bluuebunny/crossref_metadata_2025 huggingface dataset:
Accurate, two-state ab initio study of the ground and first-excited states of He2+, including exact treatment of all Born–Oppenheimer correction terms
Authors: Xie Junkai , Poirier Bill , Gellene Gregory I.
Published: May 2005

Born–Oppenheimer (BO) potentials for the ground and first-excited electronic states of He2+ are determined using high level ab initio techniques for internuclear separations R of 1.2–100 bohrs and accurately fit to analytical functions. In the present formulation, the BO potentials are nuclear mass independent, and the corresponding BO approximation is obtained by ignoring four terms of the full rovibronic Hamiltonian. These four Born–Oppenheimer correction (BOC) terms are as follows: (1) mass polarization, (2) electronic orbital angular momentum, (3) first derivative with respect to R, and (4) second derivative with respect to R. In order to enable an exact rovibronic calculation, each of the four BOC terms are computed as a function of R, for the two electronic states and for their coupling, without any approximation or use of empirical parameters. Each of the BOC terms is found to make a contribution to the total energy over at least some portion of the range of R investigated. Interestingly, the most significant coupling contribution arises from the electronic orbital angular momentum term, which is evidently computed for the first time in this work. Although several BOC curves exhibit a nontrivial dependence on R, all are accurately fit to analytical functions. The resulting functions, together with the BO potentials, are used to compute exact rovibronic energy levels for He3He+3,He3He+4, and He4He+4. Comparison to available high quality experimental data indicates that the present BOC potentials provide the most accurate representation currently available of both the low- and high-lying levels of the ground electronic state and the bound levels of the excited state.
An efficient approach for theoretical study on the low-energy isomers of large fullerenes C90–C140
Authors: Cai Wensheng , Xu Lei , Shao Nan , Shao Xueguang , Guo Qingxiang
Published: May 2005

An approach that consists of a molecular mechanics method based on the second generation reactive empirical bond order (REBO) potential and the more accurate semiempirical method PM3 (Parametric Method No. 3) was proposed to predict the energetically favored isomers of the fullerenes from C90 to C140 at the semiempirical level. All the 578 701 isolated-pentagon-rule isomers of fullerenes from C90 to C140 were enumerated from topological structures and systematically searched using an energy minimization method to select the best 100 low-energy isomers based on the REBO potential for each fullerene. Then these candidate isomers were further optimized by PM3 and ranked again to determine the top low-energy isomers. This approach was applied to calculate the energetically favored isomers of C90–C140. The results of C90–C120 are in good agreement with the published results by quantum-chemical methods. Furthermore, the top five low-energy isomers of C90–C120, as well as C122–C140 which have scarcely been systematically studied before, are also predicted with the approach. The analysis of the structures showed that the hexagon-neighbor rule is an important factor to the stability of C90–C140. The time cost for the systematical search based on the REBO potential was also discussed. It indicates that the approach proposed is efficient for predicting the energetically favored isomers of large fullerenes at the semiempirical level.
Resonance hyper-Raman excitation profiles of a donor-acceptor substituted distyrylbenzene: One-photon and two-photon states
Authors: Shoute Lian C. T. , Bartholomew Glenn P. , Bazan Guillermo C. , Kelley Anne Myers
Published: May 2005

Resonance Raman and resonance hyper-Raman spectra of the “push-pull” conjugated molecule 1-(4′-dihexylaminostyryl)-4-(4″-nitrostyryl)benzene in acetone have been measured at excitation wavelengths from 485 to 356 nm (two-photon wavelengths for the nonlinear spectra), resonant with the first two bands in the linear absorption spectrum. The theory of resonance hyper-Raman scattering intensities is developed and simplified using assumptions appropriate for intramolecular charge-transfer transitions of large molecules in solution. The absorption spectrum and the Raman, hyper-Rayleigh, and hyper-Raman excitation profiles, all in absolute intensity units, are quantitatively simulated to probe the structures and the one- and two-photon transition strengths of the two lowest-energy allowed electronic transitions. All four spectroscopic observables are reasonably well reproduced with a single set of excited-state parameters. The two lowest-energy, one-photon allowed electronic transitions have fairly comparable one-photon and two-photon transition strengths, but the higher-energy transition is largely localized on the nitrophenyl group while the lower-energy transition is more delocalized.
Wave packet study of the UV photodissociation of the Ar2HBr complex
Authors: Pouilly B. , Monnerville M. , Gatti F. , Meyer H.-D.
Published: May 2005

The photodissociation dynamics of the Ar2HBr van der Waals molecule is studied using the multiconfiguration time-dependent Hartree method. Standard Jacobian coordinates are used to describe the molecule. Two four-dimensional calculations are carried out where the rotation of the Ar2 molecule and, in addition, either the vibration of Ar2-Br or that of Ar2 are frozen. The time-evolution of the probability density in the different modes and the calculation of the dissociative flux show that the dissociating hydrogen atom preferentially moves out of the plane defined by Ar2 and Br. A comprehensive study of the cage effect in the process is presented.
Hydrogen-bonded acetic acid dimers: Anharmonic coupling and linear infrared spectra studied with density-functional theory
Authors: Dreyer Jens
Published: May 2005

