bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of effective permeability and resonance frequency for barium-ferrite∕epoxy composites
Authors: Li Z. W. , Gan Y. B. , Xin Xu , Lin G. Q.
Published: April 2008

Effective static permeability μ0,e and effective resonance frequency fR,e have been studied for barium-ferrite∕epoxy composites with various volume concentrations p. As compared to bulk material, effective μ0,e is significantly small and effective fR,e is shifted to higher frequency. Further, both μ0,e and fR,e show nonlinear dependence on p. To understand these characteristics, a model that considers two-particle system and the demagnetizing interaction between the two particles in composites is proposed. Based on the model, two equations have been derived to predict the dependence of μ0,e and fR,e on p, which is consistent with the experimental result for barium-ferrite composites with c-plane anisotropy. In addition, an important correlation (μ0,e−1)fR,e2=pC, which is similar to Snoek’s law, is also obtained from the equations.
Phonon confinement and electron transport in GaAs-based quantum cascade structures
Authors: Gao X. , Botez D. , Knezevic I.
Published: April 2008

We present a detailed investigation of the effects that optical-phonon confinement has on the electronic transport properties of GaAs-based midinfrared multiple-quantum-well (MQW) quantum cascade lasers (QCLs). The macroscopic dielectric continuum model is used to describe the interface (IF) and confined (CF) optical phonon modes. Dispersions of the IF modes are obtained by using the transfer matrix method with periodic boundary conditions. Normalization coefficients of the IF and CF potentials are derived in detail for MQW structures consisting of arbitrary combinations of binary and ternary alloys. Interstage and intrastage scattering rates due to all the IF and CF modes are calculated for both Γ- and X-valley electrons. The IF and CF scattering processes, in addition to the electron-electron and intervalley phonon scattering, are fully incorporated into the multivalley Monte Carlo simulation of a deep-active-well 6.7μm GaAs-based MQW QCL. At both 77K and room temperature, we find that phonon confinement enhances the electron-polar optical phonon scattering rates to a relatively small extent and induces minor corrections to the current, population inversion, and the electronic temperature with respect to the results obtained in the bulk-phonon approximation. Therefore, the bulk-phonon approximation in transport simulations of GaAs-based QCLs remains valuable due to its simplicity and high accuracy.
Work function thermal stability of RuO2-rich Ru–Si–O p-channel metal-oxide-semiconductor field-effect transistor gate electrodes
Authors: Ťapajna M. , Rosová A. , Dobročka E. , Štrbík V. , Gaži Š. , Fröhlich K. , Benko P. , Harmatha L. , Manke C. , Baumann P. K.
Published: April 2008

We report on thermal stability of the effective work function (EWF) of RuO2-rich Ru–Si–O gate electrodes intended for high-performance p-channel metal-oxide-semiconductor field-effect transistors. The Ru–Si–O thin films, with the composition 15% and 40% of SiO2, were grown by atomic vapor deposition at either 380 or 450°C on SiO2∕Si substrate. The Ru–Si–O thin film with 15% of SiO2 deposited at 450°C was evaluated as the most thermally stable gate electrode showing the EWF of 5.0eV after rapid thermal annealing (RTA) at 800°C∕10s in nitrogen followed by forming gas annealing (FGA). Transmission electron microscopy studies show that Ru–Si–O films are composed of RuO2-rich nanograins embedded in the SiO2-rich amorphous matrix. The Ru–Si–O films show enhanced thermal stability, as we observe reduction of RuO2 to Ru nanograins without disintegration of the layers after RTA at 900°C∕10s and subsequent FGA 430°C∕30min. Resistivity of the Ru–Si–O films as a function of temperature was found to be dependent on composition as well as deposition temperature. Resistivity of the Ru–Si–O film with 15% of SiO2 deposited at 450°C shows metalliclike character with a residual resistivity ratio of 1.3. The effect of RTA and FGA on the resistivity of the Ru–Si–O films is discussed in terms of the increase in connectivity and grain size.
Transmittance and optical constants of Ce films in the 6–1200eV spectral range
Authors: Fernández-Perea Mónica , Aznárez José A. , Larruquert Juan I. , Méndez José A. , Poletto Luca , Garoli Denis , Marco Malvezzi A. , Giglia Angelo , Nannarone Stefano
Published: April 2008

The optical constants of Ce films were obtained in the 6–1200eV range from transmittance measurements obtained at room temperature. Thin films of Ce were deposited by evaporation in ultrahigh vacuum conditions and their transmittance was measured in situ. Ce films were deposited onto grid-supported, thin C films. Transmittance measurements of various film thicknesses were used to obtain the extinction coefficient k of Ce films at each individual photon energy investigated. The refractive index n of Ce was calculated with the Kramers–Krönig analysis using the current k data, which were extended toward smaller and larger energies with available data from literature and extrapolations. Ce has a low-absorption band right below O2,3 edge, with lowest absorption at 16.1eV. This makes Ce a promising material for the development of new filters and multilayer coatings below Ce O2,3 edge, in which few developments have been performed due to the lack of low-absorption materials. A good consistency of the data was evaluated through f and inertial sum rules.
Continuous wave operation of a spiral-shaped microcavity laser
Authors: Kim Chil-Min , Cho Jinhang , Lee Jinhyung , Rim Sunghwan , Lee Sang Hun , Oh Kwang Ryung , Kim Jong Hoi
Published: April 2008

