ALBERT

Description: The article addresses old ‘west-east discourses’ and how they continue to develop in the high north, and, not least, in the Norwegian petroleum debate. Adopting a discourse analytical perspective the author shows how environmental safety is used as an argument in favour of Norway producing oil in the Barents Sea at the earliest possible moment. This is only feasible if a connection is made in the public mind between Russia and the environment. These views, it is argued, stem from ideas about Russia that gained currency after the demise of the Soviet Union. While they perhaps have less to do with Russia's petroleum industry and environmental performance today, they nevertheless have a strong impact on how challenges in the high north and Arctic region are perceived. And, perhaps even more importantly, they define freedom of action and available options. In this paper all references to government departments refer to those of Norway.

Description: A study of the morphology of the vortical skeleton behind a flapping NACA0030 wing with a finite aspect ratio of 3, is undertaken. The motivation for this work originates with the proposal that thrust can be efficiently produced by flapping aerofoils. The test condition corresponds to a Strouhal number of 0.35, Reynolds number, based on aerofoil chord, of 600 and an amplitude of flapping, equal to the chord length of the wing. This test condition corresponds to the optimal thrust-producing case in infinite-span flapping wings. This study investigates the effect of wing three-dimensionality on the structure of the wake-flow. This is accomplished here, by quantitatively describing the spatio-temporal variations in the velocity, vorticity and Reynolds stresses for the finite-span-wing case.Preliminary flow visualizations suggest that the presence of wingtip vortices for the three-dimensional-wing case, create a different vortical structure to the two-dimensional-wing case. In the case of a two-dimensional-wing, the flow is characterized by the interaction of leading- and trailing-edge vorticity, resulting in the formation of a clear reverse Kármán vortex street at the selected test condition. In the case of a three-dimensional-wing, the flow exhibits a high degree of complexity and three-dimensionality, particularly in the midspan region. Using phase-averaged particle image velocimetry measurements of the forced oscillatory flow, a quantitative analysis in the plane of symmetry of the flapping aerofoil was undertaken. Using a triple decomposition of the measured velocities, the morphological characteristics of the spanwise vorticity is found to be phase correlated with the aerofoil kinematics. Reynolds stresses in the direction of oscillation are the dominant dissipative mechanism. The mean velocity profiles resemble ajet, indicative of thrust production. Pairs of strong counter-rotating vortices from the leading- and trailing-edge of the aerofoil are shed into the flow at each half-cycle. The large-scale structure of the flow is characterized by constructive merging of spanwise vorticity. The midspan region is populated by cross-sections of interconnected vortex rings.

Description: The effectiveness of international environmental cooperation is a theoretical and methodological challenge that has captured the interest of scholars and students of international relations in the recent years. This article is an evaluation of international environmental cooperation in northwest Russia by applying an approach developed in the Institutional Dimensions of Global Environmental Change (IDGEC) research programme of the International Human Dimension Programme (IHDP). The IDGEC approach emphasises the importance of complex diagnostics of institutional environmental arrangements in terms of performance. The approach relates to the effects of international environmental cooperation in terms of sustainability, efficiency, fairness, and robustness. The article focuses on Russian and Nordic experiences of international environmental cooperation, and the assessment of performance has been done by the participants themselves. According to the results of interviews and questionnaires, the cooperation is considered institutionally effective and robust in general. However, views about the environmental effects vary. Some problems exist that are related to sustainability and fairness, but the most critical issue is the lack of domestic environmental capacity in Russia.

Description: In this study, we performed simulations of turbulent flow over rectangular ribs transversely mounted on one side of a plane in a channel, with the other side being smooth. The separation between ribs is large enough to avoid forming stable vortices in the spacing, which exhibitsk-type, or sand-grain roughness. The Reynolds numberReτof our representative direct numerical simulation case is 460 based on the smooth-wall friction velocity and the channel half-width. The roughness heighthis estimated as 110 wall units based on the rough-wall friction velocity. The velocity profile and kinetic energy budget verify the presence of an equilibrium, logarithmic layer aty≳2h. In the roughness sublayer, however, a significant turbulent energy flux was observed. A high-energy region is formed by the irregular motions just above the roughness. Visualizations of vortical streaks, disrupted in all three directions in the roughness sublayer, indicate that the three-dimensional flow structure of sand-grain roughness is replicated by the two-dimensional roughness, and that this vortical structure is responsible for the high energy production. The difference in turbulence structure between smooth- and rough-wall layers can also be seen in other flow properties, such as anisotropy and turbulence length scales.

Description: A model for simulating the process of growth, collapse and rebound of a cavitation bubble travelling along the flow through a convergent–divergent nozzle producing a cavitating water jet is established. The model is based on the Rayleigh–Plesset bubble dynamics equation using as inputs ambient pressure and velocity profiles calculated with the aid of computational fluid dynamics (CFD) flow modelling. A variable time-step technique is applied to solve the highly nonlinear second-order differential equation. This technique successfully solves the Rayleigh–Plesset equation for wide ranges of pressure variation and bubble original size and saves considerable computing time. Inputs for this model are the pressure and velocity data from CFD calculation. To simulate accurately the process of bubble growth, collapse and rebound, a heat transfer model, which includes the effects of conduction plus radiation, is developed to describe the thermodynamics of the incondensable gas inside the bubble. This heat transfer model matches previously published experimental data well. Assuming that single bubble behaviour also applies to bubble clouds, the calculated distance from the nozzle exit travelled by the bubble to the point where the bubble size becomes invisible is taken to be equal to the bubble cloud length observed. The predictions are compared with experiments carried out in a cavitation cell and show good agreement for different nozzles operating at different pressure conditions.

Description: An experimental study, investigating the mean flow and turbulence in the wind drift layer formed beneath short wind waves was conducted. The degree to which these flows resemble the flows that occur in boundary layers adjacent to solid walls (i.e. wall-layers) was examined. Simultaneous DPIV (digital particle image velocimetry) and infrared imagery were used to investigate these near-surface flows at a fetch of 5.5 m and wind speeds from 4.5 to 11 m s−1. These conditions produced short steep waves with dominant wavelengths from 6 cm to 18 cm. The mean velocity profiles in the wind drift layer were found to be logarithmic and the flow was hydrodynamically smooth at all wind speeds. The rate of dissipation of turbulent kinetic energy was determined to be significantly greater in magnitude than would occur in a comparable wall-layer. Microscale breaking waves were detected using the DPIV data and the characteristics of breaking and non-breaking waves were compared. The percentage of microscale breaking waves increased abruptly from 11% to 80% as the wind speed increased from 4.5 to 7.4 m s−and then gradually increased to 90% as the wind speed increased to 11 m s−. At a depth of 1 mm, the rate of dissipation was 1.7 to 3.2 times greater beneath microscale breaking waves compared to non-breaking waves. In the crest–trough region beneath microscale breaking waves, 40% to 50% of the dissipation was associated with wave breaking. These results demonstrated that the enhanced near-surface turbulence in the wind drift layer was the result of microscale wave breaking. It was determined that the rate of dissipation of turbulent kinetic energy due to wave breaking is a function of depth, friction velocity, wave height and phase speed as proposed by Terrayet al. (1996). Vertical profiles of the rate of dissipation showed that beneath microscale breaking waves there were two distinct layers. Immediately beneath the surface, the dissipation decayed as ζ−0.7and below this in the second layer it decayed as ζ−2. The enhanced turbulence associated with microscale wave breaking was found to extend to a depth of approximately one significant wave height. The only similarity between the flows in these wind drift layers and wall-layers is that in both cases the mean velocity profiles are logarithmic. The fact that microscale breaking waves were responsible for 40%–50% of the near-surface turbulence supports the premise that microscale breaking waves play a significant role in enhancing the transfer of gas and heat across the air–sea interface.

Description: Results are presented from experimental investigations into the motion of a heavy ellipsoid in a horizontal rotating cylinder, which has been completely filled with highly viscous fluid. The motion can be conveniently classified using the ratio between the maximum radius of curvature of the ellipsoid κmaxand the radius of the drumRd. If κmax

Description: Electric conduction from an electrolyte solution into a charge selective solid, such as ion exchange membrane or electrode, becomes unstable when the electrolyte concentration near the interface approaches zero owing to diffusion limitation. The sequence of events leading to instability is as follows: upon the decrease of the interface concentration, the electric double layer at the interface transforms from its common quasi-equilibrium structure to a different, non-equilibrium one. The key feature of this new structure is an extended space charge added to the usual one of the quasi-equilibrium electric double layer. The non-equilibrium electro-osmotic slip related to this extended space charge renders the quiescent conductance unstable. A unified asymptotic picture of the electric double-layer undercurrent, encompassing all regimes from quasi-equilibrium to the extreme non-equilibrium one, is developed and employed for derivation of a universal electro-osmotic slip formula. This formula is used for a linear stability study of quiescent electric conduction, yielding the precise parameter range of instability, compared with that in the full electroconvective formulation. The physical mechanism of instability is traced both kinematically, in terms of non-equilibrium electro-osmotic slip, and dynamically, in terms of forces acting in the electric double layer.