Anharmonic vibrational force field calculations provide a quantitative understanding of the width and substructure of the linear IR-absorption spectrum of the O–H stretching mode in acetic acid dimers (CH3–COOH)2 and (CD3–COOH)2. Anharmonic coupling of the high-frequency υOH mode to fingerprint and low-frequency modes is included resulting in 11- and 9-dimensional vibrational Hamiltonians. A sixth-order force field covering up to three-body interactions is used. Force constants are calculated by fitting one-dimensional potential-energy surfaces and a finite difference procedure applying density-functional theory [Becke 3 Lee–Yang–Parr 6–311+G(d,p)]. It is demonstrated that both anharmonic coupling to low-frequency modes as well as Fermi resonance coupling with fingerprint modes are important mechanisms explaining the line shape of the O–H stretching IR-absorption band in acetic acid dimers.
The spheromak confinement device
Authors: Jarboe T. R.
Published: May 2005

A general definition of the spheromak is given. The nature of helicity conservation and its importance to the spheromak concept are discussed. The reactor advantages, stability properties, and β limits are covered. Several successful formation schemes and steady state sustainment methods are presented. How they each inject helicity and to what extent they depend on helicity-conserving relaxation is discussed. What helicity conservation tells us about relaxation and what it does not tell us is covered. The major outstanding spheromak issues are presented.
Pulsed-power-driven high energy density physics and inertial confinement fusion research
Authors: Matzen M. Keith , Sweeney M. A. , Adams R. G. , Asay J. R. , Bailey J. E. , Bennett G. R. , Bliss D. E. , Bloomquist D. D. , Brunner T. A. , Campbell R. B. , Chandler G. A. , Coverdale C. A. , Cuneo M. E. , Davis J.-P. , Deeney C. , Desjarlais M. P. , Donovan G. L. , Garasi C. J. , Haill T. A. , Hall C. A. , Hanson D. L. , Hurst M. J. , Jones B. , Knudson M. D. , Leeper R. J. , Lemke R. W. , Mazarakis M. G. , McDaniel D. H. , Mehlhorn T. A. , Nash T. J. , Olson C. L. , Porter J. L. , Rambo P. K. , Rosenthal S. E. , Rochau G. A. , Ruggles L. E. , Ruiz C. L. , Sanford T. W. L. , Seamen J. F. , Sinars D. B. , Slutz S. A. , Smith I. C. , Struve K. W. , Stygar W. A. , Vesey R. A. , Weinbrecht E. A. , Wenger D. F. , Yu E. P.
Published: May 2005

The Z accelerator [R. B. Spielman, W. A. Stygar, J. F. Seamen et al., Proceedings of the 11th International Pulsed Power Conference, Baltimore, MD, 1997, edited by G. Cooperstein and I. Vitkovitsky (IEEE, Piscataway, NJ, 1997), Vol. 1, p. 709] at Sandia National Laboratories delivers ∼20MA load currents to create high magnetic fields (>1000T) and high pressures (megabar to gigabar). In a z-pinch configuration, the magnetic pressure (the Lorentz force) supersonically implodes a plasma created from a cylindrical wire array, which at stagnation typically generates a plasma with energy densities of about 10MJ∕cm3 and temperatures >1keV at 0.1% of solid density. These plasmas produce x-ray energies approaching 2MJ at powers >200TW for inertial confinement fusion (ICF) and high energy density physics (HEDP) experiments. In an alternative configuration, the large magnetic pressure directly drives isentropic compression experiments to pressures >3Mbar and accelerates flyer plates to >30km∕s for equation of state (EOS) experiments at pressures up to 10Mbar in aluminum. Development of multidimensional radiation-magnetohydrodynamic codes, coupled with more accurate material models (e.g., quantum molecular dynamics calculations with density functional theory), has produced synergy between validating the simulations and guiding the experiments. Z is now routinely used to drive ICF capsule implosions (focusing on implosion symmetry and neutron production) and to perform HEDP experiments (including radiation-driven hydrodynamic jets, EOS, phase transitions, strength of materials, and detailed behavior of z-pinch wire-array initiation and implosion). This research is performed in collaboration with many other groups from around the world. A five year project to enhance the capability and precision of Z, to be completed in 2007, will result in x-ray energies of nearly 3MJ at x-ray powers >300TW.
Fourier transform microwave spectroscopy of vinyldiacetylene, vinyltriacetylene, and vinylcyanodiacetylene
Authors: Thorwirth S. , McCarthy M. C. , Dudek J. B. , Thaddeus P.
Published: May 2005

The rotational spectra of the three carbon chain molecules vinyldiacetylene (hex-1-ene-3,5-diyne, C6H4), vinyltriacetylene (oct-1-ene-3,5,7-triyne, C8H4), and its cyano analog vinylcyanodiacetylene (1-cyanohex-5-ene-1,3-diyne, C7H3N) have been observed for the first time by Fourier transform microwave spectroscopy of a supersonic molecular beam. The molecules were observed as products of an electrical discharge through selected precursor mixtures: ethylene/diacetylene and vinylacetylene/diacetylene for the pure hydrocarbon molecules and vinylacetylene/cyanoacetylene for vinylcyanodiacetylene. The measurements yield precise sets of rotational constants that compare very well with theoretical constants obtained by quantum chemical calculations at the B3LYP/cc-pVTZ level of theory. Since these three carbon chains are similar in structure and composition to known astronomical molecules and because of their significant polarity, all three are candidates for radio astronomical detection.
Role of nonlinear toroidal coupling in electron temperature gradient turbulence
Authors: Lin Z. , Chen L. , Zonca F.
Published: May 2005

