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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Towards patient selection for cranial proton beam therapy – Assessment of current patient-individual treatment decision strategies

Dutz, Almut 27 November 2020 (has links)
Proton beam therapy shows dosimetric advantages in terms of sparing healthy tissue compared to conventional photon radiotherapy. Those patients who are supposed to experience the greatest reduction in side effects should preferably be treated with proton beam therapy. One option for this patient selection is the model-based approach. Its feasibility in patients with intracranial tumours is investigated in this thesis. First, normal tissue complication probability models for early and late side effects were developed and validated in external cohorts based on data of patients treated with proton beam therapy. Acute erythema as well as acute and late alopecia were associated with high-dose parameters of the skin. Late mild hearing loss was related to the mean dose of the ipsilateral cochlea. Second, neurocognitive function as a relevant side effect for brain tumour patients was investigated in detail using subjective and objective measures. It remained largely stable during recurrence-free follow-up until two years after proton beam therapy. Finally, potential toxicity differences were evaluated based on an individual proton and photon treatment plan comparison as well as on models predicting various side effects. Although proton beam therapy was able to achieve a high relative reduction of dose exposure in contralateral organs at risk, the associated reduction of side effect probabilities was less pronounced. Using a model-based selection procedure, the majority of the examined patients would have been eligible for proton beam therapy, mainly due to the predictions of a model on neurocognitive function.:1. Introduction 2. Theoretical background 2.1 Treatment strategies for tumours in the brain and skull base 2.1.1 Gliomas 2.1.2 Meningiomas 2.1.3 Pituitary adenomas 2.1.4 Tumours of the skull base 2.1.5 Role of proton beam therapy 2.2 Radiotherapy with photons and protons 2.2.1 Biological effect of radiation 2.2.2 Basic physical principles of radiotherapy 2.2.3 Field formation in radiotherapy 2.2.4 Target definition and delineation of organs at risk 2.2.5 Treatment plan assessment 2.3 Patient outcome 2.3.1 Scoring of side effects 2.3.2 Patient-reported outcome measures – Quality of life 2.3.3 Measures of neurocognitive function 2.4 Normal tissue complication probability models 2.4.1 Types of NTCP models 2.4.2 Endpoint definition and parameter fitting 2.4.3 Assessment of model performance 2.4.4 Model validation 2.5 Model-based approach for patient selection for proton beam therapy 2.5.1 Limits of randomised controlled trials 2.5.2 Principles of the model-based approach 3. Investigated patient cohorts 4. Modelling of side effects following cranial proton beam therapy 4.1 Experimental design for modelling early and late side effects 4.2 Modelling of early side effects 4.2.1 Results 4.2.2 Discussion 4.3 Modelling of late side effects 4.3.1 Results 4.3.2 Discussion 4.4 Interobserver variability of alopecia and erythema assessment 4.4.1 Patient cohort and experimental design 4.4.2 Results 4.4.3 Discussion 4.5 Summary 5. Assessing the neurocognitive function following cranial proton beam therapy 5.1 Patient cohort and experimental design 5.2 Results 5.2.1 Performance at baseline 5.2.2 Correlation between subjective and objective measures 5.2.3 Time-dependent score analyses 5.3 Discussion and conclusion 5.4 Summary 6. Treatment plan and NTCP comparison for patients with intracranial tumours 6.1 Motivation 6.2 Treatment plan comparison of cranial proton and photon radiotherapy 6.2.1 Patient cohort and experimental design 6.2.2 Results 6.2.3 Discussion 6.3 Application of NTCP models 6.3.1 Patient cohort and experimental design 6.3.2 Results 6.3.3 Discussion 6.4 Summary 7. Conclusion and further perspectives 8. Zusammenfassung 9. Summary
142

Implementation of the Integrated Landscape Approach in Mexico with Empahsis on policies and multilevel governance initiatives

