Scalar soliton quantization with generic moduli

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credArticle funded by SCOAP3. CP is a Royal Society Research Fellow and partly supported by the U.S. Department of Energy under grants DOE-SC0010008, DOE-ARRA-SC0003883 and DOE-DE-SC0007897. ABR is supported by the Mitchell Family Foundation. We would like to thank the Mitchell Institute at Texas A&M and the NHETC at Rutgers University respectively for hospitality during the course of this work. We would also like to acknowledge the Aspen Center for Physics and NSF grant 1066293 for a stimulating research environment which led to questions addressed in this paper

Costs of Inducible Defence along a Resource Gradient

In addition to having constitutive defence traits, many organisms also respond to predation by phenotypic plasticity. In order for plasticity to be adaptive, induced defences should incur a benefit to the organism in, for example, decreased risk of predation. However, the production of defence traits may include costs in fitness components such as growth, time to reproduction, or fecundity. To test the hypothesis that the expression of phenotypic plasticity incurs costs, we performed a common garden experiment with a freshwater snail, Radix balthica, a species known to change morphology in the presence of molluscivorous fish. We measured a number of predator-induced morphological and behavioural defence traits in snails that we reared in the presence or absence of chemical cues from fish. Further, we quantified the costs of plasticity in fitness characters related to fecundity and growth. Since plastic responses may be inhibited under limited resource conditions, we reared snails in different densities and thereby levels of competition. Snails exposed to predator cues grew rounder and thicker shells, traits confirmed to be adaptive in environments with fish. Defence traits were consistently expressed independent of density, suggesting strong selection from predatory molluscivorous fish. However, the expression of defence traits resulted in reduced growth rate and fecundity, particularly with limited resources. Our results suggest full defence in predator related traits regardless of resource availability, and costs of defence consequently paid in traits related to fitness

Minority ethnic students and science participation: a qualitative mapping of achievement, aspiration, interest and capital

In the UK, the ‘leaky pipeline’ metaphor has been used to describe the relationship between ethnicity and science participation. Fewer minority ethnic students continue with science in post-compulsory education, and little is known about the ways in which they participate and identify with science, particularly in the secondary school context. Drawing on an exploratory study of 46 interviews and 22 h of classroom observations with British students (aged 11–14) from Black Caribbean, Bangladeshi, Pakistani, Indian and Chinese ethnic backgrounds, this paper identified five ‘types’ of science participation among minority ethnic students. The five types of science participation emerged from an analysis of students’ science achievement, science aspiration, science interest and science capital. The characteristics of the five types are as follows: Science adverse students have no aspirations towards science and lacked interest, achievement and capital in science. Science intrinsic students have high science aspirations, interest and capital but low science attainment. Students who are science intermediate have some aspirations, interest and capital in science, with average science grades. Science extrinsic students achieve highly in science, have some science capital but lacked science aspirations and/or interest. Science prominent students are high science achievers with science aspirations, high levels of interest and capital in science. The findings highlight that minority ethnic students participate in science in diverse ways. Policy implications are suggested for each type as this paper provides empirical evidence to counter against public (and even some academic) discourses of minority ethnic students as a homogeneous group

Specificity quantification of biomolecular recognition and its implication for drug discovery

Highly efficient and specific biomolecular recognition requires both affinity and specificity. Previous quantitative descriptions of biomolecular recognition were mostly driven by improving the affinity prediction, but lack of quantification of specificity. We developed a novel method SPA (SPecificity and Affinity) based on our funneled energy landscape theory. The strategy is to simultaneously optimize the quantified specificity of the “native” protein-ligand complex discriminating against “non-native” binding modes and the affinity prediction. The benchmark testing of SPA shows the best performance against 16 other popular scoring functions in industry and academia on both prediction of binding affinity and “native” binding pose. For the target COX-2 of nonsteroidal anti-inflammatory drugs, SPA successfully discriminates the drugs from the diversity set, and the selective drugs from non-selective drugs. The remarkable performance demonstrates that SPA has significant potential applications in identifying lead compounds for drug discovery

Differences in Cell Division Rates Drive the Evolution of Terminal Differentiation in Microbes