We report a continuous wave laser output of a spiral-shaped InGaAs microcavity laser. When the boundary of the cavity is selectively pumped by current injection with a dc current, the laser generates a directional emission around the notch. We investigate the characteristics of the cw laser operation and observe whispering gallery type modes, whose Q factor is about 7000.
Enhanced thermal conductivity and viscosity of copper nanoparticles in ethylene glycol nanofluid
Authors: Garg J. , Poudel B. , Chiesa M. , Gordon J. B. , Ma J. J. , Wang J. B. , Ren Z. F. , Kang Y. T. , Ohtani H. , Nanda J. , McKinley G. H. , Chen G.
Published: April 2008

This study investigates the thermal conductivity and viscosity of copper nanoparticles in ethylene glycol. The nanofluid was prepared by synthesizing copper nanoparticles using a chemical reduction method, with water as the solvent, and then dispersing them in ethylene glycol using a sonicator. Volume loadings of up to 2% were prepared. The measured increase in thermal conductivity was twice the value predicted by the Maxwell effective medium theory. The increase in viscosity was about four times of that predicted by the Einstein law of viscosity. Analytical calculations suggest that this nanofluid would not be beneficial as a coolant in heat exchangers without changing the tube diameter. However, increasing the tube diameter to exploit the increased thermal conductivity of the nanofluid can lead to better thermal performance.
Analysis of the off current in nanocrystalline silicon bottom-gate thin-film transistors
Authors: Esmaeili-Rad Mohammad R. , Sazonov Andrei , Nathan Arokia
Published: April 2008

The off current in bottom-gate nanocrystalline silicon (nc-Si) thin-film transistor (TFT) is shown to be determined by the conductivity of the channel layer and by the quality of the interface with the passivation nitride. Indeed, the presence of fixed charges at the nc-Si∕passivation nitride interface serves to increase the band bending, leading to an increase in the off current by about two orders of magnitude. In contrast, when the nc-Si channel layer is capped with hydrogenated amorphous silicon (a-Si:H), the off current decreases and is determined by the bulk conductivity of nc-Si, as the a-Si:H makes a less defective interface with the passivation nitride. The general effect of the gate and passivation nitride interfaces on band bending and transfer characteristics of the TFT is analyzed by numerical simulations. We find that the band bending due to fixed charges at the gate nitride interface is modulated by a negative gate voltage, while that due to fixed charges at the passivation nitride interface is not, leading to a high off current.
Overlayer effects in the critical-point analysis of ellipsometric spectra: Application to InxGa1−xAs alloys
Authors: Ghong T. H. , Kim T. J. , Jung Y. W. , Kim Y. D. , Aspnes D. E.
Published: April 2008

We investigate the effect of incomplete removal of semiconductor overlayers on critical-point (CP) parameters determined from the analysis of ellipsometric spectra. An approximate analytic expression shows that CP energies and broadening parameters should be relatively unaffected for isolated CPs if the dielectric response of the overlayer varies slowly with energy. The results are confirmed by model calculations for InAs, which show that the energies of the E1 and E1+Δ1 CP structures that are commonly used for compositional analysis of semiconductor alloys are relatively unaffected. We also analyze overlayer-removal data for a series of InxGa1−xAs alloy samples. Consistent with the above, the amplitudes and phases are affected significantly for all CPs, while the energies of the well-separated E1 and E1+Δ1 transitions are relatively invariant. The results show that accurate values of composition can be obtained from the analysis of the E1 and E1+Δ1 CP structures, even if complete removal of overlayers is not achieved.
Optical properties of rocksalt and zinc blende AlN phases: First-principles calculations
Authors: Cheng Y. C. , Wu X. L. , Zhu J. , Xu L. L. , Li S. H. , Chu Paul K.
Published: April 2008

We investigate the electronic structures and optical properties of the wurtzite, zinc blende, and rocksalt AlN phases at their structural phase transition pressures by the ultrasoft pseudopotential density functional method. We employ the Perdew–Burke–Eruzerhof form of the generalized gradient approximation available in the CASTEP code with the plane-wave basis sets to expand the periodic electron density. The dielectric function and optical properties such as reflectivity, absorption coefficient, refractive index, and electron energy-loss function are presented in a wide energy range between 0 and 50eV. Our results reveal that for rocksalt AlN phase, the intensity of N 2p orbitals in the conduction bands obviously decreases when the pressure increases from 15to17GPa. The calculated optical properties indicate that the zinc blende and wurtzite AlN phases have some similar features but the rocksalt AlN phase has other characteristics.
In-line phase-contrast imaging of a biological specimen using a compact laser-Compton scattering-based x-ray source
Authors: Ikeura-Sekiguchi H. , Kuroda R. , Yasumoto M. , Toyokawa H. , Koike M. , Yamada K. , Sakai F. , Mori K. , Maruyama K. , Oka H. , Kimata T.
Published: April 2008

