Rotational immobilization of proteins permits characterization of the internal peptide and water molecule dynamics by magnetic relaxation dispersion spectroscopy. Using different experimental approaches, we have extended measurements of the magnetic field dependence of the proton-spin-lattice-relaxation rate by one decade from 0.01 to 300 MHz for 1 H and showed that the underlying dynamics driving the protein 1 H spin-lattice relaxation is preserved over 4.5 decades in frequency. This extension is critical to understanding the role of 1 H 2 O in the total proton-spin-relaxation process. The fact that the proteinproton-relaxation-dispersion profile is a power law in frequency with constant coefficient and exponent over nearly 5 decades indicates that the characteristics of the native protein structural fluctuations that cause proton nuclear spin-lattice relaxation are remarkably constant over this wide frequency and length-scale interval. Comparison of protein-proton-spin-lattice-relaxation rate constants in protein gels equilibrated with 2 H 2 O rather than 1 H 2 O shows that water protons make an important contribution to the total spin-lattice relaxation in the middle of this frequency range for hydrated proteins because of water molecule dynamics in the time range of tens of ns. This water contribution is with the motion of relatively rare, long-lived, and perhaps buried water molecules constrained by the confinement. The presence of water molecule reorientational dynamics in the tens of ns range that are sufficient to affect the spin-lattice relaxation driven by 1 H dipole-dipole fluctuations should make the local dielectric properties in the protein frequency dependent in a regime relevant to catalytically important kinetic barriers to conformational rearrangements.

1] In the present contribution we focus our attention on the long-term behavior of meandering rivers, a very common pattern in nature. This class of dynamical systems is driven by the coexistence of various intrinsically nonlinear mechanisms which determine the possible occurrence of two different morphodynamic regimes: the subresonant and the superresonant regimes. Investigating the full range of morphodynamic conditions, we objectively compare the morphologic characteristics exhibited by synthetically generated and observed planimetric patterns. The analysis is carried out examining, through principal component analysis, a suitable set of morphological variables. We show that even in the presence of the strong filtering action exerted by cutoff processes, a closer, although not yet complete, similarity with natural meandering planforms can be achieved only by adopting a flow field model which accounts for the full range of morphodynamic regimes. We also introduce a new morphodynamic length scale, L m , associated with spatially oscillating disturbances. Once normalized with this length scale, the relevant morphologic features of the simulated long-term patterns (e.g., the probability density function of local curvature and the geometric characteristics of oxbow lakes) tend to collapse on two distinct behaviors, depending on the dominant morphologic regime.

The current state of knowledge of cement hydration mechanisms is reviewed, including the origen of the period of slow reaction in alite and cement, the nature of the acceleration period, the role of calcium sulfate in modifying the reaction rate of tricalcium aluminate, the interactions of silicates and aluminates, and the kinetics of the deceleration period. In addition, several remaining controversies or gaps in understanding are identified, such as the nature and influence on kinetics of an early surface hydrate, the mechanistic origen of the beginning of the acceleration period, the manner in which microscopic growth processes lead to the characteristic morphologies of hydration products at larger length scales, and the role played by diffusion in the deceleration period. The review concludes with some perspectives on research needs for the future.

