Dislocation-Mediated Melting: The One-Component Plasma Limit

The melting parameter $\Gamma_m$ of a classical one-component plasma is estimated using a relation between melting temperature, density, shear modulus, and crystal coordination number that follows from our model of dislocation-mediated melting. We obtain $\Gamma_m=172\pm 35,$ in good agreement with the results of numerous Monte-Carlo calculations.Comment: 8 pages, LaTe

Quantum geometrodynamics: whence, whither?

Quantum geometrodynamics is canonical quantum gravity with the three-metric as the configuration variable. Its central equation is the Wheeler--DeWitt equation. Here I give an overview of the status of this approach. The issues discussed include the problem of time, the relation to the covariant theory, the semiclassical approximation as well as applications to black holes and cosmology. I conclude that quantum geometrodynamics is still a viable approach and provides insights into both the conceptual and technical aspects of quantum gravity.Comment: 25 pages; invited contribution for the Proceedings of the seminar "Quantum Gravity: Challenges and Perspectives", Bad Honnef, Germany, April 200

Exact Hypersurface-Homogeneous Solutions in Cosmology and Astrophysics

A framework is introduced which explains the existence and similarities of most exact solutions of the Einstein equations with a wide range of sources for the class of hypersurface-homogeneous spacetimes which admit a Hamiltonian formulation. This class includes the spatially homogeneous cosmological models and the astrophysically interesting static spherically symmetric models as well as the stationary cylindrically symmetric models. The framework involves methods for finding and exploiting hidden symmetries and invariant submanifolds of the Hamiltonian formulation of the field equations. It unifies, simplifies and extends most known work on hypersurface-homogeneous exact solutions. It is shown that the same framework is also relevant to gravitational theories with a similar structure, like Brans-Dicke or higher-dimensional theories.Comment: 41 pages, REVTEX/LaTeX 2.09 file (don't use LaTeX2e !!!) Accepted for publication in Phys. Rev.

Data from: A cross-seasonal perspective on local adaptation: metabolic plasticity mediates responses to winter in a thermal-generalist moth

The physiological and ecological impact of the thermal environment across life-stages can result in trade-offs that determine fitness and population dynamics. Understanding mechanisms and consequences of local adaptation for any organism that overwinters requires taking a cross-seasonal perspective. We used a trait-based approach to distinguish variation among ecotypes in ecological and physiological responses to overwintering conditions. We used fall webworms (Hyphantria cunea; Lepidoptera: Arctiidae) from Ottawa, Ontario and Columbus Ohio, representing the centre and periphery of the native range. We hypothesised that populations would be locally adapted to their overwintering environments, with fitness maximised under natal overwintering conditions. We predicted that this local adaptation would result from modulation of rates of energy use, growth and development. Each ecotype had higher overwinter survival in their natal compared to non-natal winter environment, and this was associated with larger pupal mass, size and carbohydrate reserves at the end of winter. This suggests that the ecotypes are locally adapted to winter conditions. Larger adults laid more eggs, but there was no effect of ecotype or environment on fecundity. Pupae overwintering at warm, energetically demanding southern temperatures suppressed metabolic rates in autumn, and developed more quickly in the spring, compensating for energetic demands of warmer winters. Northern ecotypes had lower thermal sensitivity of metabolism, leading to higher metabolic rates at cool temperatures that correlated with faster post-winter development. Local adaptation to winter conditions suggests performance of peripheral populations may not be enhanced by warming winters. Decoupling of winter and growing season temperatures may negatively impact ectotherms

DNA vaccines against tuberculosis.

&lt;p&gt;DNA plasmids encoding Mycobacterium tuberculosis antigen 85 (Ag85) were tested as vaccines in animal models. Ag85 DNA induced relevant immune responses (i.e. T helper (Th) cells, Th1 cytokines and cytotoxic T lymphocytes) and was protective in mouse and guinea pig models of mycobacterial disease. Therefore, DNA vaccination holds promise as an effective means of preventing tuberculosis in humans. Furthermore, this technique is amenable to identifying the protective antigens of M. tuberculosis.&lt;/p&gt;</p