Description: The water-shipping problem is modelled in a two-dimensional framework and studied experimentally and numerically for the case of a fixed barge-shaped structure. The analysis represents the second step of the research discussed in Grecoet al. (J. Fluid Mech., vol. 525, 2005, p. 309). The numerical investigation is performed by using both a boundary element method and a domain-decomposition strategy. The model tests highlight the occurrence of dam-breaking-type water on deck, (a) with and (b) without an initial plunging phase, and (c) an unusual type of water shipping connected with blunt water–deck impacts here called a hammer-fist type event never documented before. Cases (a) and (c) are connected with the most severe events and the related features and green-water loads are discussed in detail. A parametric analysis of water-on-deck phenomena has also been carried out in terms of the local incoming waves and bow flow features. We classify such phenomena in a systematic way to provide a basis for further investigations of water-on-deck events. The severity of (a)-type water-on-deck events is analysed in terms of initial cavity area and water-front velocity along the deck. The former increases as the square power of the modified incoming-wave (front-crest) steepness while the latter scales with its square-root. The two-dimensional investigation gives useful quantitative information in terms of water-front velocity for comparison with three-dimensional water-on-deck experiments on fixed bow models interacting with wave packets.

Description: The irrotational flow past two slender bodies of revolution at angles of yaw, translating in parallel paths in very close proximity, is analysed by extending the classical slender body theory. The flow far away from the two bodies is shown to be a direct problem, which is represented in terms of two line sources along their longitudinal axes, at the strengths of the variation rates of their cross-section areas. The inner flow near the two bodies is reduced to the plane flow problem of the expanding (contracting) and lateral translations of two parallel circular cylinders with different radii, which is then solved analytically using conformal mapping. Consequently, an analytical flow solution has been obtained for two arbitrary slender bodies of revolution at angles of yaw translating in close proximity. The lateral forces and yaw moments acting on the two bodies are obtained in terms of integrals along the body lengths. A comparison is made among the present model for two slender bodies in close proximity, Tuck & Newman's (1974) model for two slender bodies far apart, and VSAERO (AMI)–commercial software based on potential flow theory and the boundary element method (BEM). The attraction force of the present model agrees well with the BEM result, when the clearance,h0, is within 20% of the body length, whereas the attraction force of Tuck & Newman is much smaller than the BEM result whenh0is within 30% of the body length, but approaches the latter whenh0is about half the body length. Numerical simulations are performed for the three typical manoeuvres of two bodies: (i) a body passing a stationary body, (ii) two bodies in a meeting manoeuvre (translating in opposite directions), and (iii) two bodies in a passing manoeuvre (translating in the same direction). The analysis reveals the orders of the lateral forces and yaw moments, as well as their variation trends in terms of the manoeuvre type, velocities, sizes, angles of yaw of the two bodies, and their proximity, etc. These irrotational dynamic features are expected to provide a basic understanding of this problem and will be beneficial to further numerical and experimental studies involving additional physical effects.

Description: The flow associated with a synthetic jet transitioning to turbulence in an otherwise quiescent external flow is examined using time-accurate three-dimensional numerical simulations. The incompressible Navier–Stokes solver uses a second-order accurate scheme for spatial discretization and a second-order semi-implicit fractional step method for time integration. The simulations are designed to model the experiments of C. S. Yaoet al. (Proc. NASA LaRC Workshop, 2004) which have examined, in detail, the external evolution of a transitional synthetic jet in quiescent flow. Although the jet Reynolds and Stokes numbers in the simulations match with the experiment, a number of simplifications have been made in the synthetic jet actuator model adopted in the current simulations. These include a simpler representation of the cavity and slot geometry and diaphragm placement. Despite this, a reasonably good match with the experiments is obtained in the core of the jet and this indicates that for these jets, matching of these key non-dimensional parameters is sufficient to capture the critical features of the external jet flow. The computed results are analysed further to gain insight into the dynamics of the external as well as internal flow. The results indicate that near the jet exit plane, the flow field is dominated by the formation of counter-rotating spanwise vortex pairs that break down owing to the rapid growth of spanwise instabilities and transition to turbulence a short distance from the slot. Detailed analyses of the unsteady characteristics of the flow inside the jet cavity and slot provide insights that to date have not been available from experiments.

Description: A general proof that more energy flows upscale than downscale in two-dimensional turbulence and barotropic quasi-geostrophic (QG) turbulence is given. A proof is also given that in surface QG turbulence, the reverse is true. Though some of these results are known in restricted cases, the proofs given here are pedagogically simpler, require fewer assumptions and apply to both forced and unforced cases.

Description: The local linear stability of forced, stationary long waves produced by topography or potential vorticity (PV) sources is examined using a quasi-geostrophic barotropic model. A multiple scale analysis yields coupled equations for the background stationary wave and low-frequency (LF) disturbance field. Forcing structures for which the LF dynamics are Hamiltonian are shown to yield conservation laws that provide necessary conditions for instability and a constraint on the LF structures that can develop. Explicit knowledge of the forcings that produce the stationary waves is shown to be crucial to predicting a unique LF field. Various topographies or external PV sources can be chosen to produce stationary waves that differ by asymptotically small amounts, yet the LF instabilities that develop can have fundamentally different structures and growth rates. If the stationary wave field is forced solely by topography, LF oscillatory modes always emerge. In contrast, if the stationary wave field is forced solely by PV, two LF structures are possible: oscillatory modes or non-oscillatory envelope modes. The development of the envelope modes within the context of a linear LF theory is novel.An analysis of the complex WKB branch points, which yields an analytical expres-sion for the leading-order eigenfrequency, shows that the streamwise distribution of absolute instability and convective growth is central to understanding and predicting the types of LF structures that develop on the forced stationary wave. The location of the absolute instability region with respect to the stationary wave determines whether oscillatory modes or envelope modes develop. In the absence of absolute instability, eastward propagating wavetrains generated in the far field can amplify via local convective growth in the stationary wave region. If the stationary wave region is streamwise symmetric (asymmetric), the local convective growth results in a local change in wave energy that is transient (permanent).

Description: This paper presents combined theoretical and experimental studies of the two-dimensional piston-like steady-state motions of a fluid in a moonpool formed by two rectangular hulls (e.g. a dual pontoon or catamaran). Vertical harmonic excitation of the partly submerged structure in calm water is assumed. A high-precision analytically oriented linear-potential-flow method, which captures the singular behaviour of the velocity potential at the corner points of the rectangular structure, is developed. The linear steady-state results are compared with new experimental data and show generally satisfactory agreement. The influence of vortex shedding has been evaluated by using the local discrete-vortex method of Graham (1980). It was shown to be small. Thus, the discrepancy between the theory and experiment may be related to the free-surface nonlinearity.

Description: This paper presents a study of the global response of a fluid to impulsive and localized forcing; it has been motivated by the recent laboratory experiments on the locomotion of water-walking insects reported in Hu, Chan & Bush (Nature, vol. 424, 2003, p. 663). These insects create both waves and vortices by their rapid leg strokes and it has been a matter of some debate whether either form of motion predominates in the momentum budget. The main result of this paper is to argue that generically both waves and vortices are significant, and that in linear theory they take up the horizontal momentum with share 1/3 and 2/3, respectively.This generic result, which depends only on the impulsive and localized nature of the forcing, is established using the classical linear impulse theory, with adaptations to weakly compressible flows and flows with a free surface. Additional general comments on experimental techniques for momentum measurement and on the wave emission are given and then the theory is applied in detail to water-walking insects.Owing to its generality, this kind of result and the methods used to derive it should be applicable to a wider range of wave–vortex problems in the biolocomotion of water-walking animals and elsewhere.

Description: The Regenerative Enclosed Life Support Module Simulator (REMS) was designed to simulate the conditions aboard the International Space Station (ISS). This unique terrestrial, encapsulated environment for humans and their associated organisms allowed investigations into the microbial communities within an enclosed habitat system, primarily with respect to diversity, phylogeny and the possible impact on human health. To assess time- and/or condition-dependent changes in microbial diversity within REMS, a total of 27 air samples were collected during three consecutive months. The microbial burden and diversity were elucidated using culture-dependent and culture-independent molecular methods. The results indicate that during controlled conditions the total microbial burden detected by culture-dependent techniques (below a detectable level to 102 cells m−3of air) and intracellular ATP assay was significantly low (102–103 cells m−3of air), but increased during the uncontrolled post-operation phase (∼104 cells m−3of air). Only Gram-positive and α-proteobacteria grew under tested culture conditions, with a predominant occurrence ofMethylobacterium radiotolerans, andSphingomonas yanoikuyae. Direct DNA extraction and 16S rDNA sequencing methodology revealed a broader diversity of microbes present in the REMS air (51 species). Unlike culture-dependent analysis, both Gram-positive and proteobacteria were equally represented, while members of a few proteobaterial groups dominated (Rhodopseudomonas,Sphingomonas,Acidovorax,Ralstonia,Acinetobacter,Pseudomonas, andPsychrobacter). Although the presence of several opportunistic pathogens warrants further investigation, the results demonstrated that routine maintenance such as controlling the humidity, crew’s daily cleaning, and air filtration were effective in reducing the microbial burden in the REMS.

Description: Experimentation and theory are used to study the long-term dynamics of a two-dimensional density current flowing into a two-layer stratified basin. When the initial Richardson number,$hbox{it Ri}_{ ho}^{hbox{scriptsizeit in}}$, characterizing the ratio of the background stratification to the buoyancy flux of the density current, is less than the critical value of$hbox{it Ri}_{ ho}^{*} ,{=}, 21-27$, it is found that the density current penetrates the stratified interface. This result is ostensibly independent of slope for angles between 30° and 90°. If the current does not initially penetrate the interface, then it slowly increases the density of the top layer until the interfacial density difference is reduced sufficiently to drive penetration. The time scale for this to occur,$t_{p} ,{=}, (hbox{it Ri}^{hbox{scriptsizeit in}}_{ ho} - hbox{it Ri}_{ ho}^{*}) L/B^{1/3}$, is explicitly a function of the buoyancy fluxBand the length of the basinL. The initial Richardson number,$hbox{it Ri}^{hbox{scriptsizeit in}}_{ ho}$, is a function of depth, the initial reduced gravity of the interface and a weak function of slope angle. In the absence of initial penetration for very steep slopes of 75° and 90°, we observe that penetrative convection at the interface leads to significant local entrainment. In consequence, the top layer thickens and the interfacial entrainment rate increases as the fifth power of the interfacial Froude number. In contrast, such a process is not observed at comparable interfacial Froude numbers on lower slopes of 30°, 45° and 60°, thereby demonstrating the important role of impact angle on penetrative convection. We attribute the increased interfacial entrainment by the steep density currents as the result of the transition from an undular bore to a turbulent hydraulic jump at the point where the density current intrudes. We discuss the applicability of the observed circulation to the stability of the Arctic halocline where we find$0.56,{lesssim}, t_{p} ,{lesssim},1.2$years for a range of contemporary oceanographic conditions.