Pedroza Arceo, Norma Mercedes 22 November 2021 (has links)
Holistic and multidisciplinary approaches where both conservation and development goals are in place is one of the global orientations towards sustainability. Science has come together with practical experiences and lessons learned that highlight the critical importance of working at a ‘Landscape’ level. Landscapes are a pivotal scale for both sustainability and sustainable development. Because landscapes are needed to articulate and interconnect local, subnational, national, and therefore, global goals. International efforts in regards to sustainable rural development are not new; however, they are currently pointing to an Integrated Landscape Approach (ILA). Despite that, there is not yet a universal definition of the ILA; there are some principles or prescriptions that are useful for the assessment of current specific efforts of ILA implementation. In the present thesis, a multi-criteria policy analysis of ILA in Mexico was performed with the aims to identify and analyze multi-level governance initiatives, and policy frameworks, and contribute to the investigation if the landscape approach makes a difference in terms of conservation and sustainable development goals. International frameworks, national policies, and in particular Mexican landscape initiatives were analyzed and discussed. Along with the document analysis, key informant interviews were carried out. The findings confirm that the Landscape Sustainability science framework can be adequate to sustain further multidisciplinary research on ILA. Additionally, the ILA in Mexico has been promoted through at least 10 national policies and 15 landscape initiatives with evident signs of consistency with the ILA aims and principles. It was found that there are several challenges for effective ILA implementation, such as long-term finance and planning and inter-sectorial collaboration within common policy goals. Among these, major “bottlenecks” of effective ILA implementation lie on a Good Landscape Governance and the Willingness of Government (“political will”) and Stakeholders to pursue the ILA. The ILA is not the one and only solution for sustainability and sustainable development at the landscape level. Indeed, the ILA still needs scientifically sound research and more long-term capital investments. The findings of this study help to understand that the ILA is an alternative to interconnect the human, social, environmental and economic dimensions within each particular landscape for an effective problem solving, decision-making and implementation of sustainable development.:1. Introduction.................................................................................................................................... 8 1.1. Integrated Landscape Approach for Sustainable Forestry.................................................... 8 1.2. Justification on the study focus on Policy and Multilevel Governance in Mexico............. 11 2. Objectives..................................................................................................................................... 15 2.1. Overall research objective ................................................................................................... 15 2.2. Specific research objectives and Research questions per specific research objective ...... 15 3. Theoretical Framework................................................................................................................ 16 3.1. The science behind: Integrated Landscape Approaches..................................................... 16 3.2. Conceptual Framework: Integrated Landscape Approach ................................................. 19 3.3. Principles and criteria for Integrated Landscape Approaches............................................ 24 3.4. Environmental and Forestry context in Mexico.................................................................. 26 4. Methodological Framework......................................................................................................... 31 4.1. Research Design ................................................................................................................... 31 4.2. Indicator matrix assessment for the study.......................................................................... 32 4.3. Stakeholders and key informants interviews...................................................................... 33 4.4. Data analysis......................................................................................................................... 34 5. Results........................................................................................................................................... 35 5.1. National framework for ILA ................................................................................................. 35 5.2. ILA Initiatives in Mexico....................................................................................................... 39 5.3. Findings from interviews analysis with key Informants..................................................... 46 6. Discussion ..................................................................................................................................... 49 6.1. The international vision ....................................................................................................... 49 6.1.1 Synthesis knowledge for Integrated Landscape Approaches............................................ 51 6.2. The national vision and the initiatives experiences............................................................ 53 6.3. Lessons learned and barriers for implementing ILA: the Mexican experience.................. 60 7. Conclusion .................................................................................................................................... 64 7.1 Summation ................................................................................................................................. 64 7.2 Suggestions for further research ............................................................................................... 65 7.3 Limitations of the study and methodological critique.............................................................. 66 8. References.................................................................................................................................... 68
143

Data for evidence: Defining, collecting and analysing specific data from pedelec accidents as an example of individual, targeted road safety work for new forms of mobility

Panwinkler, Tobias 19 December 2022 (has links)
Cycling, as one of the oldest forms of mobility, is currently experiencing a renaissance. It supports active mobility and can have a positive influence on public health, the environment, climate and the traffic situation. Pedelecs (bicycles with an electric motor supporting the user up to a speed of 25 kmph) represent a new form of active mobility and are currently enjoying great popularity as they have the same benefits compared to conventional bicycles and, in addition, make cycling accessible to new user groups. With the growing number of pedelecs, however, potential for conflict also increases. Unfortunately, the majority of accidents cannot yet be analysed accordingly, as pedelec-specifiic characteristics are missing from the accident data. This fact in itself has already been proven as a barrier. Most accident studies focusing on pedelecs are based on police data from standardised accident forms [e.g. 1, 2, 3, 4]. Their findings can be summarised in the following key statements: Accidents with pedelecs are less frequent but more severe than those with conventional bicycles. For both, accidents on urban roads dominate, but pedelec accidents occur significantly more often on rural roads than conventional bicycle accidents. And: injured pedelec users, especially those fatally injured, are on average significantly older than injured users of conventional bicycles. But, standardised accident forms were initially designed for accidents with double-track motor vehicles, in particular passenger cars. Accidents with bicycles (especially pedelecs), are difficult to categorise with this systematic as important information is missing. For example, 'falling on ground' is not an accident category as cars normally won't do so, but for pedelec accidents, this information is fundamental. This acts as a barrier as bicycle-specific causes of accidents cannot be analysed. However, accident statistics are the most important basis for evidence-based measures in road safety work. The aim of this paper is therefore to identify and categorise pedelec-specific accident characteristics and to evaluate pedelec accidents on the basis of these characteristics to identify frequent and severe accident constellations. [From: Introduction]
144

