bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental determination of anisotropy and demagnetizing factors of single Co nanowires by magnetoresistance measurements
Authors: Brands M. , Dumpich G.
Published: July 2005

We have investigated the low-temperature magnetoresistance (MR) behavior of Co nanowires with varying widths between 40nm and 5.2μm prepared by high-resolution electron-beam lithography. The wires have a thickness of 20nm and are protected from oxidation by a 10nm carbon cap layer. The magnetoresistance—for magnetic fields applied transversal or perpendicular to the wire—is negative and can be attributed to anisotropic magnetoresistance. The MR curves exhibit a strong dependence on the wire width from which the shape anisotropy and the demagnetizing factors can be deduced. The experimental results are in perfect agreement with the theoretical values for the demagnetization tensor of the general ellipsoid. During the magnetization rotation process a minor contribution from domain-wall nucleation and annihilation occurs.
Interface trap passivation for SiO2∕(0001¯) C-terminated 4H-SiC
Authors: Dhar S. , Feldman L. C. , Wang S. , Isaacs-Smith T. , Williams J. R.
Published: July 2005

Interface trap passivation at the SiO2∕carbon-terminated (0001¯) face of 4H-SiC utilizing nitridation and hydrogenation has been evaluated. The SiO2∕SiC interface, created by dry thermal oxidation on the C face, shows appreciably higher interface state density near the conduction band compared to the (0001) Si face. A postoxidation anneal in nitric oxide followed by a postmetallization anneal in hydrogen results in dramatic reduction of the trap density by over an order of magnitude near the conduction band. The electrical measurements have been correlated with the interfacial chemistry.
Substrate influence on the growth of Co-doped La0.5Sr0.5TiO3−δ epitaxial thin films
Authors: Ranchal R. , Bibes M. , Barthélémy A. , Bouzehouane K. , Guyard S. , Jacquet E. , Contour J.-P , Pascanut C. , Berthet P. , Dragoe N.
Published: July 2005

We report on the growth of thin films of the diluted magnetic oxide Co-doped La0.5Sr0.5TiO3−δ on SrTiO3 and LaAlO3 substrates. The films are ferromagnetic at room temperature, with no indications of parasite phases from high-resolution x-ray diffraction experiments. The structural mismatch with the substrate is shown to have a strong impact on the growth mechanisms and, consequently, on the surface morphology. In this sense, to grow the films on SrTiO3, for which the mismatch is minimized, appears to be more appropriate for the future integration of Co-doped La0.5Sr0.5TiO3−δ layers into heterostructures for perpendicular transport.
Numerical calculation of the Hamada basis vectors for three-dimensional toroidal magnetic configurations
Authors: Talmadge J. N. , Gerhardt S. P.
Published: July 2005

The moment equation approach to neoclassical transport is used to calculate neoclassical particle and heat fluxes, impurity transport, the ambipolar electric field, and momentum damping rates. These equations are often written in Hamada coordinates which makes it easier to obtain analytic solutions. However, previous simplifying assumptions used to evaluate the basis vectors analytically are often invalid for advanced stellarator configurations. In this paper, a numerical method is presented by which the Hamada basis set can be determined for an arbitrary three dimensional toroidal confinement device by integrating along a magnetic field line. The method is applied to the magnetic configuration in the Helically Symmetric Experiment [F. S. B. Anderson, A. F. Almagri, D. T. Anderson, P. G. Matthews, J. N. Talmadge, and J. L. Shohet, Fusion Technol. 27, 273 (1995)] and compared to the large-aspect-ratio tokamak approximation to the basis set. The results indicate that the numerical technique is a more accurate method to specify the basis vectors, especially in a device with negligible toroidal curvature.
Thermoelectric properties of delafossite-type layered oxides AgIn1−xSnxO2
Authors: Yasukawa Masahiro , Ikeuchi Kaoru , Kono Toshio , Ueda Kazushige , Hosono Hideo
Published: July 2005

The thermoelectric properties of delafossite-type layered oxides AgIn1−xSnxO2 that consist of alternating layers of Ag and In1−xSnxO2 were investigated to elucidate their potential as a thermoelectric material. Polycrystalline materials of the AgIn1−xSnxO2 were prepared by a cation exchange reaction between NaIn1−xSnxO2 and AgCl. The solubility limit of the Sn atoms on the In sites was approximately x=0.05. The electrical conductivity and Seebeck coefficient were measured between 373 and 673K in air. Undoped AgInO2 was an n-type semiconductor with conductivities of 10−4–10−2Ω−1cm−1, and the electron carriers were generated via the formation of oxygen vacancies. AgIn0.95Sn0.05O2 was an n-type degenerate semiconductor with conductivities of 100–101Ω−1cm−1 where the Sn atoms acted as electron donors. This drastic increase in the electrical conductivity increased the thermoelectric power factor by approximately two orders of magnitude to 10−6–10−5Wm−1K−2.
Raman-scattering study of the InGaN alloy over the whole composition range
Authors: Hernández S. , Cuscó R. , Pastor D. , Artús L. , O’Donnell K. P. , Martin R. W. , Watson I. M. , Nanishi Y. , Calleja E.
Published: July 2005

