966 research outputs found
Laser induced fluorescence for axion dark matter detection: a feasibility study in YLiF:Er
We present a detection scheme to search for QCD axion dark matter, that is
based on a direct interaction between axions and electrons explicitly predicted
by DFSZ axion models. The local axion dark matter field shall drive transitions
between Zeeman-split atomic levels separated by the axion rest mass energy . Axion-related excitations are then detected with an upconversion scheme
involving a pump laser that converts the absorbed axion energy (
hundreds of eV) to visible or infrared photons, where single photon
detection is an established technique. The proposed scheme involves rare-earth
ions doped into solid-state crystalline materials, and the optical transitions
take place between energy levels of electron configuration. Beyond
discussing theoretical aspects and requirements to achieve a cosmologically
relevant sensitivity, especially in terms of spectroscopic material properties,
we experimentally investigate backgrounds due to the pump laser at temperatures
in the range K. Our results rule out excitation of the upper Zeeman
component of the ground state by laser-related heating effects, and are of some
help in optimizing activated material parameters to suppress the
multiphonon-assisted Stokes fluorescence.Comment: 8 pages, 5 figure
Temporal evolution of long-period seismicity at Etna Volcano, Italy, and its relationships with the 2004â2005 eruption
Between December 2004 and August 2005, more than 50,000 long-period events (LP) accompanied by very-long period pulses (VLP) were recorded at Mt. Etna, encompassing the effusive eruption which started in September 2004. The observed activity can be explained by the injection of a gas slug formed within the magmatic column into an overlying cavity filled by either magmatic or hydrothermal fluids, thus triggering cavity resonance. Although a large number of LP events exhibit similar waveforms before the eruption, they change significantly during and after the eruption. We study the temporal evolution of the LP-VLP activity in terms of the source movement, change of the waveforms, temporal evolution of the dominant resonance frequencies and the source Q factor and changes in the polarization of the signal. The LP source locations before and after the eruption, respectively, do not move significantly, while a slight movement of the VLP source is found. The intensity of the LP events increases after the eruption as well as their dominant frequency and Q factor, while the polarization of the signals changes from predominantly transversal to pure radial motion. Although in previous studies a link between the observed LP activity and the eruption was not found, these observations suggest that such a link was established at the latter end of the eruptive sequence, most likely as a consequence of a reestablishment of the pressure balance in the plumbing system, after it was undermined due to the discharge of large amounts of resident magma during the eruption. Based on the polarization properties of the signal and geological setting of the area, a fluid-filled crack is proposed as the most likely source geometry. The spectral analysis based on the autoregressive-models (SOMPI) is applied to the signals in order to analyse the resonance frequencies and the source Q-factors. The results suggest water and basalt at low gas volume fraction as the most likely fluids involved in the source process. Using theoretical relations for the âslow wavesâ radiated from the fluid-filled crack, we also estimate the crack size for both fluids, respectively
Temporal evolution of Long-Period seismicity at Etna Volcano, Italy, and its relationships with the 2004-2005 eruption
Between December 2004 and August 2005, more than 50,000 long-period events (LP) accompanied by very-long period pulses (VLP) were recorded at Mt. Etna, encompassing the effusive eruption which started in September 2004. The observed activity can be explained by the injection of a gas slug formed within the magmatic column into an overlying cavity filled by either magmatic or hydrothermal fluids, thus triggering cavity resonance. Although a large number of LP events exhibit similar waveforms before the eruption, they change significantly during and after the eruption. We study the temporal evolution of the LP-VLP activity in terms of the source movement, change of the waveforms, temporal evolution of the dominant resonance frequencies and the source Q factor and changes in the polarization of the signal. The LP source locations before and after the eruption, respectively, do not move significantly, while a slight movement of the VLP source is found. The intensity of the LP events increases after the eruption as well as their dominant frequency and Q factor, while the polarization of the signals changes from predominantly transversal to pure radial motion. Although in previous studies a link between the observed LP activity and the eruption was not found, these observations suggest that such a link was established at the latter end of the eruptive sequence, most likely as a consequence of a reestablishment of the pressure balance in the plumbing system, after it was undermined due to discharge of large amounts of resident magma during the eruption. Based on the polarization properties of the signal and geological setting of the area, a fluid-
filled crack is proposed as the most likely source geometry. The spectral analysis based on the autoregressive-models (SOMPI) is
applied to the signals in order to analyse the resonance frequencies and the source Q-factors. The results suggest water and basalt
with the low gas volume fraction as the most likely fluids involved in the source process. Using theoretical relations for the âslow
wavesâ radiated from the fluid-filled crack, we also estimate the crack size for both fluids, respectively
Star Architecture as Socio-Material Assemblage
