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The production of advanced high strength steels (AHSS) for use in the automotive and construction industries requires complex control of runout table (ROT) cooling. Advanced high strength steels require coiling at temperatures below 500 °C in order to produce a complex multi-phase microstructure. The research described here will investigate the boiling conditions that occur for moving plate experiments when steel is cooled towards low coiling temperatures. Experiments were performed on a pilot-scale ROT located at the University of British Columbia using industrially supplied steel plates. Tests were performed for four different speeds (0.3, 0.6, 1.0 and 1.3 m/s) and three different initial plate temperatures(350, 500 and 600 °C). Each plate was instrumented with thermocouples in order to record the thermal history of the plate. The results show that cooling is more effective at slower speeds within the stagnation zone for surface temperatures over 200 °C. Outside the stagnation zone regardless of speed cooling is primarily governed by air convection and radiation with minor effects from latent heat caused by splashing water. The maximum peak heat flux value increases with decreasing speed and occurs at a surface temperature of approximately 200 °C, regardless of speed. Below a surface temperature of 200 °C, speed has a negligible effect on peak heat flux. The maximum integrated heat flux seems to vary with speed according to a second order polynomial.

The production of advanced high strength steels (AHSS) for use in the automotive and construction industries requires complex control of runout table (ROT) cooling. Advanced high strength steels require coiling at temperatures below 500 °C in order to produce a complex multi-phase microstructure. The research described here will investigate the boiling conditions that occur for moving plate experiments when steel is cooled towards low coiling temperatures. Experiments were performed on a pilot-scale ROT located at the University of British Columbia using industrially supplied steel plates. Tests were performed for four different speeds (0.3, 0.6, 1.0 and 1.3 m/s) and three different initial plate temperatures(350, 500 and 600 °C). Each plate was instrumented with thermocouples in order to record the thermal history of the plate. The results show that cooling is more effective at slower speeds within the stagnation zone for surface temperatures over 200 °C. Outside the stagnation zone regardless of speed cooling is primarily governed by air convection and radiation with minor effects from latent heat caused by splashing water. The maximum peak heat flux value increases with decreasing speed and occurs at a surface temperature of approximately 200 °C, regardless of speed. Below a surface temperature of 200 °C, speed has a negligible effect on peak heat flux. The maximum integrated heat flux seems to vary with speed according to a second order polynomial.

The production of advanced high strength steels (AHSS) for use in the automotive and construction industries requires complex control of runout table (ROT) cooling. Advanced high strength steels require coiling at temperatures below 500 °C in order to produce a complex multi-phase microstructure. The research described here will investigate the boiling conditions that occur for moving plate experiments when steel is cooled towards low coiling temperatures. Experiments were performed on a pilot-scale ROT located at the University of British Columbia using industrially supplied steel plates. Tests were performed for four different speeds (0.3, 0.6, 1.0 and 1.3 m/s) and three different initial plate temperatures(350, 500 and 600 °C). Each plate was instrumented with thermocouples in order to record the thermal history of the plate. The results show that cooling is more effective at slower speeds within the stagnation zone for surface temperatures over 200 °C. Outside the stagnation zone regardless of speed cooling is primarily governed by air convection and radiation with minor effects from latent heat caused by splashing water. The maximum peak heat flux value increases with decreasing speed and occurs at a surface temperature of approximately 200 °C, regardless of speed. Below a surface temperature of 200 °C, speed has a negligible effect on peak heat flux. The maximum integrated heat flux seems to vary with speed according to a second order polynomial. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Em metalurgia, a busca pela qualidade, baixo custo e alta produtividade têm feito empresas e institutos de pesquisa trabalharem juntos, procurando novas tecnologias que supram as necessidades do mercado. Dentre essas novas tecnologias, se destaca o processo de lingotamento contínuo de tiras de aço, utilizando o conceito de twin roll, cuja proposição inicial foi sugerida no século XIX por Henry Bessemer. Este trabalho apresenta a modelagem, análise e controle de um sistema de bobinamento de tiras de aço produzidas através de lingotamento contínuo do tipo twin roll , em uma planta localizada no Instituto de Pesquisas Tecnológicas de São Paulo. As características do processo foram primeiramente apresentadas. A modelagem matemática do sistema de bobinamento foi realizada, levando-se em consideração os componentes envolvidos no sistema. As variações paramétricas foram então evidenciadas. O sistema de controle foi primeiramente implementado utilizando-se um controlador do tipo PID, pelo fato desse tipo de controle ser altamente difundido industrialmente. Para maior precisão do sistema de controle, propôs-se a introdução de um sensor ultrasônico para medição das variações do raio de bobinamento. Por último realizou-se o projeto de um compensador robusto utilizando a metodologia LQG/LTR. Para a realização das simulações utilizou-se o programa Matlab/simulink. / In metallurgy, the quest for quality, low cost, and high productivity have resulted in companies and research institutes working together to find new technologies to satisfy the customer demand. Among these new technologies is the direct steel strip casting, using the twin roll concept suggested in the 19th century by Henry Bessemer. This work presents the modelling, analysis and control of a steel strip coiling system using twin roll direct casting, in a plant installed at the Technological Research Institute of Sao Paulo. The characteristics of the process are first introduced. The mathematic modelling of the coiling system used, take into account the system components. The parametric changes were adressed. The control system was first implemented using a PID controller as this kind of control is highly used in the industry. An ultrasonic sensor was introduced in the system to improve the control precision by coiling radius measurement. Last a robust compensator using the LQG/LTR method was designed. The simulations were done using Matlab/Simulink software.