We present Raman-scattering measurements on InxGa1−xN over the entire composition range of the alloy. The frequencies of the A1(LO) and E2 modes are reported and show a good agreement with the one-mode behavior dispersion predicted by the modified random-element isodisplacement model. The A1(LO) mode displays a high intensity relative to the E2 mode due to resonant enhancement. For above band-gap excitation, the A1(LO) peak displays frequency shifts as a function of the excitation energy due to selective excitation of regions with different In contents, and strong multiphonon scattering up to 3LO is observed in outgoing resonance conditions.
The dependence of the radiation damage formation on the substrate implant temperature in GaN during Mg ion implantation
Authors: Whelan S. , Kelly M. J. , Gwilliam R. , Jeynes C. , Bongiorno C.
Published: July 2005

In pursuit of p-type doping, we have implanted GaN with Mg ions at 200 and 500keV with the substrate temperature maintained at −150 (cold) or +300°C (hot) during ion irradiation. The samples have been annealed at 1000°C postion implantation. The radiation damage peak position (and its profile), the dopant distribution, and the damage stability during annealing were all shown to be dependent upon the GaN substrate temperature during implantation. The damage peak position in the solid was reduced for cold implantation. The dopant distribution in the solid depends upon the implant temperature and in agreement with the damage measurements, the Mg range is shallower in GaN for cold implants when compared to hot implants. The trends observed suggest that the dynamic defect annealing rate during irradiation is reduced for cold implantation, and the subsequent increase in the damage level (scattering centers) formed during the damage buildup reduces the ion range in the solid. In turn, the reduced ion range subsequently limits the final damage range. The rate of damage removal during thermal annealing in the samples implanted at cold temperature was increased: this is explained by the greater complexity of defects caused during high-temperature implantation, due to the raised level of dynamic defect annealing.
Study of 7-azaindole in its first four singlet states
Authors: Catalán J. , de Paz J. L. G.
Published: July 2005

The molecular structure and properties of 7-azaindole in its first four singlet states were studied with a view to improving current understanding of the photophysical behavior of its C2h dimer. This dimer, which exhibits a double proton transfer via its two hydrogen bonds upon electronic excitation, has for 35years been used as a model for the photophysical behavior of DNA base pairs. Electronic excitation of 7-azaindole simultaneously increases its acidity and basicity; these changes facilitate a concerted mechanism for the double proton transfer in the dimer. In this work, we found the acidity and basicity changes to occur only in its first π,π* excited singlet state.
Scaling properties for a classical particle in a time-dependent potential well
Authors: Leonel Edson D. , McClintock P. V. E.
Published: July 2005

Some scaling properties for a classical particle interacting with a time-dependent square-well potential are studied. The corresponding dynamics is obtained by use of a two-dimensional nonlinear area-preserving map. We describe dynamics within the chaotic sea by use of a scaling function for the variance of the average energy, thereby demonstrating that the critical exponents are connected by an analytic relationship.
Sonic resonance in a sandwiched electrorheological panel
Authors: Tang Hong , Luo Chunrong , Zhao Xiaopeng
Published: July 2005

We have studied the sound transmission properties of a flexible sandwiched electrorheological (ER) panel. It shows that, at a frequency range of 80–150Hz, the sound pressure level spectrum exhibits a resonant peak. The resonant peak makes a shift to high frequency and the phase of the transmitted wave changes with an increase of the applied electric field. A vibration-radiation model is set up to simulate the sound radiating process and verifies a resonant effect in the ER panel in qualitative agreement with experiments. The tunable resonance effect in the ER panel would be useful in constructing tunable phononic crystals and other acoustic devices.
Polarization-controllable TE21 mode converter
Authors: Chang T. H. , Yu C. F. , Fan C. T.
Published: July 2005

We report the concept and development of a Ka-band mode and polarization converter that efficiently converts a TE10 rectangular waveguide mode into either a linearly or a circularly polarized TE21 cylindrical waveguide mode. The converter is composed of a power-dividing section, a mode-converting section, and a polarization-transitioning section. The converting process in each section is displayed and the working principles are discussed. A prototype has been built and tested. The measured results agree well with the numerical calculations for both linear and circular polarizations. The measured optimum back-to-back transmission is 94% with a 1-dB bandwidth of 4.1 GHz for the linear polarization. As for the circular polarization, the measured optimum transmission is 97%, but the corresponding bandwidth is indistinct due to some resonant dips. The reasons and impact for the dips are discussed. A bandwidth of 3.9 GHz is obtained for a single circular converter; meanwhile, an approach to eliminating these unwanted dips is presented in theory. For further diagnostics, the field pattern of either polarization is directly displayed on a temperature-sensitive liquid crystal display sheet, where the electric field strength can be discerned from the color spectrum. In addition to high conversion efficiency and broad bandwidth, this converter features easy construction, high mode purity, and polarization controllability.
Miniaturized multipurpose cell for in situ investigation of sputtered thin films with x-ray techniques
Authors: Lützenkirchen-Hecht D. , Bruder K. , Haake U. , Keil P. , Markert C. , Ringpfeil C. , Frahm R.
Published: July 2005

The design of a miniaturized sputter deposition chamber for the in situ study of thin film growth processes with x rays is reported. X-ray diffraction experiments, grazing incidence x-ray reflectometry, as well as x-ray fluorescence analysis are possible. Due to its compact design and low weight, the chamber can be used in conjunction with conventional x-ray reflectometers and laboratory x-ray diffractometers as well, i.e., very detailed in situ studies of reactive and nonreactive sputtering processes and the resulting film properties are possible. The construction of the chamber is described in detail and first results obtained in situ with different techniques are presented, indicating that experiments that were previously restricted to synchrotron radiation facilities are now possible even with laboratory equipment.
Magnetic properties and microstructures of Fe–Pt thin films sputter deposited under partial nitrogen gas flow
Authors: You C. Y. , Takahashi Y. K. , Hono K.
Published: July 2005

