bluuebunny/crossref_metadata_2025 huggingface dataset:
Phonological Acquisition in Bilingual Spanish–English Speaking Children
Authors: Fabiano-Smith Leah , Goldstein Brian A.
Published: February 2010

Purpose

In this study, the authors aimed to determine how between-language interaction contributes to phonological acquisition in bilingual Spanish–English speaking children.

Method

A total of 24 typically developing children, ages 3;0 (years;months) to 4;0, were included in this study: 8 bilingual Spanish–English speaking children, 8 monolingual Spanish speakers, and 8 monolingual English speakers. Single word and connected speech samples were obtained for each child. This study examined interaction between the two languages of bilingual children during phonological acquisition through the measurement of (a)
transfer
(the frequency and types of phonological transfer present in the speech of bilingual children); (b)
deceleration
(a slower rate of acquisition for bilinguals as compared with monolinguals); and (c)
acceleration
(a faster rate of acquisition for bilinguals as compared with monolinguals.

Results

Findings demonstrated that (a) transfer was evident in the productions of bilingual children, (b) differences were found in accuracy between monolingual and bilingual children, and (c) sound frequency did not predict differential accuracy of either phonetically similar sounds between languages or phonetically dissimilar sounds specific to Spanish or English.

Implications

The results from this study indicate that transfer, deceleration, and a possible variation of the acceleration hypothesis occur in bilingual phonological acquisition. Evidence was found for separation and interaction between the bilingual children’s 2 languages (J. Paradis & F. Genesee, 1996).
Initial Acquisition of Mental Graphemic Representations in Children with Language Impairment
Authors: Wolter Julie A. , Apel Kenn
Published: February 2010

Purpose

The authors examined initial acquisition of mental graphemic representations (MGRs) for a set of pseudowords in children with language impairment (LI). They also determined whether the linguistic properties of the words (i.e., phonotactic and orthotactic probabilities) influenced MGR learning and whether the ability to acquire initial MGRs was related to performance on reading and spelling measures. The authors compared these children’s initial acquisition of MGRs to a group of children with typical language (TL) skills.

Method

A written fast mapping procedure was administered to 25 kindergarten children with LI and 31 with TL. During the procedure, the children were exposed to novel pseudowords varying in phonotactic and orthotactic probabilities in a computer-based, storybook reading task and then were asked to generate and identify those pseudoword spellings. Additionally, reading and spelling tasks were administered.

Results

Children with LI acquired some initial MGRs as evidenced by their ability to identify some pseudowords; however, their ability to identify and generate pseudowords was significantly poorer than that of the comparison group. Similar to their TL peers, the ability to identify pseudoword spellings by children with LI was affected by the linguistic properties of words, and written fast mapping performance was related to spelling performance. However, unlike the comparison group, written fast mapping performance of children with LI was not related to performance on a reading composite measure.

Conclusions

The authors propose that children with LI are less robust at developing initial MGRs than are children with TL and that this poor ability to acquire initial MGRs likely places them at risk for later literacy deficits.
Conversational Language Use as a Predictor of Early Reading Development: Language History as a Moderating Variable
Authors: DeThorne Laura Segebart , Petrill Stephen A. , Schatschneider Chris , Cutting Laurie
Published: February 2010

Purpose

The present study examined the nature of concurrent and predictive associations between conversational language use and reading development during early school-age years.

Method

Language and reading data from 380 twins in the Western Reserve Reading Project were examined via phenotypic correlations and multilevel modeling on exploratory latent factors.

Results

In the concurrent prediction of children’s early reading abilities, a significant interaction emerged between children’s conversational language abilities and their history of reported language difficulties. Specifically, conversational language concurrently predicted reading development above and beyond variance accounted for by formal vocabulary scores, but only in children with a history of reported language difficulties. A similar trend was noted in predicting reading skills 1 year later, but the interaction was not statistically significant.

Conclusions

Findings suggest a more nuanced view of the association between spoken language and early reading than is commonly proposed. One possibility is that children with and without a history of reported language difficulties rely on different skills, or the same skills to differing degrees, when completing early reading-related tasks. Future studies should examine the causal link between conversational language and early reading specifically in children with a history of reported language difficulties.
Operation and upgrade of diagnostic neutral beam injector RUDI at TEXTOR tokamak
Authors: Listopad A. A. , Coenen J. W. , Davydenko V. I. , Deichuli P. P. , Ivanov A. A. , Mishagin V. V. , Savkin V. Ya. , Schalt W. , Schweer B. , Shulzhenko G. I. , Stupishin N. V. , Uhlemann R.
Published: February 2010

The status and the executing modernization of RUssian Diagnostic Injector (RUDI) are described. The ion source consists of arc plasma emitter and multiaperture four-electrode ion optical system. The present ion optical system with round beamlets is to be replaced by new slit apertures system for the reducing beam angular divergence in one direction. Due to enlarged dimensions and transparency of new ion optical system the extracted ion beam current will be by 50% increased. For the extension of beam pulse duration from 4 s to 8–10 s an optimized metal-ceramic arc-discharge channel is introduced. In the paper, the optical measurements results of beam parameters, including the profile of species distribution, scanned by custom-built multichannel spectroscope, are also presented.
Measurements of the highest acceleration gradient for ions produced with a long laser pulse
Authors: Margarone D. , Krasa J. , Laska L. , Velyhan A. , Mocek T. , Prokupek J. , Krousky E. , Pfeifer M. , Gammino S. , Torrisi L. , Ullschmied J. , Rus B.
Published: February 2010