Laser-Compton scattering (LCS) x-ray sources have recently attracted much attention for their potential use at local medical facilities because they can produce ultrashort pulsed, high-brilliance, and quasimonochromatic hard x rays with a small source size. The feasibility of in-line phase-contrast imaging for a “thick” biological specimens of rat lumbar vertebrae using the developed compact LCS-X in AIST was investigated for the promotion of clinical imaging. In the higher-quality images, anatomical details of the spinous processes of the vertebrae are more clearly observable than with conventional absorption radiography. The results demonstrate that phase-contrast radiography can be performed using LCS-X.
Optical properties of diatom silica frustule with special reference to blue light
Authors: Yamanaka Shigeru , Yano Rei , Usami Hisanao , Hayashida Nobuaki , Ohguchi Masakatsu , Takeda Hiroyuki , Yoshino Katsumi
Published: April 2008

Using fresh water diatom, identified as Melosira variance which is growing faster than other algae in the ponds, we characterized the ultrastructure of its silica frustule by electron microscopic observations. On hypothesizing that the ultrastructure has some meanings in photosynthesis, behaviors of a single frustule toward light irradiation were analyzed using an optical fiber. We found that the frustule absorbed light mainly in the blue wavelength region. The theoretical analyses of optical properties supported experimental results and suggested a strong interaction between blue light and inner silica materials. It is speculated that the interaction served for partial extinction of excessive irradiation of blue light and for enhancing photosynthesis of the diatom.
Delamination and magnetism softening of polycrystalline La0.9Ba0.1MnO3
Authors: Cui Yimin , Wang Rongming , Zhang Liuwan
Published: April 2008

Two ferromagnetic transitions have been found by temperature dependence ac susceptibility experiments on as-prepared bulk polycrystalline La0.9Ba0.1MnO3. Investigation indicates that the higher temperature transition (TCh) can be attributed to the oxygen excessive phase La0.9Ba0.1MnO3+δ at the surface, while the lower temperature transition (TCl) can be attributed to the interior stoichiometric phase La0.9Ba0.1MnO3 of the samples. Softening of ferromagnetic system near TCl has been observed in La0.9Ba0.1MnO3, which can be explained by the freezing of misorder of metal ion at higher temperature.
The two-dimensional phase of boron nitride: Few-atomic-layer sheets and suspended membranes
Authors: Pacilé D. , Meyer J. C. , Girit Ç. Ö. , Zettl A.
Published: April 2008

We describe the synthesis of very thin sheets (between a few and ten atomic layers) of hexagonal boron nitride (h-BN), prepared either on a SiO2 substrate or freely suspended. Optical microscopy, atomic force microscopy, and transmission electron microscopy have been used to characterize the morphology of the samples and to distinguish between regions of different thicknesses. Comparison is made to previous studies on single- and few-layer graphene. This synthesis opens the door to experimentally accessing the two-dimensional phase of boron nitride.
Optical loss in silicon microphotonic waveguides induced by metallic contamination
Authors: Barwicz Tymon , Holzwarth Charles W. , Rakich Peter T. , Popović Miloš A. , Ippen Erich P. , Smith Henry I.
Published: April 2008

Propagation losses are paramount to the performance of microphotonic devices. In silicon photonics, the expected contribution of known propagation-loss mechanisms is often insufficient to account for all the observed loss. Here, we identify a loss mechanism that we believe has not yet been reported in the literature. We observe loss reaching 70dB∕cm in silicon wire waveguides patterned in proximity of metals with low temperatures of silicide formation. The loss is attributed to formation of a dilute silicide at the waveguide sidewalls during reactive-ion etching. Sputtered metal atoms originate from exposed metal on the wafer surface or from the reactive-ion etcher chamber and react with the bare silicon of the waveguide sidewall being formed.
Dependence of electronic and optical properties on a high-frequency field for carbon nanotubes
Authors: Liao Wenhu , Zhou Guanghui , Ding Kai-He
Published: April 2008

We theoretically study the electronic structure, transport, and optical properties for a zigzag single-wall carbon nanotube (CNT) connected to two normal conductor leads under the irradiation of an external electromagnetic field at low temperatures, with particular emphasis on the features of high-frequency response. Using the standard nonequilibrium Green’s function techniques, we examine the time-averaged density of states (DOS), the conductivity, the dielectric function, and the electron energy loss spectra for the system with photon polarization parallel with the tunneling current direction, respectively. Through some numerical examples, it is shown that the DOS is strongly dependent on the incident electron energy, the strength, and frequency of the applied field. For higher electron energies in comparison with lead-nanotube coupling energy, the system conductance decreases with increasing field strength and increases with increasing field frequency, respectively, and shows some oscillation structures. Moreover, the optical functions for the system have also a rich structure with the variation of field frequency. It may demonstrate that this transport dependence on the external field parameters can be used to give the energy spectra information of CNTs and to detect the high-frequency microwave irradiation.
Anomalous magnetic ordering in b-axis-oriented orthorhombic HoMnO3 thin films
Authors: Lin T. H. , Hsieh C. C. , Shih H. C. , Luo C. W. , Uen T. M. , Wu K. H. , Juang J. Y. , Lin J.-Y. , Hsu C.-H. , Liu S. J.
Published: April 2008