Continuous Fe100−xPtx thin films (x=44, 50, 56, 60, and 65) with a thickness of around 80 nm were prepared by dc magnetron sputtering under a mixture of argon and nitrogen gases. The maximum coercivity was obtained at the Fe56Pt44 off-stoichiometric composition after postannealing for L10 ordering. For the equiatomic and Pt-rich films, partial nitrogen flow during sputtering deteriorated the in-plane coercivity of the postannealed samples due to conglomeration of smaller grains and the presence of L12FePt3 phase. After postannealing for L10 ordering, the Fe-rich films grown in argon and mixture of argon and nitrogen atmospheres are both composed of L10 fct phase only, and the enhancement of the degree of order and strong preferential in-plane alignment of the c axis in the presence of nitrogen causes in-plane coercivity increase. By introducing nitrogen during sputtering, an in-plane coercivity of 1303kA∕m (16.4 kOe) was obtained for the continuous Fe56Pt44 thin film annealed at 700 °C.
Off-axis electron holography of pseudo-spin-valve thin-film magnetic elements
Authors: Kasama T. , Barpanda P. , Dunin-Borkowski R. E. , Newcomb S. B. , McCartney M. R. , Castaño F. J. , Ross C. A.
Published: July 2005

Magnetic remanent states in a rectangular array of 75×280-nm2NiFe∕Cu∕Co thin-film pseudo-spin-valve elements are studied using off-axis electron holography in the transmission electron microscope (TEM). An approach based on focused ion-beam milling is used to minimize damage to the magnetic properties of the elements during preparation for TEM examination in plan-view geometry. Experimental electron holographic phase images are used to measure the switching fields of the Co and NiFe layers in each of three adjacent elements separately, and comparisons with micromagnetic simulations are used to infer the true magnetic thicknesses and widths of the layers. Demagnetizing fields are included in the discussion of the results, and the possibility that the conclusions may be affected by the procedure used to analyze the holograms is discussed.
Microstructural and electrical properties of La0.7Ca0.3MnO3 thin films grown on SrTiO3 and LaAlO3 substrates using metal-organic deposition
Authors: Daoudi Kais , Tsuchiya Tetsuo , Yamaguchi Iwao , Manabe Takaaki , Mizuta Susumu , Kumagai Toshiya
Published: July 2005

La 0.7 Ca 0.3 MnO 3 (LCMO) thin films have been prepared on LaAlO3 and SrTiO3 (STO) (001) single-crystal substrates by the metal-organic deposition process. These films were characterized by transmission electron microscopy (TEM) and temperature dependence of the resistance R(T). The microstructure of the LCMO films and LCMO/substrate interfaces were investigated through cross-sectional TEM observations. High-resolution TEM (HRTEM) observations and electron-diffraction patterns demonstrate the (001) epitaxial growth on both the LAO and STO substrates. The local structure of the LCMO film depends on the type of substrate. HRTEM observations along the LCMO/STO interface display a good epitaxy throughout the entire film without any microstructural defects. On the contrary, in the LCMO film and in the region close to the LAO substrate, we note the presence of misfit dislocations and twins. The temperature coefficient of resistance (TCR) was calculated from the temperature dependence of the resistance measurements. The LCMO/LAO system exhibits a TCR value of 27.5%∕K compared with the 10%∕K measured for the LCMO/STO system.
Colloidal aggregation in polymer blends
Authors: Benhamou M. , Ridouane H. , Hachem E.-K. , Derouiche A. , Rahmoune M.
Published: July 2005

We consider here a low-density assembly of colloidal particles immersed in a critical polymer mixture of two chemically incompatible polymers. We assume that, close to the critical point of the free mixture, the colloids prefer to be surrounded by one polymer (critical adsorption). As result, one is assisted to a reversible colloidal aggregation in the nonpreferred phase, due the existence of a long-range attractive Casimir force between particles. This aggregation is a phase transition driving the colloidal system from dilute to dense phases, as the usual gas–liquid transition. We are interested in a quantitative investigation of the phase diagram of the immersed colloids. We suppose that the positions of particles are disordered, and the disorder is quenched and follows a Gaussian distribution. To apprehend the problem, use is made of the standard φ4 theory, where the field φ represents the composition fluctuation (order parameter), combined with the standard cumulant method. First, we derive the expression of the effective free energy of colloids and show that this is of Flory–Huggins type. Second, we find that the interaction parameter u between colloids is simply a linear combination of the isotherm compressibility and specific heat of the free mixture. Third, with the help of the derived effective free energy, we determine the complete shape of the phase diagram (binodal and spinodal) in the (Ψ,u) plane, with Ψ as the volume fraction of immersed colloids. The continuous “gas–liquid” transition occurs at some critical point K of coordinates (Ψc=0.5,uc=2). Finally, we emphasize that the present work is a natural extension of that, relative to simple liquid mixtures incorporating colloids.
Etching process of silicon dioxide with nonequilibrium atmospheric pressure plasma
Authors: Yamakawa Koji , Hori Masaru , Goto Toshio , Den Shoji , Katagiri Toshirou , Kano Hiroyuki
Published: July 2005

