bluuebunny/crossref_metadata_2025 huggingface dataset:
Frank Lloyd Wright and Feminism: Mamah Borthwick's Letters to Ellen Key
Authors: Borthwick Mamah , Friedman Alice T.
Published: April 2006

Eleven recently discovered letters in the Royal Library in Stockholm, written by Mamah Bouton Borthwick and Frank Lloyd Wright to Ellen Key, the Swedish social theorist and feminist reformer, between 1911 and 1914, shed new light on Key's influence, not only on the couple's image of themselves as radical reformers, but also on the design and concept of Taliesin, the house that Wright built as a residence, workshop, and retreat for them in 1913. These letters reveal that Borthwick, a client and neighbor of Wright's in Oak Park, discovered Key's writings soon after she and Wright abandoned their families and fled to Europe in 1909; from that point until August 1914, when Borthwick was murdered by a deranged servant at Taliesin, both she and Wright became avid disciples of Key's philosophy, and looked to her for guidance and support. It has long been known that Key's many publications on subjects such as marriage, divorce, birth control, children's education, and individual freedom, were read with interest by Wright and Borthwick, and that Borthwick was named Key's "only authorized translator" in English. The letters, analyzed in the context of close readings of Key's most significant and widely read texts, offer new insights into the meaning of Key's writings for the couple, revealing an explicit connection between Key's ideas and Taliesin, which Borthwick describes as having been "founded on Ellen Key's ideal of love." The texts provide further evidence of the feminist influence on Wright's emerging ideas about individual responsibility, artistic freedom, the family, and household life.
Daughters increase longevity of fathers, but daughters and sons equally reduce longevity of mothers
Authors: Jasienska Grazyna , Nenko Ilona , Jasienski Michal
Published: April 2006

Reproduction is energetically and physiologically expensive, and an individual investing resources into producing offspring should suffer costs such as deterioration in health condition and possibly shorter life span. Since the energetic and nutritional demands of pregnancy and breastfeeding render reproductive costs much higher in women than in men, women with a large number of children should show signs of deterioration in condition, while men with large families should not. However, whether reproductive costs reduce longevity in women is still questionable, and in men this issue has not been adequately addressed. In addition, since sons are energetically more expensive to produce than daughters, having sons should have a more pronounced negative impact on maternal longevity than having daughters. Here we document a striking disparity in the impact of children on the life span of mothers and fathers in a Polish rural population. We show for the first time that number of daughters was positively related to a longer life span of their fathers, increasing their longevity on average by 74 weeks per daughter born, while number of sons did not have a significant effect on paternal longevity. In contrast, in women, the number of daughters and number of sons reduced maternal longevity and did so to the same extent, on average by 95 weeks per son or daughter, indicating that for women, the costs of having sons and daughters are similar. Am. J. Hum. Biol. 18:422–425, 2006. © 2006 Wiley‐Liss, Inc.
Attention‐deficit hyperactivity disorder and fluctuating asymmetry in another college sample
Authors: Stevenson J.C. , Everson P.M. , Williams D.C. , Hipskind G. , Mahoney E.R. , Mehler M. , Cawley M. , Chamberlin W. , Watts L.
Published: April 2006

Attention deficit/hyperactivity disorder (AD/HD) represents a developmental lag that may be reflected in fluctuating asymmetry (FA), i.e., differences from perfect symmetry in traits that display bilateral symmetry. Burton et al. (2003 Am. J. Hum. Biol. 15:601–619) found a statistical trend for FA to increase (as dermatoglyphic index or as total index) as the behavioral measure for AD/HDness (Rasch logit values derived from the Wender Utah Rating Scale, or WURS) increased in males but not in females. The objective here was to do a similar study in an independently collected sample of college students (n = 222; 61 male, 161 female) not selected for AD/HD, looking at FA vs. symptoms for AD/HD based on Rasch versions of responses to the Diagnostic and Statistical Manual of Mental Disorders (DSM IV) (Barkley and Murphy 1998 Attention‐Deficit Hyperactivity Disorder, New York: Guilford Press, p. 95–96) and the more comparable shortened WURS. FAs were lowest for body and ear height, and highest for eye width and nose width, and ranged from 0.01 ± 0.001 (mean ± SE) for foot and ankle widths to 0.13 ± 0.01 in eye and nose widths for both sexes; the sexes did not differ significantly. Males displayed higher AD/HD symptom rates overall. There was a significant correlation between body FA and the WURS measure in females after Bonferroni correction (P = 0.002, r2 = 0.058). Thus, AD/HD symptoms levels increased with an increase in body FA in female college students not selected for AD/HD. Am. J. Hum. Biol. 18:402–414, 2006. © 2006 Wiley‐Liss, Inc.
Asymmetric Synthesis of (2‐Carbamoyloxy‐1‐alkenyl)cyclopropanes by Intramolecular Cycloalkylation.
Authors: Brandau Sven , Hoppe Dieter
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
New Boron Reagents for Designed Organic Synthesis. Part 2. Cinnamic Acids Synthesis in the Presence of Sodium Tetramethoxyborate‐Lithium Chloride.
Authors: Chiriac Constantin I. , Tanasa Fulga , Onciu Marioara
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Aromatization of 1,4‐Dihydropyridines in the Presence of Methanesulfonic Acid/NaNO2/Wet SiO2 under Both Heterogeneous and Solvent Free Conditions.
Authors: Niknam Khodabakhsh , Zolfigol Mohammah Ali , Razavian Seyed Mehdi , Mohammahpoor‐Baltork Iraj
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Preparation of 2,5,7‐Trithiabicyclo[2.2.1]heptane from 1,2‐Bis‐triisopropylsilanylsulfanyl Alkenes.
Authors: Gareau Yves , Juteau Helene , Tsou Nancy N. , Ball Richard G.
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
New Megastigmane Glucosides from Excoecaria cochinchinensis Lour. var. cochinchinensis.
Authors: Giang Phan Minh , Son Phan Tong , Matsunami Katsuyoshi , Otsuka Hideaki
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Small Molecular anti‐Cytokine Agents
Authors: Wagner Gerd , Laufer Stefan
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Long‐Lived Charge‐Transfer States in Compact Donor—Acceptor Dyads
Authors: Verhoeven Jan W. , van Ramesdonk Hendrik J. , Groeneveld Michiel M. , Benniston Andrew C. , Harriman Anthony
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Photochemical Approach to Probing Different DNA Structures
Authors: Xu Yan , Sugiyama Hiroshi
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Concentration on curves for nonlinear Schrödinger Equations
Authors: Del Pino Manuel , Kowalczyk Michal , Wei Jun‐Cheng
Published: April 2006

