bluuebunny/crossref_metadata_2025 huggingface dataset:
The phase behavior, structure, and dynamics of rodlike mesogens with various flexibility using dissipative particle dynamics simulation
Authors: Zhang Zunmin , Guo Hongxia
Published: October 2010

We present a systematic dissipative particle dynamics (DPD) study on the phase behavior, structure, and dynamics of rodlike mesogens. In addition to a rigid fused-bead-chain model with RATTLE constraint method, we also construct a semirigid model in which the flexibility is controlled by the bending constant of kϕ. Using this notation, the rigid model has an infinite bending constant of kϕ=∞. Within the parameter space studied, both two kinds of models exhibit the nematic and smectic-A phases in addition to the isotropic and solid phases. All of the phase transitions are accompanied by the discontinuities in the thermodynamical, structural, and dynamical quantities and the hysteresis around the transition points, and are therefore first order. Note that the obtained solid state exhibits an in-layer tetragonal packing due to the high density. For the rigid model, the simulations show that the liquid crystal phases can be observed for mesogens with at least five beads and the nematic phase is the first one to appear. More importantly, the phase diagram of seven-bead-chain models is obtained as a function of kϕ and temperature. It is found that decreasing the value of kϕ reduces the anisotropy of molecular shape and the orientational ordering, and thereby shifts the liquid crystal phases to the lower temperature end of the phase diagram. Due to the different kϕ dependence of phase transition temperatures, the nematic phase range exhibits a more marked narrowing than the smectic-A phase as kϕ is reduced, implying that the flexibility has a destabilizing effect on the nematic and smectic-A phases. We also have investigated the anisotropic translational diffusion in liquid crystal phases and its temperature and flexibility dependence. In our study, we find that the phases formed, their statical and dynamic properties, as well as the transition properties are in close accord with those observations in real thermotropic liquid crystals. It is clear that both the rigid and semirigid models we used are valuable models with which to study the behavior of thermotropic liquid crystals using DPD algorithm.
Dual-mode sensing platform based on colloidal gold functionalized porous silicon
Authors: Jiao Yang , Koktysh Dmitry S. , Phambu Nsoki , Weiss Sharon M.
Published: October 2010

We report a dual-mode sensing platform based on a single layer porous silicon (PSi) film impregnated with colloidal gold nanoparticles. This gold-coated PSi film supports both quantification of molecular binding via reflectance measurements and molecular identification via surface enhanced Raman scattering (SERS). A detection sensitivity of approximately 400 nm/RIU was demonstrated through binding of benzenethiol molecules. Identification of the unique SERS peaks was possible with uniform signal intensity across the sample and a detection limit below 1 μM.
Quantum path integral simulation of isotope effects in the melting temperature of ice Ih
Authors: Ramírez R. , Herrero C. P.
Published: October 2010

The isotope effect in the melting temperature of ice Ih has been studied by free energy calculations within the path integral formulation of statistical mechanics. Free energy differences between isotopes are related to the dependence of their kinetic energy on the isotope mass. The water simulations were performed by using the q-TIP4P/F model, a point charge empirical potential that includes molecular flexibility and anharmonicity in the OH stretch of the water molecule. The reported melting temperature at ambient pressure of this model (T=251 K) increases by 6.5±0.5 and 8.2±0.5 K upon isotopic substitution of hydrogen by deuterium and tritium, respectively. These temperature shifts are larger than the experimental ones (3.8 and 4.5 K, respectively). In the classical limit, the melting temperature is nearly the same as that for tritiated ice. This unexpected behavior is rationalized by the coupling between intermolecular interactions and molecular flexibility. This coupling makes the kinetic energy of the OH stretching modes larger in the liquid than in the solid phase. However, the opposite behavior is found for intramolecular modes, which display larger kinetic energy in ice than in liquid water.
Entropic forces and directed alignment of hard squares in suspensions of rods and disks
Authors: Triplett Derek A. , Fichthorn Kristen A.
Published: October 2010

We use Monte Carlo simulations in two dimensions to study the depletion forces between two hard squares in a suspension of hard rods or disks. We determine the effects of size and concentration of rods and disks on the potential of mean force between the squares. Both rods and disks produce a short-range depletion attraction between the two squares. The depletion interaction can be strong enough to outweigh the (rotational) entropic repulsion between the squares at certain sizes and concentrations of the rods and disks. We also probe the relative orientation that two squares adopt as they approach each other and we observe rich behavior, in which the relative orientation depends on the size, concentration, and shape of the depletion agent. Simple models based on the ideas of Asakura and Oosawa [J. Chem. Phys. 22, 1255 (1954)] can explain trends in the potentials of mean force obtained from the simulations.
Pulling the Finger off Disrupts Agency, Embodiment and Peripersonal Space
Authors: Newport Roger , Preston Catherine
Published: October 2010

