bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydraulic control by a wide weir in a rotating fluid
Authors: Sambuco E. , Whitehead J. A.
Published: March 2006

Flow control by a wide, deep weir in a rotating fluid is investigated theoretically and experimentally. A strong (vertical) vorticity constraint due to frame rotation is combined with conservation of the Bernoulli function along streamlines and a standard hydraulic control assumption to show that the volume flux over the barrier is
\[
Q = g^{-1}\left[\frac{2}{3}g(H - b_0)-\frac{1}{3}f^2l^2 \right]^{\frac{3}{2}},
\]
where H is the depth of the fluid column upstream, bo is the crest height, f is the Coriolis parameter, and l is a length-scale measure of the breadth of the weir. The component of the velocity parallel to the weir crest is computed from conservation of potential vorticity to be v = −fl; perpendicular to the crest, we recover the standard hydraulic relation u = (gh0)½.

Experimental investigations of upstream height and streamline deflexion as functions of rotation are described. It is found that agreement with theory is good up to a certain rate of rotation, above which the finite width of the experimental weir becomes important.
A study of a stably stratified hydromagnetic fluid in a rotating cylinder
Authors: Loper David E.
Published: March 2006

Slow, steady, mechanically driven, axisymmetric motion of a stably stratified, electrically conducting, rotating fluid is studied. Attention is focused upon the parameter values for which hydromagnetic effects first become important in a rotating stratified fluid and upon the nature of their influence on the interior flow of that fluid. It is found that hydromagnetic effects are able to alter the flow of a stratified rotating fluid at much weaker magnetic field strengths than the flow of an unstratified fluid. Specifically, the interior azimuthal flow is altered ifE/α2[Lt ] σS[Lt ] 1 or ifE[Lt ] α2and 1 [Lt ] σS, whereE= ν/ΩL2,$E = \nu/\Omega L^2,\quad\alpha^2 = \overline{\sigma}B^2/\rho\Omega $and$S = \overline{\alpha}\Delta Tg\nu/\Omega^2\kappa L$. The hydromagnetic effects act to decrease the vertical shear in the azimuthal flow from the levels which would occur in the absence of magnetic fields.
Turbulent flow past a porous plate
Authors: Graham J. M. R.
Published: March 2006

The method of Vickery for calculating the drag of plane lattice structures normal to a turbulent stream is extended to cases of increased solidity. The analysis incorporates an extended version of Taylor's theory for the flow through a porous plate, and a simplified version of Hunt's analysis of the distortion of a turbulent flow by the mean flow field of a body. Some comparisons are made with experimental data.
Brownian motion in thin sheets of viscous fluid
Authors: Saffman P. G.
Published: March 2006

The drag on a cylindrical particle moving in a thin sheet of viscous fluid is calculated. It is supposed that the sheet is embedded in fluid of much lower viscosity. A finite steady drag is obtained, which depends logarithmically on the ratio of the viscosities. The Einstein relation is used to determine the diffusion coefficient for Brownian motion of the particle, with application to the movement of molecules in biological membranes. In addition, the Brownian motion is calculated using the Langevin equation, and a logarithmically time-dependent diffusivity is obtained for the case when the embedding fluid has zero viscosity.
Self-similar, time-dependent flows with a free surface
Authors: Longuet-Higgins Michael S.
Published: March 2006

A simple derivation is given of the parabolic flow first described by John (1953) in semi-Lagrangian form. It is shown that the scale of the flow decreases liket−3, and the free surface contracts about a point which lies one-third of the way from the vertex of the parabola to the focus.

The flow is an exact limiting form of either a Dirichlet ellipse or hyperbola, as the timettends to infinity.

Two other self-similar flows, in three dimensions, are derived. In one, the free surface is a paraboloid of revolution, which contracts liket−2about a point lying one-quarter the distance from the vertex to the focus. In the other, the flow is non-axisymmetric, and the free surface contracts liket−5.

The parabolic flow is shown to be one of a general class of self-similar flows in the plane, described by rational functions of degreen. The parabola corresponds ton= 2. Whenn= 3 there are two new flows. In one of these the scale varies ast12/7and the free surface has the appearance of a trough filling up. In the other, the free surface resembles flow round the end of a rigid wall; the scale varies ast−4·17.
Inviscid secondary motions in a tube of slowly varying ellipticity
Authors: Sobey Ian J.
Published: March 2006

Inviscid methods of treating secondary flows due to streamline curvature are well known in the literature. The development of secondary motions at high Reynolds number in a bifurcation characteristic of the lung airways or the cardiovascular system is considered. In particular, the secondary motions in the initial section of a bifurcation, which can be considered a tube of slowly varying ellipticity, are calculated. Providing viscous effects are confined to regions near the walls, the calculated velocity field agrees with experimental observation. Thus the structure of the secondary motions can be considered an effect of stretching of vortex lines by the tube boundary.
Magnetohydrodynamic flow due to the discharge of an electric current in a hemispherical container
Authors: Sozou C. , Pickering W. M.
Published: March 2006

