bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymer nanocomposite photovoltaics utilizing CdSe nanocrystals capped with a thermally cleavable solubilizing ligand
Authors: Seo Jangwon , Kim Won Jin , Kim Sung Jin , Lee Kwang-Sup , Cartwright A. N. , Prasad Paras N.
Published: April 2009

We demonstrate a relative improvement in power conversion efficiency of polymer nanocomposite photovoltaic cells consisting of poly(3-hexylthiophene) (P3HT) functionalized CdSe nanocrystals. Thermal deprotection processing of the tert-buthoxycarbonyl moiety in the carbamate ligand surrounding the surface of CdSe nanocrystal significantly shortened the length of the ligand between nanocrystals and between the nanocrystal and the polymer matrix. The resulting device performance was investigated as a function of the composition ratio of P3HT/CdSe and the heating temperature. This simple and straightforward ligand deprotection strategy resulted in a significant increase in current density due to improvement of charge transport between the constituent materials.
Elastic and adhesive properties of alkanethiol self-assembled monolayers on gold
Authors: DelRio Frank W. , Jaye Cherno , Fischer Daniel A. , Cook Robert F.
Published: April 2009

Elastic and adhesive properties of alkanethiol [CH3(CH2)n−1SH] self-assembled monolayers on gold are investigated by atomic force microscopy and correlated with surface structure via near edge x-ray absorption fine structure spectroscopy. As the chain length n decreases from 18 to 5, the elastic modulus of the monolayer film, Efilm, decreases from 1.0 to 0.15 GPa and the work of adhesion, w, increases from 82.8 to 168.3 mJ m−2. The Efilm and w trends are interpreted in terms of the dichroic ratios, RI, which reveal distinct changes in chain orientation, order, and coverage over the range of n.
Electrically pumped quantum post vertical cavity surface emitting lasers
Authors: Kim Hyochul , Rakher Matthew T. , Bouwmeester Dirk , Petroff Pierre M.
Published: April 2009

We demonstrate low threshold electrically pumped lasing in oxide apertured vertical cavity surface emitting lasers with quantum posts (QPs) as the active medium. A lasing threshold current as low as 12 μA is achieved at 7 K and room temperature continuous wave lasing is also demonstrated in the cavities with quality factors of ∼10 000. At low temperature, the QP devices show remarkably lower lasing current thresholds compared to equivalent quantum dot devices.
Photoluminescence dynamics in GaAs/AlAs quantum wells modulated by one-dimensional standing surface acoustic waves
Authors: Sogawa Tetsuomi , Sanada Haruki , Gotoh Hideki , Yamaguchi Hiroshi , Miyashita Sen , Santos Paulo V.
Published: April 2009

The effects of standing surface acoustic waves (SAWs) on carrier dynamics in GaAs/AlAs quantum wells are investigated by spatially and time-resolved photoluminescence (PL) spectroscopy. We found that the PL spectra vary considerably depending on the position and the phase of the standing SAW field. The PL spectra are characterized by oscillations in the PL intensity and emission energy due to the motion of free carriers and excitons driven by the piezoelectric fields as well as by the strain-induced band-gap gradient. It is also demonstrated that the positions of the nodes and antinodes of the standing SAW are precisely controlled.
Transient expression of theArftumor suppressor during male germ cell and eye development inArf-Crereporter mice
Authors: Gromley Adam , Churchman Michelle L. , Zindy Frederique , Sherr Charles J.
Published: April 2009

TheArftumor suppressor is expressed transiently during mouse male germ cell and eye development. Its inactivation compromises spermatogenesis as mice age and leads to aberrant postnatal proliferation of cells in the vitreous of the eye, resulting in blindness. In the testis, expression of p19Arfis limited to spermatogonia but is extinguished completely in spermatocytes, suggesting thatArfplays a physiologic role in setting the balance between mitotic and meiotic germ cell division. A knock-in allele encoding Cre recombinase regulated by the mouse cellularArfpromoter was used to traceArfgene induction in vivo. Interbreeding to a reporter strain that expresses Cre-dependent YFP provided proof-of-principle that theArf-Creallele was appropriately expressed in the male germ cell lineage. However, Cre expression resulted in male sterility, limiting germ line transmission of the knock-in allele to females.Arf-null mice fail to resorb the hyaloid vasculature within the ocular vitreous where pericyte-like cells that express the PDGF-β receptor (Pdgfrβ) proliferate aberrantly and destroy the retina and lens. Interbreeding ofArf-Crefemales to males containing “floxed” (FL)Arfalleles yieldedArfCre/FLprogeny that exhibited variably penetrant defects in visual acuity ranging to total blindness. Crossing theArfCre/FLalleles onto aPdgfrβFL/FLbackground normalized all histopathology and restored vision fully.
Mythological Themes in Iranian Culture and Art: Traditional and Contemporary Perspectives
Authors: Saadi-Nejad Manya
Published: April 2009