We consider the problem

where p > 1, ε > 0 is a small parameter, and V is a uniformly positive, smooth potential. Let Γ be a closed curve, nondegenerate geodesic relative to the weighted arc length ∫Γ Vσ, where σ = (p + 1)/(p − 1) − 1/2. We prove the existence of a solution uϵ concentrating along the whole of Γ, exponentially small in ε at any positive distance from it, provided that ε is small and away from certain critical numbers. In particular, this establishes the validity of a conjecture raised in 3 in the two‐dimensional case. © 2006 Wiley Periodicals, Inc.
Dithiolato‐Bridged [MRu2] (M = Rh, Ir, Ru) Triangular 50e– Cluster Complexes Synthesized by Complete Metal Framework Reconstruction
Authors: Nakagawa Norikiyo , Murata Masaki , Sugimoto Manabu , Nishihara Hiroshi
Published: April 2006

A method for synthesizing triangular dithiolene‐bridged trinuclear cluster complexes [{LM(S2C6H4)}Ru2(CO)4(S2C6H4)] [M = Rh, L = (η5‐C5Me5); M = Ir, L = (η5‐C5Me5); M = Ru, L = (η6‐C6Me6)] by complete reconstruction of the metal framework was developed. The complexes thus obtained have 50 electrons around the metal atoms, indicating 3c4e– bonds; their molecular structures were determined by X‐ray diffraction analyses and theoretical calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Adaptation of the properties of spastic muscle with wrist extension deformity
Authors: Smeulders Mark J.C. , Kreulen Michiel
Published: April 2006

To show that human muscle may adapt to tendon transfer, adaptation of flexor carpi ulnaris (FCU) function was studied by measuring active and passive length–force characteristics at initial operation and at reoperation in a case of extension deformity secondary to FCU tendon transfer. At reoperation, FCU was 20 mm shorter; active force decreased ∼10%, indicating atrophy; and passive force increased, reflecting increased stiffness. FCU fiber length was unchanged. The presented case shows that human forearm muscle may adapt to a transferred function. Muscle Nerve, 2006
Carpal tunnel syndrome in older adults
Authors: Blumenthal Scott , Herskovitz Steven , Verghese Joe
Published: April 2006

The clinical and electrophysiologic characteristics of carpal tunnel syndrome (CTS) in elderly adults are not well established. We examined age differences in clinical, functional, and electrophysiologic features in elderly adults referred to a neuromuscular service for evaluation of symptoms suggestive of CTS. Of 415 consecutive subjects referred over an 18‐month period, 343 met clinical criteria for CTS. There were 158 young (≤50 years), 115 middle‐aged (51–64 years), and 70 elderly adults (≥65 years). There were no age differences in the duration of CTS symptoms, hand function, or presence of autonomic symptoms. The elderly adults had a higher prevalence of thenar weakness and thenar atrophy than younger subjects. Electrophysiologic abnormalities were more common and more severe in the older subjects. Our study shows that although there are no age differences in subjective complaints of CTS, older adults had objective clinical and electrophysiologic evidence of a more severe median nerve entrapment. The findings suggest that greater attention needs to be paid to objective evidence of CTS severity rather than subjective complaints when evaluating elderly adults presenting for clinical evaluation of CTS. Muscle Nerve, 2006
Studies of the wall shear stress in a turbulent pulsating pipe flow
Authors: Mao Zhuo-Xiong , Hanratty Thomas J.
Published: April 2006

