bluuebunny/crossref_metadata_2025 huggingface dataset:
Low thermal hysteresis pyroelectric response near the ferroelectric/antiferroelectric phase transition in Pb0.97La0.02(Zr0.42Sn0.40Ti0.18)O3 ceramics
Authors: Zhang Hongling , Chen Xuefeng , Cao Fei , Wang Genshui , Dong Xianlin , Gu Yan , He Hongliang , Liu Yusheng
Published: October 2010

The phase state of Pb0.97La0.02(Zr0.42Sn0.40Ti0.18)O3 (PLZST2) ceramics was studied by transmission electron microscopy analysis as well as polarization versus electric field (P-E) hysteresis loops. The initial state of this PLZST2 composition is ferroelectric (FE) and it transforms into antiferroelectric (AFE) as temperature increases. Change in polarization during this FE/AFE phase transition results in large pyroelectric response. A pyroelectric coefficient maximum about 220×10−8 C cm−2 K−1 is obtained for 3 kV/mm poled sample. Reversible pyroelectric response with large pyroelectric coefficient (>75×10−8 C cm−2 K−1) and low thermal hysteresis (<1.5 °C) is obtained under a dc bias of 0.6 kV/mm.
Microwave properties of epitaxial (111)-oriented Ba0.6Sr0.4TiO3 thin films on Al2O3(0001) up to 40 GHz
Authors: Yang Lihui , Ponchel Freddy , Wang Genshui , Rémiens Denis , Légier Jean-Fançois , Chateigner Daniel , Dong Xianlin
Published: October 2010

Perovskite Ba0.6Sr0.4TiO3 (BST) thin films have been grown on Al2O3(0001) substrates without/with inserting an ultrathin TiOx seeding layer by rf magnetron sputtering. X-ray diffraction and pole figure studies reveal that the film with the TiOx layer (12-Å-thick) is highly oriented along the (111) direction and exhibits a good in-plane relationship of BST(111)∥Al2O3(0001). The high frequency dielectric measurements demonstrate that the complex permittivity (ε=ε′−jε″) is well described by a Curie–von Scheidler dispersion with an exponent of 0.40. The resulting epitaxial BST films show high permittivity (∼428) and tunability (∼41%, at 300 kV/cm and 40 GHz) and their microwave properties (1–40 GHz) potentially could be made suitable for tunable devices.
A neutron camera system for MAST
Authors: Cecconello M. , Turnyanskiy M. , Conroy S. , Ericsson G. , Ronchi E. , Sangaroon S. , Akers R. , Fitzgerald I. , Cullen A. , Weiszflog M.
Published: October 2010

A prototype neutron camera has been developed and installed at MAST as part of a feasibility study for a multichord neutron camera system with the aim to measure the spatial and time resolved 2.45 MeV neutron emissivity profile. Liquid scintillators coupled to a fast digitizer are used for neutron/gamma ray digital pulse shape discrimination. The preliminary results obtained clearly show the capability of this diagnostic to measure neutron emissivity profiles with sufficient time resolution to study the effect of fast ion loss and redistribution due to magnetohydrodynamic activity. A minimum time resolution of 2 ms has been achieved with a modest 1.5 MW of neutral beam injection heating with a measured neutron count rate of a few 100 kHz.
Sensitive surface loop-gap microresonators for electron spin resonance
Authors: Twig Ygal , Suhovoy Ekaterina , Blank Aharon
Published: October 2010

This work presents the design, construction, and experimental testing of unique sensitive surface loop-gap microresonators for electron spin resonance (ESR) measurements. These resonators are made of “U”-shaped gold structures with typical sizes of 50 and 150 μm that are deposited on a thin (220 μm) rutile substrate and fed from the rear by a microstrip line. This allows accommodating a large flat sample above the resonator in addition to having variable coupling properties. Such resonators have a very small volume which, compared to previous designs, improves their absolute spin sensitivity by a factor of more than 2 (based on experimental results). They also have a very high microwave field-power conversion ratio of up to 86 gauss/√Hz. This could facilitate the use of very short excitation pulses with relatively low microwave power. Following the presentation and the discussion of the experimental results, ways to further increase sensitivity significantly are outlined.
A surface work function measurement technique utilizing constant deflected grazing electron trajectories: Oxygen uptake on Cu(001)
Authors: Ermakov A. V. , Ciftlikli E. Z. , Syssoev S. E. , Shuttleworth I. G. , Hinch B. J.
Published: October 2010

We report on the application of a novel nondestructive in-vacuum technique for relative work function measurements, employing a grazing incidence electron deflection above a sample with a planar surface. Two deflected electron beam detectors are used as a position sensitive detector to control feedback to the sample potential as the sample work function changes. With feedback the sample potential exactly follows the surface sample-size averaged work function variation, so that the deflected beam trajectory remains stable. We also discuss methods to optimize the initial electron trajectories for this method, so as to minimize unwanted effects such as from uncontrolled external magnetic fields. As the electron beam does not impinge on the surface in this new technique electron induced desorption, ionization, dissociation, and/or decomposition is not induced at the interface. Importantly also the technique allows for free access to the surfaces enabling simultaneous deposition/evaporation and/or application of other surface characterization methods. We demonstrate its application in concurrent measurements of helium atom reflectivity and work function changes taking place during molecular oxygen exposure of a Cu(001) surface. A work function measurement sensitivity and stability is demonstrated at ∼10 mV at a sampling rate of 1 Hz and after application of an ∼7 s smoothing routine. In comparison to the helium atom reflectivity measurements, the work function measurements are more sensitive to the initial O uptake, and less so to the final coverage variations and possible surface reordering at higher O coverages.
Electronic and optical properties of GaN/AlN quantum dots on Si(111) subject to in-plane uniaxial stresses and variable excitation
Authors: Moshe O. , Rich D. H. , Birner S. , Povolotskyi M. , Damilano B. , Massies J.
Published: October 2010