In Iran, ancient mythical elements are very much alive in the present as a part of the fabric of ordinary people's lives and worldview. This paper explores the relationship between culture, myth, and artistic production in contemporary Iran, using the specific examples of symbols and mythological themes evoked in the work of painter/writer Aydin Aghdashloo and photographer/video artist Shirin Neshat. The paintings of Aghdashloo, in which he deliberately damages beautifully-executed classical style Persian miniatures, convey a sense that the angelic forces have failed and that the world is succumbing to the destructive and degenerative activities of the demonic. The photographs, videos and installations of Neshat likewise draw heavily on cultic forms inherited from ancient Iranian tradition. It is important to note that in none of these cases does the artist use mythological themes and symbols to express their original cultural meaning; rather, they appropriate well-known elements of ancient Iranian culture and imbue them with new meanings relevant to contemporary issues and understandings. What these examples do illustrate is the persistent resonance of ancient Iranian culture among Iranians up to the present day. Iranian artists have demonstrated the effectiveness of evoking their target audience's deep sense of cultural identity to convey contemporary messages using ancient cultural concepts, sometimes on a subconscious level.
An examination of phylogenetic models of substitution rate variation among lineages
Authors: Ho Simon Y.W.
Published: April 2009

Molecular evolutionary rates can show significant variation among lineages, complicating the task of estimating substitution rates and divergence times using phylogenetic methods. Accordingly, relaxed molecular clock models have been developed to accommodate such rate heterogeneity, but these often make the assumption of rate autocorrelation among lineages. In this paper, I examine the validity of this assumption.
Design complexity in termite-fishing tools of chimpanzees (
Pan troglodytes
)
Authors: Sanz Crickette , Call Josep , Morgan David
Published: April 2009

Adopting the approach taken with New Caledonian crows (
Corvus moneduloides
), we present evidence of design complexity in one of the termite-fishing tools of chimpanzees (
Pan troglodytes
) in the Goualougo Triangle, Republic of Congo. Prior to termite fishing, chimpanzees applied a set of deliberate, distinguishable actions to modify herb stems to fashion a brush-tipped probe, which is different from the form of fishing tools used by chimpanzees in East and West Africa. This means that ‘brush-tipped fishing probes’, unlike ‘brush sticks’, are not a by-product of use but a deliberate design feature absent in other chimpanzee populations. The specialized modifications to prepare the tool for termite fishing, measures taken to repair non-functional brushes and appropriate orientation of the modified end suggest that these wild chimpanzees are attentive to tool modifications. We also conducted experimental trials that showed that a brush-tipped probe is more effective in gathering insects than an unmodified fishing probe. Based on these findings, we suggest that chimpanzees in the Congo Basin have developed an improved fishing probe design.
The α-proteobacteria: the Darwin finches of the bacterial world
Authors: Ettema Thijs J.G. , Andersson Siv G.E.
Published: April 2009

The α-proteobacteria represent one of the most diverse bacterial subdivisions, displaying extreme variations in lifestyle, geographical distribution and genome size. Species for which genome data are available have been classified into a species tree based on a conserved set of vertically inherited core genes. By mapping the variation in gene content onto the species tree, genomic changes can be associated with adaptations to specific growth niches. Genes for adaptive traits are mostly located in ‘plasticity zones’ in the bacterial genome, which also contain mobile elements and are highly variable across strains. By physically separating genes for information processing from genes involved in interactions with the surrounding environment, the rate of evolutionary change can be substantially enhanced for genes underlying adaptation to new growth habitats, possibly explaining the ecological success of the α-proteo-bacterial subdivision.
The genome sizes of megabats (Chiroptera: Pteropodidae) are remarkably constrained
Authors: Smith Jillian D.L. , Gregory T. Ryan
Published: April 2009

It has long been recognized that bats and birds contain less DNA in their genomes than their non-flying relatives. It has been suggested that this relates to the high metabolic demands of powered flight, a notion that is supported by the fact that pterosaurs also appear to have exhibited small genomes. Given the long-standing interest in this question, it is surprising that almost no data have been presented regarding genome size diversity among megabats (family Pteropodidae). The present study provides genome size estimates for 43 species of megabats in an effort to fill this gap and to test the hypothesis that all bats, and not just microbats, possess small genomes. Intriguingly, megabats appear to be even more constrained in terms of genome size than the members of other bat families.
Raising the sauropod neck: it costs more to get less
Authors: Seymour Roger S.
Published: April 2009

The long necks of gigantic sauropod dinosaurs are commonly assumed to have been used for high browsing to obtain enough food. However, this analysis questions whether such a posture was reasonable from the standpoint of energetics. The energy cost of circulating the blood can be estimated accurately from two physiological axioms that relate metabolic rate, blood flow rate and arterial blood pressure: (i) metabolic rate is proportional to blood flow rate and (ii) cardiac work rate is proportional to the product of blood flow rate and blood pressure. The analysis shows that it would have required the animal to expend approximately half of its energy intake just to circulate the blood, primarily because a vertical neck would have required a high systemic arterial blood pressure. It is therefore energetically more feasible to have used a more or less horizontal neck to enable wide browsing while keeping blood pressure low.
Foraging segregation between two closely related shearwaters breeding in sympatry
Authors: Navarro Joan , Forero Manuela G. , González-Solís Jacob , Igual José Manuel , Bécares Juan , Hobson Keith A.
Published: April 2009

