bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient solution of the electric and magnetic current combined‐field integral equation with the multilevel fast multipole algorithm and block‐diagonal preconditioning
Authors: Ergül Ö. , Gürel L.
Published: November 2009

We consider the efficient solution of electromagnetics problems involving dielectric and composite dielectric‐metallic structures, formulated with the electric and magnetic current combined‐field integral equation (JMCFIE). Dense matrix equations obtained from the discretization of JMCFIE with Rao‐Wilton‐Glisson functions are solved iteratively, where the matrix‐vector multiplications are performed efficiently with the multilevel fast multipole algorithm. JMCFIE usually provides well conditioned matrix equations that are easy to solve iteratively. However, iteration counts and the efficiency of solutions depend on the contrast, i.e., the relative variation of electromagnetic parameters across dielectric interfaces. Owing to the numerical imbalance of off‐diagonal matrix partitions, solutions of JMCFIE become difficult with increasing contrast. We present a four‐partition block‐diagonal preconditioner (4PBDP), which provides efficient solutions of JMCFIE by reducing the number of iterations significantly. 4PBDP is useful, especially when the contrast increases, and the standard block‐diagonal preconditioner fails to provide a rapid convergence.
Hydrocolloid gelling agents and their applications
Authors: de Vries Joop
Published: November 2009

The most important hydrocolloid food gelling agents are gelatine, starch, pectin, carrageenan and alginate, but also agar, celluloses, gellan gum, konjac, milk proteins and soy proteins can be used as gelling agents. Xanthan gum is widely used in weakly gelled type foods such as salad dressings. Dairy dessert gels, jams and table jellies are typical examples of gelled foods, but also meat products or noodles can be gels. Hydrocolloids can form molecular gels through association of parts of the molecules forming ‘junction zones’. The type of binding in the junction zone and the amount of molecules forming the junction zones are the most important hydrocolloid interactions are charge effects, steric hindrance, excluded volume effects and incompatibility. If particles are present, adsorption and depletion flocculation can take place. Gel properties are important for flavour release from gelled foods, whereas the clarity and surface smoothness of gels mainly depend on the presence and structure of insoluble components.
New forms of xanthan gum with enhanced properties
Authors: Morrison Neil A. , Clark Ross , Talashek Todd , Yuan C. Ronnie
Published: November 2009

Xanthan gum is a viscous polysaccharide produced by fermentation of the bacterium Xanthomonas campestris. The efficient stabilization and suspension properties of xanthan are related to its structural features: high molecular weight and extended conformation. New studies have shown that the levels of acetate and pyruvate substituents can affect both structural and functional properties. Differential Scanning Calorimetry and Atomic Force Microscopy results show that low acetate xanthan gum adopts a less ordered, more flexible conformation. These conformational changes result in a novel product, which has enhanced functional properties, such as increased acid stability and enhanced interaction with galactomannans.
Influence of hydrocolloids in low-moisture foods – a food polymer science approach
Authors: Levine Harry , Slade Louise
Published: November 2009

The “food polymer science” (FPS) approach was developed to study glasses and glass transitions, and their effects on processing, product quality and storage stability, in foods. Since 1980, this “new” approach to food research – beyond that of the “water activity” concept of moisture management – has been fruitfully used to understand structure-function relationships, the effects of plasticization by water – as illustrated by means of state diagrams – on thermal, mechanical, rheological and textural properties, and physical (meta)stability in the non-equilibrium glassy solid state, vs. instability in the rubbery or viscous liquid state.

Key concepts of the EPS approach, especially as it has been widely applied in the decade of the 90's to low-moisture, hydrocolloid-containing food systems, include a practical understanding of the significance of the glass transition temperature, Tg, and its temperature range, how Tg is defined for multi-component, aqueous amorphous blends, and how Tg relates to the relative mobilities of individual components, including water, in such blends. Due to water's well-known plasticizing effect on many different food polymer systems, Tg decreases monotonically with increasing moisture content, but the linear relationship is between Tg and system relative humidity (% RH), rather than moisture content. Like the glass transition itself, plasticization is a kinetic process, so the mere presence of water is not a guarantee that softening or other changes in rheological properties have already occurred.

Selected examplex of some applications of the FPS approach to studies on food processing, product properties and storage stability will be given, which illustrate the significant progress made in recent years, based on amorphous product technology. With a focus on low-moisture baked goods such as cookies and crackers, we'll first discuss the relationships among the sensory textural attribute of crispness, the glassy solid state below Tg, moisture uptake, and resulting water plasticization that leads to a loss of crispness for the rubbery liquid state above Tg. Then we'll discuss the detrimental influence of water-soluble pentosans (high MW, non-starch polysaccharides), one of the three functional components found in all wheat flous used for biscuit making, and how Nabisco's patented pentosanase enzyme technology has been commercialized to successfully overcome several different negative effects of soluble pentosans in biscuit flours.
Pediatric Benign Vocal Fold Lesions: A Team Approach
Authors: Woodnorth Geralyn Harvey , Nuss Roger C.
Published: November 2009

Many children with dysphonia present with benign vocal fold lesions, including bilateral vocal fold nodules, cysts, vocal fold varices, and scarring. Evaluation and treatment of these children are best undertaken in a thoughtful and coordinated manner involving both the speech-language pathologist and the otolaryngologist. The goals of this article are (a) to describe the team evaluation process based on a “whole system” approach; (b) to discuss etiological factors and diagnosis; and (c) to review current medical, behavioral, and surgical treatments for children with different types of dysphonia.
Special Considerations in the Management of the Pediatric Voice and Airway Patient
Authors: Kelchner Lisa , de Alarcon Alessandro , Weinrich Barbara , Brehm Susan Baker
Published: November 2009

Children who need or have undergone airway reconstruction often present challenges for the treating otolaryngologist and speech-language pathologist. Crucial care issues include establishing a patent laryngeal and tracheal airway that meets the demands of childhood development. Related concerns, such as maintaining functional and structural support for voicing and active airway protection, require specialized management approaches.

