bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantity and proliferation rate of mesenchymal stem cells in human cord blood during gestation
Authors: Ma Lan‐Lan , Meng Fan‐Biao , Shi Ping , Li Gang , Pang Xi‐Ning
Published: January 2012

UCB (umbilical cord blood) as a resource of MSCs (mesenchymal stem cells) is widely accepted, but the quantity and characteristics of UCB‐MSCs from different gestational ages have not been well studied. We have quantified the number of MSCs in UCB at different gestational ages using a multi‐colour flowcytometer and compared the cell proliferation rates of these UCB‐MSCs. Defining MSCs as CD44+/CD105+/CD34 −/CD45 population, their numbers declined in the UCB at the gestational age. Proliferation rates were significantly higher in UCB before term than at full term. Non‐full term UCB samples may be a better source of MSCs.
Adiabatic nonlinear waves with trapped particles. I. General formalism
Authors: Dodin I. Y. , Fisch N. J.
Published: January 2012

A Lagrangian formalism is developed for a general nondissipative quasiperiodic nonlinear wave with trapped particles in collisionless plasma. The adiabatic time-averaged Lagrangian density L is expressed in terms of the single-particle oscillation-center Hamiltonians; once those are found, the complete set of geometrical-optics equations is derived without referring to the Maxwell-Vlasov system. The number of trapped particles is assumed fixed; in particular, those may reside close to the bottom of the wave trapping potential, so they never become untrapped. Then their contributions to the wave momentum and the energy flux depend mainly on the trapped-particle density, as an independent parameter, and the phase velocity rather than on the wave amplitude a explicitly; hence, L acquires a-independent terms. Also, the wave action is generally not conserved, because it can be exchanged with resonant oscillations of the trapped-particle density. The corresponding modification of the wave envelope equation is found explicitly and the new action flow velocity is derived. Applications of these results are left to the other two papers of the series, where specific problems are addressed pertaining to properties and dynamics of waves with trapped particles.
Quantum transport of Au-S-S-Au nanoscale junctions
Authors: Yu Jing-Xin , Chen Xiang-Rong , Sanvito Stefano , Cheng Yan
Published: January 2012

Transport in S2 molecules sandwiched between Au electrodes is investigated with a combination of density functional theory and the non-equilibrium Green’s function method. We consider four different configurations and find that their conductances are related to the details of the bonding geometry. When S2 connects to pyramidal-shaped electrodes at the top site, the transmission is governed by a resonance and is strongly affected by the bias. In contrast, the transport of the remaining three configurations is through several closely spaced broad molecular orbitals, and the transmission coefficient is almost flat around the Fermi level.
Strong nonlinear effects in conductivity of thin metallic samples (Review Article)
Authors: Voloshin I. F. , Makarov N. M. , Fisher L. M. , Yampol’skii V. A.
Published: January 2012

A series of works, dealt with nontrivial nonlinear stationary and nonstationary phenomena accompanying the flow of the transport current through thin pure single-crystal samples of metals at low temperatures, are discussed. The mechanism of the nonlinearity is magnetidynamical and related with an effect of the intrinsic magnetic field of the current on electron trajectories and, thus, on metal conductivity. The magnetodynamic nonlinearity leads to the nontrivial effect of drop of the resistance in thin samples with increasing the current. At high currents when a radius of curvature of electron trajectories in the intrinsic field of the current becomes smaller than cross sectional dimensions the effect of pinching of the current appears (pinch effect). In this case with increasing the current, the drop of the resistance is replaced by its increase. Experimental investigations of nonlinear current-voltage characteristics of thin cadmium and tungsten samples are also discussed. In these experiments, not only predictions of the theory are confirmed but new nonlinear effects accompanying the flow of strong currents were found. In particular, generation of self-oscillations of voltage in the regime of a given current was found. With increasing the current, the spectrum of the self-oscillations evolves, following a determined scenario with the transition from discrete to continuous, that indicates the appearance of a chaotic regime.
Analysis of ultranarrow ferromagnetic domain walls
Authors: Jenkins C. A. , Paul D. I.
Published: January 2012

New materials with high magnetic anisotropy will have domains separated by ultranarrow ferromagnetic walls with widths on the order of a few unit cells, approaching the limit where the elastic continuum approximation often used in micromagnetic simulations is accurate. The limits of this approximation are explored, and the static and dynamic interactions with intrinsic crystalline defects and external driving fields are modeled. The results developed here will be important when considering the stability of ultrahigh-density storage media.
Barrierless hole injection through sub-bandgap occupied states in organic light emitting diodes using substoichiometric MoOx anode interfacial layer
Authors: Vasilopoulou Maria , Palilis Leonidas C. , Georgiadou Dimitra G. , Kennou Stella , Kostis Ioannis , Davazoglou Dimitris , Argitis Panagiotis
Published: January 2012

In this letter, highly efficient hole injection was demonstrated in hole only devices based on organic semiconductors with different highest occupied molecular orbital level and transport properties. The barrierless hole injection was achieved by using a substoichiometric MoOx thin film (consisting of 65% Mo+6 and 35% Mo+5) as a higly effective anode interfacial layer. The current in these devices was found to be space charge limited, achieved due to the formation of highly efficient anode ohmic contact via the excellent band alignment through occupied gap states at the ITO/MoOx and MoOx/organic semiconductor modified interface. Quite remarkably, the efficiency of hole injection was found to be almost independent of the MoOx thickness, which is indicative of perfect band alignment at the anode interface.
Uniformly valid asymptotic flow analysis in curved channels
Authors: Zagzoule M. , Cathalifaud P. , Cousteix J. , Mauss J.
Published: January 2012

