bluuebunny/crossref_metadata_2025 huggingface dataset:
On the origin of Saturn's outer auroral emission
Authors: Grodent Denis , Radioti Aikaterini , Bonfond Bertrand , Gérard Jean‐Claude
Published: August 2010

Ultraviolet Hubble Space Telescope images reveal a faint but distinct auroral emission equatorward of the main ring of emission of Saturn's southern polar region. This outer auroral emission is only visible near the nightside limb for the strongly tilted viewing geometry achieved in January 2004. We model the limb‐brightening amplification of this emission, and we show that the observations are compatible with an ∼7° wide emission ring approximately centered on the 67°S parallel. The 1.7 kR brightness of this emission requires an injected electron energy flux of ∼0.3 mW m−2. The outer auroral emission maps to a region of the equatorial plane between 4 and 11 RS. We suggest that a population of suprathermal electrons observed by Cassini can provide more than the required energy flux without the need for field‐aligned acceleration. This auroral UV emission may also be associated with energetic neutral oxygen and hydrogen atoms originating from the energetic protons and O+ of magnetosphere and/or with a secondary infrared auroral oval.
Modeling photoelectron transport in the Martian ionosphere at Olympus Mons and Syrtis Major: MGS observations
Authors: Haider S. A. , Seth S. P. , Brain D. A. , Mitchell D. L. , Majeed T. , Bougher S. W.
Published: August 2010

We have calculated photoelectron flux, ion production rates, and electron densities in the Martian ionosphere close to Syrtis Major and Olympus Mons at coordinates 5°N, 30°E and 15°N, 210°E, respectively. In the regions of Olympus Mons and Syrtis Major the magnetic fields are horizontal and vertical, respectively. These calculations are made at solar zenith angle 78° during moderate solar activity using transport and local loss models of photoelectrons based on the yield spectrum method. The vertical transport of photoelectrons is inhibited by horizontal magnetic fields at Olympus Mons. In this case we have used a local loss calculation. Photoelectron transport is allowed in the vertical magnetic fields at Syrtis Major. In this case we have developed and applied a photoelectron transport model. The estimated ion production rates are then used in a one‐dimensional continuity and vertical diffusion model to calculate ion and electron density. It is found that photoelectron transport reduces the flux by an order of magnitude between energy range 1 to 20 eV at higher altitude (>250 km). In this region the production rates and densities are decreased by factors of 2.5 to 5 due to transport of photoelectrons.
Reflection and transmission of atmospheric gravity waves in a stably sheared horizontal wind field
Authors: Huang Kai Ming , Zhang Shao Dong , Yi Fan
Published: August 2010

Applying a second‐order fully nonlinear numerical scheme, we have investigated the characteristics of reflection and transmission of atmospheric gravity wave packets in a vertically sheared horizontal wind. When the leading edge of incident wave arrives at the reflecting level predicted by the linear theory, the wave reflection begins to occur. In the reflection process, the reflection and incident waves are superposed with obvious phase staggering, which is different from the wave reflection in a meridionally sheared horizontal wind. In the evanescent region, the wave phase has only weak variation; the wave amplitude decays with the sheared wind growth and vice versa, which is in good agreement with the evanescent wave configuration predicted by the linear theory. Some spectral components of the incident wave can penetrate through the evanescent region and produce a transmitted wave. Both the reflection and transmission coefficients slightly decrease with the moderate increase of the initial amplitude of the incident wave, which is because a large‐amplitude wave can induce a strong mean flow; moreover, the wave‐induced mean flow plays a more significant role in transferring the energy from the waves to the background flow than in enhancing the transmission of the waves. This is distinguished from the wave reflection in a sheared flow under the wave propagation distance smaller than the density scale height, in which the mean flow induced by a larger‐amplitude wave significantly strengthens the transmission of the wave. The simulation shows that the reflection loop predicted by the linear theory is not a common phenomenon in the wave reflection. Several groups of simulated cases indicate that the reflection and transmission coefficients depend on not only the amplitude, frequency, and wavenumbers of the incident wave but also the strength and thickness of the evanescent region. The reflection coefficient increases but the transmission coefficient decreases with the relative evanescent thickness growth, and once the strength and thickness of the evanescent region are large enough, the wave hardly penetrates through the sheared wind zone, and the reflection coefficient approaches a constant value, too. Except for the disappearance of the evanescent region, the total sum of the reflection and transmission coefficients of the wave pseudoenergy flux is slightly <1 because of the interaction between the wave and flow. These results suggest that the effects of wave reflection and transmission should be correctly included in the parameterization of gravity waves to attain more realistic middle atmospheric climatology from general circulation models.
“Elevated heat pump” hypothesis for the aerosol‐monsoon hydroclimate link: “Grounded” in observations?
Authors: Nigam Sumant , Bollasina Massimo
Published: August 2010