Multicellular differentiated organisms are composed of cells that begin by developing from a single pluripotent germ cell. In many organisms, a proportion of cells differentiate into specialized somatic cells. Whether these cells lose their pluripotency or are able to reverse their differentiated state has important consequences. Reversibly differentiated cells can potentially regenerate parts of an organism and allow reproduction through fragmentation. In many organisms, however, somatic differentiation is terminal, thereby restricting the developmental paths to reproduction. The reason why terminal differentiation is a common developmental strategy remains unexplored. To understand the conditions that affect the evolution of terminal versus reversible differentiation, we developed a computational model inspired by differentiating cyanobacteria. We simulated the evolution of a population of two cell types –nitrogen fixing or photosynthetic– that exchange resources. The traits that control differentiation rates between cell types are allowed to evolve in the model. Although the topology of cell interactions and differentiation costs play a role in the evolution of terminal and reversible differentiation, the most important factor is the difference in division rates between cell types. Faster dividing cells always evolve to become the germ line. Our results explain why most multicellular differentiated cyanobacteria have terminally differentiated cells, while some have reversibly differentiated cells. We further observed that symbioses involving two cooperating lineages can evolve under conditions where aggregate size, connectivity, and differentiation costs are high. This may explain why plants engage in symbiotic interactions with diazotrophic bacteria

Luminescence characteristics of quartz from Brazilian sediments and constraints for OSL dating

This study analyzes the optically stimulated luminescence (OSL) characteristics of quartz grains from fluvial, eolian and shallow marine sands of northeastern and southeastern Brazil, with especial focus on the applicability of the single-aliquot regenerative dose (SAR) dating protocol. All analyzed Brazilian sediments presented relatively high OSL sensitivity and good behavior regarding their luminescence characteristics relevant for radiation dose estimation. However, some samples from the Lençóis Maranhenses region in northeastern Brazil showed inadequate OSL sensitivity correction, hampering the implementation of the SAR protocol and their ability to behave as a natural dosimeter. While the shallow marine and eolian samples showed a narrow and reliable dose distribution, the fluvial sample had a wide dose distribution, suggesting incomplete bleaching and natural doses estimates dependent on age models

The Drosophila TRPP Cation Channel, PKD2 and Dmel/Ced-12 Act in Genetically Distinct Pathways during Apoptotic Cell Clearance

Apoptosis, a genetically programmed cell death, allows for homeostasis and tissue remodelling during development of all multi-cellular organisms. Phagocytes swiftly recognize, engulf and digest apoptotic cells. Yet, to date the molecular mechanisms underlying this phagocytic process are still poorly understood. To delineate the molecular mechanisms of apoptotic cell clearance in Drosophila, we have carried out a deficiency screen and have identified three overlapping phagocytosis-defective mutants, which all delete the fly homologue of the ced-12 gene, known as Dmel\ced12. As anticipated, we have found that Dmel\ced-12 is required for apoptotic cell clearance, as for its C. elegans and mammalian homologues, ced-12 and elmo, respectively. However, the loss of Dmel\ced-12 did not solely account for the phenotypes of all three deficiencies, as zygotic mutations and germ line clones of Dmel\ced-12 exhibited weaker phenotypes. Using a nearby genetically interacting deficiency, we have found that the polycystic kidney disease 2 gene, pkd2, which encodes a member of the TRPP channel family, is also required for phagocytosis of apoptotic cells, thereby demonstrating a novel role for PKD2 in this process. We have also observed genetic interactions between pkd2, simu, drpr, rya-r44F, and retinophilin (rtp), also known as undertaker (uta), a gene encoding a MORN-repeat containing molecule, which we have recently found to be implicated in calcium homeostasis during phagocytosis. However, we have not found any genetic interaction between Dmel\ced-12 and simu. Based on these genetic interactions and recent reports demonstrating a role for the mammalian pkd-2 gene product in ER calcium release during store-operated calcium entry, we propose that PKD2 functions in the DRPR/RTP pathway to regulate calcium homeostasis during this process. Similarly to its C. elegans homologue, Dmel\Ced-12 appears to function in a genetically distinct pathway

Pathogen-induced hatching and population-specific life-history response to water-borne cues in brown trout (Salmo trutta)

Hatching is an important niche shift, and embryos in a wide range of taxa can either accelerate or delay this life-history switch in order to avoid stage-specific risks. Such behavior can occur in response to stress itself and to chemical cues that allow anticipation of stress. We studied the genetic organization of this phenotypic plasticity and tested whether there are differences among populations and across environments in order to learn more about the evolutionary potential of stress-induced hatching. As a study species, we chose the brown trout (Salmo trutta; Salmonidae). Gametes were collected from five natural populations (within one river network) and used for full-factorial in vitro fertilizations. The resulting embryos were either directly infected with Pseudomonas fluorescens or were exposed to waterborne cues from P. fluorescens-infected conspecifics. We found that direct inoculation with P. fluorescens increased embryonic mortality and induced hatching in all host populations. Exposure to waterborne cues revealed population-specific responses. We found significant additive genetic variation for hatching time, and genetic variation in trait plasticity. In conclusion, hatching is induced in response to infection and can be affected by waterborne cues of infection, but populations and families differ in their reaction to the latter

