bluuebunny/crossref_metadata_2025 huggingface dataset:
Interface width effect on the classical Rayleigh–Taylor instability in the weakly nonlinear regime
Authors: Wang L. F. , Ye W. H. , Li Y. J.
Published: May 2010

In this paper, the interface width effects (i.e., the density gradient effects or the density transition layer effects) on the Rayleigh–Taylor instability (RTI) in the weakly nonlinear (WN) regime are investigated by numerical simulation (NS). It is found that the interface width effects dramatically influence the linear growth rate in the linear growth regime and the mode coupling process in the WN growth regime. First, the interface width effects decrease the linear growth rate of the RTI, particularly for the short perturbation wavelengths. Second, the interface width effects suppress (reduce) the third-order feedback to the fundamental mode, which induces the nonlinear saturation amplitude (NSA) to exceed the classical prediction, 0.1λ. The wider the density transition layer is, the larger the NSA is. The NSA in our NS can reach a half of its perturbation wavelength. Finally, the interface width effects suppress the generation and the growth of the second and the third harmonics. The ability to suppress the harmonics’ growth increases with the interface width but decreases with the perturbation wavelength. On the whole, in the WN regime, the interface width effects stabilize the RTI, except for an enhancement of the NSA, which is expected to improve the understanding of the formation mechanism for the astrophysical jets, and for the jetlike long spikes in the high energy density physics.
Effects of line-tying on magnetohydrodynamic instabilities and current sheet formation
Authors: Huang Yi-Min , Bhattacharjee A. , Zweibel Ellen G.
Published: May 2010

An overview of some recent progress on magnetohydrodynamic stability and current sheet formation in a line-tied system is given. Key results on the linear stability of the ideal internal kink mode and resistive tearing mode are summarized. For nonlinear problems, a counterexample to the recent demonstration of current sheet formation by Low and Janse [Astrophys. J. 696, 821 (2009)] is presented, and the governing equations for quasistatic evolution of a boundary driven, line-tied magnetic field are derived. Some open questions and possible strategies to resolve them are discussed.
Dusty plasma diagnostics methods for charge, electron temperature, and ion density
Authors: Liu Bin , Goree J. , Fortov V. E. , Lipaev A. M. , Molotkov V. I. , Petrov O. F. , Morfill G. E. , Thomas H. M. , Ivlev A. V.
Published: May 2010

Diagnostic methods are developed to measure the microparticle charge Q and two plasma parameters, electron temperature Te, and ion density ni, in the main plasma region of a dusty plasma. Using video microscopy to track microparticles yields a resonance frequency, which along with a charging model allows an estimation of Q and Te. Only measurements of microparticle position and velocity are required, unlike other methods that use measurements of Te and plasma parameters as inputs. The resonance frequency measurement can also be used with an ion drag model to estimate ni. These methods are demonstrated using a single-layer dusty plasma suspension under microgravity conditions.
A tunable radio-frequency magnetic probe
Authors: Sun B. , Yuan G. Y. , Huo W. G. , Ding Z. F.
Published: May 2010

A tunable center-tapped transformer is proposed to increase the output of a rf magnetic probe and improve the signal-to-noise ratio. The tuning is implemented by a variable capacitor connected parallel with the primary winding of the tunable center-tapped transformer. Undesirable common-to-differential conversion is reduced by installing a compensating capacitor. In addition, a planar Faraday shield is installed between the windings of the transformer to further suppress the electrostatic coupling. It is found that tuning the variable capacitor can result in a resonance in the output voltage of the rf magnetic probe. The largest output voltage, achieved with the tunable magnetic probe under the optimal condition, is higher than that with a conventional one by an order of magnitude. Effects of the compensating capacitance on the common-mode output voltage are studied and discussed. Influences of parameters such as cable length, the coupling coefficient, and the step-up ratio of the transformer on the output voltage are also presented. Analytical derivations and numerical calculations based on the equivalent circuit are performed to elucidate the characteristics of the differential mode.
Weakly chirped pulses in frequency resolved coherent spectroscopy
Authors: Christensson Niklas , Avlasevich Yuri , Yartsev Arkady , Müllen Klaus , Pascher Torbjörn , Pullerits Tönu
Published: May 2010

The role of weakly chirped pulses (time bandwidth product, ΔνΔτ<0.61) on three-pulse photon echo signals has been systematically studied. Pulses with varying chirp were characterized with frequency resolved optical gating (FROG) and used to measure spectrally resolved three-pulse photon echoes of a dye in solution. The weakly chirped pulses give rise to markedly different echo signals for population times below ∼100 fs. The chirped pulses can decrease or enhance spectral signatures of an excited state absorption transition in the echo signal. Furthermore, the observed dephasing dynamics depend on the phase of the electric fields. Simulations based on a three-level model and the electric fields retrieved from the FROG traces give a good agreement for photon echo experiments with both transform limited and chirped pulses. The simulations also allow for a numerical investigation of effects of chirp in two-dimensional spectroscopy. For a two-level system, the chirped pulses result in nonelliptical two-dimensional spectra that can erroneously be interpreted as spectral heterogeneity with frequency dependent dephasing dynamics. Furthermore, chirped pulses can give rise to “false” cross peaks when strong vibrational modes are involved in the system-bath interaction.
The influence of step geometry on the desorption characteristics of O2, D2, and H2O from stepped Pt surfaces
Authors: van der Niet Maria J. T. C. , den Dunnen Angela , Juurlink Ludo B. F. , Koper Marc T. M.
Published: May 2010