Description: Direct numerical simulations (DNS) of stenotic flows under conditions of steady inlet flow were discussed in Part 1 of this study. DNS of pulsatile flow through the 75% stenosed tube (by area) employed for the computations in Part 1 is examined here. Analogous to the steady flow results, DNS predicts a laminar post-stenotic flow field in the case of pulsatile flow through the axisymmetric stenosis model, in contrast to previous experiments, in which intermittent disturbed flow regions and turbulent breakdown were observed in the downstream region. The introduction of a stenosis eccentricity, that was 5% of the main vessel diameter at the throat, resulted in periodic, localized transition to turbulence. Analysis in this study indicates that the early and mid-acceleration phases of the time period cycle were relatively stable, with no turbulent activity in the post-stenotic region. However, towards the end of acceleration, the starting vortex, formed earlier as the fluid accelerated through the stenosis at the beginning of acceleration, started to break up into elongated streamwise structures. These streamwise vortices broke down at peak flow, forming a turbulent spot in the post-stenotic region. In the early part of deceleration there was intense turbulent activity within this spot. Past the mid-deceleration phase, through to minimum flow, the inlet flow lost its momentum and the flow field began to relaminarize. The start of acceleration in the following cycle saw a recurrence of the entire process of a starting structure undergoing turbulent breakdown and subsequent relaminarization of the post-stenotic flow field. Peak wall shear stress (WSS) levels occurred at the stenosis throat, with the rest of the vessel experiencing much lower levels. Turbulent breakdown at peak flow resulted in a sharp amplification of instantaneous WSS magnitudes across the region corresponding to the turbulent spot, accompanied by large axial and circumferential fluctuations, even while ensemble-averaged axial shear stresses remained mostly low and negative. WSS levels dropped rapidly after the mid-deceleration phase, when the relaminarization process took over, and were almost identical to laminar, axisymmetric shear levels through most of the acceleration phase.

Description: We investigate experimentally the force generated by the unsteady vortex formation of low-aspect-ratio normal flat plates with one end free. The objective of this study is to determine the role of the free end, or tip, vortex. Understanding this simple case provides insight into flapping-wing propulsion, which involves the unsteady motion of low-aspect-ratio appendages. As a simple model of a propulsive half-stroke, we consider a rectangular normal flat plate undergoing a translating start-up motion in a towing tank. Digital particle image velocimetry is used to measure multiple perpendicular sections of the flow velocity and vorticity, in order to correlate vortex circulation with the measured plate force. The three-dimensional wake structure is captured using flow visualization. We show that the tip vortex produces a significant maximum in the plate force. Suppressing its formation results in a force minimum. Comparing plates of aspect ratio six and two, the flow is similar in terms of absolute distance from the tip, but evolves faster for aspect ratio two. The plate drag coefficient increases with decreasing aspect ratio.

Description: Using the Boussinesq approximation, a set of depth-integrated wave equations for long-wave propagation over a mud bed is derived. The wave motions above the mud bed are assumed to be irrotational and the mud bed is modelled as a highly viscous fluid. The pressure and velocity are required to be continuous across the water–mud interface. The resulting governing equations are differential–integral equations in terms of the depth-integrated horizontal velocity and the free-surface displacement. The effects of the mud bed appear in the continuity equation in the form of a time integral of weighted divergence of the depth-averaged velocity. Damping rates for periodic waves and solitary waves are calculated. For the solitary wave case, the velocity profiles in the water column and the mud bed at different phases are discussed. The effects of the viscous boundary layer above the mud–water interface are also examined.

Description: During extended deployment at an ocean observatory off the coast of New Jersey, a bottom-mounted five-beam acoustic Doppler current profiler measured large-scale velocity structures that we interpret as Langmuir circulations filling the entire water column. These circulations are the large-eddy structures of wind-wave-driven turbulent flows that occur episodically when a shallow water column experiences prolonged strong wind forcing. Many observational characteristics agree with former descriptions of Langmuir circulations in deep water. The three-dimensional velocity field reveals quasi-organized structures consisting of pairs of surface-intensified counter-rotating vortices, aligned approximately downwind. Maximum downward velocities are stronger than upward velocities, and the downwelling region of each cell, defined as a pair of vortices, is narrower than the upwelling region. Maximum downward vertical velocity occurs at or above mid-depth, and scales approximately with wind speed. The estimated crosswind scale of cells is roughly 3–6 times their vertical scale, set under these conditions by water depth. The long axis of the cells appears to lie at an angle ∼10°–20° to the right of the wind. A major difference from deep-water observations is strong near-bottom intensification of the downwind ‘jets’ found typically centred over downwelling regions. Accessible observational features such as cell morphology and profiles of mean velocities, turbulent velocity variances, and shear stress components are compared with the results of associated large-eddy simulations (reported in Part 2) of shallow water flows driven by surface stress and the Craik–Leibovich vortex forcing generally used to represent generation of Langmuir cells. A particularly sensitive diagnostic for identification of Langmuir circulations as the energy-containing eddies of the turbulent flow is the depth trajectory of invariants of the turbulent stress tensor, plotted in the Lumley ‘triangle’ corresponding to realizable turbulent flows. When Langmuir structures are present in the observations, the Lumley map is distinctly different from that of surface-stress-driven Couette flow, again in agreement with the large-eddy simulations (LES). Unlike the LES, observed velocity fields contain two distinct and significant scales of variability, documented by wavelet analysis of observational records of vertical velocity. Variability with periods of many minutes is that expected from Langmuir cells drifting past the instrument at the slowly time-varying crosswind velocity. Shorter period variability, of the order of 1–2 min, has roughly the observed periodicity of surface wave groups, suggesting a connection with the wave groups themselves and/or the wave breaking associated with them in high wind conditions.

Description: Lagrangian auto- and cross-correlation functions of the rate of strains2, enstrophy ω2, their respective production terms −sijsjkskiand ωiωjsij, and material derivatives, Ds2/Dtand Dω2/Dtare estimated using experimental results obtained through three-dimensional particle tracking velocimetry (three-dimensional-PTV) in homogeneous turbulence atReλ=50. The autocorrelation functions are used to estimate the Lagrangian time scales of different quantities, while the cross-correlation functions are used to clarify some aspects of the interaction mechanisms between vorticity ω and the rate of strain tensorsij, that are responsible for the statistically stationary, in the Eulerian sense, levels of enstrophy and rate of strain in homogeneous turbulent flow. Results show that at the Reynolds number of the experiment these quantities exhibit different time scales, varying from the relatively long time scale of ω2to the relatively shorter time scales ofs2, ωiωjsijand −sijsjkski. Cross-correlation functions suggest that the dynamics of enstrophy and strain, in this flow, is driven by a set of different-time-scale processes that depend on the local magnitudes ofs2and ω2. In particular, there are indications that, in a statistical sense, (i) strain production anticipates enstrophy production in low-strain–low-enstrophy regions (ii) strain production and enstrophy production display high correlation in high-strain–high-enstrophy regions, (iii) vorticity dampening in high-enstrophy regions is associated with weak correlations between −sijsjkskiands2and between −sijsjkskiand Ds2/Dt, in addition to a marked anti-correlation between ωiωjsijand Ds2/Dt. Vorticity dampening in high-enstrophy regions is thus related to the decay ofs2and its production term, −sijsjkski.

Description: Transverse jets arise in many applications, including propulsion, effluent dispersion, oil field flows, and V/STOL aerodynamics. This study seeks a fundamental, mechanistic understanding of the structure and evolution of vorticity in the transverse jet. We develop a high-resolution three-dimensional vortex simulation of the transverse jet at large Reynolds number and consider jet-to-crossflow velocity ratiosrranging from 5 to 10. A new formulation of vorticity-flux boundary conditions accounts for the interaction of channel wall vorticity with the jet flow immediately around the orifice. We demonstrate that the nascent jet shear layer contains not only azimuthal vorticity generated in the jet pipe, but wall-normal and azimuthal perturbations resulting from the jet–crossflow interaction. This formulation also yields analytical expressions for vortex lines in the near field as a function ofr.Transformation of the cylindrical shear layer emanating from the orifice begins with axial elongation of its lee side to form sections of counter-rotating vorticity aligned with the jet trajectory. Periodic roll-up of the shear layer accompanies this deformation, creating complementary vortex arcs on the lee and windward sides of the jet. Counter-rotating vorticity then drives lee-side roll-ups in the windward direction, along the normal to the jet trajectory. Azimuthal vortex arcs of alternating sign thus approach each other on the windward boundary of the jet. Accordingly, initially planar material rings on the shear layer fold completely and assume an interlocking structure that persists for several diameters above the jet exit. Though the near field of the jet is dominated by deformation and periodic roll-up of the shear layer, the resulting counter-rotating vorticity is a pronounced feature of the mean field; in turn, the mean counter-rotation exerts a substantial influence on the deformation of the shear layer. Following the pronounced bending of the trajectory into the crossflow, we observe a sudden breakdown of near-field vortical structures into a dense distribution of smaller scales. Spatial filtering of this region reveals the persistence of counter-rotating streamwise vorticity initiated in the near field.

