1,920 research outputs found
Teachers as mediators: an exploration of situated English teaching
Within the context of lower secondary English teaching in South West England, this study identifies in broad terms the competing goals between which English teachers mediate and the explicit and hidden tensions that result. To understand the interactions of competing goals, teachersâ goal-oriented behaviours are referenced to a set of idealised ârole typesâ based on the dimensions of goals, norms, discourses and practices. It is asserted that competing goals, significant to particular educational circumstances, emanate from various sometimes contradictory local, national and perhaps broader social and cultural influences on practice. Yet the teachers observed moved smoothly between goal-oriented behaviours in a continuous and comfortable style, easily and without reflecting any tensions between them. Thus, this article elaborates an account of situated English teaching
Varieties of teacher expertise in teaching Danish language and literature in lower secondary schools
No-go theorem for bimetric gravity with positive and negative mass
We argue that the most conservative geometric extension of Einstein gravity
describing both positive and negative mass sources and observers is bimetric
gravity and contains two copies of standard model matter which interact only
gravitationally. Matter fields related to one of the metrics then appear dark
from the point of view of an observer defined by the other metric, and so may
provide a potential explanation for the dark universe. In this framework we
consider the most general form of linearized field equations compatible with
physically and mathematically well-motivated assumptions. Using gauge-invariant
linear perturbation theory, we prove a no-go theorem ruling out all bimetric
gravity theories that, in the Newtonian limit, lead to precisely opposite
forces on positive and negative test masses.Comment: 19 pages, no figures, journal versio
Bistable Gradient Networks II: Storage Capacity and Behaviour Near Saturation
We examine numerically the storage capacity and the behaviour near saturation
of an attractor neural network consisting of bistable elements with an
adjustable coupling strength, the Bistable Gradient Network (BGN). For strong
coupling, we find evidence of a first-order "memory blackout" phase transition
as in the Hopfield network. For weak coupling, on the other hand, there is no
evidence of such a transition and memorized patterns can be stable even at high
levels of loading. The enhanced storage capacity comes, however, at the cost of
imperfect retrieval of the patterns from corrupted versions.Comment: 15 pages, 12 eps figures. Submitted to Phys. Rev. E. Sequel to
cond-mat/020356
Multimetric extension of the PPN formalism: experimental consistency of repulsive gravity
Recently we discussed a multimetric gravity theory containing several copies
of standard model matter each of which couples to its own metric tensor. This
construction contained dark matter sectors interacting repulsively with the
visible matter sector, and was shown to lead to cosmological late-time
acceleration. In order to test the theory with high-precision experiments
within the solar system we here construct a simple extension of the
parametrized post-Newtonian (PPN) formalism for multimetric gravitational
backgrounds. We show that a simplified version of this extended formalism
allows the computation of a subset of the PPN parameters from the linearized
field equations. Applying the simplified formalism we find that the PPN
parameters of our theory do not agree with the observed values, but we are able
to improve the theory so that it becomes consistent with experiments of
post-Newtonian gravity and still features its promising cosmological
properties.Comment: 19 pages, no figures, journal versio
Human Time-Frequency Acuity Beats the Fourier Uncertainty Principle
The time-frequency uncertainty principle states that the product of the
temporal and frequency extents of a signal cannot be smaller than .
We study human ability to simultaneously judge the frequency and the timing of
a sound. Our subjects often exceeded the uncertainty limit, sometimes by more
than tenfold, mostly through remarkable timing acuity. Our results establish a
lower bound for the nonlinearity and complexity of the algorithms employed by
our brains in parsing transient sounds, rule out simple "linear filter" models
of early auditory processing, and highlight timing acuity as a central feature
in auditory object processing.Comment: 4 pages, 2 figures; Accepted at PR
Presence of alkaloids and cyanogenic glycosides in fruits consumed by sympatric bonobos and the Nkundo people at LuiKotale/Salonga National Park, Democratic Republic of Congo and its relationship to food choice
Reconstructing depositional rates and their effect on paleoenvironmental proxies : the case of the Lau Carbon Isotope Excursion in Gotland, Sweden
Variations in depositional rates affect the temporal depositional resolutions of proxies used for paleoenvironmental reconstructions; for example, condensation can make reconstructed environmental changes appear very abrupt. This is commonly addressed by transforming proxy data using age models, but this approach is limited to situations where numerical ages are available or can be reliably inferred by correlation. Here we propose a new solution, in which relative age models are constructed based on proxies for depositional rates. As a case study, we use the onset of the late Silurian Lau Carbon Isotope Excursion (LCIE) in Gotland, Sweden. The studied succession is a gradual record of shallowing upward in a tropical, neritic carbonate platform. As proxies for depositional rates we tested thorium concentration, carbonate content, and the concentration of pelagic palynomorphs. These three proxies were used to create relative age models using the previously published DAIME model. We applied these models to transform the delta C-13(carb) values as well as concentrations of selected redox-sensitive elements. The three relative age models yielded qualitatively similar results. In our case study, variations in depositional rates resulted in peaks of redox proxies appearing up to 76% higher when taken at face value, compared to when accounting for these rates. In the most extreme cases, our corrections resulted in a reversal in the stratigraphic trend of elemental concentrations. This approach can be applied and developed across depositional setting and types of paleoenvironmental proxies. It provides a flexible tool for developing quantitative models to improve our understanding of the stratigraphic record
Cannabinoids, the endocannabinoid system, and pain: a review of preclinical studies
This narrative review represents an output from the International Association for the Study of Pain's global task force on the use of cannabis, cannabinoids, and cannabis-based medicines for pain management, informed by our companion systematic review and meta-analysis of preclinical studies in this area. Our aims in this review are (1) to describe the value of studying cannabinoids and endogenous cannabinoid (endocannabinoid) system modulators in preclinical/animal models of pain; (2) to discuss both pain-related efficacy and additional pain-relevant effects (adverse and beneficial) of cannabinoids and endocannabinoid system modulators as they pertain to animal models of pathological or injury-related persistent pain; and (3) to identify important directions for future research. In service of these goals, this review (1) provides an overview of the endocannabinoid system and the pharmacology of cannabinoids and endocannabinoid system modulators, with specific relevance to animal models of pathological or injury-related persistent pain; (2) describes pharmacokinetics of cannabinoids in rodents and humans; and (3) highlights differences and discrepancies between preclinical and clinical studies in this area. Preclinical (rodent) models have advanced our understanding of the underlying sites and mechanisms of action of cannabinoids and the endocannabinoid system in suppressing nociceptive signaling and behaviors. We conclude that substantial evidence from animal models supports the contention that cannabinoids and endocannabinoid system modulators hold considerable promise for analgesic drug development, although the challenge of translating this knowledge into clinically useful medicines is not to be underestimated
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