Duration models are often concerned with time intervals between trades, longer durations indicating a lack of trading activities. In this thesis, we study parameter estimation for the Autoregressive Conditional Duration (ACD) and Stochastic Conditional Duration (SCD) models. Maximum likelihood methods can usually be used in the case of ACD models. However, the SCD models are based on the assumption that durations are generated by a dynamic stochastic latent variable which is often perturbed by Exponential, Weibull, Gamma or Log-Normal distributed innovations. This makes the use of maximum likelihood methods difficult. One alternative method of parameter estimation, in this case, consists in using quasi-maximum likelihood after transforming the original nonlinear model into a state-space model and using the Kalman filter, a similar filtering scheme or the Generalized Method of Moments (GMM). We use the nonlinear filter and GMM method to analyze the Quadratic Stochastic Conditional duration model as well.

Duration models are often concerned with time intervals between trades, longer durations indicating a lack of trading activities. In this thesis, we study parameter estimation for the Autoregressive Conditional Duration (ACD) and Stochastic Conditional Duration (SCD) models. Maximum likelihood methods can usually be used in the case of ACD models. However, the SCD models are based on the assumption that durations are generated by a dynamic stochastic latent variable which is often perturbed by Exponential, Weibull, Gamma or Log-Normal distributed innovations. This makes the use of maximum likelihood methods difficult. One alternative method of parameter estimation, in this case, consists in using quasi-maximum likelihood after transforming the original nonlinear model into a state-space model and using the Kalman filter, a similar filtering scheme or the Generalized Method of Moments (GMM). We use the nonlinear filter and GMM method to analyze the Quadratic Stochastic Conditional duration model as well.

Thalassaemia and sickle cell disease (SCD) are the most widely distributed blood genetic disorders that occur at a high frequency in some populations including the Mediterranean region, parts of the Middle East, South East Asia and the Indian subcontinent. It is estimated that thalassaemia major affects 100,000 newborn every year world-wide. The high incidence of these chronic haemolytic diseases in developing countries poses a high load on the national economy because of the expensive treatment protocols and the considerably high morbidity rates of these patients. Repeated blood transfusion to keep haemoglobin above an acceptable level requires well-equipped blood banks with expensive facilities to screen, store and manipulate blood and blood products. Iron chelation therapy is an essential part of treatment to avoid or delay the deleterious effects of iron overload on different organs including the liver, heart, pancreas and endocrine glands. This inquires injecting deferoxamine subcutaneously for 12 hours daily with a special pump. Both deferoxamine and pumps are expensive and therefore not accessible for all patients. In developing countries, the majority of transfusion-dependent patients with chronic haemolytic anaemia (thalassaemia and SCD) suffer from the consequences of sub-optimal treatment. The mortality rate is still high and usually patients die before the age of 30 years. They also suffer from chronic multi-organ damage including cardiac failure, liver cirrhosis, insulin-dependent diabetes mellitus, growth and pubertal failure and many skeletal abnormalities and fractures. In developed countries the introduction of high transfusion regimes and efficient chelation therapy improved survival rates and prevented cardiac and hepatic damage. However, a majority of thalassaemic patients still have significant growth and pubertal abnormalities, bone disease and multiple endocrine disorders. In Egypt the incidence of thalassaemia major ranges between 0.1 - 0.2% which gives very high patient load on the medical services. In our University of Alexandria Children's Hospital, Alexandria, Egypt. The Haematology clinic has an average of 150 thalassaemic children registered. The same problem is encountered by me in the Royal Hospital, Muscat, Oman, with high prevalence of SCD and thalassaemia and suboptimal treatment. Because of the restricted economic resources, both hospitals adopt a low transfusion therapy (to keep haemoglobin above 9 g/dl) with IM chelation 3 times per week. With this form of sub-optimal treatment we observed that a large number of our thalassaemic children have severe growth and pubertal failure/delay, beside other hepatic, cardiac and skeletal abnormalities. In fact they constitute 40% of patients attending our Endocrinology clinic. This stimulated me to perform an extensive study to survey growth and pubertal development in theses patients (study-1) and investigate the different factors that might affect their growth and pubertal development (studies 4 through 10) a \veU as bone mass density (studies > 1,12). The frequent involvement of the liver in these patients led us to study some hepatic functions and the prevalence of transfusion-associated hepatitis B surface antigenaemia and hepatitis-C virus antibody scropositivity in relation to their linear growth (studies 2,3). We studied the nutritional intake of these patients, their intestinal absorption of D-Xylosc and 48-h stool fat content in relation to their body mass index, subcutaneous 'at thickness and mid-arm circumference (studies 4,5,9). Their defective linear growth urged us to investigate their growth hormone (GH) secretion (spontaneous nocturnal as well as after provocation) and insulin-like growth factor-I (IGF-I) and IGK-binding protein-3 (IGKBl'3) concentrations. Our findings demonstrated high prevalence of defective GH secretion in these children that necessitated imaging of their hypothalamic pituitary area. Imaging studies revealed original data about structural abnormalities in the anterior pituitary gland, different degrees of pituitary atrophy and empty sella and infiltration the gland as well as the mid-brain by hacniosidrin in thalassaemic children, the mechanism of these findings was explained (studies 4-6,10). Because of their slow growth, the presence of abnormal GH/IGF-I/BP3 axis, and structural abnormalities of the pituitary gland, the next step dealt with the response of IGF-I to exogenous GH and the clinical response of their linear growth to GH therapy for a year or more (studies 4,9). Based on the fact that these patients have high prevalence of bone pains and osteoporosis during late childhood and have high risk of spontaneous fracture thereafter, we measured their bone mass density to investigate the relation between the former and the degree of iron load, growth parameters, and different anabolic hormone concentrations in these patients (studies 11,12).

