6,192 research outputs found
Adaptive plasticity in the mouse mandible
BACKGROUND: Plasticity, i.e. non-heritable morphological variation, enables organisms to modify the shape of their skeletal tissues in response to varying environmental stimuli. Plastic variation may also allow individuals to survive in the face of new environmental conditions, enabling the evolution of heritable adaptive traits. However, it is uncertain whether such a plastic response of morphology constitutes an evolutionary adaption itself. Here we investigate whether shape differences due to plastic bone remodelling have functionally advantageous biomechanical consequences in mouse mandibles. Shape characteristics of mandibles from two groups of inbred laboratory mice fed either rodent pellets or ground pellets mixed with jelly were assessed using geometric morphometrics and mechanical advantage measurements of jaw adductor musculature. RESULTS: Mandibles raised on diets with differing food consistency showed significant differences in shape, which in turn altered their biomechanical profile. Mice raised on a soft food diet show a reduction in mechanical advantage relative to mice of the same inbred strain raised on a typical hard food diet. Further, the soft food eaters showed lower levels of integration between jaw regions, particularly between the molar and angular region relative to hard food eaters. CONCLUSIONS: Bone remodelling in mouse mandibles allows for significant shifts in biomechanical ability. Food consistency significantly influences this process in an adaptive direction, as mice raised on hard food develop jaws better suited to handle hard foods. This remodelling also affects the organisation of the mandible, as mice raised on soft food appear to be released from developmental constraints showing less overall integration than those raised on hard foods, but with a shift of integration towards the most solicited regions of the mandible facing such a food, namely the incisors. Our results illustrate how environmentally driven plasticity can lead to adaptive functional changes that increase biomechanical efficiency of food processing in the face of an increased solicitation. In contrast, decreased demand in terms of food processing seems to release developmental interactions between jaw parts involved in mastication, and may generate new patterns of co-variation, possibly opening new directions to subsequent selection. Overall, our results emphasize that mandible shape and integration evolved as parts of a complex system including mechanical loading food resource utilization and possibly foraging behaviour
Annotated bibliography on hypoxia and its effects on marine life, with emphasis on the Gulf of Mexico
This bibliography contains 73 annotated references from publications and reports concerning hypoxia, .,;
2.0 ppm dissolved oxygen concentration, in the Gulf of Mexico. Instances of hypoxia from similar habitats and
the effects of low oxygen levels on marine or estuarine organisms are also included. (PDF file contains 15 pages.
100 GHz Spaced 10 Gbit/s WDM over 10 degrees C to 70 degrees C using an uncooled DBR laser
100 GHz spaced 10 Gbit/s (NRZ, PRBS 2(31)-1) WDM transmission is demonstrated with an uncooled DBR laser. The wavelength of the laser was stabilised within 2 GHz from 10 degrees C to 70 degrees C using a predicting algorithm. (C) 2004 Optical Society of America
South-West extension of the hard X-ray emission from the Coma cluster
We explore the morphology of hard (18-30 keV) X-ray emission from the Coma
cluster of galaxies. We analyze a deep (1.1 Ms) observation of the Coma cluster
with the ISGRI imager on board the \emph{INTEGRAL} satellite. We show that the
source extension in the North-East to South-West (SW) direction ()
significantly exceeds the size of the point spread function of ISGRI, and that
the centroid of the image of the source in the 18-30 keV band is displaced in
the SW direction compared to the centroid in the 1-10 keV band. To test the
nature of the SW extension we fit the data assuming different models of source
morphology. The best fit is achieved with a diffuse source of elliptical shape,
although an acceptable fit can be achieved assuming an additional point source
SW of the cluster core. In the case of an elliptical source, the direction of
extension of the source coincides with the direction toward the subcluster
falling onto the Coma cluster. If the SW excess is due to the presence of a
point source with a hard spectrum, we show that there is no obvious X-ray
counterpart for this additional source, and that the closest X-ray source is
the quasar EXO 1256+281, which is located from the centroid of the
excess. The observed morphology of the hard X-ray emission clarifies the nature
of the hard X-ray "excess" emission from the Coma cluster, which is due to the
presence of an extended hard X-ray source SW of the cluster core.Comment: 7pages, 10 figure
Alien Registration- Lafond, Marie L. (Auburn, Androscoggin County)
https://digitalmaine.com/alien_docs/30277/thumbnail.jp
Decoherence and entropy of primordial fluctuations II. The entropy budget
We calculate the entropy of adiabatic perturbations associated with a
truncation of the hierarchy of Green functions at the first non trivial level,
i.e. in a self-consistent Gaussian approximation. We give the equation
governing the entropy growth and discuss its phenomenology. It is parameterized
by two model-dependent kernels. We then examine two particular inflationary
models, one with isocurvature perturbations, the other with corrections due to
loops of matter fields. In the first model the entropy grows rapidely, while in
the second the state remains pure (at one loop).Comment: 28 page
Conceptualizing human resilience in the face of the global epidemiology of cyber attacks
Computer security is a complex global phenomenon where different populations interact, and the infection of one person creates risk for another. Given the dynamics and scope of cyber campaigns, studies of local resilience without reference to global populations are inadequate. In this paper we describe a set of minimal requirements for implementing a global epidemiological infrastructure to understand and respond to large-scale computer security outbreaks. We enumerate the relevant dimensions, the applicable measurement tools, and define a systematic approach to evaluate cyber security resilience. From the experience in conceptualizing and designing a cross-national coordinated phishing resilience evaluation we describe the cultural, logistic, and regulatory challenges to this proposed public health approach to global computer assault resilience. We conclude that mechanisms for systematic evaluations of global attacks and the resilience against those attacks exist. Coordinated global science is needed to address organised global ecrime
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