An ultrahigh etch rate (14μm∕min) of SiO2 and a high selectivity of SiO2∕Si over 200 were achieved using a microwave-excited nonequilibrium atmospheric pressure plasma source employing He, NF3, and H2O gases, which have been developed for application to microelectromechanical systems and other bionanotechnology fields. In order to clarify the etching mechanism, two diagnostic methods have been performed: (1) imaging of plasma emission with an intensified charge-coupled device camera, and (2) absorption measurements using Fourier transform infrared spectroscopy. The etching characteristics are discussed in relation to the spatial distributions of the species involved. The etch rate depended considerably on the distance between the plasma and the substrate. Some radicals generated from the feed gases reached the substrate directly, while other radicals recombined into different species, which reached the substrate. An abundance of HF molecules were produced through a reaction between radicals generated by the atmospheric pressure discharge of NF3 and H2O. From these measurements, it has been found that the HF molecules generated played a role in producing the high etch rate of SiO2 and high etch selectivity of SiO2∕Si.
Photolysis wavelength dependence of the translational anisotropy and the angular momentum polarization of O2(aΔg1) formed from the UV photodissociation of O3
Authors: Hancock Gus , Horrocks Sophie J. , Pearson Paul J. , Ritchie Grant A. D. , Tibbetts Daniel F.
Published: July 2005

The translational anisotropy and angular momentum polarization of the O2(aΔg1,v=0;J=15–27) molecular photofragment produced from the UV photodissociation of O3 in the range from 270 to 300 nm have been determined using resonance-enhanced multiphoton ionization in conjunction with time-of-flight mass spectrometry. At the shortest photolysis wavelengths used, the fragments exhibit the anisotropic vector correlations expected from a prompt dissociation via the B21←A11 transition. Deviations from this behavior are observed at longer photolysis wavelengths with, in particular, the angular momentum orientation showing a significant reduction in magnitude. This indicates that the dissociation can no longer be described by a purely impulsive model and a change in geometry of the dissociating molecule is implied. This observation is substantiated by the variation of the translational anisotropy with photolysis wavelength. We also observe that the bipolar moments describing the angular momentum polarization of the odd J states probed are consistently lower in magnitude than those of the even J states and that this variation is observed for all photolysis wavelengths.
Spectral equation-of-state theory for dense, partially ionized matter
Authors: Ritchie Burke
Published: July 2005

The Schrödinger equation is solved in time and space to implement a finite-temperature equation-of-state theory for dense, partially ionized matter. The time-dependent calculation generates a spectrum of quantum states. Eigenfunctions are calculated from a knowledge of the spectrum and used to calculate the electronic pressure and energy. Results are given for Be and LiD and compared with results from the INFERNO model [D. A. Liberman, Phys. Rev. B 20, 4981 (1979)].
Stage-II-screening device for testing of heterogeneous catalysts in gas phase reactions with Fourier transform infrared analysis
Authors: Brüning Rainer , Scholz Peter , Ondruschka Bernd
Published: July 2005

The construction of a stage-II-screening device for heterogeneous catalysts in gas phase reactions under ambient pressure is described. The concentrations of the reaction products are determined by Fourier transform infrared analysis in combination with a chemometric interpretation of the obtained spectra. Thus, fast high-precision product analyses with complete mass balances are feasible, within the limits of accuracy of the measurements. The device is designed to screen up to 17 catalysts in one testing cycle. It is possible to determine temperature-conversion-selectivity dependencies as well as long-term measurements under constant conditions. With the help of the device described, the catalytic properties of new materials were parallel tested for the oxidative dehydrogenation of isopropanol.
Fully reflective deep ultraviolet to near infrared spectrometer and entrance optics for resonance Raman spectroscopy
Authors: Schulz B. , Bäckström J. , Budelmann D. , Maeser R. , Rübhausen M. , Klein M. V. , Schoeffel E. , Mihill A. , Yoon S.
Published: July 2005

We present the design and performance of a new triple-grating deep ultraviolet to near-infrared spectrometer. The system is fully achromatic due to the use of reflective optics. The minimization of image aberrations by using on- and off- axis parabolic mirrors as well as elliptical mirrors yields a strong stray light rejection with high resolution over a wavelength range between 165 and 1000nm. The Raman signal is collected with a reflective entrance objective with a numerical aperture of 0.5, featuring a Cassegrain-type design. Resonance Raman studies on semiconductors and on correlated compounds, such as LaMnO3, highlight the performance of this instrument, and show diverse resonance effects between 1.96 and 5.4eV.
Plasma expansion in the presence of a dipole magnetic field
Authors: Winske D. , Omidi N.
Published: July 2005

Simulations of the initial expansion of a plasma injected into a stationary magnetized background plasma in the presence of a dipole magnetic field are carried out in two dimensions with a kinetic ion, massless fluid electron (hybrid) electromagnetic code. For small values of the magnetic dipole, the injected ions have large gyroradii compared to the scale length of the dipole field and are essentially unmagnetized. As a result, these ions expand, excluding the ambient magnetic field and plasma to form a diamagnetic cavity. However, for stronger magnetic dipoles, the ratio of the gyroradii of the injected ions to the dipole field scale length is small so that they remain magnetized, and hence trapped in the dipole field, as they expand. The trapping and expansion then lead to additional plasma currents and resulting magnetic fields that not only exclude the background field but also interact with the dipole field in a more complex manner that stretches the closed dipole field lines. A criterion to distinguish between the two regimes is derived and is then briefly discussed in the context of applying the results to the plasma sail scheme for the propulsion of small spacecraft in the solar wind.
Spectral and dynamical features of the electron bunch accelerated by a short-pulse high intensity laser in an underdense plasma
Authors: Bulanov Sergei V. , Yamagiwa Mitsuru , Esirkepov Timur Zh. , Koga James K. , Kando Masaki , Ueshima Yutaka , Saito Kanji , Wakabayashi Daisuke
Published: July 2005