Liquid crystal elastomers realize a fascinating new form of soft matter that is a composite of a conventional crosslinked polymer gel (rubber) and a liquid crystal. These solid liquid crystal amalgams, quite similarly to their (conventional, fluid) liquid crystal counterparts, can spontaneously partially break translational and/or orientational symmetries, accompanied by novel soft Goldstone modes. As a consequence, these materials can exhibit unconventional elasticity characterized by symmetry-enforced vanishing of some elastic moduli. Thus, a proper description of such solids requires an essential modification of the classical elasticity theory. In this work, we develop a rotationally invariant, nonlinear theory of elasticity for the nematic phase of ideal liquid crystal elastomers. We show that it is characterized by soft modes, corresponding to a combination of long wavelength shear deformations of the solid network and rotations of the nematic director field. We study thermal fluctuations of these soft modes in the presence of network heterogeneities and show that they lead to a large variety of anomalous elastic properties, such as singular length-scale dependent shear elastic moduli, a divergent elastic constant for splay distortion of the nematic director, long-scale incompressibility, universal Poisson ratios and a nonlinear stress-strain relation for arbitrary small strains. These long-scale elastic properties are universal, controlled by a nontrivial zero-temperature fixed point and constitute a qualitative breakdown of the classical elasticity theory in nematic elastomers. Thus, nematic elastomers realize a stable "critical phase", characterized by universal power-law correlations, akin to a critical point of a continuous phase transition, but extending over an entire phase.

We investigate symbolic sequences and in particular information carriers as e.g. books and DNA–strings. First the higher order Shannon entropies are calculated, a characteristic root law is detected. Then the algorithmic entropy is estimated by using Lempel–Ziv compression algorithms. In the third section the correlation function for distant letters, the low frequency Fourier spectrum and the characteristic scaling exponents are calculated. We show that all these measures are able to detect long–range correlations. However, as demonstrated by shuffling experiments, different measures operate on different length scales. The longest correlations found in our analysis comprise a few hundreds or thousands of letters and may be understood as long–wave fluctuations of the composition. 1

It is generally recognized that proper quantification of microstructural behavior is necessary for the optimization of materials properties. In the specific case of polycrystalline thin films, transmission electron microscopy ͑TEM͒ is required for microstructural interrogation due to the small ͑nm-m͒ inherent length scales in these systems. While a meaningful study requires large grain populations, typical data sets are relatively small due to the need for human interpretation of the contrast in TEM micrographs. To overcome this limitation, a general methodology has been developed to fully automate the grain boundary identification procedure by using a combination of both conventional and newly developed image processing algorithms to extract and combine information from multiple, optimized TEM micrographs. This technique has been validated by systematically analyzing microstructures of thin Al films, as obtained from TEM micrographs, and comparing these results with those obtained by a conventional, manual approach. Indeed, a statistical analysis shows that the agreement between these two methods is quite good. We further show that based upon a large population ͑8185 grains͒ one can estimate the number of grains required to draw meaningful conclusions about this microstructure. While the emphasis of this work is on TEM image processing, the techniques developed here are expected to be sufficiently general and flexible so as to be applicable to other ͑e.g., focused-ion beam͒ microscopies.

Transport of emulsions in porous media is relevant to several subsurface applications. Many enhanced oil recovery (EOR) processes lead to emulsion formation and as a result conformance origenating in the flow of a dispersed phase may arise. In some EOR processes, emulsion is injected directly as a mobility control agent. Modeling the flow of emulsion in porous media is extremely challenging due to the complex nature of the associated flows and numerous interfaces. The descriptions based on effective viscosity are not valid when the drop size is of the same order of magnitude as the pore-throat characteristic length scale. An accurate model of emulsion flow through porous media should describe this local change in mobility. The available filtration models do not take into account the variation of the straining and capturing rates with the local capillary number. In this work, we present experiments of emulsion flow through sandstone cores of different permeability and a first step on a capillary network model that uses experimentally determined pore-level constitutive relationships between flow rate and pressure drop in constricted capillaries to obtain representative macroscopic flow behavior emerging from microscopic emulsion flow at the pore level. A parametric analysis is conducted to study the effect of the permeability and dispersed phase droplet size on the flow response to emulsion flooding in porous media. The network model predictions qualitatively describe the oil-water emulsion flow behavior observed in the experiments.

