bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical and magnetic interaction along a defective single-walled carbon nanotube channel
Authors: Lee Yun-Hi , Noh Ji-Young
Published: April 2009

We study the electrical and magnetic interaction in a low conduction regime for laterally as-grown defective single-walled carbon nanotube channel as functions of bias and gate voltage, combined with direct current and magnetic phase image by current-atomic force microscopy and magnetic force microscopy. For the SWNT field effect transistor at very low bias direct imaging of the current flow on the 0.9 and 2 nm diameter single-walled nanotube (SWNT) devices revealed that locally conducting islands occur along the SWNT channel, and become an origin of electrical behavior in the stage of minimal conduction. In contrast, the homogenous magnetic interaction along the as-laterally-grown individual SWNT channel observed by magnetic force measurements suggest a hint that as-grown single SWNT channel may be a reliable candidate for use in magnetoelectronics, regardless of whether clean or defective SWNT.
Theoretical investigation of the fundamental mode frequency of A6 magnetron
Authors: Fan Yu-Wei , Liu Jing , Zhong Hui-Huang , Shu Ting , Li Zhi-Qiang
Published: April 2009

The fundamental mode frequency of A6 magnetron is investigated theoretically by the equivalent circuit method, and an exact theoretical formula as a function of structure dimensions is derived. The theoretical results are compared with the simulation and experimental results, and the relative errors, which are calculated according to the theoretical and simulation or experimental frequencies, are less than 3%. So the validity of the theoretical formula is verified. In addition, this approach can also be used in other configurations but some changes need to be made in the formula according to the specific structures.
Structural properties of glucose-dimethylsulfoxide solutions probed by Raman spectroscopy
Authors: Paolantoni Marco , Gallina Maria Elena , Sassi Paola , Morresi Assunta
Published: April 2009

Raman spectroscopy was employed to achieve a molecular level description of solvation properties in glucose-dimethylsulfoxide (DMSO) solutions. The analysis of Raman spectra confirms the importance of the dipole-dipole interaction in determining structural properties of pure DMSO; the overall intermolecular structure is maintained in the whole 20–75 °C temperature range investigated. The blueshift of the CH stretching modes observed at higher temperatures points out that CH3⋯O contacts contribute to the cohesive energy of the DMSO liquid system. The addition of glucose perturbs the intermolecular ordering of DMSO owing to the formation of stable solute-solvent hydrogen bonds. The average number of OH⋯OS contacts (3.2±0.3) and their corresponding energy (∼20 kJ/mol) were estimated. Besides, the concentration dependence of the CH stretching bands and the behavior of the noncoincidence effect on the SO band, suggest that the dipole-dipole and CH3⋯O interactions among DMSO molecules are disfavored within the glucose solvation layer. These findings contribute to improve our understanding about the microscopic origin of solvent properties of DMSO toward more complex biomolecular systems.
The National Ignition Facility: Ushering in a new age for high energy density science
Authors: Moses E. I. , Boyd R. N. , Remington B. A. , Keane C. J. , Al-Ayat R.
Published: April 2009

The National Ignition Facility (NIF) [E. I. Moses, J. Phys.: Conf. Ser. 112, 012003 (2008); https://lasers.llnl.gov/], completed in March 2009, is the highest energy laser ever constructed. The high temperatures and densities achievable at NIF will enable a number of experiments in inertial confinement fusion and stockpile stewardship, as well as access to new regimes in a variety of experiments relevant to x-ray astronomy, laser-plasma interactions, hydrodynamic instabilities, nuclear astrophysics, and planetary science. The experiments will impact research on black holes and other accreting objects, the understanding of stellar evolution and explosions, nuclear reactions in dense plasmas relevant to stellar nucleosynthesis, properties of warm dense matter in planetary interiors, molecular cloud dynamics and star formation, and fusion energy generation.
Improved tunnel magnetoresistance of magnetic tunnel junctions with Heusler Co2FeAl0.5Si0.5 electrodes fabricated by molecular beam epitaxy
Authors: Tezuka N. , Ikeda N. , Mitsuhashi F. , Sugimoto S.
Published: April 2009

The authors have developed a magnetic tunnel junction of Co2FeAl0.5Si0.5 electrodes and a MgO barrier fabricated by molecular beam epitaxy and observed that this device had a tunnel magnetoresistance ratio of 386% at approximately 300 K and 832% at 9 K. The lower Co2FeAl0.5Si0.5 electrode was annealed during and after deposition resulting in a highly ordered structure with small roughness. This highly ordered structure could be obtained by annealing treatment even at low temperatures. Furthermore, a weak temperature dependence of the tunnel magnetoresistance ratio was observed for the developed magnetic tunnel junction.
Decay of vortex rings in a rotating fluid
Authors: Brend M. A. , Thomas P. J.
Published: April 2009

Vortex rings propagating through a rotating fluid, along the axis of rotation, are studied experimentally. The length, xd, traveled by the rings until they have completely decayed is measured. In agreement with theoretical arguments based on the Taylor–Proudman theorem it is observed that the value of xd decreases with decreasing Rossby number, Ro. For the parameter range investigated here we determine an overall, global trend for the scaling of the mean decay length that can be roughly summarized by the expression (xd/D)¯=4.77 Ro1.06, where D is the diameter of the generator nozzle used to produce the vortex rings.
Fingerprints of random flows?
Authors: Wilkinson Michael , Bezuglyy Vlad , Mehlig Bernhard
Published: April 2009

