bluuebunny/crossref_metadata_2025 huggingface dataset:
Restoration of shoulder function with nerve transfers in traumatic brachial plexus palsy patients
Authors: Terzis Julia K. , Kostas Ioannis , Soucacos Panayotis N.
Published: April 2006

Shoulder stabilization is of utmost importance in upper extremity reanimation following paralysis from devastating injuries. Although secondary procedures such as tendon and muscle transfers have been used, they never achieve a functional recovery comparable to that following successful reinnervation of the supraspinatus, deltoid, teres minor, and infraspinatus muscles. Early restoration of suprascapular and axillary nerve function through timely brachial plexus reconstruction offers a good opportunity to restore shoulder‐joint stability, adequate shoulder abduction, and external rotation function. Overall, in our series, 79% of patients achieved good and excellent shoulder abduction (muscle grade, +3 or more), and 55% of patients achieved good or excellent shoulder external rotation after reinnervation of the suprascapular nerve. The best results were seen when direct neurotization of the suprascapular nerve from the distal spinal accessory nerve or neurotization by the C5 root was carried out. Concomitant neurotization of the axillary nerve yields improved outcomes in shoulder abduction and external rotation function. © 2006 Wiley‐Liss, Inc. Microsurgery, 2006.
Simultaneous synthesis of silver nanoparticles and poly(2,5‐dimethoxyaniline) in poly(styrene sulfonic acid)
Authors: Huang Li‐Ming , Tsai Ching‐Chun , Wen Ten‐Chin , Gopalan A.
Published: April 2006

Silver nanoparticles were formed in situ along with poly(2,5‐dimethoxyaniline) (PDMA) in an interconnected network matrix (reactor), comprising the electronic conductive polymer, PDMA, and a polyelectrolyte, poly(styrene sulfonic acid) (PSS), through the simultaneous reduction of Ag+ ions and polymerization of 2,5‐dimethoxyaniline. In situ ultraviolet‐visible spectroscopy showed that peaks corresponding to the plasmon resonance of silver nanoparticles at 411 nm and the polaronic transition of PDMA at 438 nm provided evidences for the simultaneous formation of silver nanoparticles and PDMA. Transmission electron microscopy and size distribution analysis revealed the presence of spherical silver nanoparticles with an average diameter of 12 nm in the composite. X‐ray photoelectron spectroscopy showed that the amine units in PDMA changed to imine units upon the formation of silver nanoparticles. A comprehensive mechanism for the formation of the PDMA‐PSS‐Ag nanocomposite is proposed. A 10‐fold increase in the conductivity was noticed for the PDMA–PSS–Ag nanocomposite (1 S/cm) in comparison with the PDMA–PSS composite (0.1 S/cm). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3843–3852, 2006
Epoxy/polyhedral oligomeric silsesquioxane nanocomposites from octakis(glycidyldimethylsiloxy)octasilsesquioxane and small‐molecule curing agents
Authors: Liu Ying‐Ling , Chang Gung‐Pei , Hsu Keh‐Ying , Chang Feng‐Chih
Published: April 2006

Epoxy/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were obtained from octakis(glycidyldimethylsiloxy)octasilsesquioxane (OG) and diglycidyl ether of bisphenol A cured with small‐molecule curing agents of diethylphosphite (DEP) and dicyandiamide (DICY). An increase in the POSS contents of the nanocomposites and an improvement in the nanocomposite homogeneity were observed with the use of the small‐molecule curing agents. Phosphorus in DEP and nitrogen in DICY also performed synergism with POSS for thermal stability enhancement and flammability improvement in the nanocomposites. The nanocomposites possessing high OG contents exhibited good thermal stability, improved flammability, and high storage moduli. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3825–3835, 2006
Novel, well‐defined polystyrene with a fluorine cluster end‐capped group: Synthesis, characterization, and surface properties
Authors: Li Hong , Zhang Yong Ming , Zhang Heng , Xue Min Zhao , Liu Yan Gang
Published: April 2006

Novel, well‐defined fluorinated polystyrene was synthesized for the first time via the controlled radical polymerization of styrene through a relatively simple process and was characterized with 1H NMR, 19F NMR, and gel permeation chromatography. The surface properties of polystyrene and poly(acrylonitrile‐co‐butadiene‐co‐styrene) films were modified with the obtained polymers. X‐ray photoelectron spectroscopy measurements of the air‐side surface composition of the modified poly(acrylonitrile‐co‐butadiene‐co‐styrene) films showed that fluorine enriched the outermost surface, resulting in fantastic surface properties that came close to those of poly(tetrafluoroethylene). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3853–3858, 2006
Delayed cuticular penetration and enhanced metabolism of deltamethrin in pyrethroid‐resistant strains of Helicoverpa armigera from China and Pakistan
Authors: Ahmad Mushtaq , Denholm Ian , Bromilow Richard H
Published: April 2006

