Localization and diffusion in polymer quantum field theory

Polymer quantization is a non-standard approach to quantizing a classical system inspired by background independent approaches to quantum gravity such as loop quantum gravity. When applied to field theory it introduces a characteristic polymer scale at the level of the fields classical configuration space. Compared with models with space-time discreteness or non-commutativity this is an alternative way in which a characteristic scale can be introduced in a field theoretic context. Motivated by this comparison we study here localization and diffusion properties associated with polymer field observables and dispersion relation in order to shed some light on the novel physical features introduced by polymer quantization. While localization processes seems to be only mildly affected by polymer effects, we find that polymer diffusion differs significantly from the "dimensional reduction" picture emerging in other Planck-scale models beyond local quantum field theory.Comment: 16 pages, 5 figure

The CorDis Corpus Mark-up and Related Issues

CorDis is a large, XML, TEI-conformant, POS-tagged, multimodal, multigenre corpus representing a significant portion of the political and media discourse on the 2003 Iraqi conflict. It was generated from different sub-corpora which had been assembled by various research groups, ranging from official transcripts of Parliamentary sessions, both in the US and the UK, to the transcripts of the Hutton Inquiry, from American and British newspaper coverage of the conflict to White House press briefings and to transcriptions of American and British TV news programmes. The heterogeneity of the data, the specificity of the genres and the diverse discourse analytical purposes of different groups had led to a wide range of coding strategies being employed to make textual and meta-textual information retrievable. The main purpose of this paper is to show the process of harmonisation and integration whereby a loose collection of texts has become a stable architecture. The TEI proved a valid instrument to achieve standardisation of mark-up. The guidelines provide for a hierarchical organisation which gives the corpus a sound structure favouring replicability and enhancing the reliability of research. In discussing some examples of the problems encountered in the annotation, we will deal with issues like consistency and re-usability, and will examine the constraints imposed on data handling by specific research objectives. Examples include the choice to code the same speakers in different ways depending on the various (institutional) roles they may assume throughout the corpus, the distinction between quotations of spoken or written discourse and quotations read aloud in the course of a spoken text, and the segmentation of portions of news according to participants interaction and use of camera/voiceover

Are carrier-to-noise algorithms equivalent in all situations?

This paper describes methods to estimate the carrier to noise ratio in GNSS application

A fully digital model for Kalman filters

The Kalman filter is a mathematical method, whose purpose is to process noisy measurements in order to obtain an estimate of some relevant parameters of a system. It represents a valuable tool in the GNSS area, with some of its main applications related to the computation of the user PVT solution and to the integration of GNSS receivers with INS or other sensors. The Kalman filter is based on a state space representation, that describes the analyzed system as a set of differential equations that establishes the connections between the inputs, the outputs and the state variables of the analyzed system. In the continuous time domain there exists a large class of physical processes with a time evolution well described by means of stochastic differential equations. A typical problem is the need for an equivalent system in the discrete time, due to the discrete nature of the data to be processed. In the literature, it is quite common to solve this problem in the continuous time domain and to approximate the solution using a Taylor series approximation, to obtain an approximate discrete time version of the continuous time problem. By the way, other methods exist, based on the possibility to transform a continuous-time system to a discrete-time system by means of transformations from the Laplace complex plane to the z plane. These methods are widely used in the digital signal processing community, for example, to design digital filters from their analog counterparts. The main advantage of this approach is that it is very easily implemented by applying some mechanical rules. Moreover the nature of the approximation introduced by the Laplace-z transformation is a-priori known and clearly readable in the frequency domain. In the following the classical methods based on the Taylor approximation and on the Laplace-z transformations will be analyzed and compare

Probing the spacetime fabric: from fundamental discreteness to quantum geometries

This thesis deals primarily with the phenomenology associated to quan- tum aspects of spacetime. In particular, it aims at exploring the phenomeno- logical consequences of a fundamental discreteness of the spacetime fabric, as predicted by several quantum gravity models and strongly hinted by many theoretical insights. The first part of this work considers a toy-model of emergent spacetime in the context of analogue gravity. The way in which a relativistic Bose\u2013 Einstein condensate can mimic, under specific configurations, the dynamics of a scalar theory of gravity will be investigated. This constitutes proof-of- concept that a legitimate dynamical Lorentzian spacetime may emerge from non-gravitational (discrete) degrees of freedom. Remarkably, this model will emphasize the fact that in general, even when arising from a relativis- tic system, any emergent spacetime is prone to show deviations from exact Lorentz invariance. This will lead us to consider Lorentz Invariance Viola- tions as first candidate for a discrete spacetime phenomenology. Having reviewed the current constraints on Lorentz Violations and stud- ied in depth viable resolutions of their apparent naturalness problem, the second part of this thesis focusses on models based on Lorentz invariance. In the context of Casual Set theory, the coexistence of Lorentz invariance and discreteness leads to an inherently nonlocal scalar field theory over causal sets well approximating a continuum spacetime. The quantum as- pects of the theory in flat spacetime will be studied and the consequences of its non-locality will be spelled out. Noticeably, these studies will lend support to a possible dimensional reduction at small scales and, in a clas- sical setting, show that the scalar field is characterized by a universal non- minimal coupling when considered in curved spacetimes. Finally, the phenomenological possibilities for detecting this non-locality will be investigated. First, by considering the related spontaneous emission of particle detectors, then by developing a phenomenological model to test nonlocal effects using opto-mechanical, non-relativistic systems. In both cases, one could be able to cast in the near future stringent bounds on the non-locality scal