We consider the patterns formed by small rodlike objects advected by a random flow in two dimensions. An exact solution indicates that their direction field is nonsingular. However, we find from simulations that the direction field of the rods does appear to exhibit singularities. First, “scar lines” emerge where the rods abruptly change direction by π. Later, these scar lines become so narrow that they “heal over” and disappear, but their ends remain as point singularities, which are of the same type as those seen in fingerprints. We give a theoretical explanation for these observations.
Self-assembly of densely packed and aligned bilayer ZnO nanorod arrays
Authors: Chow L. , Lupan O. , Heinrich H. , Chai G.
Published: April 2009

We present a method of self-assembly of densely packed and aligned bilayer ZnO nanorod arrays in a hydrothermal synthesis process. The alkali hydrothermal environment first induced the growth of hydrotalcitelike zincowoodwardite plates, which provide a lattice-matched surface for the self-assembly of ZnO nanorod arrays. The high packing density of the ZnO nanorod arrays demonstrates efficient nucleation and growth processes of ZnO on the zincowoodwardite. The interfacial phenomena involved in the growth of ZnO and self-assembly are discussed. The two-dimensional arrays of ZnO nanorods may find future applications in nanoelectronics and nanophotonics.
Intersubband exchange interaction induced by optically excited electron spins in GaAs/AlGaAs quantum wells
Authors: Morita K. , Sanada H. , Matsuzaka S. , Ohno Y. , Ohno H.
Published: April 2009

Spin-dependent intersubband excitonic interactions have been investigated in GaAs/AlGaAs quantum wells by two-color pump and probe spectroscopy. We generated spin-polarized electrons in the lowest subband by resonant excitation of the heavy-hole exciton (E1-HH1) and observed polarization-dependent broadening of the second-subband exciton resonance (E2-HH2 and E2-LH1). The exchange interaction between the first and the second-subband excitons is found to play a crucial role in polarization-dependent spectral modulation as well as spin-independent Coulomb screening.
On the effects of an imposed magnetic field on the elliptical instability in rotating spheroids
Authors: Herreman W. , Le Bars M. , Le Gal P.
Published: April 2009

The effects of an imposed magnetic field on the development of the elliptical instability in a rotating spheroid filled with a conducting fluid are considered. Theoretical and experimental studies of the spin-over mode, as well as a more general short-wavelength Lagrangian approach, demonstrate that the linear growth rate of the instability and the square amplitude of the induced magnetic field fall down linearly with the square of the imposed magnetic field. Application of the results to the Galilean moon Io confirms the fundamental role played by the elliptical instability at the planetary scale.
Length control of He atmospheric plasma jet plumes: Effects of discharge parameters and ambient air
Authors: Xiong Q. , Lu X. , Ostrikov K. , Xiong Z. , Xian Y. , Zhou F. , Zou C. , Hu J. , Gong W. , Jiang Z.
Published: April 2009

The effects of various discharge parameters and ambient gas on the length of He atmospheric plasma jet plumes expanding into the open air are studied. It is found that the voltage and width of the discharge-sustaining pulses exert significantly stronger effects on the plume length than the pulse frequency, gas flow rate, and nozzle diameter. This result is explained through detailed analysis of the I-V characteristics of the primary and secondary discharges which reveals the major role of the integrated total charges of the primary discharge in the plasma dynamics. The length of the jet plume can be significantly increased by guiding the propagating plume into a glass tube attached to the nozzle. This increase is attributed to elimination of the diffusion of surrounding air into the plasma plume, an absence which facilitates the propagation of the ionization front. These results are important for establishing a good level of understanding of the expansion dynamics and for enabling a high degree of control of atmospheric pressure plasmas in biomedical, materials synthesis and processing, environmental and other existing and emerging industrial applications.
Gate-controlled nonvolatile graphene-ferroelectric memory
Authors: Zheng Yi , Ni Guang-Xin , Toh Chee-Tat , Zeng Ming-Gang , Chen Shu-Ting , Yao Kui , Özyilmaz Barbaros
Published: April 2009

In this letter, we demonstrate a nonvolatile memory device in a graphene field-effect-transistor structure using ferroelectric gating. The binary information, i.e., “1” and “0”, is represented by the high and low resistance states of the graphene working channels and is switched by controlling the polarization of the ferroelectric thin film using gate voltage sweep. A nonvolatile resistance change exceeding 200% is achieved in our graphene-ferroelectric hybrid devices. The experimental observations are explained by the electrostatic doping of graphene by electric dipoles at the ferroelectric/graphene interface.
Analysis of hole transport in a polyfluorene-based copolymer— evidence for the absence of correlated disorder
Authors: de Vries R. J. , van Mensfoort S. L. M. , Shabro V. , Vulto S. I. E. , Janssen R. A. J. , Coehoorn R.
Published: April 2009

The presence of spatial correlation between the disordered transport site energies in semiconducting polymers used in organic electronic devices is known to affect the mobility. However, it is not established whether such a correlation is present in relevant polymers. We study hole transport in a polyfluorene-based copolymer and provide evidence for the absence of spatially correlated disorder in this material, based on an analysis of the current-voltage characteristics of sandwich-type devices. Distinguishing correlated from uncorrelated disorder, which we achieve on the basis of the hopping site density, is shown to be highly relevant for the development of quantitative device models.
Selective area wavelength tuning of InAs/GaAs quantum dots obtained by TiO2 and SiO2 layer patterning
Authors: Lee H. S. , Rastelli A. , Kiravittaya S. , Atkinson P. , Bof Bufon C. C. , Mönch I. , Schmidt O. G.
Published: April 2009

