8,499 research outputs found
Time Delay Compensation and Stability Analysis of Networked Predictive Control Systems Based on Hammerstein Model
A novel approach is proposed for a networked control system with random delays containing a nonlinear process based on a Hammerstein model. The method uses a time delay two step generalized predictive control (TDTSGPC), which consists of two parts, one is to deal with the input nonlinearity of the Hammerstein model and the other is to compensate the network induced delays in the networked control system. Theoretical results using the Popov theorem are presented for the closed-loop stability of the system in the case of a constant delay. Simulation examples illustrating the validity of the approach are presented
Encoding of temporal probabilities in the human brain
Anticipating the timing of future events is a necessary precursor to preparing actions and allocating resources to sensory processing. This requires elapsed time to be represented in the brain and used to predict the temporal probability of upcoming events. While neuropsychological, imaging, magnetic stimulation studies, and single-unit recordings implicate the role of higher parietal and motor-related areas in temporal estimation, the role of earlier, purely sensory structures remains more controversial. Here we demonstrate that the temporal probability of expected visual events is encoded not by a single area but by a wide network that importantly includes neuronal populations at the very earliest cortical stages of visual processing. Moreover, we show that activity in those areas changes dynamically in a manner that closely accords with temporal expectations
The proqol-21: A revised version of the professional quality of life (ProQOL) scale based on Rasch analysis
The Professional Quality of Life scale is a measure intended to provide practitioners and researchers with an indication of a caring professional’s compassion satisfaction, burnout, and secondary traumatic stress. While this measure has been used extensively in nursing research, owing to the relevancy of patient-care associated satisfaction and fatigue within this profession, information regarding the construct validity of this measure is less well represented in the literature. We examined the construct validity of the Professional Quality of Life scale using a Rasch analysis procedure on each of its three scales, as a means of substantiating their measurement adequacy. Responses on the Professional Quality of Life scale from 1615 registered nurses (age x̅ = 46.48 years, SD = 11.78) were analysed. While support for the measurement adequacy (invariance, person/item fit, and unidimensionality) of the compassion satisfaction scale was found, the burnout and secondary traumatic stress scales did not demonstrate adequate measurement properties. We instead present an alternative measurement model of these subscales, involving items from each, to form a robust measure of compassion fatigue, and provide recoding, scoring, and normed scores for both measures. Our findings indicate that use of the Professional Quality of Life scale’s burnout and secondary traumatic stress scales may require caution, while our revised compassion satisfaction and fatigue scales provide robust measurement options for practitioners and researchers
Temporal Variability of the X-ray Emission of the Crab Nebula Torus
We have analyzed five ROSAT HRI images of the Crab Nebula spanning the years
1991 to 1997 and have found significant changes in the emission structure of
the X-ray torus surrounding the pulsar. Certain regions increase in brightness
by about 20% over the six years, while others show decreases in surface
brightness. The origin of these changes is unclear, but a possible explanation
is that the bulk velocity of the synchrotron radiating electrons has decreased
on the order of 20% as well.Comment: 15 pages plus 6 figures, figure 1 and figure 6 are in color, to
appear in The Astrophysical Journal, Jan 1, 1999, Vol. 510, #
Critical review of the impacts of grazing intensity on soil organic carbon storage and other soil quality indicators in extensively managed grasslands
Acknowledgements This work contributes to the N-Circle project (grant number BB/N013484/1), and CINAg (BB/N013468/1) Virtual Joint Centres on Agricultural Nitrogen (funded by the Newton Fund via UK BBSRC/NERC), U-GRASS (grant number NE/M016900/1), the Belmont Forum/FACCE-JPI DEVIL project (grant number NE/M021327/1), Soils-R-GGREAT (grant number NE/P019455/1), ADVENT (grant number NE/M019713/1), Sêr Cymru LCEE-NRN project, Climate-Smart Grass and the Scottish Government’s Strategic Research Programme.Peer reviewedPublisher PD
Bound on the multiplicity of almost complete intersections
Let be a polynomial ring over a field of characteristic zero and let be a graded ideal of height which is minimally generated by
homogeneous polynomials. If where has degree
and has height , then the multiplicity of is
bounded above by .Comment: 7 pages; to appear in Communications in Algebr
A global picture of quantum de Sitter space
Perturbative gravity about a de Sitter background motivates a global picture
of quantum dynamics in `eternal de Sitter space,' the theory of states which
are asymptotically de Sitter to both future and past. Eternal de Sitter physics
is described by a finite dimensional Hilbert space in which each state is
precisely invariant under the full de Sitter group. This resolves a
previously-noted tension between de Sitter symmetry and finite entropy.
Observables, implications for Boltzmann brains, and Poincare recurrences are
briefly discussed.Comment: 17 pages, 1 figure. v2: minor changes, references added. v3: minor
changes to correspond to PRD versio
Geographic Variation in the Effects of Heat Exposure on Maximum Sprint Speed and Hsp70 Abundance in Populations of the Western Fence Lizard, Scelopolus occidentalis
We examined whether western fence lizards Sceloporus occidentalis
occurring in thermally divergent environments display differential
responses to high temperature in locomotor performance
and heat-shock protein (Hsp) expression. We measured
maximum sprint speed in S. occidentalis from four populations
at paired latitudes and elevations before and after exposure to
an experimental heat treatment and then quantified hind-limb
muscle Hsp70 expression. Lizards collected from northern or
high-elevation collection sites suffered a greater reduction in
sprint speed after heat exposure than lizards collected from
southern or low-elevation sites. In addition, lizards from northern
collection sites also exhibited an increase in Hsp70 expression
after heat exposure, whereas there was no effect of
heat exposure on Hsp70 expression in lizards from southern
collection sites. Across all groups, there was a negative relationship
between Hsp70 expression and sprint speed after thermal
stress. This result is significant because (a) it suggests that
an increase in Hsp70 alone cannot compensate for the immediate
negative effects of high-temperature exposure on sprint
speed and (b) it demonstrates a novel correlation between an
emergent property at the intersection of several physiological
systems (locomotion) and a cellular response (Hsp70 expression).
Ultimately, geographic variation in the effects of heat on
sprint speed may translate into differential fitness and population
viability during future increases in global air temperatures
Geographic Variation in the Effects of Heat Exposure on Maximum Sprint Speed and Hsp70 Abundance in Populations of the Western Fence Lizard, Scelopolus occidentalis
We examined whether western fence lizards Sceloporus occidentalis
occurring in thermally divergent environments display differential
responses to high temperature in locomotor performance
and heat-shock protein (Hsp) expression. We measured
maximum sprint speed in S. occidentalis from four populations
at paired latitudes and elevations before and after exposure to
an experimental heat treatment and then quantified hind-limb
muscle Hsp70 expression. Lizards collected from northern or
high-elevation collection sites suffered a greater reduction in
sprint speed after heat exposure than lizards collected from
southern or low-elevation sites. In addition, lizards from northern
collection sites also exhibited an increase in Hsp70 expression
after heat exposure, whereas there was no effect of
heat exposure on Hsp70 expression in lizards from southern
collection sites. Across all groups, there was a negative relationship
between Hsp70 expression and sprint speed after thermal
stress. This result is significant because (a) it suggests that
an increase in Hsp70 alone cannot compensate for the immediate
negative effects of high-temperature exposure on sprint
speed and (b) it demonstrates a novel correlation between an
emergent property at the intersection of several physiological
systems (locomotion) and a cellular response (Hsp70 expression).
Ultimately, geographic variation in the effects of heat on
sprint speed may translate into differential fitness and population
viability during future increases in global air temperatures
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