<p>At the same time as many urban economies are developing into 24-hour societies it is becoming increasingly popular amongst shift workers to compress their working hours. This is done by working longer shifts (>8h) and/or restricting free time (<16h) in between shifts – the main reasons are to gain longer bouts of free time and extra free weekends. However, there is a limited knowledge of the effects of such arrangements on sleep and wakefulness. Thus, the main purposes of the present thesis were to evaluate the effects of long working hours (in the form of 12h shifts) and short recovery periods. Another aim was to evaluate possible mechanisms that could suggest why some individuals develop problems with shift work while others do not.</p><p>We used a combination of methods - sleep diaries, wake diaries, blood samples and objective measures of sleep and cognitive performance - across whole or large parts of shift schedules to evaluate acute effects of particularly demanding working periods, as well as the total effects of a shift cycle. Study I evaluated the effect of changing from an 8h- to a 12h-shift system. Study II evaluated the effects of long shifts in a shift schedule with both 8h- and 12h-shifts. Study III evaluated the effects of several consecutive short recovery periods (8-9h of recovery) and whether satisfaction with ones’ work hours was associated to problems with sleep and sleepiness. Study IV evaluated whether endocrinological markers of catabolic (cortisol) and anabolic (testosterone) activity changed across a shift sequence and whether satisfaction were related to them. Study V was a laboratory simulation of the effects of a short recovery period (4h of sleep) and whether a short nap could counteract any detrimental effects.</p><p>There was no convincing evidence for 12h shifts inducing more problems with sleep and sleepiness than 8h shifts. With regard to recovery time between shifts, the shortest recovery times (only 8h) seriously shortened sleep duration and increased sleepiness, while 12h of recovery (between two consecutive 12h shifts) was judged as having no or limited effects on acute measures. The problems with the shortest recovery periods were worse in a schedule with several consecutive shifts and less pronounced in a schedule with few consecutive shifts. With regard to individual differences, it was found that subjects being dissatisfied with their working hours were vulnerable to short recovery periods, which was evident by less sufficient sleep and an accumulation of sleepiness across work periods with limited recovery time. Interestingly, these problems disappeared when they were allowed to recover after the work period. In addition, dissatisfied male shift workers had lower testosterone levels at the end of work periods, indicating disturbed anabolic activity. The simulated quick return supported that curtailed sleep affected sleepiness and performance and that a short nap could counteract these effects temporarily.</p><p>It is concluded that long shifts (up to 12h) may be acceptable, whereas short recovery time (8h or less) is not. Most of the problems with short recovery periods were related to short sleep and sleepiness, and there is, clearly, a subgroup of workers that suffer more from this than others. It is argued that insufficient sleep and low testosterone levels (in males) might be key factors for developing shift intolerance, mainly by reducing the capacity to recover from shift work.</p>

At the same time as many urban economies are developing into 24-hour societies it is becoming increasingly popular amongst shift workers to compress their working hours. This is done by working longer shifts (&gt;8h) and/or restricting free time (&lt;16h) in between shifts – the main reasons are to gain longer bouts of free time and extra free weekends. However, there is a limited knowledge of the effects of such arrangements on sleep and wakefulness. Thus, the main purposes of the present thesis were to evaluate the effects of long working hours (in the form of 12h shifts) and short recovery periods. Another aim was to evaluate possible mechanisms that could suggest why some individuals develop problems with shift work while others do not. We used a combination of methods - sleep diaries, wake diaries, blood samples and objective measures of sleep and cognitive performance - across whole or large parts of shift schedules to evaluate acute effects of particularly demanding working periods, as well as the total effects of a shift cycle. Study I evaluated the effect of changing from an 8h- to a 12h-shift system. Study II evaluated the effects of long shifts in a shift schedule with both 8h- and 12h-shifts. Study III evaluated the effects of several consecutive short recovery periods (8-9h of recovery) and whether satisfaction with ones’ work hours was associated to problems with sleep and sleepiness. Study IV evaluated whether endocrinological markers of catabolic (cortisol) and anabolic (testosterone) activity changed across a shift sequence and whether satisfaction were related to them. Study V was a laboratory simulation of the effects of a short recovery period (4h of sleep) and whether a short nap could counteract any detrimental effects. There was no convincing evidence for 12h shifts inducing more problems with sleep and sleepiness than 8h shifts. With regard to recovery time between shifts, the shortest recovery times (only 8h) seriously shortened sleep duration and increased sleepiness, while 12h of recovery (between two consecutive 12h shifts) was judged as having no or limited effects on acute measures. The problems with the shortest recovery periods were worse in a schedule with several consecutive shifts and less pronounced in a schedule with few consecutive shifts. With regard to individual differences, it was found that subjects being dissatisfied with their working hours were vulnerable to short recovery periods, which was evident by less sufficient sleep and an accumulation of sleepiness across work periods with limited recovery time. Interestingly, these problems disappeared when they were allowed to recover after the work period. In addition, dissatisfied male shift workers had lower testosterone levels at the end of work periods, indicating disturbed anabolic activity. The simulated quick return supported that curtailed sleep affected sleepiness and performance and that a short nap could counteract these effects temporarily. It is concluded that long shifts (up to 12h) may be acceptable, whereas short recovery time (8h or less) is not. Most of the problems with short recovery periods were related to short sleep and sleepiness, and there is, clearly, a subgroup of workers that suffer more from this than others. It is argued that insufficient sleep and low testosterone levels (in males) might be key factors for developing shift intolerance, mainly by reducing the capacity to recover from shift work.