We have studied the excitation- and polarization-dependent optical properties of GaN/AlN self-assembled quantum dots (QDs) grown on Si(111) substrates. Ensembles of QDs were subject to various external stress configurations that resulted from the thermal expansion coefficient mismatch between the GaN/AlN layers and the Si(111) substrate and ranged from in-plane uniaxial stress, primarily along the ⟨112¯0⟩ directions, to in-plane biaxial stress, having magnitudes ranging from 20–30 kbar. Limited regions of uniaxial stress were obtained by exploiting naturally occurring microcracks that form during the postgrowth cooling. These microcracks act as stressors in order to create the highly localized regions of uniaxial stress. The local strain tensors for such QDs, which are subject to an interfacial stress perturbation, have been determined by modeling the dependence of the QD excitonic transition energy on the interfacial stress. Cathodoluminescence (CL) measurements of the excitonic transitions exhibit an in-plane linear polarization anisotropy in close proximity to microcracks. The polarization anisotropy is strongly dependent on the sample temperature and the electron beam excitation conditions used to excite the QD ensemble. Localized CL spectroscopy of the QDs exhibits emissions from both the ground and excited states, whose relative contributions depend on the level of excitation and temperature. Experimental results indicate that the polarization anisotropy vanishes at high temperatures (∼300 K) with an increasing excitation of the QDs, while the anisotropy decreases more slowly with excitation at low temperatures (∼60 K). A theoretical modeling of the effect of carrier filling on the polarization anisotropy and the excitonic transition energy was performed, as based on three-dimensional self-consistent solutions of the Schrödinger and Poisson equations using the 6×6 k⋅p and effective mass methods for calculations of the e-h wave functions and electron and hole quasi-Fermi levels for varying levels of state filling. We attribute carrier filling and a thermal excitation of holes into higher energy QD hole states during excitation to account for the observed gradual decrease in the polarization anisotropy with an increasing electron-hole pair excitation density at T=300 K.
Development of a compact tomography camera system using a multianode photomultiplier tube for compact torus experiments
Authors: Tomuro H. , Asai T. , Iguchi K. , Takahashi Ts. , Hirano Y.
Published: October 2010

A compact tomography camera system consisting of a photomultiplier tube, a multislit optical system, and a band-pass interference filter has been developed. The viewing area and spatial resolution can be configured by the arrangement of the slit system. The camera system has been specially designed for self-organized compact torus experiments having strong magnetohydrodynamics events with a submicrosecond time-scale. The developed system has been tested on a field-reversed configuration formed by the field-reversed theta-pinch. Performance evaluation of the system has been performed by comparison to the former optical system.
Kinetic theory of electrostatic “bounce” modes in two-dimensional current sheets
Authors: Tur A. , Louarn P. , Yanovsky V.
Published: October 2010

The role of trapped particles in the destabilization of two-dimensional (2D) current sheets is investigated for applications to theories of magnetospheric substorms. Considering a 2D “Lembège and Pellat” equilibrium, the linearized gyrokinetic Vlasov–Maxwell equations are solved for electrostatic perturbations with periods close to the typical electron bounce period (τbe). The particle bounce motion is approximated to its first Fourier component (ωb=2π/τb) which allows the explicit time integration of Vlasov equation and the calculation of the nonlocal particle response. The dispersion equation of the electrostatic bounce modes is derived from the quasineutrality condition. It is shown that the bounce modes exist in a narrow domain of electron-to-ion temperature ratio (Te/Ti varying from 0.2 to 1.4), with large growth rates (δ∼0.2ω), leading to current sheet destabilization over time scales of 1–2 min.
Ultrashort electron pulses as a four-dimensional diagnosis of plasma dynamics
Authors: Zhu P. F. , Zhang Z. C. , Chen L. , Li R. Z. , Li J. J. , Wang X. , Cao J. M. , Sheng Z. M. , Zhang J.
Published: October 2010

We report an ultrafast electron imaging system for real-time examination of ultrafast plasma dynamics in four dimensions. It consists of a femtosecond pulsed electron gun and a two-dimensional single electron detector. The device has an unprecedented capability of acquiring a high-quality shadowgraph image with a single ultrashort electron pulse, thus permitting the measurement of irreversible processes using a single-shot scheme. In a prototype experiment of laser-induced plasma of a metal target under moderate pump intensity, we demonstrated its unique capability of acquiring high-quality shadowgraph images on a micron scale with a-few-picosecond time resolution.
High performance multiwall carbon nanotube bolometers
Authors: Lu Rongtao , Shi Jack J. , Baca F. Javier , Wu Judy Z.
Published: October 2010

High infrared bolometric photoresponse has been observed in multiwall carbon nanotube (MWCNT) films at room temperature. The observed detectivity D∗ in exceeding 3.3×106 cm Hz1/2/W on MWCNT film bolometers is a factor of 7 higher than that obtained on the single-wall CNT (SWCNT) counterparts. The response time of about 1–2 ms on MWCNT bolometers is more than an order of magnitude shorter than that of SWCNT bolometers. The observed high performance may be attributed to the naturally suspended inner-shell structure in a MWCNT, which enhances photon absorption and restricts bolometer external thermal link to environment.
Silicon carbide oxidation in the presence of cesium: Modeling and analysis
Authors: Chatterjee Aveek , Piao Hong , Matocha Kevin , Fronheiser Jody , Tilak Vinayak , Smentkowski Vincent
Published: October 2010