Description: The decay of a passive scalar in a sinusoidal shear flow translating in the cross-stream direction at a constant speeduis studied in the limit of small diffusivity κ. The decay rate, obtained by solving an eigenvalue problem, is found to tend to a non-zero constant as κ→0 whenuis of order κ1/2. This result, establishing that fast decay is possible in shear flows, is fragile however: because of the existence of pseudomodes, the addition of a small noise leads to decay rates that decrease to zero with κ as κ2/5.

Description: Direct numerical simulation is used to study a round turbulent jet in a laminar crossflow. The ratio of bulk jet velocity to free-stream crossflow velocity is 5.7 and the Reynolds number based on the bulk jet velocity and the jet exit diameter is 5000. The mean velocity and turbulent intensities from the simulations are compared to data from the experiments by Su & Mungal (2004) and good agreement is observed. Additional quantities, not available from experiments, are presented. Turbulent kinetic energy budgets are computed for this flow. Examination of the budgets shows that the near field is far from a state of turbulent equilibrium – especially along the jet edges. Also – in the near field – peak kinetic energy production is observed close to the leading edge, while peak dissipation is observed toward the trailing edge of the jet. The results are used to comment upon the difficulty involved in predicting this flow using RANS computations. There exist regions in this flow where the pressure transport term, neglected by some models and poorly modelled by others, is significant. And past the jet exit, the flow is not close to established canonical flows on which most models appear to be based.

Description: The theory of Wagner from 1932 for the normal symmetric impact of a two-dimensional body of small deadrise angle on a half-space of ideal and incompressible liquid is extended to derive the second-order corrections for the locations of the higher-pressure jet-root regions and for the upward force on the impactor using a systematic matched-asymptotic analysis. The second-order predictions for the upward force on an entering wedge and parabola are compared with numerical and experimental data, respectively, and it is concluded that a significant improvement in the predictive capability of Wagner's theory is afforded by proceeding to second order.

Description: SUMMARYThe purpose of the current work was to study phosphorus (P) metabolism in growing sheep supplemented with different levels of dicalcium phosphate using an extant mathematical model. Twelve male non-castrated Santa Inês sheep, weighing 23 (±2·2) kg, received a basal diet unsupplemented or supplemented with dicalcium phosphate to provide 1·5, 3·0, 4·5 g of P/animal per day (treatments T1 to T4, respectively). After 3 weeks adaptation, 7·4 MBq of32P was injected into the jugular vein of each animal. Samples of blood, faeces and urine were collected every day during a 7-day period and thereafter the animals were sacrificed and samples from liver, kidney, heart, muscle and bone were collected for specific activity and inorganic P determinations. The flows between gut and plasma were similar for each treatment except for T1, which showed the lowest values for both flows (P

Description: SUMMARYMedial claws from the right hind feet were obtained post mortem from four 19–20-month-old beef heifers and from four 28-month-old first-calving dairy heifers 3–4 days postpartum. X-ray diffraction (XRD) studies were undertaken on samples of soft and hard (cornified) integumental tissues of dorsal wall, sole and heel (bulb) for varying sites and planes of exposure. The measurements were interpreted as defining diffraction patterns and intermolecular spacings of cytoskeletal and extracellular fibrous structural proteins. The orientation of these proteins was examined in relation to physical characteristics and function including bearing of body weight by these tissues.Physical measurements taken included impression hardness which showed typically greater values for wall than sole and variable differences between horn of dairy and beef origin and husbandry systems. Claws from dairy heifers had significantly smaller values for toe (dorsal wall) angle, claw height and heel height and thickness of solear horn and heel soft tissue. Although few were studied, the results reflected typical husbandry origins and indicated the susceptibility to the lesion formation well recognized in postpartum dairy cattle.Typical XRD patterns for horn samples showed defined arcs of reflectance on the equatorial axis consistent with findings for the presence of α-helices in fibrils reported to occur in other hard-keratin-containing integumental tissues. However, reflectance on the meridional axis also reported for these other tissues was not detected. A similar defined pattern was obtained for less than 0·10 of samples of internal soft pre-cornified epidermal and attached dermal tissue although the values for intermolecular ‘d’ spacing for these were consistent with those reported for type I collagen. Diffuse reflection patterns were thus evident for the majority of samples of soft tissue epidermis and dermis and also for adipose tissue of the digital cushion.The formation of defined arcs of reflectance allowed the determination of fibril alignment in wall and solear horn. For the orientated samples of dorsal wall horn tissue, the outer layer showed a longitudinal angle of orientation essentially maintained proximal to distal. This pattern was maintained throughout the depth of horn at the proximal site. In contrast, layers in mid-wall and towards the distal edge showed a greater circumferential (horizontal) orientation in sections collected anterior to posterior towards the inner corial, including laminar, tissues. The orientation of fibrils in inner wall horn appears to relate to the direction of load-bearing forces in connecting horn to the distal phalanx. Horizontal alignment of fibrils was observed in the sole. In presenting the long axis of cells to the ground surface this orientation may facilitate erosive forces and contribute to the thinning of cornified sole horn under adverse underfoot conditions.

Description: The flapping coupling between two filaments is studied theoretically and experimentally in this paper. A temporal linear instability analysis is carried out based on a simplified hydrodynamic model. The dispersion relationship between the eigen-frequency ω and wavenumberkis expressed by a quartic equation. Two special cases of flapping coupling, i.e. two identical filaments having the same length and two filaments having different lengths, are studied in detail. In the case of two identical filaments, the theoretical analysis predicts four coupling modes, i.e. the stretched-straight mode, the antisymmetrical in-phase mode, the symmetrical out-of-phase mode and the indefinite mode. The theory also predicts the existence of an eigenfrequency jump during transition between the in-phase and out-of-phase modes, which has been observed in previous experiments and numerical simulations. In the case of two filaments having different lengths, four modes similar to those in the former case are identified theoretically. The distribution of coupling modes for both the cases is shown in two planes. One is a dimensionless plane ofSvs.U, whereSis the density ratio of solid filament to fluid andU2is the ratio of fluid kinetic energy to solid elastic potential energy. The other is a dimensional plane of the half-distance (h) between two filaments vs. the filament length (L). Relevant experiments are carried out in a soap-film tunnel and the stable and unstable modes are observed. Theory and experiment are compared in detail. It should be noted that the model used in our analysis is a very simplified one that can provide intuitional analytical results of the coupling modes as well as their qualitative distributions. The factors neglected in our model, such as vortex shedding, viscous and nonlinear effects, do not allow the model to predict results precisely consistent with the experiments. Moreover, the Strouhal numbers of the flapping filaments are found to be generally around a fixed value in the experiments for both cases, implying that the filaments try to maintain a lower potential energy state.

Description: Numerical simulations on a β-plane are used to further understand the formation of zonal flows from small-scale fluctuations. The dynamics of ‘reduced models’ are computed by restricting the nonlinear term to include a subset of triad interactions in Fourier space. Reduced models of near-resonant triads are considered, as well as the complement set of non-resonant triads. At moderately small values of the Rhines number, near-resonant triad interactions are shown to be responsible for the generation of large-scale zonal flows from small-scale random forcing. Without large-scale drag, both the full system and the reduced model of near resonances produce asymmetry between eastward and westward jets, in favour of stronger westward jets. When large-scale drag is included, the long-time asymmetry is reversed in the full system, with eastward jets that are thinner and stronger than westward jets. Then the reduced model of near resonances exhibits a weaker asymmetry, but there are nevertheless more eastward jets stronger than a threshold value.

Description: Free surface potential flows past disturbances in a channel are considered. Three different types of disturbance are studied: (i) a submerged obstacle on the bottom of a channel; (ii) a pressure distribution on the free surface; and (iii) an obstruction in the free surface (e.g. a sluice gate or a flat plate). Surface tension is neglected, but gravity is included in the dynamic boundary condition. Fully nonlinear solutions are computed by boundary integral equation methods. In addition, weakly nonlinear solutions are derived. New solutions are found when several disturbances are present simultaneously. They are discovered through the weakly nonlinear analysis and confirmed by numerical computations for the fully nonlinear problem.

Description: A numerical description of heterogeneous propellant combustion enables us to examine the spatial and temporal fluctuations in the flow field arising from the heterogeneity. Particular focus is placed on the fluctuations in a zone intermediate between the combustion field (where reaction is important) and the chamber flow domain, for these define boundary conditions for simulations of the turbulent chamber flow. The statistics of the temperature field and the normal velocity field are described, and characteristic length scales and time scales are identified. The length scales are small compared to any relevant length scale of the chamber flow, and so the boundary conditions for this flow at any mesh point are statistically independent of those at any other mesh point. But the temporal correlations at a fixed point are significant, and affect the nature of the chamber flow in a variety of ways. We describe the fluctuations in the head-end pressure that arise because of them, and contrast these results with those calculated using a white-noise assumption.