In this paper we consider the flow field induced in an incompressible viscous conducting fluid in a hemispherical bowl by a symmetric discharge of electric current from a point source at the centre of the plane end of the hemisphere. This plane end is a free surface. We construct an analytic solution for the slow viscous flow and a numeriacl solution for the nonlinear problem. The streamlines in an axial cross-section form two sets of closed loops, one on either side of the axis. Our computations indicate that, for a given fluid, when the discharged current reaches a certain magnitude the velocity field breaks down. This breakdown probably originates at the vertex of the hemispherical container.
The stability of short waves on a straight vortex filament in a weak externally imposed strain field
Authors: Tsai Chon-Yin , Widnall Sheila E.
Published: March 2006

The stability of short-wave displacement perturbations on a vortex filament of constant vorticity in a weak externally imposed strain field is considered. The circular cross-section of the vortex filament in this straining flow field becomes elliptical. It is found that instability of short waves on this strained vortex can occur only for wavelengths and frequencies at the intersection points of the dispersion curves for an isolated vortex. Numerical results show that the vortex is stable at some of these points and unstable at others. The vortex is unstable at wavelengths for which ω = 0, thus giving some support to the instability mechanism for the vortex ring proposed recently by Widnall, Bliss & Tsai (1974). The growth rate is calculated by linear stability theory. The previous work of Crow (1970) and Moore & Saffman (1971) dealing with long-wave instabilities is discussed as is the very recent work of Moore & Saffman (1975).
Laminar flow in a curved pipe with varying curvature
Authors: Murata S. , Miyake Y. , Inaba T.
Published: March 2006

The steady laminar motion of fluid through pipes of circular cross-section, the curvature of whose centre-line varies locally, is analysed theoretically. The flow in three kinds of pipes whose centre-lines are specified by
\[
\hat{y} = a(1+\kappa^2\hat{x}^2)^{\frac{1}{2}},\quad\hat{y} = a\tan h\kappa\hat{x}\quad{\rm and}\quad\hat{y} = a\sin\kappa\hat{x}
\]
are treated as the examples of once-, twice- and periodically-curved pipes, respectively. The analysis is valid for any other two-dimensionally curved pipes, when centre-line curvature is small. At very small Reynolds number, the position of maximum axial velocity shifts towards the inner side of the pipe section; at large Reynolds number, on the contrary, it tends to the outer side, owing to centrifugal force. Furthermore, in the latter case, adaptation of the flow follows the change of mean-flow direction, with a phase lag.
Numerical simulation of the transition from three- to two-dimensional turbulence under a uniform magnetic field
Authors: Schumann U.
Published: March 2006

The transition of homogeneous turbulence from an initially isotropic three-dimensional to a quasi-two-dimensional state is simulated numerically for a conducting, incompressible fluid under a uniform magnetic fieldB0. The magnetic Reynolds number is assumed to be small, so that the induced fluctuations of the magnetic field are small compared with the imposed magnetic fieldB0, and can be computed from a quasi-static approximation. If the imposed magnetic field is strong enough, all variations of the flow field in the direction ofB0are damped out. This effect is important e.g. in the design of liquid-metal cooling systems for fusion reactors, and the properties of the final state are relevant to atmospheric turbulence. An extended version of the code of Orszag & Patterson (1972) is used to integrate the Navier-Stokes equations for an incompressible fluid. The initial hydrodynamic Reynolds number is 60. The magnetic interaction numberNis varied between zero and 50. Periodic boundary conditions are used. The resolution corresponds to 323points in real space. The full nonlinear simulations are compared with otherwise identical linear simulations; the linear results agree with the nonlinear ones within 3% for about one-fifth of the large-scale turnover time. This departure is a consequence of the return-to-equilibrium tendencies caused mainly by energy transfer towards high wavenumbers. The angular energy transfer and the energy exchange between different components are smaller, and become virtually zero for large values ofN. ForN≈ 50 we reach a quasi-two-dimensional state. Here, the energy transfer towards high wavenumbers is reduced for the velocity components perpendicular toB0but relatively increased for the component parallel toB0. The overall behaviour is more similar to three-than to purely two-dimensional turbulence. This finding is of great importance for turbulence models of the atmosphere. The realization of a purely two-dimensional state does not seem to be possible for decaying turbulence. The magnetic field causes highly intensified pressure fluctuations, which contribute to the redistribution of the anisotropic Lorentz forcing.
The dispersion of a buoyant solute in laminar flow in a straight horizontal pipe. Part 1. Predictions from Erdogan & Chatwin's (1967) paper
Authors: Barton N. G.
Published: March 2006

This work is concerned with the dispersion of a buoyant solute in a straight horizontal pipe of circular cross-section where dispersion is affected by molecular diffusion, the laminar flow along the pipe and density currents. Erdogan & Chatwin (1967) have derived an equation for the mean concentration $\overline{C}$ of a buoyant solute using a relatively simple asymptotic model, and have predicted that the dispersion induced by buoyancy effects depends on the Péclet number of the flow. In this part of this study an approximate expression is derived for $\overline{C}$ from Erdogan & Chatwin's equation, and an asymptotic form is obtained for the second moment of distributions of buoyant solutes. The examination of the second moment leads to a simple, but important, result: the dispersion induced by density currents at large times is small compared with the dispersion induced by density currents at times when transient effects are significant.
Axisymmetric turbulent boundary layer along a circular cylinder at constant pressure
Authors: Afzal Noor , Narasimha R.
Published: March 2006

