bluuebunny/crossref_metadata_2025 huggingface dataset:
Manipulating emission of CdTeSe nanocrystals embedded in three-dimensional photonic crystals
Authors: Vion Céline , Barthou Carlos , Bénalloul Paul , Schwob Catherine , Coolen Laurent , Gruzintev Alex , Emel’chenko Gennadii , Masalov Vladimir , Frigerio Jean-Marc , Maître Agnès
Published: June 2009

We report experimental and theoretical results on the photoluminescence of CdTeSe nanocrystals, embedded in a silica opaline structure by infiltration of a highly diluted solution. Strong modification of emission diagrams of embedded nanocrystals have been observed in good agreement with theoretical models. At macroscopic scale, we measured the difference of nanocrystals emission lifetime embedded either in an opal for which the emission is in the gap, or in an opal of smaller balls diameter for which the emission is outside the gap. The photonic bandgap effect leads to a lifetime increase of the order of 10%. These lifetime variations are shown to be in good agreement with the calculated local density of states modification due to the pseudogap.
Symmetry reduction of quasi-free states
Authors: Torre C. G.
Published: June 2009

Given a group-invariant quasi-free state on the algebra of canonical commutation relations (CCR), we show how group averaging techniques can be used to obtain a symmetry-reduced CCR algebra and reduced quasi-free state. When the group is compact, this method of symmetry reduction leads to standard results which can be obtained using other methods. When the group is noncompact, the group averaging prescription relies on technically favorable conditions which we delineate. As an example, we consider symmetry reduction of the usual vacuum state for a Klein–Gordon field on Minkowski spacetime by a noncompact subgroup of the Poincaré group consisting of a 1-parameter family of boosts, a 1-parameter family of spatial translations and a set of discrete translations. We show that the symmetry-reduced CCR algebra and vacuum state correspond to that used by each of Berger, Husain, and Pierri for the polarized Gowdy T3 quantum gravity model.
Relaxor ferroelectric-like high effective permittivity in leaky dielectrics/oxide semiconductors induced by electrode effects: A case study of CuO ceramics
Authors: Li Ming , Feteira Antonio , Sinclair Derek C.
Published: June 2009

The electrical behavior of copper oxide (CuO) ceramics sintered at 920 °C has been characterized by a combination of fixed, radio frequency (rf) capacitance measurements, and impedance spectroscopy (IS). Fixed rf capacitance measurements on ceramics with sputtered Au electrodes revealed a temperature- and frequency-dependent high effective permittivity of ∼104 in the temperature range of 150–320 K. The response is similar to that observed for relaxor-ferroelectrics, however, the magnitude of the effect can be suppressed by thermal annealing of the ceramics with Au electrodes in air at 300 °C or by changing the work function of the electrode material by using In–Ga as opposed to Au. IS data analysis revealed the ceramics to be electrically heterogeneous semiconductors with a room temperature dc resistivity <104 Ω cm, consisting of semiconducting grains with relative permittivity, εr, <10 and slightly more resistive grain boundaries with “effective” permittivity, εeff, of ∼110. Samples with Au electrodes exhibited an additional low frequency response with εeff∼104. dc bias experiments showed the capacitance behavior of this additional response to obey the Mott–Schottky law and thus confirm it to be a non-Ohmic electrode contact. We conclude, therefore, that an electrode rather than a grain boundary effect is the primary source for the high effective permittivity in CuO ceramics, although the latter is also present and does give additional effective permittivity. This work demonstrates how an extrinsic effect associated with non-Ohmic electrode contacts can; (i) dominate the rf capacitance spectra of leaky dielectrics/oxide semiconductors over a wide temperature and frequency range; and, (ii) manifest a dielectric response more typically associated with relaxor-ferroelectrics.
Structure, thermal stability, and optical properties of boron modified nanocrystalline anatase prepared by chemical vapor synthesis
Authors: Ahmad Md. Imteyaz , Bhattacharya S. S. , Hahn Horst
Published: June 2009

Boron modified nanocrystalline anatase titania powders with boron contents varying from 0.5 to 6.2 wt % were synthesized by a chemical vapor synthesis process. High temperature x-ray diffraction studies revealed that the anatase powders containing more boron were more stable at higher temperatures. When present in small quantities (about 0.5 wt % or less), boron went into the structure of titania and lowered the direct band gap to 3.41 eV. On the other hand, higher boron contents resulted in smaller anatase crystallite sizes and partially offset the redshift. However, the excess boron formed boron oxide which probably coated the surface of the nanoparticles/crystallites resulting in improved high temperature stability of the anatase phase.
Local atomic structure around Ni, Nb, and Zr atoms in Ni–Nb–Zr–H glassy alloys studied by x-ray absorption fine structure method
Authors: Oji H. , Handa K. , Ide J. , Honma T. , Yamaura S. , Inoue A. , Umesaki N. , Emura S. , Fukuhara M.
Published: June 2009