Coral reefs are suffering unprecedented declines in coral cover and species diversity. These changes are often associated with  substantial shifts in community structure to new dominant organisms. Ultimately, these “phase shifts” can be persistent and very difficult to return from. Building insurance against degradation and decreasing the likelihood of reefs undergoing shifts to undesirable states will require sustainable management practices that uphold coral reef resilience. This thesis consists of five papers that contribute new knowledge useful for managing the resilience of coral reefs, and other marine ecosystems. Paper I shows how the morphology of natural substrate (dead coral colonies) can significantly influence coral recruitment patterns. Paper II focuses on larval lipid levels, a key determinant of coral dispersal potential, in a common Caribbean coral (Favia fragum). It shows that i) lipid levels exhibit a significant, non-linear reduction throughout the larval release period of F. fragum and ii) exposure to a common pollutant (copper) could potentially lead to a more rapid lipid consumption in the larvae. Paper III presents a broader analysis of the different undesirable states a coral reef can shift to as a consequence of reef degradation. It concludes that different states are caused by different driving factors and that management must explicitly acknowledge this. Paper IV proposes a suite of resilience indicators that can help managers assess when a coral-dominated reef might be moving towards a shift to an undesirable state. These indicators capture key-processes occuring on different temporal and spatial scales and signal resilience loss early enough for managers to take appropriate measures. Finally, Paper V reviews the feedback loops that reinforce the undesirable states of five important marine ecosystems and suggests certain strategies that can ease the restoration back to healthier conditions. Managing these critical feedbacks will recquire monitoring the processes underpinning these feedbacks, breaking already established feedbacks loops through large-scale management trials and acknowledging transdisciplinary solutions that move management beyond the discipline of ecology / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 5: In progress.

Numerous studies have been done in the area of nurse scheduling, since this is a complex area with a lot of aspects that has to be taken into account. An interesting but little studied subject is how the requirements for the scheduling affect the possibility to construct a feasible schedule, or how the requirements affect the quality of the schedule. Of special interest is the effect of the composition of the workforce and of the change in scheduling rules. What is missing is results showing which composition and changes that are possible, and if so what is needed to be able to follow through with them. The changes tested in our simulation study are changes that is up for discussion at many wards in Sweden today, with topics such as split shifts and high part-time work percentages within the staff. In order to simulate various scheduling requirements and changes, an integer linear model for creating nurse schedules is developed. The results provide some insight into the dependence between scheduling requirements and the resulting schedules. In particular our simulation results indicate that there is an inherent conflict between high part-time work percentages and split or long work shifts. Our results can be used as a basis for future research on these topics in the area of nurse scheduling.