The viability of the elevated heat pump hypothesis, a mechanism proposed by Lau and Kim (2006) for absorbing aerosols' impact on South Asian summer monsoon hydroclimate, is assessed from a careful review of these authors' own analysis and others since then. The lack of appreciation of the spatial distribution of the aerosol‐related precipitation signal over the Indian subcontinent, its east–west asymmetric structure, in particular, apparently led to the development of this hypothesis. Its key elements have little observational support, and the hypothesis is thus deemed untenable. Quite telling is the observation that local precipitation signal over the core aerosol region is negative, i.e., increased loadings are linked with suppressed precipitation and not more as claimed by the hypothesis. Finally, motivated by the need to address causality, the analysis of contemporaneous aerosol‐monsoon links by Bollasina et al. (2008) is extended by examining the structure of hydroclimate lagged regressions on aerosols. It is shown that findings obtained from contemporaneous analysis can be safely interpreted as representing the impact of aerosols on precipitation, not vice versa. The possibility that both are shaped by a slowly evolving, large‐scale circulation pattern cannot however be ruled out.
Comparison of interfacial partitioning tracer test and high‐resolution microtomography measurements of fluid‐fluid interfacial areas for an ideal porous medium
Authors: Narter Matt , Brusseau Mark L.
Published: August 2010

Fluid‐fluid interfacial area for porous media systems can be measured with the aqueous phase interfacial partitioning tracer test (IPTT) method or with high‐resolution microtomography. The results of prior studies have shown that interfacial areas measured with the IPTT method are larger than values measured with microtomography. The observed disparity has been hypothesized to result from the impact of porous medium surface roughness on film‐associated interfacial area, wherein the influence of surface roughness is characterized to some extent by the IPTT method but not by microtomography due to resolution constraints. This hypothesis was tested by using the two methods to measure interfacial area between an organic immiscible liquid and water for an ideal glass beads medium that has no measurable surface roughness. The tracer tests yielded a mean interfacial area of 2.8 (±5 cm−1), while microtomography produced an interfacial area of 2.7 (±2 cm−1). Maximum specific interfacial areas, equivalent to areas normalized by nonwetting fluid volume, were calculated and compared to measures of the specific solid surface area. The normalized interfacial areas were similar to the specific solid surface area calculated using the smooth sphere assumption and to the specific solid surface area measured using the N2/Brunauer, Emmett, and Teller (BET) method. The results presented herein indicate that both the IPTT and microtomography methods provide robust characterization of fluid‐fluid interfacial area and that they are comparable in the absence of the impact of surface roughness.
Air‐water flows in the presence of staggered and row boulders under macroroughness conditions
Authors: Pagliara S. , Carnacina I. , Roshni T.
Published: August 2010

Free surface flow over a rough bed at steep slopes entrains large amounts of air bubbles due to the high interaction between the free surface and the bed materials. The assessment of mixed air‐water flow features in the presence of a three‐dimensional bed configuration from macroroughness to intermediate roughness conditions can hardly be accomplished with aeration models developed for smooth or stepped bed configurations. Two‐phase flow properties were measured over rough bed materials in a setup assembled at the PITLAB center at the University of Pisa, Pisa, Italy. Coarser protruding materials were incorporated over the rough bed to intensify the aeration in the mixed air‐water flow. Flow discharges ranging between 0.02 and 0.09 m2/s and slopes between 0.18 and 0.44 were tested. A detailed study of the air‐water inner layer and flow features over staggered and row coarser material arrangement over the base material was carried out. Results were compared with literature data on free surface flow over smooth and stepped beds.
Fossil clams from a serpentinite‐hosted sedimented vent field near the active smoker complex Rainbow, MAR, 36°13′N: Insight into the biogeography of vent fauna
Authors: Lartaud Franck , de Rafelis Marc , Oliver Graham , Krylova Elena , Dyment Jérôme , Ildefonse Benoît , Thibaud Remy , Gente Pascal , Hoisé Eva , Meistertzheim Anne‐Leïla , Fouquet Yves , Gaill Françoise , Le Bris Nadine
Published: August 2010

Hydrothermal circulation at ultramafic‐hosted sites supports a large variety of high‐ and low‐temperature hydrothermal vents and associated ecosystems. The discovery of abundant fossil vesicomyid and thyasirid shell accumulations at the ridge crest, approximately 2.5 km east of the active Rainbow vent field on the Mid‐Atlantic Ridge (MAR, 36°13′N), increased our knowledge regarding the diversity of vent communities at slow spreading ridges. Bivalve molluscs of the family Vesicomyidae were represented by the genus Phreagena. Here we present the first record of this genus in the Atlantic Ocean. This second vesicomyid species known from the MAR, Phreagena sp., was found to be associated with a Thyasira species that is affiliated with T. southwardae (at the Logatchev vent field on the MAR) and with T. vulcolutre (in the Gulf of Cadiz). These two clams have close relationships with seep taxa along the continental margin, and were likely associated with sedimented vent fields. δ18O and δ13C analyses of the shells suggested that the burrowing bivalve Thyasira could incorporate isotopically light carbon, derived from the oxidation of methane in the sediment, while the signature of Phreagena sp. shells denoted a different carbonate source. 14C dating of the shells denoted that the hydrothermal activity in the Rainbow area began at least ∼25.5 kyr BP, which is similar to the model of the hydrothermal vent field distribution that was proposed for the Logatchev hydrothermal site. The results provide new insight regarding the diversity of chemosynthetic fauna on the MAR over geologic time. Ultramafic‐hosted, on‐axis sedimented vent fields extend the range of habitats for chemosynthetic communities, underlying the need to further explore the geology of these types of environments on slow‐spreading ridges and to determine their role in the ecology of deep‐sea vent communities.
IR spectroscopy of clay minerals and clay nanocomposites
Authors: Madejová Jana , Pálková Helena , Komadel Peter
Published: August 2010