A constant-pressure axisymmetric turbulent boundary layer along a circular cylinder of radiusais studied at large values of the frictional Reynolds numbera+(based upona) with the boundary-layer thickness δ of ordera. Using the equations of mean motion and the method of matched asymptotic expansions, it is shown that the flow can be described by the same two limit processes (inner and outer) as are used in two-dimensional flow. The condition that the two expansions match requires the existence, at the lowest order, of a log region in the usual two-dimensional co-ordinates (u+,y+). Examination of available experimental data shows that substantial log regions do in fact exist but that the intercept is possibly not a universal constant. Similarly, the solution in the outer layer leads to a defect law of the same form as in two-dimensional flow; experiment shows that the intercept in the defect law depends on δ/a. It is concluded that, except in those extreme situations wherea+is small (in which case the boundary layer may not anyway be in a fully developed turbulent state), the simplest analysis of axisymmetric flow will be to use the two-dimensional laws with parameters that now depend ona+or δ/aas appropriate.
Thermosolutal convection in a solution with large negative Soret coefficient
Authors: Caldwell Douglas R.
Published: March 2006

The large negative Soret coefficient of 1N-LiI gives rise in a Rayleigh-Bénard experiment to a density distribution which is observed to stabilize the fluid layer for values of the Rayleigh number as large as 196 times the value of 1708 for the onset of convection in a pure fluid. The Soret transport also affects the convective heat flux. A power law relating heat flux and temperature difference is found with the same exponent as is found in pure fluids but with a lower value of the multiplicative constant. The Rayleigh number at the onset of power-law behaviour depends on the Soret coefficient. Three types of oscillation are seen: transient oscillations at onset, low frequency fluctuations at low Rayleigh number, and higher frequency oscillations similar to those observed in pure water. The intermediate state found after onset in NaCl solutions is not found in LiI.
Large amplitude lunate-tail theory of fish locomotion
Authors: Chopra M. G.
Published: March 2006

The two-dimensional theory of lunate-tail propulsion is extended to motions of arbitrary amplitude, regular or irregular, so that an accurate comparison may be made with the actual lunate-tail propulsion of scombroid fishes and cetacean mammals. There is no restriction at all on the amplitude of motion but the tail's angle of attack relative to its instantaneous path through the water is assumed to remain small. The theory is applied to the regular finite amplitude motion of a thin aerofoil with a rounded leading edge to take advantage of the suction force and a sharp trailing edge to ensure smooth tangential flow past the rear tip. This can represent the vertical motions of the horizontal lunate tails of large aspect ratio with which cetacean mammals propel themselves or the horizontal undulations of the vertical lunate tails of certain fast fishes. The dependence of the thrust, the hydromechanical propulsive efficiency and the energy wasted in churning up the eddying wake on the reduced frequency, the angle of attack and the amplitude of motion is exhibited.
Internal waves in a circular channel
Authors: Yang W. H. , Yih Chia-Shun
Published: March 2006

The frequencies of the first four sloshing internal wave modes in two superposed fluid layers contained in a circular channel are calculated for two positions of the free surface and for various ratios of the depths of the two layers. Flow patterns are given for the first four sloshing modes for the case in which the fluids occupy a semicircular space and the depth of the upper layer is one-quarter of the radius.

It is hoped that the results obtained will provide a guide for estimating the frequencies of sloshing internal wave modes in long lakes.
The far field of high frequency convected singularities in sheared flows, with an application to jet-noise prediction
Authors: Balsa Thomas F.
Published: March 2006

The purpose of the present paper is to derive expressions for the pressure fields of various high frequency convected singularities immersed in a unidirectional sheared flow. These expressions include the simultaneous effects of fluid and source convection and refraction. These results are then combined to predict the far-field directivity of cold round jets. It is found that the agreement between experiment and the present theory is quite good at a source Strouhal number of unity but that this agreement deteriorates as the source frequency is increased. Our theoretical results show the explicit form of the ‘refraction integral’ and that convective amplification for the pressure of a quadrupole is increased by a factor of (1 —MJcos Θ)−1over the classical results, whereMJis the jet Mach number and Θ is the angle from the jet axis. Thus acoustic/mean-flow interaction not only implies refraction but also additional convective amplification duenotto source convection but to fluid motion.
On the two-dimensional mixing region
Authors: Champagne F. H. , Pao Y. H. , Wygnanski I. J.
Published: March 2006

An experimental investigation of the two-dimensional incompressible mixing layer was carried out. The measurements provide new information on the development of the mean and turbulent fields towards a self-preserving state and on the higher-order statistical characteristics of the turbulent field. The relevance of initial conditions to the development of the flow is discussed in the light of both present and previous data. Measurements of spectra, probability densities and moments to eighth order of all three velocity-component fluctuations at various transverse positions across the flow were carried out using an on-line digital data acquisition system. The probability density distributions of the derivative and the squared derivative of the longitudinal and lateral velocity fluctuations were also determined. Direct measurements of moments to eighth order of the velocity derivatives were attempted and are discussed in the light of the simultaneously measured histograms. The problems in obtaining higher-order statistical data are considered in some detail. Estimates of the integral time scale of many of the higher-order statistics are presented. The high wave-number structure was found to be locally anisotropic according to both spectral and turbulent velocity-gradient moment requirements. Higher-order spectra to fourth order of the longitudinal velocity fluctuations were measured and are discussed. Finally the lognormality of the squared longitudinal and lateral velocity-derivative fluctuations was investigated and the universal lognormal constant μ was evaluated.
Turbulence correlations in a compressible wake
Authors: Demetriades A.
Published: March 2006