Ultrafast plasma light ion streams have been produced using the 300 ps, kJ-class iodine laser, operating at PALS Centre in Prague. Ion detection was performed through standard ion collectors (IC) in time-of-flight configuration (TOF), shielded by thin metallic absorbers. This new diagnostics technique has been theoretically studied and experimentally tested in order to cut the long photopeak contribution and to analyze the ultrafast particle signal. Processing the obtained experimental IC-TOF data, including deconvolution processes of the TOF signals, UV/soft-x-ray photopeak absorption, and ion transmission calculations for different metallic filters, is shown. Mainly amorphous carbon (graphite) targets have been irradiated in order to limit the maximum number of ion charge states and to focus our study on demonstrating the validity of the proposed investigation technique. Maximum ion energy and acceleration gradient estimations as a function of the laser energy and focal spot diameter are reported.
Study of ion beam extraction and transport from an electron cyclotron resonance ion source
Authors: Saminathan S. , Mironov V. , Beijers J. P. M. , Kremers R. , Brandenburg S.
Published: February 2010

We have started an experimental and theoretical program to better understand the extraction and transport of intense multiply charged ion beams from an electron cyclotron resonance ion source (ECRIS). In this paper we present the first results of this program concerning a simple, monocomponent He+ beam extracted from an ECRIS. We have calculated the ion trajectories starting from the ECRIS plasma electrode up to the image plane of the analyzing magnet taking into account space-charge effects and fringe fields. The initial phase-space distribution of the He+ beam at the extraction aperture has been calculated with a particle-in-cell code. To check the simulations we have measured beam profiles with a viewing screen both before and after the analyzing magnet. In addition also measurements with a pepperpot emittance meter located behind the analyzing magnet have been performed. We find good agreement between these measurements and simulations showing that (i) there is a significant compensation of the space charge and that (ii) our analyzing magnet causes a severe increase in effective beam emittance.
IONEX: A meshfree ion extraction code based on “particle in cloud of points” concept
Authors: Galkin S. A. , Grubert J. E. , Cluggish B. P. , Barov N. , Kim J. S.
Published: February 2010

Ion Extraction (IONEX) is an ion extraction modeling code, developed at FAR-TECH, Inc., based on the meshless particle-in-cloud-of-points concept. IONEX self-consistently solves motion equations for ions and Poisson’s equation for the electrostatic field, assuming a Boltzmann distribution for the electrons. IONEX is capable of handling multiple species and is graphical user interface-driven. The two-dimensional version is benchmarked with IGUN. The basic algorithm and sample runs are presented.
Spectroscopic investigation of OCS (p-H2)n (n=1–16) complexes inside helium droplets: Evidence for superfluid behavior
Authors: Grebenev Slava , Sartakov Boris G. , Toennies J. Peter , Vilesov Andrey F.
Published: February 2010

Up to 16 parahydrogen and orthodeuterium molecules have been assembled around an OCS carbonyl sulfide chromophore molecule inside the pure He4 and mixed He4∕He3 droplets at temperatures of 0.38 and 0.15K, respectively. The infrared spectra of the resulting complexes exhibit a sequence of rotationally resolved vibrational ν3 bands in the vicinity of 2060cm−1, which are sufficiently separated to assign them to clusters with specific numbers of attached molecules for n=1–16. The present article contains the first complete analysis of the spectra for n=2–8 and a full documentation of the results for n=8–15 briefly described in a short report [Europhys. Lett. 83, 66008 (2008)]. Distinct rotational Q-branches are observed for all OCS-(o-D2)n clusters at the He droplet temperatures of 0.38K and 0.15K, indicating that the (o-D2)n shell rotates nearly freely about the molecular OCS axis. In the case of OCS-(p-H2)n at 0.38K, the Q-branch is seen for most n, with the exception of n=5, 6 and n=12. At 0.15K, the Q-branch has disappeared for all n⩾11, indicating that the axial rotations are no longer active. Previously, the absence of a Q-branch for n=5 and 6 was explained by the high group symmetry of the bosonic p-H2 rigid (donut) rings around the OCS molecule. This model, however, fails in explaining the disappearance of the Q-branch for n⩾11. In essential agreement with recent path-integral Monte Carlo calculations, the observed phenomenon is attributed to the onset of superfluidity in the multiring p-H2 shell and the related permutations of bosonic p-H2 molecules. A floppy shell model, which accounts for the effect of tunneling and exchange of molecules within the clusters, is able to explain the postulated superfluid behavior of the p-H2 shell at low temperatures. Within this model the activation of states of low axial symmetry is responsible for the appearance of the Q-branch at higher temperatures.
In situ temperature measurements through i-anvils in diamond anvil cells
Authors: Gondé C. , Bureau H. , Burchard M. , Henry S. , Simon G. , Meijer J. , Kubsky S.
Published: February 2010