The pediatric airway reconstruction literature is limited, given that this is a relatively low incidence population and the fact that there are few pediatric airway/voice centers who manage large numbers of these children. Most published articles highlight the success of the various surgical procedures to accomplish reconnection of the upper and lower airway and, thus, decannulation, while others also have attempted to characterize voice outcomes. Frequently, clinical discussions lament the airway/voice “trade-off” that can occur when trying to expand an airway to achieve comfortable, safe respiration and yet maintain or acquire an acceptable voice quality. As a child grows, these circumstances can complicate management decisions, causing concern for parents, patients, and clinicians alike. The following is an overview of the main issues surrounding the assessment and treatment of the pediatric airway patient from both the physician and speech-language pathologist's perspective.
Improvisation during Process-Technology Adoption: A Longitudinal Study of a Software Firm
Authors: Tjørnehøj Gitte , Mathiassen Lars
Published: November 2009

Most software firms struggle to take advantage of the potential benefits of software process improvement (SPI) as they adopt this technology into the complex and dynamic realities of their day-to-day operation. Such efforts are therefore typically fluctuating between management's attempt to control SPI technology adoption and events that causes the process to drift in unpredictable directions. To further understand how management's attempt to control the process is complemented by drifting, this article investigates the role of improvisation in adoption of SPI technology in a Danish software firm, SmallSoft, over a 10-year period (1996–2005). We found that micro-level and macro-level improvisations interacted, often in uncoordinated ways, to shape SPI technology adoption at SmallSoft. The improvisations enhanced employee creativity, motivation and empowerment, created momentum in the adoption process despite constrained resources, and, most importantly, helped adapt SPI technology to the everyday practices at SmallSoft. However, we also identified un-called for improvisations and outcomes that were uncoordinated with SmallSoft's goals. Based on these findings we discuss how management in small software firms can exploit improvisations to facilitate adoption of complex technologies like SPI.
A conformal extension theorem based on null conformal geodesics
Authors: Lübbe Christian
Published: November 2009

In this article we describe the formulation of null geodesics as null conformal geodesics and their description in the tractor formalism. A conformal extension theorem through an isotropic singularity is proven by requiring the boundedness of the tractor curvature and its derivatives to sufficient order along a congruence of null conformal geodesic. This article extends earlier work by Lübbe and Tod, J. Math. Phys. 50, 112501 (2009) (“An extension theorem for conformal gauge singularities,” e-print arXiv:0710.5552).
Diffracted magneto-optical Kerr effect of a Ni magnetic grating
Authors: Kim J. B. , Lu Y. H. , Cho M. H. , Lee Y. P. , Rhee J. Y. , Lee J.-H. , Ho K.-M.
Published: November 2009

We report the results of a joint experimental and theoretical investigation focused on the magneto-optical (MO) properties of one-dimensional magnetic grating structure made of Ni. It was found that the longitudinal Kerr rotation of the second-order diffracted beam is nearly three times larger than that of the zeroth-order beam. The calculational results further confirmed the experimental ones, and almost perfectly reproduced the measured hysteresis loops of the longitudinal MO Kerr rotation, elucidating the origin of the enhanced MO rotation.
Terahertz microfluidic sensor based on a parallel-plate waveguide resonant cavity
Authors: Mendis Rajind , Astley Victoria , Liu Jingbo , Mittleman Daniel M.
Published: October 2009

We describe a terahertz optical resonator that is ideally suited for highly sensitive and noninvasive refractive-index monitoring. The resonator is formed by machining a rectangular groove into one plate of a parallel-plate waveguide, and is excited using the lowest-order transverse-electric (TE1) waveguide mode. Since the resonator can act as a channel for fluid flow, it can be easily integrated into a microfluidics platform for real-time monitoring. Using this resonator with only a few microliters of liquid, we demonstrate a refractive-index sensitivity of 3.7×105 nm/refractive-index-unit, the highest ever reported in any frequency range.
Integrable higher order deformations of Heisenberg supermagnetic model
Authors: Guo Jia-Feng , Wang Shi-Kun , Wu Ke , Yan Zhao-Wen , Zhao Wei-Zhong
Published: November 2009

The Heisenberg supermagnet model is an integrable supersymmetric system and has a close relationship with the strong electron correlated Hubbard model. In this paper, we investigate the integrable higher order deformations of Heisenberg supermagnet models with two different constraints: (i) S2=3S−2I for S∊USPL(2/1)/S(U(2)×U(1)) and (ii) S2=S for S∊USPL(2/1)/S(L(1/1)×U(1)). In terms of the gauge transformation, their corresponding gauge equivalent counterparts are derived.
Influence of flow confinement on the drag force on a static cylinder
Authors: Semin B. , Hulin J. P. , Auradou H.
Published: October 2009

