Pine sandhill are integral pyrogenic communities in the southeastern United States. Though once widespread, habitat destruction, fire suppression and fragmentation have reduced the population to nearly 3%. It is important to learn as much as possible about these unique areas in order to implement best management practices to conserve and restore the existing populations of these communities. Fire is central to the maintenance of pine sandhill communities and two conceptual hypothesis regarding burn frequency have come to light in maintaining the unique species composition and richness of these areas. The first is the Intermediate Disturbance Hypothesis which suggests that intermediate fire regime maintains species diversity. The second is the Most Frequent Fire Hypothesis suggests that these areas should be burned as frequently as fuels allow. We used species area curves and species area relationships to answer the following questions about a pine sandhill community in the burn plot area of the University of South Florida Ecological Research Area (ERA). What are the patterns of species richness and how do they change with spatial scale? What are the factors contributing to the heterogeneity of this area and how much are they contributing? Do similarly burned areas have similar species composition? Do our results shed some light on the Intermediate Disturbance Hypothesis or Most Frequent Fire Hypothesis? We found that physical distance contributed more to species compositional and spatial patterns than burn regime or elevation, whose effects were small. On this particular scale, the results did not support either the Intermediate Disturbance Hypothesis or Most Frequent Fire Hypothesis, as acquisition rates of species in all burn regimes were quite similar. There was no obvious pattern of increased species richness with frequent or intermediate burning. Our results suggest a need for a dynamic plan for the conservation, preservation and management of pine sandhill communities. One must consider as many factors as possible when managing these lands, as every sandhill is unique. More research should be conducted on these ecologically sensitive and diminished areas in order to formulate best management practices to conserve, protect and restore pine sandhill in the southeastern United States.

Many software reliability growth models have beenanalyzed for measuring the growth of software reliability. In this dissertation, regression methods are explored to study software reliability models. First, two parametric linear models are proposed and analyzed, the simple linear regression and transformed linearregression corresponding to a power law process. Some software failure data sets do not follow the linear pattern. Analysis of popular real life data showed that these contain outliers andleverage values. Linear regression methods based on least squares are sensitive to outliers and leverage values. Even though the parametric regression methods give good results in terms of error measurement criteria, these results may not be accurate due to violation of the parametric assumptions. To overcome these difficulties, nonparametric regression methods based on ranks are proposed as alternative techniques to build software reliability models. In particular, monotone regre ssion and rank regression methods are used to evaluate the predictive capability of the models. These models are applied to real life data sets from various projects as well as to diverse simulated data sets. Both the monotone and the rank regression methods are robust procedures that are less sensitive to outliers and leverage values. In particular, the regression approach explains predictive properties of the mean time to failure for modeling the patterns of software failure times.In order to decide on model preference and to asses predictive accuracy of the mean time between failure time estimates for the defined data sets, the following error measurements evaluative criteria are used: the mean square error, mean absolute value difference, mean magnitude of relative error, mean magnitude oferror relative to the estimate, median of the absolute residuals, and a measure of dispersion. The methods proposed in this dissertation, when applied to real software failure data, give lesserror in terms of all the measurement criteria compared to other popular methods from literature. Experimental results show that theregression approach offers a very promising technique in software reliability growth modeling and prediction.

Recommendation systems are emerging as an important business application as the demand for personalized services in E-commerce increases. Collaborative filtering techniques are widely used for predicting a user's preference or generating a list of items to be recommended. In this thesis, we develop several new approaches for collaborative filtering based on model combination and kernel smoothing. Specifically, we start with an experimental study that compares a wide variety of CF methods under different conditions. Based on this study, we formulate a combination model similar to boosting but where the combination coefficients are functions rather than constant. In another contribution we formulate and analyze a local variation of matrix factorization. This formulation constructs multiple local matrix factorization models and then combines them into a global model. This formulation is based on the local low-rank assumption, a slightly different but more plausible assumption about the rating matrix. We apply this assumption to both rating prediction and ranking problems, with both empirical validations and theoretical analysis. We contribute with this thesis in four aspects. First, the local approaches we present significantly improve the accuracy of recommendations both in rating prediction and ranking problems. Second, with the more realistic local low-rank assumption, we fundamentally change the underlying assumption for matrix factorization-based recommendation systems. Third, we present highly efficient and scalable algorithms which take advantage of parallelism, suited for recent large scale datasets. Lastly, we provide an open source software implementing the local approaches in this thesis as well as many other recent recommendation algorithms, which can be used both in research and production.

