36 research outputs found

    Corrections to flat-space particle dynamics arising from space granularity

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    The construction of effective Hamiltonians describing corrections to flat space particle dynamics arising from the granularity of space at very short distances is discussed in the framework of an heuristic approach to the semiclassical limit of loop quantum gravity. After some general motivation of the subject, a brief non-specialist introduction to the basic tools employed in the loop approach is presented. The heuristical semiclassical limit is subsequently defined and the application to the case of photons and spin 1/2 fermions is described. The resulting modified Maxwell and Dirac Hamiltonians, leading in particular to Planck scale corrections in the energy-momentum relations, are presented. Alternative interpretations of the results and their limitations, together with other approaches are briefly discussed along the text. Three topics related to the above methods are reviewed: (1) The determination of bounds to the Lorentz violating parameters in the fermionic sector, obtained from clock comparison experiments.(2) The calculation of radiative corrections in preferred frames associated to space granularity in the framework of a Yukawa model for the interactions and (3) The calculation of synchrotron radiation in the framework of the Myers-Pospelov effective theories describing Lorentz invariance violations, as well as a generalized approach to radiation in Planck scale modified electrodynamics. The above exploratory results show that quantum gravity phenomenology provides observational guidance in the construction of quantum gravity theories and opens up the possibility of probing Planck scale physics.Comment: 49 pages, 6 figures and 4 tables. Extended version of the talk given at the 339-th WE-Heraeus-Seminar: Special Relativity, will it survive the next 100 years?, Potsdam, february 200

    Neoadjuvant Therapy in Early Breast Cancer:Treatment Considerations and Common Debates in Practice

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    Neoadjuvant treatment offers a number of benefits for patients with early breast cancer, and is an important option for consideration by multidisciplinary teams. Despite literature showing its efficacy, the use of neoadjuvant therapy varies widely. Here we discuss the clinical evidence supporting the use of neoadjuvant therapy in early stage breast cancer, including patient selection, monitoring response, surgery and radiotherapy considerations, with the aim of assisting multidisciplinary teams to determine patient suitability for neoadjuvant treatment

    Geological Carbon Sequestration in the Context of Two-Phase Flow in Porous Media: A Review

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    This is an Accepted Manuscript of an article published in Critical Reviews in Environmental Science and Technology on 21 May 2014, available online: http://dx.doi.org/10.1080/10643389.2014.924184In this review, various aspects of geological carbon sequestration are discussed in relation to the principles of two-phase flow in porous media. Literature reports on geological sequestration of CO2 show that the aquifer storage capacity, sealing integrity of the caprock and the in situ processes, e.g., the displacement of brine by supercritical CO2 (scCO2), convection-diffusion-dissolution processes involving scCO2 and brine, geochemical reactions, and mineral precipitation depend on the fluid-fluid-rock characteristics as well as the prevailing subsurface conditions. Considering the complexity of the interrelationships among various processes, experimental investigations and network of mathematical functions are required for the ideal choice of geological site with predictable fluid-fluid-rock behaviours that enhance effective monitoring. From a thorough appraisal of the existing publications, recommendations are made for improvement in the existing simulators to fully couple the entire processes involved in the sequestration operations and in situ mechanisms which include injection rate and pressure, brine displacement, simultaneous flow of free and buoyant phases of CO2, various trapping mechanisms, convection-diffusion-dissolution processes, scCO2-brine-rock reactions, precipitation of the rock minerals and the consequences on the hydraulic and hydrogeological properties in the course of time as well as the quantity of injected CO2. Suggestion is made for the inclusion of leakage parameters on site-specific basis to quantify the risks posed by the prevailing fluid-fluid-rock characteristics as well as their immediate and future tendencies. Calls are also made for thorough investigations of factors that cause non-uniqueness of the two-phase flow behaviour with suggestions for the use of appropriate experimental techniques. The review comprehensively synthesizes the available knowledge in the geological carbon sequestration in a logical sequence
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