bluuebunny/crossref_metadata_2025 huggingface dataset:
Focusing of intense subpicosecond laser pulses in wedge targets
Authors: Levy M. C. , Kemp A. J. , Wilks S. C. , Divol L. , Baring M. G.
Published: October 2011

Two dimensional particle-in-cell simulations characterizing the interaction of ultraintense short pulse lasers in the range 1018 ≤ I ≤ 1020 W/cm2 with converging target geometries are presented. Seeking to examine intensity amplification in high-power laser systems, where focal spots are typically non-diffraction limited, we describe key dynamical features as the injected laser intensity and convergence angle of the target are systematically varied. We find that laser pulses are focused down to a wavelength with the peak intensity amplified by an order of magnitude beyond its vacuum value and develop a simple model for how the peak location moves back towards the injection plane over time. This performance is sustained over hundreds of femtoseconds and scales to laser intensities beyond 1020 W/cm2 at 1 μm wavelength.
Analytic model of effective screened Coulomb interactions in a multilayer system
Authors: Ouerdane H.
Published: October 2011

The main objective of the present work is the development of an analytically tractable model of screened electron-electron and electron-exciton interactions in layered systems composed of two parallel semiconductor quantum wells separated by a dielectric layer. These systems are promising for superconductivity with excitons-polaritons, and spin manipulation. Polarization effects induced by the dielectric mismatch in the nanostructure are taken into account using the image charge method. The obtained analytic expressions are used to calculate screened electron-electron and electron-exciton interactions; these are compared to results computed using other recently published models.
The direct measurement of ablation pressure driven by 351-nm laser radiation
Authors: Fratanduono D. E. , Boehly T. R. , Celliers P. M. , Barrios M. A. , Eggert J. H. , Smith R. F. , Hicks D. G. , Collins G. W. , Meyerhofer D. D.
Published: October 2011

The instantaneous scaling of ablation pressure to laser intensity is directly inferred for ramp compression of diamond targets irradiated by 351-nm light. Continuously increasing pressure profiles from 100 to 970 GPa are produced by direct-drive laser ablation at intensities up to 7 × 1013 W/cm2. The free-surface velocity on the rear of the target is used to directly infer the instantaneous ablation-pressure profile at the front of the target. The laser intensity on target is determined by laser power measurements and fully characterized laser spots. The ablation pressure is found to depend on the laser intensity as P(GPa)=42(±3)[I(TW/cm2)]0.71(±0.01).
Generation of high-current electron beam in a wide-aperture open discharge
Authors: Bokhan P. A. , Zakrevsky Dm. E. , Gugin P. P.
Published: October 2011

In the present study, it was examined generation of nanosecond-duration electron-beam (EB) pulses by a wide-aperture open discharge burning in helium or in a mixture of helium with nitrogen and water vapor. In the experiments, a discharge cell with coaxial electrode geometry, permitting radial injection of the electron beam into operating lasing medium, was used, with the cathode having radius 2.5 cm and length 12 cm. It was shown possible to achieve an efficient generation of a high-intensity electron beam (EB pulse power ∼250 MW and EB pulse energy up to 4 J) in the kiloampere range of discharge currents (up to 26 kA at ∼12 kV discharge voltage). The current-voltage characteristics of the discharge proved to be independent of the working-gas pressure. The existence of an unstable dynamic state of EB, conditioned by the presence of an uncompensated space charge accumulated in the discharge cell due to the exponential growth of the current in time during discharge initiation and the hyperbolic growth of current density in the direction towards the tube axis, was revealed. The obtained pulsed electron beam was used to excite the self-terminated laser on He 21P10-21S0 transition. The oscillations developing in the discharge cell at high discharge currents put limit to the pumping energy and emissive power of the laser excited with the radially converging electron beam.
A new Monte Carlo method for getting the density of states of atomic cluster systems
Authors: Soudan J.-M. , Basire M. , Mestdagh J.-M. , Angelié C.
Published: October 2011

A novel Monte Carlo flat histogram algorithm is proposed to get the classical density of states in terms of the potential energy, g(Ep), for systems with continuous variables such as atomic clusters. It aims at avoiding the long iterative process of the Wang-Landau method and controlling carefully the convergence, but keeping the ability to overcome energy barriers. Our algorithm is based on a preliminary mapping in a series of points (called a σ-mapping), obtained by a two-parameter local probing of g(Ep), and it converges in only two subsequent reweighting iterations on large intervals. The method is illustrated on the model system of a 432 atom cluster bound by a Rydberg type potential. Convergence properties are first examined in detail, particularly in the phase transition zone. We get g(Ep) varying by a factor 103700 over the energy range [0.01 < Ep < 6000 eV], covered by only eight overlapping intervals. Canonical quantities are derived, such as the internal energy U(T) and the heat capacity CV(T). This reveals the solid to liquid phase transition, lying in our conditions at the triple point. This phase transition is further studied by computing a Lindemann-Berry index, the atomic cluster density n(r), and the pressure, demonstrating the progressive surface melting at this triple point. Some limited results are also given for 1224 and 4044 atom clusters.
Empirical model of whistler anisotropy instability
Authors: Yoon Peter H. , Seough Jung Joon , Lee Junggi , An Junmo , Lee Jae Ok
Published: October 2011

