Three-dimensional Character Research Articles

Phase diagram for antiferromagnetism and superconductivity in the pressure-induced heavy-fermion superconductorCe2RhIn8probed byI115n-NQR

We present a phase diagram for the antiferromagnetism and superconductivity in ${\text{Ce}}_{2}{\text{RhIn}}_{8}$ probed by In-NQR studies under pressure $(P)$. The quasi-two-dimensional character of antiferromagnetic spin fluctuations in the paramagnetic state at $P=0$ evolves into a three-dimensional character because of the suppression of antiferromagnetic order for $Pg{P}_{\text{QCP}}\ensuremath{\sim}1.36\text{ }\text{GPa}$ (QCP: quantum critical point). Nuclear-spin-lattice relaxation rate $1/{T}_{1}$ measurements revealed that the superconducting order occurs in the $P$ range 1.36--1.84 GPa, with maximum ${T}_{c}\ensuremath{\sim}0.9\text{ }\text{K}$ around ${P}_{\text{QCP}}\ensuremath{\sim}1.36\text{ }\text{GPa}$.

Candide en Dannemarc ou l'optimisme des honnetes gens

In 1760, a year after the publication of Candide, there appeared a sequel, Candide: Seconde partie. This competent pastiche, published anonymously, is now known to be the work of the abbé Dulaurens; at the time, Grimm (in order to protect Voltaire) attributed it, implausibly and mischievously, to Thorel de Campigneulles, a journalist of impeccably orthodox views. Campigneulles seems to have taken his revenge a few years later by publishing, also anonymously, Candide en Dannemarc, a continuation of the work which he had been falsely accused of writing, in effect Candide Part Three. Édouard Langille's edition is to be welcomed: although the novel's literary qualities are minimal, it is an intriguing example of that important fictional sub-genre, the suite. Whereas Dulaurens continued Voltaire's novel by attempting to imitate Voltaire's style, and so perpetuate its ideology, Campigneulles quite deliberately sets out to refute Voltaire's critique of optimism by having Candide mature into a happy three-dimensional character. Freed from the dungeons of a bloodthirsty baron, Candide marries his beloved Zénoïde, a classy Danish blonde (Cunégonde having been conveniently killed off by Dulaurens), and the young couple live happily and boringly ever after, with Candide becoming a wise and trusted adviser to the monarch. Two encounters towards the end of the novel, with Martin (remember him?) and Jean-Jacques Rousseau, serve to reaffirm Candide's new-found philosophical serenity. Candide en Dannemarc, with its worthy and platitudinous sentiments, did not enjoy the same success as Dulaurens' more raucous Seconde partie (which was often reprinted, sometimes together with Candide), but even so it went through three editions (and not two, as claimed here, p. 4): the octavo edition published in Rouen in 1767 was followed by a duodecimo edition in the same year, and an octavo edition in 1769. The 1769 edition contains a dedication, not reproduced here, but apart from that the variants between these three editions are of no consequence. (There is a confusion in the textual apparatus: most of the variants attributed to the 1769 edition in fact first appeared in the 1767 duodecimo edition.) The text is extensively annotated: the linguistic notes are especially useful, but some of the explanatory notes are oddly judged: does the likely reader of an edition such as this need to be told, for example, that Tacitus was a Roman historian? The introduction presents the content of the novel, and argues that the early chapters set in a prison anticipate gothic fiction. Importantly, Langille confirms the attribution of this work to Thorel de Campigneulles, and so it is a pity the author's name does not figure on the title page of this edition. There is no reference here to any of the recent scholarship on this Grub Street figure, and in particular his links with Voltaire would be worth following up. A writer who satirized La Nouvelle Héloïse in an epistolary novel written by a monkey to his teacher (Le Nouvel Abaillard, 1763) clearly deserves further attention.