Subarachnoid hemorrhage (SAH) is a disease with high risk of mortality and morbidity. Elderly patients have an even higher risk of poor outcome. The incidence of SAH increases with age and the elderly constitute a substantial and increasing proportion of the population. Thus, the management of elderly SAH patients is an imminent clinical challenge. Time trends in clinical management and outcome were investigated in 281 SAH patients aged ≥65 years admitted over an 18-year period. The volume of elderly patients, especially patients ≥70 years and patients in worse clinical condition increased over time. The proportion of patients with favorable outcome increased over time, without an increase in severely disabled patients. Technical results and clinical outcome of endovascular aneurysm treatment (EVT) was investigated in 62 elderly SAH patients. EVT can be performed in elderly SAH patients with high technical success, acceptable aneurysm occlusion degree, acceptable procedural complication rate, and fair outcome results. EVT was compared to neurosurgical clipping (NST) in 278 elderly SAH patients in the International Subarachnoid Aneurysm Trial. In good grade elderly SAH patients, EVT should probably be the favored treatment for internal carotid and posterior communicating artery aneurysms, while elderly patients with middle cerebral artery aneurysms appear to benefit from NST. Occurrence of secondary insults and their impact on clinical deterioration were studied in 99 patients with severe SAH. High intracranial pressure increased and high cerebral perfusion pressure decreased the risk of clinical deterioration. Elderly patients had less intracranial hypertension insults and more hypertensive, hypotensive and hypoxemic insults. Good outcome was achieved in 24% of elderly patients with severe SAH, and the proportion of severe disability was similar to that of younger patients. Patient age was not a significant predictor for vasospasm in 413 SAH patients when admission and treatment variables were adjusted for with multiple logistic regression.

Η περιέλιξη του σώματος είναι ένα φαινόμενο που συναντάται αποκλειστικά στα Γαστερόποδα και παρουσιάζει ιδιαίτερο ενδιαφέρον για τη γενετική, την εξελικτική και την αναπτυξιακή βιολογία. Η κατεύθυνση της περιέλιξης (δεξιόστροφη ή αριστερόστροφη) καθορίζεται από ένα άγνωστο γονίδιο, το οποίο παρουσιάζει μητρικό επηρεασμό. Στα περισσότερα είδη, τα άτομα αντίστροφης περιέλιξης δεν μπορούν να ζευγαρώσουν, συνεπώς η αλλαγή στην κατεύθυνση της περιέλιξης προκαλεί αναπαραγωγική απομόνωση. Η συντριπτική πλειονότητα των ειδών στο γένος Albinaria έχει αριστερόστροφη περιέλιξη. Οι μόνες δεξιόστροφες μορφές εμφανίζονται αποκλειστικά στη νότια Πελοπόννησο. Όλες οι δεξιόστροφες μορφές θεωρείται, με βάση τα μορφολογικά δεδομένα, ότι ανήκουν σε ένα είδος, το Albinaria voithii. Ωστόσο, επειδή η μορφολογική και η γενετική διαφοροποίηση στα χερσαία μαλάκια και ειδικότερα στο γένος Albinaria συχνά δείχνει αντικρουόμενα αποτελέσματα και καθώς δεν υπάρχουν στοιχεία σχετικά με τη φυλογένεση του συγκεκριμένου ζώου, δεν έχει αποσαφηνιστεί εάν όλοι οι δεξιόστροφοι πληθυσμοί συγκροτούν μία μονοφυλετική ομάδα και αν η αντιστροφή της περιέλιξης συνέβη μία ή περισσότερες φορές. Επιπλέον, πολλές φορές τα δεξιόστροφα άτομα ζουν συμπάτρια με αριστερόστροφα, αλλά σπανίως διασταυρώνονται με αυτά. Προκύπτει έτσι το ερώτημα εάν η αντιστροφή της περιέλιξης εμφανίστηκε ως ένα μέσο μείωσης της γονιδιακής ροής για να αποφευχθεί η δημιουργία υβριδίων με χαμηλή αρμοστικότητα. Σε αυτήν την εργασία ελέγξαμε εάν οι δεξιόστροφοι πληθυσμοί της Albinaria συγκροτούν μια μονοφυλετική ομάδα και εάν αντιστοίχως το φαινόμενο της αντιστροφής της περιέλιξης έχει συμβεί μία ή περισσότερες ανεξάρτητες φορές. Για το σκοπό αυτό χρησιμοποιήσαμε αριστερόστροφα και δεξιόστροφα άτομα που συλλέχθηκαν από 25 τοποθεσίες της Πελοποννήσου. Στις 10 περιοχές υπήρχαν μόνο αριστερόστροφοι αντιπρόσωποι, στις 8 μόνο δεξιόστροφοι, ενώ στις υπόλοιπες 