Empirical formulae for the real frequency and growth rate associated with the whistler anisotropy instability are obtained. The electrons are assumed to have an anisotropic distribution function, with Maxwellian parallel distribution. Under such an assumption complex roots of the dispersion relation depend only on two dimensionless parameters, namely, the temperature anisotropy factor A = T⊥e/T∥e − 1, where T⊥e and T∥e are the perpendicular and parallel electron temperatures, respectively, and parallel electron beta, β∥ = (8πnT∥e/B2)1/2, where n and B are the plasma density and magnetic field intensity, respectively. Comparison against exact numerical roots show that analytical formulae describe the whistler instability over a wide range of parallel electron beta and temperature anisotropy factor. The present result may be useful for circumstances in which the use of exact numerical roots becomes impractical, such as in the radiation belt quasi-linear transport coefficient calculation.
Theoretical and experimental study of the microwave cut-off probe for electron density measurements in low-temperature plasmas
Authors: Li Bin , Li Hong , Wang Huihui , Xie Jinlin , Liu Wandong
Published: October 2011

The microwave cut-off probe for the electron density measurement in low-temperature plasmas is described in this article. It is based on the wave cutoff in an unmagnetized plasma. The measurement principle is analyzed theoretically using a model of plasma slab. Because of the high-pass characteristic of plasma, the waves above the cut-off frequency can penetrate the plasma slab, whereas the lower frequency waves are reflected from the cut-off layer. Therefore, an obvious critical point can be observed in the wave transmission spectrum. The abscissa of the critical point indicates the cut-off frequency, which is directly related to the maximum electron density between transmitting/receiving antennas of the cut-off probe. The measured electron densities are in agreement with the data obtained by the Langmuir probe. Experimental results show that the microwave cut-off probe can be used to diagnose the plasmas with a wide range of parameters.
Ultra high-density silicon nanowires for extremely low reflection in visible regime
Authors: Pei Ting-Hang , Thiyagu Subramani , Pei Zingway
Published: October 2011

We fabricated large-area, vertically aligned silicon nanowire (SiNW) arrays on Si substrates employing catalytic etching on a polystyrene nanosphere template. The density of SiNWs was as high as 1010/cm2, and the bottom radii of SiNWs ranged between 30 and 60 nm. The reflection from the SiNW layer was approximately 0.1% over the spectral range of 300–800 nm for SiNWs longer than 750 nm. Effective medium theory was applied to explain this extremely low reflection, and it was confirmed that the incident light scatters randomly inside cone-like SiNWs, which lengthens the actual traveling path of light.
Processing weak electrical signals with threshold-potential nanostructures showing a high variability
Authors: Manzanares José A. , Cervera Javier , Mafé Salvador
Published: October 2011

We explore the processing of weak electrical signals in parallel arrays of bio-inspired threshold nanostructures showing a high variability in their threshold potentials. We consider a two-state canonical model that incorporates the basic properties demonstrated experimentally. The model is inspired by the voltage-gated ion channels in biological membranes and shows that the nanostructure variability can allow significant transmission of sub-threshold signals. Implications for the design of practical devices are briefly discussed.
Enhanced Rashba effect in transverse magnetic fields observed on InGaAs/GaAsSb resonant tunneling diodes at temperatures up to T = 180 K
Authors: Silvano de Sousa J. , Detz H. , Klang P. , Gornik E. , Strasser G. , Smoliner J.
Published: October 2011

A huge Rashba splitting enhanced by an in-plane magnetic field is observed in non-magnetic InGaAs resonant tunneling diodes with GaAsSb barriers. At T = 4 K, the current resonances split by the Rashba effect reveal peak to valley ratios up to 2.5:1 and the energy spacing between the split peaks reaches 30 meV at B = 5 T. The observed peak splitting can be observed at temperatures up to T = 180 K and higher. The Rashba parameters determined on four different samples are between α = 0.38 eVÅ and α = 0.78 eV Å, which are consistent with theoretical values reported for InAs quantum wells under external electric fields.
Structural design of AlN/GaN superlattices for deep-ultraviolet light-emitting diodes with high emission efficiency
Authors: Kamiya Katsumasa , Ebihara Yasuhiro , Shiraishi Kenji , Kasu Makoto
Published: October 2011

We demonstrate on the basis of first-principles calculations that a AlN/GaN superlattice with one or two GaN monolayers is efficient for near-band-edge C-plane emission of deep-ultraviolet light-emitting diodes. We find that such superlattices lead to a significant increase of the C-plane components of the optical matrix element up to 57% relative to GaN bulk. At the same time, the energy gap of these superlattices is in the deep-UV region, where the shortest emission wavelength is 224 nm. This is remarkably shorter than that in Al-rich AlGaN alloys.
Al and Fe co-doped transparent conducting ZnO thin film for mediator-less biosensing application
Authors: Saha Shibu , Gupta Vinay
Published: October 2011