Alamethicin Aggregation in Lipid Membranes

X-ray scattering features induced by aggregates of alamethicin (Alm) were obtained in oriented stacks of model membranes of DOPC(diC18:1PC) and diC22:1PC. The first feature obtained near full hydration was Bragg rod in-plane scattering near 0.11 A(-1) in DOPC and near 0.08 A(-1) in diC22:1PC at a 1:10 Alm:lipid ratio. This feature is interpreted as bundles consisting of n Alm monomers in a barrel-stave configuration surrounding a water pore. Fitting the scattering data to previously published molecular dynamics simulations indicates that the number of peptides per bundle is n = 6 in DOPC and n >or= 9 in diC22:1PC. The larger bundle size in diC22:1PC is explained by hydrophobic mismatch of Alm with the thicker bilayer. A second diffuse scattering peak located at q(r) approximately 0.7 A(-1) is obtained for both DOPC and diC22:1PC at several peptide concentrations. Theoretical calculations indicate that this peak cannot be caused by the Alm bundle structure. Instead, we interpret it as being due to two-dimensional hexagonally packed clusters in equilibrium with Alm bundles. As the relative humidity was reduced, interactions between Alm in neighboring bilayers produced more peaks with three-dimensional crystallographic character that do not index with the conventional hexagonal space groups.

The parallel dynamics of drift wave turbulence in the WEGA stellarator

The three-dimensional structure of turbulence in the edge (inside the last closed flux surface) of the WEGA stellarator is studied focusing on the parallel dynamics. WEGA as a small stellarator with moderate plasma parameters offers the opportunity to study turbulence with Langmuir probes providing high spatial and temporal resolution. Multiple probes with radial, poloidal and toroidal resolution are used to measure density fluctuations. Correlation analysis is used to reconstruct a 3D picture of turbulent structures. We find that these structures originate predominantly on the low field side and have a three-dimensional character with a finite averaged parallel wavenumber. The ratio between the parallel and perpendicular wavenumber component is in the order of 10−2. The parallel dynamics are compared at magnetic inductions of 57 and 500 mT. At 500 mT, the parallel wavelength is in the order of the field line connection length . A frequency resolved measure of k∥/kθ shows a constant ratio in this case. At 57 mT the observed k∥ is much smaller than at 500 mT. However, the observed small average value is due to an averaging over positive and negative components pointing parallel and antiparallel to the magnetic field vector.

Fluctuation conductivity along the c-axis and parallel to the ab-planes in melt-textured YBa2Cu3O7− samples doped with Y211 phase

Abstract We report measurements of in-plane and out-of-plane fluctuation conductivity under low applied magnetic fields up to 500 Oe in two melt-textured YBa2Cu3O7−δ (YBCO) samples. 3D-Gaussian and genuine critical 3D-XY-E fluctuation regimes were identified in the conductivity parallel to the ab plane. In addition, a regime beyond 3D-XY was observed in the immediate vicinity of the superconducting transition of the in-plane fluctuation conductivity. The 3D-XY-E scaling was also identified in the fluctuation conductivity along the c-axis in the sample with smaller content of the Y2BaCuO5 (Y211) phase. This result indicates that the superconducting state in YBCO has a three-dimensional character, in contradiction to some studies suggesting that critical phenomenology is fundamentally distinct in orientations parallel or perpendicular to the Cu–O2 planes of the high-temperature superconductors. However, the results suggests the presence of a sub-dominant order-parameter component in YBCO that has an appreciable projection along the c-axis.

LANDAU LEVEL SPECTROSCOPY OF DIRAC-LIKE FERMIONS IN MULTILAYER GRAPHENE

The results of spectroscopic (magneto-transmission and Raman scattering) studies1–8 of multilayers of carbon which are thermally decomposed from carbon-terminated surface of silicon carbide, and of thin layers of highly oriented pyrolytic and natural graphite were presented. Those carbon multilayers on silicon carbide which are not directly affected by the SiC / C interface and which in consequence are nearly charge neutral show the magneto-optical properties identical with the properties characteristic of a single graphite sheet, graphene. Inter Landau level transitions in this multilayer graphene have been studied in a wide spectral range from far-infrared to almost visible region. The dispersion relations of electronic states are found to reflect the form of the Dirac cone with almost perfect electron-hole symmetry and only weak deviations from linearity at high energies. Cyclotron resonance transition in multilayer graphene can be observed in magnetic fields down to 40 mT, and its width is practically independent on temperature up to 300 K. Such parameters as carrier mobility and minimal conductivity as well as the possibility to probe the immediate vicinity of the Dirac point were evaluated and discussed in detail. For comparison, the magneto-optical properties of thin layers of bulk graphite were also reported. The Dirac like electronic dispersion relations are also found in these systems, but only in the vicinity of the particular (H) point of the Brillouin zone. In general, the measured spectra are, however, more complex and reflect the three-dimensional character of graphene layers with Bernal stacking. Note from Publisher: This article contains the abstract only.