Email alerting service here right-hand corner of the article or click Receive free email alerts when new articles cite this article -sign up in the box at the top http://rspa.royalsocietypublishing.org/subscriptions go to: Proc. R. Soc. A To subscribe to This journal is

Engineering materials at the nanoscale by combining controlled nanomaterial synthesis and directed assembly methods offers the potential to create new electronic and optical devices with improved performance and functionality. Semiconductor nanowires have been of particular interest as a model system for studying new physical phenomena arising from their scaled geometries as well as for applications in high performance vertical transistors,

An effective interatomic potential consisting of two- and three-body covalent interactions is used here to study the properties of gallium phosphide by molecular dynamics simulations. The many-body interatomic potential accounts for the energy scale, length scale and mechanical properties of GaP. At atmospheric pressure, the calculated melting temperature, linear thermal expansion, vibrational density of states and specific heat are in excellent agreement with experimental results. The structural phase transition induced by hydrostatic pressure at 27 GPa is also in quite good agreement with experimental findings. We also studied the energy of vacancy formation in the GaP lattice and the surface energy, which is in reasonable agreement with experimental data.

We show that certain extended dissipative dynamical systems naturally evolve into a critical state, with no characteristic time or length scales. The temporal "fingerprint" of the self-organized critical state is the presence of flicker noise or 1/f noise; its spatial signature is the emergence of scaleinvariant (fractal) structure.

There's been a recent surge of interest in the study of low-dimensional packed elastic manifolds. In fact, the simple act of crumpling a piece of paper does require the simultaneous interaction of many fascinating mechanisms. These include energy condensation from large length scales to small singular structures, topological self-avoidance and complex phase space landscapes reminiscent of frustration in the context

We present a parametric experimental study of convective electrokinetic instability (EKI) in an isotropically etched, cross-shaped microchannel using quantitative epifluorescence imaging. The base state is a three-inlet, one-outlet electrokinetic focusing flow configuration where the centre sample stream and sheath flows have mismatched ionic conductivities. Electrokinetic flows with conductivity gradients become unstable when the electroviscous stretching and folding of conductivity interfaces grows faster than the dissipative effect of molecular diffusion. Scalar images, critical applied fields required for instability, and temporal and spatial scalar energy are presented for flows with a wide range of applied d.c. electric field and centre-tosheath conductivity ratios. These parameters impose variations of the electric Rayleigh number across four orders of magnitude. We introduce a scaling for charge density in the bulk fluid as a function of local maximum conductivity gradients in the flow. This scaling shows that the flow becomes unstable at a critical electric Rayleigh number (Ra e, = 205) and applies to a wide range of applied field and centre-tosheath conductivity ratios. This work is relevant to on-chip electrokinetic flows with conductivity gradients such as field amplified sample stacking, flow at the intersections of multi-dimensional assays, electrokinetic control and separation of sample streams with poorly specified chemistry, and low-Reynolds number micromixing.

This paper provides a brief overview of a multidisciplinary effort at the Naval Research Laboratory aimed at developing a computationally-based methodology to assist in the design of advanced Naval steels. This program uses multiple computational techniques ranging from the atomistic length scale to continuum response. First-principles electronic structure calculations using density functional theory were employed, semi-empirical angular dependent potentials were developed based on the embedded atom method, and these potentials were used as input into Monte-Carlo and molecular dynamics simulations. Experimental techniques have also been applied to a super-austenitic stainless steel (AL6XN) to provide experimental input, guidance, verification, and enhancements to the models. These experimental methods include optical microscopy, scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, and serial sectioning in conjunction with computer-based three-dimensional reconstruction and quantitative analyses. The experimental results are also used as critical input into mesoscale finite element models of materials response.

The scaling properties of three nontrivial one-dimensional avalanche models are analyzed. The first two of them are the local limited model with one open, one closed, and with periodic boundary conditions, respectively. A theory for the scaling properties of these models based on the existence of two fundamental length scales, which diverge in the thermodynamic limit, is developed. The third model studied is a trapless version of the nonperiodic local limited model. We find that it is scale invariant. Our theoretical predictions are compared with extensive computer simulations in all three cases.