This study is devoted to in situ temperature measurement in diamond anvil cells (DACs) with intelligent anvils (i-anvils). I-anvils consist of diamonds implanted with B and/or C ions, situated below the diamond’s surface at a depth of 1–3 μm; forming sensors which are placed below the culet at the location of the DAC’s sample chamber. I-anvils can be employed as temperature or pressure sensors, exploiting their electrical properties. We have tested the sensor’s behavior with temperatures up to 900 °C, at ambient pressure and up to 6 GPa in real experimental conditions in two types of DAC. For this purpose, we performed experiments in four different i-anvils at temperatures up to 900 °C. We have compared the signal measured by the sensors with the temperature measured by a thermocouple attached to the i-anvil. The temperature gradient between the sample chamber and the thermocouple position was taken into account by phase transition measurements of calibration standards. Reproducible laws of current variation with temperature have been established. We conclude that i-anvils are reliable and sensitive to measure the temperature in-situ in DACs with an accuracy of better than 1 °C.
Thermal stability and rehybridization of carbon bonding in tetrahedral amorphous carbon
Authors: Grierson D. S. , Sumant A. V. , Konicek A. R. , Friedmann T. A. , Sullivan J. P. , Carpick R. W.
Published: February 2010

We perform a quantitative investigation of the energetics of thermally induced sp3→sp2 conversion of carbon-carbon bonds in tetrahedral amorphous carbon (ta-C) films by using near-edge x-ray absorption fine structure (NEXAFS) and Raman spectroscopy. We investigate the evolution of the bonding configuration in ta-C thin films subjected to high temperature annealing in flowing Argon gas using a rapid thermal annealing furnace over the range of 200–1000 °C. We observe no substantial change in bonding structure below 600 °C. Changes in the NEXAFS and Raman spectra start to appear above 600 °C, and by 1000 °C a significant increase in the sp2 bonding in the film is observed. No oxygen bonding is detected in the NEXAFS spectra, but we do observe an isosbestic point, demonstrating that the thermally driven sp3→sp2 conversion reaction occurs without passing through an intermediate transition state. This allows us to use NEXAFS spectra of thermally annealed ta-C films to quantitatively determine that the activation energy for directly converting the sp3-bonded carbon to the sp2-bonded configuration is 3.5±0.9 eV.
Preparation and properties of heavily doped and strongly compensated Ge films on GaAs
Authors: Mitin V. F.
Published: February 2010

We present and generalize the preparation conditions and properties of heavily doped and strongly compensated (HDSC) Ge films obtained by deposition in the vacuum onto the semi-insulating GaAs (100) substrates. A possibility of formation of Ge films with various doping levels and compensation degrees (in particular, fully compensated) is demonstrated. Heavily doped and fully compensated Ge single-crystalline thin (∼0.1 μm) films obtained have high resistivity (up to 140 Ω cm), conductance activation energy as high as half the bandgap of Ge, low free charge carrier mobility (∼50 cm2/V s), and concentration (∼1014–1015 cm−3). The electrical and optical properties of the films are explained with allowance made for the presence of large-scale fluctuations of electrostatic potential in Ge. Under certain conditions, a two-dimensional potential relief may exist in thin HDSC Ge films, as well as two-dimensional percolation may occur.
Negative salt effect in an acid-base diode: Simulations and experiments
Authors: Roszol L. , Várnai A. , Lorántfy B. , Noszticzius Z. , Wittmann M.
Published: February 2010

The paper describes a new phenomenon discovered in the electrolytic analog of a semiconductor diode. As an example, the phenomenon is studied in the 0.1M KOH–0.1M HCl diode where the alkaline and the acidic reservoirs are connected by a hydrogel cylinder. First the traditional, so-called positive salt effect is discussed. In that case some salt is added to the alkaline reservoir of a reverse biased electrolyte diode and as a result, close to a critical concentration of the added salt the electric current increases sharply. The so-called negative salt effect appears as a suppression of the positive one. It is shown by numerical simulations, by approximate analytical formulae, and also by experiments that the high current caused by the salt contamination in the alkaline reservoir can be mostly suppressed by relatively small salt concentrations in the acidic reservoir. Thus a straightforward application of the negative salt effect would be the sensitive detection of nonhydrogen cations in an acidic medium (e.g., in ion chromatography).
Optical characterization of a-As2S3 thin films prepared by magnetron sputtering
Authors: Tan W. C. , Solmaz M. E. , Gardner J. , Atkins R. , Madsen C.
Published: February 2010

It is well known that thermally evaporated a-As2S3 thin films are prone to oxidation when exposed to ambient environment. These As2O3 crystals can have a devastating effect on propagating light by introducing a major source of scattering loss in submicron optically integrated circuits. Magnetron sputtering a-As2S3 not only produces films that have optical properties closer to their equilibrium state like their bulk glass counter parts, the as-deposited films also show no detectable signs of As2O3 crystals in them when they are exposed to the ambient environment. These attributes are unique to a magnetron sputtered a-As2S3 film and are probably caused by the “photoannealing” effect from the visible light emitted by the argon plasma during the sputtering process. The optical properties of a magnetron sputtered a-As2S3 film and its propagation loss on a Ti diffused LiNbO3 waveguide are reported here. The thin film results agree closely with published data on As2S3 bulk glass, and the optical properties of the as-deposited film are found to be closer to its bulk glass values than films made by thermal evaporation and pulsed laser deposition. The TM propagation loss at λ=1.5 μm of the as-deposited a-As2S3 waveguide on Ti:LiNbO3 was 0.20±0.05 dB/cm.
Ellipsometry of graphene on a substrate
Authors: Meera V. , Setlur Girish S.
Published: February 2010