Ultrastructural surface characteristics of seminiferous tubules from men with varicocele.

Testicular biopsies were obtained from 40 otherwise healthy men with diagnosed varicocele and processed for scanning electron microscopy. Testis biopsies from two men with scrotal pain served as control. The seminiferous epithelium was variably affected, ranging from what appeared to be essentially normal to severely altered. In tubules in which normal cellular associations were compromised, the surface anatomy of the tubule epithelium was distorted, adluminal sertoli cell cytoplasm was truncated and there was an apparent displacement, reduction in number and, in some extreme cases, absence, of germ cells. Visualization of the varicocele-affected seminiferous epithelium by the scanning electron microscope reveals more fully the extent and three-dimensional character of adluminal compartment dissolution and reconfirms our four stage classification of seminiferous tubules in this pathology.

Simulation of Damage Percolation Within Aluminum Alloy Sheet

A combined experimental and analytical approach is used to study damage initiation and evolution in three-dimensional second phase particle fields. A three-dimensional formulation of a damage percolation model is developed to predict damage nucleation and propagation through random-clustered second phase particle fields. The proposed approach is capable of capturing the three-dimensional character of damage phenomena and the three stages of ductile fracture, namely, void nucleation, growth, and coalescence, at the level of discrete particles. An in situ tensile test with X-ray tomography is utilized to quantify material damage during deformation in terms of the number of nucleated voids and porosity. The results of this experiment are used for both the development of a clustering-sensitive nucleation criterion and the validation of the damage percolation predictions. The evolution of damage in aluminum alloy AA5182 has been successfully predicted to match that in the in situ tensile specimen. Two forms of second phase particle field input data were considered: (1) that measured directly with X-ray tomography and (2) fields reconstructed statistically from two-dimensional orthogonal sections. It is demonstrated that the adoption of a cluster-sensitive void nucleation criterion, as opposed to a cluster-insensitive nucleation criterion, has a significant effect in promoting predicted void nucleation to occur within particle clusters. This behavior leads to confinement of void coalescence to within clusters for most of the duration of deformation followed by later development of a macrocrack through intracluster coalescence. The measured and reconstructed second phase particle fields lead to similar rates of predicted damage accumulation and can be used interchangeably in damage percolation simulations.

A compressible wall-adapting similarity mixed model for large-eddy simulation of the impinging round jet

Wall-jet interaction is studied with large-eddy simulation (LES) in which a mixed-similarity subgrid scale (SGS) closure is combined with the wall-adapting local eddy-viscosity (WALE) model for the eddy-viscosity term. The macrotemperature and macropressure are introduced to deduce a weakly compressible form of the mixed-similarity model, and the relevant formulation for the energy equation is deduced accordingly. LES prediction capabilities are assessed by comparing flow statistical properties against experiment of an unconfined impinging round jet at Reynolds numbers of 23 000 and 70 000. To quantify the benefit of the proposed WALE-similarity mixed model, the lower Reynolds number simulations are also performed using the standard WALE and Lagrangian dynamic Smagorinsky approaches. The unsteady compressible Navier–Stokes equations are integrated over 2.9 M, 3.5 M, and 5.5 M node Cartesian grids with an explicit fourth-order finite volume solver. Nonreflecting boundary conditions are enforced using a methodology accounting for the three-dimensional character of the turbulent flow at boundaries. A correct wall scaling is achieved from the combination of similarity and WALE approaches; for this wall-jet interaction, the SGS closure terms can be computed in the near-wall region without the necessity of resorting to additional specific treatments. The possible impact of turbulent energy backscatter in such flow configurations is also addressed. It is found that, for the present configuration, the correct reproduction of reverse energy transfer plays a key role in the estimation of near-wall statistics, especially when the viscous sublayer is not properly resolved.