The influence of confinement on the drag force F on a static cylinder in a viscous flow inside a rectangular slit of aperture h0 has been investigated from experimental measurements and numerical simulations. At low enough Reynolds numbers, F varies linearly with the mean velocity and the viscosity, allowing for the precise determination of drag coefficients λ∥ and λ⊥ corresponding, respectively, to a mean flow parallel and perpendicular to the cylinder length L. In the parallel configuration, the variation in λ∥ with the normalized diameter β=d/h0 of the cylinder is close to that for a two-dimensional (2D) flow invariant in the direction of the cylinder axis and does not diverge when β=1. The variation in λ∥ with the distance from the midplane of the model reflects the parabolic Poiseuille profile between the plates for β⪡1 while it remains almost constant for β∼1. In the perpendicular configuration, the value of λ⊥ is close to that corresponding to a 2D system only if β⪡1 and/or if the clearance between the ends of the cylinder and the side walls is very small: in that latter case, λ⊥ diverges as β→1 due to the blockage of the flow. In other cases, the side flow between the ends of the cylinder and the side walls plays an important part to reduce λ⊥: a full three-dimensional description of the flow is needed to account for these effects.
Structural and optical properties of Zn0.9Mn0.1O/ZnO core-shell nanowires designed by pulsed laser deposition
Authors: Kaydashev V. E. , Kaidashev E. M. , Peres M. , Monteiro T. , Correia M. R. , Sobolev N. A. , Alves L. C. , Franco N. , Alves E.
Published: November 2009

Core-shell ZnO/ZnMnO nanowires on a-Al2O3 and GaN (buffer layer)/Si (111) substrates were fabricated by pulsed laser deposition using a Au catalyst. Two ZnO targets with a Mn content of 10% were sintered at 1150 and 550 °C in order to achieve the domination in them of paramagnetic MnO2 and ferromagnetic Mn2O3 phases, respectively. Cluster mechanism of laser ablation as a source of possible incorporation of secondary phases to the wire shell is discussed. Raman spectroscopy under excitation by an Ar+ laser revealed a broad peak related to the Mn-induced disorder and a redshift in the A1-LO phonon. Resonant Raman measurements revealed an increase in the multiphonon scattering caused by disorder in ZnO upon doping by Mn. Besides the UV emission, a vibronic green emission band assisted by a ∼71 meV LO phonon is also observed in the photoluminescence spectra. Core-shell structures with smooth shells show a high exciton to green band intensity ratio (∼10) even at room temperature.
Spectrally narrowed edge emission from leaky waveguide modes in organic light-emitting diodes
Authors: Gan Zhengqing , Tian Yun , Lynch David W. , Kang Ji-hun , Park Q-Han , Shinar Joseph
Published: November 2009

A dramatic spectral line narrowing of the edge emission at room temperature from tris(quinolinolate) Al (Alq3), N,N′-diphenyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine (NPD), 4,4′-bis(2,2′-diphenyl-vinyl)-,1′-biphenyl (DPVBi), and some guest-host small molecular organic light-emitting diodes (OLEDs), fabricated on indium tin oxide (ITO)-coated glass, is described. In all but the DPVBi OLEDs, the narrowed emission band emerges above a threshold thickness of the emitting layer, and narrows down to a full width at half maximum of only 5–10 nm. The results demonstrate that this narrowed emission is due to irregular waveguide modes that leak from the ITO to the glass substrate at a grazing angle. While measurements of variable stripe length l devices exhibit an apparent weak optical gain 0≤g≤1.86 cm−1, there is no observable threshold current or bias associated with this spectral narrowing. In addition, in the phosphorescent guest-host OLEDs, there is no decrease in the emission decay time of the narrowed edge emission relative to the broad surface emission. It is suspected that the apparent weak optical gain is due to misalignment of the axis of the waveguided mode and the axis of the collection lens of the probe. However, it is not clear if such a misalignment can account for all the effects of the observed evolution of the edge-emission spectra with l.
A separable shadow Hamiltonian hybrid Monte Carlo method
Authors: Sweet Christopher R. , Hampton Scott S. , Skeel Robert D. , Izaguirre Jesús A.
Published: November 2009

Hybrid Monte Carlo (HMC) is a rigorous sampling method that uses molecular dynamics (MD) as a global Monte Carlo move. The acceptance rate of HMC decays exponentially with system size. The shadow hybrid Monte Carlo (SHMC) was previously introduced to reduce this performance degradation by sampling instead from the shadow Hamiltonian defined for MD when using a symplectic integrator. SHMC’s performance is limited by the need to generate momenta for the MD step from a nonseparable shadow Hamiltonian. We introduce the separable shadow Hamiltonian hybrid Monte Carlo (S2HMC) method based on a formulation of the leapfrog/Verlet integrator that corresponds to a separable shadow Hamiltonian, which allows efficient generation of momenta. S2HMC gives the acceptance rate of a fourth order integrator at the cost of a second-order integrator. Through numerical experiments we show that S2HMC consistently gives a speedup greater than two over HMC for systems with more than 4000 atoms for the same variance. By comparison, SHMC gave a maximum speedup of only 1.6 over HMC. S2HMC has the additional advantage of not requiring any user parameters beyond those of HMC. S2HMC is available in the program PROTOMOL 2.1. A Python version, adequate for didactic purposes, is also in MDL (http://mdlab.sourceforge.net/s2hmc).
Electrocaloric effect in BaTiO3 thin films
Authors: Cao Hai-Xia , Li Zhen-Ya
Published: November 2009