Monolayer graphene deposited on a dielectric substrate material is investigated theoretically using Maxwell’s equations to study its optical properties. Optical quantities such as reflected polarization and reflection coefficient are important since they are able to provide information about the conductivity tensor of the graphene layer. This study can be considered as a general one which gives the suspended graphene as its limiting case. The focus of this study is the effect of substrate on graphene (suspended) optical properties for which a comparison between the suspended graphene and graphene on substrate is made here at each stage. An investigation of the reflection coefficient reveals the presence of Brewster’s-like phenomena which is not observable in suspended graphene.
Cooperative and diminutive hydrogen bonding in Y⋯HCN⋯HCN and NCH⋯Y⋯HCN trimers (Y=BF,CO,N2)
Authors: McDowell Sean A. C. , Buckingham A. David
Published: February 2010

A computational study of the cooperative effect of hydrogen bonding in Y⋯HCN⋯HCN and its diminutive effect in NCH⋯Y⋯HCN (Y=BF,CO,N2) linear complexes relative to the Y⋯HCN dimer was undertaken at the MP2∕6-311++G(2d,2p) level of theory. It was found that the additional hydrogen bond in Y⋯HCN⋯HCN leads to an enhanced Y⋯HCN dissociation energy, extended H–C bond length, and larger redshift of the H–C stretch relative to Y⋯HCN, while opposite features are observed in NCH⋯Y⋯HCN. The cooperativity is diminished as the hardness of the Y atom directly bonded to the HCN molecule increases. A particularly interesting result is that the small bond contraction and blueshift associated with the H–C bond in BF⋯HCN is converted to a small bond extension and redshift on the formation of the BF⋯HCN⋯HCN trimer.
Nonlinear and saturable absorption characteristics of amorphous InSe thin films
Authors: Yüksek Mustafa , Kürüm Ulaş , Yaglioglu H. Gul , Elmali Ayhan , Ateş Aytunç
Published: February 2010

We prepared very thin amorphous InSe films and investigated the thickness dependence of the nonlinear absorption by pump-probe and open aperture Z-scan techniques. While thinner films (20 and 52 nm) exhibit saturable absorption, thicker films (70 and 104 nm) exhibit nonlinear absorption for 4 ns, 65 ps, and 44 fs pulse durations. This behavior is attributed to increasing localized defect states in the energy band gap as the film thickness increases. We developed a theoretical model incorporating one photon, two photon, and free carrier absorptions and their saturations to derive the transmission in the open aperture Z-scan experiment. The theory of open aperture Gaussian beam Z-scan based on the Adomian decomposition method was used to fit the experimental curves. Nonlinear absorption coefficients along with saturation intensity thresholds were extracted from fitting the experimental results for all pulse durations. The lowest saturation threshold was found about 3×10−3 GW/cm2 for 20 nm film thickness with nanosecond pulse duration and increased about four orders of magnitude for 104 nm film thickness.
A possible mathematics for the unification of quantum mechanics and general relativity
Authors: Kryukov A.
Published: February 2010

This paper summarizes and generalizes a recently proposed mathematical framework that unifies the standard formalisms of special relativity and quantum mechanics. The framework is based on Hilbert spaces H of functions of four space-time variables x,t, furnished with an additional indefinite inner product invariant under Poincaré transformations, and isomorphisms of these spaces that preserve the indefinite metric. The indefinite metric is responsible for breaking the symmetry between space and time variables and for selecting a family of Hilbert subspaces that are preserved under Galileo transformations. Within these subspaces the usual quantum mechanics with Schrödinger evolution and t as the evolution parameter is derived. Simultaneously, the Minkowski space-time is isometrically embedded into H, Poincaré transformations have unique extensions to isomorphisms of H and the embedding commutes with Poincaré transformations. The main new result is a proof that the framework accommodates arbitrary pseudo-Riemannian space-times furnished with the action of the diffeomorphism group.
Argon nucleation in a cryogenic supersonic nozzle
Authors: Sinha Somnath , Bhabhe Ashutosh , Laksmono Hartawan , Wölk Judith , Strey Reinhard , Wyslouzil Barbara
Published: February 2010

We have measured pressures p and temperatures T corresponding to the maximum nucleation rate of argon in a cryogenic supersonic nozzle apparatus where the estimated nucleation rates are J=1017±1 cm−3 s−1. As T increases from 34 to 53 K, p increases from 0.47 to 8 kPa. Under these conditions, classical nucleation theory predicts nucleation rates of 11–13 orders of magnitude lower than the observed rates while mean field kinetic nucleation theory predicts the observed rates within 1 order of magnitude. The current data set appears consistent with the measurements of Iland et al. [J. Chem. Phys. 127, 154506 (2007)] in the cryogenic nucleation pulse chamber. Combining the two data sets suggests that classical nucleation theory fails because it overestimates both the critical cluster size and the excess internal energy of the critical clusters.
Prepulse effects on the generation of high energy electrons in fast ignition scheme
Authors: Cai Hong-bo , Mima Kunioki , Sunahara Atsushi , Johzaki Tomoyuki , Nagatomo Hideo , Zhu Shao-ping , He X. T.
Published: February 2010

