90 research outputs found
Energy and electromagnetism of a differential form
Let X be a smooth manifold of dimension 1+n endowed with a lorentzian metric
g, and let T be the electromagnetic energy tensor associated to a 2-form F. In
this paper we characterize this tensor T as the only 2-covariant natural tensor
associated to a lorentzian metric and a 2-form that is independent of the unit
of scale and satisfies certain condition on its divergence. This
characterization is motivated on physical grounds, and can be used to justify
the Einstein-Maxwell field equations. More generally, we characterize in a
similar manner the energy tensor associated to a differential form of arbitrary
order k. Finally, we develop a generalized theory of electromagnetism where
charged particles are not punctual, but of an arbitrary fixed dimension p. In
this theory, the electromagnetic field F is a differential form of order 2+p
and its electromagnetic energy tensor is precisely the energy tensor associated
to F.Comment: 28 pages. Referee's suggestions added. To appear in Journal of
Mathematical Physic
Free CR distributions
There are only some exceptional CR dimensions and codimensions such that the
geometries enjoy a discrete classification of the pointwise types of the
homogeneous models. The cases of CR dimensions and codimensions are
among the very few possibilities of the so called parabolic geometries. Indeed,
the homogeneous model turns out to be \PSU(n+1,n)/P with a suitable parabolic
subgroup . We study the geometric properties of such real
-dimensional submanifolds in for all . In
particular we show that the fundamental invariant is of torsion type, we
provide its explicit computation, and we discuss an analogy to the Fefferman
construction of a circle bundle in the hypersurface type CR geometry
k-Dirac operator and parabolic geometries
The principal group of a Klein geometry has canonical left action on the
homogeneous space of the geometry and this action induces action on the spaces
of sections of vector bundles over the homogeneous space. This paper is about
construction of differential operators invariant with respect to the induced
action of the principal group of a particular type of parabolic geometry. These
operators form sequences which are related to the minimal resolutions of the
k-Dirac operators studied in Clifford analysis
Rarita-Schwinger Type Operators on Spheres and Real Projective Space
In this paper we deal with Rarita-Schwinger type operators on spheres and
real projective space. First we define the spherical Rarita-Schwinger type
operators and construct their fundamental solutions. Then we establish that the
projection operators appearing in the spherical Rarita-Schwinger type operators
and the spherical Rarita-Schwinger type equations are conformally invariant
under the Cayley transformation. Further, we obtain some basic integral
formulas related to the spherical Rarita-Schwinger type operators. Second, we
define the Rarita-Schwinger type operators on the real projective space and
construct their kernels and Cauchy integral formulas.Comment: 21 pages. arXiv admin note: text overlap with arXiv:1106.358
“I just let him cry...”: Designing socio-technical interventions in families to prevent mental health disorders
Interventions that help children develop protective factors against mental health disorders are an inherently social endeavour, relying on a number of actors from within the family as well as the school context. Little work thus far in CSCW and HCI has examined the potential of technology to support or enhance such interventions. This paper provides the first steps to unpacking this socio-technical design space, focusing on emotional regulation (ER) as a specific instance of a protective factor. We combine a user-centred approach to understanding lived experiences of families (interviews, design workshops) with an expert-led understanding of what makes interventions psychologically effective. Our findings suggest the potential of technology to enable a shift in how prevention interventions are designed and delivered: empowering children and parents through a new model of ‘child-led, situated interventions’, where participants learn through actionable support directly within family life, as opposed to didactic in-person workshops and a subsequent ‘skills application’. This conceptual model was then instantiated in a technology probe, which was deployed with 14 families. The promising field study findings provide an initial proof-of-concept validation of the proposed approach
ManneqKit Cards:A Kinesthetic Empathic Design Tool Communicating Depression Experiences