Global gyrokinetic particle simulation and nonlinear gyrokinetic theory find that electron temperature gradient (ETG) instability saturates via nonlinear toroidal coupling, which is a nonlocal interaction in the wave vector space that transfers energy successively from unstable modes to damped modes preferentially with lower toroidal mode numbers. The electrostatic ETG turbulence is dominated by nonlinearly generated radial streamers. The length of the streamers scales with the device size, which is longer than the distance between mode rational surfaces and electron radial excursions. Both fluctuation intensity and transport level at saturation are independent of the streamer length, and are much smaller than the mixing length estimates.
Phosphorus: First principle simulation of a liquid–liquid phase transition
Authors: Ghiringhelli Luca M. , Meijer Evert Jan
Published: May 2005

We report a Car–Parrinello molecular dynamics study of the liquid–liquid phase transition in phosphorus. We employed a gradient corrected density functional (B-LYP) to describe the electronic structure and performed simulations at constant pressure. Upon increasing pressure we observed, along the 1500 K isotherm, a structural transition converting the molecular P4 liquid into an atomic liquid with a network structure. Our calculations suggest this transition to be first order with a discontinuous density increase accompanied by an insulator into metal transition. The transition pressure is significantly higher than obtained by employing the less accurate local density functional (LDA) [Morishita, Phys. Rev. Lett. 87, 105701 (2001)], which matches the experimental value for the pressure. We argue why the LDA result should be considered fortuitous. The change of the calculated structure factor upon the transition shows the same trend as experimentally observed. Analysis of the structural changes during the phase transition revealed that a chain of linked and opened up (“butterfly”) P4 molecules may serve as a seed triggering the transition from the molecular to the network phase.
Time-dependent neoclassical viscosity
Authors: Garcia-Perciante A. L. , Callen J. D. , Shaing K. C. , Hegna C. C.
Published: May 2005

A time-dependent closure for the parallel viscous force is calculated in a bumpy cylinder magnetic field geometry using a Chapman–Enskog-like approach. The calculation is valid for all times and field modulations, and is expressed as a dynamic evolution in time. Two important applications are presented: modification of the frequency-dependent electrical conductivity due to the interaction between trapped and circulating particles, and the parallel flow evolution which can be extended to axisymmetric geometries.
Wavelength and decay length of density overshoot structure in supercritical, collisionless bow shocks
Authors: Saxena R. , Bale S. D. , Horbury T. S.
Published: May 2005

Above some critical Mach number, quasiperpendicular collisionless shocks are known to exhibit “overshoot” and “undershoot” structure thought to be associated with the motion of ions trapped at the shock front. Using spacecraft potential data from the Cluster spacecraft, the overshoot/undershoot density structure at 56 crossings of the quasiperpendicular bow shock is studied. The envelope of the absolute value of the density, in most cases, decays exponentially and these envelopes are fitted to a decaying function from which we calculate the decay length scale. The overshoot/undershoot wavelength is also estimated using the zero crossings of the density profile and a good correlation between the average wavelength and the convected ion gyroradius is found: the wavelength is approximately two to three times the ion gyroradius. There is no evidence of a strong correlation between the wavelength and the ion inertial length. Similar results are found for the decay length, which also seems to be ordered by the convected ion gyroradius.
Internal polarization fields in GaN∕AlGaN multiple quantum wells with different crystallographic orientations
Authors: Kuokstis E. , Sun W. H. , Chen C. Q. , Yang J. W. , Khan M. Asif
Published: May 2005

We investigate the built-in electrostatic polarization fields in GaN∕AlGaN multiple quantum wells (MQWs) fabricated by the deposition of layers on sapphire substrates with different crystallographic surfaces. The analysis of the photoluminescence (PL) spectra of MQWs grown over (0001) C-plane, (112¯0) A-plane, and (11¯02) R-plane sapphire, as well as the theoretical calculations, revealed the formation of a strong (up to ∼1.7MV∕cm) built-in electrostatic field due to the spontaneous polarization and piezoelectric field in MQWs on C- and A-plane sapphire, whereas there was no indication of polarization in the identical structures grown on R-plane sapphire. The PL dynamics with the increase of excitation can be explained by quantum-confined Stark effect and screening of the built-in electrostatic field due to photoinjected carriers. The internal electrostatic-field-free quantum structures grown on R-plane sapphire may be promising for ultraviolet region optoelectronic applications due to higher emission intensity and stable spectral parameters.
Hydrogen gettering and strain-induced platelet nucleation in tensilely strained Si0.4Ge0.6/Ge for layer exfoliation applications
Authors: Pitera Arthur J. , Fitzgerald E. A.
Published: May 2005

