Retraction Note: An apoptosis-enhancing drug overcomes platinum resistance in a tumour-initiating subpopulation of ovarian cancer.

This Article has been retracted; see accompanying Retraction Note

Nest-site philopatry and the evolution of temperature-dependent sex determination

Despite intensive research, there is no clear empirical evidence to explain the evolution and persistence of temperature-dependent sex determination in reptiles. A recent hypothesis presented by Reinhold proposes that natal homing could lead directly to the evolution of temperature-dependent sex determination. According to his hypothesis, daughters are produced in rare high-quality sites (associated with higher survival rates) to which they return and use to nest, thus deriving higher fitness than sons for whom the quality of the natal patch does not affect their reproductive output if they survive to maturity. We performed an initial empirical evaluation of several assumptions and predictions of this hypothesis as applied to painted turtles (Chrysemys picta), using data from five consecutive nesting seasons, on a major nesting beach. Females were somewhat philopatric to microgeographic sites and to vegetation cover types within the nesting beach, consistent with one of the assumptions of Reinhold’s hypothesis. The variables we examined that influence hatchling fitness (predation, hatching success and sex ratio) were not stable at microgeographic nesting sites or at vegetation cover types. Predation was repeatable within females, whereas hatching success and sex ratio were not. Contrary to Reinhold’s hypothesis, females did not nest more frequently in open sites (which tend to produce more females) than in patches with more vegetation (which tend to produce more males). Furthermore, preferred nest sites (as measured by nest density) did not produce predominantly females. However, nests with higher hatching success tended to produce slightly more females (although the magnitude of this effect was very small). Therefore, Reinhold’s hypothesis is not applicable to C. picta at the level studied – that is, within a nesting beach over a 5 year period – because most of the essential conditions were not met by our data

Temperature-Dependent Sex Determination under Rapid Anthropogenic Environmental Change: Evolution at a Turtle’s Pace?

Organisms become adapted to their environment by evolving through natural selection, a process that generally transpires over many generations. Currently, anthropogenically driven environmental changes are occurring orders of magnitude faster than they did prior to human influence, which could potentially outpace the ability of some organisms to adapt. Here, we focus on traits associated with temperature-dependent sex determination (TSD), a classic polyphenism, in a model turtle species to address the evolutionary potential of species with TSD to respond to rapid climate change. We show, first, that sex-ratio outcomes in species with TSD are sensitive to climatic variation. We then identify the evolutionary potential, in terms of heritability, of TSD and quantify the evolutionary potential of 3 key traits involved in TSD: pivotal temperature, maternal nest-site choice, and nesting phenology. We find that these traits display different patterns of adaptive potential: pivotal temperature exhibits moderate heritable variation, whereas nest-site choice and nesting phenology, with considerable phenotypic plasticity, have only modest evolutionary potential to alter sex ratios. Therefore, the most likely response of species with TSD to anthropogenically induced climate change may be a combination of microevolution in thermal sensitivity of the sex-determining pathway and of plasticity in maternal nesting behavior

Reduction of Dilute Ising Spin Glasses

The recently proposed reduction method for diluted spin glasses is investigated in depth. In particular, the Edwards-Anderson model with \pm J and Gaussian bond disorder on hyper-cubic lattices in d=2, 3, and 4 is studied for a range of bond dilutions. The results demonstrate the effectiveness of using bond dilution to elucidate low-temperature properties of Ising spin glasses, and provide a starting point to enhance the methods used in reduction. Based on that, a greedy heuristic call ``Dominant Bond Reduction'' is introduced and explored.Comment: 10 pages, revtex, final version, find related material at http://www.physics.emory.edu/faculty/boettcher

Stability of the replica-symmetric saddle-point in general mean-field spin-glass models

Within the replica approach to mean-field spin-glasses the transition from ergodic high-temperature behaviour to the glassy low-temperature phase is marked by the instability of the replica-symmetric saddle-point. For general spin-glass models with non-Gaussian field distributions the corresponding Hessian is a $2^n\times 2^n$ matrix with the number $n$ of replicas tending to zero eventually. We block-diagonalize this Hessian matrix using representation theory of the permutation group and identify the blocks related to the spin-glass susceptibility. Performing the limit $n\to 0$ within these blocks we derive expressions for the de~Almeida-Thouless line of general spin-glass models. Specifying these expressions to the cases of the Sherrington-Kirkpatrick, Viana-Bray, and the L\'evy spin glass respectively we obtain results in agreement with previous findings using the cavity approach

First IBEX observations of the terrestrial plasma sheet and a possible disconnection event

The Interstellar Boundary Explorer (IBEX) mission has recently provided the first all-sky maps of energetic neutral atoms (ENAs) emitted from the edge of the heliosphere as well as the first observations of ENAs from the Moon and from the magnetosheath stagnation region at the nose of the magnetosphere. This study provides the first IBEX images of the ENA emissions from the nightside magnetosphere and plasma sheet. We show images from two IBEX orbits: one that displays typical plasma sheet emissions, which correlate reasonably well with a model magnetic field, and a second that shows a significant intensification that may indicate a near-Earth (similar to 10 R(E) behind the Earth) disconnection event. IBEX observations from similar to 0.5-6 keV indicate the simultaneous addition of both a hot (several keV) and colder (similar to 700 eV) component during the intensification; if IBEX directly observed magnetic reconnection in the magnetotail, the hot component may signify the plasma energization