Neste trabalho, estudamos a existência de deslocamentos isométricos no produto de espaços de Banach, munido tanto com a norma infinito como com a norma 1. Em alguns casos, assumimos que pelo menos um dos espaços envolvidos no produto é estritamente convexo e isso deu origem a resultados interessantes. Ainda, exploramos os deslocamentos isométricos em C(X), mostrando como classificá-los de acordo com dois tipos. / In this work, we study the existence of isometric shifts on the product of Banach spaces, equipped with the norms infinity or 1. In some cases, we assume that at least one of these spaces on the product is strictly convex and obtain interesting results. Besides, we explore isometric shifts on C(X), showing how to sort them on two groups.

Neste trabalho, estudamos a existência de deslocamentos isométricos no produto de espaços de Banach, munido tanto com a norma infinito como com a norma 1. Em alguns casos, assumimos que pelo menos um dos espaços envolvidos no produto é estritamente convexo e isso deu origem a resultados interessantes. Ainda, exploramos os deslocamentos isométricos em C(X), mostrando como classificá-los de acordo com dois tipos. / In this work, we study the existence of isometric shifts on the product of Banach spaces, equipped with the norms infinity or 1. In some cases, we assume that at least one of these spaces on the product is strictly convex and obtain interesting results. Besides, we explore isometric shifts on C(X), showing how to sort them on two groups.

