bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of mucosal mast cell activation by short interfering RNAs targeting syntaxin4
Authors: Liu Shuang , Nugroho Agung Endro , Shudou Masachika , Maeyama Kazutaka
Published: May 2011

Mucosal mast cells (MMCs) have an important role in allergic inflammation, and effective antagonists are required for their regulation. To discover a possible mechanism of controlling the activation of MMCs, we investigated the expression and function of syntaxin4, one of the soluble membrane N‐ethylmaleimide‐sensitive factor attachment protein receptor (SNARE) proteins, in RBL‐2H3 cells, which is a rat mucosal mast cell line. Syntaxin4 silencing was induced by transfection of short interfering RNAs (siRNAs). Syntaxin4 was knocked down in mast cells at both the mRNA and protein levels. The release of granule contents that are involved in inflammation, such as histamine and hexosaminidase, was significantly suppressed by the gene silencing of syntaxin4. Silencing of this gene was also induced in the trachea and bronchi of rats by intratracheal application of the siRNAs using an atelocollagen delivery system. The activation of MMCs, which was monitored by the level of rat mast cell protease‐II (RMCPII) in the bronchoalveolar lavage fluid (BALF), was inhibited, and asthmatic airway constriction was prevented by administration of the syntaxin/atelocollagen complex. These results indicate that siRNAs targeting syntaxin4 can stabilize mucosal mast cells and may have beneficial therapeutic effects on the asthmatic response.
Sclerodermatous chronic graft‐versus‐host disease induced by host T‐cell‐mediated autoimmunity
Authors: Lee You Jeong , Min Hye Sook , Kang Eun Ha , Park Hyo Jin , Jeon Yoon Kyung , Kim Ju Hyun , Wu Hong Gyun , Lee Eun‐Bong , Park Chung‐Gyu , Yoon Sung‐Soo , Park Seong Hoe , Jung Kyeong Cheon
Published: May 2011

Despite a long‐standing hypothesis that chronic graft‐versus‐host disease (cGVHD) is an autoimmune disorder, most mouse models of cGVHD have been developed on the assumption that donor T cells are essential for its development. Here we show that cGVHD may be caused by autoreactive host T cells in mice that have been lethally irradiated and grafted with T‐cell‐depleted allogeneic bone marrow cells. In this chimera, host T cells derived from radioresistant intrathymic T‐cell precursors caused dermal fibrosis and periportal inflammation, without the requirement for donor T cells. The lack of host DCs within the thymus after high‐dose irradiation allowed autoreactive host T cells to escape thymic negative selection. Moreover, the homeostatic expansion of these T cells may augment their autoreactivity. These findings indicate that host T‐cell‐mediated cGVHD is an autoimmune process that occurs following the grafting of T‐cell‐depleted BM cells into hosts with functioning thymuses. We propose, based on the present data, that host T‐cell‐dependent autoimmunity is a potential mechanism by which cGVHD is induced.
Dimorphisme sexuel et cavités faciales : étude volumétrique en imagerie 3D
Authors: Bassil-Nassif Nayla , Bouserhal Joseph , Treil Jacques , Braga José , Garcia Robert
Published: May 2011

Introduction : L’objectif de ce travail est d’étudier le dimorphisme sexuel au niveau des volumes des cavités faciales dans une population adulte jeune. Méthodes : L’échantillon sélectionné comporte 60 sujets, âgés entre 18 et 30 ans, ayant bénéficié d’un examen scanner de la tête. Ils sont divisés en deux groupes identiques selon le sexe. Les cavités orbitaires, ethmoïdo-nasale et buccale sont délimitées par des points sur les acquisitions scanner 3D et leurs volumes mesurés à l’aide du logiciel AMIRA®, alors que les deux sinus maxillaires sont segmentés et leurs volumes calculés. Le test Kolmogorov-Smirnov est utilisé pour démontrer la normalité des variables, suivi du test « t » de Student pour la comparaison des moyennes (p < 0,05). Résultats : Les moyennes des volumes des cavités orbitaires, ethmoïdo-nasales, buccales et des sinus maxillaires sont plus grandes chez les hommes, alors que le dimorphisme sexuel n’a pas été mis en évidence au niveau du rapport des volumes de chacune des cavités sur le volume facial total. Conclusion : Les volumes absolus des cavités faciales étudiées sont plus grands chez les hommes, mais pas les volumes relatifs, ce qui pourrait s’expliquer par l’existence d’une différence cranio-faciale de taille, et non de forme, entre les hommes et les femmes.
Proposition de classification des syndromes malformatifs cranio-maxillo-faciaux
Authors: Delforge Antoine , Raoul Gwenaël , Wiss Axel , Kerbrat Jean-Baptiste , Ferri Joël
Published: May 2011

La conduite orthodontique à tenir face à un patient porteur d’une malformation cranio-maxillo-faciale n’est pas formellement établie et ne fait à ce jour l’objet d’aucun consensus. Les auteurs proposent, au vu de l’ensemble des cas qu’ils suivent dans leur service et de la bibliographie actuelle sur chaque pathologie, de classer ces syndromes en quatre catégories physiopathologiques afin de conseiller pour chaque classe une prise en charge adaptée. En connaissant l’étiopathogénie d’une affection, on l’appréhende et la traite différemment. Plus de cinquante cas ont été répertoriés, mais il a été décidé de ne présenter que les pathologies les plus typiques sur le plan physiopathologique. Cette classification comprend les anomalies organiques d’une ou de plusieurs matrices fonctionnelles, les anomalies localisées des structures anatomiques, les anomalies généralisées du tissu mésenchymateux, les syndromes mixtes.
Wave function engineering: Other phases of Si for photovoltaic applications
Authors: Cohen Marvin L. , Malone Brad D.
Published: May 2011