Description: We consider the flapping stability and response of a thin two-dimensional flag of high extensional rigidity and low bending rigidity. The three relevant non-dimensional parameters governing the problem are the structure-to-fluid mass ratio, μ = ρsh/(ρfL); the Reynolds number,Rey=VL/ν; and the non-dimensional bending rigidity,KB=EI/(ρfV2L3). The soft cloth of a flag is represented by very low bending rigidity and the subsequent dominance of flow-induced tension as the main structural restoring force. We first perform linear analysis to help understand the relevant mechanisms of the problem and guide the computational investigation. To study the nonlinear stability and response, we develop a fluid–structure direct simulation (FSDS) capability, coupling a direct numerical simulation of the Navier–Stokes equations to a solver for thin-membrane dynamics of arbitrarily large motion. With the flow grid fitted to the structural boundary, external forcing to the structure is calculated from the boundary fluid dynamics. Using a systematic series of FSDS runs, we pursue a detailed analysis of the response as a function of mass ratio for the case of very low bending rigidity (KB= 10−4) and relatively high Reynolds number (Rey= 103). We discover three distinct regimes of response as a function of mass ratio μ: (I) a small μ regime of fixed-point stability; (II) an intermediate μ regime of period-one limit-cycle flapping with amplitude increasing with increasing μ; and (III) a large μ regime of chaotic flapping. Parametric stability dependencies predicted by the linear analysis are confirmed by the nonlinear FSDS, and hysteresis in stability is explained with a nonlinear softening spring model. The chaotic flapping response shows up as a breaking of the limit cycle by inclusion of the 3/2 superharmonic. This occurs as the increased flapping amplitude yields a flapping Strouhal number (St= 2Af/V) in the neighbourhood of the natural vortex wake Strouhal number,St≃ 0.2. The limit-cycle von Kármán vortex wake transitions in chaos to a wake with clusters of higher intensity vortices. For the largest mass ratios, strong vortex pairs are distributed away from the wake centreline during intermittent violent snapping events, characterized by rapid changes in tension and dynamic buckling.

Description: The governing equations for the two-point correlations of the turbulent fluctuating velocity in the temporally evolving wake were analysed to determine whether they could have equilibrium similarity solutions. It was found that these equations could have such solutions for a finite-Reynolds-number wake, where the two-point velocity correlations could be written as a product of a time-dependent scale and a function dependent only on similarity variables. It is therefore possible to collapse the two-point measures of all the scales of motions in the temporally evolving wake using a single set of similarity variables. As in an earlier single-point analysis, it was found that the governing equations for the equilibrium similarity solutions could not be reduced to a form that was independent of a growth-rate dependent parameter. Thus, there is not a single ‘universal’ solution that describes the state of the large-scale structures, so that the large-scale structures in the far field may depend on how the flow is generated.The predictions of the similarity analysis were compared to the data from two direct numerical simulations of the temporally evolving wakes examined previously. It was found that the two-point velocity spectra of these temporally evolving wakes collapsed reasonably well over the entire range of scales when they were scaled in the manner deduced from the equilibrium similarity analysis. Thus, actual flows do seem to evolve in a manner consistent with the equilibrium similarity solutions.

Description: This paper examines the consistency of the exact scaling laws for isotropic magnetohydrodynamic (MHD) turbulence in numerical simulations with large magnetic Prandtl numbersPmand withPm= 1. The exact laws are used to elucidate the structure of the magnetic and velocity fields. Despite the linear scaling of certain third-order correlation functions, the situation is not analogous to the case of Kolmogorov turbulence. The magnetic field is adequately described by a model of a stripy (folded) field with direction reversals at the resistive scale. At currently available resolutions, the cascade of kinetic energy is short-circuited by the direct exchange of energy between the forcing-scale motions and the stripy magnetic fields. This non-local interaction is the defining feature of isotropic MHD turbulence.

Description: SUMMARYThe development of the genetic control of nematode resistance in growing lambs is of biological interest, as well as being important in terms of designing practical strategies to breed for increased nematode resistance. The current paper demonstrates the use of random regression techniques for quantifying the development of the heritability of faecal egg count (Fec), the indicator of nematode resistance, in growing lambs and predicted inter-age genetic and phenotypic correlations for Fec. Fec data from 732 lambs, collected at 4-week intervals fromc. 8–24 weeks of age, were analysed using random regression techniques. Random effects fitted in the model included genetic, individual animal environmental, litter and residual random effects. Output (co)variance components were interpolated to weekly time points. Individual variance components showed complex patterns of change over time; however, the estimated heritability increased smoothly with age, from 0·10 to 0·38, and showed more stable time trends than were obtained from univariate analyses of Fec at individual time points. Inter-age correlations decreased as the time interval between measurements increased. Genetic correlations were always positive, with 0·6 of all possible inter-age correlations being greater than 0·80. Phenotypic correlations were lower, and decreased more quickly as the time interval between measurements increased. The results presented confirm biological understanding of the development of immunity to nematode infections in growing lambs. Additionally, they provide a tool to determine optimal sampling ages when assessing lambs' relative resistance to nematode infections.

Description: SUMMARYSince many soils used for growing potatoes in the UK are likely to be close to their plastic limit for cultivation during early spring, there exists the potential for soil compaction to occur during planting which will restrict root penetration. A series of experiments showed that soil compaction delayed emergence, reduced rate of leaf appearance and ground cover expansion, shortened canopy cover duration and restricted light interception, which combined to reduce tuber yield. Rooting density and maximum depth of rooting were reduced, particularly where compaction was shallow. In some soils, irrigation helped alleviate some of the effects of compaction but in others it exacerbated their severity. Using a cone penetrometer, relationships between rate of root penetration and soil resistance (Ω) were established from a number of experiments and replicated blocks in commercial fields and an overall relationship of the formy=16·3–4·08Ω mm/day was produced. Root penetration rates ofc. 20 mm/day were measured in the intensively-cultivated ridge zone but growth rates were halved at a Ω of 1·5 MPa. A survey of 602 commercial fields showed that two thirds of fields had Ωs ⩾3 MPa (where root growth rates would be

Description: The hypothesis of the explosion of a number of planets and moons of our Solar System during its 4.6-billion-year history is in excellent accord with all known observational constraints, even without adjustable parameters orad hochelper hypotheses. Many of its boldest predictions have been fulfilled. In most instances, these predictions were judged highly unlikely by the current standard models. Moreover, in several cases, the entire exploded planet model was at risk of being falsified if the predictions failed. The successful predictions include: (1) satellites of asteroids; (2) satellites of comets; (3) salt water in meteorites; (4) ‘roll marks’ leading to boulders on asteroids; (5) the time and peak rate of the 1999 Leonid meteor storm; (6) explosion signatures for asteroids; (7) the strongly spiked energy parameter for new comets; (8) the distribution of black material on slowly rotating airless bodies; (9) splitting velocities of comets; (10) the asteroid-like nature ofDeep Impacttarget Comet Tempel 1; and (11) the presence of high-formation-temperature minerals in theStardustcomet dust sample return. In physics and astronomy, hypotheses are either falsified if their predictions fail, or proved to be of value if they succeed. By all existing evidence, the exploded planet hypothesis has proved far more useful than the half-dozen or so hypotheses it would replace. Among the many important corollaries are these. (a) Perhaps as many as six former planets of our Solar System have exploded over its 4.6-billion-year history. (b) In particular, Mars is not an original planet, but a former moon of an exploded planet. (c) As a major player in Solar System evolution, the exploded planet scenario must be considered as a likely propagation vehicle for the spread of biogenic organisms. We conclude with a brief mention of three possible planetary explosion mechanisms.

Description: The degree and nature of association between trace metals (Cu, Pb, Zn, Ni, Ag, & Cd) and cyanobacterial mats, phytoplankton and sediments has been assessed in the Lake Vanda region of the Wright Valley, Victoria Land. Trace metal:Fe ratios and SEM imaging confirmed that apparent trace metal enrichment in cyanobacterial mats, relative to the sediment beneath, was due to incorporation of fine (sub-micron) sediment particles in the muciligenous matrix of the mat. In suspended particulate material (SPM) filtered from the oxic water of Lake Vanda and the Onyx River, the degree of trace metal binding to the SPM did not appear to correlate with phytoplankton content. Instead a positive correlation was observed between Fe and trace metal content. The SPM at the top of the lake water column, where only the finest sediment remains suspended, had the highest trace metal concentrations. It is concluded that the trace metal content of cyanobacterial mats and phytoplankton samples is primarily due to incorporation of fine sediment particles of high surface area which therefore enhance trace metal adsorption capacity. This reinforces the existing hypothesis that trace metal solubility in this environment is primarily controlled by abiotic processes.

Description: The statistical properties of fully developed planar turbulent Couette–Poiseuille flow result from the simultaneous imposition of a mean wall shear force together with a mean pressure force. Despite the fact that pure Poiseuille flow and pure Couette flow are the two extremes of Couette–Poiseuille flow, the statistical properties of the latter have proved resistant to scaling approaches that coherently extend traditional wall flow theory. For this reason, Couette–Poiseuille flow constitutes an interesting test case by which to explore the efficacy of alternative theoretical approaches, along with their physical/mathematical ramifications. Within this context, the present effort extends the recently developed scaling framework of Weiet al. (2005a) and associated multiscaling ideas of Fifeet al. (2005a,b) to fully developed planar turbulent Couette–Poiseuille flow. Like Poiseuille flow, and contrary to the structure hypothesized by the traditional inner/outer/overlap-based framework, with increasing distance from the wall, the present flow is shown in some cases to undergo abalance breakingandbalance exchangeprocess as the mean dynamics transition from a layer characterized by a balance between the Reynolds stress gradient and viscous stress gradient, to a layer characterized by a balance between the Reynolds stress gradient (more precisely, the sum of Reynolds and viscous stress gradients) and mean pressure gradient. Multiscale analyses of the mean momentum equation are used to predict (in order of magnitude) the wall-normal positions of the maxima of the Reynolds shear stress, as well as to provide an explicit mesoscaling for the profiles near those positions. The analysis reveals a close relationship between the mean flow structure of Couette–Poiseuille flow and two internal scale hierarchies admitted by the mean flow equations. The averaged profiles of interest have, at essentially each point in the channel, a characteristic length that increases as a well-defined ‘outer region’ is approached from either the bottom or the top of the channel. The continuous deformation of this scaling structure as the relevant parameter varies from the Poiseuille case to the Couette case is studied and clarified.