The results of the theoretical consideration and two-dimensional particle in cell simulation of electron acceleration with a short-pulse intense laser propagating through a finite length underdense plasma layer are presented. The fast electron energy spectrum and emittance are analyzed for moderate to high intensity and for different plasma density. It is shown that for laser pulse lengths above the plasma wake wavelength the wakefield accelerated electrons are further accelerated by the electromagnetic wave.
A generalization of Connes-Kreimer Hopf algebra
Authors: Byun Jungyoon
Published: July 2005

“Bonsai” Hopf algebras, introduced here, are generalizations of Connes-Kreimer Hopf algebras, which are motivated by Feynman diagrams and renormalization. We show that we can find operad structure on the set of bonsais. We introduce a differential on these bonsai Hopf algebras, which is inspired by the tree differential. The cohomologies of these are computed here, and the relationship of this differential with the appending operation ∗ of Connes-Kreimer Hopf algebras is investigated.
Regularization of singular eigenfunctions of an operator with continuous spectra: With applications for ballooning modes in toroidally rotating tokamaks
Authors: Furukawa M. , Yoshida Z. , Tokuda S.
Published: July 2005

Eigenfunction expansions of fields encounter practical difficulty when the generating operator has continuous spectra (as is common in magnetohydrodynamics theories). An appropriate “weight function” may remove the singularity of the eigenfunctions belonging to the continuous spectrum and the complete set of regularized (square-integrable) eigenfunctions can be obtained. As an example, this method has been applied for ballooning modes in toroidally rotating tokamaks. While the weight function truncates the long-term behavior of modes, the regularized eigenfunctions can describe transient behavior within a finite time.
Melting dynamics of finite clusters in dusty plasmas
Authors: Ivanov Yuriy , Melzer André
Published: July 2005

The nonequilibrium melting dynamics of finite two-dimensional dust clusters is investigated experimentally. Nonequilibrium melting is induced by placing a single particle in the layer below the actual cluster which leads to unstable oscillations of the lower particle. The dynamic and thermodynamic properties during the two-step melting process have been investigated. Using the novel technique of singular value decomposition, the driving modes have been unambiguously related to the unstable oscillation. These modes are not accessible by normal mode analysis. Further it has been observed that angular melting occurred prior to the radial melting. Also, clusters with smaller number of particles revealed stronger heating than larger. This behavior is attributed to constant energy input by the unstable oscillation. Finally, clusters consisting of smaller particles are found to be more susceptible to fluctuations of the plasma parameters leading to a less pronounced two-step melting.
Quantum electrodynamical effects in dusty plasmas
Authors: Marklund M. , Stenflo L. , Shukla P. K. , Brodin G.
Published: July 2005

A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is predicted. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a dusty plasma, where quantum electrodynamical photon-photon scattering is taken into account. Specifically, we consider a dusty electron-positron-ion plasma and show that the propagation of the new mode is admitted. It could be of significance for the physics of supernova remnants and in neutron star formation.
Ellipsoidal Coulomb crystals in a linear radio-frequency trap
Authors: Fröhlich U. , Roth B. , Schiller S.
Published: July 2005

A static quadrupole potential breaks the cylindrical symmetry of the effective potential of a linear rf trap. For a one-component liquid plasma at low temperature, the resulting equilibrium charge distribution is predicted to be an ellipsoid. Laser-cooled Be+9 ellipsoidal ion crystals were produced and good agreement was found between their shapes and the cold fluid prediction. In two-species mixtures, containing Be+9 and sympathetically cooled ions of lower mass, a sufficiently strong static quadrupole potential produces a complete spatial separation of the species.
Control of the natural frequency of the (2,0) mode of liquid bridges using active electrostatic fields
Authors: Wei Wei , Thiessen David B. , Marston Philip L.
Published: July 2005

We demonstrate that active stiffening of a capillary bridge through the application of an appropriate Maxwell stress projection can be used to raise the frequency of bridge oscillations. The stress projection is proportional to the mode amplitude. This approach may be useful for suppressing the response of capillary systems to ambient vibrations. The amount of stiffening has a simple dependence on a dimensionless gain and it also depends on the slenderness of the bridge. Using a Plateau tank, we demonstrate a simple method for inferring the dimensionless gain.
When is it energetically favorable for a rivulet of perfectly wetting fluid to split?
Authors: Wilson S. K. , Duffy B. R.
Published: July 2005

We determine when it is energetically favorable for a thin rivulet of perfectly wetting fluid (i.e., a thin rivulet with zero contact angle) on the underside of a planar substrate to split into two or more subrivulets.
Effects of post-deposition annealing in O2 on the electrical characteristics of LaAlO3 films on Si
Authors: Miotti L. , Bastos K. P. , Driemeier C. , Edon V. , Hugon M. C. , Agius B. , Baumvol I. J. R.
Published: July 2005