K+ channel openers restore verapamil-inhibited lung fluid resolution and transepithelial ion transport

<p>Abstract</p> <p>Background</p> <p>Lung epithelial Na⁺channels (ENaC) are regulated by cell Ca²⁺signal, which may contribute to calcium antagonist-induced noncardiogenic lung edema. Although K⁺channel modulators regulate ENaC activity in normal lungs, the therapeutical relevance and the underlying mechanisms have not been completely explored. We hypothesized that K⁺channel openers may restore calcium channel blocker-inhibited alveolar fluid clearance (AFC) by up-regulating both apical and basolateral ion transport.</p> <p>Methods</p> <p>Verapamil-induced depression of heterologously expressed human αβγ ENaC in <it>Xenopus </it>oocytes, apical and basolateral ion transport in monolayers of human lung epithelial cells (H441), and <it>in vivo </it>alveolar fluid clearance were measured, respectively, using the two-electrode voltage clamp, Ussing chamber, and BSA protein assays. Ca²⁺signal in H441 cells was analyzed using Fluo 4AM.</p> <p>Results</p> <p>The rate of <it>in vivo </it>AFC was reduced significantly (40.6 ± 6.3% of control, <it>P </it>< 0.05, n = 12) in mice intratracheally administrated verapamil. K_Ca3.1(1-EBIO) and K_ATP(minoxidil) channel openers significantly recovered AFC. In addition to short-circuit current (Isc) in intact H441 monolayers, both apical and basolateral Isc levels were reduced by verapamil in permeabilized monolayers. Moreover, verapamil significantly altered Ca²⁺signal evoked by ionomycin in H441 cells. Depletion of cytosolic Ca²⁺in αβγ ENaC-expressing oocytes completely abolished verapamil-induced inhibition. Intriguingly, K_V(pyrithione-Na), K _Ca3.1(1-EBIO), and K_ATP(minoxidil) channel openers almost completely restored the verapamil-induced decrease in Isc levels by diversely up-regulating apical and basolateral Na⁺and K⁺transport pathways.</p> <p>Conclusions</p> <p>Our observations demonstrate that K⁺channel openers are capable of rescuing reduced vectorial Na⁺transport across lung epithelial cells with impaired Ca²⁺signal.</p

Plastic Traits of an Exotic Grass Contribute to Its Abundance but Are Not Always Favourable

In herbaceous ecosystems worldwide, biodiversity has been negatively impacted by changed grazing regimes and nutrient enrichment. Altered disturbance regimes are thought to favour invasive species that have a high phenotypic plasticity, although most studies measure plasticity under controlled conditions in the greenhouse and then assume plasticity is an advantage in the field. Here, we compare trait plasticity between three co-occurring, C4 perennial grass species, an invader Eragrostis curvula, and natives Eragrostis sororia and Aristida personata to grazing and fertilizer in a three-year field trial. We measured abundances and several leaf traits known to correlate with strategies used by plants to fix carbon and acquire resources, i.e. specific leaf area (SLA), leaf dry matter content (LDMC), leaf nutrient concentrations (N, C∶N, P), assimilation rates (Amax) and photosynthetic nitrogen use efficiency (PNUE). In the control treatment (grazed only), trait values for SLA, leaf C∶N ratios, Amax and PNUE differed significantly between the three grass species. When trait values were compared across treatments, E. curvula showed higher trait plasticity than the native grasses, and this correlated with an increase in abundance across all but the grazed/fertilized treatment. The native grasses showed little trait plasticity in response to the treatments. Aristida personata decreased significantly in the treatments where E. curvula increased, and E. sororia abundance increased possibly due to increased rainfall and not in response to treatments or invader abundance. Overall, we found that plasticity did not favour an increase in abundance of E. curvula under the grazed/fertilized treatment likely because leaf nutrient contents increased and subsequently its' palatability to consumers. E. curvula also displayed a higher resource use efficiency than the native grasses. These findings suggest resource conditions and disturbance regimes can be manipulated to disadvantage the success of even plastic exotic species