Orthorhombic HoMnO3 films with well-aligned crystallographic orientations were deposited on LaAlO3(110) single crystal substrates by using pulsed laser deposition. The nearly perfect b-axis-oriented films provide the opportunity of investigating the orientation-dependent physical property of this material. The temperature dependent magnetization evidently displays an antiferromagnetic ordering near 42K, irrespective to the direction of applied field. Furthermore, the theoretically expected lock-in transition was clearly observed at around 30K when field was applied along the c axis and was undetectable along the a and b axes. The 30K transition was suppressed to 26K when the applied field increased from 100to500Oe.
Partial frequency band gap in one-dimensional magnonic crystals
Authors: Kostylev M. , Schrader P. , Stamps R. L. , Gubbiotti G. , Carlotti G. , Adeyeye A. O. , Goolaup S. , Singh N.
Published: April 2008

Collective spin wave modes propagating in an array of magnetic stripes coupled by dynamic dipole interaction are investigated by Brillouin light scattering. It is demonstrated that this structure supports propagation of discrete spin waves at any angle with respect to the stripes length. The data are interpreted using a theoretical model based on the Bloch wave approach. It is shown that, due to the one-dimensional artificial periodicity of the medium, the gaps in the spin wave spectrum are partial: the frequency passbands for propagation along the direction of periodicity overlap with the stop bands for propagation along the stripes.
Improved electrical performance of carbon nanotube thin film transistors by utilizing composite networks
Authors: Li Jiantong , Zhang Zhi-Bin , Östling Mikael , Zhang Shi-Li
Published: April 2008

This work presents a simple scheme of using composite carbon nanotube networks (c-CNNs) to significantly improve the electrical performance of long-channel thin film transistors based on single-walled carbon nanotubes (SWCNTs). Such c-CNNs comprise two sets of SWCNTs. A primary set consists of dense arrays of perfectly aligned long SWCNTs along the transistor channel direction. A secondary set is composed of short SWCNTs either randomly orientated or perpendicularly aligned with respect to the channel. While retaining a high on/off current ratio, the drive current in such c-CNNs is much higher than that in currently studied systems with single CNNs or SWCNT arrays.
Magnetic resonance hybridization and optical activity of microwaves in a chiral metamaterial
Authors: Li T. Q. , Liu H. , Li T. , Wang S. M. , Wang F. M. , Wu R. X. , Chen P. , Zhu S. N. , Zhang X.
Published: April 2008

The propagation of microwaves through a chiral metamaterial based on a magnetic dimer is experimentally studied. As proposed by our previous theoretical model, two resonance peaks are obtained in the transmission spectrum; these originate from the hybridization effect of magnetic resonance modes in this system. Optical activity is also observed in the transmission wave. The polarization state dramatically changes around the resonance frequency: the transmitted wave becomes elliptically polarized with its major polarization axis approximately perpendicular to that of the linear incident wave. This coupled magnetic dimer system provides a practical method to optically design tunable active medium and device.
Near-field thermal radiation between two closely spaced glass plates exceeding Planck’s blackbody radiation law
Authors: Hu Lu , Narayanaswamy Arvind , Chen Xiaoyuan , Chen Gang
Published: April 2008

This work reports experimental studies on radiative heat flux between two parallel glass surfaces. Small polystyrene particles are used as spacers to maintain a micron-sized gap between two optical flats. By carefully choosing the number of particles and performing the measurement in a high-vacuum environment, the experiment is designed to ensure that the radiative heat flux is the dominant mode of heat transfer. The experimental results clearly demonstrate that the radiative heat flux across micron-sized gaps can exceed the far-field upper limit given by Planck’s law of blackbody radiation. The measured radiative heat flux shows reasonable agreement with theoretical predictions.
High performance bi-dimensional resonant grating filter at 850nm under high oblique incidence of ∼60°
Authors: Hernandez S. , Gauthier-Lafaye O. , Fehrembach A.-L. , Bonnefont S. , Arguel P. , Lozes-Dupuy F. , Sentenac A.
Published: April 2008

We present an experimental demonstration of a polarization quasi-independent narrow-band (less than 0.8nm) filter operating under high oblique incidence. The structure is a resonant grating with a hexagonal lattice which has been carefully designed to ensure polarization quasi-independence of the narrow-band resonance peak over a wide angular range around 60° of incidence. A good agreement between experimental results and theoretical calculations is shown.
Electrocaloric characteristics in reactive sintered 0.87Pb(Mg1∕3Nb2∕3)O3–0.13PbTiO3
Authors: Hagberg Juha , Uusimäki Antti , Jantunen Heli
Published: April 2008

Only little data have been published on direct electrocaloric measurement of Pb(Mg1∕3Nb2∕3)O3–PbTiO3 (PMN-PT) ceramics. In this paper, the electrocaloric characteristics of 0.87PMN-0.13PT ceramic were determined by direct measurements. A strong transition in the electrocaloric effect was found at about 18°C, which is the same as the depolarization temperature Td. The maximum electrocaloric temperature rise was ΔT=0.558°C at TECm=70°C and E=2400kV∕m, well above the transition at Td=18°C. The existence of two maximums could be an indication of several mechanisms being responsible for the electrocaloric effect.
Domain structure of adaptive orthorhombic phase in [110]-poled Pb(Mg1∕3Nb2∕3)O3–30.5%PbTiO3 single crystal
Authors: Wang H. , Zhu J. , Zhang X. W. , Tang Y. X. , Luo H. S.
Published: April 2008