7 περιοχές υπήρχε συμπάτρια παρουσία αριστερόστροφων και δεξιόστροφων πληθυσμών. Η εκτίμηση της γενετικής ποικιλότητας και ο προσδιορισμός των φυλογενετικών σχέσεων αυτών των πληθυσμών έγινε χρησιμοποιώντας έναν πυρηνικό (ITS1) και δύο μιτοχονδριακούς μοριακούς δείκτες (COΙ και 16S). Οι φυλογενετικές αναλύσεις του πυρηνικού και των μιτοχονδριακών δεικτών οδήγησαν στην παραγωγή δέντρων ανόμοιας τοπολογίας. Τα δέντρα των μιτοχονδριακών δεικτών έχουν τρεις δεξιόστροφους και τρεις αριστερόστροφους κλάδους, ενώ στα δέντρα του πυρηνικού υπάρχουν δύο αριστερόστροφοι κλάδοι, ένας δεξιόστροφος και ένας με αριστερόστροφα και δεξιόστροφα άτομα. Από τις φυλογενετικές αναλύσεις του πυρηνικού δείκτη συμπεραίνουμε ότι τα δεξιόστροφα άτομα δεν συγκροτούν μία μονοφυλετική ομάδα και ότι η δεξιοστροφία στο γένος Albinaria έχει εμφανιστεί ανεξάρτητα τουλάχιστον δύο φορές, καθώς τα δεξιόστροφα άτομα τοποθετούνται σε δύο διαφορετικούς κλάδους, αλλά το δεξιόστροφο αλληλόμορφο εμφανίστηκε μόνο μία φορά. Επίσης, η εμφάνιση της δεξιοστροφίας πρέπει να είναι ένα παλιό εξελικτικό γεγονός που συνέβη πριν από αρκετά εκατομμύρια χρόνια, καθώς τα συμπάτρια αριστερόστροφα και δεξιόστροφα άτομα δεν έχουν πρόσφατο κοινό πρόγονο. Ακόμα, μπορούμε να συμπεράνουμε ότι δεν υπάρχει γονιδιακή ροή ανάμεσα στα συμπάτρια δεξιόστροφα και αριστερόστροφα άτομα, επειδή αυτά τοποθετούνται σε διαφορετικούς κλάδους. Μία πιθανή ερμηνεία της τοπολογίας του δέντρου των μιτοχονδριακών δεικτών είναι ότι ο μητρικός κυτταροπλασματικός παράγοντας που καθορίζει την κατεύθυνση της περιέλιξης στο έμβρυο, πιθανώς συμπαρασύρει τη μεταβίβαση ενός τύπου μιτοχονδρίου. / Body coiling is a phenomenon occurring exclusively in gastropods and it has important implications for their genetics, evolution and development. The direction of coiling (dextral or sinistral) is determined by an unknown gene that has maternal effect. In most species, individuals with reverse coiling cannot mate, thus the inversion of coiling might cause reproductive isolation. The vast majority of species and populations in the pulmonate genus Albinaria coil sinistrally. The only dextral morphs can be found restricted in southern Peloponissos and according to their morphology they belong to a single species, Albinaria voithii. However, morphological and genetic differentiation in mollusks, (especially in genus Albinaria), often show conflicting results and since phylogenetic studies are lacking, it is not clear whether all dextral populations form a monophyletic group and if the inversion of coiling has occurred more than once. Moreover, dextral populations are often found in sympatry with sinistral ones, but rarely mate with them. Therefore, it is interesting to examine if the inversion of coiling emerged as a means to reduce gene flow and the production of unfitted hybrids. In this study we tested whether dextral populations form a monophyletic group and if the inversion of coiling occurred independently more than once. For this purpose we used dextral and sinistral individuals collected from 25 localities in Peloponissos. In 10 localities there were only sinistral populations, in 8 only dextral ones, while in the remaining 7 localities sympatric sinistral and dextral populations were found. The assessment of genetic diversity and the determination of phylogenetic relationships of these populations were performed using a nuclear (ITS1) and two mitochondrial markers (COI and 16S). Phylogenetic analyses of nuclear and mitochondrial markers produced trees with different topologies. Trees of mitochondrial markers have three dextral and three sinistral clades, whereas the trees of nuclear marker have two sinistral clades, one dextral and one clade with both sinistral and dextral individuals. From the phylogenetic analyses of the nuclear marker we can conclude that dextral individuals do not form a monophyletic group and that dextrality has evolved independently at least twice within the genus Albinaria, as dextral