Measurements are presented of the time variation of the wall shear stress caused by the imposition of a sinusoidal oscillation on a turbulent pipe flow. The amplitude of the oscillation is small enough that a linear response is obtained and the dimensionless frequency, ω+ = ων/u*2, is large compared with that studied by most previous investigators. The most striking feature of the results is a relaxation effect, similar to that observed for flow over a wavy surface, whereby the phase angle characterizing the temporal variation of the wall shear stress undergoes a sharp change over a rather narrow range of ω+. At ω+ larger than the median frequency of the turbulence there appears to be an interaction between the imposed flow oscillation and the turbulence fluctuations in the viscous sublayer, which is not described by present theories of turbulence.
Coherent structures and turbulence
Authors: Hussain A. K. M. Fazle
Published: April 2006

This is a personal statement on the present state of understanding of coherent structures, in particular their spatial details and dynamical significance. The characteristic measures of coherent structures are discussed, emphasizing coherent vorticity as the crucial property. We present here a general scheme for educing structures in any transitional or fully turbulent flow. From smoothed vorticity maps in convenient flow planes, this scheme recognizes patterns of the same mode and parameter size, and then phase-aligns and ensemble-averages them to obtain coherent structure measures. The departure of individual realizations from the ensemble average denotes incoherent turbulence. This robust scheme has been used to educe structures from velocity data using a rake of hot wires as well as direct numerical simulations and can educe structures using newer measurement techniques such as digital image processing. Our recent studies of coherent structures in several free shear flows are briefly reviewed. Detailed data in circular and elliptic jets, mixing layers, and a plane wake reveal that incoherent turbulence is produced at the ‘saddles’ and then advected to the ‘centres’ of the structures. The mechanism of production of turbulence in shear layers is the stretching of longitudinal vortices or ‘ribs’ which connect the predominantly spanwise ‘rolls’; the ribs induce spanwise contortions of rolls and cause mixing and dissipation, mostly at points where they connect with rolls. We also briefly discuss the role of coherent structures in aerodynamic noise generation and argue that the structure breakdown process, rather than vortex pairing, is the dominant mechanism of noise generation. The ‘cut-and-connect’ interaction of coherent structures is proposed as a specific mechanism of aerodynamic noise generation, and a simple analytical model of it shows that it can provide acceptable predictions of jet noise. The coherent-structures approach to turbulence, apart from explaining flow physics, has also enabled turbulence management via control of structure evolution and interactions. We also discuss some new ideas under investigation: in particular, helicity as a characteristic property of coherent structures.
Quantum turbulence
Authors: Donnelly Russell J. , Swanson Charles E.
Published: April 2006

We present a review of quantum turbulence, that is, the turbulent motion of quantized vortex lines in superfluid helium. Our discussion concentrates on the turbulence produced by steady, uniform heat flow in a pipe, but touches on other turbulent flows as well. We have attempted to motivate the study of quantum turbulence and discuss briefly its connection with classical turbulence. We include background on the two-fluid model and mutual friction theory, examples of modern experimental techniques, and a brief survey of the phenomenology. We discuss the important recent insights that vortex dynamics has provided to the understanding of quantum turbulence, from simple scaling arguments to detailed numerical simulations. We conclude with a discussion of open questions in this field.
Three-dimensional instabilities of nonlinear gravity-capillary waves
Authors: Zhang Jun , Melville W. K.
Published: April 2006

Linear three-dimensional instabilities of nonlinear two-dimensional uniform gravitycapillary waves are studied using numerical methods. The eigenvalue system for the stability problem is generated using a Galerkin method and differs in detail from techniques used to study the stability of pure gravity waves (McLean 1982) and pure capillary waves (Chen & Saffman 1985). It is found that instabilities develop in the neighbourhood of the linear (triad, quartet and quintet) resonance curves. Further, both sum and difference triad ressonances are unstable for sufficiently steep waves in consequence of which Hasselmann's (1967) theorem is restricted to weakly nonlinear waves. The appearance of a superharmonic two-dimensional instability and bifurcation to three-dimensional waves are noted.
Report on the First International Workshop on Water Waves and Floating Bodies
Authors: Evans D. V. , Newman J. N.
Published: April 2006

A workshop was held at MIT in February 1986 for specialists performing theoretical research on the interactions of water waves with floating or submerged bodies. The principal applications of this field are related to ship hydrodynamics and to wave loadings on offshore platform. In addition to the traditional approach based on linearization of the wave and body motions, substantial progress has been made on nonlinear problems including both analytical and numerical studies. Subsequent workshops are planned on an annual basis.
Flow about a fluid sphere at low to moderate Reynolds numbers
Authors: Oliver D. L. R. , Chung J. N.
Published: April 2006

The steady-state equations of motion are solved for a fluid sphere translating in a quiescent medium. A semi-analytical series truncation method is employed in conjunction with a cubic finite-element scheme. The range of Reynolds numbers investigated is from 0.5 to 50. The range of viscosity ratios is from 0 (gas bubble) to 107 (solid sphere). The flow structure and the drag coefficients agree closely with the limited available experimental measurements and also compare favourably with published finite-difference solutions. The strength of the internal circulation was found to increase with increasing Reynolds number. The flow patterns and the drag coefficient show little variation with the interior Reynolds number. Based on the numerical results, predictive equations for drag coefficients are recommended for both moderate- and low-Reynolds-number flows.
Turbulence statistics in fully developed channel flow at low Reynolds number
Authors: Kim John , Moin Parviz , Moser Robert
Published: April 2006