The laminar incompressible flow in a two-dimensional curved channel having at its upstream and downstream extremities two tangent straight channels is considered. A global interactive boundary layer (GIBL) model is developed using the approach of the successive complementary expansions method (SCEM) which is based on generalized asymptotic expansions leading to a uniformly valid approximation. The GIBL model is valid when the non dimensional number μ=δRe13 is O(1) and gives predictions in agreement with numerical Navier-Stokes solutions for Reynolds numbers Re ranging from 1 to 104 and for constant curvatures δ=HRc ranging from 0.1 to 1, where H is the channel width and Rc the curvature radius. The asymptotic analysis shows that μ, which is the ratio between the curvature and the thickness of the boundary layer of any perturbation to the Poiseuille flow, is a key parameter upon which depends the accuracy of the GIBL model. The upstream influence length is found asymptotically and numerically to be O(Re17).
Fast on-wafer electrical, mechanical, and electromechanical characterization of piezoresistive cantilever force sensors
Authors: Tosolini G. , Villanueva L. G. , Perez-Murano F. , Bausells J.
Published: January 2012

Validation of a technological process requires an intensive characterization of the performance of the resulting devices, circuits, or systems. The technology for the fabrication of micro and nanoelectromechanical systems (MEMS and NEMS) is evolving rapidly, with new kind of device concepts for applications like sensing or harvesting are being proposed and demonstrated. However, the characterization tools and methods for these new devices are still not fully developed. Here, we present an on-wafer, highly precise, and rapid characterization method to measure the mechanical, electrical, and electromechanical properties of piezoresistive cantilevers. The setup is based on a combination of probe-card and atomic force microscopy technology, it allows accessing many devices across a wafer and it can be applied to a broad range of MEMS and NEMS. Using this setup we have characterized the performance of multiple submicron thick piezoresistive cantilever force sensors. For the best design we have obtained a force sensitivity ℜF = 158μV/nN, a noise of 5.8 μV (1 Hz–1 kHz) and a minimum detectable force of 37 pN with a relative standard deviation of σr ≈ 8%. This small value of σr, together with a high fabrication yield >95%, validates our fabrication technology. These devices are intended to be used as bio-molecular detectors for the measurement of intermolecular forces between ligand and receptor molecule pairs.
An experimental study of transitional pulsatile pipe flow
Authors: Trip R. , Kuik D. J. , Westerweel J. , Poelma C.
Published: January 2012

The transitional regime of a sinusoidal pulsatile flow in a straight, rigid pipe is investigated using particle image velocimetry. The main aim is to investigate how the critical Reynolds number is affected by different pulsatile conditions, expressed as the Womersley number and the oscillatory Reynolds number. The transition occurs in the region of Re = 2250-3000 and is characterized by an increasing number of isolated turbulence structures. Based on velocity fields and flow visualizations, these structures can be identified as puffs, similar to those observed in steady flow transition. Measurements at different Womersley numbers yield similar transition behavior, indicating that pulsatile effects do not play a role in the regime that is investigated. Variations of the oscillatory Reynolds number also appear to have little effect, so that the transition here seems to be determined only by the mean Reynolds number. For larger mean Reynolds numbers, a second regime is observed: here, the flow remains turbulent throughout the cycle. The turbulence intensity varies during the cycle, but has a phase shift with respect to the mean flow component. This is caused by a growth of kinetic energy during the decelerating part and a decay during the accelerating part of the cycle. Flow visualization experiments reveal that the flow develops localized turbulence at several random axial positions. The structures quickly grow to fill the entire pipe in the decelerating phase and (partially) decay during the accelerating phase.
Efficient polymer solar cell employing an oxidized Ni capped Al:ZnO anode without the need of additional hole-transporting-layer
Authors: Chen T. L. , Betancur R. , Ghosh D. S. , Martorell Jordi , Pruneri V.
Published: January 2012

We show that an effective transparent electrode for bulk-heterostructure organic solar cells (OSCs) can be produced by uniformly depositing a few nm of Ni on a film of aluminum-doped zinc oxide (AZO). After deposition, the Ni capping layer is O2 plasma treated to form a bilayer of Ni/NiO, as it is evidenced by x-ray photoelectron spectroscopy analysis. The oxidized Ni capped AZO electrode can act as anode and hole-transporting-layer in OSCs, providing an enhancement in transparency, environmental stability, and injection/collection of charges. The S-shaped feature of the IV curve for the OSC using AZO electrodes in conjunction with NiO transporting layer is not present in the case of the proposed electrode structure, clearly indicating the significant role of the Ni metallic interlayer in reducing the energy barrier. The relevant role played by the Ni was further confirmed when a NiO layer was deposited on top of the AZO/Ni bilayer. In that case, the S-shape was not present while a 90% photo-conversion efficiency relative to the ITO/NiO cell was achieved.
On the effective thermoelectric properties of layered heterogeneous medium
Authors: Yang Y. , Xie S. H. , Ma F. Y. , Li J. Y.
Published: January 2012

The effective thermoelectric behavior of layered heterogeneous medium is studied, with the distribution of temperature, electric potential, and heat flux solved rigorously from the governing equations, and the effective thermoelectric properties defined through an equivalency principle. It is discovered that the effective thermoelectric figure of merit of a composite medium can be higher than all of its constituents even in the absence of size and interface effects, in contrast to previous studies. This points toward a new route for high figure of merit thermoelectric materials.
Impact of luminescence quenching on relaxation-oscillation frequency in solid-state lasers
Authors: Agazzi Laura , Bernhardi Edward H. , Wörhoff Kerstin , Pollnau Markus
Published: January 2012