In this work we have focused on investigating the interaction of cesium (Cs) atom/ion with the oxidant and carbon cluster defects at the SiC/SiO2 interface using atomistic scale computational techniques and experimental characterization methods. We observe that Cs behaves significantly different from sodium (Na) at the SiC/SiO2 interface. Our analyses indicate that Cs tends to form a strong bond with the incoming oxygen molecule, leading to the formation of Cs oxide and suboxides. Results suggest that Cs does not reduce the penetration barrier of the impinging oxidant (O2 molecule). Also, unlike Na, Cs is unable to increase the Fermi energy of SiC/SiO2 interface. Finally, lateral metal–oxide–semiconductor field-effect transistors (MOSFETs) were fabricated (using Cs) yielding mobilities less than 1 cm2/V s versus ∼100 cm2/V s fabricated using Na.
Structural and electrical characteristics of high quality (100) orientated-Zn3N2 thin films grown by radio-frequency magnetron sputtering
Authors: Xing G. Z. , Wang D. D. , Yao B. , Qune L. F. N. Ah , Yang T. , He Q. , Yang J. H. , Yang L. L.
Published: October 2010

We report on highly crystalline zinc nitride (Zn3N2) thin films which were grown by rf magnetron sputtering on quartz substrates. The substrate temperature during growth is found to strongly affect the crystal quality of the thin films. The chemical bonding states were determined by x-ray photoelectron spectroscopy. Large chemical shifts in core-level N 1s peaks with binding energy of 396.4 eV were observed as compared to N 1s of free amine (398.8 eV), indicating Zn–N bond formation. Two N 1s states were found: one is N1 formed by Zn–N bonds and another is (N2) produced by substitution of N molecules at N ion sites, which leads to larger lattice constants, consistent with x-ray diffraction results. Temperature-dependent Hall effect measurements of our Zn3N2 films exhibited distinct conduction mechanisms at specific different temperature ranges.
The two- to three-dimensional growth transition of InAs/GaAs epitaxy layer studied by reflectance difference spectroscopy
Authors: Zhou G. Y. , Chen Y. H. , Tang C. G. , Liang L. Y. , Jin P. , Wang Z. G.
Published: October 2010

In this work, we have adopted reflectance difference spectroscopy to study the evolution of InAs layer grown at different temperatures in GaAs matrix. Associated with the two- to three-dimensional growth transition of InAs layer, the transition energies and the in-plane optical anisotropy of InAs wetting layer exhibit abrupt changes. This provides a new way to decide the critical thickness hc for the growth transition. The obtained hcs are compared with those determined by atomic force microscope measurement, and discrepancy is found at high temperatures. The origin of the difference is clarified and the variations in hc with temperature are further discussed.
Memory effect in cadmium telluride quantum dots doped ferroelectric liquid crystals
Authors: Kumar A. , Prakash J. , Khan Mohd Taukeer , Dhawan S. K. , Biradar A. M.
Published: October 2010

A pronounced memory effect has been observed in cadmium telluride quantum dots (CdTe-QDs) doped ferroelectric liquid crystals (FLCs) by using dielectric and electro-optical methods. The memory effect has been attributed to the charge storage on the CdTe-QDs upon the application of dc bias across the sample cell. The FLC molecules remain in the switched state in vicinity of the charge stored on QDs even after removal of bias. It has been observed that the memory effect depends on doping concentrations of CdTe-QDs and the FLC material used.
Hydrogen compounds of group-IV nanosheets
Authors: Lew Yan Voon L. C. , Sandberg E. , Aga R. S. , Farajian A. A.
Published: October 2010

The structural and electronic properties of the hydrides of silicene and germanene have been studied using ab initio calculations. The trend for the M–H (M=C, Si, and Ge) bond lengths, and corresponding bond energies, is consistent with the atomic size trend, and comparable to those of MH4 hydrides. Band structures were also obtained for the buckled configuration, which is the stable form for both silicene and germanene. Upon hydrogenation, both silicane (indirect gap) and germanane (direct gap) are semiconducting.
Functionalizing self-assembled GaN quantum dot superlattices by Eu-implantation
Authors: Magalhães S. , Peres M. , Fellmann V. , Daudin B. , Neves A. J. , Alves E. , Monteiro T. , Lorenz K.
Published: October 2010

Self-assembled GaN quantum dots (QDs) stacked in superlattices (SL) with AlN spacer layers were implanted with Europium ions to fluences of 1013, 1014, and 1015 cm−2. The damage level introduced in the QDs by the implantation stays well below that of thick GaN epilayers. For the lowest fluence, the structural properties remain unchanged after implantation and annealing while for higher fluences the implantation damage causes an expansion of the SL in the [0001] direction which increases with implantation fluence and is only partly reversed after thermal annealing at 1000 °C. Nevertheless, in all cases, the SL quality remains very good after implantation and annealing with Eu ions incorporated preferentially into near-substitutional cation sites. Eu3+ optical activation is achieved after annealing in all samples. In the sample implanted with the lowest fluence, the Eu3+ emission arises mainly from Eu incorporated inside the QDs while for the higher fluences only the emission from Eu inside the AlN-buffer, capping, and spacer layers is observed.
A class of vortex filament solitons in fluids, plasmas, and superconductors
Authors: Perline Ron
Published: October 2010