Short-term habituation of eye-movement responses induced by galvanic vestibular stimulation (GVS) in the alert guinea pig

In a recent study, we showed that primary afferent neurons innervating all vestibular end organs were sensitive to galvanic vestibular stimulation (GVS) in guinea pigs. In order to determine the three-dimensional character of eye movements induced by GVS, changes in eye position were recorded using digital video oculography during delivery of bilateral GVS ranging in intensity between 20 and 80 μA. Pulses were delivered in repetitive trains in order to also ascertain the involvement of vestibular habituation. At low intensities of GVS (up to 40 μA), maintained changes in eye position were induced toward the anode and away from the cathode. These eye movements were predominantly vertical with some horizontal eye movement and very little or no torsion. At higher intensities of GVS (>40 μA), horizontal nystagmus was initially observed, as well as an overall deviation of the beating field toward the anode. Nystagmus was found to habituate rapidly over successive presentations of GVS, whereas the tonic deviation of the eye remained consistent without any detectible habituation. The direction of eye movements induced by GVS was similar to that observed in humans during trans-mastoidal GVS, and the threshold differences between tonic and phasic components for GVS were also similar to previous human GVS studies. The observed habituation appears to be more specific to the phasic VOR component in quadrupedal animals such as guinea pigs, and this may reflect a considerable emphasis placed on otolithic stimulation in these animals during complex locomotor activities.

Verification of a numerical model for the prediction of low slope vertical slot fishway hydraulics

A numerical model has been developed to predict the three-dimensional flow character within low slope vertical slot fishways (VSFs). The model solves the three dimensional Reynolds averaged Navier-Stokes equations, closed with the renormalised k-ॉ turbulence formulations. The model employs the volume of fluid method to deal with the free surface. Results are presented for velocities and surface elevations utilising two fishway designs from prototype and laboratory studies. The respective data from these studies are directly compared to the numerical model predictions forming the basis of verification. The model is shown to predict critical design velocities, slot flow characteristics, flow recirculation and water surface elevations well enough to be useful in low slope VSF design.

Character of magnetic excitations in a quasi-one-dimensional antiferromagnet near the quantum critical points: Impact on magnetoacoustic properties

We report results of magnetoacoustic studies in the quantum spin-chain magnet ${\text{NiCl}}_{2}\text{\ensuremath{-}}4\text{SC}{({\text{NH}}_{2})}_{2}$ (DTN) having a field-induced ordered antiferromagnetic (AF) phase. In the vicinity of the quantum critical points (QCPs) the acoustic ${c}_{33}$ mode manifests a pronounced softening accompanied by energy dissipation of the sound wave. The acoustic anomalies are traced up to $T>{T}_{N}$, where the thermodynamic properties are determined by fermionic magnetic excitations, the ``hallmark'' of one-dimensional (1D) spin chains. On the other hand, as established in earlier studies, the AF phase in DTN is governed by bosonic magnetic excitations. Our results suggest the presence of a crossover from a 1D fermionic to a three-dimensional bosonic character of the magnetic excitations in DTN in the vicinity of the QCPs.

Life: Coming to a Screen Near You

Today, hundreds of thousands of people across the globe are regular participants in online virtual worlds such as Second Life, Google Lively, Twinity, and There. Twentyfive years from now, the hundreds of millions of participants in such virtual worlds such as these will come to regard them as a primary medium through which their normal daily transactions are carried out. At that point, these fantasy-filled virtual worlds will, like the imaginary world of Borges' scholars, become, for all intents and purposes, real. For today's casual participant, entering one of these virtual worlds feels very much like joining a multi-player video game. The participant designs a three-dimensional cartoonish character, commonly called an avatar, from a set of possible characteristics. The avatar can be tall or short, with any color of hair and any number of other features and qualities selected from a range of available options. The participant then controls the avatar just as they would a character in a video game, only with far greater means of communication and expression. The avatar can enter buildings, interact with other avatars by text, speech, or gesture, visit restaurants, bars, schools, churches, and nightclubs, stroll through art exhibitions, attend balls, and go to press conferences. All of these structures and spaces are created by other participants in the virtual world.