Description: In this paper, we use numerical simulation and laboratory experimental observation to show that fire whirls can be generated spontaneously through the interaction between a central flame and surrounding organized or randomly distributed flames. The momentum of the air stream entrained by the main flame decreases as it crosses a surrounding flame, so that the main flame rotates if surrounding flames are arranged in such a way as to block the passage of the air stream directed towards the centre of the main flame and to favour flows in a particular circumferential direction. An analysis is performed to study the role of the rotation speed in the flame height. It is found that the flame height initially decreases to a minimum owing to the inflow boundary layer wind reducing the initial vertical velocity of gas for low rotation speed and to entrainment enhancement reducing the rising time, and then it increases owing to the pressure reduction at the centre of the rotating vortex and entrainment suppression extending the rising time.

Description: We investigate aspects of hovering insect flight by finding the optimal wing kinematics which minimize power consumption while still providing enough lift to maintain a time-averaged constant altitude over one flapping period. In particular, we study the flight of three insects whose masses vary by approximately three orders of magnitude: fruitfly (Drosophila melanogaster), bumblebee (Bombus terrestris), and hawkmoth (Manduca sexta). Here, we model an insect wing as a rigid body with three rotational degrees of freedom. The aerodynamic forces are modelled via a quasi-steady model of a thin plate interacting with the surrounding fluid. The advantage of this model, as opposed to the more computationally costly method of direct numerical simulation via computational fluid dynamics, is that it allows us to perform optimization procedures and detailed sensitivity analyses which require many cost function evaluations. The optimal solutions are found via a hybrid optimization algorithm combining aspects of a genetic algorithm and a gradient-based optimizer. We find that the results of this optimization yield kinematics which are qualitatively and quantitatively similar to previously observed data. We also perform sensitivity analyses on parameters of the optimal kinematics to gain insight into the values of the observed optima. Additionally, we find that all of the optimal kinematics found here maintain the same leading edge throughout the stroke, as is the case for nearly all insect wing motions. We show that this type of stroke takes advantage of a passive wing rotation in which aerodynamic forces help to reverse the wing pitch, similar to the turning of a free-falling leaf.

Description: Direct numerical simulations (DNS) of steady and pulsatile flow through 75% (by area reduction) stenosed tubes have been performed, with the motivation of understanding the biofluid dynamics of actual stenosed arteries. The spectral-element method, providing geometric flexibility and high-order spectral accuracy, was employed for the simulations. The steady flow results are examined here while the pulsatile flow analysis is dealt with in Part 2 of this study. At inlet Reynolds numbers of 500 and 1000, DNS predict a laminar flow field downstream of an axisymmetric stenosis and comparison to previous experiments show good agreement in the immediate post-stenotic region. The introduction of a geometric perturbation within the current model, in the form of a stenosis eccentricity that was 5% of the main vessel diameter at the throat, resulted in breaking of the symmetry of the post-stenotic flow field by causing the jet to deflect towards the side of the eccentricity and, at a high enough Reynolds number of 1000, jet breakdown occurred in the downstream region. The flow transitioned to turbulence about five diameters away from the stenosis, with velocity spectra taking on a broadband nature, acquiring a -5/3 slope that is typical of turbulent flows. Transition was accomplished by the breaking up of streamwise, hairpin vortices into a localized turbulent spot, reminiscent of the turbulent puff observed in pipe flow transition, within which r.m.s. velocity and turbulent energy levels were highest. Turbulent fluctuations and energy levels rapidly decayed beyond this region and flow relaminarized. The acceleration of the fluid through the stenosis resulted in wall shear stress (WSS) magnitudes that exceeded upstream levels by more than a factor of 30 but low WSS levels accompanied the flow separation zones that formed immediately downstream of the stenosis. Transition to turbulence in the case of the eccentric stenosis was found to be manifested as large temporal and spatial gradients of shear stress, with significant axial and circumferential variations in instantaneous WSS.

Description: Panspermia, the dissemination of life through space, would require resistance to the conditions found in space, including UV light. All known life forms depend on DNA to store information. In an effort to understand the liabilities of DNA to UV light and modes of DNA protection in terrestrial life forms, we established UV–VUV (125–340 nm) absorption spectra for dry DNA and its polymerized components and mononucleotides, as well as for a selection of potential UV screens ubiquitous in all organisms, including proteins, selected amino acids and amines (polyamines and tyramine). Montmorillonite clay was included as a potential abiotic UV screen. Among the potential screens tested, adenosine triphosphate (ATP) appeared to be particularly attractive, because its UV absorption spectrum was similar to that of DNA. We suggest that the use of ATP in UV protection could have pre-dated its current role in energy transfer. Spectroscopy also showed that UV absorption varied according to nucleotide content, suggesting that base pair usage could be a factor in adaptation to given UV environments and the availability of UV screens.

Description: About 5400 cal yr BP, a large landslide formed a 〉 400-m-tall dam in the upper Marsyandi River, central Nepal. The resulting lacustrine and deltaic deposits stretched 〉 7 km upstream, reaching a thickness of 120 m.14C dating of 7 wood fragments reveals that the aggradation and subsequent incision occurred remarkably quickly (∼ 500 yr). Reconstructed volumes of lacustrine (∼ 0.16 km3) and deltaic (∼ 0.09 km3) deposits indicate a bedload-to-suspended load ratio of 1:2, considerably higher than the ≤ 1:10 that is commonly assumed. At the downstream end of the landslide dam, the river incised a new channel through ≥ 70 m of Greater Himalayan gneiss, requiring a minimum bedrock incision rate of 13 mm/yr over last 5400 yr. The majority of incision presumably occurred over a fraction of this time, suggesting much higher rates. The high bedload ratio from such an energetic mountain river is a particularly significant addition to our knowledge of sediment flux in orogenic environments.

Description: AUSTIN, TEXAS--Here at the 17th Annual National Conference on Artificial Intelligence, four teams of engineers fielded mechanical contestants in the first annual urban ruin search-and-rescue competition--a simulated catastrophe created to test intelligent lifesaving robots that may one day lead rescuers to people trapped in the precarious rubble of collapsed buildings. The competition indicated that the technology still has a way to go.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sincell, M -- New York, N.Y. -- Science. 2000 Aug 11;289(5481):846a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17839147" target="_blank"〉PubMed〈/a〉

Description: Disaffection with the European Union's (E.U.'s) flagship research effort has found a sympathetic ear in the program's upper echelons. Last week, the E.U.'s top two research officials said they are pushing for big changes in the successor to Europe's 5-year, $17 billion Framework 5, including stronger efforts to coordinate research across the continent and to support innovative projects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Koenig, R -- New York, N.Y. -- Science. 2000 Sep 22;289(5487):2019b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17799385" target="_blank"〉PubMed〈/a〉

Description: Eighth graders from the United States are still running in the middle of the global pack when it comes to science and math achievement, according to the latest results from the Third International Mathematics and Science Study. And Asian nations continue to lead the way, with Singapore and Taiwan emerging as the star performers among the 38 participating countries. The news is not good for U.S. science and math educators, who have spent much of the decade pursuing reforms aimed at raising student achievement.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Holden, C -- New York, N.Y. -- Science. 2000 Dec 8;290(5498):1866.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17742044" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brisbin, I L Jr -- Austad, S -- Jacobson, S K -- New York, N.Y. -- Science. 2000 Nov 10;290(5494):1093b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17743252" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brownell, R L Jr -- Tillman, M F -- di Sciara, G N -- Berggren, P -- Read, A J -- New York, N.Y. -- Science. 2000 Dec 1;290(5497):1696a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17798206" target="_blank"〉PubMed〈/a〉

Description: Officials at NASA's Ames Research Center in Moffett Field, California, would like to trade the use of part of their land for a new building largely dedicated to NASA's nascent astrobiology program, the core of which is a 2-year-old virtual institute based at Ames. Although some scientists applaud the idea, others say that it undermines the idea of a virtual institute and that operating costs would take money away from higher priorities. Two panels have offered conflicting opinions, which may be aired at a meeting next week.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lawler, A -- New York, N.Y. -- Science. 2000 Jul 7;289(5476):23a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17832956" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mehl-Madrona, L -- Katz, M -- Curry, E P -- Bribiesca, L B -- New York, N.Y. -- Science. 2000 Jul 14;289(5477):245b-6b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17750401" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Steele, E J -- Blanden, R V -- New York, N.Y. -- Science. 2000 Jun 30;288(5475):2318d-9d.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17769837" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Farr, N L -- New York, N.Y. -- Science. 2000 Jun 9;288(5472):1747c.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17836686" target="_blank"〉PubMed〈/a〉

Description: Relativistic outflows or "jets" are collimated streams of high-energy electrons that emit synchrotron radiation at radio wavelengths and have bulk velocities that are a substantial fraction of the speed of light. They trace the outflow of enormous amounts of energy and matter from a central supermassive black hole in distant radio galaxies. As Fender explains in this Perspective, much smaller, more local sources may also produce such jets. Data presented by Paredes et al. point toward association of one such source, a relatively faint x-ray binary, with a gamma-ray source. This and similar pairs may contribute substantially to the production of high-energy particles and photons within our galaxy.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fender, R P -- New York, N.Y. -- Science. 2000 Jun 30;288(5475):2326.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17769841" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bunnett, J F -- New York, N.Y. -- Science. 2000 Dec 8;290(5498):1895b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17742052" target="_blank"〉PubMed〈/a〉