We consider the Uby–Isichenko–Yankov (UIY) equation for vortex filament dynamics in plasmas and superconductors. This is a perturbation of the localized induction equation (LIE), which is itself an integrable model of filament motion in an ideal fluid. We present a novel class of solutions for a time-modulated modification of UIY; namely, vortex configurations which are evolving spherical curves of varying radius. These solutions can be considered as generalizations of a well-known class of soliton solutions for LIE.
Microstructure and optical characterization of CdTe quantum dots synthesized in a record minimum time
Authors: Patra S. , Pradhan S. K.
Published: October 2010

The CdTe quantum dots (QDs) are synthesized at room temperature in a record minimum time of 5 min by mechanical alloying the stoichiometric mixture of Cd and Te powders under Ar in a high energy planetary ball mill. Microstructure characterization of ball milled CdTe powders by x-ray diffraction employing the Rietveld structure refinement method reveals that the stoichiometric cubic CdTe phase is formed after 15 min of milling and in the course of milling upto 4 h, size of the isotropic QDs reaches ∼5 nm which is close to that obtained by transmission electron microscope (∼4.5 nm) and quite below the Bohr exciton radius of CdTe (∼6.9 nm). These QDs contain significant amount of stacking and twin faults. Microstructure characterization by high resolution TEM corroborates the findings of the x-ray analysis where the presence of stacking and twin faults on (111) plane are clearly noticed. A distinct blueshift with the decreasing particle size of the QDs in absorbance spectrum confirms the size quantization. Optical band gap of these QDs are very different from the bulk CdTe and changes with increasing milling time and that can be fine tuned with varying milling time.
Magnetoelectric coupling in Ca3CoMnO6
Authors: Kaushik S. D. , Rayaprol S. , Saha J. , Mohapatra N. , Siruguri V. , Babu P. D. , Patnaik S. , Sampathkumaran E. V.
Published: October 2010

Magnetic structure and dielectric response of Ca3CoMnO6 have been studied as a function of temperature and applied magnetic field. Neutron diffraction experiments at low temperatures reveal changes in the magnetic structure in the temperature range 2–10 K. The pristine magnetic structure undergoes significant change with the application of magnetic field at these temperatures. Dielectric measurements reveal the presence of magnetoelectric coupling below magnetic ordering temperature (TN=15 K). The present work brings out the existence of a correlation between magnetic structure and dielectric properties.
Enhanced high temperature thermoelectric properties of Bi-doped c-axis oriented Ca3Co4O9 thin films by pulsed laser deposition
Authors: Sun T. , Hng H. H. , Yan Q. Y. , Ma J.
Published: October 2010

Ca 3 − x Bi x Co 4 O 9  (x=0–0.4) thin films were deposited on single-crystal sapphire (0001) substrates by pulsed laser deposition. Structural characterizations indicated that these thin films exhibited perfect c-axis orientation and were well crystallized. Surface chemical states analysis confirmed Bi-substitution for Ca in the thin films with x<0.4. For the thin film with x=0.4, excessive Bi were found isolated within the film. Due to their perfect orientation, in-plane electrical properties of these thin films measured from 300 to 740 K were found to be comparable to those of the single crystals. Furthermore, Bi-substitution was noted for the reduced electrical resistivity and enhanced Seebeck coefficient. The above superior properties resulted in a high power factor of 0.81 mW m−1 K−2 at 740 K for thin film Ca2.7Bi0.3Co4O9, which was about 29% improvement as compared to that of pure Ca3Co4O9 thin film. The results suggested that Bi-doped Ca3Co4O9 thin films could be a promising candidate for thermoelectric applications at elevated temperatures.
Highly specular carbon nanotube absorbers
Authors: Wang X. J. , Wang L. P. , Adewuyi O. S. , Cola B. A. , Zhang Z. M.
Published: October 2010

Specular black materials have important applications, such as in absolute cryogenic radiometers, space-borne spectroradiometers, and some energy conversion devices. While vertically aligned carbon nanotubes (VACNT) can have close-to-unity absorptance, so far the reported reflection has been essentially diffuse. This letter describes a highly specular black absorber made of VACNT. Both the bidirectional reflectance distribution function and specular reflectance were measured at the wavelength λ=635 nm using a laser scatterometer. The ordinary and extraordinary optical constants were obtained by fitting the specular reflectance, calculated from modified reflectance formulae for light incident from air to a uniaxial medium, considering surface roughness. Furthermore, the absorptance at λ=635 nm was shown to be 0.994±0.002, based on the measured directional-hemispherical reflectance.
Ultrashallow Ohmic contacts for n-type Ge by Sb δ-doping
Authors: Sawano K. , Hoshi Y. , Kasahara K. , Yamane K. , Hamaya K. , Miyao M. , Shiraki Y.
Published: October 2010

We demonstrate ultrashallow Ohmic contacts for n-Ge by the Sb δ-doping and low-temperature Ge homoepitaxy. We find that the segregation effect of Sb on Ge(111) is lower than that on Ge(100) for growth temperatures below 400 °C. Consequently, we achieve the δ-doping for Ge(111), having very high concentrations above 1020 cm−3 and abrupt profiles within nanometer-scale widths. By introducing the δ-doping to atomically controlled metal/Ge Schottky contacts, completely symmetric current-voltage characteristics, that is, low-resistivity Ohmic contacts are obtained owing to the effective tunneling conduction through the Schottky barrier.
Structural and charge trapping properties of two bilayer (Ge+SiO2)/SiO2 films deposited on rippled substrate
Authors: Buljan M. , Grenzer J. , Holý V. , Radić N. , Mišić-Radić T. , Levichev S. , Bernstorff S. , Pivac B. , Capan I.
Published: October 2010