Recent applications of infrared (IR) spectroscopy in research of clays and clay minerals are reviewed. After a brief description of the structures of clay minerals and basic principles of IR spectroscopy, the selected most interesting papers published in this area in 2007–2009 are discussed. The potential of both middle-IR and near-IR spectroscopy and different sampling techniques used in the investigation of clay minerals occurring on Earth and Mars is presented, including the utilisation of clay materials in the industry and in protection of the environment. Finally, the theoretical studies of the vibrational properties of the clay minerals are considered.
Bioinorganic electrochemistry
Authors: Schulzke Carola
Published: August 2010

This report describes some recent and exciting results obtained using electrochemical methods in a bioinorganic context, followed by a more specialised discussion with respect to temperature dependent studies.
Femtosecond mid-infrared spectroscopy of liquid water and aqueous solutions
Authors: Bakker H. J.
Published: August 2010

In this chapter we report on the results obtained on the dynamics of water and aqueous solutions with nonlinear femtosecond vibrational spectroscopic techniques like transient absorption spectroscopy, infrared photon-echo spectroscopy, and two-dimensional vibrational spectroscopy. These techniques allow the real-time study of the energy relaxation, hydrogen-bond and molecular reorientation dynamics of selected subensembles of water molecules.

For different isotopic variations of pure liquid water it is found that the excited molecular vibrations of the water molecule relax on a time scale ranging from 0.2 to 2 picoseconds, depending on the character of the vibration (stretch, bend). The hydrogen-bond dynamics and the molecular reorientation take place on two distinct time scales: on a time scale <100 femtoseconds associated with local variations in the length of the hydrogen bonds and librational motions, and a time scale of 1–3 picoseconds associated with the collective reorganizations of the hydrogen-bond network.

For aqueous solutions of ions and hydrophobic molecular groups it is observed that the water molecules hydrating these ions/molecular groups have 3–5 times slower reorientation and hydrogen-bond dynamics than the water molecules in bulk liquid water. For water molecules near interfaces like the surfaces of reverse micelles similar effects are observed. Finally, recent results on the role of water molecules in the transfer of protons and hydroxide ions through liquid water are described. It is found that water molecules actively participate in this transfer by conducting the charge of the proton/hydroxide ions over chains of hydrogen-bonded water molecules.
Time resolved spectroscopy of inorganic complexes
Authors: Keyes Tia E. , Forster Robert J. , Blackledge Charles
Published: August 2010

Time resolved spectroscopy has revolutionised our understanding of photochemical and photophysical reactions of inorganic complexes. In this review, we briefly describe the most common time resolved optical spectroscopic methods applied to inorganic complexes and outline some examples and highlights from the recent literature. The review is not intended to be exhaustive, but highlights key recent papers from coordination chemistry, supramolecular chemistry, carbonyl chemistry and bioinorganic chemistry, as well as, recent insights from ultrafast spectroscopy into the photophysics of important prototypes such as [Ru(bpy)3]2+ and [Cu(dmp)2]+. A brief perspective is then presented which discusses areas where time resolved spectroscopy of inorganic complexes could play a particularly important role in the next few years.
In situ photochemistry with NMR detection of organometallic complexes
Authors: Ball Graham E.
Published: August 2010

A review focusing on the application of NMR spectroscopy to the study of organometallic photochemistry where the photochemical step is performed in situ, i.e. the irradiation of the sample takes place within the probe of the NMR spectrometer. Various experimental designs, taken from all areas of chemical and biological study, that facilitate in situ irradiation are discussed, paying attention to light sources and light delivery methods. The literature covering the application of the in situ method across the field of organometallic chemistry is then reviewed. There is particular emphasis on studies of reactive organometallic compounds with weakly coordinating ligands such as alkane, xenon and other “solvent” species, as complexes with short lifetimes benefit most from application of the in situ illumination method.
Mass spectrometry in organometallic chemistry
Authors: Scott McIndoe J.
Published: August 2010

There are unique challenges associated with applying mass spectrometry (MS) to the analysis of organometallic compounds. High reactivity, a lack of volatility, and/or sensitivity to heat, oxygen and water all conspire to make the transfer of material into the gas phase without decomposition fraught with difficulty, and low polarity provides the additional complication that ionisation is not always trivial. Various methodological and technological developments over the last decade have improved the situation, but organometallic chemists are still faced with a bewildering array of options and there is yet to emerge a one-size-fits-all solution.
Synthetic vaccines based on N- and O-glycopeptides–molecular tools for immunotherapy and diagnostics
Authors: Westerlind Ulrika , Kunz Horst
Published: August 2010