The penetration and metabolism of [14C]deltamethrin was studied in susceptible and resistant Chinese and Pakistani strains of Helicoverpa armigera (Hübner), which were resistant to deltamethrin by 330‐ and 670‐fold, respectively. The penetration of deltamethrin into resistant individuals was significantly slower than into susceptible individuals over a 24‐h period. The time taken for 50% penetration of the applied deltamethrin was 1 h for the susceptible strain and 6 h for both of the resistant strains. The internal radioactivity was reduced by the larvae of resistant strains much faster than by the susceptible larvae. After 48 h, 40% of the penetrated deltamethrin was still inside the larvae of the susceptible strain, in comparison with 1.5–5% in the Pakistani strain and 8–14% in the Chinese strain. Both of the resistant strains produced methanol‐soluble and water‐soluble metabolites, but the susceptible strain produced methanol‐soluble metabolites only. By 12, 24 and 48 h after dosing, the amount of methanol‐soluble metabolites excreted by the resistant strains was almost double that of the susceptible strain. Both of the resistant strains also excreted 5–7% of the penetrated dose as a water‐soluble metabolite after 48 h. In comparison with the Chinese strain, the Pakistani strain exhibited slower penetration, lower internal content and faster excretion of deltamethrin, which correlated with the higher resistance of the Pakistani strain. These findings show that the resistant Pakistani and Chinese strains of H. armigera possess mechanisms of reduced cuticular penetration and enhanced metabolism of deltamethrin and perhaps other pyrethroids. Copyright © 2006 Society of Chemical Industry
Photon‐assisted tunneling in ac driven double quantum dot spin pumps
Authors: Sánchez R. , Platero G. , Aguado R. , Cota E.
Published: April 2006

In this work, we study the effect of an applied ac gate voltage on the spin filtering and pumping properties of a lateral double quantum dot, in the Coulomb blockade and weak coupling regimes, considering not only the effect of the ac potential on the inter‐dot tunneling but also on the tunneling through the leads. This last effect accounts for additional photon absorption and emission processes and therefore affects the spin polarization of the pumped current. In particular, we find that the spin down filtering property can be affected depending on the intensity of the ac field. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conductance control in quantum wires by attached quantum dots
Authors: Orellana P. , Domínguez‐Adame F.
Published: April 2006

The electronic transport of two quantum dots side‐coupled to a quantum wire is studied by means of the two impurity Anderson Hamiltonian. The conductance is found to be a superposition of a Fano and a Breit–Wigner resonances as a function of the Fermi energy, provided the gate voltages of the quantum dots are slightly different. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon nanotubes for biological devices
Authors: García A. , Bustero I. , Muñoz R. , Goikotxea L. , Obieta I.
Published: April 2006

The unique properties of carbon nanotubes open attractive possibilities in many applications areas, for instance as biological devices. Multi Wall Carbon Nanotubes (MWNT) have been synthesized by Chemical Vapour Deposition (CVD) and the influence of certain process variables in the final product yield have been studied. In addition, purification treatment applied at synthesized carbon nanotubes, has been developed. Biocompatibility tests have demonstrated that purified carbon nanotubes are non‐cytotoxic. Finally, a functionalization process is developed to help in carbon nanotubes‐biomolecule interaction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electric force microscopy of individually charged semiconductor nanoparticles
Authors: Diesinger H. , Mélin T. , Barbet S. , Deresmes D. , Stiévenard D.
Published: April 2006

Charge injection experiments by electrostatic force microscopy are performed on single semiconductor nanoparticles. Different methods of detecting the stored charge are used. Although the amount of charge stored in particles of realistic shape can be determined quantitatively, we present here a qualitative comparison between Q (V ) hysteresis curves observed on silicon and GaN quantum dots, in dry nitrogen and in ultra high vacuum. For silicon dots in dry atmosphere, we find a hysteresis behavior entirely different from the one observed on GaN dots in ultra high vacuum. The contribution of interface states to hysteresis is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature effects on the magnetic properties of antiferromagnetically coupled amorphous Co0.74Si0.26/Si multilayers
Authors: Zárate L. , Quirós C. , Vélez M. , Yaacoub N. , Meny C. , Pérez‐Junquera A. , Martín J. I. , Alameda J. M.
Published: April 2006

The effect of temperature on the magnetic properties of antiferromagnetically coupled amorphous Co0.74Si0.25/Si multilayers has been investigated by Magneto‐Optical Transverse Kerr Effect and Superconducting Quantum Interference Device. The studied temperature range has been varied between 5 K (15 K for Kerr loops) and room temperature. The results show that the Curie temperature of the multilayers is close to room temperature and that the antiferromagnetic exchange coupling can only be detected at temperatures close to the Curie temperature. When the temperature is decreased, the coercive field of the single films composing the multilayer increases, masking the antiferromagnetic coupling below 250 K. Field‐Cooling and Zero‐Field‐Cooling measurements suggest the presence of a small superparamagnetic contribution. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Field and temperature dependence of Bloch walls across the thickness in Gd0.28Co0.72/Gd0.12Co0.88 exchange coupled double layers
Authors: Zárate R. , Martín J. I. , Pérez‐Junquera A. , Vélez M. , Meny C. , Alameda J. M.
Published: April 2006

The characteristics of the Bloch walls across the thickness that appear at high fields in Gd0.28Co0.72/Gd0.12Co0.88 exchange coupled double layers have been studied by transverse Kerr effect. From the modelling of the magneto‐optical response the wall thickness is obtained as a function of magnetic field H and temperature. Wall thickness is found to decrease as H –1/2 in agreement with theoretical predictions. On the other hand, the thickness of the wall when it is created at the interface increases linearly with temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐linear effects in the quenching of fluorescent semiconductor nanoparticles by paramagnetic species
Authors: Scaiano J. C. , Laferrière Marie , Galian Raquel E. , Maurel Vincent , Billone Paul
Published: April 2006