We report on structural properties and charge trapping in [(Ge+SiO2)/SiO2]×2 films deposited by magnetron sputtering on a periodically corrugated-rippled substrate and annealed in vacuum and forming gas. The rippled substrate caused a self-ordered growth of Ge quantum dots, while annealing in different environments enabled us to separate charge trapping in quantum dots from the trapping at the dot-matrix and matrix-substrate interfaces. We show that the charge trapping occurs mainly in Ge quantum dots in the films annealed in the forming gas, while Si–SiO2 interface trapping is dominant for the vacuum annealed films.
Heteroepitaxy of single-crystal LaLuO3 on GaAs(111)A by atomic layer deposition
Authors: Liu Yiqun , Xu Min , Heo Jaeyeong , Ye Peide D. , Gordon Roy G.
Published: October 2010

We demonstrate that LaLuO3 films can be grown epitaxially on sulfur-passivated GaAs(111)A substrates by atomic layer deposition (ALD). Transmission electron microscopy and x-ray diffraction analyses reveal that the oxide film exhibits a cubic structure with a lattice mismatch of −3.8% relative to GaAs. The epitaxial layer has a high degree of crystalline perfection and is relaxed. Electrical characterizations performed on this structure show interfaces with a low interface state density of ∼7×1011 cm−2 eV−1. The measured dielectric constant is around 30, which is close to its bulk crystalline value. In contrast, ALD LaLuO3 is polycrystalline on GaAs(100) and amorphous on Si(111).
On electromechanical stability analysis of dielectric elastomer actuators
Authors: Xu Bai-Xiang , Mueller Ralf , Klassen Markus , Gross Dietmar
Published: October 2010

Based on the total stress concept, explicit results of the equilibrium state and the critical electric field are obtained for dielectric elastomer actuators. Criticality is discussed in the frame of structure stability and electric breakdown. Specific results are given for four commonly used material models.
Nanoslot laser
Authors: Kita Shota , Hachuda Shoji , Nozaki Kengo , Baba Toshihiko
Published: October 2010

We propose and demonstrate photonic crystal nanolaser with a nanoslot. Using high-aspect etching process, we succeed in fabricating a 30-nm-wide nanoslot device and room temperature lasing in both air and liquids. As an index sensor, it exhibits a high sensitivity of 410 nm per refractive index unit, as well as low temperature dependence in water. These behaviors and theoretical analysis suggest that the mode is strongly localized in the nanoslot. This device will be effective for enhancing light-matter interaction in cavity quantum electro dynamics, nonlinear optics, and biosensing.
Lateral confinement of electrons in vicinal N-polar AlGaN/GaN heterostructure
Authors: Nath Digbijoy N. , Keller Stacia , Hsieh Eric , DenBaars Steven P. , Mishra Umesh K. , Rajan Siddharth
Published: October 2010

We studied orientation dependent transport in vicinal N-polar AlGaN/GaN heterostructures. We observed significant anisotropy in the current carrying charge parallel and perpendicular to the miscut direction. A quantitative estimate of the charge anisotropy was made based on gated transmission line measurement and Hall measurements. The formation of electrostatically confined one-dimensional channels is hypothesized to explain charge anisotropy. A mathematical model was used to verify that polarization charges distributed on miscut structure can create lateral one-dimensional confinement in vicinal substrates. This polarization-engineered electrostatic confinement observed is promising for new research on low-dimensional physics and devices besides providing a template for manufacturable one-dimensional devices.
Terahertz generation and power limits in In0.53Ga0.47As photomixer coupled to transverse-electromagnetic-horn antenna driven at 1.55 μm wavelengths
Authors: Mangeney J. , Meng F. , Gacemi D. , Peytavit E. , Lampin J. F. , Akalin T.
Published: October 2010

We report continuous wave generation at frequencies up to 2 THz using ion-irradiated In0.53Ga0.47As photomixers coupled to transverse-electromagnetic-horn antennae driven at ∼1.55 μm wavelength. Output powers up to 0.1 μW at 700 GHz have been achieved. The dependence of the output power on incident optical power and the bias voltage is analyzed in the both regimes of Ohmic transport and recombination-limited transport. The fundamental limitations of the performance of the photomixer devices based on photoconductive phenomenon in recombination-limited transport are analyzed.
Effect of germanium on the kinetics of boron-oxygen defect generation and dissociation in Czochralski silicon
Authors: Yu Xuegong , Wang Peng , Yang Deren
Published: October 2010

We have investigated the kinetics of boron-oxygen (B–O) defect generation and dissociation in germanium-doped Czochralski (GCZ) silicon. It is found that the activation energies for the B–O defect generation and dissociation in the GCZ silicon are around 0.63 eV and 1.52 eV, respectively, both larger than those in the conventional CZ silicon. The corresponding pre-exponential factors also are enhanced by two orders of magnitude due to Ge doping. It is believed that the Ge cannot only cause a higher energy barrier for oxygen-dimer (O2i) diffusion, due to its modulation on the crystal field in silicon lattice but also enhance the capture cross-section of Bs for O2i, as a result of Ge–B complex formation, as predicted by first-principle calculation. These results are significant for us to understand the mechanism of Ge influencing on the B–O defects in CZ silicon.
Efficacy of combination anthelmintics against multiple resistant strains of sheep nematodes
Authors: Le Jambre L. F. , Martin P. J. , Johnston A.
Published: October 2010