While depression is a mood disorder with significant societal impact, the experiences of people living with depression are yet not easy to access. HCI’s tenet to understand users, particularly addressed by the empathic design approach, has prioritized verbal communication of such experiences. We introduce ManneqKit, a kinesthetic empathic design tool consisting of 15 cards with bodily postures and vignettes leveraging the nonverbal aspects of depression experiences. We report ManneqKit’s co-design with 10 therapists, its piloting with 4 therapists and 10 non-therapists, and evaluation through design workshops with 9 interaction designers. Findings indicate cards’ ability to elicit non-therapists’ increased empathy, and richer emotional depictions when compared to text-based description of depression symptoms. We discuss the value of these findings for interaction design in supporting richer understanding of vulnerable users experiencing depression, for more sensitive conceptual designs in the ideation stage, and more nuanced ethical values underpinning the overall design process
The TA Framework: Designing Real-time Teaching Augmentation for K-12 Classrooms
Recently, the HCI community has seen increased interest in the design of
teaching augmentation (TA): tools that extend and complement teachers'
pedagogical abilities during ongoing classroom activities. Examples of TA
systems are emerging across multiple disciplines, taking various forms: e.g.,
ambient displays, wearables, or learning analytics dashboards. However, these
diverse examples have not been analyzed together to derive more fundamental
insights into the design of teaching augmentation. Addressing this opportunity,
we broadly synthesize existing cases to propose the TA framework. Our framework
specifies a rich design space in five dimensions, to support the design and
analysis of teaching augmentation. We contextualize the framework using
existing designs cases, to surface underlying design trade-offs: for example,
balancing actionability of presented information with teachers' needs for
professional autonomy, or balancing unobtrusiveness with informativeness in the
design of TA systems. Applying the TA framework, we identify opportunities for
future research and design.Comment: to be published in Proceedings of the 2020 CHI Conference on Human
Factors in Computing Systems, 17 pages, 10 figure
Babesia spp. in ticks and wildlife in different habitat types of Slovakia
Background: Babesiosis is an emerging and potentially zoonotic disease caused by tick-borne piroplasmids of the Babesia genus. New genetic variants of piroplasmids with unknown associations to vectors and hosts are recognized.
Data on the occurrence of Babesia spp. in ticks and wildlife widen the knowledge on the geographical distribution and circulation of piroplasmids in natural foci. Questing and rodent-attached ticks, rodents, and birds were screened for the presence of Babesia-specific DNA using molecular methods. Spatial and temporal differences of Babesia spp. prevalence in ticks and rodents from two contrasting habitats of Slovakia with sympatric occurrence of Ixodes ricinus and Haemaphysalis concinna ticks and co-infections of Candidatus N. mikurensis and Anaplasma phagocytophilum were investigated.
Results: Babesia spp. were detected in 1.5 % and 6.6 % of questing I. ricinus and H. concinna, respectively.
Prevalence of Babesia-infected I. ricinus was higher in a natural than an urban/suburban habitat. Phylogenetic analysis showed that Babesia spp. from I. ricinus clustered with Babesia microti, Babesia venatorum, Babesia canis, Babesia
capreoli/Babesia divergens, and Babesia odocoilei. Babesia spp. amplified from H. concinna segregated into two monophyletic clades, designated Babesia sp. 1 (Eurasia) and Babesia sp. 2 (Eurasia), each of which represents a yet undescribed novel species. The prevalence of infection in rodents (with Apodemus flavicollis and Myodes glareolus prevailing) with B. microti was 1.3 % in an urban/suburban and 4.2 % in a natural habitat. The majority of infected rodents (81.3 %) were positive for spleen and blood and the remaining for lungs and/or skin. Rodent-attached I. ricinus (accounting for 96.3 %) and H. concinna were infected with B. microti, B. venatorum, B. capreoli/B. divergens, Babesia sp. 1 (Eurasia), and Babesia sp. 2 (Eurasia). All B. microti and B. venatorum isolates were identical to known zoonotic strains from Europe. Less than 1.0 % of Babesia-positive ticks and rodents carried Candidatus N. mikurensis or A. phagocytophilum.Inst. de PatobiologíaFil: Hamsikova, Zuzana. Slovak Academy of Sciences. Institute of Zoology; EslovaquiaFil: Kazimirová, Mária. Slovak Academy of Sciences. Institute of Zoology; EslovaquiaFil: Harustiakova, Danka. Masaryk University. Faculty of Medicine and Faculty of Science, Institute of Biostatistics and Analyses; República ChecaFil: Mahrikova, Lenka. Slovak Academy of Sciences. Institute of Zoology; EslovaquiaFil: Slovak, Mirko. Slovak Academy of Sciences. Institute of Zoology; EslovaquiaFil: Berthova, Lenka. Slovak Academy of Sciences. Biomedical Research Center. Institute of Virology; EslovaquiaFil: Kocianova, Elena. Slovak Academy of Sciences. Biomedical Research Center. Institute of Virology; EslovaquiaFil: Schnittger, Leonhard. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patobiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
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