For this experiment a visual illusion was created in which the participant's finger looked and felt as though it was being stretched to twice its normal length until it snapped and the tip came off. It was then stabbed with virtual weapons while skin conductance was measured. Sometimes the fingertip moved under the participant's own control and sometimes it moved independently. Curiously, detaching the tip of the finger destroyed the underlying ownership for the remaining stump as well as for the tip itself, even when the tip was under participants' control. These results have implications for theories of agency, embodiment, and tool-use.
Regard and Perceptions of Size in Soccer: Better is Bigger
Authors: Masters Rich , Poolton Jamie , van der Kamp John
Published: October 2010

Celebrated people often seem larger than life. In a series of experiments, and with observational data, we asked whether an association exists between regard for the action capabilities of soccer players and perceptual estimations of their size. Higher regard resulted in overestimations of size, and momentary modifications of apparent action capability resulted in overestimations or underestimations of size directly related to performance success or failure, respectively.
The Exploitation of Gestalt Principles by Magicians
Authors: Barnhart Anthony S
Published: October 2010

Magicians exploit a host of psychological principles in deceiving their audiences. Psychologists have recently attempted to pinpoint the most common psychological tendencies exploited by magicians. This paper highlights two co-occurring principles that appear to be the basis for many popular magic tricks: accidental alignment and good continuation.
The Globular Cluster System of NGC 5128: Ages, Metallicities, Kinematics and Structural Parameters
Authors: Woodley K. A. , Gómez M.
Published: October 2010

We review our recent studies of the globular cluster system of NGC 5128. First, we have obtained low-resolution, high signal-to-noise spectroscopy of 72 globular clusters using Gemini-S/GMOS to obtain the ages, metallicities, and the level of alpha enrichment of the metal-poor and metal-rich globular cluster subpopulations. Second, we have explored the rotational signature and velocity dispersion of the galaxy's halo using over 560 globular clusters with radial velocity measurements. We have also compared the dependence of these properties on galactocentric distance and globular cluster age and metallicity. Using globular clusters as tracer objects, we have analyzed the mass, and mass-to-light ratio of NGC 5128. Last, we have measured the structural parameters, such as half-light radii, of over 570 globular clusters from a superb 1.2-square-degree Magellan/IMACS image. We will present the findings of these studies and discuss the connection to the formation and evolution of NGC 5128.
NGC 5128: The Giant Beneath
Authors: Harris Gretchen L. H.
Published: October 2010

This paper reviews what has been learned about the old stellar population of NGC 5128, the only large elliptical galaxy close enough that we can currently observe individual stars as faint as the horizontal branch. Although its galaxy type is still a matter of debate, the uncertainties over distance are now largely resolved; comparison of five stellar distance indicators gives d= 3.8±0.1 Mpc. The globular cluster system, which was once perplexingly invisible, is now known to be predominantly old with a substantial metal-rich component. The globular cluster system (GCS) total population and luminosity function are normal and the clusters follow the same fundamental plane relation as those in the Milky Way and M31. Finally, the halo out to at least ∼7reff is dominated by metal-rich stars which are also predominantly old, with age and metallicity tantalizingly similar to the majority of globular clusters.
Early Australian Optical and Radio Observations of Centaurus A
Authors: Robertson Peter , Cozens Glen , Orchiston Wayne , Slee Bruce , Wendt Harry
Published: October 2010

The discovery of the radio source Centaurus A and its optical counterpart NGC 5128 were important landmarks in the history of Australian astronomy. NGC 5128 was first observed in August 1826 by James Dunlop during a survey of southern objects at the Parramatta Observatory, west of the settlement at Sydney Cove. The observatory had been founded a few years earlier by Thomas Brisbane, the new governor of the British colony of New South Wales. Just over 120 years later, John Bolton, Gordon Stanley and Bruce Slee discovered the radio source Centaurus A at the Dover Heights field station in Sydney, operated by CSIRO's Radiophysics Laboratory (the forerunner to CSIRO Astronomy and Space Sciences). This paper will describe this early historical work and summarize further studies of Centaurus A by other Radiophysics groups up to 1960.
TeV Gamma Rays from Ultrahigh Energy Cosmic Ray Interactions in the Cores of Active Galactic Nuclei: Lessons from Centaurus A
Authors: Kachelrieß M. , Ostapchenko S. , Tomàs R.
Published: October 2010

TeV gamma rays have been observed from blazars as well as from radio galaxies like M 87 and Centaurus A. In leptonic models, gamma rays above the pair production threshold can escape from the ultrarelativistic jet, because large Lorentz factors reduce the background photon densities compared to those required for isotropic emission. Here we discuss an alternative scenario, where very high energy photons are generated as secondaries from ultrahigh energy cosmic rays interactions in the cores of active galactic nuclei. We show that TeV gamma-rays can escape from the core despite large infrared and ultraviolet backgrounds. For the special case of Centaurus A, we study whether the various existing observations from the far infrared to the ultrahigh energy range can be reconciled within this picture.
Centaurus A at Ultra-High Energies
Authors: Clay Roger W. , Whelan Benjamin J. , Edwards Philip G.
Published: October 2010