Broad-spectrum anthelmintics were tested for their efficacy in either single active or combination formulations against multiple anthelmintic-resistant strains of Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis. Three efficacy trials based on post mortem worm counts showed that the triple and quadruple combinations of benzimidazoles, levamisole, macrocyclic lactones and closantel were effective against most strains that were resistant to each of the components when drenched individually. Consequently, use of any one of these classes of anthelmintics by itself against multiple-resistant strains would lead to a rapid increase in the level of resistance. When used in combinations, the anthelmintics reduced the survival rate of most strains to <5%. However, because some strains of T. circumcincta and T. colubriformis were found to be resistant to all combinations currently marketed in Australia, it is clear that combinations should be used before resistance levels become too high.
Effect of body condition and suckling restriction with and without presence of the calf on cow and calf performance
Authors: Quintans G. , Banchero G. , Carriquiry M. , López-Mazz C. , Baldi F.
Published: October 2010

Nutrition and suckling are largely recognised as the most important factors affecting the postpartum period and consequently the reproductive efficiency of beef cattle. The aim of this study was to evaluate the effects of body condition score (BCS) and suckling restriction with and without the presence of the calf on milk production, reproductive efficiency and calf performance. Sixty-three crossbred (Angus × Hereford) multiparous cows were managed to maintain different BCS at calving and thereafter (low vs moderate; L, n = 31 and M, n = 32). Within each group of BCS (L and M) at week 9 postpartum (66 ± 0.88 days postpartum) cows were assigned to three suckling treatments (ST): (i) suckling ad libitum (S, n = 20); (ii) calves fitted with nose plates during 14 days remaining with their dams (NP, n = 22); and (iii) calves were completely removed from their dams for 14 days, and thereafter returned (CR, n = 21). Milk production was assessed by milking procedure at Day 65 (the day before onset of ST) and every 20–22 days until the end of the experiment. Cows were bled via jugular venipuncture every 28 days from Day –98 (Day 0 = calving) until Day 66. From Day 66 cows were bled every 7 days until the end of the mating period (Day 128). Concentrations of progesterone, non-esterified fatty acids and β-hydroxybutyrate acid and insulin were measured. Presence of corpus luteum (CL) was recorded and maximum follicle diameter was measured in all cows from the onset of the ST (Day 66) and during the following 4 weeks (until Day 94) in a weekly frequency. At Day 94, more cows (P < 0.001) in NP and in CR had CL compared with S cows (68, 57 and 21% for NP, CR and S, respectively). At that time, more cows in M-BCS presented CL than cows in L-BCS (77 vs 25; P < 0.0001). Within M-BCS, there were no differences in milk production between ST groups, while L-BCS cows with NP or CR produced less milk than S cows. Calf liveweight at weaning was 159.3 ± 3.1, 150.1 ± 2.9 and 147.0 ± 3.1 kg for S, NP and CR, respectively (P < 0.001). Suckling restriction with and without the presence of the calf had similar effects on reproductive performance, milk production and calf growth, while BCS interacted with ST to influence milk production. These results indicate that temporary suckling restriction could be an excellent management tool to increase reproductive performance of cows in moderate condition.
Effect of nutrition pre-breeding and during pregnancy on breeding performance of ewe lambs
Authors: Mulvaney F. J. , Morris S. T. , Kenyon P. R. , Morel P. C. H. , West D. M.
Published: October 2010

The objective of the present studies was to investigate the effect of differing nutritional levels before breeding and during the pregnancy period on the breeding activity, conception rate (proportion pregnant/ewe lambs bred), pregnancy rate (proportion pregnant/ewe lambs joined with the ram) and the number of fetuses identified at pregnancy diagnosis. In Study 1, ewe lambs were allocated to either ‘medium’ or ‘ad lib’ levels of herbage from 4 days before the start of the breeding period (P –4) to P64. In Study 2, four different pre-breeding nutritional groups (‘maintenance’, ‘medium’, ‘medium/ad lib’ and ‘ad lib’) were utilised from P –17 until P5. The ‘medium/ad lib’ group involved a nutritional switch from the ‘medium’ to the ‘ad lib’ group at P –4 and remained in the ‘ad lib’ until P5. At P5, all ewe lambs that were identified as bred (crayon-marked by ram) were allocated to either ‘medium’ or ‘ad lib’ levels of nutrition until P122. In Study 1, more (P < 0.05) ewe lambs were bred, identified as pregnant at P64 and more fetuses identified at P64 in the ‘ad lib’ group compared with the ‘medium’ group. In Study 2, fewer (P < 0.05) ‘maintenance’ pre-breeding group ewe lambs were bred over the 5-day breeding period compared with the other pre-breeding groups but the proportion of the ewe lambs pregnant at P53 did not differ (P > 0.05). In addition, more (P < 0.05) fetuses were identified at pregnancy diagnosis in the ‘ad lib’ pre-breeding group compared with all other pre-breeding groups. Post-breeding nutrition did not affect (P > 0.05) the proportion of ewe lambs displaying oestrus post-breeding, pregnancy rate or the number of fetuses identified at pregnancy diagnosis per ewe lamb present. This indicates that New Zealand pastoral farmers should aim to allow ad libitum levels of nutrition immediately before the start of the breeding period to pregnancy diagnosis to maximise the number of fetuses at pregnancy diagnosis.
Evaluation of two training programs aimed to improve early lactation performance of heifers in a pasture-based automated milking system
Authors: Donohue R. H. , Kerrisk K. L. , Garcia S. C. , Dickeson D. A. , Thomson P. C.
Published: October 2010

