1,688 research outputs found
Geophysical aspects of very long baseline neutrino experiments
Several proposed experiments will send beams of neutrinos through the Earth
along paths with a source-receiver distance of hundreds or thousands of
kilometers. Knowledge of the physical properties of the medium traversed by
these beams, in particular the density, will be necessary in order to properly
interpret the experimental data. Present geophysical knowledge allows the
average density along a path with a length of several thousand km to be
estimated with an accuracy of about per cent. Physicists planning
neutrino beam experiments should decide whether or not this level of
uncertainty is acceptable. If greater accuracy is required, intensive
geophysical research on the Earth structure along the beam path should be
conducted as part of the preparatory work on the experiments.Comment: 8 pages, uses elsart.cls. Talk given at 3rd International Workshop on
Neutrino Factory based on Muon Storage Rings (NuFACT'01), Tsukuba, Japan,
24-30 May 200
On Observables in Supersymmetric Gauge Theories
PhDThere has been great progress in recent years in the understanding of the mathematical structure of scattering amplitudes in Quantum Field Theory as well as the development of powerful methods for their calculation, particularly in the arena of N = 4 Super Yang-Mills where hidden and manifest symmetries lead to striking simplifications.
In this thesis, we will discuss the extensions of such methods away from
the case of on-shell amplitudes in conformal N = 4.
After introducing the necessary mathematical background and physical setting, we consider in Chapter Three the form factors of BPS operators in N = 4 Super Yang- Mills. These objects have several physical applications, and share many properties with scattering amplitudes. However, they are off-shell, which makes them a natural
starting point to set out in the direction of correlation functions. After demonstrating
the computation of form factors by BCFW recursion and unitarity based methods,
we go on to show how the scalar form factor can be supersymmetrised to encompass the full stress-tensor multiplet.
In Chapter Four, we discuss the Sudakov form factor in ABJM Theory. This
object, which first appears at two loops and controls the IR divergences of the theory, is computed by generalised unitarity. In particular, we note that the maximal transcendentality of three dimensional integrals is related to particular triple cuts.
Finally, in Chapter Five we consider massive amplitudes on the Coulomb Branch
of N = 4 at one loop. Here we find that vertex cut conditions inherited from the embedding of the theory in String Theory lead to a restricted class of massive integrals
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The elemental mechanism of transcriptional pausing.
Transcriptional pausing underlies regulation of cellular RNA biogenesis. A consensus pause sequence that acts on RNA polymerases (RNAPs) from bacteria to mammals halts RNAP in an elemental paused state from which longer-lived pauses can arise. Although the structural foundations of pauses prolonged by backtracking or nascent RNA hairpins are recognized, the fundamental mechanism of the elemental pause is less well-defined. Here we report a mechanistic dissection that establishes the elemental pause signal (i) is multipartite; (ii) causes a modest conformational shift that puts γ-proteobacterial RNAP in an off-pathway state in which template base loading but not RNA translocation is inhibited; and (iii) allows RNAP to enter pretranslocated and one-base-pair backtracked states easily even though the half-translocated state observed in paused cryo-EM structures rate-limits pause escape. Our findings provide a mechanistic basis for the elemental pause and a framework to understand how pausing is modulated by sequence, cellular conditions, and regulators
La variation de la morphologie pronominale dans les variétés parlées dans les Alpes-Maritimes
We examine the pronoun morphology of Occitan dialects in the French Department of Alpes-Maritimes in order to better account for three phenomena that exist in certain Romance varieties: 1) the variable linear orders of clitic pronouns, 2) syncretism and 3) opacity.
We analyse data from the PAM (Parlers des Alpes-Maritimes, Dalbera 1994) in the form of questionnaires that the participant translates from French into his own dialect. We systematically compare the forms of pronouns as well as their linear orders. We compare the approaches proposed to account for these three phenomena in other Romance languages. An approach using morphological models gives us the flexibility to account for the facts observed.