Selective area wavelength tuning of InAs quantum dots (QDs) in GaAs matrix is achieved by patterning TiO2 and SiO2 layers on the sample surface followed by rapid thermal processing. After heat treatment, the QD emission under the SiO2 capped areas shows pronounced blueshifts compared with regions capped with TiO2/SiO2, where interdiffusion is strongly suppressed. Finite element calculations of the strain generated by the different thermal expansion coefficients of GaAs, SiO2, and TiO2 at high temperature are used to interpret the results. This method may provide a simple route to achieve monolithic integration of optoelectronic devices based on QDs.
Non-IPR C60 solids
Authors: Löffler Daniel , Bajales Noelia , Cudaj Marcus , Weis Patrick , Lebedkin Sergei , Bihlmeier Angela , Tew David P. , Klopper Wim , Böttcher Artur , Kappes Manfred M.
Published: April 2009

Films comprising predominantly novel isomers of C60 [=C60(nIPR)] have been generated by low energy ion beam deposition of vibronically excited C60+ onto graphite followed by selective sublimation of C60(Ih) from the deposited isomer mixture. The incident ions were generated by electron impact ionization/fragmentation of sublimed C70. Images of the C60(nIPR) films obtained by applying atomic force microscopy show aggregates, which we attribute to covalently interlinked C60(nIPR) units. The covalent bonds are inferred from the significantly higher thermal stability of the C60(nIPR) films compared to the C60(Ih) van der Waals solid–as measured by thermal desorption with mass spectrometric detection of the C60 mass channel (the only desorbable species). In contrast to the characteristic doublet structure of the occupied valence band in the ultraviolet photoelectron spectrum of pure C60(Ih), the valence band of C60(nIPR) films exhibits a triplet feature with the additional peak occurring at a binding energy of ∼2.6 eV. This is an indicator of the electronic modifications induced by intermolecular bonding. C60(nIPR) films exhibit a narrower band gap than found for C60(Ih). They also have significantly different chemical reactivity toward incorporation of thermal energy deuterium atoms. In order to model the experimental photoelectron spectra, various covalently linked oligomers of C#180960(C2v), the second most stable conventional 60-atom fullerene cage, were calculated by means of the density functional theory. These spectral predictions together with analogous previous observations on related fullerene solids such as C58 lead us to infer that C60(nIPR) films consist of fullerene cage isomers containing one or more adjacent pentagon pairs, which mediate covalent cage-cage interconnection.
Theoretical evidence of barrier-free proton transfer in 7-azaindole-water cluster anions
Authors: Chen Hsing-Yin , Young Po-Yu , Hsu Sodio C. N.
Published: April 2009

Water clusters of 7-azaindole (7AI) and its radical anion with up to three water molecules have been investigated by B3LYP and MP2 methods. While the adiabatic electron affinities (AEAs) of 7AI(H2O)n=0,1 and the most stable configuration of 7AI(H2O)2 were calculated to be negative, the AEAs of 7AI(H2O)3 were found to be positive, consistent with the experimental observation that the cluster anions of 7AI−(H2O)n start to appear continuously in mass spectra when n≥3. However, some high-energy configurations of 7AI(H2O)2 were found to have potential for capturing excess electrons and forming stable anions. The B3LYP approach was shown to systematically overestimate the AEA due to its insufficient description of buckling of conjugated ring induced by electron attachment. The computational results show that the activation energy of proton transfer in 7AI−(H2O)n decreases as the number of water molecule increases. For n=3, electron attachment was found to induce a barrier-free proton transfer from water to 7AI−, resulting in the formation of a neutral radical of protonated 7AI solvated by a water cluster of hydroxyl anion, OH−(H2O)2. The protonated structures were found to be lower in energy than the fully tautomerized structures where the tautomeric 7AI radical anion is solvated by a neutral water cluster. In addition, the tautomeric structures were found to be kinetically unstable with respect to the reverse transformation to the protonated structures. These results indicate that the protonated configuration of 7AI−(H2O)3 is the major species detected in molecular beam experiments. This conclusion was further confirmed by the calculations of vertical detachment energies of cluster anions. The van der Waals structures of 7AI−(H2O)3, in which the water molecules locate over the 7AI conjugated ring and point their O−H bonds toward the π-electron cloud, were explored as well. Comparison of the protonation energies for DNA base anions and 7AI anion suggests that analogous proton-transfer reactions might occur in the water clusters of DNA base anions with only few water molecules.
Characterization of microrod arrays by image analysis
Authors: Hillebrand Reinald , Grimm Silko , Giesa Reiner , Schmidt Hans-Werner , Mathwig Klaus , Gösele Ulrich , Steinhart Martin
Published: April 2009

The uniformity of the properties of array elements was evaluated by statistical analysis of microscopic images of array structures, assuming that the brightness of the array elements correlates quantitatively or qualitatively with a microscopically probed quantity. Derivatives and autocorrelation functions of cumulative frequency distributions of the object brightnesses were used to quantify variations in object properties throughout arrays. Thus, different specimens, the same specimen at different stages of its fabrication or use, and different imaging conditions can be compared systematically. As an example, we analyzed scanning electron micrographs of microrod arrays and calculated the percentage of broken microrods.
Epitaxial growth and transport properties of Bi2Sr2Co2Oy thin films by metal organic deposition
Authors: Wang Shufang , Zhang Zicai , He Liping , Chen Mingjing , Yu Wei , Fu Guangsheng
Published: April 2009