We review the importance of Centaurus A in high-energy astrophysics as a nearby object with many of the properties expected of a major source of very high-energy cosmic rays and gamma rays. We examine observational techniques and the results so far obtained in the energy range from 200 GeV to above 100 EeV and attempt to fit those data to expectations of Centaurus Aas an astrophysical source from very high to ultra-high energies.
The Supermassive Black Hole at the Heart of Centaurus A: Revealed by the Kinematics of Gas and Stars
Authors: Neumayer Nadine
Published: October 2010

At less than 4 Mpc distance the radio galaxy NGC 5128 (Centaurus A) is the prime example to study the supermassive black hole and its influence on the environment in great detail. To model and understand the feeding and feedback mechanisms one needs an accurate determination of the mass of the supermassive black hole. The aim of this review is to give an overview of the recent studies that have been dedicated to measure the black hole mass in Centaurus A from both gas and stellar kinematics. It shows how the advancement in observing techniques and instrumentation drive the field of black hole mass measurements and concludes that adaptive optics assisted integral field spectroscopy is the key to identify the effects of the AGN on the surrounding ionised gas. Using data from SINFONI at the ESO Very Large Telescope, the best-fit black hole mass is MBH = 4.5(+1.7, −1.0) × 107 M⊙ (from H2 kinematics) and MBH = (5.5 ± 3.0) × 107 M⊙ (from stellar kinematics). This is one of the cleanest gas-versus-star comparisons of a MBH determination, and brings Centaurus A into agreement with the MBH−σ relation.
Lipid and mercury profiles of 61 mid-trophic species collected off south-eastern Australia
Authors: Pethybridge H. , Daley R. , Virtue P. , Butler E. C. V. , Cossa D. , Nichols P. D.
Published: October 2010

Total mercury (Hg) concentrations and lipid composition data, including fatty acid profiles, for 61 mid‐trophic species (fish, cephalopods, crustaceans) collected from continental slope waters off south‐east Australia were examined. Overall, Hg concentrations were greatest in fish (0.01–0.30 μg g–1 ww) (with highest content found in barracouta (Thyrsites atun) and whiptails (Coelorinchus fasciatus)), compared with cephalopods (0.01 and 0.17 μg g–1 ww) and crustaceans (<0.04 μg g–1 ww). Lipid composition varied between species and within habitat (mesopelagic, bathypelagic and benthic). Mean total lipid content ranged from 0.5 to 13.2% ww, and in most species was dominated by triacylglycerols and phospholipids. In fish and squid, fatty acids were generally dominated by monounsaturated fatty acids, whereas crustaceans were higher in polyunsaturated fatty acids. Multidimensional scaling analyses separated species into groupings according to their fatty acid composition that could be interpreted with taxonomic, trophic and habitat information. Discriminant function analyses indicated the most influential (predictor) fatty acids for each group. Biochemical profile classifications can be used in wider trophodynamic studies to understand contaminant transfer, trophic relationships and community dynamics in marine environments.
Influence of the choice of physical and chemistry variables on interpreting patterns of sediment contaminants and their relationships with estuarine macrobenthic communities
Authors: Chariton Anthony A. , Roach Anthony C. , Simpson Stuart L. , Batley Graeme E.
Published: October 2010

A primary objective of contaminated sediment risk assessments is to identify if contaminant enrichment is eliciting an ecological response. Using complementary environmental and biotic datasets, we examined five scenarios with respect to: dataset complexity; metal extraction; normalisation of organics; the inclusion/exclusion of acid-volatile sulfide data, and iron and manganese concentrations. Spatial distributions of abiotic variables were examined by principal components analysis, with canonical correspondence analysis used to examine the total and partitioning of biological variation. Metals were the dominant contaminant and explained the largest proportion of variation in the macrobenthic data. Extraction procedure and carbon normalisation of organics had little influence on the overall analysis. Porewater metal data was essential for interpretation, with excess of acid-volatile sulfide over simultaneously extractable metals being a poor surrogate. In the canonical correspondence analyses, the inclusion of Fe/Mn accentuated the covariation between the ecological and contaminant variables. Multimodel comparisons aided interpretation by emphasising specific relationships among environmental variables and their interactions with the biotic data. Furthermore, for future examinations of the described system, the findings can be used to reduce the collection of redundant environmental variables or variables that are poorly correlated with changes in macrobenthic assemblages.
Effects of La Niña on recruitment and abundance of juveniles and adults of benthic community-structuring species in northern Chile
Authors: Gaymer Carlos F. , Palma Alvaro T. , Vega J. M. Alonso , Monaco Cristián J. , Henríquez Luis A.
Published: October 2010

The El Niño Southern Oscillation (ENSO) has been associated with dramatic changes in adult populations of shallow benthic community-structuring species in northern Chile. However, early ontogenetic stages are more likely to be affected by physical processes associated with ENSO (e.g. increased temperature, upwelling), potentially reflected in differences in recruitment intensity. We evaluated recruitment and abundance of juveniles and adults of the major benthic community-structuring groups (kelps, sea urchins, sea stars, crabs and rockfish) during a period affected by La Niña followed by a period of neutral conditions. Recruitment was several times higher during neutral conditions for sea urchins and sea stars. Lower recruitment during La Niña was probably caused by offshore larval transport caused by increased upwelling. Recruitment of crabs tended to be higher during neutral conditions, but this varied among sites. In contrast to invertebrates, kelp abundance seemed to be controlled by post-settlement processes, as reflected by fewer kelp juveniles after La Niña when the abundance of herbivore fishes strongly increased. Our results highlight the importance of evaluating the effects of ENSO at early ontogenetic stages rather than on adult populations, which are less likely to be affected in an upwelling-dominated system.
Assessment of the benthic biota of a deep coastal ecosystem by remote and in situ sampling techniques
Authors: Waddington Kris I. , Meeuwig Jessica J. , Evans Scott N. , Bellchambers Lynda M.
Published: October 2010