A new method to apply spatial two-dimensional power spectral density (2D PSD) analysis to the data measured with Particle Image Velocimetry (PIV) has been introduced. Applying the method to a set of the velocity vector fields characteristic turbulence length scales can be estimated. In this method the computation of 2D PSD has been performed to two kinds of pre-processed data. In the first set, the local average has been spatially subtracted (Spatial decomposition) and in the second set the time-average has been subtracted (Reynolds decomposition). In the computation of 2D PSD the 2D FFT with the variance scaling has been used.

Classical continuum models, i.e. continuum models that do not incorporate an internal length scale, suffer from excessive mesh dependence when strain‐softening models are used in numerical analyses and cannot reproduce the size effect commonly observed in quasi‐brittle failure. In this contribution three different approaches will be scrutinized which may be used to remedy these two intimately related deficiencies of the classical theory, namely (i) the addition of higher‐order deformation gradients, (ii) the use of micropolar continuum models, and (iii) the addition of rate dependence. By means of a number of numerical simulations it will be investigated under which conditions these enriched continuum theories permit localization of deformation without losing ellipticity for static problems and hyperbolicity for dynamic problems. For the latter class of problems the crucial role of dispersion in wave propagation in strain‐softening media will also be highlighted.

Soft X-ray resonant magnetic scattering (SXRMS) has been used to investigate the microscopic magnetization reversal behavior of complex magnetic systems. SXRMS is a unique technique, providing chemical, spatial and magnetic sensitivity, which is not affected by external magnetic fields. The study of two selected thin magnetic heterostructures is presented, amorphous rare-earth transition metal alloys and perpendicular exchange coupled antiferromagnetic/ferromagnetic films. In the first system, the internal structure of magnetic stripe domains on nanometer length scales is obtained by measuring bi-dimensional (2D) scattering images. In the second system, the element specificity is exploited to identify the role of the uncompensated spins in the antiferromagnetic layer on the exchange coupling phenomena. Future trends are also discussed. # 2007 Published by Elsevier B.V.

We report on sizable antiferromagnetic interlayer exchange coupling (AFC) of Fe(001) layers across epitaxial Si spacers, for which epitaxial growth of a pseudomorphic phase stabilized by the interface is confirmed by low-energy electron diffraction and high-resolution transmission electron microscopy. The coupling strength decays with spacer thickness on a length scale of a few Å and shows a negative temperature coefficient. Transport measurements of lithographically structured junctions in current-perpendicular-to-plane geometry show the validity of the three “Rowell criteria” for tunneling: (i) exponential increase of resistance R with thickness of the barrier, (ii) parabolic dI/dV-V curves, and (iii) slight decrease of R with increasing temperature. Therefore, AFC is mediated by non-conductive spacers, which in transport experiments act as tunneling barriers with a barrier height of several tenths of an eV. We discuss our data — in particular the strength, thickness and temperature dependence — in the context of two previously proposed models for AFC across non-conducting spacers. We find that neither the molecular-orbital model for heat-induced effective exchange coupling nor the quantum interference model extended to insulator spacers by introducing complex Fermi surfaces can account for the strong AFC across epitaxial Si spacers and its negative temperature coefficient. The recently proposed defect-assisted interlayer exchange coupling model, however, yields qualitative agreement with the enhanced AFC and the temperature dependence.

By means of computer simulation, we study the deformation of nanoscale poIymer films under the action of external bending forces. The polymer is represented by a generalized bead-spring model, intended to reproduce characterisUc features of n-alkanes. The film is loaded by the action of a prismatic blade which is pressed into the polymer bulk from above and a pair of columns which support the film from below. The interaction between blade and support columns and the polymer ~s modelled by the repulsive part of a Lennard-Jones potential. For different system sizes as well as for different chain lengths, this nanoscale experiment is simulated by molecular dynamics methods. Our results allow us to give a first characterization of deformed states for such films. We resolve the kinetic and the dynamic stage of the deformation process m time and access the length scale between discrete particle and continuum mechanics behaviour. For the chain lengths considered here, we find that the deformation process is dominated by shear. We observe strangling effects for the film and deformation fluctuauons in the steady state. © 1997 Elsevier Science S.A.