L'objectif de cette thèse est de modéliser les changements en chaîne historiques dans les théories phonologiques modernes. Martinet (1952, 1955, 1970) distingue deux principales catégories de changements en chaîne: les chaînes de propulsion et les chaînes de traction. Les chaînes de propulsion seront traitées dans la première partie de cette thèse (chapitres 2 et 3). Afin de modéliser les chaînes de propulsion, un modèle existant est utilisé: La théorie de préservation du contraste de Łubowicz (2003, 2012). Concernant la modélisation des chaînes de traction, qui sera principalement traitée dans la seconde partie de le thèse (chapitres 4 et 5), une nouvelle théorie sera proposée, basée sur les travaux phonétiques de De Boer (2001). Cette proposition est basée sur la notion des domaines piliers. Le chapitre 1 s'ouvre sur l'observation que ni les théories dérivationnelles orientées vers l'input – type SPE – ni les théories orientées vers l'output, comme la théorie de l'optimalité de Prince & Smolensky (TO) sont en mesure de formaliser les changements en chaîne. Dans les théories dérivationnelles, il est possible d'obtenir une bonne description des changements en chaîne. Cependant, afin de faire cela, nous devons briser les liens unissant les différentes étapes des changements en chaîne. Par conséquent, nous perdons l'interdépendance systémique entre les stades, ce qui est au cœur des changements en chaîne. Concernant la théorie de l'optimalité, sa structure stricte sur deux niveaux se révèle problématique dans le cas des changements en chaîne. Dans un changement en chaîne schématique comme /a/ → [e] > /e/ → [i], il est impossible pour la TO, dans la même analyse, de faire en sorte que [e] soit un candidat optimal et /e/ un candidat bloqué. Dans le chapitre 2, nous analysons et comparons plusieurs amendements à la théorie de l'optimalité proposés pour rendre compte des changements en chaîne. Beaucoup d'entre eux ne sont pas satisfaisants dans le cas des changements en chaîne car ils ne parviennent pas à modéliser la force systémique des changements en chaîne. La seule théorie qui semble accomplir cet objectif est la théorie de préservation du contraste (CPT) de Łubowicz. Cette théorie est basée sur les notions de contraste, préservation du contraste et elle évalue des scénarios au lieu de candidats individuels. La préservation du contraste est accomplie à travers la transformation du contraste. La notion de transformation du contraste signifie que les niveaux de contraste du système pré-changement sont préservés dans le système post-changement mais leur nature change. Une observation sur la CPT est que Łubowicz l'avait originellement conçue pour les changements en chaîne synchroniques. Dans le chapitre 2, nous démontrons que la CPT est en mesure de modéliser la force systémique qui donne aux changements en chaîne diachroniques leur cohérence. Ainsi, dans le chapitre 3, nous décidons de tester la validité de la CPT sur de véritables changements en chaîne historiques. Nous avançons deux études de cas sur deux changements en chaîne. Le premier, bien connu, est le changement en chaîne vocalique du Grand Changement Vocalique Anglais (English Great Vowel Shift). L'autre changement en chaîne est la Seconde Mutation Consonantique allemande (High German Consonant Shift). Nous démontrons que la CPT est en mesure de rendre compte de ces deux changements en chaîne. Au terme du chapitre 3, la CPT est testée sur une autre catégorie de changements en chaîne : les changements en chaîne observés dans l'acquisition de la langue maternelle. Le changement en chaîne étudié est s → θ → f. Ce changement en chaîne est différent des deux autres car il n'y a pas de nouveau niveau de contraste créé. Le dernier stade du changement en chaîne se conclut par une fusion. Encore une fois, la CPT peut rendre compte de ce changement en chaîne de manière satisfaisante. / The aim of this thesis is to formalise historical chain shifts within modern phonological theories. Martinet (1952, 1955, 1970) distinguishes two main categories of chain shifts: push chains and pull chains. Push chains will be dealt with in the first main part of this thesis (chapters 2 and 3). For modelling of push chains, an existing model is used: Łubowicz's (2003, 2012) Contrast Preservation Theory. For modelling pull chains, which will be the focus of the second part of this thesis (chapters 4 and 5), a new theory will be proposed, based on the phonetic work by De Boer (2001). This proposition is based on the notion of the pillar domains (domaines piliers). Chapter 1 starts with the observation that neither the derivational, SPE-like, theories or output driven theories like Prince's & Smolensky's Optimality Theory (OT) are able to formalise chain shifts properly. Within the derivational theories, it is possible to get a correct description of a chain shift. However, in order to do that, we have to break the links between the different stages of the chain shift. Therefore, one loses the systemic interdependence of the different stages, which is the essence of the chain shift. As regards to Optimality Theory, it is the two-level structure of the theory which proves problematic for chain shifts. In a theoretical chain shift such as /a/ → [e] > /e/ → [i], it is impossible for OT to make, in the same analysis, [e] an optimal candidate and /e/ a non-optimal one. In chapter 2, we analyse and compare several output-driven propositions that have been made to account for chain shifts. Many of them are not satisfactory because they do not manage to model the systemic motivation of chain shifts. The only theory that seems able to complete this objective is Łubowicz's Contrast Preservation Theory (CPT). This theory is based on the notions of contrast, contrast preservation and it evaluates scenarios rather than individual candidates. Contrast preservation is achieved through contrast transformation. The term contrast transformation indicates that the contrast levels of the input system are preserved but that their nature is different in the output system. One observation about CPT is that Łubowicz designed it for synchronic chain shifts. In chapter 2, we prove that CPT is able to model the perceptible coherence in diachronic chain shifts. In chapter 3, thus we decide to test the validity of CPT on actual historical chain shifts. It is tested on two cases. One is the well-known vocalic chain shift the Great Vowel Shift in English. The other one is the Second German Sound Shift (or High German Consonant Shift). We demonstrate that CPT is able to account for both of these chain shifts. At the end of chapter 3, CPT is tested on another type of chain shifts, i.e. chain shifts in first-language acquisition. The studied chain shift is s → θ → f. This chain shift is different from the other two because there is no new contrast level created. The last stage of this chain shift ends with a merger . Once again, CPT can account for this chain shift in a coherent way.

[pt] Estudaremos dinâmicas simbólicas associadas a alfabetos finitos. Consideraremos seqüências bi-infinitas e espaços com memória finita. Estudaremos propriedades invariantes por conjugação. Analisaremos a relação entre os espaços de seqüências e propriedades de matrizes não negativas. O principal exemplo desta correlação é o Teorema de Perron- Frobenius que relaciona a entropia de um espaço de seqüências e os autovalores de uma matriz não negativa associada ao espaço. Neste contexto, certos grafos e suas propriedades aparecem de forma natural. / [en] We study symbolic dynamics associated to finite alphabets. We consider bi-infinite sequences and spaces with finite memory. We pay attention to properties which are invariant by conjugations. We analyze the relation between spaces of sequences and properties of non-negative matrices. The main example is given by the Perron-Frobenius theorem relating the entropy of a space of sequences and the eigerrvalues of a non-negative matrix associated to the space. In this setting, certain graphs and their properties appear in a natural way.