LaAlO 3 films were deposited on p-type Si(100) by sputtering from a LaAlO3 target. C×V characteristics were determined in nonannealed and O2-annealed capacitors having LaAlO3 films as dielectric and RuO2 as top electrode. Thermal annealing in O2 atmosphere reduced flat band voltage to acceptable values for advanced Si-based devices. O16–O18 isotopic substitution was characterized by Rutherford backscattering spectrometry and nuclear resonant reaction profiling. Chemical analysis of the films was accomplished by x-ray photoelectron spectroscopy. The electrical improvements observed after thermal annealing in O2 were attributed to the incorporation of oxygen from the gas phase, possibly healing oxygen vacancies in the films and providing mobile oxygen to the interface.
Replicative generation of metal microstructures by template-directed electrometallization
Authors: Thom I. , Hähner G. , Buck M.
Published: July 2005

Copper structures were produced by electrochemical deposition onto patterned self-assembled monolayers (SAMS) of thiols adsorbed on polycrystalline gold substrates and subsequent transfer to an insulating substrate. Selective metal deposition was achieved by use of thiols which differ in their electrochemical blocking properties, namely hexadecane thiol [CH3(CH2)15SH] and ω-(4′-methyl-biphenyl-4-yl)-methanethiol (CH3–C6H4–C6H4–CH2–SH). Besides control of the blocking properties, the SAM served to minimize adhesion between the metal deposit and the substrate, thus, allowing the transfer of the metal pattern. Since the process is replicative, it represents a very simple and fast route to generating metal patterns.
Electron transport in ZnO thin films
Authors: Makino T. , Segawa Y. , Tsukazaki A. , Ohtomo A. , Kawasaki M.
Published: July 2005

Epitaxial n-type ZnO films grown by a laser molecular-beam epitaxy method were investigated by the temperature-dependent Hall-effect technique. The 300K carrier concentration and mobility were about ns∼1016cm−3 and 440cm2∕Vs, respectively. Transport characteristics are calculated by solving the Boltzmann transport equation using a variational method. Mobility limit of 430cm2∕Vs was calculated at 300K. The temperature dependence of the mobility for an undoped film is calculated and agrees favorably well with experimental data if physical parameters are chosen so as to approach those. In the experimental “mobility versus concentration” curve, unusual phenomenon was observed, i.e., mobilities at ns∼5×1018cm−3 are significantly smaller than those at higher densities above ∼1020cm−3. It is qualitatively explained in terms of electron-plasmon interaction.
Strong light-matter coupling at room temperature in simple geometry GaN microcavities grown on silicon
Authors: Semond F. , Sellers I. R. , Natali F. , Byrne D. , Leroux M. , Massies J. , Ollier N. , Leymarie J. , Disseix P. , Vasson A.
Published: July 2005

The reflectance spectra of simple design GaN-based microcavities have been studied in the 5 K–300 K range. The epitaxial structure consists of the silicon substrate and the stack of buffer layers as the back mirror, a GaN active layer, and a 100 Å thick aluminium layer as the top mirror. Active layer thicknesses of λ∕2, λ, or 3λ∕2 were investigated. The samples with GaN thicknesses λ∕2 and λ display an anticrossing behavior between the cavity and exciton modes, with measured Rabi splittings of 47 and 60 meV, respectively, both at 5 K and room temperature.
Single-molecule studies of repressor–DNA interactions show long-range interactions
Authors: Wang Y. M. , Tegenfeldt Jonas O. , Reisner W. , Riehn R. , Guan Xiao-Juan , Guo Ling , Golding Ido , Cox Edward C. , Sturm James , Austin Robert H.
Published: July 2005

We have performed single-molecule studies of GFP–LacI repressor proteins bound to bacteriophage λ DNA containing a 256 tandem
lac
operator insertion confined in nanochannels. An integrated photon molecular counting method was developed to determine the number of proteins bound to DNA. By using this method, we determined the saturated mean occupancy of the 256 tandem
lac
operators to be 13, which constitutes only 2.5% of the available sites. This low occupancy level suggests that the repressors influence each other even when they are widely separated, at distances on the order of 200 nm, or several DNA persistence lengths.
Endothelial expression of constitutively active
Notch4
elicits reversible arteriovenous malformations in adult mice
Authors: Carlson Timothy R. , Yan Yibing , Wu Xiaoqing , Lam Michael T. , Tang Gale L. , Beverly Levi J. , Messina Louis M. , Capobianco Anthony J. , Werb Zena , Wang Rong
Published: July 2005

Direct communication between arteries and veins without intervening capillary beds is the primary pathology of arteriovenous malformations (AVMs). Although Notch signaling is implicated in embryonic arteriovenous (AV) differentiation, its function in the adult mammalian vasculature has not been established due to the embryonic lethality that often occurs in both gain- and loss-of-function mutants. We expressed a constitutively active
Notch4
,
int3
, in the adult mouse endothelium by using the tetracycline-repressible system to suppress
int3
during embryogenesis.
int3
caused profound blood vessel enlargement and AV shunting, which are hallmarks of AVM, and led to lethality within weeks of its expression. Vessel enlargement, a manifestation of AVM, occurred in an apparently tissue-specific fashion; the liver, uterus, and skin were affected.
int3
-mediated vascular defects were accompanied by arterialization, including ectopic venous expression of
ephrinB2
, increased smooth muscle cells, and up-regulation of endogenous Notch signaling. Remarkably, the defective vessels and illness were reversed upon repression of
int3
expression. Finally, endothelial expression of a constitutively active
Notch1
induced similar hepatic vascular lesions. Our results provide gain-of-function evidence that Notch signaling in the adult endothelium is sufficient to render arterial characteristics and lead to AVMs.
Ontological analysis of gene expression data: current tools, limitations, and open problems
Authors: Khatri Purvesh , Drăghici Sorin
Published: July 2005