We present first-principles electronic structural calculations of the quasiparticle and optical spectra of two silicon phases, Si-XII and the recently predicted phase of Si in the body-centered-tetragonal structure. The quasiparticle spectra calculated within the GW approximation predict that both of these materials are indirect bandgap semiconductors with small bandgaps. The optical spectra of these materials are obtained by solving the Bethe-Salpeter equation taking into account electron-hole interactions. Comparison is made to other phases of silicon commonly used in photovoltaic applications. The results suggest the possible utility of these materials as photovoltaics.
Injection, detection and gate voltage control of spins in the spin field effect transistor
Authors: Chang Joonyeon , Cheol Koo Hyun , Eom Jonghwa , Hee Han Suk , Johnson Mark
Published: May 2011

We demonstrate electrical spin injection and gate voltage control of spin precession in an InAs quantum well channel that has Permalloy injector and detector, and is covered by a gate oxide and a Au gate electrode. The electrical injection and detection of ballistic spin-polarized electrons are characterized using conventional lateral spin valve techniques. An external magnetic field is used to overcome the shape anisotropy of the magnetizations of injector and detector. We can then inject spins that have both spin orientation and velocity along the axis of the channel, and we observe an oscillatory channel conductance as a function of monotonically increasing gate voltage. This conductance oscillation is the hallmark of a spin field effect transistor. After presenting the basic results, we discuss issues associated with (1) the Hanle effect in a two-dimensional electron gas with high spin-orbit interaction and (2) the observation of a conductance oscillation in a multimode (two-dimensional) channel.
Vortex stability and permanent flow in nonequilibrium polariton condensates
Authors: Tosi G. , Sanvitto D. , Baudisch M. , Karimi E. , Piccirillo B. , Marrucci L. , Lemaître A. , Bloch J. , Viña L.
Published: May 2011

We study the effects of imprinting a single-quantized vortex on the steady state of a microcavity exciton-polariton condensate generated via parametric scattering. Interestingly we observe two distinct regimes: In the first case, at low polariton densities, the effect of the pulsed probe, containing the vortex state, is to generate a gain response in the condensate lasting for tens of picoseconds during which no dissipation of the circulating currents is detected. In the second regime, at higher densities, the gain lasts much less and the circulation is imprinted directly into the steady state, which acquires permanent rotation for as long as the vortex remains within the condensate. We use two different ways of measuring the circulation of the condensate and demonstrate that in both cases, polariton condensation in the parametric scattering regime can sustain permanent supercurrents.
Spiking computation and stochastic amplification in a neuron-like semiconductor microstructure
Authors: Samardak A. S. , Nogaret A. , Janson N. B. , Balanov A. , Farrer I. , Ritchie D. A.
Published: May 2011

We have demonstrated the proof of principle of a semiconductor neuron, which has dendrites, axon, and a soma and computes information encoded in electrical pulses in the same way as biological neurons. Electrical impulses applied to dendrites diffuse along microwires to the soma. The soma is the active part of the neuron, which regenerates input pulses above a voltage threshold and transmits them into the axon. Our concept of neuron is a major step forward because its spatial structure controls the timing of pulses, which arrive at the soma. Dendrites and axon act as transmission delay lines, which modify the information, coded in the timing of pulses. We have finally shown that noise enhances the detection sensitivity of the neuron by helping the transmission of weak periodic signals. A maximum enhancement of signal transmission was observed at an optimum noise level known as stochastic resonance. The experimental results are in excellent agreement with simulations of the FitzHugh-Nagumo model. Our neuron is therefore extremely well suited to providing feedback on the various mathematical approximations of neurons and building functional networks.
Blue light emission from strongly photoexcited and electron-doped SrTiO3
Authors: Yamada Yasuhiro , Kanemitsu Yoshihiko
Published: May 2011

We studied photoluminescence (PL) spectrum and dynamics of undoped and electron-doped SrTiO3. At low temperatures below 100 K, we observed two band-edge PL peaks and a broad PL band in strongly photoexcited SrTiO3 and electron-doped SrTiO3 samples. In electron-doped samples, the peak energy of the broad PL band depends on the excitation photon energy at low temperatures: it changes from 2.5 to 2.9 eV with the excitation photon energy. On the other hand, the PL dynamics is independent of the excitation photon energy and is explained by a simple model involving single-carrier trapping and Auger recombination. From the PL spectrum and dynamics under different excitation photon energies, the PL processes in SrTiO3 are discussed.
Anisotropic strain effects on the photoluminescence emission from heteroepitaxial and homoepitaxial nonpolar (Zn,Mg)O/ZnO quantum wells
Authors: Chauveau J.-M. , Teisseire M. , Kim-Chauveau H. , Morhain C. , Deparis C. , Vinter B.
Published: May 2011