Space-time correlations have been measured in the turbulent supersonic wake behind a slender axisymmetric body. The data were obtained with two independently-positioned hot-wire anemometers, and interpreted with the aid of an extension of compressible anemometry theory. Comparison with earlier single-point Eulerian spectra showed a breakdown of Taylor's hypothesis near the wake edge, and thus also the expected differences in the scale lengths. The eddy convection speed appears equal to that of the mean flow, and the eddy shape is inclined to the wake axis, although it becomes nearly parallel to it at the wake edge. As a consequence, radial and longitudinal space correlation functions appear nearly equal. An upstream-downstream asymmetry was noted in the latter.
On a rotational flow disturbed by gravity
Authors: Greenspan H. P.
Published: March 2006

We examine a rapidly rotating flow that exhibits periodic vortex detachment. Specifically, the rotation/symmetry axis of a fluid-filled cylinder is set perpendicular to gravity. A free buoyant cylindrical float placed within the container is acted upon by both centrifugal and gravitational forces, the competition of which causes fluid motion and, in certain parameter ranges, flow instability. The motion is determined, a criterion for separation is advanced, preliminary experiments and data are described and the relationship of this phenomenon to other examples of vortex shedding in rotating fluids is discussed.
Mass transport in the bottom boundary layer of cnoidal waves
Authors: Isaacson M. De St Q.
Published: March 2006

This study deals with the mass-transport velocity within the bottom boundary layer of cnoidal waves progressing over a smooth horizontal bed. Mass-transport velocity distributions through the boundary layer are derived and compared with that predicted by Longuet-Higgins (1953) for sinusoidal waves. The mass transport at the outer edge of the boundary layer is compared with various theoretical results for an inviscid fluid based on cnoidal wave theory and also with previous experimental results. The effect of the viscous boundary layer is to establish uniquely the bottom mass transport and this is appreciably greater than the somewhat arbitrary prediction for an inviscid fluid.
Free convection and the burning of a horizontal fuel surface
Authors: Clarke J. F. , Riley N.
Published: March 2006

The free-convective flow induced when a semi-infinite horizontal fuel surface burns in a quiescent oxidizing atmosphere is considered. For high values of the Grashof number the dominant feature of the flow is a boundary layer close to the surface within which there is a flame or intense reaction zone. An outer flow or fire-wind is induced by entrainment into this boundary layer. A simple experiment supports this overall picture of the flow.
Structure of a linear array of hollow vortices of finite cross-section
Authors: Baker G. R. , Saffman P. G. , Sheffield J. S.
Published: March 2006

Free-streamline theory is employed to construct an exact steady solution for a linear array of hollow, or stagnant cored, vortices in an inviscid incompressible fluid. If each vortex has area A and the separation is L, there are two possible shapes if A½/L is less than a critical value 0.38 and none if it is larger. The stability of the shapes to two-dimensional, periodic and symmetric disturbances is considered for hollow vortices. The more deformed of the two possible shapes is found to be unstable while the less deformed shape is stable.
Oxygen vibrational and dissociation relaxation behind regular reflected shocks
Authors: Oertel H.
Published: March 2006

The oxygen vibrational and dissociation relaxation behind regular reflected shocks has been calculated and measured. Numerical calculations using published rate coefficients supplied the relaxation-zone data needed to estimate the range of most useful experimental conditions. Then photographs of the shock reflexion were taken using a complementary double-exposure interferometer. The density profiles in the relaxation zones behind the reflected shocks were measured by means of a multibeam laser-differential interferometer. The results of these experiments confirmed the theoretical model adopted for the calculations within a certain range of experimental conditions, but clearly revealed the need for revising the rate coefficients. New calculations with different vibrational relaxation times and dissociation rate coefficients then had the result that the best fit of calculated to measured profiles was obtained when the following values were inserted.

Vibration\begin{eqnarray*} & p\tau_v = A_v\exp(B_vT^{-\frac{1}{3}}),\\ & A_v = (2.1\pm 0.2)\times 10^{-5}\,{\rm kg/ms},\quad B_v = 129\,{}^{\circ}{\rm K}^{\frac{1}{3}}. \end{eqnarray*}

Dissociation: O2+ O_2[rlarr ] 2O + O_2\begin{eqnarray*} & {\mathop {k_1}\limits^{\rightharpoonup}} = A_1T^{-2.5}\exp (-\theta_D/T),\\ & A_1 = (6.2 \pm 0.5)\times 10^{18}\,{\rm m}^3\,{}^{\circ}{\rm K}^{2.5}/{\rm mol}\,{\rm s},\quad\theta_D = 59\,136\,{}^{\circ}{\rm K}. \end{eqnarray*}

Dissociation: O2+ O[rlarr ]3O\begin{eqnarray*} & {\mathop {k_1}\limits^{\rightharpoonup}} = A_2T^{-1.0}\exp (-\theta_D/T),\\ & A_2 = (4.0 \mp 0.5)\times 10^{-13}\,{\rm m}^3\,{}^{\circ}{\rm K}/{\rm mol}\,{\rm s}. \end{eqnarray*}
Density profiles in argon and nitrogen shock waves measured by the absorption of an electron beam
Authors: Alsmeyer H.
Published: March 2006