Trophic segregation has been proposed as a major mechanism explaining the coexistence of closely related animal taxa. However, how such segregation varies throughout the annual cycle is poorly understood. Here, we examined the feeding ecology of the two subspecies of Cory's shearwater,
Calonectris diomedea diomedea
and
Calonectris diomedea borealis
, breeding in sympatry in a Mediterranean colony. To study trophic segregation at different stages, we combined the analysis of isotope values (
δ
15
N,
δ
13
C) in blood obtained during incubation and in feathers moulted during chick-rearing and wintering periods with satellite-tracking data during the chick-rearing period. Satellite-tracking and stable isotope data of the first primary feather revealed that
C. d. borealis
foraged mainly in the Atlantic whereas
C. d. diomedea
foraged exclusively in the Mediterranean. This spatial segregation could reflect the foraging behaviour of the
C. d. borealis
individuals before they arrived at the Mediterranean colony. Alternatively, greater wing loading of
C. d. borealis
individuals may confer the ability to fly across the strong winds occurring at the at the Gibraltar strait. Isotope values of the eighth secondary feather also support segregation in wintering areas between the two forms:
C. d. diomedea
wintered mainly in association with the Canary current, whereas
C. d. borealis
wintered in the South African coast. Overall, our results show that spatial segregation in foraging areas can display substantial variation throughout the annual cycle and is probably a major mechanism facilitating coexistence between closely related taxa.
Response of cricket and spider motion-sensing hairs to airflow pulsations
Authors: Kant R. , Humphrey J. A. C.
Published: April 2009

Closed-form analytical solutions are presented for the angular displacement, velocity and acceleration of motion-sensing filiform hairs exposed to airflow pulsations of short time duration. The specific situations of interest correspond to a spider intentionally moving towards a cricket, or an insect unintentionally moving towards or flying past a spider. The trichobothria of the spiderCupiennius saleiand the cercal hairs of the cricketGryllus bimaculatusare explored. Guided by earlier work, the spatial characteristics of the velocity field due to a flow pulsation are approximated by the local incompressible flow field due to a moving sphere. This spatial field is everywhere modulated in time by a Gaussian function represented by the summation of an infinite Fourier series, thus allowing an exploration of the spectral dependence of hair motion. Owing to their smaller total inertia, torsional restoring constant and total damping constant, short hairs are found to be significantly more responsive than long hairs to a flow pulsation. It is also found that the spider trichobothria are underdamped, while the cercal hairs of the cricket are overdamped. As a consequence, the spider hairs are more responsive to sudden air motions. Analysis shows that while two spiders of different characteristic sizes and lunge velocities can generate pulsations with comparable energy content, the associated velocity fields display different patterns of spatial decay with distance from the pulsation source. As a consequence, a small spider lunging at a high velocity generates a smaller telltale far-field velocity signal than a larger spider lunging at a lower velocity. The results obtained are in broad agreement with several of the observations and conclusions derived from combined flow and behavioural experiments performed by Casaset al. for running spiders, and by Dangleset al. for spiders and a physical model of spiders lunging at crickets.
Correction for Huber
et al.
, Hard prey, soft jaws and the ontogeny of feeding mechanics in the spotted ratfish
Hydrolagus colliei
Authors: Huber Daniel R. , Dean Mason N. , Summers Adam P.
Published: April 2009

Correction for ‘Hard prey, soft jaws and the ontogeny of feeding mechanics in the spotted ratfish
Hydrolagus colliei
’ by Daniel R. Huber, Mason N. Dean and Adam P. Summers (J. R. Soc. Interface
5
, 941–952.
(doi:
10.1098/rsif.2007.1325
)).

On page 948, figure 7(
b
) was printed incorrectly. The correct version of figure 7 is printed below.
Analysis of dynamic morphogen scale invariance
Authors: Umulis David M.
Published: April 2009

During the development of some tissues, fields of multipotent cells differentiate into distinct cell types in response to the local concentration of a signalling factor called a morphogen. Typically, individual organisms within a population differ in size, but their body plans appear to be scaled versions of a common template. Similarly, closely related species may differ by three or more orders of magnitude in size, yet common structures between species scale to have similar proportions. In standard reaction–diffusion equations, the morphogen range has a length scale that depends on a balance between kinetic and transport processes and not on the length or size of the field of cells being patterned. However, as shown here for a class of morphogen-patterning systems, a number of conditions lead to scale invariance of the morphogen distribution at equilibrium and during the transient approach to equilibrium. Equilibrium scale invariance requires conservation of the total binding site number and total input flux. Dynamic scale invariance additionally requires sufficient binding to slow the diffusion of ligand. The equations derived herein can be extended to the study of other perturbations to gain further insight into the processes regulating the robustness and scaling of morphogen-mediated pattern formation.
Deformation of metallic liquid drop by electric field for contacts in molecular–organic electronics
Authors: Bag M. , Gupta D. , Arun N. , Narayan K.S.
Published: April 2009

