2,297 research outputs found
Secrecy Results for Compound Wiretap Channels
We derive a lower bound on the secrecy capacity of the compound wiretap
channel with channel state information at the transmitter which matches the
general upper bound on the secrecy capacity of general compound wiretap
channels given by Liang et al. and thus establishing a full coding theorem in
this case. We achieve this with a stronger secrecy criterion and the maximum
error probability criterion, and with a decoder that is robust against the
effect of randomisation in the encoding. This relieves us from the need of
decoding the randomisation parameter which is in general not possible within
this model. Moreover we prove a lower bound on the secrecy capacity of the
compound wiretap channel without channel state information and derive a
multi-letter expression for the capacity in this communication scenario.Comment: 25 pages, 1 figure. Accepted for publication in the journal "Problems
of Information Transmission". Some of the results were presented at the ITW
2011 Paraty [arXiv:1103.0135] and published in the conference paper available
at the IEEE Xplor
Natural Connections Demonstration Project, 2012- 2016: Final Report
This report presents the key findings from the Natural Connections Demonstration Project, that aimed to encourage teachers to take curricular learning outdoors. The project was commissioned by DEFRA, Natural England and Historic England, and delivered by a team at Plymouth University. 125 schools contributed to the evaluation which found that: 1. schools most likely to engage with outdoor learning displayed strong leadership and were open-minded about trying new things 2. schools reported a statistically-significant increase in the amount of time spent on outdoor learning activity across the project 3. Schools adopted many different models of outdoor learning 4. Schools invested time, goodwill, energy and funding in outdoor learning 5. Over 90 per cent of responding schools agreed that outdoor learning was useful for curriculum delivery 6. Outdoor learning had positive impacts for teachers and pupils 7. the project model of distributed independent brokerage was found to have the capacity to unlock latent demand for outdoor learning in schools, and to support schools in embedding low-cost outdoor learning practice
Improved parameters for extrasolar transiting planets
We present refined values for the physical parameters of transiting
exoplanets, based on a self-consistent and uniform analysis of transit light
curves and the observable properties of the host stars. Previously it has been
difficult to interpret the ensemble properties of transiting exoplanets,
because of the widely different methodologies that have been applied in
individual cases. Furthermore, previous studies often ignored an important
constraint on the mean stellar density that can be derived directly from the
light curve. The main contributions of this work are 1) a critical compilation
and error assessment of all reported values for the effective temperature and
metallicity of the host stars; 2) the application of a consistent methodology
and treatment of errors in modeling the transit light curves; and 3) more
accurate estimates of the stellar mass and radius based on stellar evolution
models, incorporating the photometric constraint on the stellar density. We use
our results to revisit some previously proposed patterns and correlations
within the ensemble. We confirm the mass-period correlation, and we find
evidence for a new pattern within the scatter about this correlation: planets
around metal-poor stars are more massive than those around metal-rich stars at
a given orbital period. Likewise, we confirm the proposed dichotomy of planets
according to their Safronov number, and we find evidence that the systems with
small Safronov numbers are more metal-rich on average. Finally, we confirm the
trend that led to the suggestion that higher-metallicity stars harbor planets
with a greater heavy-element content.Comment: To appear in The Astrophysical Journal. 23 pages in emulateapj
format, including figures and tables. Figures 7, 8, and 9 are low resolution;
higher resolution versions will be available from the journal when published.
Acknowledgement added, and minor changes made to TrES-3 and TrES-4 in the
Appendi
Long Term Functional and Esthetic Outcomes After Fibula Free Flap Reconstruction of the Mandible
Objectives: To report functional and esthetic outcomes, after fibula free flap (FFF) reconstruction of the mandible for oral cancer, assessed by physicians, non-clinicians and patients.
Materials and Methods: Twenty-five long term survivors from oral cancer after FFF reconstruction were recalled for head and neck examination by surgeons and patient reported outcomes, using EORTC, QLQ C-30, H&N-35 and FACE-Q questionnaires.
Results: Physicians reported 64% restoration of functionality compared to normal. Patients reported high scores on QLQ-C30, but lower scores on H&N-35. Esthetic scores were reported higher by clinicians than non-clinicians. The decline in function and appearance was attributed to loss of lower dentition, trismus, mal occlusion, xerostomia and tissue atrophy.