The chapters of this thesis focus two different issues that arise in clinical trials and propose novel methods to address them. The first issue arises in the analysis of data with non-ignorable missing observations. The second issue concerns the development of methods that provide physicians better tools to understand and treat diseases efficiently by using each patient's characteristics and personal biomedical profile. Inherent to most clinical trials is the issue of missing data, specially those that arise when patients drop out the study without further measurements. Proper handling of missing data is crucial in all statistical analyses because disregarding missing observations can lead to biased results. In the first two chapters of this thesis, we deal with the "worst-rank score" missing data imputation technique in pretest-posttest clinical trials. Subjects are randomly assigned to two treatments and the response is recorded at baseline prior to treatment (pretest response), and after a pre-specified follow-up period (posttest response). The treatment effect is then assessed on the change in response from baseline to the end of follow-up time. Subjects with missing response at the end of follow-up are assign values that are worse than any observed response (worst-rank score). Data analysis is then conducted using Wilcoxon-Mann-Whitney test. In the first chapter, we derive explicit closed-form formulas for power and sample size calculations using both tied and untied worst-rank score imputation, where the worst-rank scores are either a fixed value (tied score) or depend on the time of withdrawal (untied score). We use simulations to demonstrate the validity of these formulas. In addition, we examine and compare four different simplification approaches to estimate sample sizes. These approaches depend on whether data from the literature or a pilot study are available. In second chapter, we introduce the weighted Wilcoxon-Mann-Whitney test on un-tied worst-rank score (composite) outcome. First, we demonstrate that the weighted test is exactly the ordinary Wilcoxon-Mann-Whitney test when the weights are equal. Then, we derive optimal weights that maximize the power of the corresponding weighted Wilcoxon-Mann-Whitney test. We prove, using simulations, that the weighted test is more powerful than the ordinary test. Furthermore, we propose two different step-wise procedures to analyze data using the weighted test and assess their performances through simulation studies. Finally, we illustrate the new approach using data from a recent randomized clinical trial of normobaric oxygen therapy on patients with acute ischemic stroke. The third and last chapter of this thesis concerns the development of robust methods for treatment groups identification in personalized medicine. As we know, physicians often have to use a trial-and-error approach to find the most effective medication for their patients. Personalized medicine methods aim at tailoring strategies for disease prevention, detection or treatment by using each individual subject's personal characteristics and medical profile. This would result to (1) better diagnosis and earlier interventions, (2) maximum therapeutic benefits and reduced adverse events, (3) more effective therapy, and (4) more efficient drug development. Novel methods have been proposed to identify subgroup of patients who would benefit from a given treatment. In the last chapter of this thesis, we develop a robust method for treatment assignment for future patients based on the expected total outcome. In addition, we provide a method to assess the incremental value of new covariate(s) in improving treatment assignment. We evaluate the accuracy of our methods through simulation studies and illustrate them with two examples using data from two HIV/AIDS clinical trials.

The numerical solution of Stein (aka discrete Lyapunov) equations is the primary step in Newton's method for the solution of discrete-time algebraic Riccati equations (DARE). Here we present a low-rank Smith method as well as a low-rank alternating-direction-implicit-iteration to compute low-rank approximations to solutions of Stein equations arising in this context. Numerical results are given to verify the efficiency and accuracy of the proposed algorithms.