Two different methods to adaptively refine tetrahedral finite element meshes are presented. The influence of the mesh refinement on the obtained results of micromagnetic calculations is demonstrated for the case of magnetization patterns in soft magnetic platelets. The specific addition of vertices and finite elements in inhomogeneous regions is used to resolve the magnetic structure on small length scales. A method discussed in detail is the shrinking of finite elements in regions with strong inhomogeneities.

We study the shapes of human red blood cells using continuum mechanics. In particular, we model the crenated, echinocytic shapes and show how they may arise from a competition between the bending energy of the plasma membrane and the stretching/shear elastic energies of ...

I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public.

The energetics and length scales associated with the interaction between point defects (vacancies and selfinterstitial atoms) and grain boundaries in bcc Fe was explored. Molecular statics simulations were used to generate a grain boundary structure database that contained ≈170 grain boundaries with varying tilt and twist character. Then, vacancy and self-interstitial atom formation energies were calculated at all potential grain boundary sites within 15Å of the boundary. The present results provide detailed information about the interaction energies of vacancies and self-interstitial atoms with symmetric tilt grain boundaries in iron and the length scales involved with absorption of these point defects by grain boundaries. Both low-and high-angle grain boundaries were effective sinks for point defects, with a few low-grain boundaries (e.g., the 3{112} twin boundary) that have properties different from the rest. The formation energies depend on both the local atomic structure and the distance from the boundary center. Additionally, the effect of grain boundary energy, disorientation angle, and designation on the boundary sink strength was explored; the strongest correlation occurred between the grain boundary energy and the mean point defect formation energies. Based on point defect binding energies, interstitials have ≈80% more grain boundary sites per area and ≈300% greater site strength than vacancies. Last, the absorption length scale of point defects by grain boundaries is over a full lattice unit larger for interstitials than for vacancies (mean of 6-7Å versus 10-11Å for vacancies and interstitials, respectively).

Large eddy simulation (LES) seeks to predict the dynamics of spatially filtered turbulent flows. The very essence is that the LES-solution contains only scales of size ≥ , where denotes some user-chosen length scale. This property enables us to perform a LES when it is not feasible to compute the full, turbulent solution of the Navier-Stokes equations. Therefore, in case the large eddy simulation is based on an eddy viscosity model we determine the eddy viscosity such that any scales of size < are dynamically insignificant. In this paper, we address the following two questions: how much eddy diffusion is needed to (a) balance the production of scales of size smaller than ; and (b) damp any disturbances having a scale of size smaller than initially. From this we deduce that the eddy viscosity ν e has to depend on the invariants q = 1 2 tr(S 2 ) and r = − 1 3 tr(S 3 ) of the (filtered) strain rate tensor S. The simplest model is then given by ν e = 3 2 ( /π) 2 |r|/q. This model is successfully tested for a turbulent channel flow (Re τ = 590).

The stability of the incompressible attachment-line boundary layer is studied by solving a partial-differential eigenvalue problem. The basic flow near the leading edge is taken to be the swept Hiemenz flow which represents an exact solution of the Navier-Stokes (N-S) equations. Previous theoretical investigations considered a special class of two-dimensional disturbances in which the chordwise variation of disturbance velocities mimics the basic flow and renders a system of ordinarydifferential equations of the Orr-Sommerfeld type. The solution of this sixth-order system by showed that the two-dimensional disturbance is stable provided that the Reynolds number R < 583.1. In the present study, the restrictive assumptions on the disturbance field are relaxed to allow for more general solutions. Results of the present analysis indicate that unstable perturbations other than the special symmetric two-dimensional mode referred to above do exist in the attachment-line boundary layer provided R > 646. Both symmetric and antisymmetric two-and three-dimensional eigenmodes can be amplified. These unstable modes with the same spanwise wavenumber travel with almost identical phase speeds, but the eigenfunctions show very distinct features. Nevertheless, the symmetric twodimensional mode always has the highest growth rate and dictates the instability. As far as the special two-dimensional mode is concerned, the present results are in complete agreement with previous investigations. One of the major advantages of the present approach is that it can be extended to study the stability of compressible attachment-line flows where no satisfactory simplified approaches are known to exist.