Taking inspiration from new materialism and assemblage, the chapter deals with star architects and iconic buildings as socio-material network effects that do not pre-exist action, but are enacted in practice, in the materiality of design crafting and city building. Star architects are here conceptualized as part of broader assemblages of actors and practices âmaking star architectureâ a reality, and the buildings they design are considered not just as unique and iconic objects, but dis-articulated as complex crafts mobilizing skills, technologies, materials, and forms of knowledge not necessarily ascribable to architecture. Overcoming narrow criticism focusing on the symbolic order of icons as unique creations and alienated repetitions of capitalist development, the chapterâs main aim is to widen the scope of critique by bridging culture and economy, symbolism and practicality, making star architecture available to a broad, fragmented arena of (potential) critics, unevenly equipped with critical tools and differentiated experiences
Ontologies, Mental Disorders and Prototypes
As it emerged from philosophical analyses and cognitive research, most concepts exhibit typicality effects, and resist to the efforts of defining them in terms of necessary and sufficient conditions. This holds also in the case of many medical concepts. This is a problem for the design of computer science ontologies, since knowledge representation formalisms commonly adopted in this field do not allow for the representation of concepts in terms of typical traits. However, the need of representing concepts in terms of typical traits concerns almost every domain of real world knowledge, including medical domains. In particular, in this article we take into account the domain of mental disorders, starting from the DSM-5 descriptions of some specific mental disorders. On this respect, we favor a hybrid approach to the representation of psychiatric concepts, in which ontology oriented formalisms are combined to a geometric representation of knowledge based on conceptual spaces
Exploring Values in Museum Artifacts in the SPICE Project: A Preliminary Study
This document describes the rationale, the implementation and a preliminary evaluation of a semantic reasoning tool developed in the EU H2020 SPICE project to enhance the diversity of perspectives experienced by museum visitors. The tool, called DEGARI 2.0 for values, relies on the commonsense reasoning framework , and exploits an ontological model formalizing the Haidtâs theory of moral values to associate museum items with combined values and emotions. Within a museum exhibition, this tool can suggest cultural items that are associated not only with the values of already experienced or preferred objects, but also with novel items with different value stances, opening the visit experience to more inclusive interpretations of cultural content. The system has been preliminarily tested, in the context of the SPICE project, on the collection of the Hecht Museum of Haifa
Semantically Aware Text Categorisation for Metadata Annotation
In this paper we illustrate a system aimed at solving a longstanding and challenging problem: acquiring a classifier to automatically annotate bibliographic records by starting from a huge set of unbalanced and unlabelled data. We illustrate the main features of the dataset, the learning algorithm adopted, and how it was used to discriminate philosophical documents from documents of other disciplines. One strength of our approach lies in the novel combination of a standard learning approach with a semantic one: the results of the acquired classifier are improved by accessing a semantic network containing conceptual information. We illustrate the experimentation by describing the construction rationale of training and test set, we report and discuss the obtained results and conclude by drawing future work.</p
The ESPRI project: astrometric exoplanet search with PRIMA I. Instrument description and performance of first light observations
The ESPRI project relies on the astrometric capabilities offered by the PRIMA
facility of the Very Large Telescope Interferometer for the discovery and study
of planetary systems. Our survey consists of obtaining high-precision
astrometry for a large sample of stars over several years and to detect their
barycentric motions due to orbiting planets. We present the operation
principle, the instrument's implementation, and the results of a first series
of test observations. A comprehensive overview of the instrument infrastructure
is given and the observation strategy for dual-field relative astrometry is
presented. The differential delay lines, a key component of the PRIMA facility
which was delivered by the ESPRI consortium, are described and their
performance within the facility is discussed. Observations of bright visual
binaries are used to test the observation procedures and to establish the
instrument's astrometric precision and accuracy. The data reduction strategy
for astrometry and the necessary corrections to the raw data are presented.
Adaptive optics observations with NACO are used as an independent verification
of PRIMA astrometric observations. The PRIMA facility was used to carry out
tests of astrometric observations. The astrometric performance in terms of
precision is limited by the atmospheric turbulence at a level close to the
theoretical expectations and a precision of 30 micro-arcseconds was achieved.
In contrast, the astrometric accuracy is insufficient for the goals of the
ESPRI project and is currently limited by systematic errors that originate in
the part of the interferometer beamtrain which is not monitored by the internal
metrology system. Our observations led to the definition of corrective actions
required to make the facility ready for carrying out the ESPRI search for
extrasolar planets.Comment: 32 pages, 39 figures, Accepted for publication in Astronomy and
Astrophysic
Higher-level Knowledge, Rational and Social Levels Constraints of the Common Model of the Mind
We present the input to the discussion about the computational framework known as Common Model of Cognition (CMC) from the working group dealing with the knowledge/rational/social levels. In particular, we present a list of the higher level constraints that should be addressed within such a general framework
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