We study and use the behaviour of a metallic liquid drop in the presence of an external electric field (EF). The droplet profile is governed by the stabilizing surface energy and the destabilizing electrostatic energy, with a critical voltage beyond which the droplet becomes unstable. We explore the EF-induced behaviour of low melting temperature alloy in the liquid state and observe that the droplet modifications in the linear response regime can be retained upon cooling the drop to the solid state. We demonstrate that this procedure can be used as an electrode with precise dimensions for applications in molecular and polymer electronics.
Correction for Chandrasekar
et al.
, On the complete integrability and linearization of certain second-order nonlinear ordinary differential equations
Authors: Chandrasekar V. K. , Senthilvelan M. , Lakshmanan M.
Published: April 2009

Correction for ‘On the complete integrability and linearization of certain second-order nonlinear ordinary differential equations’ by V. K. Chandrasekar, M. Senthilvelan and M. Lakshmanan (Proc. R. Soc. A
461
, 2451–2476.
(doi:
10.1098/rspa.2005.1465
)).

The sentence preceeding equation (4.48) is incorrect and should read as follows.
A radial basis function method for the shallow water equations on a sphere
Authors: Flyer Natasha , Wright Grady B.
Published: April 2009

The paper derives the first known numerical shallow water model on the sphere using radial basis function (RBF) spatial discretization, a novel numerical methodology that does not require any grid or mesh. In order to perform a study with regard to its spatial and temporal errors, two nonlinear test cases with known analytical solutions are considered. The first is a global steady-state flow with a compactly supported velocity field, while the second is an unsteady flow where features in the flow must be kept intact without dispersion. This behaviour is achieved by introducing forcing terms in the shallow water equations. Error and time stability studies are performed, both as the number of nodes are uniformly increased and the shape parameter of the RBF is varied, especially in the flat basis function limit. Results show that the RBF method is spectral, giving exceptionally high accuracy for low number of basis functions while being able to take unusually large time steps. In order to put it in the context of other commonly used global spectral methods on a sphere, comparisons are given with respect to spherical harmonics, double Fourier series and spectral element methods.
Chloroplast two-component systems: evolution of the link between photosynthesis and gene expression
Authors: Puthiyaveetil Sujith , Allen John F.
Published: April 2009

Two-component signal transduction, consisting of sensor kinases and response regulators, is the predominant signalling mechanism in bacteria. This signalling system originated in prokaryotes and has spread throughout the eukaryotic domain of life through endosymbiotic, lateral gene transfer from the bacterial ancestors and early evolutionary precursors of eukaryotic, cytoplasmic, bioenergetic organelles—chloroplasts and mitochondria. Until recently, it was thought that two-component systems inherited from an ancestral cyanobacterial symbiont are no longer present in chloroplasts. Recent research now shows that two-component systems have survived in chloroplasts as products of both chloroplast and nuclear genes. Comparative genomic analysis of photosynthetic eukaryotes shows a lineage-specific distribution of chloroplast two-component systems. The components and the systems they comprise have homologues in extant cyanobacterial lineages, indicating their ancient cyanobacterial origin. Sequence and functional characteristics of chloroplast two-component systems point to their fundamental role in linking photosynthesis with gene expression. We propose that two-component systems provide a coupling between photosynthesis and gene expression that serves to retain genes in chloroplasts, thus providing the basis of cytoplasmic, non-Mendelian inheritance of plastid-associated characters. We discuss the role of this coupling in the chronobiology of cells and in the dialogue between nuclear and cytoplasmic genetic systems.
Brain organization and the origin of insects: an assessment
Authors: Strausfeld Nicholas James
Published: April 2009

Within the Arthropoda, morphologies of neurons, the organization of neurons within neuropils and the occurrence of neuropils can be highly conserved and provide robust characters for phylogenetic analyses. The present paper reviews some features of insect and crustacean brains that speak against an entomostracan origin of the insects, contrary to received opinion. Neural organization in brain centres, comprising olfactory pathways, optic lobes and a central neuropil that is thought to play a cardinal role in multi-joint movement, support affinities between insects and malacostracan crustaceans.
Predator crypsis enhances behaviourally mediated indirect effects on plants by altering bumblebee foraging preferences
Authors: Ings Thomas C. , Chittka Lars
Published: April 2009