We have compared the desorption characteristics of O2, D2, and H2O from the Pt(533) surface to the Pt(553) surface using temperature programmed desorption. Both surfaces consist of four atom wide (111) terraces interrupted by monoatomic steps of the different step geometries: (100) versus (110), respectively. We find that desorption is influenced significantly by the presence of step sites and the geometry of those sites. In general, molecules and atoms are thought to be bound more strongly to step sites than to terrace sites. Our D2 desorption data from Pt(553) provide an anomalous counterexample to this common belief since D atoms on this surface appear to be bound stronger by terrace sites. We also show that it is not possible to say a priori which step geometry will bind atoms or molecules stronger: recombinatively desorbing O atoms are bound stronger to (100) sites, whereas H2O molecules are bound stronger to (110) sites. Furthermore, the amount of adatoms or molecules that are affected by the presence of steps varies for the different species, as is evident from the various step: terrace ratios of ∼1:1.3 for O2 (O), ∼1:3 for D2 (D), and ∼1:1 for H2O. This indicates that, in contrast to deuterium, more oxygen atoms and water molecules are affected by the presence of steps than would be expected on geometrical arguments alone.
Nonlinear studies of fast electron current pulse propagation in a two dimensional inhomogeneous plasma
Authors: Yadav Sharad Kumar , Das Amita
Published: May 2010

The evolution of fast current and magnetic field pulse structures through an inhomogeneous plasma medium was reported in recent publications [Yadav et al., Phys. Plasmas 15, 062308 (2008); Yadav et al., Phys. Plasmas 16, 040701 (2009)]. The evolution characteristics have been investigated here in further detail. Following specific issues have been addressed; (i) characterization of the phenomena of trapping versus transmission of the current pulse structures through a high density plasma region, (ii) interaction of the current pulse with plasma density inhomogeneity at various incidence angles, and (iii) destabilization of sharp sheared current layers resulting from the interaction with an elongated plasma density inhomogeneity. It is also illustrated that the destabilization of the current pulse trapped in an elongated high density plasma region forms a novel stable coherent nonlinear pattern of alternating signed vortices arranged as beads along the density profile.
XH-stretching overtone transitions calculated using explicitly correlated coupled cluster methods
Authors: Lane Joseph R. , Kjaergaard Henrik G.
Published: May 2010

We have calculated XH-stretching (where X=O, C, F, Cl) fundamental and overtone transitions for three diatomics and a few small molecules using a local mode model. The potential energy curves and dipole moment functions are calculated using the recently developed explicitly correlated coupled cluster with single doubles and perturbative triples theory [CCSD(T)-F12] with the associated VXZ-F12 (where X=D, T, Q) basis sets. We find that the basis set convergence of calculated frequencies and oscillator strengths obtained with the explicitly correlated method is much more rapid than with conventional CCSD(T) and the Dunning type correlation consistent basis sets. Furthermore, CCSD(T)-F12 frequencies and oscillator strengths obtained with the VTZ-F12 and VQZ-F12 basis sets are found to be in excellent agreement with the CCSD(T) complete basis set limit. We find that comparison of CCSD(T)-F12 frequencies with experiment is less good. The inclusion of explicit correlation exposes the inherent error of the CCSD(T) method to overestimate vibrational frequencies, which is normally compensated by basis set incompleteness error. As a consequence, we suggest that conventional CCSD(T) in combination with the aug-cc-pVTZ or aug-cc-pVQZ basis sets is likely to yield calculated XH-stretching frequencies in closest agreement with experiment.
Low-frequency isotropic and anisotropic Raman spectra of aromatic liquids
Authors: Heisler Ismael A. , Meech Stephen R.
Published: May 2010

The Raman spectra below 300 wavenumbers of six different aromatic molecular liquids have been measured with a time and polarization resolved optical Kerr effect technique. The isotropic and anisotropic contributions were determined to yield the complete third order response, and thus a more detailed description of the microscopic liquid dynamics. The anisotropic contributions accurately reproduced previously published results. Both the isotropic and anisotropic Raman spectral densities shift toward lower frequencies with decreasing molecular weights. The first moment of the isotropic spectral densities scales linearly with the inverse square root of the molecular weight, which is consistent with interaction-induced dynamics in these liquids being driven mainly by motions with a translational character. Also, the isotropic spectral densities could be fit to a single Bucaro–Litovitz function. The exponent δ of this function increases monotonically with the inverse square root of the molecular weight. A possible physical origin of this behavior is discussed.
Properties of liquid water from a systematic refinement of a high-rank multipolar electrostatic potential
Authors: Shaik Majeed S. , Liem Steven Y. , Popelier Paul L. A.
Published: May 2010

We build on previous work [S. Y. Liem and P. L. A. Popelier, J. Chem. Theory Comput. 4, 353 (2008)], where for the first time, a high-rank multipolar electrostatic potential was used in molecular dynamics simulations of liquid water at a wide range of pressures and temperatures, and using a multipolar Ewald summation. Water is represented as a rigid body, with atomic multipole moments defined by quantum chemical topology partitioning its gas phase electron density. The effect of the level of theory on the local structure of liquid water is systematically addressed. Values for Lennard-Jones (LJ) parameters are optimized, for both oxygen and hydrogen atoms, against bulk properties. The best LJ parameters were then used in a set of simulations at 30 different temperatures (1 atm) and another set at 11 different pressures (at 298 K). Inclusion of the hydrogen LJ parameters significantly increases the self-diffusion coefficient. The behavior of bulk properties was studied and the local water structure analyzed by both radial and spatial distribution functions. Comparisons with familiar point-charge potentials, such as TIP3P, TIP4P, TIP5P, and simple point charge, show the benefits of multipole moments.
The linear regime of the two-plasmon decay instability in inhomogeneous plasmas
Authors: Yan R. , Maximov A. V. , Ren C.
Published: May 2010