Deep coastal ecosystems (>35 m) occur on the continental shelf of many regions and are poorly understood relative to shallow-water ecosystems. These ecosystems frequently support commercially important benthic-associated species, such as the western rock lobster – the most valuable single-species fishery in Australia. We used remote (towed video) and in situ (diver collection) sampling techniques to investigate the benthic biota of deep coastal ecosystems along the temperate west coast of Australia. We tested the hypotheses that (1) there is no difference in benthic assemblage structure between shallow and deep coastal ecosystems, (2) there is no difference in benthic assemblage structure between locations, and (3) both sampling techniques provide comparable descriptions of benthic assemblages. Deep coastal ecosystems were found to have significant algal and sponge assemblages, suggesting that a reduction in irradiance with depth is not constraining algal distribution. Differences in sponge, algal and macroinvertebrate community composition were detected at a regional scale between study locations. Both sampling techniques identified differences in the composition of benthic assemblages according to location, and yielded similar outcomes with respect to sponge and algal assemblages, suggesting that a single method of habitat classification can be used in future studies to determine broad scale patterns in benthic assemblage composition.
Accepting final counts from repeat readings of otoliths: should a common criterion apply to the age estimation of fish?
Authors: Marriott Ross J. , Mapstone Bruce D. , Ballagh Aaron C. , Currey Leanne M. , Penny Ann , Williams Ashley J. , Jackson Gary , Lou Dongchun , Mapleston Amos J. , Jarvis Nicholas D. C. , Keay Ian S. , Newman Stephen J.
Published: October 2010

Multiple readings of otoliths are often carried out to assess the repeatability and reliability of increment counts for estimating fish age. Various criteria have been used to assign or discard age estimates from repeated counts when discrepancies occur although the reasons for doing so are usually not stated or justified. Trends in relative frequencies (percentage disagreement, PD) and magnitudes (inter-read discrepancy, IRD) of otolith-count discrepancies were explored for 15 species of fish collected from a range of locations around Australia to explore generality in the best explanatory model(s) for otolith-count discrepancies and, hence, the most appropriate criterion for accepting or rejecting age estimates from multiple-count data. Increasing discrepancies with increasing age, according to a constant per-increment probability of error, was the best-approximating model for 9 of the 15 species for PD data but for only two species for IRD data. Our results indicated disproportionately higher rates of rejection of estimates from older age groups if exact agreement between repeated counts was required for age acceptance. Results varied with the reader, region and the method of otolith reading, indicating that multiple criteria for accepting or rejecting counts from multiple readings may be required among or even within species.
Effect of geomorphological setting and rainfall on nutrient exchange in mangroves during tidal inundation
Authors: Adame María Fernanda , Virdis Bernardino , Lovelock Catherine E.
Published: October 2010

One of the key ecosystem services provided by mangroves is their role in mediating nutrient exchange, thereby protecting coastal ecosystems from negative impacts of nutrient enrichment. In this study, we tested whether geomorphological setting and level of rainfall affect the intensity and direction of nutrient exchange. Our hypotheses were that tidal mangroves retain more nutrients than riverine mangroves and that nutrient retention is stronger during periods of high rainfall. Concentrations of soluble reactive phosphorus (SRP), nitrogen oxides (NOx–-N) and ammonium (NH4+) were measured from water entering and leaving the mangroves during tidal cycles. Our results show that nutrient concentrations were higher in the flood tide compared with the ebb tide by up to 28% for NOx–-N, 51% for SRP and 83% for NH4+, suggesting retention by the mangroves. Geomorphological setting determined nutrient exchange to some extent, with some riverine sites receiving more nutrients than tidal sites and thus, being more important in nutrient retention. Rainfall was important in determining nutrient exchange as it enhanced SRP and NH4+ retention. These results show that mangroves can improve water quality of creeks and rivers, and underscore the need for conservation of mangroves over a range of geomorphological settings.
Teichoic acids are temporal and spatial regulators of peptidoglycan cross-linking in
Staphylococcus aureus
Authors: Atilano Magda L. , Pereira Pedro M. , Yates James , Reed Patricia , Veiga Helena , Pinho Mariana G. , Filipe Sérgio R.
Published: October 2010