Predators of pollinators can influence pollination services and plant fitness via both consumptive (reducing pollinator density) and non-consumptive (altering pollinator behaviour) effects. However, a better knowledge of the mechanisms underlying behaviourally mediated indirect effects of predators is necessary to properly understand their role in community dynamics. We used the tripartite relationship between bumblebees, predatory crab spiders and flowers to ask whether behaviourally mediated effects are localized to flowers harbouring predators, or whether bees extend their avoidance to entire plant species. In a tightly controlled laboratory environment, bumblebees (Bombus terrestris) were exposed to a random mixture of equally rewarding yellow and white artificial flowers, but foraging on yellow flowers was very risky: bees had a 25 per cent chance of receiving a simulated predation attempt by ‘robotic’ crab spiders. As bees learnt to avoid ‘dangerous’ flowers, their foraging preferences changed and they began to visit fewer yellow flowers than expected by chance. Bees avoided spider-free yellow flowers as well as dangerous yellow flowers when spiders were more difficult to detect (the colour of yellow spiders was indistinguishable from that of yellow flowers). Therefore, this interaction between bee learning and predator crypsis could lead flower species harbouring cryptic predators to suffer from reduced reproductive success.
Proximity is not a proxy for parentage in an animal-dispersed Neotropical canopy palm
Authors: Sezen Uzay U. , Chazdon Robin L. , Holsinger Kent E.
Published: April 2009

We used parentage analysis to estimate seedling recruitment distances and genetic composition of seedling patches centred around reproductive trees of the animal-dispersed Neotropical canopy palm
Iriartea deltoidea
in two 0.5 ha plots within second-growth forest and one 0.5 ha plot in adjacent old-growth forest at La Selva Biological Field Station in north-eastern Costa Rica. Seedlings were significantly spatially aggregated in all plots, but this pattern was not due to dispersal limitation. More than 70 per cent of seedlings were dispersed at least 50 m from parent trees. Few seedlings were offspring of the closest reproductive trees. Seedling patches observed beneath reproductive trees originate from dozens of parental trees. Observed patterns of seedling distribution and spatial genetic structure are largely determined by the behaviour of vertebrate seed dispersers rather than by spatial proximity to parental trees.
How chimpanzees look at pictures: a comparative eye-tracking study
Authors: Kano Fumihiro , Tomonaga Masaki
Published: April 2009

Surprisingly little is known about the eye movements of chimpanzees, despite the potential contribution of such knowledge to comparative cognition studies. Here, we present the first examination of eye tracking in chimpanzees. We recorded the eye movements of chimpanzees as they viewed naturalistic pictures containing a full-body image of a chimpanzee, a human or another mammal; results were compared with those from humans. We found a striking similarity in viewing patterns between the two species. Both chimpanzees and humans looked at the animal figures for longer than at the background and at the face region for longer than at other parts of the body. The face region was detected at first sight by both species when they were shown pictures of chimpanzees and of humans. However, the eye movements of chimpanzees also exhibited distinct differences from those of humans; the former shifted the fixation location more quickly and more broadly than the latter. In addition, the average duration of fixation on the face region was shorter in chimpanzees than in humans. Overall, our results clearly demonstrate the eye-movement strategies common to the two primate species and also suggest several notable differences manifested during the observation of pictures of scenes and body forms.
Ants recognize foes and not friends
Authors: Guerrieri Fernando J. , Nehring Volker , Jørgensen Charlotte G. , Nielsen John , Galizia C. Giovanni , d'Ettorre Patrizia
Published: April 2009

Discriminating among individuals and rejecting non-group members is essential for the evolution and stability of animal societies. Ants are good models for studying recognition mechanisms, because they are typically very efficient in discriminating ‘friends’ (nest-mates) from ‘foes’ (non-nest-mates). Recognition in ants involves multicomponent cues encoded in cuticular hydrocarbon profiles. Here, we tested whether workers of the carpenter ant
Camponotus herculeanus
use the presence and/or absence of cuticular hydrocarbons to discriminate between nest-mates and non-nest-mates. We supplemented the cuticular profile with synthetic hydrocarbons mixed to liquid food and then assessed behavioural responses using two different bioassays. Our results show that (i) the presence, but not the absence, of an additional hydrocarbon elicited aggression and that (ii) among the three classes of hydrocarbons tested (unbranched, mono-methylated and dimethylated alkanes; for mono-methylated alkanes, we present a new synthetic pathway), only the dimethylated alkane was effective in eliciting aggression. Our results suggest that carpenter ants use a fundamentally different mechanism for nest-mate recognition than previously thought. They do not specifically recognize nest-mates, but rather recognize and reject non-nest-mates bearing odour cues that are novel to their own colony cuticular hydrocarbon profile. This begs for a reappraisal of the mechanisms underlying recognition systems in social insects.
Location, location, location: larvae position inside the nest is correlated with adult body size in worker bumble-bees (Bombus impatiens)
Authors: Couvillon Margaret J. , Dornhaus Anna
Published: April 2009

Social insects display task-related division of labour. In some species, division of labour is related to differences in body size, and worker caste members display morphological adaptations suited for particular tasks. Bumble-bee workers (Bombusspp.) can vary in mass by eight- to tenfold within a single colony, which previous work has linked to division of labour. However, little is known about the proximate mechanism behind the production of this wide range of size variation within the worker caste. Here, we quantify the larval feeding inBombus impatiensin different nest zones of increasing distance from the centre. There was a significant difference in the number of feedings per larva across zones, with a significant decrease in feeding rates as one moved outwards from the centre of the nest. Likewise, the diameter of the pupae in the peripheral zones was significantly smaller than that of pupae in the centre. Therefore, we conclude that the differential feeding of larvae within a nest, which leads to the size variation within the worker caste, is based on the location of brood clumps. Our work is consistent with the hypothesis that some larvae are ‘forgotten’, providing a possible first mechanism for the creation of size polymorphism inB. impatiens.
Accommodating natural and sexual selection in butterfly wing pattern evolution
Authors: Oliver Jeffrey C. , Robertson Kendra A. , Monteiro Antónia
Published: April 2009

