bluuebunny/crossref_metadata_2025 huggingface dataset:
A method to evaluate the three-dimensional roughness of fracture surfaces in brittle geomaterials
Authors: Tatone Bryan S. A. , Grasselli Giovanni
Published: December 2009

Conventionally, the evaluation of fracture surface roughness in brittle geomaterials, such as concrete and rock, has been based on the measurement and analysis of two-dimensional profiles rather than three-dimensional (3D) surfaces. The primary reason for doing so was the lack of tools capable of making 3D measurements. However, in recent years, several optical and mechanical measurement tools have become available, which are capable of quickly and accurately producing high resolution point clouds defining 3D surfaces. This paper provides a methodology for evaluating the surface roughness and roughness anisotropy using these 3D surface measurements. The methodology is presented step-by-step to allow others to easily adopt and implement the process to analyze their own surface measurement data. The methodology is demonstrated by digitizing a series of concrete fracture surfaces and comparing the estimated 3D roughness parameters with qualitative observations and estimates of the well-known roughness coefficient, Rs.
The subtleties of explicitly correlated Z-averaged perturbation theory: Choosing an R12 method for high-spin open-shell molecules
Authors: Wilke Jeremiah J. , Schaefer Henry F.
Published: December 2009

Explicitly correlated MP2-R12 and coupled cluster R12 methods have proven to be effective in achieving the basis set limit of correlated wave function methods. However, correlated methods for high-spin open-shell states are typically based on semicanonical orbitals, leading to an unrestricted formalism, which for double excitations requires three independent sets of amplitudes. In contrast, Z-averaged perturbation theory redefines the Hamiltonian with a symmetric exchange operator, thereby allowing a spin-restricted formulation with equivalent α and β subspaces. In the current work, we present a preliminary study of explicitly correlated ZAPT for second-order perturbation theory. The superior basis set convergence of R12 methods is demonstrated for a set of atomization energies, showing the R12 results to be competitive with common basis set extrapolation techniques, albeit at a fraction of the cost. Given the efficiency gains associated with the symmetric exchange operator, we suggest ZAPT as a candidate for reducing the cost of current open-shell MP2-R12 and CCSD(T)-R12 computations.
Global phase diagrams for a compressible polymer-solvent system using the full Tompa model
Authors: Gençaslan Mustafa , Keskin Mustafa
Published: December 2009

We present the global phase diagrams for a compressible polymer-solvent system at the mathematical double point and its environment by using the full Tompa model for varying numbers of segments in each polymer chain. A principal transition mechanism is a mathematical double point at which two critical lines meet and exchange branches. We present the critical lines in the density-density and the P, T planes in detail. The locations of all significant features of the phase diagrams are described and compared with Scott and van Konynenburg phase diagram classifications. We find the type II, type III or type IV phase diagram behaviors of the Scott and van Konynenburg classifications. It is also found that the critical lines and phase behavior are extremely sensitive to small modifications in the chain length parameter.
Impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field
Authors: Shalygin V. A. , Vorobjev L. E. , Firsov D. A. , Panevin V. Yu. , Sofronov A. N. , Melentyev G. A. , Antonov A. V. , Gavrilenko V. I. , Andrianov A. V. , Zakharyin A. O. , Suihkonen S. , Törma P. T. , Ali M. , Lipsanen H.
Published: December 2009

We report on the observation and experimental studies of impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field. The terahertz electroluminescence is observed in a wide range of doping levels (at noncompensated donor density from 4.5×1016 to 3.4×1018 cm−3). Spectra of terahertz luminescence and photoconductivity are studied by means of Fourier transform spectrometry. Distinctive features of the spectra can be assigned to intracenter electron transitions between excited and ground states of silicon and oxygen donors and to hot electron transitions to the donor states.
Role of photovoltaic effects on characterizing emission properties of InGaN/GaN light emitting diodes
Authors: Song Jae-Ho , Kim Ho-Jong , Ahn Byung-Jun , Dong Yanqun , Hong Sayong , Song Jung-Hoon , Moon Youngboo , Yuh Hwan-Kuk , Choi Sung-Chul , Shee Sangkee
Published: December 2009

Strong photovoltaic effects on photoluminescence (PL) spectra in InGaN/GaN blue light emitting diodes were investigated. Due to severe carrier escape from quantum wells, significant photovoltaic effects occur in PL measurement in open-circuit condition, which strongly affect the PL peak position and intensity. We reveal that proper correlation between electroluminescence and PL peak positions cannot be obtained without proper consideration of the photovoltaic effects. By changing sample temperature and the PL excitation power, the generated photovoltage varies in the range of 2.0 to 2.6 V. We show that in the open-circuit condition, which is the usual case, the determination of radiative efficiency by measuring the PL intensity ratio of low-and high-temperature cannot be accurate, and the excitation intensity dependent PL cannot be solely intrinsic either. Both the absorption of incident laser and the carrier escape from the quantum well are bias-sensitive. By a simple and straightforward method, we determined that 51% of photogenerated carriers escaped in short-circuit condition.
On a fourth order degenerate parabolic equation in higher space dimensions
Authors: Li Junjie
Published: December 2009