A direct numerical simulation of a turbulent channel flow is performed. The unsteady Navier-Stokes equations are solved numerically at a Reynolds number of 3300, based on the mean centreline velocity and channel half-width, with about 4 × 106grid points (192 × 129 × 160 inx, y, z). All essential turbulence scales are resolved on the computational grid and no subgrid model is used. A large number of turbulence statistics are computed and compared with the existing experimental data at comparable Reynolds numbers. Agreements as well as discrepancies are discussed in detail. Particular attention is given to the behaviour of turbulence correlations near the wall. In addition, a number of statistical correlations which are complementary to the existing experimental data are reported for the first time.
A conformal-mapping technique for topographic-wave problems: semi-infinite channels and elongated basins
Authors: Johnson E. R.
Published: April 2006

The basis of the conformal-mapping method for topographic-wave problems of Johnson (1985) is discussed in greater detail by considering the invariance under conformal mapping of the linear, barotropic, potential-vorticity equation, noted in Davis (1983). A method is presented for using this property to construct further solutions for waves propagating over varying topography. Results are given for semi-infinite channels and elongated basins. A coordinate system is constructed that approaches a Cartesian system exponentially fast with distance from end-walls. For exponentially sloping topography the solutions for infinite channels, semi-infinite channels, and basins have the same structure and dispersion relation as waves in an elliptical basin, discussed in Johnson (1987). The structures presented there can thus be considered as in some sense universal for exponentially sloping topography.
Scanning currents in Stokes flow and the efficient feeding of small organisms
Authors: Childress S. , Koehl M. A. R. , Miksis M.
Published: April 2006

The feeding behaviour of many small, free-swimming organisms involves the creation of a scanning current by the coordinated movement of a group of appendages. In this paper, we study the generation of scanning currents in Stokes flow in a number of simple models, utilizing the movement of Stokeslets, spheres, or stalks to set up an average scanning drift in a suitable far-field formulation. Various mechanisms may then be classified by the rate of decay at infinity of the mean scanning current. In addition, optimal scanning can be investigated by minimizing the mean power-required to create a current of prescribed amplitude. The simple mechanisms for scanning described here provide a framework within which the appendage movements of small aquatic organisms can be analysed and the relative merits of scanning and swimming strategies can be investigated.
Rayleigh-Taylor instability of fluid layers
Authors: Baker G. R. , Mccrory R. L. , Verdon C. P. , Orszag S. A.
Published: April 2006

It is shown that the Rayleigh-Taylor instability of an accelerating incompressible, inviscid fluid layer is the result of pressure gradients, not gravitational acceleration. As in the classical Rayleigh-Taylor instability of a semi-infinite layer, finite fluid layers form long thin spikes whose structure is essentially independent of the initial thickness of the layer. A pressure maximum develops above the spike that effectively uncouples the flow in the spike from the rest of the fluid. Interspersed between the spikes are rising bubbles. The bubble motion is seriously affected by the thickness of the layer. For thin layers, the bubbles accelerate upwards exponentially in time and the layer thins so rapidly that it may disrupt at finite times.
Resonant reflection of water waves in a long channel with corrugated boundaries
Authors: Liu Philip L.-F.
Published: April 2006

A one-dimensional wave equation is derived for water-wave propagations in a long channel with corrugated boundaries. The amplitude and the wavelength of boundary undulations are assumed to be smaller than and in the same order of magnitude as the incident wavelength, respectively. When the Bragg reflection condition (i.e. the wavenumber of the boundary undulations is twice that of the incident wavenumber) is nearly satisfied, significant wave reflection could occur. Coupled equations for transmitted and reflected wave fields are derived for the near resonant coupling. The detuning mechanism is attributed to the slight deviation in the wavenumber of the corrugated boundaries from the Bragg wavenumber. Analytical solutions are obtained for the cases where the boundary undulations are within a finite region. The application of the present theory to the design of a harbour resonator is discussed.
Symmetry breaking in periodic and solitary gravity-capillary waves on water of finite depth
Authors: Zufiria Juan A.
Published: April 2006

A weakly nonlinear model is developed from the Hamiltonian formulation of water waves, to study the bifurcation structure of gravity-capillary waves on water of finite depth. It is found that, besides a very rich structure of symmetric solutions, non-symmetric Wilton's ripples exist. They appear via a spontaneous symmetrybreaking bifurcation from symmetric solutions. The bifurcation tree is similar to that for gravity waves. The solitary wave with surface tension is studied with the same model close to a critical depth. It is found that the solution is not unique, and that further non-symmetric solitary waves are possible. The bifurcation tree has the same structure as for the case of periodic waves. The possibility of checking these results in low-gravity experiments is postulated.
Dynamics of ideal fluid flows over an uneven bottom
Authors: Benilov Eugene S.
Published: April 2006