We report on the properties of nonpolar a-plane (Zn,Mg)O/ZnO quantum wells (QW) grown by molecular beam epitaxy on r plane sapphire and a plane ZnO substrates. For the QWs grown on sapphire, the anisotropy of the lattice parameters of the (Zn,Mg)O barrier gives rise to an unusual in-plane strain state in the ZnO QWs, which induces a strong blue-shift of the excitonic transitions, in addition to the confinement effects. We observe this blue-shift in photoluminescence excitation experiments. The photoluminescence excitation energies of the QWs are satisfactorily simulated when taking into account the variation of the exciton binding energy with the QW width and the residual anisotropic strain. Then we compare the photoluminescence properties of homoepitaxial QWs grown on ZnO bulk substrate and heteroepitaxial QWs grown on sapphire. We show that the reduction of structural defects and the improvement of surface morphology are correlated with a strong enhancement of the photoluminescence properties: reduction of full width at half maximum, strong increase of the luminescence intensities. The comparison convincingly demonstrates the interest of homoepitaxial nonpolar QWs for bright UV emission applications.
Combined diffusion-driven and convective flow in a tilted square container
Authors: Page Michael A.
Published: May 2011

Asymptotic analytical solutions are derived for the configuration posed by Quon [Phys. Fluids 26, 632 (1983)] for diffusion-driven flow in a tilted square container when the diffusive parameter R is small. The key regions of the asymptotic structure are outlined and the leading-order solutions are determined in most of those regions. The analysis follows that in Page and Johnson [J. Fluid Mech. 629, 299 (2009)] and Page [Q. J. Mech. Appl. Math. (in press)] but includes an additional “R1/4-layer” region. Analytical solutions are compared with numerical results for small R and display excellent agreement. It is also shown that the solutions and flow structure are applicable over a wide range of Prandtl numbers.
Effects of SrTiO3/TiO2 buffer layer on structural and electrical properties of BiFeO3 thin films grown on GaN (0002)
Authors: Luo W. B. , Zhu J. , Zeng H. Z. , Liao X. W. , Chen H. , Zhang W. L. , Li Y. R.
Published: May 2011

BiFeO3(BFO) films were deposited by pulsed laser deposition on GaN(0002)/c-sapphire. X-ray diffraction data show that BFO(111) epitaxial films was deposited on SrTiO3/TiO2 double-layer buffered GaN, compared to the polycrystalline film grown directly on GaN. The epitaxial relationships of BFO film with SrTiO3/TiO2 buffer layers were BFO [11-2](111)//GaN [1-100](0002) as revealed by XRD phi scans. Furthermore, BFO films on SrTiO3/TiO2 buffer exhibited enhanced electric properties compared to these deposited directly on GaN. The remnant polarization was improved about 30% while the leakage current was reduced by nearly three orders of magnitude. The epitaxial growth promoted by the SrTiO3/TiO2 buffer layer is a pivotal parameter in the improved electric properties of BFO films on GaN (0002).
The uses of the refined matrix model recursion
Authors: Brini Andrea , Mariño Marcos , Stevan Sébastien
Published: May 2011

We study matrix models in the β-ensemble by building on the refined recursion relation proposed by Chekhov and Eynard. We present explicit results for the first β-deformed corrections in the one-cut and the two-cut cases, as well as two applications to supersymmetric gauge theories: the calculation of superpotentials in \documentclass[12pt]{minimal}\begin{document}${\cal N}=1$\end{document}N=1 gauge theories, and the calculation of vevs of surface operators in superconformal \documentclass[12pt]{minimal}\begin{document}${\cal N}=2$\end{document}N=2 theories and their Liouville duals. Finally, we study the β-deformation of the Chern–Simons matrix model. Our results indicate that this model does not provide an appropriate description of the Ω-deformed topological string on the resolved conifold, and therefore that the β-deformation might provide a different generalization of topological string theory in toric Calabi–Yau backgrounds.
Testing the equation of state and electrical conductivity of copper by the electrical wire explosion in air: Experiment and magnetohydrodynamic simulation
Authors: Barysevich A. E. , Cherkas S. L.
Published: May 2011

We perform experiments on testing the equations of state and electrical conductivity of copper in three different regimes of copper wire electrical explosion, when the inserted energy (i) is slightly exceeded, (ii) is approximately equal, and (iii) is substantially exceeded the energy needed for the wire complete evaporation. Magnetohydrodynamic simulation is performed. The results predicted by the two different equations of state are compared with the experiment. Empirical expression for the copper electrical conductivity is presented. Parameters in this expression is fit on every of two equations of state. Map of copper conductivity is plotted.
Nonlinear heating of underdense collisional plasma by a laser pulse
Authors: Abari M. Etehadi , Shokri B.
Published: May 2011

The nonlinear interaction of a laser pulse with a homogenous unmagnetized underdense plasma, taking ohmic heating and the effects of ponderomotive force into account, is theoretically studied. Since the ponderomotive force modifies the electrons density and temperature distribution, the nonlinear dielectric permittivity of plasma is obtained in non-relativistic regime. Furthermore, electric and magnetic fields, electron density, temperature distribution, and the effective permittivity variations are obtained in terms of plasma length by making use the steady state solutions of the Maxwell and hydrodynamic equations. It is shown that the oscillations wave length of electric and magnetic fields decreases when the laser intensity increases. At the same time, in this case, electron density oscillations become highly peaked. Also, the amplitude of the electron temperature oscillations increase and their wavelength decreases.
Time reversed acoustics techniques for elastic imaging in reverberant and nonreverberant media: An experimental study of the chaotic cavity transducer concept
Authors: Van Damme Bart , Van Den Abeele Koen , Li YiFeng , Matar Olivier Bou
Published: May 2011

