26,156 research outputs found
Understanding the Higher-Order Approach to Consciousness
Critics have often misunderstood the higher-order theory (HOT) of consciousness. Here we clarify its position on several issues, and distinguish it from other views such as the global The higher-order theory (HOT) of consciousness has often been misunderstood by critics. Here we clarify its position on several issues, and distinguish it from other views such as the global workspace theory (GWT) and early sensory models (e.g. first-order local recurrency theories). For example, HOT has been criticized for over-intellectualizing consciousness. We show that while higher-order states are cognitively assembled, the requirements are actually considerably less than often presumed. In this sense HOT may be viewed as an intermediate position between GWT and early sensory views. Also, we clarify that most proponents of HOT do not stipulate consciousness as equivalent to metacognition or confidence. Further, compared to other existing theories, HOT can arguably account better for complex everyday experiences, such as of emotions and episodic memories. This makes HOT particularly useful as a framework for conceptualizing pathological mental states
Exploring the challenges of implementing e-health: a protocol for an update of a systematic review of reviews.
There is great potential for e-health to deliver cost-effective, quality healthcare and spending on e-health systems by governments and healthcare systems is increasing worldwide. However, the literature often describes problematic and unsuccessful attempts to implement these new technologies into routine clinical practice. To understand and address the challenges of implementing e-health, a systematic review was conducted in 2009, which identified several conceptual barriers and facilitators to implementation. As technology is rapidly changing and new e-health solutions are constantly evolving to meet the needs of current practice, an update of this review is deemed necessary to understand current challenges to the implementation of e-health. This research aims to identify, summarise and synthesise currently available evidence, by undertaking a systematic review of reviews to explore the barriers and facilitators to implementing e-health across a range of healthcare settings
The relation between gas density and velocity power spectra in galaxy clusters: high-resolution hydrodynamic simulations and the role of conduction
Exploring the ICM power spectrum can help us to probe the physics of galaxy
clusters. Using high-resolution 3D plasma simulations, we study the statistics
of the velocity field and its relation with the thermodynamic perturbations.
The normalization of the ICM spectrum (density, entropy, or pressure) is
linearly tied to the level of large-scale motions, which excite both gravity
and sound waves due to stratification. For low 3D Mach number M~0.25, gravity
waves mainly drive entropy perturbations, traced by preferentially tangential
turbulence. For M>0.5, sound waves start to significantly contribute, passing
the leading role to compressive pressure fluctuations, associated with
isotropic (or slightly radial) turbulence. Density and temperature fluctuations
are then characterized by the dominant process: isobaric (low M), adiabatic
(high M), or isothermal (strong conduction). Most clusters reside in the
intermediate regime, showing a mixture of gravity and sound waves, hence
drifting towards isotropic velocities. Remarkably, regardless of the regime,
the variance of density perturbations is comparable to the 1D Mach number. This
linear relation allows to easily convert between gas motions and ICM
perturbations, which can be exploited by Chandra, XMM data and by the
forthcoming Astro-H. At intermediate and small scales (10-100 kpc), the
turbulent velocities develop a Kolmogorov cascade. The thermodynamic
perturbations act as effective tracers of the velocity field, broadly
consistent with the Kolmogorov-Obukhov-Corrsin advection theory. Thermal
conduction acts to damp the gas fluctuations, washing out the filamentary
structures and steepening the spectrum, while leaving unaltered the velocity
cascade. The ratio of the velocity and density spectrum thus inverts the
downtrend shown by the non-diffusive models, allowing to probe the presence of
significant conductivity in the ICM.Comment: Accepted by A&A; 15 pages, 10 figures; added insights and references
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Further studies of X-ray structure of the Perseus cluster
The X-ray sources in the Perseus cluster have been studied by many authors. Available data on the spatial and spectral distributions are examined and summarized. Based on these observations, a consistent model is proposed for the production of X-rays and gamma-rays in the region around NGC 1275. It is shown that good agreement with observations is obtained by assuming the emission of soft X-rays for thermal bremsstrahlung and of hard X-rays and gamma-rays from the inverse Compton process
On modular signs
We consider some questions related to the signs of Hecke eigenvalues or
Fourier coefficients of classical modular forms. One problem is to determine to
what extent those signs, for suitable sets of primes, determine uniquely the
modular form, and we give both individual and statistical results. The second
problem, which has been considered by a number of authors, is to determine the
size, in terms of the conductor and weight, of the first sign-change of Hecke
eigenvalues. Here we improve significantly the recent estimate of Iwaniec,
Kohnen and Sengupta.Comment: 23 pages, 1 figure; new version with new coauthor and strong
improvements of two of the two main results
Quantifying properties of ICM inhomogeneities
We present a new method to identify and characterize the structure of the
intracluster medium (ICM) in simulated galaxy clusters. The method uses the
median of gas properties, such as density and pressure, which we show to be
very robust to the presence of gas inhomogeneities. In particular, we show that
the radial profiles of median gas properties are smooth and do not exhibit
fluctuations at locations of massive clumps in contrast to mean and mode
properties. It is shown that distribution of gas properties in a given radial
shell can be well described by a log-normal PDF and a tail. The former
corresponds to a nearly hydrostatic bulk component, accounting for ~99% of the
volume, while the tail corresponds to high density inhomogeneities. We show
that this results in a simple and robust separation of the diffuse and clumpy
components of the ICM. The FWHM of the density distribution grows with radius
and varies from ~0.15 dex in cluster centre to ~0.5 dex at 2r_500 in relaxed
clusters. The small scatter in the width between relaxed clusters suggests that
the degree of inhomogeneity is a robust characteristic of the ICM. It broadly
agrees with the amplitude of density perturbations in the Coma cluster. We
discuss the origin of ICM density variations in spherical shells and show that
less than 20% of the width can be attributed to the triaxiality of the cluster
gravitational potential. As a link to X-ray observations of real clusters we
evaluated the ICM clumping factor with and without high density
inhomogeneities. We argue that these two cases represent upper and lower limits
on the departure of the observed X-ray emissivity from the median value. We
find that the typical value of the clumping factor in the bulk component of
relaxed clusters varies from ~1.1-1.2 at r_500 up to ~1.3-1.4 at r_200, in
broad agreement with recent observations.Comment: 16 pages, 12 figure, accepted to MNRA
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