A linear fluid code solving the equations for the two-plasmon decay (TPD) instability has been developed and used to study the TPD instability. Both absolute and convective modes are observed in the simulations using this code, which show that the absolute modes are located close to the quarter-critical-density surface while the convective modes are located in the lower-density region. The maximum growth rates of the absolute modes measured in the simulations agree well with the theoretical results in the limits of large and small values of the parameter β∝Te2/(Iλ2), where Te is the electron temperature, I is the laser intensity, and λ is the laser wavelength. The simulation results also agree with the β-dependent threshold for absolute TPD. A derivation of the convective gain that retains the dependence on electron temperature and perpendicular mode number is presented and it is in good agreement with the simulation results.
Stability of planar buoyant jets in stratified fluids
Authors: Schofield Samuel P. , Restrepo Juan M.
Published: May 2010

We consider the flow structure and stability of a planar saline jet descending into a stable, density-stratified fluid. The jet exhibits a rapid acceleration on release, then deceleration, as it encounters the more dense surrounding fluid, yet retains its slender shape due to the low salt diffusion. As the jet descends it entrains fresher water which as it encounters the increasingly dense ambient fluid returns toward the nozzle forming a recirculation zone. Our numerical simulations agree qualitatively with previous experiments and thus serve as a tool to explain the basic kinematics of the jet. We also use numerical means to capture the three instability modes: an antisymmetric instability in the jet core, a symmetric instability in the jet core, and a symmetric instability in the entrained conduit of less saline water. For the dominant antisymmetric instability we determine the range of parameters that demarcate stable and unstable regions.
Large amplitude relativistic plasma waves
Authors: Coffey Timothy
Published: May 2010

Relativistic, longitudinal plasma oscillations are studied for the case of a simple water bag distribution of electrons having cylindrical symmetry in momentum space with the axis of the cylinder parallel to the velocity of wave propagation. The plasma is required to obey the relativistic Vlasov–Poisson equations, and solutions are sought in the wave frame. An exact solution for the plasma density as a function of the electrostatic field is derived. The maximum electric field is presented in terms of an integral over the known density. It is shown that when the perpendicular momentum is neglected, the maximum electric field approaches infinity as the wave phase velocity approaches the speed of light. It is also shown that for any nonzero perpendicular momentum, the maximum electric field will remain finite as the wave phase velocity approaches the speed of light. The relationship to previously published solutions is discussed as is some recent controversy regarding the proper modeling of large amplitude relativistic plasma waves.
Plasma formation using a capillary discharge in water and its application to the sterilization of E. coli
Authors: Hong Yong Cheol , Park Hyun Jae , Lee Bong Ju , Kang Won-Seok , Uhm Han Sup
Published: May 2010

An underwater electrical discharge in a narrow dielectric capillary provides the details of the evolution of microbubbles to plasma as formed by a tungsten electrode inserted in the capillary. An increase in the applied voltage forms microbubbles after water fills the capillary. A further increase in the voltage generates a surface discharge through the boundary of the bubble, elongating the bubble shape, and eventually forming plasma by electrical breakdown. This produces atomic oxygen, atomic hydrogen, and hydroxyl radicals from dissociation of water vapor. Also, a bactericidal test in normal saline solution showed that more than 99.6% of the bacterial cells were killed within 8 s, resulting from chlorine-containing species, in particular hypochlorous acid as a major bactericidal agent.
Electron transport in rubrene single-crystal transistors
Authors: Bisri Satria Zulkarnaen , Takenobu Taishi , Takahashi Tetsuo , Iwasa Yoshihiro
Published: May 2010

We report a study of impurity effects on the electron transport of rubrene single crystals. A significant improvement of electron carrier mobility up to 0.81 cm2/V s is achieved by performing multiple purifications of single crystals and device aging inside an N2-filled glove box. The hole/electron mobility ratio obtained is in good agreement with the reported theoretical calculation, suggesting that the intrinsic electron transport of organic semiconductors is also exploitable in a manner similar to that of hole transport.
Ellipsometric study of single-crystal γ-InSe from 1.5 to 9.2 eV
Authors: Choi S. G. , Aspnes D. E. , Fuchser A. L. , Martinez-Tomas C. , Sanjosé V. Muñoz , Levi D. H.
Published: May 2010

We report the component E⃑⊥ĉ of the pseudodielectric-function tensor ⟨ε(E)⟩=⟨ε1(E)⟩+i⟨ε2(E)⟩ of γ-phase single-crystal InSe, obtained from 1.5 to 9.2 eV by vacuum-ultraviolet spectroscopic ellipsometry with the sample at room temperature. Overlayer artifacts were reduced as far as possible by measuring fresh surfaces prepared by cleavage. Accurate critical-point energies of observed structures were obtained by a combined method of spectral analysis.
Theoretical studies on the structure of interacting colloidal suspensions by spin-echo small angle neutron scattering
Authors: Li Xin , Shew Chwen-Yang , Liu Yun , Pynn Roger , Liu Emily , Herwig Kenneth W. , Smith Gregory S. , Robertson J. Lee , Chen Wei-Ren
Published: May 2010