The adaptation success of inexperienced heifers to a pasture-based automated milking system (AMS) is likely to influence the viability and feasibility of the system. This study evaluated two heifer training programs designed to improve adaptation success to determine their impact on early lactation performance within a pasture-based AMS. The two training programs involved heifers calving in spring 2007 (S07) and autumn 2008 (A08) being managed as members of the milking herd for 2 weeks, starting 2 months before their expected calving date. In each calving season, heifers were randomised into two treatment groups with one being fed and teat sprayed (FTS) while visiting the milking stations, while the other group passed through (PT) the milking stations. Milk yield, milking frequency and waiting time were selected as indicators of early lactation performance within an AMS and were reported as values relative to those measured by their experienced herdmates (within calving season). Longer relative waiting times (hours spent in pre-milking area where experienced herdmates = 1.0; FTS: 1.36 vs PT: 1.95; P = 0.006) may have been one cause of the low relative milk production levels reported (range 0.49 S07PT–0.78 A08PT). The milking frequencies of the heifers were in line with their experienced herdmates (range 0.83 S07PT–1.10 A08PT). There were no significant differences between the two training programs, indicating that farmers could adopt either program and expect similar early lactation heifer performance. The choice of program would more likely be affected by AMS utilisation levels, costs of consumables (teat spray and concentrate feed) and any existing desire to feed concentrate to heifers during the training period.
Glucocerebrosidase gene-deficient mouse recapitulates Gaucher disease displaying cellular and molecular dysregulation beyond the macrophage
Authors: Mistry Pramod K. , Liu Jun , Yang Mei , Nottoli Timothy , McGrath James , Jain Dhanpat , Zhang Kate , Keutzer Joan , Chuang Wei-Lien , Mehal Wajahat Z. , Zhao Hongyu , Lin Aiping , Mane Shrikant , Liu Xuan , Peng Yuan Z. , Li Jian H. , Agrawal Manasi , Zhu Ling-Ling , Blair Harry C. , Robinson Lisa J. , Iqbal Jameel , Sun Li , Zaidi Mone
Published: October 2010

In nonneuronopathic type 1 Gaucher disease (GD1), mutations in the glucocerebrosidase gene (GBA1) gene result in glucocerebrosidase deficiency and the accumulation of its substrate, glucocerebroside (GL-1), in the lysosomes of mononuclear phagocytes. This prevailing macrophage-centric view, however, does not explain emerging aspects of the disease, including malignancy, autoimmune disease, Parkinson disease, and osteoporosis. We conditionally deleted the GBA1 gene in hematopoietic and mesenchymal cell lineages using an Mx1 promoter. Although this mouse fully recapitulated human GD1, cytokine measurements, microarray analysis, and cellular immunophenotyping together revealed widespread dysfunction not only of macrophages, but also of thymic T cells, dendritic cells, and osteoblasts. The severe osteoporosis was caused by a defect in osteoblastic bone formation arising from an inhibitory effect of the accumulated lipids LysoGL-1 and GL-1 on protein kinase C. This study provides direct evidence for the involvement in GD1 of multiple cell lineages, suggesting that cells other than macrophages may be worthwhile therapeutic targets.
Distinct functions of antigen-specific CD4 T cells during murineMycobacterium tuberculosisinfection
Authors: Reiley William W. , Shafiani Shahin , Wittmer Susan T. , Tucker-Heard Glady's , Moon James J. , Jenkins Marc K. , Urdahl Kevin B. , Winslow Gary M. , Woodland David L.
Published: October 2010

The immune response elicited afterMycobacterium tuberculosis(Mtb) infection is critically dependent on CD4 T cells during both acute and chronic infection. How CD4 T-cell responses are maintained throughout infection is not well understood, and evidence from other infection models has suggested that, under conditions of chronic antigen stimulation, T cells can undergo replicative exhaustion. These findings led us to determine whether subpopulations of CD4 T cells existed that displayed markers of terminal differentiation or exhaustion during murine Mtb infection. Analysis of antigen-specific effector CD4 T cells revealed that programmed death-1 (PD-1) and the killer cell lectin-like receptor G1 (KLRG1) delineated subpopulations of T cells. PD-1–expressing CD4 T cells were highly proliferative, whereas KLRG1 cells exhibited a short lifespan and secreted the cytokines IFNγ and TNFα. Adoptive transfer studies demonstrated that proliferating PD-1–positive CD4 T cells differentiated into cytokine-secreting KLRG1-positive T cells, but not vice versa. Thus, proliferating PD-1–positive cells are not exhausted, but appear to be central to maintaining antigen-specific effector T cells during chronic Mtb infection. Our findings suggest that antigen-specific T-cell responses are maintained during chronic mycobacterial infection through the continual production of terminal effector cells from a proliferating precursor population.
Human RORγt
+
T
H
17 cells preferentially differentiate from naive FOXP3
+
Treg in the presence of lineage-specific polarizing factors
Authors: Valmori Danila , Raffin Caroline , Raimbaud Isabelle , Ayyoub Maha
Published: October 2010