Epitaxial Bi2Sr2Co2Oy thin films have been grown on LaAlO3 (001) by metal organic deposition. Detailed x-ray diffraction texture measurements reveal the excellent c-axis and ab-plane alignments. At 300 K, the ab-plane power factor is estimated to be more than two times larger than that of the single crystals due to the very low resistivity and the reasonably large Seebeck coefficient of the films. In addition, a large ab-plane negative magnetoresistance of 38% related to the suppression of the spin scattering is also observed in the films at low temperature.
Unified theory of gas damping of flexible microcantilevers at low ambient pressures
Authors: Bidkar Rahul A. , Tung Ryan C. , Alexeenko Alina A. , Sumali Hartono , Raman Arvind
Published: April 2009

Predicting the gas damping of microcantilevers oscillating in different vibration modes in unbounded gas at low pressures is relevant for increasing the sensitivity of microcantilever-based sensors. While existing free-molecular theories are valid only at very high Knudsen numbers, continuum models are valid only at very low Knudsen numbers. We solve the quasisteady Boltzmann equation and compute a closed-form fit for gas damping of rectangular microcantilevers that is valid over four orders of magnitude of Knudsen numbers spanning the free-molecular, the transition, and the low pressure slip flow regimes. Experiments are performed using silicon microcantilevers under controlled pressures to validate the theory.
Mechanism of gas breakdown near Paschen’s minimum in electrodes with one-dimensional nanostructures
Authors: Hou Zhongyu , Cai Bingchu , Liu Hai
Published: April 2009

The mechanism of the gaseous breakdown in the electrode system with one-dimensional (1D) nanomaterial film is investigated. The hypothesis is suggested that the functionality of the 1D nanostructures in the breakdown is the averaged flux-convergence-effect of multiple nanoelectrodes to the electric field distribution, which leads to a convergence band model for discharge modeling. Theoretical deductions are examined by experiments in air and N2 at pressures (p) near the Paschen’s minimum with gap sizes (d) of ∼335 μm and pd range of 0.01–1 Torr cm. It is suggested that the increased efficiency of the secondary processes and the discharge’s lateral spreading may characterize the breakdown mechanism in electrodes with 1D nanostructures.
A new deconvolution method for large eddy simulation
Authors: Germano M.
Published: April 2009

In this paper we present and we briefly discuss a new way to derive approximate deconvolution subgrid models for the large eddy simulation of turbulent flows.
Effect of In–Ga intermixing on the electronic states in self-assembled InAs quantum dots probed by nanogap electrodes
Authors: Shibata K. , Jung M. , Cha K. M. , Sotome M. , Hirakawa K.
Published: April 2009

We have investigated the effect of In–Ga intermixing on the electronic states in single self-assembled InAs quantum dots (QDs) coupled to nanogap metallic electrodes. The orbital quantization energies of the QDs and the tunnel resistances exhibited a strong dependence on growth temperature, TG, due to In–Ga intermixing during QD formation. When the intermixing was suppressed by reducing TG to 470 °C, the electron wave functions in the QDs become more extended in space and QD-electrode coupling sufficiently strong to form the Kondo singlet states at 4.3 K was realized even in a small QD of ∼45 nm diameter.
In-plane anisotropy of polarized photoluminescence in M-plane (101¯) ZnO and MgZnO/ZnO multiple quantum wells
Authors: Matsui Hiroaki , Tabata Hitoshi
Published: April 2009

Highly polarized photoluminescence (PL) from M-plane ZnO layers and MgZnO/ZnO quantum wells (QWs) grown on ZnO substrates were observed. The energy difference between PL peaks of E⊥c and E∥c corresponded to that between A- and C-excitonic transitions. The polarization degree (P=0.43) at 300 K in QWs was slightly low due to confinement-induced admixture of the Pz orbital to A-excitonic states compared with the ZnO layers (P=0.49). Furthermore, layers with anisotropic compressive strains also showed high polarization anisotropy (P=0.55) at 300 K due to bounded excitonic emissions that reflected the selection rule.
Nonthermal origin of electromigration at gold nanojunctions in the ballistic regime
Authors: Umeno A. , Hirakawa K.
Published: April 2009

We have investigated the electromigration process at gold nanojunctions as small as several tens of atoms. Junction conductance showed successive drops by one conductance quantum, corresponding to one-by-one removal of gold atoms, only when the junction voltage exceeded certain critical values. The peak position in the histogram of the observed critical voltages agreed with the activation energies for surface diffusion of gold atoms. This fact indicates that the elementary process of electromigration in such small junctions is the self-diffusion of metal atoms driven by microscopic kinetic energy transfer from a single conduction electron to a single metal atom.
Bimodal magnetic force microscopy: Separation of short and long range forces
Authors: Li Jason W. , Cleveland Jason P. , Proksch Roger
Published: April 2009