To elucidate hydrogen effects on the atomic configuration of Ni–Nb–Zr–H glassy alloys exhibiting proton-tunneling-induced Coulomb oscillation, we investigated the local atomic configuration around the Ni, Nb, and Zr atoms by x-ray absorption fine structure (XAFS) method. The analysis of the XAFS spectra indicates that there is the significant difference in structural response between the Zr 30 and the Zr 40 at. % alloys when hydrogen atoms are charged; charging the hydrogen atoms basically does not alter the local structures around the three atoms for the Zr 30 at. % alloy but induces the elongation of the Zr–Zr, Zr–Nb, and Nb–Ni distances for the Zr 40 at. % alloy. The distorted icosahedral Zr5Ni5Nb3 clusters assembled in randomly packed manners for the possible models in the Ni–Nb–Zr glassy alloy are proposed. The sites where hydrogen atoms occupy are also inferred.
Enhanced photoluminescence in [Er2O3/TiO2]m photonic crystals
Authors: Grishin A. M. , Khartsev S. I. , Dzibrou D. O.
Published: June 2009

We survey optical properties of [Er2O3/TiO2]6/Er2O32/[TiO2/Er2O3]6 photonic crystals (PCs) pulsed laser deposited on to the glass substrates. The dispersion relations of refractive indexes and extinction coefficients of the constituent materials were obtained from the comparison of experimental and simulated transmission spectra of single layer Er2O3 and TiO2 reference films. Based on these data several PCs have been designed and grown to match stop band and cavity mode resonance at wavelengths close to the 523 nm Er3+-ion Fraunhofer S43/2 absorption line. Precise control of chemical composition and uniform multilayer thickness enable achievement of superior optical performance of sintered PCs. Obtained dispersion relations were combined with the 2×2 transfer matrix formalism to compute PC transmittance that appeared to be in a good agreement with the experimental spectra. Pumping PCs with 514 nm light source we observed a strong photoluminescence (PL) at 1535 nm. In PC specially designed for the resonance wavelength λres=514 nm, C-band PL intensity experiences fivefold enhancement compared to a single layer Er2O3 film of equivalent thickness.
High thermoelectric performance BiSbTe alloy with unique low-dimensional structure
Authors: Xie Wenjie , Tang Xinfeng , Yan Yonggao , Zhang Qingjie , Tritt Terry M.
Published: June 2009

We report a detailed description of an innovative route of a melt spinning (MS) technique combined with a subsequent spark plasma sintering process in order to obtain high performance p-type Bi0.52Sb1.48Te3 bulk material, which possesses a unique low-dimensional structure. The unique structure consists of an amorphous structure, 5–15 nm fine nanocrystalline regions, and coherent interfaces between the resulting nanocrystalline regions. Measurements of the thermopower, electrical conductivity, and thermal conductivity have been performed over a range of temperature of 300–400 K. We found that MS technique can give us considerable control over the resulting nanostructure with good thermal stability during the temperature range of 300–400 K and this unique structure can effectively adjust the transport of phonons and electrons, in a manner such that it is beneficial to the overall thermoelectric performance of the material, primarily a reduction in the lattice thermal conductivity. Subsequently, this results in a maximum figure of merit ZT value of 1.56 at 300 K for p-type Bi0.52Sb1.48Te3 bulk material. This ZT value is over a 50% improvement of that of the state of the art commercial Bi2Te3 materials. We also report results of thermal cycling of this material for over one hundred cycles between 300–400 K. Our work offers an innovative route for developing high performance bismuth telluride based alloys and devices, which have even broader prospects for commercial applications. This technique may also be applicable to other thermoelectric materials.
Microstructural and ferromagnetic properties of Zn1−xCuxO thin films
Authors: Samanta K. , Bhattacharya P. , Katiyar R. S.
Published: June 2009

Room temperature ferromagnetism is observed in Zn1−xCuxO (x=0.01, 0.03, and 0.05) thin films grown on Al2O3 substrates by pulsed laser deposition technique. Raman scattering and high resolution transmission electron microscopy analyses confirm the substitution of Cu up to 3% in ZnO host lattice, and the films are nearly single crystalline. Optical transmission and photoluminescence (PL) analyses provide evidence of sp-d exchange interaction in Zn1−xCuxO thin films; the p-d exchange interaction may explain the observed room temperature ferromagnetism in Zn1−xCuxO thin films. Room temperature PL shows the green emission (∼2.60 eV) in Cu doped ZnO samples.
Annealing effect on ion conduction of nanosized CaF2/BaF2 multilayers
Authors: Guo X. X. , Matei I. , Jin-Phillipp N. Y. , van Aken P. A. , Maier J.
Published: June 2009

The transient part of the ion conductivity enhancement in CaF2/BaF2 heterolayers on annealing at elevated temperatures is investigated. It is well established that annealed heterolayers exhibit a strongly increased F− conductivity parallel to the interfaces and a substantial but less strong enhancement perpendicular to the interfaces [N. Sata et al., Nature 408, 946 (2000) and X. X. Guo et al., Appl. Phys. Lett. 91, 103102 (2007)]. This is explained by a F− redistribution from BaF2 to CaF2 as a consequence of contact equilibrium. As to the behavior during annealing, two remarkable features are observed: (i) freshly prepared films show an even higher conductance enhancement if measured in the parallel direction, which decreases on annealing toward the equilibrium situation, while (ii) in the perpendicular direction the conductance variation is very small and of opposite sign. On the basis of the conductivity experiments as a function of temperature, layer-thickness, and anisotropy, in combination with structural investigations by transmission electron microscopy, we conclude that in agreement with earlier experience on composite materials, a high density of unstable defects is formed close to the heterointerfaces during multilayer preparation, which heals off during the temper process. In the final contact equilibrium a regular array of misfit dislocations is left, enabling the epitaxial contact. By assuming that the electroactive unstable microstructural defects are arranged at the heterointerfaces and are charged by fluoride ion trapping, we can explain the experimental features including the space charge overlap using the combined Mott–Schottky and Gouy–Chapman models used previously. The results indicate that the charge density stays approximately constant during the annealing process.
Completeness of a fermionic basis in the homogeneous XXZ model
Authors: Boos H. , Jimbo M. , Miwa T. , Smirnov F.
Published: June 2009