RORγt
+
T
H
17 cells are a proinflammatory CD4
+
T-cell population associated with autoimmune tissue injury. In mice, priming of T
H
17 requires TGF-β, which alone directs the priming of FOXP3
+
regulatory T cells (Treg), in association with inflammatory cytokines. Priming of human T
H
17 cells from conventional naive CD4
+
T cells under similar conditions, however, has proved difficult to achieve. Here, we report that differentiation of human T
H
17 cells preferentially occurs from FOXP3
+
naive Treg (NTreg) in the presence of IL-2 and IL-1β and is increased by IL-23 and TGF-β. IL-1β–mediated differentiation correlated with IL-1RI expression in stimulated NTreg and was accompanied by induction of RORγt along with down-regulation of FOXP3. IL-17–secreting cells in NTreg cultures cosecreted TNF-α and IL-2 and contained distinct subpopulations cosecreting or not cosecreting IFN-γ and other T
H
17-associated cytokines. Polarized NTreg contained significant subpopulations of CCR6-expressing cells that were highly enriched in IL-17–secreting cells. Finally, analysis of CCR6 expression with respect to that of IL-1RI identified distinct IL-17–secreting subpopulations that had maintained or lost their suppressive functions. Together our results support the concept that priming of human T
H
17 from naive CD4
+
T cells preferentially takes place from FOXP3
+
Treg precursors in the presence of lineage-specific polarizing factors.
Relevance of synaptic tagging and capture to the persistence of long-term potentiation and everyday spatial memory
Authors: Wang Szu-Han , Redondo Roger L. , Morris Richard G. M.
Published: October 2010

Memory for inconsequential events fades, unless these happen before or after other novel or surprising events. However, our understanding of the neurobiological mechanisms of novelty-enhanced memory persistence is mainly restricted to aversive or fear-associated memories. We now outline an “everyday appetitive” behavioral model to examine whether and how unrelated novelty facilitates the persistence of spatial memory coupled to parallel electrophysiological studies of the persistence of long-term potentiation (LTP). Across successive days, rats were given one trial per day to find food in different places and later had to recall that day's location. This task is both hippocampus and NMDA receptor dependent. First, encoding with low reward induced place memory that decayed over 24 h; in parallel, weak tetanization of CA1 synapses in brain slices induced early-LTP fading to baseline. Second, novelty exploration scheduled 30 min after this weak encoding resulted in persistent place memory; similarly, strong tetanization—analogous to novelty—both induced late-LTP and rescued early- into late-LTP on an independent but convergent pathway. Third, hippocampal dopamine D1/D5 receptor blockade or protein synthesis inhibition within 15 min of exploration prevented persistent place memory and blocked late-LTP. Fourth, symmetrically, when spatial memory was encoded using strong reward, this memory persisted for 24 h unless encoding occurred under hippocampal D1/D5 receptor blockade. Novelty exploration before this encoding rescued the drug-induced memory impairment. Parallel effects were observed in LTP. These findings can be explained by the synaptic tagging and capture hypothesis.
Graded enhancement of p53 binding to CREB-binding protein (CBP) by multisite phosphorylation
Authors: Lee Chul Won , Ferreon Josephine C. , Ferreon Allan Chris M. , Arai Munehito , Wright Peter E.
Published: October 2010

The transcriptional activity of p53 is regulated by a cascade of posttranslational modifications. Although acetylation of p53 by CREB-binding protein (CBP)/p300 is known to be indispensable for p53 activation, the role of phosphorylation, and in particular multisite phosphorylation, in activation of CBP/p300-dependent p53 transcriptional pathways remains unclear. We investigated the role of single site and multiple site phosphorylation of the p53 transactivation domain in mediating its interaction with CBP and with the ubiquitin ligase HDM2. Phosphorylation at Thr18 functions as an on/off switch to regulate binding to the N-terminal domain of HDM2. In contrast, binding to CBP is modulated by the extent of p53 phosphorylation; addition of successive phosphoryl groups enhances the affinity for the TAZ1, TAZ2, and KIX domains of CBP in an additive manner. Activation of p53-dependent transcriptional pathways requires that p53 compete with numerous cellular transcription factors for binding to limiting amounts of CBP/p300. Multisite phosphorylation represents a mechanism for a graded p53 response, with each successive phosphorylation event resulting in increasingly efficient recruitment of CBP/p300 to p53-regulated transcriptional programs, in the face of competition from cellular transcription factors. Multisite phosphorylation thus acts as a rheostat to enhance binding to CBP/p300 and provides a plausible mechanistic explanation for the gradually increasing p53 response observed following prolonged or severe genotoxic stress.
A full-scale test of the language farming dispersal hypothesis
Authors: Hammarström Harald
Published: October 2010

One attempt at explaining why some language families are large (while others are small) is the hypothesis that the families that are now large became large because their ancestral speakers had a technological advantage, most often agriculture. Variants of this idea are referred to as the Language Farming Dispersal Hypothesis. Previously, detailed language family studies have uncovered various supporting examples and counterexamples to this idea. In the present paper I weigh the evidence from ALL attested language families. For each family, I use the number of member languages as a measure of cardinal size, member language coordinates to measure geospatial size and ethnographic evidence to assess subsistence status. This data shows that, although agricultural families tend to be larger in cardinal size, their size is hardly due to the simple presence of farming. If farming were responsible for language family expansions, we would expect a greater east-west geospatial spread of large families than is actually observed. The data, however, is compatible with weaker versions of the farming dispersal hypothesis as well with models where large families acquire farming because of their size, rather than the other way around.
Borrowability and the notion of basic vocabulary
Authors: Tadmor Uri , Haspelmath Martin , Taylor Bradley
Published: October 2010

This paper reports on a collaborative quantitative study of loanwords in 41 languages, aimed at identifying meanings and groups of meanings that are borrowing-resistant. We find that nouns are more borrowable than adjectives or verbs, that content words are more borrowable than function words, and that different semantic fields also show different proportions of loanwords. Several issues arise when one tries to establish a list of the most borrowing-resistant meanings: Our data include degrees of likelihood of borrowing, not all meanings have counterparts in all languages, many words are compounds or derivatives and hence almost by definition non-loanwords. We also have data on the age of words. There are thus multiple factors that play a role, and we propose a way of combining the factors to yield a new 100-item list of basic vocabulary, called the Leipzig-Jakarta list.