The aim of this thesis is to analyze the influence of polymorphic variants of selected locus (SCD) on the technological quality of milk. At the beginning is described, milk yields along with the mammary gland - structure, diseases associated with it, colostrum and milk production. The composition of milk includes fat, fatty acids, carbohydrates, minerals, vitamins, proteins - whey protein (-lactoglobulin, -lactalbumin), casein (-casein, -casein, -casein) The thesis also deals with the genome of cattle, genetic markers, candidate loci. Methodology describes DNA isolation, PCR, including PCR for SCD, RFLP, and determination of fatty acids by spectrophotometry. At the end of the thesis are the results, which evaluate the genotypes and alleles abundance, the milk performance indicators depending on the genotype for SCD and the evaluation of the influence of the SCD genotype on the fatty acid spectrum.

No description available.

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Die vorliegende Arbeit befasst sich mit der Einflussnahme von konjugierten Linolsäuren (CLA) und strukturverwandten Fettsäuren auf Pansenepithelzellen (PEZ) in Kultur. Die in-vitro Untersuchungen mit primär kultivierten PEZ vom Schaf haben gezeigt, dass eine 48-stündige Inkubation mit CLA C18:2 cis-9, trans-11 (c9t11) und CLA C18:2 trans-10, cis-12 (t10c12) sowie Linolsäure, Ölsäure und trans-Vaccensäure (TVA) zu Veränderungen im Fettsäuremuster der Zellen sowie in der Expression der mRNA verschiedener Proteine führte. Aus den Veränderungen im Fettsäuremuster wurde die Aufnahme sowie die Metabolisierung der supplementierten Fettsäuren abgeleitet. Als wesentlicher Metabolit der TVA wurde die c9t11 identifiziert. Mit dem Nachweis der Stearoyl-CoA-Desaturase (SCD) -mRNA in den PEZ sowie im nativen Gewebe konnte so die endogene CLA-Synthese in den PEZ bestätigt werden. Analysiert wurden außerdem mittels quantitativer rt-PCR die Expression der SCD-mRNA und die mRNA von zwei Transportproteinen, den Monocarboxylat-Transportern (MCT) 1 und 4. Von beiden ist bekannt, dass sie in den Transport kurzkettiger Fettsäuren (SCFA) involviert sind. Die Inkubation mit den einzelnen Fettsäuren führte einheitlich zur Abnahme der SCD-mRNA Expression sowie zu einem verminderten Gehalt der Hauptprodukte der SCD, der C16:1 cis-9 und der C18:1 cis-9. Bezüglich der MCT1 und 4 mRNA-Expression wurde in der Regel eine Heraufregulierung nach Zugabe der Fettsäuren beobachtet. Des Weiteren wurden regulative Einflüsse von PPARα auf die MCTs und die SCD und von PPARγ auf den MCT1 und die SCD nach c9t11-Inkubation mit entsprechenden Antagonisten-Versuchen festgestellt. Die Studien beleuchten somit grundlegende Mechanismen des Stoffwechsels von langkettigen ungesättigten Fettsäuren in PEZ und deren Einflussnahme auf Transkriptionsfaktoren und auf spezifische, für den Wiederkäuer bedeutende Transportproteine für SCFA. Die funktionelle Relevanz dieser Ergebnisse für den Pansen und den Wiederkäuer aber auch für andere Gewebe und Species muss in weiteren Studien geklärt werden.:Inhaltsverzeichnis Abkürzungsverzeichnis 3 1 