Σκοπός: Πρόσφατα δεδομένα, υποδεικνύουν ότι διαταραχή της ισορροπίας του λιπιδικού μεταβολισμού επηρεάζει τη λειτουργία των κυττάρων του οστού, με αποτέλεσμα την ανάπτυξη εκφυλιστικών και μεταβολικών νόσων, όπως η οστεοπόρωση. Στην παρούσα εργασία, μελετήσαμε τον ρόλου της απολιποπρωτεΐνης Ε (apoE), βασικού συστατικού του συστήματος μεταβολισμού των χυλομικρών και της VLDL (Very Low-Density Lipoprotein), στη ρύθμιση της οστικής ανακατασκευής και στην παθογένεια της οστεοπόρωσης, σε πειραματικά μοντέλα ποντικιών που έλαβαν δίαιτα πλούσια σε λιπαρά. Υλικά και μέθοδοι: Για τον λόγο αυτό, χρησιμοποιήσαμε μοντέλα ποντικών με έλλειψη του γονιδίου της apoE (apoE-/-) και αγρίου τύπου (C57BL/6) (ομάδα ελέγχου) που τους χορηγήθηκε για 24 εβδομάδες δίαιτα δυτικού τύπου (WTD) πλούσια σε λιπαρά (10 ζώα/ομάδα). Επιλέχθηκε η δίαιτα δυτικού τύπου διότι προσομοιάζει τις διατροφικές συνήθειες του σύγχρονου δυτικού κόσμου. Κάθε 6 εβδομάδες γινόταν μέτρηση σωματικού βάρους. Δύο και επτά ημέρες προ της ευθανασίας πραγματοποιήθηκε ενδοπεριτοναϊκή ένεση καλσεΐνης. Την 24η εβδομάδα τα ζώα θυσιάστηκαν, απομονώθηκαν χειρουργικά το μηριαίο οστό και οι οσφυϊκοί σπόνδυλοι και έγιναν ιστολογικές και ιστομορφομετρικές αναλύσεις. Με τη χρήση microCT scanner (στατική ιστομορφομετρία) εκτιμήθηκε η ποιότητα και η ποσότητα του σπογγώδους και του φλοιώδους οστού. Με τη χρώση TRAP και την εναπόθεση καλσεΐνης (δυναμική ιστομορφομετρία) ελέγχθηκε η οστική αποδόμηση και ο ρυθμός σύνθεσης νεοσχηματιζόμενου οστού, αντίστοιχα. Με τη χρήση φασματοσκοπίας Raman, αξιολογήθηκε η κατάσταση του δικτύου κολλαγόνου των μηριαίων οστών. Επιπλέον, μεσεγχυματικά κύτταρα του μυελού των οστών (BMMSC) απομονώθηκαν από το μηριαίο οστό των πειραματόζωων και καλλιεργήθηκαν με σκοπό την εκτίμηση των επιπέδων έκφρασης, τόσο σε επίπεδο πρωτεΐνης όσο και σε επίπεδο mRNA, μορίων που εμπλέκονται στην οστεοβλαστική λειτουργία [(Runx2, Osterix (Osx), Κολλαγόνο I τύπου 1a (Col1a1)], στην οστεοκλαστική λειτουργία [osteprotegerin (OPG), RANK-Ligand (RANKL), λόγος OPG/RANKL, RANK, TRAP, cathepsin Κ] καθώς και στην λιπογένεση [Peroxisome-Proliferator-Activated receptor γ (PPARγ)]. Για την εκτίμηση των επιπέδων έκφρασης των πρωτεϊνών, χρησιμοποιήσαμε τις μοριακές τεχνικές Western Blot και κυτταρομετρία ροής ενώ για την αξιολόγηση των επιπέδων έκφρασης του mRNA χρησιμοποιήσαμε τη RT-PCR. Αποτελέσματα: 1) Τα apoE-/- πειραματόζωα που έλαβαν WTD δεν ανέπτυξαν παχυσαρκία σε αντίθεση με τα C57BL/6 WTD. 2) Στον μυελό των οστών των apoE-/- WTD ποντικιών παρατηρήθηκε πλήρης απουσία λιποκυττάρων, σε αντίθεση με τα C57BL/6 WTD ζώα των οποίων ο μυελός των οστών ήταν πλούσιος σε λιποκύτταρα. 3) Ο αριθμός των οστεοκλαστών ήταν σημαντικά αυξημένος, ενώ των οστεοβλαστών σημαντικά ελαττωμένος στα apoE-/- WTD πειραματόζωα σε σύγκριση με τα C57BL/6 WTD. 4) Η στατική και η δυναμική ιστομορφομετρία έδειξαν ότι τα apoE-/- ποντίκια, σε δίαιτα δυτικού τύπου, εμφάνισαν σημαντική ελάττωση της οστικής τους μάζας. 5) Το δίκτυο του κολλαγόνου στα apoE-/- WTD ποντίκια εμφανίστηκε σημαντικά πιο σκληρό, πιο άκαμπτο και κατά συνέπεια λιγότερο ελαστικό συγκρινόμενο με αυτό των C57BL/6 WTD. 6) Τα apoE-/- WTD ποντίκια, εμφάνισαν σημαντικά μειωμένα επίπεδα έκφρασης του ρυθμιστή της οστεοβλαστογένεσης Runx2, τόσο σε επίπεδο πρωτεΐνης όσο και σε επίπεδο mRNA, συγκρινόμενα με τα C57BL/6 WTD ζώα. 7) Τα επίπεδα έκφρασης των ρυθμιστών της οστικής ανακατασκευής RANK και RANKL, ήταν σημαντικά αυξημένα στα apoE-/- WTD ποντίκια σε σχέση με τα C57BL/6 WTD ποντίκια. Αντίθετα, τα επίπεδα έκφρασης του γονιδίου της OPG καθώς και η αναλογία OPG/RANKL, ήταν σημαντικά μειωμένα στα apoE-/- WTD ποντίκια. Δεν παρατηρήθηκαν σημαντικές διαφορές στην έκφραση των οστεοκλαστικών ρυθμιστών cathepsin K και TRAP μεταξύ των δύο υπό εξέταση ομάδων ζώων. 8) Ο ρυθμιστής της λιπογένεσης PPARγ, τόσο σε επίπεδο πρωτεΐνης όσο και σε επίπεδο mRNA, ήταν σημαντικά μειωμένος στα apoE-/- WTD ποντίκια σε σχέση με τα C57BL/6 WTD. Συμπεράσματα: 1) Η έλλειψη της apoE εμπλέκεται στην ελάττωση της οστικής μάζας σε ποντίκια υπό δίαιτα δυτικού τύπου 2) Η apoE φαίνεται ότι διαδραματίζει σημαντικό ρόλο στη ρύθμιση της λειτουργίας των οστεοβλαστών, ενώ δεν είναι σαφής ο ρόλος της στη λειτουργία των οστεοκλαστών 3) Η έλλειψη της apoE, προστατεύει από την παχυσαρκία αλλά και την εναπόθεση λιποκυττάρων στον μυελό των οστών, κατόπιν λήψεως δίαιτας πλούσιας σε λιπαρά. 