An application of bimodal atomic force microscopy [T. R. Rodriguez and R. Garcia, Appl. Phys. Lett. 84, 449 (2004)] which allows simultaneous and separated imaging of both long range magnetic and shorter range topographical forces is described. This technique has a spatial resolution and a signal-to-noise ratio at least as good as other magnetic force microscopy techniques with the advantage of requiring only a single pass. Besides being an improvement on existing magnetic imaging techniques, the results also shed light on the fundamental contrast mechanisms in bimodal atomic force microscopy because the sign of the long range magnetic forces changes with the sample magnetization, but all the other sample properties such as elasticity and surface roughness remain the same. The results confirm the theoretical predictions of Rodriguez and Garcia.
What Does it Take to Become a Biotech Hot Spot?
Authors: Koo Jun , Bae Jonghoon , Kim Dohyeong
Published: April 2009

The biotech industry is considered to be the next growth engine by many policy makers and economic development scholars. However, our understanding of how the biotech industry evolves and grows is still quite limited. In this study we examine how the industry began and grew, on the basis of a case study and statistical analysis. A case study of the Raleigh–Durham area reveals that the region was fortunate to have strong political leadership accompanied by scientific, industrial, and entrepreneurial assets that set off the initial spark of the biotech growth in the region. In the study's statistical analysis we use the tripod approach to examine the growth of the biotech sector. The results show that the complex interplay of knowledge creation, commercialization, and retention factors determines the growth path of the biotech industry.
Netrin-1–α3β1 integrin interactions regulate the migration of interneurons through the cortical marginal zone
Authors: Stanco Amelia , Szekeres Charles , Patel Nikhil , Rao Sarada , Campbell Kenneth , Kreidberg Jordan A. , Polleux Franck , Anton E. S.
Published: April 2009

Cortical GABAergic interneurons, most of which originate in the ganglionic eminences, take distinct tangential migratory trajectories into the developing cerebral cortex. However, the ligand–receptor systems that modulate the tangential migration of distinct groups of interneurons into the emerging cerebral wall remain unclear. Here, we show that netrin-1, a diffusible guidance cue expressed along the migratory routes traversed by GABAergic interneurons, interacts with α3β1 integrin to promote interneuronal migration. In vivo analysis of interneuron-specific α3β1 integrin, netrin-1–deficient mice (α
3
lox/−
Dlx5/6-CIE,
netrin-1
−/−
) reveals specific deficits in the patterns of interneuronal migration along the top of the developing cortical plate, resulting in aberrant interneuronal positioning throughout the cerebral cortex and hippocampus of conditional α
3
lox/−
Dlx5/6-CIE,
netrin-1
−/−
mice. These results indicate that specific guidance mechanisms, such as netrin-1–α3β1 integrin interactions, modulate distinct routes of interneuronal migration and the consequent positioning of groups of cortical interneurons in the developing cerebral cortex.
Bursting of sensitive polymersomes induced by curling
Authors: Mabrouk Elyes , Cuvelier Damien , Brochard-Wyart Françoise , Nassoy Pierre , Li Min-Hui
Published: April 2009

Polymersomes, which are stable and robust vesicles made of block copolymer amphiphiles, are good candidates for drug carriers or micro/nanoreactors. Polymer chemistry enables almost unlimited molecular design of responsive polymersomes whose degradation upon environmental changes has been used for the slow release of active species. Here, we propose a strategy to remotely trigger instantaneous polymersome bursting. We have designed asymmetric polymer vesicles, in which only one leaflet is composed of responsive polymers. In particular, this approach has been successfully achieved by using a UV-sensitive liquid-crystalline copolymer. We study experimentally and theoretically this bursting mechanism and show that it results from a spontaneous curvature of the membrane induced by the remote stimulus. The versatility of this mechanism should broaden the range of applications of polymersomes in fields such as drug delivery, cosmetics and material chemistry.
Regulated expression of the
Leishmania major
surface virulence factor lipophosphoglycan using conditionally destabilized fusion proteins
Authors: Madeira da Silva Luciana , Owens Katherine L. , Murta Silvane M. F. , Beverley Stephen M.
Published: April 2009

Surface glycoconjugates play important roles in the infectious cycle of
Leishmania major
, including the abundant lipophosphoglycan (LPG) implicated in parasite survival in the sand fly vector and the initial stages of establishment in the mammalian host macrophage. We describe a system for inducible expression of LPG, applying a novel protein-based system that allows controlled degradation of a key LPG biosynthetic enzyme, UDP-galactopyranose mutase (UGM). This methodology relies on a mutated FK506-binding protein (FKBP) destabilizing domain (dd) fused to the protein of interest; in the absence of rapamycin analogs, such as Shld1, the dd domain is destabilized, leading to proteasomal degradation, whereas drug treatment confers stabilization. Tests in
L. major
using dd fusions to a panel of reporters and cellular proteins confirmed its functionality, with a high degree of regulation and low background, and we established the kinetics of protein activation and/or loss. Two inexpensive and widely available ligands, FK506 and rapamycin, functioned similarly to Shld1, without effect on
Leishmania
growth or differentiation. We generated parasites lacking UGM through deletion of the
GLF
gene and substitution with a
ddGLF
fusion construct, either as chromosomal knockins or through episomal complementation; these showed little or no LPG expression in the absence of inducer, whereas in its presence, high levels of LPG were attained rapidly. Complement lysis tests confirmed the correct integrity of the
Leishmania
LPG coat. These data suggest that the dd approach has great promise in the study of LPG and other pathways relevant to parasite survival and virulence.
Efficient production of mesencephalic dopamine neurons by Lmx1a expression in embryonic stem cells
Authors: Friling Stina , Andersson Elisabet , Thompson Lachlan H. , Jönsson Marie E. , Hebsgaard Josephine B. , Nanou Evanthia , Alekseenko Zhanna , Marklund Ulrika , Kjellander Susanna , Volakakis Nikolaos , Hovatta Outi , El Manira Abdeljabbar , Björklund Anders , Perlmann Thomas , Ericson Johan
Published: April 2009