Highly c-axis oriented Al and Fe co-doped ZnO (ZAF) thin film is prepared by pulsed laser deposition. Fe introduces redox centre along with shallow donor level while Al doping enhances conductivity of ZnO, thus removing the requirement of both mediator and bottom conducting layer in bioelectrode. Model enzyme (glucose oxidase), was immobilized on surface of ZAF matrix. Cyclic voltammetry and photometric assay show that prepared bio-electrode is sensitive to glucose concentration with enhanced response of 0.18 μAmM-1cm-2 and low Km ∼ 2.01 mM. The results illustrate that ZAF is an attractive matrix for realization of miniaturized mediator-less solid state biosensor.
Corrigendum to: Experimental validation of the Intergovernmental Panel on Climate Change default values for ruminant-derived methane and its carbon-isotope signature
Authors: Klevenhusen F. , Bernasconi S. M. , Kreuzer M. , Soliva C. R.
Published: October 2011

Two aspects regarding the ruminant's contribution to global methane (CH4) emissions were investigated: (i) testing the accuracy of the Intergovernmental Panel on Climate Change default values for dairy cows fed different diet types and differing slurry storage temperatures; and (ii) providing carbon-isotope (C-isotope) signature data to contribute information on the characteristics of ruminant-derived CH4 as global source. The experimental diets, fed to 18 dairy cows, were separated into forage-only (hay, C3 plant) and forage-concentrate diets (barley, C3 plant; maize, C4 plant). Accumulated slurry was stored at either 14 or 27�C. The hay diet had the highest CH4 conversion rate (Ym 7.9%). Negligible amounts of CH4 were emitted from slurries stored at low temperature. No diet effect was found at 27�C (~33 L/kg volatile solids). The isotope ratios of enteric CH4 averaged -67.7‰ (C3 plants) and -57.4‰ (C4; maize). High temperature slurry storage resulted in different enrichment factors εCO2-CH4 for maize (33.2‰) and hay (35.9‰). Compared with the Intergovernmental Panel on Climate Change default values for Ym and slurry CH4 emission the results gained in the present experiment were higher and lower, respectively. Slurry-derived CH4 was less depleted in 13C than enteric CH4, which decreases the usefulness of this signature for global ruminant-derived CH4.
Effect of lairage on lamb welfare and meat quality
Authors: Liste G. , Miranda-de la Lama G. C. , Campo M. M. , Villarroel M. , Muela E. , María G. A.
Published: October 2011

The study analysed the effect of lairage on some indicators of welfare and meat quality in lambs. Forty-eight lambs were divided into two treatments: T1 without lairage and T2 with 12 h of lairage. Blood samples were collected at slaughter to analyse cortisol, lactate, glucose, creatinine kinase, non-esterified fatty acid, white blood cells, red blood cells, haematocrit and ratio of neutrophil : lymphocytes. Meat from the M. longissimus was analysed in terms of pH 24 h post-mortem, water-holding capacity, texture and colour. Sensory analyses were performed by a trained panel. Lairage had a significant effect on stress response, but had no effect on haematological variables. The lambs with a lairage period before slaughter (T2) had significantly (P ≤ 0.001) lower values of cortisol at the time of slaughter. A similar result was observed for lactate and glucose, with T1 lambs showing significantly (P ≤ 0.05) higher values than T2 lambs. The creatinine kinase activity and non-esterified fatty acid concentrations were highest in T2 lambs (P ≤ 0.05). Instrumental and sensory meat quality were not affected, with the exception of water-holding capacity and some meat colour indicators. The water-holding capacity was significantly higher for T2 (P ≤ 0.05), while T1 lambs had a higher yellow index (P ≤ 0.05) and hue (P ≤ 0.05). The results obtained in this study suggest that animals will be less stressed at the time of slaughter with an overnight lairage compared with slaughter on arrival at the abattoir. While stress at the time of slaughter can influence meat quality, these changes were small and always within the normal commercial range.
Comparing somatic cell counts, production and milking durations of dairy cows when milked at two automatic cup-removal flow-rate thresholds
Authors: Burke J. K. , Jago J. G.
Published: October 2011

The present study evaluated the effect of two automatic cup remover (ACR) flow-rate threshold settings (0.2 and 0.4 kg/min) on somatic cell count (SCC), clinical mastitis (CM), milk production and milking duration for cows milked twice daily. In a crossover design, 161 cows were assigned to one of two groups and milked with an ACR set at either 0.2 kg/min (Group 1, n = 81) or 0.4 kg/min (Group 2, n = 80) for a 3-week period from peak lactation. Following a 1-week transition period at a milk-flow threshold setting of 0.3 kg/min for both groups, there was a further 3-week treatment period where Group 1 was milked with an ACR set at 0.4 kg/min and Group 2 set at 0.2 kg/min. The milk-flow threshold setting did not affect SCC (P > 0.05). Clinical mastitis was detected in 3% of cows, and was not more prevalent when cows were milked to a flow rate of 0.4 kg/min. Post-milking strip yields were larger when thresholds were set at 0.4 kg/min than those with 0.2 kg/min (P < 0.05). Average fat yield was not affected by treatment (P > 0.05), but average daily milk, MS and protein yields were lower (P < 0.05) for the 0.4 kg/min setting, equating to a 1% difference in production. Milking duration was reduced by 11% (P < 0.001) when cups were removed at flow rates of 0.4 kg/min, compared with 0.2 kg/min. Increasing the milk flow-rate threshold for cluster removal can reduce milking time without affecting milk quality, but may result in a minor reduction in MS production.
Abiotic affinities and spatiotemporal distribution of the endangered smalltooth sawfish, Pristis pectinata, in a south-western Florida nursery
Authors: Poulakis Gregg R. , Stevens Philip W. , Timmers Amy A. , Wiley Tonya R. , Simpfendorfer Colin A.
Published: October 2011