The domain structure of orthorhombic phase in [110]-poled Pb(Mg1∕3Nb2∕3)O3–30.5%PbTiO3 has been studied with analytical transmission electron microscopy. Convergent beam electron diffraction analysis indicates that the orthorhombic phase is an adaptive phase composed of tetragonal nanodomains while in the macroscopic scale it appear as orthorhombic due to an average effect. When poled along [110] direction, the volume ratio of the nanodomains with [100] polarization becomes equal to that of the nanodomains with [010] polarization. The nanodomain walls seem pinned, which may be a reason of the lower piezoelectric properties of orthorhombic phase.
Tolerance of pigs to sorghum ergot (Claviceps africana) during growth and finishing, and effect on conception of replacement gilts
Authors: Kopinski J. S. , Blaney B. J. , Downing J. A.
Published: April 2008

Two batches of sorghum infected with ergot were incorporated into nutritionally balanced grower and finisher diets that contained 0, 5 or 10 mg alkaloid/kg (0, 4 or 8 mg dihydroergosine/kg), or 10 mg alkaloid/kg (8 mg dihydroergosine/kg) plus 1% zeolite. The contents of ergot sclerotia in the 10 mg/kg diets were ~2% in one batch and 4% in the other; the latter batch had a heavy secondary fungal infection of Cerebella sp., which tends to limit alkaloid accumulation. These diets were each fed to four male and four female pigs as they grew from 20 to 90 kg. There were no deleterious effects on growth, feed intake and conversion even with lower plasma prolactin of 0.1 µg/L in ergot-fed pigs compared with ~1 µg/L in the control pigs. Zeolite did not counteract the ergot reduction of prolactin and had no effect on performance. Male pigs were then slaughtered, but females continued to be fed the diets for a further 3 months, when they were brought into oestrus and artificially inseminated. One month after pregnancy was confirmed, they were slaughtered and fertility was assessed. There were no significant differences in the numbers of corpora lutea or embryos between pigs fed ergot and control diets.
Phylogenetic relationships within Dendroligotrichum and Polytrichadelphus (Polytrichaceae, Polytrichopsida) in the Palaeoaustral region. Studies in austral temperate rainforest bryophytes 32
Authors: Stech Michael , Pfeiffer Tanja , Frey Wolfgang
Published: April 2008

Plastid trnT–F and atpB–rbcL spacer sequences as well as AFLP fingerprints are utilised to infer phylogenetic relationships of Dendroligotrichum and Polytrichadelphus taxa (Polytrichaceae) in the palaeoaustral region. Phylogenies based on DNA sequence data support the monophyly of each genus. Relationships within Dendroligotrichum remain ambiguous owing to low sequence divergence. AFLP fingerprinting, however, allows a clear distinction of all included Dendroligotrichum and Polytrichadelphus taxa at the species level. The morphological, distributional, ecological and molecular differences justify the recognition of the following three species in Dendroligotrichum: D. dendroides (Brid. ex Hedw.) Broth. and D. squamosum (Hook.f. & Wilson) Cardot in southern South America, as well as D. microdendron (Müll. Hal.) G.L.Sm. in New Zealand; and the following two species in Polytrichadelphus: P. magellanicus (Hedw.) Mitt. s.str. in southern South America and P. innovans (Müll. Hal.) A.Jäger in Australia and New Zealand. For Polytrichadelphus, the molecular topologies correspond with a vicariance scenario, with a basic split of taxa in the palaeoaustral region followed by migration of southern South American taxa northwards into the Neotropics. In Dendroligotrichum, substitutions and indels in the trnL intron and atpB–rbcL spacer are ambiguous in supporting either a basic split between the South American species and D. microdendron, similar to the one in Polytrichadelphus, or a trans-oceanic dispersal event between New Zealand and southern South America.
Genetic structuring in the spotted gum complex (genus Corymbia, section Politaria)
Authors: Shepherd Mervyn , Kasem Shabana , Ablett Gary , Ochieng Joel , Crawford Allison
Published: April 2008

Spotted gums (genus Corymbia, section Politaria) occur as a species replacement series along the eastern seaboard of Australia, their distributions marked by regions of disjunction and sympatry. Their taxonomy remains controversial, with species assignment often challenging and reliant on knowledge of geographic origin as well as subtle morphological or leaf-oil variation. In the present paper, we explore a classification for spotted gums, without assuming predefined geographic or taxonomic groups but instead using genetic structure at microsatellite marker loci (n = 9) and a Bayesian model-based clustering approach implemented in Structure software. The C. torelliana outgroup (n = 21; section Cadagaria) formed a well resolved cluster (minimum pairwise Fst = 0.19). Four populations were evident within the spotted gums (n = 93) but structure was weak (pairwise Fst range 0.13–0.05). Geographic distance, topography and distribution disjunction were major determinants of structure, with migration among populations approximating a linear stepping-stone model. Corymbia maculata was resolved as a taxon and had the greatest genetic distance from any other population (minimum pairwise Fst 0.08). Three clusters were evident within the northern taxa but alignment with taxonomic groupings was poor. C. citriodora material from north of a major disjunction in central Queensland formed a Northern population. C. citriodora, C. variegata and C. henryi material south of this disjunction but north of the Border Range, formed a Central population, whereas a Southern population comprised C. variegata and C. henryi from predominately south of the Border Range.
Evidence that strong positive selection drives neofunctionalization in the tandemly duplicated
polyhomeotic
genes in
Drosophila
Authors: Beisswanger Steffen , Stephan Wolfgang
Published: April 2008