In view of emerging imaging technologies based on the combination of Time Reversed Acoustics (TRA) with Nonlinear Elastic Wave Spectroscopy (NEWS) for the detection and localization of micro-damage in solids, we have investigated the benefits of chirped source signal excitation, inverse filtering techniques, and the implementation of chaotic cavity transducers to improve the quality of energy focusing, especially for weakly reverberant media. Chaotic cavity transducer focusing is defined as the hardware-software combination of a piezoelectric ceramic glued on a cavity of chaotic shape on the one hand with the reciprocal Time Reversal (or Inverse Filter) technique on the other hand. Experimental data for reverberant and nonreverberant composite plates show that the use of chirps, inverse filtering and chaotic cavity transducers significantly enhances the focusing process, and enables focusing in a nonreverberant medium using only one transducer. As a potential exploitation, the application of the chaotic cavity transducer concept for synthetic imaging is examined, revealing several properties similar to phased arrays.
On entropy-maximized velocity distributions in circularly polarized finite amplitude Alfvén waves
Authors: Nariyuki Yasuhiro
Published: May 2011

A special solution of the Vlasov-Maxwell system, which represents a circularly polarized Alfvén wave, is derived as an entropy-maximized state. It is shown that Alfvénic correlation between transverse bulk motion and magnetic field given by the entropy-maximized distribution is consistent with the equilibrium point of the single particle system. We demonstrate that as far as the monochromatic, circularly polarized magnetic field is concerned, the resultant distribution may be a relaxed state corresponding to one in the Hall-magnetohydrodynamic system. Stability of the distribution function is numerically discussed by using an ion-hybrid simulation code. Numerical results suggest that the relaxed states in nonmonochromatic waves are different from those in monochromatic waves.
Thermodynamics of DNA hybridization on surfaces
Authors: Schmitt Terry J. , Knotts Thomas A.
Published: May 2011

Hybridization of single-stranded DNA (ssDNA) targets to surface-tethered ssDNA probes was simulated using an advanced coarse-grain model to identify key factors that influence the accuracy of DNA microarrays. Comparing behavior in the bulk and on the surface showed, contrary to previous assumptions, that hybridization on surfaces is more thermodynamically favorable than in the bulk. In addition, the effects of stretching or compressing the probe strand were investigated as a model system to test the hypothesis that improving surface hybridization will improve microarray performance. The results in this regard indicate that selectivity can be increased by reducing overall sensitivity by a small degree. Taken as a whole, the results suggest that current methods to enhance microarray performance by seeking to improve hybridization on the surface may not yield the desired outcomes.
Alteration of helical vortex core without change in flow topology
Authors: Velte Clara M. , Okulov Valery L. , Hansen Martin O. L.
Published: May 2011

The abrupt expansion of the slender vortex core with changes in flow topology is commonly known as vortex breakdown. We present new experimental observations of an alteration of the helical vortex core in wall bounded turbulent flow with abrupt growth in core size, but without change in flow topology. The helical symmetry as such is preserved, although the characteristic parameters of helical symmetry of the vortex core transfer from a smooth linear variation to a different trend under the influence of a non-uniform pressure gradient, causing an increase in helical pitch without changing its sign.
An initial phase of Ge hut array formation at low temperature on Si(001)
Authors: Arapkina Larisa V. , Yuryev Vladimir A.
Published: May 2011

We report a direct STM observation of Ge hut array nucleation on the Si(001) surface during ultrahigh vacuum molecular-beam epitaxy at 360 ∘C. Nuclei of pyramids and wedges have been observed on the wetting layer M×N patches starting from the coverage of about 5.1 Å (∼3.6 ML). Further development of hut arrays consists of simultaneous growth of the formerly appeared clusters and nucleation of new ones resulting in gradual rise of hut number density with increasing surface coverage. Huts nucleate reconstructing the patch surface from the usual c(4×2) or p(2×2) structure to one of two recently described formations composed by epitaxially oriented Ge dimer pairs and chains of four dimers.
Two-dimensional axisymmetric and three-dimensional helical equilibrium in the line-tied screw pinch
Authors: Paz-Soldan C. , Brookhart M. I. , Clinch A. J. , Hannum D. A. , Forest C. B.
Published: May 2011

The line-tying condition at a conducting anode is shown to provide a localized modification to the well-understood 1-D screw pinch equilibrium in the presence of bulk plasma diamagnetism. Diamagnetic currents cannot flow near the conducting anode and are measured to disappear in a localized boundary layer, causing a weak mirror configuration that breaks 1-D equilibrium and causes large parallel pressure gradients suggestive of significant radial outflows. For sufficiently large plasma currents, the paramagnetic nature of parallel current drives the equilibrium to paramagnetism and destroys the mirror effect. At a critical plasma current, the axisymmetric equilibrium is found to transition to a long-lived, rotating, helical 3-D equilibrium state. Internal measurements of this state via multi-point correlation analysis techniques illustrate that it preserves the flux surfaces and pressure profile of the axisymmetric equilibrium. Measurements indicate that despite the fact that the flux surfaces wander at the anode, the line-tied boundary conditions are not necessarily violated.
Measurement and modeling of three-dimensional equilibria in DIII-D
Authors: Lanctot M. J. , Reimerdes H. , Garofalo A. M. , Chu M. S. , Hanson J. M. , Liu Y. Q. , Navratil G. A. , Bogatu I. N. , In Y. , Jackson G. L. , La Haye R. J. , Okayabashi M. , Park J.-K. , Schaffer M. J. , Schmitz O. , Strait E. J. , Turnbull A. D.
Published: May 2011