Understanding how endangered marine species rely on coastal habitats is vital for population recovery planning. The smalltooth sawfish (Pristis pectinata) is one of several critically endangered sawfishes worldwide known to use estuaries and rivers during their early life history. In a Florida estuary designated as critical habitat by the USA government, juveniles were monitored to characterise seasonality, recruitment, and habitat use. Stretched total length ranged from 671 to 2172 mm (n = 137, mean = 1248 mm). Sawfish were captured year round. Captures of neonates with embryonic rostral sheaths allowed refinement of the size at birth (671–812 mm) and confirmed a protracted timing of parturition (November–July), which peaked between April and May. Although sampling occurred throughout the estuary, five locations had the greatest catch rates. Most juvenile sawfish had an affinity for water <1 m deep, water >30°C, dissolved oxygen >6 mg L–1, and salinity between 18 and 30. Greater catch rates for sawfish >1 year old were associated with shoreline habitats with overhanging vegetation such as mangroves. These results detail habitat use within a recognised nursery that can be used for conservation of the first endangered marine fish species in the USA.
Seasonal variability in faecal bacteria of semiarid rivers in the Serengeti National Park, Tanzania
Authors: Strauch Ayron M.
Published: October 2011

Humans and livestock are known contributors of faecal waste to surface water. However, little is known about natural fluctuations of faecal bacteria, especially where wildlife may contribute substantial amounts of waste. I tested the hypotheses that ecological factors, including seasonal animal impacts, rainfall and physiochemical water quality, influence the abundance of total coliform (TC) and Escherichia coli faecal bacteria in five rivers of the Serengeti National Park, Tanzania. TC and E. coli are indicators commonly used to assess water quality and their abundance can be determined quantitatively by using defined-substrate technology. Results demonstrated substantial variation in faecal bacteria across rivers and seasons. In the southern two rivers, faecal bacteria increased significantly during the wet season, compared with dry-season levels, whereas there were few seasonal differences in the northern rivers, suggesting that large populations of resident wildlife in the north dampen the seasonal influence of migratory wildlife. Faecal bacteria were positively related to rainfall and total ammonia/ammonium, and had a negative quadratic relationship with salinity. The present results demonstrated that wildlife in protected regions can be major contributors of faecal bacteria to surface waters, and as demand for water resources increases, pose a significant threat to human health.
Fertility partially drives the relative success of two introduced bovines (Bubalus bubalis and Bos javanicus) in the Australian tropics
Authors: McMahon Clive R. , Brook Barry W. , Bowman David M. J. S. , Williamson Grant J. , Bradshaw Corey J. A.
Published: October 2011

Context Some large herbivores introduced to Australia have achieved population densities so high as to cause considerable ecological damage. Intriguingly, others have been relatively less successful and have correspondingly perturbed their new environments less. An excellent example is two similar-sized bovine species that established feral populations in the Northern Territory of Australia in the mid-19th century. Asian swamp buffalo (Bubalus bubalis) rapidly colonised the tropical savannas, causing ecological degradation, especially on freshwater swamps. In contrast, banteng (Bos javanicus) are restricted to their point of introduction and have caused relatively negligible ecological damage. Understanding the reasons of this differential success is of theoretical and applied interest and contributes to managing large herbivore populations for ex situ conservation and feral-animal control. Aims To compare the population structure of buffalo and banteng on the basis of shot samples, so as to construct life tables for four contemporary (low-density) buffalo populations, and collated data from previous work from three historical (high-density) buffalo populations and one banteng population (the only extant ex situ population in existence). Further, to provide a validation of age estimation with and without informed priors in a Bayesian model comparing horn length and ages estimated from tooth cementum annuli. Finally, to interpret our results in the context of relative invasion potential of the two bovid species. Key Results For both species, survival of juveniles was the most important demographic component influencing deterministic population growth. However, buffalo have the demographic capacity to recover swiftly after control because of high survival and fertility rates across a range of population densities. Fertility of buffalo was historically greater than that of banteng, and buffalo fertility increased as their populations were reduced. Conclusions These findings highlight how subtle differences in demographic rates and feeding ecology can influence the success (high population growth and range expansion) of large herbivores, knowledge which is increasingly important for managing invasive species effectively. Implications We show that that individual life-history traits and demographic performance, especially fertility, play an important role in determining the spread of invasive bovids in a novel environment.
Target-specificity of feral pig baits under different conditions in a tropical rainforest
Authors: Bengsen Andrew J. , Leung Luke K.-P. , Lapidge Steven J. , Gordon Iain J.
Published: October 2011

