1,364 research outputs found
The many sides of RCW 86: a type Ia supernova remnant evolving in its progenitor's wind bubble
We present the results of a detailed investigation of the Galactic supernova
remnant RCW 86 using the XMM-Newton X-ray telescope. RCW 86 is the probable
remnant of SN 185 A.D, a supernova that likely exploded inside a wind-blown
cavity. We use the XMM-Newton Reflection Grating Spectrometer (RGS) to derive
precise temperatures and ionization ages of the plasma, which are an indication
of the interaction history of the remnant with the presumed cavity. We find
that the spectra are well fitted by two non-equilibrium ionization models,
which enables us to constrain the properties of the ejecta and interstellar
matter plasma. Furthermore, we performed a principal component analysis on EPIC
MOS and pn data to find regions with particular spectral properties. We present
evidence that the shocked ejecta, emitting Fe-K and Si line emission, are
confined to a shell of approximately 2 pc width with an oblate spheroidal
morphology. Using detailed hydrodynamical simulations, we show that general
dynamical and emission properties at different portions of the remnant can be
well-reproduced by a type Ia supernova that exploded in a non-spherically
symmetric wind-blown cavity. We also show that this cavity can be created using
general wind properties for a single degenerate system. Our data and
simulations provide further evidence that RCW 86 is indeed the remnant of SN
185, and is the likely result of a type Ia explosion of single degenerate
origin.Comment: Accepted for publication in MNRAS. 16 pages, 13 figure
Deontic Epistemic stit Logic Distinguishing Modes of `Mens Rea\u27
Most juridical systems contain the principle that an act is only unlaw-
ful if the agent conducting the act has a `guilty mind\u27 (`mens rea\u27). Dif-
ferent law systems distinguish different modes of mens rea. For instance,
American law distinguishes between `knowingly\u27 performing a criminal
act, `recklessness\u27, `strict liability\u27, etc. I will show we can formalize several
of these categories. The formalism I use is a complete stit-logic featuring
operators for stit-actions taking effect in `next\u27 states, S5-knowledge op-
erators and SDL-type obligation operators. The different modes of `mens
rea\u27 correspond to the violation conditions of different types of obligation
definable in the logic
A Data Compression Algorithm for Wireless Sensor Networks Based on an Optimal Order Estimation Model and Distributed Coding
In many wireless sensor network applications, the possibility of exceptions occurring is relatively small, so in a normal situation, data obtained at sequential time points by the same node are time correlated, while, spatial correlation may exist in data obtained at the same time by adjacent nodes. A great deal of node energy will be wasted if data which include time and space correlation is transmitted. Therefore, this paper proposes a data compression algorithm for wireless sensor networks based on optimal order estimation and distributed coding. Sinks can obtain correlation parameters based on optimal order estimation by exploring time and space redundancy included in data which is obtained by sensors. Then the sink restores all data based on time and space correlation parameters and only a little necessary data needs to be transmitted by nodes. Because of the decrease of redundancy, the average energy cost per node will be reduced and the life of the wireless sensor network will obviously be extended as a result
The loss-limited electron energy in SN 1006: effects of the shock velocity and of the diffusion process
The spectral shape of the synchrotron X-ray emission from SN 1006 reveals the
fundamental role played by radiative losses in shaping the high-energy tail of
the electron spectrum. We analyze data from the XMM-Newton SN 1006 Large
Program and confirm that in both nonthermal limbs the loss-limited model
correctly describes the observed spectra. We study the physical origin of the
observed variations of the synchrotron cutoff energy across the shell. We
investigate the role played by the shock velocity and by the electron
gyrofactor. We found that the cutoff energy of the syncrotron X-ray emission
reaches its maximum value in regions where the shock has experienced its
highest average speed. This result is consistent with the loss-limited
framework. We also find that the electron acceleration in both nonthermal limbs
of SN 1006 proceeds close to the Bohm diffusion limit, the gyrofactor being in
the range 1.5-4. We finally investigate possible explanations for the low
values of cutoff energy measured in thermal limbs.Comment: Accepted for publication in Astronomische Nachrichten. Proceedings of
the XMM-Newton Science Workshop 201
Minimal Semantics for Action Specifications in First-order Dynamic Logic
In this paper we investigate minimal semantics for First Order Dynamic Logic formulas. The goal is to be able to write action specifications in a declarative pre/post-condition style. The declarative specification of actions comes with some well known problems: the frame problem, the qualification problem and the ramification problem. We incorporate the assumptions that are inherent to both the frame and qualification problem into the semantics of Dynamic Logic by defining orderings over Dynamic Logic models. These orderings allow us to identify for each declarative Dynamic Logic action specification a unique intended model. This unique model represents the system that must be associated with the specification given the prefential semantics that is defined by the orderings
In vivo whole-cell recording from morphologically identified mouse superior colliculus neurons
In vivo whole-cell recording when combined with morphological
characterization after biocytin labeling is a powerful technique to study
subthreshold synaptic processing in cell-type-identified neuronal populations.
Here, we provide a step-by-step procedure for performing whole-cell recordings
in the superior colliculus of urethane-anesthetized mice, a major visual
processing region in the rodent brain. Two types of visual stimulation methods
are described. While we focus on superior colliculus neurons, this protocol is
applicable to other brain areas.Comment: 29 pages including 4 figure
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