The energy distribution of the produced high energy electrons in the interaction of ultraintense picosecond laser pulses with high-Z solid targets is shown to be sensitive to the preformed plasma created by the prepulse and the amplified spontaneous emission pedestal. The created preformed plasmas, which are obtained by radiation hydrodynamic simulations for the present heating laser system at ILE, Osaka University, are seen to extend up to 30–100 μm just before the arrival of the main pulse. The dependences of the coupling efficiency of the laser energy to high energy electrons, and the energy spectra of these accelerated electrons, on this preformed plasma, are studied via a two-dimensional particle-in-cell simulation code. It is found that in a small preformed plasma case, J×B heating is dominant and the produced electron temperature agrees well with Haines’ scaling law [Haines et al., Phys. Rev. Lett., 102, 045008 (2009)]. While in a large preformed plasma case, in addition to J×B heating and/or vacuum heating, other acceleration mechanisms, such as stochastic heating, can accelerate electrons to very high energies, carrying a significant fraction of input laser energy. Even after several picoseconds, the number of high energy electrons (0.5 MeV<E<5 MeV) generated in a small preformed plasma case can be several times larger than that of a large preformed plasma case.
On the interface properties of ZnO/Si electroluminescent diodes
Authors: Pau J. L. , Piqueras J. , Rogers D. J. , Teherani F. Hosseini , Minder K. , McClintock R. , Razeghi M.
Published: February 2010

ZnO layers grown on n−-Si(100), n+-Si(100), and n−-Si(111) substrates by pulsed-laser deposition were found to give electroluminescence. Light emission was observed in the form of discrete spots for currents over 1 mA with a white appearance to the naked eye. The intensity of these spots showed an erratic behavior over time, appearing and disappearing at random, while showing an associated random telegraph noise in the current signal. Regardless the substrate used, the electroluminescence spectra had a main broadband emission centered at about 600 nm and a relatively small peak at around 380 nm which corresponds to the energy of ZnO near band edge emission. Furthermore, the devices exhibited rectifying characteristics, whose current blocking direction depended on the substrate orientation. Optimization of ZnO conductivity and performing sample growth in N2 ambient were found to be critical to enhance the emission intensity. Rutherford backscattering characterization revealed the existence of an intermixed region at the interface between ZnO and Si. To study the electronic properties at the interface, frequency dependent capacitance measurements were carried out. The junction capacitance became frequency dependent at the bias voltages at which light emission occurs due to the relatively slow trapping and generation processes at deep centers. These centers are believed to play an important role in the mechanism of light emission.
Supra-bubble regime for laser acceleration of cold electron beams in tenuous plasma
Authors: Geyko V. I. , Dodin I. Y. , Fisch N. J. , Fraiman G. M.
Published: February 2010

Relativistic electrons can be accelerated by an ultraintense laser pulse in the “supra-bubble” regime, that is, in the blow-out regime ahead of the plasma bubble (as opposed to the conventional method, when particles remain inside the bubble). The acceleration is caused by the ponderomotive force of the pulse, via the so-called snow-plow mechanism. The maximum energy gain, Δγ∼γga, is attained when the particle Lorentz factor γ is initially about γg/a, where γg is the pulse group speed Lorentz factor, and a is the laser parameter, proportional to the laser field amplitude. The scheme operates at a≲γg, yielding Δγ of up to that via wakefield acceleration for the same plasma and laser parameters, Δγ∼γg2. The interaction length is shorter than that for the wakefield mechanism but grows with the particle energy, hindering acceleration in multiple stages.
Polypeptides in alpha-helix conformation perform as diodes
Authors: Cristancho Dahiyana , Seminario Jorge M.
Published: February 2010

Molecules that resemble a semiconductor diode depletion zone are those with an intrinsic electric dipole, which were suggested as potential electronic devices. However, so far, no single molecule has met such a goal because any electron donor-acceptor linker strongly diminishes any possibility of diode behavior. We find an intrinsic diode behavior in polypeptides such as poly(L-alanine) and polyglycine in α-helix conformation, explained in terms of molecular orbital theory using ab initio methods. The application of an antiparallel electric field with respect to the molecular dipole yields a gradual increase in current through the junction because the valence and conduction orbitals approach each other reducing their gap as the bias increases. However, a parallel field makes the gap energy increase, avoiding the pass of the electrons.
Spontaneous and electric field induced quadratic optical nonlinearity in ferroelectric crystals AgNa(NO2)2
Authors: Kityk A. V. , Czaplicki R. , Klöpperpieper A. , Andrushchak A. S. , Sahraoui B.
Published: February 2010

We demonstrate the second harmonic generation (SHG) in ferroelectric AgNa(NO2)2 crystals resulting from the spontaneous and electric field induced polarizations. Relatively high effective nonlinear optic (NLO) susceptibility is combined in this crystals with the existing several phase matching geometries of NLO interaction. Anomalously large response of SHG with respect to an applied electric field has been found in the vicinity of the paraelectric-to-ferroelectric phase transition. The behavior of NLO properties in the ferroelectric phase and especially in the region of the Curie point is discussed within the phenomenological theory.
Low-pressure indium-halide discharges for fluorescent illumination applications
Authors: Hayashi Daiyu , Hilbig Rainer , Körber Achim , Schwan Stefan , Scholl Robert , Boerger Martin , Huppertz Maria
Published: February 2010