We are concerned with the existence of non-negative solutions to the following initial boundary value problem of a fourth order degenerate parabolic equation in higher space dimensions: ut+div(|u|n∇Δu)=0 in Ω×(0,T], ∂u/∂ν=(∂/∂ν)Δu=0 on ∂Ω×(0,T], and u(x,0)=u0(x) in Ω.
Magnetism of amorphous carbon nanofibers
Authors: Ma S. , Xia J. H. , Srikanth Vadali V. S. S. , Sun X. , Staedler T. , Jiang X. , Yang F. , Zhang Z. D.
Published: December 2009

Amorphous carbon nanofibers (ACNFs) have been synthesized by a thermal chemical vapor deposition technique. The ACNFs grow as two branches perpendicular to {111} facets of a catalytic copper nanoparticle. The carbon nanofibers are composed of disordered localized nanofragments which in turn consist of several graphene layers. The ACNFs show a paramagnetic characteristics at 2, 5, and 10 K. The magnetic moments are suggested to originate from a large amount of defects in the graphene layers of the nanofragments.
Magnetization profile of Ir in a MnIr/CoFe exchange bias system evaluated by hard x-ray resonant magnetic reflectivity
Authors: Doi Shuuichi , Nomura Kenji , Awaji Naoki , Hosoito Nobuyoshi , Yamagishi Ryuichiro , Suzuki Motohiro
Published: December 2009

The magnetization profile of Ir in a MnIr/CoFe exchange bias system was examined precisely by x-ray resonant magnetic reflectivity at Ir L3 absorption edge. By using a stacked multilayer sample of MgO/[Ru(40 Å)/Mn75Ir25(35 Å)/Co70Fe30(40 Å)]15/Ru, we found that the Ir was magnetized at the MnIr/CoFe interface with a width of 4.3 Å. The obtained magnetic amplitude was 0.02 r0 and the direction of magnetization was parallel to that of Co.
Development of a DNA probe using barium strontium titanate
Authors: Kocanda Martin , Abdel-Motaleb Ibrahim
Published: December 2009

In this paper we report on the development of an electronic DNA sensor probe assembly using barium strontium titanate (BST) applied by pulsed laser deposition in conjunction with optical spectroscopy and impedance spectroscopy methods. To verify the binding of the probe to the BST, Fourier transform infrared (FTIR) spectroscopy and attenuated total reflectance (ATR) techniques were employed. FTIR and ATR were employed to verify the hybridization of the probe to an oligonucleotide target. In addition to the FTIR technique, direct capacitance and impedance spectroscopy measurements were used to verify the ability of the probe binding to the ceramic substrate and also the hybridization of the target DNA strand to the probe DNA strand. The proposed design has the advantages of label-free detection and large detectable capacitance changes upon hybridization, and does not require the application of a gold electrode layer.
Effect of Fe-doping concentration on microstructure, electrical, and magnetic properties of Pb(Zr0.5Ti0.5)O3 thin films prepared by chemical solution deposition
Authors: Bai W. , Meng X. J. , Lin T. , Tian L. , Jing C. B. , Liu W. J. , Ma J. H. , Sun J. L. , Chu J. H.
Published: December 2009

The highly (l00) oriented Pb(Zr0.5Ti0.5)O3 thin films with different Fe3+ doping concentrations were fabricated on LaNiO3-coated silicon substrates by chemical solution deposition. And the microstructure, ferroelectric, leakage, and magnetic properties were investigated. The results indicate that incorporation of Fe3+ into PZT thin films can promote the degree of the lattice distortion and greatly improve the surface roughness. In comparison with the pure PZT sample, the ferroelectric hysteresis loops of Fe-doped PZT samples demonstrate larger and larger polarizations and coercive fields with the increase in Fe3+ doping amount. Moreover, leakage mechanism of present films evolves from the space charge limited conduction to the “modified” space charge limited conduction, and then returns to the space charge limited conduction with increasing Fe3+ doping concentration. The occurrence of exchange bias in these Fe-doped PZT samples implies that the magnetic exchange interaction can be explained by the bound magnetic polaron model.
Rayleigh scattering from gaseous phase nanoparticles synthesized by pulsed laser ablation of ZnO
Authors: Mohanta Antaryami , Thareja Raj K.
Published: December 2009

Rayleigh scattering and photoluminescence techniques are used to show the evidence of formation of ZnO nanoparticles in gaseous phase due to condensation of laser ablated ZnO plasma species in air. The intensity of Rayleigh scattered signal increases with the increase in time delays between the probe and the ablating pulse. Plasma emission dominates close to the target surface whereas Rayleigh scattered signal dominates at larger distances where nanoparticles are abundant. Photoluminescence spectra are observed in laser ablated ZnO plasma using fourth harmonic of a Nd:YAG (yttrium aluminum garnet) laser as an excitation source, which confirms the formation of ZnO nanoparticles in gaseous phase. The photoluminescence profiles observed from gaseous phase ZnO nanoparticles show blueshift with respect to that observed from bulk ZnO under similar excitation condition implying quantum confinement.
Enhanced laser cooling of CO2–Xe gas using (02) excitation
Authors: Shin Seungha , Kaviany Massoud
Published: December 2009

Laser irradiation with a 9.6 μm wavelength resonant with the (0200) level improves the anti-Stokes cooling of CO2 gas. Excitation of the (0200) level increases cooling by producing a larger population of (0001), despite the higher-energy photon absorption, compared to a (1000) level excitation. Further selection of macroconditions (temperature, pressure, Xe diluent atomic fraction, and geometric parameters) enhances cooling by reducing parasite gas conduction through slower thermal energy transport and increasing the nonequilibrium population of the excited (0001) level by fast species diffusion and small collisional relaxation. We include reabsorption, and then find the conditions for optimal cooling.
Generation and recombination rates at ZnTe:O intermediate band states
Authors: Wang Weiming , Lin Albert S. , Phillips Jamie D. , Metzger Wyatt K.
Published: December 2009