4) Η apoE ρυθμίζει τη διαφοροποίηση των MSC’s σε ερχόμενο στάδιο, καθώς η έλλειψή της επηρεάζει τόσο την οστεοβλαστική όσο και τη λιποβλαστική διαφοροποίηση, μετά από κατανάλωση δίαιτας δυτικού τύπου, πλούσιας σε λιπαρά. / Introduction: Recent data suggest that lipid metabolism imbalances affect bone cell function and therefore may result in the development of metabolic diseases such as osteoporosis. In the present study, we investigated the role of apoE, a plasma protein playing cardinal role in lipoprotein metabolism, in the regulation of osteoblasts, osteoclasts and lipoblasts and in the pathogenesis of osteoporosis. Material and Methods: We used apoE deficient (apoE-/-) and wild type (C57BL/6) mice (10 animals/ group). Mice were fed with standard western-type diet (WTD) for 24 weeks. Body weight measurements were obtained every 6 weeks. Two and seven days before euthanasia calcein was injected intraperitonealy for the determination of new bone formation rate. Following sacrifice, lumbar vertebrae and femora were removed and quantitative/qualitative study of the cortical and cancellous bone was performed using microCT scanner. In the tissue sections we perfomed histological (H&E) and histochemical (TRAP) analyses. Static and dynamic histomorphometry were employed for the determination of bone quality and bone cell function. Using Raman spectroscopy, the quality and biochemical composition of the collagen fibers of the examined femora were evaluated. Bone marrow mesenchymal stem cells (BMMSC) were isolated from mice femora and then assessed for the expression of the osteoblastic (Runx2, OSX, Col1a1), osteoclastic (OPG, RANKL, OPG/RANKL, RANK, TRAP, cathepsin K) and lipoblastic (PPARγ) regulators using Western Blotting, Flow Cytometry and RT-PCR. Results: 1) apoE-/- mice under WTD did not develop obesity and their BM was devoid of adipocytes, in contrast to the control mice. 2) Osteoclast number was significantly increased, while bone synthesis was significantly reduced in apoE-/- compared to the C57BL/6 mice that consumed WTD. 3) Static and dynamic histomorphometry showed that apoE-/- mice had sugnificantly reduced bone mass and impared bone architecture. 4) The collagen network in apoE-/- WTD mice was significantly stiffer and more rigid compared to the C57BL/6 WTD mice. 5) BMMSCs from apoE-/- WTD mice displayed significantly reduced Runx2 expression at both protein and mRNA levels compared to the control group. 6) The expression levels of RANK and RANKL, were significantly elevated in apoE-/- WTD mice compared to C57BL/6 WTD mice. In contrast, the gene expression levels of OPG and the ratio OPG / RANKL, were statistically significantly reduced in apoE-/- WTD mice. No significant differences were observed in the expression of cathepsin K and TRAP genes between the two test groups of animals. 7) The expression of the major lipoblastic regulator PPARγ was significantly reduced in apoE-/- WTD compared to their WT counterparts. Conclusions: 1) Low levels of apoE result in reduced bone mass following WTD. 2) apoE is implicated in the regulation of osteoblast function; nevertheless, its role in osteoclast function warrants further investigation. 3) The absence of apoE prevents obesity and BM adipocity after the consumption of WT (high-fat) diet. 4) apoE deficiency, regulates MSC differentiation at early stages, since its absence affects both the osteoblastic and lipoblastic differentiation, after the consumption of high fat diet.