The modified transverse Ising model taking into account the four-spin exchange interaction and quantum fluctuation, as well as the mechanical constraint of the substrate, is constructed and applied to investigate the electrocaloric effect (ECE) in BaTiO3 thin films. It is found that the temperature dependence of ECE strongly depends on both the four-spin exchange interaction and quantum fluctuation. Most importantly, we achieve the adiabatic temperature change ΔT=11.78 K at Tm=490 K, which can be comparable with that observed experimentally in PbZr0.95Ti0.05O3 thin films and ferroelectric polymers. Furthermore, the internal stresses resulting from the clamping effect of the substrate play a crucial role in the ECE of ferroelectric films. Control of the misfit stress by appropriate choice of substrate provides an effective means to improve the adiabatic temperature change for use in cooling or thermodielectric power conversion devices.
Linear and nonlinear optical properties of ZnO/PMMA nanocomposite films
Authors: Kulyk B. , Sahraoui B. , Krupka O. , Kapustianyk V. , Rudyk V. , Berdowska E. , Tkaczyk S. , Kityk I.
Published: November 2009

The nanoscale crystals (NCs) of ZnO were embedded into polymethylmethacrylate (PMMA) polymeric matrix and nanocomposite films were prepared by modified spin coating method. The surface of the ZnO/PMMA nanocomposite films has been investigated using atomic force and scanning electron microscopy. The prepared films are highly transparent, the ultraviolet-visible spectra show their high optical quality. The second and third harmonic generation (SHG and THG) studies of ZnO/PMMA nanocomposite films with different concentrations of ZnO NCs were carried out at λ=1.064 μm and the effective values of the second and third order nonlinear susceptibilities were estimated to be higher than that of ZnO bulk for the films at low concentration of ZnO NCs. This could indicate that surface effects in ZnO/PMMA nanocomposite films have a dominant role over bulk effects for the SHG and THG processes.
Characteristics of a velvet cathode under high repetition rate pulse operation
Authors: Xun Tao , Zhang Jian-De , Yang Han-Wu , Zhang Zi-Cheng , Fan Yu-Wei
Published: October 2009

As commonly used material for cold cathodes, velvet works well in single shot and low repetition rate (rep-rate) high-power microwave (HPM) sources. In order to determine the feasibility of velvet cathodes under high rep-rate operation, a series of experiments are carried out on a high-power diode, driven by a ∼300 kV, ∼6 ns, ∼100 Ω, and 1–300 Hz rep-rate pulser, Torch 02. Characteristics of vacuum compatibility and cathode lifetime under different pulse rep-rate are focused on in this paper. Results of time-resolved pressure history, diode performance, shot-to-shot reproducibility, and velvet microstructure changes are presented. As the rep-rate increases, the equilibrium pressure grows hyperlinearly and the velvet lifetime decreases sharply. At 300 Hz, the pressure in the given diode exceeded 1 Pa, and the utility shots decreased to 2000 pulses for nonstop mode. While, until the velvet begins to degrade, the pulse-to-pulse instability of diode voltage and current is quite small, even under high rep-rate conditions. Possible reasons for the operation limits are discussed, and methods to improve the performance of a rep-rate velvet cathode are also suggested. These results may be of interest to the repetitive HPM systems with cold cathodes.
Spin-torque driven ferromagnetic resonance in a nonlinear regime
Authors: Chen W. , de Loubens G. , Beaujour J.-M. L. , Sun J. Z. , Kent A. D.
Published: October 2009

Spin-valve based nanojunctions incorporating Co∣Ni multilayers with perpendicular anisotropy were used to study spin-torque driven ferromagnetic resonance (ST-FMR) in a nonlinear regime. Perpendicular field swept resonance lines were measured under a large amplitude microwave current excitation, which produces a large angle precession of the Co∣Ni layer magnetization. With increasing rf power the resonance lines broaden and become asymmetric, with their peak shifting to lower applied field. A nonhysteretic step jump in ST-FMR voltage signal was also observed at high powers. The results are analyzed in terms of the foldover effect of a forced nonlinear oscillator and compared to macrospin simulations. The ST-FMR nonhysteretic step response may have applications in frequency and amplitude tunable nanoscale field sensors.
An ultrasmall wavelength-selective channel drop switch using a nanomechanical photonic crystal nanocavity
Authors: Kanamori Yoshiaki , Takahashi Kazunori , Hane Kazuhiro
Published: October 2009

We propose a nanomechanical channel drop switch by controlling the submicron distance between a nanocavity and photonic crystal (PC) waveguide with an ultrasmall electrostatic comb actuator. Light propagating in the PC waveguide is coupled with a nanocavity and emitted as a drop signal under a resonant condition. The proposed switch has been fabricated by silicon micromachining. The drop efficiency has been controlled by 12.5 dB and gap change of 600 nm.
Stabilization of the potential multi-steady-state absolute instabilities in a gyrotron traveling-wave amplifier
Authors: Du Chao-Hai , Liu Pu-Kun
Published: October 2009

