30 research outputs found
Lossless quantum data compression and variable-length coding
In order to compress quantum messages without loss of information it is
necessary to allow the length of the encoded messages to vary. We develop a
general framework for variable-length quantum messages in close analogy to the
classical case and show that lossless compression is only possible if the
message to be compressed is known to the sender. The lossless compression of an
ensemble of messages is bounded from below by its von-Neumann entropy. We show
that it is possible to reduce the number of qbits passing through a quantum
channel even below the von-Neumann entropy by adding a classical side-channel.
We give an explicit communication protocol that realizes lossless and
instantaneous quantum data compression and apply it to a simple example. This
protocol can be used for both online quantum communication and storage of
quantum data.Comment: 16 pages, 5 figure
The origin and evolution of the normal Type Ia SN 2018aoz with infant-phase reddening and excess emission
SN~2018aoz is a Type Ia SN with a -band plateau and excess emission in the
infant-phase light curves 1 day after first light, evidencing an
over-density of surface iron-peak elements as shown in our previous study.
Here, we advance the constraints on the nature and origin of SN~2018aoz based
on its evolution until the nebular phase. Near-peak spectroscopic features show
the SN is intermediate between two subtypes of normal Type Ia: Core-Normal and
Broad-Line. The excess emission could have contributions from the radioactive
decay of surface iron-peak elements as well as ejecta interaction with either
the binary companion or a small torus of circumstellar material. Nebular-phase
limits on H and He~I favour a white dwarf companion, consistent with
the small companion size constrained by the low early SN luminosity, while the
absence of [O~I] and He~I disfavours a violent merger of the progenitor. Of the
two main explosion mechanisms proposed to explain the distribution of surface
iron-peak elements in SN~2018aoz, the asymmetric Chandrasekhar-mass explosion
is less consistent with the progenitor constraints and the observed blueshifts
of nebular-phase [Fe~II] and [Ni~II]. The helium-shell double-detonation
explosion is compatible with the observed lack of C spectral features, but
current 1-D models are incompatible with the infant-phase excess emission,
color, and absence of nebular-phase [Ca~II]. Although
the explosion processes of SN~2018aoz still need to be more precisely
understood, the same processes could produce a significant fraction of Type Ia
SNe that appear normal after 1 day.Comment: Submitted for publication in ApJ. 35 pages, 16 figures, 7 table
Strong Carbon Features and a Red Early Color in the Underluminous Type Ia SN 2022xkq
We present optical, infrared, ultraviolet, and radio observations of SN
2022xkq, an underluminous fast-declining type Ia supernova (SN Ia) in NGC 1784
( Mpc), from to 180 days after explosion. The
high-cadence observations of SN 2022xkq, a photometrically transitional and
spectroscopically 91bg-like SN Ia, cover the first days and weeks following
explosion which are critical to distinguishing between explosion scenarios. The
early light curve of SN 2022xkq has a red early color and exhibits a flux
excess which is more prominent in redder bands; this is the first time such a
feature has been seen in a transitional/91bg-like SN Ia. We also present 92
optical and 19 near-infrared (NIR) spectra, beginning 0.4 days after explosion
in the optical and 2.6 days after explosion in the NIR. SN 2022xkq exhibits a
long-lived C I 1.0693 m feature which persists until 5 days post-maximum.
We also detect C II 6580 in the pre-maximum optical spectra. These
lines are evidence for unburnt carbon that is difficult to reconcile with the
double detonation of a sub-Chandrasekhar mass white dwarf. No existing
explosion model can fully explain the photometric and spectroscopic dataset of
SN 2022xkq, but the considerable breadth of the observations is ideal for
furthering our understanding of the processes which produce faint SNe Ia.Comment: 38 pages, 16 figures, accepted for publication in ApJ, the figure 15
input models and synthetic spectra are now available at
https://zenodo.org/record/837925
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COVID-19 through Adverse Outcome Pathways: Building networks to better understand the disease - 3rd CIAO AOP Design Workshop
ALTEX - Alternatives to Animal ExperimentationCopyright © 2022 the author(s). On April 28-29, 2021, 50 scientists from different fields of expertise met for the 3rd online CIAO workshop. The CIAO project âModelling the Pathogenesis of COVID-19 using the Adverse Outcome Pathway (AOP) frameworkâ aims at building a holistic assembly of the available scientific knowledge on COVID-19 using the AOP framework. An individual AOP depicts the disease progression from the initial contact with the SARS-CoV-2 virus through biological key events (KE) toward an adverse outcome such as respiratory distress, anosmia or multiorgan failure. Assembling the individual AOPs into a network highlights shared KEs as central biological nodes involved in multiple outcomes observed in COVID-19 patients. During the workshop, the KEs and AOPs established so far by the CIAO members were presented and posiÂtioned on a timeline of the disease course. Modulating factors influencing the progression and severity of the disease were also addressed as well as factors beyond purely biological phenomena. CIAO relies on an interdisciplinary crowdÂsourcing effort, therefore, approaches to expand the CIAO network by widening the crowd and reaching stakeholders were also discussed. To conclude the workshop, it was decided that the AOPs/KEs will be further consolidated, inteÂgrating virus variants and long COVID when relevant, while an outreach campaign will be launched to broaden the CIAO scientific crowd.The CIAO project is steered by the Joint Research Centre of the European Commission (EC-JRC), the Humane Society International (HSI), and the Physicians Committee for Responsible Medicine (PCRM). For Jorid Birkelund SĂžrli, the research is supported by FIKA, Focused Research Effort on Chemicals in the Working Environment from the Danish Government. For Daniel Jacobson, this work was supported by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC for the US Department of Energy (LOIS:10074) and the National Institutes of Health 3RF1AG053303-01S2
Open-loop speed discrimination performance of ocular following response and perception
Bostroem KJ, Warzecha A-K. Open-loop speed discrimination performance of ocular following response and perception. VISION RESEARCH. 2010;50(9):870-882.So far, it remains largely unresolved to what extent neuronal noise affects behavioral responses. Here, we investigate, where in the human visual motion pathway noise originates that limits the performance of the entire system. In particular, we ask whether perception and eye movements are limited by a common noise source, or whether processing stages after the separation into different streams limit their performance. We use the ocular following response of human subjects and a simultaneously performed psychophysical paradigm to directly compare perceptual and oculomotor system with respect to their speed discrimination ability. Our results show that on the open-loop condition the perceptual system is superior to the oculomotor system and that the responses of both systems are not correlated. Two alternative conclusions can be drawn from these findings. Either the perceptual and oculomotor pathway are effectively separate, or the amount of post-sensory (motor) noise is not negligible in comparison to the amount of sensory noise. In view of well-established experimental findings and due to plausibility considerations, we favor the latter conclusion. (C) 2010 Elsevier Ltd. All rights reserved