Conclusion: To minimize the decline in function and appearance, immediate dental implants in FFF, better reconstruction of the temporomandibular joint, newer methods of radiotherapy to minimize xerostomia and oral exercises to prevent trismus should be considered
A NLTE line blanketed model of a solar type star
We present LTE and NLTE atmospheric models of a star with solar parameters,
and study the effect of treating many thousands of Iron group lines out of LTE
on the computed atmospheric structure, overall absolute flux distribution, and
the moderately high resolution spectrum in the visible and near UV bands. Our
NLTE modeling includes the first two or three ionization stages of 20 chemical
elements, up to and including much of the Fe-group, and includes about 20000 Fe
I and II lines. We investigate separately the effects of treating the light
metals and the Fe-group elements in NLTE. Our main conclusions are that 1) NLTE
line blanketed models with direct multi-level NLTE for many actual transitions
gives qualitatively similar results as the more approximate treatment of
Anderson (1989) for both the Fe statistical equilibrium and the atmospheric
temperature structure, 2) models with many Fe lines in NLTE have a temperature
structure that agrees more closely with LTE semi-empirical models based on
center-to-limb variation and a wide variety of spectra lines, whereas LTE
models agree more with semi-empirical models based only on an LTE calculation
of the Fe I excitation equilibrium, 3) the NLTE effects of Fe-group elements on
the model structure and flux distribution are much more important than the NLTE
effects of all the light metals combined, and serve to substantially increases
the violet and near UV flux level as a result of NLTE Fe over-ionization. These
results suggest that there may still be important UV opacity missing from the
models.Comment: Accepted for publication in The Astrophysical Journa
Involutive Categories and Monoids, with a GNS-correspondence
This paper develops the basics of the theory of involutive categories and
shows that such categories provide the natural setting in which to describe
involutive monoids. It is shown how categories of Eilenberg-Moore algebras of
involutive monads are involutive, with conjugation for modules and vector
spaces as special case. The core of the so-called Gelfand-Naimark-Segal (GNS)
construction is identified as a bijective correspondence between states on
involutive monoids and inner products. This correspondence exists in arbritrary
involutive categories
Quantum capacity under adversarial quantum noise: arbitrarily varying quantum channels
We investigate entanglement transmission over an unknown channel in the
presence of a third party (called the adversary), which is enabled to choose
the channel from a given set of memoryless but non-stationary channels without
informing the legitimate sender and receiver about the particular choice that
he made. This channel model is called arbitrarily varying quantum channel
(AVQC). We derive a quantum version of Ahlswede's dichotomy for classical
arbitrarily varying channels. This includes a regularized formula for the
common randomness-assisted capacity for entanglement transmission of an AVQC.
Quite surprisingly and in contrast to the classical analog of the problem
involving the maximal and average error probability, we find that the capacity
for entanglement transmission of an AVQC always equals its strong subspace
transmission capacity. These results are accompanied by different notions of
symmetrizability (zero-capacity conditions) as well as by conditions for an
AVQC to have a capacity described by a single-letter formula. In he final part
of the paper the capacity of the erasure-AVQC is computed and some light shed
on the connection between AVQCs and zero-error capacities. Additionally, we
show by entirely elementary and operational arguments motivated by the theory
of AVQCs that the quantum, classical, and entanglement-assisted zero-error
capacities of quantum channels are generically zero and are discontinuous at
every positivity point.Comment: 49 pages, no figures, final version of our papers arXiv:1010.0418v2
and arXiv:1010.0418. Published "Online First" in Communications in
Mathematical Physics, 201
Entanglement transmission and generation under channel uncertainty: Universal quantum channel coding
We determine the optimal rates of universal quantum codes for entanglement
transmission and generation under channel uncertainty. In the simplest scenario
the sender and receiver are provided merely with the information that the
channel they use belongs to a given set of channels, so that they are forced to
use quantum codes that are reliable for the whole set of channels. This is
precisely the quantum analog of the compound channel coding problem. We
determine the entanglement transmission and entanglement-generating capacities
of compound quantum channels and show that they are equal. Moreover, we
investigate two variants of that basic scenario, namely the cases of informed
decoder or informed encoder, and derive corresponding capacity results.Comment: 45 pages, no figures. Section 6.2 rewritten due to an error in
equation (72) of the old version. Added table of contents, added section
'Conclusions and further remarks'. Accepted for publication in
'Communications in Mathematical Physics
Covalent C–N Bond Formation through a Surface Catalyzed Thermal Cyclodehydrogenation
The integration of substitutional dopants at predetermined positions along the hexagonal lattice of graphene-derived polycyclic aromatic hydrocarbons is a critical tool in the design of functional electronic materials. Here, we report the unusually mild thermally induced oxidative cyclodehydrogenation of dianthryl pyrazino[2,3-g]quinoxalines to form the four covalent C–N bonds in tetraazateranthene on Au(111) and Ag(111) surfaces. Bond-resolved scanning probe microscopy, differential conductance spectroscopy, along with first-principles calculations unambiguously confirm the structural assignment. Detailed mechanistic analysis based on ab initio density functional theory calculations reveals a stepwise mechanism featuring a rate determining barrier of only ΔE⧧ = 0.6 eV, consistent with the experimentally observed reaction conditions
Self-adaptive quantum particle swarm optimization for dynamic environments
The quantum-inspired particle swarm optimization (QPSO) algorithm has been developed to find and track an optimum for dynamic optimization problems. Though QPSO has been shown to be effective, despite its simplicity, it does introduce an additional control parameter: the radius of the quantum cloud. The performance of QPSO is sensitive to the value assigned to this problem dependent parameter, which basically limits the area of the search space wherein new, better optima can be detected. This paper proposes a strategy to dynamically adapt the quantum radius, with changes in the environment. A comparison of the adaptive radius QPSO with the static radius QPSO showed that the adaptive approach achieves desirable results, without prior tuning of the quantum radius.http://link.springer.combookseries/5582019-10-03hj2018Computer Scienc
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