The application of the spin-echo small angle neutron scattering (SESANS) technique for structural characterization of interacting colloidal suspensions is considered in this work. The framework to calculate the theoretical SESANS correlation function is briefly laid out. A general discussion regarding the features of the SESANS correlation functions obtained from different model systems is presented. In comparison with conventional elastic scattering tools operating at the same length scale, our mean-field calculations, based on a monodisperse spherical colloidal system, show that the real-space measurement provided by SESANS presents a powerful probe for studying the intercolloid potential. The reason of this sensitivity is discussed from the standpoint of way, in which how the spatial correlations are manifested in different neutron scattering implementations. This study leads to a better understanding regarding the distinction between SANS and SESANS.
Bi ordered phases on Cu(100): Periodic arrays of dislocations influence the electronic properties
Authors: Gargiani Pierluigi , Izzo Maria Grazia , Bussolotti Fabio , Betti Maria Grazia , Achilli S. , Trioni M. I.
Published: May 2010

A single layer of bismuth deposited on the Cu(100) surface forms long range ordered structural phases at various Bi density. A highly ordered c(2×2) reconstruction is accomplished at 0.5 ML, further Bi deposition induces a c(92×2)R45° structure and a subsequent p(10×10) phase related to the formation of regular dislocations arrays. The transition from a c(2×2) superstructure to the c(92×2)R45° phase is accompanied by a sudden decrease in the work function. Photoemission measurements reveal that the Bi induced states close to the Fermi level, associated to the c(2×2) phase, are strongly quenched when the arrays of dislocations are formed, while at higher binding energies, they undergo an energy shift probably due to a confinement effect. The low-energy single particle excitations and the electron dispersion of the Bi induced states of the c(2×2) phase are compared to the electronic states deduced by theoretical band structure obtained by ab initio calculation performed within the embedding method applied to a realistic semi-infinite system.
Fabrication of two-dimensional Au@FePt core-shell nanoparticle arrays by photochemical metal deposition
Authors: Härtling Thomas , Uhlig Tino , Seidenstücker Axel , Bigall Nadja C. , Olk Phillip , Wiedwald Ulf , Han Luyang , Eychmüller Alexander , Plettl Alfred , Ziemann Paul , Eng Lukas M.
Published: May 2010

In this report, we experimentally demonstrate that single platinum nanoparticles exhibit the necessary catalytic activity for the optically induced reduction of H[AuCl4] complexes to elemental gold. This finding is exploited for the parallel Au encapsulation of FePt nanoparticles arranged in a self-assembled two-dimensional array. Magnetic force microscopy reveals that the thin gold layer formed on the FePt particles leads to a strongly increased long-term stability of their magnetization under ambient conditions.
Conduction behavior change in amorphous LaLuO3 dielectrics based on correlated barrier hopping theory
Authors: Li Kui , Xia Yidong , Xu Bo , Gao Xu , Guo Hongxuan , Liu Zhiguo , Yin Jiang
Published: May 2010

Unipolar switching behaviors have been revealed in amorphous LaLuO3, which makes it suited for not only logic but memory applications using the conventional semiconductor or the emerging nano/CMOS architectures. Such switching is comprehended with regard to the conduction behavior transition between high- and low-resistance states. The conduction in high-resistance state follows the Poole’s law, whereas the conduction in low-resistance state is dominated by percolation. The transition between these resistance states is attributed to the change in the separation between oxygen vacancy sites in the light of the correlated barrier hopping theory.
Structural effects on the lattice thermal conductivity of ternary antimony- and bismuth-containing chalcogenide semiconductors
Authors: Skoug Eric J. , Cain Jeffrey D. , Morelli Donald T.
Published: May 2010

The lattice thermal conductivities Cu3SbSe4 and Cu3SbSe3 have been measured. While the former compound exhibits classical behavior, the lattice thermal conductivity of Cu3SbSe3 is anomalously low. We speculate that, similar to the case of AgSbTe2, the low thermal conductivity in Cu3SbSe3 has its origin in strong anharmonicity induced by the presence of the two additional nonbonding electrons in the valence shell of the Sb3+ ions. Anomalously low thermal conductivity is also demonstrated in compounds in which Bi occurs in the trivalent state. The results have implications in the design of thermoelectric semiconductors with intrinsically low thermal conductivity.
Peculiar features of confinement factors in a metal-semiconductor waveguide
Authors: Li D. B. , Ning C. Z.
Published: May 2010

The concept of confinement factor (CF) is analyzed for a metal-semiconductor-metal (MSM) waveguide near the surface plasmon resonance. We show that the CF is inversely proportional to the average energy velocity, and thus can be enhanced by the slowing down of energy propagation. This slowing down in the MSM waveguide results in a value of CF as high as 105, as opposed to a value of smaller than 1 in a typically dielectric structure. Contrary to the CF in pure dielectric waveguide where it is independent of material gain, the CF in MSM waveguide shows a resonancelike dependence on material gain near the surface plasmon resonance.
Molecular dynamics study of solvation differences between cis- and transplatin molecules in water
Authors: Fu Cen-Feng , Tian Shan Xi
Published: May 2010