The cell wall of
Staphylococcus aureus
is characterized by an extremely high degree of cross-linking within its peptidoglycan (PGN). Penicillin-binding protein 4 (PBP4) is required for the synthesis of this highly cross-linked peptidoglycan. We found that wall teichoic acids, glycopolymers attached to the peptidoglycan and important for virulence in Gram-positive bacteria, act as temporal and spatial regulators of PGN metabolism, controlling the level of cross-linking by regulating PBP4 localization. PBP4 normally localizes at the division septum, but in the absence of wall teichoic acids synthesis, it becomes dispersed throughout the entire cell membrane and is unable to function normally. As a consequence, the peptidoglycan of TagO null mutants, impaired in wall teichoic acid biosynthesis, has a decreased degree of cross-linking, which renders it more susceptible to the action of lysozyme, an enzyme produced by different host organisms as an initial defense against bacterial infection.
Inhibition of pathogen-induced apoptosis by a
Coxiella burnetii
type IV effector protein
Authors: Lührmann Anja , Nogueira Catarina V. , Carey Kimberly L. , Roy Craig R.
Published: October 2010

Coxiella burnetii
and
Legionella pneumophila
are evolutionarily related pathogens with different intracellular infection strategies.
C. burnetii
persists within and is transmitted by mammalian hosts, whereas,
L. pneumophila
is found primarily in the environment associated with protozoan hosts. Although a type IV secretion system encoded by the defect in organelle trafficking (
dot
) and intracellular multiplication (
icm
) genes is a virulence determinant that remains highly conserved in both bacteria, the two pathogens encode a different array of effector proteins that are delivered into host cells by the Dot/Icm machinery. This difference suggests that adaptations to evolutionarily distinct hosts may be reflected in the effector protein repertoires displayed by these two pathogens. Here we provide evidence in support of this hypothesis. We show that a unique
C. burnetii
effector from the ankyrin repeat (Ank) family called AnkG interferes with the mammalian apoptosis pathway. AnkG was found to interact with the host protein gC1qR (p32). Either the addition of AnkG to the repertoire of
L. pneumophila
effector proteins or the silencing of p32 in mouse dendritic cells resulted in a gain of function that allowed intracellular replication of
L. pneumophila
in these normally restrictive mammalian host cells by preventing rapid pathogen-induced apoptosis. These data indicate that p32 regulates pathogen-induced apoptosis and that AnkG functions to block this pathway. Thus, emergence of an effector protein that interferes with a proapoptotic signaling pathway directed against intracellular bacteria correlates with adaptation of a pathogen to mammalian hosts.
AS160 Associates with the Na+,K+-ATPase and Mediates the Adenosine Monophosphate-stimulated Protein Kinase-dependent Regulation of Sodium Pump Surface Expression
Authors: Alves Daiane S. , Farr Glen A. , Seo-Mayer Patricia , Caplan Michael J.
Published: October 2010

The Na+,K+-ATPase is the major active transport protein found in the plasma membranes of most epithelial cell types. The regulation of Na+,K+-ATPase activity involves a variety of mechanisms, including regulated endocytosis and recycling. Our efforts to identify novel Na+,K+-ATPase binding partners revealed a direct association between the Na+,K+-ATPase and AS160, a Rab-GTPase-activating protein. In COS cells, coexpression of AS160 and Na+,K+-ATPase led to the intracellular retention of the sodium pump. We find that AS160 interacts with the large cytoplasmic NP domain of the α-subunit of the Na+,K+-ATPase. Inhibition of the activity of the adenosine monophosphate-stimulated protein kinase (AMPK) in Madin-Darby canine kidney cells through treatment with Compound C induces Na+,K+-ATPase endocytosis. This effect of Compound C is prevented through the short hairpin RNA-mediated knockdown of AS160, demonstrating that AMPK and AS160 participate in a common pathway to modulate the cell surface expression of the Na+,K+-ATPase.
c-Src–Mediated Phosphorylation of NoxA1 and Tks4 Induces the Reactive Oxygen Species (ROS)–Dependent Formation of Functional Invadopodia in Human Colon Cancer Cells
Authors: Gianni Davide , Taulet Nicolas , DerMardirossian Céline , Bokoch Gary M.
Published: October 2010

The NADPH oxidase family, consisting of Nox1-5 and Duox1-2, catalyzes the regulated formation of reactive oxygen species (ROS). Highly expressed in the colon, Nox1 needs the organizer subunit NoxO1 and the activator subunit NoxA1 for its activity. The tyrosine kinase c-Src is necessary for the formation of invadopodia, phosphotyrosine-rich structures which degrade the extracellular matrix (ECM). Many Src substrates are invadopodia components, including the novel Nox1 organizer Tks4 and Tks5 proteins. Nox1-dependent ROS generation is necessary for the maintenance of functional invadopodia in human colon cancer cells. However, the signals and the molecular machinery involved in the redox-dependent regulation of invadopodia formation remain unclear. Here, we show that the interaction of NoxA1 and Tks proteins is dependent on Src activity. Interestingly, the abolishment of Src-mediated phosphorylation of Tyr110 on NoxA1 and of Tyr508 on Tks4 blocks their binding and decreases Nox1-dependent ROS generation. The contemporary presence of Tks4 and NoxA1 unphosphorylable mutants blocks SrcYF-induced invadopodia formation and ECM degradation, while the overexpression of Tks4 and NoxA1 phosphomimetic mutants rescues this phenotype. Taken together, these results elucidate the role of c-Src activity on the formation of invadopodia and may provide insight into the mechanisms of tumor formation in colon cancers.
Will krill fare well under Southern Ocean acidification?
Authors: Kawaguchi So , Kurihara Haruko , King Robert , Hale Lillian , Berli Thomas , Robinson James P. , Ishida Akio , Wakita Masahide , Virtue Patti , Nicol Stephen , Ishimatsu Atsushi
Published: October 2010