Summary: Independent of the platform and the analysis methods used, the result of a microarray experiment is, in most cases, a list of differentially expressed genes. An automatic ontological analysis approach has been recently proposed to help with the biological interpretation of such results. Currently, this approach is the de facto standard for the secondary analysis of high throughput experiments and a large number of tools have been developed for this purpose. We present a detailed comparison of 14 such tools using the following criteria: scope of the analysis, visualization capabilities, statistical model(s) used, correction for multiple comparisons, reference microarrays available, installation issues and sources of annotation data. This detailed analysis of the capabilities of these tools will help researchers choose the most appropriate tool for a given type of analysis. More importantly, in spite of the fact that this type of analysis has been generally adopted, this approach has several important intrinsic drawbacks. These drawbacks are associated with all tools discussed and represent conceptual limitations of the current state-of-the-art in ontological analysis. We propose these as challenges for the next generation of secondary data analysis tools.

Contact:  sod@cs.wayne.edu
A heuristic approach for detecting RNA H-type pseudoknots
Authors: Huang Chun-Hsiang , Lu Chin Lung , Chiu Hsien-Tai
Published: July 2005

Motivation

RNA H-type pseudoknots are ubiquitous pseudoknots that are found in almost all classes of RNA and thought to play very important roles in a variety of biological processes. Detection of these RNA H-type pseudoknots can improve our understanding of RNA structures and their associated functions. However, the currently existing programs for detecting such RNA H-type pseudoknots are still time consuming and sometimes even ineffective. Therefore, efficient and effective tools for detecting the RNA H-type pseudoknots are needed.

Results

In this paper, we have adopted a heuristic approach to develop a novel tool, called HPknotter, for efficiently and accurately detecting H-type pseudoknots in an RNA sequence. In addition, we have demonstrated the applicability and effectiveness of HPknotter by testing on some sequences with known H-type pseudoknots. Our approach can be easily extended and applied to other classes of more general pseudoknots.

Availability

The web server of our HPknotter is available for online analysis at http://bioalgorithm.life.nctu.edu.tw/HPKNOTTER/

Contact

cllu@mail.nctu.edu.tw, chiu@cc.nctu.edu.tw
Prevalence and Outcome of Allergic Colitis in Healthy Infants with Rectal Bleeding: A Prospective Cohort Study
Authors: Xanthakos Stavra A , Schwimmer Jeffrey B , Melin‐Aldana Hector , Rothenberg Marc E , Witte David P , Cohen Mitchell B
Published: July 2005

Objectives:

Allergic colitis is often diagnosed clinically in healthy infants with rectal bleeding and often treated with costly hypoallergenic formula. The true prevalence of allergic colitis is unknown. We tested the hypothesis that allergic colitis is overdiagnosed in healthy infants with rectal bleeding. The authors also determined whether rectal bleeding in infants without allergic colitis would resolve without diet change.

Methods:

For the purposes of this study, allergic colitis was defined histologically as colonic mucosa with ≥ 6 eosinophils per high power field and/or eosinophils in colonic crypts or muscularis mucosae. We surveyed all 56 Ohio NASPGHAN members to determine standard practice regarding the evaluation of rectal bleeding in infants. In addition, infants ≤ 6 months old with rectal bleeding were recruited from the referral area of Cincinnati Children's Hospital Medical Center. All infants underwent flexible sigmoidoscopy with biopsies at 5, 10 and 15 cm. Formula or maternal diet was changed only for infants with histologic findings of allergic colitis as defined. Study subjects were followed for 9 weeks.

Results:

In the survey of NASPGHAN members, 84% indicated they would empirically change the diet of an infant with rectal bleeding to treat presumed allergic colitis. In our study population, however, only 14 of 22 (64%; 95% confidence interval, 41‐83) infants with rectal bleeding had allergic colitis. Five (23%) had normal biopsies and three (14%) had nonspecific colitis. Rectal bleeding in all infants with normal biopsies or nonspecific colitis resolved without diet change except for 1 infant subsequently diagnosed with infantile inflammatory bowel disease.

Conclusion:

A significant proportion of infants with rectal bleeding may not have allergic colitis and may undergo unnecessary, expensive formula or maternal diet changes that may discourage breast‐feeding.
Antibiotic‐Induced Mesenteric Adenopathy in an Intussusception Mouse Model: A Randomized, Controlled Trial
Authors: Spiro David M , Schmidt James M , Arnold Donald H , Cartner Samuel C , Yagmurlu Aydin
Published: July 2005

Background:

Idiopathic intussusception is a leading cause of intestinal obstruction in young children. Although the etiology remains obscure, lymphoid hyperplasia is found in a majority of cases. Antibiotics, the most frequently prescribed medication class in the pediatric population, have been recently associated with intussusception. The authors sought to determine whether enteral antibiotic exposure influences the development of mesenteric adenopathy, bowel dilation or intussusception in an animal model.