Carrier generation and recombination processes of ZnTeO thin films are studied by time-resolved photoluminescence, where carrier lifetimes at oxygen states and the conduction band are inferred to be >1 μs and <100 ps, respectively. The radiative recombination coefficient for optical transitions from oxygen states to the valence band is extracted to be 1.2×10−10 cm3 sec−1 based on the excitation dependence of decay time constants. Rate equation analysis further suggests an increase in electron lifetime at the conduction band as oxygen states occupation is critical in achieving high conversion efficiency for solar cells based on multiphoton processes in these materials.
Co doped ZnO(0001)-Zn by diffusion method and its magnetic properties
Authors: Xie W. G. , Xie F. Y. , Yu X. L. , Xue K. , Xu J. B. , Chen J. , Zhang R.
Published: December 2009

The diffusion behaviors of Co clusters on clean ZnO(0001)-Zn single crystal surface and their magnetic properties are studied. Co clusters are deposited on the clean ZnO(0001)-Zn surface at room temperature and then undergone ultrahigh vacuum annealing until fully reconstructed. The replacement of Zn2+ by Co2+ is confirmed by scanning tunneling microscopy and x-ray photoelectron spectroscopy. The Co doped ZnO shows a weak ferromagnetism at room temperature with a saturation magnetic moment of 1.08 μB/Co. Our observations indicate that surface Zn vacancies facilitate Co diffusion, and the interplay of Co ion with internal O vacancies leads to the ferromagnetism.
Phase transition in tetragonal hen egg-white lysozyme crystals
Authors: Svanidze A. V. , Huth H. , Lushnikov S. G. , Kojima Seiji , Schick C.
Published: December 2009

Lattice dynamics of tetragonal hen egg-white lysozyme crystals was studied by Brillouin light scattering and differential ac-nanocalorimetry with controlled relative humidity from 298 to 330 K. Temperature dependences of fast quasitransverse phonon velocity and integral intensity were found to exhibit anomalies in the vicinity of 306 K. An anomaly in the temperature behavior of heat capacity was also observed near this temperature. It is concluded that the anomalies point to a structural phase transition. Possible mechanisms of phase transition in lysozyme crystals are discussed.
Ionic diffusion and the topological origin of fragility in silicate glasses
Authors: Smedskjaer Morten M. , Mauro John C. , Yue Yuanzheng
Published: December 2009

Mass transport in liquids and glass is intimately connected to the structure and topology of the disordered network. To investigate this problem, we measure the ionic diffusivity and fragility of a series of iron-bearing alkali-alkaline earth silicate glasses, substituting different types of alkali and alkaline earth cations while keeping the same ratio of network modifiers. Diffusion is studied around the glass transition temperature (Tg) under a reducing atmosphere, leading to a reduction of Fe3+ to Fe2+, and inward diffusion of the modifier cations. In the SiO2–CaO–Fe2O3–A2O (A=Na, K, Rb, or Cs) glass series, we find that the Ca2+ ions diffuse faster than alkali ions and that the activation energy of the Ca2+ diffusion decreases with alkali size, a trend that is coincident with a decrease in liquid fragility. We have established a simple model for accurately describing the correlation between the fragility index (m) and Tg based on a topological consideration of the glass network. The model builds on a temperature-dependent constraint approach where the Vogel temperature serves as a rigidity percolation threshold. This follows from our derivation of the Vogel–Fulcher–Tammann equation of viscosity from the more accurate Mauro–Yue–Ellison–Gupta–Allan equation. The established model provides an excellent prediction of the relationship between fragility and Tg, except for the MgO-containing glass where Mg2+ is known to play a unique topological role in the network. This trend is in coincidence with the considerably faster inward diffusion of Mg2+ in comparison to other alkaline earth cations.
Molecular modeling of intermolecular and intramolecular excluded volume interactions for polymers at interfaces
Authors: Charlaganov M. , Leermakers F. A. M.
Published: December 2009

A hybrid modeling approach is proposed for inhomogeneous polymer solutions. The method is illustrated for the depletion problem with polymer chains up to N=103 segments in semidilute solutions and good solvent conditions. In a three-dimensional volume, a set of freely jointed chains is considered for which the translational degrees of freedom are sampled using a coarse grained Monte Carlo simulation and the conformational degrees of freedom of the chains are computed using a modified self-consistent field theory. As a result, both intramolecular and intermolecular excluded volume effects are accounted for, not only for chains near the surface, but in the bulk as well. Results are consistent with computer simulations and scaling considerations. More specifically, the depletion thickness, which is a measure for the bulk correlation length, scales as δ∝φ−0.75 and converges to the mean field result in the concentrated regime.
Theoretical analysis of anharmonic coupling and cascading Raman signals observed with femtosecond stimulated Raman spectroscopy
Authors: Mehlenbacher Randy D. , Lyons Brendon , Wilson Kristina C. , Du Yong , McCamant David W.
Published: December 2009