Context The mitigation of feral pig (Sus scrofa) impacts in north Queensland’s World Heritage tropical rainforests is constrained by the lack of an effective and target-specific poison baiting method. Aims This study aimed to determine whether easily implemented bait presentation methods or seasonal variation in bait acceptability could be used to selectively reduce the consumption of feral pig baits by non-target species. Methods We exposed manufactured feral pig baits to pigs and non-target species in the field, and compared bait encounter, sampling and consumption rates for different functional groups of species among three different types of bait presentation and composition. We then exposed baits under different seasonal conditions and related bait encounter and consumption by different functional groups to seasonally variable phenomena. Key results Shallow burial greatly reduced bait consumption by most non-target species, but not dingoes (Canis lupus dingo). Nocturnal bait distribution and seasonal baiting were less useful. Pigs showed substantial seasonal variation in physiological condition, suggesting that pigs should be more susceptible to consuming novel foods, such as baits, after periods of low rainfall. However, few pigs consumed the manufactured baits used in this study. Conclusions Manufactured baits are not currently suitable for widespread use in the region. However, shallow burial should provide an effective method of reducing non-target bait-take if baits can be made more attractive and acceptable to pigs and less acceptable to dingoes. Implications Future efforts to enable effective feral pig control in the region should focus on developing baiting materials that are more attractive to pigs and unappealing to dingoes.
Assessing the potential impact of invasive cane toads on a commercial freshwater fishery in tropical Australia
Authors: Somaweera Ruchira , Crossland Michael R. , Shine Richard
Published: October 2011

Context The toxins produced by cane toads (Rhinella marina) are fatal to many Australian predators that ingest these invasive anurans. To date, the potential economic impact of the cane toad invasion has attracted little attention. Toads have recently arrived at a large impoundment (Lake Argyle) in north-eastern Western Australia, that supports a commercial fishery for silver cobbler (shovel-nosed catfish, Arius midgleyi), raising concern that the toads may inflict significant economic damage by killing fish. Aims Our research aimed to clarify the vulnerability of silver cobblers to the eggs and larvae of cane toads by determining (a) whether catfish are adversely affected if they prey on toad eggs or tadpoles, and (b) whether surviving catfish learn to avoid cane toad eggs and tadpoles in subsequent encounters. Methods We conducted laboratory feeding trials to examine feeding responses of catfish to cane toad eggs and tadpoles in early and late developmental stages. Fish that survived exposure to toad eggs and/or tadpoles were re-tested with potential prey of the same sizes and developmental stages four days later. Key results Our laboratory trials confirmed that some catfish eat toad eggs and die; but most catfish avoided the eggs. Catfish readily consumed toad tadpoles at both early and late developmental stages, but without experiencing mortality; and soon learned not to consume this toxic new prey type. Conclusions and implications Despite potential frequent episodes of mortality of small numbers of catfish during the wet season, the overall impacts of cane toads on the Lake Argyle fishery likely will be minimal.
Evaluation of attractants for non-invasive studies of Iberian carnivore communities
Authors: Monterroso Pedro , Alves Paulo Célio , Ferreras Pablo
Published: October 2011

Context The estimation of population parameters for mammalian carnivore species is a challenging task because of their low densities and large home ranges, which make detection probabilities very low. Several factors, such as the species abundance, habitat structure or the use of an attractant affect carnivore detection probabilities; however, attractants are the most easily manipulated. Some previous research suggests that the use of effective attractants can significantly increase detection probabilities. Aims To assess the effectiveness of several attractants for Iberian carnivores, and to evaluate their usefulness for non-invasive survey methods. Methods The responses of seven carnivore species to six potential attractants were evaluated through cafeteria-like experiments with captive specimens. A selectivity index was applied to assess the relative attractiveness of each tested substance. The enclosure tests were followed by field trials with camera-trapping, using the most promising attractants for field evaluation of their efficiency. Key results Enclosure trials revealed that lynx urine was the most effective and generalist attractant because it successfully attracted six of the seven species tested. Rubbing behaviour was also induced in the greatest number of species by lynx urine. Field tests using a combination of lynx urine and valerian extract solution induced investigative behaviours in over 50% of all detection events in all species, with the exception of the Eurasian badger. Conclusions No single attractant is effective for all species. Nevertheless, a combination of lynx urine and valerian solution should efficiently attract the majority of species present in Iberian carnivore communities. Furthermore, some species exhibit a rubbing behaviour when they come in contact with the attractants. Regardless of the generalist efficiency of the lynx urine, other tested substances revealed promising results for single-species monitoring. Implications Our results provide a baseline for selecting attractants in survey and monitoring programs that focus on carnivore species. The rubbing behaviours exhibited by several of the species tested suggest the use of these attractants could improve the efficiency of field studies that rely on rub-pads for the collection of biological samples.
Suitability of acoustics as non-lethal deterrents for macropodids: the influence of origin, delivery and anti-predator behaviour
Authors: Ramp Daniel , Foale Clio Gates , Roger Erin , Croft David B.
Published: October 2011