Low-pressure gas discharges of molecular radiators were studied for fluorescent lighting applications with a goal of reducing the energy loss due to the large Stokes shift in phosphors of conventional mercury-based fluorescent lamp technology. Indium halides (InCl, InBr, and InI) were chosen as the molecular radiators that generate ultraviolet to blue light emissions. The electrical characteristics and optical emission intensities were measured in discharges containing gaseous indium halides (InCl, InBr, and InI) as molecular radiators. The low-pressure discharges in indium halide vapor showed potential as a highly efficient gas discharge system for fluorescent lighting application.
Rigid band model for prediction of magnetostriction of iron-gallium alloys
Authors: Zhang Y. N. , Cao J. X. , Wu R. Q.
Published: February 2010

Using the highly precise full potential linearized augmented plane wave method, we determined atomic structure and the magnetostriction of Fe100−xGax with x<19%. It is demonstrated that the extraordinary enhancement of magnetostrictive coefficient of Fe100−xGax at low concentration stems from intrinsic electronic origins. Moreover, we recognized the potential of using a rigid band model for the prediction of magnetostriction of intermetallic alloys, through studies of ternary alloys with Zn substitution into Fe87.5Ga12.5.
A grazier survey of the long-term productivity of leucaena (Leucaena leucocephala)-grass pastures in Queensland
Authors: Radrizzani A. , Dalzell S. A. , Kravchuk O. , Shelton H. M.
Published: February 2010

Leucaena leucocephala subsp. glabrata (leucaena)-grass pastures are productive, perennial and long-lived (>40 years). However, little is known about changes in the productivity of these pastures as they age even though they are grazed intensively and are rarely fertilised. A postal survey of beef cattle producers in Queensland who grow leucaena pastures was conducted. The questionnaire gathered information regarding: property location; extent and age of leucaena pastures; soil type; leucaena and grass establishment methodology; grazing and fertiliser management; and grazier perceptions of changes over time in leucaena productivity, grass growth and ground cover, prevalence of undesirable grasses and weeds, and livestock productivity. Graziers were asked to report on both young (≤10 years old) and aging (>10 years old) pastures under their management. Eighty-eight graziers responded describing 124 leucaena paddocks covering 11 750 ha. The survey results described the typical physical and management characteristics of leucaena pastures in Queensland. Graziers reported a decline in leucaena productivity in 58% of aging pastures, and declines in grass growth (32%) and livestock productivity (42%) associated with declining leucaena growth. Leucaena decline was greater in soil types of marginal initial fertility, particularly brigalow clay, soft wood scrub, downs and duplex soils. Maintenance fertiliser was not applied to most (98%) leucaena pastures surveyed despite significant amounts of nutrient removal, particularly phosphorus and sulphur, occurring over prolonged periods of moderate to high grazing pressure. It is predicted that large areas of leucaena pasture will continue to suffer soil nutrient depletion under current management practices. Research is needed to develop ameliorative actions to reinvigorate pasture productivity.
Evaluation of rumen probe for continuous monitoring of rumen pH, temperature and pressure
Authors: Kaur R. , Garcia S. C. , Horadagoda A. , Fulkerson W. J.
Published: February 2010

The primary objective of this study was to evaluate the accuracy of a commercially available wireless rumen probe by Kahne Limited (New Zealand) for continuous pH, temperature and pressure measurements under different ruminal conditions. In a 4 by 4 latin square design, rumen-fistulated sheep were fed diets comprising 0, 30 or 60% concentrate, with the rest of the diet being balanced for metabolisable energy and protein with maize silage and lucerne hay. Each experimental period was 10 days with the first 8 days for adaptation and the last 2 days for collection of rumen fluid samples. In the first experimental period, probes were left in the rumen of sheep for 10 days to observe drift in pH. In the other three periods, probes were repeatedly cleaned and recalibrated before each sampling period. Probes were set to read every 20 min while the samples of rumen fluid were withdrawn manually at 4-h intervals and pH recorded immediately. There was an upward drift in pH observed after 48 h of insertion of probes into the rumen. This study resulted in a minor level of agreement between the two methods as indicated by higher root mean prediction error (0.43 pH units), lower Pearson’s correlation coefficient (r = 0.46) and concordance correlation coefficient (0.46). In conclusion, these rumen probes need further advancement to be potentially used for continuous rumen pH measurements for research purposes.
Electrostatics of aquaporin and aquaglyceroporin channels correlates with their transport selectivity
Authors: Oliva Romina , Calamita Giuseppe , Thornton Janet M. , Pellegrini-Calace Marialuisa
Published: February 2010