This chapter summarizes available methods for the preparation of synthetic vaccines based on glycopeptides and recent advances in this field. It further includes results of their immunological evaluation. Syntheses of glycopeptides of defined chemical structure and conjugation of these compounds to a carrier protein or an immunostimulant are of interest for the development of new immunotherapeutics and/or antibody-based diagnostics. Since a number of years, the aberrant glycosylation of the tumorassociated mucin MUC1 forming tumor specific epitopes on the epithelial cell surface has been considered an attractive research target for the preparation of such vaccines. Examples of synthetic vaccines directed against the O-glycosylated MUC1 tandem repeats will here be given including synthetic MUC1 glycopeptides conjugated to a T-cell epitope peptide, to a carrier protein, to a lipid immunostimulant or the multimeric presentation of glycopeptides on dendrimers. Other attractive targets for immunotherapy are the viral envelope proteins HIV gp120 and HIV gp41 , which are highly glycosylated with high-mannose and complex type N-glycans. Examples will be given, which illustrate syntheses of high-mannose HIV gp120 or gp41 glycopeptides with the natural peptide backbone or with a non-natural cyclic backbone to mimic the high-mannose cluster domain of HIV gp120. In addition the synthesis and immunological evaluation of a vaccine will be described, which contains the high-mannose cluster mimotope glycopeptide conjugated to an outer membrane protein complex (OMPC) as the carrier.
Bioorthogonal chemical reporter methodology for visualization, isolation and analysis of glycoconjugates
Authors: Boons Geert-Jan
Published: August 2010

The recent development of metabolic oligosaccharide engineering combined with bioorthogonal reactions is providing unique opportunities to detect, image, and isolate glycoconjugates of living cells, tissues, and model organisms. In this methodology, exogenously-supplied non-natural sugars are fed to cells and employed by the biosynthetic machinery for the biosynthesis of neoglycoconjugates. In this way, reactive functional groups such as ketones, azides, and thiols have been incorporated into sialic acid, galactosamine, glucosamine, and fucose moieties of glycoconjugates. A range of bioorthogonal reactions have been described that functionalize the chemical ‘tags’ for imaging, isolation, and drug delivery.
Access to Information About Stuttering and Societal Knowledge of Stuttering
Authors: Gabel Rodney , Brackenbury Tim , Irani Farzan
Published: August 2010

The purpose of this study was to examine societal knowledge of stuttering, access to information sources, and the influence of information sources on knowledge of stuttering. 185 participants from Northwest Ohio were surveyed. Results of the study indicated that the general public varies in their knowledge of stuttering and that majority of participants had not accessed information about stuttering, and the few who had, did so a long time ago. Finally, access to information sources had little influence on knowledge of stuttering. Implications for future research are discussed.
Combinatorics of 1-particle irreducible n-point functions via coalgebra in quantum field theory
Authors: Mestre Ângela
Published: August 2010

We give a coalgebra structure on 1-vertex irreducible graphs which is that of a cocommutative coassociative graded connected coalgebra. We generalize the coproduct to the algebraic representation of graphs so as to express a bare 1-particle irreducible n-point function in terms of its loop order contributions. The algebraic representation is so that graphs can be evaluated as Feynman graphs.
Multisymplectic box schemes for the complex modified Korteweg–de Vries equation
Authors: Aydın A. , Karasözen B.
Published: August 2010

In this paper, two multisymplectic integrators, an eight-point Preissman box scheme and a narrow box scheme, are considered for numerical integration of the complex modified Korteweg–de Vries equation. Energy and momentum preservation of both schemes and their dispersive properties are investigated. The performance of both methods is demonstrated through numerical tests on several solitary wave solutions.
Universal structure and universal equations (PDE) for unitary ensembles
Authors: Rumanov Igor
Published: August 2010

Random matrix ensembles with unitary invariance of measure (UE) are described in a unified way using a combination of Tracy–Widom (TW) and Adler–Shiota–van Moerbeke approaches to the derivation of partial differential equations (PDEs) for spectral gap probabilities. First, general three-term recurrence relations for UE restricted to subsets of real line, or, in other words, for functions in the resolvent kernel, are obtained. Using them, simple universal relations between all TW dependent variables and one-dimensional Toda lattice τ-functions are found. A universal system of PDE for UE is derived from previous relations, which leads also to a single independent PDE for spectral gap probability of various UE. Thus, orthogonal function bases and Toda lattice are seen at the core of correspondence of different approaches. Moreover, Toda-AKNS system provides a common structure of PDE for unitary ensembles. Interestingly, this structure can be seen in two very different forms: one arises from orthogonal function-Toda lattice considerations, while the other comes from Schlesinger equations for isomonodromic deformations and their relation to TW equations. The simple example of Gaussian matrices most neatly exposes this structure.
Physics of mode selectivity of vertical-cavity surface-emitting diode lasers
Authors: Kuc Maciej , Sarzała Robert P. , Nakwaski Włodzimierz
Published: August 2010

The single-fundamental-mode operation of vertical-cavity surface-emitting diode lasers (VCSELs) is essential for most of their applications. It is well known, that it is enhanced in VCSELs exhibiting uniform current injection into their active regions. But usually this injection is far from being uniform, sometimes even with a distinct current-crowding effect at active-region edges. Therefore, in the present paper, excitation of successive cavity modes is investigated with the aid of the comprehensive VCSEL physical model taking the modern GaAs-based oxide-confined intracavity-contacted quantum-well GaInNAs/GaAs VCSEL emitting the 1.3 μm radiation as a typical VCSEL example. VCSEL operation depends on many optical, electrical, thermal, and recombination phenomena. But numerous and usually nonlinear interactions between these phenomena have been found to be equally important. Therefore, the main intention of this work is to demonstrate that, for any VCSEL design, an analysis of its mode selectivity requires a fully self-consistent comprehensive simulation of all important phenomena taking place within a laser volume together with numerous important interactions between individual physical processes. Over-simplified theoretical models may lead to faulty results.
Isomonodromic deformations, generalized Knizhnik–Zamolodchikov equations and non-skew-symmetric classical r-matrices
Authors: Skrypnyk T.
Published: August 2010