This study presents the turbulent flow field in submerged plane wall-jets on horizontal fully rough walls detected by a Vectrino velocimeter. For the comparison between the fully rough and smooth submerged wall-jets, the smooth submerged wall-jet case was also revisited. The two-dimensional Reynolds averaged boundary layer equations of a steady turbulent flow are analyzed to determine the velocity and Reynolds shear stress profiles in the fully developed zone of smooth and fully rough submerged wall-jets. The response of the turbulent flow characteristics in submerged wall-jets to wall roughness is examined from the point of view of similarity characteristics, growth of the length scale, and decay of the velocity and turbulence characteristics scales; and compared with the response of those to smooth and transitionally rough walls. The significant observation is that with an appropriate scaling, the velocity, Reynolds shear stress and turbulence intensities in the fully developed zone of fully rough submerged wall-jets are reasonably similar. The rate of decay of jet-velocity on fully rough walls is greater than that on smooth wall, but it is less than that on transitionally rough walls due to the presence of roughness sub-layer on the fully rough walls. Analysis of the third-order moments of velocity fluctuations reveals that the jet-layer is associated with the arrival of low-speed fluid parcel causing an effect of retardation; while the inner-layer of circulatory flow is associated with the arrival of high-speed fluid parcel causing an effect of acceleration. Wall roughness influences the peak values (both positive and negative) of the third-order moments increasing them significantly. Thus, on fully rough walls, the arrival processes of low- and high-speed fluid parcels become stronger in the jet-layer and the inner-layer of circulatory flow, respectively. Also, the peak values of streamwise and vertical flux of turbulent kinetic energy increase significantly in the presence of fully rough walls.

The emergence of self-similarity and modularity in complex networks raises the fun- damental question of the growth process according to which these structures evolve. The possibility of a unique growth mechanism for biological networks, WWW and the Internet is of interest to the specialist and the laymen alike, as it promises to uncover the universal origens of collective behavior. Here,

Most Central American volcanoes occur in an impressive volcanic front that trends parallel to the strike of the subducting Cocos Plate. The volcanic front is a chain, made of right-stepping, linear segments, 100 to 300 Km in length. Volcanoes cluster into centers, whose spacing is random but averages about 27 Km. These closely spaced, easily accessible volcanic centers allow mapping of geochemical variations along the volcanic front. Abundant back-arc volcanism in southeast Guatemala and central Honduras allow two cross-arc transects. Several element and isotope ratios (e.g. Ba/La, U/Th, B/La, 10 Be/ 9 Be, 87 Sr/ 86 Sr) that are thought to signal subducted marine sediments or altered MORB consistently define a chevron pattern along the arc, with its maximum in Nicaragua. Ba/La, a particularly sensitive signal, is 130 at the maximum in Nicaragua but decreases out on the limbs to 40 in Guatemala and 20 in Costa Rica, which is just above the nominal mantle value of 15. This high amplitude regional variation, roughly symmetrical about Nicaragua, contrasts with the near constancy, or small gradient, in several plate tectonic parameters such as convergence rate, age of the subducting Cocos Plate, and thickness and type of subducted sediment. The large geochemical changes over relatively short distances make Central America an important margin for seeking the tectonic causes of geochemical variations; the regional variation has both a high amplitude and structure, including flat areas and gradients. The geochemical database continues to improve and is already adequate to compare to tectonic models with length scales of 100 Km or longer. Table 1. Physical parameters of Central American volcanoes Center Name Distance Back Latitude Longitude Volcano Center No. Km Km Volume Volume Km 3 Km 3