Antarctic krill embryos and larvae were experimentally exposed to 380 (control), 1000 and 2000 µatm
p
CO
2
in order to assess the possible impact of ocean acidification on early development of krill. No significant effects were detected on embryonic development or larval behaviour at 1000 µatm
p
CO
2
; however, at 2000 µatm
p
CO
2
development was disrupted before gastrulation in 90 per cent of embryos, and no larvae hatched successfully. Our model projections demonstrated that Southern Ocean sea water
p
CO
2
could rise up to 1400 µatm in krill's depth range under the IPCC IS92a scenario by the year 2100 (atmospheric
p
CO
2
788 µatm). These results point out the urgent need for understanding the
p
CO
2
-response relationship for krill developmental and later stages, in order to predict the possible fate of this key species in the Southern Ocean.
Editorial
Authors: Meade Tom
Published: October 2010

In 2010, the Society's 350th anniversary year, it may seem that
Biographical Memoirs
is a rather youthful enterprise— it was only established as an independent publication in 1932, not much more than yesterday in the Society's terms. The journal originated from the regular obituaries given as part of the Society's annual Presidential Addresses and these were published from 1830 in
Proceedings
.
Supermacroprous chitosan–agarose–gelatin cryogels:in vitrocharacterization andin vivoassessment for cartilage tissue engineering
Authors: Bhat Sumrita , Tripathi Anuj , Kumar Ashok
Published: October 2010

The study focuses on the synthesis of a novel polymeric scaffold having good porosity and mechanical characteristics synthesized by using natural polymers and their optimization for application in cartilage tissue engineering. The scaffolds were synthesized via cryogelation technology using an optimized ratio of the polymer solutions (chitosan, agarose and gelatin) and cross-linker followed by the incubation at sub-zero temperature (−12°C). Microstructure examination of the chitosan–agarose–gelatine (CAG) cryogels was done using scanning electron microscopy (SEM) and fluorescent microscopy. Mechanical analysis, such as the unconfined compression test, demonstrated that cryogels with varying chitosan concentrations, i.e. 0.5–1% have a high compression modulus. In addition, fatigue tests revealed that scaffolds are suitable for bioreactor studies where gels are subjected to continuous cyclic strain. In order to confirm the stability, cryogels were subjected to high frequency (5 Hz) with 30 per cent compression of their original length up to 1 × 105cycles, gels did not show any significant changes in their mass and dimensions during the experiment. These cryogels have exhibited degradation capacity under aseptic conditions. CAG cryogels showed good cell adhesion of primary goat chondrocytes examined by SEM. Cytotoxicity of the material was checked by MTT assay and results confirmed the biocompatibility of the material.In vivobiocompatibility of the scaffolds was checked by the implantation of the scaffolds in laboratory animals. These results suggest the potential of CAG cryogels as a good three-dimensional scaffold for cartilage tissue engineering.
An alternative criterion in heat transfer optimization
Authors: Chen Qun , Zhu Hongye , Pan Ning , Guo Zeng-Yuan
Published: October 2010

Entropy generation is recognized as a common measurement of the irreversibility in diverse processes, and entropy generation minimization has thus been used as the criterion for optimizing various heat transfer cases. To examine the validity of such entropy-based irreversibility measurement and its use as the optimization criterion in heat transfer, both the conserved and non-conservative quantities during a heat transfer process are analysed. A couple of irreversibility measurements, including the newly defined concept
entransy
, in heat transfer process are discussed according to different objectives. It is demonstrated that although thermal energy is conserved, the accompanied system entransy and entropy in heat transfer process are non-conserved quantities. When the objective of a heat transfer is for heating or cooling, the irreversibility should be measured by the entransy dissipation, whereas for heat-work conversion, the irreversibility should be described by the entropy generation. Next, in Fourier’s Law derivation using the principle of minimum entropy production, the thermal conductivity turns out to be inversely proportional to the square of temperature. Whereas, by using the minimum entransy dissipation principle, Fourier’s Law with a constant thermal conductivity as expected is derived, suggesting that the entransy dissipation is a preferable irreversibility measurement for heat transfer.
Analytical treatment of cold field electron emission from a nanowall emitter, including quantum confinement effects
Authors: Qin Xi-Zhou , Wang Wie-Liang , Xu Ning-Sheng , Li Zhi-Bing , Forbes Richard G.
Published: October 2010