Using non-skew-symmetric classical r-matrices r12(u,v) with spectral parameters, we generalize Fuchsian systems and Schlesinger equations (isomonodromy equations) viewing the last as the nonautonomous Hamiltonian equations corresponding to the generalized Gaudin Hamiltonians. Quantizing these systems we construct generalization of Knizhnik–Zamolodchikov equations corresponding to the non-skew-symmetric classical r-matrices r12(u,v) with spectral parameters. In the case of an ordinary skew-symmetric classical r-matrix r12(u−v) depending on the difference of the spectral parameters, we reobtain, as special partial cases, a standard generalization of Fuchsian systems, Schlesinger, and Knizhnik–Zamolodchikov equations.
Depth analysis of boron diffusion in MgO/CoFeB bilayer by x-ray photoelectron spectroscopy
Authors: Lu Y. , Lépine B. , Jézéquel G. , Ababou S. , Alnot M. , Lambert J. , Renard A. , Mullet M. , Deranlot C. , Jaffrès H. , Petroff F. , George J.-M.
Published: August 2010

We have studied the boron (B) diffusion in MgO/CoFeB bilayer by x-ray photoelectron spectroscopy depth analysis. A large concentration of B (B/Mg=0.16) was found to diffuse into the MgO barrier after 350 °C annealing. The boron in MgO is in a highly oxidized B3+ state and is homogenously distributed in the whole barrier. The important B diffusion in MgO could be related to the CoFeB crystallization process which begins from the under CoFeB/Ru interface and pushes boron atoms to diffuse into the MgO barrier during annealing.
Qiang–Dong proper quantization rule and its applications to exactly solvable quantum systems
Authors: Serrano F. A. , Gu Xiao-Yan , Dong Shi-Hai
Published: August 2010

We propose proper quantization rule, ∫xAxBk(x)dx−∫x0Ax0Bk0(x)dx=nπ, where k(x)=2M[E−V(x)]/ℏ. The xA and xB are two turning points determined by E=V(x), and n is the number of the nodes of wave function ψ(x). We carry out the exact solutions of solvable quantum systems by this rule and find that the energy spectra of solvable systems can be determined only from its ground state energy. The previous complicated and tedious integral calculations involved in exact quantization rule are greatly simplified. The beauty and simplicity of the rule come from its meaning—whenever the number of the nodes of ϕ(x) or the number of the nodes of the wave function ψ(x) increases by 1, the momentum integral ∫xAxBk(x)dx will increase by π. We apply this proper quantization rule to carry out solvable quantum systems such as the one-dimensional harmonic oscillator, the Morse potential and its generalization, the Hulthén potential, the Scarf II potential, the asymmetric trigonometric Rosen–Morse potential, the Pöschl–Teller type potentials, the Rosen–Morse potential, the Eckart potential, the harmonic oscillator in three dimensions, the hydrogen atom, and the Manning–Rosen potential in D dimensions.
Scaling of the ground-state energy of relativistic ions in high locally bounded magnetic fields
Authors: Jakubassa-Amundsen D. H.
Published: August 2010

We consider the pseudorelativistic Chandrasekhar/Herbst operator hH for the description of relativistic one-electron ions in a locally bounded magnetic field. We show that for Coulomb potentials of strength γ<2/π, the spectrum of hH is discrete below m (the electron mass). For magnetic fields in the class BA(x)=B⋅1+τ2(|x1|τ+|x2|τ)ez, the ground-state energy of hH decreases according to B1/(2+τ) as B→∞ for 0≤τ<τc, where τc is some critical value, depending on γ.
High temperature Luttinger liquid conductivity in carbon nanotube bundles
Authors: Danilchenko B. A. , Shpinar L. I. , Tripachko N. A. , Voitsihovska E. A. , Zelensky S. E. , Sundqvist B.
Published: August 2010

The conductance and the current-voltage characteristics of metallic single wall carbon nanotube bundles have been measured between 4.2 and 330 K using 10–30 ns electric pulses to avoid overheating. The current-voltage characteristics at different temperatures collapse to a single curve when plotted in the specific coordinates following from the Tomonaga–Luttinger (T–L) liquid concept. Direct evidence is obtained for the existence of a T–L liquid phase up to 190 K and the system shows a transition between the T–L liquid state and a Mott insulating phase below 25 K.
Jet propulsion without inertia
Authors: Spagnolie Saverio E. , Lauga Eric
Published: August 2010

A body immersed in a highly viscous fluid can locomote by drawing in and expelling fluid through pores at its surface. We consider this mechanism of jet propulsion without inertia in the case of spheroidal bodies and derive both the swimming velocity and the hydrodynamic efficiency. Elementary examples are presented and exact axisymmetric solutions for spherical, prolate spheroidal, and oblate spheroidal body shapes are provided. In each case, entirely and partially porous (i.e., jetting) surfaces are considered and the optimal jetting flow profiles at the surface for maximizing the hydrodynamic efficiency are determined computationally. The maximal efficiency which may be achieved by a sphere using such jet propulsion is 12.5%, a significant improvement upon traditional flagella-based means of locomotion at zero Reynolds number, which corresponds to the potential flow created by a source dipole at the sphere center. Unlike other swimming mechanisms which rely on the presentation of a small cross section in the direction of motion, the efficiency of a jetting body at low Reynolds number increases as the body becomes more oblate and limits to approximately 162% in the case of a flat plate swimming along its axis of symmetry. Our results are discussed in the light of slime extrusion mechanisms occurring in many cyanobacteria.
Time- and frequency-resolved photoionization of the C A22 state of the benzyl radical, C7H7
Authors: Margraf Markus , Noller Bastian , Schröter Christian , Schultz Thomas , Fischer Ingo
Published: August 2010