Measurement of the laser relaxation-oscillation frequency as a function of pump rate allows one to determine parameters of the laser medium or cavity. We show that luminescence quenching of a fraction of the rare-earth ions in a solid-state laser affects the relaxation oscillations, resulting in incorrect values for the parameter deduced from this measurement. In the equations describing the relaxation oscillations, we replace the lifetime of the upper laser level by an effective lifetime that takes the luminescence quenching into account. In an Al2O3:Yb3+ distributed-feedback laser we observe significant quenching, with the effective lifetime being ∼18 times shorter than the intrinsic upper-laser-level lifetime.
Superalgebra realization of the 3-algebras in ${\cal N}=6, 8$N=6,8 Chern-Simons-matter theories
Authors: Chen Fa-Min
Published: January 2012

We use superalgebras to realize the 3-algebras used to construct \documentclass[12pt]{minimal}\begin{document}${\cal N}=6, 8$\end{document}N=6,8 Chern-Simons-matter (CSM) theories. We demonstrate that the superalgebra realization of the 3-algebras provides a unified framework for classifying the gauge groups of the \documentclass[12pt]{minimal}\begin{document}${\cal N}\ge 5$\end{document}N≥5 theories based on 3-algebras. Using this realization, we rederive the ordinary Lie algebra construction of the general \documentclass[12pt]{minimal}\begin{document}${\cal N}=6$\end{document}N=6 CSM theory from its 3-algebra counterpart and reproduce all known examples as well. In particular, we explicitly construct the Nambu 3-bracket in terms of a double graded commutator of PSU(2|2). The \documentclass[12pt]{minimal}\begin{document}${\cal N}=8$\end{document}N=8 theory of Bagger, Lambert and Gustavsson (BLG) with SO(4) gauge group is constructed by using several different ways. A quantization scheme for the 3-brackets is proposed by promoting the double graded commutators as quantum mechanical double graded commutators.
Electrical transport in suspended and double gated trilayer graphene
Authors: Khodkov Tymofiy , Withers Freddie , Christopher Hudson David , Felicia Craciun Monica , Russo Saverio
Published: January 2012

We present a fabrication process for high quality suspended and double gated trilayer graphene devices. The electrical transport measurements in these transistors reveal a high charge carrier mobility (higher than 20 000 cm2/Vs) and ballistic electric transport on a scale larger than 200 nm. We report a particularly large on/off ratio of the current in ABC-stacked trilayers, up to 250 for an average electric displacement of −0.08 V/nm, compatible with an electric field induced energy gap. The high quality of these devices is also demonstrated by the appearance of quantum Hall plateaus at magnetic fields as low as 500 mT.
Photoemission microscopy study of the two metal-insulator transitions in Cr-doped V2O3
Authors: Mansart B. , Barinov A. , Dudin P. , Baldassarre L. , Perucchi A. , Papalazarou E. , Metcalf P. , Lupi S. , Marsi M.
Published: January 2012

We present a spectromicroscopy study of the two distinct metal-insulator transitions in (V1−xCrx)2O3, x = 0.011. The coexistence of metallic and insulating domains was observed with scanning photoelectron microscopy for both the paramagnetic insulator-paramagnetic metal and paramagnetic metal-antiferromagnetic insulator transitions, evidencing a clear correlation between their nucleation regions. Although these two transitions are very different in nature and underlying mechanism, in both cases the morphology of their phase separation is influenced by structural inhomogeneities. These results demonstrate the general relevance of strain caused by local lattice distortions in guiding the intrinsic tendency towards phase separation in Mott materials.
Effects of stimulated emission on transport in terahertz quantum cascade lasers based on diagonal designs
Authors: Bhattacharya I. , Chan C. W. I. , Hu Q.
Published: January 2012

A hybrid Monte Carlo-density matrix transport simulator is used to analyze the transport properties of resonant-phonon type terahertz quantum cascade lasers. By comparing calculated and experimental results, the importance of stimulated emission to the interpretation of experimental data is highlighted, particularly for devices based on diagonal radiative transitions. Finally, we discuss the absence of mode competition effects on transport.
Magnetoacoustic imaging of magnetic iron oxide nanoparticles embedded in biological tissues with microsecond magnetic stimulation
Authors: Hu Gang , He Bin
Published: January 2012

We present an experimental study on magnetoacoustic imaging of superparamagnetic iron oxide (SPIO) nanoparticles embedded in biological tissues. In experiments, a large-current-carrying coil is used to deliver microsecond pulsed magnetic stimulation to samples. The ultrasound signals induced by magnetic forces on SPIO nanoparticles are measured by a rotating transducer. The distribution of nanoparticles is reconstructed by a back-projection imaging algorithm. The results demonstrated the feasibility to obtain cross-sectional image of magnetic nanoparticle targets with faithful dimensional and positional information, which suggests a promising tool for tomographic reconstruction of magnetic nanoparticle-labeled diseased tissues (e.g., cancerous tumor) in molecular or clinic imaging.
High-quality AlGaN/GaN superlattices for near- and mid-infrared intersubband transitions
Authors: Bayram C.
Published: January 2012

A pulsed layer-by-layer deposition (PLLD) technique possessing triple growth rates compared to conventional growth techniques is developed by metal−organic chemical vapor deposition to realize high-quality high-aluminum content ordered AlXGa(1−X)N (0.5 < X). X-ray diffraction, photoluminescence, and transmission measurements are employed to demonstrate control over aluminum content, structural uniformity, and optical quality in the ordered AlXGa(1−X)N. To show the feasibility of device applications, AlXGa(1−X)N as barrier and GaN as well are employed in superlattices demonstrating intersubband transitions in the infrared regime. Effects of well width and barrier aluminum content on the intersubband absorption characteristics are reported.
Influence of the rheological properties on the electrical impedance of hydrogels
Authors: Alexe-Ionescu A. L. , Barbero G. , Meyer C.
Published: January 2012