The problem of spurious oscillations induced by absolute instabilities is the most challenging one that hinders the development of the millimeter-wave gyrotron traveling-wave amplifiers (gyro-TWTs). A spurious oscillation exists as a high order axial mode (HOAM) in the interaction circuit. This paper is devoted to demonstrating the complicated steady states of these HOAMs and exploring corresponding techniques to stabilize these potential multi-steady-state absolute instabilities. The stability-oriented design principle is conveyed in a start-to-end design flow of a Ka-band TE11 mode gyro-TWT. Strong magnetic tapering near the downstream port, which is capable of cutting short the effective interaction circuit of a spurious oscillation and simultaneously boosting the amplification performance, is for the first time proposed to further improve the system stability. It is also found that an ideal prebunched electron beam in the linear stage is the necessary condition to efficient amplification in the nonlinear stage, suggesting that it is feasible to design a stable prebunching stage to replace the distributed-loss-loaded linear stage. The stability-oriented design principle provides more explicit reference for future design of a zero-drive stable gyro-TWT.
Efficient generation of quasimonoenergetic ions by Coulomb explosions of optimized nanostructured clusters
Authors: Murakami M. , Mima K.
Published: October 2009

Coulomb explosion of spherical ion clusters is studied, which are composed of homogeneous two-species (light and heavy) ions. A simple analytical model is developed to describe the explosion performance in terms of two dimensionless parameters, the charge-over-mass ratio, and the charge density ratio. One-dimensional kinetic numerical model is performed to compare with the analytical model and to evaluate the energy coupling efficiency of quasimonoenergetic ion generation. It is crucial to preform an iso-Coulomb-potential profile of the light ions in the cluster for efficient generation of quasimonoenergetic ions. By controlling the radial density profiles of the light and heavy ions, the overall coupling efficiency (equal to the summed kinetic energy of the light ions in the highest 1% energy band divided by total kinetic energy of both ions) is optimized to be >30%–40% when about 90% of the total number of light ions is contained in the thin 1% energy band.
Improved red-response in thin film a-Si:H solar cells with soft-imprinted plasmonic back reflectors
Authors: Ferry Vivian E. , Verschuuren Marc A. , Li Hongbo B. T. , Schropp Ruud E. I. , Atwater Harry A. , Polman Albert
Published: November 2009

The impact of controlled nanopatterning on the Ag back contact of an n-i-p a-Si:H solar cell was investigated experimentally and through electromagnetic simulation. Compared to a similar reference cell with a flat back contact, we demonstrate an efficiency increase from 4.5% to 6.2%, with a 26% increase in short circuit current density. Spectral response measurements show the majority of the improvement between 600 and 800 nm, with no reduction in photocurrent at wavelengths shorter than 600 nm. Optimization of the pattern aspect ratio using electromagnetic simulation predicts absorption enhancements over 50% at 660 nm.
Direct observation of individual Barkhausen avalanches in nucleation-mediated magnetization reversal processes
Authors: Im Mi-Young , Fischer Peter , Kim Dong-Hyun , Shin Sung-Chul
Published: November 2009

We report the scaling behavior of Barkhausen avalanches [H. Barkhausen, Z. Phys. 20, 401 (1919).] along the hysteresis loop of a CoCrPt alloy film with perpendicular magnetic anisotropy for every field step of 200 Oe. Individual Barkhausen avalanches are directly observed via soft x-ray microscopy with a spatial resolution of 15 nm. The Barkhausen avalanches exhibit a power-law scaling behavior, where the scaling exponent of the power-law distribution drastically changes from 1±0.04 to 1.47±0.03 as the applied field approaches the coercivity of the CoCrPt film. We infer that this is due to the coupling of adjacent domains.
Low-lying electronic states of CH3NO2 via photoelectron imaging of the nitromethane anion
Authors: Goebbert Daniel J. , Pichugin Kostyantyn , Sanov Andrei
Published: October 2009

Negative-ion photoelectron imaging at 532, 392, 355, and 266 nm is used to assign several low-lying electronic states of neutral nitromethane CH3NO2 at the geometry corresponding to the anion equilibrium. The observed neutral states include (in the order of increasing binding energy) the X A1′ ground state, two triplet excited states, a A3″ and b A3″, and the first excited singlet state, A A1″. The state assignments are aided by the analysis of the photoelectron angular distributions resulting from electron detachment from the a′ and a″ symmetry molecular orbitals and the results of theoretical calculations. The singlet-triplet (X A1′−a A3″) splitting in nitromethane is determined as 2.90+0.02/−0.07 eV, while the vibrational structure of the band corresponding to the formation of the a A3″ state of CH3NO2 is attributed to the ONO bending and NO2 wagging motions excited in the photodetachment of the anion.
Low voltage operation in picene thin film field-effect transistor and its physical characteristics
Authors: Kaji Yumiko , Kawasaki Naoko , Lee Xuesong , Okamoto Hideki , Sugawara Yasuyuki , Oikawa Shohei , Ito Akio , Okazaki Hiroyuki , Yokoya Takayoshi , Fujiwara Akihiko , Kubozono Yoshihiro
Published: November 2009

Low voltage operation of picene thin film field-effect transistor (FET) has been realized with 40 nm thick SiO2 gate dielectrics coated by two polymers, Cytop™ and polystyrene. The picene FETs operated in low absolute gate voltage |VG| below 15 V for Cytop™ coated SiO2 and 30 V for polystyrene coated SiO2 gate dielectrics, and they showed a significant O2 gas sensing effect down to ∼10 ppm. Photoemission spectrum clarified that O2 molecules penetrate into the thin films at O2/picene mole ratio of 1: 1. X-ray diffraction pattern of picene thin films showed highly oriented growth on the polymer-coated SiO2.
Failure of the constrained equilibrium hypothesis in nucleation
Authors: Bartell Lawrence S.
Published: November 2009

