g. he couldn't recite the number sequence backwards, nor decide whether a number, letter, day or month comes before or after a given target in the corresponding sequence, and he was unable to verify the order of items in a pair). Nonetheless, the patient had largely preserved quantity processing abilities (he could compare numbers and dot patterns to find the smaller or larger, and showed a standard distance effect, he could produce a number smaller or larger than a given target, and match dot patterns with Arabic numerals). Overall, CO's pattern of performance was interpreted as reflecting the involvement of different mechanisms when processing quantity or sequence order relations. Our electrophysiological study corroborated this finding since different spatio-temporal patterns of the distance effect were observed when subjects had to process numbers in a quantity comparison task or in an order judgment task. Quantity processing elicited an early distance effect over the P2p component on left parietal sites, whereas the distance effect was slightly delayed and bilaterally distributed in the numerical order judgment task; and this latter task additionally recruited prefrontal regions on a later (P3-counterpart) component. Finally, our behavioural study further emphasized the involvement of different mechanisms underlying the processing of quantity and numerical order and provided some evidence about the nature of these specific mechanisms. In the number comparison (quantity) task, the standard distance effect was proposed to reflect the involvement of a magnitude comparison mechanism; whereas the reverse distance effect observed in the numerical order verification task was taken as evidence for the recruitment of a serial search (recitation) process. Besides, the pair-order effect was also found to specifically affect order but not quantity judgments. Taken together, the data collected in the present thesis lend further support to the hypothesis that quantity and numerical order rely on distinct processing mechanisms that can be damaged selectively after cerebral lesions, that recruit similar brain areas but with a different spatio-temporal course and that show specific behavioural markers.

Numbers convey different meanings when used in different contexts (Wiese, 2003). In a cardinal context, a number will tell us how many entities are in a set and convey quantity meaning. In an ordinal context, a number will refer to the relative position (or rank) of one element within a sequence; non-numerical ordered series (e.g. the letters of the alphabet) can also be used to provide meaningful order information. Because quantity and order are linked up with each other in the cognitive number domain (the larger the quantity a number refers to, the later it is located in the conventional number sequence), the question of whether they rely on some common or distinct underlying mechanism(s) is theoretically relevant and was addressed in the present thesis. Experimental studies showed evidence of both similarities (similar distance and SNARC effects, recruitment of parietal and frontal regions, and conjoint impairment or preservation after brain damage) and dissociations (different developmental course, dissociation after cerebral lesion, and specific behavioural markers) between quantity and order neuro-functional processes. The aim of the present thesis was to clarify the relationship between numerical quantity and order processing and to test the hypothesis that they rely on (at least partially) dissociated mechanisms. We tested this hypothesis in a single case study, an electrophysiological study and in two behavioural experiments. In the neuropsychological study, we reported the case of patient CO, who showed Gerstmann syndrome after bilateral parietal damage and became unable to process sequence order relations (e.g. he couldn't recite the number sequence backwards, nor decide whether a number, letter, day or month comes before or after a given target in the corresponding sequence, and he was unable to verify the order of items in a pair). Nonetheless, the patient had largely preserved quantity processing abilities (he could compare numbers and dot patterns to find the smaller or larger, and showed a standard distance effect, he could produce a number smaller or larger than a given target, and match dot patterns with Arabic numerals). Overall, CO's pattern of performance was interpreted as reflecting the involvement of different mechanisms when processing quantity or sequence order relations. Our electrophysiological study corroborated this finding since different spatio-temporal patterns of the distance effect were observed when subjects had to process numbers in a quantity comparison task or in an order judgment task. Quantity processing elicited an early distance effect over the P2p component on left parietal sites, whereas the distance effect was slightly delayed and bilaterally distributed in the numerical order judgment task; and this latter task additionally recruited prefrontal regions on a later (P3-counterpart) component. Finally, our behavioural study further emphasized the involvement of different mechanisms underlying the processing of quantity and numerical order and provided some evidence about the nature of these specific mechanisms. In the number comparison (quantity) task, the standard distance effect was proposed to reflect the involvement of a magnitude comparison mechanism; whereas the reverse distance effect observed in the numerical order verification task was taken as evidence for the recruitment of a serial search (recitation) process. Besides, the pair-order effect was also found to specifically affect order but not quantity judgments. Taken together, the data collected in the present thesis lend further support to the hypothesis that quantity and numerical order rely on distinct processing mechanisms that can be damaged selectively after cerebral lesions, that recruit similar brain areas but with a different spatio-temporal course and that show specific behavioural markers.