We present a classical theoretical treatment of a two-dimensional Raman spectroscopy based on the initiation of vibrational coherence with an impulsive Raman pump and subsequent probing by two-pulse femtosecond stimulated Raman spectroscopy (FSRS). The classical model offers an intuitive picture of the molecular dynamics initiated by each laser pulse and the generation of the signal field traveling along the probe wave vector. Previous reports have assigned the observed FSRS signals to anharmonic coupling between the impulsively driven vibration and the higher-frequency vibration observed with FSRS. However, we show that the observed signals are not due to anharmonic coupling, which is shown to be a fifth-order coherent Raman process, but instead due to cascades of coherent Raman signals. Specifically, the observed vibrational sidebands are generated by parallel cascades in which a coherent anti-Stokes or Stokes Raman spectroscopy (i.e., CARS or CSRS) field generated by the coherent coupling of the impulsive pump and the Raman pump pulses participates in a third-order FSRS transition. Additional sequential cascades are discussed that will give rise to cascade artifacts at the fundamental FSRS frequencies. It is shown that the intended fifth-order FSRS signals, generated by an anharmonic coupling mechanism, will produce signals of ∼10−4 ΔOD (change in the optical density). The cascading signals, however, will produce stimulated Raman signal of ∼10−2 ΔOD, as has been observed experimentally. Experiments probing deuterochloroform find significant sidebands of the CCl3 bend, which has an E type symmetry, shifted from the A1 type C–D and C–Cl stretching modes, despite the fact that third-order anharmonic coupling between these modes is forbidden by symmetry. Experiments probing a 50:50 mixture of chloroform and d-chloroform find equivalent intensity signals of low-frequency CDCl3 modes as sidebands shifted from both the C–D stretch of CDCl3 and the C–H stretch of CHCl3. Such intermolecular sidebands are allowed in the cascade mechanism, but are expected to be extremely small in the fifth-order frequency modulation mechanism. Each of these observations indicates that the observed signals are due to cascading third-order Raman signals.
Electrostatically driven droplets deposited on superhydrophobic surfaces
Authors: Bormashenko Edward , Pogreb Roman , Stein Tamir , Whyman Gene , Hakham-Itzhaq Mordechai
Published: December 2009

The behavior of dielectric droplets deposited on a superhydrophobic surface and exposed to a constant and uniform electric field is investigated. The change in the droplet shape is described by a linear dependence of its eccentricity on the applied electric field. The proposed control of the droplet shape with the electric field may serve as an alternative to electrowetting technologies.
The effect of environment on the radial breathing mode of supergrowth single wall carbon nanotubes
Authors: Araujo P. T. , Fantini C. , Lucchese M. M. , Dresselhaus M. S. , Jorio A.
Published: December 2009

It has been shown that “supergrowth” single wall carbon nanotubes (SWNTs) exhibit a radial breathing mode frequency ωRBM dependence on tube diameter dt given by ωRBM=227/dt. This result gave rise to two distinct scenarios for SWNTs: one for the supergrowth radial breathing mode and another for all the other samples reported in the literature. Here we show that, by dispersing the supergrowth SWNTs in surfactant or bringing them into interacting bundles, it is possible to merge these two scenarios, where now the supergrowth SWNT properties are similar to all SWNT properties reported so far in the literature.
Spatial and temporal heterogeneity in supercooled glycerol: Evidence from wide field single molecule imaging
Authors: Mackowiak Stephan A. , Herman Tobias K. , Kaufman Laura J.
Published: December 2009

We quantify spatial and temporal heterogeneity in supercooled glycerol at T=Tg+14 K employing a widefield detection scheme and using rubrene as the probe molecule. We describe how microscopy configuration affects measured intensity, linear dichroism, and the resulting autocorrelation function. Rotational relaxation times τc of 241 probe molecules are measured, and we find spatial heterogeneity over almost three orders of magnitude present at this temperature. An approach for detecting temporally heterogeneous molecules and quantifying exchange times is introduced. Of molecules that can be assessed, ∼15% display evidence of temporal heterogeneity–changes of τc during the measurement–that are detected with the analysis technique employed. Exchanges between dynamically disparate environments occur rarely but in the proportion expected given the rarity of very slowly rotating molecules present. Heterogeneous molecules are characterized by persistence and exchange times. Median exchange and persistence times of the molecules identified as heterogeneous relative to glycerol’s structural relaxation time τα are found to be τex/τα=202 and τpers/τα=405, respectively. These results are discussed in the context of values of exchange times that have been determined in other experiments.
Temperature dependent structural properties of nanocrystalline SnS structures
Authors: Devika M. , Reddy N. Koteeswara , Patolsky Fernando , Ramesh K. , Gunasekhar K. R.
Published: December 2009

This letter explores the structural behavior of nanocrystalline tin mono sulfide (SnS) structures with respect to temperature (100–600 K). These studies emphasize that the structural properties of SnS nanocrystalline structures depend on the surrounding temperature. The lattice parameters of SnS nanocrystals slightly varied like their microstructures with the increase of temperature. These changes strongly influence the optical properties of SnS nanostructures. On the other hand, the structures exhibited higher strain (∼0.44%) than that of microstructured (0.3%) and bulk (0.12%) counterparts. The observed results are discussed under the light of existing concepts and reported.
Improved hole injection and transport of organic light-emitting devices with an efficient p-doped hole-injection layer
Authors: Zhang Dan-Dan , Feng Jing , Wang Hai , Bai Yu , Chen Qi-Dai , Liu Shi-Yong , Sun Hong-Bo
Published: December 2009