Local Learning Strategies for Data Management Components

Woltmann, Lucas 18 December 2023 (has links)
In a world with an ever-increasing amount of data processed, providing tools for highquality and fast data processing is imperative. Database Management Systems (DBMSs) are complex adaptive systems supplying reliable and fast data analysis and storage capabilities. To boost the usability of DBMSs even further, a core research area of databases is performance optimization, especially for query processing. With the successful application of Artificial Intelligence (AI) and Machine Learning (ML) in other research areas, the question arises in the database community if ML can also be beneficial for better data processing in DBMSs. This question has spawned various works successfully replacing DBMS components with ML models. However, these global models have four common drawbacks due to their large, complex, and inflexible one-size-fits-all structures. These drawbacks are the high complexity of model architectures, the lower prediction quality, the slow training, and the slow forward passes. All these drawbacks stem from the core expectation to solve a certain problem with one large model at once. The full potential of ML models as DBMS components cannot be reached with a global model because the model’s complexity is outmatched by the problem’s complexity. Therefore, we present a novel general strategy for using ML models to solve data management problems and to replace DBMS components. The novel strategy is based on four advantages derived from the four disadvantages of global learning strategies. In essence, our local learning strategy utilizes divide-and-conquer to place less complex but more expressive models specializing in sub-problems of a data management problem. It splits the problem space into less complex parts that can be solved with lightweight models. This circumvents the one-size-fits-all characteristics and drawbacks of global models. We will show that this approach and the lesser complexity of the specialized local models lead to better problem-solving qualities and DBMS performance. The local learning strategy is applied and evaluated in three crucial use cases to replace DBMS components with ML models. These are cardinality estimation, query optimizer hinting, and integer algorithm selection. In all three applications, the benefits of the local learning strategy are demonstrated and compared to related work. We also generalize the strategy’s usability for a broader application and formulate best practices with instructions for others.
145

Wave Functions of Integrable Models

Mei, Zhongtao 29 October 2018 (has links)
No description available.
146

„Ein Gefühl von Schutz und Frische“ : Eine kritische Diskursanalyse von deutschsprachiger Menstruationsproduktwerbung / "A Feeling of Protection and Freshness" : A Critical Discourse Analysis of German Menstrual Product Advertisement

Erbén, Tova January 2019 (has links)
The advertisement of menstrual products has traditionally been characterised by shame, discretion and euphemisms (Block Coutts and Berg 1993; Waschek 1995, Simes and Berg 2001). In the past few years, the theme of menstruation appears increasingly in the public eye and prompts the question of whether those qualities are still the dominant descriptors for advertising menstrual products. In order to study this, a critical discourse analysis was performed using the discourse-historical approach of Wodak and Reisigl (2016). The intention was to investigate – both qualitatively and quantitatively – how product descriptions of pads, tampons and menstrual cups are normatively and predicatively constructed, and which arguments, linguistics means and realizations are utilized for this purpose. The results suggest that qualities such as cleanliness, discretion and absence of smell as well as euphemisms (e.g. Flüssigkeit, leichte/stärkere Tage) are still quite prevalent in use. The focus on protection is also emphasized in various ways, both in the product names as well as in the frequency analysis of the adjoining texts. However, other qualities, such as comfort, indicate that progressive tendencies also exist in the advertisements of menstrual products.
147

Résultats exacts sur les modèles de boucles en deux dimensions

Ikhlef, Yacine 27 September 2007 (has links) (PDF)
En utilisant les méthodes analytiques et numériques de la Physique Statistique bidimensionnelle (matrice de transfert, invariance conforme, gaz de Coulomb, équations de Yang-Baxter, Ansatz de Bethe, Monte-Carlo), nous abordons des problèmes qui n'entrent pas dans le cadre du modèle gaussien compact : modèle de Potts antiferromagnétique critique, modèle de boucles de Brauer. Ces modèles présentent des propriétés critiques originales, comme l'apparition de degrés de liberté non-compacts. Ces propriétés apparaissent quand on introduit, dans le modèle de boucles sur réseau, des intersections entre les boucles ou une alternance des poids de Boltzmann entre les sous-réseaux. Dans le cas du modèle de Potts antiferromagnétique, nous développons l'étude de la structure issue des équations de Yang-Baxter, et nous identifions une famille d'états de Bethe associés aux degrés de liberté non-compacts. Les calculs numériques sur de grandes tailles de système permettent de conjecturer la loi d'échelle du rayon de compactification effectif. Dans le cas du modèle de Brauer avec une fugacité de boucles n = 0, nous proposons un modèle de chemin d'échappement invariant d'échelle, et nous déterminons ses propriétés critiques par des méthodes numériques. En tant qu'observable (non-locale), le chemin d'échappement caractérise les points communs et différences avec les marches aléatoires.
148