An elementary approximate analytical treatment of cold field electron emission (CFE) from a classical nanowall (i.e. a blade-like conducting structure on a flat surface) is presented. This paper first discusses basic CFE theory for situations where quantum confinement occurs transverse to the emitting direction. It develops an abstract CFE equation more general than Fowler–Nordheim type (FN-type) equations, and then applies this to classical nanowalls. With sharp emitters, the field in the tunnelling barrier may diminish rapidly with distance; an expression for the on-axis transmission coefficient for nanowalls is derived by conformal transformation. These two effects interact to generate complex emission physics, and lead to regime-dependent equations different from FN-type equations. Thus: (i) the zero-field barrier height
H
R
for the highest occupied state at 0 K is not equal to the local thermodynamic work-function
ϕ
, and
H
R
rather than
ϕ
appears in equations; (ii) in the exponent, the power dependence on macroscopic field
F
M
can be
F
−2
M
rather than
F
−1
M
; (iii) in the pre-exponential, explicit power dependences on
F
M
and
H
R
differ from FN-type equations. Departures of this general kind are expected when nanoscale quantum confinement occurs. FN-type equations are the equations that apply when no quantum confinement occurs.
Over-imitation is better explained by norm learning than by distorted causal learning
Authors: Kenward Ben , Karlsson Markus , Persson Joanna
Published: October 2010

In over-imitation, children copy even elements of a goal-directed action sequence that appear unnecessary for achieving the goal. We demonstrate in 4-year olds that the unnecessary action is specifically associated with the goal, not generally associated with the apparatus. The unnecessary action is performed flexibly: 4-year olds usually omit it if it has already been performed by an adult. Most 5-year olds do not verbally report the unnecessary action as necessary when achieving the goal, although most of them report an equivalent but necessary action as necessary. Most 5-year olds explain the necessary action in functional terms, but are unsure as to the function of the unnecessary action. These verbal measures do not support the hypothesis that children over-imitate primarily because they encode unnecessary actions as causing the goal even in causally transparent systems. In a causally transparent system, explanations for over-imitation fitting the results are that children are ignorant of the unnecessary action's purpose, and that they learn a prescriptive norm that it should be carried out. In causally opaque systems, however, for children and for adults, any action performed before achieving the goal is likely to be inferred as causally necessary—this is not over-imitation, but ordinary causal learning.
Maladaptive choice behaviour by pigeons: an animal analogue and possible mechanism for gambling (sub-optimal human decision-making behaviour)
Authors: Zentall Thomas R. , Stagner Jessica
Published: October 2010

Consistent with human gambling behaviour but contrary to optimal foraging theory, pigeons showed maladaptive choice behaviour in experiment 1 by choosing an alternative that provided on average two food pellets over an alternative that provided a certain three food pellets. On 20 per cent of the trials, choice of the two-pellet alternative resulted in a stimulus that always predicted ten food pellets; on the remaining 80 per cent of the trials, the two-pellet alternative resulted in a different stimulus that always predicted zero food pellets. Choice of the three-pellet alternative always resulted in three food pellets. This choice behaviour mimics human monetary gambling in which the infrequent occurrence of a stimulus signalling the winning event (10 pellets) is overemphasized and the more frequent occurrence of a stimulus signalling the losing event (zero pellets) is underemphasized, compared with the certain outcome associated with not gambling (the signal for three pellets). In experiment 2, choice of the two-pellet alternative resulted in ten pellets with a probability of 20 per cent following presentation of either stimulus. Choice of the three-pellet alternative continued to result in three food pellets. In this case, the pigeons reliably chose the alternative that provided a certain three pellets over the alternative that provided an average of two pellets. Thus, in experiment 1, the pigeons were responding to obtain the discriminative stimuli signalling reinforcement and the absence of reinforcement, rather than to obtain the variability in reinforcement.
Predation selects for increased immune function in male damselflies,Calopteryx splendens
Authors: Rantala Markus J. , Honkavaara Johanna , Dunn Derek W. , Suhonen Jukka
Published: October 2010

Predation selects for numerous traits in many animal species, with sick or parasitized prey often being at high risk. When challenged by parasites and pathogens, prey with poor immune functions are thus likely to be at a selective disadvantage. We tested the hypothesis that predation by birds selects for increased immune function in a wild population of male damselfliesCalopteryx splendens, while controlling for a trait known to be under selection by bird predation, dark wing-spots. We found that selection on both immune function and wing-spot size was significantly positive, and that selection on either trait was independent of selection on the other. We found no evidence of nonlinear quadratic or correlational selection. In contrast to previous studies, we found no phenotypic correlation between immune function and wing-spot size. There was also no difference in immune response between territorial and non-territorial males. Our study suggests that predation may be an important agent of selection on the immune systems of prey, and because the selection we detected was directional, has the potential to cause phenotypic change in populations.
Efficacy model for antibody-mediated pre-erythrocytic malaria vaccines
Authors: White Michael T. , Griffin Jamie T. , Riley Eleanor M. , Drakeley Chris J. , Moorman Ann M. , Sumba Peter Odada , Kazura James W. , Ghani Azra C. , John Chandy C.
Published: October 2010