Signaling factors involved in CNS development have been used to control the differentiation of embryonic stem cells (ESCs) into mesencephalic dopamine (mesDA) neurons, but tend to generate a limited yield of desired cell type. Here we show that forced expression of Lmx1a, a transcription factor functioning as a determinant of mesDA neurons during embryogenesis, effectively can promote the generation of mesDA neurons from mouse and human ESCs. Under permissive culture conditions, 75%–95% of mouse ESC-derived neurons express molecular and physiological properties characteristic of bona fide mesDA neurons. Similar to primary mesDA neurons, these cells integrate and innervate the striatum of 6-hydroxy dopamine lesioned neonatal rats. Thus, the enriched generation of functional mesDA neurons by forced expression of Lmx1a may be of future importance in cell replacement therapy of Parkinson disease.
Electrophysiological characterization of LacY
Authors: Garcia-Celma Juan J. , Smirnova Irina N. , Kaback H. Ronald , Fendler Klaus
Published: April 2009

Electrogenic events due to the activity of wild-type lactose permease from
Escherichia coli
(LacY) were investigated with proteoliposomes containing purified LacY adsorbed on a solid-supported membrane electrode. Downhill sugar/H
+
symport into the proteoliposomes generates transient currents. Studies at different lipid-to-protein ratios and at different pH values, as well as inactivation by
N
-ethylmaleimide, show that the currents are due specifically to the activity of LacY. From analysis of the currents under different conditions and comparison with biochemical data, it is suggested that the predominant electrogenic event in downhill sugar/H
+
symport is H
+
release. In contrast, LacY mutants Glu-325→Ala and Cys-154→Gly, which bind ligand normally, but are severely defective with respect to lactose/H
+
symport, exhibit only a small electrogenic event on addition of LacY-specific substrates, representing 6% of the total charge displacement of the wild-type. This activity is due either to substrate binding per se or to a conformational transition after substrate binding, and is not due to sugar/H
+
symport. We propose that turnover of LacY involves at least 2 electrogenic reactions: (
i
) a minor electrogenic step that occurs on sugar binding and is due to a conformational transition in LacY; and (
ii
) a major electrogenic step probably due to cytoplasmic release of H
+
during downhill sugar/H
+
symport, which is the limiting step for this mode of transport.
When ‘Speech Islands’ Aren’t Islands: Parallel independent development, drift, and minimal levels of contact for diffusion
Authors: Hartman Keiser Steven
Published: April 2009

This study explores the related concepts of parallel independent development and drift, highlighting in particular the challenge of quantifying isolation. I analyze the precisely synchronized spread of a sound change, the monophthongization of /aɪ/, across Pennsylvania German ‘speech islands’ in the American Midwest. A key finding is that the intensity and duration of interspeaker contact required to catalyze apparent parallel developments may have lower than expected thresholds. The significance of extensive yet low-intensity cross-migration patterns across these communities at particular points in their histories ultimately leads to an exploration of the minimal level of contact required for diffusion of a change and feeds into recent discussion on the social contexts for transmission and diffusion (e.g., Labov 2007).
Word Order in Old and Middle English
Authors: Westergaard Marit
Published: April 2009

In the history of English one finds a mixture of V2 and non-V2 word order in declaratives for several hundred years, with frequencies suggesting a relatively gradual development in the direction of non-V2. Within an extended version of a cue-based approach to acquisition and change, this paper argues that there are many possible V2 grammars, differing from each other with respect to clause types, information structure, and the behavior of specific lexical elements. This variation may be formulated in terms of micro-cues. Child language data from present-day mixed systems show that such grammars are acquired early. The apparent optionality of V2 in the history of English may thus be considered to represent several different V2 grammars in succession, and it is not necessary to refer to competition between two major parameter settings. Diachronic language development can thus be argued to occur in small steps, reflecting the loss of micro-cues, and giving the impression that change is gradual.
Intergenerational Spanish transmission in El Paso, Texas
Authors: Velázquez Isabel
Published: April 2009

This study examines the beliefs held by a group of adult Spanish-English bilinguals from El Paso, Texas regarding the vitality of Spanish in their community and the ways in which their own experience of being bilingual on the US-Mexico border has influenced their perceptions of the benefits and costs of fostering Spanish development in their children. Results show that parents’ positive attitudes toward Spanish did not translate into the investment of time and resources to foster Spanish development in their children nor, ultimately, into the use of Spanish by their children. Households where the mother perceived herself as having an active role in her children’s linguistic development and where she perceived both Spanish and a bilingual/biethnic identity as desirable for her children’s future were also households where children were expected to speak Spanish at home and where more opportunities for linguistic development were present. The author argues that these beliefs must be understood as a consequence of the underlying tensions present in the community, where intense linguistic and interethnic contact takes place every day.
The doctoral experience in science: Challenging the current orthodoxy
Authors: Cumming Jim
Published: April 2009