Quenching of quantum dot luminescence by nitroxides shows steep exponential behavior and is dependent on nanoparticle size, being most effective for the smaller particles. The interaction of CdSe nanoparticles with TEMPO (non‐binding) and 4‐amino‐TEMPO (binding) has been examined using fluorescence and electron spin resonance techniques. The data suggest that quenching involves an electron exchange mechanism. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Functionalization of atomic cobalt clusters obtained by electrochemical methods
Authors: Rodríguez Cobo Eldara , Rivas Rey José , Blanco Varela M. Carmen , Mouriño Mosquera Antonio , Torneiro Abuin Mercedes , López Quintela M. Arturo
Published: April 2006

Functionalization of magnetic nanoparticles with appropriate organic molecules is very important for many applications. In the present study, cobalt nanoparticles, with an average diameter of 2 nm corresponding to Co309 clusters were synthesised by an electrochemical method, and then coated with ADCB (4‐(9‐deceniloxi)benzoic acid), in order to protect the clusters against oxidation and to obtain a final nanostructure, which can be attached later on to many different materials, like drugs, proteins or some other biological molecules. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scalar mixing and reaction in plane liquid shear layers
Authors: Karasso P. S. , Mungal M. G.
Published: April 2006

The scalar (concentration) field of two-dimensional liquid mixing layers was investigated at post-mixing-transition conditions. The planar laser-induced fluorescence technique was used for passive scalar measurements, and for chemical product measurements. Following the approach of Koochesfahani & Dimotakis (1986), the chemical product results were used to make resolution-free estimates of mixed-fluid quantities, thus providing a check on the accuracy of the passive scalar measurements. The operating conditions were systematically varied to study the effect of various parameters (Reynolds number, speed ratio, and initial boundary-layer momentum thickness) on the structure of the layer. At conditions which are just past the mixing transition, the study essentially duplicated the results obtained by Koochesfahani & Dimotakis: the chemical-product concentration profiles at high- and low-stoichio-metric ratios (flip experiments) were symmetric and the average concentration of mixed-fluid was uniform across the layer. However, when the layer was pushed to more fully developed conditions, its scalar field evolved to an asymptotic state: the two flip chemical-product concentration profiles developed modest asymmetries, and the average mixed-fluid concentration developed a small variation across the layer, but the change was less than that observed in gases. Based on the chemical reaction data, we infer that the mixture fraction probability density function (p.d.f.) for the fully-developed liquid layer evolves from a ‘non-marching’ type to a ‘tilted’ type. Despite the observed evolution, the average mixed-fluid concentration remained fixed for all the layers past the mixing transition, while the total mixed-fluid probability (the total amount of mixed fluid normalized by the layer's width) showed only a very slight increasing tendency as the layer reached fully developed conditions. The mixture fraction p.d.f., measured by the passive scalar approach, is shown and discussed for a broad range of cases. While it overpredicts the amount of mixing, it showed a qualitatively-correct ‘non-marching’ character initially, but evolved to a qualitatively-incorrect ‘marching’ character at the asymptotic state. The reasons for the poor estimation of the p.d.f. by the passive scalar approach, at fully developed conditions, are attributed to changes in the flow and lack of resolution and suggests caution when using such measures. Furthermore, the study also showed that the Reynolds number alone is inadequate to characterize the state of the layer. A different parameter (the ‘pairing parameter’), which accounts for the initial boundary layers and scales with the number of vortex mergings, was found to better explain the evolution in the structure of the scalar field.
Axisymmetric swirling flow around a vortex breakdown point
Authors: Rusak Zvi
Published: April 2006

The structure of an axisymmetric and inviscid swirling flow around a vortex breakdown point is analysed. The model assumes that a free axisymmetric bubble surface is developed in the flow with a stagnation point at its nose. The classical Squire-Long equation for the stream function ψ(x,y) (wherey=r2/2) is transformed into a free boundary problem for the solution ofy(x, ψ). The development of the flow is studied in three regions: the approaching flow ahead of the bubble, around the bubble nose and around the separated bubble surface. Asymptotic expansions are constructed to describe the flow ahead of and behind the stagnation point in terms of the radial distance from the vortex axis and from the bubble surface, respectively. In the intermediate region around the stagnation point, the flow is approximated by an asymptotic series of similarity terms that match the expansions in the other regions. The analysis results in two possible matching processes. Analytical expressions are given for the leading term of the intermediate expansion for each of these processes. The first solution describes a swirling flow around a constant-pressure bubble surface, over which the flow is stagnant. The second solution represents a swirling flow around a pressure-varying bubble surface, where the flow expands along the bubble nose. In both solutions, the bubble nose has a parabolic shape, and both exist only whenH’ > 0 (whereH’ is the derivative at the vortex centre of the total headHwith the stream function ψ, and can be determined from the inlet conditions). This result is shown to be equivalent to Brown & Lopez's (1990) criterion for vortex breakdown. Good agreement is found in the region around the stagnation point between the pressure-varying bubble solution and available experimental data for axisymmetric vortex breakdown.
Surface-wave generation: a viscoelastic model
Authors: Miles John
Published: April 2006