individuals are placed in two different clades. However, it seems that the dextral allele appeared only once. Also, the evolution of dextrality must be an old evolutionary event that occurred before several million years, because sympatric sinistral and dextral individuals do not share a recent common ancestor. Moreover, we can conclude that there is no gene flow between sympatric dextral and sinistral individuals because they are placed in different clades. A possible scenario that explains the topology of the tree of mitochondrial markers is that the maternal cytoplasmic factor that determines the direction of coiling in the embryo probably causes the inheritance of mitochondria of a certain type.

The umbilical cord, the most important connection between fetus and placenta, which is re-sponsible for the development and maintenance of the intrauterine life, consists of a spiral structure whose blood vessels carry nutrients from mother to fetus, and catabolites from fetus to mother. Studies on number of coiling on the umbilical cord have not been relevant in the current literature. In other words, this funicular parameter is undervalued by the specialist medical community. However, some studies show an association between umbilical cord coiling and adverse perinatal outcomes. This is an analytical cross-sectional study aimed to assess the umbilical cord coiling index (UCI) during the postpartum period, and relate the UCI with perinatal outcomes in pregnant women admitted to have their births at HUSM, from June to October, 2012. A coil was defined as a complete 360 degree spiral course of the umbilical vessels around the Wharton s jelly. The UCI was defined by being the relation between the number of spirals and the length of the cord, and the values found between the 10th and 90th percentile were considered as within the limits of normality. For values under P10, the umbilical cord was hypocoiled and over P90, hypercoiled. Two hundred fifty two placentas and their cords were evaluated, but 179 births were considered for the analysis of perinatal outcomes. The average UCI was 0.17 ± 0.86 coils/cm while the hypocoiling (UCI<0.05 coils/cm) and hypercoiling (UCI> 0.28 coils/cm) represented 8.4% (n = 21) and 8.8% (n = 22) respectively. There was a significant correla-tion between the UCI and the Apgar score at 1 and 5 minute (p <0.05). Among preterm newborns, 26.3% had abnormal coiling. Among small for gestational age (SGA) 26,6% had abnormal coiling too. Only one death occurred in utero and the umbilical cord was hypercoiled (UCI = 0.42 coils/cm). There was no correlation or association between the IEC and other perinatal outcomes, such as meco-nium staining amniotic fluid, fetal distress, intrauterine growth restriction (IUGR), neonatal intensive care unit (NICU) admission and neonatal death. The results allow to conclude that the UCI can relate to adverse perinatal outcomes, although few of them in this study had statistical significance, which may be attributed to the sample size, addressing the need for further study on the subject. / O cordão umbilical, conexão mais importante entre o feto e a placenta, a qual é responsável pelo desenvolvimento e manutenção da vida intrauterina, consiste numa estrutura espiralada cujos vasos sanguíneos transportam nutrientes da mãe para o feto e catabólitos do feto para a mãe. Estudos sobre o número de espirais do cordão umbilical não têm tido relevância na literatura atual, ou seja, este parâmetro funicular é pouco valorizado pela comunidade médica especializada. No entanto, alguns estudos evidenciam a associação entre o espiralamento e os desfechos adversos perinatais. O objetivo deste estudo, transversal e analítico, foi o de avaliar o Índice de Espiralamento do Cordão umbilical (IEC) após o parto e relacioná-lo com desfechos perinatais nas gestantes admitidas para parto no Hospital Universitário de Santa Maria entre junho e outubro de 2012. Uma espiral foi definida como