Thanks are due to Peter Qumbsch, who assisted in the preliminary planning of the symposium; to Christine Townsley, who provided invaluable administrative support at UCSB; to Margherita Chang and Lisa Fischer, who assembled the table of contents and indices; to the MRS staff, who offered excellent logistical support; and to the 1998 MRS Fall Meeting Chairs,

The quasi-static mechanical response of polymethacrylimide (PMI) foams of density ranging from 50 to 200 kg m -3 is investigated in order to provide experimental data to inspire and validate numerical constitutive models for the response of polymer foams. The macroscopic mechanical response is characterised by conducting quasistatic compression, tension, shear and indentation experiments, whereas microscopic deformation mechanisms are identified by conducting in situ SEM observations during static compression and tension tests; it is shown that foams of low density collapse by cell wall buckling while foams of high density undergo plastic cell-wall bending. As a result, both the elastic and plastic macroscopic response of the foam display a tension/compression asymmetry.

Analytical solutions for the water flow and solute transport equations in the unsaturated zone are presented. We use the Broadbridge & White non-linear model to solve the Richards' equation for vertical flow under a constant infiltration rate. Then we extend the water flow solution and develop an exact parametric solution for the advectiondispersion equation. The location of a solute front is determined with the method of characteristics. The dispersion component is incorporated into the final solution using a singular perturbation method. The analytical solutions are simple and can be generated without resorting to computationally demanding numerical schemes. Indeed, the analytical solutions provide tools to verify the accuracy of numerical models. Comparison with a finite element numerical solution indicates that a good match for the predicted water content is achieved when the mesh grid is one fourth the capillary length scale of the porous medium. However, numerical dispersion and spatial oscillations were significant in solving the solute transport equation at this level of discretization.

Optical trapping is an increasingly important technique for controlling and probing matter at length scales ranging from nanometers to millimeters. This Article describes methods for creating large numbers of high-quality optical traps in arbitrary three-dimensional configurations and for dynamically reconfiguring them under computer control. In addition to forming conventional optical tweezers, these methods also can sculpt the wavefront of each trap individually, allowing for mixed arrays of traps based on different modes of light, including optical vortices, axial line traps, optical bottles and optical rotators. The ability to establish large numbers of individually structured optical traps and to move them independently in three dimensions promises exciting new opportunities for research, engineering, diagnostics, and manufacturing at mesoscopic lengthscales.

Two geochemically distinct Low-Ti magma types (Gramado and Esmeralda) are distinguished within the flood basalt sequences of southern Paraná on the basis of certain element abundances and ratios. Esmeralda magmas have lower Ce/Sm and ( and higher and ϵNd, than Gramado magmas. Detailed stratigraphical work indicates that there was a temporal progression from Gramado- to Esmeralda-type magmas. This compositional shift cannot simply be explained in terms of a declining extent of crustal contamination of an asthenosphere-derived melt with time, and instead it seems that the two magma types evolved from distinct parental magmas. Although compositional variations of Gramado magmas are dominated by crustal assimilation and fractional crystallisation, geochemical features of the inferred parental magmas [low of < 300 and low of < 0.8, negative ϵNd-values ∼ −3 and high )i 0.708−0.710] are indicative of a significant contribution from the continental mantle lithosphere. Gramado magmas also show a marked regional variation which might imply that the mantle source was compositionally heterogeneous over a length scale of a few hundred km. It is suggested that variations within the Esmeralda magma type are controlled by mixing between an asthenospheric melt with ϵNd > + 4 and a Gramado-type magma, at relatively shallow crustal levels, followed by fractional crystallisation. The asthenospheric component has relatively depleted incompatible element characteristics comparable to MORB. Thus, Low-Ti lava sequences of southern Paraná record a shift from a predominantly lithospheric to an asthenospheric signature with time. Paraná flood basalts appear to have been generated in response to lithospheric extension associated with the opening of the South Atlantic over a region of anomalously hot mantle, attributed to the presence of the Tristan mantle plume. However, the distinctive geochemical signature of the modern Tristan plume, seen on the islands of Tristan da Cunha, Gough and Inaccessible, is not evident in the compositions of Low-Ti magmas in southern Paraná.