Materials and Methods:

The authors conducted a randomized, controlled animal trial using a previously described intussusception model. Mice were gavaged with normal saline, amoxicillin‐clavulanate or azithromycin twice daily for 5 days to assess the influence of enteral antibiotic exposure on intussusception, mesenteric adenopathy and bowel dilation. One pediatric surgeon performed all laparotomies and was blinded to group designation. χ2 and Fisher exact tests were used to evaluate differences between antibiotic exposed and control groups.

Results:

Mesenteric adenopathy was identified in 4.1% of the normal saline controls compared with 54.1% (P < 0.01) and 38.9% (P < 0.01) of the amoxicillin‐clavulanate and azithromycin exposed animals, respectively. A total of four intussusceptions were observed in the antibiotic‐exposed groups combined whereas no intussusception cases were identified in the control group (P = 0.30).

Conclusions:

This is the first study to describe a significant association between antibiotic use and mesenteric adenopathy in any animal species.
Whole Body Protein Turnover and Urea Production of Preterm Small for Gestational Age Infants Fed Fortified Human Milk or Preterm Formula
Authors: de Boo Hendrina A , Cranendonk Anneke , Kulik Willem , Harding Jane E , Lafeber Harrie N
Published: July 2005

Objectives:

To investigate protein metabolism and urea production in preterm small for gestational age neonates fed a preterm formula or fortified human milk.

Methods:

Ten preterm small for gestational age neonates were fed either their own mother's milk fortified with a powdered protein mineral supplement or a special preterm formula. Protein metabolism was determined using constant steady‐state infusion of L‐[ring‐2H5]phenylalanine and L‐[1‐13C]valine. Urea production was determined from steady‐state [13C]urea kinetics.

Results:

Mean protein intake was 24% higher in the preterm formula group than in the fortified human milk group. No differences in protein turnover, synthesis and breakdown were observed between the two groups, but protein accretion was 71% to 79% higher in the preterm formula group than the fortified human milk group. Urea production rates were not different in the two groups. There was a strong negative correlation between urea production and protein accretion calculated from phenylalanine kinetics but not when calculated from valine kinetics.

Conclusions:

Preterm formula and fortified human milk appear equally well tolerated by preterm small for gestational age neonates, but protein accretion was higher in the preterm formula group. In preterm small for gestational age infants, both phenylalanine and valine kinetic methods can be used to accurately determine protein metabolism.
Neonatal and Infant Feeding: Effect on Bone Density at 4 Years
Authors: Young Rosemary J , Antonson Dean L , Ferguson Paul W , Murray Nancy D , Merkel Kim , Moore Timothy E
Published: July 2005

Objective:

The aim of this study was to determine whether the type of feeding during the first 4 months of life affects bone mineral density at 4 years of age.

Methods:

Healthy 4‐year‐old children were recruited from the offices of primary health care providers. After confirming the type of infant feeding by history, dual energy x‐ray absorptiometry analysis was obtained at the University of Nebraska Medical Center and evaluated by a radiologist blinded as to feeding type.

Results:

One hundred and seventy‐eight children completed the study (58% male, 85% Caucasian; mean age, 4.5 years). All children had exclusively consumed human milk (n = 57), an infant formula containing no palm olein oil (n = 56) or an infant formula containing palm olein oil (n = 65) during the first 4 months of life. At 4 years of age, no significant differences were noted in bone mineral content or bone mineral density (P = 0.51 and 0.89, respectively) among the three feeding groups as measured by dual energy x‐ray absorptiometry. Total body bone mineral content and bone mineral density varied by gender, with males having significantly higher values than females regardless of feeding type (P = 0.028 and P < 0.001, respectively).

Conclusion:

There is no association between the use of palm olein formula during the first 4 months of life and subsequent bone mineral content and bone mineral density in healthy 4‐year‐old children.
The Need for Nutrition Support Teams in Pediatric Units: A Commentary by the ESPGHAN Committee on Nutrition
Authors:   ESPGHAN Committee on Nutrition:, Agostoni Carlo , Axelsson Irene , Colomb Virginie , Goulet Olivier , Koletzko Berthold , Michaelsen Kim F , Puntis John W. L , Rigo Jacques , Shamir Raanan , Szajewska Hania , Turck Dominique
Published: July 2005

The reported prevalence of malnutrition in pediatric hospitals ranges from 15% to 30% of patients, with an impact on growth, morbidity and mortality. Major deficits in nutrition care have been highlighted in European hospitals, and the implementation of nutrition support teams (NSTs) has been suggested as a means to improve malnutrition diagnosis and nutrition care for hospitalized patients.

This comment by the ESPGHAN Committee on Nutrition reviews disease related‐mechanisms causing malnutrition and consequences of malnutrition and suggests a framework for implementation of NSTs in pediatric units. The recommendations by the Committee on Nutrition include: 1) Implementation of NSTs in hospitals is recommended to improve nutritional management of sick children; 2) The main tasks of the NST should include screening for nutritional risk, identification of patients who require nutritional support, provision of adequate nutritional management, education and training of hospital staff and audit of practice; 3) The NST should be multidisciplinary, with expertise in all aspects of clinical nutrition care; 4) The funds needed to support NSTs should be raised from the health care system; and 5) Further research is needed to evaluate the effects of NSTs in prevention and management of pediatric nutritional disorders, including cost effectiveness in different settings.