The Reynolds-averaged equations for turbulent flow over a deep-water sinusoidal gravity wave, z = acoskx ≡ h0(x), are formulated in the wave-following coordinates ζ, η, where x = ζ, z =η + h(ζ, η), h(ζ, 0) = h0(ζ) and h is exponentially small for kη [Gt ] 1, and closed by a viscoelastic consitutive equation (a mixing-length model with relaxation). This closure is derived from Townsend's boundary-layer-evolution equation on the assumptions that: the basic velocity profile is logarithmic in η + z0, where z0 is a roughness length determined by Charnock's similarity relation; the lateral transport of turbulent energy in the perturbed flow is negligible; the dissipation length is proportional to η + z0. A counterpart of the Orr-Sommerfeld equation for the complex amplitude of the perturbation stream function is derived and used to construct a quadratic functional for the energy transfer to the wave. A corresponding Galerkin approximation that is based on independent variational approximations for outer (quasi-laminar) and inner (shear-stress) domains yields an energy-transfer parameter β that is comparable in magnitude with that of the quasi-laminar model (Miles 1957) and those calculated by Townsend (1972) and Gent & Taylor (1976) through numerical integration of the Reynolds-averaged equations. The calculated limiting values of β for very slow waves, with Charnock's relation replaced by kz0 = constant, are close to those inferred from observation but about three times the limiting values obtained through extrapolation of Townsend's results.
Experiments on density-gradient anisotropies and scalar dissipation of turbulence in a stably stratified fluid
Authors: Thoroddsen S. T. , Van Atta C. W.
Published: April 2006

The anisotropic behaviour of density-gradient fluctuations in stably stratified grid turbulence and the consequences for simplified (isotropic) estimates of scalar dissipation rates χ were experimentally studied in a thermally stratified wind tunnel at moderate Reynolds numbers (Reλ ≃ 20). Strong stable stratifications were attained, with Brunt-Väisälä frequency N as high as 4 rad s−1. The correlation method was used to estimate the mean-square cross-stream and streamwise density gradients. Cross-stream gradients were measured using two cold wires. The mean-square vertical gradients were found to become larger than the streamwise gradients by as much as a factor of 2.2 for the largest dimensionless buoyancy times (Nt = 7). This corresponds to a 40% error in the scalar dissipation estimates based on ∂θ/∂x alone, and assuming the validity of the isotropic relations. Gradient spectral relations show that this buoyancy-induced anisotropy persists at all length scales. Better closure of the scalar variance balance was attained than in previously reported measurements by other researchers. This is attributed to our use of cold-wire temperature sensors having larger length-to-diameter ratio than used in the previous measurements.
Numerical investigation of the propagation of shock waves in rigid porous materials: development of the computer code and comparison with experimental results
Authors: Levy A. , Ben-Dor G. , Sorek S.
Published: April 2006

The governing equations of the flow field which is obtained when a thermoelastic rigid porous medium is struck head-one by a shock wave are developed using the multiphase approach. The one-dimensional version of these equations is solved numerically using a TVD-based numerical code. The numerical predictions are compared to experimental results and good to excellent agreements are obtained for different porous materials and a wide range of initial conditions.
Wave-induced boundary layer flows above and in a permeable bed
Authors: Liu Philip L.-F. , Davis Matthew H. , Downing Sean
Published: April 2006

In this paper, the oscillatory and steady streaming velocities over a permeable bed are studied both theoretically and experimentally. Three different sizes of glass beads are used to construct permeable beds in laboratory experiments: the diameters of the glass beads are 0.5 mm, 1.5 mm, and 3.0 mm, respectively. Several experiments are performed using different wave parameters. A one-component laser-doppler velocimeter (LDV) is used to measure the horizontal velocity component inside the Stokes boundary layer above the solid and permeable surfaces. It is observed that neither oscillatory nor steady velocity components vanish on the permeable surface. The ‘slip velocities’ increase with increasing permeability. Based on the laminar flow assumption and the order of magnitude of the parameters used in the experiments, a perturbation theory is developed for the oscillatory velocity and the steady wave-induced streaming in the boundary layers above and inside the permeable bed. The theory confirms many experimental observations. The theory also provides the damping rate and the phase changes caused by the permeable bed.
The effect of entrained air in violent water wave impacts
Authors: Peregrine D. H. , Thais L.
Published: April 2006

The effects of entrained air in cushioning water impact on a wall are estimated by using a flow which has many similarities to the severe flip-through impacts that have been identified for water waves hitting a vertical wall. This is a filling flow which rapidly fills a confined region, such as a crack between blocks, or the space beneath a deck projecting from the coast (Peregrine & Kalliadasis 1996). The main properties of the filling flow are easily calculated, including the high-pressure peak which corresponds to the pressure peak of a flip-through. This work extends the study of filling flows to the case where the filling liquid is an air–water mixture, thus giving explicit results for the reduction of peak pressure due to the compressibility of entrained air. The behaviour of a bubbly liquid subject to substantial pressure changes is considered. Expressions are derived for an air–water mixture treated as a compressible fluid. The reduction in pressure from the incompressible case is found to be large even for relatively small air content, and depends more on the reduction in fluid volume than any other feature of the pressure–density relation. Results are presented in such a way that they may be used to estimate compressibility corrections to both the maximum and background pressures in a flip-through wave impact if corresponding incompressible pressure values are available.
Natural convection in an enclosure having a vertical sidewall with time-varying temperature
Authors: Kwak Ho Sang , Hyun Jae Min
Published: April 2006