A detailed experiment-theory comparison reveals that linear ideal MHD theory is in quantitative agreement with external magnetic and internal soft x-ray measurements of the plasma response to externally applied non-axisymmetric fields over a broad range of beta and rotation. This result represents a significant step toward the goal of advancing the understanding of three-dimensional tokamak equilibria. Both the magnetic and soft x-ray measurements show the driven plasma perturbation increases linearly with the applied perturbation, suggesting the relevance of linear plasma response models. The magnetic and soft x-ray measurements are made at multiple toroidal and poloidal locations, allowing well resolved measurements of the global structure. The comparison also highlights the need to include kinetic effects in the MHD model once beta exceeds 80% of the kink mode limit without a conducting wall. Two distinct types of response fields are identified by the linear ideal MHD model: one that consists of localized currents at the rational surfaces that cancel the applied resonant field and another that is excited by the components of the external field that couple to the kink mode. Numerical simulations show these two fields have similar amplitudes in ITER-shaped DIII-D discharges where n = 3 fields are used to suppress edge localized modes.
Simultaneous measurement of normal and friction forces using a cantilever-based optical interfacial force microscope
Authors: Kim Byung I. , Bonander Jeremy R. , Rasmussen Jared A.
Published: May 2011

We measured normal and friction forces simultaneously using a recently developed cantilever-based optical interfacial force microscope technique for studies of interfacial structures and mechanical properties of nanoscale materials. We derived how the forces can be incorporated into the detection signal using the classical Euler equation for beams. A lateral modulation with the amplitude of nanometers was applied to create the friction forces between tip and sample. We demonstrated its capability by measuring normal and friction forces of interfacial water at the molecular scale over all distance ranges.
Investigation of lower hybrid physics through power modulation experiments on Alcator C-Mod
Authors: Schmidt A. , Bonoli P. T. , Meneghini O. , Parker R. R. , Porkolab M. , Shiraiwa S. , Wallace G. , Wright J. C. , Harvey R. W. , Wilson J. R.
Published: May 2011

Lower hybrid current drive (LHCD) is an attractive tool for off-axis current profile control in magnetically confined tokamak plasmas and burning plasmas (ITER), because of its high current drive efficiency. The LHCD system on Alcator C-Mod operates at 4.6 GHz, with ~ 1 MW of coupled power, and can produce a wide range of launched parallel refractive index (n||) spectra. A 32 chord, perpendicularly viewing hard x-ray camera has been used to measure the spatial and energy distribution of fast electrons generated by lower hybrid (LH) waves. Square-wave modulation of LH power on a time scale much faster than the current relaxation time does not significantly alter the poloidal magnetic field inside the plasma and thus allows for realistic modeling and consistent plasma conditions for different n|| spectra. Inverted hard x-ray profiles show clear changes in LH-driven fast electron location with differing n||. Boxcar binning of hard x-rays during LH power modulation allows for ~ 1 ms time resolution which is sufficient to resolve the build-up, steady-state, and slowing-down phases of fast electrons. Ray-tracing/Fokker-Planck modeling in combination with a synthetic hard x-ray diagnostic shows quantitative agreement with the x-ray data for high n|| cases. The time histories of hollow x-ray profiles have been used to measure off-axis fast electron transport in the outer half of the plasma, which is found to be small on a slowing down time scale.
Saturation of laser emission in a small mode volume organic microcavity
Authors: Brückner R. , Sudzius M. , Fröb H. , Lyssenko V. G. , Leo K.
Published: May 2011

We demonstrate that the laser output power of an organic microcavity saturates with the pump energy shortly above the lasing threshold. The extent of the saturation correlates with the volume of the optical mode and is strongly enhanced in a small-mode volume λ/2 microcavity. The laser emission characteristics under different pumping conditions unambiguously show that the effect is due to the finite number of absorbing molecules per mode that are efficiently saturated at higher pump powers. A modified set of rate equations is applied to obtain a theoretical description of the lasing dynamics and to account for the flattening of the integrated output power above the lasing threshold. These equations provide a basis to describe the occurrence of saturation at high excitation levels in dependence on the pump pulse duration and the number of absorbing molecules in the mode volume.
Vibrational spectroscopy and relaxation of an anharmonic oscillator coupled to harmonic bath
Authors: Joutsuka Tatsuya , Ando Koji
Published: May 2011