Accurate measurements of the density distribution in Ar and N2 shock waves have been made in a shock tube for the Mach number range from 1.55 to 9 and 10 respectively by the absorption of an electron beam. A modified absorption law has been used for data reduction. The density profiles were corrected for the influence of shock curvature and density rise behind the shock wave. The measurements in Ar agree to within 1% with those of Schmidt (1969) in the mean range of Ms but give a slightly smaller density gradient for Ms = 9. Comparison with various theories shows very good agreement with Bird's Monte Carlo simulation in the whole Mach number range for a simple repulsive intermolecular force law. Further, the agreement with the Mott-Smith density profile for the same interaction law is also good, and surprisingly is found to be better for lower than for higher Mach numbers. Qualitative agreement is obtained with the solutions of Hicks & Yen for hard-sphere and Maxwell molecules. The Navier-Stokes and BGK solutions are found to differ significantly from the present experiments even for the lowest measured Mach number (1·55), whereas the Burnett equation gives better agreement, especially with respect to the asymmetry of the profiles.

The measured N2 profiles agree on the whole with the shock-tube measurements of other investigators but show substantial deviations from the low density wind-tunnel experiments of Robben & Talbot (1966b) for higher Mach numbers. Bird's ‘energy sink model’ (1971) is in agreement with the measured density profiles for a realistic interaction law and a suitable rotational collision number. Rotational relaxation in nitrogen is found to be very fast for all Mach numbers. Consequently the coupling between rotational and translational relaxation is very strong.
The structure of jets from notched nozzles
Authors: Pannu S. S. , Johannesen N. H.
Published: March 2006

Jets from notched nozzles are investigated by schlieren photography and pressure traverses. It is demonstrated that the dominant feature of the flow which determines the structure far downstream is the trailing vortices shed from the swept edges of the notches.
Supersonic viscous flow over cones at large angles of attack
Authors: Fletcher Clive A. J. , Holt Maurice
Published: March 2006

Numerical solutions for the flow field about cones with nose angles of up to 30° at angles of attack up to 50° for a range of Reynolds numbers and wall temperature ratios are presented. The solutions obtained permit interaction between the inviscid region and the boundary layer on the body through the displacement-thickness effect. The solutions are valid throughout the flow field except in the region adjacent to the leeward line of symmetry. Comparisons are made with experimental results and other numerical solutions. Detailed flow structure and the variation of surface conditions with cone angle, incidence, Reynolds number and wall temperature are indicated. The numerical methods used for the inviscid flow equations are Telenin's method and the method of characteristics, while a modified form of the method of integral relations is applied to the boundary-layer equations.
Contribution towards a Reynolds-stress closure for low-Reynolds-number turbulence
Authors: Hanjalić K. , Launder B. E.
Published: March 2006

The problem of closing the Reynolds-stress and dissipation-rate equations at low Reynolds numbers is considered, specific forms being suggested for the direct effects of viscosity on the various transport processes. By noting that the correlation coefficient$\overline{uv^2}/\overline{u^2}\overline{v^2} $is nearly constant over a considerable portion of the low-Reynolds-number region adjacent to a wall the closure is simplified to one requiring the solution of approximated transport equations for only the turbulent shear stress, the turbulent kinetic energy and the energy dissipation rate. Numerical solutions are presented for turbulent channel flow and sink flows at low Reynolds number as well as a case of a severely accelerated boundary layer in which the turbulent shear stress becomes negligible compared with the viscous stresses. Agreement with experiment is generally encouraging.
The locking-on of vortex shedding due to the cross-stream vibration of circular cylinders in uniform and shear flows
Authors: Stansby P. K.
Published: March 2006

The frequencies of vortex shedding from circular cylinders forced to oscillate transversely in low-turbulence uniform and shear flows were investigated. The stream velocity in the shear flow varied linearly with spanwise distance.

In both flows the vortex shedding frequency locked on to the cylinder frequency and to submultiples of the cylinder frequency. In uniform flow the range of cylinder frequencies for locking-on was dependent on the amplitude of oscillation and Reynolds number. At the boundaries of locking-on at the cylinder frequency locked-on shedding was intermittent with unforced shedding and locking-on was accompanied by a change in wake width. At a particular cylinder frequency near mid-range it is conjectured that the wake width jumped from being greater to being less than that for the stationary cylinder. In shear flow the spanwise extent of locking-on at the cylinder frequency was explained by considering the uniform flow results and the inclination of shed vortices in shear flow. At the spanwise boundaries of this locking-on, locked-on cells were shed intermittently with unforced cells which were more stable in frequency than the corresponding cells for the stationary cylinder.
On the interaction of surface and internal gravity waves: uniformly valid solution by extended stationary phase
Authors: Hughes B. A.
Published: March 2006

Using simple Fourier transform techniques and extensions to stationary-phase methods, the behaviour of surface gravity waves is determined near triply coalescing roots of the dispersion relation. It is shown that the amplitude of the surface wave is proportional to (∂U/∂x)−¼ at the location of the triple root. Far from the triple root it satisfies conservation of action. The internal wave is modelled simply by its surface current U.