Aspects of Yang-Mills Theory : Solitons, Dualities and Spin Chains

Freyhult, Lisa January 2004 (has links)
<p>One of the still big problems in the Standard Model of particle physics is the problem of confinement. Quarks or other coloured particles have never been observed in isolation. Quarks are only observed in colour neutral bound states. The strong interactions are described using a Yang-Mills theory. These type of theories exhibits asymptotic freedom, i.e. the coupling is weak at high energies. This means that the theory is perturbative at high energies only. Understanding quark confinement requires knowledge of the non perturbative regime. One attempt has been to identify the proper order parameters for describing the low energy limit and then to write down effective actions in terms of these order parameters. We discuss one possible scenario for confinement and the effective models constructed with this as inspiration. Further we discuss solitons in these models and their properties.</p><p>Yang-Mills theory has also become important in the context of string theory. According to the AdS/CFT correspondence string theory in AdS<sub>5</sub>×S<sup>5</sup> is dual to four dimensional Yang-Mills with four supersymmetries. The duality relate the non perturbative regime of one of the theories to the perturbative regime of the other. This makes it in general hard to test this conjecture. For a special type of solutions it is however possible to use a perturbative expansion in both theories. We discuss this type of solutions and in particular we discuss a method, the Bethe ansatz, to find the solutions on the gauge theory side.</p>
149

Aspects of Yang-Mills Theory : Solitons, Dualities and Spin Chains

Freyhult, Lisa January 2004 (has links)
One of the still big problems in the Standard Model of particle physics is the problem of confinement. Quarks or other coloured particles have never been observed in isolation. Quarks are only observed in colour neutral bound states. The strong interactions are described using a Yang-Mills theory. These type of theories exhibits asymptotic freedom, i.e. the coupling is weak at high energies. This means that the theory is perturbative at high energies only. Understanding quark confinement requires knowledge of the non perturbative regime. One attempt has been to identify the proper order parameters for describing the low energy limit and then to write down effective actions in terms of these order parameters. We discuss one possible scenario for confinement and the effective models constructed with this as inspiration. Further we discuss solitons in these models and their properties. Yang-Mills theory has also become important in the context of string theory. According to the AdS/CFT correspondence string theory in AdS5×S5 is dual to four dimensional Yang-Mills with four supersymmetries. The duality relate the non perturbative regime of one of the theories to the perturbative regime of the other. This makes it in general hard to test this conjecture. For a special type of solutions it is however possible to use a perturbative expansion in both theories. We discuss this type of solutions and in particular we discuss a method, the Bethe ansatz, to find the solutions on the gauge theory side.
150

Systèmes intégrables et dualité AdS/CFT

Leurent, Sebastien 20 June 2012 (has links) (PDF)
Cette thèse est consacrée à l'étude de systèmes quantiques intégrables tels des chaînes de spins, des théories de champs à 1+1 dimensions, et la dualité AdS/CFT. Cette dualité AdS/CFT est une conjecture, émise à la fin du siècle dernier, qui relie notamment le régime non-perturbatif d'une théorie de jauge superconforme (nommée N =4 super Yang- Mills) au régime perturbatif d'une théorie de cordes dans un espace à 10 dimensions (de géométrie AdS5×S5). Ce manuscrit explore les similarités entre des chaînes de spins intégrables et des théories de champs intégrables, tels Super Yang Mills. Il commence par une étude ap- profondie des chaînes de spins intégrables pour y construire explicitement un "flot de Bäcklund" et des "opérateurs Q" polynômiaux, qui permettent de diagonaliser le Hamil- tonien. Des théories de champs intégrables sont ensuite étudiées et des "fonctions Q" sont obtenues, qui sont l'analogue des opérateurs Q construits pour les chaînes de spins. Il apparaît que de nombreuses informations sont contenue dans les propriétés analytiques des fonctions Q. Cela permet d'aboutir, dans le cadre de l'ansatz de Bethe thermody- namique, à un nombre fini d'équations non-linéaires intégrales qui encode le spectre des niveaux d'énergie de la théorie considérée (en taille finie). Ce système d'équations est équivalent au système infini d'équations, connu sous le nom de système Y, qui dans le cas de la dualité AdS/CFT avait été conjecturé assez récemment.

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