The vibrational spectroscopy and relaxation of an anharmonic oscillator coupled to a harmonic bath are examined to assess the applicability of the time correlation function (TCF), the response function, and the semiclassical frequency modulation (SFM) model to the calculation of infrared (IR) spectra. These three approaches are often used in connection with the molecular dynamics simulations but have not been compared in detail. We also analyze the vibrational energy relaxation (VER), which determines the line shape and is itself a pivotal process in energy transport. The IR spectra and VER are calculated using the generalized Langevin equation (GLE), the Gaussian wavepacket (GWP) method, and the quantum master equation (QME). By calculating the vibrational frequency TCF, a detailed analysis of the frequency fluctuation and correlation time of the model is provided. The peak amplitude and width in the IR spectra calculated by the GLE with the harmonic quantum correction are shown to agree well with those by the QME though the vibrational frequency is generally overestimated. The GWP method improves the peak position by considering the zero-point energy and the anharmonicity although the red-shift slightly overshoots the QME reference. The GWP also yields an extra peak in the higher-frequency region than the fundamental transition arising from the difference frequency of the center and width oscillations of a wavepacket. The SFM approach underestimates the peak amplitude of the IR spectra but well reproduces the peak width. Further, the dependence of the VER rate on the strength of an excitation pulse is discussed.
Communication: Electric dipole moment and hyperfine interaction of tungsten monocarbide, WC
Authors: Wang Fang , Steimle Timothy C.
Published: May 2011

The [17.6]2← X3Δ1(1,0) band of tungsten monocarbide, WC, was recorded using laser induced fluorescence both field-free and in the presence of a static electric field. The Stark induced shifts of the R(1) and Q(2) lines were analyzed to produce values for the permanent electric dipole moments, μ, of 3.90 ± 0.04 D and 2.57 ± 0.04 D for the X3Δ1(v = 0) and [17.6]2(v = 1) states, respectively. An upper limit to the Ω-doubling parameter, $\tilde o_\Delta$õΔ, of 2 MHz is established. The 183W(I = 1/2) Fermi contact parameter, bF, for the X3Δ1(v = 0) is estimated to be 1363 MHz. The results are compared with theoretical predictions and a molecular orbital correlation description.
Effect of co-adsorbed CO and reaction temperature on the dynamics of N2 desorption under steady-state N2O–CO reaction on Rh(110)
Authors: Sakurai Masataka , Kondo Takahiro , Nakamura Junji
Published: May 2011

We have investigated the effect of co-absorbed CO and reaction temperature on the angular distribution of N2 desorption by N2O decomposition under the steady state of N2O–CO reaction on Rh(110). Spatial distributions of desorbing product N2 emission have been measured at various surface temperatures and CO coverages. The decomposed N2 collimates at 48°–61° off normal in the parallel plane to [001] and [110] directions, indicating that adsorbed N2O just before the decomposition is oriented along the [001] direction. Although the inclined and collimated N2 desorption is always observed at any steady-state CO coverage and reaction temperature, the shape of the collimated N2 distribution varied dependent on the co-adsorbed CO coverage. The distribution becomes sharp and shifts toward the surface normal direction with increasing CO coverage. These effects of adsorbed CO on the angular distribution of N2 are interpreted by the collision of desorbed N2 with co-adsorbed CO.
The protein folding network indicates that the ultrafast folding mutant of villin headpiece subdomain has a deeper folding funnel
Authors: Lei Hongxing , Chen Changjun , Xiao Yi , Duan Yong
Published: May 2011

Protein folding is a dynamic process with continuous transitions among different conformations. In this work, the dynamics in the protein folding network of villin headpiece subdomain (HP35) has been investigated based on multiple reversible folding trajectories of HP35 and its ultrafast folding mutant where sub-angstrom folding was achieved. The four folding states were clearly separated on the network, validating the classification of the states. Examination of the eight conformers with different formation of the individual helices revealed high plasticity of the three helices in all the four states. A consistent feature between the wild type and mutant protein is the dominant conformer 111 (all three helices formed) in the folded state and conformers 111 and 011 (helices II and III formed) in the major intermediate state, indicating the critical role of helices II and III in the folding mechanism. When compared to the wild type, the folding landscape of the ultrafast folding mutant exhibited a deeper folding funnel towards the folded state. The very beginning of the folding (0–10 ns) was very similar for both protein variants but it soon diverged and displayed different folding pathways. Although going through the major intermediate state is the dominant pathway for both, it was also observed that some folding went through the minor intermediate state for the mutant. The intriguing difference resulting from the mutation at two residues in helix III has been carefully analyzed and discussed in details.
Communication: Mode-specific photodissociation of vibrationally excited pyrrole
Authors: Epshtein Michael , Portnov Alexander , Rosenwaks Salman , Bar Ilana
Published: May 2011

Laser-based spectroscopies coupled with molecular beam techniques facilitated the monitoring of H fragments released in ultraviolet photodissociation of pre-excited isoenergetic vibrational levels of pyrrole. Most noticeably, there was an order of magnitude larger reactivity for an eigenstate primarily consisting of two quanta of ring deformation than for another with one quantum of symmetric C–H stretch. The dynamics, the intramolecular interactions controlling the energy flow, and the mode-selectivity within a medium-sized, ten atom molecule, is discussed.
Light-induced EPR study of charge transfer in P3HT/bis-PCBM bulk heterojunctions
Authors: Krinichnyi Victor I. , Yudanova Eugenia I.
Published: May 2011