Asymptotic orders of magnitude are also given for the case ∂U/∂x = 0 at the triple root.
Single-wave run-up on sloping beaches
Authors: Spielvogel Lester Q.
Published: March 2006

Possibilities of high shoreline amplification and run-up are investigated. A shoreline amplification of magnitude 5·38 and a tsunamigenic (deep water) amplification of magnitude 5·71 are obtained from single waves without analytic or computational difficulties. It is not claimed that these are a maximum, but rather it is conjectured that arbitrarily high run-up and amplification can be obtained provided that the correct initial wave trains are chosen.
Prolonged outbreak of giardiasis with two modes of transmission
Authors: KATZ D. E. , HEISEY-GROVE D. , BEACH M. , DICKER R. C. , MATYAS B. T.
Published: March 2006

Large outbreaks of giardiasis caused by person-to-person transmission, or a combination of transmission routes, have not previously been reported. A large, prolonged giardiasis outbreak affected families belonging to a country club in a suburb of Boston, Massachusetts, during June–December 2003. We conducted a retrospective cohort study to determine the source of this outbreak. Giardiasis-compatible illness was experienced by 149 (25%) respondents to a questionnaire, and was laboratory confirmed in 97 (65%) of these cases. Of the 30 primary cases, exposure to the children's pool at the country club was significantly associated with illness (risk ratio 3·3, 95% confidence interval 1·7–6·5). In addition, 105 secondary cases probably resulted from person-to-person spread; 14 cases did not report an onset date. This outbreak illustrates the potential for Giardia to spread through multiple modes of transmission, with a common-source outbreak caused by exposure to a contaminated water source resulting in subsequent prolonged propagation through person-to-person transmission in the community. This capacity for a common-source outbreak to continue propagation through secondary person-to-person spread has been reported with Shigella and Cryptosporidium and may also be a feature of other enteric pathogens having low infectious doses.
Continuing Mycobacterium bovis transmission from animals to humans in New Zealand
Authors: BAKER M. G. , LOPEZ L. D. , CANNON M. C. , DE LISLE G. W. , COLLINS D. M.
Published: March 2006

New Zealand has a large reservoir of Mycobacterium bovis infection in wild and farmed animals. This study aimed to assess the extent of human infection with this organism and the potential contribution of these animal sources. Combined epidemiological and laboratory investigation of human tuberculosis cases over the period 1995–2002 showed that M. bovis accounted for 2·7% (54/1997) of laboratory-confirmed human tuberculosis cases, a rate of 0·2/100000 population. M. bovis isolates from humans (23) were typed using restriction endonuclease analysis (REA) and compared with isolates from wild and domestic animals (2600). Fourteen (61%) of the human isolates had REA patterns that were identical to patterns for isolates from cattle, deer, possums, ferrets, pigs, and occasionally cats. These results suggest a low level of ongoing M. bovis transmission from animal reservoirs to humans in New Zealand.
Does dog or cat ownership lead to increased gastroenteritis in young children in South Australia?
Authors: HEYWORTH J. S. , CUTT H. , GLONEK G.
Published: March 2006

The aim of this study was to investigate the relationship between dog and cat ownership and gastroenteritis in young children. A diary study of 965 children aged 4–6 years living in rural or semi-rural South Australia was undertaken. Data were collected on pet ownership, drinking water and other risk factors for gastroenteritis. Overall 89% of households had pets and dog ownership was more common than cat ownership. The multivariable models for gastroenteritis and pet ownership indicated that living in a household with a dog or cat was associated with a reduced risk of gastroenteritis (adj. OR 0·71, 95% CI 0·55–0·92; OR 0·70, % CI 0·51–0·97 respectively). This paper adds to the evidence that pets are not a major source of gastroenteritis in the home and lends support to the health benefits of pet ownership. However, this must be weighed against the potential negative consequences, such as dog bites, particularly for this age group.
Bacteraemia due to ciprofloxacin-resistant Salmonella enterica serotype Choleraesuis in adult patients at a university hospital in Taiwan, 1996–2004
Authors: WANG J.-Y. , HWANG J.-J. , HSU C.-N. , LIN L.-C. , HSUEH P.-R.
Published: March 2006

Eighty-one adult patients with Salmonella enterica serotype Choleraesuis (S. Choleraesuis) bacteraemia treated at a university hospital from 1996 to 2004 were evaluated. Multivariate analysis with a logistic regression model was used to characterize risk factors for primary bacteraemia and mycotic aneurysm and to determine the association of clinical characteristics of patients based on ciprofloxacin susceptibility of the causative organism. The incidence per 100000 discharges was 0·76 in 1996 and 3·9 in 2004. The overall rate of ciprofloxacin resistance among these isolates was 59% (87 isolates) and the annual rate increased with time from 0% prior to 2000 to 80% in 2004. Among these patients, 48 (59%) had primary bacteraemia and 13 (16%) had secondary bacteraemia with mycotic aneurysm. Seventy (86%) patients had fever at presentation, 22 (27%) developed shock during hospitalization, and eight (10%) died of S. Choleraesuis bacteraemia. Patients with immunocompromised conditions had a higher risk of developing primary bacteraemia (OR 18·442, P<0·001). Hypertension (OR 15·434, P=0·002) and male gender (OR 7·422, P=0·039) were associated with mycotic aneurysm. Patients with mycotic aneurysm were more frequently infected with ciprofloxacin-susceptible isolates (P=0·028) and ciprofloxacin-susceptible isolates were also more frequently associated with recurrent infection than ciprofloxacin-resistant isolates (P=0·038). The incidence of S. Choleraesuis bacteraemia has increased in the past 8 years, and this increase is associated with the upsurge of ciprofloxacin-resistant isolates.
ANCIENT MAYA ROYAL STRATEGIES: Creating power and identity through art
Authors: Sanchez Julia L. J.
Published: March 2006