Aquaporins are homotetrameric channel proteins, which allow the diffusion of water and small solutes across biological membranes. According to their transport function, aquaporins can be divided into “orthodox aquaporins”, which allow the flux of water molecules only, and “aquaglyceroporins”, which facilitate the diffusion of glycerol and other small solutes in addition to water. The contribution of individual residues in the pore to the selectivity of orthodox aquaporins and aquaglyceroporins is not yet fully understood. To gain insights into aquaporin selectivity, we focused on the sequence variation and electrostatics of their channels. The continuum Poisson-Boltzmann electrostatic potential along the channel was calculated and compared for ten three-dimensional-structures which are representatives of different aquaporin subfamilies, and a panel of functionally characterized mutants, for which high-accuracy three-dimensional-models could be derived. Interestingly, specific electrostatic profiles associated with the main selectivity to water or glycerol could be identified. In particular: (
i
) orthodox aquaporins showed a distinctive electrostatic potential maximum at the periplasmic side of the channel around the aromatic/Arg (ar/R) constriction site; (
ii
) aquaporin-0 (AQP0), a mammalian aquaporin with considerably low water permeability, had an additional deep minimum at the cytoplasmic side; (
iii
) aquaglyceroporins showed a rather flat potential all along the channel; and (
iv
) the bifunctional protozoan PfAQP had an unusual all negative profile. Evaluation of electrostatics of the mutants, along with a thorough sequence analysis of the aquaporin pore-lining residues, illuminated the contribution of specific residues to the electrostatics of the channels and possibly to their selectivity.
Quantitative study of synthetic Hox transcription factor–DNA interactions in live cells
Authors: Vukojević Vladana , Papadopoulos Dimitrios K. , Terenius Lars , Gehring Walter J. , Rigler Rudolf
Published: February 2010

Transcription factor–DNA interactions are life sustaining and therefore the subject of intensive research. In spite of vast effort, quantitative in vivo studies of the molecular mechanisms underlying these fundamental interactions remain challenging. In the preceding paper, we designed synthetic Sex combs reduced (Scr) peptides and validated genetically their function as transcriptional regulators. Here we present a controllable system for quantitative studies of protein–DNA interactions in live cells that enables us to “titrate” the concentration of the synthetic Scr peptides in a single cell. Using methods with single-molecule sensitivity, advanced fluorescence imaging and fluorescence correlation spectroscopy (FCS), we were able to study the kinetics of Scr-DNA interactions in live salivary gland cells, where
Scr
is normally expressed during development. We discerned freely moving Scr molecules, characterized the specific and nonspecific Scr peptide–DNA interactions, and estimated their corresponding dissociation constants (
K

d

) in vivo. Our results suggest that the synthetic Scr transcription factors find their specific target sites primarily by multiple association/dissociation events, the rapidity of which is largely owed to electrostatic interactions. Based on these new findings, we formulate a model mechanism and emulate the kinetics of Scr homeodomain–DNA interactions in live cells using numerical simulations.
Laser-printed interdigitated Ag electrodes for organic thin film transistors
Authors: Kim H , Auyeung R C Y , Lee S H , Huston A L , Piqué A
Published: February 2010

Pentacene-based thin film transistors (TFTs) with top contact (TC) and bottom contact (BC) configurations were fabricated on glass substrates using laser-printed silver nanoinks as the bottom gate and source/drain electrodes with a cross-linked poly-4-vinylphenol dielectric layer. Nanostructured source/drain Ag electrodes with various channel lengths (10–100 µm) were successfully fabricated on the pentacene layer without any damage from the Ag nanoink solvents due to the use of a semi-dry laser transfer process. Compared with the BC transistors, the TC transistors exhibited improved ohmic contact behaviour between the drain/source electrodes and the pentacene layer, which resulted in efficient charge carrier injection with higher drain current values than those obtained from the BC transistors. Analysis of the contact characteristics also showed a reduced contact resistance for the TC transistors than those from the BC transistors. The TC-TFTs exhibited a field-effect mobility of 0.11 cm2 V−1 s−1, an on/off current ratio of ∼105and a threshold voltage of −2 V in the saturation region.
Vibrational distributions of CO molecules in a dc discharge in the presence of molecular oxygen admixture
Authors: Grigoryan G M , Kochetov I V , Kurnosov A K
Published: February 2010

The influence of molecular oxygen admixture on the vibrational distribution function (VDF) of CO molecules in a dc electric discharge in He : CO : O2 mixtures was studied. It was revealed that for O2 concentrations exceeding 10% of CO content the processes of VV′ exchange between CO and O2 molecules led to essential deformation of the CO VDF shape for vibrational states near v = 20 and higher. The comparison of experimentally measured and theoretically calculated VDFs of CO gave us a chance to realize the verification of CO–O2 VV′ rate constants proposed earlier.
Controlled growth of Zn-polar ZnO film on MgAl2O4 (1 1 1) substrate using MgO buffer layer
Authors: Zeng Zhaoquan , Liu Yuzi , Yuan Hongtao , Mei Zengxia , Du Xiaolong , Jia Jinfeng , Xue Qikun , Zhang Ze , Salamo Gregory J
Published: February 2010