This thesis presents several statistical analysis on a cooperative project with Dr. Pallas and Yuting Mao from Biology Department of Georgia State University. This research concludes the impact of cauterize size of animals’ midbrain on auditory and visual response in brains. Besides some already commonly used statistical analysis method, such as MANOVA and Frequency Test, a unique combination of Permutation Test, Kolmogorov-Smirnov Test and Wilcoxon Rank Sum Test is applied to our non-parametric data. Some simulation results show the Permutation Test we used has very good powers, and fits the need for this study. The result confirms part of the Biology Department’s hypothesis statistically and enhances more complete understanding of the experiments and the potential impact of helping patients with Acquired Brain Injury.

We describe a fast method for the evaluation of an arbitrary high-dimensional multivariate algebraic polynomial in Chebyshev form at the nodes of an arbitrary rank-1 Chebyshev lattice. Our main focus is on conditions on rank-1 Chebyshev lattices allowing for the exact reconstruction of such polynomials from samples along such lattices and we present an algorithm for constructing suitable rank-1 Chebyshev lattices based on a component-by-component approach. Moreover, we give a method for the fast, exact and stable reconstruction.

When designing controllers with robust performance and stabilization requirements, H-infinity synthesis is a common tool to use. These controllers are often obtained by solving mathematical optimization problems. The controllers that result from these algorithms are typically of very high order, which complicates implementation. Low order controllers are usually desired, since they are considered more reliable than high order controllers. However, if a constraint on the maximum order of the controller is set that is lower than the order of the so-called augmented system, the optimization problem becomes nonconvex and it is relatively difficult to solve. This is true even when the order of the augmented system is low. In this thesis, optimization methods for solving these problems are considered. In contrast to other methods in the literature, the approach used in this thesis is based on formulating the constraint on the maximum order of the controller as a rational function in an equality constraint. Three methods are then suggested for solving this smooth nonconvex optimization problem. The first two methods use the fact that the rational function is nonnegative. The problem is then reformulated as an optimization problem where the rational function is to be minimized over a convex set defined by linear matrix inequalities (LMIs). This problem is then solved using two different interior point methods. In the third method the problem is solved by using a partially augmented Lagrangian formulation where the equality constraint is relaxed and incorporated into the objective function, but where the LMIs are kept as constraints. Again, the feasible set is convex and the objective function is nonconvex. The proposed methods are evaluated and compared with two well-known methods from the literature. The results indicate that the first two suggested methods perform well especially when the number of states in the augmented system is less than 10 and 20, respectively. The third method has comparable performance with two methods from literature when the number of states in the augmented system is less than 25.