We show that tensilely strained epitaxial layers getter interstitially dissolved hydrogen and accelerate the nucleation of platelets. Both of these result in subsurface crack propagation leading to surface blistering and eventual exfoliation of a H+-implanted semiconductor surface. In this work, a strained Si0.4Ge0.6 layer was used to enhance the exfoliation kinetics of relaxed Ge/Si1−xGex/Si virtual substrates by gettering hydrogen and providing a preferential nucleation site for platelets. Using platelet morphology and strain relaxation data, a nucleation and growth model was formulated accounting for both chemical and strain energy contributions to the free energy of platelet formation, revealing two kinetically limited growth regimes for platelets in tensilely strained Si0.4Ge0.6 films. Low-temperature (<200°C) annealing nucleates 1011-cm−2 platelets which grow in the strain-limited regime with minimal loss of hydrogen to surface effusion. At 250 °C, platelet growth is diffusion limited, requiring transport of H2 molecules to the strained layer. Subsequent annealing of strained Si0.4Ge0.6/Ge gettering structures at a temperature exceeding 300 °C results in significantly improved surface blistering kinetics over samples which do not contain a gettering layer. Incorporation of tensilely strained layers has the potential of reducing the implantation dose and annealing temperature necessary for layer transfer. Combined with virtual substrate bonding, they provide a promising solution for economical integration of high-performance semiconductors with silicon.
Bifurcations from the endpoints of the essential spectrum in the linearized nonlinear Schrödinger problem
Authors: Cuccagna Scipio , Pelinovsky Dmitry
Published: May 2005

We study bifurcations of eigenvalues from the endpoints of the essential spectrum in the linearized nonlinear Schrödinger problem in three dimensions. We show that a resonance and an eigenvalue of positive energy at the endpoint may bifurcate only to a real eigenvalue of positive energy, while an eigenvalue of negative energy at the endpoint may also bifurcate to complex eigenvalues.
Spectroscopic ellipsometry of SrBi2Ta2−xNbxO9 ferroelectric thin films
Authors: Yang Pingxiong , Guo Ming , Shi Meirong , Meng Xiangjian , Huang Zhimin , Chu Junhao
Published: May 2005

Optical properties of the ferroelectric thin-film SrBi2Ta2−xNbxO9(0⩽x⩽2) solid-solution system were investigated by spectroscopic ellipsometry from the infrared to the ultraviolet-visible region. Optical constants and the band-gap energies were determined by multilayer analysis of the respective pseudodielectric functions. With increasing x, it is found that the refractive index slightly increases in the infrared and rises from 2.0 to 2.3 in the visible region, and the band-gap energy shifts from 4.17 to 3.61 eV at room temperature. A possible explanation for the experimental observations, the reduced extension of the Nb 4d orbital, is mentioned.
Control of the Mg doping profile in III-N light-emitting diodes and its effect on the electroluminescence efficiency
Authors: Köhler K. , Stephan T. , Perona A. , Wiegert J. , Maier M. , Kunzer M. , Wagner J.
Published: May 2005

The influence of the Mg doping profile on the electroluminescence (EL) efficiency of (AlGaIn)N quantum well (QW) light-emitting diodes, grown by low-pressure metal-organic vapor-phase epitaxy on sapphire, has been investigated. The actual Mg profile close to the active region was found to be influenced by segregation as well as by diffusion during growth. In a first experiment, diffusion of the Mg dopants towards the QW region through a not intentionally doped narrow GaN spacer layer, separating the topmost GaInN quantum well from the AlGaN:Mg electron-blocking barrier, was controlled by the growth temperature of the AlGaN:Mg barrier and GaN:Mg contact layer. Starting from low growth temperatures, an increase in Mg concentration close to the active region results in an improved hole injection and thus increased EL efficiency. However, for a too high growth temperature, an excessive spread of the Mg atoms into the active region leads to nonradiative recombination in the QW active region and thus a reduction in EL output. In a second experiment, identical structures were prepared with the Mg-doped (Al)GaN layers grown at lower temperature to minimize Mg diffusion. Instead, the nominal Mg doping level in the GaN spacer layer was varied systematically. Secondary-ion-mass spectrometry revealed that almost identical Mg doping profiles close the QW active region, and in turn very similar EL efficiencies, can be achieved by both approaches when appropriate growth parameters are used.
Field distribution on metallic and dielectric nanoparticles observed with a fluorescent near-field optical probe
Authors: Aigouy L. , Mortier M. , Giérak J. , Bourhis E. , De Wilde Y. , Corstjens P. , Tanke H. J.
Published: May 2005

The electromagnetic field distribution around the metallic and dielectric nanoparticles illuminated by a focused Gaussian beam has been investigated by scanning near-field optical microscopy. The probe used in this study is made of a small fluorescent particle attached at the tip extremity and that behaves like a local nanodetector of light. An enhancement of the fluorescence is clearly visible on 250-nm-sized gold particles. This enhancement is due to an increase of the incident electromagnetic field on the gold particle. This effect, which is observable on images performed in planes both parallel and perpendicular to the surface, presents a circular symmetry when the exciting laser beam is normal to the surface and randomly polarized. When the excitation light is linearly polarized, the fluorescence distribution exhibits an oval shape in the polarization direction. This fluorescence enhancement is barely visible for latex dielectric particles of similar size.
Magnetic dot arrays with multiple storage layers
Authors: Albrecht M. , Hu G. , Moser A. , Hellwig O. , Terris B. D.
Published: May 2005

An approach to increasing the data storage density of magnetic recording was investigated wherein dot arrays are combined with multiple magnetic storage layers. The latter consists of two magnetically decoupled perpendicular Co∕Pd multilayer stacks. As a result of the difference in the coercivity between the two stacks, the orientation of the remanent magnetization of each stack can be set independent of the orientation of the other layer. Therefore, each dot allows storing four different magnetization states, which give rise to four different readback signal levels. Thus, the investigated media structure allows doubling the storage density in magnetic recording applications. It was found that even for thick spacer layers a weak magnetostatic coupling of the storage layers is present preferring ferromagnetic alignment of the storage layers.
Electron-phonon relaxation rates and optical gain in a quantum cascade laser in a magnetic field
Authors: Radovanović J. , Milanović V. , Ikonić Z. , Indjin D. , Harrison P.
Published: May 2005