Visual patterns in animals may serve different functions, such as attracting mates and deceiving predators. If a signal is used for multiple functions, the opportunity arises for conflict among the different functions, preventing optimization for any one visual signal. Here we investigate the hypothesis that spatial separation of different visual signal functions has occurred in
Bicyclus
butterflies. Using phylogenetic reconstructions of character evolution and comparisons of evolutionary rates, we found dorsal surface characters to evolve at higher rates than ventral characters. Dorsal characters also displayed sex-based differences in evolutionary rates more often than did ventral characters. Thus, dorsal characters corresponded to our predictions of mate signalling while ventral characters appear to play an important role in predator avoidance. Forewing characters also fit a model of mate signalling, and displayed higher rates of evolution than hindwing characters. Our results, as well as the behavioural and developmental data from previous studies of
Bicyclus
species, support the hypothesis that spatial separation of visual signal functions has occurred in
Bicyclus
butterflies. This study is the first to demonstrate, in a phylogenetic framework, that spatial separation of signals used for mate signalling and those used for predator avoidance is a viable strategy to accommodate multiple signal functions. This signalling strategy has important ramifications on the developmental evolution of wing pattern elements and diversification of butterfly species.
The higher the better: sentinel height influences foraging success in a social bird
Authors: Radford Andrew N. , Hollén Linda I. , Bell Matthew B.V.
Published: April 2009

In all social species, information relevant to survival and reproduction can be obtained in two main ways: through personal interaction with the environment (i.e. ‘personal’ information) and from the performance of others (i.e. ‘public’ information). While public information is less costly to obtain than personal information, it may be inappropriate or inaccurate. When deciding how much to rely on public information, individuals should therefore assess its potential quality, but this possibility requires empirical testing in animals. Here, we use the sentinel system of cooperatively breeding pied babblers (
Turdoides bicolor
) to investigate how behavioural decisions of foragers are influenced by potential variation in the quality of anti-predator information from a vigilant groupmate. When sentinels moved to a higher position, from where their probability of detecting predators is likely to be greater, foragers reduced their vigilance, spread out more widely and were more likely to venture into the open. Consequently, they spent more time foraging and increased their foraging efficiency, resulting in a profound increase in biomass intake rate. The opposite behavioural changes, and consequent foraging outcomes, were found when sentinels moved lower. A playback experiment demonstrated that foragers can use vocal cues alone to assess sentinel height. This is the first study to link explicitly a measure of the potential quality of public information with a fitness measure from those relying on the information, and our results emphasize that a full understanding of the evolution of communication in complex societies requires consideration of the reliability of information.
Arabidopsis Protein Kinases GRIK1 and GRIK2 Specifically Activate SnRK1 by Phosphorylating Its Activation Loop
Authors: Shen Wei , Reyes Maria Ines , Hanley-Bowdoin Linda
Published: April 2009

SNF1-related kinases (SnRK1s) play central roles in coordinating energy balance and nutrient metabolism in plants. SNF1 and AMPK, the SnRK1 homologs in budding yeast (Saccharomyces cerevisiae) and mammals, are activated by phosphorylation of conserved threonine residues in their activation loops. Arabidopsis (Arabidopsis thaliana) GRIK1 and GRIK2, which were first characterized as geminivirus Rep interacting kinases, are phylogenetically related to SNF1 and AMPK activating kinases. In this study, we used recombinant proteins produced in bacteria to show that both GRIKs specifically bind to the SnRK1 catalytic subunit and phosphorylate the equivalent threonine residue in its activation loop in vitro. GRIK-mediated phosphorylation increased SnRK1 kinase activity in autophosphorylation and peptide substrate assays. These data, together with earlier observations that GRIKs could complement yeast mutants lacking SNF1 activation activities, established that the GRIKs are SnRK1 activating kinases. Given that the GRIK proteins only accumulate in young tissues and geminivirus-infected mature leaves, the GRIK-SnRK1 cascade may function in a developmentally regulated fashion and coordinate the unique metabolic requirements of rapidly growing cells and geminivirus-infected cells that have been induced to reenter the cell cycle.
Broken gears in the avian molecular clock: new phylogenetic analyses support stem galliform status forGallinuloides wyomingensisand rallid affinities forAmitabha urbsinterdictensis
Authors: Ksepka Daniel T.
Published: April 2009