A 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine thin film doped with Fe3O4 has been demonstrated an efficient p-type hole-injection layer (HIL) in organic light-emitting devices (OLEDs). The tris-(8-hydroxyquinoline) aluminum-based OLEDs with the p-type HIL exhibit a very low turn-on voltage of 2.4 V and a high luminance of 29 360 cd/m2 at 8 V, while it is 3 V and 6005 cd/m2, respectively, for the nondoped devices. The improvement in the device performance is clarified as arising from the improved hole injection and transport by the results of ultraviolet/visible/near-infrared absorption, x-ray photoelectron spectra and current density-voltage characteristics of hole-only devices.
Application of a composite plasmonic substrate for the suppression of an electromagnetic mode leakage in InGaN laser diodes
Authors: Perlin Piotr , Holc Katarzyna , Sarzyński Marcin , Scheibenzuber Wolfgang , Marona Łucja , Czernecki Robert , Leszczyński Mike , Bockowski Michał , Grzegory Izabella , Porowski Sylwester , Cywiński Grzegorz , Firek Piotr , Szmidt Jan , Schwarz Ulrich , Suski Tadek
Published: December 2009

We demonstrate an InGaN laser diode, in which the waveguiding quality of the device is improved by the introduction of highly doped (plasmonic) layer constituting an upper part of the GaN substrate. Thanks to this, we were able to suppress the electromagnetic mode leakage into the substrate without generating additional strain in the structure, in contrast to the typical design relying on thick AlGaN claddings. The plasmonic substrate is built as a stack of gallium nitride layers of various electron concentrations deposited by a combination of hydride epitaxy and high-pressure solution method. The mentioned improvements led to the reduction of the threshold current density of our devices down to 2 kA/cm2 and to the optimization of the near and far field pattern.
Morphology and defect properties of the Ge–GeO2 interface
Authors: Tsetseris L. , Pantelides S. T.
Published: December 2009

Ge-based devices, currently being pursued as replacement of their Si counterparts, typically contain a germanium oxide layer next to the substrate. Here we show using first-principles calculations that, in contrast to Si technology, hydrogenation and fluorination are not effective ways of passivating Ge–GeO2 interfacial Pb centers with a Ge dangling bond (DB). Moreover, we identify DB geometries that differ from the Pb structures and we find that the Ge–GeO2 boundary has a higher atomic-scale roughness than the Si–SiO2 interface. These key differences in interface morphology and defect properties are consistent with experimental data.
Photoluminescence properties of midinfrared dilute nitride InAsN epilayers with/without Sb flux during molecular beam epitaxial growth
Authors: Chen Rui , Phann S. , Sun H. D. , Zhuang Q. , Godenir A. M. R. , Krier A.
Published: December 2009

We report on the comparative studies of photoluminescence (PL) properties of molecular beam epitaxy grown dilute InAsN epilayers with and without antimony (Sb) flux during the growth. Both samples exhibit strong midinfrared (MIR) emission at room temperature, while the sample with Sb flux has much higher intensity. At low temperatures, these samples exhibit totally different PL features in terms of line width, peak position, intensity, and their dependences on temperature and excitation density. Our results clearly indicate that part of Sb atoms serve as a surfactant that effectively improves the optical quality of MIR dilute nitrides.
Thermodynamic line tension of a molecular solid
Authors: Rusanov A. I.
Published: December 2009

For a molecular solid with dispersion forces, a particular expression is derived relating thermodynamic line tension to thermodynamic surface tension and the crystal spacing. Using recent data on the local Irving–Kirkwood stress tensor at the slit edge, local surface tension near the crystal edge and the line tension of the edge are estimated. This is the first estimation of the thermodynamic line tension for a molecular cubic crystal in the literature.
Microchannel flows with superhydrophobic surfaces: Effects of Reynolds number and pattern width to channel height ratio
Authors: Cheng Y. P. , Teo C. J. , Khoo B. C.
Published: December 2009

Superhydrophobic surfaces are widely adopted for reducing the flow resistance in microfluidic channels. The structures on the superhydrophobic surfaces may consist of longitudinal grooves, transverse grooves, posts, holes, etc. In this paper their effective slip performances are systematically studied and compared in detail through numerical simulations. The numerical results show that channel wall confinement effects have a positive influence on the effective slip length for square posts and longitudinal grooves, and a negative influence for square holes and transverse grooves. Square posts, holes, and transverse grooves all exhibit deteriorating effective slip performances at higher Reynolds numbers, while the effective slip performance of longitudinal grooves remains independent of the Reynolds number. For small pattern width to channel height ratios and at low Reynolds numbers, for low shear-free fractions, the effective slip length of square posts is equivalent of that of transverse grooves, and both geometries yield effective slip lengths which are in turn lower than those of square holes and longitudinal grooves. With increasing shear-free fractions, the effective slip length of square posts surpasses that of square holes and longitudinal grooves, but it becomes lower than that of longitudinal grooves at high Reynolds numbers or large pattern width to channel height ratios. Scaling laws for the effective slip length of superhydrophobic surfaces with square posts, square holes, and transverse grooves have previously been reported for shear-driven flows. This study extends the validity of these scaling laws to pressure-driven channel flows, even at high Reynolds numbers. The findings in this study serve as a useful guide for applications involving the reduction in flow resistance in microchannels containing superhydrophobic surfaces.
Four-component relativistic theory for nuclear magnetic shielding: Magnetically balanced gauge-including atomic orbitals
Authors: Cheng Lan , Xiao Yunlong , Liu Wenjian
Published: December 2009