We present a model for calculating the optical gain in a midinfrared GaAs∕AlGaAs quantum cascade laser in a magnetic field, based on solving the set of rate equations that describe the carrier density in each level, accounting for the optical- and acoustic-phonon scattering processes. The confinement caused by the magnetic field strongly modifies the lifetimes of electrons in the excited state and results in pronounced oscillations of the optical gain as a function of the field. Numerical results are presented for the structure designed to emit at λ∼11.4μm, with the magnetic field varying in the range of 10–60T. The effects of band nonparabolicity are also included.
Generation of continuous-wave terahertz radiation using a two-mode titanium sapphire laser containing an intracavity Fabry–Perot etalon
Authors: Stone Michael R. , Naftaly Mira , Miles Robert E. , Mayorga Ivan C. , Malcoci Andrei , Mikulics Martin
Published: May 2005

Continuous-wave terahertz (THz) radiation was generated by photomixing two modes of a titanium sapphire laser. The laser was induced to oscillate on two modes by placing a Fabry–Perot etalon in the laser resonator. The frequency of terahertz radiation, which was equal to the difference frequency of the two modes, was varied by adjusting the free spectral range (FSR) of the etalon. Photomixing was performed by logarithmic spiral antennas fabricated on low-temperature-grown GaAs; and the emitted THz radiation was characterized. The THz power, measured by a Golay cell, was 1μW at 0.3THz and 0.7μW at 0.5THz. The THz frequency, as determined by a Fourier transform interferometer, was seen to correspond to the etalon FSR. The current-voltage characteristics of photomixers were also determined, and photocurrent modulation was observed by the autocorrelation of the laser beam.
Vibrational spectroscopy of individual doping centers in a monolayer organic crystal
Authors: Nazin G. V. , Qiu X. H. , Ho W.
Published: May 2005

A scanning tunneling microscope (STM) is used to study individual Ag doping centers in a monolayer of C60 molecules supported on a thin Al2O3 film grown on the NiAl(110) surface. Vibronic states of the doping centers are observed with differential conductance (dI∕dV) spectroscopy. The double-barrier nature of the junction results in bipolar transport: same states participate in charge transport at both bias voltage polarities. Identification of the dI∕dV features corresponding to bipolar conduction enables a new mode of vibrational spectroscopy with STM.
Functionalization of single-walled carbon nanotubes using isotropic plasma treatment: Resonant Raman spectroscopy study
Authors: Utegulov Zhandos N. , Mast David B. , He Peng , Shi Donglu , Gilland Robert F.
Published: May 2005

Functionalization of single-walled carbon nanotubes (SWNTs) by isotropic plasma treatment was studied using resonant Raman spectroscopy. It was shown that plasma-induced functionalization results in the uniaxial isotropic constriction of the nanotubes but preserves their overall structural integrity. It was demonstrated that NH3∙H2O and hexamethyldisiloxan plasmas yield various types of conductivity for semiconducting SWNTs.
Solution of the general dynamic equation along approximate fluid trajectories generated by the method of moments
Authors: Hagmeijer Rob , IJzermans Rutger H. A. , Put Frits
Published: May 2005

We consider condensing flow with droplets that nucleate and grow, but do not slip with respect to the surrounding gas phase. To compute the local droplet size distribution, one could solve the general dynamic equation and the fluid dynamics equations simultaneously. To reduce the overall computational effort of this procedure by roughly an order of magnitude, we propose an alternative procedure, in which the general dynamic equation is initially replaced by moment equations complemented with a closure assumption. The key notion is that the flow field obtained from this so-called method of moments, i.e., solving the moment equations and the fluid dynamics equations simultaneously, approximately accommodates the thermodynamic effects of condensation. Instead of estimating the droplet size distribution from the obtained moments by making assumptions about its shape, we subsequently solve the exact general dynamic equation along a number of selected fluid trajectories, keeping the flow field fixed. This alternative procedure leads to fairly accurate size distribution estimates at low cost, and it eliminates the need for assumptions on the distribution shape. Furthermore, it leads to the exact size distribution whenever the closure of the moment equations is exact.
Rapid lateral solidification of pure Cu and Au thin films encapsulated in SiO2
Authors: Kline J. E. , Leonard J. P.
Published: May 2005

Excimer laser melting and lateral resolidification is demonstrated in 200nm thick Cu and Au elemental metal thin films encapsulated between SiO2 layers. Projection irradiation is used to selectively and completely melt lines 3to30μm wide in the metal film—with rapid lateral solidification originating from the unmelted sidewalls of the molten region—resulting in large columnar grains, extending transversely to the middle of the line. Transmission electron microscopy reveals twinning structures and other defects typical of rapid solidification. Encapsulation and control of the fluence are found to be crucial parameters necessary to prevent film dewetting while molten.
Heteroepitaxial gold (111) rings on mica substrates
Authors: Zhang X. W. , Chen N. F. , Yan F. , Goedel Werner A.
Published: May 2005