A bounded operator T on a complex separable Hilbert space is said to be homogeneous if '(T ) is unitarily equivalent to T for all ' in M•ob, where M•ob is the M•obius group. A complete description of all homogeneous weighted shifts was obtained by Bagchi and Misra. The first examples of irreducible bi-lateral homogeneous 2-shifts were given by Koranyi. We describe all irreducible homogeneous 2-shifts up to unitary equivalence completing the list of homogeneous 2-shifts of Koranyi. After completing the list of all irreducible homogeneous 2-shifts, we show that every homogeneous operator whose associated representation is a direct sum of three copies of a Complementary series representation, is reducible. Moreover, we show that such an operator is either a direct sum of three bi-lateral weighted shifts, each of which is a homogeneous operator or a direct sum of a homogeneous bi-lateral weighted shift and an irreducible bi-lateral 2-shift. It is known that the characteristic function T of a homogeneous contraction T with an associated representation is of the form T (a) = L( a) T (0) R( a); where L and R are projective representations of the M•obius group M•ob with a common multiplier. We give another proof of the \product formula". We point out that the defect operators of a homogeneous contraction in B2(D) are not always quasi-invertible (recall that an operator T is said to be quasi-invertible if T is injective and ran(T ) is dense). We prove that when the defect operators of a homogeneous contraction in B2(D) are not quasi-invertible, the projective representations L and R are unitarily equivalent to the holomorphic Discrete series representations D+ 1 and D++3, respectively. Also, we prove that, when the defect operators of a homogeneous contraction in B2(D) are quasi-invertible, the two representations L and R are unitarily equivalent to certain known pairs of representations D 1; 2 and D +1; 1 ; respectively. These are described explicitly. Let G be either (i) the direct product of n-copies of the bi-holomorphic automorphism group of the disc or (ii) the bi-holomorphic automorphism group of the polydisc Dn: A commuting tuple of bounded operators T = (T1; T2; : : : ; Tn) is said to be homogeneous with respect to G if the joint spectrum of T lies in Dn and '(T); defined using the usual functional calculus, is unitarily equivalent to T for all ' 2 G: We show that a commuting tuple T in the Cowen-Douglas class of rank 1 is homogeneous with respect to G if and only if it is unitarily equivalent to the tuple of the multiplication operators on either the reproducing kernel Hilbert space with reproducing kernel n 1 i=1 (1 ziwi) i or Q n i i n; are positive real numbers, according asQG is as in (i) or 1 ; where ; i, 1 i i=1 (1 z w ) (ii). Finally, we show that a commuting tuple (T1; T2; : : : ; Tn) in the Cowen-Douglas class of rank 2 is homogeneous with respect to M•obn if and only if it is unitarily equivalent to the tuple of the multiplication operators on the reproducing kernel Hilbert space whose reproducing kernel is a product of n 1 rank one kernels and a rank two kernel. We also show that there is no irreducible tuple of operators in B2(Dn), which is homogeneous with respect to the group Aut(Dn):

This thesis examines how early warning signals perform when tested on climate systems thought to exhibit future tipping point behaviour. A tipping point in a dynamical system is a large and sudden change to the state of the system, usually caused by changes in external forcing. This is due to the state the system occupies becoming unstable, causing the system to settle to a new stable state. In many cases, there is a degree of irreversibility once the tipping point has been passed, preventing the system from reverting back to its original state without a large reversal in forcing. Passing tipping points in climate systems, such as the Amazon rainforest or the Atlantic Meridional Overturning Circulation, is particularly dangerous as the effects of this will be globally felt. Fortunately there is potential for early warning signals, designed to warn that the system is approaching a tipping point. Generally, these early warning signals are based on analysis of the time series of the system, such as searching for ‘critical slowing down’, usually estimated by an increasing lag-1 autocorrelation (AR(1)). The idea here is that as a system’s state becomes less stable, it will start to react more sluggishly to short term perturbations. While early warning signals have been tested extensively in simple models and on palaeoclimate data, there has been very little research into how these behave in complex models and observed data. Here, early warning signals are tested on climate systems that show tipping point behaviour in general circulation models. Furthermore, it examines why early warning signals might fail in certain cases and provides prospect for more ‘system specific indicators’ based on properties of individual tipping elements. The thesis also examines how slowing down in a system might affect ecosystems that are being driven by it.