Durch die vorliegende Studie wurde der Einfluss von Strukturelementen auf das Liege- und Aggressionsverhalten von Pferden in Gruppenhaltung untersucht. Die Strukturelemente sollten Rückzugsmöglichkeiten bieten, sowie in ihrem Bereich zur Aufhebung der Individualdistanz führen und dadurch die Fläche relativ vergrößern. Für die Versuche stellte das Haupt- und Landesgestüt Marbach drei unabhängige Pferdegruppen mit verschiedener Herdengröße zur Verfügung, die jeweils in Einraum- Innenlaufställen gehalten wurden. Die Datenerfassung fand zwischen 23 und sieben Uhr statt. Insgesamt wurden 336 Stunden Videomaterial ausgewertet. Beim Ruheverhalten wurden mit Hilfe des event-sampling-Verfahrens die Parameter Gesamtliegedauer, Dauer in Seitenlage, Dauer der Einzelphasen in Seitenlage und Abliegehäufigkeit pro Nacht erfasst. Es wurden Versuchsphasen ohne Strukturelemente und mit hängenden Planen als Strukturierung durchgeführt. Im ersten Stall kamen außerdem über einander gestapelte Strohballen zum Einsatz. Diese Art der Strukturierung stellte sich jedoch als nicht praktikabel heraus und führte im Vergleich zu den Planen zu einer signifikanten Verschlechterung der Gesamtliegedauer. In Stall 1 konnte man eine tendenzielle Verbesserung der Parameter Gesamtliegedauer und Gesamtdauer in Seitenlage durch das Anbringen von Planen sehen. In Stall 3 dagegen verschlechterte sich das Ruheverhalten in den Versuchsphasen mit Planen gegenüber den Versuchsphasen ohne Struktur. Die Werte der Gesamtdauer in Seitenlage nahmen signifikant ab. In Stall 2 zeigten sich keine Unterschiede in den verschiedenen Versuchsphasen. Möglicherweise ist die Wirkung der Strukturelemente auf das Liegeverhalten abhängig von der Flächengröße. Stall 1 hatte bezogen auf die Leitlinien des BMELV die größte und Stall 3 die kleinste Fläche. Bei den anderen Parametern des Liegeverhaltens gab es keine signifikanten Unterschiede in den verschiedenen Versuchsphasen. Mit Hilfe des time-sampling-Verfahrens wurde die Anzahl gleichzeitig liegender Pferde und gleichzeitig liegender Pferde in Seitenlage bestimmt. Auch hier zeigten sich keine Unterschiede in den verschiedenen Versuchsphasen. Bei der Gegenüberstellung der Werte der Gesamtliegedauer und der Gesamtdauer in Seitenlage mit dem Alter der Pferde (Stall 1 und Stall 3) und mit dem Integrationszeitpunkt (Stall 1) konnte kein Zusammenhang festgestellt werden. Beim Aggressionsverhalten wurden mit Hilfe des event-sampling-Verfahrens in den Ställen 2 und 3 verschiedene Arten von Aggressionen erfasst, die dann in die drei Intensitätsgrade Low-Level-, Mid-Level- und High-Level-Aggressionen unterteilt wurden. Neben der Anzahl wurde die Dauer der verschiedenen Aggressionen bewertet. Insgesamt konnte eine positive Wirkung der Planen auf das Aggressionsverhalten beobachtet werden. Die Gesamtanzahl an Aggressionen nahm in beiden Ställen tendenziell in den Versuchsphasen mit Planen ab. In Stall 3 konnte, wenn man die Aggressionen stundenweise betrachtet, ein signifikanter Unterschied festgestellt werden. Auch der Hinterhandschlag und die Aggressionen, welche das Ruheverhalten stören, verringerten sich tendenziell nach dem Anbringen von Strukturelementen. In beiden Ställen nahm die relative Häufigkeit von Mid-Level-Aggressionen nach dem Anbringen von Planen zu. Dagegen konnte bei den High-Level-Aggressionen und in Stall 3 bei den Low-Level-Aggressionen eine relative Abnahme beobachtet werden. Sowohl die Anzahl als auch die Dauer der Mid-Level-Aggressionen verringerten sich in Stall 3 stundenweise betrachtet signifikant in den Versuchsphasen mit Planen. In Stall 2 war bei den High-Level-Aggressionen sowohl bei der Dauer als auch bei der Anzahl eine signifikante Abnahme zu sehen. Wenn man das Aggressionsverhalten in Bezug zu der Fläche in den zwei Ställen betrachtet, schien diese vor allem einen Einfluss auf die High-Level-Aggressionen zu nehmen. Mit Hilfe des Rangindex der Pferde im Stall 3 wurde eine Rangordnung aufgestellt. Zwischen dem Platz der Pferde in der Rangordnung und den Parametern des Ruheverhaltens (Gesamtliegedauer, Gesamtdauer in Seitenlage) sowie dem Alter der Pferde konnte kein Zusammenhang festgestellt werden. Zwischen dem Rangindex und der Gesamtanzahl an Aggressionen bestand dagegen ein hoch signifikanter Zusammenhang. Im Rahmen dieser Studie ist das Anbringen von Strukturelementen in Bezug auf das Aggressionsverhalten in Einraum-Innenlaufställen von Pferden zu empfehlen. Die Wirkung auf das Liegeverhalten der Pferde sollte in weiteren Studien untersucht werden.