Context Auditory devices used to deter wildlife are a potentially humane and effective way of minimising deleterious interactions with humans and their livelihoods and have been used successfully for many species around the world. Acoustic cues can be used to manipulate anti-predator behaviour, encouraging animals to forage elsewhere. Employing acoustics derived from natural sources to make use of innate behavioural responses has been suggested to outperform novel or artificial sounds; however, anti-predator strategies vary among sympatric species and will influence the utility of acoustic stimuli for deterring wildlife. Aims We aimed to test the interaction between the source of origin (natural or novel) and species traits (anti-predator strategy – grouping behaviour) on the efficacy of using acoustic stimuli to elicit alarm responses for two species in the family Macropodidae commonly associated with browsing on forest plantation seedlings; the red-necked pademelon (Thylogale thetis) and the red-necked wallaby (Macropus rufogriseus banksianus). Methods We tested these factors in captivity using playback experiments of acoustic stimuli and monitored the behavioural responses of subjects. Results Red-necked pademelons exhibited strong responses to bioacoustic and novel stimuli but did not greatly differentiate among them. Short-term habituation to predator calls was detected whereas responsiveness to novel sounds increased. Red-necked wallabies most strongly responded to conspecific distress calls, showing no sign of short-term habituation. Conclusions Results from the present and other studies suggest that bioacoustic deterrents, particularly those utilising natural conspecific sounds, aimed at communicating danger, have the potential to play an important role in non-lethal wildlife management, although that responsiveness varies with the form of anti-predator strategies employed. Implications If alarm responses translate into subjects vacating targeted areas, then there is some potential to implement non-lethal acoustic deterrents for macropodids alongside other management measures aimed at preventing impacts on primary production. Problematically, our experiments showed that without accurate acoustic delivery, particularly of sounds with infrasonic components, the development of effective bioacoustic deterrents may remain stymied.
Rapid and efficient reprogramming of somatic cells to induced pluripotent stem cells by retinoic acid receptor gamma and liver receptor homolog 1
Authors: Wang Wei , Yang Jian , Liu Hui , Lu Dong , Chen Xiongfeng , Zenonos Zenon , Campos Lia S. , Rad Roland , Guo Ge , Zhang Shujun , Bradley Allan , Liu Pentao
Published: October 2011

Somatic cells can be reprogrammed to induced pluripotent stem cells (iPSCs) by expressing four transcription factors: Oct4, Sox2, Klf4, and c-Myc. Here we report that enhancing RA signaling by expressing RA receptors (RARs) or by RA agonists profoundly promoted reprogramming, but inhibiting it using a RAR-α dominant-negative form completely blocked it. Coexpressing Rarg (RAR-γ) and Lrh-1 (liver receptor homologue 1; Nr5a2) with the four factors greatly accelerated reprogramming so that reprogramming of mouse embryonic fibroblast cells to ground-state iPSCs requires only 4 d induction of these six factors. The six-factor combination readily reprogrammed primary human neonatal and adult fibroblast cells to exogenous factor-independent iPSCs, which resembled ground-state mouse ES cells in growth properties, gene expression, and signaling dependency. Our findings demonstrate that signaling through RARs has critical roles in molecular reprogramming and that the synergistic interaction between Rarg and Lrh1 directs reprogramming toward ground-state pluripotency. The human iPSCs described here should facilitate functional analysis of the human genome.
Conversion of the enzyme guanylate kinase into a mitotic-spindle orienting protein by a single mutation that inhibits GMP-induced closing
Authors: Johnston Christopher A. , Whitney Dustin S. , Volkman Brian F. , Doe Chris Q. , Prehoda Kenneth E.
Published: October 2011

New protein functions can require complex sequence changes, but the minimal path is not well understood. The guanylate kinase enzyme (GK
enz
), which catalyzes phosphotransfer from ATP to GMP, evolved into the GK domain (GK
dom
), a protein-binding domain found in membrane associate guanylate kinases that function in mitotic spindle orientation and cell adhesion. Using an induced polarity assay for GK
dom
function, we show that a single serine to proline mutation is sufficient to switch extant GK
enz
into a functional GK
dom
. The mutation blocks catalysis (GK
enz
function) but allows protein binding and spindle orientation (GK
dom
function). Furthermore, whereas the GK
enz
undergoes a large closing motion upon GMP binding, fluorescence quenching and NMR demonstrate that the S → P mutation inhibits GMP-induced GK movements. Disrupting GK closing with a mutation at a different position also leads to GK
dom
function, suggesting that blocking the GK
enz
closing motion is sufficient for functional conversion of GK
enz
to GK
dom
. Although subtle changes in protein function can require complex sequence paths, our work shows that entirely new functions can arise from single mutations that alter protein dynamics.
Glial-conditional deletion of aquaporin-4 (
Aqp4
) reduces blood–brain water uptake and confers barrier function on perivascular astrocyte endfeet
Authors: Haj-Yasein Nadia Nabil , Vindedal Gry Fluge , Eilert-Olsen Martine , Gundersen Georg Andreas , Skare Øivind , Laake Petter , Klungland Arne , Thorén Anna Elisabeth , Burkhardt John Michael , Ottersen Ole Petter , Nagelhus Erlend Arnulf
Published: October 2011