Investigation of the vortex induced unsteadiness of a separation bubble via time-resolved and scanning PIV measurements

A transitional separation bubble on the suction side of an SD7003 airfoil is considered. The transition process that forces the separated shear layer to reattach seems to be governed by Kelvin–Helmholtz instabilities. Large scale vortices are formed due to this mechanism at the downstream end of the bubble. These vortices possess a three-dimensional structure and detach from the recirculation region, while other vortices are formed within the bubble. This separation of the vortex is a highly unsteady process, which leads to a bubble flapping. The structure of these vortices and the flapping of the separation bubble due to these vortices are temporally and spatially analyzed at angles of attack from 4° to 8° and chord-length based Reynolds numbers Rec = 20,000–60,000 using time-resolved PIV measurements in a 2D and a 3D set-up, i.e., stereo-scanning PIV measurements are done in the latter case. These measurements complete former studies at a Reynolds number of Rec = 20,000. The results of the time-resolved PIV measurements in a single light-sheet show the influence of the angle of attack and the Reynolds number. The characteristic parameters of the separation bubble are analyzed focusing on the unsteadiness of the separation bubble, e.g., the varying size of the main recirculation region, which characterizes the bubble flapping, and the corresponding Strouhal number are investigated. Furthermore, the impact of the freestream turbulence is investigated by juxtaposing the current and former results. The stereo-scanning PIV measurements at Reynolds numbers up to 60,000 elucidate the three-dimensional character of the vortical structures, which evolve at the downstream end of the separation bubble. It is shown that the same typical structures are formed, e.g., the c-shape vortex and the screwdriver vortex at each Reynolds number and angle of attack investigated and the occurrence of these patterns in relation to Λ-structures is discussed. To evidence the impact of the freestream turbulence, these results are compared with findings of former measurements.

Champ de vitesses et contraintes de cisaillement dans un collecteur d’assainissement

The presence of sediment at the bottom of the collectors is of interest for hydraulic and environmental reasons. Design rules enable avoiding silting in a wide range of situation, but are not suited for accurately assessing risk for a particular facility. The stress at the bottom is a determining parameter for the processes of sedimentation and erosion and results from the velocity field in a cross section. This article presents an experimental and numerical approach of the space distribution of the velocities and shear stresses in a collector of sewers network. The results show that, for the narrow channels, it is necessary to take into account the three-dimensional character of the flow. Numerical modeling provides the lower cost for the results that is difficult to acquire in experiments. On the other hand a total evaluation of the average shear stress seems less adapted to describe the reality of shear stress in the section.

Pattern formation in the ferrocyanide-iodate-sulfite reaction: The control of space scale separation

We revisit the conditions for the development of reaction-diffusion patterns in the ferrocyanide-iodate-sulfite bistable and oscillatory reaction. This hydrogen ion autoactivated reaction is the only example known to produce sustained stationary lamellar patterns and a wealth of other spatio-temporal phenomena including self-replication and localized oscillatory domain of spots, due to repulsive front interactions and to a parity-breaking front bifurcation (nonequilibrium Ising-Bloch bifurcation). We show experimentally that the space scale separation necessary for the observation of stationary patterns is mediated by the presence of low mobility weak acid functional groups. The presence of such groups was overlooked in the original observations made with hydrolyzable polyacrylamide gels. This missing information made the original observations difficult to reproduce and frustrated further experimental exploitation of the fantastic potentialities of this system. Using one-side-fed spatial reactors filled with agarose gel, we can reproduce all the previous pattern observations, in particular the stationary labyrinthine patterns, by introducing, above a critical concentration, well controlled amounts of polyacrylate chains in the gel network. We use two different geometries of spatial reactors (annular and disk shapes) to provide complementary information on the actual three-dimensional character of spatial patterns. We also reinvestigate the role of other feed parameters and show that the system exhibits both a domain of spatial bistability and of large-amplitude pH oscillations associated in a typical cross-shape diagram. The experimental method presented here can be adapted to produce patterns in the large number of oscillatory and bistable reactions, since the iodate-sulfite-ferrocynide reaction is a prototype of these systems.