Ancient Maya monumental art was designed to enact the physical, social, and ritual hierarchy. Physically, sculpture created barriers and access patterns that altered movement through sites. Monumental architecture separated ritual participants in buildings from audiences in the plazas below. Access to monuments and portrayals on monuments in part defined social and power hierarchies. Motifs were altered to communicate various forms of power appropriate to each context and audience. Complex supernatural themes and ritual roles demonstrated hierarchical differences among the ruler and other nobles, while more simplistic representations of a powerful ruler demonstrated the separation of the ruler from commoners.
AGENCY AND THE “STAR WAR” GLYPH: A historical reassessment of Classic Maya astrology and warfare
Authors: Aldana Gerardo
Published: March 2006

Several studies over the past 20 years have argued for an explicit connection between a hieroglyphic record of war, the so-called star war, and the observation of Venus. To the last, these studies have relied on statistical treatments or simple numerical coincidence to substantiate their claims. In this paper I challenge the results of these studies on two levels. First, I demonstrate that the iconographic evidence that inspired the association between Venus and the “star war” verb is itself unstable; then I appeal to the historical contexts of the rulers engaged in this warfare to see if, as individuals, there is evidence that they held such a belief. In both cases, I show that the evidence does not support a ritual timing of Classic Maya warfare by the phases of Venus. At end, I turn to philological consideration to propose a new reading for the “star war” verb.
ANTHROPOMORPHIC PEG-BASED SCULPTURES FROM THE BANDERAS VALLEY OF COASTAL WEST MEXICO
Authors: Mountjoy Joseph B. , Beltrán José C.
Published: March 2006

Both the accidental as well as the purposeful discovery of a large number of anthropomorphic peg-based sculptures in the Banderas Valley in the states of Jalisco and Nayarit during the 1990s have provided a corpus of contextual and iconographic data that, along with conquest-period ethnographic data, allow for an assessment of the date and function of such figures. In addition, because of the similarity of these sculptural figures to ones of comparable dates in Central America, the case for significant pre-Hispanic coastal contacts between the two areas is reinforced.
THE OBSIDIAN BLADE SEQUENCE AT EL UJUXTE, A LATE PRECLASSIC SITE ON THE SOUTH COAST OF GUATEMALA
Authors: Nance C. Roger , de Leeuw Jan
Published: March 2006

Systematic data on about 1,200 blades from this site were summarized in terms of three ceramic phases (defined by Love 2002b) for the same site. That is, we assigned blades to phases based on the ceramic content of each provenience. Regular phase-by-phase decreases occurred in blade dimensions, weights, and length-to-width ratios. We predicted these results based on earlier findings from the site of La Blanca (Nance and Kirk 1991). The trend appears also within the latest Pitahaya phase, even at the level of the excavation unit. Blade densities decrease through Pitahaya deposits, as well, and the blade sequence is discussed in terms of an increased scarcity of obsidian or obsidian blades traded to the region.
THE OBSIDIAN TRADE TO THE TUXTLAS REGION AND ITS IMPLICATIONS FOR THE PREHISTORY OF SOUTHERN VERACRUZ, MEXICO
Authors: Santley Robert S. , III Philip J. Arnold
Published: March 2006

Evidence from the Tuxtla Mountains in southern Veracruz suggests that Teotihuacan established a base at Matacapan, the region's top-ranking center, sometime during the Early Classic period. This development in Tuxtlas's prehistory was associated with the founding of Matacapan, a major shift in settlement pattern, and the presence of substantial amounts of Fine Buff, a lower fired variant of Fine Orange that resembles Copa ware, a common Middle Classic-period ceramic service ware at Teotihuacan. Teotihuacan's influence at Matacapan, as monitored ratios of candelero- and tripod support to rim sherds, increased markedly in the succeeding early Middle Classic period but declined in the late Middle Classic and early Late Classic periods. At the same time, Teotihuacan's influence extended well into the countryside, where it was present not only at other large sites, but also at small villages and hamlets. These developments were associated with changes in the amount and kind of obsidian traded to the Tuxtlas. The total volume of obsidian traded to the Tuxtlas in the Middle and Late Classic periods was huge: from 7.5 to 19.6 metric tons per year. Matacapan had preferred status as far as the consumption of green obsidian was concerned, and in general, pre-Hispanic settlements in the Tuxtlas consumed more of this material than neighboring areas such as La Mixtequilla and the Hueyapan region. When Teotihuacan declined in importance and its influence throughout Mesoamerica waned, a much smaller amount of obsidian—in particular, material from Pachuca—was traded to the Tuxtlas. This is precisely what we would expect if the Central Mexican city was no longer the conveyor of obsidian over long distances, and some other center—perhaps Cantona or El Tajin—replaced Teotihuacan as the primary distributor of obsidian to southern Veracruz.
NAHUA LOAN WORDS FROM THE EARLY CLASSIC PERIOD: Words for cacao preparation on a Río Azul ceramic vessel
Authors: Macri Martha J.
Published: March 2006

