355 research outputs found

    Dynamical Mean-Field Theory of Electron-Phonon Interactions in Correlated Systems: Application to Isotope Effects on Electronic Properties

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    We use a recently developed formalism (combining an adiabatic expansion and dynamical mean-field theory) to obtain expressions for isotope effects on electronic properties in correlated systems. As an example we calculate the isotope effect on electron effective mass for the Holstein model as a function of electron-phonon interaction strength and doping. Our systematic expansion generates diagrams neglected in previous studies, which turn out to give the dominant contributions. The isotope effect is small unless the system is near a lattice instability. We compare this to experiment.Comment: 6 pages, 4 figures; added discussion of isotope effect away from half fillin

    Randomization‐based statistical inference: A resampling and simulation infrastructure

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143752/1/test12156_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143752/2/test12156.pd

    On the distribution of spinal premotor interneurons

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    The activity of flexor and extensor motor neurons is tightly regulated by a network of interneurons in the spinal cord. The introduction of rabies retrograde monosynaptic tracing has provided a powerful method to map interneurons directly connected to motor neurons so as to visualize premotor circuits. Previous strategies have used AAV for complementing rabies glycoprotein expression in motor neurons to obtain selectivity in transsynaptic transfer to identify premotor interneurons innervating specific motor neuron pools These studies revealed differences in the location of flexor and extensor premotor interneurons. Here, we report that by using a genetic approach to complement rabies glycoprotein expression in motor neurons, we did not observe any differences in the distribution of flexor and extensor premotor interneurons. In order to identify possible causes for these paradoxical findings, we discuss advantages and caveats of the experimental designs and suggest ways forward to resolve possible ambiguities. Furthermore, to obtain a complete picture of existing approaches and results we ask for contributions from the scientific community describing the use of additional mouse models, viral constructs, and complementation methods. The aim is to generate an open, comprehensive database to understand the specific organisation of premotor circuits

    Life path analysis: scaling indicates priming effects of social and habitat factors on dispersal distances

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    1. Movements of many animals along a life-path can be separated into repetitive ones within home ranges and transitions between home ranges. We sought relationships of social and environmental factors with initiation and distance of transition movements in 114 buzzards Buteo buteo that were marked as nestlings with long-life radio tags. 2. Ex-natal dispersal movements of 51 buzzards in autumn were longer than for 30 later in their first year and than 35 extra-natal movements between home ranges after leaving nest areas. In the second and third springs, distances moved from winter focal points by birds that paired were the same or less than for unpaired birds. No post-nuptial movement exceeded 2 km. 3. Initiation of early ex-natal dispersal was enhanced by presence of many sibs, but also by lack of worm-rich loam soils. Distances travelled were greatest for birds from small broods and with relatively little short grass-feeding habitat near the nest. Later movements were generally enhanced by the absence of loam soils and short grassland, especially with abundance of other buzzards and probable poor feeding habitats (heathland, long grass). 4. Buzzards tended to persist in their first autumn where arable land was abundant, but subsequently showed a strong tendency to move from this habitat. 5. Factors that acted most strongly in ½-km buffers round nests, or round subsequent focal points, usually promoted movement compared with factors acting at a larger scale. Strong relationships between movement distances and environmental characteristics in ½-km buffers, especially during early ex-natal dispersal, suggested that buzzards became primed by these factors to travel far. 6. Movements were also farthest for buzzards that had already moved far from their natal nests, perhaps reflecting genetic predisposition, long-term priming or poor habitat beyond the study area