With the aid of the creation operators introduced in our previous works, we show how to construct a basis of the space of quasilocal operators for the homogeneous XXZ chain.
New electromagnetic particle simulation code for the analysis of spacecraft-plasma interactions
Authors: Miyake Yohei , Usui Hideyuki
Published: June 2009

A novel particle simulation code, the electromagnetic spacecraft environment simulator (EMSES), has been developed for the self-consistent analysis of spacecraft-plasma interactions on the full electromagnetic (EM) basis. EMSES includes several boundary treatments carefully coded for both longitudinal and transverse electric fields to satisfy perfect conductive surface conditions. For the longitudinal component, the following are considered: (1) the surface charge accumulation caused by impinging or emitted particles and (2) the surface charge redistribution, such that the surface becomes an equipotential. For item (1), a special treatment has been adopted for the current density calculated around the spacecraft surface, so that the charge accumulation occurs exactly on the surface. As a result, (1) is realized automatically in the updates of the charge density and the electric field through the current density. Item (2) is achieved by applying the capacity matrix method. Meanwhile, the transverse electric field is simply set to zero for components defined inside and tangential to the spacecraft surfaces. This paper also presents the validation of EMSES by performing test simulations for spacecraft charging and peculiar EM wave modes in a plasma sheath.
Effect of the exchange-correlation potential and of surface relaxation on the description of the H2O dissociation on Cu(111)
Authors: Fajín José L. C. , Illas Francesc , Gomes José R. B.
Published: June 2009

The role of the exchange-correlation density functional (PBE, PW91, RevPBE) and of surface relaxation in the determination of the adsorption energies, reaction energy barriers, and reaction rate constants has been analyzed taking water dissociation on Cu(111) surface as a test case. The PBE and PW91 functionals yield similar adsorption geometries and, adsorption and activation energies, but differ significantly from RevPBE results. For each of the functionals tested, surface relaxation was found to have only a minor effect on the calculated (co)adsorption geometries and (co)adsorption energies. The calculated energy barriers for water dissociation are more affected by the functional used, especially in the case of the RevPBE, with obvious implications on the calculated energy barriers and derived reaction rate constants.
Electron transport in carbon nanotube-silicon heterodimensional heterojunction array: An experimental investigation
Authors: Kuo Teng-Fang , Tzolov Marian B. , Straus Daniel A. , Xu Jimmy
Published: June 2009

Current-voltage experiments on a highly ordered array of carbon nanotubes interfaced with silicon reveal interesting features arising from the regular array of heterojunctions between one-dimensional (1D) and three-dimensional materials. At high temperature, the vertically aligned and ordered nanotubes behave as an array of point junction contacts to the silicon below, which merge into a planar junction as temperature decreases. This model is further supported by the observation of signature space charge limited conduction, whose origin is attributed to deep levels in the silicon substrate and to the strong field enhancement due to the quasi-1D nanotubes.
Absence of reptation in highly confined polymers
Authors: Srivastava S. , Basu J. K.
Published: June 2009

We present results of mechanical stress relaxation measurements on polymers confined at the air-water interface in the form of a monolayer. Systematic measurements allow, to our knowledge, for the first time, observation of the scaling of the stress relaxation time of the highly confined polymers as a function of both surface concentration and molecular weight. The observed scaling is found to be very close to that expected for motion of unentangled polymer solutions with hydrodynamic interactions. Our experimental observations thus clearly rule out the possibility of entanglement and hence reptation as a mode of relaxation in such highly confined polymeric systems.
Charge and spin dynamics in VO2 nanorods
Authors: Lee Kyu Won , Kweon Hyocheon , Park Jitae , Lee Cheol Eui
Published: June 2009

Electrical conductivity and photoconductivity measurements were carried out on vanadium dioxide (VO2) nanorods prepared by the hydrothermal treatment of vanadium pentoxide gels. While the structural properties of the nanorods resembled those of the Cr-doped VO2, the charge and spin dynamics appears to resemble those of the Nb-doped VO2. The magnetic and (photo)electrical properties of the nanorods can be understood in terms of localization of itinerant electrons giving rise to a spin-polarized (S=3/2) V4+ pair, dominant at higher temperatures, or to a (S=1) V3+ ion out of a V4+ ion pair, dominant at lower temperatures.
Amplified piezoelectric transduction of nanoscale motion in gallium nitride electromechanical resonators
Authors: Faucher Marc , Grimbert Bertrand , Cordier Yvon , Baron Nicolas , Wilk Arnaud , Lahreche Hacène , Bove Philippe , François Marc , Tilmant Pascal , Gehin Thomas , Legrand Christiane , Werquin Matthieu , Buchaillot Lionel , Gaquière Christophe , Théron Didier
Published: June 2009

A fully integrated electromechanical resonator is described that is based on high mobility piezoelectric semiconductors for actuation and detection of nanoscale motion. We employ the two-dimensional electron gas present at an AlGaN/GaN interface and the piezoelectric properties of this heterostructure to demonstrate a resonant high-electron-mobility transistor enabling the detection of strain variation. In this device, we take advantage of the polarization field divergence originated by mechanical flexural modes for generating piezoelectric doping. This enables a modulation of carrier density which results in a large current flow and thus constitutes a motion detector with intrinsic amplification.
10-nm-thick quinary (AlCrTaTiZr)N film as effective diffusion barrier for Cu interconnects at 900 °C
Authors: Chang Shou-Yi , Chen Dao-Sheng
Published: June 2009