We show that the anomalous frequency dependence of the real part of the electrical impedance of hydrogels can be interpreted by taking into account their non-Newtonian character, according to which the effective viscosity, η, depends on the frequency of the imposed deformation. Our experimental results are in good agreement with the Poisson–Nernst–Planck model if the ionic viscosity is taken proportional to the macroscopic one, measured by means of a viscositymeter, and the diffusion coefficient is assumed frequency dependent according to the formula of Stokes D = KBT/(κη), where κ is a shape coefficient. From this result it follows that the non-Newtonian character of complex liquid can be investigated by means of the impedance spectroscopy technique.
Optical properties of cobalt slanted columnar thin films passivated by atomic layer deposition
Authors: Schmidt Daniel , Schubert Eva , Schubert Mathias
Published: January 2012

Optical properties of passivated metal slanted columnar thin films from cobalt within the visible spectral region are reported. Glancing angle deposition is utilized to grow slanted nanocolumns which have been conformally coated with Al2O3 by a subsequent atomic layer deposition process. A generalized anisotropic Bruggeman effective medium approximation has been employed to analyze spectroscopic generalized ellipsometry data. The modified homogenization approach allows for determination of biaxial (monoclinic) optical and structural properties as well as fractions of three film constituents. The conformal alumina passivation layer preserves the pristine metal character of the nanostructures and prevents oxidation and aging effects.
Manipulating the size distribution of supported gold nanostructures
Authors: Sundar A. , Hughes R. A. , Farzinpour P. , Gilroy K. D. , Devenyi G. A. , Preston J. S. , Neretina S.
Published: January 2012

Gold nanostructures, with a wide size distribution, are confined between a metal foil and the oxide substrate upon which they were formed. When heated the surface energy gradient between the oxide and foil results in a net migration of gold atoms from the nanostructure to the foil. With time, the nanostructures show a size reduction and a narrowed size distribution. The narrowing results from the formation of foil contact points with only the largest nanostructures, a characteristic which leaves small nanostructures intact while consuming larger ones. Also demonstrated is the size reduction of arrayed gold structures to nanoscale dimensions.
A very low energy compact electron beam ion trap for spectroscopic research in Shanghai
Authors: Xiao J. , Fei Z. , Yang Y. , Jin X. , Lu D. , Shen Y. , Liljeby L. , Hutton R. , Zou Y.
Published: January 2012

In this paper, a new compact low energy electron beam ion trap, SH-PermEBIT, is reported. This electron beam ion trap (EBIT) can operate in the electron energy range of 60–5000 eV, with a current density of up to 100 A/cm2. The low energy limit of this machine sets the record among the reported works so far. The magnetic field in the central drift tube region of this EBIT is around 0.5 T, produced by permanent magnets and soft iron. The design of this EBIT allows adjustment of the electron gun's axial position in the fringe field of the central magnetic field. This turned out to be very important for optimizing the magnetic field in the region of the electron gun and particularly important for low electron beam energy operation, since the magnetic field strength is not tunable with permanent magnets. In this work, transmission of the electron beam as well as the upper limit of the electron beam width under several conditions are measured. Spectral results from test operation of this EBIT at the electron energies of 60, 315, 2800, and 4100 eV are also reported.
Reentrant dipole glass properties in (1 − x)BaTiO3 − xBiScO3, 0.1 ≤ x ≤ 0.4
Authors: Bharadwaja S. S. N. , Trolier-McKinstry S. , Cross L. E. , Randall C. A.
Published: January 2012

Dielectrics that provide higher electrostatic energy densities are urgently required for power electronic applications; recent observations in the solid solution of (1 − x)BaTiO3 − xBiScO3 show promise, and low temperature re-entrant dipole glass behavior is inferred. Here, direct observations of switchable polarization freezing in the reentrant dipole-glass (1 − x)BaTiO3 − xBiScO3, 0.1 ≤ x ≤ 0.4 are reported. As the temperature is decreased, the switchable polarization increases rapidly, reaches a maximum value at the reentrant temperature (TR) before disappearing at low temperatures. With measurement electric field (E), the TR is found to increase in (1 − x)BaTiO3 − xBiScO3, 0.1 ≤ x ≤ 0.4, as a function of x.
Coupling effects in inductive discharges with radio frequency substrate biasing
Authors: Schulze J. , Schüngel E. , Czarnetzki U.
Published: January 2012

Low pressure inductively coupled plasmas (ICP) operated in neon at 27.12 MHz with capacitive substrate biasing (CCP) at 13.56 MHz are investigated by phase resolved optical emission spectroscopy, voltage, and current measurements. Three coupling mechanisms are found potentially limiting the separate control of ion energy and flux: (i) Sheath heating due to the substrate biasing affects the electron dynamics even at high ratios of ICP to CCP power. At fixed CCP power, (ii) the substrate sheath voltage and (iii) the amplitude as well as frequency of plasma series resonance oscillations of the RF current are affected by the ICP power.
Nonlinear optical properties of low temperature annealed silicon-rich oxide and silicon-rich nitride materials for silicon photonics
Authors: Minissale S. , Yerci S. , Dal Negro L.
Published: January 2012