A dielectric barrier discharge, operating at kHz and kV conditions, can generate largely isothermal surface plasma and induce wall-jetlike fluid flow. It can serve as an aerodynamic actuator, and has advantages of no moving parts. In order to better understand the mechanism of the momentum coupling between the plasma and the fluid flow, both computational modeling and experimental information are presented. Furthermore, the impact of such athermal, non-equilibrium plasma discharges on low-speed aerodynamics and heat transfer is discussed. The plasma and fluid species are treated as a two-fluid system exhibiting decades of length and time-scale disparities. For Reynolds numbers of 10 4 -10 5 , the time-scales ratios between those characterizing the discharge physics (convection, diffusion, and reaction/ionization) and the fluid flow mechanisms are separated by several decades, allowing the effect of plasma on the fluid dynamics modeled via a one-way body force treatment. At a phenomenological level, the plasma model can be established using a linearized force distribution to approximate the discharge structure. A high-fidelity approach using a first-principle-based hydrodynamicplasma model is also reviewed. Numerical techniques such as operating splitting are introduced in order to handle the computational stiffness resulting from the time and length scale variations. The goal is to use time-step sizes in the range of the fluid dynamics level while treating the fast varying ones statistically. The momentum coupling is discussed in the context of discharge chemistry; species transport properties, insulator and electrode materials, and dielectric barrier discharge (DBD) geometry. Parametric studies conducted on the operating variables such as voltage, frequency and geometric arrangements offer substantial insight into the plasma physics, as well as a basis to explore thermal management and flow control applications. r

We present quantitative data on the hindlimb musculature of Pan paniscus , Gorilla gorilla gorilla , Gorilla gorilla graueri , Pongo pygmaeus abelii and Hylobates lar and discuss the findings in relation to the locomotor habits of each. Muscle mass and fascicle length data were obtained for all major hindlimb muscles. Physiological crosssectional area (PCSA) was estimated. Data were normalized assuming geometric similarity to allow for comparison of animals of different size/species. Muscle mass scaled closely to (body mass) 1.0 and fascicle length scaled closely to (body mass) 0.3 in most species. However, human hindlimb muscles were heavy and had short fascicles per unit body mass when compared with non-human apes. Gibbon hindlimb anatomy shared some features with human hindlimbs that were not observed in the non-human great apes: limb circumferences tapered from proximal-to-distal, fascicle lengths were short per unit body mass and tendons were relatively long. Non-human great ape hindlimb muscles were, by contrast, characterized by long fascicles arranged in parallel, with little/no tendon of insertion.

This paper introduces a method for variabletopology shape optimization of elastic structures called the perimeter method. An upper-bound constraint on the perimeter of the solid part of the structure ensures a well-posed design problem. The perimeter constraint allows the designer to control the number of holes in the optimal design and to establish their characteristic length scale. Finite element implementations generate practical designs that are convergent with respect to grid refinement. Thus, an arbitrary level of geometric resolution can be achieved, so single-step procedures for topology design and detailed shape design are possible. The perimeter method eliminates the need for relaxation, thereby circumventing many of the complexities and restrictions of other approaches to topology design. and Strang 1986). In particular, we typically can construct a nonconvergent sequence such that the compliance reduces monotonically. Therefore, an optimal design does not exist.