Two-dimensionally arranged gold rings were prepared by depositing a polymeric membrane bearing a dense array of uniform pores onto a mica substrate, filling the pores with a solution of a gold precursor, evaporation of the solvent and calcinations. The epitaxy of gold rings is confirmed by x-ray diffraction measurements, and the epitaxial relationship between gold rings and the mica was found to be Au(111)[1-10]∥mica(001)[010]. The polar and azimuthal angular spreads are 0.3° and 1°, respectively, which is at least equal to or better than the quality of the corresponding epitaxial gold-film on mica.
Electrical characteristics of postdeposition annealed HfO2 on silicon
Authors: Puthenkovilakam Ragesh , Sawkar Monica , Chang Jane P.
Published: May 2005

Electrical characteristics of ultrathin HfO2 films on p-type silicon (100) substrates were determined by capacitance-voltage and current density-voltage measurements. The as-deposited HfO2 films showed a dielectric constant of ∼22, a leakage current density of 5A∕cm2 and an interface state density of 6.5×1012cm2eV−1 at an equivalent oxide thickness (EOT) of 7.6Å due to the poor quality of HfO2∕Si interface. However, annealing in O2 and NH3 significantly reduced the interface state densities to 8.4×1011cm2eV−1 and 7.38×1011cm2eV−1, respectively, although the annealing increased the EOTs to 12.3Å and 11.3Å respectively, due to the growth of an additional interfacial layer. The forming gas anneal with either H2 or D2, however, significantly improved the quality of the HfO2∕Si interface without affecting the EOT. Postdeposition annealing in all chemistries decreased the leakage current densities by orders of magnitude at the same EOT compared to that of SiO2. The current transport mechanism in the as-deposed HfO2 sample is determined to be direct tunneling, and an Al∕HfO2 barrier height of 1.3eV and a HfO2∕Si barrier height of 1.4eV were obtained. The latter is in good agreement with the band offset determined by x-ray photoelectron spectroscopy analysis and ab initio calculations.
Molecular systematics of Australian carrion-breeding blowflies (Diptera:Calliphoridae) based on mitochondrial DNA
Authors: Wallman J. F. , Leys R. , Hogendoorn K.
Published: May 2005

Carrion-breeding blowflies have substantial ecological and forensic importance. Because morphological recognition of their immatures is difficult, sequencing of the mtDNA of these flies may assist with their identification. Molecular phylogenetic analysis based on DNA sequences can also clarify evolutionary relationships. In this study, the mitochondrial genes CO1, CO2, ND4 and ND4L were sequenced for 34 species of blowflies, among which are almost all species known or suspected to breed in carrion in Australia. The resulting sequences were analysed using parsimony and maximum-likelihood Bayesian techniques. The results showed that the combination of these four genes should identify most species reliably, although some very closely related taxa could still be misdiagnosed. The data also helped clarify the life histories of Calliphora centralis Malloch, 1927, C. fuscofemorata Malloch, 1927 and C. gilesi Norris, 1994, which have hitherto only been suspected carrion breeders, and revealed that the current subgeneric assignment of taxa within Calliphora Robineau-Desvoidy, based on morphology, requires revision. Unexpectedly, both Chrysomya rufifacies (Macquart, 1843) and Lucilia cuprina (Wiedemann, 1830) were paraphyletic; each probably comprises two distinct species. The application of a molecular-clock approach to the study of the evolutionary divergence of the carrion-breeding blowflies suggests that the speciation of at least the endemic Australian taxa may have been the result of increasing aridification in Australia during the last five million years.
Characterization of the lipid composition at the proximal root regions of human hair
Authors: Masukawa Y. , Narita H. , Imokawa G.
Published: May 2005

The hair lipid composition collected from 44 Japanese females between 1 and 81 years of age was examined for eight lipids including hydrocarbons (HCs), squalene (SQ), wax esters (WEs), triglycerides (TGs), fatty acids (FAs), cholesterol (CH), ceramides (CERs), and 18‐methyl eicosanoic acid (MEA). In this study, the 5‐cm length from the proximal root end of hair fibers, which had never been exposed to any chemical treatment, was used after 5‐min incubation with hexane following shampooing. Hair lipids were extracted with solvent and subsequent alkali‐solvent and were then analyzed by a combination of chromatography. Although the average contents of the lipids showed great fluctuations among individuals, there were significant correlations between the levels of each lipid, which allowed for the classification of the hair lipids into four groups: group A: SQ, WEs, TGs, and FAs (designated as endogenous lipids based upon their sebum origin); group B: CH and CERs (designated as endogenous lipids); group C: HC (unknown origin); and group D: MEA (the other endogenous lipid). A principal component analysis for eight lipids revealed that the hair lipid composition was characterized by a predominant negative correlation between each lipid for groups A and B. This negative correlation suggests that the endogenous lipids in group B serve as a barrier against the penetration of predominantly sebum‐derived exogenous lipids (group A). Endogenous lipids consisting of CH and CERs (group B) and MEA (group D) should be designated as intrinsic internal lipids of human hair.
L‐Ergothioneine scavenges superoxide and singlet oxygen and suppresses TNF‐α and MMP‐1 expression in UV‐irradiated human dermal fibroblasts
Authors: Obayashi K. , Kurihara K. , Okano Y. , Masaki H. , Yarosh D. B.
Published: May 2005