The classical molecular dynamics (MD) simulations for the solvation properties of cis- and transplatins in water are performed with the Lennard-Jones plus Coulomb electrostatic potential parameters that are optimized with ab initio potential energies of the water-platin systems. Two hydration shells are found both for cis- and transplatins. The first shell of water molecules is closer to transplatin than cisplatin. The average number and lifetime of the intermolecular hydrogen bonds (HBs) estimated from the MD trajectories indicate that the Cl and NH3 ligands are the main groups involved in the intermolecular HBs with water. In comparison with cisplatin, there are more HBs around transplatin and these HBs show the longer lifetime. The distinctly different solvation structures between cis- and transplatins are further revealed with the spatially anisotropic distributions of the first hydration shells.
A simplified design of the staggered herringbone micromixer for practical applications
Authors: Du Yan , Zhang Zhiyi , Yim ChaeHo , Lin Min , Cao Xudong
Published: May 2010

We demonstrated a simple method for the device design of a staggered herringbone micromixer (SHM) using numerical simulation. By correlating the simulated concentrations with channel length, we obtained a series of concentration versus channel length profiles, and used mixing completion length Lm as the only parameter to evaluate the performance of device structure on mixing. Fluorescence quenching experiments were subsequently conducted to verify the optimized SHM structure for a specific application. Good agreement was found between the optimization and the experimental data. Since Lm is straightforward, easily defined and calculated parameter for characterization of mixing performance, this method for designing micromixers is simple and effective for practical applications.
Thermodynamic stability limits of simple monoatomic materials
Authors: Gallington Leighanne C. , Bongiorno Angelo
Published: May 2010

This computational study addresses the thermodynamical stability of superheated crystals. Molecular dynamics simulations are employed to derive the caloric curves of the solid and liquid phases of a material. Caloric curves are used to derive thermodynamic state functions, the parameters of the equilibrium melting phase transition, and the regions of thermodynamical stability of the liquid and solid phases. Molecular dynamics trajectories are also analyzed to gain insight on the mechanisms leading to the instability of the homogeneous superheated solid phase. This study shows that in simple and homogeneous solids the configurational entropy is not zero and that its excitations can occur without disrupting the crystallinity of the lattice. The superheating and supercooling limits of the solid and liquid phases are found to correspond to states of equal entropy and enthalpy.
Computation of induced electric field and temperature elevation in human due to lightning current
Authors: Nagai T. , Hirata A.
Published: May 2010

The present study investigated induced electric field and temperature elevation in specific tissues/organs of an anatomically based human body model for the lightning current. The threshold amplitude of the current inducing ventricular fibrillation and skin burning are estimated from computed induced electric field and temperature elevation with formulas for electrical stimulation and thermal damage. The computational results obtained herein were reasonably consistent with clinical observation.
On the energy harvesting potential of piezoaeroelastic systems
Authors: Erturk A. , Vieira W. G. R. , De Marqui C. , Inman D. J.
Published: May 2010

This paper investigates the concept of piezoaeroelasticity for energy harvesting. The focus is placed on mathematical modeling and experimental validations of the problem of generating electricity at the flutter boundary of a piezoaeroelastic airfoil. An electrical power output of 10.7 mW is delivered to a 100 kΩ load at the linear flutter speed of 9.30 m/s (which is 5.1% larger than the short-circuit flutter speed). The effect of piezoelectric power generation on the linear flutter speed is also discussed and a useful consequence of having nonlinearities in the system is addressed.
p-type Bi0.4Sb1.6Te3 nanocomposites with enhanced figure of merit
Authors: Fan Shufen , Zhao Junnan , Guo Jun , Yan Qingyu , Ma Jan , Hng Huey Hoon
Published: May 2010

We report enhanced figure of merit, ZT, in p-type Bi0.4Sb1.6Te3 nanocomposites fabricated by a rapid and high throughput method of mixing nanostructured Bi0.4Sb1.6Te3 particles obtained through melt spinning with micronsized particles obtained via solid state reaction. Due to effective scattering of phonons over a wide wavelength spectrum, low thermal conductivity, and moderately good power factor were obtained in the nanocomposites to achieve ZT above 1.5 at room temperature. A maximum ZT of 1.80 was attained at 43 °C for the nanocomposite consisting 40 wt % nanoinclusions. This was a 56% increment over the bulk sample, and the highest ZT reported for Bi2Te3-based materials.
Evidence for substitutional boron in doped single-walled carbon nanotubes
Authors: Ayala P. , Reppert J. , Grobosch M. , Knupfer M. , Pichler T. , Rao A. M.
Published: May 2010

Precise determination of acceptors in the laser ablation grown B doped single-walled carbon nanotubes (SWCNTs) has been elusive. Photoemission spectroscopy finds evidence for subpercent substitutional B in this material, which leads to superconductivity in thin film SWNT samples.
Investigation of E1(LO) phonon-plasmon coupled modes and critical points in In1−xGaxN thin films by optical reflectance measurements
Authors: Thakur J. S. , Dixit A. , Danylyuk Y. V. , Sudakar C. , Naik V. M. , Schaff W. J. , Naik R.
Published: May 2010

Low energy optical modes of molecular beam epitaxy-grown In1−xGaxN thin films with 0≤x≤0.6 are investigated using infrared reflectance measurements. We found that the reflectance of the films for wave vectors in the range from 600 to 800 cm−1 is determined by the high energy E1(LO)-plasmon coupled modes. In the higher energy regime of the UV-visible reflectance spectrum of InN, critical points with energies 4.75, 5.36, and 6.12 eV belonging to A and B structures are observed. The energies of these critical points increase with increasing values of x, similar to the band gap energy of these films.
1550 nm band optical input module with superconducting single-flux-quantum circuit
Authors: Shinada Satoshi , Terai Hirotaka , Wang Zhen , Wada Naoya
Published: May 2010