Galliformes (landfowl) have been the focus of numerous divergence dating studies that seek a refined understanding of the early radiation of living birds. The Eocene fossil birdsAmitabha urbsinterdictensis(Bridger Formation) andGallinuloides wyomingensis(Green River Formation) have been used extensively in studies dealing with the timing of evolution in crown Galliformes. Divergence estimates from studies incorporating these fossils as calibration points suggest that multiple galliform lineages radiated in the Cretaceous and survived the Cretaceous–Tertiary mass extinction. However, the phylogenetic position of both fossils has been disputed, particularly with regard to crown or stem status. In order to resolve this debate, a new study ofA. urbsinterdictensisandG. wyomingensiswas undertaken. Further preparation and re‐examination of theA. urbsinterdictensisholotype indicates this fossil falls outside both crown and stem Galliformes, and reveals evidence for a relationship with Rallidae (rails). In order to reassess the status ofG. wyomingensis, a matrix of 120 morphological characters was constructed by revising and expanding on previous studies. Phylogenetic analyses using this matrix placeG. wyomingensisbasal to all crown Galliformes. Stem placement ofG. wyomingensisis retained and resolution is improved in combined analyses incorporating sequence data from cytochromeb, NADH dehydrogenase subunit 2, mitochondrial control region, 12S rDNA, and nuclear ovomucoid intron G. All evidence indicates thatA. urbsinterdictensisandG. wyomingensisare inappropriate internal calibration points for Galliformes and may have contributed to overestimation of divergence event ages. Though stem galliforms existed in the Cretaceous, the divergence of crown lineages in the Cretaceous remains inconclusively demonstrated. Because few galliform fossils have been evaluated phylogenetically, further investigations into the tempo of galliform evolution must await identification of proper fossil calibration points.

 © The Willi Hennig Society 2009.
Correlated morphological and colour differences among females of the damselflyIschnura elegans
Authors: ABBOTT JESSICA K. , GOSDEN THOMAS P.
Published: April 2009

Abstract1. The female‐limited colour polymorphic damselflyIschnura eleganshas proven to be an interesting study organism both as an example of female sexual polymorphism, and in the context of the evolution of colour polymorphism, as a model of speciation processes.

2. Previous research suggests the existence of correlations between colour morph and other phenotypic traits, and the different female morphs inI. elegansmay be pursuing alternative phenotypically integrated strategies. However, previous research on morphological differences in southern Swedish individuals of this species was only carried out on laboratory‐raised offspring from a single population, leaving open the question of how widespread such differences are.

3. The present study therefore analysed multi‐generational data from 12 populations, investigating morphological differences between the female morphs in the field, differences in the pattern of phenotypic integration between morphs, and quantified selection on morphological traits.

4. It was found that consistent morphological differences indeed existed between the morphs across populations, confirming that the previously observed differences were not simply a laboratory artefact. It was also found, somewhat surprisingly, that despite the existence of sexual dimorphism in body size and shape, patterns of phenotypic integration differed most between the morphs and not between the sexes. Finally, linear selection gradients showed that female morphology affected fecundity differently between the morphs.

5. We discuss the relevance of these results to the male mimicry hypothesis and to the existence of potential ecological differences between the morphs.
Rainfall in arid zones: possible effects of climate change on the population ecology of blue cranes
Authors: Altwegg Res , Anderson Mark D.
Published: April 2009

1. Understanding the demographic mechanisms through which climate affects population dynamics is critical for predicting climate change impacts on biodiversity. In arid habitats, rainfall is the most important forcing climatic factor. Rainfall in arid zones is typically variable and unpredictable, and we therefore hypothesise that its seasonality and variability may be as important for the population ecology of arid zone animals as its total amount.

2. Here we examine the effect of these aspects of rainfall on reproduction and age specific survival of blue cranes (Anthropoides paradiseus Lichtenstein) in the semi‐arid eastern Nama Karoo, South Africa. We then use our results to predict the effect of changes in rainfall at the population level.

3. Using combined capture‐mark‐resighting and dead‐recovery models, we estimated average survival of cranes to be 0·53 in their first year, 0·73 in their second and third year, and 0·96 for older birds.

4. We distinguished between three seasons, based on the blue cranes’ breeding phenology: early breeding season, late breeding season and nonbreeding season. Cranes survived better with increasing rainfall during the late but not early breeding season. Based on road counts and success of monitored nests, reproduction was positively associated with rainfall during the early but not late breeding season.

5. A matrix population model predicted that population growth rate would increase with increasing rainfall. A stochastic analysis showed that variation in early breeding season rainfall increased population growth slightly due to the nonlinear relationship between rainfall and reproduction. This effect was opposed by the effect of variation in late breeding season rainfall on survival and overall, variation in rainfall had a negligible effect on population growth.

6. Our results allow predictions to be made for a range of climate‐change scenarios. For example, a shift in seasonality with drier springs but wetter summers would likely decrease reproduction but increase survival, with little overall effect on population growth.
Causal diagrams for encoding and evaluation of information bias
Authors: Shahar Eyal
Published: April 2009

Background  Epidemiologists and clinical researchers usually classify bias into three main categories: confounding, selection bias and information bias. Previous authors have described the first two categories in the logic and notation of causal diagrams, formally known as directed acyclic graphs (DAG).