The
polyhomeotic
(
ph
) locus in
Drosophila melanogaster
consists of the two tandemly duplicated genes
ph-d
(distal) and
ph-p
(proximal). They code for transcriptional repressors belonging to the Polycomb group proteins, which regulate homeotic genes and hundreds of other loci. Although the duplication of
ph
occurred at least 25 million to 30 million years ago, both copies are very similar to each other at both the DNA and the protein levels, probably because of the action of frequent gene conversion. Despite this homogenizing force, differential regulation of both transcriptional units suggests that the functions of the duplicates have begun to diverge. Here, we provide evidence that this functional divergence is driven by positive selection. Based on resequencing of an ≈30-kb region around the
ph
locus in an African sample of
D. melanogaster
X chromosomes, we identified a selective sweep, estimated its age and the strength of selection, and mapped the target of selection to a narrow interval of the
ph-p
gene. This noncoding region contains a large intron with several regulatory elements that are absent in the
ph-d
duplicate. Our results suggest that neofunctionalization has been achieved in the
Drosophila ph
genes through the action of strong positive selection and the inactivation of gene conversion in part of the gene.
Water inertial reorientation: Hydrogen bond strength and the angular potential
Authors: Moilanen David E. , Fenn Emily E. , Lin Yu-Shan , Skinner J. L. , Bagchi B. , Fayer Michael D.
Published: April 2008

The short-time orientational relaxation of water is studied by ultrafast infrared pump-probe spectroscopy of the hydroxyl stretching mode (OD of dilute HOD in H
2
O). The anisotropy decay displays a sharp drop at very short times caused by inertial orientational motion, followed by a much slower decay that fully randomizes the orientation. Investigation of temperatures from 1°C to 65°C shows that the amplitude of the inertial component (extent of inertial angular displacement) depends strongly on the stretching frequency of the OD oscillator at higher temperatures, although the slow component is frequency-independent. The inertial component becomes frequency-independent at low temperatures. At high temperatures there is a correlation between the amplitude of the inertial decay and the strength of the O-D

O hydrogen bond, but at low temperatures the correlation disappears, showing that a single hydrogen bond (OD

O) is no longer a significant determinant of the inertial angular motion. It is suggested that the loss of correlation at lower temperatures is caused by the increased importance of collective effects of the extended hydrogen bonding network. By using a new harmonic cone model, the experimentally measured amplitudes of the inertial decays yield estimates of the characteristic frequencies of the intermolecular angular potential for various strengths of hydrogen bonds. The frequencies are in the range of ≈400 cm
−1
. A comparison with recent molecular dynamics simulations employing the simple point charge-extended water model at room temperature shows that the simulations qualitatively reflect the correlation between the inertial decay and the OD stretching frequency.
Is breeding of farmland wading birds depressed by a combination of predator abundance and grazing?
Authors: van der Wal R , Palmer S.C.F
Published: April 2008

Agri-environment schemes have been implemented across Europe to counter biodiversity loss in agricultural landscapes and halt the continual decline of farmland birds, including waders. Such schemes provide financial compensation for changes in agricultural practice, including livestock grazing regimes. Scheme uptake has been variable, partly because farmers believe that other factors, notably predation, are key to wader population declines. On the basis of wader breeding surveys across Shetland, UK, we show that predator density and livestock grazing, through reducing sward height, interact to influence territoriality and thereby are likely to affect wader breeding success. Our results appear to reflect views of both farmers and government agencies, which indicates that future agri-environment schemes would benefit from genuine stakeholder participation to maximize scheme uptake, implementation and beneficial effects on biodiversity. Our findings also imply that agri-environment schemes will reap the greatest benefits for waders through reducing stocking rate where avian predators are abundant.
Long-term persistence of GM oilseed rape in the seedbank
Authors: D'Hertefeldt Tina , Jørgensen Rikke B , Pettersson Lars B
Published: April 2008

Coexistence between genetically modified (GM) and non-GM plants is a field of rapid development and considerable controversy. In crops, it is increasingly important to understand and predict the GM volunteer emergence in subsequent non-GM crops. Theoretical models suggest recruitment from the seedbank over extended periods, but empirical evidence matching these predictions has been scarce. Here, we provide evidence of long-term GM seed persistence in conventional agriculture. Ten years after a trial of GM herbicide-tolerant oilseed rape, emergent seedlings were collected and tested for herbicide tolerance. Seedlings that survived the glufosinate herbicide (15 out of 38 volunteers) tested positive for at least one GM insert. The resulting density was equivalent to 0.01 plants m
−2
, despite complying with volunteer reduction recommendations. These results are important in relation to debating and regulating coexistence of GM and non-GM crops, particularly for planting non-GM crops after GM crops in the same field.
Book reviews
Authors: Pippard Brian
Published: April 2008

Four book reviews in the May 2004 issue of
Notes
and Records
P.M. Harman,
The natural philosophy of
James Clerk Maxwell
. Crosbie Smith,
The science of energy.
A cultural history of energy physics in Victorian Britain
.
H.A. Bethe,
Selected works of Hans A. Bethe, with
commentary
. Mario A.J. Mariscotti,
El secreto atómico de
Humuel. Cronica del origen de la energia atómica en la Argentina.
The new millennium
Authors: Cook A.
Published: April 2008