A numerical study is performed for time-varying natural convection of an incompressible Boussinesq fluid in a sidewall-heated square cavity. The temperature at the cold sidewall Tc is constant, but at the hot sidewall a time-varying temperature condition is prescribed, $ T_H = \overline{T_H} + \Delta T^{\prime} \sin ft $. Comprehensive numerical solutions are found for the time-dependent Navier–Stokes equations. The numerical results are analysed in detail to show the existence of resonance, which is characterized by maximal amplification of the fluctuations of heat transfer in the interior. Plots of the dependence of the amplification of heat transfer fluctuations on the non-dimensional forcing frequency ω are presented. The failure of Kazmierczak & Chinoda (1992) to identify resonance is shown to be attributable to the limitations of the parameter values they used. The present results illustrate that resonance becomes more distinctive for large Ra and Pr ∼ 0(1). The physical mechanism of resonance is delineated by examining the evolution of oscillating components of flow and temperature fields. Specific comparisons are conducted for the resonance frequency ωr between the present results and several other previous predictions based on the scaling arguments.
Surface ripples due to steady breaking waves
Authors: Duncan James H. , Dimas Athanassios A.
Published: April 2006

Breaking waves generated by a two-dimensional hydrofoil moving near a free surface at constant speed (U∞), angle of attack and depth of submergence were studied experimentally. The measurements included the mean and fluctuating shape of the breaking wave, the surface ripples downstream of the breaker and the vertical distribution of vertical and horizontal velocity fluctuations at a single station behind the breaking waves. The spectrum of the ripples is highly peaked and shows little variation in both its peak frequency and its shape over the first three wavelengths of the wavetrain following the breaker. For a given speed, as the breaker strength is increased, the high-frequency ends of the spectra are nearly identical but the spectral peaks move to lower frequencies. A numerical instability model, in conjunction with the experimental data, shows that the ripples are generated by the shear flow developed at the breaking region. The spectrum of the vertical velocity fluctuations was also found to be highly peaked with the same peak frequency as the ripples, while the corresponding spectrum of the horizontal velocity fluctuations was found not to be highly peaked. The root-mean-square (r.m.s.) amplitude of the ripples (νrms) increases with increasing speed and with decreasing depth of submergence of the hydrofoil, and decreases as x-1/2 with increasing distance x behind the breaker. The quantity (gνrms)/(U∞Vrms) (where Vrms is the maximum r.m.s. vertical velocity fluctuation and g is the gravitational acceleration) was found to be nearly constant for all of the measurements.
Identification of priority habitats for conservation of the Sierra Madre sparrow Xenospiza baileyi in Mexico
Authors: Cabrera-García Leonardo , Montes José Alejandro Velázquez , Weinmann Martha Elena Escamilla
Published: April 2006

The Sierra Madre sparrow Xenospiza baileyi, categorized as Endangered on the IUCN Red List, is endemic to Mexico. The subalpine bunch grasslands of the Transverse Volcanic Belt in the south of the Valley of Mexico are the last remaining habitat of this species. We conducted a detailed survey for the Sierra Madre sparrow using the point count method, and then described the species' habitat using a phytosociological approach. The two sets of information were pooled into a single analytical framework to identify priority habitats for the species. Eight vegetation communities were distinguished. The Festuca lugens-Muhlenbergia quadridentata and Stipa ichu bunch grassland communities had the highest densities of the Sierra Madre sparrow. Intensive burning and grazing activities and agricultural encroachment have restricted sparrow occupancy. Landscape analysis helped to delineate core grassland areas for the species and grassland strips and islands that could potentially act as habitat corridors. From the information generated in this study, which was shared with the local communities, we are establishing a participatory socio-ecological investigation for conservation of the Sierra Madre sparrow's habitat.
A semi‐Lagrangian Crank‐Nicolson algorithm for the numerical solution of advection‐diffusion problems
Authors: Spiegelman Marc , Katz Richard F.
Published: April 2006

We present a hybrid method for the numerical solution of advection‐diffusion problems that combines two standard algorithms: semi‐Lagrangian schemes for hyperbolic advection‐reaction problems and Crank‐Nicolson schemes for purely diffusive problems. We show that the hybrid scheme is identical to the two end‐member schemes in the limit of infinite and zero Peclet number and remains accurate over a wide range of Peclet numbers. This scheme does not have a CFL stability criterion allowing the choice of time step to be decoupled from the spatial resolution. We compare numerical results with an analytic solution and test both an operator split version of our method and a combined version that solves advection and diffusion simultaneously. We also compare results of simple explicit and implicit numerical schemes and show that the semi‐Lagrangian Crank‐Nicolson (SLCN) scheme is both faster and more accurate on the same problem. We then apply the combined SLCN scheme to a more geologically relevant benchmark for calculating the thermal structure of a subduction zone. This problem demonstrates that the SLCN scheme can remain stable and accurate at large Courant numbers even in flows with highly curved streamlines. Finally, we introduce a variable order interpolation scheme for the semi‐Lagrangian schemes that reduces interpolation artifacts for sharp fronts without introducing numerical diffusion.
Evaluation of soil moisture in the Florida State University climate model–National Center for Atmospheric Research community land model (FSU‐CLM) using two reanalyses (R2 and ERA40) and in situ observations
Authors: Boisserie M. , Shin D. W. , LaRow T. E. , Cocke S.
Published: April 2006