It is recognized only recently that the incorporation of the magnetic balance condition is absolutely essential for four-component relativistic theories of magnetic properties. Another important issue to be handled is the so-called gauge problem in calculations of, e.g., molecular magnetic shielding tensors with finite bases. It is shown here that the magnetic balance can be adapted to distributed gauge origins, leading to, e.g., magnetically balanced gauge-including atomic orbitals (MB-GIAOs) in which each magnetically balanced atomic orbital has its own local gauge origin placed on its center. Such a MB-GIAO scheme can be combined with any level of theory for electron correlation. The first implementation is done here at the coupled-perturbed Dirac–Kohn–Sham level. The calculated molecular magnetic shielding tensors are not only independent of the choice of gauge origin but also converge rapidly to the basis set limit. Close inspections reveal that (zeroth order) negative energy states are only important for the expansion of first order electronic core orbitals. Their contributions to the paramagnetism are therefore transferable from atoms to molecule and are essentially canceled out for chemical shifts. This allows for simplifications of the coupled-perturbed equations.
Suppression of Alk8-mediated Bmp signaling cell-autonomously induces pancreatic β-cells in zebrafish
Authors: Chung Won-Suk , Andersson Olov , Row Richard , Kimelman David , Stainier Didier Y. R.
Published: December 2009

Bmp signaling has been shown to regulate early aspects of pancreas development, but its role in endocrine, and especially β-cell, differentiation remains unclear. Taking advantage of the ability in zebrafish embryos to cell-autonomously modulate Bmp signaling in single cells, we examined how Bmp signaling regulates the ability of individual endodermal cells to differentiate into β-cells. We find that specific temporal windows of Bmp signaling prevent β-cell differentiation. Thus, future dorsal bud-derived β-cells are sensitive to Bmp signaling specifically during gastrulation and early somitogenesis stages. In contrast, ventral pancreatic cells, which require an early Bmp signal to form, do not produce β-cells when exposed to Bmp signaling at 50 hpf, a stage when the ventral bud-derived extrapancreatic duct is the main source of new endocrine cells. Importantly, inhibiting Bmp signaling within endodermal cells via genetic means increased the number of β-cells, at early and late stages. Moreover, inhibition of Bmp signaling in the late stage embryo using dorsomorphin, a chemical inhibitor of Bmp receptors, significantly increased β-cell neogenesis near the extrapancreatic duct, demonstrating the feasibility of pharmacological approaches to increase β-cell numbers. Our in vivo single-cell analyses show that whereas Bmp signaling is necessary initially for formation of the ventral pancreas, differentiating endodermal cells need to be protected from exposure to Bmps during specific stages to permit β-cell differentiation. These results provide important unique insight into the intercellular signaling environment necessary for in vivo and in vitro generation of β-cells.
Mechanism of active targeting in solid tumors with transferrin-containing gold nanoparticles
Authors: Choi Chung Hang J. , Alabi Christopher A. , Webster Paul , Davis Mark E.
Published: December 2009

PEGylated gold nanoparticles are decorated with various amounts of human transferrin (Tf) to give a series of Tf-targeted particles with near-constant size and electrokinetic potential. The effects of Tf content on nanoparticle tumor targeting were investigated in mice bearing s.c. Neuro2A tumors. Quantitative biodistributions of the nanoparticles 24 h after i.v. tail-vein injections show that the nanoparticle accumulations in the tumors and other organs are independent of Tf. However, the nanoparticle localizations within a particular organ are influenced by the Tf content. In tumor tissue, the content of targeting ligands significantly influences the number of nanoparticles localized within the cancer cells. In liver tissue, high Tf content leads to small amounts of the nanoparticles residing in hepatocytes, whereas most nanoparticles remain in nonparenchymal cells. These results suggest that targeted nanoparticles can provide greater intracellular delivery of therapeutic agents to the cancer cells within solid tumors than their nontargeted analogs.
The relationship between verbal and gestural contributions in conversation
Authors: Gerwing Jennifer , Allison Meredith
Published: December 2009

Gestures and their concurrent words are often said to be meaningfully related and co-expressive. Research has shown that gestures and words are each particularly suited to conveying different kinds of information. In this paper, we describe and compare three methods for investigating the relationship between gestures and words: (1) an analysis of deictic expressions referring to gestures, (2) an analysis of the redundancy between information presented in words vs. in gestures, and (3) an analysis of the semantic features represented in words and gestures. We also apply each of these three methods to one set of data, in which 22 pairs of participants used words and gestures to design the layout of an apartment. Each of the three analyses revealed a different picture of the complementary relationship between gesture and speech. According to the deictic analysis, participant speakers marked only a quarter of their gestures as providing essential information that was missing from the speech, but the redundancy analysis indicated that almost all gestures contributed information that was not in the words. The semantic feature analysis showed that participants conveyed spatial information in their gestures more often than in their words. A follow-up analysis showed that participants contributed categorical information (i.e., the name of each room) in their words. Of the three methods, the semantic feature analysis yielded the most complex picture of the data, and it served to generate additional analyses. We conclude that although analyses of deictic expressions and redundancy are useful for characterizing gesture use in differing conditions, the semantic feature method is best for exploring the complementary, semantic relationship between gesture and speech.
Branches, fables, exempla, échantillons de lune mangée
Authors: Barre Aurélie , Leplatre Olivier
Published: December 2009