Einleitung 5 Allgemein 5 1.1 CLA-Nomenklatur 6 1.2 Bildung von CLAs und deren Vorkommen 7 1.3 CLA-Supplementierung beim Rind 9 1.4 Zu CLAs strukturverwandte Fettsäuren im Pansen 10 1.5 Potenzielle Wirkungen von CLAs und strukturverwandten Fettsäuren auf das Pansenepithel 11 1.5.1 Aufbau und Bedeutung des Pansenepithels 11 1.5.2 Resorption von langkettigen Fettsäuren über das Pansenepithel 11 1.5.3 Veränderungen der Fettsäurezusammensetzung nach Supplementierung 11 1.5.3.1 Metabolisierung 12 1.5.3.2 SCD und die endogene Synthese von CLA c9t11 13 1.5.4 CLA-Targets im Pansenepithel 15 1.5.4.1 SCD 15 1.5.4.2 Monocarboxylattransporter 16 1.5.4.3 PPAR als Transkriptionsfaktor für die SCD und die MCTs 19 2 Zielstellung 21 3 Originalarbeit 22 4 Ergänzung zur Originalarbeit 43 4.1 Nachweis von SCD-mRNA im nativen Pansenepithel des Schafes 43 Zusammenfassung der Arbeit 44 Literaturverzeichnis 49 Anhang (Supplemental Material) 59 Erklärung zum Eigenanteil der Dissertationsschrift 67 Erklärung über die eigenständige Abfassung der Arbeit 69 Publikationen und Vorträge im Rahmen der Dissertation 70

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

The global nature of current supply chains – in combination with disruptive events like the Covid-19 pandemic – has highlighted the need for increased supply chain resilience (SCRes). Contemporary research has primarily focused on proactive SCRes strategies and, to some degree, neglected the reactive strategies for building SCRes. As pro- and reactive measures are needed for building SCRes, the study explores how businesses employ reactive SCRes recovery strategies to handle extreme supply chain disruption (SCD).  One sector of the economy experiencing SCD as an effect of the Coronavirus is the automobile industry, which is generally used to measure international health. With the exploratory nature of the purpose and the influential role of the automobile industry, the study employed a qualitative methodology where the strategies utilized by automobile industry actors are used as the case to discover and contribute with empirical evidence for reactive SCRes strategies. The empirical data was derived through semi-structured interviews with supply chain executives from the automobile industry.  The findings indicate that companies within the automobile industry employ three main reactive SCRes strategies: communication, crisis teams, and workforce measures, to handle the adverse outcomes of the Covid-19 pandemic. Moreover, the results suggest that crucial organizational capabilities are flexibility and velocity to handle turmoil within supply chains. Furthermore, based on a holistic perspective, the study indicates that the four formative capabilities of SCRes: flexibility, velocity, visibility, and collaboration, along with pro- and reactive SCRes strategies, are interconnected. As such, all capabilities appear to be pervading in the three reactive SCRes strategies. The study, therefore, implies that all capabilities of SCRes and both pro- and reactive strategies are necessary for the development of more resilient supply chains.