The structure and dynamics of the C A22 electronically excited state of the benzyl radical, C7H7, were investigated by nanosecond and femtosecond pump-probe photoionization. A free jet of benzyl radicals was generated by flash pyrolysis from the precursors 2-phenylethyl nitrite and toluene. Nanosecond multiphoton ionization spectra show a number of vibronic bands that are excited in the wavelength range of 290–310 nm. At excitation wavelengths of 305, 301, and 298 nm, rapid biexponential decay of the excited states was observed. Lifetimes at the C-state origin (305 nm excitation) are 400 fs and 4.5 ps. The lifetimes decrease with increasing excitation energy. The dynamics can be understood within a two-step internal conversion to the electronic ground state.
Late-time attractor for the cubic nonlinear wave equation
Authors: Szpak Nikodem
Published: August 2010

We apply our recently developed scaling technique for obtaining late-time asymptotics to the cubic nonlinear wave equation and explain the appearance and approach to the two-parameter attractor found recently by Bizon and Zenginoglu.
The role of fcc tetrahedral subunits in the phase behavior of medium sized Lennard-Jones clusters
Authors: Saika-Voivod Ivan , Poon Louis , Bowles Richard K.
Published: August 2010

The free energy of a 600-atom Lennard-Jones cluster is calculated as a function of surface and bulk crystallinity in order to study the structural transformations that occur in the core of medium sized clusters. Within the order parameter range studied, we find the existence of two free energy minima at temperatures near freezing. One minimum, at low values of both bulk and surface order, belongs to the liquid phase. The second minimum exhibits a highly ordered core with a disordered surface and is related to structures containing a single fcc-tetrahedral subunit, with an edge length of seven atoms (l=7), located in the particle core. At lower temperatures, a third minimum appears at intermediate values of the bulk order parameter which is shown to be related to the formation of multiple l=6 tetrahedra in the core of the cluster. We also use molecular dynamics simulations to follow a series of nucleation events and find that the clusters freeze to structures containing l=5, 6, 7, and 8 sized tetrahedra as well as those containing no tetrahedral units. The structural correlations between bulk and surface order with the size of the tetrahedral units in the cluster core are examined. Finally, the relationships between the formation of fcc tetrahedral subunits in the core, the phase behavior of medium sized clusters and the nucleation of noncrystalline global structures such as icosahedra and decahedra are discussed.
Reduction in resistivity of 50 nm wide Cu wire by high heating rate and short time annealing utilizing misorientation energy
Authors: Onuki Jin , Khoo Khyoupin , Sasajima Yasushi , Chonan Yasunori , Kimura Takashi
Published: August 2010

The resistivities and microstructures for 50 nm Cu wires fabricated by high heating rate (3 K/s) and short time (1 min) annealing using infrared rapid thermal annealing equipment have been investigated as a function of annealing temperature and compared to those properties for wires fabricated by a slow heating rate (0.08 K/s), long time (30 min) conventional H2 annealing process. The resistivity of wires annealed by the new process decreased substantially with increasing annealing temperature from 573 to 773 K. The resistivity had its lowest value between 773 and 873 K, and it increased rapidly with annealing temperature above 923 K. The average ρ value was 2.98 μΩ cm for 773 K new process wires, whereas average ρ values were about 3.55 μΩ cm for 573 K and 3.42 μΩ cm for 673 K conventionally H2 annealed wires. This resistivity value for the new process wires was about 16% lower than the value for wires annealed at 573 K and 13% lower than the value for the wires annealed at 673 K by the conventional H2 annealing process. The substantial resistivity decrease in the new process Cu wires is mainly attributed to uniform grain size coarsening and high (111) orientation effects by the high temperature and high rate heating, while the resistivity increase at higher heating temperatures above 923 K for new process wires is mainly attributed to the reaction between Cu and Ta/TaN barriers; the greater the extent of the reaction, the higher the resistivity.
The effect of plasmonic particles on solar absorption in vertically aligned silicon nanowire arrays
Authors: Lin Chenxi , Povinelli Michelle L.
Published: August 2010

In this paper, we used the finite-difference time domain method to determine whether metallic caps provide plasmonic enhancement of absorption in vertically aligned silicon nanowire arrays. Metallic caps result naturally from the vapor-liquid-solid growth process, which uses metal catalyst particles to initiate growth. We found that gold, copper, and silver catalysts all decrease the integrated optical absorption across the solar spectrum.
Effects of yttrium doping on the thermoelectric properties of Hf0.6Zr0.4NiSn0.98Sb0.02 half-Heusler alloys
Authors: Zhu T. J. , Xiao K. , Yu C. , Shen J. J. , Yang S. H. , Zhou A. J. , Zhao X. B. , He J.
Published: August 2010