Quelques vers d’une étrange aventure évoquée par Renart dans “Le Jugement de Renart” sont le point de départ d’une réflexion sur le reflet de lune et ses déclinaisons littéraires. Ces vers composent une structure archétypale autour du miroitement de la lune devenue à la surface de l’eau, sous l’impulsion du désir ou de la ruse animale, un appétissant fromage. L’histoire de l’astre mangé retracée dans cette étude a pour points de repère toute une série de fables (Marie de France, Jean de La Fontaine…), et d’exempla, de Pierre Alphonse à Nicole Bozon, qui appartiennent à la mémoire collective et déploient le schéma d’une survivance imaginaire. Les éléments s’y ordonnent selon de multiples combinaisons, interrogeant le statut de l’image et son rapport au désir. Blancs enfants de choeur de la Lune, Et lunologues éminents, Leur Eglise ouvre à tout venant, Claire d’ailleurs comme pas une. (J. Laforgue, “Pierrots”)
L’homme sur l’arbre et l’escargot
Authors: Sánchez Santiaga Hidalgo
Published: December 2009

L’article se propose de faire la lumière sur une scène représentée dans un chapiteau du cloître de Pampelune, sculptée au début du XIVe siècle. On y reconnaît un homme sur un chêne où se trouve un escargot. Sous l’arbre guettent, gueule ouverte, deux dragons. Les détails du chapiteau sont examinés, puis interprétés à la lumière de deux fables du recueil d’Eudes de Cheriton : d’abord, la parabole des plaisirs illusoires du monde ou de l’homme poursuivi par la licorne, un récit d’origine orientale et transmis vers l’Occident par le Calila et Dimna, puis diffusé par divers canaux ; ensuite, la fable De Testudine, laquelle fait référence à l’escargot. Le sens moral du chapiteau, destiné à une communauté de chanoines réguliers, peut être lu ainsi comme un avertissement contre les dangers des séductions du monde, particulièrement contre la richesse.
Renard e il suo Autore
Authors: Lecco Margherita
Published: December 2009

L’étude porte sur le tardif Renart le Contrefait, qui, dans le groupe des épigones renardiens, occupe une place intermédiaire entre, d’un côté, Renart le Bestourné et le Couronnement Renart, qui transforment le renard en allégorie satirique, et, de l’autre, Renart le Novel, qui mélange les tons et les messages et “casse” l’allégorie autant que le personnage de Renard traditionnel. L’étude se focalise en particulier sur l’Auteur, le narrateur et le protagoniste. Le sujet intéresse dans la mesure où l’auteur déclare, au début, se servir de Renard pour pouvoir dire des choses sans avoir à subir des représailles. L’Auteur prend le masque de Renard pour dire ’par escript couvert’ ce qu’il n’ose pas exprimer ouvertement. Petit à petit, toutefois, Renard “devient autonome”. L’essentiel se joue alors par les avant-textes qui sont convoqués, ici analysés dans leur fonctionnalité. Cela se passe par trois dédoublements: L’Auteur (A) devient personnage (lorsqu’il parle de sa vie: c’est B), et se cache derrière le personnage de Renard (C), qui se superpose à sa voix, en mêlant les fonctions d’auteur, de narrateur et de personnage (D). Entre les pôles de A et de D, toute l’histoire de l’homme se déroule, à travers bien de textes anciens et modernes, répartis en thèmes/fils conducteurs qui donnent un ordre à une oeuvre décousue et totalisante.
La faune marine dans le Voyage de Saint Brendan anglo-normand
Authors: Saux Françoise H.M. Le
Published: December 2009

Le Voyage de St Brendan présente un univers hybride, à la fois suffi samment réaliste pour y reconnaître des phénomènes scientifiquement vérifiables et profondément symbolique dans ses connotations. Les animaux marins qui y figurent ne sont en rien anthropomorphes, mais se démarquent aussi nettement de l’image donnée par les bestiaires, dans la mesure où leurs actions et caractéristiques ne sont pas en soi porteuses de sens. La faune aquatique est à la fois une menace et une présence protectrice, la providence divine déterminant de cas en cas la nature des rencontres entre moines et poissons, baleines et monstres marins. Ces bêtes sont en elles-mêmes moralement neutres, guidées par l’instinct; mais Benedeit exploite ce trait pour mettre en exergue la soumission de ces créatures à la volonté du Créateur, et leur importance pour Brendan et ses compagnons.
Fable and Lutheranization in 16th and early 17th century Sweden
Authors: Zillén Erik
Published: December 2009

This paper argues that the Reformation and the adoption of Lutheranism as a state religion had a great and lasting impact on the history of the Aesopic fable in Sweden. During the 16th and early 17th century, it is shown, the genre was explicitly Lutheranized and ascribed vital functions in the process of Lutheran confessionalization within the Swedish national state. In particular, it is demonstrated how the fable – following the models of Melanchthon and Luther – was used in the teaching of classical languages at school and, in the Swedish language, served as an instrument for the moral and religious education of the common people.
Metacognitive monitoring and strategic behaviour in working memory performance
Authors: Touron Dayna R. , Oransky Natalie , Meier Matthew E. , Hines Jarrod C.
Published: December 2009