Two problems of the stability of ideal fluid flows over an uneven bottom are considered. The first is the study of stratified flow with a ‘rigid lid’. We use the method of multiple scales to derive an equation describing the evolution of internal waves corresponding to different modes and wave vectors. For the case of sinusoidal bottom irregularities we have constructed a solution describing the increase in time of the internal wave field - this proves the instability of the basic flow. The phenomenon is interpreted as a result of interaction (mutual generation) of internal waves with energies of opposite signs. Our consideration is based on the Hamiltonian approach which enables us to prove in the most simple way the existence of waves carrying negative energy. The case of random (not sinusoidal) bottom irregularities is also studied. Using the kinetic equation for the amplitudes of internal waves derived in the paper, we have established that the basic flow remains unstable as well. In the second part of the paper we consider the homogeneous flows with a free upper boundary. It is shown that this problem can be reduced to the previous one, with the only difference being that the role of unstable perturbations is now played by the surface (not internal) gravity waves. The Hamiltonian approach is consistently applied and allows us to take into account the nonlinearity of waves.
Brownian diffusion in concentrated suspensions of interacting particles
Authors: Rallison J. M.
Published: April 2006

In this paper we set out to calculate the self-diffusivity of a Brownian particle in a concentrated suspension. The problem is treated by regarding the neighbours of a test particle as forming a ‘cage’. For short time t < tc, say, the particle is partially constrained by the cage and an equation is proposed to describe the coupled dynamics of particle and cage. The equation is shown to be asymptotically exact in some cases and acceptably accurate for other simple systems by comparing with Monte Carlo simulations. For times t > tc, the particle diffuses sufficiently far to escape its original cage (and finds itself in a new one). A quantitative estimate for tc is proposed and verified for a system of rod-like particles by numerical simulation. By combining these two ingredients an estimate of the long-time (t [Gt ] tc) self-diffusivity of a particle is made. For rod-like particles tc is the reptation time, and the result here is compared with the theory of Doi & Edwards (1978a, b), and with experiment. For a system of spheres comparison is made with the tracer light-scattering experiments of Kops-Werkhoven & Fijnaut (1982). In both cases good agreement is found when the particle concentration is sufficiently high.
On the receptivity of free shear layers to two-dimensional external excitation
Authors: Balsa Thomas F.
Published: April 2006

In this paper, we study the receptivity of a typical free shear layer to pulse-type and periodic excitation. We do this by solving the initial-value problem completely and studying its long-time behaviour. This leads to a wave packet for the pulse. By the superposition of many wave packets, we generate a spatial instability mode when the flow is convectively unstable. This establishes a general and simple relationship between the receptivities for pulse-type and sinusoidal excitations. We find that a shear layer is very receptive to high-frequency disturbances that are generated near the centreline of the layer.
Mathematical and physical modelling of doublediffusive convection of aqueous solutions crystallizing at a vertical wall
Authors: Thompson Mollie E. , Szekely Julian
Published: April 2006

Solidification of a double-diffusive liquid from a vertical wall in a rectangular cavity is investigated using both mathematical and physical modelling. A two-dimensional mathematical model is developed to simulate the process of solidification in a two-component liquid containing a denser solute. Observations on the solidification behaviour of aqueous sodium carbonate solutions are used to verify the results of the mathematical analysis. The theory and experiments provide a clear picture of the role of double-diffusion in producing vertical compositional and density stratification in an initially homogeneous liquid during solidification. The development of horizontally oriented convection cells in the stratified liquid is correlated with the magnitude of the destabilizing lateral temperature difference across the liquid region.
Upstream motions in stratified flow
Authors: Castro I. P. , Snyder W. H.
Published: April 2006

In this paper experimental measurements of the time-dependent velocity and density perturbations upstream of obstacles towed through linearly stratified fluid are presented. Attention is concentrated on two-dimensional obstacles which generate turbulent separated wakes at Froude numbers, based on velocity and body height, of less than 0.5. The form of the upstream columnar modes is shown to be largely that of first-order unattenuating disturbances, which have little resemblance to the perturbations described by small-obstacle-height theories. For two-dimensional obstacles the disturbances are similar to those found by Wei, Kao & Pao (1975) and it is shown that provided a suitable obstacle drag coefficient is specified, the lowest-order modes (at least) are quantitatively consistent with the results of the Oseen inviscid model.