We developed an optical input module with a superconducting single-flux-quantum (SFQ) circuit for application of ultrafast photonic networks in the near future. The optical input module, consisting of a built-in photodiode (PD) with a coplanar waveguide transmission line, was fabricated on an InP substrate and flip-chip bonded with the SFQ circuit on a Si substrate. The fabricated PD showed photosensitivities of more than 0.2 A/W for the wavelength range 1480 to 1530 nm at 4.2 K. SFQ pulses were generated by less than 1 mW optical pulse input.
Synthesis and optical properties of GaN/ZnO solid solution nanocrystals
Authors: Han Wei-Qiang , Liu Zhenxian , Yu Hua-Gen
Published: May 2010

We devised a synthesis route to prepare narrow band gap GaN/ZnO solid solution nanocrystals via nitriding a homogeneous Ga-Zn-O nanoprecursor. The nanocrystals were characterized by several following methods: x-ray diffractometer, transmission electron microscopy, ultraviolet-visible diffuse reflection, and Raman spectroscopy. Here, we can control the composition of nanocrystals by the nitridation temperature. From 550 to 850 °C, the corresponding crystalline size varies from 6.1 to 27 nm. It has been demonstrated that the sample prepared at 650 °C had the narrowest band gap of 2.21 eV. Microstructural investigations show that the (101) surface is the predominantly exposed one for the GaN/ZnO solid solution nanocrystals. We also discuss the influence of chemical disorder based on the Raman spectra acquired.
Communications: Monovalent ion condensation at the electrified liquid/liquid interface
Authors: Laanait Nouamane , Yoon Jaesung , Hou Binyang , Vanysek Petr , Meron Mati , Lin Binhua , Luo Guangming , Benjamin Ilan , Schlossman Mark L.
Published: May 2010

X-ray reflectivity studies demonstrate the condensation of a monovalent ion at the electrified interface between electrolyte solutions of water and 1,2-dichloroethane. Predictions of the ion distributions by standard Poisson–Boltzmann (Gouy–Chapman) theory are inconsistent with these data at higher applied interfacial electric potentials. Calculations from a Poisson–Boltzmann equation that incorporates a nonmonotonic ion-specific potential of mean force are in good agreement with the data.
First order structural transformation and inverse magnetocaloric effect in melt-spun Ni–Mn–Sn ribbons
Authors: Babita I , Patil S I , Ram S
Published: May 2010

First order structural transformation (FOST) and inverse magnetocaloric effect (IMCE) were investigated in melt-spun ribbons of Ni49Mn37.4Sn13.6 and Ni50Mn34.5Sn15.5 Heusler alloys. Thermal and magnetic characterization of the ribbons revealed the existence of FOST. Interestingly, in the Ni49Mn37.4Sn13.6 ribbon, the structural transformation occurs prior to magnetic transition incongruous to that observed in the Ni50Mn34.5Sn15.5 ribbons. In addition to FOST, the ribbons also exhibit a large IMCE at low magnetic field. A maximum positive magnetic entropy change ΔS
M ∼ 6.0 J kg−1 K−1 and ∼1.6 J kg−1 K−1 for a field change of 2 T was observed in the Ni49Mn37.4Sn13.6 and Ni50Mn34.5Sn15.5 ribbons, respectively.
The magnetostructural transformation and magnetocaloric effect in Co-doped MnNiGe1.05 alloys
Authors: Zhang Chengliang , Wang Dunhui , Cao Qingqi , Ma Shengcan , Xuan Haicheng , Du Youwei
Published: May 2010

A series of MnNi1−x
Co
x
Ge1.05 (x = 0, 0.03, 0.05, 0.07, 0.09, and 0.11) alloys were prepared by the arc-melting method. With increasing content of Co, a first-order magnetostructural transformation between the antiferromagnetic TiNiSi-type phase and the ferromagnetic Ni2In-type phase was observed. A magnetic and crystallographic phase diagram for MnNi1−x
Co
x
Ge1.05 alloys was proposed in this paper. Owing to the abrupt and large jump of magnetization around the magnetostructural transformation, MnNi1−x
Co
x
Ge1.05 (x = 0.07, 0.09, 0.11) alloys show large and positive magnetic entropy changes at relatively low field.
The influence of film thickness on photovoltaic effect for the Fe3O4/SrTiO3:Nb heterojunctions
Authors: Wei A D , Sun J R , Chen Y Z , Lü W M , Shen B G
Published: May 2010

Fe3O4 films with the thickness ranging from 5 to 160 nm have been grown on SrTiO3 : Nb (0.05wt%) substrates by the pulsed laser deposition technique. The good quality of the Fe3O4 film was confirmed by x-ray diffraction and magnetic analyses. It is found that the interfacial barrier of the resultant junctions, determined by the photovoltaic technique, decreases as film thickness increases from ∼5 to ∼40 nm, with a relative change of ∼20%, and saturates at a value of ∼1.2 eV above the thickness of 40 nm. Variation of lattice strains in the Fe3O4 film may be the reason for the thickness dependence of the interfacial barrier.
Plasma chemistry and diagnostic in an Ar–N2–H2 microwave expanding plasma used for nitriding treatments
Authors: Touimi S , Jauberteau J L , Jauberteau I , Aubreton J
Published: May 2010