Methods  I examine common types of information bias – disease‐related and exposure‐related – from the perspective of causal diagrams.

Results  Disease or exposure information bias always involves the use of an effect of the variable of interest – specifically, an effect of true disease status or an effect of true exposure status. The bias typically arises from a causal or an associational path of no interest to the researchers. In certain situations, it may be possible to prevent or remove some of the bias.

Conclusions  Common types of information bias, just like confounding and selection bias, have a clear and helpful representation within the framework of causal diagrams.
Satisfaction of osteoarthritis patients with provided care is not related to the disease‐specific quality of life
Authors: Rosemann Thomas , Wensing Michel , Szecsenyi Joachim , Grol Richard
Published: April 2009

Background  Osteoarthritis (OA) has a high prevalence in primary care. Patient satisfaction is an important indicator for the quality of care provided to OA patients. Little is known about satisfaction of patients with this condition in a primary care setting in Germany. The aim of the study was to assess current satisfaction of patients and reveal possible disease and quality of life related predictors.

Methods/Design  Seventy‐five German GPs approached 1250 patients with OA consecutively. Sociodemographics, OA‐specific quality of life (GERMAN‐AIMS2‐SF), co‐morbidities and depression (using PHQ‐9) were assessed. Patient satisfaction was measured by means of the European Task Force on Patient Evaluations of General Practice (EUROPEP) instrument. A stepwise linear regression analysis with the EUROPEP score as dependent variable controlled for the amount of GP visits was performed to assess predictors of satisfaction.

Results  A total of 1021 OA patients returned the questionnaire. The adjusted R2 of the final model was 0.270 (P < 0.001). The main predictors were the PHQ‐9 score (beta = −0.372; P < 0.001), age (beta = −0.185; P < 0.001), living alone (beta = −0.209; P < 0.001) and number of co‐morbidities (beta = −0.152; P < 0.001). The only disease‐related factor which remained as predictor of patient satisfaction was duration of OA (beta = −0.105; P = 0.008).

Discussion  The finding that depression and social factors are more important for patient satisfaction with provided care than disease‐related aspects suggests that these factors need to be considered carefully in treatment. This represents a big challenge within an increasingly specialized health care system. The General Practitioner as the regular and first‐choice provider of health care seems to be the most appropriate instance who can accomplish this.
Morphological characterization of the tunic in the edible ascidian, Halocynthia roretzi (Drasche), with remarks on ‘soft tunic syndrome’ in aquaculture
Authors: Hirose E , Ohtake S‐I , Azumi K
Published: April 2009

‘Soft tunic syndrome’ is a serious problem in the aquaculture of the edible ascidian, Halocynthia roretzi (Drasche), and often leads to mass mortality. Here, we describe the tunic morphology of intact and diseased ascidians to reveal structural differences between them. Morphologically, diseased tunics are not very different from intact tunics, although the former are thinner and softer than the latter. While several types of cells are distributed in the tunic, the cell types and their cytomorphologies were almost identical in both groups. As bacterial/protozoan cells were not found in either intact or diseased tunics, they are not the direct cause of soft tunic syndrome. The most remarkable difference was in the bundles of tunic fibres that compose the tunic matrix; in intact tunics, the thick bundles interlace to form a firm matrix, whereas in soft tunics, the tunic fibres do not form thick bundles. Furthermore, areas of low fibre density were found in diseased tunics. Therefore, soft tunic syndrome probably causes inhibition of bundle formation and degradation of tunic bundles, creating areas of low fibre density, although the causes remain unknown.
Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapour pressure deficit as soil dries in a drained loblolly pine plantation
Authors: DOMEC JEAN‐CHRISTOPHE , NOORMETS ASKO , KING JOHN S. , SUN GE , MCNULTY STEVEN G. , GAVAZZI MICHAEL J. , BOGGS JOHNNY L. , TREASURE EMRYS A.
Published: April 2009

The study examined the relationships between whole tree hydraulic conductance (Ktree) and the conductance in roots (Kroot) and leaves (Kleaf) in loblolly pine trees. In addition, the role of seasonal variations inKrootandKleafin mediating stomatal control of transpiration and its response to vapour pressure deficit (D) as soil‐dried was studied. Compared to trunk and branches, roots and leaves had the highest loss of conductivity and contributed to more than 75% of the total tree hydraulic resistance. Drought altered the partitioning of the resistance between roots and leaves. As soil moisture dropped below 50%, relative extractable water (REW),Krootdeclined faster thanKleaf. AlthoughKtreedepended on soil moisture, its dynamics was tempered by the elongation of current‐year needles that significantly increasedKleafwhen REW was below 50%. After accounting for the effect ofDongs, the seasonal decline inKtreecaused a 35% decrease ingsand in its sensitivity toD, responses that were mainly driven byKleafunder high REW and byKrootunder low REW. We conclude that not only water stress but also leaf phenology affects the coordination betweenKtreeandgsand the acclimation of trees to changing environmental conditions.