The (Y,Sb) codoped (Hf0.6Zr0.4)1−xYxNiSn0.98Sb0.02 (x=0, 0.01, 0.015, 0.02, and 0.025) half-Heusler alloys were prepared by levitation melting and spark plasma sintering. The effects of Y doping on the electrical conductivity, the Seebeck coefficient, and the thermal conductivity have been investigated in the temperature range of 300–900 K. It was found that the Y doping decreased the carrier concentration and electrical conductivity due to the introduction of hole carriers. The thermal conductivity was also reduced upon Y doping, mainly due to the reduced carrier thermal conductivity. The Y-doping substantially increased the Seebeck coefficient because of the decrease in carrier concentration. Pisarenko plot showed that the measured room temperature Seebeck coefficients agrees well with the predicted single parabolic band behavior as a function of the carrier concentration, suggesting that no additional mechanisms cause the extra enhancement of Seebeck coefficient in the Y–Sb codoped half-Heusler alloys. The figure of merit ZT of 1% Y-doped sample was increased by a factor of about 25% than that of the undoped sample.
Field-induced control of universal fluorescence intermittency of a quantum dot light emitter
Authors: Lee J. D. , Maenosono S.
Published: August 2010

With the nonstochastic quantum mechanical study of a quantum dot light emitter, we find that fluorescence intermittency statistics are universal and insensitive to the microscopic nature of the tunneling fluctuation between quantum dot and trapping state. We also investigate the power-law exponent θ and the crossover time τC of the on-time (τon) probability P(τon)∝τon−θ (for τon≲τC) and ∝e−Γτon (for τon≳τC) under an optical field of given energy and strength. For easy off-resonance excitation, it is found in both numerical and analytic ways that τC−1 is proportional to the intensity of the optical field (i.e., the square of the field strength) independent of the internal parameters of a quantum dot. Furthermore, it is also found that θ=2 in the limit of vanishing field strength is the upper bound of the exponent and θ becomes less than 2 as the field strength increases.
Coherent elastic waves in a one-dimensional polymer hypersonic crystal
Authors: Walker P. M. , Sharp J. S. , Akimov A. V. , Kent A. J.
Published: August 2010

Using the methods of picosecond acoustics, we inject high amplitude hypersonic wavepackets into a polymer superlattice and optically detect the propagating coherent elastic waves. The spectrum of the optically detected signal shows the elastic modes typical for folded phonon dispersion curves. The experimental results and related modeling show the feasibility of using polymer one-dimensional hypersonic crystals as acoustic devices in the gigahertz frequency range.
Negative dielectrophoretic capture of bacterial spores in food matrices
Authors: Koklu Mehti , Park Seungkyung , Pillai Suresh D. , Beskok Ali
Published: August 2010

A microfluidic device with planar square electrodes is developed for capturing particles from high conductivity media using negative dielectrophoresis (n-DEP). Specifically, Bacillus subtilis and Clostridium sporogenes spores, and polystyrene particles are tested in NaCl solution (0.05 and 0.225 S/m), apple juice (0.225 S/m), and milk (0.525 S/m). Depending on the conductivity of the medium, the Joule heating produces electrothermal flow (ETF), which continuously circulates and transports the particles to the DEP capture sites. Combination of the ETF and n-DEP results in different particle capture efficiencies as a function of the conductivity. Utilizing 20 μm height DEP chambers, “almost complete” and rapid particle capture from lower conductivity (0.05 S/m) medium is observed. Using DEP chambers above 150 μm in height, the onset of a global fluid motion for high conductivity media is observed. This motion enhances particle capture on the electrodes at the center of the DEP chamber. The n-DEP electrodes are designed to have well defined electric field minima, enabling sample concentration at 1000 distinct locations within the chip. The electrode design also facilitates integration of immunoassay and other surface sensors onto the particle capture sites for rapid detection of target micro-organisms in the future.
Influence of magnetic substrate in the transport critical current of superconducting tapes
Authors: Sanchez Alvaro , Del-Valle Nuria , Navau Carles , Chen Du-Xing
Published: August 2010

An important effect on the critical-current density Jc in a superconducting tape is found when the tape is above a soft ferromagnetic substrate, as is the case with many coated conductors. Here, a model is presented to analyze the complex magnetic interaction between the induced currents in the superconductor and the poles in the magnet. We find that transport Jc decreases at nonzero applied fields when there is a magnetic substrate and this reduction can be controlled by changing the magnet thickness. The model presented here can, therefore, become a useful tool for understanding and optimizing superconductor-magnet systems.
Dynamical organization of the cytoskeletal cortex probed by micropipette aspiration
Authors: Brugués Jan , Maugis Benoit , Casademunt Jaume , Nassoy Pierre , Amblard François , Sens Pierre
Published: August 2010

Bleb-based cell motility proceeds by the successive inflation and retraction of large spherical membrane protrusions (“blebs”) coupled with substrate adhesion. In addition to their role in motility, cellular blebs constitute a remarkable illustration of the dynamical interactions between the cytoskeletal cortex and the plasma membrane. Here we study the bleb-based motions of
Entamoeba histolytica
in the constrained geometry of a micropipette. We construct a generic theoretical model that combines the polymerization of an actin cortex underneath the plasma membrane with the myosin-generated contractile stress in the cortex and the stress-induced failure of membrane-cortex adhesion. One major parameter dictating the cell response to micropipette suction is the stationary cortex thickness, controlled by actin polymerization and depolymerization. The other relevant physical parameters can be combined into two characteristic cortex thicknesses for which the myosin stress (
i
) balances the suction pressure and (
ii
) provokes membrane-cortex unbinding. We propose a general phase diagram for cell motions inside a micropipette by comparing these three thicknesses. In particular, we theoretically predict and experimentally verify the existence of saltatory and oscillatory motions for a well-defined range of micropipette suction pressures.
Public perceptions of energy consumption and savings
Authors: Attari Shahzeen Z. , DeKay Michael L. , Davidson Cliff I. , Bruine de Bruin Wändi
Published: August 2010