We investigate the nonlinear optical properties of Si-rich silicon oxide (SRO) and Si-rich silicon nitride (SRN) samples as a function of silicon content, annealing temperature, and excitation wavelength. Using the Z-scan technique, we measure the non-linear refractive index n2 and the nonlinear absorption coefficient β for a large number of samples fabricated by reactive co-sputtering. Moreover, we characterize the nonlinear optical parameters of SRN in the broad spectral region 1100-1500 nm and show the strongest nonlinearity at 1500 nm. These results demonstrate the potential of the SRN matrix for the engineering of compact devices with enhanced Kerr nonlinearities for silicon photonics applications.
Electronic and optical properties of CoX2O4 (X = Al, Ga, In) alloys
Authors: Feng Chunbao , Yin Wan-Jian , Nie Jinlan , Zu Xiaotao , Huda Muhammad N. , Wei Su-Huai , Al-Jassim Mowafak M. , Turner John A. , Yan Yanfa
Published: January 2012

The electronic and optical properties of Co based spinel oxides, CoX2O4 (X = Al, Ga, In) are calculated using first-principle density functional theory. We show that the desirable properties for solar photoconversion can be obtained by controlling the alloy compositions. The ability to manipulate the electronic and optical properties is attributed to the different s-orbital energies and sizes of the cations. Our calculated bandgaps as function of composition provide detailed practical guidance for synthesizing Co based spinel oxides with electronic and optical properties necessary to achieve high efficiency photoelectrochemical decomposition of water for hydrogen production by sunlight.
Improvement of temperature-stability in a quantum well laser with asymmetric barrier layers
Authors: Zhukov Alexey E. , Kryzhanovskaya Natalia V. , Zubov Fedor I. , Shernyakov Yuri M. , Maximov Mikhail V. , Semenova Elizaveta S. , Yvind Kresten , Asryan Levon V.
Published: January 2012

We fabricated and tested a quantum well laser with asymmetric barrier layers. Such a laser has been proposed earlier to suppress bipolar carrier population in the optical confinement layer and thus to improve temperature-stability of the threshold current. As compared to the conventional reference laser structure, our laser with asymmetric barrier layers demonstrates reduced internal optical loss, lower threshold current density at elevated temperatures, and higher characteristic temperature (143 vs. 99 K at 20 °C).
Different strain relief behaviors in Al0.35Ga0.65N/GaN multiple quantum wells on GaN/Sapphire templates with AlN/GaN supperlattices and low-temperature AlN interlayers
Authors: Huang C. C. , Xu F. J. , Song J. , Xu Z. Y. , Wang J. M. , Zhu R. , Chen G. , Wang X. Q. , Yang Z. J. , Shen B. , Chen X. S. , Lu W.
Published: January 2012

Strain relief behaviors in Al0.35Ga0.65N/GaN multiple quantum wells (MQWs) grown on GaN/sapphire templates with either AlN/GaN supperlattices (SLs) or low-temperature AlN (LT-AlN) interlayers (ILs) between the MQWs and templates have been investigated. These two IL techniques can both effectively relieve the tensile strain in the MQWs, leading to crack-free surfaces and high crystalline quality. Further analysis shows that there are two distinct strain relief channels. In the case of adopting AlN/GaN SLs IL, microcracks and misfit dislocations account for strain relief in the MQWs. Microcracks are first generated in the IL, followed by activating formation of misfit dislocations. Then, the microcracks are immediately filled up by the subsequent epilayers. Contrastively, strain relief by using LT-AlN IL is mainly through the self relaxation process of the MQWs by surface roughening and strain compensation effect of LT-AlN IL.
Metal-assisted electroless fabrication of nanoporous p-GaN for increasing the light extraction efficiency of light emitting diodes
Authors: Wang Ruijun , Liu Duo , Zuo Zhiyuan , Yu Qian , Feng Zhaobin , Xu Xiangang
Published: January 2012

We report metal-assisted electroless fabrication of nanoporous p-GaN to improve the light extraction efficiency of GaN-based light emitting diodes (LEDs). Although it has long been believed that p-GaN cannot be etched at room temperature, in this study we find that Ag nanocrystals (NCs) on the p-GaN surface enable effective etching of p-GaN in a mixture of HF and K2S2O8 under ultraviolet (UV) irradiation. It is further shown that the roughened GaN/air interface enables strong scattering of photons emitted from the multiple quantum wells (MQWs). The light output power measurements indicate that the nanoporous LEDs obtained after 10 min etching show a 32.7% enhancement in light-output relative to the conventional LEDs at an injection current of 20 mA without significant increase of the operating voltage. In contrast, the samples etched for 20 min show performance degradation when compared with those etched for 10 min, this is attributed to the current crowding effect and increased surface recombination rate.
Chemical data quantify
Deepwater Horizon
hydrocarbon flow rate and environmental distribution
Authors: Ryerson Thomas B. , Camilli Richard , Kessler John D. , Kujawinski Elizabeth B. , Reddy Christopher M. , Valentine David L. , Atlas Elliot , Blake Donald R. , de Gouw Joost , Meinardi Simone , Parrish David D. , Peischl Jeff , Seewald Jeffrey S. , Warneke Carsten
Published: January 2012