A pure rocksalt MgO buffer layer was used to modify the surface structure of MgAl2O4 (1 1 1) substrates to achieve growth of a Zn-polar ZnO film by radio frequency plasma-assisted molecular beam epitaxy. It is found that this pure rocksalt MgO buffer layer plays a crucial role in 30° rotation domain elimination, surface morphology improvement and Zn-polarity control of the ZnO film, as demonstrated by in situ reflection high-energy electron diffraction and ex situ transmission electron microscopy. Atomic force microscopy observation also illustrates a smooth surface for the ZnO film.
Dependence of upconversion emission intensity on Yb3+ concentration in Er3+/Yb3+ co-doped flake shaped Y2(MoO4)3 phosphors
Authors: Lu Weili , Cheng Lihong , Zhong Haiyang , Sun Jiashi , Wan Jing , Tian Yue , Chen Baojiu
Published: February 2010

Yttrium molybdate phosphors with fixed Er3+ and various Yb3+ concentrations were synthesized via a co-precipitation method. The crystal structure and the morphology of the phosphor were characterized by means of x-ray diffraction and field-emission scanning electron microscopy. Under 980 nm excitation, red and green upconversion emissions centred at 660, 553 and 530 nm were observed. Quantitative analyses on the dependence of upconversion emission intensity on the working current of a laser diode (LD) indicated that two-photon processes are responsible for both red and green upconversion emissions in both cases of low and high Yb3+ concentrations. The relationship between the emission intensity ratio of 2H11/2 →4I15/2 to 4S3/2 →4I15/2 and the working current of the LD was studied for the samples doped with low and high Yb3+ concentrations. Finally, a set of rate equations was established based on the possible upconversion mechanism, and an empirical formula was proposed to describe the Yb3+ concentration dependence of upconversion emission intensity; the empirical formula fits well with the experimental data.
Remembrance of Dead Cells Past: Discovering That the Extracellular Matrix Is a Cell Survival Factor
Authors: Schwartz Martin A.
Published: February 2010

In 1992, Jere Meredith and I followed up on a serendipitous observation and showed that matrix deprivation can lead to apoptosis. Our article in Molecular Biology of the Cell, together with work form Steve Frisch's lab, helped establish the paradigm that integrin signals control cell survival in a variety of systems. It has been a pleasure to watch that work take on a life of its own as other investigators have explored its role in processes such as cavitation, regression of the mammary gland at the end of pregnancy, cancer metastasis, and tumor resistance to chemotherapy. Recently, we described an exception to the paradigm: In some tumors, reagents that activate integrin signaling enhance apoptosis in response to chemotherapy.
The Yeast Formin Bnr1p Has Two Localization Regions That Show Spatially and Temporally Distinct Association with Septin Structures
Authors: Gao Lina , Liu Wenyu , Bretscher Anthony
Published: February 2010

Formins are conserved eukaryotic proteins that direct the nucleation and elongation of unbranched actin filaments. The yeast formins, Bni1p and Bnr1p, assemble actin cables from the bud cortex and bud neck, respectively, to guide overall cell polarity. Here we examine the regions of Bnr1p responsible for bud neck localization. We define two non-overlapping regions, Bnr1p-L1 (1-466) and Bnr1p-L2 (466-733), that can each localize to the bud neck independently of endogenous Bnr1p. Bnr1p-L1 and Bnr1p-L2 localize with septins at the bud neck, but show slightly differently spatial and temporal localization, reflecting the localization (Bnr1p-L1) or cell cycle timing (Bnr1p-L2) of full-length Bnr1p. Bnr1p is known to be very stably localized at the bud neck, and both Bnr1p-L1 and Bnr1p-L2 also show relatively stable localization there. Overexpression of Bnr1p-L1, but not Bnr1p-L2, disrupts septin organization at the bud neck. Thus Bnr1p has two separable regions that each contribute to its bud neck localization.
Assigning roles to DNA regulatory motifs using comparative genomics
Authors: Buske Fabian A. , Bodén Mikael , Bauer Denis C. , Bailey Timothy L.
Published: February 2010

Motivation: Transcription factors (TFs) are crucial during the lifetime of the cell. Their functional roles are defined by the genes they regulate. Uncovering these roles not only sheds light on the TF at hand but puts it into the context of the complete regulatory network.

Results: Here, we present an alignment- and threshold-free comparative genomics approach for assigning functional roles to DNA regulatory motifs. We incorporate our approach into the Gomo algorithm, a computational tool for detecting associations between a user-specified DNA regulatory motif [expressed as a position weight matrix (PWM)] and Gene Ontology (GO) terms. Incorporating multiple species into the analysis significantly improves Gomo's ability to identify GO terms associated with the regulatory targets of TFs. Including three comparative species in the process of predicting TF roles in Saccharomyces cerevisiae and Homo sapiens increases the number of significant predictions by 75 and 200%, respectively. The predicted GO terms are also more specific, yielding deeper biological insight into the role of the TF. Adjusting motif (binding) affinity scores for individual sequence composition proves to be essential for avoiding false positive associations. We describe a novel DNA sequence-scoring algorithm that compensates a thermodynamic measure of DNA-binding affinity for individual sequence base composition. Gomo's prediction accuracy proves to be relatively insensitive to how promoters are defined. Because Gomo uses a threshold-free form of gene set analysis, there are no free parameters to tune. Biologists can investigate the potential roles of DNA regulatory motifs of interest using Gomo via the web (http://meme.nbcr.net).

Contact:  t.bailey@uq.edu.au

Supplementary information:  Supplementary data are available at Bioinformatics online.