In this study, an ultrathin quinary nitride film (AlCrTaTiZr)N of only 10 nm thick has been developed as a diffusion barrier layer for Cu interconnects. The (AlCrTaTiZr)N nanocomposite film was constructed of nanocrystallites embedded in an amorphous matrix. At an extremely high temperature of 900 °C, the Si/(AlCrTaTiZr)N/Cu film stack remained thermally stable. Neither interdiffusion between Si and Cu through the (AlCrTaTiZr)N layer nor formation of any silicides occurred. The nanocomposite structure and severe lattice distortions attributed to the addition of multiple elements were expected as the dominant factors for the superior diffusion resistance of the (AlCrTaTiZr)N film.
Regulatory T cell differentiation of thymocytes does not require a dedicated antigen-presenting cell but is under T cell-intrinsic developmental control
Authors: Wirnsberger Gerald , Mair Florian , Klein Ludger
Published: June 2009

The majority of regulatory T cells (T
regs
) are believed to be of thymic origin. It has been hypothesized that this may result from unique intrathymic environmental cues, possibly requiring a dedicated antigen-presenting cell (APC). However, T cell-intrinsic developmental regulation of the susceptibility to T
reg
differentiation remains a mutually non-exclusive scenario. We found that upon exposure of monoclonal T cells of sequential developmental stages to a thymic microenvironment expressing cognate antigen, the efficiency of T
reg
induction inversely correlated with progressive maturation. This inclination of immature thymocytes toward T
reg
differentiation was even seen in an APC-free in vitro system, providing only TCR stimulation and IL-2. In support of quantitative but not qualitative features of external cues being critical, thymic epithelial cells as well as different thymic dendritic cell (DC)-subtypes efficiently induced T
reg
development of immature thymocytes, albeit at strikingly different optimal doses of cognate antigen. We propose that the intrinsically high predisposition of immature thymocytes to T
reg
development may contribute to the predominantly thymic origin of the T
reg
repertoire. The underlying instructive stimulus, however, does not require unique features of a dedicated APC and can be delivered by hematopoietic as well as epithelial thymic stromal cells.
Visual and statistical comparison of metagenomes
Authors: Mitra Suparna , Klar Bernhard , Huson Daniel H.
Published: June 2009

Background: Metagenomics is the study of the genomic content of an environmental sample of microbes. Advances in the through-put and cost-efficiency of sequencing technology is fueling a rapid increase in the number and size of metagenomic datasets being generated. Bioinformatics is faced with the problem of how to handle and analyze these datasets in an efficient and useful way. One goal of these metagenomic studies is to get a basic understanding of the microbial world both surrounding us and within us. One major challenge is how to compare multiple datasets. Furthermore, there is a need for bioinformatics tools that can process many large datasets and are easy to use.

Results: This article describes two new and helpful techniques for comparing multiple metagenomic datasets. The first is a visualization technique for multiple datasets and the second is a new statistical method for highlighting the differences in a pairwise comparison. We have developed implementations of both methods that are suitable for very large datasets and provide these in Version 3 of our standalone metagenome analysis tool MEGAN.

Conclusion: These new methods are suitable for the visual comparison of many large metagenomes and the statistical comparison of two metagenomes at a time. Nevertheless, more work needs to be done to support the comparative analysis of multiple metagenome datasets.

Availability: Version 3 of MEGAN, which implements all ideas presented in this article, can be obtained from our web site at: www-ab.informatik.uni-tuebingen.de/software/megan.

Contact:  mitra@informatik.uni-tuebingen.de

Supplementary information:  Supplementary data are available at Bioinformatics online.
Executing multicellular differentiation: quantitative predictive modelling of C.elegans vulval development
Authors: Bonzanni Nicola , Krepska Elzbieta , Feenstra K. Anton , Fokkink Wan , Kielmann Thilo , Bal Henri , Heringa Jaap
Published: June 2009

Motivation: Understanding the processes involved in multi-cellular pattern formation is a central problem of developmental biology, hopefully leading to many new insights, e.g. in the treatment of various diseases. Defining suitable computational techniques for development modelling, able to perform in silico simulation experiments, is an open and challenging problem.

Results: Previously, we proposed a coarse-grained, quantitative approach based on the basic Petri net formalism, to mimic the behaviour of the biological processes during multicellular differentiation. Here, we apply our modelling approach to the well-studied process of Caenorhabditis elegans vulval development. We show that our model correctly reproduces a large set of in vivo experiments with statistical accuracy. It also generates gene expression time series in accordance with recent biological evidence. Finally, we modelled the role of microRNA mir-61 during vulval development and predict its contribution in stabilizing cell pattern formation.

Contact:  feenstra@few.vu.nl

Supplementary information:  Supplementary data are available at Bioinformatics online.
Intra‐aortic balloon counterpulsation as a bridge to heart transplantation does not impair long‐term survival
Authors: Gjesdal Ola , Gude Einar , Arora Satish , Leivestad Torbjørn , Andreassen Arne K. , Gullestad Lars , Aaberge Lars , Brunvand Harald , Edvardsen Thor , Geiran Odd R. , Simonsen Svein
Published: June 2009

Aims

There are few studies of the use of intra‐aortic balloon pump (IABP) treatment as a bridge to heart transplantation (HTx). This is the first study to compare long‐term clinical and haemodynamic outcomes in IABP‐treated HTx patients and electively transplanted patients.