The purpose of this investigation is to find whether solutions of the Becker–Döring–Tunitskii coupled differential equations can yield results closely paralleling those found in molecular dynamics (MD) simulations of freezing. What is investigated, in particular, is the validity of the constrained equilibrium hypothesis (CEH). It is shown that the MD results cannot be reproduced unless the CEH is violated. A physically plausible reason for the violation is proposed. In addition, methods for determining the size of critical nuclei are examined. It is found that a new criterion for identifying that size, a criterion incorporating the CEH, can be significantly in error. Methods for avoiding the use of the CEH are briefly discussed.
In situ high-pressure study of diborane by infrared spectroscopy
Authors: Song Yang , Murli Chitra , Liu Zhenxian
Published: November 2009

As the simplest stable boron hydride in its condensed phase, diborane exhibits an interesting structural chemistry with uniquely bridged hydrogen bonds. Here we report the first room-temperature infrared (IR) absorption spectra of solid diborane compressed to pressures as high as 50 GPa using a diamond anvil cell. At room temperature and 3.5 GPa, the IR spectrum of diborane displays rich sharply resolved fundamentals and overtones of the IR active bands, consistent with the previous low-temperature IR measurements of condensed diborane at ambient pressure. When compressed stepwise to 50 GPa, several structural transformations can be identified at pressures of ∼3.5 GPa, ∼6.9 GPa and ∼14.7 GPa, as indicated by the changes in the band profile as well as the pressure dependence of the characteristic IR modes and bandwidths. These transformations can be interpreted as being enhanced intermolecular interactions resulting from compression. The geometry of the four-member ring of B2H6, however, does not seem to be altered significantly during the transformations and the B2H6 molecule remains chemically stable up to 50 GPa.
Exciton switching and Peierls transitions in hybrid inorganic-organic self-assembled quantum wells
Authors: Pradeesh K. , Baumberg J. J. , Prakash G. Vijaya
Published: October 2009

The switching behavior of exciton absorption and photoluminescence is systematically explored in hybrid inorganic-organic multiple quantum well structures, based on (C12H25NH3)2PbI4 thin films and single crystals. Two structural phases found between 15 and 75 °C, based on orthorhombic and monoclinic unit cells, show different optical excitons which are demonstrated to arise from the reversible crumpling of the quantum well layers. Structural flips can be controlled by annealing or film thickness, with different thermal hysteresis behavior observed for single crystals and thin films.
Effect of electric field on the stability of an oscillatory contaminated film flow
Authors: Samanta Arghya
Published: November 2009

The stability of the viscous liquid film on an oscillating plane is investigated in the presence of both insoluble surfactant on the film surface and uniform electric field, acting normal to the plane. In this problem main motivation is to study the combine effect of surfactant and electric field on the stability of the liquid film. Here liquid is treated as a perfect conductor and the air above the liquid film is also treated as a perfect dielectric. The linear stability analysis is performed using the long-wave perturbation method based on Floquet theory. It is observed that two Floquet modes exist due to the presence of surfactant and both modes can be unstable. The growth rate corresponding to the Floquet modes increase with the presence of an electric field and decrease with the presence of surfactant.
The Science Case for PILOT III: the Nearby Universe
Authors: Lawrence J. S. , Ashley M. C. B. , Bailey J. , Barrado y Navascues D. , Bedding T. R. , Bland-Hawthorn J. , Bond I. , Bruntt H. , Burton M. G. , Cioni M.-R. , Eiroa C. , Epchtein N. , Kiss L. , Lagage P. O. , Minier V. , Mora A. , Olsen K. , Persi P. , Saunders W. , Stello D. , Storey J. W. V. , Tinney C. , Yock P.
Published: November 2009

PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.5-m optical/infrared telescope to be located at Dome C on the Antarctic plateau. The atmospheric conditions at Dome C deliver a high sensitivity, high photometric precision, wide-field, high spatial resolution, and high-cadence imaging capability to the PILOT telescope. These capabilities enable a unique scientific potential for PILOT, which is addressed in this series of papers. The current paper presents a series of projects dealing with the nearby Universe that have been identified as key science drivers for the PILOT facility. Several projects are proposed that examine stellar populations in nearby galaxies and stellar clusters in order to gain insight into the formation and evolution processes of galaxies and stars. A series of projects will investigate the molecular phase of the Galaxy and explore the ecology of star formation, and investigate the formation processes of stellar and planetary systems. Three projects in the field of exoplanet science are proposed: a search for free-floating low-mass planets and dwarfs, a program of follow-up observations of gravitational microlensing events, and a study of infrared light-curves for previously discovered exoplanets. Three projects are also proposed in the field of planetary and space science: optical and near-infrared studies aimed at characterising planetary atmospheres, a study of coronal mass ejections from the Sun, and a monitoring program searching for small-scale Low Earth Orbit satellite debris items.
The PULSE@Parkes Project: a New Observing Technique for Long-Term Pulsar Monitoring
Authors: Hobbs G. , Hollow R. , Champion D. , Khoo J. , Yardley D. , Carr M. , Keith M. , Jenet F. , Amy S. , Burgay M. , Burke-Spolaor S. , Chapman J. , Danaia L. , Homewood B. , Kovacevic A. , Mao M. , McKinnon D. , Mulcahy M. , Oslowski S. , van Straten W.
Published: November 2009