Description: Twice burned by mission failures last year, NASA managers last week unveiled a new 15-year blueprint for Mars exploration. The revamped strategy allows for doing more science, but at a slower pace, while delaying a sample return until well into the next decade.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lawler, A -- New York, N.Y. -- Science. 2000 Nov 3;290(5493):915a-6a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17749180" target="_blank"〉PubMed〈/a〉

Description: Most materials become narrower in cross section when stretched, but some materials, such as foams, have the counterintuitive property of becoming fatter when stretched (they have a negative Poisson's ratio). In this Perspective, Lakes discusses how his unusual property may arise in isotropic and anisotropic materials. He highlights the study by Baughman et al., who show that anisotropic materials with a negative Poisson's ratio in one direction can be incompressible, i.e., without an overall change in volume upon stretching. This behavior is predicted for materials with very high density, such as neutron star crusts, or very low density, such as ion plasmas, and the validity of the prediction is demonstrated with experimental data for ion plasmas.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lakes, R -- New York, N.Y. -- Science. 2000 Jun 16;288(5473):1976-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17835108" target="_blank"〉PubMed〈/a〉

Description: Maryland is the most research-intensive state in the country, according to a new report that describes in unprecedented detail where the federal government's annual $80 billion research budget is spent. Its authors hope the report will raise public awareness about research as well as inform politicians.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mervis, J -- New York, N.Y. -- Science. 2000 Jun 23;288(5474):2115b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17758899" target="_blank"〉PubMed〈/a〉

Description: Until the past year, Alex Chao, a senior physicist at the Stanford Linear Accelerator Center, tended to keep his views to himself. But the Wen Ho Lee case turned Chao into a reluctant activist who has contributed money for Lee's defense, helped organize rallies in the San Francisco Bay area, and talked to his neighbors about the injustice he believes Lee and other Asian Americans have suffered.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lawler, A -- New York, N.Y. -- Science. 2000 Nov 10;290(5494):1073.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17743249" target="_blank"〉PubMed〈/a〉

Description: Academic scientists are hoping that two new reports calling for increased funding of research and education and an improved climate for commercializing new technology will finally boost an R&D budget that has been stagnant since 1996. One report argues for a variety of measures to reduce the country's reliance on such low-tech commodities as agriculture and precious metals and stimulate innovation. The second report, based on an innovation summit held in February, recommends spending $1.4 billion over 5 years on research, facilities, and education.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Finkel, E -- New York, N.Y. -- Science. 2000 Oct 13;290(5490):255-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17734105" target="_blank"〉PubMed〈/a〉

Description: Angered and emboldened by the Wen Ho Lee case, many Asian-American researchers at national laboratories are decrying their status as "high-tech coolies"--and demanding change. It's a sudden and surprising turn of events for a community that traditionally has avoided political organization, legal recourse, and conflict with authority. And given the growing numerical muscle of Asian Americans in both public and private labs, the budding movement--if sustained--will be felt far beyond the secure fences of the Department of Energy's weapons labs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lawler, A -- New York, N.Y. -- Science. 2000 Nov 10;290(5494):1072-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17743248" target="_blank"〉PubMed〈/a〉

Description: For several years now, road runoff and erosion stemming in part from the operations of the Plum Creek Timber Co. have choked Elk Creek, known as the best bull trout spawning stream in the West, with sediment, raising fears of even further decline in this endangered species. Now, in an effort to mitigate its harmful effects and avert regulatory action, Plum Creek has designed a Native Fish Habitat Conservation Plan covering 17 fish species, including the bull trout.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wuethrich, B -- New York, N.Y. -- Science. 2000 Jul 21;289(5478):385.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17840573" target="_blank"〉PubMed〈/a〉

Description: The National Institute of General Medical Sciences (NIGMS) is using a novel funding approach to bind together researchers in cutting-edge fields at many institutions, allowing them to transcend their individual areas of expertise. NIGMS has awarded $5 million a year for 5 years to a group of scientists studying cellular signaling. To speed their findings into the public domain and make them available for use in drug testing, members of the project have agreed to post new results in a public database and forgo some patent and authorship claims.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fisher, K -- New York, N.Y. -- Science. 2000 Sep 15;289(5486):1854a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17839925" target="_blank"〉PubMed〈/a〉

Description: In this month's essay, Paul J. Crutzen and Veerabhadran Ramanathan chart some of the courses by which atmospheric sciences evolved from their beginnings, with curious scientists teasing apart the complexity of the air they breathe, into an ever more multidisciplinary enterprise that routinely generates globally consequential knowledge. The authors chronicle developments in chemistry and meteorology up to the early 1970s, before the possibility of human influence beyond the local scale became actualized. To illustrate how humanity's hand has grown to have global effects, they zero in on two contemporary issues: atmospheric ozone and global warming.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉New York, N.Y. -- Science. 2000 Oct 13;290(5490):299-304.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17734112" target="_blank"〉PubMed〈/a〉

Description: Steve C. Wang is a lecturer in the Department of Statistics at Harvard University. He earned his B.S. from Cornell University and his Ph.D. in statistics from the University of Chicago. He has taught statistics and mathematics at the University of Chicago and Williams College. His research interests include applying statistics to paleobiology, endocrine diseases, and image recognition.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wang, S C -- New York, N.Y. -- Science. 2000 Sep 1;289(5484):1477.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17839518" target="_blank"〉PubMed〈/a〉

Description: A New York congressman who sided with environmentalists to kill a nuclear research reactor at Brookhaven National Laboratory in Upton, New York, has been defeated in a stunning primary upset. Representative Michael Forbes lost last week by a narrow margin to Regina Seltzer, the 71-year-old widow of a Brookhaven chemist. The defeat is welcome news to many Brookhaven scientists.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lawler, A -- New York, N.Y. -- Science. 2000 Sep 22;289(5487):2021b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17799387" target="_blank"〉PubMed〈/a〉

Description: Whether the University of Belgrade was ruined or saved in May 1998 depends on one's political views. That was when the regime of Slobodan Milosevic pushed through the Serb parliament the University Act, a law that gave the minister of higher education the right to appoint deans at Serbian universities.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stone, R -- New York, N.Y. -- Science. 2000 Oct 27;290(5492):691.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17780504" target="_blank"〉PubMed〈/a〉

Description: Four months before it goes into effect, a $605 million program to help Canadian universities attract and retain the best scientific talent has ignited a furor within Canadian academe. Research-intensive universities have begun aggressively shopping for prospective candidates, using the new chairs as bait. Smaller universities say that has left them fending off talent raids.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kondro, W -- New York, N.Y. -- Science. 2000 Jun 23;288(5474):2112.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17758896" target="_blank"〉PubMed〈/a〉

Description: Europe is in a growth phase--growing in size as several countries are negotiating to join the European Union (EU) and growing in maturity as its institutions evolve to meet better the needs of its citizens. One aspect of this maturation is the realization that the EU structures to support science have failed in many respects and need a drastic overhaul. The European Life Scientists Organization (ELSO) was created last year to pull together molecular life scientists into a coherent body that can work toward improving conditions for research in Europe.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simons, K -- Featherstone, C -- New York, N.Y. -- Science. 2000 Nov 10;290(5494):1099-101.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17743255" target="_blank"〉PubMed〈/a〉

Description: As magnetic devices become smaller and faster, it is becoming increasingly important to understand the dynamics of magnetic domains on small spatial and temporal scales. In their Perspective, Miltat and Thiaville highlight the report by Acremann et al., whose magnetooptical microscope combines state of the art space and time resolution, thus allowing the precessional motion of magnetic domains to be studied directly. The dynamics they observe are complex, indicating that in both the space and time domains, neither the magnetization nor the applied field should be viewed as uniform.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Miltat, J -- Thiaville, A -- New York, N.Y. -- Science. 2000 Oct 20;290(5491):466-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17844284" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Murphy, K -- Frazer, K A -- Loots, G -- Rubin, E M -- New York, N.Y. -- Science. 2000 Jun 30;288(5475):2319a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17769838" target="_blank"〉PubMed〈/a〉

Description: Stone slabs bearing images of an animal and a half-human, half-beast figure were uncovered during excavations by an Italian team at the Fumane Cave northwest of Verona. The images are believed to be at least as ancient as some found in the Grotte Chauvet in southern France--the current record holder at 32,000 years--and possibly even older. More important, cave art experts say, the new paintings bolster other evidence that humans engaged in sophisticated symbolic expression much earlier than once thought.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Balter, M -- New York, N.Y. -- Science. 2000 Oct 20;290(5491):419-21.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17844275" target="_blank"〉PubMed〈/a〉

Description: Newt Gingrich introduces the concept of an "opportunities-based budget", as an approach to federal research and development funding. Policy-makers should not frame the debate on science funding in terms of percentage of increase. Rather, a systematic analysis of the promise of opportunities should be conducted and the funds allotted accordingly. This article is a call to rethink how lawmakers are funding the discoveries upon which future generations will rely.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gingrich, N -- New York, N.Y. -- Science. 2000 Nov 17;290(5495):1303.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17787232" target="_blank"〉PubMed〈/a〉