Discussion of some results of similar measurements upstream of three-dimensional obstacles, the importance of towing tank endwalls and the relevance of the Foster & Saffman (1970) theory for the limit of zero Froude number is also included.
The breakdown of steady convection
Authors: Lennie T. B. , Mckenzie D. P. , Moore D. R. , Weiss N. O.
Published: April 2006

Two-dimensional convection in a Boussinesq fluid with infinite Prandtl number, confined between rigid horizontal boundaries and stress-free lateral boundaries, has been investigated in a series of numerical experiments. In a layer heated from below steady convection becomes unstable to oscillatory modes caused by the formation of hot or cold blobs in thermal boundary layers. Convection driven by internal heating shows a transition from steady motion through periodic oscillations to a chaotic regime, owing to the formation of cold blobs which plunge downwards and eventually split the roll. The interesting feature of this idealized problem is the interaction between constraints imposed by nonlinear dynamics and the obvious spatial structures associated with the sinking sheets and changes in the preferred cell size. These spatial structures modify the bifurcation patterns that are familiar from transitions to chaos in low-order systems. On the other hand, even large-amplitude disturbances are constrained to show periodic or quasi-periodic behaviour, and the bifurcation sequences can be followed in considerable detail. There are examples of quasi-periodic behaviour followed by intermittency, of period-doubling cascades and of transitions from quasi-periodicity to chaos, associated with a preference for narrower rolls as the Rayleigh number is increased.
Turbulence suppression in combustion-driven magnetohydrodynamic channels
Authors: Reis J. C. , Kruger C. H.
Published: April 2006

The effects of a magnetic field on core turbulence, mean-velocity boundary-layer profiles, turbulence-intensity boundary-layer profiles and turbulent spectral-energy distributions have been experimentally determined for combustion-driven magneto-hydrodynamic (MHD) flows. The turbulence suppression of the core was found to be similar to that of liquid-metal MHD flows, even though the turbulent structure was entirely different. The mean-velocity and turbulence-intensity boundary-layer profiles were affected much less than those of liquid-metal flows, primarily because the low-temperature thermal boundary layer reduced the electrical conductivity near the wall. No spectral dependence of turbulence suppression was observed in the core.
Electro-acoustic effects in a dilute suspension of spherical particles
Authors: O'Brien R. W.
Published: April 2006

Sound waves can be generated in a colloid by the application of an alternating electric field. In this paper we describe the method for calculating this and the related electro-acoustic phenomenon of electric fields generated by sound waves. As an illustration of the procedure, we obtain formulae for these two effects for a suspension of spherical particles with thin double layers, in a parallel plate geometry.
Numerical modelling of nonlinear effects in laminar flow through a porous medium
Authors: Coulaud O. , Morel P. , Caltagirone J. P.
Published: April 2006

This paper deals with the introduction of a nonlinear term into Darcy's equation to describe inertial effects in a porous medium. The method chosen is the numerical resolution of flow equations at a pore scale. The medium is modelled by cylinders of either equal or unequal diameters arranged in a regular pattern with a square or triangular base. For a given flow through this medium the pressure drop is evaluated numerically.

The Navier-Stokes equations are discretized by the mixed finite-element method. The numerical solution is based on operator-splitting methods whose purpose is to separate the difficulties due to the nonlinear operator in the equation of motion and the necessity of taking into account the continuity equation. The associated Stokes problems are solved by a mixed formulation proposed by Glowinski & Pironneau.

For Reynolds numbers lower than 1, the relationship between the global pressure gradient and the filtration velocity is linear as predicted by Darcy's law. For higher values of the Reynolds number the pressure drop is influenced by inertial effects which can be interpreted by the addition of a quadratic term in Darcy's law.

On the one hand this study confirms the presence of a nonlinear term in the motion equation as experimentally predicted by several authors, and on the other hand analyses the fluid behaviour in simple media. In addition to the detailed numerical solutions, an estimation of the hydrodynamical constants in the Forchheimer equation is given in terms of porosity and the geometrical characteristics of the models studied.
Excitation of waves trapped by submerged slender structures, and nonlinear resonance
Authors: Aranha J. A. P.
Published: April 2006

In a companion paper the existence of trapped waves over submerged cylinders has been analysed, and a necessary condition for their excitation was derived. In the present paper, this study is extended to obtain physically more important results. First we consider a more realistic geometry, namely a finite, although slender, cylinder. Second we derive the necessary and sufficient conditions for the excitation of trapped modes; and lastly, the induced resonant response is studied with the multiple-scales technique. It is shown then that the wave amplitude satisfies an equation similar to the resonant nonlinear oscillator.
Investigation of the flow between a pair of circular cylinders in the flopping regime
Authors: Kim H. J. , Durbin P. A.
Published: April 2006

The wakes of a pair of circular cylinders are grossly unsteady when the cylinders are separated in a direction normal to the approaching flow by less than one cylinder diameter. The wakes flop randomly between two asymmetric states. The time-scale for the flopping is several orders of magnitude longer than the timescale of vortex shedding, and also several orders of magnitude longer than the timescale for instability of the separating shear layers. When a splitter plate is positioned suitably on the centreline of the cylinders, the flopping can be stopped and the flow made to assume either of the asymmetric states, or a symmetric steady state. For a range of plate positions a new, periodic oscillation occurs. Acoustic excitation can also destroy the flopping mean flow, replacing it by a symmetric flow.
Ordered motion in the turbulent boundary layer over wind waves
Authors: Kawamura H. , Toba Y.
Published: April 2006