    La mutación de la biblioteca en los inicios del siglo XXI

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    El papel que las bibliotecas desempeñan en la actualidad ha sido cuestionado en numerosas ocasiones, a causa de la revolución tecnológica a la que se está asistiendo, la cual pondría en amenaza el papel básico que hasta ahora tenían éstas. Pero la realidad es que se observa una tendencia en la que cada vez se construyen más bibliotecas y más complejas. Por lo que se torna harto interesante descubrir hacia dónde camina la arquitectura en este sentido. A este respecto, se advierte un cambio de paradigma respecto al papel que juega la biblioteca en la actualidad, provocando a su vez una respuesta en cuanto a la arquitectura bibliotecaria. Los cambios sociales que se han producido de la mano del desarrollo de la tecnología, se han visto implicados de forma directa e indirecta en este cambio de paradigma, presentando los desafíos a los que se enfrenta la arquitectura actual. Debido a la incertidumbre que se presenta de cara a este nuevo periodo, en base a los constantes cambios que se manifiestan debido a la rápida evolución que sufren las nuevas tecnologías, y de cara a las demandas de esta nueva sociedad, se torna fundamental la aplicación del principio de la flexibilidad en los nuevos espacios bibliotecarios, pero se rehúye de la clásica solución espacial donde el espacio se vuelve uniforme, sin apenas expresión plástica ni variedad. Por otro lado, se presentan los temidos efectos que la globalización tiene sobre el planeta, a cualquier escala, y que parecen llevar todo hacia una tendencia universalista. Por lo que se hace interesante el estudio de la arquitectura bibliotecaria desde diferentes ópticas a nivel cultural, tomando como referencia la cultura occidental, debido a su importante papel de cara al origen de este proceso, así como la cultura oriental, definida prácticamente como la antítesis de ésta. Sobre la base de lo planteado, la presente investigación, a modo de primera toma de contacto, ha pretendido abrir un campo de estudio a través del cual se puedan identificar nuevas formas de aplicar la flexibilidad en los espacios bibliotecarios, de cara a que éstos no se vuelvan caducos en cuanto al diseño que presentan, además de poner el causa los procesos de globalización que pretenden reducir la realidad actual, en base a procesos de homogeneización; por lo que se busca identificar procesos de hibridación en la arquitectura actual, a través de los cuales poder identificar si se producen diferencias entre las distintas culturas, valorando en qué medida se incluyen las cuestiones de carácter local en las obras que representan cada una de estas culturas. A través de la metodología empleada, basada en los estudios de caso individual y en el análisis comparativo de éstos, se han podido evidenciar líneas que muestran esa evolución de la arquitectura actual, en la que se torna evidente la importancia que tiene la flexibilidad en el nuevo escenario, así como la posibilidad de aplicarla de diversa manera, además de reconocerse los mencionados procesos de hibridación, permitiendo establecer diferencias entre las dos culturas, desmontando así la ambiciosa visión de carácter unilateral que se tenía sobre la globalización.Abstract: The role played by libraries nowadays has been frequently questioned in view of the technological revolution currently underway, which would seem to threaten the basic function libraries had up until now. However, what we are actually seeing is a trend in which a growing number of increasingly complex libraries are being built. Therefore, it is of interest to take a look at where architecture in this sector is heading. The truth is, a change can be observed in what is considered to be the model role of libraries today, which in turn leads to a different response in terms of their architecture. The social changes that have taken place as a result of developments in technology have played both a direct and indirect role in such a change of model and represent the challenges facing current architecture. Given the uncertainty that exists these days due to the constant changes occurring as a result of the rapid evolution of new technologies and of society’s new demands, it has become essential to build a flexibility component into all new library design concepts, while shying away from the classic solution of uniform spaces with little plastic variety or expression. On the other hand, the effects of globalisation present at all scales of life on this planet inevitably arise and tend to drive everything towards a common universality. So it is interesting to study the architecture of libraries from different cultural perspectives, firstly in Western culture, given the important role it has played in the origin of this process, and subsequently from the viewpoint of Oriental culture, practically defined as the antithesis of the former. On the basis of the above premises, this paper seeks to stand as the initial contact in a line of research that identifies new ways of applying flexibility into the architecture of libraries so that they do not become obsolete in terms of their design, as well as identifying the globalisation processes that seek to reduce current reality through homogenisation procedures. Therefore, it aims to identify hybridisation processes in current architecture that serve to ascertain whether distinctions occur between different cultures and to assess the extent to which local issues find a place in iconic buildings representing each of those cultures. By means of the methodology used, based on individual case studies and comparative analysis of each, certain traits have been revealed that show an evolution in contemporary architecture, in which greater importance is given in this new scenario to flexibility and the ability to apply it in different ways, as well as acknowledging the aforementioned hybridization processes, enabling differences between the two cultures to be identified and thus any narrow-minded view of globalization as a unilateral phenomenon to be dismantled

    A novel mixed-methods platform study protocol for investigating new surgical devices, with embedded shared learning: Ibra-net breast lesion localisation study

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    Introduction: New medical devices must have adequate research, such that outcomes are known, enabling patients to be consented with knowledge of the safety and efficacy of the device to be implanted. Device trials are challenging due to the learning curve and iterative assessment of best practice. This study is designed to pilot a national collaborative approach to medical device introduction by breast surgeons in the UK, using breast localisation devices as an exemplar. The aim is to develop an effective and transferable surgical device platform protocol design, with embedded shared learning. Methods and analysis: The iBRA-net localisation study is a UK based prospective, multi-centre platform study, comparing the safety and efficacy of novel localisation devices with wire-guided breast lesion localisation for wide local excision, using Magseed® as the pilot intervention group. Centres performing breast lesion localisation for wide local excision or excision biopsy will be eligible to participate if using one of the included devices. Further intervention arms will be added as new devices are CE marked. Outcomes will be collected via an online database. The primary outcome measure will be identification of the index lesion. Participating surgeons will be asked to record shared learning events via online questionnaires and focus group interviews to inform future study arms. Ethics and dissemination: The study will aim to collect data on 950 procedures for each intervention (Magseed® and wire localisation) from UK breast centres over an 18-month period. Shared learning will be prospectively evaluated via thematic analysis to refine breast localisation technique and to promote early identification of potential pitfalls and problems. Results will be presented at national and international conferences and published in peer reviewed journals. Registration: This is a UK national audit registered with Manchester University NHS Foundation Trust

    North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part I: Mean states

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    Simulation characteristics from eighteen global ocean–sea-ice coupled models are presented with a focus on the mean Atlantic meridional overturning circulation (AMOC) and other related fields in the North Atlantic. These experiments use inter-annually varying atmospheric forcing data sets for the 60-year period from 1948 to 2007 and are performed as contributions to the second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II). The protocol for conducting such CORE-II experiments is summarized. Despite using the same atmospheric forcing, the solutions show significant differences. As most models also differ from available observations, biases in the Labrador Sea region in upper-ocean potential temperature and salinity distributions, mixed layer depths, and sea-ice cover are identified as contributors to differences in AMOC. These differences in the solutions do not suggest an obvious grouping of the models based on their ocean model lineage, their vertical coordinate representations, or surface salinity restoring strengths. Thus, the solution differences among the models are attributed primarily to use of different subgrid scale parameterizations and parameter choices as well as to differences in vertical and horizontal grid resolutions in the ocean models. Use of a wide variety of sea-ice models with diverse snow and sea-ice albedo treatments also contributes to these differences. Based on the diagnostics considered, the majority of the models appear suitable for use in studies involving the North Atlantic, but some models require dedicated development effort
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