The simulated soil moisture from the Florida State University (FSU) climate model coupled to the National Center for Atmospheric Research community land model (CLM2) is evaluated using two reanalyses (the European Centre for Medium‐Range Weather Forecasts 40‐year Reanalysis (ERA40) and the National Centers for Environmental Prediction/Department of Energy Reanalysis 2 (R2)) and in situ observations in Illinois and China from the Global Soil Moisture Data Bank. While the soil moisture was prescribed in the previous FSU climate model, the implementation of the CLM2 within the FSU model (hereafter FSU‐CLM) provides a prognostic soil moisture (both soil liquid water and soil ice) in 10 vertical layers. For the first layer (∼0–10 cm) the comparison of the soil moisture annual cycle between the FSU‐CLM and the two reanalyses shows that in the Northern Hemisphere (NH) the FSU‐CLM and the ERA40 are in phase but they are out of phase with the R2. While a parameterization of the soil ice process is included in both the FSU‐CLM and ERA40, it is not included in the R2. In this study, we found that the soil ice plays a key role in determining the soil moisture variation over the NH. The two reanalyses and the FSU‐CLM are also compared with in situ observations. The FSU‐CLM turns out to follow the annual cycle of the in situ observations better than both reanalyses.
A seasonal study of methyl bromide concentrations in the North Atlantic (35°–60°N)
Authors: Tokarczyk Ryszard , Moore Robert M.
Published: April 2006

Methyl bromide concentrations in and over the North Atlantic were examined during spring, summer, and fall 2003. The results demonstrate that seasonality plays a great role in controlling methyl bromide fluxes from and into the ocean in this area. The North Atlantic acted as a sink of the atmospheric gas during the spring, a source during the summer, and a weak sink during the fall. The annual air‐sea flux of methyl bromide from the North Atlantic area between 30°N and 60°N (approximately 15.4 × 106 km2) was estimated to be in the range of −0.3 to −0.6 Gg y−1, with the methyl bromide flux varying between −4.0 × 106 ± 1 × 106 g d−1, 1.6 × 106 ± 0.6 × 106 g d−1, and −0.6 × 106 ± 0.4 × 106 g d−1 in spring, summer, and fall, respectively. Methyl bromide production necessary to balance air‐sea exchange with oceanic losses was greater in the southern part than in the northern part of the studied area; no oceanic production was necessary to balance methyl bromide loss from the Arctic waters around 60°N. While the regional contribution to the methyl bromide global oceanic flux is small, it is also complex and dynamic. Our data suggest that in this part of the ocean the flux is not so much dependent on sea surface temperature as it is on other, still unknown environmental variables.
Evidence for indurated sand dunes in the Martian north polar region
Authors: Schatz Volker , Tsoar Haim , Edgett Kenneth S. , Parteli Eric J. R. , Herrmann Hans J.
Published: April 2006

We investigate the relevance of induration as an explanation for the occurrence of dunes of unusual morphology in the Martian north polar region. The evidence for induration of aeolian deposits on Mars is reviewed. An explanation for rounded, elongated barchans in Chasma Boreale is presented. The role played by induration in the formation of linear dunes is discussed. Our arguments are supported by the results of a computer simulation model.
Spatial gradients in the plasmasphere from Cluster
Authors: Darrouzet F. , De Keyser J. , Décréau P. M. E. , Lemaire J. F. , Dunlop M. W.
Published: April 2006

The Cluster mission allows the study of the plasmasphere with four‐point measurements, including its overall density distribution, plasmaspheric plumes close to the plasmapause, and density irregularities inside the plasmasphere. The purpose of this letter is to examine the geometry and orientation of the overall density structure and of the magnetic field. We present a typical Cluster plasmasphere crossing for which we compute the four‐point spatial gradient of the electron density and the magnetic field strength, and we compare the direction of both gradients with the local field vector. We discuss the role of the gradient components along and transverse to field lines; transverse density gradients, in particular, are found to suggest the presence of azimuthal density variations.
Three‐dimensional spatial distribution of scatterers in Galeras volcano, Colombia
Authors: Carcolé E. , Ugalde A. , Vargas C. A.
Published: April 2006

A three‐dimensional spatial distribution of relative scattering coefficients is estimated for the Galeras volcano, Colombia, by an inversion of the coda wave envelopes from 1564 high quality seismic recordings at 31 stations of the Galeras seismograph network. The inversion reveals a highly non‐uniform distribution of relative scattering coefficients in the region for the two analyzed frequency bands (4‐8 and 8‐12 Hz). Strong scatterers show frequency dependence, which is interpreted in terms of the scale of the heterogeneities producing scattering. Two zones of strong scattering are detected: the shallower one is located at a depth from 4 km to 8 km under the summit whereas the deeper one is imaged at a depth of ∼37 km from the Earth's surface. Both zones may be associated with the magmatic plumbing system beneath Galeras volcano. The second strong scattering zone may be related to a deeper magma reservoir that feeds the system.
Influence of the annual Arctic Oscillation on the negative correlation between Okhotsk Sea ice and Amur River discharge
Authors: Ogi Masayo , Tachibana Yoshihiro
Published: April 2006