Detailed airborne, surface, and subsurface chemical measurements, primarily obtained in May and June 2010, are used to quantify initial hydrocarbon compositions along different transport pathways (i.e., in deep subsurface plumes, in the initial surface slick, and in the atmosphere) during the
Deepwater Horizon
oil spill. Atmospheric measurements are consistent with a limited area of surfacing oil, with implications for leaked hydrocarbon mass transport and oil drop size distributions. The chemical data further suggest relatively little variation in leaking hydrocarbon composition over time. Although readily soluble hydrocarbons made up ∼25% of the leaking mixture by mass, subsurface chemical data show these compounds made up ∼69% of the deep plume mass; only ∼31% of the deep plume mass was initially transported in the form of trapped oil droplets. Mass flows along individual transport pathways are also derived from atmospheric and subsurface chemical data. Subsurface hydrocarbon composition, dissolved oxygen, and dispersant data are used to assess release of hydrocarbons from the leaking well. We use the chemical measurements to estimate that (7.8 ± 1.9) × 10
6
kg of hydrocarbons leaked on June 10, 2010, directly accounting for roughly three-quarters of the total leaked mass on that day. The average environmental release rate of (10.1 ± 2.0) × 10
6
kg/d derived using atmospheric and subsurface chemical data agrees within uncertainties with the official average leak rate of (10.2 ± 1.0) × 10
6
kg/d derived using physical and optical methods.
Testing zooplankton secondary production models against Daphnia magna growth
Authors: Gómez May , Martínez Ico , Mayo Ismael , Morales José Miguel , Santana Angelo , Packard Ted T.
Published: January 2012

Gómez, M., Martínez, I., Mayo, I., Morales, J. M., Santana, A., and Packard, T. T. 2012. Testing zooplankton secondary production models against Daphnia magna growth. – ICES Journal of Marine Science, 69: 421–428. Modelling secondary production rates in the zooplankton is essential for population ecology studies, but assessing these rates is difficult and rarely done. Here, five secondary production models are tested by measuring Daphnia magna growth. To provide a range of growth rates, Daphnia were cultured under three different nutrition regimes (yeast, cornflour, and phytoplankton). Length and biomass were monitored daily in three simple time-course experiments to provide the growth rates, which ranged from 0.11 to 0.30 d–1 with secondary production rates of 350–643 µg dry mass d−1. Secondary production was predicted best by the freshwater crustacean-based model of Stockwell and Johannsson (1997). Marine copepod-based marine models were totally unsuitable.
Hoarseness
Authors: Biggs Timothy C.
Published: January 2012

An estimated 50 000 patients in the UK are referred annually to ear, nose and throat (ENT) specialist services with hoarseness of voice. Dysphonia describes any alteration to the voice, with hoarseness referring to a deeper and slightly harsher quality to the sound. Any change in the voice can indicate a number of different pathologies both within the larynx and beyond. Many causes will be benign but malignancy should always be considered. This article summarizes the management of patients presenting with hoarseness in primary care.
Genetic Structure of Clavibacter michiganensis subsp. michiganensis Populations in Michigan Commercial Tomato Fields
Authors: Quesada-Ocampo L. M. , Landers N. A. , Lebeis A. C. , Fulbright D. W. , Hausbeck M. K.
Published: January 2012

Clavibacter michiganensis subsp. michiganensis, causal agent of bacterial canker of tomato, is distinguished into four fingerprint types (A, B, C, and D) using BOX-polymerase chain reaction (PCR). To characterize the variation within the C. michiganensis subsp. michiganensis population in Michigan, 718 strains of C. michiganensis subsp. michiganensis were isolated from infected foliage and fruit collected from 14 and 9 Michigan commercial tomato fields in 1997 and 1998, respectively. The frequency of PCR types detected with BOX-PCR in all strains, and Bayesian cluster analysis, pairwise differentiation index comparisons, and genetic diversity estimates of 96 strains genotyped for six virulence-related genes revealed that C. michiganensis subsp. michiganensis populations in Michigan tomato fields are geographically structured. A multilocus haplotype cladogram was also consistent with geographic stratification in C. michiganensis subsp. Michiganensis populations. Some regions had strains predominantly of only one PCR type or belonging mostly to one genetic cluster, while other regions presented more diversity of occurrence of PCR types and genetic clusters. Results derived from this study provide information about the genetic structure of C. michiganensis subsp. michiganensis populations in Michigan and genetic diversity of C. michiganensis subsp. michiganensis inocula, which is key in developing disease management strategies.
First Report of Mango Malformation Disease Caused by Fusarium mangiferae in Spain
Authors: Crespo M. , Cazorla F. M. , Hermoso J. M. , Guirado E. , Maymon M. , Torés J. A. , Freeman S. , de Vicente A.
Published: January 2012

Mango (Mangifera indica L.) malformation disease (MMD) is one of the most important diseases affecting this crop worldwide, which causes severe economic losses because of the reduction of productivity. Symptoms of MMD in Spain were observed for the first time in April of 2006 in three mango orchards in the Axarquia Region (southern Spain). Symptoms included an abnormal development of vegetative shoots with shortened internodes and dwarfed leaves and hypertrophied short and thickened panicles. In the years of 2006, 2009, and 2010, isolates of Fusarium were obtained from vegetative shoots and floral tissue of symptomatic mango trees from 21 different orchards of cvs. Keitt, Kent, Osteen, Tommy Atkins, and a variety of minor commercial cultivars, all showing typical symptoms of MMD. Different Fusarium-like strains were isolated from infected tissues. Colonies from single-spored isolates possessed dark purple-to-salmon-colored mycelium when grown on potato dextrose agar medium. On fresh carnation leaf agar medium, mycelium contained aerial conidiophores possessing three- to five-celled macroconidia and abundant microconidia in false heads from mono- and polyphialides; while cream-orange-colored sporodochia were produced on the surface of the medium, typical for Fusarium mangiferae. The identification of 37 isolates was confirmed as F. mangiferae by species-specific PCR analysis with the primer pair 1-3 F/R that amplified a 608-bp DNA fragment from all Spanish isolates as well as a representative Israeli control strain, Fus 34, also designated as MRC7560 (2). Pathogenicity using four representative isolates, UMAF F02, UMAF F10, UMAF F17, and UMAF F38 of F. mangiferae from Spain as well as isolate MRC7560, was tested on 2-year-old healthy mango seedlings cv. Keitt by inoculating 15 buds from three different trees with a 20-μl conidial suspension (5 × 107 conidia per ml) per isolate (1). This experiment was conducted twice with two independent sets of plants and at different times (March and November 2010). Typical mango malformation symptoms were detected after bud break in March 2011, 5 and 12 months after inoculation. Symptoms were observed for 60% of the inoculated buds with the four F. mangiferae Spanish isolates and 75% with the MRC7560 control strain, but not with water-inoculated control plants. Recovered isolates from the infected floral and vegetative malformed buds were identical morphologically to those inoculated, and the specific 608-bp fragment described for F. mangiferae was amplified with specific-PCR, thus fulfilling Koch's postulates. To our knowledge, this is the first report of mango malformation disease caused by F. mangiferae in Spain and Europe.