Ergothioneine (EGT) is a sulfur‐containing amino acid, and is presumed to function as a natural antioxidant. The purpose of this study was to identify the nature of the antioxidant activity and investigate the effects of EGT on UV‐induced cellular response. In chemical studies, EGT scavenged the superoxide anion radical (•O2–) and singlet oxygen (1O2). In cultured fibroblasts, EGT suppressed TNF‐α upregulation by UVB irradiation. In addition, in fibroblasts exposed to UV‐A, EGT suppressed the expression of matrix metalloproteinase 1 (MMP‐1) protein by nearly 50% and reduced MMP‐1 mRNA expression. From these results, we conclude that EGT scavenges reactive oxygen species generated by both type I and type II photosensitization and suppresses both TNF‐α expression and MMP‐1 at their transcriptional level. EGT may reduce skin anti‐aging effects after UV irradiation by the scavenging of •O2– and 1O2, and reducing signals for protease and inflammatory activity.
A study of the photolightening mechanism of red hair with visible and ultraviolet light: comparison with blond hair
Authors: Takahashi T. , Nakamura K.
Published: May 2005

The photolightening behavior of red hair was investigated. Red hair was found to lighten to a similar extent by irradiation from both ultraviolet (UV) and visible (VIS) light. Under the same irradiating conditions, blond hair was lightened by VIS light but did not lighten by UV light until it was washed after irradiation. These different photolightening behaviors of red and blond hair are supposed to be due to differences in their melanin compositions. The dominant type of melanin in red hair is pheomelanin; while blond hair investigated in the previous work contained both eumelanin and pheomelanin, with mainly eumelanin. Consequently, in this investigation, the photolightening behaviors of red and blond hair were compared to clarify the differences in photosensitivity between the two types of melanin. It has been proven that chemically intact melanin in red hair is considerably more photolabile to UV light than VIS light. Also, it is much more easily decomposed by UV light than melanin granules in blond hair, although they are both similarly decomposed by VIS light. This indicates that pheomelanin is far more sensitive to UV light than eumelanin, while these two types of melanin are similarly sensitive to VIS light. This leads to the following hypothetical photolightening mechanism of red hair: When UV light is irradiated on red hair, the light is absorbed by hair protein and attenuated before it reaches the melanin granules. However, since pheomelanin is highly sensitive to UV light, even the attenuated UV light decomposes the pheomelanin to some extent. As a result, UV light lightens red hair without the need for subsequent washing, in contrast to blond hair, which consists of mainly eumelanin.
Predicting clinical severity in sickle cell anaemia
Authors: Steinberg M. H.
Published: May 2005

The ability to predict the phenotype of an individual with sickle cell anaemia would allow a reliable prognosis and could guide therapeutic decision making. Some risk factors for individual disease complications are known but are insufficiently precise to use for prognostic purposes; predicting the global disease severity is not yet possible. Genetic association studies, which attempt to link gene polymorphisms with selected disease subphenotypes, may eventually provide useful methods of foretelling the likelihood of certain complications and allow better individualized treatment.
Bone involvement in sickle cell disease
Authors: Almeida Antonio , Roberts Irene
Published: May 2005

Bone involvement is the commonest clinical manifestation of sickle cell disease both in the acute setting such as painful vaso‐occlusive crises, and as a source of chronic, progressive disability such as avascular necrosis. Management of these problems is often difficult because of the diagnostic imprecision of most laboratory and imaging investigations and because of the lack of evidence for most surgical procedures in sickle cell disease. This review first discusses the acute problems related to bone involvement in sickle cell disease, with particular reference to differentiating infection from infarction, and then describes the long‐term effects of sickle cell disease on bone mineral density, growth, and chronic bone and joint damage.
Co‐existence of multiple subclones in TEL‐AML1 at diagnosis of acute lymphoblastic leukaemia in association with submicroscopic deletion of AML1
Authors: Rothman Rachel , Trakhtenbrot Luba , Bielorai Bella , Izraeli Shai , Ishoev Galina , Amariglio Ninette , Rechavi Gideon , Toren Amos
Published: May 2005

The TEL/AML1 (ETV6/RUNX1) fusion gene is the most common genetic rearrangement in paediatric acute lymphoblastic leukaemia (ALL). Although considered to be a low‐risk leukaemia, it is associated with a relapse rate of 10–20%. The coexistence of different subclones at diagnosis, based on polymerase chain reaction (PCR) studies of IG/TCR gene rearrangement, with differential response to chemotherapy, was recently reported in this subtype of ALL. We wished to demonstrate such subclones at diagnosis by a recently developed technique of quantitative multiparametric fluorescence in situ hybridization (FISH). Bone marrow cells from 80 paediatric patients with ALL at diagnosis were analysed for the presence of the TEL/AML1 fusion gene by interphase FISH. Fourteen patients were positive for the translocation. Four of them had several subclones associated with various combinations of additional chromosomal abnormalities. The most striking was an atypical and unexpected hybridization pattern consistent with a submicroscopic deletion of the 5′ region of the AML1 breakpoint. Other abnormalities included TEL deletion, trisomy and tetrasomy 21 as well as double TEL‐AML1 fusion. The presence of numerous subclones in about 25% of patients with TEL/AML1+ ALL suggests extensive clonal evolution by the time of diagnosis.
Phenotype and frequency of Epstein–Barr virus‐infected cells in pretreatment blood samples from patients with Hodgkin lymphoma
Authors: Khan Gulfaraz , Lake Annette , Shield Lesley , Freeland June , Andrew Linda , Alexander Freda E. , Jackson Robert , Taylor Penelope R. A. , McCruden Elizabeth A. B. , Jarrett Ruth F.
Published: May 2005