A journal of the history of science seems almost obliged to mark the transition from one millennium to another, artificial though that may be. It seems even more contrived for a journal that is about science related to The Royal Society, for our history spans not even a millennium but almost exactly one–third of that period. Yet the history of science in those years has much to teach us today about the practice and use of science and to help in promoting its understanding among the wider public. The Society and its Fellows have been particularly deeply involved in the development of a number of disciplines, and so we have essays on representative topics—time, microscopy, exploration, geology and planetary studies, together with some cautionary tales about prediction—though not the only ones that could have been included. One topic, the science of materials, is represented by a book review. As is usual for the first issue of a year, we include the President's Address to the Anniversary Meeting—his last, and the last of the millennium
Analytical solution for ground motion of a half space with a semi-cylindrical canyon and a beeline crack
Authors: Liu Gang , Ji Baohua , Liu Diankui
Published: April 2008

In earthquake engineering and strong motion seismology, an important issue is to describe and analyse the displacement amplitudes and the relative phases of motions of infrastructures on or nearby the ground surface. In this paper, the influence of a beeline crack on the ground motion of a half space with a semi-cylindrical canyon under anti-plane loading is studied. A novel method combining Green's function and complex functions that can consider very irregular topography is developed for deriving the function of ground motion of the half space. Analytical expressions for the displacement and stress in the half space are obtained. Our results show that the positions and dimensions of the canyon and the beeline crack have a big influence on the ground motion. The crack can amplify the amplitudes of the motion significantly, and its influence cannot be neglected until the distance between the crack and the ground reaches up to 100 times more than the dimension of the crack.
A hybrid analytical–numerical method for solving evolution partial differential equations. I. The half-line
Authors: Flyer N , Fokas A.S
Published: April 2008

A new method, combining complex analysis with numerics, is introduced for solving a large class of linear partial differential equations (PDEs). This includes any linear constant coefficient PDE, as well as a
limited
class of PDEs with variable coefficients (such as the Laplace and the Helmholtz equations in cylindrical coordinates). The method yields novel integral representations, even for the solution of classical problems that would normally be solved via the Fourier or Laplace transforms. Examples include the heat equation and the first and second versions of the Stokes equation for arbitrary initial and boundary data on the half-line. The new method has advantages in comparison with classical methods, such as avoiding the solution of ordinary differential equations that result from the classical transforms, as well as constructing integral solutions in the complex plane which converge exponentially fast and which are uniformly convergent at the boundaries. As a result, these solutions are well suited for numerics, allowing the solution to be computed at any point in space and time without the need to time step. Simple deformation of the contours of integration followed by mapping the contours from the complex plane to the real line allow for fast and efficient numerical evaluation of the integrals.
Molecular anatomy of the cytoplasmic domain of bovine growth hormone receptor, a quantitative trait locus
Authors: Varvio S.-L , Iso-Touru T , Kantanen J , Viitala S , Tapio I , Mäki-Tanila A , Zerabruk M , Vilkki J
Published: April 2008

Quantitative trait loci (QTL) studies have indicated growth hormone receptor (GHR) as a candidate gene affecting cattle milk yield and composition. In order to characterize genetic variation at GHR in cattle, we studied European and East African breeds with different histories of selection, andBos grunniens,Ovis aries,Sus scrofa,Bison bisonandRangifer tarandusas references. We sequenced most of the cytoplasmic domain (900 bp of exon 10), 89 bp of exon 8, including the putative causative mutation for the QTL effect, and 390 bp of intron 8 for comparison. In the cytoplasmic domain, seven synonymous and seven non-synonymous single nucleotide polymorphisms (SNP) were identified in cattle. Three non-synonymous SNPs were found in sheep and one synonymous SNP in yak, while other studied species were monomorphic. Three major haplotypes were observed, one unique to African breeds, one unique to European breeds and one shared. Bison and yak haplotypes are derivatives of the European haplotype lineage. Most of the exon 10 non-synonymous cattle SNPs appear at phylogenetically highly conserved sites. The polymorphisms in exon 10 cluster around a ruminant-specific tyrosine residue, suggesting that this site may act as an additional signalling domain of GHR in ruminants. Alternative explanations for the persistent polymorphism include balancing selection, hitch-hiking, pleiotropic or sexually antagonistic fitness effects or relaxed functional constraints.
Social networks in the lek-mating wire-tailed manakin (
Pipra filicauda
)
Authors: Ryder Thomas B , McDonald David B , Blake John G , Parker Patricia G , Loiselle Bette A
Published: April 2008

How social structure interacts with individual behaviour and fitness remains understudied despite its potential importance to the evolution of cooperation. Recent applications of network theory to social behaviour advance our understanding of the role of social interactions in various contexts. Here we applied network theory to the social system of lek-mating wire-tailed manakins (
Pipra filicauda
, Pipridae, Aves). We analysed the network of interactions among males in order to begin building a comparative framework to understand where coordinated display behaviour lies along the continuum from solitary to obligately cooperative dual-male displays in the family Pipridae. Network degree (the number of links from a male to others) ranged from 1 to 10, with low mean and high variance, consistent with the theory for the evolution of cooperation within social networks. We also assessed factors that could predict social and reproductive success of males. Four network metrics,
degree
,
eigenvector centrality
,
information centrality
and
reach
, some of which assess circuitous as well as the shortest (geodesic) paths of male connectivity, predicted male social rise. The duration of a male's territorial tenure during the 4 years of the study predicted his probability of siring offspring.
Enhancement of chromatic contrast increases predation risk for striped butterflies
Authors: Stobbe Nina , Schaefer H. Martin
Published: April 2008