uma volta completa do cordão em torno da geleia de Warton. O IEC foi definido como a relação entre o número de espirais e o comprimento do cordão umbilical, sendo que os valores encontrados entre os percentis 10 e 90 foram considerados dentro dos limites de normalidade. Para valores abaixo do P10, o cordão umbilical era hipoespiralado e acima do P90, hiperespiralado. Foram avaliadas 252 placentas e seus cordões, sendo que, para a análise dos desfechos perinatais, 179 nascimentos foram considerados. O IEC médio foi de 0,17±0,86 espirais/cm, enquanto o hipoespiralamento (IEC<0,05 espirais/cm) e o hiperespiralamento (IEC>0,28 espirais/cm) representaram 8,4% (n=21) e 8,8% (n=22) respectivamente. Houve correlação significante entre o IEC e o índice de Apgar de primeiro e de quinto minuto (p<0,05). Dos recém-nascidos pré-termo, 26,3% tinham um IEC anormal, assim como 26,6% dos pequenos para a idade gestacional. No único óbito ocorrido in útero, o cordão era hiperespiralado (IEC=0,42 espirais/cm). Não houve correlação ou associação entre o IEC e outros desfechos perinatais, tais como presença de mecônio no líquido amniótico, sofrimento fetal agudo, crescimento intrauterino restrito, internação em UTI neonatal e óbito neonatal. Os resultados permitem concluir que o IEC pode se relacionar a desfechos perinatais adversos, embora no presente estudo poucos deles tivessem significância estatística, fato que pode ser atribuído ao tamanho da amostra estudada, o que remete para a necessidade de novos estudos a respeito.

Em metalurgia, a busca pela qualidade, baixo custo e alta produtividade têm feito empresas e institutos de pesquisa trabalharem juntos, procurando novas tecnologias que supram as necessidades do mercado. Dentre essas novas tecnologias, se destaca o processo de lingotamento contínuo de tiras de aço, utilizando o conceito de twin roll, cuja proposição inicial foi sugerida no século XIX por Henry Bessemer. Este trabalho apresenta a modelagem, análise e controle de um sistema de bobinamento de tiras de aço produzidas através de lingotamento contínuo do tipo twin roll , em uma planta localizada no Instituto de Pesquisas Tecnológicas de São Paulo. As características do processo foram primeiramente apresentadas. A modelagem matemática do sistema de bobinamento foi realizada, levando-se em consideração os componentes envolvidos no sistema. As variações paramétricas foram então evidenciadas. O sistema de controle foi primeiramente implementado utilizando-se um controlador do tipo PID, pelo fato desse tipo de controle ser altamente difundido industrialmente. Para maior precisão do sistema de controle, propôs-se a introdução de um sensor ultrasônico para medição das variações do raio de bobinamento. Por último realizou-se o projeto de um compensador robusto utilizando a metodologia LQG/LTR. Para a realização das simulações utilizou-se o programa Matlab/simulink. / In metallurgy, the quest for quality, low cost, and high productivity have resulted in companies and research institutes working together to find new technologies to satisfy the customer demand. Among these new technologies is the direct steel strip casting, using the twin roll concept suggested in the 19th century by Henry Bessemer. This work presents the modelling, analysis and control of a steel strip coiling system using twin roll direct casting, in a plant installed at the Technological Research Institute of Sao Paulo. The characteristics of the process are first introduced. The mathematic modelling of the coiling system used, take into account the system components. The parametric changes were adressed. The control system was first implemented using a PID controller as this kind of control is highly used in the industry. An ultrasonic sensor was introduced in the system to improve the control precision by coiling radius measurement. Last a robust compensator using the LQG/LTR method was designed. The simulations were done using Matlab/Simulink software.