References: (1) S. Freeman et al. Phytopathology 89:456, 1999. (2) Q. I. Zheng and R. C. Ploetz. Plant Pathol. 51:208, 2002.
The Importance of Multilocus Sequence Typing: Cautionary Tales from the BacteriumXylella fastidiosa
Authors: Nunney L. , Elfekih S. , Stouthamer R.
Published: January 2012

Microbial identification methods have evolved rapidly over the last few decades. One such method is multilocus sequence typing (MLST). MLST is a powerful tool for understanding the evolutionary dynamics of pathogens and to gain insight into their genetic diversity. We illustrate the importance of accurate typing by reporting on three problems that have arisen in the study of a single bacterial species, the plant pathogen Xylella fastidiosa. Two of these were particularly serious since they concerned contamination of important research material that has had detrimental consequences for Xylella research: the contamination of DNA used in the sequencing of an X. fastidiosa genome (Ann-1) with DNA from another X. fastidiosa strain, and the unrecognized mislabeling of a strain (Temecula1) distributed from a culture collection (ATCC). We advocate the routine use of MLST to define strains maintained in culture collections and emphasize the importance of confirming the purity of DNA submitted for sequencing. We also present a third example that illustrates the value of MLST in guiding the choice of taxonomic types. Beyond these situations, there is a strong case for MLST whenever an isolate is used experimentally, especially where genotypic differences are suspected to influence the outcome.
Alteribacillus bidgolensis gen. nov., sp. nov., a moderately halophilic bacterium from a hypersaline lake, and reclassification of

Bacillus persepolensis

as Alteribacillus persepolensis comb. nov.
Authors: Didari Maryam , Amoozegar Mohammad Ali , Bagheri Maryam , Schumann Peter , Spröer Cathrin , Sánchez-Porro Cristina , Ventosa Antonio
Published: January 2012

A novel Gram-stain-positive, moderately halophilic bacterium, designated strain P4BT, was isolated from water of the hypersaline Aran-Bidgol lake in Iran and characterized taxonomically by using a polyphasic approach. Cells of strain P4BT were non-motile rods producing ellipsoidal endospores at a central position in non-swollen sporangia. Strain P4BT was strictly aerobic and catalase- and oxidase-positive. It was able to grow at NaCl concentrations of 0.5–12.5 % (w/v), with optimum growth occurring at 5–7.5 % (w/v) NaCl. The optimum temperature and pH for growth were 35 °C and pH 7.0. On the basis of 16S rRNA gene sequence analysis, strain P4BT was shown to belong to the phylum

Firmicutes

and shared highest similarity with

Bacillus persepolensis

HS136T (97.1 %) and

Bacillus salarius

BH169T (95.1 %). However, it shared only 91.3 % 16S rRNA gene sequence similarity with

Bacillus subtilis subsp. subtilis

DSM 10T, indicating that strain P4BT might not be a member of the genus

Bacillus

. The DNA G+C content of this new isolate was 38.9 mol%. DNA–DNA hybridization experiments revealed a low level of relatedness between strain P4BT and

B. persepolensis

HS136T (6 %). The major cellular fatty acids of strain P4BT were iso-C15 : 0 and anteiso-C15 : 0, as for

B. persepolensis

HS136T but in contrast to

B. salarius

DSM 16461T and

B. subtilis subsp. subtilis

DSM 10T. Its polar lipid pattern consisted of phosphatidylglycerol, an aminoglycolipid and an unknown phospholipid. This polar lipid profile was similar to that obtained for

B. persepolensis

DSM 21632T but different from those of

B. salarius

DSM 16461T and

B. subtilis subsp. subtilis

DSM 10T. The isoprenoid quinones were MK-7 (88 %) and MK-8 (2 %). The peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid. All these features indicate placement of strain P4BT within the

Firmicutes

, closely related to

B. persepolensis

but with features clearly distinct from those of the genus

Bacillus

and other related genera. On the basis of these data, strain P4BT is considered to represent a novel species of a new genus, for which the name Alteribacillus bidgolensis gen. nov., sp. nov. is proposed. The type strain of Alteribacillus bidgolensis is P4BT ( = CCM 7963T = CECT 7998T = DSM 25260T = IBRC-M 10614T = KCTC 13821T). It is also suggested to transfer

B. persepolensis

to this new genus, as Alteribacillus persepolensis comb. nov. The type strain of Alteribacillus persepolensis is HS136T ( = CCM 7595T = DSM 21632T = JCM 15720T = LMG 25222T).
Enteractinococcus coprophilus gen. nov., sp. nov., of the family