Many prey species have evolved defensive colour patterns to avoid attacks. One type of camouflage, disruptive coloration, relies on contrasting patterns that hinder predators' ability to recognize an object. While high contrasts are used to facilitate detection in many visual communication systems, they are thought to provide misleading information about prey appearance in disruptive patterns. A fundamental tenet in disruptive coloration theory is the principle of ‘maximum disruptive contrast’, i.e. disruptive patterns are more effective when higher contrasts are involved. We tested this principle in highly contrasting stripes that have often been described as disruptive patterns. Varying the strength of chromatic contrast between stripes and adjacent pattern elements in artificial butterflies, we found a strong negative correlation between survival probability and chromatic contrast strength. We conclude that too high a contrast leads to increased conspicuousness rather than to effective camouflage. However, artificial butterflies that sported contrasts similar to those of the model speciesLimenitis camillasurvived equally well as background-matching butterflies without these stripes. Contrasting stripes do thus not necessarily increase predation rates. This result may provide new insights into the design and characteristics of a range of colour patterns such as sexual, mimetic and aposematic signals.
Minor Antenna Proteins CP24 and CP26 Affect the Interactions between Photosystem II Subunits and the Electron Transport Rate in Grana Membranes of Arabidopsis
Authors: de Bianchi Silvia , Dall'Osto Luca , Tognon Giuseppe , Morosinotto Tomas , Bassi Roberto
Published: April 2008

We investigated the function of chlorophyll a/b binding antenna proteins Chlorophyll Protein 26 (CP26) and CP24 in light harvesting and regulation of photosynthesis by isolating Arabidopsis thaliana knockout lines that completely lacked one or both of these proteins. All three mutant lines had a decreased efficiency of energy transfer from trimeric light-harvesting complex II (LHCII) to the reaction center of photosystem II (PSII) due to the physical disconnection of LHCII from PSII and formation of PSII reaction center depleted domains in grana partitions. Photosynthesis was affected in plants lacking CP24 but not in plants lacking CP26: the former mutant had decreased electron transport rates, a lower ΔpH gradient across the grana membranes, reduced capacity for nonphotochemical quenching, and limited growth. Furthermore, the PSII particles of these plants were organized in unusual two-dimensional arrays in the grana membranes. Surprisingly, overall electron transport, nonphotochemical quenching, and growth of the double mutant were restored to wild type. Fluorescence induction kinetics and electron transport measurements at selected steps of the photosynthetic chain suggested that limitation in electron transport was due to restricted electron transport between QA and QB, which retards plastoquinone diffusion. We conclude that CP24 absence alters PSII organization and consequently limits plastoquinone diffusion.
The Receptor Kinase CORYNE ofArabidopsisTransmits the Stem Cell–Limiting Signal CLAVATA3 Independently of CLAVATA1
Authors: Müller Ralf , Bleckmann Andrea , Simon Rüdiger
Published: April 2008

Stem cells in shoot and floral meristems of Arabidopsis thaliana secrete the signaling peptide CLAVATA3 (CLV3) that restricts stem cell proliferation and promotes differentiation. The CLV3 signaling pathway is proposed to comprise the receptor kinase CLV1 and the receptor-like protein CLV2. We show here that the novel receptor kinase CORYNE (CRN) and CLV2 act together, and in parallel with CLV1, to perceive the CLV3 signal. Mutations in CRN cause stem cell proliferation, similar to clv1, clv2, and clv3 mutants. CRN has additional functions during plant development, including floral organ development, that are shared with CLV2. The CRN protein lacks a distinct extracellular domain, and we propose that CRN and CLV2 interact via their transmembrane domains to establish a functional receptor.
Life Histories and Survival Strategies Amongst Sexually Trafficked Girls in Nepal
Authors: Simkhada Padam
Published: April 2008

Many girls involved in sex work in Asia do so because they are compelled by economic circumstances and social inequality. Some enter sex work voluntarily, others do so by force or deception, sometimes involving migration across international borders. Nepalese girls involved in sex work via trafficking are the focus of this article, which aims at increasing our understanding of the context of sex trafficking, the methods and means of trafficking, living conditions in brothels and survival strategies among trafficked girls. Girls trafficked from Nepal to India are typically unmarried, illiterate and very young. Key routes to sex trafficking include employment‐induced migration to urban areas, deception (through false marriage or visits) and abduction. Past initiatives towards their needs have adopted a welfare approach; such initiatives alone are inadequate as they ignore the importance of empowerment of women in the migration process and skill development in community re‐integration. Anti‐trafficking interventions need to be considered at (i) community level before movement begins; (ii) urban centres which are both source and transitory centres for trafficking; (iii) trafficking level when girls are highly mobile and in brothels; and (iv) return from trafficking as girls to move back into the community.