8,138 research outputs found
Locking classical information
It is known that the maximum classical mutual information that can be
achieved between measurements on a pair of quantum systems can drastically
underestimate the quantum mutual information between those systems. In this
article, we quantify this distinction between classical and quantum information
by demonstrating that after removing a logarithmic-sized quantum system from
one half of a pair of perfectly correlated bitstrings, even the most sensitive
pair of measurements might only yield outcomes essentially independent of each
other. This effect is a form of information locking but the definition we use
is strictly stronger than those used previously. Moreover, we find that this
property is generic, in the sense that it occurs when removing a random
subsystem. As such, the effect might be relevant to statistical mechanics or
black hole physics. Previous work on information locking had always assumed a
uniform message. In this article, we assume only a min-entropy bound on the
message and also explore the effect of entanglement. We find that classical
information is strongly locked almost until it can be completely decoded. As a
cryptographic application of these results, we exhibit a quantum key
distribution protocol that is "secure" if the eavesdropper's information about
the secret key is measured using the accessible information but in which
leakage of even a logarithmic number of key bits compromises the secrecy of all
the others.Comment: 32 pages, 2 figure
The nuclear contacts and short range correlations in nuclei
Atomic nuclei are complex strongly interacting systems and their exact
theoretical description is a long-standing challenge. An approximate
description of nuclei can be achieved by separating its short and long range
structure. This separation of scales stands at the heart of the nuclear shell
model and effective field theories that describe the long-range structure of
the nucleus using a mean- field approximation. We present here an effective
description of the complementary short-range structure using contact terms and
stylized two-body asymptotic wave functions. The possibility to extract the
nuclear contacts from experimental data is presented. Regions in the two-body
momentum distribution dominated by high-momentum, close-proximity, nucleon
pairs are identified and compared to experimental data. The amount of
short-range correlated (SRC) nucleon pairs is determined and compared to
measurements. Non-combinatorial isospin symmetry for SRC pairs is identified.
The obtained one-body momentum distributions indicate dominance of SRC pairs
above the nuclear Fermi-momentum.Comment: Accepted for publication in Physics Letters. 6 pages, 2 figure
Oxygen Cost of Recreational Horse-Riding in Females
Version: as accepted for publication.BACKGROUND: The purpose of this study was to characterize the physiological demands of a riding session comprising different types of recreational horse riding in females. METHODS: Sixteen female recreational riders (aged 17 to 54 years) completed an incremental cycle ergometer exercise test to determine peak oxygen consumption (VOāpeak) and a 45-minute riding session based upon a British Horse Society Stage 2 riding lesson (including walking, trotting, cantering and work without stirrups). Oxygen consumption (VOā), from which metabolic equivalent (MET) and energy expenditure values were derived, was measured throughout. RESULTS: The mean VOā requirement for trotting/cantering (18.4 Ā± 5.1 mlĀ·kgā»Ā¹Ā·minā»Ā¹; 52 Ā± 12% VOāpeak; 5.3 Ā± 1.1 METs) was similar to walking/trotting (17.4 Ā± 5.1 mlĀ·kgā»Ā¹Ā·minā»Ā¹; 48 Ā± 13% VOāpeak; 5.0 Ā± 1.5 METs) and significantly higher than for work without stirrups (14.2 Ā± 2.9 mlĀ·kgā»Ā¹Ā·minā»Ā¹; 41 Ā± 12% VOāpeak; 4.2 Ā± 0.8 METs) (P = .001). CONCLUSIONS: The oxygen cost of different activities typically performed in a recreational horse riding session meets the criteria for moderate intensity exercise (3-6 METs) in females, and trotting combined with cantering imposes the highest metabolic demand. Regular riding could contribute to the achievement of the public health recommendations for physical activity in this population
A Gradual Process for Integrating E-learning in a Higher Education Institute
In: A.J. Kallenberg and M.J.J.M. van de Ven (Eds), 2002, The New Educational Benefits of ICT in Higher Education: Proceedings. Rotterdam: Erasmus Plus BV, OECR
ISBN 90-9016127-9We describe an incremental process for integrating E-learning in a higher education institute. Our basic assumption is that the burden of integrating E-learning lies mainly on the shoulders of the teachers. We suggest a process based on XML technologies that enables the teachers to: (1) separate content from presentation and concentrate on content (2) develop learning materials incrementally and implement easily at each stage (3) reuse any learning materials they have already prepared (4) reuse learning materials prepared by other teachers. In this paper we describe the process along with the various roles of each of the following: the technology, the support technical team, the individual teacher and the evolving community of practice
Late-Time Photometry of Type Ia Supernova SN 2012cg Reveals the Radioactive Decay of Co
Seitenzahl et al. (2009) have predicted that roughly three years after its
explosion, the light we receive from a Type Ia supernova (SN Ia) will come
mostly from reprocessing of electrons and X-rays emitted by the radioactive
decay chain , instead of positrons from the
decay chain that dominates the SN light at
earlier times. Using the {\it Hubble Space Telescope}, we followed the light
curve of the SN Ia SN 2012cg out to days after maximum light. Our
measurements are consistent with the light curves predicted by the contribution
of energy from the reprocessing of electrons and X-rays emitted by the decay of
Co, offering evidence that Co is produced in SN Ia explosions.
However, the data are also consistent with a light echo mag fainter
than SN 2012cg at peak. Assuming no light-echo contamination, the mass ratio of
Ni and Ni produced by the explosion, a strong constraint on any
SN Ia explosion model, is , roughly twice Solar. In
the context of current explosion models, this value favors a progenitor white
dwarf with a mass near the Chandrasekhar limit.Comment: Updated to reflect the final version published by ApJ. For a video
about the paper, see https://youtu.be/t3pUbZe8wq
Pair modeling with DynaLearn - Students' attitudes and actual effects
With DynaLearn learners can construct scientific knowledge by manipulating icons and their in-ter-relationships, using a diagrammatic representation. The diagrams represent models that can be simulated, confronting learners with the logical consequences of the knowledge they expressed. Such modeling activities are highly advocated by science educators. Learning from the construction and debugging processes of modeling can be enhanced by collaboration. The modeling elements can serve as anchors for discussing, justifying, and explaining the model. Researchers have suggested various ways of supporting collaboration. In this study we employed Pair Modeling, which is an adaptation of the pair programming technique that is used for enhancing collaborative programming both in the industry and in academia. In this paper we present encouraging results for the use of this collaboration technique based on assignments' scores, observations, and a ques-tionnaire. Students' attitudes were neutral on the average, but the average score of the group that employed Pair Modeling was significantly higher than the average score of the control group that employed unstructured pair collaboration. We discuss the implications of the obtained results and the limitations of the study
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