Tissue- and cell-specific deletion of the
Aqp4
gene is required to differentiate between the numerous pools of aquaporin-4 (AQP4) water channels. A glial-conditional
Aqp4
knockout mouse line was generated to resolve whether astroglial AQP4 controls water exchange across the blood–brain interface. The conditional knockout was driven by the glial fibrillary acidic protein promoter. Brains from conditional
Aqp4
knockouts were devoid of AQP4 as assessed by Western blots, ruling out the presence of a significant endothelial pool of AQP4. In agreement, immunofluorescence analysis of cryostate sections and quantitative immunogold analysis of ultrathin sections revealed no AQP4 signals in capillary endothelia. Compared with litter controls, glial-conditional
Aqp4
knockout mice showed a 31% reduction in brain water uptake after systemic hypoosmotic stress and a delayed postnatal resorption of brain water. Deletion of astroglial
Aqp4
did not affect the barrier function to macromolecules. Our data suggest that the blood–brain barrier (BBB) is more complex than anticipated. Notably, under certain conditions, the astrocyte covering of brain microvessels is rate limiting to water movement.
Edge pedestal characteristics in JET and JT-60U tokamaks under variable toroidal field ripple
Authors: Urano H. , Saibene G. , Oyama N. , Parail V. , de Vries P. , Sartori R. , Kamada Y. , Kamiya K. , Loarte A. , Lönnroth J. , Sakamoto Y. , Salmi A. , Shinohara K. , Takenaga H. , Yoshida M.
Published: October 2011

The effects of toroidal field (TF) ripple on the edge pedestal characteristics were examined in the TF ripple scan experiments at the plasma current I
p of 1.1 MA in JET and JT-60U. The TF ripple amplitude δR was defined as a value averaged over the existing ripple wells at the separatrix on the outer midplane. By the installation of ferritic inserts (FIs), δR was reduced from 1% to 0.6% at 3.2T (0.5% at 2.2 T) in JT-60U. In JET, δR was varied from 0.08% to 1% by feeding different currents to the odd and even set of coils out of 32 TF coils. The pedestal pressure p
ped was similar for the cases before and after the installation of FIs in JT-60U. Similarly, no clear difference in p
ped was also observed in the variation of δR in JET. The core and edge toroidal rotation clearly shifted in the counter-direction by increased δR. However, there were no changes in the spatial profiles of electron density, electron temperature and ion temperature. By the installation of FIs in JT-60U, the ELM frequency f
ELM decreased by ∼20%, while the ELM energy loss increased by 50–150%. The increased ELM loss power by 30% suggests a reduction of inter-ELM transport with the reduced δR. In JET, f
ELM increased only slightly with increased δR while the edge toroidal rotation frequency decreased as δR increased. From the inter-machine similarity experiment at 1.1 MA, TF ripple less than 1% does not strongly affect the pedestal pressure. However, in the single TF ripple scan at the higher I
p of 2.6 MA in JET, it clearly decreases with the increased δR, accompanying with a strong density pump out at large TF ripple. These results suggests that the effect of TF ripple on H-mode properties becomes stronger in the plasmas with higher I
p or lower edge collisionality of ripple diffusion.
Control of magnetic islands in the STOR-M tokamak using resonant helical fields
Authors: Elgriw S. , Liu D. , Asai T. , Hirose A. , Xiao C.
Published: October 2011

The resonant interaction between magnetohydrodynamic (MHD) instability modes and the externally applied helical magnetic field is demonstrated in the Saskatchewan Torus-Modified (STOR-M) tokamak. The study is conducted both numerically and experimentally using a 2D MHD equilibrium code in the former and an (l = 2, n = 1) helical coil carrying a short current pulse in the latter. It is shown numerically that the resonant helical current can efficiently suppress the magnetic islands resonating on the (m = 2, n = 1) magnetic surface when the value of the safety factor at the plasma edge is relatively low (⩽4). It is also found numerically that (2, 1) islands are induced when the applied helical current exceeds a threshold. The experimental study is performed in STOR-M during low-q ohmic discharges with high MHD activities. The amplitude and frequency of (2, 1) Mirnov fluctuations are significantly reduced after the activation of the resonant field. Lesser suppression in sideband islands is also observed. Moreover, a phase of improved plasma confinement, characterized by a reduction in Hα emission level, a reduction in loop voltage and an increase in the soft x-ray emission, is induced after application of the resonant field.
Relations between metrics of almost positive curvature on the Gromoll-Meyer sphere
Authors: Dearricott Owen
Published: October 2011

We give a simplified proof that Wilhelm’s metric on the Gromoll-Meyer sphere has positive curvature almost everywhere. We determine that its zero locus coincides with that of the almost positively curved metric of Eschenburg and Kerin.
A simple test of vocal individual recognition in wild meerkats
Authors: Townsend Simon W. , Allen Colin , Manser Marta B.
Published: October 2011

Individual recognition is thought to be a crucial ability facilitating the evolution of animal societies. Given its central importance, much research has addressed the extent of this capacity across the animal kingdom. Recognition of individuals vocally has received particular attention due, in part, to the insights it provides regarding the cognitive processes that underlie this skill. While much work has focused on vocal individual recognition in primates, there is currently very little data showing comparable skills in non-primate mammals under natural conditions. This may be because non-primate mammal societies do not provide obvious contexts in which vocal individual recognition can be rigorously tested. We addressed this gap in understanding by designing an experimental paradigm to test for individual recognition in meerkats (Suricata suricatta) without having to rely on naturally occurring social contexts. Results suggest that when confronted with a physically impossible scenario—the presence of the same conspecific meerkat in two different places—subjects responded more strongly than during the control, a physically possible setup. We argue that this provides the first clear evidence for vocal individual recognition in wild non-primate mammals and hope that this novel experimental design will allow more systematic cross-species comparisons of individual recognition under natural settings.
Elastodynamics of radially inhomogeneous spherically anisotropic elastic materials in the Stroh formalism
Authors: Norris A. N. , Shuvalov A. L.
Published: October 2011