In some Romance languages, clitic pronouns are ordered from left to right depending on an increase in structural complexity (morphological specification) of a hierarchical feature geometry (for example, person, number, gender, case). We use a hypothesis called the Least Leafy to the Left (Heap 1998: 240) based on the geometric design where the markedness is determined by the number of contrasts present in a hierarchy. This constraint, based on morphological models that allow under-specification, better represents variable linear orders and, when the under-specification of features cannot account for variable linear orders, we use alignment constraints which depend on the grammatical case. Within the framework of variable OT (Optimality Theory) (Reynolds 1994; see also Antilla 1995), these two constraints can have variable rankings. We show that morphological models can also represent syncretic forms as well as an opaque form
Collective responsibility in the risk society: health as a catalyst for socio-technological innovation, ecological citizenship and sustainability
In 1987 the Brundtland Report defined sustainable development as meeting the needs of the present without compromising the ability of future generations to meet their needs. This widely employed definition has successfully promoted a sustainable approach to social and environmental policies and human rights across countries which have signed up to it. While climate change discourses have prompted discussions about of the future trajectory of human society, this thesis argues that the concept of sustainability has failed to be anchored conceptually to the everyday practices of global citizens. These discourses have encouraged social and technological innovations which focus on meeting these risks. There remain, however, significant inequalities among the world’s citizens in their capacity to access resources and their capacity mitigate climate risks. this thesis explores the risk factors which climate change poses, the sustainability discourses which have emerged from these debates, and their role in promoting an equitable, open, transparent and accessible form of cosmopolitan ecological citizenship. This is examined through desk research exploring policy and legislation, a review of case studies including social and technological innovators working in the field of sustainability, and primary qualitative research. I propose a model of ecological citizenship based on the premise that climate change poses risks to the physical, social and psychological health and wellbeing of the individual and communities, and that these risks are universal. This I label the Biopsychosocial Model of Ecological Citizenship, or BiMEC for short. I argue that these risks represent breaches of fundamental rights to health. Further, upholding the right to health is a collective responsibility for all human beings and these collective responses to these risks emerge in the form of social and technological innovations which address them. Finally, I argue that they are realisable through equal access to these fundamental rights
An Empirical Examination of Two Models of Cultural Causation
The traditional macroscopic model of cultural causation advanced by Weber and modified by Parsons assumes that values provide orientation for human action. Thus, values are conceptualized as the intervening link between culture and behavior and in general, are viewed as predictive of human action. Swidler (1986) contends that values are a poor predictor of behavior. As an a/tentative model, Swidler asserts that cultures provide actors with a limited array of behavioral options. Because this array is finite and indicative of a particular cultural setting, inuacultural behavioral similatities are observable. We empirically test the link between culture and behavior in a situation which Swidler defines as "unsettled lives." Our findings offer little support for the traditionally assumed link between values and behavior. The theoretical implications of our findings are discussed and an expansion of Swidler's model is offered
Carers looking after an adult with an intellectual disability and behaviours that challenge: attributions, emotional reactions and helping behaviour
Background: Previous studies have suggested that paid and family carers’ practical responses, or helping behaviour, can influence the development and maintenance of behaviours that challenge. Therefore, it is important that we understand how best to support carers to respond in a helpful way at times of difficult to manage behaviour. This thesis portfolio comprises of two main sections. The first section involves a systematic review which utilises Weiner’s Attributional Model of Helping Behaviour (1985) as a framework to explore attributions and emotions. These factors are proposed to influence paid and family carers’ willingness to help a child or adult with an intellectual disability (ID) and behaviours that challenge. The second section involves an empirical study which aims to explore the qualitative experiences of family carers looking after an adult relative with an ID and behaviours that challenge. There is a lack of knowledge relating to the experience of family carers, with existing research focusing primarily on the experiences of paid carers, using quantitative methodology.
Method: The review involved a thorough search of online databases and reference lists to identify relevant articles, as defined by predetermined eligibility criteria. Fifteen articles were identified, which were synthesised and evaluated using an adapted quality rating scale. The empirical study involved conducting semi-structured interviews with nine family carers about their lived experience of caring for an adult relative with an ID and behaviours that challenge. Interviews were recorded, transcribed and analysed using interpretive phenomenological analysis (IPA).
Results: The systematic review found evidence that emotions were associated with helping behaviour, however evidence that emotions acted as a mediating variable between attributions and helping behaviour was inconclusive. There was evidence of an association between carer’s optimism that the behaviour will change and the likelihood of offering help to a person, however optimism for change was not measured across studies. From the empirical study analysis, five subordinate themes emerged from the interviews; ‘searching for the reason’, ‘negative emotions and behaviours that challenge’, ‘tag-team approach – stronger together, ‘limited support’ and ‘impact of caring’. Included in this were seven subthemes.
Discussion: Studies included in the review provided, at best, partial support for Weiner’s model and offered limited understanding of carer’s responses to behaviours that challenge. A number of theoretical and methodological limitations of Weiner’s model and of the studies that have explored the model are described. As a result, these findings are not generalisable to real-life caregiving situations, particularly to those looking after an adult relative with an ID. This review found a lack of studies related to family carers, despite this being a population that also provide a significant amount of care and support at times of behaviours that challenge. Study limitations, implications for clinical practice and recommendations for future research are discussed
Ecosystem Services in Decision Making: Time to Deliver
Over the past decade, efforts to value and protect ecosystem services have been promoted by many as the last, best hope for making conservation mainstream – attractive and commonplace worldwide. In theory, if we can help individuals and institutions to recognize the value of nature, then this should greatly increase investments in conservation, while at the same time fostering human well-being. In practice, however, we have not yet developed the scientific basis, nor the policy and finance mechanisms, for incorporating natural capital into resource- and land-use decisions on a large scale. Here, we propose a conceptual framework and sketch out a strategic plan for delivering on the promise of ecosystem services, drawing on emerging examples from Hawai‘i. We describe key advances in the science and practice of accounting for natural capital in the decisions of individuals, communities, corporations, and governments
Ecosystem Services in Decision Making: Time to Deliver
Over the past decade, efforts to value and protect ecosystem services have been promoted by many as the last, best hope for making conservation mainstream – attractive and commonplace worldwide. In theory, if we can help individuals and institutions to recognize the value of nature, then this should greatly increase investments in conservation, while at the same time fostering human well-being. In practice, however, we have not yet developed the scientific basis, nor the policy and finance mechanisms, for incorporating natural capital into resource- and land-use decisions on a large scale. Here, we propose a conceptual framework and sketch out a strategic plan for delivering on the promise of ecosystem services, drawing on emerging examples from Hawai‘i. We describe key advances in the science and practice of accounting for natural capital in the decisions of individuals, communities, corporations, and governments
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