12,295 research outputs found
The search for novel analgesics: re-examining spinal cord circuits with new tools
In this perspective, we propose the absence of detailed information regarding spinal cord
circuits that process sensory information remains a major barrier to advancing analgesia.
We highlight recent advances showing that functionally discrete populations of neurons in
the spinal cord dorsal horn play distinct roles in processing sensory information. We then
discuss new molecular, electrophysiological, and optogenetic techniques that can be
employed to understand how dorsal horn circuits process tactile and nociceptive
information. We believe this information can drive the development of entirely new classes
of pharmacotherapies that target key elements in spinal circuits to selectively modify
sensory function and blunt pain
Model Atmospheres for Irradiated Stars in pre-Cataclysmic Variables
Model atmospheres have been computed for M dwarfs that are strongly
irradiated by nearby hot companions. A variety of primary and secondary
spectral types are explored in addition to models specific to four known
systems: GD 245, NN Ser, AA Dor, and UU Sge. This work demonstrates that a
dramatic temperature inversion is possible on at least one hemisphere of an
irradiated M dwarf and the emergent spectrum will be significantly different
from an isolated M dwarf or a black body flux distribution. For the first time,
synthetic spectra suitable for direct comparison to high-resolution
observations of irradiated M dwarfs in non-mass transferring post-common
envelope binaries are presented. The effects of departures from local
thermodynamic equilibrium on the Balmer line profiles are also discussed.Comment: Accepted for publication in ApJ; 12 pages, 10 figure
Cytokinin Accumulation and an Altered Ethylene Response Mediate the Pleiotropic Phenotype of the Pea Nodulation Mutant R50 (\u3cem\u3esym16\u3c/em\u3e)
R50 (sym16), a pleiotropic mutant of Pisum sativum L., is short, has thickened internodes and roots, and has a reduced number of lateral roots and nodules. Its low nodule phenotype can be restored with the application of ethylene inhibitors; furthermore, it can be mimicked by applying cytokinins (CKs) to the roots of the parent line #8216;Sparkle’. Here, we report on the etiolation phenotypes of R50 and ‘Sparkle’, and on the interactive roles of ethylene and CKs in these lines. R50 displayed an altered etiolation phenotype, as it was shorter and thicker, and had more developed leaves than dark-grown ‘Sparkle’. Shoot morphological differences induced by exogenous ethylene or CKs were found to be less severe for R50. Ethylene inhibitor application induced root and shoot elongation and encouraged apical hook opening in both etiolated lines. Liquid chromatography–tandem mass spectrometry analysis indicated that CK concentrations in R50 were higher than in ‘Sparkle’, particularly in mature shoots where the levels were maintained at elevated concentrations. These differences indicate a reduction in the CK catabolism of R50. The accumulation of CKs can be directly related to several traits of R50, with the reduced number of nodules and altered shoot ethylene response being likely indirect effects
Tempo and intensity of pre-task music modulate neural activity during reactive task performance
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2013 The Authors.Research has shown that not only do young athletes purposively use music to manage their emotional state (Bishop, Karageorghis, & Loizou, 2007), but also that brief periods of music listening may facilitate their subsequent reactive performance (Bishop, Karageorghis, & Kinrade, 2009). We report an fMRI study in which young athletes lay in an MRI scanner and listened to a popular music track immediately prior to performance of a three-choice reaction time task; intensity and tempo were modified such that six excerpts (2 intensities × 3 tempi) were created. Neural activity was measured throughout. Faster tempi and higher intensity collectively yielded activation in structures integral to visual perception (inferior temporal gyrus), allocation of attention (cuneus, inferior parietal lobule, supramarginal gyrus), and motor control (putamen), during reactive performance. The implications for music listening as a pre-competition strategy in sport are discussed
If a safety aid is present, there must be danger: the paradoxical effects of hand sanitizer during a contamination exposure task
Perceptions of danger often arise in the context of feared threat cues, but individuals also rely on other heuristics that lead them to infer danger in ambiguous situations. For example, individuals may interpret their own anxiety or safety-seeking behaviors as indicators of threat. Another potential source of danger information is the mere availability of safety aids in the environment. Although assumed to be helpful, safety aids might paradoxically elicit, rather than alleviate, anxiety. The present study was designed to assess the degree to which concern-relevant safety aids exacerbate distress. Participants (N = 71) completed several self-report measures and engaged in a contamination-related behavioral avoidance task (BAT) in the presence or absence of a 2L hand sanitizer dispenser. Results showed that participants higher in trait contamination aversion and in the presence of hand sanitizer endorsed greater inferences of danger, hypervigilance, peak BAT anxiety and disgust, BAT avoidance, and urges to wash following the BAT. Theoretical and clinical implications of the paradoxical inference of danger from the presence of safety aids are discussed
Forestry in reconstruction South Africa : imperial visions, colonial realities
Abstract: The British military conquest and political annexation of the former South African Republic (ZAR) and Orange Free State at the end of the South African War/Second Anglo-Boer War (1899–1902) meant that the break-away Boer republics were finally integrated within British South Africa and the wider British Empire, a goal that elites in London had pursued since the British government annexed the fledgling Natalia Republic within the British-controlled Natal Colony in 1843.3 Among a broader suite of reforms, reconstruction officials established government forestry programs in the Transvaal and Orange Free State (renamed the Orange River Colony from 1900–1910..
Stability of Filters for the Navier-Stokes Equation
Data assimilation methodologies are designed to incorporate noisy
observations of a physical system into an underlying model in order to infer
the properties of the state of the system. Filters refer to a class of data
assimilation algorithms designed to update the estimation of the state in a
on-line fashion, as data is acquired sequentially. For linear problems subject
to Gaussian noise filtering can be performed exactly using the Kalman filter.
For nonlinear systems it can be approximated in a systematic way by particle
filters. However in high dimensions these particle filtering methods can break
down. Hence, for the large nonlinear systems arising in applications such as
weather forecasting, various ad hoc filters are used, mostly based on making
Gaussian approximations. The purpose of this work is to study the properties of
these ad hoc filters, working in the context of the 2D incompressible
Navier-Stokes equation. By working in this infinite dimensional setting we
provide an analysis which is useful for understanding high dimensional
filtering, and is robust to mesh-refinement. We describe theoretical results
showing that, in the small observational noise limit, the filters can be tuned
to accurately track the signal itself (filter stability), provided the system
is observed in a sufficiently large low dimensional space; roughly speaking
this space should be large enough to contain the unstable modes of the
linearized dynamics. Numerical results are given which illustrate the theory.
In a simplified scenario we also derive, and study numerically, a stochastic
PDE which determines filter stability in the limit of frequent observations,
subject to large observational noise. The positive results herein concerning
filter stability complement recent numerical studies which demonstrate that the
ad hoc filters perform poorly in reproducing statistical variation about the
true signal
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