Newly obtained observational discharge data reveal the cause of a significant negative correlation between Amur River discharge and Okhotsk Sea ice at multiyear timescales. The annually integrated Arctic Oscillation (AO) influences both summer discharge and winter ice. Summer discharge is larger and winter ice is reduced during positive AO years. Annual AO also influences the annual horizontal moisture flux convergence in the river basin. When the annual AO is positive, the annual mean air temperatures are warm over Eurasia, particularly over the Amur River basin and the Okhotsk. Consequently, autumn SSTs are warmer in the Okhotsk Sea. The warmer autumn SSTs suppress ice formation during the following winter. Freshwater from the river is not the main control of multiyear ice variability. Consideration of the annual AO provides a new look at climate system persistence at multi‐seasonal scales.
Homocysteine- and cysteine-mediated growth defect is not associated with induction of oxidative stress response genes in yeast
Authors: Kumar Arun , John Lijo , Alam Md. Mahmood , Gupta Ankit , Sharma Gayatri , Pillai Beena , Sengupta Shantanu
Published: April 2006

Intracellular thiols like cysteine, homocysteine and glutathione play a critical role in the regulation of important cellular processes. Alteration of intracellular thiol concentration results in many diseased states; for instance, elevated levels of homocysteine are considered to be an independent risk factor for cardiovascular disease. Yeast has proved to be an excellent model system for studying many human diseases since it carries homologues of nearly 40% of human disease genes and many fundamental pathways are highly conserved between the two organisms. In the present study, we demonstrate that cysteine and homocysteine, but not glutathione, inhibit yeast growth in a concentration-dependent manner. Using deletion strains (str2Δ and str4Δ) we show that cysteine and homocysteine independently inhibit yeast growth. Transcriptional profiling of yeast treated with cysteine and homocysteine revealed that genes coding for antioxidant enzymes like glutathione peroxidase, catalase and superoxide dismutase were down-regulated. Furthermore, transcriptional response to homocysteine did not show any similarity to the response to H2O2. We also failed to detect induction of reactive oxygen species in homocysteine- and cysteine-treated cells, using fluorogenic probes. These results indicate that homocysteine- and cysteine-induced growth defect is not due to the oxidative stress. However, we found an increase in the expression of KAR2 (karyogamy 2) gene, a well-known marker of ER (endoplasmic reticulum) stress and also observed HAC1 cleavage in homocysteine- and cysteinetreated cells, which indicates that homocysteine- and cysteine-mediated growth defect may probably be attributed to ER stress. Transcriptional profiling also revealed that genes involved in one-carbon metabolism, glycolysis and serine biosynthesis were up-regulated on exogenous addition of cysteine and homocysteine, suggesting that cells try to reduce the intracellular concentration of thiols by up-regulating the genes involved in their metabolism.
Activation of the superoxide-producing phagocyte NADPH oxidase requires co-operation between the tandem SH3 domains of p47phox in recognition of a polyproline type II helix and an adjacent α-helix of p22phox
Authors: Nobuhisa Ikuo , Takeya Ryu , Ogura Kenji , Ueno Noriko , Kohda Daisuke , Inagaki Fuyuhiko , Sumimoto Hideki
Published: April 2006

Activation of the superoxide-producing phagocyte NADPH oxidase, crucial for host defence, requires an SH3 (Src homology 3)-domain-mediated interaction of the regulatory protein p47phox with p22phox, a subunit of the oxidase catalytic core flavocytochrome b558. Although previous analysis of a crystal structure has demonstrated that the tandem SH3 domains of p47phox sandwich a short PRR (proline-rich region) of p22phox (amino acids 151–160), containing a polyproline II helix, it has remained unknown whether this model is indeed functional in activation of the oxidase. In the present paper we show that the co-operativity between the two SH3 domains of p47phox, as expected from the model, is required for oxidase activation. Deletion of the linker between the p47phox SH3 domains results not only in a defective binding to p22phox but also in a loss of the activity to support superoxide production. The present analysis using alanine-scanning mutagenesis identifies Pro152, Pro156 and Arg158 in the p22phox PRR as residues indispensable for the interaction with p47phox. Pro152 and Pro156 are recognized by the N-terminal SH3 domain, whereas Arg158 contacts with the C-terminal SH3 domain. Amino acid substitution for any of the three residues in the p22phox PRR abrogates the superoxide-producing activity of the oxidase reconstituted in intact cells. The bis-SH3-mediated interaction of p47phox with p22phox thus functions to activate the phagocyte oxidase. Furthermore, we provide evidence that a region C-terminal to the PRR of p22phox (amino acids 161–164), adopting an α-helical conformation, participates in full activation of the phagocyte oxidase by fortifying the association with the p47phox SH3 domains.
Localization of GRP78 to mitochondria under the unfolded protein response
Authors: Sun Fang-Chun , Wei Shou , Li Chia-Wei , Chang Yuo-Sheng , Chao Chih-Chung , Lai Yiu-Kay
Published: April 2006