An accumulating body of data suggests that the Epstein–Barr virus (EBV), a lymphotropic herpesvirus, is involved in the pathogenesis of a proportion of cases of Hodgkin lymphoma (HL). In this study, we showed that the frequency of circulating EBV‐infected cells was significantly higher (P < 0·001) in pretreatment blood samples from EBV‐associated cases when compared with non‐EBV‐associated cases. We further showed that in patients with EBV‐associated disease, the virus persisted in the peripheral blood in memory B cells. This phenotype is consistent with that seen in healthy seropositive controls, post‐transplant patients and patients with acute infectious mononucleosis. The data suggest that an increased frequency of EBV carrying B cells in peripheral blood is associated with EBV‐associated HL.
Use of mycophenolate mofetil for chronic, refractory immune cytopenias in children with autoimmune lymphoproliferative syndrome
Authors: Koneti Rao V. , Dugan Faith , Dale Janet K. , Davis Joie , Tretler Jean , Hurley John K. , Fleisher Thomas , Puck Jennifer , Straus Stephen E.
Published: May 2005

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of apoptosis associated most often with heritable FAS mutations leading to lymphadenopathy, hypersplenism and chronic refractory autoimmune cytopenias. Mycophenolate mofetil (MMF) was used to treat cytopenias in 13 ALPS patients aged 9 months to 17 years from a cohort of 118 children (aged < 18 years) and 82 adults. Twelve responded for a median follow‐up of 49 weeks (range 38–240 weeks), defined by maintenance of adequate blood counts and reduction in dosage or cessation of other immunosuppressive agents. This preliminary experience suggests that MMF may spare steroid usage in patients with ALPS‐associated cytopenias.
Interphase molecular cytogenetic screening for chromosomal abnormalities of prognostic significance in childhood acute lymphoblastic leukaemia: a UK Cancer Cytogenetics Group Study
Authors: Harrison Christine J. , Moorman Anthony V. , Barber Kerry E. , Broadfield Zoë J. , Cheung Kan L. , Harris Rachel L. , Reza Jalali G. , Robinson Hazel M. , Strefford Jonathan C. , Stewart Adam , Wright Sarah , Griffiths Mike , Ross Fiona M. , Harewood Louise , Martineau Mary
Published: May 2005

Interphase fluorescence in situ hybridization (iFISH) was used independently to reveal chromosomal abnormalities of prognostic importance in a large, consecutive series of children (n = 2367) with acute lymphoblastic leukaemia (ALL). The fusions, TEL/AML1 and BCR/ABL, and rearrangements of the MLL gene occurred at frequencies of 22% (n = 447/2027) (25% in B‐lineage ALL), 2% (n = 43/2027) and 2% (n = 47/2016) respectively. There was considerable variation in iFISH signal patterns both between and within patient samples. The TEL/AML1 probe showed the highest incidence of variation (59%, n = 524/884), which included 38 (2%) patients with clustered, multiple copies of AML1. We were thus able to define amplification of AML1 as a new recurrent abnormality in ALL, associated with a poor prognosis. Amplification involving the ABL gene, a rare recurrent abnormality confined to T ALL patients, was identified for the first time. The use of centromeric probes revealed significant hidden high hyperdiploidy of 33% and 59%, respectively, in patients with normal (n = 21/64) or failed (n = 32/54) cytogenetic results. The iFISH contributed significantly to the high success rate of 91% (n = 2114/2323) and the remarkable abnormality detection rate of 89% (n = 1879/2114). This study highlights the importance of iFISH as a complementary tool to cytogenetics in routine screening for significant chromosomal abnormalities in ALL.
Do children do what they say? Responses to hypothetical and real‐life social problems in children with mild intellectual disabilities and behaviour problems
Authors: Van Nieuwenhuijzen M. , Bijman E. R. , Lamberix I. C. W. , Wijnroks L. , De Castro B. Orobio , Vermeer A. , Matthys W.
Published: May 2005

Background  Most research on children's social problem‐solving skills is based on responses to hypothetical vignettes. Just how these responses relate to actual behaviour in real‐life social situations is, however, unclear, particularly for children with mild intellectual disabilities (MID).

Method  In the present study, the spontaneous and selected responses of 56 children with MID to hypothetical situations from the Social Problem‐Solving Test for children with MID (SPT‐MID) were compared to their actual behaviour in comparable staged standardized real‐life conflict situations. Correlations to externalizing behaviour problems were assessed using the Teacher's Report Form (TRF).

Results  The results show children with MID and accompanying externalizing behaviour problems to behave more aggressively in the staged real‐life conflicts and provide more spontaneous aggressive responses to the hypothetical vignettes than children with MID and no accompanying externalizing behaviour problems; they did not, however, select more aggressive responses from the hypothetical options provided. A moderate correlation was found between the aggressiveness of the spontaneous responses in the hypothetical situations and actual behaviour in the staged real‐life situations. In addition, both the spontaneous aggressive responses under hypothetical circumstances and the actual aggressive behaviour under staged real‐life circumstances were related to teacher‐rated aggressive behaviour in the classroom.

Conclusions  It is concluded that the hypothetical vignettes from the SPT‐MID do provide information on both the actual behaviour and knowledge of social problem‐solving skills of children with MID.