Patient survival post liver transplant (LT) is important to both the patient and the center's accreditation, but over the years physicians have noticed that distant patients struggle with post LT care. I hypothesized that patient's distance from the transplant center had a detrimental effect on post LT survival. I suspected Hepatitis C (HCV) and Hepatocellular Carcinoma (HCC) patients would deteriorate due to their recurrent disease and there is a need for close monitoring post LT. From the current literature it was not clear if patients' distance from a transplant center affects outcomes post LT. Firozvi et al. (Firozvi AA, 2008) reported no difference in outcomes of LT recipients living 3 hours away or less. This study aimed to examine outcomes of LT recipients based on distance from a transplant center. I hypothesized that the effect of distance from a LT center was detrimental after adjusting for HCV and HCC status. Methods: This was a retrospective single center study of LT recipients transplanted between 1996 and 2012. 821 LT recipients were identified who qualified for inclusion in the study. Survival analysis was performed using standard methods as well as a newly developed Monte Carlo (MC) approach for change point detection. My new methodology, allowed for detection of both a change point in distance and a time by maximizing the two parameter score function (M2p) over a two dimensional grid of distance and time values. Extensive simulations using both standard distributions and data resembling the LT data structure were used to prove the functionality of the model. Results: Five year survival was 0.736 with a standard error of 0.018. Using Cox PH it was demonstrated that patients living beyond 180 miles had a hazard ratio (HR) of 2.68 (p-value<0.004) compared to those within 180 miles from the transplant center. I was able to confirm these results using KM and HCV/HCC adjusted AFT, while HCV and HCC adjusted LR confirmed the distance effect at 180 miles (p=0.0246), one year post LT. The new statistic that has been labeled M2p allows for simultaneous dichotomization of distance in conjunction with the identification of a change point in the hazard function. It performed much better than the previously available statistics in the standard simulations. The best model for the data was found to be extension 3 which dichotomizes the distance Z, replacing it by I(Z>c), and then estimates the change point c and tau. Conclusions: Distance had a detrimental effect and this effect was observed at 180 miles from the transplant center. Patients living beyond 180 miles from the transplant center had 2.68 times the death rate compared to those living within the 180 mile radius. Recipients with HCV fared the worst with the distance effect being more pronounced (HR of 3.72 vs. 2.68). Extensive simulations using different parameter values in both standard simulations and simulations resembling LT data, proved that these new approaches work for dichotomizing a continuous variable and finding a point beyond which there is an incremental effect from this variable. The recovered values were very close to the true values and p-values were small.

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Cette thèse s’appuie sur une base de données que j’ai constituée. Cette base de donnée regroupe des statistiques commerciales, des PIB, des taux des change et des tariffs douaniers, mais aussi des variables couramment utilisées dans les études basées sur le modèle de gravité : distance, liens coloniaux et linguistiques. Dans le chapitre 2, je montre que la mondialisation du dix-neuvième siècle avait déjà débuté vers 1840 en Europe, alors qu’elle a seulement commencé à la fin du siècle pour le reste du monde. Dans le chapitre 3, je montre que l’effet frontière a été réduit de moitié pendant la Première et pendant la Seconde mondialisation. Je montre aussi que l’effet de la distance a approximativement doublé dans le même temps. Dans le chapitre 4, je montre que l’élasticité du commerce aux couts de commerce (i.e. trade elasticity) n’a pas changé de manière significative entre le début et la fin du dix-neuvième siècle. Dans le chapitre 5, je montre que la Grande Bretagne a bénéficié de la plus grande part de l’effet de création de commerce du au canal de Suez, alors que la cote occidentale de l’Amérique Latine a bénéficié d’environ 40% de l’effet sur le commerce du canal de Panama. Je montre aussi que les estimations de l’élasticité de la distance dans la dimension temporelle rendent possible de réconcilier l’élasticité de la distance avec les estimations communes de ses composants : l’élasticité du commerce aux couts de commerce et l’élasticité des couts de commerce à la distance maritime. / This thesis relies on a data set that I put together. The data set gathers trade statistics, GDP, exchange rate and tariff data as well as gravity-related variables including distance, colonial and linguistic links. In chapter 2, I show that the globalization of the nineteenth century had already begun in the 1840s in Europe, while it only began in the late nineteenth century for the rest of the world. In chapter 3, I show that the border effect was halved over the course of both the First and the Second Globalization. I also find that the distance effect roughly doubled during both periods of globalization. In chapter 4, I show that the trade elasticity did not change significantly over the course of the First Globalization. In chapter 5, I show that Britain benefited from most of the trade creating effect of the Suez Canal, while the western coast of Latin America benefited from about 40% of the trade effect of the Panama Canal. I also show that time dimension estimates of the distance elasticity make it possible to reconcile the distance elasticity with the common estimates for its components: the trade elasticity and the elasticity of trade costs to shipping distance.

This dissertation is based on the Kida-Smith (1995) model of "The encoding and retrievability of numerical data." It is concerned with the variable conditions under which a positive affective response (i.e., a decision or opinion that results in a positive valence) on previously viewed accounting information may and may not influence current decision-making. An affective response to accounting numbers may adversely influence decisions made based on those numbers. Prior research has found that individuals recall information that is consistent with prior decisions more readily than they recall inconsistent information. Research has also shown that current judgements are biased toward prior decisions or judgements. These biases may cause current decisions to be suboptimal or dysfunctional. Two 2x2 experiments were conducted to examine four hypotheses. These hypotheses concerned (1) the influence of an affective response on an investment decision when the differences between two sets of accounting numbers are small and when the differences are large, (2) the influence of an affective response on the recall of numerical data, (3) the influence of time on the recall of numerical data given an affective response, and (4) the influence of an affective response on an investment decision when the level of cognitive processing at the time the affective response is produced is low and when the level of processing is high. The first experiment used graduate students in an accounting course to investigate the influence of differences between numerical amounts on decision making. It also investigated the influence of time between the encoding and retrieval on recall of numerical amounts. The second experiment used accounting practitioners to investigate the influence of differences between numerical amounts on decision making, and to examine the influence of different levels of cognitive processing at the time of encoding on decision making. Results indicate that an affective response does produce suboptimal decisions. In the case of accounting practitioners, however, the influence of the affective response is mitigated when the magnitude of the difference between the accounting numbers previously viewed and those undergoing current examination is large rather than small. The affective response did not significantly influence the recall of numerical amounts. There was no significant change in the influence of the affective response on recalled amounts with increased time between encoding and retrieval. Also, there were no significant changes in decision-making with increased processing at the time of encoding. / Ph. D.

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