Ammonoids were collected from the Chainman Formation (Mississippian) of southeastern Nevada and southwestern Utah, the Phosphoria Formation (Permian) of southeastern Idaho and westernmost Wyoming, and the Thaynes Formation (Triassic) of northeastern Nevada and southeastern Idaho. The collections are interpreted to represent unwinnowed, untransported death assemblages of ammonoids which were subject to chemical conditions of the nekto-benthic environment. Associated lithologies were sampled and geochemically analyzed for content of phosphate and organic matter. Ammonoid fossil collections, combined with ammonoids ilustrated in the literature, were subjected to the graphical W and D analysis of Raup (1967). The basic parameteres involved in the description of shell-coiling geometry are whorl expansion rate, W, and the distance of the generating curve from the axis of coiling of the shell, D. Values of W determined range from 1.32 to 3.96, which correspond to slight and rapid increases in whorl height during coiling. Values of D determined range from 0.02 to 0.55, which correspond to extremes of involute and evolute coiling· geometries, respectively. Body chamber length corresponds with shell coiling geometry. Values determined in this study range from 10° to 540°. Corresponding W values are 3.96 and 1.50, whereas corresponding D values are 0.02 and 0.40, respectively. Average body chamber length in analyzed ammonoids is observed to decrease from 297° to 209° from Mississippian to Triassic time. Increase in apertural area accompanied this trend, and a possible consequence was that a greater range of prey sizes was afforded ammonoids with shorter body chambers. Life-orientation, described as the angle between the apertural plane and the gravitational vector, is calculated entirely on shell form and other geometrical considerations. Recent observations concerning Nautilus, combined with fossil evidence of epizoan encrustation suggest that ammonoids had an ability to control orientation, which is not observed from preservable morphology. From Mississippian to Triassic time, no trends in reconstructed life-orientation can be substantiated, based solely on Wand D values. Rotational stability during directed locomotion is important for conservation of the energy budget of this nektonic carnivorous organ­ ism. This property is calculated by the distance between the center of buoyancy and the center of gravity of the ammonoid. Values deter­ mined range from .04 (very unstable) to .16 (very stable). Corres­ ponding W values are 1.50 and 4.00 where corresponding D values are 0.20 and 0.02, respectively. A trend toward increasing average rota­tional stability (.07 to .10) is noted for amrnonoids from Mississippian to Triassic time. Efficiency in the utilization of calcium carbonate is the ratio of internal volume of the shell to volume of shell material. Values determined range from 5.80 to 7.25. Corresponding W values are 4.00 and 1.50, corresponding D values are 0.02 and 0.54, respectively. Abundant ammonoids found in black, phosphatic limestones rich in organic matter have an average efficiency value of 6.2. Abundant ammonoids from corresponding light-colored crystalline carbonates have an average efficiency value of 6.02, and indicate no correlation between effi­ciency and abundance. Size-frequency distributions are utilized in recognition of oppor­tunistic species of ammonoids. High numerical abundance, high mortality rate of juveniles, small size and conservation of calcium carbonate typifies the paleo-opportunistic species Cravenoceras, Psuedogastrio­ceras and Ophiceras. Biovolume-relative abundance distributions are useful in discerning the carrying capacity of the habitat both in number of individuals and species diversity. A large area under the biovolume-relative abun­dance profile indicates diversification under optimum environmental conditions; a small area under the profile indicates colonization of a stressful habitat. The Chainman, Phosphoria and Thaynes (Columbites Zone) Formations have ammonoid assemblages which show small areas under the biovolume-relative abundance profile, characteristic of anoxic environmental stress. The Permian stratigraphic units correlative with the Phosphoria Formation have ammonoid assemblages which show large areas under the profile and the associated lithologies, i.e., light­ gray,crystalline carbonates, suggest environments which could support a diversified ammonoid fauna, including large-sized species. Ontogenetic variation produces changes in the body chamber length, life orientation, rotational stability, and utilization of calcium carbonate of the analyzed genera of ammonoids. These ontogenetic variations usually resulted in the development of more involute shell-coiling geometries. Corresponding size-frequency distributions suggest increased mortality rates during ontogeny for some genera (Paracravenoceras, Medlicottia) which show decreasing efficiency in the utilization of calcium carbonate. (182 pages)