Methods and results

This was a retrospective study of all adult HTx recipients between 2001 and 2007. Thirty‐two patients (aged 50 ± 13 years) treated with IABP, as a bridge to HTx due to severe hypo‐perfusion, were compared with 135 electively transplanted patients (aged 54 ± 11 years). The mean time from onset of IABP to HTx was 21 ± 16 days. Clinical condition improved during IABP treatment. Serum creatinine decreased from 128 ± 56 to 102 ± 29 µmol/L (P < 0.01), aspartate transaminase from 682 ± 1299 to 63 ± 89 U/L (P = 0.01), and ALAT from 483 ± 867 to 126 ± 284 U/L (P = 0.02). Intra‐aortic balloon pump treatment related complications were few. Mortality was similar in the IABP and control groups at 30 days post‐HTx (6.2 vs.3.7%, P = 0.54), at 1 year (9.4 vs.11.1%, P = 0.80), and beyond. Long‐term clinical and haemodynamic indices were similar in the two groups.

Conclusion

Intra‐aortic balloon pump treatment stabilizes patients in end‐stage heart failure, is safe, well tolerated, and is successful in bridging acutely decompensated patients to transplantation. Complications are few and manageable. Following IABP and HTx, short‐ and long‐term survival, biochemical and invasive and non‐invasive haemodynamic outcomes were similar to those in electively transplanted patients.
High Prevalence of Soil-transmitted Helminths in Western Kenya: Failure to Implement Deworming Guidelines in Rural Nyanza Province
Authors: Riesel Johanna N. , Ochieng’ Frederick O. , Wright Peter , Vermund Sten H. , Davidson Mario
Published: June 2009

Soil-transmitted helminth (STH) infections affect an estimated 2 billion people world wide. Children experience the greatest morbidity, limiting their potential in academic and physical endeavors. Our study assessed the prevalence of STH infections in primary school-aged children in a rural village in the Nyanza Province of Kenya. Over two-thirds (68%) of the sampled population tested positive using a direct smear microscopic analysis of single stool samples. Only heavy worm infections would be detected with this technique; thus 68% is a minimum estimate of prevalence. Prior to our study, there were no deworming programs in this village, despite WHO and Kenyan government guidelines supporting regular deworming programs. Our study demonstrates the significant burden of STH infections in a rural Kenyan village and highlights the need for deworming programs in similar venues. We also demonstrate that with basic infrastructure and community involvement, regular deworming can be implemented effectively in remote, rural communities.
Maternal yolk androgens stimulate territorial behaviour in black-headed gull chicks
Authors: Müller Wendt , Dijkstra Cor , Groothuis Ton G. G.
Published: June 2009

Avian eggs contain substantial amounts of maternal androgens. The concentrations of these yolk androgens are affected by the maternal environment, such as the level of social competition, parasite exposure or food conditions. Since yolk androgens have been shown to affect a wide array of offspring traits, they may adjust the chicks to the expected post-hatching environment, but experimental evidence is still scarce. We investigate in colonial breeding black-headed gulls whether high concentrations of yolk androgens, such as those found in environments with high numbers of social interactions, facilitate aggressiveness and territorial behaviour of the chicks. Black-headed gulls are highly suitable for this, as the semi-precocial chicks defend the natal territory and food against intruders. We manipulated yolk androgen concentrations and investigated their role in both within-nest and between-nest aggression. We found that chicks hatching from androgen-treated eggs defended the natal territory more often than their nest mates from control eggs, without increasing sibling aggression. This suggests that variation in yolk androgen concentrations in relation to the social environment of the mother may indeed allow adjustment of the offspring's behaviour to the expected frequency of territorial interactions with conspecifics post-hatching.
Courtship dives of Anna's hummingbird offer insights into flight performance limits
Authors: Clark Christopher James
Published: June 2009

Behavioural displays are a common feature of animal courtship. Just as female preferences can generate exaggerated male ornaments, female preferences for dynamic behaviours may cause males to perform courtship displays near intrinsic performance limits. I provide an example of an extreme display, the courtship dive of Anna's hummingbird (Calypte anna). Diving male Anna's hummingbirds were filmed with a combination of high-speed and conventional video cameras. After powering the initial stage of the dive by flapping, males folded their wings by their sides, at which point they reached an average maximum velocity of 385 body lengths s−1(27.3 m s−1). This is the highest known length-specific velocity attained by any vertebrate. This velocity suggests their body drag coefficient is less than 0.3. They then spread their wings to pull up, and experienced centripetal accelerations nearly nine times greater than gravitational acceleration. This acceleration is the highest reported for any vertebrate undergoing a voluntary aerial manoeuvre, except jet fighter pilots. Stereotyped courtship behaviours offer several advantages for the study of extreme locomotor performance, and can be assessed in a natural context.
The effect of cryptic female choice on sex allocation in simultaneous hermaphrodites
Authors: van Velzen Ellen , Schärer Lukas , Pen Ido
Published: June 2009