Dislocation-cracks interaction during fatigue: A discrete dislocation dynamics simulation

In this article, the effect of different shape cracks on fatigue behavior in metals is investigated with the help of the discrete dislocation dynamics technique. The cracks are represented as distributions of infinitesimal dislocation loops. The distribution is determined by an integral equation satisfying stress-free boundary conditions and containing a singular kernel of the third type. The stress field in the cracked domain is calculated using a superposition principle coupled with an iterative technique. The derived stress fields describe the interaction between the cracks and the dislocations into the framework of dislocation dynamics. The simulation results provide an insight on the three-dimensional character of the dislocation structure around the cracks and its relation to the crack shapes. The effect of the cracks on the macroscopic yield stress is also determined for various crack sizes and shapes.

Vertical structure of the quasi-two-dimensional velocity field of a viscous incompressible flow and the problem of nonlinear friction

An approximate theory is constructed to describe quasi-two-dimensional viscous incompressible flows. This theory takes into account a weak circulation in the vertical plane and the related divergence of the two-dimensional velocity field. The role of the nonlinear terms that are due to the interaction between the vortex and potential components of velocity and the possibility of taking into account the corresponding effects in the context of the concept of bottom friction are analyzed. It is shown that the nonlinear character of friction is a consequence of the three-dimensional character of flow, which results in the effective interaction of vortices with vertical and horizontal axes. An approximation of the effect of this interaction in quasi-two-dimensional equations is obtained with the use of the coefficient of nonlinear friction. The results based on this approximation are compared to the data of laboratory experiments on the excitation of a spatially periodic fluid flow.

Three-dimensional features of the turbulent flow through a planar sudden expansion

An experimental investigation of the turbulent flow downstream of a planar sudden expansion has been performed by means of a 2D particle image velocimetry (PIV) technique. Flow fields at the Reynolds number of 104 have been measured in several mutually perpendicular planes of a channel having an expansion ratio of 3 and an aspect ratio of 10. As usual for large expansion ratios, the separated flow exhibits a strong asymmetry about the expansion axis and, consequently, very different reattachment lengths on the two side walls of the channel. The mean flow turns out to be substantially symmetric about the midspan plane and strong three-dimensional effects are observed in wide portions of the separation bubbles adjacent to the upper and lower walls. The reattachment lengths exhibit significant spanwise variations that are particularly pronounced in the longer reattachment line. Measurements performed in a single flow plane at Re=4⋅104 show that the influence of the Reynolds number on the mean flow is not completely negligible in the considered variation range. Based on a careful analysis of the PIV data, a model of the three-dimensional mean flow structure in the separation bubbles has been conjectured and it is provided in the paper. The present investigation contributes to clarifying the controversial three-dimensional character of the turbulent flow in a planar sudden expansion and provides accurate and detailed reference data for numerical simulations.

A three-dimensional unstructured mesh finite element shallow-water model, with application to the flows around an island and in a wind-driven, elongated basin

We present a new three-dimensional, unstructured mesh finite element shallow-water model. The current configuration is suitable for studying unstratified flows and the evolution of passive tracers. The model has a free surface and is hydrostatic. The mesh is unstructured in the horizontal and extruded towards the seabed in the direction parallel to the local gravity vector to generate a mesh made up of prisms. The mesh moves in the vertical and accommodates the free-surface motions. We describe the numerical treatment of the hydrodynamical equations with the finite element method. A discontinuous representation is used in the vertical for all velocity components. The horizontal velocity components are non-conforming in the horizontal, which is particularly appropriate for advection-dominated flows. The model is validated against a realistic tidal flow around a shallow-water island for which field measurements are available and is shown to operate successfully. The three-dimensional character of the flow is emphasized by use of a passive tracer. We also assess the model’s ability to represent the vertical structure of the horizontal flow field by applying it to a wind-driven flow experiment in an elongated rectangular basin.