Drawing on the literature this article identifies five characteristics that are frequently attributed to the doctoral student experience in the natural and physical sciences. These are then used to assist with the interpretation of qualitative data derived from a study in the earth sciences at a research‐intensive university in Australia. Case narrative is employed to synthesise three insider perspectives—a candidate and her co‐supervisors—as well as to capture the particularity of the contemporary doctoral enterprise. While similarities to the current orthodoxy can be identified in this study, it is the subtle variations and significant points of departure that reveal a higher level of complexity than is generally acknowledged.
Reported school experiences of young people living with sickle cell disorder in England
Authors: Dyson Simon Martin , Abuateya Hala , Atkin Karl , Culley Lorraine , Dyson Sue Elizabeth , Rowley Dave ,   Members of the Sickle Cell and Education (SCED) Group
Published: April 2009

A survey of 569 young people with sickle cell disorder (SCD) in England has found such pupils miss considerable periods of time from school, typically in short periods of two or three days. One in eight has school absences equating to government‐defined ‘persistent absence’. Students with SCD report that they are not helped to catch up after these school absences. Half the children reported not being allowed to use the toilet when needed and not being allowed water in class; a third reported being made to take unsuitable exercise and being called lazy when tired. Children perceived both physical environment (temperature, school furniture) and social environment (being upset by teachers or other pupils) as triggers to episodes of their illness. Policy initiatives on school absences; preventive measures to ensure maintenance of good health; and measures to prevent perceived social attitudes precipitating ill health would also support children with other chronic illnesses at school.
Self‐modelling as a relapse intervention following speech‐restructuring treatment for stuttering
Authors: Cream Angela , O'Brian Sue , Onslow Mark , Packman Ann , Menzies Ross
Published: April 2009

Background: Speech restructuring is an efficacious method for the alleviation of stuttered speech. However, post‐treatment relapse is common.

Aims: To investigate whether the use of video self‐modelling using restructured stutter‐free speech reduces stuttering in adults who had learnt a speech‐restructuring technique and subsequently relapsed.

Methods & Procedures: Participants were twelve adults who had previously had speech‐restructuring treatment for stuttering and relapsed. They were video recorded for 1 hour within the clinic, practising their speech‐restructuring technique. The videos were then edited to remove all observable stuttering. Participants then viewed the resulting video of themselves using restructured stutter‐free speech each day for 1 month and were instructed to speak as they did on the video. Beyond‐clinic speech samples and self‐report severity data were collected before and after the intervention.

Outcomes & Results: Very large effect sizes were found. The mean per cent syllables stuttered was 7.7 pre‐intervention and 2.3 post‐intervention. For all but one participant there was a reduction in stuttering from pre‐intervention to post‐intervention. These results were verified with self‐report data. Speech naturalness was not compromised by the video self‐modelling procedure.

Conclusion & Implications: Video self‐modelling as a relapse management tool does not involve excessive time expenditure by the clinician or the client. The study indicates video self‐modelling is potentially useful for managing relapse after speech‐restructuring treatment for stuttering, and in some cases may be a stand‐alone procedure to manage relapse. Phase II and III trials are warranted to determine the size and duration of the effect. It is suggested video self‐modelling could also be included in a relapse management plan.
Cognitive predictors of language development in children with specific language impairment (SLI)
Authors: van Daal John , Verhoeven Ludo , van Balkom Hans
Published: April 2009

Background: Language development is generally viewed as a multifactorial process. There are increasing indications that this similarly holds for the problematic language development process.

Aims: A population of 97 young Dutch children with specific language impairment (SLI) was followed over a 2‐year period to provide additional evidence for the existence of underlying language factors. Furthermore, the children's language development was related to their non‐verbal intellectual reasoning capacity.

Methods & Procedures: The language abilities were assessed via the administration of an extensive battery of language tests. Cognition was assessed via administration of the Raven progressive matrices, short‐term memory capacity via administration of the Digit Span task.

Outcomes & Results: The results provide empirical support for distinct language factors for children with language problems. The detected factors were labelled: phonology, lexical–semantics, syntax, and speech production, and were found to be stable and interrelated. Short‐term memory showed strong relations with the language factor syntax and medium relations with the other language factors. Intellectual capacity showed weak to medium relations with three language factors but no relation with the factor speech.

Conclusions & implications: The language development of 5‐ and 6‐year‐old Dutch children with SLI appears to be divided into four language factors. The language factors are very stable in this sample and correspond with language factors found in recent studies on language development in children with SLI. Short‐term auditory memory turns out to play an important role in the problematic language acquisition of children with SLI. It is recommended that children with SLI should be assessed on possible deficits in information processing and/or short‐term memory. The existence of such deficits calls for specific neuropsychological intervention.
Humanin Inhibits Neuronal Cell Death by Interacting with a Cytokine Receptor Complex or Complexes Involving CNTF Receptor α/WSX-1/gp130
Authors: Hashimoto Yuichi , Kurita Megumi , Aiso Sadakazu , Nishimoto Ikuo , Matsuoka Masaaki
Published: April 2009

