1,022 research outputs found
Content-Based Video Retrieval in Historical Collections of the German Broadcasting Archive
The German Broadcasting Archive (DRA) maintains the cultural heritage of
radio and television broadcasts of the former German Democratic Republic (GDR).
The uniqueness and importance of the video material stimulates a large
scientific interest in the video content. In this paper, we present an
automatic video analysis and retrieval system for searching in historical
collections of GDR television recordings. It consists of video analysis
algorithms for shot boundary detection, concept classification, person
recognition, text recognition and similarity search. The performance of the
system is evaluated from a technical and an archival perspective on 2,500 hours
of GDR television recordings.Comment: TPDL 2016, Hannover, Germany. Final version is available at Springer
via DO
It's OK not to be OK: Shared Reflections from two PhD Parents in a Time of Pandemic
Adopting an intersectional feminist lens, we explore our identities as single and coâparents thrust into the new reality of the UK COVIDâ19 lockdown. As two PhD students, we present shared reflections on our intersectional and divergent experiences of parenting and our attempts to protect our work and families during a pandemic. We reflect on the social constructions of âmasculinitiesâ and âemphasized femininitiesâ as complicated influence on our roles as parents. Finally, we highlight the importance of time and selfâcare as ways of managing our shared realities during this uncertain period. Through sharing reflections, we became closer friends in mutual appreciation and solidarity as we learned about each otherâs struggles and vulnerabilities
Immigrant populations, work and healthâa systematic literature review
Objectives This paper summarizes the information on immigrant occupational health available from recent
studies, incorporating varied study designs.
Methods A systematic search was carried out in PubMed employing terms of interest to the study and related
terms supplied by the same search engine. Articles were selected through the following process: (i) reading
the title and abstract, in English or Spanish, for the period 1990â2005, (ii) reading of the entire text of selected
articles; (iii) making a manual search of the relevant citations in the selected articles; (iv) eliminating articles
without a focus on the themes of central interest (immigration, work, and health), and (v) reading and analyzing
the definitive article set. No quality criteria were used in the article selection.
Results The location of studies was not straightforward and required careful thought about the search terms.
The included 48 papers were often multifaceted and difficult to categorize. They generally came from countries
historically associated with immigration and described occupational risk factors, health consequences, and the
social, economic, and cultural influences on worker health. They were also based on data, surveillance, training,
and preventive measures that were inadequate.
Conclusions Increased migration is a reality in industrialized countries all over the world, and it has social,
political, and economic consequences for migrating groups, as well as for their sending and host societies. More
reliable data, targeted appropriate interventions, and enforcement of existing regulations are necessary to improve
the health of immigrant workers. Furthermore, studies in sending and developing countries should be encouraged
to form a more complete understanding of this complex situation
Development of the electroweak phase transition and baryogenesis
We investigate the evolution of the electroweak phase transition, using a
one-Higgs effective potential that can be regarded as an approximation for the
Minimal Supersymmetric Standard Model. The phase transition occurs in a small
interval around a temperature T_t below the critical one. We calculate this
temperature as a function of the parameters of the potential and of a damping
coefficient related to the viscosity of the plasma. The parameters that are
relevant for baryogenesis, such as the velocity and thickness of the walls of
bubbles and the value of the Higgs field inside them, change significantly in
the range of temperatures where the first-order phase transition can occur.
However, we find that in the likely interval for T_t there is no significant
variation of these parameters. Furthermore, the temperature T_t is in general
not far below the temperature at which bubbles begin to nucleate.Comment: 26 pages, 7 figures; typos corrected, reference adde
Strong Coupling Corrections to the Ginzburg-Landau Theory of Superfluid ^{3}He
In the Ginzburg-Landau theory of superfluid He, the free energy is
expressed as an expansion of invariants of a complex order parameter. Strong
coupling effects, which increase with increasing pressure, are embodied in the
set of coefficients of these order parameter invariants\cite{Leg75,Thu87}.