Radical pairs, polarons and fullerene anion radicals photoinduced by photons with energy of 1.98 – 2.73 eV in bulk heterojunctions formed by poly(3-hexylthiophene) (P3HT) with bis(1-[3-(methoxycarbonyl)propyl]-1-phenyl)-[6.6]C62 (bis-PCBM) fullerene derivative have been studied by direct light-induced EPR (LEPR) method in a wide temperature range. A part of photoinduced polarons are pinned in trap sites which number and depth are governed by an ordering of the polymer/fullerene system and energy of initiating photons. It was shown that dynamics and recombination of mobile polarons and counter fullerene anion radicals are governed by their exchange- and multi-trap assisted diffusion. Relaxation and dynamics parameters of both the charge carriers were determined separately by the steady-state saturation method. These parameters are governed by structure and conformation of the carriers’ microenvironment as well as by the energy of irradiating photons. Longitudinal diffusion of polarons was shown to depend on lattice phonons of crystalline domains embedded into an amorphous polymer matrix. The energy barrier required for polaron interchain hopping is higher than that its intrachain diffusion. Pseudorotation of fullerene derivatives in a polymer matrix was shown to follow the activation Pike model.
From ‘Flood Defence’ to ‘Flood Risk Management’: Exploring Governance, Responsibility, and Blame
Authors: Butler Catherine , Pidgeon Nick
Published: May 2011

In the UK there has been a gradual transition in both the framing of flooding as a policy issue and the strategies employed to achieve policy objectives. This has involved a widely recognised shift from policies of ‘flood defence’ to ‘flood risk management’ (FRM), entailing both changes in approaches to FRM—such as greater advocacy of soft flood management approaches—and redistributions of responsibility—including more emphasis on the responsibilities of private citizens. In this paper, we utilise interviews with professionals working in flood risk (total participant n = 44) and discussion groups (participant n = 50) with public(s) that live in one of three UK cities which experienced major flooding in 2007 (Sheffield, Oxford, Gloucester) to examine some of the ways in which these policy transitions are being defined, negotiated, and contested. Drawing on governmentality theory, we reexamine contemporary shifts in FRM and open up discussion around the potential for emergent difficulties connected to the contemporary emphasis on relations of responsibility.
Equalising Spending Needs of Subnational Governments in a Developing Country: The Case of Tanzania
Authors: Allers Maarten A , Ishemoi Lewis J
Published: May 2011

Decentralisation of government creates fiscal disparities: some subnational governments can provide their citizens with more public services than others. Many countries try to equalise fiscal disparities by targeting grants at disadvantaged jurisdictions. This is especially difficult for developing countries, where data are scarce. We develop a method to estimate spending needs of local governments in developing countries. We apply this method to health spending by Tanzanian districts, but it can be used in other areas and other countries as well. We use our estimates to derive an equalising grant allocation formula. A comparison with the existing grant allocation indicates that more deprived districts should receive higher grants than they obtain now.
Economic and Political Foundations of Local Tax Structures: An Empirical Investigation of the Tax Mix of Flemish Municipalities
Authors: Geys Benny , Revelli Federico
Published: May 2011

Building on the revenue structure theory developed by Hettich and Winer, with this paper we are the first to investigate the economic and political determinants of local tax mix choices. We thereby use panel data on 289 municipalities in the Flemish region of Belgium (period 1995–2002), where local governments enjoy extensive fiscal autonomy and have a wide choice of available tax instruments. Estimating a system of five reduced-form equations for the five central revenue sources (income, property, business, user fees, and other own revenues), our results show that economics plays a significantly more important role than politics in shaping the local tax mix. Moreover, supporting theoretical predictions about marginal cost equalization across available tax instruments, absolute reliance on each revenue source increases as the overall revenue requirement gets larger (a ‘scale effect’).
Root and shoot growth by seedlings of annual and perennial medic, and annual and perennial wheat
Authors: Ward P. R. , Palta J. A. , Waddell H. A.
Published: May 2011

Perennial plants such as lucerne are now widely acknowledged as one means of controlling the expansion of dryland salinity in southern Australia. However, their inclusion in farming systems is limited by poor seedling vigour, thought to be associated with greater allocation of biomass to perennating organs in roots, and poor adaptation to some soils and climatic conditions in south-western Australia. For this reason, interest in other perennial options such as perennial wheat is increasing. In this research we compared early (29-day) seedling growth and root : shoot ratios for annual and perennial medics (Medicago truncatula and M. sativa), and for annual and perennial wheat (Triticum aestivum and Triticum × Agropyron cross). For the medics, the annual reached the 6-leaf stage after 29 days and produced more root and shoot biomass than lucerne (4-leaf stage after 29 days), but there was no difference in root : shoot ratio or depth of root growth. For wheat, there were no differences in root growth, shoot growth, or root : shoot ratio between the annual and perennial lines (Zadoks growth stages 23 and 21, respectively, after 29 days). The poor competitive performance of M. sativa seedlings relative to M. truncatula was not due to changed allocation of biomass to shoots, but was related more to seed size (2.7 and 5.0 mg, respectively). This does not seem to occur to the same extent in perennial wheat lines, suggesting that their seedling performance may be more competitive.
The Relativistic Electromagnetic Equations in a Material Medium
Authors: Taylor NW
Published: May 2011

It is shown how the general relativistic electromagnetic equations for a material medium can be expressed in the form of a single four-vector density equation. The field tensor has six different complex components instead of three, as in the case of a, free medium. The classical equations are obtained by separating the real and imaginary parts.
The Surface Temperature of the Moon
Authors: Jaeger JC
Published: May 2011