Humanin (HN) inhibits neuronal death induced by various Alzheimer's disease (AD)-related insults via an unknown receptor on cell membranes. Our earlier study indicated that the activation of STAT3 was essential for HN-induced neuroprotection, suggesting that the HN receptor may belong to the cytokine receptor family. In this study, a series of loss-of-function tests indicated that gp130, the common subunit of receptors belonging to the IL-6 receptor family, was essential for HN-induced neuroprotection. Overexpression of ciliary neurotrophic factor receptor α (CNTFR) and/or the IL-27 receptor subunit, WSX-1, but not that of any other tested gp130-related receptor subunit, up-regulated HN binding to neuronal cells, whereas siRNA-mediated knockdown of endogenous CNTFR and/or WSX-1 reduced it. These results suggest that both CNTFR and WSX-1 may be also involved in HN binding to cells. Consistent with these results, loss-of-functions of CNTFR or WSX-1 in neuronal cells nullified their responsiveness to HN-mediated protection. In vitro–reconstituted binding assays showed that HN, but not the other control peptide, induced the hetero-oligomerization of CNTFR, WSX-1, and gp130. Together, these results indicate that HN protects neurons by binding to a complex or complexes involving CNTFR/WSX-1/gp130.
Systematic analysis of synchronized oscillatory neuronal networks reveals an enrichment for coupled direct and indirect feedback motifs
Authors: Dong Chao-Yi , Lim Jisoon , Nam Yoonkey , Cho Kwang-Hyun
Published: April 2009

Motivation: Synchronized bursting behavior is a remarkable phenomenon in neural dynamics. So, identification of the underlying functional structure is crucial to understand its regulatory mechanism at a system level. On the other hand, we noted that feedback loops (FBLs) are commonly used basic building blocks in engineering circuit design, especially for synchronization, and they have also been considered as important regulatory network motifs in systems biology. From these motivations, we have investigated the relationship between synchronized bursting behavior and feedback motifs in neural networks.

Results: Through extensive simulations of synthetic spike oscillation models, we found that a particular structure of FBLs, coupled direct and indirect positive feedback loops (PFLs), can induce robust synchronized bursting behaviors. To further investigate this, we have developed a novel FBL identification method based on sampled time-series data and applied it to synchronized spiking records measured from cultured neural networks of rat by using multi-electrode array. As a result, we have identified coupled direct and indirect PFLs.

Conclusion: We therefore conclude that coupled direct and indirect PFLs might be an important design principle that causes the synchronized bursting behavior in neuronal networks although an extrapolation of this result to in vivo brain dynamics still remains an unanswered question.

Contact:  ckh@kaist.ac.kr; ynam@kaist.ac.kr

Supplementary Material:  Supplementary data are available at Bioinformatics online.
Patterns of late gadolinium enhancement are associated with ventricular stiffness in patients with advanced non‐ischaemic dilated cardiomyopathy†
Authors: Choi Eui‐Young , Choi Byoung Wook , Kim Sung‐Ai , Rhee Sang Jae , Shim Chi Young , Kim Young Jin , Kang Seok‐Min , Ha Jong‐Won , Chung Namsik
Published: April 2009

Aims

Despite the prognostic importance of ventricular filling and ventricular–arterial interaction in patients with advanced systolic heart failure, the structural determinants of these parameters have not been fully studied. We aimed to investigate whether patterns of late gadolinium enhancement (LGE) on cardiac magnetic resonance affect ventricular elastic properties or performance in patients with non‐ischaemic dilated cardiomyopathy (DCM).

Methods and results

Patients (n = 49) with markedly reduced systolic function (left ventricular (LV) ejection fraction <35%) due to longstanding non‐ischaemic DCM underwent contrast‐enhanced cardiac magnetic resonance after comprehensive echo‐Doppler evaluations. The single beat‐derived end‐diastolic elastance, end‐systolic elastance, arterial elastance, and dyssynchrony indices were measured by echo. On the basis of LGE patterns, patients could be divided into three groups: non‐LGE (n = 18), non‐midwall LGE (n = 13), and midwall LGE (n = 18). The midwall LGE group had lower LV systolic longitudinal velocity (4.6 ± 1.7 for non‐LGE vs. 4.3 ± 1.2 for non‐midwall LGE vs. 3.5 ± 1.0 cm/s for midwall LGE, P = 0.025), higher end‐diastolic elastance index (0.41 ± 0.21 vs. 0.46 ± 0.31 vs. 0.85 ± 0.51 respectively, P = 0.008), and a more impaired ventriculoarterial coupling index (3.14 ± 1.53 vs. 2.88 ± 1.94 vs. 5.52 ± 3.18, P = 0.006) than other subgroups.

Conclusion

Patients with midwall LGE had a higher ventricular stiffness index and more impaired ventriculoarterial coupling when compared with other non‐ischaemic DCM patients.
Cocaine self-administration alters the relative effectiveness of multiple memory systems during extinction
Authors: Gabriele Amanda , Setlow Barry , Packard Mark G.
Published: April 2009

Rats were trained to run a straight-alley maze for an oral cocaine or sucrose vehicle solution reward, followed by either response or latent extinction training procedures that engage neuroanatomically dissociable “habit” and “cognitive” memory systems, respectively. In the response extinction condition, rats performed a runway approach response to an empty fluid well. In the latent extinction condition, rats were placed at the empty fluid well without performing a runway approach response. Rats trained with the sucrose solution displayed normal extinction behavior in both conditions. In contrast, rats trained with the cocaine solution showed normal response extinction but impaired latent extinction. The selective impairment of latent extinction indicates that oral cocaine self-administration alters the relative effectiveness of multiple memory systems during subsequent extinction training.