474 research outputs found
Self-report form of the horse-rider relationship scale| Validation in an equestrian eventing setting
Linear feedback control of transient energy growth and control performance limitations in subcritical plane Poiseuille flow
Suppression of the transient energy growth in subcritical plane Poiseuille
flow via feedback control is addressed. It is assumed that the time derivative
of any of the velocity components can be imposed at the walls as control input,
and that full-state information is available. We show that it is impossible to
design a linear state-feedback controller that leads to a closed-loop flow
system without transient energy growth.
In a subsequent step, full-state feedback controllers -- directly targeting
the transient growth mechanism -- are designed, using a procedure based on a
Linear Matrix Inequalities approach. The performance of such controllers is
analyzed first in the linear case, where comparison to previously proposed
linear-quadratic optimal controllers is made; further, transition thresholds
are evaluated via Direct Numerical Simulations of the controlled
three-dimensional Poiseuille flow against different initial conditions of
physical interest, employing different velocity components as wall actuation.
The present controllers are effective in increasing the transition thresholds
in closed loop, with varying degree of performance depending on the initial
condition and the actuation component employed
Emotion perception and electrophysiological correlates in Huntington\u27s disease
Objective This study aimed to characterise, emotion perception deficits in symptomatic Huntington\u27s disease (HD) via the use of event-related potentials (ERPs). Methods ERP data were recorded during a computerised facial expression task in 11 HD participants and 11 matched controls. Expression (scrambled, neutral, happy, angry, disgust) classification accuracy and intensity were assessed. Relationships between ERP indices and clinical disease characteristics were also examined. Results Accuracy was significantly lower for HD relative to controls, due to reduced performance for neutral, angry and disgust (but not happy) faces. Intensity ratings did not differ between groups. HD participants displayed significantly reduced visual processing amplitudes extending across pre-face (P100) and face-specific (N170) processing periods, whereas subsequent emotion processing amplitudes (N250) were similar across groups. Face-specific and emotion-specific derivations of the N170 and N250 (\u27neutral minus scrambled\u27 and \u27each emotion minus neutral\u27, respectively) did not differ between groups. Conclusions Our data suggest that the facial emotion recognition performance deficits in HD are primarily related to neural degeneration underlying \u27generalised\u27 visual processing, rather than face or emotional specific processing. Significance ERPs are a useful tool to separate functionally discreet impairments in HD, and provide an important avenue for biomarker application that could more-selectively track disease progression
Cremona groups of real surfaces
We give an explicit set of generators for various natural subgroups of the real Cremona group BirR(P2). This completes and unifies former results by several authors
The High Energy view of the Broad Line Radio Galaxy 3C 111
We present the analysis of Suzaku and XMM-Newton observations of the
broad-line radio galaxy (BLRG) 3C 111. Its high energy emission shows
variability, a harder continuum with respect to the radio quiet AGN population,
and weak reflection features. Suzaku found the source in a minimum flux level;
a comparison with the XMM-Newton data implies an increase of a factor of 2.5 in
the 0.5-10 keV flux, in the 6 months separating the two observations. The iron
K complex is detected in both datasets, with rather low equivalent width(s).
The intensity of the iron K complex does not respond to the change in continuum
flux. An ultra-fast, high-ionization outflowing gas is clearly detected in the
XIS data; the absorber is most likely unstable. Indeed, during the XMM-Newton
observation, which was 6 months after, the absorber was not detected. No clear
roll-over in the hard X-ray emission is detected, probably due to the emergence
of the jet as a dominant component in the hard X-ray band, as suggested by the
detection above ~ 100 keV with the GSO on-board Suzaku, although the present
data do not allow us to firmly constrain the relative contribution of the
different components. The fluxes observed by the gamma-ray satellites CGRO and
Fermi would be compatible with the putative jet component if peaking at
energies E ~ 100 MeV. In the X-ray band, the jet contribution to the continuum
starts to be significant only above 10 keV. If the detection of the jet
component in 3C 111 is confirmed, then its relative importance in the X-ray
energy band could explain the different observed properties in the high-energy
emission of BLRGs, which are otherwise similar in their other multiwavelength
properties. Comparison between X-ray and gamma-ray data taken at different
epochs suggests that the strong variability observed for 3C 111 is probably
driven by a change in the primary continuum.Comment: Accepted for publication in MNRAS; 15 pages, 9 figures, 5 table
XMM-Newton and Suzaku analysis of the Fe K complex in the Seyfert 1 galaxy Mrk 509
We report on partially overlapping XMM-Newton (~260 ks) and Suzaku (~100 ks)
observations of the iron K band in the nearby, bright Seyfert 1 galaxy Mrk 509.
The source shows a resolved neutral Fe K line, most probably produced in the
outer part of the accretion disc. Moreover, the source shows further emission
blue-ward of the 6.4 keV line due to ionized material. This emission is well
reproduced by a broad line produced in the accretion disc, while it cannot be
easily described by scattering or emission from photo-ionized gas at rest. The
summed spectrum of all XMM-Newton observations shows the presence of a narrow
absorption line at 7.3 keV produced by highly ionized outflowing material. A
spectral variability study of the XMM-Newton data shows an indication for an
excess of variability at 6.6-6.7 keV. These variations may be produced in the
red wing of the broad ionized line or by variation of a further absorption
structure. The Suzaku data indicate that the neutral Fe Kalpha line intensity
is consistent with being constant on long timescales (of a few years) and they
also confirm as most likely the interpretation of the excess blueshifted
emission in terms of a broad ionized Fe line. The average Suzaku spectrum
differs from the XMM-Newton one for the disappearance of the 7.3 keV absorption
line and around 6.7 keV, where the XMM-Newton data alone suggested variability.Comment: MNRAS in pres
High-resolution X-ray spectroscopy of the low and high states of the Seyfert 1 galaxy NGC 4051 with Chandra LETGS
Methods. We analyse two observations taken with the Low Energy Transmission
Grating Spectrometer of Chandra. We investigated the spectral response to a
sudden flux decrease by a factor of 5, which occurred during the second
observation. Results. We detect a highly ionised absorption component with an
outflow velocity of -4670 km/s, one of the highest outflow velocity components
observed in a Seyfert 1 galaxy. The spectra contain a relativistic O VIII Ly
alpha line, and four absorption components spanning a range in ionisation
parameter xi between 0.07 and 3.19. An emission component producing radiative
recombination continua of C VI and C V appears during the low state. The black
body temperature decreases with the drop in flux observed in the second
observation. Conclusions. For all absorber components we exclude that the
ionisation parameter linearly responded to the decrease in flux by a factor of
5. The variability of the absorber suggest that at least three out of four
detected components are located in the range 0.02-1 pc. ABRIDGEDComment: Accepted by A&A, 14 pages, 9 figure
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