Results of numerical calculations are given for (i) the fall in surface temperature during a lunar eclipse, (ii) the variation in surface temperature at the equator during a lunation, and (iii) the variation in microwave temperature at the equator during a lunation. These calculations are made on the assumption that heat is lost from the surface by radiation according to the fourth power law. Two models are considered, firstly, that in which the surface material of the Moon is homogeneous, and secondly, that in which it consists of a thin skin of poor conductor on a better conducting sub-stratum.
Emission of Radiation from Model Hydrogen Chromospheres
Authors: Jefferies JT
Published: May 2011

On the basis of earlier work of Giovanelli (1949), the characteristics of the radiation fields of Ha, La, L�, and the Lyman continuum have been calculated for model solar atmospheres consisting of a photosphere and an overlying chromosphere which scatters coherently, and which is isothermal at one of a number of kinetic temperatures in the range 1 � 104 to 2�5�l05 �K.
Angular Correlation Between ?-Particles and ?-Rays in the Be9(d,?)Li7?*Li7 Reaction
Authors: Uebergang RG , Tanner NW
Published: May 2011

The angular correlation of the ?-particles and ?-rays in the Be9(d,?)Li7?*Li7 reaction has been measured. The results show no significant departure from isotropy. The most plausible explanation is that the lowest excited state of Li7 has spin 1/2.
The Absorption of the Hard Component of Cosmic Rays in Water
Authors: Dyer AJ
Published: May 2011

The differential and integral range spectra of the hard component of cosmic rays in water have been measured down to a depth of 18�3 m. of water, and the integral results confirm the work of Ehmert (1937) and Wilson (1938) in this region. A lack of statistical accuracy in the differential measurements prevents the possible observation of an anomaly corresponding to 2�5 BeV./c. momentum. A comparison of the range and momentum spectra on the basis of the energy loss data of Halpern and Hall shows satisfactory agreement. The absolute value of the differential intensity is found to be 20 per cent. higher than that given by Rossi (1948) but agrees with the more recent result of York (1952).
An Estimate of the Density and Motion of Solar Material from Observed Characteristics of Solar Radio Outbursts
Authors: K Sen Hari
Published: May 2011

The theory of radio wave generation by multistream charge interaction (Feinstein and Sen 1951) is extended and applied to the observations made by Australian workers (Wild 1950) of the spectrum of outbursts of solar radio-frequency radiation in the frequency range 70?130 Mc/s. The dispersion equation is derived as a function of the velocity of solar material erupting into a static corona and of the temperatures and densities of the material and the corona. The application of the dispersion equation to the Australian data (loc. cit.) enables an estimate to be made of the velocity (?500 km./s.) and the particle density (?108 cm.?3) of the moving solar material.
Corrigenda
Authors: Lawrance R
Published: May 2011

The graphical results of Figure 7 of this paper are referred to: If we plot log mobility v. log conductivity, we expect a straight line with a slope of 45�, assuming that the number of carriers remains constant over the conductivity range considered. The slope of the straight line in Figure 7 is not 45�, and does not correctly describe the results presented in Table 3.
Conduction of Heat in the Semi-infinite Solid, with a Short Table of an Important Integral
Authors: Smith RCT
Published: May 2011

The solution of a problem in heat conduction is expressed in terms of the integral . This integral is tabulated for various values of a and U.
On the Standard Errors in the Fitting of Polynomials to Unequally Spaced Observations
Authors: Guest PG
Published: May 2011

From the observed values of the independent variable two parameters are derived which specify the departure from uniform spacing. Expressions are obtained for the standard errors of the coefficients and fitted values in terms of these parameters, and numerical tables for the estimation of the errors are given. It is shown that the errors calculated in this way lie within a few per cent. of the exact least squares values for polynomials of the first and second degree, but when the polynomial is of the third degree the deviations may be much greater.
The Southern Auroral Zone as Defined by the Position of Homogeneous Arcs
Authors: Jacka F
Published: May 2011

Observations on homogeneous arcs (H.A.) made at Macquarie Island (geomagnetic coordinates 60�7 �S., 243�1 �E.) are examined. The latitude of H.A. is found to be significantly dependent on the geomagnetic planetary disturbance index Kp and the time of day. For given values of Kp and time the probability distribution of latitude of H.A. has a sharply defined mode about 0.5� north of the mean.
Radar Observations of Rain at Sydney, New South Wales
Authors: Day GA
Published: May 2011

The radar echoes received from rain during systematic observations carried out from January 1950 to January 1951 at the Radiophysics Laboratory, Sydney, N.S.W., are illustrated and described. Examples of echoes from melting and upper bands, non-freezing and frontal showers, thunderstorms, and echo masses are shown by vertical cross sections of the atmosphere through the point of observation.
The Scattering of 1 MeV Electrons and Positrons
Authors: McDonell JA
Published: May 2011

Electrons and positrons of energy 1 MeV were selected by a �-ray spectrometer and scattered by a gold foil. The scattered particles were detected by a coincidence Geiger counter arrangement, using the same geometry for electrons and positrons. The results show that the ratio of the fraction of electrons scattered through an angle ? to the fraction of positrons scattered through ? varies with ?, and the magnitudes of the ratios agree with those predicted by theory. It is also inferred that there is a difference between the multiple scattering of electrons and positrons under the same scattering conditions.