The discovery of words in a Nahua language on a Maya ceramic vessel provides evidence of Nahua influence in the Maya region as early asa.d.480, centuries earlier than previously believed. The words are spelled in syllabic Maya signs painted on a pot known to have contained chocolate (Hall et al. 1990). The words occur within the context of the primary standard sequence, a well-known Maya formula, and describe the chocolate drink that among the later Mexica (Aztec) was reserved for “rulers and esteemed noblewomen.” This new reading supports the Uto-Aztecan etymology ofcacaoproposed by Karin Dakin and Søren Wichmann (2000) and their assertion that an economically and militarily powerful Nahua-speaking people were responsible for the spread of the wordcacaointo southern Mesoamerica. More broadly, these findings have implications for the role of Uto-Aztecan speakers in the formation and spread of Mesoamerican civilization.
RECONSTRUCTING AGRICULTURAL SELF-SUFFICIENCY AT CHUNCHUCMIL, YUCATAN, MEXICO
Authors: Dahlin Bruce H. , Beach Timothy , Luzzadder-Beach Sheryl , Hixson David , Hutson Scott , Magnoni Aline , Mansell Eugenia , Mazeau Daniel E.
Published: March 2006

The Pakbeh Regional Economy Program is studying the vexing questions of economic life among the ancient Maya in northwestern Yucatan, Mexico. The region constitutes an ideal laboratory in which to investigate these questions, as it has very limited agricultural potential and fewer options for intensification than are found in the southern and central lowlands, yet many times more people lived here during the Classic period than can eke out a living today, and it has abundant evidence of market trade. Because crop yields in outfields are very low, and known intensification techniques are possibly incapable of sufficient yield enhancement, we anticipated that it would be an easy task to demonstrate that this population was dependent on imports of food and other necessities of life from beyond the region and therefore had a complex exchange economy. Twelve years later, we report on how wrong we were. We are still struggling with an evaluation of agricultural insufficiency. We explore the many and varied lines of evidence we have pursued and the confounding factors inherent in them, including problems with reconstructing ancient population size, equating contemporary and historical crop yields and farming practices, as well as ancient with modern environmental conditions, and hypothesizing potential forms of agricultural intensification, including intensive fertilization and other yield enhancement techniques, and reliance on alternative crops. The best that we can say at this juncture is that using contemporary production and consumption standards, the most conservative population estimates, and the most liberal estimates of available land in the surrounding region, we can conclude only that regional agricultural self-sufficiency remains unlikely but not proved. What initially seemed like an archaeological “no-brainer” has required us to delve into the realm of archaeological epistemology that we would like to share with our colleagues.
BURIAL PRACTICES AT TEOTIHUACAN IN THE EARLY POSTCLASSIC PERIOD: The Vaillant and Linné Excavations (1931–1932)
Authors: Elson Christina M. , Mowbray Kenneth
Published: March 2006

In 1931 and 1932, George Vaillant and Sigvald Linné excavated 34 burials and 17 offerings dating to the Early Postclassic period (a.d.900–1150). The features were located on the ruins of the Classic-period site of Teotihuacan and within the boundaries of a roughly 25–50 ha zone identified by the Teotihuacan Mapping Project as having a dense Early Postclassic-period occupation. The results of Vaillant's excavations have not been published. An examination of the Vaillant–Linné data sheds new light on Early Postclassic-period mortuary ritual and social organization. The identification of several types of burials shows that local people conducted primary and secondary mortuary rituals and indicates the presence of at least two social strata at the site. The content of the burials and offerings supports a division of the Early Postclassic period into two local phases, Mazapan (ca.a.d.900–1000) and Atlatongo (ca.a.d.1000–1100/1150), with these features dating to the earlier phase.
THE MIDDLE FORMATIVE OF YUCATAN IN CONTEXT: The view from Yaxuna
Authors: Stanton Travis W. , Ardren Traci
Published: March 2006

Assumptions concerning the late dating of Middle Formative ceramics in the northern Maya lowlands and similarities between this region and areas to the south underlie mainstream interpretations that the northern Maya lowlands was slower to develop cultural complexity. This paper is a re-evaluation of these assumptions and their impact on interpretations of Formative interaction. Recent research at Yaxuna, Yucatan, Mexico is discussed in light of alternative approaches to the study of sociopolitical interaction among early complex societies.
Genetische Diagnostik akuter Leukämien – ein praktischer Leitfaden
Authors: Meyer-Monard
Published: March 2006

Akute Leukämien entstehen durch eine Ansammlung von unreifen Vorstufen. Dieser unkontrollierten Proliferation liegen genetische Aberrationen zugrunde. Mittels zytogenetischer und molekularbiologischer Analyse werden diese genetischen Veränderungen bei Diagnose einer akuten Leukämie erfasst. Sie spielen eine wichtige Rolle in der Klassifizierung der Leukämie und sind ein wichtiger prognostischer Marker. Die Kenntnis dieser genetischen Veränderungen beeinflussen somit die Intensität der Behandlung. Die pathologischen Genprodukte können auch Zielscheibe von spezifischen Therapien sein. Auch das Erfassen von minimaler residueller Krankheit kann mittels molekularen Methoden erfolgen. Das Erfassen und Verfolgen von genetischen Anomalien der leukämischen Zelle ist ein unabdingbarer Bestandteil des modernen Mangement der akuten Leukämien.