4,499 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
Search for a Standard Explanation of the Pioneer Anomaly
The data from Pioneer 10 and 11 shows an anomalous, constant, Doppler
frequency drift that can be interpreted as an acceleration directed towards the
Sun of a_P = (8.74 \pm 1.33) x 10^{-8} cm/s^2. Although one can consider a new
physical origin for the anomaly, one first must investigate the contributions
of the prime candidates, which are systematics generated on board. Here we
expand upon previous analyses of thermal systematics. We demonstrate that
thermal models put forth so far are not supported by the analyzed data.
Possible ways to further investigate the nature of the anomaly are proposed.Comment: Changes made for publicatio
Accurate theoretical fits to laser ARPES EDCs in the normal phase of cuprate superconductors
Anderson has recently proposed a theory of the strange metal state above Tc
in the high Tc superconductors. [arXiv:cond-mat/0512471] It is based on the
idea that the unusual transport properties and spectral functions are caused by
the strong Mott- Hubbard interactions and can be computed by using the formal
apparatus of Gutzwiller projection. In ref. 1 Anderson computed only the
tunneling spectrum and the power-law exponent of the infrared conductivity. He
had calculated the energy distribution curves (EDCs) in angle resolved
photoemission spectroscopy (ARPES) but was discouraged when these differed
radically from the best ARPES measurements available at the time, and did not
include them. In this letter we compare the spectral functions computed within
this model to the novel laser-ARPES data of the Dessau group.These are found to
capture the shape of the experimental EDCs with unprecedented accuracy and in
principle have only one free parameter
Anderson et al. Reply (to the Comment by Katz on Pioneer 10/11)
We conclude that Katz's proposal (anisotropic heat reflection off of the back
of the spacecraft high-gain antennae, the heat coming from the RTGs) does not
provide enough power and so can not explain the Pioneer anomaly.Comment: LaTex, 3 pages, Phys. Rev. Lett. (to be published
Anderson et al. Reply (to the Comment by Murphy on Pioneer 10/11)
We conclude that Murphy's proposal (radiation of the power of the main-bus
electrical systems from the rear of the craft) can not explain the anomalous
Pioneer acceleration.Comment: LaTex, 3 pages, Phys. Rev. Lett. (to be published
New Product Theorems for Z-Cyclic Whist Tournaments
AbstractThe aim of this note is to show how existing product constructions for cyclic and 1-rotational block designs can be adapted to provide a highly effective method of obtaining product theorems for whist tournaments
Breakdown of Strong-Coupling Perturbation Theory in Doped Mott Insulators
We show that doped Mott insulators, such as the copper-oxide superconductors,
are asymptotically slaved in that the quasiparticle weight, , near
half-filling depends critically on the existence of the high energy scale set
by the upper Hubbard band. In particular, near half filling, the following
dichotomy arises: when the high energy scale is integrated out but Z=0
in the thermodynamic limit when it is retained. Slavery to the high energy
scale arises from quantum interference between electronic excitations across
the Mott gap. Broad spectral features seen in photoemission in the normal state
of the cuprates are argued to arise from high energy slavery.Comment: Published versio
Comparing stakeholder attitudes toward white-tailed deer and rare plant management in Canaan Valley, West Virginia
Canaan Valley, West Virginia, USA provides habitat for many plants considered rare in West Virginia. The local white-tailed deer (Odocoileus virginianus Zimm.) are a popular attraction for visitors as well as resident and nonresident hunters. However, concerns exist over the impact of white-tailed deer herbivory on rare plant communities in the wetlands. We evaluated stakeholder attitudes regarding white-tailed deer management and rare plant conservation by mailing surveys to property owners in Canaan Valley and Tucker County, WV, and providing surveys to visitors at Canaan Valley State Park and National Wildlife Refuge. Individuals that had incurred crop damage were more likely to view the Canaan Valley population as overabundant while nonresident landowners placed higher values on the conservation of rare plants and plant communities in Canaan Valley. We found that hunters were more likely than nonhunters to support white-tailed deer management actions. Results of this survey may help managers to direct management and education goals toward actual rather than perceived stakeholder attitudes
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