1,777 research outputs found
Complete Boolean algebras are Bousfield lattices
Given a complete Heyting algebra we construct an algebraic tensor
triangulated category whose Bousfield lattice is the Booleanization of the
given Heyting algebra. As a consequence we deduce that any complete Boolean
algebra is the Bousfield lattice of some tensor triangulated category. Using
the same ideas we then give two further examples illustrating some interesting
behaviour of the Bousfield lattice.Comment: 10 pages, update to clarify the products occurring in the main
constructio
Supersymmetry and the Cosmic Ray Positron Excess
We explore several supersymmetric alternatives to explain predictions for the
cosmic ray positron excess. Light sneutrino or neutralino LSP's, and a
fine-tuned model designed to provide a delta-function input, can give adequate
statistical descriptions of the reported HEAT data if non-thermal production of
the relic cold dark matter density dominates and/or if ``boost factors''(that
could originate in uncertainties from propagation or local density
fluctuations) to increase the size of the signal are included. All the
descriptions can be tested at the Tevatron or LHC, and some in other WIMP
detecting experiments.Comment: 15 pages, 3 figure
Shaping, imaging and controlling plasmonic interference fields at buried interfaces
Filming and controlling plasmons at buried interfaces with nanometer (nm) and
femtosecond (fs) resolution has yet to be achieved and is critical for next
generation plasmonic/electronic devices. In this work, we use light to excite
and shape a plasmonic interference pattern at a buried metal-dielectric
interface in a nanostructured thin film. Plasmons are launched from a
photoexcited array of nanocavities and their propagation is filmed via
photon-induced near-field electron microscopy (PINEM). The resulting movie
directly captures the plasmon dynamics, allowing quantification of their group
velocity at approximately 0.3c, consistent with our theoretical predictions.
Furthermore, we show that the light polarization and nanocavity design can be
tailored to shape transient plasmonic gratings at the nanoscale. These results,
demonstrating dynamical imaging with PINEM, pave the way for the fs/nm
visualization and control of plasmonic fields in advanced heterostructures
based on novel 2D materials such as graphene, MoS, and ultrathin metal
films.Comment: 16 pages, 5 figures, 3 supplementary figure
Design and implementation of a fs-resolved transmission electron microscope based on thermionic gun technology [post-print]
In this paper, the design and implementation of a femtosecond-resolved ultrafast transmission electron microscope is presented, based on a thermionic gun geometry. Utilizing an additional magnetic lens between the electron acceleration and the nominal condenser lens system, a larger percentage of the electrons created at the cathode are delivered to the specimen without degrading temporal, spatial and energy resolution significantly, while at the same time maintaining the femtosecond temporal resolution. Using the photon-induced near field electron microscopy effect (PINEM) on silver nanowires the cross-correlation between the light and electron pulses was measured, showing the impact of the gun settings and initiating laser pulse duration on the electron bunch properties. Tuneable electron pulses between 300 fs and several ps can be obtained, and an overall energy resolution around 1 eV was achieved
Imaging in myeloma with focus on advanced imaging techniques.
In recent years, there have been major advances in the imaging of myeloma with whole body MRI incorporating diffusion-weighted imaging, emerging as the most sensitive modality. Imaging is now a key component in the work-up of patients with a suspected diagnosis of myeloma. The International Myeloma Working Group now specifies that more than one focal lesion on MRI or lytic lesion on whole body low-dose CT or fludeoxyglucose (FDG) PET/CT fulfil the criteria for bone damage requiring therapy. The recent National Institute for Health and Care Excellence myeloma guidelines recommend imaging in all patients with suspected myeloma. In addition, there is emerging data supporting the use of functional imaging techniques (WB-DW MRI and FDG PET/CT) to predict outcome and evaluate response to therapy. This review summarises the imaging modalities used in myeloma, the latest guidelines relevant to imaging and future directions
Dark Matter detection via lepton cosmic rays
Recent observations of lepton cosmic rays, coming from the PAMELA and FERMI
experiments, have pushed our understanding of the interstellar medium and
cosmic rays sources to unprecedented levels. The imprint of dark matter on
lepton cosmic rays is the most exciting explanation of both PAMELA's positron
excess and FERMI's total flux of electrons. Alternatively, supernovae are
astrophysical objects with the same potential to explain these observations. In
this work, we present an updated study of the astrophysical sources of lepton
cosmic rays and the possible trace of a dark matter signal on the positron
excess and total flux of electrons.Comment: 6 pages and 3 figures. Proceedings for PASCOS 2010, Valencia, Spai
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Health Researchers' Use of Social Media: Scoping Review.
BackgroundHealth researchers are increasingly using social media in a professional capacity, and the applications of social media for health researchers are vast. However, there is currently no published evidence synthesis of the ways in which health researchers use social media professionally, and uncertainty remains as to how best to harness its potential.ObjectiveThis scoping review aimed to explore how social media is used by health researchers professionally, as reported in the literature.MethodsThe scoping review methodology guided by Arksey and O'Malley and Levac et al was used. Comprehensive searches based on the concepts of health research and social media were conducted in MEDLINE, EMBASE, CINAHL, PsycINFO, ERIC, and Web of Science databases, with no limitations applied. Articles were screened at the title and abstract level and at full text by two reviewers. One reviewer extracted data that were analyzed descriptively to map the available evidence.ResultsA total of 8359 articles were screened at the title and abstract level, of which 719 were also assessed at full text for eligibility. The 414 articles identified for inclusion were published in 278 different journals. Studies originated from 31 different countries, with the most prevalent being the United States (52.7% [218/414]). The health discipline of the first authors varied, with medicine (33.3% [138/414]) being the most common. A third of the articles covered health generally, with 61 health-specific topics. Papers used a range of social media platforms (mean 1.33 [SD 0.7]). A quarter of the articles screened reported on social media use for participant recruitment (25.1% [104/414]), followed by practical ways to use social media (15.5% [64/414]), and use of social media for content analysis research (13.3% [55/414]). Articles were categorized as celebratory (ie, opportunities for engagement, 72.2% [299/414]), contingent (ie, opportunities and possible limitations, 22.7% [94/414]) and concerned (ie, potentially harmful, 5.1% [21/414]).ConclusionsHealth researchers are increasingly publishing on their use of social media for a range of professional purposes. Although most of the sentiment around the use of social media in health research was celebratory, the uses of social media varied widely. Future research is needed to support health researchers to optimize their social media use
Homotopy Theoretic Models of Type Theory
We introduce the notion of a logical model category which is a Quillen model
category satisfying some additional conditions. Those conditions provide enough
expressive power that one can soundly interpret dependent products and sums in
it. On the other hand, those conditions are easy to check and provide a wide
class of models some of which are listed in the paper.Comment: Corrected version of the published articl
Review on Neutrino Telescopes
I will discuss the motivations for Neutrino Astronomy and its prospects given
the current experimental scenario, which is the main focus of this paper. I
will also go through the first results of the IceCube detector deep in the ice
and of the ANTARES undersea telescope underlying complementary aspects, common
and different challenges. It is an exciting time for this science since the
first completed undersea detector is successfully taking data and the first
cubic kilometer detector is going to be shortly more than half-way from its
completion in Antarctica.Comment: Proceeding of CRIS2008 Conference, Salina, Sept. 2008, 9 pages, 8
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