This paper reports on the mass spectrometry analysis performed downstream a microwave discharge in an Ar–N2–H2 gas mixture under nitriding conditions. Investigations are focused on the main simple radicals NH2, NH and N, and on the molecular species NH3 and N2H2 produced. Because of wall desorptions due to catalytic effects, we must develop a specific method taking into account both wall desorption and the dissociative ionization effects in order to correct the mass spectrometer signal intensity. The relative concentrations of the above-mentioned species are studied in various gas mixtures. Correlations are made between the plasma chemistry and the plasma parameters (electron density and energy electron distribution function), measured by means of a Langmuir probe spatially resolved within the plasma expansion. These results show the efficiency of ternary gas mixtures (Ar–N2–H2) in producing electrons and N
x
H
y
species used in plasma nitriding processes.
Orientation control and thermoelectric properties of FeSb2 films
Authors: Sun Ye , Zhang Eryun , Johnsen Simon , Sillassen Michael , Sun Peijie , Steglich Frank , Bøttiger Jørgen , Iversen Bo Brummerstedt
Published: May 2010

FeSb2 has a high potential for technological applications due to its colossal thermoelectric power, giant carrier mobility and large magnetoresistance. Earlier, growth of ⟨1 0 1⟩-textured FeSb2 films on quartz (0 0 0 1) substrates has been reported. Here magnetron sputtering is used to obtain ⟨0 0 2⟩-textured FeSb2 films by employing a pre-deposited FeSb2 thin-film layer as template. The in-plane thermoelectric properties of FeSb2 films with different orientations were studied and compared. The anisotropy of FeSb2 is shown to have an important effect on the transport properties of FeSb2 films. Orientation control of the FeSb2 films could be significant for their property optimization and thus highlight their application potential.
UMA and MABP domains throw light on receptor endocytosis and selection of endosomal cargoes
Authors: de Souza Robson F. , Aravind L.
Published: May 2010

Interactions of the ESCRT complexes are critical for endosomal trafficking. We identify two domains with potential significance for this process. The MABP domain present in metazoan ESCRT-I/MVB12 subunits, Crag, a regulator of protein sorting, and bacterial pore-forming proteins might mediate novel membrane interactions in trafficking. The UBAP1-MVB12-associated UMA domain found in MVB12 and UBAP1 defines a novel adaptor that might recruit diverse targets to ESCRT-I.

Contact:  aravind@ncbi.nlm.nih.gov

Supplementary information:  Supplementary data are available at ftp://ftp.ncbi.nih.gov/pub/aravind/UMA/MVB12.html.
Evaluation of the GenoType Mycobacteria Direct assay for direct detection of the Mycobacterium tuberculosis complex obtained from sputum samples
Authors: Kiraz Nuri , Saglik Imran , Kiremitci Abdurrahman , Kasifoglu Nilgun , Akgun Yurdanur
Published: May 2010

An increase in the prevalence of tuberculosis (TB) in recent years has accelerated the search for novel tools for the rapid diagnosis of TB infection. This study evaluated the GenoType Mycobacteria Direct (GTMD) assay (Hain Lifescience) for direct detection of theMycobacterium tuberculosiscomplex (MTBC) from sputum samples and compared it with conventional methods. The GTMD test is a commercial assay produced using strip techniques and works based on a nucleic acid sequence-based amplification technique. This test allows 23S rRNA amplification-based detection of MTBC,Mycobacterium avium,Mycobacterium intracellulare,Mycobacterium kansasiiandMycobacterium malmoensedirectly from decontaminated clinical samples within 6 h. In the present study, 115 sputum samples were processed to detect acid-fast bacilli (AFB) using two microscopy methods (carbol fuchsin and fluorescent staining), two culture methods [Löwenstein–Jensen (LJ) and BACTEC 12B media] and the GTMD test. The results showed that 86 of the samples were positive by direct microscopy, 84 were positive by BACTEC 12B culture, 73 were positive by LJ culture and 95 were positive by the GTMD test. All of the isolates turned out to be MTBC. Moreover, the sensitivity and specificity of the GTMD test for MTBC in patients were 97 and 58 %, respectively, taking the culture combination as the gold standard. When the test was compared with culture of samples from anti-TB-treated patients, the sensitivity and specificity for the test were 100 and 15 %, respectively. Low specificity in treated people might arise from depressed proliferation of AFB. As the two methods target the same living bacilli, the difference is obviously notable. When the culture results and clinical findings of the patients were evaluated together (true-positive specimens), the sensitivity and specificity values of the GTMD test for all patients were 97 and 90 %, respectively. However, both of these values increased to 100 % for the patients receiving anti-TB treatment. These results implied that, to determine whether the patient's sputum contains living AFB, more sensitive techniques should be employed during the follow-up of the patients. These observations suggest that the GTMD method can be useful for early diagnosis of clinically and radiologically suspicious TB cases where smears are negative forMycobacterium. In addition, the use of a GTMD test in smear-positive cases is helpful and practical in order to identify MTBC quickly. This allows more rapid treatment decisions and infection control precautions.
Identification of P1 types and variants of Mycoplasma pneumoniae during an epidemic in Chile
Authors: Martínez María A. , Ruiz Mauricio , Zunino Enna , Luchsinger Vivian , Aguirre Raúl , Avendaño Luis F.
Published: May 2010