Sex allocation theory for simultaneous hermaphrodites has focused primarily on the effects of sperm competition, but the role of mate choice has so far been neglected. We present a model to study the coevolution of cryptic female choice and sex allocation in simultaneous hermaphrodites. We show that the mechanism of cryptic female choice has a strong effect on the evolutionary outcome: if individuals remove a fixed proportion of less-preferred sperm, the optimal sex allocation is more female biased (i.e. more biased towards egg production) than without cryptic female choice; conversely, if a fixed amount of sperm is removed, sex allocation is less female-biased than without cryptic female choice, and can easily become male biased (i.e. biased towards sperm production). Under male-biased sex allocation, hermaphroditism can become unstable and the population can split into pure males and hermaphrodites with a female-biased allocation. We discuss the idea that the evolution of sex allocation may depend on the outcome of sexual conflict over the fate of received sperm: the sperm donor may attempt to manipulate or by-pass cryptic female choice and the sperm recipient is expected to resist such manipulation. We conclude that cryptic female choice can have a strong influence on sex allocation in simultaneous hermaphrodites and strongly encourage empirical work on this question.
The benefits of social capital: close social bonds among female baboons enhance offspring survival
Authors: Silk Joan B. , Beehner Jacinta C. , Bergman Thore J. , Crockford Catherine , Engh Anne L. , Moscovice Liza R. , Wittig Roman M. , Seyfarth Robert M. , Cheney Dorothy L.
Published: June 2009

Sociality has evolved in many animal taxa, but primates are unusual because they establish highly differentiated bonds with other group members. Such bonds are particularly pronounced among females in species like baboons, with female philopatry and male dispersal. These relationships seem to confer a number of short-term benefits on females, and sociality enhances infant survival in some populations. However, the long-term consequences of social bonds among adult females have not been well established. Here we provide the first direct evidence that social relationships among female baboons convey fitness benefits. In a group of free-ranging baboons,
Papio cynocephalus ursinus
, the offspring of females who formed strong social bonds with other females lived significantly longer than the offspring of females who formed weaker social bonds. These survival benefits were independent of maternal dominance rank and number of kin and extended into offspring adulthood. In particular, females who formed stronger bonds with their mothers and adult daughters experienced higher offspring survival rates than females who formed weaker bonds. For females lacking mothers or adult daughters, offspring survival was closely linked to bonds between maternal sisters. These results parallel those from human studies, which show that greater social integration is generally associated with reduced mortality and better physical and mental health, particularly for women.
Pushed for time or saving on fuel: fine-scale energy budgets shed light on currencies in a diving bird
Authors: Shepard Emily L. C. , Wilson Rory P. , Quintana Flavio , Gómez Laich Agustina , Forman Dan W.
Published: June 2009

Animals may forage using different currencies depending on whether time minimization or energy maximization is more pertinent at the time. Assessment of net energy acquisition requires detailed information on instantaneous activity-specific power use, which varies according to animal performance, being influenced, for example, by speed and prey loading, and which has not been measured before in wild animals. We used a new proxy for instantaneous energy expenditure (overall dynamic body acceleration), to quantify foraging effort in a model species, the imperial shagPhalacrocorax atriceps, during diving. Power costs varied nonlinearly with depth exploited owing to depth-related buoyancy. Consequently, solutions for maximizing the gross rate of gain and energetic efficiency differed for dives to any given depth. Dive effort in free-ranging imperial shags measured during the breeding season was consistent with a strategy to maximize the gross rate of energy gain. We suggest that the divergence of time and energy costs with dive depth has implications for the measurement of dive efficiency across diverse diving taxa.
Real-time PCR detection of the mg219 gene of unknown function of Mycoplasma genitalium in men with and without non-gonococcal urethritis and their female partners in England
Authors: Chalker Victoria J. , Jordan Karen , Ali Tahir , Ison Cathy
Published: June 2009

Real-time PCR was employed to detect a region of the Mycoplasma genitalium
mg219 gene, a gene of unknown function, in clinical samples. Amplification of DNA and signal production from 15 other species of human mycoplasmas and 14 other bacteria and viruses did not occur. Using a panel of 208 genital and rectal samples, the sensitivity when compared to the modified mgpa gene (encoding the major surface protein MgPa) real-time PCR assay was found to be 100 % and the specificity of the assay 99.5 % with a positive predictive value of 80 % and a negative predictive value of 100 %. The mg219 gene was found to be in all strains of M. genitalium and was highly conserved. M. genitalium was detected in 3.9 % (11/280, 95 % CI 2.1–6.9) of all male specimens, in 7.7 % (10/130, 95 % CI 4.1–13.7) of patients with non-gonococcal urethritis (NGU) and in 0.7 % (1/150, 95 % CI <0.01–4.1) of patients without urethritis. The presence of M. genitalium was significantly associated with NGU (P ≤0.01; 95 % Cl 0.88–0.98) and non-chlamydial-non-gonococcal urethritis (P=0.0005; 95 % Cl 0.84–0.97).
Prevalence of multidrug-resistant Helicobacter pylori in Bulgaria
Authors: Boyanova Lyudmila
Published: June 2009