The turbulent boundary layer over young wind waves (C/u* ∼ 1, where C is the phase speed of wind waves and u* is the friction velocity) has been investigated in a laboratory tank. Ordered motions have been found, and their structures studied in detail. Visualization of the outer boundary layer (0.4δ–1δ, where δ is the boundary-layer thickness) by paraffin mist has demonstrated the existence of a train of large-scale ordered motions having a horizontal lengthscale that corresponds to the wavelength of the underlying wind waves. Hot-wire measurements combined with the visualization have shown that the passage of the outer boundary-layer bulge is related to the occurrence of a low-speed air mass, usually accompanied by an upward velocity to produce large Reynolds stress. In the vicinity of the wave surface (0–0.15δ), flow separation occurs over these wind waves. Instantaneous velocity shear measurements, using two hot wires 0.15 cm apart vertically, have detected a high-shear layer at the edge of the separation bubbles. This high-shear layer, the potential site for generating much turbulence, reattaches on the windward side of the preceding wind waves. A pressure rise and a shear-stress spike, expected near the reattachment region, could be the mechanisms for supplying energy to the wind waves.

The bursting phenomena over wind waves have been examined in detail in the logarithmic boundary layer (0.15δ–0.3δ). The bursting phenomena are a major mechanism for producing Reynolds stress and have a specific relationship with the phase of the wind wave. To explain the bursting phenomena, two mechanisms (not present in the boundary layer over a flat plate) are proposed, involving air-flow separation and the large-scale ordered motions, respectively. The two mechanisms are a ‘big burst’ related to the discharge of a whole separation bubble, and a ‘small burst’ which is the upward bursting of a low-speed air mass from the unstable separated shear layer into the ordered motions passing over a separation bubble.
Bede's uera lex historiae explained
Authors: Goffart Walter
Published: April 2006

Walter Walter Goffart 31 Temple Court New Haven, CT 06511203 787 4120 In closing the preface to the ‘Historia Ecclesiastica’ Bede mentions the possibility of disputed truth, refers to ‘common report’, and invokes the, or a, ‘vera lex historiae’, literally, ‘true law of history’. Oddly, Bede seems to be disclaiming responsibility for his mistakes. These lines continue to be ‘a crux much commented upon’. Bede clarifies the meaning of this ‘law’ in four passages featuring the adverb ‘simpliciter’. They allow us to see that the ‘truth’ he sometimes departs from is not the opposite of ‘error’, but simply reflects an historian's duty to convey what everyone at a particular time believed to be true.
Miniature hybrid plasma focus extreme ultraviolet source driven by 10kA fast current pulse
Authors: Mohanty S. R. , Sakamoto T. , Kobayashi Y. , Song I. , Watanabe M. , Kawamura T. , Okino A. , Horioka K. , Hotta E.
Published: April 2006

A miniature hybrid plasma focus device, operated in xenon gas medium and driven by a 10kA fast current pulse, has been used to generate extreme ultraviolet radiation in the range of 6–15nm. At present the radiation characteristics from xenon plasma were mainly assessed qualitatively using standard tools such as visible light framing camera, extreme ultraviolet (EUV) pinhole camera, and EUV photodiode. Strong pinching of xenon plasma is indicative from both visible and EUV imagings. The maximum size of the EUV emitting zone is estimated to be of the order of 0.21×1.55mm and the estimated value is within the accepted value as benchmarked by industries. The EUV intensity measurement by photodiode showed fairly isotropic radiation at least in a half solid angle. This device can be developed further as a competent source for EUV metrology or lithography applications.
Does soil determine the boundaries of monodominant rain forest with adjacent mixed rain forest and maquis on ultramafic soils in New Caledonia?
Authors: Read J. , Jaffré T. , Ferris J.M. , McCoy S. , Hope G. S.
Published: April 2006

Aim  To determine the soil characteristics of Nothofagus‐dominated rain forests in an ultramafic region (i.e. soils having high concentrations of metals including Mg, Fe and Ni), and whether soil characteristics may explain the location of monodominant rain forest in relation to adjacent mixed rain forest and maquis (shrub‐dominated vegetation).

Location  New Caledonia.

Methods  Soil characteristics were compared among six Nothofagus‐dominated rain forests from a range of altitudes and topographic positions. At four of these sites, comparisons were made with soils of adjacent mixed rain forest and maquis.

Results  Soil characteristics varied among the monodominant Nothofagus forests, largely due to differences between ultramafic soils and soils influenced by non‐ultramafic intrusions. The soils of all vegetation types had low concentrations of nutrients, particularly P, K and Ca (both total and extractable/exchangeable), and high total concentrations of Ni, Fe, Cr and Mn. There were significant differences between the rain forests and adjacent maquis in soil concentrations of several elements (N, P, Ca, Mg and Mn), more so in surface soils than at depth, but much of this pattern may be caused by effects of vegetation on the soil, rather than of soil on the vegetation. However, there were no significant differences in soil concentrations of any mineral elements between Nothofagus forest and adjacent mixed rain forest.