The ubiquitously expressed molecular chaperone GRP78 (78 kDa glucose-regulated protein) generally localizes to the ER (endoplasmic reticulum). GRP78 is specifically induced in cells under the UPR (unfolded protein response), which can be elicited by treatments with calcium ionophore A23187 and sarcoplasmic/endoplasmic reticulum Ca2+-ATPase inhibitor TG (thapsigargin). By using confocal microscopy, we have demonstrated that GRP78 was concentrated in the perinuclear region and co-localized with the ER marker proteins, calnexin and PDI (protein disulphide-isomerase), in cells under normal growth conditions. However, treatments with A23187 and TG led to diminish its ER targeting, resulting in redirection into a cytoplasmic vesicular pattern, and overlapping with the mitochondrial marker MitoTracker. Cellular fractionation and protease digestion of isolated mitochondria from ER-stressed cells suggested that a significant portion of GRP78 is localized to the mitochondria and is protease-resistant. Localizations of GRP78 in ER and mitochondria were confirmed by using immunoelectron microscopy. In ER-stressed cells, GRP78 mainly localized within the mitochondria and decorated the mitochondrial membrane compartment. Submitochondrial fractionation studies indicated further that the mitochondria-resided GRP78 is mainly located in the intermembrane space, inner membrane and matrix, but is not associated with the outer membrane. Furthermore, radioactive labelling followed by subcellular fractionation showed that a significant portion of the newly synthesized GRP78 is localized to the mitochondria in cells under UPR. Taken together, our results indicate that, at least under certain circumstances, the ER-resided chaperone GRP78 can be retargeted to mitochondria and thereby may be involved in correlating UPR signalling between these two organelles.
Determination of the CO3− bond strength via the resonant two-photon photodissociation threshold: Electronic and vibrational spectroscopy of CO3−∙Arn
Authors: Bopp Joseph C. , Diken Eric G. , Headrick Jeffrey M. , Roscioli Joseph R. , Johnson Mark A. , Midey Anthony J. , Viggiano A. A.
Published: April 2006

We use a two-laser pump-probe technique coupled with messenger atom tagging to determine the bond energy of O− to CO2 in the CO3− ion, a prevalent species in the upper atmosphere. In this technique, the argon-tagged ion is first electronically excited using a visible laser, then irradiated with a tunable near-infrared beam across the CO2⋯O− dissociation threshold while O− products are monitored. This method yields a bond energy of 2.79±0.05eV, which is about 0.5eV higher than previously reported. Combining this with the well-known heats of formation of O− and CO2, 105.6 and −393.1kJ∕mol, respectively [Thermodynamic Properties of Individual Substances, edited by L. V. Gurvich, I. V. Veyts, and C. B. Alcock (Hemisphere, New York, 1989), Vol. 1 and CODATA Thermodynamic Tables, edited by O. Garvin, V. B. Parker, and J. H. J. White (Hemisphere, New York, 1987)], yields the CO3− heat of formation: ΔH00=−556.7±4.8kJ∕mol. The one-photon (i.e., linear) infrared and electronic spectra of CO3− are also presented and compared to those obtained previously. The one-photon electronic spectrum is nearly identical to two-photon spectra, implying that argon does not significantly perturb the ion or its symmetry. The infrared spectrum is drastically different than that obtained in an argon matrix, however, indicating that the ion is likely distorted in the matrix environment.
Ab initio studies of layering behavior of liquid sodium surfaces and interfaces
Authors: Walker Brent G. , Marzari Nicola , Molteni Carla
Published: April 2006

We have studied the liquid surface of sodium with extensive ab initio molecular dynamics simulations based on ensemble density-functional theory. We find clear evidence of layering in the direction perpendicular to the surface that persists to temperatures more than 100K above the melting point. We also observe clear Friedel oscillations in the electronic density response to the presence of a surface, but their direct effect on atomic layering is ruled out. A careful finite-size effect analysis accompanies our results, showing that liquid slabs 20–25Å thick capture the essential details of the surface structure. We conclude that geometrical confinement is the common cause for layer formation, which is similar to what happens at a liquid-solid interface: at a free liquid surface, the rapid decay of the electronic density from the bulk liquid value to zero in the vapor forms a hard wall against which the atoms pack. Finally, we predict x-ray reflectivities from ab initio molecular dynamics data that include some of the large surface-normal wave vector-transfer regions that, for alkali metals, are not accessible to experiments.
The bend angle of water in ice Ih and liquid water: The significance of implementing the nonlinear monomer dipole moment surface in classical interaction potentials
Authors: Fanourgakis George S. , Xantheas Sotiris S.
Published: April 2006

The implementation of the physically accurate nonlinear dipole moment surface of the water monomer in the context of the Thole-type, polarizable, flexible interaction potential results in the only classical potential, which, starting from the gas phase value for the bend angle (104.52°), reproduces its experimentally observed increase in the ice Ih lattice and in liquid water. This is in contrast to all other classical potentials to date, which predict a decrease of the monomer bend angle in ice Ih and in liquid water with respect to the gas phase monomer value. Simulations under periodic boundary conditions of several supercells consisting of up to 288molecules of water used to sample the proton disorder in the ice Ih lattice yield an average value of ϑHOH(Ih)=108.4°±0.2° for the minimized structures (T=0K) and 108.1°±2.8° at T=100K. Analogous simulations for liquid water predict an average value of ϑHOH(liquid)=106.3°±4.9° at T=300K. The increase of the monomer bend angle of water in condensed environments is attributed to the use of geometry-dependent charges that are used to describe the nonlinear character of the monomer’s dipole moment surface. Our results suggest a new paradigm in the development of classical interaction potential models of water that can be used to describe condensed aqueous environments.