The PULSE@Parkes project has been designed to monitor the rotation of radio pulsars over time spans of days to years. The observations are obtained using the Parkes 64-m and 12-m radio telescopes by Australian and international high school students. These students learn the basis of radio astronomy and undertake small projects with their observations. The data are fully calibrated and obtained with the state-of-the-art pulsar hardware available at Parkes. The final data sets are archived and are currently being used to carry out studies of 1) pulsar glitches, 2) timing noise, 3) pulse profile stability over long time scales and 4) the extreme nulling phenomenon. The data are also included in other projects such as gamma-ray observatory support and for the Parkes Pulsar Timing Array project. In this paper we describe the current status of the project and present the first scientific results from the Parkes 12-m radio telescope. We emphasise that this project offers a straightforward means to enthuse high school students and the general public about radio astronomy while obtaining scientifically valuable data sets.
Direct observation of twisting steps during Rad51 polymerization on DNA
Authors: Arata Hideyuki , Dupont Aurélie , Miné-Hattab Judith , Disseau Ludovic , Renodon-Cornière Axelle , Takahashi Masayuki , Viovy Jean-Louis , Cappello Giovanni
Published: November 2009

The human recombinase hRad51 is a key protein for the maintenance of genome integrity and for cancer development. Polymerization and depolymerization of hRad51 on duplex DNA were studied here using a new generation of magnetic tweezers, measuring DNA twist in real time with a resolution of 5°. Our results combined with earlier structural information suggest that DNA is somewhat less extended by hRad51 than by RecA (4.5 vs. 5.1 Å per base pair) and untwisted by 18.2° per base pair. They also confirm a stoichiometry of 3–4 bp per protein in the hRad51-dsDNA nucleoprotein filament. At odds with earlier claims, we show that after initial deposition of a multimeric nucleus, nucleoprotein filament growth occurs by addition/release of single proteins, involving DNA twisting steps of 65° ± 5°. Simple numeric simulations show that this mechanism is an efficient way to minimize nucleoprotein filament defects. Nucleoprotein filament growth from a preformed nucleus was observed at hRad51 concentrations down to 10 nM, whereas nucleation was never observed below 100 nM in the same buffer. This behavior can be associated with the different stoichiometries of nucleation and growth. It may be instrumental in vivo to permit efficient continuation of strand exchange by hRad51 alone while requiring additional proteins such as Rad52 for its initiation, thus keeping the latter under the strict control of regulatory pathways.
Relapsing fever
Borrelia
binds to neolacto glycans and mediates rosetting of human erythrocytes
Authors: Guo Betty P. , Teneberg Susann , Münch Robert , Terunuma Daiyo , Hatano Ken , Matsuoka Koji , Ångström Jonas , Borén Thomas , Bergström Sven
Published: November 2009

A hallmark of acute relapsing fever borreliosis is severe bacteremia. Some
Borrelia
species, such as
B. duttonii
and
B. crocidurae
, associate with erythrocytes and induce aggregation recognized as erythrocyte rosetting. Erythrocyte rosettes contribute to disease severity by increased tissue invasiveness (such as invasion of CNS and encephalitis), hemorrhaging, and reduced blood flow in affected microcapillaries. Here we report that relapsing fever
Borrelia
binds to neolacto (Galβ4GlcNAcβ3Galβ4Glcβ1)–carrying glycoconjugates that are present on human erythrocytes. This interaction is of low affinity but is compensated for by the multivalency of neo-lacto-oligosaccharides on the erythrocyte cell surface. Hence, the protein–carbohydrate interaction is dependent on multivalent neolacto-glycans to mediate binding.
High-pressure highly reduced nitrides and oxides from chromitite of a Tibetan ophiolite
Authors: Dobrzhinetskaya Larissa F. , Wirth Richard , Yang Jingsui , Hutcheon Ian D. , Weber Peter K. , Green Harry W.
Published: October 2009

The deepest rocks known from within Earth are fragments of normal mantle (≈400 km) and metamorphosed sediments (≈350 km), both found exhumed in continental collision terranes. Here, we report fragments of a highly reduced deep mantle environment from at least 300 km, perhaps very much more, extracted from chromite of a Tibetan ophiolite. The sample consists, in part, of diamond, coesite-after-stishovite, the high-pressure form of TiO
2
, native iron, high-pressure nitrides with a deep mantle isotopic signature, and associated SiC. This appears to be a natural example of the recently discovered disproportionation of Fe
2+
at very high pressure and consequent low oxygen fugacity (fO
2
) in deep Earth. Encapsulation within chromitite enclosed within upwelling solid mantle rock appears to be the only vehicle capable of transporting these phases and preserving their low-fO
2
environment at the very high temperatures of oceanic spreading centers.
Oscillatory recruitment of signaling proteins to cell tips promotes coordinated behavior during cell fusion
Authors: Fleissner André , Leeder Abigail C. , Roca M. Gabriela , Read Nick D. , Glass N. Louise
Published: November 2009