Research indicates that cognitive age differences can be influenced by metacognitive factors. This research has generally focused on simple memory tasks. Age differences in working memory (WM) performance are pronounced, but are typically attributed to basic cognitive deficits rather than metacognitive factors. However, WM performance can be influenced by strategic behaviour that might be driven by metacognitive monitoring. In the current project, we attempted to connect these lines of research by examining age differences in metacognitive WM monitoring and strategies. In Experiment 1, younger and older adult participants completed a computerized operation span task in conditions that either required or did not require monitoring reports. Participants in the monitoring condition predicted and postdicted global performance for each block and rated their responses following each trial within a block. In Experiment 2, participants also reported their trial-level strategic approach. In contrast to the age equivalence typically found for simple memory monitoring, results demonstrated age differences in WM monitoring accuracy. Overall age differences in strategy use were not found, but using effective strategies benefited older adults’ performance more than younger adults'. Furthermore, age-related differences in the WM task appear to be mediated by the accuracy of performance monitoring.
Two measures of task-specific inhibition
Authors: Astle Duncan E. , Jackson Georgina M. , Swainson Rachel
Published: December 2009

Inhibition has been implicated as an important mechanism for task-set control, ensuring the efficient selection of the to-be-performed task over alternative possibilities. Across three experiments we demonstrated the effects of two potentially different types of task inhibition. The first is the inhibition of a task that concurrently affords an incongruent response, which is labelled dimension inhibition (Goschke, 2000). Using targets that afford three tasks, we demonstrated that this only occurs when a single alternative task affords an incongruent response, with the inhibition being specific to that task. The second type of inhibition that we observed was backwards inhibition—the suppression of a recently abandoned task-set (Mayr & Keele, 2000). Unlike dimension inhibition, backwards inhibition was not triggered by the response incongruence of the unperformed tasks, or even whether the target afforded responses via the unperformed tasks. These two purported types of inhibition did not co-occur, and neither did the factors of response congruence and whether that task was recently abandoned interact. We therefore suggest that task-specific inhibition can be applied/triggered differently depending upon the paradigm, perhaps depending upon the extent to which alternative tasks, and therefore potentially other responses, are triggered by the target.
A large-scale comparison of prospective and retrospective memory development from childhood to middle age
Authors: Maylor Elizabeth A. , Logie Robert H.
Published: December 2009

We present the first large-scale comparison of prospective memory (PM) and retrospective memory (RM) from 8 to 50 years of age ( N = 318,614). Participants in an Internet study were asked to remember to click on a smiley face (single-trial event-based PM test) and to indicate whether/where a picture had changed from study to test (single-trial RM test), in both cases after retention intervals filled with working-memory tests and questionnaires. Both PM and RM improved during childhood; however, whereas maximal PM was reached by teenagers, with approximately linear decline through the 20s–40s, RM continued to improve through the 20s and 30s. On both tests, females outperformed males and achieved maximal success at earlier ages. Strikingly, 10–11-year-old girls performed significantly better than females in their late 20s on the PM test. The presence of the smiley face at encoding and temporal uncertainty (expecting it “later” rather than at the “end” of the test) both benefited PM; these effects decreased and increased, respectively, from childhood to middle age. The findings demonstrate that in a cross-sectional study (a) developmental trajectories are qualitatively different between PM and RM, and (b) the relative influence of PM cues differs between younger and older ages.
Toward a Theory of Status Consumption in Less Industrialized Countries
Authors: Üstüner Tuba , Holt Douglas B.
Published: December 2009

How does status consumption operate among the middle classes in less industrialized countries (LICs)—those classes that have the spending power to participate effectively in consumer culture? Globalization research suggests that Bourdieu’s status consumption model, based upon Western research, does not provide an adequate explanation. And what we call the global trickle-down model, often invoked to explain LIC status consumption, is even more imprecise. We study the status consumption strategies of upper-middle-class Turkish women in order to revise three of Bourdieu’s most important concepts—cultural capital, habitus, and consumption field—to propose a theory specific to the LIC context. We demonstrate that cultural capital is organized around orthodox practice of the Western Lifestyle myth, that cultural capital is deterritorialized and so accrues through distant textbook-like learning rather than via the habitus, and that the class faction with lower cultural capital indigenizes the consumption field to sustain a national social hierarchy.
Resonances of a nonlinear SDOF system with time-delay in linear feedback control
Authors: El-Bassiouny A F , El-kholy S
Published: December 2009

The primary and subharmonic resonances of a nonlinear single-degree-of-freedom (SDOF) system under feedback control with a time delay have been studied by means of an asymptotic perturbation technique. Both external (forcing) and parametric excitations have been included. By means of the averaging method and multiple scales method, two slow-flow equations for the amplitude and phase of the primary and subharmonic resonances and all other parameters are obtained, respectively. The steady state solutions (fixed points) for the original system are investigated. The stability of the fixed points is examined by using the variational method. The effect of the feedback gains, time-delay, the coefficient of cubic term, the coefficients of external and parametric excitations on the steady state responses are investigated and the results are presented as plots of the steady state response amplitude versus the detuning parameter. The results obtained by the two methods are in excellent agreement. There exist saddle node bifurcations for the case of primary resonance and the solutions lose stability for the case of resonance subharmonic.