Micrococcaceae

, isolated from Panthera tigris amoyensis faeces, and transfer of

Yaniella fodinae

Dhanjal et al. 2011 to the genus Enteractinococcus as Enteractinococcus fodinae comb. nov.
Authors: Cao Yan-Ru , Jiang Yi , Jin Rong-Xian , Han Li , He Wen-Xiang , Li You-Long , Huang Xue-Shi , Xue Quan-Hong
Published: January 2012

A novel actinobacterium, designated strain YIM 100590T, was isolated from Panthera tigris amoyensis faeces collected from Yunnan Wild Animal Park in Yunnan province, south-west China. Phylogenetic analysis based on 16S rRNA gene sequence data showed that strain YIM 100590T is a member of the family

Micrococcaceae

. Cells were coccoid to oval (0.7–1.5 µm in diameter) occurring singly or in clusters. Growth was observed at 10–37 °C (optimum 28 °C) and at pH 7.0–11.0 (optimum pH 8.0). The major fatty acids were iso-C15 : 0 (32.22 %), anteiso-C15 : 0 (31.64 %) and iso-C16 : 0 (17.38 %). The peptidoglycan was of A4α type (l-Lys–Gly–l-Glu). The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides, dimannosyl diacylglycerol, an unknown glycolipid and two unknown phospholipids. The quinone system comprised menaquinones MK-7 (91.9 %) and MK-8 (8.3 %). The DNA G+C content of strain YIM 100590T was 56.2 mol%. Chemotaxonomic data indicated that the strain belongs to the family

Micrococcaceae

. On the basis of morphological and chemotaxonomic data and phylogenetic analysis, strain YIM 100590T is considered to represent a novel species of a new genus within the family

Micrococcaceae

, for which the name Enteractinococcus coprophilus gen. nov., sp. nov. is proposed. The type strain of Enteractinococcus coprophilus is YIM 100590T ( = DSM 24083T = JCM 17352T).

Yaniella fodinae

DSM 22966T was transferred to the new genus as Enteractinococcus fodinae comb. nov. (type strain G5T = DSM 22966T = JCM 17931T = MTCC 9846T).
Nocardioides lianchengensis sp. nov., an actinomycete isolated from soil
Authors: Zhang Jian , Ma Yuchao , Yu Huimin
Published: January 2012

A novel Gram-stain-positive, aerobic, rod-shaped bacterium, designated strain D94-1T, was isolated from soil collected in Liancheng county, Fujian province, PR China. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain D94-1T was a member of the genus

Nocardioides

and was most closely related to

Nocardioides salarius

DSM 18239T (98.54 % 16S rRNA gene sequence similarity),

Nocardioides marinisabuli

DSM 18965T (98.30 %),

Nocardioides basaltis

KCTC 19365T (98.10 %) and

Nocardioides dokdonensis

KCTC 19309T (97.76 %). Phenotypic characteristics and DNA–DNA relatedness data served to distinguish strain D94-1T from

N. salarius

,

N. marinisabuli

,

N. basaltis

and

N. dokdonensis

. The chemotaxonomic properties of strain D94-1T were consistent with those of the genus

Nocardioides

: the cell-wall peptidoglycan type was based on ll-diaminopimelic acid, the predominant menaquinone was MK-8(H4) and the major fatty acids were iso-C16 : 0 (29.15 %) and anteiso-C17 : 0 (21.0 %). The DNA G+C content was 71.8 mol%. On the basis of the evidence presented in this study, strain D94-1T represents a novel species of the genus

Nocardioides

, for which the name Nocardioides lianchengensis sp. nov. is proposed. The type strain is D94-1T ( = DSM 24663T = CGMCC 4.6858T).
Deinococcus humi sp. nov., isolated from soil
Authors: Srinivasan Sathiyaraj , Lee Jae-Jin , Lim Sangyong , Joe Minho , Kim Myung Kyum
Published: January 2012

A Gram-staining-positive, strictly aerobic, spherical, non-motile, red-pigmented bacterium, designated strain MK03T, was isolated from a soil sample collected in South Korea. The taxonomic position of the novel strain was investigated using a polyphasic approach. In phylogenetic analyses based on 16S rRNA gene sequences, strain MK03T was placed in a clade formed by members of the genus

Deinococcus

in the family

Deinococcaceae

and appeared to be most closely related to

Deinococcus aerolatus

5516T-9T (97.4 % sequence similarity),

Deinococcus marmoris

AA-63T (97.2 %),

Deinococcus radiopugnans

ATCC 19172T (97.2 %) and

Deinococcus saxicola

AA-1444T (96.9 %). The genomic DNA G+C content of the novel strain was 64.5 mol%. The chemotaxonomic characteristics of strain MK03T were typical of members of the genus

Deinococcus

: MK-8 was identified as the predominant respiratory quinine, the major fatty acids were C16 : 1ω7c, C15 : 1ω6c, C16 : 0 and C15 : 0, ornithine was found to be the diamino acid in the cell-wall peptidoglycan and the novel strain showed resistance to gamma radiation, with a D10 value (i.e. the dose required to reduce the bacterial population by 10-fold) in excess of 9 kGy. In hybridization experiments, only low DNA–DNA relatedness values (11.6–34.5 %) were recorded between the novel strain and its closest relatives in the genus

Deinococcus

. Based on the phylogenetic, chemotaxonomic, phenotypic and DNA–DNA relatedness data, strain MK03T represents a novel species of the genus

Deinococcus

, for which the name Deinococcus humi sp. nov. is proposed. The type strain is MK03T ( = KCTC 13619T  = JCM 17915T).