Main conclusions  We found no evidence for soil mediation of boundaries of Nothofagus rain forest with mixed rain forest, and little evidence for the boundaries of either forest type with maquis. We suggest that the local abrupt boundaries of these monodominant Nothofagus forests are directly related to temporal factors, such as time since the last wildfire and frequency of wildfire, and that disturbance is therefore a major causal factor in the occurrence of these forests.
Stem CO2 release under illumination: corticular photosynthesis, photorespiration or inhibition of mitochondrial respiration?
Authors: WITTMANN CHRISTIANE , PFANZ HARDY , LORETO FRANCESCO , CENTRITTO MAURO , PIETRINI FABRIZIO , ALESSIO GIORGIO
Published: April 2006

In illuminated stems and branches, CO2 release is often reduced. Many light‐triggered processes are thought to contribute to this reduction, namely photorespiration, corticular photosynthesis or even an inhibition of mitochondrial respiration. In this study, we investigated these processes with the objective to discriminate their influence to the overall reduction of branch CO2 release in the light. CO2 gas‐exchange measurements of young birch (Betula pendula Roth.) branches (< 1.5 cm) performed under photorespiratory (20% O2) and non‐photorespiratory (< 2%) conditions revealed that photorespiration does not play a pre‐dominant role in carbon exchange. This suppression of photorespiration was attributed to the high CO2 concentrations (Ci) within the bark tissues (1544 ± 227 and 618 ± 43 µmol CO2 mol−1 in the dark and in the light, respectively). Changes in xylem CO2 were not likely to explain the observed decrease in stem CO2 release as gas‐exchange measurements before and after cutting of the branches did not effect CO2 efflux to the atmosphere. Combined fluorescence and gas‐exchange measurements provided evidence that the light‐dependent reduction in CO2 release can pre‐dominantly be attributed to corticular refixation, whereas an inhibition of mitochondrial respiration in the light is unlikely to occur. Corticular photosynthesis was able to refix up to 97% of the CO2 produced by branch respiration, although it rarely led to a positive net photosynthetic rate.
Expression of tobacco ethylene receptor NTHK1 alters plant responses to salt stress
Authors: CAO WAN‐HONG , LIU JUN , ZHOU QI‐YUN , CAO YANG‐RONG , ZHENG SHU‐FANG , DU BAO‐XING , ZHANG JIN‐SONG , CHEN SHOU‐YI
Published: April 2006

Ethylene has been regarded as a stress hormone involved in many stress responses. However, ethylene receptors have not been studied for the roles they played under salt stress condition. Previously, we characterized an ethylene receptor gene NTHK1 from tobacco, and found that NTHK1 is salt‐inducible. Here, we report a further investigation towards the function of NTHK1 in response to salt stress by using a transgenic approach. We found that NTHK1 promotes leaf growth in the transgenic tobacco seedlings but affects salt sensitivity in these transgenic seedlings under salt stress condition. Differential Na+/K+ ratio was observed in the control Xanthi and NTHK1‐transgenic plants after salt stress treatment. We further found that the NTHK1 transgene is also salt‐inducible in the transgenic plants, and the higher NTHK1 expression results in early inductions of the ACC (1‐aminocyclopropane‐1‐carboxylic acid) oxidase gene NtACO3 and ethylene responsive factor (ERF) genes NtERF1 and NtERF4 under salt stress. However, NTHK1 suppresses the salt‐inducible expression of the ACC synthase gene NtACS1. These results indicate that NTHK1 regulates salt stress responses by affecting ion accumulation and related gene expressions, and hence have significance in elucidation of ethylene receptor functions during stress signal transduction.
Steatosis in chronic hepatitis C: Relationship to the virus and host risk factors
Authors: Matos Carla AL , Perez Renata M , Pacheco Mauricio S , Figueiredo‐Mendes Claudio G , Lopes‐Neto Edmundo , Oliveira Evandro B , Lanzoni Valeria P , Silva Antonio EB , Ferraz Maria LG
Published: April 2006

Background:  Steatosis occurs frequently in hepatitis C. However, the mechanisms leading to this lesion are still unknown, and the role of steatosis in the progression of the disease remains controversial. The aim of the present paper was to determine the prevalence of steatosis in hepatitis C and its association with hepatitis C virus (HCV) genotype, viral load and the presence of risk factors for steatosis, and to analyze the association between steatosis and the intensity of liver disease.

Methods:  Patients infected with HCV who underwent liver biopsy were included. Patients coinfected with hepatitis B virus and/or human immunodeficiency virus and those previously treated for hepatitis C were excluded. The following risk factors for steatosis were investigated: obesity (body mass index [BMI] > 25 kg/m2), diabetes mellitus, hyperlipidemia, alcoholism, and use of potential steatosis‐inducing drugs. Histological analysis evaluated the presence of steatosis, the degree of periportal activity and staging. Patients with and without steatosis were compared regarding demographic, epidemiological, laboratory and histological characteristics. Logistic regression analysis was applied to identify variables that were independently associated with the presence of steatosis.

Results:  Ninety patients (55 men, 35 women) with a mean age of 45 ± 13 years were included. The prevalence of steatosis was 67%. Variables that remained independently associated with steatosis were age, female gender, obesity and genotype 3.

Conclusions:  The prevalence of steatosis in hepatitis C was high. Risk factors usually related to steatosis such as age, female gender and obesity, as well as genotype 3, were independently associated with the presence of steatosis. Steatosis was not independently associated with the intensity of histological liver disease.