The aim of this study was to evaluate the presence and prevalence of multidrug antibacterial resistance inHelicobacter pyloriin Bulgaria from 2005 to 2008. The resistance in 828 untreated adults, 124 treated adults and 105 untreated children was, respectively, 26.5, 50.8 and 16.2 % for metronidazole; 18.4, 45.2 and 19 % for clarithromycin; 1, 2.4 and 0 % for amoxicillin; 4.4, 10.6 and 1.9 % for tetracycline; and 9, 14.5 and 5.8 % for ciprofloxacin. Triple resistance to the evaluated agents was uncommon and was detected in 1 % of the untreated children, 3.5 % of the untreated adults and 13.6 % of the treated adults. FiveH. pyloristrains were resistant to amoxicillin, metronidazole and clarithromycin, two of them exhibiting quadruple resistance. Resistance to four of the five antibacterials tested was found in 0.7 % of the untreated and 1.8 % of the treated adults. The overall level of multidrug resistance in the treated adults (15.4 %) was higher than that in the untreated adults (4.2 %,P=0.0001) and the untreated children (1 %,P=0.0001). The presence of multidrugH. pyloriresistance in Bulgaria could be associated with many factors, among them the slightly increasing national use of macrolides, lincosamides and streptogramins and of quinolones since 2000, the significant increase in primaryH. pyloriclarithromycin resistance, the high tetracycline use between 1994 and 1999, and, in individual cases, the use of azithromycin-based regimens or reuse of nitroimidazoles. In conclusion, for the first time in a European country during the last 5 years,H. pyloristrains harbouring a worrying quadruple antibacterial resistance were found in treated as well as in untreated patients.H. pylorisusceptibility patterns have a tendency to become unpredictable and should be monitored constantly at both national and global levels.
High-Throughput Quantification of Root Growth Using a Novel Image-Analysis Tool
Authors: French Andrew , Ubeda-Tomás Susana , Holman Tara J. , Bennett Malcolm J. , Pridmore Tony
Published: June 2009

Measuring the dynamics of plant growth is fundamental to the understanding of plant development processes. This paper describes a high-throughput, automatic method to trace Arabidopsis (Arabidopsis thaliana) seedling roots grown on agarose plates. From the trace, additional software can quantify length, curvature, and stimulus response parameters such as onset of gravitropism. The method combines a particle-filtering algorithm with a graph-based method to trace the center line of a root. This top-down approach is robust to a variety of noise effects and is reasonably flexible across different image sets. The resulting tool requires minimal interaction from the user and is able to process long time-lapse sequences with user interaction only required on the first frame. The tool is described first, followed by its use on two sample data sets, one measuring root length and the other additionally analyzing the gravitropic response and curvature. The tool, RootTrace, is open source; both the program and source code will be available online.
Presence of HCV‐RNA after ultracentrifugation of serum samples during the follow‐up of chronic hepatitis C patients with a sustained virological response may predict reactivation of hepatitis C virus infection
Authors: CASTILLO I. , BARTOLOMÉ J. , QUIROGA J. A. , BARRIL G. , CARREÑO V.
Published: June 2009

Background  Concentration of viral particles by ultracentrifugation of serum prior to PCR allows detection of hepatitis C virus (HCV) RNA in patients with undetectable viral RNA by conventional PCR assays.

Aim  To analyse if HCV‐RNA is detected after serum ultracentrifugation in chronic hepatitis C patients with a sustained virological response to antiviral therapy (defined as serum HCV‐RNA negativity by conventional assays 6 months after the end of therapy).

Methods  HCV‐RNA was tested using real‐time PCR in ultracentrifuged sera collected during the post‐treatment follow‐up (mean: 42 ± 27 months) in 57 sustained virological responders (SVR).

Results  After serum ultracentrifugation, HCV‐RNA was detected on at least one occasion during the follow‐up in 29/57 (51%) SVR. Thirteen (23%) of these 57 SVR suffered a reactivation 18 ± 8 months after the end of therapy (reappearance of serum HCV‐RNA detectable by conventional assays). Among reactivated patients, 11/13 (85%) had HCV‐RNA in ultracentrifuged serum samples (detectable 10 ± 5 months before reactivation), while HCV‐RNA was positive after ultracentrifugation in 18/44 (41%) long‐term SVR (P = 0.01). Persistence of detectable HCV‐RNA after serum ultracentrifugation was associated with reactivation (P = 0.001).

Conclusions  Serum ultracentrifugation prior to PCR allows detection of HCV‐RNA in SVR and its persistence may predict late reactivation.
Epistasis and the evolutionary dynamics of measured genotypic values during simulated serial bottlenecks
Authors: JARVIS J. P. , CHEVERUD J. M.
Published: June 2009

The evolutionary effects of epistasis have been primarily explored analytically and most empirical studies have utilized yeast, viral and bacterial populations. Empirical analyses in multi‐cellular organisms are rare because of experimental constraints. Here, we report the results of a genome‐wide scan for two‐way epistasis in 16 traits related to body size and composition in F2 mice from the LG/J by SM/J intercross. We analyze two‐locus genotypic values at quantitative trait loci (QTL), which provides an especially detailed view of epistatic architectures, to evaluate their predicted evolutionary consequences via Monte Carlo simulations. Epistatic profiles vary, but all traits show complicated genetic architectures which are largely hidden in single locus QTL scans. On average, detected epistatic effects are comparable in size to marginal effects. Simulations demonstrate an expected preservation, and often inflation, of heritable variance across several generations of small effective population size for many identified epistatic pairs over a range of starting allele frequencies.
Microbial colonisation of artificial and deep‐sea sediments in the Arctic Ocean
Authors: Kanzog Corinna , Ramette Alban
Published: June 2009