Cell-cell communication is essential for coordinating physiological responses in multicellular organisms and is required for various developmental processes, including cell migration, differentiation, and fusion. To facilitate communication, functional differences are usually required between interacting cells, which can be established either genetically or developmentally. However, genetically identical cells in the same developmental state are also capable of communicating, but must avoid self-stimulation. We hypothesized that such cells must alternate their physiological state between signal sending and receiving to allow recognition and behavioral changes. To test this hypothesis, we studied cell communication in the filamentous fungus
Neurospora crassa
, a simple and experimentally amenable model system. In
N. crassa
, germinating asexual spores (germlings) of identical genotype chemotropically sense others in close proximity, show attraction-mediated directed growth, and ultimately undergo cell fusion. Here, we report that two proteins required for cell fusion, a MAP kinase (MAK-2) and a protein of unknown molecular function (SO), exhibit rapid oscillatory recruitment to the plasma membranes of interacting germlings undergoing chemotropic interactions via directed growth. Using an inhibitable MAK-2 variant, we show that MAK-2 kinase activity is required both for chemotropic interactions and for oscillation of MAK-2 and SO to opposing cell tips. Thus,
N. crassa
germlings undergoing chemotropic interactions rapidly alternate between two different physiological states, associated with signal delivery and response. Such spatiotemporal coordination of signaling allows genetically identical and developmentally equivalent cells to avoid self-stimulation and to coordinate their behavior to achieve the beneficial physiological outcome of cell fusion.
Recent human-to-poultry host jump, adaptation, and pandemic spread of
Staphylococcus aureus
Authors: Lowder Bethan V. , Guinane Caitriona M. , Ben Zakour Nouri L. , Weinert Lucy A. , Conway-Morris Andrew , Cartwright Robyn A. , Simpson A. John , Rambaut Andrew , Nübel Ulrich , Fitzgerald J. Ross
Published: November 2009

The impact of globalization on the emergence and spread of pathogens is an important veterinary and public health issue.
Staphylococcus aureus
is a notorious human pathogen associated with serious nosocomial and community-acquired infections. In addition,
S. aureus
is a major cause of animal diseases including skeletal infections of poultry, which are a large economic burden on the global broiler chicken industry. Here, we provide evidence that the majority of
S. aureus
isolates from broiler chickens are the descendants of a single human-to-poultry host jump that occurred approximately 38 years ago (range, 30 to 63 years ago) by a subtype of the worldwide human ST5 clonal lineage unique to Poland. In contrast to human subtypes of the ST5 radiation, which demonstrate strong geographic clustering, the poultry ST5 clade was distributed in different continents, consistent with wide dissemination via the global poultry industry distribution network. The poultry ST5 clade has undergone genetic diversification from its human progenitor strain by acquisition of novel mobile genetic elements from an avian-specific accessory gene pool, and by the inactivation of several proteins important for human disease pathogenesis. These genetic events have resulted in enhanced resistance to killing by chicken heterophils, reflecting avian host-adaptive evolution. Taken together, we have determined the evolutionary history of a major new animal pathogen that has undergone rapid avian host adaptation and intercontinental dissemination. These data provide a new paradigm for the impact of human activities on the emergence of animal pathogens.
A mechanism for functional segregation of mitochondrial and cytosolic genetic codes
Authors: Español Yaiza , Thut Daniel , Schneider André , de Pouplana Lluís Ribas
Published: October 2009

The coexistence of multiple gene translation machineries is a feature of eukaryotic cells and a result of the endosymbiotic events that gave rise to mitochondria, plastids, and other organelles. The conditions required for the integration of these apparatuses within a single cell are not understood, but current evidence indicates that complete ablation of the mitochondrial protein synthesis apparatus and its substitution by its cytosolic equivalent is not possible. Why certain mitochondrial components and not others can be substituted by cytosolic equivalents is not known. In trypanosomatids this situation reaches a limit, because certain aminoacyl-tRNA synthetases are mitochondrial specific despite the fact that all tRNAs in these organisms are shared between cytosol and mitochondria. Here we report that a mitochondria-specific lysyl-tRNA synthetase in
Trypanosoma
has evolved a mechanism to block the activity of the enzyme during its synthesis and translocation. Only when the enzyme reaches the mitochondria is it activated through the cleavage of a C-terminal structural extension, preventing the possibility of the enzyme being active in the cytosol.
Cyclodextrin overcomes deficient lysosome-to-endoplasmic reticulum transport of cholesterol in Niemann-Pick type C cells
Authors: Abi-Mosleh Lina , Infante Rodney E. , Radhakrishnan Arun , Goldstein Joseph L. , Brown Michael S.
Published: November 2009

A handoff model has been proposed to explain the egress from lysosomes of cholesterol derived from receptor-mediated endocytosis of LDL. Cholesterol is first bound by soluble Niemann-Pick C2 (NPC2) protein, which hands off the cholesterol to the N-terminal domain of membrane-bound NPC1. Cells lacking NPC1 or NPC2 accumulate LDL-derived cholesterol in lysosomes and fail to deliver LDL cholesterol to the endoplasmic reticulum (ER) for esterification by acyl-CoA acyltransferase (ACAT) and for inhibition of sterol regulatory element-binding protein cleavage. Here, we support this model by showing that the cholesterol transport defect in NPC1 mutant cells is restricted to lysosomal export. Other cholesterol transport pathways appear normal, including the movement of cholesterol from the plasma membrane to the ER after treatment of cells with 25-hydroxycholesterol or sphingomyelinase. The NPC1 or NPC2 block in cholesterol delivery to the ER can be overcome by 2-hydroxypropyl-β-cyclodextrin, which leads to a marked increase in ACAT-mediated cholesterol esterification. The buildup of cholesteryl esters in the cytosol is expected to be much less toxic than the buildup of free cholesterol in the lysosomes of patients with mutations in NPC1 or NPC2.