Patient selection for partial breast irradiation by intraoperative radiation therapy: Can magnetic resonance imaging be useful?- perspective from radiation oncology point of view

The guidelines of the European and American Societies of Radiation Oncology (GEC-ESTRO and ASTRO) defined the selection criteria to offer partial breast irradiation (PBI) after lumpectomy in patients with low risk breast cancer regardless pre-operative staging. A recent publication by Tallet et al. explored the impact of preoperative magnetic resonance imaging (MRI) on patient eligibility for PBI. From their study, an ipsilateral BC was detected in 4% of patients, excluding these patients from intraoperative radiotherapy (IORT). The authors suggested that preoperative MRI should be used routinely for patient's candidate to IORT, because of the rate of ipsilateral breast cancer detected. In view of Tallet's article, we analyzed some aspects of this issue in order to envisage some possible perspective on how to better identify those patients who could benefit from PBI, especially using IORT. From historical studies, the risk of breast cancer recurrence outside index quadrant without irradiation is in the range of 1.5-3.5%. MRI sensitivity for detection of invasive cancer is reported up to 100%, and it is particularly useful in dense breast. Other imaging technique did not achieve the same sensibility and specificity as conventional MRI. Of note, none of randomized trials published and ongoing on PBI included preoperative MRI as part of staging. To perform a preoperative MRI in PBI setting is an interesting issue, but the available data suggest that this issue should be preferably studied in the setting of prospective clinical trials to clarify the role of MRI and the clinical meaning of the discovered additional foci. \ua9 Journal of Thoracic Disease

Missing upper incisors: A retrospective study of orthodontic space closure versus implant

Background: The aim of this retrospective study was to compare the esthetic, periodontal, and functional outcomes of orthodontic space closure versus implant substitution in patients with missing maxillary incisors 5 years after completion of treatment. Methods: The study group consisted of ten patients treated with orthodontic space closure (six males, four females, mean age 19 ± 2.1 years at the completion of treatment) and ten patients treated with implant insertion (five males, five females, mean age 20 ± 1.4 years at the time of implant insertion). Tooth mobility, plaque index, probing depth, infraocclusion, open gingival embrasure (black triangle), and temporomandibular joint function were recorded at the 5.6 years follow-up. Self-perceived dental esthetic appearance was also evaluated through a visual analog scale (VAS) questionnaire. T-test was used to evaluate the data. Results: All patients were equally satisfied with the appearance of their teeth 5.6 ± 0.4 years after the completion of treatment. No statistically significant differences were found in relation to the VAS scores of the subjects (P < 0.857). No significant differences were found in tooth mobility, plaque index (P < 0.632), and the prevalence of signs and symptoms of temporomandibular disorders. However, significant infraocclusion was noticed in all implant patients (P < 0.001). Probing depth was also significantly higher in implant patients (P < 0.001). Conclusions: Orthodontic space closure and implant of missing maxillary incisors produced similar, well-accepted esthetic results. None of the treatments impaired temporomandibular joint function. Nevertheless, infraocclusion was evident in implant patients. Space closure patients also showed better periodontal health in comparison with implant patients

Late Pleistocene and Holocene distribution history of the Eurasian beaver in Italy

The genus Castor first appeared in the Palaearctic region during the Late Miocene, while the current species, Castor fiber, is widely accepted to have emerged in the Early Pleistocene. In the Last Glacial Maximum (Late Pleistocene), the beaver disappeared from most of the Western Palaearctic, only surviving in a few relic areas including the south-eastern Alpine Chain as shown by new data. After the subsequent extended repopulation in the warmer phases of the Lateglacial and in the early Holocene, the species once again disappeared locally from several countries, including Italy, between the 17th and the 20th centuries. Direct or indirect persecution by humans seems to be the main cause of beaver extinction in Europe. In Low Medieval Italy, it is more likely that the disappearance of the beaver between the 16th and 17th centuries was due to habitat alteration and human population pressure. Numerous reclamations have been carried out since the late Middle Ages, mostly in the easternmost area of the Po Valley, the last beaver refuge in Italy. Eurasian beaver was common in the northern and widespread in the central part of Italy, but always absent in southern Italy, probably due to unfavourable hydrological conditions of watercourses in the latter

Which Arabic and Why? Policies, Politics, and Teaching

[One day, the famous grammarian] al-Farrā’ made several mistakes while speaking in the presence of Hārūn al-Rašīd. [The vizier] Ja‘far b. Yaḥyā al-Barmakī pointed this out to the caliph, who said: “Al-Farrā’, are you speaking incorrectly?”. “Commander of the Faithful”, replied al-Farrā’, “while it is natural for the Beduins to inflect words correctly, for citydwellers [like me] it is not. When I prepare, I speak correctly; when I speak off the cuff, I make mistakes”. Al-Rašīd appreciated al-Farrā’’s words. (Ibn Ḫallikān, 1968-72, vol. 6, 147