Experiments can be used to determine four independent combinations of the
coefficients of the five fourth order invariants. This leaves the
phenomenological description of the thermodynamics near incomplete.
Theoretical understanding of these coefficients is also quite limited. We
analyze our measurements of the magnetic susceptibility and the NMR frequency
shift in the -phase which refine the four experimental inputs to the
phenomenological theory. We propose a model based on existing experiments,
combined with calculations by Sauls and Serene\cite{Sau81} of the pressure
dependence of these coefficients, in order to determine all five fourth order
terms. This model leads us to a better understanding of the thermodynamics of
superfluid He in its various states. We discuss the surface tension of
bulk superfluid He and predictions for novel states of the superfluid
such as those that are stabilized by elastic scattering of quasiparticles from
a highly porous silica aerogel.Comment: 9 pages, 7 figures, 2 table
Transport coefficients in the early universe
We calculate numerically the electrical conductivity , heat
conductivity and shear viscosity of the hot plasma present in
the early universe for the temperature interval 1\MeV\lsim T\lsim 10\GeV. We
use the Boltzmann collision equation to compute all the scattering matrix
elements and regulate them by the thermal masses of the - and -channel
particles. No leading order approximation is needed because of the numerical
integration routines used.Comment: LaTeX, 24 pages, 7 ps figure
Cosmological Magnetic Fields from Primordial Helical Seeds
Most early Universe scenarios predict negligible magnetic fields on
cosmological scales if they are unprocessed during subsequent expansion of the
Universe. We present a new numerical treatment of the evolution of primordial
fields and apply it to weakly helical seeds as they occur in certain early
Universe scenarios. We find that initial helicities not much larger than the
baryon to photon number can lead to fields of about 10^{-13} Gauss with
coherence scales slightly below a kilo-parsec today.Comment: 4 revtex pages, 2 postscript figures include
Constraints on the Electrical Charge Asymmetry of the Universe
We use the isotropy of the Cosmic Microwave Background to place stringent
constraints on a possible electrical charge asymmetry of the universe. We find
the excess charge per baryon to be in the case of a uniform
distribution of charge, where is the charge of the electron. If the charge
asymmetry is inhomogeneous, the constraints will depend on the spectral index,
, of the induced magnetic field and range from
() to (). If one could further
assume that the charge asymmetries of individual particle species are not
anti-correlated so as to cancel, this would imply, for photons, ; for neutrinos, ; and for heavy (light) dark
matter particles ().Comment: New version to appear in JCA
Entanglement-Enhanced Quantum Key Distribution
We present and analyze a quantum key distribution protocol based on sending
entangled N-qubit states instead of single-qubit ones as in the trail-blazing
scheme by Bennett and Brassard (BB84). Since the qubits are sent individually,
an eavesdropper is limited to accessing them one by one. In an intercept-resend
attack, this fundamental restriction allows one to make the eavesdropper's
information on the transmitted key vanish if even one of the qubits is not
intercepted. The implied upper bound 1/(2N) for Eve's information is further
shown not to be the lowest since in the case N = 2, the information can be
reduced to less than 30% of that in BB84. In general, the protocol is at least
as secure as BB84.Comment: 7 pages, 5 figures, new result
Magnetic Fields from Phase Transitions
The generation of primordial magnetic fields from cosmological phase
transitions is discussed, paying particular attention to the electroweak
transition and to the various definitions of the `average' field that have been
put forward. It is emphasised that only the volume average has dynamical
significance as a seed for galactic dynamos. On rather general grounds of
causality and energy conservation, it is shown that, in the absence of MHD
effects that transfer power in the magnetic field from small to large scales,
processes occurring at the electroweak transition cannot generate fields
stronger than Gauss on a scale of 0.5 Mpc. However, it is
implausible that this upper bound could ever be reached, as it would require
all the energy in the Universe to be turned into a magnetic field coherent at
the horizon scale. Non-linear MHD effects seem therefore to be necessary if the
electroweak transition is to create a primordial seed field.Comment: 6pp RevTeX. Correct finished version supplie
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