This study was conducted to determine the types of M. pneumoniae prevalent in adults presenting with community-acquired pneumonia during an epidemic period, and to scrutinize a variable region of the RepMP4 element for the detection of P1 variants. All 23 clinical specimens PCR-positive for M. pneumoniae obtained in two hospitals in Santiago, Chile, from 2005 to 2006 were typed by a multiplex PCR directly and then the RepMP4 fragment of 18 specimens was sequenced. A predominance of M. pneumoniae type 2 was found, 18 (78.3 %) specimens being grouped as type 2 and 5 (21.7 %) as type 1. Co-infection of M. pneumoniae with other respiratory pathogens was found in 10/23 (43.4 %) patients, but their frequency was not related to the M. pneumoniae type. Sequence analysis revealed a single nucleotide polymorphism, a transition mutation, in 50 % of amplicons belonging to type 1 and in 71.4 % of amplicons of type 2. The nucleotide changes were synonymous in each P1 variant. In conclusion, during the 2005–2006 epidemic in Santiago, both types of M. pneumoniae circulated. Although the analysed area in the RepMP4 was small, we detected the existence of P1 variants in the two types of this organism.
The endolysins of bacteriophages CMP1 and CN77 are specific for the lysis of Clavibacter michiganensis strains
Authors: Wittmann Johannes , Eichenlaub Rudolf , Dreiseikelmann Brigitte
Published: May 2010

Putative endolysin genes of bacteriophages CMP1 and CN77, which infect Clavibacter michiganensis subsp. michiganensis and C. michiganensis subsp. nebraskensis, respectively, were cloned and expressed in Escherichia coli. The His-tagged endolysin of CMP1 consists of 306 amino acids and has a calculated molecular mass of 34.8 kDa, while the His-tagged endolysin of CN77 has 290 amino acids with a molecular mass of 31.9 kDa. The proteins were purified and their bacteriolytic activity was demonstrated. The bacteriolytic activity of both enzymes showed a host range which was limited to the respective C. michiganensis subspecies and did not affect other bacteria, even those closely related to Clavibacter. Due to the high specificity of the CMP1 and CN77 endolysins they may be useful tools for biocontrol of plant-pathogenic C. michiganensis without affecting other bacteria in the soil.
Identification of non-coding RNAs in environmental vibrios
Authors: Silveira Ana Cristina G. , Robertson Kelly L. , Lin Baochuan , Wang Zheng , Vora Gary J. , Vasconcelos Ana Tereza R. , Thompson Fabiano L.
Published: May 2010

The discovery of non-coding RNA (ncRNA) has been mainly limited to laboratory model systems and human pathogenic bacteria. In this study, we begin to explore the ncRNA diversity in four recently sequenced environmental Vibrio species (Vibrio alginolyticus 40B, Vibrio communis 1DA3, Vibrio mimicus VM573 and Vibrio campbellii BAA-1116) by performing in silico searches using Infernal and Rfam for the identification of putative ncRNA-encoding genes. This search method resulted in the identification of 31–38 putative ncRNA genes per species and the total ncRNA catalogue spanned an assortment of regulatory mechanisms (riboswitches, cis-encoded ncRNAs, trans-encoded ncRNAs, modulators of protein activity, ribonucleoproteins, transcription termination ncRNAs and unknown). We chose to experimentally validate the identifications for V. campbellii BAA-1116 using a microarray-based expression profiling strategy. Transcript hybridization to tiled probes targeting annotated V. campbellii BAA-1116 intergenic regions revealed that 21 of the 38 predicted ncRNA genes were expressed in mid-exponential-phase cultures grown in nutrient-rich medium. The microarray findings were confirmed by testing a subset of three highly expressed (6S, tmRNA and TPP-2) and three moderately expressed (CsrB, GcvB and purine) ncRNAs via reverse transcription PCR. Our findings provide new information on the diversity of ncRNA in environmental vibrios while simultaneously promoting a more accurate annotation of genomic intergenic regions.
Functions of Heteromeric and Homomeric Isoamylase-Type Starch-Debranching Enzymes in Developing Maize Endosperm
Authors: Kubo Akiko , Colleoni Christophe , Dinges Jason R. , Lin Qiaohui , Lappe Ryan R. , Rivenbark Joshua G. , Meyer Alexander J. , Ball Steven G. , James Martha G. , Hennen-Bierwagen Tracie A. , Myers Alan M.
Published: May 2010

Functions of isoamylase-type starch-debranching enzyme (ISA) proteins and complexes in maize (Zea mays) endosperm were characterized. Wild-type endosperm contained three high molecular mass ISA complexes resolved by gel permeation chromatography and native-polyacrylamide gel electrophoresis. Two complexes of approximately 400 kD contained both ISA1 and ISA2, and an approximately 300-kD complex contained ISA1 but not ISA2. Novel mutations of sugary1 (su1) and isa2, coding for ISA1 and ISA2, respectively, were used to develop one maize line with ISA1 homomer but lacking heteromeric ISA and a second line with one form of ISA1/ISA2 heteromer but no homomeric enzyme. The mutations were su1-P, which caused an amino acid substitution in ISA1, and isa2-339, which was caused by transposon insertion and conditioned loss of ISA2. In agreement with the protein compositions, all three ISA complexes were missing in an ISA1-null line, whereas only the two higher molecular mass forms were absent in the ISA2-null line. Both su1-P and isa2-339 conditioned near-normal starch characteristics, in contrast to ISA-null lines, indicating that either homomeric or heteromeric ISA is competent for starch biosynthesis. The homomer-only line had smaller, more numerous granules. Thus, a function of heteromeric ISA not compensated for by homomeric enzyme affects granule initiation or growth, which may explain evolutionary selection for ISA2. ISA1 was required for the accumulation of ISA2, which is regulated posttranscriptionally. Quantitative polymerase chain reaction showed that the ISA1 transcript level was elevated in tissues where starch is synthesized and low during starch degradation, whereas ISA2 transcript was relatively abundant during periods of either starch biosynthesis or catabolism.