Description: Europe's most advanced high-security pathogen lab has claimed its first human casualty--and it hasn't even opened for business. On 28 June, the Marcel Merieux Foundation, which funded the construction of the $8 million facility in Lyons, banned lab director Susan Fisher-Hoch from the premises and launched legal proceedings to dismiss her. Fisher-Hoch's most egregious offense, it appears, was speaking with the press.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Balter, M -- New York, N.Y. -- Science. 2000 Jul 14;289(5477):228b-9b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17750397" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉The International Human Genome Sequencing Consortium -- New York, N.Y. -- Science. 2000 Sep 1;289(5484):1471b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17839516" target="_blank"〉PubMed〈/a〉

Description: Scientists studying the latest high-resolution photos of the martian south polar ice cap think they may have found additional clues to its ebb and flow. These hints of the planet's bizarre atmosphere come from a new class of dramatic-looking terrain features whose dark, multilimbed, vaguely radial designs have earned them the moniker "black spiders," and another group of dusky, spreading features called "dark fans." At a recent gathering here of Mars researchers, a planetary scientist proposed that the spiders might be subsurface gas channels, visible through an unusually transparent section of the martian ice.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lovett, R A -- New York, N.Y. -- Science. 2000 Sep 15;289(5486):1853a-4a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17839924" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Karpen, J T -- Krimigis, S M -- Appleby, J F -- Lawler, A -- New York, N.Y. -- Science. 2000 Aug 25;289(5483):1296.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17772991" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉C Clarke, S A -- New York, N.Y. -- Science. 2000 Aug 4;289(5480):727.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17819565" target="_blank"〉PubMed〈/a〉

Description: The Large Magellanic Cloud (LMC), a satellite of the Milky Way, is an important yardstick by which most intergalactic distances are measured. But as Cole explains in this Perspective, how far away the LMC is remains a matter of dispute, with far reaching implications in cosmology. But observations of Cepheids and of eclipsing binaries, two types of stars that allow absolute luminosity and thus absolute distances to be determined, are promising to resolve this important issue in the not too distant future.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cole, A A -- New York, N.Y. -- Science. 2000 Aug 18;289(5482):1149-50.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17833402" target="_blank"〉PubMed〈/a〉

Description: By exploiting the symmetry of randomness, three mathematicians have revealed the geometric underpinnings of the frenetic random dance called Brownian motion. The methods they used seem likely to apply to other random processes, some as familiar as the flow of water through a filter. The proof was presented at the recent Current Developments in Mathematics 2000 conference sponsored by Harvard University and the Massachusetts Institute of Technology.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mackenzie, D -- New York, N.Y. -- Science. 2000 Dec 8;290(5498):1883-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17742050" target="_blank"〉PubMed〈/a〉

Description: When a diatomic molecule is broken up into its constituent atoms, these very energetic atoms provide a large driving force for further reaction. Diatomic molecules often do not undergo productive chemistry, however, because the energy needed to break the diatomic bond is also high. In his Perspective, Thorp discusses the work by MacBeth et al., who have synthesized a nonheme iron complex that reacts with O2 to produce two equivalents of a metal-oxo complex. The complex elegantly mimic the ability of some enzymes to influence metal ion coordination spheres.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thorp, H H -- New York, N.Y. -- Science. 2000 Aug 11;289(5481):882-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17839155" target="_blank"〉PubMed〈/a〉

Description: A new finding, based on x-rays from distant neutron stars, could be the first clear evidence of a weird relativistic effect called frame dragging, in which a heavy chunk of spinning matter wrenches the space-time around it like an eggbeater. Using data from NASA's Rossi X-ray Timing Explorer, three astronomers in Amsterdam found circumstantial evidence for frame dragging in the flickering of three neutron stars in binary systems. They announced their results in the 1 September issue of The Astrophysical Journal.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schilling, G -- New York, N.Y. -- Science. 2000 Sep 1;289(5484):1448a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17839511" target="_blank"〉PubMed〈/a〉

Description: Forest fires burning in the western United States have already scorched over 2.5 million hectares this summer. Now a federal proposal to prevent them by paying loggers to cut smaller trees is generating heat among ecologists, who say the approach may not be right for all forests--or all fires.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Macneil, J S -- New York, N.Y. -- Science. 2000 Sep 1;289(5484):1448b-9b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17839512" target="_blank"〉PubMed〈/a〉

Description: Titanic explosions that emit powerful flashes of energetic gamma rays are one of astronomy's hottest mysteries. Now an analysis of the nearest gamma ray burst yet detected has added weight to the popular theory that they are expelled during the death throes of supermassive stars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schilling, G -- New York, N.Y. -- Science. 2000 Jul 7;289(5476):29.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17832958" target="_blank"〉PubMed〈/a〉

Description: The results of Chinese field trials reinforce the accepted scientific wisdom that planting different varieties of a crop in the same field holds down the spread of certain diseases and improves yields. And this time researchers seem to have convinced farmers, too.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Normile, D -- New York, N.Y. -- Science. 2000 Aug 18;289(5482):1122b-3b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17833396" target="_blank"〉PubMed〈/a〉

Description: Last month the High Energy Transient Explorer 2, the first satellite dedicated to spotting gamma ray bursts, rocketed successfully into orbit, bolstering a handful of x-ray satellites whose instruments are trained on the mysterious explosions. But some researchers say setbacks to the fleet have left unfortunate gaps in coverage.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schilling, G -- New York, N.Y. -- Science. 2000 Nov 3;290(5493):927.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17749185" target="_blank"〉PubMed〈/a〉

Description: Most astrophysicists puzzling over what causes gamma ray bursts--short, intense explosions of high-energy photons that occur deep in space--now agree that the answer is a hypernova, the blast of energy released when a supermassive star collapses into a black hole. Two papers in this issue of Science (pp. 953 and 955), reporting on new x-ray observations of two gamma ray bursts, argue that the hypernova model tells only half of the story. On its way to becoming a black hole, the authors propose, the supermassive star actually collapses twice.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schilling, G -- New York, N.Y. -- Science. 2000 Nov 3;290(5493):926-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17749184" target="_blank"〉PubMed〈/a〉

Description: When the dimensions of matter are reduced to the nanometer scale and beyond, strange properties often emerge. In their Perspective, Tosatti and Prestipino discuss the weird gold nanowire structures reported by Kondo and Takayanagi. They explain why the wires may be helical and only form certain "magic" sizes. Other metals may form similarly strange structures with unusual properties.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tosatti, E -- Prestipino, S -- New York, N.Y. -- Science. 2000 Jul 28;289(5479):561-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17832069" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cottrell, R D -- Tarduno, J A -- Sager, W W -- Koppers, A A -- New York, N.Y. -- Science. 2000 Jun 30;288(5475):2283a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17769831" target="_blank"〉PubMed〈/a〉

Description: Primitive meteorites provide a glimpse into the early history of our solar system, but some of the most primitive meteorites are also rarely found on Earth. In his Perspective, Grossman explains why the fall of the Tagish Lake meteorite on 18 January 2000 in British Columbia, Canada, was a lucky event for meteorite researchers. The first analysis of the meteorite is reported by Brown et al. Well-preserved organic matter in the meteorite provides a unique opportunity to study the nature and origin of organic matter that may have accreted on early Earth and played a role in the origin of life.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Grossman, J N -- New York, N.Y. -- Science. 2000 Oct 13;290(5490):283-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17734110" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schlesinger, M E -- Ramankutty, N -- Andronova, N -- Margolis, M -- Kerr, R A -- New York, N.Y. -- Science. 2000 Jul 28;289(5479):547b-8b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17832062" target="_blank"〉PubMed〈/a〉

Description: Last week, computer industry titan Gordon Moore and his wife, Betty, announced that they are creating a $5-billion-plus foundation to support scientific research, conservation, and higher education. Once fully funded within a few years, the foundation is expected to rank among the dozen largest charities based in the United States.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Malakoff, D -- New York, N.Y. -- Science. 2000 Nov 24;290(5496):1481b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17771219" target="_blank"〉PubMed〈/a〉

Description: When University of California, Irvine, developmental biologist Susan Bryant married David Gardiner, Gardiner took a soft-money position as a researcher at Irvine. Because Gardiner was flexible in his goals and committed to raising children, it seemed a better choice than trying to get two jobs somewhere else, he recalls. And 17 years and two children later, Gardiner says that decision was right for them as a couple--and that he has learned to endure the indignities that come with the territory.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barinaga, M -- New York, N.Y. -- Science. 2000 Sep 22;289(5487):2025.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17799388" target="_blank"〉PubMed〈/a〉

Description: President Bill Clinton last week signed an executive order creating the Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve. Marine scientists say that the megareserve, which holds nearly 70% of the nation's reefs, will help protect some of the globe's most pristine ocean habitats.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Malakoff, D -- New York, N.Y. -- Science. 2000 Dec 8;290(5498):1873b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17742048" target="_blank"〉PubMed〈/a〉

Description: High-quality crystals of the organic molecular semiconductors tetracene and pentacene were used to prepare metal-insulator-semiconductor (MIS) structures exhibiting hole and electron mobilities exceeding 10(4) square centimeters per volt per second. The carrier concentration in the channel region of these ambipolar field-effect devices was controlled by the applied gate voltage. Well-defined Shubnikov-de Haas oscillations and quantized Hall plateaus were observed for two-dimensional carrier densities in the range of 10(11) per square centimeter. Fractional quantum Hall states were observed in tetracene crystals at temperatures as high as approximately 2 kelvin.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schon, J H -- Kloc, C -- Batlogg, B -- New York, N.Y. -- Science. 2000 Jun 30;288(5475):2338-40.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17769842" target="_blank"〉PubMed〈/a〉