A method for solving elastodynamic problems in radially inhomogeneous elastic materials with spherical anisotropy is presented, i.e. materials having
c

ijkl

=
c

ijkl

(
r
) in a spherical coordinate system {
r
,
θ
,
ϕ
}. The time-harmonic displacement field
u
(
r
,
θ
,
ϕ
) is expanded in a separation of variables form with dependence on
θ
,
ϕ
described by vector spherical harmonics with
r
-dependent amplitudes. It is proved that such separation of variables solution is generally possible only if the spherical anisotropy is restricted to transverse isotropy (TI) with the principal axis in the radial direction, in which case the amplitudes are determined by a first-order ordinary differential system. Restricted forms of the displacement field, such as
u
(
r
,
θ
), admit this type of separation of variables solution for certain lower material symmetries. These results extend the Stroh formalism of elastodynamics in rectangular and cylindrical systems to spherical coordinates.
Alternative derivation of the Feigel effect and call for its experimental verification
Authors: Croze Ottavio A.
Published: October 2011

A recent theory by Feigel predicts the finite transfer of momentum from a quantum vacuum to a fluid placed in strong perpendicular electrical and magnetic fields. The momentum transfer arises because of the optically anisotropic magnetoelectric response induced in the fluid by the fields. After summarizing Feigel's original assumptions and derivation (corrected of trivial mistakes), we rederive the same result by a simpler route, validating Feigel's semiclassical approach. We then derive the stress exerted by the vacuum on the fluid that, if the Feigel hypothesis is correct, should induce a Poiseuille flow in a tube with maximum speed at ≈100 μm s
−1
(2000 times larger than Feigel's original prediction). An experiment is suggested to test this prediction for an organometallic fluid in a tube passing through the bore of a high-strength magnet. The predicted flow can be measured directly by tracking microscopy or indirectly by measuring the flow rate (≈1 ml min
−1
) corresponding to the Poiseuille flow. A second experiment is also proposed, whereby a ‘vacuum radiometer’ is used to test a recent prediction that the net force on a magnetoelectric slab in the vacuum should be zero.
Promiscuity and the evolution of cooperative breeding
Authors: Leggett Helen C. , El Mouden Claire , Wild Geoff , West Stuart
Published: October 2011

Empirical data suggest that low levels of promiscuity have played a key role in the evolution of cooperative breeding and eusociality. However, from a theoretical perspective, low levels of promiscuity can favour dispersal away from the natal patch, and have been argued to select against cooperation in a way that cannot be explained by inclusive fitness theory. Here, we use an inclusive fitness approach to model selection to stay and help in a simple patch-structured population, with strict density dependence, where helping increases the survival of the breeder on the patch. Our model predicts that the level of promiscuity has either no influence or a slightly positive influence on selection for helping. This prediction is driven by the fact that, in our model, staying to help leads to increased competition between relatives for the breeding position—when promiscuity is low (and relatedness is high), the best way to aid relatives is by dispersing to avoid competing with them. Furthermore, we found the same results with an individual-based simulation, showing that this is not an area where inclusive fitness theory ‘gets it wrong’. We suggest that our predicted influence of promiscuity is sensitive to biological assumptions, and that if a possibly more biologically relevant scenario were examined, where helping provided fecundity benefits and there was not strict density dependence, then low levels of promiscuity would favour helping, as has been observed empirically.
Relationship satisfaction and outcome in women who meet their partner while using oral contraception
Authors: Roberts S. Craig , Klapilová Kateřina , Little Anthony C. , Burriss Robert P. , Jones Benedict C. , DeBruine Lisa M. , Petrie Marion , Havlíček Jan
Published: October 2011

Hormonal variation over the menstrual cycle alters women's preferences for phenotypic indicators of men's genetic or parental quality. Hormonal contraceptives suppress these shifts, inducing different mate preference patterns among users and non-users. This raises the possibility that women using oral contraception (OC) choose different partners than they would do otherwise but, to date, we know neither whether these laboratory-measured effects are sufficient to exert real-world consequences, nor what these consequences would be. Here, we test for differences in relationship quality and survival between women who were using or not using OC when they chose the partner who fathered their first child. Women who used OC scored lower on measures of sexual satisfaction and partner attraction, experienced increasing sexual dissatisfaction during the relationship, and were more likely to be the one to initiate an eventual separation if it occurred. However, the same women were more satisfied with their partner's paternal provision, and thus had longer relationships and were less likely to separate. These effects are congruent with evolutionary predictions based on cyclical preference shifts. Our results demonstrate that widespread use of hormonal contraception may contribute to relationship outcome, with implications for human reproductive behaviour, family cohesion and quality of life.