In a national online survey, 505 participants reported their perceptions of energy consumption and savings for a variety of household, transportation, and recycling activities. When asked for the most effective strategy they could implement to conserve energy, most participants mentioned curtailment (e.g., turning off lights, driving less) rather than efficiency improvements (e.g., installing more efficient light bulbs and appliances), in contrast to experts’ recommendations. For a sample of 15 activities, participants underestimated energy use and savings by a factor of 2.8 on average, with small overestimates for low-energy activities and large underestimates for high-energy activities. Additional estimation and ranking tasks also yielded relatively flat functions for perceived energy use and savings. Across several tasks, participants with higher numeracy scores and stronger proenvironmental attitudes had more accurate perceptions. The serious deficiencies highlighted by these results suggest that well-designed efforts to improve the public's understanding of energy use and savings could pay large dividends.
Loss of lysophosphatidylcholine acyltransferase 1 leads to photoreceptor degeneration in
rd11
mice
Authors: Friedman James S. , Chang Bo , Krauth Daniel S. , Lopez Irma , Waseem Naushin H. , Hurd Ron E. , Feathers Kecia L. , Branham Kari E. , Shaw Manessa , Thomas George E. , Brooks Matthew J. , Liu Chunqiao , Bakeri Hirva A. , Campos Maria M. , Maubaret Cecilia , Webster Andrew R. , Rodriguez Ignacio R. , Thompson Debra A. , Bhattacharya Shomi S. , Koenekoop Robert K. , Heckenlively John R. , Swaroop Anand
Published: August 2010

Retinal degenerative diseases, such as retinitis pigmentosa and Leber congenital amaurosis, are a leading cause of untreatable blindness with substantive impact on the quality of life of affected individuals and their families. Mouse mutants with retinal dystrophies have provided a valuable resource to discover human disease genes and helped uncover pathways critical for photoreceptor function. Here we show that the
rd11
mouse mutant and its allelic strain, B6-
JR2845
, exhibit rapid photoreceptor dysfunction, followed by degeneration of both rods and cones. Using linkage analysis, we mapped the
rd11
locus to mouse chromosome 13. We then identified a one-nucleotide insertion (c.420–421insG) in exon 3 of the
Lpcat1
gene. Subsequent screening of this gene in the B6-
JR2845
strain revealed a seven-nucleotide deletion (c.14–20delGCCGCGG) in exon 1. Both sequence changes are predicted to result in a frame-shift, leading to premature truncation of the lysophosphatidylcholine acyltransferase-1 (LPCAT1) protein. LPCAT1 (also called AYTL2) is a phospholipid biosynthesis/remodeling enzyme that facilitates the conversion of palmitoyl-lysophosphatidylcholine to dipalmitoylphosphatidylcholine (DPPC). The analysis of retinal lipids from
rd11
and B6-
JR2845
mice showed substantially reduced DPPC levels compared with C57BL/6J control mice, suggesting a causal link to photoreceptor dysfunction. A follow-up screening of
LPCAT1
in retinitis pigmentosa and Leber congenital amaurosis patients did not reveal any obvious disease-causing mutations. Previously, LPCAT1 has been suggested to be critical for the production of lung surfactant phospholipids and biosynthesis of platelet-activating factor in noninflammatory remodeling pathway. Our studies add another dimension to an essential role for LPCAT1 in retinal photoreceptor homeostasis.
Direct mapping of nanoscale compositional connectivity on intact cell membranes
Authors: van Zanten Thomas S. , Gómez Jordi , Manzo Carlo , Cambi Alessandra , Buceta Javier , Reigada Ramon , Garcia-Parajo Maria F.
Published: August 2010

Lateral segregation of cell membranes is accepted as a primary mechanism for cells to regulate a diversity of cellular functions. In this context, lipid rafts have been conceptualized as organizing principle of biological membranes where underlying cholesterol-mediated selective connectivity must exist even at the resting state. However, such a level of nanoscale compositional connectivity has been challenging to prove. Here we used single-molecule near-field scanning optical microscopy to visualize the nanolandscape of raft ganglioside GM1 after tightening by its ligand cholera toxin (CTxB) on intact cell membranes. We show that CTxB tightening of GM1 is sufficient to initiate a minimal raft coalescence unit, resulting in the formation of cholesterol-dependent GM1 nanodomains < 120 nm in size. This particular arrangement appeared independent of cell type and GM1 expression level on the membrane. Simultaneous dual color high-resolution images revealed that GPI anchored and certain transmembrane proteins were recruited to regions proximal (< 150 nm) to CTxB-GM1 nanodomains without physical intermixing. Together with in silico experiments, our high-resolution data conclusively demonstrate the existence of raft-based interconnectivity at the nanoscale. Such a linked state on resting cell membranes constitutes thus an obligatory step toward the hierarchical evolution of large-scale raft coalescence upon cell activation.