Antibodies to the pre-erythrocytic antigens, circumsporozoite protein (CSP), thrombospondin-related adhesive protein (TRAP) and liver-stage antigen 1, have been measured in field studies of semi-immune adults and shown to correlate with protection from
Plasmodium falciparum
infection. A mathematical model is formulated to estimate the probability of sporozoite infection as a function of antibody titres to multiple pre-erythrocytic antigens. The variation in antibody titres from field data was used to estimate the relationship between the probability
of P. falciparum
infection per infectious mosquito bite and antibody titre. Using this relationship, we predict the effect of vaccinations that boost baseline CSP or TRAP antibody titres. Assuming the estimated relationship applies to vaccine-induced antibody titres, then single-component CSP or TRAP antibody-mediated pre-erythrocytic vaccines are likely to provide partial protection from infection, with vaccine efficacy of approximately 50 per cent depending on the magnitude of the vaccine-induced boost to antibody titres. It is possible that the addition of a TRAP component to a CSP-based vaccine such as RTS,S would provide an increase in infection-blocking efficacy of approximately 25 per cent should the problem of immunological interference between antigens be overcome.
Spatial and temporal signatures of fragility and threshold proximity in modelled semi-arid vegetation
Authors: Bailey R. M.
Published: October 2010

Understanding the behaviour of complex environmental systems, particularly as critical thresholds are approached, is vitally important in many contexts. Among these are the moisture-limited vegetation systems in semi-arid (SA) regions of the World, which support approximately 36 per cent of the human population, maintain considerable biodiversity and which are susceptible to rapid stress-induced collapse. Change in spatially self-organized vegetation patterning has previously been proposed as a means of identifying approaching thresholds in these systems. In this paper, a newly developed cellular automata model is used to explore spatial patterning and also the temporal dynamics of SA vegetation cover. Results show, for the first time, to my knowledge, in a cellular automata model, that ‘critical slowdown’ (a pronounced reduction in post-perturbation recovery rates) provides clear signals of system fragility as major thresholds are approached. A consequence of slowing recovery rates is the appearance of quasi-stable population states and increased potential for perturbation-induced multi-staged population collapse. The model also predicts a non-patterned cover where environmental stress levels are high, or where more moderate stress levels are accompanied by frequent perturbations. In the context of changing climatic and environmental pressures, these results provide observable indicators of fragility and threshold proximity in SA vegetation systems that have direct relevance to management policies.
Mite dispersal among the Southern Ocean Islands and Antarctica before the last glacial maximum
Authors: Mortimer E. , Jansen van Vuuren B. , Lee J. E. , Marshall D. J. , Convey P. , Chown S. L.
Published: October 2010

It has long been maintained that the majority of terrestrial Antarctic species are relatively recent, post last glacial maximum, arrivals with perhaps a few microbial or protozoan taxa being substantially older. Recent studies have questioned this ‘recolonization hypothesis’, though the range of taxa examined has been limited. Here, we present the first large-scale study for mites, one of two dominant terrestrial arthropod groups in the region. Specifically, we provide a broad-scale molecular phylogeny of a biologically significant group of ameronothroid mites from across the maritime and sub-Antarctic regions. Applying different dating approaches, we show that divergences among the ameronothroid mite genera
Podacarus
,
Alaskozetes
and
Halozetes
significantly predate the Pleistocene and provide evidence of independent dispersals across the Antarctic Polar Front. Our data add to a growing body of evidence demonstrating that many taxa have survived glaciation of the Antarctic continent and the sub-Antarctic islands. Moreover, they also provide evidence of a relatively uncommon trend of dispersals from islands to continental mainlands. Within the ameronothroid mites, two distinct clades with specific habitat preferences (marine intertidal versus terrestrial/supralittoral) exist, supporting a model of within-habitat speciation rather than colonization from marine refugia to terrestrial habitats. The present results provide additional impetus for a search for terrestrial refugia in an area previously thought to have lacked ice-free ground during glacial maxima.
Unravelling the structure of species extinction risk for predictive conservation science
Authors: Lee Tien Ming , Jetz Walter
Published: October 2010

Extinction risk varies across species and space owing to the combined and interactive effects of ecology/life history and geography. For predictive conservation science to be effective, large datasets and integrative models that quantify the relative importance of potential factors and separate rapidly changing from relatively static threat drivers are urgently required. Here, we integrate and map in space the relative and joint effects of key correlates of The International Union for Conservation of Nature-assessed extinction risk for 8700 living birds. Extinction risk varies significantly with species' broad-scale environmental niche, geographical range size, and life-history and ecological traits such as body size, developmental mode, primary diet and foraging height. Even at this broad scale, simple quantifications of past human encroachment across species' ranges emerge as key in predicting extinction risk, supporting the use of land-cover change projections for estimating future threat in an integrative setting. A final joint model explains much of the interspecific variation in extinction risk and provides a remarkably strong prediction of its observed global geography. Our approach unravels the species-level structure underlying geographical gradients in extinction risk and offers a means of disentangling static from changing components of current and future threat. This reconciliation of intrinsic and extrinsic, and of past and future extinction risk factors may offer a critical step towards a more continuous, forward-looking assessment of species' threat status based on geographically explicit environmental change projections, potentially advancing global predictive conservation science.