Although environmental factors such as grain size and organic carbon content may influence the distribution of microbes in marine sediments, there has been little experimental study of the topic to date. To investigate how those sediment variables affect microbial colonisation under in situ conditions, deep‐sea sediments and artificial sediments (glass beads, sands) were incubated in the Arctic deep sea at 2500 m water depth with or without chitin, one of the most important carbon polymers in marine environments. Microbial abundance, biomass, chitobiase activity and changes in community structure were monitored after 7 days and 1 year. In control sediments without chitin addition, no significant changes in microbial abundance, biomass and activity were observed after 1 year. In the presence of chitin, however, considerable increases in these parameters were recorded in all three sediment types tested. Regardless of chitin addition, natural deep‐sea sediments were always associated with higher values of microbial abundance, biomass and activity compared with artificial sediments. Sediment type was always found to be the most significant factor explaining variation in enzymatic activity and bacterial community structure as compared to the effects of chitin amount, incubation time, and changes in cell number or biomass. Overall, this is the first in situ study that has addressed the effects of multiple factors and their interactions on abundance, biomass, activity and community structure of microbial communities in the deep Arctic Ocean.
Meta‐analysis of physiological effects of skin‐to‐skin contact for newborns and mothers
Authors: Mori Rintaro , Khanna Rajesh , Pledge Debbie , Nakayama Takeo
Published: June 2009

Background:  Skin‐to‐skin care has been adopted all over the world, although physiological changes during or after it have not been evaluated very well. The purpose of the present study was therefore to investigate whether skin‐to‐skin contact for newborn babies and their mothers affects body temperature, heart rate and oxygen saturation of the babies.

Methods:  Studies investigating body temperature, heart rate and oxygen saturation of babies during and/or after skin‐to‐skin contact were systematically searched and reviewed. Meta‐analyses to examine the effects and meta‐regression analyses to investigate correlations between the effects and birthweight, duration of the care, environmental temperature, and resources of the setting, were conducted.

Results:  A total of 23 studies were included. Meta‐analyses showed evidence of an increase in body temperature (weighted mean difference [WMD] 0.22°C, P < 0.001) and a decrease in saturation of babies (WMD −0.60%; P= 0.01) during skin‐to‐skin care, compared with those before skin‐to‐skin care. Increase in body temperature was more evident in middle–low‐income settings (WMD, 0.61°C, P < 0.001) than high‐income settings (WMD 0.20°C, P < 0.001). Both the positive effect on body temperature and the negative effect on saturation were more marked in cold environments than where the environmental temperature was higher (WMD 0.18°C, P < 0.001; WMD −0.82%, P= 0.02).

Conclusion:  Skin‐to‐skin care is effective in increasing the body temperature of babies, especially where resources are limited and the environment is cold. Decreased oxygen saturation of the babies, however, warrants further prospective studies to confirm the findings.
Matrix composition and community structure analysis of a novel bacterial pyrite leaching community
Authors: Ziegler Sibylle , Ackermann Sonia , Majzlan Juraj , Gescher Johannes
Published: June 2009

Here we describe a novel bacterial community that is embedded in a matrix of carbohydrates and bio/geochemical products of pyrite (FeS2) oxidation. This community grows in stalactite‐like structures – snottites – on the ceiling of an abandoned pyrite mine at pH values of 2.2–2.6. The aqueous phase in the matrix contains 200 mM of sulfate and total iron concentrations of 60 mM. Micro‐X‐ray diffraction analysis showed that jarosite [(K,Na,H3O)Fe3(SO4)2(OH)6] is the major mineral embedded in the snottites. X‐ray absorption near‐edge structure experiments revealed three different sulfur species. The major signal can be ascribed to sulfate, and the other two features may correspond to thiols and sulfoxides. Arabinose was detected as the major sugar component in the extracellular polymeric substance. Via restriction fragment length polymorphism analysis, a community was found that mainly consists of iron oxidizing Leptospirillum and Ferrovum species but also of bacteria that could be involved in dissimilatory sulfate and dissimilatory iron reduction. Each snottite can be regarded as a complex, self‐contained consortium of bacterial species fuelled by the decomposition of pyrite.
The role of pioglitazone in modifying the atherogenic lipoprotein profile
Authors: Hanefeld M.
Published: June 2009

Pioglitazone, a thiazolidinedione, has established efficacy in improving glycaemic control in patients with type 2 diabetes. Pioglitazone also improves components of the mixed dyslipidaemia profile common in these patients, as typified by raised levels of plasma triglycerides, low levels of HDL cholesterol (HDL‐C) and a raised proportion of LDL cholesterol (LDL‐C) occurring as the small dense subfraction. In head‐to‐head trials, pioglitazone has consistently shown superior benefits on LDL‐C and HDL‐C as well as triglycerides compared with rosiglitazone and sulphonylureas. Pioglitazone used as monotherapy or combination therapy reduces levels of small dense LDL3 particles while raising levels of larger and less atherogenic LDL fractions. In addition, pioglitazone reduces cholesterol load and particle numbers of LDL3. Importantly, the differential effects of pioglitazone on LDL subfractions are complimentary and additive to those of simvastatin. Pioglitazone increases total HDL‐C levels by 10–20%, mainly because of an increase in the larger HDL2 subfraction. Pioglitazone also significantly reduces plasma triglyceride levels by 10–25%. In recent studies, pioglitazone significantly reduced carotid and coronary atherosclerosis compared with the sulphonylurea glimepiride. The antidyslipidaemic effects of pioglitazone – in particular, improvements in HDL‐C and reduction of small dense LDL3– may have contributed to these effects.